Doctor of Philosophy
School of Electrical, Computer and Telecommunications Engineering
Mendis, Nishad, Design of Wind Dominated Hybrid Remote Area Power Supply Systems, Doctor of Philosophy thesis, School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, 2012. http://ro.uow.edu.au/theses/3489
Hybrid remote area power supply (RAPS) systems can be regarded as an emerging power generation technology for rural and remote communities. These power systems combine the best features of conventional (e.g. diesel based power generation) and non-conventional (e.g. renewable energy) power generation technologies. Hybridisation of such energy sources provides superior performance in terms of efficiency, lower carbon emission levels, reduced generation cost and improved supply quality and reliability.
Although hybrid RAPS systems seem to offer promising solutions, there are various challenges associated with design and operation of such generating schemes which include: (a) voltage and frequency regulation on customer side, (b) control coordination between the system components (e.g. energy storage, dump load), (c) development of individual control strategies for each system component and (d) maximum power extraction from renewable energy resources. This thesis addresses the above stated issues in relation to wind based RAPS systems where the wind turbine generator performs as the main source of energy. In this regard, two types of popular wind turbine generator technologies, namely: doubly fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) are considered to form RAPS systems. In addition, auxiliary system components such as an energy storage system, dump load and other types of generating schemes including diesel and hydrogen are combined with wind turbine generator to perform the hybrid operation.
Robust control strategies are developed for the converter systems of the wind turbine generators with a view to regulate the voltage and frequency on the load side. In addition, a battery storage system and a dump load are integrated to regulate the power balance of the RAPS systems. Moreover, separate configurations of the dump load are proposed for DFIG based and PMSG based RAPS systems. Individual controllers are implemented for the battery storage systems and dump loads whose operation is managed through a coordinated control approach. The coordinated control approach is designed to perform as an integrated controller of the RAPS system which manages the power flow between the system components and coordinate responses of individual components in a designated manner. In addition, control strategies are developed to operate the wind turbine generators on their maximum power tracking characteristics to ensure optimum system performance.
Operation of a battery storage system is coordinated with a supercapacitor with a view to improve the battery life by reducing ripple content of battery current. Two different power electronic configurations are proposed to interface the hybrid energy storage (i.e. battery storage and supercapacitor) of DFIG based and PMSG based RAPS systems. The operation of the hybrid energy storage system is coordinated through the implementation of an energy management algorithm which is developed with a view to reduce the depth of discharge and ripple content of the battery current.
Applicability of a dual mode operation of diesel generating system (i.e. either as a synchronous condenser or as synchronous generator) for wind based RAPS system is examined. The dual mode operating mechanism is controlled via a friction clutch that helps to improve the fuel economy by avoiding the low load factor operation of the diesel generating scheme. Technical viability of such a diesel generating scheme is implemented giving due consideration to its modelling aspects together with respective controllers. Also, reactive power management schemes are implemented between the wind energy conversion system and diesel generating system.
To improve the autonomy of operation of the RAPS systems, hydrogen based generating schemes are introduced. In this regard, the technical feasibility of integrating a hydrogen based generating system consisting of a fuel cell system, an electrolyser and a storage tank to a wind based RAPS system is examined. Individual control strategies are implemented for each component of the hydrogen storage system and their functions are coordinated to perform as a self generating unit.
The performance evaluation utilising linearised component based RAPS system is also undertaken with a view to compare the results that are obtained using the corresponding detailed models. Above stated DFIG based and PMSG based RAPS systems are also investigated under changing wind and varying load conditions. Through simulation studies it is revealed that the proposed control strategies developed for the RAPS systems are capable in regulating the voltage and frequency on the load side while extracting the maximum power from wind.