Stationary battery systems in the main world markets: Part 1: Overview of the state-of-the-art

The role of energy storage systems (ESSs) is becoming more and more important in modern power grids, mainly because of the higher penetration of intermittent renewable energy sources (RESs), such as solar and wind power, spurred by advantageous support policies carried out in several countries. The fluctuation nature of the energy produced by RESs is indeed leading to emerging power quality issues or to renewable curtailments. ESSs can be used to balance generation and demand of electricity over time, allowing a higher penetration of RESs into the power network. The energy storage industry is evolving rapidly, and new electrochemical technologies are entering the market. Besides, most elect…

Technological and legislative status point of stationary energy storages in the EU

Abstract European renewable generation has been supported through several policy instruments in the last decades, and this has caused a significant growth of the renewable energy sector, spurred by the ambitious climate and energy policy targets. Despite this impetuous growth, the electricity infrastructure is not yet ready to accept increasing shares of variable renewable energy sources (RES) generation, and this is causing grid balance challenges, due to the inherently variable nature of the PV and wind energy. In order to overcome this issue, allowing higher shares of renewable generation in the energy sector, energy storage (ES) systems are becoming increasingly competitive in the globa…

Support Policies for Photovoltaic Systems in Europe

Financial measures for supporting wind power systems in Europe: A comparison between green tags and feed’in tariffs

Distributed Generation demonstrates to be able to significantly influence the electric power system, bringing considerable benefits to the quality of service and improving the energetic efficiency of the distribution network. In particular, in the last few years, Distributed Generation from renewable energy sources is considerably increased thanks to the many support policies promoted worldwide with the aim of facing the environmental issue and the problem of the permanent rise of prices of the fossil energy. In this contest, after a brief review on the financing strategies carried out in Europe in the last decade for promoting the recourse to renewable energy, the paper presents a comparis…

Battery storage systems for peak load shaving applications: Part 1: Operating strategy and modification of the power diagram

Battery Energy Storage Systems (BESSs) are gaining more and more attention in the current global energy landscape, thanks to some peculiar characteristics such as the versatility, modularity, scalability, fast response time, etc. BESSs can advantageously be used in the ancillary services market, in order to provide all the services necessary to ensure the stability and the reliability of the power system. Among other applications, BESS can also be used to shift electricity demand from on-peak to off-peak periods, also contributing to relieve peak demand charges, thus ensuring a saving for the customers. The BESS is charged when the electricity prices are the lowest (during the night) and di…

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…

DE.DU.ENER.T. project: A prototype of a sustainable energy microsystem

The paper presents a prototype of a microsystem for the integration and the optimal management of renewable energy sources in order to attain a reduction of the total energy consumption of a not residential building. The system composed by the building and the prototype is an energy sustainable microsystem and is located in Italy in the city of Valderice. The microsystem 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. In the paper the purposes of the DE.DU.ENER.T. project are presented and …

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…

Inseguitori solari: diverse tipologie e analisi tecnico-economica

L’utilizzo di strutture di sostegno ad inseguimento, nella realizzazione di impianti fotovoltaici, permette di ottenere un considerevole aumento dell’energia elettrica prodotta dagli stessi impianti. L’incremento di producibilità dipende dalla tipologia di inseguitore considerata (monoassiale o biassiale) ed, in misura minore, dalla località del sito d’installazione dell’impianto fotovoltaico. Nel presente testo, dopo aver preso in rassegna le diverse tipologie di strutture ad inseguimento, descrivendone le configurazioni strutturali, le tipologie di comando ed i meccanismi di movimentazione, viene svolta un’analisi di producibilità in funzione della latitudine del sito d’installazione dell…

Evolving non-dominated solutions in multiobjective service restoration for automated distribution networks

Abstract The problem here dealt with is that of Service Restoration (SR) in automated distribution networks. In such networks, configuration and compensation level as well as loads insertion status can be remotely controlled. The considered SR problem should be handled using Multiobjective Optimization, MO, techniques since its solution requires a compromise between different criteria. In the adopted formulation, these criteria are the supply of the highest number of loads and the minimum power losses. The Authors propose a new MO approach, the Non-dominated Sorting Fuzzy Evolution Strategy, NS_FES, which uses part of the Non-dominated Sorting Genetic Algorithm, NSGA, proposed by K. Deb. Th…

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…

Effects of electrical and mechanical parameters on the transient voltage stability of a fixed speed wind turbine

Abstract In this paper the dynamic behaviour of a wind turbine connected to the grid is examined. The model of the fixed speed wind turbine has been developed with the Simulink simulation tool (Matlab Inc.) It is composed of the induction generator, the shaft system, an aerodynamic model of the wind turbine rotor and the pitch control system. Using this model, a three-phase fault is applied close to the wind turbine and cleared by disconnecting the faulty line. The rigorous implementation of the simulink model allowed the authors to evaluate the exact dependence of various electrical parameters for the induction generator on voltage stability. Furthermore, the effects of wind turbine mechan…

An analysis of feed’in tariffs for solar PV in six representative countries of the European Union

Abstract In this paper, after a brief review on the main support policies for Photovoltaic (PV) systems in Europe, the specific situations of six representative countries (France, Germany, Greece, Italy, Spain and the U.K.) are examined, with the purpose of highlighting the main differences in the implementation of the feed’in tariff (FiT) support policies adopted for PV systems. In particular, a comparison based on the calculation of economic indexes, as the Discounted Cash Flows (DCF), the Pay-Back-Period (PBP), the Net Present Value (NPV) and the Internal Rate of Return (IRR), for different sized PV systems shows that a specific FiT can sometimes be inconvenient for the producer and that…

Analisi economico-finanziaria degli investimenti sul fotovoltaico in Italia

Alla luce del meccanismo incentivante vigente in Italia a favore degli impianti fotovoltaici e dei risultati raggiunti in termini di numero di impianti e potenza installata, si riporta un’analisi di sensitività degli indici di redditività dell’investimento e le prospettive di sviluppo potenziale del fotovoltaico in Italia sino al 2020.

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…

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…

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…

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…

Fuel Cell in configurazione Range Extender

L’obiettivo che questo articolo si propone di perseguire è di valutare la fattibilità tecnica e le implicazioni conseguenti alla sostituzione, in un gruppo di continuità statico, delle batterie tradizionali con le celle a combustibile, quali sorgenti di energia in corrente continua. La configurazione circuitale proposta, denominata fuel cell in configurazione range extender, presenta una struttura estremamente versatile e modulare sotto almeno due punti di vista. In primo luogo il sistema si integra perfettamente con i gruppi di continuità statici tradizionali, per i quali è sufficiente sostituire i pacchi batteria con uno stack di celle a combustibile. In secondo luogo per modificare le ca…

Financial Measures for Supporting Wind Power Systems in Europe: A Comparison between Green Tags and Feed’in Tariffs

Distributed Generation demonstrates to be able to significantly influence the electric power system, bringing considerable benefits to the quality of service and improving the energetic efficiency of the distribution network. In particular, in the last few years, Distributed Generation from renewable energy sources is considerably increased thanks to the many support policies promoted worldwide with the aim of facing the environmental issue and the problem of the permanent rise of prices of the fossil energy. In this contest, after a brief review on the financing strategies carried out in Europe in the last decade for promoting the recourse to renewable energy, the paper presents a comparis…

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…

Battery storage systems for peak load shaving applications: Part 2: Economic feasibility and sensitivity analysis

This paper is the second of a two-part series, aiming to evaluate the economic feasibility of electrochemical storage systems in peak load shaving applications. The battery energy storage system (BESS) is considered to be added to a private facility, with the aim of reducing the customer electricity bill. The BESS is charged during the night, when the electricity prices are the lowest and discharged during the daily hours, when the prices are the highest, contemporary achieving a leveling of the daily usage pattern. The economical evaluations are carried out considering four different electrochemical technologies: lithium-ion (li-ion), advanced lead-acid, sodium-sulphur (NaS) and flow batte…

An improved method for determining voltage collapse proximity of radial distribution networks

The two-bus equivalent model is commonly used for voltage stability studies in both distribution and transmission systems. The paper presents a simple method to evaluate, for each bus, the parameters which define the equivalent circuit of a radial distribution network. In particular, a straightforward way for determining the Thévenin equivalent impedance behind a load node is proposed, which allows to better identify the maximum loading point beyond which the voltage collapse takes place in the network. Simulation results show that the proposed method is significantly more accurate than other existing methods on evaluating the critical power at a particular node (i.e. the weak node of the n…

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…

Fixed speed wind turbine generator model validation and dynamic simulation using Matlab/Simulink

In the last two decades an increasing amount of electricity has been generated from renewable sources in order to mitigate the environmental impact of the conventional power plants. In the next future wind turbines may affect the behaviour of electrical power system. This paper describes the model of a typical fixed speed wind turbine connected to the grid; the model is developed in the simulation tool Matlab/Simulink. It’s composed by the aerodynamic system, the shaft model (two-mass system), the induction generator (fifth order model) and the stall control system of the wind turbine rotor. The validation of the wind turbine model is made in steady-state operation, and the results are veri…

Influence of ANN parameters on the performance of a refined procedure to solve the load-flow problem

In recent years, interest in the application of Artificial Neural Networks (ANN) to electrical power systems has grown rapidly. In particular the use of ANN in the solution of the load-flow problem in wide electrical networks is an interesting research topic, because it constitutes a good alternative to the classical numerical algorithms. In this paper a refined solution strategy based on statistical methods, on a particular Grouping Genetic Algorithm (GGA) and on Progressive Learning Network (PLN) is presented. Tests on the solution of load-flow equations of the standard IEEE 118 bus network confirm the good potential of this approach; in particular the search for optimal values of the PLN…

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…

Simulation of photovoltaic installation connected to the grid with storage system

Abstract In the present paper, a new approach for the management of energy resources in a research laboratory is proposed and evaluated. A simulation study for the photovoltaic (PV) installation was conducted under the Tunisian-Italian cooperation project DE.DU.ENER.T, using renewable energy and economic criteria. The aim of the study is to improve the energy efficiency in order to minimize the electricity cost consumed in the laboratory. A Hybrid Renewable Energy System consisting of a photovoltaic field of 12KWc was installed to reduce the exorbitant bills, due to intensive energy equipment such as drying ovens and workstations, using sustainable, green and clean sources. In addition, a s…

Economic impact of Ice Thermal Energy Storage Systems in residential buildings in presence of double-tariffs contracts for electricity

Thermal energy storage is one of the most important methods of demand-side load management, thanks to the capacity of reducing significantly the peak power demand for air conditioning in buildings. Thermal Energy Storage Systems (TESS) are indeed used for producing and storing cooling capacity during off-peak hours (in particular during night hours) to meet the following day's air conditioning requirements. The current paper presents a study on the effects of the installation of Ice TESS for cooling on the power daily profile of residential buildings, and examines the economic repercussions on the electricity billing. With reference to this second theme, the paper examines, in particular, t…

Risk evaluation and creep in conventional conductors caused by high temperature operation

The advent of electricity market deregulation, the increased operating and overload temperatures of transmission line conductors have caused concern among TSOs (Transmission System Operators) and DSOs (Distribution System Operators) about the effect of elevated temperatures on conventional bare conductors of existing line. Nowadays building new lines is very difficult cause of increased costs to obtain rights of way, public intervention, etc.... Cost and lead times required to place new lines into service are now increased and the business in electric market is reduced for the limited possibility of transmission. Therefore, utilities are attempting to gain as much capacity as possible modif…

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…

Stationary battery technologies in the U.S.: Development Trends and prospects

Abstract In the last years, stationary battery systems started to attract the attention of stakeholders thanks to their unique ability to decouple power generation and load over time, providing the ancillary services necessary for the stability and the reliability of the electrical system. This is especially true in the presence of high levels of penetration of renewable energy technologies, like wind and solar photovoltaic (PV), because of increased fluctuations in the electricity produced by these renewable sources. Despite the growing interest in energy storage technologies, the academic literature has not completely assessed the development trends of this sector. In order to fill this g…

Comparative analysis of different supporting measures for the production of electrical energy by solar PV and Wind systems: Four representative European cases

Abstract In the 9th of March 2007, the European Council decided a fixing goal of 20% contribution of the renewable energy sources (RES) on the total European electric energy production in 2020. In order to reach such an ambitious goal, all the European countries are adopting different support policies for encouraging the installations of RES-based generation systems. In this paper, after a brief review on the main support policies for RES in Europe, the specific situations of four representative countries (France, Germany, Italy and Spain) are examined, with the purpose of putting into evidence the main differences in the support policies adopted for Photovoltaic (PV) and Wind systems. In p…

Technical and Economical Aspects on Integrated PV-UPS Systems

This paper shows a technical-economical analysis of a novel Uninterruptible Power Systems (UPS) configuration, in which the backup batteries would be replaced by a photovoltaic (PV) system. Many interesting technical and economical issues concerning the proposed configuration are discussed against the traditional UPS and backup batteries solution. Moreover the technical solutions concerning the proposed integrated system realized using a double conversion UPS are motivated. Finally the operating costs of the proposed integrated PV-UPS system and the classical system with UPS and batteries with different sizes, and as the back-up time varies, are also compared and interesting results have be…

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.

Wind Turbine Mechanical Characteristics and Grid Parameters Influence on the Transient Voltage Stability of a Fixed Speed Wind Turbine

This paper describes the effect of wind turbine mechanical characteristic of construction and grid parameters on the transient voltage stability of a fixed speed wind turbine (FSWT) connected to a simple grid. The model of FSWT has been developed in Matlab/Simulink. Using this model, a three-phase fault is applied close to the wind turbine (WT) and cleared by disconnecting the faulted line. The effects of mechanical construction of WT and of grid parameters on the voltage stability of this simple case are evaluated and discussed. The considered parameters are the inertia coefficient of the WT, the short-circuit power at the connection bus, the hub-generator resonant frequency, the wind spee…

Experimental study of the combined RES-based generators and electric storage systems for public buildings

Abstract In the present paper, a new approach to the management of energy resources in the Research and Technology Centre of Energy (CRTEn -Tunisia) is proposed and evaluated by the monitoring of a PV installation realized for the cooperation project DE.DU.ENER.T, using renewable energy and economic criteria. The aim of this project is to improve energy efficiency order to minimize the electricity cost consumed at the CRTEn laboratory. According to the bills of electricity received, we noticed that there is a high consumption of electrical current. So, we targeted to install a photovoltaic field of 12KWc to reduce these bills by using the sustainable, green and clean sources. A theoretical …

Voltage collapse proximity indicators for radial distribution networks

Based on the single-line equivalent system of a radial distribution network, two simple methods to evaluate two efficient voltage collapse proximity indicators are presented and discussed. The two methods differ on the determination of the parameters which define the equivalent system from which the indicators are derived. Both methods can be conveniently used jointly for on-line applications to assess the state of a distribution system from the viewpoint of voltage stability; the first to monitoring the stability margin of the whole system loading, the second to sharpen the stability analysis at the critical node when the system operating point is in the vicinity of the loadability limit. …

Modeling, Simulation and Experimental Verification of a Static Series Compensator (SSC) for Voltage Sag Mitigation

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.

Transient stability simulation of a fixed speed wind turbine by Matlab/Simulink

This paper describes the dynamic behavior of a typical fixed speed wind turbine connected to the grid; the model is developed in the simulation tool Matlab/Simulink and created as a modular structure. The pitch control system is used for stabilization of the wind turbine at grid faults. In this way, voltage stability of the system with grid-connected wind turbines can be improved by using blade-angle control for a temporary reduction of the wind turbine power during a short-circuit fault in the grid. This paper shows a new variable control for maintaining of voltage stability, when a three-phase fault is applied close to the wind turbine and cleared by disconnecting the affected line. In th…

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…

Effects of Electrical Parameters of Induction Generator on the Transient Voltage Stability of a Fixed Speed Wind Turbine

This paper describes the effect of electrical parameters of the induction generator on the transient voltage stability of a fixed speed wind turbine connected to a simple grid; the dynamic behavior of a wind turbine connected to the grid is examined. The model of the fixed speed wind turbine has been developed in the simulation tool Matlab/Simulink. Itpsilas composed by the induction generator, the shaft system, the aerodynamic model of the wind turbine rotor and the pitch control system. Using this model, a three-phases fault is applied close to the wind turbine and cleared by disconnecting the faulted line. The effect of different electrical parameters of the induction generator on the vo…

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…

Demand side management and Distributed on Site actions benefits

Global warming and energy demand are nowadays becoming one of the major issues of the third millennium, mainly because human activities seem to have a clear impact on the raise of CO2 emissions as never it has been experienced in the past. Among the different factors affecting CO2 emissions, energy demand from buildings constitutes one of the most important actors. Energy Management (EM) actions can reduce the energy consumption of the system and minimize peaks-level, by using a distributed control over every house. These local actions can greatly contribute to reduce the impact on the global CO2 emissions. An evaluation of the potential energy saving and CO2 emissions reduction on building…

Independent energetic grids for a smart island: Model and design of a microgrid for a small Italian island

Unlike many Italian peninsular areas, which are increasingly turning to a diverse supply of renewable resources to generate electricity, Italian not-interconnected small islands continue to rely on oil for their electricity and other energy needs (e.g. transports). Small-scale electricity systems, that are not connected to a larger electricity grid, are usually more expensive. The present paper proposes the functional design of an innovative Smart Grid which allows changing an Italian small not-interconnected island, Pantelleria, into a smart island, towards a more sustainable energy model. In detail, a techno-economic feasibility study is performed in order to design a Smart Grid at Pantel…

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…

Study and simulation of photovoltaic installation connected to the grid with storage system

In the present paper, a new approach to the management of energy resources in a research laboratory is proposed and evaluated by a simulation for the PV installation realized for the Tunisian-Italian cooperation project DE.DU.ENER.T, using renewable energy and economic criteria. The aim of this project is to improve energy efficiency order to minimize the electricity cost consumed at the laboratory, because according to the bills of electricity received we noticed that there is a high consumption of electrical current, from the STEG grid, and especially by the energy intensive equipment such as drying ovens and all the workstations. So we targeted to install a photovoltaic field of 12KWc to…

Monitoring of renewable energy prototype for the DEDUENERT research project

In this paper, we present a renewable energy sustainable micro-system installed upon a platform located in the Research and Technology Centre of Energy in Borj Cedria Techno park (Tunisia). This prototype has been conceived within the ENPI (European Neighborhood and Partnership Instrument) cross-border cooperation Italy-Tunisia 2007–2013 research project framework. This project's overall goal is to develop a common strategy for the deployment of renewable energy and energy efficiency by endorsing the cooperation between Italy and Tunisia. The focus is to implement the use of sustainable energy microsystems that generate electricity from various renewable sources (solar thermal, photovoltaic…

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…

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.

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…

Fast solution of radial distribution networks with automated compensation and reconfiguration

Abstract Optimal operation of radial distribution networks with automated compensation and reconfiguration requires the solution of a combinatorial optimisation problem, since the variables are the on/off status of capacitor banks and the open/close status of tie-switches. The solution approaches recently proposed use iterative algorithms such as genetic algorithms, simulated annealing and tabu search, for which the network needs to be solved in different configurations and at different compensation levels. The aim of this evaluation is that of attributing a quality index to each solution so that all the solutions can be suitably ordered. In an automated network, any configuration can be ob…

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…

Stationary battery systems in the main world markets: Part 2: Main trends and prospects

Stationary battery systems are gaining a lot of interest in recent years, mainly because of their ability to balance generation and demand of electricity over time. The intermittent nature of renewable generation connected to the power grid is causing major stability and reliability issues in the power system, that can be solved also using stationary storage systems, able to provide the ancillary services necessary to the proper operation of the power network. Despite the considerable advantages offered by these technologies, the electrochemical storage industry is still in the nascent state and it is important to identify the main trends and prospects in relation to future technical develo…

Transient stability analysis for symmetrical and unsymmetrical faults in mixed three-phase and six-phase power systems

Abstract The aim of this paper is to analyse the transient stability of a three-phase power system with six-phase lines interconnected by three-phase to six-phase transformers. For these mixed power systems a transient stability analysis is performed under all main types of disturbances (short-circuits, generator and load rejection, line outages), particularly in the case of faults at six-phase buses. A generalized procedure to evaluate transient stability is explained in detail. It is based on the symmetrical components method, which allows one to consider also unsymmetrical faults both at three-phase and six-phase buses. For every possible unsymmetrical short-circuit an equivalent fault a…

A Package for the Analysis of Automated MV Distribution Networks

A fuzzy-logic based evolutionary multiobjective approach for automated distribution networks management

In this paper, a methodology to treat constrained scheduling problems based on the repeated application of a fuzzy-logic-based multiobjective algorithm is presented. The application domain is that of automated distribution systems management. In particular, the problem of voltage regulation and power loses minimization is here considered. The classical formulation of the problem of optimal control of shunt capacitor banks and under load tap changers, ULTC, located at high voltage/medium voltage (HV/MV) substations has been coupled with the optimal control of tie-switches and capacitor banks on the feeders of a large radially operated meshed distribution system with the aim of attaining mini…

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…

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…

On the effects of HV/MV stations on global grounding systems

The METERGLOB project has faced the issue of the identification of Global Grounding Systems. One of the main point of the problem is to define if an interconnection of single grounding systems gives place to a Global Grounding System in any condition and for every kind of ground fault. This paper focuses the attention on what happens in the case of single line to ground fault inside a HV/MV station whose ground electrode is connected to the cable' shields of the MV lines outgoing the station and supplying the secondary substations of a given area.

Voltage Regulation and Power Losses Minimization in Automated Distribution Networks by an Evolutionary Multiobjective Approach

In this paper, the problem of voltage regulation and power losses minimization for automated distribution systems is dealt with. The classical formulation of the problem of optimal control of shunt capacitor banks and Under Load Tap Changers located at HV/MV substations has been coupled with the optimal control of tie-switches and capacitor banks on the feeders of a large radially operated meshed distribution system with the aim of attaining minimum power losses and the flattening of the voltage profile. The considered formulation requires the optimization of two different objectives; therefore the use of adequate multiobjective heuristic optimization methods is needed. The heuristic strate…

Feasibility analysis and study of a grid-connected hybrid electric system: Application in the building sector

This paper represents the feasibility study and analysis of a grid-connected hybrid (PV-Wind) system with battery, realized within the project DE.DU.ENER.T and installed in the research centre CRTEn located in the northern Tunisia in the city of Borj-Cedria. The main objective of this work is to exploit renewable sources of electrical energy production to electrify the desired building. So, to minimize electricity consumption costs, reduce the adverse effects of pollutants products from the diesel power systems and sometimes happen to sell the surplus of energy produced. The HOMER (Hybrid Optimization Model of Electric Renewable) software is used to estimate system size and its performance …

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…

Feed-in Tariffs for Grid-connected PV Systems: The Situation in the European Community

Distributed generation demonstrates to be able to significantly influence the electric power system bringing considerable benefits to the quality of service and improving the energetic efficiency of the distribution network. In particular, in the last few years, distributed generation from renewable sources is considerably increased thanks to the many support policies promoted worldwide with the aim of facing the environmental issue and the problem of the permanent rise of prices of the fossil energy. In this contest the paper presents a study of the "feed-in tariffs" financing measure carried out, at present, in many European countries and responsible of the increase in these last years of…

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…

Economic analysis of different supporting policies for the production of electrical energy by solar photovoltaics in western European Union countries

Abstract Within various renewable energy technologies, photovoltaics (PV) today attracts considerable attention due to its potential to contribute a major share of renewable energy in the future. However, PV market development is, undoubtedly, dependent on the political support of any given country. In this paper, after a brief analysis of national support policies in PV technology in western European Union (EU) countries, the authors perform an economic analysis of the main support mechanisms as implemented in the same countries, based on the calculation of the cash flow, the Net Present Value (NPV) and the Internal Rate of Return (IRR) indices. The analysis shows that in some situations s…

A simple operation strategy of battery storage systems under dynamic electricity pricing: An Italian case study for a medium-scale public facility

In the electricity market, wholesale energy prices depend on the balance between energy production and load demand. In the last few years, electricity market has become more and more flexible as many utilities have started to replace the fixed retail prices schemes with prices changing during the day. Dynamic pricing, also known as Real-Time Pricing (RTP), reflects the trend of the wholesale market and allows to reduce the volatility of the wholesale prices, also contributing to a reduction of demand peaks. Electricity customers take advantage of dynamic pricing by shifting their consumption according to the real-time prices or by using Battery Energy Storage Systems (BESS) to shift electri…

Comparative economic analysis of support policies for solar PV in the most representative EU countries

Abstract The purpose of this paper is to study the positions of some European Union (EU) countries on the development of PV systems. After a review of the main support policies for PV systems in Europe, the specific situations of five representative countries (France, Germany, Greece, Italy and the U.K.) are examined, with the purpose of describing the main differences in their implementation of support policies adopted for PV systems. In particular, comparisons based on economic indexes such as the net present value (NPV) and the internal rate of return (IRR) are carried out for different sized PV systems, showing that in some situations support policies can be inconvenient for the PV syst…

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…

On the Interconnections of HV–MV Stations to Global Grounding Systems

The interconnection of grounding systems of HV-MV stations via the armors of medium voltage cables, is herein analyzed to verify the effects on touch voltages in ground-fault conditions. The major contributions of this paper are two: the analysis of the impact of an HV ground-fault on a global grounding system (GGS), and the analysis of the parameters that may affect safety due to the interconnection between HV-MV stations and the GGS. The authors have analyzed cases when the connection of an HV-MV station to a GGS improves safety, and then may introduce hazards under ground-fault conditions. Two main issues are herein discussed: 1) the transfer of dangerous voltages to substations, due to …

Economical Analysis of Financial Supports for Large-Scale Photovoltaic PV plants in Eastern Europeen Union Countries

Today, photovoltaic (PV) attracts considerable interest among renewable energy sources (RES), because of its potential to significantly contribute to the future of clean energies. However, PV development is strongly related to the support policies introduced by national governments. The modification or fading out of such support schemes can strongly influence the development of the PV market in any given country. Although the PV market in European developing countries is still quite small, it has been growing rapidly in recent years. Until 2006, the installation of small off-grid PV plants prevailed in eastern EU countries. Starting from 2008, large-scale on-grid PV plants have been put int…

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 …

Economic analysis of different supporting policies for the production of electrical energy by solar photovoltaics in eastern European Union countries

Today, photovoltaic (PV) attracts considerable interest in relation to renewable energy technologies, because of its potential to contribute significantly to the future of renewable energy. However, PV market development is related strongly to the support policies introduced by national governments, defined in national laws. The modification or fading out of such incentive schemes can strongly influence the development of the PV market in any given country. In this paper, after a brief review of national support policies in PV technology in eastern European Union (EU) countries, the authors perform an economic analysis of the main support mechanisms that are implemented in these countries. …

UPS fuel cell based: An innovative back-up system

The aim of the paper is to evaluate the technical feasibility and aspects related to the use, in an Uninterruptible Power Supply (UPS), of fuel cells instead of traditional electrochemical batteries. The proposed system, named UPS-FCB (Fuel Cell Based) presents a modular and versatile system configuration; particularly it is possible to integrate it with traditional UPS. Moreover the system features can be modified in terms of power, reliability, back-up time, etc., by changing the power devices. A detailed experimental analysis has been carried out on a passive stand-by UPS integrated with a FCB; experimental results can be easily extended to the other possible system architectures. © 2007…

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…

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…

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…

ECONOMIC ANALYSIS OF SUPPORT POLICIES IN PHOTOVOLTAIC SYSTEMS: A COMPARISON BETWEEN THE TWO MAIN EUROPEAN MARKETS

The development of the photovoltaic (PV) sector in the last decade was spurred by the implementation of various support strategies aimed at reducing the gap between PV energy cost and the energy price for conventional generation. The deployment of support policies has pushed the reduction of PV energy costs, but despite this PV is still not very competitive and its development still requires adequate support mechanisms, simple grid connection procedures, and so on. This chapter provides a technical-economic analysis of investments in PV systems, evaluating the positioning of the main European markets (Germany and Italy), with the purpose of highlighting the main differences in the implement…

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…