Predictive Constant Extinction Angle Control of LCC-HVDC Receiving End Converter

Based on the two aspects of DC current prediction and critical extinction voltage-time area, the existing constant extinction angle control is improved. Assuming DC current Id changes at a constant rate, and the rate of DC current change corresponding to the beginning of commutation is taken as the rate of DC current change during the entire commutation period, that is, dId/dt. At the same time, considering the influence of the commutation voltage change on the extinction angle γ in the transient process, the concept of the critical extinction voltage time area is introduced, and the condition that the extinction voltage time area should meet the critical extinction area during transient operation is derived. The γ control reference value γref expression is adjusted, and the trigger angle α value is obtained by combining the DC current prediction. In this way, when the system is operating in a transient process, the trigger angle α can be adaptively adjusted by comprehensively considering the change of Id and the change of the commutation voltage. The simulation shows that the improved control strategy effectively reduces the probability of commutation failure and improves the stability of the AC bus voltage.