Robust Multi-Objective Optimal dispatch of Distributed Energy Resources in Micro-Grids

Modern distribution systems are implemented through micro grids: small power networks where generation is close to consumption and ICT supports the coordinated management of the different energy resources. In such systems, the central control unit manages energy dispatch from the different sources according to different criteria (technical, economical and environmental) and takes care of tertiary regulation. Such optimization for the tertiary regulation is performed with a time interval that typically is of 24 hours. This is due to the fact that it is necessary to take into account the charge and discharge cycles of storage systems. On the other hand, such long time leads to large errors in…

A contribution to solve the problem of attributing harmonic distorsion disturbance responsability.

Technical-economical evaluation for distributed storage applications. An Italian case study for a medium-scale public facility

Time-of-use energy cost management involves the use of storage by customers to reduce their electricity bills. This can be accomplished by charging the storage during off-peak time periods, when electricity energy prices are low, and discharging it during times when on-peak energy prices are applied. This article addresses the question whether it is economically viable to install medium-scale distributed storage devices in the power system designed to lower the electricity cost for a customer-side application, assuming flexible electricity tariffs. The technical/economical evaluation is carried out referring to Lithium ion (Li-ion), Sodium Sulphur (NaS) and Vanadium Redox Battery (VRB) tech…

New High Voltage Interconnections with Islands in the Mediterranean Sea: Malta and Sicily. Analysis of the Effects on Renewable Energy Sources Integration and Benefits for the Electricity Market

The present paper shows the benefits coming from the operation of the recent electrical high voltage (HV) interconnections between Sicily, Malta and mainland Italy. These new interconnections allow zonal prices of electricity considerably lower than in the past, ensuring greater flexibility to the system and a better integration of Renewable Energy Sources (RES). After briefly illustrating the two high-voltage electrical systems (Sicily and Malta), and having provided a description of the interconnection cable with Malta and its protection devices, the authors hypothesized two modes of operation (Sicily-Malta system islanded or interconnected to the rest of Europe). For the first case (isla…

Real-time pricing for aggregates energy resources in the Italian energy market

Abstract Over the last decade, the architecture of the energy market has radically changed. In many countries end-users are now able to directly access the market, which has given rise to the question of how they can actively participate in that market. End-users can comprise a critical mass through aggregation that is carried out by a third party – to wit the “loads aggregator.” This paper proposes a new framework for generating feasible real-time price curves for those end-users in a demand-response management process. The underlying algorithm generates output curves as the solution to a constrained optimization problem whose objective function is the aggregator's economic benefit. A case…

A New Solution to Mitigate Voltage Dips on Electrical Distribution Systems: the Fault Decoupling Device.

Contract for the support of household appliances control and monitoring application interworking specification

An Investigation of Protection Devices Coordination Effects on Distributed Generators Capacity in Radial Distribution Systems

In the recent years, with the concept of Smart Grid, there are a great interest in integration of renewable energy based distributed generation (DG) units at distribution level. Along with a number of benefits, penetration of DG units in the distribution system imposes some serious challenges; protection requirements turns up as one of the most critical challenge in DG integration. In this paper the possibility and the potentiality of occurring mis-coordination between protection devices in radial distribution network is studied. The impacts of protection devices coordination on DG capacity are investigated. The penetration level, number, and location of interconnected DGs are used as param…

A Multi-Port Approach to Solve Distribution Networks with Meshes and PV Nodes

A new methodology based on the backward/forward (b/f) technique for the load flow solution in distribution systems is here proposed. The methodology takes efficiently into account the fixed voltage nodes and uses a reduced bus impedance matrix. In this way, it is possible to attain, for the unknowns at the PV nodes, the same values that are attainable solving the network with the methods adopted for transmission systems. With the same methodology it is possible to take into account also the meshes. If the network contains only meshes, the relevant model is linear and it is the one including the compensation currents. The presence of PV nodes introduces non linearity in the model and an iter…

Studio di fattibilità e progettazione preliminare di dimostratori di reti elettriche di distribuzione per la transizione verso reti attive. Report 2 – Simulazioni e valutazioni di progetto per gli scenari selezionati

A new approach to increase the integration of RES in a mediterranean island by using HTLS conductors

Today, in many countries, it is very difficult to build new power lines, especially because of right of way authorization problems. Furthermore, the production of electricity from renewable sources is growing more and more. For these reasons Terna S.p.A. (Italian TSO) has to take advantage of existing overhead transmission lines. In order to increase the transmission capacity and the exportation of RES (Renewable Energy Sources) from Sicily to the mainland, the existing high-voltage power grid in Sicily has been studied and analysed by Neplan®, which is a powerful software tool able to analyze, plan, optimize and simulate electrical power grids. This paper, after a description of existing p…

A bidirectional converter for the integration of LiFePO4 batteries with RES-based generators. Part II: Laboratory and field tests

This paper presents a device for controlling and connecting combined Renewable Energy Sources (RES)-based generators and electric storage systems to the supply utility grid. The device is a bidirectional converter that can be controlled in order to facilitate the interface between the low voltage grid and small generators combined with Li-ion batteries, contemporary addressing the requirements of the reference technical standards for users connection and providing different ancillary services. The paper describes the laboratory and field test activities carried out by the DEIM of the University of Palermo and ENEA during 2013.

No-Load Energization of Very Long EHV Mixed Overhead-Cable Lines

New dispatching strategy for the integration of active-demand and distributed storage in the electricity market

The proliferation of Distributed Generation (DG) in power systems calls for a redesign of electricity network management, which should be able to accommodate large amounts of intermittent generation. This issue requires a discussion about the current dispatching regulation, giving distributed storage systems and qualified electricity consumption the opportunity to provide ancillary services to the distribution grid. In this work, a new dispatching strategy for the integration of active-demand and distributed storage in the Italian electricity market is presented. The strategy is focused on a distribution Smart Grid (SG), where customers can indirectly participate to the Day-Ahead (DA) and t…

Designing an Energy Management System for smart houses

Most advantages that the smart grid will bring derive from its capability of improving reliability performance and customers' responsiveness and encouraging greater efficiency decisions by the customers. In this optic, the paper presents an innovative Energy Management System for smart houses, allowing the optimization of the electricity cost and electrical energy consumption and, at the same time, preserving the end-user comfort.

Energy self-consumers and renewable energy communities in Italy: New actors of the electric power systems

Abstract The new European Directive RED-II on the promotion of the use of renewable energy sources has introduced the concept of the Renewable Energy Community. This new entity has the potential to change the relations among end-users and the latter and the other actors of the energy sector. In particular, the electrical sector appears the most influenced by the implementation of this paradigm. Indeed, the need for self-consumption and for exploiting the full potential of renewable energy in a Renewable Energy Community influences how the end-users exchange energy with the power grid, the rules for their connection to the grid, the implementation of Demand Response and other energy manageme…

Automazione delle reti elettriche di distribuzione e trasferimento internazionale di know how

Challenges and directions for Blockchain technology applied to Demand Response and Vehicle-to-Grid scenarios

Abstract Nowadays, Blockchain is considered a consolidated technology supporting many different applications that integrate well with Artificial Intelligence and the Internet of Things, and supports the creation of Decentralized Autonomous Organizations. Within this wider framework, the energy blockchain applications are now deserving more and more attention, since blockchain architectures, on one hand, provide transparency and solve the information asymmetry problem, on the other, provide disintermediation. In this way, the dream of an energy market closer to end-users becomes a reality, although, still, the regulatory framework is not clear, especially for what concerns the tokenization o…

Transition of a Distribution System towards an Active Network. Part I: Preliminary Design and Scenario Perspectives

In an European perspective, the focus of Smart Grids initiatives (SET Plan - Strategic Energy Technology Plan) is strictly linked with the main commitment to achieve the goals of the Climate and Energy Package 20-20-20, at the light of the three main pillars of the European energy policy: competitiveness, sustainability and security of supply. Smart grid technologies will enable load levelling of the electrical grid, allowing a power company to run cleaner power sources - such as hydroelectric, wind, or solar - while reducing the need to use carbon-emitting gas, coal, or oil plants to meet peak demand. In this framework the proposed paper refers about the technical economical feasibility st…

Esperienze di ricerca in un progetto congiunto Università-Impresa per l’automazione delle reti elettriche di distribuzione e il trasferimento internazionale di know how

Ant Colony Search algorithm for optimal strategical planning of electrical distribution systems expansion

Strategical planning is one of many research fields in the design of electrical distribution systems. The problem of strategical planning is a multiobjective combinatorial problem and the search space may often be quite large concerning to the options. The aim is to identify a strategy of expansion of a given distribution system in a given timeframe. For this problem, the search space is created beforehand by running a multiobjective optimisation algorithm for the optimal design of distribution networks for different load levels related to different years. The sets of Pareto-optimal solutions obtained for each load level at each year are equivalent in terms of the considered objectives, the…

Synthetic Inertia Impact on Inter-Area Oscillations of the Continental Europe Power System

The overall kinetic energy reduction due to increasing share of converter-interfaced generation (CIG) has been investigated so far by several works for systems of different types and sizes. The so called synthetic inertia is one of the most common and reviewed solutions to the issue of system inertia reduction. The paper investigates the effects of synthetic inertia as frequency service provided by the CIG sources for the Continental Europe (CE) synchronous area using a detailed large scale dynamic model. The model - provided in the basic form by the System Protection & Dynamics (SP&D) group of the ENTSOE - is properly developed substituting a determined amount of synchronous machin…

The BAC factor method: Application to a real Italian not-residential building

The paper focuses the evaluation of the impact of Building Automation Control (BAC) systems on not-residential buildings. In particular, this work shows how the control, monitoring and automation actions considered by the European Standard EN 15232 can influence the electric and thermal energy consumptions of the University of Palermo DEIM (Department of Energy, Information Engineering and Mathematical Models) building. After evaluating the building energy consumptions, by using the CEI Guide 205-18, the BAC systems are chosen and sized and an economic evaluation of their installation cost is also carried out.

The Energy Market Impact of Climate Change on Electricity Generation in Europe

In this paper, the policy trend in Europe towards the emission reduction target in the energy sector, as planned from the Paris Agreement, is analyzed. Although renewable energy sources are improving their share, the large use of coal as primary fuel and the uncertainty about nuclear production makes the transition hard. It's well known that future emission patterns from energy generation influence the climate change trend, but as shown in the following, there is also a reverse interrelation, due to the different environmental conditions caused by climate change affecting all generation technologies. Furthermore, energy prices, which derive from this changed framework likewise will influenc…

A Single-Point Strategy for the Harmonic Sources Detection in Power Systems.

Load modelling influence on voltage stability assessment in distribution systems. Part I: Stability index and critical power for a single-line system

The single-line equivalent model is commonly used for voltage stability studies in both distribution and transmission systems. Referring to a single-line system, in the companion paper [1] the authors presented the theoretical aspects of voltage stability related to the load characteristics. In particular, expressions of the stability index for constant power, constant impedance and constant current loads, singularly and in all the possible combinations have been obtained. This index indicates how far the load node is from its voltage collapse point, allowing the maximum load power beyond which voltage collapse takes place to be evaluated. In this paper a simple method to evaluate the param…

Ancillary Services in the Energy Blockchain for Microgrids

The energy blockchain is a distributed Internet protocol for energy transactions between nodes of a power system. Recent applications of the energy blockchain in microgrids only consider the energy transactions between peers without considering the technical issues that can arise, especially when the system is islanded. One contribution of the paper is, thus, to depict a comprehensive framework of the technical and economic management of microgrids in the blockchain era, considering, for the first time, the provision of ancillary services and, in particular, of the voltage regulation service. When more PV nodes are operating in the grid, large reactive power flows may appear in the branches…

Methodologies for the Exploitation of Existing Energy Corridors. GIS Analysis and DTR Applications

The exploitation of power lines currently in operation has now become a common practice among electric system operators. The construction of new power lines requires taking economic, political and social problems into consideration. This paper considers two methodologies adopted by the Italian Transmission System Operator (TSO), Terna S.p.A.: Dynamic Thermal Rating (DTR) and Laser Imaging Detection and Ranging-Geographic Information System (L-GIS). DTR systems dynamically calculate the real transport capacity of a power line. The L-GIS system allows, after the geo-referencing of the power line, the management of any interference between the line and the nearby obstacles, permitting the opti…

Improving angle stability by switching shunt reactors in mixed overhead cable lines. An Italian 400 kV case study

Stringent environmental constraints make the construction of new transmission overhead lines more and more difficult. Alternatively, today it is possible to use cable lines for high (HV) and extra-high (EHV) voltage systems. The configuration of the so-called mixed lines can create some problems in the operation of the electrical system, both during steady-state and transient conditions. In particular, the system stability is one of the main concerns when analyzing the dynamic response of power systems. In this paper, the study of angular stability of a system containing a mixed line is presented: a specific control logic applied to the shunt reactors of the mixed line is proposed as improv…

Optimal Set Points Regulation of Distributed Generation Units in Micro-grids under Islanded Operation

The present work studies the problem of optimizing the power production levels of dispersed generation units in islanded microgrids. The problem is intrinsically multi-objective with non linear objectives and constraints, thus the solution approach is based on evolutionary optimization and uses the Non dominated Sorting Genetic Algorithm II. The objectives are calculated based on the solution of the load flow problem. The latter problem is more complicated when in the considered system a physical node with a sufficiently large production capability is not available, because all the generation node of the systems have similar and limited generation capability. In this paper, the issue has be…

A new formulation of the optimal compensation and reconfiguration problem including minimum load nodes unavailability for automated distribution networks

This paper deals with a new formulation of the optimal operation of electrical distribution networks problem in regular working state. In the new deregulated energy market providing reliable and economical service to customers is a primary task. The multiobjective formulation of the reconfiguration and compensation problem used in this paper considers as a primary object also the minimisation of the load nodes unavailability (UA) expressed in probabilistic terms. Therefore, the objectives to be attained through the optimisation strategy are: minimal power losses operation, minimum UA of the load nodes, load balancing among the HV/MV transformers, and voltage profile regularisation. The appl…

Performances of the Fault Decoupling Device when unbalanced and multiple faults occur on distribution systems.

Nowadays industrial processes are largely based on electronic devices such as programmable logic controllers and adjustable speed drives. Consequently, industrial equipments became less tolerant towards power supply disturbances. Voltage dips due to faults are surely among the worst disturbances for industrial equipments. A paper machine can be affected by disturbances of only 10% voltage drop lasting for 100 ms. A voltage dip of 75% (of the nominal voltage) with a duration shorter than 100 ms results in material loss in the range of thousands of US Dollars for semiconductors industry [1].

A comparison of two innovative customer power devices for Smart Micro-Grids

The paper presents a comparison of two prototypes of innovative Customer Power Devices designed for applications in Smart Micro-Grids. The devices are both equipped with Energy Storage Systems, consisting in Lithium batteries and have been assembled, independently, by the DIAEE of the University of Rome 'La Sapienza' and the DEIM of the University of Palermo in collaboration with the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In the paper, the characteristics and the operating modes of the devices are examined and some consideration on their application in Low Voltage Smart Micro-Grids are provided. © 2015 IEEE.

A New Crowded Comparison Operator in Constrained Multiobjective Optimization for Capacitors Sizing and Siting in Electrical Distribution Systems

This paper presents a new Crowded Comparison Operator (CCO) for NSGA-II to solve the Multiobjective and constrained problem of optimal capacitors placement in electrical distribution systems.

Strategie e scenari di aggregazione delle risorse distribuite nel mercato elettrico

L’articolo espone una modalità per ampliare la base di partecipazione di soggetti connessi alla rete elettrica (aggregatori di carico, sistemi di accumulo distribuiti, ecc.) ai mercati dei servizi già regolamentati, sfruttando opportune azioni di controllo di tipo Demand Response.

A model for reactive power tracing by addition of fictitious nodal injections

Abstract This paper proposes an efficient solution to the problem of reactive power flow tracing in electrical transmission networks. For such systems, the tracing techniques used for active power flows cannot be used straightforwardly, due to reactive power variations induced by the line reactances, these variations often being comparable to the powers delivered to the loads. In other words, as is well known, in transmission systems the reactive flows are strongly influenced by the inductive and capacitive effects of the network, making the tracing of power flow and allocation of losses more critical. In this paper, after discussing some methodological aspects, an approach based on the use…

Experimental validation of the BAC factor method for lighting systems

In the last few years, many buildings have been equipped with Building Automation and Control (BAC) systems. BAC systems can be used to achieve a significant reduction of the electrical consumption and to have all the well acknowledged benefits from the daylight (e.g. occupant comfort, health, well-being and productivity). For this reason, Standard EN 15232 "Energy performance of buildings — Impact of Building Automation, Controls and Building Management" puts into evidence the importance of the presence of BAC and Technical Building Management (TBM) systems, suggests a classification of these systems, explains their main functionalities and presents a simplified method to estimate their im…

Some improvements in solving radial distributions networks through the backward/forward method

In the electrical radial distribution networks analysis, the backward/forward method shows good features in terms of robustness, independence from load nature, small use of hardware resources and limited calculation time. In the present paper, some procedures to improve the b/f method with the aim of reducing the calculation time are presented. The adopted procedures regard the choice of the initial values of the nodes voltages and the way in which the convergence criterion is applied. The results of some tests carried out on some electrical test systems here reported have shown the efficiency of the proposed methodology in terms of calculation time reduction, especially when solving heavil…

On the roadmap to supergrid in Sicily: LiDAR technology and HTLS conductors for uprating the 150 kV lines

Difficulties in building new power lines in Italy because of authorization problems, and the production of electricity from renewable sources growing more and more, induces Terna S.p.A. (Italian TSO) to take advantage of existing overhead transmission lines. In order to increase the transmission capacity, Terna has used a software in GIS (Geographic Information System) environment which allows for the management of the interferences according to all the legislative bonds by referring to the LIDAR (Laser Imaging Detection and Ranging) remote sensing technology. This paper, after a description of the GIS and the LiDAR technology, shows how the calculation of the current capacity of some High …

ANALYSIS OF IMPACTS ON ELECTRIC POWER SYSTEM OPERATION OF LOAD MANAGEMENT IN RESIDENTIAL AND TERTIARY BUILDINGS

Load management includes all the techniques, logics, actions and programs through which the electric utilities and the customers are able to manage loads absorption in a more prudent and efficient way; it determines economic benefits for the users, but also allows a network management and operation simpler and cheaper, determining technical and economic benefits. The present paper constitutes a detailed study of interventions and techniques to control demand in the residential and tertiary sectors and the effects that these actions have on the entire electrical system and its management. It discusses the implications of such control actions in terms of reduction of network losses and relate…

Economic impact of medium-scale battery storage systems in presence of flexible electricity tariffs for end-user applications

This article addresses the question if it is cost-effective to use medium-scale battery storage systems for time-of-use (TMO) energy cost applications at a consumer level, assuming flexible electricity tariffs in the Italian electricity market. TMO application allows customers to reduce their electricity bill charging the storage when off-peak time periods are applied and discharge it during on-peak periods, when electricity energy prices are high. The analysis is carried out taking into account three different electrochemical storage technologies. The economical comparison shows that, at the current costs of storage technologies and at the electricity tariffs currently offered in Italy, th…

A New Device for the Control and the Connection to the Grid of Combined RES-based Generators and Electric Storage Systems

In this paper a new device for the control and the connection to the supply utility grid of combined RES-based generators and electric storage systems is presented. The device is a bidirectional converter that can be controlled so as to facilitate the interface between the low voltage grid and photovoltaic or wind generators combined with batteries, contemporary addressing the requirements of the reference technical standards for users connection and providing different ancillary services. In the paper the functioning of the device and its circuit diagram are described, the single parts are shown and the potentiality of its control system are commented. © 2013 IEEE.

Smart renewable generation for an islanded system. Technical and economic issues of future scenarios

The subject addressed in this paper is the analytical study of the transition of an energy generation system for a real MV/LV distribution system from one that is “fuel-based” to a distributed and smart “renewables-based” system. The paper outlines both the technical and the economic issues related to such a transition from one type of system to the other. The study is carried out for a real islanded network located in the Island of Pantelleria (Mediterranean Sea). The results obtained are presented and discussed, putting into evidence the technical, environmental and economic benefits of using smart technologies and renewable energy sources.

Transient stability assessment of SMIB System with Mixed overhead-cable line – Sensitivity analysis

Steady-state security analysis on the transmission grid for various scenarios of wind generation in Sicily

The proposed paper is part of a research aimed at assessing the impact of wind generation on the transmission grid of Sicily, second among the Italian regions for wind power installed. After describing the current state of wind energy generation in Sicily, the paper reports and comments the results of the steady-state security analysis done for various scenarios of wind penetration. For each scenario (maximum and minimum load conditions), the redistribution of power flows on the transmission network, the voltage profiles at nodes, the analysis of contingencies and losses variations are reported.

Sicilia-Malta: il nuovo collegamento RTN a 220 kV in corrente alternata

Descrizione dettagliata degli aspetti tecnologici e delle prestazioni funzionali di maggiore rilevanza sui cavi utilizzati, sui sistemi e sulle logiche di protezione contro i guasti. Vantaggi, potenzialità e criticità legate all’esercizio.

Multi-objective strategies for management and design of distributed electric storage systems in a Mediterranean island

The paper proposes an analytical study about the design and operation of distributed Electrical Storage Systems(ESS) in an active distribution network supplying a Mediterranean island, according to different criteria. The approach is based on the application of a multi-objective optimization algorithm (NSGA-II) that outputs a set of optimized schedules of the ESS in different configurations when operated according to different criteria (minimum energy losses in the grid, total generation cost, greenhouse gas emissions, limiting the fluctuations of the generation from fossil fuel plants). Moreover the variability of the voltage profile has been investigated also by a comparison with a refere…

An Efficient Procedure for Solving Radial Distribution Networks through the Backward/Forward Method

In the paper, after having presented the general backward/forward methodology for radial systems analysis, a new b/f procedure showing some interesting features that improve its performance in terms of convergence speed and calculation effort is presented. The features that fundamentally are responsible for such improvements concern the main steps of the b/f procedure. The starting voltage profile solution is different from the flat profile and is suitably modified. In the backward phase and starting from the second iteration, the branch currents variations due to the loads changes are evaluated; the latter variations are calculated on the basis of the difference of nodal voltages at the be…

HTLS Conductors: A Way to Optimize RES Generation and to Improve the Competitiveness of the Electrical Market—A Case Study in Sicily

Stringent environmental constraints make more difficult to identify new energy corridors and build new power lines. The increase in the generation of electricity from renewable energy sources (RESs) makes the operation of electrical systems increasingly difficult in some areas. The transmission system operators (TSOs), in Italy Terna, are forced to exploit the existing overhead transmission lines, increasing the possibility of dispatching energy, in particular RES, optimizing the transmission capacity. Therefore, after a brief presentation of the Sicilian electricity system and a brief description of high-temperature low-sag (HTLS) conductors, a case study is presented. It is shown how it i…

A Simulation Analysis for Assessing the Reliability of AC/DC Hybrid Microgrids - Part I: Underground Station and Car Parking

This paper reports the results of a simulation study with the aim of evaluating the capability of two portions of a hybrid AC/DC MV/LV network of maintaining their operation in off-grid mode during the loss of the main AC grid due to a failure. In particular, the study aims to verify, in the case of islanded operation of the two microgrids, the continuity of the electricity service by exploiting the local generation plants, Energy Storage Systems (ESSs), and other flexible resources managed by suitable algorithms in different energy scenarios. The analysis was carried out considering two microgrids: an underground station and a car parking with Electric Vehicles (EVs). For assessing the per…

Dispositivi risonanti per migliorare la qualità del servizio nelle reti di distribuzione passive e attive

An algorithm for simulating end-user behaviour in a real time pricing market

The energy market has changed radically over the last decade, mainly due to an increased penetration of renewable energies. Now the end users have directly access to the energy market and can actively take part to the electricity market. Electricity customers can indeed modify their behavior through Demand Response, namely by means of pricing strategies that support a change in the end-users habits. This can be accomplished through a 'loads aggregator', a third party that collects the requests and signals for Active Demand-based services coming from the markets and the different actors of energy market. This paper describes a simulation framework to generate the simulated optimal behavior o…

Transition of a distribution system towards an active network. Part II: Economical analysis of selected scenario

This paper outlines the economical issues related to the transition of the energy generation for a real MV/LV distribution system from a ‘fuel based’ one to a distributed and smart ‘renewables based’ one. It is the prosecution of a companion paper, which addressed the technical issues connected to such transition. The study has been carried out by University of Palermo and ENEA (Italy), on a portion of real MV/LV distribution system of the research center ENEA of Casaccia (Rome, Italy). The analysis is carried out for a specific scenario chosen among those proposed in the companion paper.

Modeling Energy Demand Aggregators for Residential Consumers

International audience; Energy demand aggregators are new actors in the energy scenario: they gather a group of energy consumers and implement a demand- response paradigm. When the energy provider needs to reduce the current energy demand on the grid, it can pay the energy demand aggregator to reduce the load by turning off some of its consumers loads or postponing their activation. Currently this operation involves only greedy energy consumers like industrial plants. In this paper we want to study the potential of aggregating a large number of small energy consumers like home users as it may happen in smart grids. In particular we want to address the feasibility of such approach by conside…

Influence of losses partition criteria on power flow tracing

The paper proposes a methodology for tracing active power flow which also considers power losses partition. It requires the partition of the active power losses in each line over different flow components. Then, the differences arising from the selection of different criteria for the allocation of the mutual terms (deriving from the non-linearity of losses) are investigated. Power flows tracing and losses allocation at each generator (or load) must be carried out simultaneously; therefore, a suitable order is required for the analysis of nodes and lines in a network. A procedure for the direct evaluation of all the components of the power flows and of the losses in the lines assigned to the…

DEMAND Project: An algorithm for the assessment of the prosumers’ flexibility

Demand side aggregation represents an important opportunity for ancillary services provision due to the potential that the coordinated management of distributed resources has on affecting power systems' operation. In this framework, the Aggregator has a main role and takes on different relationships with the other actors of the power system, usually becoming a mediator between the prosumers and the distribution system operator. The DEMAND project introduces a new point of view in demand side aggregation by proposing a new framework where the Aggregator is no more needed and prosumers can share and combine their flexibility in a new aggregation platform called Virtual Aggregation Environment…

Dynamic Control of Static Converters for the Transition from Grid-on to Grid-off Operation of AC/DC Microgrids

In this paper, specific control logics defined for generators, controllable loads and electric energy storage systems are illustrated in order to improve the reliability of AC/DC hybrid microgrids in their grid-off operation following failure events such as short-circuits, line breaks, sudden disconnections of generating units or loads, etc. After defining specific control schemes, these were modelled in a digital environment and finally tested with dynamic simulations. Finally, the paper highlights the role of virtual synchronous machine control for the self-healing capacity of islanded hybrid microgrids.

DEMAND Project: A Peak Load Shaving Strategy for End-User Consumers

Battery energy storage systems (BESS) are becoming increasingly widespread in modern power systems, thanks to the important benefits they can provide to the electricity grid. Indeed, BESS can be used in time shifting applications, storing energy during off-peak periods and discharging during peak times (when the cost of electricity is high). When BESS are used for peak shaving purposes, they also contribute to relieve peak demand charges, thus ensuring a saving for the consumers. This paper describes a peak load shaving strategy defined within the DEMAND project. The strategy is able to guarantee the flattest daily power diagram and the maximum benefit for the electricity consumers, reducin…

Angle Stability Improvement by Switching Shunt Reactors in Mixed Overhead-Cable Lines

A new backward/forward method for solving radial distribution networks with PV nodes

Abstract In this paper, a new backward/forward (b/f) methodology for the analysis of distribution systems with constant power loads is presented. In the proposed method, at each iteration, the loads are considered as constant impedances; in the backward sweep all the network variables (bus voltages and branch currents) are evaluated considering a scaling factor which is determined at the end of the backward phase. Indeed the forward sweep is eliminated and the node voltages calculation does not demand the sequentiality needed in the b/f methodology. The developed method, although deriving conceptually from the b/f methodology, presents only the backward phase in which all the network variab…

Maximizing energy transfer and RES integration using dynamic thermal rating. Italian TSO experience

The production of electricity from wind and other renewable sources is rapidly increasing all over the world, causing significant changes in the management of electrical systems. The current structural asset is not adequate to manage this growing generation of energy. The hypothesis of construction of new power lines would mean taking into consideration economic, political and social problems. The following paper reports the experience gained by the Italian TSO, Terna S.p.A, on the use of the DTR (Dynamic Thermal Rating), which is able to dynamically calculate the real transport capacity of an overhead power line. The results obtained are en- couraging as they show how it is possible to inc…

A bottom-up approach for the evaluation of the flexible quota of aggregated loads

The paper presents a bottom-up approach for building the aggregated load profile of numerous passive/active users connected to the low voltage electrical system. The approach is based on the Monte Carlo method and on the knowledge of the single electric and thermal loads, generators and thermal and geometrical characteristics of the building of the single end-user. The method proposed is able to differentiate the quota of flexible and not flexible aggregate load.

Multiobjective ant colony search algorithm optimal electrical distribution system planning

A dynamic multiobjective, MO, algorithm based on the ant colony search, the multiobjective ant colony search algorithm, MOACS, is presented. The application domain is that of dynamic planning for electrical distribution systems. A time horizon of H years has been considered during which the distribution system are modified according to the new internal (loads) and external (market, reliability, power quality) requirements. In this scenario, the objectives the Authors consider most important for utilities in strategical planning are: the quality requirement connected to the decrease of the expected number of interruptions per year and customer, in the considered time frame, and the choice fo…

An overview of a novel LC resonant device able to improve Power Quality in active and passive distribution networks

Nowadays power distribution systems are under a rapid evolution. The widespread penetration of distributed generation is bringing about new operating conflicts, which are adding to traditional power quality issues. The paper aims to analyse the performance of a new LC device able to improve power quality in electrical distribution systems, even in presence of distributed generation units. The different possible applications of the device are shown and the performances are proved by means of computer simulation. The first experimental results are also presented.

Optimal Electrical Distribution Systems Reinforcement Planning Using Gas Micro Turbines by Dynamic Ant Colony Search Algorithm

Distribution systems management is becoming an increasingly complicated issue due to the introduction of new energy trading strategies and new technologies. In this paper, an optimal reinforcement strategy to provide reliable and economic service to customers in a given time frame is investigated. In the new deregulated energy market and considering the incentives coming from the political and economical fields, it is reasonable to consider distributed generation (DG) as a viable option for systems reinforcement. In the paper, the DG technology is considered as a possible solution for distribution systems capacity problems, along several years. Therefore, compound solutions comprising the i…

Energy Management via Connected Household Appliances

The study reported hereafter provides results based on a campaign of simulations conducted by University of Palermo on the basis of its knowledge in the field Energy Value Chain and in the field of Energy Management (EM) for household appliances. Inputs from CECED Convergence WG has been fundamental to base that study on realistic data and cases. Moreover, the so called EM study, offers also a clear picture about the opportunity to have energy management applications and services in house, being those opportunities strictly related to the cost of in- frastructure needed and to the benefits belonging to different actors in the energy value chain. Energy savings have been considered both in t…

Attenuation of low frequency magnetic fields produced by HV underground power cables

High-voltage underground cable systems are becoming more common as the demand for electrical power within urban centers increase, also considering the difficulties in building new overhead power lines in the vicinity of city centers because of authorization issues. Therefore, interest towards the evaluation of magnetic fields produced by high-voltage power lines has been triggered during the last decade and concern about effects on human health of exposure to extra low frequency (ELF) magnetic fields due to power lines has been increasing as well. Hence, the evaluation of the magnetic field produced by underground power cables is important in order to develop methods for mitigating their in…

Innovative algorithms for the management of combined RES-BESS systems

The issue of the optimal management of the available energy resources also at end-user level is getting more and more attention. The paper deals with the definition of innovative algorithms for managing electrical storage systems in hybrid photovoltaic and wind plants, also taking into account different pricing periods and a grid emergency condition in which the Utility can request an injection of power by the end-user. Application examples for explaining the operation of the algorithms are presented.

Analysis of the new submarine interconnection system between Italy and Malta: Simulation of transmission network operation

In this paper, some simulations of the interconnected Sicilian and Maltese transmission systems are performed, in order to assess this new system configuration. The HVAC submarine interconnection between Italy and Malta came into operation in 2015 and is part of a European programme for transmission grid interconnection improvement. This new line has been built in order to allow a better management of the power system of both the islands. Firstly, a brief description of the interconnection system is given. Moreover, the transmission systems of Sicily and Malta are depicted and their structures are shown. The simulations are carried out by means of a model of the interconnected system create…

An Energy Blockchain, a Use Case on Tendermint

The recent advances in distributed energy systems require new models for exchanging energy among prosumers in microgrids. The blockchain technology promises to solve the digital issues related to distributed systems without a trusted authority and to allow quick and secure energy transactions, which are verified and cryptographically protected. Transactions are approved and subsequently recorded on all the machines participating in the blockchain. This work demonstrates how users, which are nodes of the energy and digital networks, exchange energy supported by a customized blockchain based on Tendermint. We focus on the procedures for generating blocks and defining data structures for stori…

Considering power quality in expansion planning of distribution systems. IEEE PES General Meeting 2004, June 6-10, Denver, Colorado USA.

On the Impact of Heat Pumps Electric Load on the Power Consumption of Lampedusa

The present paper reports the results of a simulation study regarding the impact of the adoption of heat pumps for domestic hot water production in the island of Lampedusa (Italy). In the study, it has been assumed to replace electric storage water heaters with heat pumps at every dwelling of the about four thousand domestic end-users of the island and, in addition, to control the heat pump operation in order to enhance some parameters that characterize the quality of the generation and distribution system of the island (power peak, energy losses and voltage drop). According to the results of the simulations, while the replacement of electric storage water heaters with heat pumps is able to…

On the effects of BAC systems and load control programs on the utility grid

The electricity demand increasing for the comfort improvement in residential buildings is nowadays stressing the MV and LV networks in urban areas. In this framework, the Distribution System Operators (DSO) are exposed to the risk of reliability decrease and there is, earlier than expected, the issue of new and substantial investments for enhancing the network infrastructure. Nevertheless, DSOs have a very strong inclination to defer investment in new facilities in favour of more "flexible measures" for improving the life of the existing components. Solutions of this type are primarily based on demand management, i.e. activities aimed at encouraging the end-users to a different/smart electr…

Multiobjective Ant Colony Search Algorithm for optimal electrical distribution system strategical planning

A load model for EV parking lots

In the next years, electric mobility will be one of the issues electric utilities will have to face. The detailed modeling of the electric load generated by the presence of Electric Vehicles, EV, parking lots will be essential to simulate the different working conditions of new distribution systems. Also the detailed modeling will allow to deduce technical and economical aspects, allowing Distribution Systems Operators to devise the right incentives for EV customers. Such as, or maybe more than, residential loading the EV loading is strongly variable because it is connected to the human behavior, the modeling thus has to include stochastic terms. Moreover, to get realistic load profile for …

A comparative analysis of different methods of reactive power pricing

Load Flow Solution of radial distribution networks with ZI loads

In this paper, a methodology to solve radial distribution networks, with constant current and/or impedance loads, is proposed. The techniques currently available to solve such systems are based either on iterative methods or on the bus impedance matrix. The method developed is the extension of a technique that is valid to solve networks made of impedances with one supply point. The methodology can be applied to directly and rapidly solve large distribution systems in which the loads are modeled as constant current/impedance. It is also able to solve meshed systems having voltage-dependent loads, inside an iterative backward/forward method.

FROM FUEL BASED GENERATION TO SMART RENEWABLE GENERATION: PRELIMINARY DESIGN FOR AN ISLANDED SYSTEM. PART II: SELECTION OF FUTURE SCENARIO AND ECONOMICAL ISSUES

The subject addressed in this paper is the analytical study of the transition of the energy generation system for a real MV/LV distribution system from a ‘fuel based’ one to a distributed and smart ‘renewables based’ one. The paper outlines the economical issues related to such transition from one type of system to the other and it is the prosecution of a companion work addressing the technical topics concerning this subject. The study is carried out for a real islanded MV/LV distribution network.

Inertial response of isolated power networks with wind power plants

The constant increase of power generation provided by renewable energy source (RES) power plants is causing a progressive reduction of the overall inertia of the power systems. Especially in the case of small, isolated power networks, the replacement of conventional generation plants with RES power plants can affect significantly the frequency response of the system. The critical low-inertia conditions can be improved by the introduction of specific additional controls to the RES power converters. These control schemes are known as “synthetic inertia” or “virtual inertia” controls. The paper analyzes the impact of a derivative-based inertial control on a small, isolated power system, with a…

Analysis and simulations of the primary frequency control during a system split in continental europe power system

The occurrence of system separations in the power system of Continental Europe has been observed in recent decades as a critical event which might cause power imbalances higher than the reference incident specified per system design, representing an actual challenge for the stability and safe operation of the system. This work presents an analysis and simulations of the primary frequency control in the Continental Europe synchronous area in conditions of system separation. The adopted approach is based on fundamental aspects of the frequency-containment reserve process. The analysis takes an actual event into consideration, which determined the separation of the system in January 2021. The …

A New Platform for Automatic Bottom-Up Electric Load Aggregation

In this paper, a new virtual framework for load aggregation in the context of the liberalized energy market is proposed. Since aggregation is managed automatically through a dedicated platform, the purchase of energy can be carried out without intermediation as it happens in peer-to-peer energy transaction models. Differently from what was done before, in this new framework, individual customers can join a load aggregation program through the proposed aggregation platform. Through the platform, their features are evaluated and they are clustered according to their reliability and to the width of range of regulation allowed. The simulations show the deployment of an effective clustering and …

An Innovative Conversion Device to the Grid Interface of Combined RES-Based Generators and Electric Storage Systems

This paper is focused on the development of an innovative device, which is based on a bidirectional converter, for the interface to the supply utility grid of combined renewable-energy-source-based generators and electric storage systems. The device can be controlled so as to ease the interface between the low-voltage grid and photovoltaic or wind generators combined with lithium-ion $\hbox{LiFePO}_{4} $ batteries, taking into account the requirements of the reference technical standards for users connection and offering different ancillary services. The operational functioning of the device, the architecture, and its electronic components, as well as laboratory and field test activities an…

Backward solution of PV nodes in radial distribution networks

In this paper an iterative backward methodology to solve radial distribution networks with fixed voltage (PV) nodes and with constant power loads or mixed loads (with at least one component with constant power) is proposed. The method developed, although deriving conceptually from the backward/forward (b/f) methodology, presents only the backward phase in which all the network variables are evaluated. In themethods developed up until nowfor the solution of such systems, PV nodes are taken into account at the end of each iteration by evaluating, based on the known quantities of the network, the unknowns associated with PV nodes. In the methodology developed here the unknowns relevant to PV n…

2015–2020. Sicily and Italy as electricity hub in the mediterranean area for the development of the European power grids interconnections

Falling demand and explosion of Renewable Energy Sources (RES) are redesigning the criteria for planning the power grids interconnections by ENTSO-E. In particular, the interconnections between networks of different countries have been acquiring importance more and more, in view of an unique European market for electricity and an increase of RES. Italy and Sicily, placed in the centre of the Mediterranean Sea, play a fundamental role as a bridge between Central Europe, North Africa area and Mediterranean islands (electricity hub). This paper aims to show how power system exchanges tend to follow the direction from South to North, and how the impact of North-African power — mainly generated …

Constrained Robust MultiObjective Optimization for Reactive Design in Distribution Systems

This paper presents a new formulation including robustness of solution of constrained multiobjective design or reactive power compensation. The algorithm used for optimization is the NSGA-II (Non dominated Sorting Genetic Algorithm II) with a special crowded comparison operator for constraints handling. The need for including the issue of robustness of solutions derives from the simple observation that loads are uncertain in distribution systems and their estimation is often affected by errors. In design problems it is desirable to consider the loads with a certain range of variation. In this paper the NSGA-II algorithm is applied to efficiently solve the issue and the solutions attained co…

Investigating the effect of distributed generators on traditional protection in radial distribution systems

The recent changes in power network structure, development in green energy technologies and increased attention on environmental concerns have led to increase the installation of renewable energy based distributed generations (DG) in distribution networks. The increasing penetration of distributed generation in the distribution power system creates new technical and economical challenges; protection is one important topic of these challenges. High penetration of DG will have unfavorable impact on the traditional protection methods; the impact depends on the number, location and size of injected DG. To ensure safe and selective protection devices coordination, the impact of DG should be take…

Studio di fattibilità e progettazione preliminare di dimostratori di reti elettriche di distribuzione per la transizione verso reti attive. Report 1 – Caratterizzazione delle reti attuali e analisi di possibili scenari di sviluppo

New Energy Corridors in the Euro-Mediterranean Area: The Pivotal Role of Sicily

The present paper deals with the new opportunities deriving from the interconnections of the European and North African transmission systems. In order to achieve a single international market for electricity exchanges, interconnections between networks in different countries are becoming increasingly important and Sicily, for its geographical position in the middle of the Mediterranean Sea, will undoubtedly play an important role as an electrical bridge between Europe and the North Africa in the near future. The paper, presenting the actual electro-energetic context of Tunisia, reports the new important interconnection already realized in South Italy (in particular in Sicily) and describe t…

Mitigation of 50 Hz magnetic field produced by an overhead transmission line

Power transmission utilities are challenged by the need to expand transmission system capacity to meet growing energy demands. The impact of high voltage overhead transmission lines on the environment represents a hot topic in the context of transport and distribution of electrical energy. In particular, interest towards the effects of extra low frequency (ELF) magnetic fields generated by high-voltage power transmission lines has been increasing significantly during the last decade, giving rise to a number of policy initiatives and research activities. Therefore, the evaluation of the magnetic field generated by conductors of overhead lines is of primary importance in order to develop meth…

A Compensation Based Method to Model PV Nodes in Backward/Forward Distribution Network Analysis

PurposeThis paper proposes to identify a new model of the fixed voltage nodes (PV nodes) for medium voltage distribution systems analysis. The model is used within backward/forward (b/f) analysis method applied to solve radial and weakly meshed systems.Design/methodology/approachThe model is based on the compensation currents method for multi‐port systems which has been extensively used, within b/f analysis methods, to take into account the presence of meshes and PV nodes.FindingsTest results prove the approach to be more efficient and precise than previous methodologies and put into evidence the good performance of the proposed model in terms of speed and convergence properties.Research li…

Applications of the Fault Decoupling Device to Improve the Operation of LV Distribution Networks

The aim of this paper is to present the operating principle of a new resonant device, called the fault decoupling device (FDD), able to improve power quality in electrical distribution systems. In low-voltage networks, this device can be employed in order to mitigate voltage dips due to faults or large induction motor startup. Moreover, in the presence of distributed-generation (DG) units, the FDD allows one to obtain various benefits such as a reduction of the fault current in each node of the network and an increase in the voltage at the DG unit node. In order to show the performances of the FDD, analytical studies and computer simulations were carried out which took into account various …

Economic feasibility of a customer-side energy storage in the Italian electricity market

Electricity prices show significant short-term variations during the day due to the need of balancing supply and demand in real time. Normally, customers are not exposed to these variations but pay a constant electricity price. In an attempt to reduce the volatility of the wholesale prices, several utilities are moving from conventional fixed-rate pricing schemes to new market-based models, where the electricity price can fluctuate during the day depending on the market conditions. Examples of time-dependent pricing schemes are Time-Of-Use (TOU) tariffs, where the electricity price can take two or three price levels during the day, or Real-Time Pricing (RTP) tariffs, where the energy price …

Impact of building automation control systems and technical building management systems on the energy performance class of residential buildings: An Italian case study

Abstract The paper focuses on the evaluation of the impact on residential buildings of building automation control (BAC) and technical building management (TBM) systems. This work shows how the control, monitoring and automation functions considered by the European Standard EN 15232 can considerably influence the energy performance of a single-family test house and, consequently, its energy performance class. The study puts into evidence that the benefit that can be drawn from the installation of BAC and TBM systems depends on the type of technical appliances in the household and on the starting energy performance class. Finally, the economic impact due to the introduction of BACS or TBM fu…

FROM FUEL BASED GENERATION TO SMART RENEWABLE GENERATION: PRELIMINARY DESIGN FOR AN ISLANDED SYSTEM. PART I: TECHNICAL ISSUES AND FUTURE SCENARIOS

The subject addressed in this paper is the analytical study of the transition of the energy generation system for a real MV/LV distribution system from a ‘fuel based’ one to a distributed and smart ‘renewables based’ one. The paper outlines the technical issues related to such transition from one type of system to the other. The study is carried out for a real islanded MV/LV distribution network located in the Island of Pantelleria. The economical issues regarding the above transition are focused in a companion paper.

Maximizing energy transfer and RES integration using dynamic thermal rating

Abstract The production of electricity from wind and other renewable sources is rapidly increasing all over the world, causing significant changes in the management of electrical systems. The current structural asset is not adequate to manage this growing generation of energy. The hypothesis of construction of new power lines would mean taking into consideration economic, political and social problems. The following paper reports the experience gained by the Italian TSO, Terna S.p.A, on the use of the DTR (Dynamic Thermal Rating), which is able to dynamically calculate the real transport capacity of an overhead power line. The results obtained are encouraging as they show how it is possible…

Effect of voltage deviations on power distribution losses in presence of DG technology

Integration of distributed generation (DG) units in power distribution network has become increasingly attractive multi-faceted paradigm as economic and environmental factors drive new technologies to be more efficient and less polluting than their earlier counterparts. The installation of DGs impacts critically on the planning and operating characteristics of the distribution network. Type, location, number and capacity of DG are essential factors for studying the effect of DGs on the system behavior. In this paper the effect of DG on the power losses of a distribution network is investigated for different types of DG units. Also, the impact of DG on the voltage profile is demonstrated bef…

Experimentation of sustainable energy microsystems: The DE.DU.ENER.T. research project

The paper focuses on an energy sustainable prototype micro-system installed upon a roof of a building in Valderice (Italy). This micro-system has been conceived in the ENPI (European Neighborhood and Partnership Instrument) cross-border cooperation Italy - Tunisia 2007–2013 DE.DU.ENER.T. (Le DEveloppement DUrable dans la production ENERgetique dans le Territoire) research project framework. The main aim of this project is the construction of a sustainable energy micro-system prototype suitable for the optimal integration and management of renewable energy resources (photovoltaic, wind and solar thermal) and to reduce the building's energy consumption. In the paper the project and the protot…

ICT applications for improving the generation and distribution efficiency of a small mediterranean island

The paper presents a study on the opportunities offered by ICT for improving the efficiency of the generation and distribution system of a small island. The island taken into consideration is the Italian Lampedusa island. In the paper, the power distribution system of the island is described and the summer and winter daily load profiles are examined in order to define the more suitable control actions for improving the generation and distribution efficiency of the power system. Finally the architecture of an idoneous control system for the smart grid is proposed and an evaluation of the purchase and installation costs of components and devices for the transition of a traditional house towar…

Analysis of some renewable energy uses and demand side measures for hotels on small Mediterranean islands: A case study

Abstract Tourist activity strongly influences the energy consumption and the overall load profile of communities with isolated energy systems. One example is hotel sectors on small islands that are not connected to mainland energy distribution grids. The use of solar energy systems could be a smart option for reducing energy consumption and tackling seasonal fluctuation. The operation of a weak and isolated electric grid requires attention to the management of power profiles in very short time frames. Energy storage (thermal or electric), as well as building automation control technologies, can be utilised for these aims. In this context, the present paper illustrates a study conducted at a…

Smart multi-carrier energy system: Optimised energy management and investment analysis

This paper proposes an optimised Energy Management System for a multi-carrier hub, which integrates two energy distribution networks, for hydrogen and electricity. The economic sustainability of a real-life instantiation of such a system has been analysed as well. The Energy Management System has been developed by means of a multi-objective optimisation algorithm, the Non-dominated Sorting Genetic Algorithm II, implemented using MATLAB®. The achieved results consist in a series of set-points defining the working conditions of the plant for a chosen time horizon. Data provided by this process also show the effectiveness of the adopted optimisation approach. The financial analysis is performe…

A heuristic approach for optimal operation of grid connected source-battery-load systems

In the paper an optimal management procedure for a system composed of a renewable energy source, storage batteries and a load, permanently connected to a distribution network, is presented. The issue follows two objectives: a) maximum economic benefit for the system, and b) minimum energy exchange with the network. The operation cost of storage facilities, as well as the technical and economic constraints on power exchanges between the system and the network and the technical constraints about charging and discharging cycles of the batteries are considered. The effectiveness of the management procedure is numerically tested and the results are presented.

Building Automation and Control Systems and Electrical Distribution Grids: A Study on the Effects of Loads Control Logics on Power Losses and Peaks

Growing home comfort is causing increasing energy consumption in residential buildings and a consequent stress in urban medium and low voltage distribution networks. Therefore, distribution system operators are obliged to manage problems related to the reliability of the electricity system and, above all, they must consider investments for enhancing the electrical infrastructure. The purpose of this paper is to assess how the reduction of building electricity consumption and the modification of the building load profile, due to load automation, combined with suitable load control programs, can improve network reliability and distribution efficiency. This paper proposes an extensive study on…

Load modelling influence on voltage stability assessment in distribution systems. Part II: Extension to a complex radial system and applications

The single-line equivalent model is commonly used for voltage stability studies in both distribution and transmission systems. Referring to a single-line system, in the companion paper [1] the authors presented the theoretical aspects of voltage stability related to the load characteristics. In particular, expressions of the stability index for constant power, constant impedance and constant current loads, singularly and in all the possible combinations have been obtained. This index indicates how far the load node is from its voltage collapse point, allowing the maximum load power beyond which voltage collapse takes place to be evaluated. In this paper a simple method to evaluate the param…

Characterization of a small Mediterranean island end-users’ electricity consumption: The case of Lampedusa

Abstract The paper presents the results of a study carried out on Lampedusa Island (Italy) and based on the survey of electricity consumption data. The main outcomes of the study are: • the characterization of the energy demand of private houses and hotels in Italian small islands with significant touristic flows during the summer period; • the identification of inefficient use of the electric loads; • the construction of aggregated load profiles for clusters of homogeneous domestic end-user to be used for implementing Demand Response strategies. The study shows how electricity consumption in Mediterranean small islands are very high with respect to the national average and lays the basis f…

An original control strategy of storage systems for the frequency stability of autonomous grids with renewable power generation

This work examines the operation of the autonomous power system of a geographical island assuming the integration of significant generation shares from renewable energy sources and the installation of the required storage systems. The frequency stability of the system is investigated considering different operating conditions, in terms of load demand and renewable power generation. The main focus of the work is an original control strategy specifically designed for power converters interfacing storage units to the grid. The proposed strategy is based on an extended frequency droop control, which selects specific droop settings depending on the operating mode—charge or discharge—of the stora…

GIS systems and LIDAR technology for the operation of HV lines. Sicilian transmission network applications

The difficulties to build new power lines within the national territory cause of authorization problems, and the evermore growing production of electricity from renewable sources, induces Terna S.p.A. (Italian TSO) to take advantage of existing overhead transmission lines. Therefore, in order to increase the transmission capacity, and to optimize the maintenance and management of power lines, for some years Terna has been using a software in GIS environment (Geographic Information System) that referring to the LIDAR (Laser Imaging Detection and Ranging) remote sensing technology, allows to manage the interferences according to all the requirements and legislative bonds and to fulfill the im…

The Blockchain in Microgrids for Transacting Energy and Attributing Losses

In recent years novel models for energy distribu- tion appeared and islanded microgrids quest for new ways to exchange energy between consumers and producers without the need of central authorities. The blockchain mechanism has emerged as a distributed solution for recording energy transactions in power systems. The blockchain has been used to permit users bartering and selling energy and to keep track of such exchanges without exposing them to tampering. In this work, we consider a novel application of the blockchain in islanded microgrids that includes also annotating energy losses caused by energy transactions, in order to have a more realistic matching between the physical status of the…

Decoupled solution of radial and weakly meshed distribution networks through a backward method

A methodology for the analysis of radial or weakly meshed distribution systems supplying voltage dependent loads is developed. The solution process is iterative and, at each step, the loads are simulated by means of impedances. The network is divided into two sub-networks which must be solved separately and sequentially; in the first, named RP-net, only the lines resistances and the loads shunt equivalent resistances are considered; in the second, named XQ-net, only the lines reactances and the shunt equivalent reactances are taken into account. After a brief presentation of the b/f method, which is currently the most commonly used technique to solve distribution networks, the proposed meth…

Verifying the effect of distributed generators on voltage profile, power losses and protection system in radial distribution networks

In the recent years the electrical power networks are undergoing rapid restructuring and developing process worldwide. Advancement in technologies and concern about the environmental impacts have led to increase interconnection of renewable energy based distributed generations (DGs) in distribution networks. The DGs have significant impacts on the distribution systems; these impacts may be either positively or negatively depending on the modified interconnected DG distribution network structure. It will be necessary to consider many issues concerning these impacts. In this paper, an investigation of DGs impacts on voltage profile, power losses, and protection system in radial distribution n…

Economic feasibility of stationary electrochemical storages for electric bill management applications: The Italian scenario

Battery energy storage systems (BESSs) are expected to become a fundamental element of the electricity infrastructure, thanks to their ability to decouple generation and demand over time. BESSs can also be used to store electricity during low-price hours, when the demand is low, and to meet the demand during peak hours, thus leading to savings for the consumer. This work focuses on the economic viability of BESS from the point of view of the electricity customer. The analysis refers to a lithium-ion (Li-ion), an advanced lead-acid, a zinc-based, a sodium-sulphur (NaS) and a flow battery. The total investment and replacement costs are estimated in order to calculate the cumulated cash flow, …

Multi-objective optimized management of electrical energy storage systems in an islanded network with renewable energy sources under different design scenarios

The subject addressed in this paper is the definition of some strategies for the design and the optimaized management of EES (Electrical Energy Storage) systems, for an existing islanded distribution network supplying the Island of Pantelleria (Italy) in the Mediterranean Sea. In the paper the authors have drawn interesting conclusions through the application of an efficient MO (multi-objective) optimization algorithm, the NSGA-II, minimizing the energy losses in the grid, the total electricity generation cost and the greenhouse gas emissions. The results obtained for different installation scenarios of the EES are presented and discussed, putting into evidence the technical, environmental …

Technical and economical assessment of distributed electrochemical storages for load shifting applications: An Italian case study

Time-of-use (TOU) energy cost management involves the use of energy storage systems (ESSs) by customers to reduce their electricity bills. The ESS is charged during off-peak time periods, when electricity energy prices are low, and discharged during times when on-peak energy prices are applied. This article addresses the question whether it is economically viable to install medium-scale distributed ESSs designed to lower the electricity cost for a customer-side application, assuming flexible electricity tariffs. The technical/economical evaluation is carried out referring to lithium-ion (Li-ion), sodium sulfur (NaS) and vanadium redox battery (VRB) technologies, performing a parametric anal…

A Simulation Analysis for Assessing the Reliability of AC/DC Hybrid Microgrids - Part II: Port Area and Residential Area

This paper reports the second part of a simulation study with the aim of evaluating the ability of two portions of a hybrid AC/DC MV/LV network in maintaining their operation in off-grid mode during the loss of the main AC grid due to a failure. In particular, this paper follows a dual purpose: first, it analysis two microgrids in a residential area and a port zone capability of operating in islanded mode, applying a probabilistic approach, while there is different energy use cases, and second is to evaluate some reliability indicators.

Impact of non-programmable renewable sources in Day-Ahead Market in Sicily. Reasons to make more flexible and smarter the national transmission grid.

This article describes technical and market aspects that characterize the Sicilian electrical system, the non-programmable renewable sources impacts on the energy markets (Day-Ahead Market and ancillary services market) and on Sicilian system operation, to evaluate the grid integration of renewable energy sources in a future Sicilian smart grid.

Le fonti rinnovabili in Sicilia: impatti sul mercato zonale e sulla gestione del sistema elettrico

L’articolo descrive gli aspetti tecnici e di mercato del sistema elettrico siciliano mettendo in evidenza le cause che hanno portato all’aumento del prezzo zonale nelle ore serali, gli effetti che le FRNP hanno sui mercati elettrici (MGP e MSD) e sulla gestione del sistema elettrico siciliano.

Impact of Demand Response Control Logic on Isolated Island's Distribution Networks

The work presents the results of a study regarding the impact of some Demand Response control logics on an isolated distribution network. The proposed control is divided into precise steps in which the coordination between the general aggregator controller and the single local Energy Management Systems is developed and illustrated with details. The control is applied to the flexible loads and to the storage systems of photovoltaic plants installed at the end-users' houses and connected to the network. The study is carried out delivering a suitable network model of the island's system, with the implementation of load profiles for all the loads of the network for a total simulation time of 24…

Large Scale Control of Deferrable Domestic Loads in Smart Grids

International audience; In this paper, we investigate a realistic and low-cost deployment of large scale direct control of inelastic home appliances whose energy demand cannot be shaped, but simply deferred. The idea is to exploit 1) some simple actuators to be placed on the electric plugs for connecting or disconnecting appliances with heterogeneous control interfaces, including non-smart appliances, and 2) the Internet connections of customers for transporting the activation requests from the actuators to a centralized controller. Our solution requires no interaction with home users: in particular, it does not require them to express their energy demand in advance. A queuing theory model …

A double-shell design approach for multiobjective optimal design of microgrids

This work develops a new double shell approach to optimal design for multi-objective optimally managed systems. The cost of each design solution can be defined by the evaluation of operational issues and capital costs. In most systems, the correct definition of operational issues can be deduced by means of the solution of a multi-objective optimization problem. The evaluation of each design solution must thus be deduced using the outcome of a multi-objective optimization run, namely a Pareto hyper-surface in the n-dimensional space of operational objectives. In the literature, the design problem is usually solved by considering a single objective formulation of the operational issue. In thi…

A Package for the Analysis of Automated MV Distribution Networks

A Bidirectional Converter for the Integration of LiFePO4 Batteries with RES-based Generators Part I: Revising and Finalizing Design

This paper presents a device for controlling and connecting combined Renewable Energy Sources (RES)-based generators and electric storage systems to the supply utility grid. The device is a bidirectional converter that can be controlled in order to facilitate the interface between the low voltage grid and small generators combined with lithium-ion LiFePO4 batteries, contemporary addressing the requirements of the reference technical standards for users connection and providing different ancillary services. The paper describes the revising and finalizing activities carried out by the DEIM of the University of Palermo and ENEA during 2013.

A Simple Operating Strategy of Small-Scale Battery Energy Storages for Energy Arbitrage under Dynamic Pricing Tariffs

Price arbitrage involves taking advantage of an electricity price difference, storing electricity during low-prices times, and selling it back to the grid during high-prices periods. This strategy can be exploited by customers in presence of dynamic pricing schemes, such as hourly electricity prices, where the customer electricity cost may vary at any hour of day, and power consumption can be managed in a more flexible and economical manner, taking advantage of the price differential. Instead of modifying their energy consumption, customers can install storage systems to reduce their electricity bill, shifting the energy consumption from on-peak to off-peak hours. This paper develops a deta…

A Methodology for Exploiting Smart Prosumers’ Flexibility in a Bottom-Up Aggregation Process

The electrical power system is evolving in a way that requires new measures for ensuring its secure and reliable operation. Demand-side aggregation represents one of the more interesting ways to provide ancillary services by the coordinated management of a multitude of different distributed resources. In this framework, aggregators play the main role in ensuring the effectiveness of the coordinated action of the distributed resources, usually becoming mediators in the relation between distribution system operators and smart prosumers. The research project DEMAND recently introduced a new concept in demand-side aggregation by proposing a scheme without a central aggregator where prosumers ca…

A distributed minimum losses optimal power flow for islanded microgrids

Abstract In this work, the minimum losses optimal power dispatch problem for islanded microgrids with distributed energy resources (DER) is solved by means of a distributed heuristic approach. Optimal power management is performed almost in real time, with a predefined schedule, i.e. every 5 min, and the solution is applied to generators when the current operating solution violates voltage or current constraints or when the current configuration produces too large power losses. The operating point of both inverter-interfaced generation units as well as rotating production systems can be modified simply using local information. The latter are voltage measurements and power injections or load…

Minimum Losses Reconfiguration of MV Distribution Networks through Local Control of Tie Switches

This paper deals with the problem of optimal reconfiguration of radial distribution networks for minimum loss operation. The proposed control strategy of the open-closed status of the tie-switches is distributed, since every MV/LV node is provided with local controllers having some measured entities as input. It also does not prevent the system from the future implementation of centralized control; instead it may represent the first step toward a complete automation of the distribution system. The proposed strategy is indeed organized in hierarchic levels, the highest of which may be in the future a central control. After introducing the general problem of networks reconfiguration, a review…

Crowded comparison operators for constraints handling in NSGA-II for optimal design of the compensation system in electrical distribution networks

This paper proposes an improvement of an efficient multiobjective optimization algorithm, Non-dominated Sorting Genetic Algorithm II, NSGA-II, that has been here applied to solve the problem of optimal capacitors placement in distribution systems. The studied improvement involves the Crowded Comparison Operator and modifies it in order to handle several constraints. The problem of optimal location and sizing of capacitor banks for losses reduction and voltage profile flattening in medium voltage (MV) automated distribution systems is a difficult combinatorial constrained optimization problem which is deeply studied in literature. In this paper, the efficiency of the proposed Crowded Compari…

Frequency dynamics of power systems with temporally distributed disturbances

Abstract The frequency dynamics and stability of power systems is essentially affected by nature and characteristics of the disturbances occurring in the system. Conventionally, frequency transients are examined assuming a single disturbance applied at a given time. However, actual incidents in the power systems can be generally composed of a temporal sequence of events, and thus characterized by multiple power imbalances of different magnitudes and time offsets. The consideration of the effects of the temporal distribution of power imbalances is important for two main reasons: the impact on the frequency dynamics of the system in terms of frequency metrics such as minimum instantaneous fre…

Contribution to solve the problem of attributing harmonic distorsion disturbance responsability

Multiobjective design of distributed reactive power production in a deregulated electric market

Abstract Reactive flows compensation optimal design for losses reduction in MV automated distribution systems is a problem deeply studied in literature. In this paper, the design problem is formulated considering the new deregulated energy market. These new operational conditions allow the MV grid operator to consider the generation of reactive energy also as a service that can be sold to the transmission system above. In this case, the transmission system would be helped in all the working conditions in which a strong modulation of the reactive flow through the HV/MV node is required. Then, for the MV grid operator, the compensation system optimal design problem is therefore that of the se…

Optimal pricing strategies in real-time electricity pricing environments: An Italian case study

The energy market has changed radically over the last decade, mainly due to an increased penetration of renewable energies. Now the end users have directly access to the energy market and can actively take part to the electricity market. Electricity customers can indeed modify their behavior through Demand Response (DR), namely by means of pricing strategies that support a change in the end-users habits. This can be accomplished through a 'loads aggregator', a third party that collects the requests and signals for Active Demand-based services coming from the markets and the different power system participants. This paper describes a new framework able to optimally select the real-time prici…

Design, modeling, and simulation of a photovoltaic water pumping system

Electric pumps cannot be fed in those areas where they are not connected to the electric public distribution grid. In those areas, it is useful to feed electric pumps by means of the electricity generated from renewable energy sources plants. Among these, the Solar Water Pumping Systems feed electric pump thanks to the electricity generated by a photovoltaic plant. In this paper, a whole SWPS is fully designed, modelled, and simulated in Matlab environment. The proposed implementation is an useful tool for SWPS testing.

Numerical implementation of active power flow tracing methods: Practical implications on transmission networks and DR programs support

The goal of this paper is to demonstrate the powerful contribution of the electric active power flow tracing methods on studying the electric transmission systems operating conditions. The tracing methods allow to impute to every generation unit and/or load the responsibility of the power flows of all the elements connected to the network. This study propose the numerical implementation of two different tracing methods on two transmission networks through Matlab® scripts developed on purpose; then the analysis is focused on identifying the loads which mostly affect the power line flows of the system. The results of this analysis point out the loads on which the application of the Demand Res…

DEMAND Project: Bottom-Up Aggregation of Prosumers in Distribution Networks

The paper explains the concept of the DEMAND project, whose aim is to develop a technical framework for allowing a Bottom-Up aggregation of prosumers connected to the distribution grid. Load and generation aggregation is a very current issue given the great potential that the coordinated management of distributed resources has on power systems operation and design. The novelty in DEMAND is the absence of a physical aggregator and the recourse to a virtual aggregation environment (VAE) for allowing the exchange of information among the prosumers in order to provide a service to the DSO. After a general description of the research project, the paper presents the services that the aggregated c…

An Analysis of the Intertial Response of Small Isolated Power Systems in Presence of Generation from Renewable Energy Sources

Renewable Energy Sources are posing critical issues related to the mining of power systems stability, essentially due to a decrement of the inertial response during system's contingencies. As a consequence, to preserve the security and the reliability of the system, it is necessary to adopt new frequency adjustments mechanisms. This issue becomes particularly critical in isolated power systems, like those of small islands not supplied by the main grid, in the case of high shares of production from unpredictable renewabies such as photovoitaic and wind sources. In this framework, the present work deals with the analysis of the variation of the inertia time constant of a small island in vario…

Damping Provision by Different Virtual Synchronous Machine Schemes

The adoption of virtual synchronous machine (VSM) schemes for the control of power converters is gaining more and more attention both in academia and industry. The VSM control strategies fall into the category of grid-forming converter controls, and they are intended for a range of different applications, providing specific services and different kinds of support to the grid. The paper investigates the possibility of damping provision to the system by VSM power converters. Different schemes are considered and compared, showing the opportunity of the investigated solutions through combined modal and time domain analyses. A specific modification of the power synchronization loop is recognized…

A NEW REPRESENTATION OF ENERGY STORAGE SYSTEMS OPERATION USING FOURIER THEORY IN OPTIMAL SMART GRIDS MANAGEMENT

This paper investigates the possibility to use a new modeling of Energy Storage Systems based on zero integral functions. Such functions represent the course of the energy level stored in batteries during the solution of optimal management problems in smart-grids. Storage devices, such as all the other components that are required to meet an integral capacity constraint along the dispatch time, must show the same State of Charge at the start and at the end of the timeframe considered for operation. In this paper, a set of sinusoidal functions have been used for the synthesis of the charge and discharge course of energy Storage Systems. Such representation allows to eliminate the difficult c…

Architetture e logiche di controllo ottimale di microreti per la razionalizzazione energetica Report 1 – Identificazione ed analisi di architetture e logiche di controllo ottimale di microreti per la razionalizzazione energetica

Il presente Rapporto descrive le attività svolte dal personale del DIEET dell’Università degli Studi Palermo nell’ambito della prima fase delle attività di ricerca dal titolo: “ARCHITETTURE E LOGICHE DI CONTROLLO OTTIMALE DI MICRORETI PER LA RAZIONALIZZAZIONE ENERGETICA’”, oggetto dell’Accordo di Collaborazione tra ENEA e DIEET sottoscritto in data 24 febbraio 2011. In fase di avvio delle attività, DIEET ed ENEA hanno concordato: che le reti sulle quali sviluppare le analisi e le successive simulazioni devono essere reti esistenti al fine di orientare il presente studio ad una successiva sperimentazione sul campo. Le attività sono state condotte in sinergia con il personale tecnico designat…

Single-Point Strategies for the Detection of Harmonic Sources in Power Systems

A Technical Approach to the Energy Blockchain in Microgrids

The present paper considers some technical issues related to the “energy blockchain” paradigm applied to microgrids. In particular, what appears from the study is that the superposition of energy transactions in a microgrid creates a variation of the power losses in all the branches of the microgrid. Traditional power losses allocation in distribution systems takes into account only generators while, in this paper, a real-time attribution of power losses to each transaction involving one generator and one load node is done by defining some suitable indices. Besides, the presence of P–V nodes increases the level of reactive flows and provides a more complex technical perspective. For this re…

A Simple Method to Assess Loadability of Radial Distribution Networks

This paper proposes a simple method to asses loadability in radial distribution systems. The relevant problem of voltage stability has been dealt with in past times with reference to higher voltage systems for generation and transmission. In more recent papers, the problem has been considered also at distribution level, since the new electrical energy market requirements and the increasing loadings are now more and more influencing these systems. The proposed method is based on a static approach and proceeds by first evaluating the stability indices and then the different loadability factors (related to real, reactive and apparent power). These calculations are carried out by identifying, s…

Application of Monte Carlo technique to evaluate the power injectable on electrical grid by wind farms

This paper is part of a research aimed at assessing the impact of wind generation on the transmission grid of Sicily, second among the Italian regions for wind power installed. To assess the maximum degree of wind generation penetrability in full compliance with the safe operation of the system, it seemed necessary to investigate the reports of contemporary winds and their territorial correlations when load assumes the peak or the minimum. Given the nature of the problem, it has been used a method of analysis based on the application of stochastic simulation techniques type Monte Carlo. In the paper, after describing the current state of wind energy generation in Sicily and development scen…

Extension and Tuning of Virtual Synchronous Machine to Avoid Oscillatory Instability in Isolated Power Networks

The risk of oscillatory instability introduced by virtual synchronous machines (VSM) control in isolated power networks is investigated. The considered control is a common scheme widely studied in literature, in several configurations and for different case studies. The impact of the VSM control on the system stability is examined for the existing power network of a Mediterranean island. The VSM control is implemented within the power converters interfacing the energy storage systems (ESS) installed in the network. Simulations and analysis show the occurrence of oscillatory instability in the system, with the ESS-VSM and the synchronous machines of the network progressively swinging against…

I Sistemi GIS e la tecnologia LIDAR nella gestione degli elettrodotti AT. Applicazioni nella rete elettrica siciliana.

L’articolo, dopo la descrizione dei sistemi GIS e della tecnologia LIDAR, riporta il calcolo della portata in corrente di alcuni elettrodotti AT all’interno del territorio siciliano, al fine di sfruttare al meglio le linee esistenti e di verificare i franchi elettrici imposti dal DM n. 449 del 1988

2015-2020. Sicily and Italy as Electricity Hub in the Mediterranean Area for the Development of the European Power Grids Interconnections

Falling demand and explosion of Renewable Energy Sources (RES) are redesigning the criteria for planning the power grids interconnections by ENTSO-E. In particular, the interconnections between networks of different countries have been acquiring importance more and more, in view of an unique European market for electricity and an increase of RES. Italy and Sicily, placed in the centre of the Mediterranean Sea, play a fundamental role as a bridge between Central Europe, North Africa area and Mediterranean islands (electricity hub). This paper aims to show how power system exchanges tend to follow the direction from South to North, and how the impact of North-African power – mainly generated …

Definition and application of innovative control logics for residential energy optimization

In this paper different innovative control logics for electric and thermal loads control in residential buildings are presented. The designed control logics are implementable in residential buildings thanks to Building Automation Control Systems (BACS) and Technical Building Management (TBM) systems. They have been tested using a simulation tool developed by the authors that is able to assess their effects on residential buildings having various characteristics and equipments. An application example is presented.

A Novel Operating Strategy for Customer-Side Energy Storages in Presence of Dynamic Electricity Prices

In the wholesale energy market, electricity prices are determined by the balance between supply and demand. Normally, customers are not exposed to these variations but pay a constant electricity price. In an attempt to reduce demand peaks, several utilities are moving from a conventional fixed-rate pricing scheme to a new market-based model, based on time-of-use or real-time pricing, able to closely reflect the wholesale energy price. Electricity customers can thus take profit from the installation of storage systems, shifting their energy consumption from on-peak to off-peak periods. This paper presents a novel charging strategy to manage customer storage systems in presence of hourly elec…

Distraplan: a flexible tool for strategical planning of electrical distribution systems considering distributed generation.

The paper here presented describes and shows DISTRAPLAN (Distribution Strategical Planning), software tool for strategical planning of distribu tion networks at Medium and Low voltage. The software aims at the identification and comparison of network configur ations, optimized in the long term with identification of special features in relation to the main technical-economical-environmental aspects, such as: the number of HV/MV and MV/LV substations, total length of the MV and LV lines and relevant sections, maximum required energy and power, instal lation and losses costs, etc. DISTRAPLAN, in both the main procedures into which it is articulated (strategical planning and evaluation of the …

Metodi di Previsione del Collasso di Tensione nelle Reti Elettriche di Distribuzione

Vari tipi di eventi contingenti, perturbazioni o situazioni di funzionamento critiche, possono portare un sistema elettrico in condizioni di instabilità e al blackout. Il termine stabilità di tensione è riferito in genere ad un sistema elettrico che si trova a lavorare in prossimità della condizione di carico massimo e non più in grado di soddisfare ulteriori incrementi del carico stesso, pena un progressivo e rapido abbassamento della tensione nei nodi della rete e il blackout del sistema per collasso della tensione. Nella memoria vengono presentate due diverse metodologie per lo studio della stabilità delle reti radiali di distribuzione e la previsione del collasso di tensione. La prima m…

Energy and environmental impacts of home automation components

Life Cycle Assessment is applied to estimate the life cycle energy and environmental impacts of five components used in the home automation systems: an electricity meter, an actuator with an integrated current sensor, a web server audio/video, an interface with infrared emitter, a multimedia touch screen. For each component, the impacts related to “one unit of product” (selected as functional unit) are assessed following a “from cradle to grave” approach, including the manufacturing, operation and end-of-life steps. The results showed that the operation step gives a contribution higher than 54% on primary energy consumption and variable from about 54% to about 99% on environmental impacts, …

An execution, monitoring and replanning approach for optimal energy management in microgrids

abstract This work develops a new approach for optimal energy management of electrical distribution ‘smart-grids’. Optimality aims at improving sustainability through the minimization of carbon emissions and atreducing production costs and maximizing quality. Input data are the forecasted loads and productionsfrom renewable generation units, output data are a set of control actions for the actuators. Theconsidered electrical distribution system includes storage units that must be considered over a 24 h timeinterval, to consider an entire charge and discharge cycle. The objectives for the optimal management ofdistributed (renewables and not) generation are technical, economical and environme…

A contribution to solve the problem of attributing harmonic distortion responsibility

Owing to the proliferation of loads which draw nonsinusoidal currents, the current and voltage distortion in distribution systems is ever increasing. The correct identification of the source of distortion is important for attributing the responsibility of disturbances to utility and customers. In this paper, a new classification of the possible classes of responsibility is proposed, defining some conditions, based on the improvement of the method of decomposition of the current into conforming and nonconforming components, and of the method based on the evaluation of the sign of harmonic active powers, which allows their identification.

A New Method for the Price Determination of the Reactive Power Supply

This paper addresses the development of an accurate model for the pricing of reactive power supply as an ancillary service. Reactive power supply is one of the most important ancillary services in the field of transmission systems security. The present work is focused on building a reactive power market at which the Distributors can also take part in injecting reactive power at the connected HV/MV nodes. The authors have studied the particular case of the reactive power supplied by sub-transmission or distribution networks, connected to the nodes of the transmission system. The aim of this work is to establish a reactive power price by crossing demand and offer curves.

La protezione dall’arco elettrico: quadri normativi a confronto

Innovative control logics for a rational utilization of electric loads and air-conditioning systems in a residential building

The paper focuses on the evaluation of the impact on residential buildings of innovative control logics defined for a rational utilization of the electric loads and air-conditioning systems. The control logics are implementable thanks to a Decision Support and Energy Management Systems developed by the same authors and easily installable in new and still-existing houses. The paper shows how a significant reduction of the primary energy consumption can be obtained by controlling the air-conditioning units together with the other electric loads of the house. After having explained how the control logics operate, a simulation tool is described, developed for a preliminary evaluation of their e…

A backward sweep method for power flow solution in distribution networks

Abstract A methodology for the analysis of radial or weakly meshed distribution systems supplying voltage dependent loads is here developed. The solution process is iterative and, at each step, loads are simulated by means of impedances. Therefore, at each iteration, it is necessary to solve a network made up only of impedances; for this kind of network, all the voltages and currents can be expressed as linear functions of a single unknown current (in radial systems) or of two unknown currents for each independent mesh (for meshed systems). The methodology has been called “backward” since the unique equation, in case of radial network, and the linear system of equations, in case of meshed n…

System Stability of a Small Island's Network with Different Levels of Wind Power Penetration

The reduction of the inertial response of the generation system has been one of the main obstacles to the penetration of high sharing of renewable energy sources in islanded systems. This issue can be solved thanks to innovative control that makes wind turbines able to provide the so-named synthetic inertia. The paper investigates some scenarios with different levels of wind power penetration in a small island whose grid is not supplied by the main grid, by the use of the software NEPLAN 360, simulating the wind power plants accordingly to the standard IEC 61400-27. The aim of the paper is to assess the maximum level of penetration in the island of wind generation, with traditional control …

Multi-objective long term optimal dispatch of distributed energy resources in micro-grids

The amount of distributed generators in power distribution systems is evermore increasing, and the potential benefits and drawbacks are becoming clearer. The optimal management of Distributed Energy Resources (DER) in microgrids is essential to guarantee their best exploitation. Optimal operation allows to maximize their benefits, such as reduction of network energy losses, reduction of carbon emissions and to minimize the negative effects of a strong DER penetration, such as the increase of infrastructural investment and operational costs. Hence, DER management is a multi-objective problem in which many objectives of interest, often conflicting, need to be optimized simultaneously. In this…

Architetture e logiche di controllo ottimale di microreti per la razionalizzazione energetica Report 2 Applicazioni in reti di distribuzione

Il presente Rapporto descrive, le attività svolte dal personale del DIEET dell’Università degli Studi Palermo nell’ambito della seconda fase delle attività di ricerca dal titolo: “ARCHITETTURE E LOGICHE DI CONTROLLO OTTIMALE DI MICRORETI PER LA RAZIONALIZZAZIONE ENERGETICA’”, oggetto dell’Accordo di Collaborazione tra ENEA e DIEET sottoscritto in data 24 febbraio 2011. Il presente Rapporto riporta le implementazioni della logica di controllo con una particolare attenzione al software che sovrintende alla gestione energeticamente efficiente dei sistemi individuati. Le implementazioni sono sviluppate in un ambiente di programmazione ad oggetti con una grafica di interfaccia che consente di se…

Transparency in transactive energy at distribution level

A recent report from the German Energy Agency analyzes the possible introduction of the blockchain technology in energy transactions in power distribution. The issue deserves attention since the extensive digitalization of business models puts new challenges to utilities in the power sector. The German decision makers in the energy field claim that blockchain appears as a close perspective and, at the same time, the Gartner hypecycle puts this technology at the peak of inflated expectations in 2016. Diffuse perception however provides hints for further investigation on the topic. This paper provides insight into the problem of peer-to-peer energy exchange from a technical perspective, provi…

Alcune osservazioni sui principali metodi per l’attribuzione delle responsabilità della distorsione armonica nelle reti di distribuzione dell’energia elettrica

A feasibility study of some DSM enabling solutions in small islands: The case of Lampedusa

Abstract The paper addresses the issue of the transition from a traditional electrical system without automation to a newer active and smart system allowing the possibility of implementing Demand Side Management policies, for little islands not supplied by the main grid. In particular, the paper focuses on two main topics related to the definition of: • an effective control, monitoring and communication system as a tool for the full exploitation of the opportunities given by Demand Response policies; • some solutions for the automation of the end-users’ electrical installations, in order to offer to the utility flexibility to be used for the improvement of the generation and distribution ef…

Sustainable integration of Renewable Energy Systems in a Mediterranean island: a case study

Starting from a previous technical and economical feasi-bility study, this paper analyzes the integration of Renewable Energy Sources into an existing territory with specified features of the natu-ral landscape and of the built environment. The work puts into evi-dence that territories development must use suitable tools and rules based on integrated knowledge, since technical feasibility studies do not assess the sustainability of the proposed infrastructures within the built environment and landscape. The studied system is in the is-land of Pantelleria situated between Sicily and northern Africa.

An optimal operating strategy for combined RES–based Generators and Electric Storage Systems for load shifting applications

This paper focuses on an optimal operating strategy of combined RES-based generators and electric storage systems for small/medium-scale public facilities. The operating strategy can be used in load shifting applications in response to a time-of-use (TOU) rate design with differential pricing for on- and off-peak usage. Load shifting applications can be exploited by customers using battery energy storage systems (BESS) in order to reduce their electricity bill, charging the storage when off-peak time periods are applied and discharging it during on-peak periods, when electricity energy prices are high. The operating strategy is implemented within a bidirectional converter that provides an i…

Integration Issues of Distributed Generators Considering Faults in Electrical Distribution Networks

In the recent years there is a great interest in integration of distributed generation (DG) units at distribution level; this integration leads to planning as well as operational challenges. Some possibilities to handle grid planning issues are addressed in this paper. Effects on grid protection, fault current level, and voltage profile are investigated and described for different types of DG units; the classification of DG units is based on their terminal characteristics in terms of real and reactive power delivering capability. Different scenarios for mis-coordination problems caused by DG interconnection are discussed. The effect of the DG on the voltage profile of a distribution network…

A laboratory setup for the evaluation of the effects of BACS and TBM systems on lighting

The paper focuses on the evaluation of the impact of Building Automation Control Systems (BACS) and Technical Building Management (TBM) systems on the performance of the lighting system in a residential building. In particular, this work shows a laboratory setup, installed at the DEIM of the University of Palermo, for simulating a typical apartment. The paper describes the laboratory, the lighting system and the BAC system installed and the test facility for evaluating the electricity consumption in presence and in absence of automation. The laboratory has been built within a research project funded by the Italian Minister of University and Research in the framework of the PON Smart Cities …

Feasible Domain-Driven Genetic Operators for Distribution Systems Optimal Reconfiguration

In this paper, the problem of minimum losses reconfiguration in weakly meshed medium voltage (MV) distribution systems is dealt with. The presence of meshes can either be a cause of the presence of particular loads, favoured customer (FC) nodes, requiring a double supply path or of distributed generation (DG) nodes, that cannot work in islanded mode. The problem has been brought back to the more general problem of radial networks reconfiguration with the major aim of minimising power losses subject to constraints on voltage drops at load nodes and current in branches as well as on the partition of power generated among supply nodes in the network. The problem is non-linear and combinatorial…

Analisi e definizione di strategie di gestione e controllo di sistemi di accumulo elettrico per applicazioni in reti di distribuzione attive automatizzate Report 2 – Applicazioni in reti isolate e interconnesse

Il presente Report riferisce sui contenuti e sui risultati della seconda fase delle attività svolte nell’ambito della ricerca dal titolo: “Analisi e definizione di strategie di gestione e controllo di sistemi di accumulo elettrico per applicazioni in reti di distribuzione attive automatizzate”, oggetto dell’Accordo di Collaborazione tra ENEA e DIEET sottoscritto nel corso del 2011, e in relazione agli esiti della prima fase della ricerca, di cui si riferisce nel precedente Report [1]. Le attività sono state condotte in sinergia con il personale tecnico di ENEA e sono state svolte prevalentemente all’interno dei locali e dei laboratori del DIEET di Palermo. Il Report è articolato in due part…

Sviluppo, messa a punto e sperimentazione di un sistema combinato batterie al litio-ferro-fosfato/FER per applicazioni in bassa tensione. Report 2 -Test e prove di funzionamento, anche in connessione con la rete elettrica di distribuzione.

Il presente documento costituisce il report dell’attività svolta nel periodo aprile - settembre 2013 avente per oggetto: “Sviluppo, messa a punto e sperimentazione di un sistema combinato batterie al litio-ferrofosfato/FER per applicazioni in bassa tensione”. Nel corso di tale attività, sono state eseguite molteplici prove in condizioni reali di funzionamento, integrando il sistema sviluppato (comprendente il pacco-batterie al litio-ferro-fosfato per una capacità complessiva di 16 kWh e l’insieme degli apparati di interfaccia - di potenza e di segnale - di controllo e di protezione), in una rete elettrica di distribuzione di bassa tensione attualmente in esercizio, al fine di verificare spe…

Analisi e definizione di strategie di gestione e controllo di sistemi di accumulo elettrico per applicazioni in reti di distribuzione attive automatizzate Report 1 – Analisi dello stato dell’arte

Il presente Report riferisce sui contenuti e sui risultati della prima fase delle attività svolte nell’ambito della ricerca dal titolo: “Analisi e definizione di strategie di gestione e controllo di sistemi di accumulo elettrico per applicazioni in reti di distribuzione attive automatizzate”, oggetto dell’Accordo di Collaborazione tra ENEA e DIEET sottoscritto nel corso del 2011. Nel corso della prima fase delle attività, a partire da un inquadramento generale dei diversi tipi di accumulo di energia elettrica (elettrochimico, meccanico ed elettrico), è stata condotta un’analisi preliminare su metodologie, sistemi d’interfaccia e tecniche di controllo dei sistemi di accumulo, in una visione …

Sviluppo, messa a punto e sperimentazione di un sistema combinato batterie al litio-ferro-fosfato/FER per applicazioni in bassa tensione. Report 1 –Sviluppo sperimentale e perfezionamento degli apparati di controllo e comunicazione.

Il presente documento costituisce il report dell’attività svolta nel periodo ottobre 2012 – marzo 2013 avente per oggetto: “Sviluppo, messa a punto e sperimentazione di un sistema combinato batterie al litioferro-fosfato/FER per applicazioni in bassa tensione”. L’attività s’inquadra come avanzamento delle ricerche svolte nel corso di collaborazioni precedenti con lo sviluppo sperimentale e la realizzazione prototipale di un sistema di controllo ed interfaccia verso la rete di un sistema combinato di accumulo elettrico-generazione FER, della taglia di 20 kW, progettato per applicazioni in bassa tensione tali da consentire l’implementazione di funzionalità innovative improntate al modello “sm…