Sarath Perera

Bio: Sarath Perera is an academic researcher from University of Wollongong. The author has contributed to research in topics: Electric power system & AC power. The author has an hindex of 25, co-authored 200 publications receiving 2873 citations. Previous affiliations of Sarath Perera include University UCINF.

Distribution System Planning With Incorporating DG Reactive Capability and System Uncertainties

Abstract: Distributed generation (DG) systems are considered an integral part in future distribution system planning. The active and reactive power injections from DG units, typically installed close to the load centers, are seen as a cost-effective solution for distribution system voltage support, energy saving, and reliability improvement. This paper proposes a novel distribution system expansion planning strategy encompassing renewable DG systems with schedulable and intermittent power generation patterns. The reactive capability limits of different renewable DG systems covering wind, solar photovoltaic, and biomass-based generation units are included in the planning model and the system uncertainties such as load demand, wind speed, and solar radiation are also accounted using probabilistic models. The problem of distribution system planning with renewable DG is formulated as constrained mixed integer nonlinear programming, wherein the total cost will be minimized with optimal allocation of various renewable DG systems. A solution algorithm integrating TRIBE particle swarm optimization (TRIBE PSO) and ordinal optimization (OO) is developed to effectively obtain optimal and near-optimal solutions for system planners. TRIBE PSO, OO, and the proposed algorithm are applied to a practical test system and results are compared and presented.

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

Abstract: 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

Abstract: 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.

Management of Low- and High-Frequency Power Components in Demand-Generation Fluctuations of a DFIG-Based Wind-Dominated RAPS System Using Hybrid Energy Storage

Abstract: 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.

Microgrids of commercial buildings: strategies to manage mode transfer from grid connected to islanded mode

Abstract: Microgrid systems located within commercial premises are becoming increasingly popular and their dynamic behavior is still uncharted territory in modern power networks. Improved understanding in design and operation is required for the electricity utility and building services design sectors. This paper evaluates the design requirements for a commercial building microgrid system to facilitate seamless mode transition considering an actual commercial building microgrid system. A dynamic simulation model of the proposed microgrid system is established (utilizing DIgSILENT Power Factory) to aid the development of planning and operational philosophy for the practical system. An economic operational criterion is developed for the microgrid to incorporate selective mode transition in different time intervals and demand scenarios. In addition, a multi-droop control strategy has been developed to mitigate voltage and frequency variations during mode transition. Different system conditions considering variability in load and generation are analyzed to examine the responses of associated microgrid network parameters (i.e., voltage and frequency) with the proposed mode transition strategy during planned and unplanned islanding conditions. It has been demonstrated that despite having a rigorous mode transition strategy, control of certain loads such as direct online (DOL) and variable-speed-drive (VSD) driven motor loads is vital for ensuring seamless mode-transition, in particular for unplanned islanding conditions.

Teaching for quality learning at university

Abstract: by J. Biggs and C. Tang, Maidenhead, England, Open University Press, 2007, 360 pp., £29.99, ISBN-13: 978-0-335-22126-4

Inertia response and frequency control techniques for renewable energy sources: A review

Abstract: Preservation of the environment has become the main motivation to integrate more renewable energy sources (RESs) in electrical networks. However, several technical issues are prevalent at high level RES penetration. The most important technical issue is the difficulty in achieving the frequency stability of these new systems, as they contain less generation units that provide reserve power. Moreover, new power systems have small inertia constant due to the decoupling of the RESs from the AC grid using power converters. Therefore, the RESs in normal operation cannot participate with other conventional generation sources in frequency regulation. This paper reviews several inertia and frequency control techniques proposed for variable speed wind turbines and solar PV generators. Generally, the inertia and frequency regulation techniques were divided into two main groups. The first group includes the deloading technique, which allow the RESs to keep a certain amount of reserve power, while the second group includes inertia emulation, fast power reserve, and droop techniques, which is used to release the RESs reserve power at under frequency events.

Self-Healing Resilient Distribution Systems Based on Sectionalization Into Microgrids

Abstract: This paper proposes a novel comprehensive operation and self-healing strategy for a distribution system with both dispatchable and nondispatchable distributed generators (DGs). In the normal operation mode, the control objective of the system is to minimize the operation costs and maximize the revenues. A rolling-horizon optimization method is used to schedule the outputs of dispatchable DGs based on forecasts. In the self-healing mode, the on-outage portion of the distribution system will be optimally sectionalized into networked self-supplied microgrids (MGs) so as to provide reliable power supply to the maximum loads continuously. The outputs of the dispatchable DGs will be rescheduled accordingly too. In order to take into account the uncertainties of DG outputs and load consumptions, we formulate the problems as a stochastic program. A scenario reduction method is applied to achieve a tradeoff between the accuracy of the solution and the computational burden. A modified IEEE 123-node distribution system is used as a test system. The results of case studies demonstrate the effectiveness of the proposed methodology.

High-temperature superconductor fault current limiters: concepts, applications, and development status

Abstract: The application of superconducting fault current limiters (SCFCLs) in power systems is very attractive because SCFCLs offer superior technical performance in comparison to conventional devices to limit fault currents. Negligible impedance at normal conditions, fast and effective current limitation within the first current rise and repetitive operation with fast and automatic recovery are the main attributes for SCFCLs. In recent years there has been a significant progress in the research and development (R&D) of SCFCLs. This paper gives an extended review of different SCFCL concepts, SCFCL applications and the R&D status. Within the first part of this paper the most important SCFCLS and, to a limited extent, non-superconducting fault current limiter (FCL) concepts are explained and compared. The second part reviews interesting SCFCL applications at the distribution and transmission voltage level and the third part shows in detail the R&D status. It can be summarized that SCFCLs are, at present, not commercially available but several successful field tests demonstrated the technical feasibility of SCFCLs. First distribution level applications are expected soon. Considerable economical and technical benefits can be achieved by applying SCFCLs at the distribution and transmission voltage level.