A novel active power conversion system based on modular multilevel converter in microgrid

The paper proposes a new active power conversion system (APCS) applied in microgrid for the connection and flexible power transmission between the main grid and the microgrid and power quality improvement. APCS is composed of three voltage sourced converters (VSCs), ie., main-grid VSC, shunt VSC, and series VSC, which all adopt modular multilevel converter (MMC) topology. The paper analyzes grid-connected and island operating modes of the APCS and proposes control strategy for every MMC-VSC. The models of the microgrid and the APCS are built in PSCAD/EMTDC, and the operating modes and control strategies are achieved to verify the functions of the APCS in power quality improvement and flexible power transmission.