Continuous Commutation Failure Suppression Using Dynamic Reactive Power Control in the Hybrid UHV AC/DC Power System

For hybrid Ultra High Voltage (UHV) AC/DC power grid, it is necessary to use the interaction between them to enhance system stability. The voltage stability of AC system can avoid continuous commutation failures and blocking in multiple HVDC transmission systems. In this paper, dynamic reactive power control in UHV AC system for HVDC continuous commutation failure suppression is proposed. The voltage and reactive power characteristics of UHV AC system are analyzed. The control is divided into two stages according to the AC bus voltage of HVDC. In different voltage stage, the adjustable and fixed shunt reactors are switched off in turn. Then the UHV AC system can output reactive power to the receiving end grid based on capacitance characteristics of long transmission lines. That can improve the utilization efficiency of the dynamic reactive power resource in the whole power grid to support the dynamic voltage and suppress the continuous communication failure. Finally, the detailed simulation results verify the effectiveness of the strategy.