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In a standalone hybrid wind-diesel-battery system, the battery lifetime is often optimistically over-predicted by hybrid system designers and battery manufacturers. As a result, battery replacement takes place more often than required. One of the reasons is due to the underestimation of battery wear from the short charge–discharge cycles, otherwise known as microcycles. A microcycle takes place when the power generation closely matches the load demand. The detrimental effect of microcycles on a battery-based standalone hybrid renewable energy system was previously investigated, however, only from the perspective of short-term renewable energy fluctuations. This research paper provides a new insight on the battery lifetime reduction, resulting from microcycles that are generated through the tower shadow phenomena. Downwind wind turbines are considered here, as their tower shadow effects are more significant compared to the upwind counterpart. This paper briefly presents the modeling of tower shadow profiles for both tubular and four-leg tower configurations. Experimental results have shown that the microcycles due to this nonideal effect are significant in a battery-based standalone hybrid system. The quantification of the battery lifetime reduction due to this effect is demonstrated. Finally, the paper concludes with a sensitivity analysis of the battery lifetime reduction for different tower configurations, operating at different load conditions. [ABSTRACT FROM PUBLISHER]

In this paper, the possibility of utilizing a wind turbine to recapture a portion of the kinetic energy losses of a car, irrespective of being a traditional car that is propelled by an internal combustion engine or an electric vehicle (EV) that is propelled by an electric motor, is appraised. To investigate the topic, a small wind turbine has been inserted at the back of the condenser of a car to recover a portion of the kinetic energy of wind passing through the condenser's crisscrossed bars. A portion of this wind is caused by wind existing outside the car, and the main portion is caused by the kinetic energy originating from the car movement. In the absence of the wind turbine, the wind passing through the condenser's crisscrossed bars hits the middle part of the car's chassis and loses its energy. Thus, not only the wind turbine uses a portion of the kinetic energy losses of the car to produce electricity but also, since it has been embedded at the back of the condenser, it has no impact on the aerodynamic coefficient of the car, i.e., it does not produce any extra resistive force. When the car is parked, and there is no kinetic energy resulting from the car movement, a small flow of wind available outside the car is converted into electricity stored in the car's battery. To realize the proposed scheme, a 100-W wind turbine, a permanent-magnet synchronous generator coupled to the turbine, and a novel built hybrid power generation system combining the wind-driven generator's output power with that of the car's battery have been embedded in an EV having a total weight of 1855 kg. Experimental measurements conducted under realistic operation of the EV are given that prove the traveling range of the EV and the power efficiency of the EV's power supply are enhanced by, 6.4 km and 0.2% respectively, by recovering only a portion of the kinetic energy losses of the EV. These two benefits also prove the novelty and contributions of this work in successfully recovering a portion of the kinetic energy losses of a car by using a small wind turbine embedded in the car. [ABSTRACT FROM AUTHOR]

This paper presents the performance of a controller for adjusting the power generated by the permanent magnet generator (PMG) in a wind energy conversion system (WECS), which has generated-charged battery units (BUs). The proposed controller is based on the Lagrangian relaxation unit commitment (LRUC) method to determine a command value for the PMG electromagnetic torque ($T_{e}^{*}$) at each wind speed. The determined value of $T_{e}^{*}$ is set to calculate command values for $q$ -axis currents that are required by the controllers operating the generator-side and charging power electronic converters (PECs). The performance of the LRUC-based controller is experimentally evaluated for a grid-connected 7.5-kW PMG-based WECSs with 4.44-kW BUs, when operated under various wind speeds and/or charging and discharging modes of the BUs. Performance results show that the proposed controller is capable of initiating fast and accurate responses to adjust the power generation of the PMG to meet the demands of the generator-side and charging PECs for different wind speeds, and/or charging and discharging of the BUs. These performance features are found to have minor sensitivity to the changes in wind speed, and/or levels of charging the BUs. [ABSTRACT FROM AUTHOR]

Plug-in electric vehicles (PEVs) tend to be treated as a new form of the mobile energy storage system with the potentiality to promote energy management in microgrids (MGs) and smart grid. However, a conflict of interest exists regarding the optimal capacity configuration and the optimal economic dispatch of PEVs. On one hand, MGs can maximize their benefits by mobile energy transmission as much as possible. On the other hand, MGs can also minimize total cost by reducing the investment cost of PEV charging/discharging infrastructures. Both objective functions need to be considered simultaneously. This paper presents a cooperative optimization method for capacity configuration and economic dispatch of electric vehicles in MGs considering across-time-and-space energy transmission (ATSET). Considering the differences of electricity prices in different time and space, the impact of ATSET on MG economic operation is analyzed, and a two-loop optimization model is utilized to optimize capacity configuration and economic dispatch of PEVs. Improved particle swarm optimization is used to implement cooperative optimization procedure, and the effectiveness of the proposed method is validated by detailed case studies. Results show that the total costs of the MG system and PEV owners can be reduced by the proposed cooperative optimization method. [ABSTRACT FROM AUTHOR]

This paper presents a passivity-based control (PBC) scheme for the switched reluctance generator (SRG) in small-scale wind energy conversion systems for dc microgrid applications. The main objective is to stabilize the output voltage in case the system supplies constant power loads (CPLs) and operates with maximum power point tracking (MPPT). Stability improvement and dc-link ripple reduction in the presence of CPLs is achieved using system-level modeling of SRG-based dc microgrid through the Euler-Lagrange system (ELS) from the viewpoint of the machine physical structure. Compared with other control methods, the proposed MPPT method based on passivity-based speed controller employs the back electromotive force (EMF) in the generation process as a position-dependent voltage source to overcome the major challenge of SRG complicated uncertain dynamic model. To deal with the time-varying inductance and back EMF of SRG, an adaptation mechanism is incorporated in the proposed adaptive PBC and the control design is constructed by using the Lyapunov theorem where the closed-loop stability is ensured. The effectiveness of the proposed method in avoiding instability effects of SRG and CPL with voltage ripple reduction and precise wind turbine speed tracking is investigated with simulation results and validated with experimental by using a four-phase, 8/6 SRG drive system. [ABSTRACT FROM AUTHOR]

High penetration of wind energy requires fast-acting dispatchable resources to manage energy imbalance in the power grid. Battery energy storage systems (BESS) are considered as an essential tool to decrease the power and energy imbalance between the scheduled generation (day ahead forecast) and the actual wind farm output. Control methodology or battery management greatly impacts performance of the ESS. Better performance of BESS reduces the minimum required size of batteries for wind variability mitigation. This paper proposes a novel control method for BESS to fulfill a production commitment. This method, called “predictive controller,” is based on updated forecast data to improve the performance of the energy storage and consequently reduce the required size of energy storage. The Sodium–Sulfur (NaS) type battery is selected for the simulation purposes. Results show that the predictive controller reduces the error (between scheduled generation and actual wind farm output) more than the simple method (also known as minute-by-minute method) and other proposed methods in the literature. Also, a new formulation for the battery lifetime estimation is introduced, and it is used to analyze the impact of the proposed method on the battery lifetime depreciation. [ABSTRACT FROM PUBLISHER]

This paper provides steady-state and transient analysis of the equivalent circuit of the 1 MWh battery tied to the grid for wind integration. It also discusses the installation of a 1 MWh battery system at Reese Technology Center (RTC) in Lubbock, Texas. The research involves deploying energy storage devices for application with wind turbine model to understand the transient behavior of the system under three phase fault conditions. A 1 MW/1 MWh battery storage system at the RTC is connected to the South Plains Electric Cooperative (SPEC) grid. The batteries are used for energy storage and for mitigation of transient conditions grid dynamics. In this paper, the equivalent circuit of the 1 MWh battery is modeled in PSCAD and analyzed for its charge and discharge characteristics under transient fault conditions when it is tied to the grid for wind integration. [ABSTRACT FROM AUTHOR]

Load management is usually not considered in details during the planning stage due to its complexity and uncertainty in nature. However, this practice is changed in microgrids since the load composition in microgrids is more specific and manageable. In addition, the development of advanced metering infrastructure provides a more convenient mechanism for data collection and system control. This paper presents an integrated resources planning model based on optimal direct load control (DLC) (such as control of the air-conditioning load) in microgrids for load shifting and peak shaving to reduce/defer investments and minimize total social costs. This paper begins with the introduction of DLC and the models of the relevant distributed generation resources, including photovoltaic, wind turbines, diesel engines, and batteries. An algorithm is presented to combine the microgrid planning and DLC strategy. The results of the case study show that the proposed model provides an effective approach for the least cost planning in microgrids by using load management as competitive virtual power sources. [ABSTRACT FROM PUBLISHER]

This paper presents the energy management for the decentralized generation systems (DGS) using the wind turbine with photovoltaic (PV) panels and the energy storage devices. For a high penetration level of the wind/PV generation, the energy storage device with a fast response is necessary to cover the shortfall or overflow of generation due to sudden variations of the wind or the sun. In addition, the requested energy by the residential appliances presents random behavior, which can be lower or higher than the produced energy from the renewable sources. Using the wind turbine and the PV power generation system with energy storage will reduce the fluctuations of the wind power and the load ones. The energy storage system requires capital investment; thus, it is important to estimate the reasonable storage capacities without an overflow size for the desired applications. In addition, a good strategy for energy management is necessary to reduce the variation impacts of the wind energy and the load for the battery and the residential appliances. The contribution of this paper is focused on energy management based on the frequency approach using the wind/load's fluctuating power sharing and the polynomial controllers. First, this method enables reducing for the battery and the microgrid the impacts of the microcycles due to the wind/load's power fluctuations. Second, it allows estimating the energy storage capacity without the overflow size. The performances of the proposed method are evaluated through some simulations and experimental tests using the summer load profile and the winter ones. [ABSTRACT FROM PUBLISHER]

This paper presents a control of a microgrid at an isolated location fed from wind and solar based hybrid energy sources. The machine used for wind energy conversion is doubly fed induction generator (DFIG) and a battery bank is connected to a common dc bus of them. A solar photovoltaic (PV) array is used to convert solar power, which is evacuated at the common dc bus of DFIG using a dc–dc boost converter in a cost effective way. The voltage and frequency are controlled through an indirect vector control of the line side converter, which is incorporated with droop characteristics. It alters the frequency set point based on the energy level of the battery, which slows down over charging or discharging of the battery. The system is also able to work when wind power source is unavailable. Both wind and solar energy blocks have maximum power point tracking (MPPT) in their control algorithm. The system is designed for complete automatic operation taking consideration of all the practical conditions. The system is also provided with a provision of external power support for the battery charging without any additional requirement. A simulation model of system is developed in MATLAB environment and simulation results are presented for various conditions, e.g., unavailability of wind or solar energies, unbalanced and nonlinear loads, and low state of charge of the battery. Finally, a prototype of the system is implemented using a 5-kW solar PV array simulator and a 3.7-kW wound rotor induction machine and experimental results are produced to reaffirm the theoretical model and design. [ABSTRACT FROM PUBLISHER]

This paper presents the design, control, and experimental investigation of an autonomous wind–solar hybrid energy system feeding 3-phase 4-wire loads. The wind energy block consisting of a double fed induction generator (DFIG) is equipped with maximum power point tracking (MPPT) algorithm. The control of DFIG consists of two converters, namely rotor side converter (RSC) and load side converter (LSC) connected back to back at dc link. The MPPT operation requires speed control, which is realized using field oriented control through RSC. The rotor position required for vector control is estimated with model reference and adaptive system algorithm. The voltage and frequency control is realized through LSC. The solar photovoltaic (PV) power is extracted using a dc–dc boost converter to the common dc link. The dc–dc converter is also equipped with MPPT algorithm to extract maximum power from the incident irradiance. The system is modeled in MATLAB and its performance is presented at conditions, e.g., unbalanced nonlinear load, varying wind speeds, and solar irradiation. Under all these conditions, currents flowing through stator windings of DFIG are balanced with low total harmonics distortion (THD). The THDs of load voltages under all operating conditions are also within requirement of IEEE 519 standard. Finally, simulated results are validated experimentally by developing a prototype of the system using a 5-kW solar array simulator and a 3.7-kW DFIG. [ABSTRACT FROM AUTHOR]

In the future power system with high penetration of renewables, renewable energy is expected to undertake part of the responsibility for frequency regulation, just as the conventional generators. Wind power and battery storage are complementary in accuracy and durability when providing frequency regulation. Therefore, it would be profitable to combine wind power and battery storage as a physically connected entity or a virtual power plant to provide both energy and frequency regulation in the markets. This paper proposes a real-time cooperation scheme to exploit their complementary characteristics and an optimal bidding strategy for them in joint energy and regulation markets, considering battery cycle life. The proposed cooperation scheme is adopted in a real-time battery operating simulation and then incorporated into the optimal bidding model. The scheme could improve the wind regulation performance score and allow for more regulation bids without affecting the battery life, thus significantly increasing the overall revenue. The validity of the proposed scheme and strategy are proved by the case study. [ABSTRACT FROM PUBLISHER]

In a wind-battery hybrid power system, minimal battery capacity is a crucial requirement to achieve economic operation. In this paper, an optimal power control strategy based on a first-order low-pass filter is proposed to minimize the battery capacity by adjusting the filter smoothing time constant. We demonstrate the mathematical relationship between the filter smoothing time constant and the fluctuation mitigation requirement during one sampling time, so the optimal filter smoothing time constant can be easily computed to minimize the battery capacity. Moreover, an online short-term power control is also considered to maintain the battery state of charge within a safe range and to regulate the battery power below its rating. The proposed power management approach is simple and easy to implement. In order to verify the effective features of the proposed power management approach, a case study is carried out along with some experimental verification. [ABSTRACT FROM AUTHOR]

This paper proposes a versatile control strategy for a standalone wound rotor induction generator (WRIG) with back-to-back converters supported by a battery at dc-link. The principal feature of the study is the operation of the generator as a commanded current source, to supply only sinusoidal current as desired, and the operation of battery fed Front End Converter (FEC) as a constant voltage source, which adapts to varying load conditions. Further, in implementing this feature, in a significant deviation from conventional approaches, to Rotor Side Converter (RSC) and FEC are redefined with a view to achieve versatility and reliability in stand-alone operation. In particular, the RSC is employed to track the maximum power (instead of load voltage and frequency control), whereas the FEC maintains a constant load voltage and frequency. It is revealed that there are multiple benefits of the proposed strategy such as inherent load balancing; capability to support critical loads solely by battery through the FEC as in an uninterruptible power supply (UPS), especially at low wind speeds; compensating unbalanced or harmonic load currents via FEC (as in an active power filter); and smooth transition between the MPPT mode and the UPS mode by synchronization. Simulation results of a 2-MW wind turbine, along with test results of a 2.3-kW laboratory setup, validate the proposed strategy. [ABSTRACT FROM AUTHOR]

The feasibility study of a power system is aimed at determining whether the system can adequately satisfy the load. The study will usually include other purposes, such as estimating the life-cycle cost of the system. This paper summarizes the main capabilities of current software packages for feasibility analysis of distributed energy resources. The document presents a short description of models, dispatch strategies, and economic indicators implemented in some packages. The test cases included in this paper will illustrate the scope of a feasibility study considering off-grid and grid-connected distributed resources. [ABSTRACT FROM AUTHOR]

In part II of this two-part paper, the improved particle swarm optimization (IPSO) algorithm for solving the microgrid (MG) day-ahead cooling and electricity coordinated scheduling is proposed. Significant improvements are made in comparison with the conventional PSO algorithm from two aspects. First, the mandatory correction is implemented to ensure the complex coupled constraints among the components of a particle are met after the particle's position is updated, which could enhance the algorithm performance when solving the problem including complex constraints. Second, it is assumed that a solution denoted by a particle occupies a neighboring area, the size of which decreases from a certain value to nearly zero as the iteration step increases to its limitation, which helps to avoid the pre-maturity of algorithm. For an MG composed of the combined cooling, heating and power (CCHP) units, PV panels, wind turbines, and storage batteries, a range of case studies under different MG operating modes are carried out through simulations. The simulation results demonstrate the proposed multi time-scale, multi energy-type coordinated MG scheduling solution can achieve the co-optimization of multi energy-type supply to meet customer's cooling and electricity demands, and make the MG be controllable as seen from the connected main grid. [ABSTRACT FROM AUTHOR]

Due to substantial generation and demand fluctuations in standalone green microgrids, energy management strategies are becoming essential for the power sharing and voltage regulation purposes. The classical energy management strategies employ the maximum power point tracking (MPPT) algorithms and rely on batteries in case of possible excess or deficit of energy. However, in order to realize constant current-constant voltage (IU) charging regime and increase the life span of batteries, energy management strategies require being more flexible with the power curtailment feature. In this paper, a coordinated and multivariable energy management strategy is proposed that employs a wind turbine and a photovoltaic array of a standalone DC microgrid as controllable generators by adjusting the pitch angle and the switching duty cycles. The proposed strategy is developed as an online nonlinear model predictive control (NMPC) algorithm. Applying to a sample standalone dc microgrid, the developed controller realizes the IU regime for charging the battery bank. The variable load demands are also shared accurately between generators in proportion to their ratings. Moreover, the DC bus voltage is regulated within a predefined range, as a design parameter. [ABSTRACT FROM AUTHOR]

This paper presents a new strategy to control the generated power from energy sources existing in autonomous and isolated microgrids. In this particular study, the power system consists of a power electronic converter supplied by a battery bank, which is used to form the ac grid (grid former converter), an energy source based on a wind turbine with its respective power electronic converter (grid supplier converter), and the power consumers (loads). The main objective of this proposed strategy is to control the state of charge of the battery bank limiting the voltage on its terminals by controlling the power generated by the energy sources. This is done without using dump loads or any physical communication among the power electronic converters or the individual energy source controllers. The electrical frequency of the microgrid is used to inform the power sources and their respective converters about the amount of power that they need to generate in order to maintain the battery-bank charging voltage below or equal its maximum allowable limit. Experimental results are presented to show the feasibility of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

To improve the wind energy dispatchability in the presence of non-Gaussian wind power uncertainties, this paper presents a stochastic coordinated control scheme for the doubly-fed-induction-generator–based wind-battery hybrid systems (WBHS). The proposed control scheme has a two-layer structure. Based on the non-Gaussian distributional wind power forecasts, an upper layer stochastic predictive controller coordinates the operation of wind and battery subsystems. The computed power references are passed to the lower layer wind and battery controllers for execution. This way, the combined power output of WBHS is brought to the desired dispatch levels. The salient feature of the proposed scheme is that it optimizes the control actions over the non-Gaussian wind power predictive distributions, thus handling the non-Gaussian uncertainties in wind power. The simulation results on actual wind data demonstrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents the design, implementation, and field measurements of a prototype marine-current power generation system (MCPGS) for capturing energy from marine current. The studied prototype MCPGS employs the flowing marine-current energy near the Cross-Sea Bridge, Peng-Hu Island, Taiwan. The design of the prototype MCPGS has to meet the practical marine-current flowing conditions and the severe environmental conditions in the ocean of Peng-Hu Island. The designed MCPGS unit consists of a three-blade marine-current turbine, a gearbox, a three-phase permanent-magnet generator, and a power converter that is used for converting generated energy to be stored in the battery. Field measured results for the studied MCPGS under different practical marine-current speeds in Peng-Hu Island are performed and analyzed. [ABSTRACT FROM AUTHOR]

Utilizing the optimal capacity of a battery in wind–battery hybrid power systems is crucial to minimize costs. In this paper, we modify the min–max dispatch method to effectively integrate wind power into the grid. In line with the dispatch principle, we define a lifetime cost function, which indicates the battery energy storage system cost of dispatching 1 kWh of wind energy, to determine the optimal battery capacity. By using the optimal battery capacity, the operation costs are minimized, and the hybrid system is able to dispatch the scheduled power at any dispatching time. Moreover, the short-term power dispatch control is also considered; we smooth the transient power between two consecutive dispatching intervals and control the state of charge of the battery by an online control algorithm. To evaluate the performance of the proposed optimization method and the short-term power dispatch control, we perform several numerical studies with a 3-MW wind turbine generator and real wind speed data. [ABSTRACT FROM AUTHOR]

This paper presents a direct power control (DPC) of a single voltage source converter (VSC)-based doubly fed induction generator (DFIG) for wind energy conversion system (WECS) without using a rotor position sensor. The proposed control algorithm performs independent control of both stator active and reactive powers by selecting the appropriate voltage vectors of the RSC (Rotor Side Converter). In this method, stator flux position in the rotor reference frame is estimated from the stator flux and the slip angle. In this algorithm, the rotor position sensor is eliminated and a position sensorless algorithm is used for estimating the rotor position. Simulation and experimental results of a 3.7 kW DFIG system are presented to demonstrate the performance of the proposed WECS under steady state and dynamic changes in real power, reactive power and wind speed. For the validation of the control algorithm, the proposed algorithm is also applied on installed high rating DFIG-based WECS. [ABSTRACT FROM AUTHOR]

A medium-voltage (MV) wind turbine generator (WTG)-battery energy storage (BESS) grid interface converter topology with medium-frequency (MF) transformer isolation is introduced in this paper. The system forms a three-port network in which several series stacked ac-ac converters transform the low-frequency (50/60 Hz) utility MV into MF (0.4 to 2 kHz) ac voltage by modulating it with MF square wave. This voltage is then fed to the MF transformer primary windings. The secondary and tertiary windings interface with the WTG side and the BESS side, respectively, after power conversion. The power generated by WTG is transferred to the MF transformer secondary windings through a three-phase pulse width modulation (PWM) rectifier and a three-phase PWM inverter, whereas the power transfer between the BESS and the tertiary winding occurs through a three-phase PWM inverter. It is shown that the utility grid sinusoidal currents, the battery current, and the WTG output currents can be controlled to be of good quality using PI and DQ control strategies. Thus, the proposed MF transformer-based three-port topology results in smaller converter weight/volume. Moreover, the control can handle voltage sags/swells and provide low voltage ride-through capability. Simulation waveforms along with experimental results are shown as proof of concept. [ABSTRACT FROM AUTHOR]

This paper presents a control strategy for managing the demand-generation fluctuations using a hybrid energy storage system in a wind-dominated remote area power supply (RAPS) system consisting of a doubly fed induction generator (DFIG), a battery storage system, a supercapacitor, a dump load, and main loads. Operation of a battery storage system is coordinated with a supercapacitor with a view to improving the performance of the battery. In this regard, the battery storage system is connected to the load side of the RAPS system, whereas the supercapacitor is connected to the dc bus of the back-to-back converter of the DFIG. The operation of the hybrid energy storage system is coordinated through the implementation of a power management algorithm, which is developed with a view to reducing the depth of discharge and ripple content of the battery current. In addition, the dump load is connected to the load side of the RAPS system, which utilizes the power in situations that cannot be handled via an energy storage system. In addition, a coordination method has been developed and proposed to coordinate the power flows among all system components with a view to regulating the power flow and thereby ensuring the robust voltage and frequency control on the load side while capturing the maximum power from wind. [ABSTRACT FROM PUBLISHER]

To accommodate the wind power fluctuations, a hybrid energy storage system (HESS) consisting of a battery energy storage system (BESS) and a supercapacitor is evaluated in this paper. A probabilistic approach for economically determining the power capacity specification for the HESS is proposed. This method would allow the capacities of the BESS and the supercapacitor to be properly designed to optimize the characteristics of high energy density of the BESS and high power density of the supercapacitor. Results show that the supercapacitor within the HESS helps to process the high frequency fluctuations, which contributes to the extension of the BESS lifetime. In addition, the supercapacitor helps to address the peaks in wind power fluctuations without the severe penalty of round-trip losses associated with a BESS. The proposed approach has been simulated using real wind data from an existing wind power plant in Iowa. [ABSTRACT FROM PUBLISHER]

In this paper, a single-phase multilevel inverter with battery balancing is proposed. The input of each individual inverter is directly connected to a battery. The combination of batteries can be controlled according to the batteries' voltages to implement the battery-balancing function. The operational principle of the proposed system is first described, and then, the design equation is derived. Experiments show that the battery-balancing discharge function is achieved. Finally, a prototype is designed and implemented to verify the feasibility and excellent performance. [ABSTRACT FROM PUBLISHER]

The necessity to solve global warming problems by reducing \CO2 emission in the electricity generation field had led to increasing interest in microgrids (MGs), particularly those containing the renewable sources such as solar and wind generation. Wind speed fluctuations cause high variations in the output power of a wind turbine which cause fluctuations in frequency and voltage of the MG during islanding mode and originate stability problems. In this paper, three techniques are proposed for solving and reducing the consequences of this problem. In the first technique, we develop a new fuzzy logic pitch angle controller. In the second technique, we design an energy-storage ultracapacitor which directly smoothes the output power of the wind turbine and enhances the performance of the MG during the islanding mode. In the third technique, storage batteries are used to support the MG in the islanding mode. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of an energy management system (EMS) with fuzzy control for a dc microgrid system. Modeling, analysis, and control of distributed power sources and energy storage devices with MATLAB/Simulink are proposed, and the integrated monitoring EMS is implemented with LabVIEW. To improve the life cycle of the battery, fuzzy control manages the desired state of charge. The RS-485/ZigBee network has been designed to control the operating mode and to monitor the values of all subsystems in the dc microgrid system. [ABSTRACT FROM AUTHOR]

This paper is analyzing the operation of a stand-alone wind turbine system with variable-speed permanent-magnet synchronous generator (PMSG) and a system for storing energy during wind speed and load variations. Energy storage devices are required for power balance and power quality in stand-alone wind energy systems. Initially, the holistic model of the entire system is achieved, including the PMSG, the boost converter, and the storage system. The power absorbed by the connected loads can be effectively delivered and supplied by the proposed wind turbine and energy storage systems, subject to an appropriate control method. The main purpose is to supply 230-V/50-Hz domestic appliances through a single-phase inverter. The simulation results, validated by experimental testing, show a good prediction of the electrical parameter waveforms. The control system is implemented on a dSPACE DS1103 real-time board. Furthermore, the results confirm the stability of the supply. [ABSTRACT FROM PUBLISHER]

This paper deals with a control algorithm for two parallel-operated doubly fed induction generators (DFIGs) driven by wind turbines in a three-phase four-wire autonomous system feeding local loads. The proposed autonomous wind energy conversion system (AWECS) is using back-to-back-connected pulsewidth-modulated insulated-gate-bipolar-transistor-based voltage source converters with a battery energy storage system at their dc link. The system utilizes separate rotor-side converters for each DFIG for maximum power tracking (MPT) through its rotor speed control. However, a common dc bus and a battery bank and stator-side converter are used for voltage and frequency control at the stator terminals of the DFIGs. A delta–star transformer is connected between the stator-side converter and the stator terminals of DFIGs for optimizing the voltage of dc bus, and the load-side neutral is connected to the neutral of the star side of the transformer. The proposed electromechanical system is modeled and simulated in MATLAB using Simulink and Sim Power Systems set toolboxes. The performance of the proposed AWECS is presented to demonstrate its capability of MPT, stator voltage and frequency control, harmonic elimination, load balancing, and load leveling. [ABSTRACT FROM PUBLISHER]

In this paper, a buck-type power converter as the battery charger for the stand-alone wind power system is proposed. The proposed power converter can harvest the maximum power from the wind turbine while generating pulsating current for the battery bank to improve the charging efficiency. The maximum power point tracking function is realized by the constant on-time control, the circuit parameter design of the power converter, and the characteristics of wind turbine. The pulsating battery charging current is implemented by the discontinuous conduction mode operation of the proposed power converter. Also, the overspeed protection of the wind turbine can be naturally achieved when high power output occurs. Circuit simplicity and high reliability are the major advantages of the proposed power converter. Hardware experimental results from a 400-W prototype circuit are presented to verify the performance of the proposed power converter. [ABSTRACT FROM AUTHOR]

This paper deals with a new isolated wind–hydro hybrid generation system employing one squirrel-cage induction generator (SCIG) driven by a variable-speed wind turbine and another SCIG driven by a constant-power hydro turbine feeding three-phase four-wire local loads. The proposed system utilizes two back-to-back-connected pulsewidth modulationcontrolled insulated-gate-bipolar-transistor-based voltage-source converters (VSCs) with a battery energy storage system at their dc link. The main objectives of the control algorithm for the VSCs are to achieve maximum power tracking (MPT) through rotor speed control of a wind-turbine-driven SCIG under varying wind speeds and control of the magnitude and the frequency of the load voltage. The proposed wind-hydro hybrid system has a capability of bidirectional active- and reactive-power flow, by which it controls the magnitude and the frequency of the load voltage. The proposed electromechanical system using SCIGs, an MPT controller, and a voltage and frequency controller are modeled and simulated in MATLAB using Simulink and Sim Power System set toolboxes, and different aspects of the proposed system are studied for various types of linear, nonlinear, and dynamic loads, and under varying wind-speed conditions. The performance of the proposed system is presented to demonstrate its capability of MPT, voltage and frequency control (VFC), harmonic elimination, and load balancing. [ABSTRACT FROM AUTHOR]