Research on methods of measuring extinction angle and measures to suppress repetitive commutation failures through equivalent DC input resistance

摘要

Accurate, simple identification and suppression of repetitive commutation failures are of great significance to the safe and stable operation of the line-commutated converter-based high-voltage direct current (LCC-HVDC). Through the analysis of mathematical models of inverter side converter and DC transmission system. This paper proposes a variable that has an important influence on commutation failure: equivalent DC input resistance. Therefore, a measurement method is proposed, which takes into account the phase deviation of the fundamental commutation line voltage and uses equivalent DC input resistance as the input of the established mathematical model to measure the extinction angle. Meanwhile, according to the characteristics of equivalent DC input resistance, a method based on constant equivalent DC input resistance (EDCIR) to suppress repetitive commutation failures is proposed. Finally, several simulations are conducted on the CIGRE HVDC benchmark and GuiguangII model to validate the effectiveness of the proposed measurement method(TPMM) in the accuracy and suppression of commutation failure. The simulation results show that the proposed measurement method has the same accuracy as the measured extinction angle method and is higher than that of the minimum voltage drop method commonly used in practical engineering in judging commutation failure. At the same time, the proposed method to suppress can effectively reduce the number of commutation failures under single-phase and threephase ground faults comparing with voltage-dependent current order limiter (VDCOL) and commutation failure prevention and control (CFPREV).