A Novel Low-Cost DC Chopper for Offshore Wind VSC-HVDC System by Using Thyristors Instead of Full-Control Devices

Voltage source converter based high voltage direct current (VSC-HVDC) technology has a broad application prospect in high-capacity offshore wind power transmission, and it is of great importance to achieve fault ride through (FRT) of offshore wind VSC-HVDC systems. The existing dc chopper cannot meet the requirements of high performance and low cost at the same time, which limits its further promotion and application. In this article, a novel low-cost dc chopper based on thyristor-
LC
circuit (TLC-DCC) is proposed, which uses a low-cost semicontrol device, namely the thyristor, and generates dc current zero-crossing through the cooperation of an
LC
circuit to realize the reliable turn off of the energy consumption module, thus providing a new idea for solving the FRT problem. In addition, the TLC-DCC control strategy and key parameter coordination method are proposed. To verify the effectiveness of TLC-DCC, a 4 kV/2.4 MW prototype is built. On this basis, the characteristics of TLC-DCC are analyzed, and the simulation results show that TLC-DCC can realize FRT under different short-circuit conditions. Compared with the existing dc chopper, TLC-DCC has the great advantage of reducing the total cost by 38% with the same performance.