Open-circuit Fault Riding Through of Receiving AC Terminal in HVDC Transmission System for Offshore Wind Farms

Abstract

Abstract Flexible high voltage direct current (HVDC) transmission system is indispensable for long-distance and high power transmission capacity in offshore wind farms. The AC open-circuit fault of the receiving terminal is quite severe, where the power transmission might be suddenly cut down to zero. As a result, a severe over-voltage will occur on the HVDC side and modular multilevel converter (MMC) submodule capacitor. In this paper, the over-voltage suppression mechanism is put forward to augment the AC open circuit fault at the sending and receiving terminal of the MMC-HVDC system. First, the formulation mechanism of DC over-voltage in the MMC-HVDC integrated wind farm is studied. Then, three different over-voltage suppression mechanisms, namely wind turbine pitch control, crowbar control, and submodule redundancy, are put forward to suppress the aforesaid over-voltage in the MMC-HVDC system. The simulations are carried out in PSCAD based on a test case, and the simulation results are used to confirm the efficiency of the proposed overvoltage suppression techniques.