Overvoltage Mechanism and Suppression Method for LCC-HVDC Rectifier Station Caused by Sending End AC Faults

This letter analyzes the mechanism of the AC bus overvoltage at the LCC-HVDC rectifier station caused by the sending-end AC faults. Firstly, the influence of commutation failure on relevant electrical quantities is analyzed. After the commutation failure disappears, the inverter switches to constant current control. Under the joint action of the constant current control of the rectifier, the DC current and the trigger angle of the rectifier decrease rapidly, which reduces the reactive power absorbed by the rectifier. With the recovery of HVDC transmission capacity, the sending end AC bus voltage sharply rises, which increases the reactive power output of the filter. Reactive power redundancy occurs in the sending end AC bus leading to overvoltage. The suppression method proposed in this letter can effectively increase the reactive power absorbed by the LCC-HVDC rectifier during fault recovery. Besides, the method can also significantly enhance the minimum value of the inverter extinction angle and avoid possible commutation failure. The effectiveness and applicability of the strategy are confirmed through Electromagnetic Transient simulation.