Control Strategy for VSC-HVDC under Unbalanced Grid Voltages

摘要

This paper describes the use of an unbalanced control strategy to solve the faults occur in AC grid side of High voltage direct current based on Voltage Source Converter (VSC-HVDC) system. This method divides the voltage and current parameters into negative-sequence and positive-sequence. It can be obtained that the negative-sequence appears as double-frequency component in the positive-sequence synchronous reference frame; while, it appears as dc component in the negative-sequence synchronous reference frame. To mitigate the unfavourable impact of the unbalance fault, such as the DC link ripples, the dual vector control algorithm in dq synchrounous reference frame is designed. Simulation results demonstrate the validity and the effectiveness of the proposed control scheme.