Partial discharge detection and localization along medium voltage cables

In the last years different partial discharge (PD) measuring techniques have been developed because PD diagnostic is the most widely tool to evaluate the insulation condition of a power cable. Recently non-conventional methods and sensors have been used in order to reach improved results in PD measurements. The purpose of this work is to perform measurements that allow to study the variation of pulses when they travel along a MV cable and to locate the pulse source through the time arrival difference of the pulses obtained from two sensors installed separately.

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…

Regulating blockchain for sustainability? The critical relationship between digital innovation, regulation, and electricity governance

Abstract Blockchain technology has found several innovative applications in the electricity industry. However, its potential has still to be discovered. This is partly due to the role that regulation plays in electricity markets. To be introduced, experimented with, and eventually adopted on a commercial scale, blockchain-supported innovations need to fit the existing regulatory framework or the rules to be reshaped or updated. We focus on energy regulators' possible responses to the blockchain-enhanced market operations (both from the incumbents and potential newcomers), suggesting a monitoring mechanism that can support innovation.

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 two-end traveling wave fault location system for MV cables based on LoRa technology

In this paper a new low cost device is proposed for fault location in power distribution system. The device is part of a system that should include several units installed in couples at the two ends of MV cable lines. Their low cost justifies a widespread installation of these devices, moreover other functionalities could be considered so as to enrich the potential of the system for MV cables monitoring and asset management. The system exploits a two-end traveling wave technique, low complexity and low cost solutions both for the analog front end as well as for the communication infrastructure. A LoRa network is indeed considered as wireless modulation technique perfectly suited when commun…

Electrostatic synchronous generator model of an Inverter-Based Distributed Generators

In this paper, the idea of modelling the Inverter-Based Distributed Generators by using the concept of Electrostatic synchronous machines is discussed. A mathematical model of the inverter has been established which depends on the dc bus voltage, modulation index and frequency of the system. Two mathematical models have been developed: a small signal model and a steady-state model. These mathematical models will be helpful in studying the stability of a microgrid; especially when studying the transient stability performance of on-grid operation of converter-based distributed generator with multi-machine microgrid. Simulation results using Matlab/Simulink are carried out.

Optimizing droop coefficients for minimum cost operation of islanded micro-grids

This paper shows how minimum cost energy management can be carried out for islanded micro-grids considering an expanded state that also includes the system's frequency. Each of the configurations outputted by the energy management system at each hour are indeed technically sound and coherent from the point of view of generation-consumption balancing by exploiting a frequency dependent load flow algorithm. A Glow-worm Swarm Optimization (GSO) algorithm carried out in a 24 hour time frame provides optimized results. A test has been carried out for a residential PV-Storage-Microturbine islanded micro-grid to show the feasibility as well as the efficiency of the proposed approach and results ar…

Urban Energy Hubs Economic Optimization and Environmental Comparison in Italy and Vietnam

This paper aims to perform the minimization of the yearly energy supply cost from the main electricity and natural gas grids related to an energy district, considering the installation of different equipments. The case study refers to energy consumption of a medium density urban district and involves the exploitation of different energy sources and devices (photovoltaic systems, electrical energy storage, heat pumps and cogenerators). The analysis of the district energy supply is accomplished through an energy hub model. After a cost analysis related to the considered energy systems, a MILP algorithm was used for the optimization of a cost function and the simulation of various scenarios. M…

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…

A modified IEEE 802.11 protocol for reliable data transmission in automated power distribution systems

A high level of power quality in distribution networks is obtained by means of a diagnostic software, that establishes on-line the status of the network, by elaborating the measured data. An efficient telecommunication system is necessary, from whose reliability depends the security of the timely interventions on the network in case of fault. In the paper, after a brief examination of the diagnostic method, the telecommunication system is examined. The WiFi system has been considered most suitable, for its economy, for the diagnostic service, besides it is not suitably reliable for how it is managed by the IEEE 802.11 protocol for this application. In this work a new protocol derived by the…

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 methodology for assessing the impact of salinity gradient power generation in urban contexts

Abstract The paper proposes a methodology to assess the potential impact of salinity gradient power technology in urban contexts. The idea to employ such energy source in urban contexts derives from the observation that, among the energy districts outputs, low-salinity treated wastewater can be used to produce electricity if a suitable source of high salinity feed (seawater of a salt-works) is also available. The methodology uses the HOMER software for assessing the district’s electric energy production, consumption and exchange with the main grid. Then, starting from the total gross surface and the number of inhabitants of the district, some possible realistic scenarios characterized by di…

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…

Frequency constrained optimal Power Flow based on Glow-worm Swarm Optimization in Islanded Microgrids

This work presents an application of a swarm optimization method to solve the optimal power flow problem taking into account the constraints of frequency and line ampacity in three-phase islanded Microgrids. Each generation unit is equipped with a Power Electronics Interface. In the considered formulation, the droop control parameters are considered as variables to be adjusted by a higher control level, while the frequency is kept in rated bounds. Another typical constraint for OPF formulation, the max ampacity of each line, is also considered. Two case studies with different dimensions and electrical features have been considered and the obtained results show the efficiency of the proposed…

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…

Nonlinear droop control for minimum power losses operation in islanded microgrids

In this work, a modified primary regulation technique is proposed to control one of the inverter interfaced units feeding an islanded microgrid. The proposed approach employs an off-line minimum losses Optimal Power Flow, OPF, to extract a lookup table for the composition of the droop curve. Simulations prove that generators reach an operating point that corresponds to a minimum loss operation for the relevant power flow distribution. Since OPF has been implemented with frequency and voltage dependent models, the results of the modified droop are stable and also energy efficient. Further studies will address further analysis on systems showing different R/X ratio and modeling of more genera…

Active load sharing technique for on-line efficiency optimization in DC microgrids

Recently, DC power distribution is gaining more and more importance over its AC counterpart achieving increased efficiency, greater flexibility, reduced volumes and capital cost. In this paper, a 24-120-325V two-level DC distribution system for home appliances, each including three parallel DC-DC converters, is modeled. An active load sharing technique is proposed for the on-line optimization of the global efficiency of the DC distribution network. The algorithm aims at the instantaneous efficiency optimization of the whole DC network, based on the on-line load current sampling. A Look Up Table, is created to store the real efficiencies of the converters taking into account components toler…

Current and Voltage Behaviour During a Fault in a HV/MV System: Methods and Measurements

When a single line to ground fault happens on the MV side of a HV/MV system, only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In fact the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real single line to ground fault was made and fault currents were measured in the faulty substation and in four neighbouring substations. In this paper the problem of fault current distribution is introduced, the te…

A new approach to calibrate the thermal conditions in space charge measurements on HVDC mini-cables

The PEA method is currently widespread used for space charge measurements in mini-cables in order to qualify the behavior of semicon-dielectric-semicon compound under electric and thermal stress. The main goal of this research is to quantitatively evaluate the relationship between the thermal boundary conditions applied to cables or mini-cables and the maximum local electric field due to the accumulated space charge. Hitherto, several research groups have obtained thermal gradients over the dielectric's radius heating the conductor by Joule effect due to an induced current. In this paper, a numerical approach is offered to calibrate the heat exchange boundary conditions to apply to a sample…

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 ACCURATE MODEL FOR STEADY-STATE AND DYNAMIC ANALYSIS OF THE SICILIAN NETWORK WITH HVDC INTERCONNECTIONS

Sicily is one of the first Italian regions for installed power from renewable energy plants, especially photovoltaic and wind plants, and a crucial point for the Mediterranean energy hub. Its role as nexus between the European and the African Continents is becoming more and more significant due to the realization in a short time of the so called Tyrrhenian link and the High Voltage Direct Current (HVDC) connection with Tunisia. In this framework, the paper presents a model of the Sicily power generation and transmission system, including the Tyrrhenian link and two equivalent buses representing the Sardinian power network and the rest of the Continental Europe (CE) synchronous area, for both …

Effect of Polarity Reversal on the Partial Discharge Phenomena

In the field of High Voltage Direct Current (HVDC) transmission, the space charge accumulation phenomenon and the Partial Discharges (PD) phenomena are considered the main causes of dielectric ageing. During the years, the degradation effect of both phenomena under constant DC stress has been widely studied by several researchers. In case of polarity reversal, typically carried out to control bi-directional power flow between interconnected High Voltage transmission systems, the space charge movement may not synchronously follow the electric field polarity. This could make the moment of reversing polarity a very critical one, where space charge injected during preceding polarity produces hi…

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…

Impact of RES penetration on the frequency dynamics of the 500 kV vietnamese power system

The increase of renewable energy sources (RES) typically operating as converter-interfaced generation (CIG) is progressively causing a significant change of power systems operation paradigm. The reduction of the overall available kinetic energy and the consequent impact on the dynamic response of the system is a relevant issue currently under investigation in academic and industrial scopes. The work analyzes the impact of different CIG penetration in the three areas of the 500 kV Vietnamese power system, North, Center and South. The system is modified substituting conventional synchronous generation with converter-interfaced generation. The models of power converters and corresponding contr…

EVOLUTIVE ALGORITHMS FOR OPTIMAL SIZING OF HYDROGEN STORAGE FOR WIND FARMS

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…

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…

A Peer-to-Peer Market Algorithm for a Blockchain Platform

In an era of technological revolution in which everything becomes smarter and connected, the blockchain can introduce a new model for energy transactions able to grant more simplicity, security and transparency for end-users. The blockchain technology is characterized by a distributed architecture without a trusted and centralized authority, and, therefore, it appears as the perfect solutions for managing exchanges between peers. In this paper, a market algorithm that can be easily transferred to a smart contract for maximizing the match between produced and consumed energy in a micro-grid is presented. The algorithm supports energy transactions between peers (both producers and consumers) …

The Acoustic Wave Behavior Within the PEA Cell for Space Charge Measurement

In order to evaluate the acoustic wave behavior within the Pulsed Electro Acoustic (PEA) cell, a simulation model has been developed in this work. The model, implemented in Matlab environment, is based on the analogy between acoustic and electrical quantities. Therefore, it was possible to model the PEA cell as cascade connected lossy transmission lines. The model has been validated theoretically by making a comparison with a simulation result found in literature. The experimental validation has also been made by using the PEA cell of the LEPRE high voltage lab. In addition, four graphs have been realized. Two of them can be used to establish in easy and fast way to obtain the minimum groun…

Multiobjective service restoration in distribution networks using an evolutionary approach and fuzzy sets

Abstract In this article, the service restoration (SR) problem in electrical distribution networks is dealt with using an evolutionary strategy (ES) with a fuzzy definition of the conflicting objectives. The normal operation status allows the remote control of tie-switches, of capacitor banks and load connection. When a permanent fault occurs, the same remote control actions can be performed with the aim of restoring the service in the concerned areas. The status of these remotely controllable elements is the boolean optimisation variables for the SR problem. Besides this, here the SR problem is dealt with in a multiple objectives (MO) formulation. Indeed, the power losses’ term is consider…

Different Measurement Setup Configurations for Space Charge test in Mini Cable Specimens with the PEA Method

Under DC stress, the space charge accumulation is believed one of the most responsible of dielectrics ageing. For this reason, due to the increase of the HVDC transmission, a recommendation has been proposed. The latter want to introduce the space charge measure, with the PEA method, in cable specimens during the prequalification or type tests. Considering the several issues related to this kind of measures the aim of the proposed work is find a measurement setup for mini cable specimens which is able to provide a clear and clean space charge profile. Therefore, different tests have been made in this work. In particular, the length of the cable specimen, the width of the pulse electrodes, a…

Improved primary regulation for minimum energy losses in islanded microgrids

In this paper, an improved primary regulation is proposed for grid forming units supplying islanded microgrids. A minimum losses Optimal Power Flow is run off-line to devise the operating set points composing the primary regulation curve. In this way, after load perturbations, generators can reach an optimized operating point for a given and unique minimum losses energy flows distribution. The idea is to skip the hierarchical control architecture and provide a feasible and optimized operating point. A case study over 24 hours shows the effectiveness of this new approach as well as the improved operation quality of the system.

An analytical model for PQ sources in backward/forward methods for distribution networks analysis

In this paper a model of PQ sources useful for distribution systems analysis is developed. In the considered systems there are, in addition to HV/MV sources, other PQ buses, namely active and reactive power supply nodes (Vδ nodes). The general solution strategy is an iterative forward/backward method, in which the state variables are the node voltages. If it is weakly meshed, the network is turned into radial by means of cuts and compensation currents. After the presentation of the general problem, the equations expressing the unknowns for the PQ nodes are treated in detail. These equations belong to the backward sweep of the algorithm. The methodology has been implemented and applied so as…

Different Space Charge Behavior of Materials Used in AC and DC Systems

The aim of the present work is to evaluate the behavior, from the space charge accumulation phenomenon point of view, of three different XLPE specimens used as insulation materials in high voltage systems. Considering that under DC stress the charge accumulation is more relevant as compared to the AC case, in the specimens for DC applications additives are typically added. In this work, three different specimens are analyzed. One is a free additive sample used conventionally under AC stress and two others include different additives that are used under DC stress. In order to measure the space charge accumulation, the Pulsed Electro Acoustic (PEA) method has been employed. For each sample, t…

Energy efficient operation in smart grids: optimal management of shiftable loads and storage systems

In this paper, the authors analyze the impact of the participation of customers to the sustainable implementation of energy rational strategies in microgrids. The management of shiftable loads is compared to the control of real and reactive storage systems in smart grids. An optimization algorithm is used as analysis tool to assess the impact of such control variables in different conditions. The results clearly indicate that if shiftable loads are of suitable size, they have a more promising as tools to both reduce losses and to flatten the peak load through the HV/MV bus. Many tests have been carried out on a real experimental MV system in the area of Rome Italy.

The Global Grounding System: Definitions and guidelines

The present paper presents the preliminary results of the ongoing Italian METERGLOB project on the contribution given by the exposed conductive parts to a Global Grounding System. One of the expected results of METERGLOB is to carry out guidelines for the identification of a Global Grounding System. These guidelines must be defined on the basis of the definitions and methods present in the current international standards on grounding and safety. In the paper some definitions and elements to be taken into account for the identification of a Global Grounding System are given.

Tracing battery usage for second life market with a blockchain-based framework

This work describes the design of a platform based on a permissioned blockchain for sharing relevant information among the actors involved in grid service provision programs. The information collected by a proprietary monitoring on-board system accessing the central unit of the Electric Vehicle, EV, is then sent to a dropbox folder owned by the car owner and then written on a blockchain platform. The platform could be supplied from similar data from the grid operator collected on the grid during the provision of services. In this way data can be validated and used for tracing the health status of the EV's battery. The design of customized smart contract allows to acquire the profiles of bat…

Contributed Review: Review of thermal methods for space charge measurement.

The space charge accumulation phenomenon has garnered great interest over the last two decades because of the increased use of direct current in high voltage electrical systems. In this context, a significant relevance has been achieved by the thermal methods, used for solid dielectrics. This paper presents a review of this non-destructive measurement system used for the measurement of space charge. The thermal pulse method, the thermal step method, and the laser intensity modulation method are described. For each configuration, the principle of operation, the thicknesses analyzed, and the spatial resolution are described, reporting also the main related applications

Practical tables for the design of the grounding systems in distribution networks in presence of metallic interconnection

The present paper deals with the dependence of the ground current, due to a single-line-to-ground fault in a secondary substation, on the electrical and geometrical parameters of a Medium Voltage distribution network in which a metallic interconnection between the grounding systems is realized. Examining different situations, some easy-to-use tables are provided for a practical approach to the design of the ground electrodes of the secondary substations in these networks. The relevance of the work is due to the lack in the international standards of specific indications on how to consider the presence of the interconnection elements in distribution networks.

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…

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…

Reconfiguration Techniques of Partial Shaded PV Systems for the Maximization of Electrical Energy Production

In this paper, the research of the optimal layout of photovoltaic (PV) modules in a PV array giving the maximum output power under different shaded working conditions is carried out. The particular condition of non uniform solar exposition of the modules is analyzed. The study of the different configurations has been carried out starting from a circuital model used for the design of PV cells and for the simulation of the working behavior of PV arrays. The attained results appear to be interesting although the complexity of the problem in mathematical terms is huge when the number of panels is high. Moreover, the results confirm that this approach often allows to attain a higher electrical e…

Online optimization of a multi-conversion-level DC home microgrid for system efficiency enhancement

In this paper, an on-line management system for the optimal efficiency operation of a multi-bus DC home distribution system is proposed. The operation of the system is discussed with reference to a distribution system with two conversion stages and three voltage levels. In each of the conversion stages, three paralleled DC/DC converters are implemented. A Genetic Algorithm performs the on-line optimization of the DC network’s global efficiency, generating the optimal current sharing ratios of the concurrent power converters. The overall DC/DC conversion system including the optimization section is modelled using MATLAB/Simulink. Thanks to the implemented online algorithm, considering …

On the hazardous situations due to the presence of HV/MV substations in urban areas

The paper focuses on the hazardous situations that can rise in urban areas in case of earth fault inside a High Voltage/Medium Voltage station. IEEE and IEC/EN Standards and technical documents are examined and discussed, in order to propose some practical guidelines for a safe integration of such installations in contexts characterized by the presence of low voltage systems and not trained persons.

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…

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…

A new technique for partial discharges measurement under DC periodic stress

The aim of the present work is to recognize the type of defect in insulating materials employed in DC electrical systems. This analysis, under AC stress, is carried out by using the Phase Resolved method (PRPD). While, under constant voltage stress this method cannot be performed and measurements show complexities. In order to overcome these problems, a new technique is proposed, based on the application of a periodic continuous waveform. Simulation results, carried out by using a model based on a time-variable conductance of an air void defect, showed the PRPD pattern that can be obtain. Furthermore, compared to the constant DC stress, the measurement duration became lower and the discharg…

Valutazione degli effetti di sistemi BAC e TBM sulle prestazioni energetiche

Le prestazioni energetiche degli edifici dipendono non solo dall’aspetto termico ma anche da fattori elettrici come: • La presenza di generatori di energia elettrica o termica da Fonti di Energia Rinnovabile (FER) e sistemi di cogenerazione (CHP); • La presenza di sistemi di controllo automatico dell’edificio (BACS) e sistemi di gestione tecnica dell’edificio (TBM). Per promuovere l’efficientamento energetico degli edifici, gli Stati membri dell’Unione Europea hanno seguito diverse strade. In particolare, negli ultimi decenni diverse politiche di incentivazione hanno attuato finanziamenti locali di generatori da FER.

A multi-agent system reinforcement learning based optimal power flow for islanded microgrids

In this paper, a distributed intelligence algorithm is used to manage the optimal power flow problem in islanded microgrids. The methodology provides a suboptimal solution although the error is limited to a few percent as compared to a centralized approach. The solution algorithm is multi-agent based. According to the method, couples of agents communicate with each other only if the buses where they are located are electrically connected. The overall prizing system required for learning uses a feedback from an approximated model of the network. Based on the latter, a distributed reiforcement learning algorithm is implemented to minimize the joule losses while meeting operational constraints…

Minimum power losses by using droop coefficients regulation method with voltage and frequency constraints in islanded microgrids

In this paper, a droop coefficients regulation methodology is proposed for an islanded microgrid to optimize the power losses. Based on the P-f and Q-V relations to adjust the droop coefficients at every loading condition, the optimized operating set point generates minimum power losses operation while satisfying the constraints of voltage and frequency limitation. A 9-bus case study is here implemented to show the effectiveness of this new approach as well as the improved operation quality of the system.

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 …

Optimal Placements of SVC Devices in Low Voltage Grids with High Penetration of PV Systems

With the increase of load demand and distributed photovoltaic (PV) systems on the electric grid, maintaining the required voltage tolerance at the point delivery (customer homes/businesses) is becoming more challenging for electric power utilities. In a residential neighborhood, the peak load typically occurs in the early evening hours while maximum PV generation occurs during mid day. As a result, the lowest voltage operating points occur in the evening hours; whereas the highest voltage operating point occur during the day, when the PV systems are injecting more power than what is locally consumed. Static VAR Compensators (SVCs) can be used to mitigate voltage violations and smooth out th…

Adaptive and Dynamic Ant Colony Search Algorithm for Optimal Distribution Systems Reinforcement Strategy

The metaheuristic technique of Ant Colony Search has been revised here in order to deal with dynamic search optimization problems having a large search space and mixed integer variables. The problem to which it has been applied is an electrical distribution systems management problem. This kind of issues is indeed getting increasingly complicated due to the introduction of new energy trading strategies, new environmental constraints and new technologies. In particular, in this paper, the problem of finding the optimal reinforcement strategy to provide reliable and economic service to customers in a given time frame is investigated. Utilities indeed need efficient software tools to take deci…

Influence of LV neutral grounding on global earthing systems

International Standards define a Global Earthing System as an earthing net created interconnecting local Earthing Systems (generally through the shield of MV cables and/or bare buried conductors). In Italy, the regulatory authority for electricity and gas requires distributors to guarantee the electrical continuity of LV neutral conductor. This requirement has led to the standard practice of realizing “reinforcement groundings” along the LV neutral conductor path and at users’ delivery cabinet. Moreover, in urban high-load scenarios (prime candidates to be part of a Global Earthing System), it is common that LV distribution scheme creates, through neutral conductors, an effective connection…

A practical method to test the safety of HV/MV substation Grounding Systems

The adequacy of a Grounding System (GS) to the safety conditions has to be periodically tested by measurements. The test methods and techniques used to verify the electrical characteristics of the GS include the measurements of step and touch voltages. The goal of the test is to verify that touch voltage and step voltage remain below a safe value in all the zones of the installation. The measurements can present some operational difficulties. The purpose of this paper is to present the procedure, step-by-step, of a practical method of measuring touch/step voltages in grounding systems located in urban or industrial areas with reduced accessibility. The suggested method uses auxiliary curren…

A Feasibility Study for the Transition to Electric Mobility in the Island of Favignana

The energy transition and climate neutrality are a short time scenario as climate concerns are rising fast. Small islands are natural microgrids in which the energy transition is subjected to economic and regulatory constraints and highly challenged by technical issues. As a first step, the Mediterranean island of Favignana has been considered in this study, to assess how electric mobility could impact the power system. According to the plans from the local decision makers, the island is moving towards a full public electric mobility in the near term, also due to the participation in the BloRin project. For this reason, a feasibility study about the technical and environmental impact of ele…

An Integrated System for Efficient Management of Distribution Networks: The System's Architecture and the Telecommunication Infrastructure

Modern distribution systems must keep up with high power quality standards due to the new regulations of the European Community and of the different national legislations. Efficient faults management is one of the basic tasks utilities must accomplish and this objective can be attained if and only if automation is present and efficient diagnostic procedures have been implemented in the centralized or distributed units all over the network. In this paper, the architecture of an integrated system for management of modern distribution systems is presented. The system includes routines for normal on-line optimal operation of distribution systems and for outage management, the latter including f…

Economic impact of BACS and TBM systems on residential buildings

The paper presents the results of a study on the economic impact of building automation control systems and technical building management systems on residential buildings. The different functions considered by European Standard EN 15232 and having impact on the energy performance of buildings are applied to a test house, varying its energy efficiency class. The economic impact due to the introduction of each BACS or TBM function is evaluated using the BAC factors method, considering the real costs for the purchase and the installation of the components that implement the specific functions and the yearly energy costs of the building before and after their installation.

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…

Blockchain-based DR logic: a trade-off between system operator's and customer's needs

This paper describes a way to include the end users of the electrical network in the Demand Response mechanism using the Blockchain technology and the Smart Contract concepts, thus developing a distributed system where customers can communicate directly with the system operator to provide their flexibility in a transparent, secure and traceable way.The historical data on energy consumption and production of the customers is recorded on the Blockchain, with the Smart Contract evaluating the baseline and the potential support that each customer can provide to fulfill the requested load adaptation communicated by the grid operator. The baseline and the optimal power reduction for a customer (e…

Voltage Profile Improvement for Soc Son's Low-Voltage Grid with High Penetration of PV Systems by Optimizing the Location of SVC Devices

This paper presents a method that is applied to optimize the placement of Static VAR compensators in a real low-voltage grid in the Vietnamese territory. In this way, the voltage profile of the distribution grid turns to be improved. A heuristic method, the Binary Particle Swarm Optimization, is used to find a solution to this problem within the Matlab environment. A case study that considers a high penetration of rooftop PV systems in a branch of Soc Son distribution grid is implemented to show the efficiency of the optimization method for this specific application.

Analysis of the limitations of WiFi communications managed by the IEEE 802.11 protocol in data transmission in automated power distribution systems

This paper presents a study on the performances of the IEEE 802.11 protocol used in a Medium Voltage networks management system, carried out using a model for the simulation of WiFi chains architectures. The results of the simulations give some practical indications for the use of the IEEE 802.11 protocol also in presence of transmissions characterized by rigid time intervals, for which this protocol is usually not suitable. Finally the whole communications system is presented.

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…

Optimal reconfiguration of weakly meshed distribution systems

In this paper the problem of optimal reconfiguration for weakly meshed systems is dealt with; meshes are created by the presence of Favoured Customers (FC) requiring supply through two different paths in order to guarantee the maximum service continuity. Aim of the reconfiguration is to attain a network that operates with minimum power losses, and in order to account for particular needs of the FC loads, that shows the minimum overall yearly fault rate on the branches where the power required by the loads flows. Moreover the constraints concerning the bus voltage profiles, the current in branches and the power balance among HV/MV transformers supplying the network must be full-filled. Due t…

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…

Mathematical modelling of an inverter-based distributed generator

In this paper, a modeling approach of a three phase power inverter based on an electrostatic synchronous machine is presented. By the proposed approach, any inverter-based distributed generator in a microgrid can be replaced by an equivalent electrostatic machine. This paper aims to promote the use of the proposed modeling approach in the analysis of microgrid stability. Thanks to the proposed modeling approach, transient performances of on-grid operation of converter-based distributed generators could be easily analyzed by multi-machine models. Parameters of the equivalent synchronous electrostatic machine model are derived to achieve equivalence with the inverter model. Small signal model…

Multi-Objective Optimization of Urban Microgrid Energy Supply According to Economic and Environmental Criteria

This study is focused on the optimization of the annual cost and greenhouse impact related to the supply of natural gas and electricity of an urban microgrid through the installation of components as renewable energy sources, energy storage units and converters. As input parameters of the optimization model, the energy demand of a medium density urban district was estimated, while average costs and emissions of equipment were collected in market reports and literature. The outputs of the model are the optimal size and the schedule of each component. Moreover, optimization analysis was carried out for two different scenarios, comparing Italian and Vietnamese energy system cost and environmen…

An efficient diagnostic technique for distribution systems based on under fault voltages and currents

Service continuity is one of the major aspects in the definition of the quality of the electrical energy, for this reason the research in the field of faults diagnostic for distribution systems is spreading ever more. Moreover the increasing interest around modern distribution systems automation for management purposes gives faults diagnostics more tools to detect outages precisely and in short times. In this paper, the applicability of an efficient fault location and characterization methodology within a centralized monitoring system is discussed. The methodology, appropriate for any kind of fault, is based on the use of the analytical model of the network lines and uses the fundamental co…

Partial discharge behavior under single phase half and full-bridge rectifier

The aim of the present work is to simulate partial discharges (PDs) phenomena under voltage stress close to the Direct Current (DC) waveform. The employed waveforms have been realized by using a full-wave and a half-wave rectifiers. After that, in order to generate a steadier voltage supply, a capacitive filter has been inserted in the output of the half-wave rectifier. Simulations have been carried out by modifying a previous software used in the case of Alternating Current (AC). Finally, experimental tests have been carried out in order to validate simulation results.

PV systems in the vertical walls: A comparison of innovative structures

This paper presents the performance comparison of PV windows with the purpose of tracing the behavior of next-generation systems, which could favor architectonical integration. More in detail, a dye sensitized solar cell (DSSC) and blue and grey thin film silicon panels have been analyzed. The systems can be placed behind a window or behind a wall of glass blocks. The three generation systems are then compared in terms of both efficiency and Fill Factor.

A new methodology for distribution systems faults identification, location and characterization

PurposeIdentify a new methodology for fault characterization, identification and location in electrical distribution systems, based on the use of matrix algebra.Design/methodology/approachThe developed diagnostic methodology is based on a high precision analytical model of the network using a distributed parameters representation.FindingsTest results have proved the approach to be efficient and precise, while providing a generalized quadripolar model of a line affected by the most common kinds of fault.Research limitations/implicationsGeneralization to a greater number of fault cases, experimental tests.Practical implicationsUtilities are quite interested in such items, since the new requir…

Smart district energy optimization of flexible energy units for the integration of local energy storage

Several changes are involving electrical power systems, especially distribution networks. For this reason, the actors in charge of managing and operating reliably these grids are facing many technical issues regarding demand and supply balancing, Renewable Energy Sources and Electric Vehicles integration, peak load shaving, etc. In this context, many energy actions have been implemented for providing services to the power system managers by means of prosumers' demand and/or supply flexibility. This study reports the development of a centralized energy management solution for smart grids equipped with local storage devices, RES, consumers and other energy facilities in a district context. Th…

Service restoration in compensated distribution networks using a hybrid genetic algorithm

In this paper a genetic algorithm (GA) based approach to the service restoration (SR) problem in automated distribution networks is presented. Normal operation within the network comprises both automatic reconfiguration and compensation so as to reduce power losses, allow load balancing and improve the voltage profile. In the restorative state, the reconfiguration is performed together with compensation, taking mainly into account the load supply requirement and secondarily, the losses reduction requirement. After a general discussion on the restoration problem together with a short review of recent papers on the topic, a solution strategy is proposed. Then, a short account about classical …

A Matrix Model For An Energy Management System Based On Multi-Carrier Energy Hub Approach

The INGRID FP7 European co-funded project studies several methodologies concerning hydrogen production and storage, aiming to provide services to electricity system operators for suitably balancing electrical supply and demand. In such a context, the problem of integrating different carriers into a single multi-hub optimiser represents a challenging topic for the research. This paper depicts the Energy Management System (EMS) of the plant which will be developed and built as a prototype of the INGRID system. The approach followed for the EMS design and development takes the cue from the matrix model presented in the rest of the paper, as well as the general optimisation problem formulation …

ON THE POTENTIAL IMPACT OF GREEN HYDROGEN FACILITIES ON THE PLANNING OF RES PLANTS IN SICILY

A recent report on climate change and global warming, soil and oceans and the cryosphere [1] highlighted the disastrous effects that would be produced if climate change were not stopped.

A new architecture for Smart Contracts definition in Demand Response Programs

The present paper shows the possibility to use a smart contract for defining a distributed Demand Response mechanism. The use of the blockchain and smart contracts for the Demand Response mechanism allows the creation of an automatic system, where network users can communicate with the DSO to provide their flexibility. The blockchain ensures that the same information is shared among the users of the grid, while preserving user privacy. The DSO notifies the request to increase or reduce the load in a given period of the day using channels, a native abstraction of Hyperledger Fabric. The smart contract computes the support provided by each user to fulfill the requested load adaptation and aut…

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 …

Smart grid integrated green data centres as ancillary service providers

In this paper a review of Green Data Centres facilities to support smart grids operation is proposed. The paper describes the ancillary services a Green Data Centre can provide both in terms of spinning reserve provision and different regulation services. In the application section, a real electrical grid hosting a data centre is considered. The infrastructure is owned by Engineering S.p.A. and is installed in northern Italy. The system has been considered as connected to the MV distribution grid in presence of other renewable energy sources. The impact of possible power management operations over the considered data centre has been studied by means of a simulation software and the spinning…

Flexibility Services in a Mediterranean Small Island to Minimize Costs and Emissions Related to Electricity Production from Fossil Fuels

In last years, the energy efficiency in non-interconnected islands became an important topic, since the electricity production is often based on diesel generators, thus contributing to the global warming. Italian government recently emitted two decrees to promote the introduction of renewable energy technologies in 21 non-interconnected islands, both for electrical and thermal uses. In this paper, the economic and environmental feasibility of the introduction of renewable energies in the island of Pantelleria was assessed adopting an optimization approach. Furthermore, the flexibility provided from the local desalination plant and the domestic water heaters was evaluated. The final demands …

Interconnections criteria of grounding grids in global grounding systems

A Global Grounding System is defined as the combination of local grounding systems, obtained by their interconnection, which ensures, thanks to their proximity, that no dangerous touch voltages can arise. The interconnection of grounding systems via the armors of the MV cables, between secondary substations and HV/MV stations is herein analyzed to verify the effects on touch voltages in ground-fault conditions. In particular, two main issues are discussed: 1) the transfer of dangerous voltages to secondary substations, due to ground-faults occurring at the HV/MV station; 2) the reduction in the magnitude of the ground potential rise due to ground-fault conditions at secondary substations, t…

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…

Interpretation of PEA Output Signal in a Multilayer Specimen

The aim of the present work is to evaluate the acoustic waves behavior within the Pulsed Electro-Acoustic (PEA) cell, in case of a multilayer specimen, in order to avoid misinterpretation of the output signal. Due to the reflection phenomenon of the acoustic waves travelling within the PEA cell, the output signal could be distorted. Because this aspect, for a given PEA cell with certain ground electrode and absorber thicknesses, depends on the sound velocity and thickness of the specimen under test, the latter must be carefully sized. For this aim, some useful relationships, that must be taken into account are given and described. In particular, a three layers sample simulating an air void …

Experimental Tests

This chapter presents the outcomes of the experimental implementation of the architecture described in Chap. 4 running a hardware testbed for the emulation of domestic electrical load profiles. Besides it shows how this experimental scenario integrates both with the legacy metering architecture and with the blockchain platform. Finally, the integrated use with an Energy Management System designed on purpose is also described with the aim of ensuring intervention and automating the end user’s response to a DR event.

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 …

Improving the energy efficiency of an islanded distribution network using classical and innovative computation methods

The paper presents the analysis of some potentially suitable actions for reducing the energy losses of an islanded Medium Voltage distribution network, with the aim of improving electricity distribution efficiency. For this purpose, four actions are considered: 1) increasing the network's rated voltage; 2) reactive power compensation through static capacitor banks; 3) reactive power compensation through switchable capacitor banks; 4) installation of distributed photovoltaic (PV) generation. The first two measures are typically taken into account by the distribution system operators and can be examined by means of classical design methods, whereas the latter two more innovative actions are t…

Energy Management Systems and tertiary regulation in hierarchical control architectures for islanded microgrids

In this paper, the structure of the highest level of a hierarchical control architecture for micro-grids is proposed. Such structure includes two sub-levels: the Energy Management System, EMS, and the tertiary regulation. The first devoted to energy resources allocation in each time slot based on marginal production costs, the latter aiming at finding the match between production and consumption satisfying the constraints set by the EMS level about the energy production in each time slot. Neglecting the efficiency of the different energy generation systems as well as that of the infrastructure for electrical energy distribution, the problem dealt with by the EMS sub-level is linear and can …

Reliability Analysis of a Stand-Alone PV System for the Supply of a Remote Electric Load

The work presents a reliability analysis of a stand-alone photovoltaic system for the supply of electric loads located in remote areas not easily reachable by the low voltage distribution network. The analysis is performed by characterizing the electric load behavior by means of a Montecarlo approach for taking into account the stochastic variability of the electrical energy demand. A Montecarlo approach is used also for evaluating the electricity production of the stand alone photovoltaic system as a function of the hourly solar irradiation of the installation site. The variability both of the load and of the energy production are correlated and the probability that the load can remain uns…

DEMAND Project: A Proposal for a Bottom-Up Aggregation Platform

In many countries, a great number of electricity market operators have developed Demand Response (DR) programs with different purposes. In this framework, load aggregation represents an important issue, linked to the potential that the coordinated management of distributed resources has on affecting power systems' operation.