Author

Yujie Yin

Issuing Body

Mississippi State University

Advisor

Fu, Yong

Committee Member

Karimi-Ghartemani, Masoud

Committee Member

Choi, Seungdeog

Committee Member

Park, Chanyeop

Date of Degree

12-1-2020

Document Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy

Abstract

Microgrids form small-scale power grids with distributed energy resources such as wind generators, photovoltaic panels, fuel cells, energy storage systems, and controllable loads. The characteristics of a microgrid include bi-directional power flows, flexible modes of operation, as well as variable short circuit currents. Due to the weak injection of fault current and short period nature, the connection of microgrids to the distribution systems or sub-transmission systems creates serious challenges to existing over-current based protection systems. The protection of microgrids is gaining substantial attentions in recent years because of large-scale deployment of microgrids and its impacts to existing electricity infrastructures. New protection methodologies and solutions applicable for microgrids are studied and presented in this dissertation. To effectively protect the microgrids, three areas of study are conducted based on the latest technologies in the protection systems, computing platforms, and communication networks. Firstly, the Point of Interconnection protection using distance protection with residual voltage compensation method for an ungrounded microgrid network is presented. This study resolves the challenging issues of detecting single-phase-to-ground fault at the interconnection line of microgrid. It can correctly identify the fault, properly measure the fault location, and timely isolate the fault without jeopardizing the stability of downstream microgrid system and/or causing dangerous overvoltage and arcing conditions. Secondly, the distribution substation busbar protection using the synchrophasor data is studied to realize fast and reliable bus differential protection. Comparing with other busbar protection schemes, this method has the advantages of low cost, easy configuration, fast expansion, and no circuit limitation. Lastly, an adaptive protection solution for distribution feeders with microgrids is developed and tested using RTDS. This study focuses on providing a framework for microgrid over-current coordination to improve the reliability and dependability of the protected network. Overall, the research studies presented in this dissertation will provide the power industries with new insights and methodologies on microgrid protection. Together with other protection functions, the proposed methods can provide effective microgrid protection against dangerous faults, reduce arcing condition, increase the possibility of seamless islanding, and consequently improve the reliability and resilience of microgrids.

URI

https://hdl.handle.net/11668/20844

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