Nishad Mendis

Management of Battery-Supercapacitor Hybrid Energy Storage and Synchronous Condenser for Isolated Operation of PMSG Based Variable-Speed Wind Turbine Generating Systems

Standalone operation of a wind turbine generating system under fluctuating wind and variable load conditions is a difficult task. Moreover, high reactive power demand makes it more challenging due to the limitation of reactive capability of the wind generating system. A Remote Area Power Supply (RAPS) system consisting of a Permanent Magnet Synchronous Generator (PMSG), a hybrid energy storage, a dump load and a mains load is considered in this paper. The hybrid energy storage consists of a battery storage and a supercapacitor where both are connected to the DC bus of the RAPS system. An energy management algorithm (EMA) is proposed for the hybrid energy storage with a view to improve the performance of the battery storage. A synchronous condenser is employed to provide reactive power and inertial support to the RAPS system. A coordinated control approach is developed to manage the active and reactive power flows among the RAPS components. In this regard, individual controllers for each RAPS component have been developed for effective management of the RAPS components. Through simulation studies carried out using detailed model in MATLAB Simulink, it has been demonstrated that the proposed method is capable of achieving: a) robust voltage and frequency regulation (in terms of their acceptable bandwidths), b) effective management of the hybrid storage system, c) reactive power capability and inertial support by the synchronous condenser, and d) maximum power extraction from wind.

Standalone Operation of Wind Turbine-Based Variable Speed Generators With Maximum Power Extraction Capability

The application of variable speed wind generators in hybrid remote area power supply (RAPS) systems provides opportunities for improved voltage and frequency control together with maximum power point tracking (MPPT), where limited research outcomes exist. The study presented in this paper covers two such hybrid systems: 1) permanent magnet synchronous generator (PMSG) and 2) doubly fed induction generator (DFIG) as wind turbine technologies together with a battery storage and a dump load. The battery storage system and dump load are able to assist in maintaining the active power balance during over and under generation conditions as well as sudden load changes. Through simulation studies, it has been demonstrated that both RAPS systems are able to regulate the load side voltage and frequency within the acceptable limits while extracting the maximum power from wind, which is an inherent capability of variable speed generators. The two RAPS systems and their associated control strategies have been developed and their performance is investigated using SimPowerSystems blocksets in MATLAB.

An Effective Power Management Strategy for a Wind–Diesel–Hydrogen-Based Remote Area Power Supply System to Meet Fluctuating Demands Under Generation Uncertainty

This paper addresses power management strategies, including technical issues and control methodologies, for a wind-dominated hybrid remote area power supply (RAPS) system. The system consists of a doubly fed induction generator, a diesel generator, a hydrogen-based generation scheme, and mains loads. The goal is to maximize power extraction from the wind generator under generation uncertainty. For active power management, a hydrogen-based generation scheme consisting of an electrolyser and a fuel cell system is integrated to the RAPS system. Developed control strategies contribute to achieve the following objectives: 1) load side voltage and frequency regulation; 2) maximum power extraction from wind; and 3) regulating diesel generator operation at low load conditions. Simulation studies with a real-life data set are used to evaluate the proposed architecture and prove the control objectives, and it has been observed that all the proposed objectives are met within satisfactory limits.

Control coordination of a wind turbine generator and a battery storage unit in a Remote Area Power Supply system

A novel hybrid Remote Area Power Supply (RAPS) system consisting of a Doubly Fed Induction Generator (DFIG) based wind turbine and a battery Energy Storage System (ESS) is investigated in this paper. The proposed RAPS system also consists of a dummy load and its controller. The battery energy storage system is used as a buffer which is connected to the DC link of the DFIG. The dummy load which is connected to the AC side of the system is used to absorb the energy associated with over generation, a situation which cannot be handled through the battery system. Control coordination of the dummy load and battery storage system helps maintain the system instantaneous power balance thus ensuring the regulation of the system frequency. The suitability of the proposed RAPS system is assessed in terms of the bandwidth of voltage regulation capability. Small signal model analysis although simpler to perform, is undertaken with a view to compare some of the corresponding results with those obtained using detailed models. Detailed modular simulation of the system is discussed in relation to the system voltage, frequency, DC link stability of the doubly fed induction generator and power sharing among different system components. The model of the entire system has been developed using SimPowerSystem toolbox in MATLAB.

A control approach for voltage and frequency regulation of a Wind-Diesel-battery based hybrid remote area power supply system

A novel Remote Area Power Supply (RAPS) system consisting of a Doubly Fed Induction Generator (DFIG) wind turbine generator, synchronous diesel generator system, battery storage system and a dump load is considered in this paper. A control coordination strategy is formulated with a view to regulate the system voltage and frequency within acceptable limits while extracting the maximum power available from the wind. The battery storage unit is used to provide a smooth state transition from Wind-Only (WO) to Wind-Diesel (WD) mode while enabling the DFIG to operate in its maximum power point tracking mode of operation. The dump load is used to absorb the excess energy which cannot be utilised through the battery storage system. The entire RAPS system has been modelled using SimPowerSystem toolbox in MATLAB.

A novel control strategy for stand-alone operation of a wind dominated RAPS system

This paper presents a novel control strategy for a high penetrated wind based hybrid Remote Area Power Supply (RAPS) system. The proposed RAPS system consists of a Permanent Magnet Synchronous Generator (PMSG) based variable speed wind turbine and a battery energy storage system with a dump load for DC bus voltage control and a diesel generator as a back-up supply. An integrated control approach based on active and reactive power balance of the proposed RAPS system has been proposed and developed with a view to regulate the voltage and frequency within an acceptable bandwidth. The proposed integrated control algorithm is implemented by developing controller for the individual system components in the RAPS system including wind energy conversion system, diesel generator, battery storage and dump load while coordinating their responses to achieve optimal operation. The optimised operation for the proposed RAPS system is realised by operating the wind turbine generator on its maximum power extraction mode while restricting the operation of diesel generating system at low-load conditions. In addition to the detailed model, which associated with non-linear high order characteristic of each system components, a linearlised model of the RAPS system is presented with a view to compare the active power sharing among the system components. The suitability of the proposed control strategy has been tested under varying system conditions including fluctuating wind and variable load.

Application of a hybrid energy storage in a remote area power supply system

A novel topology of a hybrid energy storage is proposed for a standalone Remote Area Power Supply (RAPS) system consisting of a Doubly Fed Induction Generator (DFIG), dump load and mains loads. In this regard, the behaviour of a hybrid energy storage unit consisting of battery storage and a supercapacitor is examined. The battery storage is designed to meet the energy requirement of the system while the supercapacitor is used to respond to rapid power fluctuations of the RAPS system. The battery storage is connected to the AC side of the system through an inverter while the supercapacitor is connected to the DC link of the back-to-back converter system of the DFIG via a two stage bi-directional buck boost converter. A control strategy is adopted for the hybrid energy storage system in which the operation of the battery is limited to a lower Depth of Discharge (DOD). The dump load is used to absorb excess energy in the system which cannot be utilised by the energy storage system. The entire RAPS system has been modelled using MATLAB Simulink.

Remote Area Power Supply System: An Integrated Control Approach Based on Active Power Balance

This article presents a novel control strategy for a high-penetration, wind-based hybrid remote area power supply (RAPS) system. The proposed RAPS system consists of a permanent magnet synchronous generator (PMSG)-based variable-speed wind turbine and a battery energy storage system (ESS) with a dump load for dc bus voltage control and a diesel generator as a backup supply. An integrated control approach based on the active power balance of the proposed RAPS system has been proposed and developed to regulate the voltage and frequency within an acceptable bandwidth. The proposed integrated control algorithm is implemented by developing a controller for the individual system components in the RAPS system, including the wind energy conversion system, the diesel generator, the battery storage system, and the dump load, while coordinating their response to achieve optimal operation. The optimal operation for the proposed RAPS system is realized by operating the wind turbine generator (WTG) at its maximum power extraction mode while restricting the operation of the diesel generating system at low-load conditions. In addition to the detailed model, which mainly comprises nonlinear high-order characteristics of each system component, a linearized model of the RAPS system is presented to compare the active power sharing among the system components. Laboratory-based experimental tests have been conducted to validate the coordinated approach, and the results are presented in this article.

Autonomous operation of wind-battery hybrid power system with maximum power extraction capability

The hybrid operation of a remote area power system consisting of a Doubly Fed Induction Generator (DFIG) based wind turbine, a battery storage unit and a dummy load is investigated in this paper. The battery storage unit operates as a source or load, depending on the wind power output and loading conditions of the system. The battery storage is connected to the AC side of the wind energy system through a three phase inverter to supply both active and reactive power. A dummy load is also incorporated into the AC side of the system. The design criteria of the controllers for each component (ie. DFIG, battery storage system and dummy load) and an approach for control coordination of the entire system are presented in this paper. The suitability of the proposed control coordination strategy and individual system controllers are tested in relation to the system voltage, frequency and DC link stability of the DFIG under variable wind and changing load conditions. The maximum power extraction capability from wind is also achieved throughout the operation.

Voltage quality behaviour of a wind turbine based Remote Area Power System

The power quality behaviour of a Remote Area Power System (RAPS) consisting of a Doubly Fed Induction Generator (DFIG), its main loads and a dummy load is presented in this paper. The dummy load is used to maintain the power balance of the system under changing wind and loading conditions. The performance of the remote area power system subject to various loading conditions has been evaluated in terms of the voltage quality, an aspect which has not received much attention in the past. The existing Distributed Generation (DG) power quality standards are taken as the basis to compare the voltage quality of the simulated waveforms. The simulation results indicate that the system evaluated is able to maintain the load bus bar voltage and frequency within tight limits whereas a better harmonic performance can be achieved if adequate filtering is employed. The model was developed using SimPowerSystem tool box in MATLAB.