Analysis and Design for Voltage Equalization in RB-IGCT Based Hybrid Commutated Converter Applications

To solve the problem of commutation failure in high voltage direct current (HVDC) transmission system, a novel hybrid commutated converter (HCC) based on reverse blocking integrated gate commutated thyristor (RB-IGCT) is proposed. Compared to traditional line commutated converter (LCC), HCC mitigates commutation failure by utilizing the controllable turnoff characteristics of RB-IGCT, so it is necessary to solve the problem of device series turnoff voltage equalization. This article theoretically analyzes the mechanism of RB-IGCT turnoff process without dynamic avalanche injection in HCC applications, and obtains the key factors affecting voltage establishment. Then, turnoff process simulation between devices with different factors is conducted to analyze the impact of each factor on the voltage sharing characteristics. Finally, turnoff delay time and turnoff loss are proposed as engineering available device matching parameters. Single pulse turnoff tests suitable for HCC working conditions are conducted on the proposed device matching method, and the experimental results confirmed the feasibility of the proposed matching method.