The influence of open-phase operation of inverter side AC subsystem on commutation process and countermeasures

Commutation failure can lead to DC power fluctuation or even DC pole blocking, threatening the safety and stability of power system. As an abnormal operation state, open-phase operation of inverter side AC subsystem (OPOISAS) occurs at times and affects commutation process. In this paper, the influence of OPOISAS on commutation process is analyzed first. And the analysis shows that the larger the negative-sequence voltage amplitude (NSVA) of the commutation bus is, the greater the risk of commutation failure will be. To deal with the risk of commutation failure, the formula of the negative-sequence voltage of commutation bus during OPOISAS is deduced. Based on the formula, the law of NSVA variation with different factors is analyzed. Meanwhile, several countermeasures are given from the perspective of system planning and operation to reduce the risk of commutation failure during OPOISAS. Simulation results demonstrate that the analysis is correct and the countermeasures are effective.

Automated summary

This paper analyzes the impact of open-phase operation of the inverter side AC subsystem on the commutation process, revealing that a larger negative-sequence voltage amplitude of the commutation bus increases the risk of commutation failure. A formula for the negative-sequence voltage of the commutation bus during open-phase operation is deduced to address this risk, with analysis on the variation of the negative-sequence voltage under different factors and countermeasures from the perspective of system planning and operation given to reduce the risk of commutation failure. Simulation results confirm the accuracy of the analysis and effectiveness of the countermeasures.