Coordinated Black-start Strategy for Offshore Wind Farms and VSC-HVDC System

For the voltage-source-converter based high voltage direct current (VSC-HVDC) transmission system with offshore wind farms (OWFs) integration, which functions as one of the primary power sources for local grids, possessing black-start capabilities can enhance the rapid recovery of the power system after significant blackouts, and is becoming an urgent need. However, the black-start process of the VSC-HVDC system with OWFs integration is a complicated process, which needs the coordination of a lot of devices. In this paper, a comprehensive black-start strategy is proposed. A diesel generator is utilized as the black-start source to start offshore WTs. The grid-forming controlled WTs will then maintain the frequency and voltage of the offshore AC system. The VSC-HVDC system is energized and started from the offshore AC system. The offshore VSC controls the DC voltage and the onshore VSC establishes the onshore passive AC grid. Based on the above strategies, the black-start source configuration, the overall black-start path, the black-start operation sequence, and a case study based on a 2000MW VSCHVDC system with OWFs integration are presented. A detailed simulation model of the studied system is built in PSCAD/EMTDC, and the effectiveness of the proposed method is verified.