마이크로그리드의 분산전원 출력 조절을 위한 MVDC 제어

Abstract

In isolated microgrids, power system reliability and stability problems arise with peak demand load and renewable power generation facilities. In order to solve such surplus power and insufficient power problems, research on the balance of power supply and demand through bi-directional power trans -mission in connection with other systems using MVDC (Medium voltage direct current distribution) or HVDC (High voltage direct current transmission) is being actively conducted. This paper proposes a method to automatically control distributed power output by connecting MVDC between microgrids. The proposed method operates a microgrid based on the constant voltage variable frequency control of MVDC. In addition, the power supply and demand situation of the connected microgrid is identified through the magnitude of the DC link voltage. According to the frequency determined in MVDC, the output of BESS(Battery energy storage system) is adjusted, and MPPT(Maximum power point tracking) control, or curtailment control, is performed for wind power generation and photovoltaics. Also, depending on the frequency, the diesel generator starts and stops to supply power at peak load. To verify the proposed protection system, an isolated microgrid was modeled through the PSCAD/EMTDC program. According to simulation analysis results, it was confirmed that all power generation facilities would automatically control the output according to the frequency determined by MVDC.