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

Abstract

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 system. 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 paper, a novel low-cost DC chopper based on thyristor- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> circuit (TLC-DCC) is proposed, which uses a low-cost semi-control device, namely the thyristor, and generates DC current zero-crossing through the cooperation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> 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. In order to verify the effectiveness of the TLC-DCC, a 4 kV/2.4 MW prototype is built. On this basis, the characteristics of the TLC-DCC are analyzed, and the simulation results show that the 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.