독립형 마이크로그리드의 과도 안정도를 고려한 다중 ESS 설계에 관한 연구

Abstract

This dissertation proposes a design method considering the transient stability of a stand-alone microgrid based on multi-ESS(Energy stroage system), The proposed method contributes to securing transient stability of the power system by maintaining the output margin of the CVCF ESS. In this system, the auxiliary ESS prepares for disturbances such as cut-off accidents. In addition, the three-phase reactive current components and the unbalanced current components are shared with the CVCF ESS to prevent PCS(Power conversion system) overload situations. In the event of a CVCF ESS failure that cannot be operated in a single ESS, the power system is restored by switching roles with the auxiliary ESS. To verify the transient stability analysis, Floriana Island, in the Galapagos Islands of Ecuador, was selected as a sample model, and its simulation model, which made by the PSCAD/EMTDC program, was applied with actual power system parameters such as weather data and power load of the island. The assumed accident simulation analysis to verify the transient stability improvement effect was performed based on a total of five cases that may occur in the actual microgrid. In the case of transient stability, the operation of the voltage relay and the overload of the inverter-based facilities were checked. The recovery process for the CVCF ESS dropout was also presented compared with the single and multi-ESS cases. As a result of the transient state analysis in multi-ESS based on power balance control, it was confirmed that 130% overload occurred due to the lack of output margin of the CVCF ESS when renewable energy rapidly increased. However, in the proposed method, only a momentary voltage rise was shown. Therefore, the design method considering transient stability will be able to contribute to stable microgrid operation. And in the event of a long-term failure of the CVCF ESS, it can be economically helpful to the microgrid by the switching roles of auxiliary ESS.