Study on AC Transient Overvoltage Suppression of LCC-HVDC Sending End System Based on DC Current Control Optimization

The receiving end system AC fault of the line-commutated-converter based high voltage direct current (LCC-HVDC) system will lead to commutation failure (CF) in inverter. During the fault and its recovery, AC transient low voltage and transient overvoltage (TOV) will occur in the sending end system. The TOV has the risk of triggering the disorderly off-grid of the nearby renewable power generations, and in a serious situation, it will threaten the power system can not maintain secure and steady operation. Therefore, this paper analyzes the mechanism involved of the AC transient voltage during the AC fault and the recovery period first. It reveals that the key factor causing the TOV of the sending end system is the setting of the DC current reference value. Then, a DC current reference value limit method based on the AC TOV sampling value is proposed, which is used to accelerate DC current recovery and suppress the TOV of sending end system. Finally, based on the CIGRE Benchmark test model, the transient voltage analysis results and the validity of the designed control method are demonstrated by electromagnetic transient simulation.