| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 95 === Nowadays, Distributed Generation Systems (DGSs), such as wind power and solar power and so on, are extensively installed in Taiwan. The generated electricity is fed into the utility electrical network. The power system will be operated and generate electricity disjointed with the electrical facilities of renewable energy, if the utility power is in a forced outage and results in stopping supplying power to the local load. Besides, if the electrical facilities of the DGSs don’t detect this condition immediately and separate from the utility power system, then it will still feed the power to local loads and it will become an Islanding Event. That will be most likely to hurt maintenance workers of the utility and cause electric shock events. Moreover, islanding operation will also cause electricity-sensitive facilities to be damaged and lead to malfunction in protect relays in the distribution system.
Generally speaking, the detection techniques for the islanding event are divided into two groups. The first one is active detection method and the second one is passive detection method; however, there still exist non-detection zones for the passive detection method. The thesis applies Matlab/Simulink software to simulate the situations of wind-generation-system (WGS) in parallel with the utility. That includes vector surge relay (VSR) and rate-of-change-of frequency (ROCOF). This thesis proposed a method based on finite difference approximation to reduce the non-detection zone which is defined with islanding effect of the WGS. The detection time and disturbed reactive power are estimated for detecting islanding.
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