Frequency control for microgrids using enhanced STATCOM and supercapacitor energy storage

The face of electricity generation, transmission and distribution is changing due to economic, technology and environmental incentives. Recently, interactive and intelligent electricity grid structures which consist of interconnected small/medium sized generators, power electronic technologies and energy storage elements have been developed to address the major shortcomings of the traditional electricity grid structure. Microgrids are key elements of these emerging grid structures. Although microgrids are accepted as possible solutions to power quality and power stability issues in ac power systems, the uncertainty in the ability of microgrids to cope with severe fluctuating load and fault conditions is a major concern in the operation of these new grid structures. This project was aimed at improving frequency control within a microgrid. Four objectives were identified and addressed to meet this aim. I. A weak microgrid network using an emulated internal combustion engine generator and associated loads was modelled. The emulation of a diesel generating set was achieved with a vector controlled induction motor driving a synchronous generator. The diesel engine emulation was achieved by incorporating a single delay into the speed control loop of the vector controlled induction motor. The modelled microgrid network is a very useful tool for the development of novel control schemes for frequency control within a microgrid. II. Simulation studies were carried out to investigate how a weak power system can be strengthened through the use of enhanced STATCOM and Supercapacitor energy storage. This assisted in understanding the limitations and performances of the novel algorithms proposed for frequency control improvement. III. Novel open and closed loop control algorithms for frequency control within a microgrid were proposed. The advantage of the open loop control scheme is its simplicity but the functionality of the control action is limited with the knowledge of the diesel engine transfer function and load current being important requirements. A closed loop control scheme was employed to address the limitations of the open loop control scheme. IV. A laboratory prototype of the microgrid network was developed and used in validating the novel control schemes proposed. The thesis describes the novel algorithms for frequency control using an intelligent STAtic COMpensator (STATCOM) and SuperCapacitor Energy Storage System (SCESS). The benefits and effectiveness of the proposed algorithms are given in the simulation and experimental results.EThOS - Electronic Theses Online ServiceGBUnited Kingdo