Mechanism and Analysis of HCC to Suppress DC Commutation Failure

This article addresses the issue of commutation failure in high-voltage direct current transmission systems based on the line-commutated converter (LCC) topology. It proposes a solution using a hybrid commutated converter (HCC) topology based on reverse-blocking integrated gate commutated thyristor (IGCT) devices to mitigate commutation failures. Firstly, it introduces the mechanism of commutation failure in LCC and discusses in detail the process and factors that contribute to commutation failure. Next, it analyzes the principles behind HCC's enhanced commutation capabilities, which are achieved by utilizing IGCTs with faster reverse recovery speeds, allowing for a smaller minimum extinction angle. Finally, the article conducts simulation analyses on two critical operating conditions: insufficient extinction time and grid undervoltage. The results demonstrate that HCC on the inverter side can increase the commutation margin and significantly reduce the risk of commutation failure, validating the effectiveness of HCC in suppressing DC commutation failures.