Search

Electric vehicles are the most promising sustainable transport technology for solving problems linked to the internal combustion engine vehicles. Wireless charging reduce the main problems associated with electric vehicles, driving range, charging time and size and cost of the battery. Inductive power transfer is the most promising technology for dynamic wireless charging of electric vehicles, which can be used to supply the motors and charge the battery while moving. This paper presents a comparative study of a dynamic wireless power transfer system for charging electric vehicles driving on three stretches of traffic road (motorway, highway and urban stretch) in Cadiz (Spain). The study analyses the electricity consumption demanded by the dynamic wireless power transfer system and the battery state-of-charge of the electric vehicles that travel the stretch to evaluate the increase of autonomy, the length of the stretch or speed of the vehicle for achieving a specific increase of state-of-charge. The results show a great dependence on stretch of road, with large fluctuations in the urban stretch and more stability in the highway and motorway. This study could help to design stretches of roads with dynamic wireless power transfer and to quantify the power and energy demanded by the system.

Although electric vehicles (EVs) are experiencing a considerable upsurge, the technology associated with them is still under development. This study focused on the control and operation of a medium-voltage direct-current (MVDC) microgrid with an innovative decentralized control system, which was used as a fast charging station (FCS) for EVs. The FCS was composed of a photovoltaic (PV) system, a Li-ion battery energy storage system (BESS), two 48 kW fast charging units for EVs, and a connection to the local grid. With this configuration and thanks to its decentralized control, the FCS was able to work as a stand-alone system most of the time though with occasional grid support. This paper presents a new decentralized energy management system (EMS) with two options to control the power sources of the FCS. The choice of the power source depends on the MVDC bus voltage, the state-of-charge (SOC) of the BESS, and the control option of the EMS. This control was tested by simulating the FCS, when connected to several EVs and under different sun irradiance conditions. Simulation results showed that the FCS operated smoothly and effectively, which confirms the feasibility of using this technology in EVs.

This paper presents an overview of the state-of-the-art of research on control strategies or energy management systems for DC networks and microgrids. For this purpose, a systematic literature review was performed, which classified the research on the topic and identified the interconnections between the different approaches described in the publications selected. The work reviewed was initially classified into two main categories, based on a set of distinguishing characteristics identified in the control strategies. These categories were the following: (1) active load sharing (which includes the subcategories of centralized control and of master–slave control; (2) droop control methods. A third ad hoc category was also established for the approaches that did not fit in the other two categories. Additionally, secondary topics affecting the control strategies were also analyzed, such as the configuration of DC networks, commonly used control methods and factors, communication system relevance, and finally, the simulation and experimental techniques used for validation. Moreover, this systematic review permitted the identification of current research gaps as well as the proposal of new research lines. The results obtained not only are useful as a guide for researchers, who are starting out in the field, but they also highlight interesting research questions that more experienced researchers can actively pursue.

The use of distributed charging stations based on renewable energy sources for electric vehicles has increased in recent years. Combining photovoltaic solar energy and batteries as energy storage system, directly tied into a medium voltage direct current bus, and with the grid support, results to be an interesting option for improving the operation and efficiency of electric vehicle charging stations. In this paper, an electric vehicle charging station supplied by photovoltaic solar panels, batteries and with grid connection is analysed and evaluated. A decentralized energy management system is developed for regulating the energy flow among the photovoltaic system, the battery and the grid in order to achieve the efficient charging of electric vehicles. The medium voltage direct current bus voltage is the key parameter for controlling the system. The battery is controlled by a model predictive controller in order to keep the bus voltage at its reference value. Depending on the state-of-charge of the battery and the bus voltage, the photovoltaic system can work at maximum power point tracking mode or at bus voltage sustaining mode, or even the grid support can be needed. The results demonstrate the proper operation and energy management of the electric vehicle charging station under study.

This paper is focused on the study of particle swarm optimization (PSO)-based PI controllers for the power control of a grid-connected inverter supplied from a hybrid renewable energy system. It is composed of two renewable energy sources (wind turbine and photovoltaic – PV – solar panels) and two energy storage systems (battery and hydrogen system, integrated by fuel cell and electrolyzer). Three PSO-based PI controllers are implemented: (1) conventional PI controller with offline tuning by PSO algorithm based on the integral time absolute error (ITAE) index; (2) PI controllers with online self-tuning by PSO algorithm based on the error; and (3) PI controllers with online self-tuning by PSO algorithm based on the ITAE index. To evaluate and compare the three controllers, the hybrid renewable energy system and the grid-connected inverter are simulated under changes in the active and reactive power values, as well as under a grid voltage sag. The results show that the online PSO-based PI controllers that optimize the ITAE index achieves the best response.

This paper presents a novel energy dispatching based on Model Predictive Control (MPC) for off-grid photovoltaic (PV)/wind turbine/hydrogen/battery hybrid systems. The renewable energy sources supply energy to the hybrid system and the battery and hydrogen system are used as energy storage devices. The denominated “hydrogen system” is composed of fuel cell, electrolyzer and hydrogen storage tank. The MPC generates the reference powers of the fuel cell and electrolyzer to satisfy different objectives: to track the load power demand and to keep the charge levels of the energy storage devices between their target margins. The modeling of the hybrid system was developed in MATLAB-Simulink, taking into account datasheets of commercially available components. To show the proper operation of the proposed energy dispatching, a simpler strategy based on state control was presented in order to compare and validate the results for long-term simulations of 25 years (expected lifetime of the system) with a sample time of one hour.

This paper presents a comparative study of four sizing methods for a stand-alone hybrid generation system integrating renewable energies (photovoltaic panels and wind turbine) and backup and storage system based on battery and hydrogen (fuel cell, electrolyzer and hydrogen storage tank). Two of them perform a technical sizing. In one case, the sizing is based on basic equations, and in the other case, an optimal technical sizing is achieved by using Simulink Design Optimization. The other two methods perform an optimal techno-economical sizing by using the hybrid system optimization software HOMER and HOGA, respectively. These methods have been applied to design a stand-alone hybrid system which supplies the load energy demand during a year. A MATLAB-Simulink model of the hybrid system has been used to simulate the performance of hybrid system designed by each method for the stand-alone application under study in this work. The results are reported and discussed in the paper.

This paper presents two novel hourly energy supervisory controls (ESC) for improving long-term operation of off-grid hybrid systems (HS) integrating renewable energy sources (wind turbine and photovoltaic solar panels), hydrogen system (fuel cell, hydrogen tank and electrolyzer) and battery. The first ESC tries to improve the power supplied by the HS and the power stored in the battery and/or in the hydrogen tank, whereas the second one tries to minimize the number of needed elements (batteries, fuel cells and electrolyzers) throughout the expected life of the HS (25 years). Moreover, in both ESC, the battery state-of-charge (SOC) and the hydrogen tank level are controlled and maintained between optimum operating margins. Finally, a comparative study between the controls is carried out by models of the commercially available components used in the HS under study in this work. These ESC are also compared with a third ESC, already published by the authors, and based on reducing the utilization costs of the energy storage devices. The comparative study proves the right performance of the ESC and their differences.

Improving grid connection of wind farms is a relevant issue to be addressed, especially for fixed-speed wind turbines. Certain elements, such as FACTS (Flexible AC Transmission Systems), are able to perform voltage and reactive power regulation in order to support voltage stability of wind farms, and compensate reactive power consumption from the grid. Several devices are grouped under the name of FACTS, which embrace different technologies and operating principles. Here, three of them are evaluated and compared, namely STATCOM (Static Synchronous Compensator), SVC (Static Var Compensator) and SSSC (Static Synchronous Series Compensator). They have been modeled in MATLAB / Simulink, and simulated under various scenarios, regarding both normal operation and grid fault conditions. Their response is studied together with the case when no FACTS are implemented. Results show that SSSC improves the voltage stability of the wind farm, whereas STATCOM and SVC provide additional reactive power.

Hybrid systems comprising battery energy storage systems (BESSs) and wind power generation entail considerable advances on the grid integration of renewable energy. Doubly fed induction generators (DFIGs) stand out among different wind turbine (WT) technologies. On the other hand, electrochemical batteries have proved to be valid for these purposes. In this paper, a comparative analysis is carried out between two alternative configurations for hybrid WT-BESS systems, where the BESS is connected either outside or inside the DFIG. The modeling of these two configurations and the control systems applied for achieving the coordinate operation of the energy sources (DFIG and batteries) are illustrated. The hybrid systems under study are evaluated by simulation under normal operation (wind speed fluctuations and grid demand changes) and grid faults. Simulation results show that both configurations improve the grid integration capability of the WT, although the configuration with external BESS presents better results since it can provide additional active/reactive power injection. Copyright © 2014 John Wiley & Sons, Ltd.

Energy storage systems (ESSs) appear as a viable solution to some of the stability and intermittency problems of wind power generation. As a consequence, it is crucial to develop adequate control strategies that allow the coordinate operation of both energy sources. Moreover, in order to minimize the impact of large wind farms on the power system, many countries have set strict grid codes that wind power generators must accomplish. Hence, it is also necessary to pay due attention to the fault ride through capabilities of these hybrid systems. In this paper two different hybrid configurations are modeled in MATLAB/Simulink, consisting on a doubly fed induction generator driven wind turbine and electrochemical batteries as ESS. They are simulated and compared under various operating conditions (i.e. real fluctuating wind speed input with variable active and reactive power grid demand, voltage sags, three-phase and single-phase fault to ground, and overvoltage). A conventional wind turbine without ESS is also considered as a base-case in order to highlight the main benefits of the hybrid schemes. The results show that by implementing one of the presented control strategies, it is possible to enhance the response to faults of the hybrid systems, achieving higher active power injection and helping the recovery to steady-state, thus improving the grid connection capabilities of hybrid wind farms.

Integrating energy storage systems (ESS) with wind turbines results to be an interesting option for improving the grid integration capability of wind energy. This paper presents and evaluates a wind hybrid system consisting of a 1.5 MW doubly-fed induction generator (DFIG) wind turbine and double battery-ultracapacitor ESS. Commercially available components are used in this wind hybrid system. A novel supervisory control system (SCS) is designed and implemented, which is responsible for setting the active and reactive power references for each component of the hybrid system. A fuzzy logic controller, taking into account the grid demand, power generation prediction, actual DFIG power generation and state-of-charge (SOC) of the ESSs, sets the active power references. The reactive power references are proportionally delivered to each element regarding their current limitations in the SCS. The appropriate control of the power converters allows each power source to achieve the operation defined by the SCS. The wind hybrid system and SCS are assessed by simulation under wind fluctuations, grid demand changes, and grid disturbances. Results show an improved performance in the overall response of the system with the implementation of the SCS.

This paper describes and evaluates an adaptive neuro-fuzzy inference system (ANFIS)-based energy management system (EMS) of a grid-connected hybrid system. It presents a wind turbine (WT) and photovoltaic (PV) solar panels as primary energy sources, and an energy storage system (ESS) based on hydrogen (fuel cell -FC-, hydrogen tank and electrolyzer) and battery. All of the energy sources use dc/dc power converters in order to connect them to a central DC bus. An ANFIS-based supervisory control system determines the power that must be generated by/stored in the hydrogen and battery, taking into account the power demanded by the grid, the available power, the hydrogen tank level and the state-of-charge (SOC) of the battery. Furthermore, an ANFIS-based control is applied to the three-phase inverter, which connects the hybrid system to grid. Otherwise, this new EMS is compared with a classical EMS composed of state-based supervisory control system based on states and inverter control system based on PI controllers. Dynamic simulations demonstrate the right performance of the ANFIS-based EMS for the hybrid system under study and the better performance with respect to the classical EMS.

This paper evaluates a hybrid powertrain based on fuel cell (FC), battery, and supercapacitor (SC) for the “Urbos 3” tramway, which currently operates powered by SC in the city of Zaragoza, Spain. Due to the dynamic limitations of the main energy source, a proton-exchange-membrane (PEM) FC, other energy secondary sources (ESSs), battery and SC, are needed to supply the vehicle power demand. Moreover, these energy sources allow the energy recovery during regenerative braking. The different sources are connected to a dc bus through dc-dc converters which adapt their variable voltages to the bus voltage and allow the control of energy flow between the sources and the load. The components of the hybrid tramway have been modeled in Matlab/Simulink and are based on commercially available devices. The energy management system used in this work to achieve a proper operation of the energy sources of the hybrid powertrain is based on predictive control. Simulations for the real cycle of the tramway show the suitability of the proposed powertrain and control strategy.

The entry into force of Royal Decree-Law 1/2012 has led to the elimination of the support schemes to promote the use of the energy from renewable energy sources existing to date in Spain, and thus, certain standstill of this sector activity. In this context, some renewable technologies, mainly photovoltaic solar, can find in self-consumption an alternative for promoting their development and use. The self-consumption in the form of net-metering is mainly characterized by the possibility that the consumer can generate in situ part of the consumed electricity and use the network as storage or supply system. This option is still under study by the Government, so that there is a draft of Royal Decree that has not yet been approved. The aim of this paper is to analyze the economic viability of the net-metering mode in dwellings with small power photovoltaic facilities, considering those options that can contribute to make them viable.

This paper focuses on describing a control strategy for a real tramway, in Zaragoza (Spain), whose current propulsion system is to be replaced by a hybrid system based on fuel cell (FC) as primary energy source and batteries and ultracapacitors (UCs) as secondary energy sources. Due to its slow dynamic response, the FC needs other energy sources support during the starts and accelerations, which are used as energy storage devices in order to harness the regenerative energy generated during brakings and decelerations. The proposed energy management system is based on an operation mode control, which generates the FC reference power, and cascade controls, which define the battery and UC reference powers in order to achieve a proper control of the DC bus voltage and states of charge (SOC) of battery and UC. The simulations, performed by using the real drive cycle of the tramway, show that the proposed hybrid system and energy management system are suitable for its application in this tramway.

Electric vehicles are the most promising sustainable transport technology for solving the environmental, economic and social problems associated to the internal combustion engine vehicles. The research and development of new charging methods is necessary for a further integration of electric vehicles in transport sector. Inductive power transfer is the most promising technology for dynamic wireless charging of electric vehicles, which can be used to supply the motors and/or charge the battery of the electric vehicle while it is moving. This charging system can help to reduce the size and cost of the battery, increase the driving range and expand the use of electric vehicles. This paper presents an analysis methodology of a Dynamic Wireless Charging system applied to evaluate the power and energy requirements for charging electric vehicles moving along a stretch of the A-381 Highway in Cadiz (Spain). The study shows the great dependency of the energy transferred to the electric vehicles with the speed and the great variability of power and energy requirements related to the daily traffic.

Currently, electric vehicles (EV) are going through an important emergence, nevertheless, the technology associated to them is still under development. This paper presents a fast charging station (FCS) for EVs supplied by renewable energy with a novel decentralized control of the system. The fast CS is composed of a photovoltaic (PV) system, an energy storage system (ESS), and a connection with the local grid. Thanks to this configuration, the FCS is able to work as a stand-alone system most of the time, with occasional grid support. The proposed control is based on the voltage control of the common medium voltage DC (MVDC) bus, to which all the energy sources are connected. Thus, depending on its voltage, the PV system, the ESS or the grid are used to supply the energy demanded by the EVs. To show the viability of this control, the charging of two EVs is simulated under different operating conditions. Simulation results show the proper operation of the FCS.

Electric power systems will need to accommodate large amounts of renewables and a growing number of DC loads with reduced costs and losses. Medium-voltage DC distribution lines can play a key role. Moreover, a higher availability and reliability of the power supply can be achieved with energy storage systems (ESSs). In this paper, a hybrid configuration merging both concepts is evaluated. A medium-voltage DC distribution system with an integrated ESS has been proposed, modelled, and simulated. Voltage source converters have been used for the AC/DC conversions. The ESS is connected to the DC bus through a dual active bridge enabling bidirectional power flow while covering a large voltage gap. The controllers for all converters and a supervisory control scheme have been implemented. Simulations show the capability of the hybrid configuration to fulfill variable grid demand regardless of the wind power generation, thus transforming a fluctuating source into a dispatchable supply.

SUMMARY This article presents a comparative study among four control strategies for the energy management of a fuel cell (FC) battery–powered hybrid system applied to a surface tramway of 400 kW, which, at present, operates as catenary-powered tramway in the center of Seville, Spain. The proposed hybrid system is composed of a polymer electrolyte membrane FC with a unidirectional dc/dc boost converter and a rechargeable nickel–metal hydride battery with a bidirectional dc/dc converter, both of which are coupled to a traction dc bus. This configuration allows a suitable control of the energy of the hybrid tramway and the traction dc bus voltage. The polymer electrolyte membrane FC and nickel–metal hydride battery models are designed from commercially available components. The control strategies presented in this work are as follows: (i) control strategy based on operating states of the tramway (state machine control), (ii) control strategy based on cascade control loops (cascade control), (iii) control strategy based on fuzzy logic (fuzzy logic control), and (iv) control strategy based on the fuel consumption minimization (equivalent consumption minimization strategy. The control strategies are tested and compared for the real driving cycle of the tramway. The simulation results reflect the optimal performance of the presented control systems. Copyright © 2012 John Wiley & Sons, Ltd.

This paper deals with the modeling and control of a hybrid system integrating a doubly-fed induction generator (DFIG) wind turbine and batteries as energy storage system (ESS). The modeling of the mechanical and electrical main components of a 1.5 MW wind turbine is described. Specific focus is to be taken on the power converter of the DFIG, since it allows the interconnection of the ESS to the generator and a proper energy management. A lead-acid battery is used as energy storage device, which is connected through a bidirectional DC/DC converter to the DC bus of the DFIG power converter. A new supervisory control system, responsible for the coordinate operation of power sources (DFIG wind turbine and ESS), is described and evaluated by simulation under wind speed fluctuations and grid demand changes. It is based on using the wind turbine as primary power source and the ESS as auxiliary power source, providing or storing the power mismatching between the actual wind power and grid demand, whenever the battery state-of-charge (SOC) remains within the recommended limits. This configuration increases the generation capability and smooths the output power fluctuations caused by the wind speed variability, and therefore, improves the grid integration of wind turbines.

This paper describes the confi guration, modelling and control of a new hybrid propulsion system for the Zaragoza tramway.The new tramway confi guration is composed by a Proton-Exchange- Membrane Fuel-Cell (PEM FC) as main energy source and a Li-ion battery and an Ultra-Capacitor (UC) as energy storage systems. Thus, the battery supports to the FC during the starting and absorbs the power generated by the regenerative braking. Otherwise, the UC, which is the element with the fastest dynamic response, acts mainly during power peaks which are beyond the operation range of the FC and battery. The FC, battery and UC provide with DC/DC converters which allow their connection to the DC bus and control the energy exchange. The new energy management system described is composed by three control loops in cascade for the FC converter and two control loops for the battery and UC. This control system has been evaluated for the real driving cycle of the tramway. The results show how the control system is valid for its application in this hybrid system.

This paper focuses on describing a control strategy for a real surface tramway powered by a hybrid system based on fuel cell and battery. This tramway, called Metro Centro , serves the centre of Seville, a city in Spain. Currently, it operates as catenary-powered tramway. The configuration and modeling of all principal components of the hybrid system are briefly described. The models, implemented in MATLAB-Simulink environment, have been designed from commercially available components. The implemented control is based on an equivalent consumption minimization strategy. It allows a suitable energy management of the hybrid system, minimizing the hydrogen consumption.

This paper presents a hybrid electric power system for a real surface tramway. The hybrid system consists of two electrical energy sources integrating a single dc/dc converter to provide the power demanded by the tramway loads (four electric traction motors and auxiliary services): (1) a Polymer Electrolyte Membrane (PEM) fuel cell (FC) as the primary and (2) a rechargeable Ni–MH battery as electrical energy storage to supplement the FC over the driving cycle. According to the requirements of the real driving cycle of the tramway, it was considered a 200 kW PEM FC system with two FCs connected in parallel and a 34 Ah Ni–MH battery. The PEM FC and Ni–MH battery models were designed from commercially available components. The power conditioning system provides the appropriate power for the tramway. It is composed of: (1) a unique dc/dc boot converter which adapts the FC output voltage to the 750 V traction standard dc bus; (2) three phase inverters to drive properly each electric motors; and (3) a braking chopper to dissipate excess of regenerative braking energy. Suitable state machine control architecture is presented for the hybrid system, its objective being to provide demanded power by the driving cycle, optimizing the energy generated. Following this objective, a new state machine control strategy based on eight states decides the operating point of each component of the system and a cascade control structure allows achieving the operating points determined by the strategy. Simulation results of the real driving cycle of the tramway check the adequacy of the hybrid electric power system.

This paper describes the configuration, modeling, and control of a fuel cell (FC)-battery-powered hybrid system for the Metro Centro tramway in Seville, Spain. The proposed hybrid system presents a polymer electrolyte membrane FC as the primary energy source and a nickel-metal hydride cell battery as the secondary energy source, which supplements the output of the FC during tramway acceleration or whenever else needed and cruise and for energy recovery during braking. The tramway presents a traction system which is composed of four traction induction motor drives. The hybrid system also supplies the power for the auxiliary services. The power conditioning system is composed of two converters: 1) a boost-type unidirectional dc/dc converter for the FC and 2) a boost-type bidirectional dc/dc converter for the battery. The energy management system (EMS) of the hybrid tramway determines the reference signals for the electric motor drives, FC, and power converters in order to regulate accurately the power from the two electrical sources. EMS also determines the reference signal for energy dissipation in braking chopper when required during regenerative braking. In this paper, the proposed hybrid system is evaluated for the real driving cycle of the tramway. The results demonstrate the hybrid system capability to meet appropriate driving cycle.

This paper describes the modelling and control system of a direct-drive PMSG wind turbine for effective active and reactive power generation control and voltage control at the grid connection point. This study focuses on the maximum power capability of the wind turbine, which is limited by its generator and power converter. The ability of this model and control strategy are assessed by means of simulations and discussed at length. The results of our study show that a PMSG wind turbine is able to actively participate in grid operation because it can independently control active and reactive power production (operating as a PQ node) or the active power and voltage at the connection node (operating as a PV node).

Since energy consumption and pollution levels are increasing worldwide, the traditional fossil fuel-based generation methods are open to debate. A considerable number of countries are promoting the use of renewable resources in order to set a new energetic scenario. Wind power generation needs to improve some specific aspects that hinder its development. Several devices have been designed and are currently in use to solve the problem of energy volatility, since they are able to store energy in different forms for a given period of time. All these devices have different characteristics; therefore, they behave dissimilarly under certain operating conditions. Lead-acid batteries are being used either for energy or power applications. However, there exist other devices that may provide better performance. These devices are here described and compared, coming to the conclusion that some of them will substitute current technology in the near future if they are able to improve several indicated aspects.

As a result of the increasing wind farms penetration on power systems, the wind farms begin to influence power system, and therefore the modeling of wind farms has become an interesting research topic. In this paper, new equivalent models of wind farms equipped with wind turbines based on squirrel-cage induction generators and doubly-fed induction generators are proposed to represent the collective behavior on large power systems simulations, instead of using a complete model of wind farms where all the wind turbines are modeled. The models proposed here are based on aggregating wind turbines into an equivalent wind turbine which receives an equivalent wind of the ones incident on the aggregated wind turbines. The equivalent wind turbine presents re-scaled power capacity and the same complete model as the individual wind turbines, which supposes the main feature of the present equivalent models. Two equivalent winds are evaluated in this work: (1) the average wind from the ones incident on the aggregated wind turbines with similar winds, and (2) an equivalent incoming wind derived from the power curve and the wind incident on each wind turbine. The effectiveness of the equivalent models to represent the collective response of the wind farm at the point of common coupling to grid is demonstrated by comparison with the wind farm response obtained from the detailed model during power system dynamic simulations, such as wind fluctuations and a grid disturbance. The present models can be used for grid integration studies of large power system with an important reduction of the model order and the computation time.

As a result of the increasing wind power penetration on power systems, the wind farms are today required to participate actively in grid operation by an appropriate generation control. This paper presents a comparative study on the performance of three control strategies for DFIG wind turbines. The study focuses on the regulation of the active and reactive power to a set point ordered by the wind farm control system. Two of them (control systems 1 and 2) are based on existing strategies, whereas the third control system (control system 3) presents a novel control strategy, which is actually a variation of the control system 2. The control strategies are evaluated through simulations of DFIG wind turbines, under normal operating conditions, integrated in a wind farm with centralized control system controlling the wind farm generation at the connection point and computing the power reference for each wind turbine according to a proportional distribution of the available power. The three control systems present similar performance when they operate with power optimization and power limitation strategies. However, the control system 3 with down power regulation presents a better response with respect to the reactive power production, achieving a higher available reactive power as compared with the other two. This is a very important aspect to maintain an appropriate voltage control at the wind farm bus.

As a result of increasing wind farms penetration in power systems, the wind farms begin to influence power system, and thus the modelling of wind farms has become an interesting research topic. Nowadays, doubly fed induction generator based on wind turbine is the most widely used technology for wind farms due to its main advantages such as high-energy efficiency and controllability, and improved power quality. When the impact of a wind farm on power systems is studied, the behavior of the wind farm at the point common coupling to grid can be represented by an equivalent model derived from the aggregation of wind turbines into an equivalent wind turbine, instead of the complete model including the modelling of all the wind turbines. In this paper, a new equivalent model of wind farms with doubly fed induction generator wind turbines is proposed to represent the collective response of the wind farm by one single equivalent wind turbine, even although the aggregated wind turbines operate receiving different incoming winds. The effectiveness of the equivalent model to represent the collective response of the wind farm is demonstrated by comparing the simulation results of equivalent and complete models both during normal operation and grid disturbances.

This paper presents a new Energy Management System (EMS) for a microgrid based on four energy sources: a wind turbine (WT), photovoltaic (PV) solar panels, a battery, and a hydrogen system, which is composed of a fuel cell (FC) and an electrolyzer. This novel control strategy optimizes the total cost of the hybrid system (generation and reposition costs) through lifetime estimations calculated hourly for each energy storage device (the battery and hydrogen system). This control strategy links the expected lifespans of the energy sources to their generation costs, i.e., when the lifespan is low, the generation cost increases and, consequently, this energy source will start to be used less. The performance of the novel EMS, including these estimations, was tested for an isolated load located in Alora (Spain) and compared with two simpler EMSs: EMS-1, which considered fixed generation costs and lifetimes, and EMS-2, which prioritized the use of the battery. Simulation results show the appropriate behavior for the novel EMS to optimize the generation costs and the number of required elements throughout the expected lifetime of the hybrid system (25 years).

This paper is about Astrodata, a Supervisory, Control and Data Adquisition system (SCADA). It was designed and implemented employing two important concepts: the effective cost and the sustainable automation. The SCADA is working at the Radio Astronomical Station of Havana. This solution has demonstrated to be more economical than the former solution implemented.

The increasing wind power penetration on power systems requires the development of adequate wind farms models for representing the dynamic behaviour of wind farms on power systems. The behaviour of a wind farm can be represented by a detailed model including the modelling of all wind turbines and the wind farm electrical network. But this detailed model presents a high order model if a wind farm with high number of wind turbines is modelled and therefore the simulation time is long. The development of equivalent wind farm models enables the model order and the computation time to be reduced when the impact of wind farms on power systems is studied. In this paper, equivalent models of wind farms with fixed speed wind turbines are proposed by aggregating wind turbines into an equivalent wind turbine that operates on an equivalent wind farm electrical network. Two equivalent wind turbines have been developed: one for aggregated wind turbines with similar winds, and another for aggregated wind turbines under any incoming wind, even with different incoming winds. The proposed equivalent models provide high accuracy for representing the dynamic response of wind farm on power system simulations with an important reduction of model order and simulation time compare to that of the complete wind farm modelled by the detailed model.

This paper is about Low Cost Automation. In it, a basic background about Havana Radioastronomical Station is described. It is showed a Real Time Supervisory and Control System named Astrodata. The System employs Virtual Instruments and Distributed I/O. Transfer information from sensors to computer it is made by communication network. Astrodata creates a database for off-line data processing. Data's primary processing is made by system on-line.

This chapter provides a basic understanding of modelling of wind turbines, including both the mechanical and electrical systems, and control schemes that enable a suitable operation of the wind turbines. An overview of the most widely used wind turbine concepts is performed and their models for integration in large power system dynamic simulations are described. The wind turbine concepts studied are: fixed-speed squirrel cage induction generator (FS-SCIG), wound rotor induction generator (WRIG) with variable rotor resistance (VRR), doubly fed induction generator (DFIG), and direct drive synchronous generator (DDSG).

This paper presents a comparative study of two new methods for voltage harmonic compensation of a stand-alone single phase inverter-based FC. The system under study is composed of: 1) Proton-Exchange-Membrane (PEM) FC including a unidirectional DC/DC converter, which converts the DC voltage delivered by the FC to the DC bus voltage; 2) single-phase pulse width modulated (PWM) inverter; 3) transformer; 4) L passive filter; and 5) linear and non-linear loads. The dynamic model of this system and the controls applied to the PWM inverter for voltage regulation and harmonic compensation are detailed in this paper. Simulation results show the effectiveness of the two purposed methods for voltage harmonic compensation to acceptable levels defined in grid codes.

This paper presents a sizing method and supervisory control for the suitable energy management of a stand-alone hybrid system with photovoltaic (PV) solar panels, hydrogen subsystem and battery. The battery and hydrogen subsystem, composed of fuel cell (FC), electrolyzer and hydrogen storage tank, act as energy storage and support system. A sizing method based on Simulink Design Optimization (SDO) of MATLAB is used to perform a technical optimization of the components of the hybrid system. The dynamic model of the designed hybrid system is detailed in this paper. The models, implemented in MATLAB-Simulink environment, are designed from commercially available components. It is designed, primarily, to satisfy the load power demand and, secondly, to maintain certain level at the hydrogen tank (hydrogen energy reserve), and at the state of charge (SOC) of the battery bank to extend its life.

In recent years, Fuel Cells (FC) have gained interest as energy source for stand-alone and grid connected applications, because they are very high-efficiency and multi-fuel power generators that require neither the burning of conventional fuels nor the mechanical equipment of conventional power generators. When FC are used with inverters for supplying AC loads, harmonic distortion in the supply voltage results in increased heating losses in loads, excite resonances and overload customer power factor correction equipment. Sensitivity of customer equipment to voltage distortion may be dependent on both the magnitude of the distortion levels and the specific harmonic components. For these reasons, it is important to keep the voltage harmonics within recommended levels. This paper presents a new method for voltage harmonic compensation of a stand-alone single phase inverter-based FC. The system under study is composed of: 1) Proton- Exchange-Membrane (PEM) FC including a unidirectional DC/DC converter, which converts the DC voltage delivered by the FC to the DC bus voltage; 2) single-phase pulse width modulated (PWM) inverter; 3) transformer; 4) L passive filter; and 5) linear and non-linear loads. The dynamic model of this system and the control applied to the PWM inverter for voltage regulation and harmonic compensation are detailed in this paper. Simulation results show the effectiveness of the purposed method for voltage harmonic compensation to acceptable levels defined in grid codes.

This paper presents a comparative study of four sizing methods for a stand-alone hybrid generation system integrating renewable energies (photovoltaic panels and wind turbine) and backup and storage system based on battery and hydrogen (fuel cell, electrolyzer and hydrogen storage tank). Two of them perform a technical sizing. In one case, the sizing is based on basic equations, and in the other case, an optimal technical sizing is achieved by using Simulink Design Optimization. The other two methods perform an optimal techno-economical sizing by using the hybrid system optimization software HOMER and HOGA, respectively.

Energy storage is key to expanding the use of wind power, since it allows the wind turbines to smooth the power fluctuations caused by the intermittent and largely unpredictable nature of wind power. This paper presents the modeling and control of a doubly fed induction generator (DFIG) wind turbine with a lead-acid battery as energy storage system. A supervisory control system is developed for a suitable energy management of the energy sources. The modeling and control of this hybrid generation system is evaluated by simulation under different operating conditions.

This paper compares two control strategies of a fuel cell (FC)-battery powered hybrid system integrating two dc/dc converters for the Metro-Centro tramway (400 kW) from Seville, Spain. Besides, modeling of each component is briefly presented. These models have been implemented in MATLAB/SIMULINK environment. A Polymer Electrolyte Membrane (PEM) FC is used in this work. The FC model characteristics are selected from a Nuvera 127 kW PEM FC. Two PEM FCs connected in parallel operate as primary energy source and a group of Ni-MH battery supplements the output of the FC during tramway acceleration or whenever else needed and provides regenerative braking energy recapture capability. Finally, the simulation results of both control configurations (Cascade and States Control Strategies) are presented for the real driving cycle of the tramway. The results demonstrate the hybrid system capability to meet appropriate driving cycle in both cases.

This paper compares two control configurations for a fuel cell (FC)-battery powered hybrid system for the Metro-Centro tramway (800 kW) from Seville, Spain. Besides, modeling of each components is briefly presented. These models have been implemented in MATLAB/SIMULINK environment. Polymer Electrolyte Membrane (PEM) FC model used in the simulations realized is a simplification of Jay T. Pukrushpan et al. model. The model characteristics are selected from a Nuvera 127 kW PEM FC. Four of this PEM FC´s are the primary energy source and a group of Ni-MH battery supplements the output of the FC during tramway acceleration or whenever else needed and provides regenerative braking energy recapture capability. Finally, the simulation results for both control configurations (States and Cascade Control Strategies) are presented for the real driving cycle of the tramway. The results demonstrate the hybrid system capability to meet appropriate driving cycle in both caseshese instructions give you basic guidelines for preparing camera-ready papers for conference proceedings.

This paper presents the arrangement, modeling and control of a hybrid system for a tramway. In order to supply the power consumption of the tramway (due to the auxiliary services and four traction induction motor drives), the hybrid system presents two power sources: 1) a Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) as primary energy source; and 2) a Ni-MH battery as secondary energy source, which serves as a supplement to the FC for tramway acceleration or for energy recovery during braking. In addition, a braking chopper is required to absorb the regenerative energy produced by motors deceleration when it cannot be absorbed by the battery due to its limitations. Both FC and battery are coupled to a dc/dc power converter, which enables an active control of the two power sources. An energy management system (EMS) is responsible for: 1) the appropriate distribution of the power demanded by the tramway between the power sources; and 2) the braking chopper operation when required during regenerative braking. The simulation results show the hybrid system capability to allow the tramway to properly follow the driving cycle.

This paper presents a fuel cell-battery powered hybrid system for transport applications, more specifically for a tramway. It uses a Polymer Electrolyte Membrane (PEM) fuel cell (FC) as primary energy source and a Ni-MH battery as secondary energy source, which serves as a supplement to the FC during the driving cycle. The hybrid system supplies the power consumption of the auxiliary services and the traction system, which is composed of four traction induction motor drives. The energy management system (EMS) of the hybrid tramway fixes the reference signals for: 1) the FC dc/dc boost converter in order to accurately distribute power between two electrical sources; 2) the electric motor drives; 3) energy dissipation in the braking chopper when required during regenerative braking. The proposed hybrid system is assessed for a real driving cycle. The results show the hybrid system capability to allow the tramway to properly follow the driving cycle.

Doubly fed induction generators based wind turbines are today one of the most widely used generation systems in wind farms due to the ability of variable speed operation and with decoupled control of active and reactive power. Nowadays these wind turbines are operating without generation limits, but the increasing wind power penetration in power systems must lead to that the wind farms have to operate with production limits imposed by the electrical system operators to maintain the stability of the electrical network. In this paper, a new control system of doubly fed induction generators based wind turbines is proposed for the control of active and reactive powers according to the imposed power limitations. This control system presents an active power controller, reactive power controller and pitch angle controller, in order to operate the wind turbine with optimum power efficiency or with limited active power and the demanded reactive power. This generation control provides a better grid integration of doubly fed induction generators

To determine the potential impacts of fuel cells on future distribution system, dynamic models of fuel cells should be created, reduced in order, and scattered throughout test feeders. This paper presents the implementation of an efficient method for computing low order linear system models of solid oxide fuel cells (SOFCs) from time domain simulations. The method is the Box-Jenkins algorithm for calculating the transfer function of a linear system from samples of its input and output.

In this paper, a new reduced model of wind farms with doubly-fed induction generators wind turbines is proposed for representing all the wind turbines of a wind farm by one single equivalent wind turbine. The simulation results demonstrate the effectiveness of the proposed reduced model to represent the collective response of a wind farm in the point of common coupling to grid during power system dynamic simulations. This model can be used for voltage and angle stability investigations of large power system with an important reduction of the model order and computation time.