Overvoltage Suppression Strategy for Sending AC Grid with High Penetration of Wind Power in the LCC-HVDC System under Commutation Failure

With the increase of wind power installation capacity, the LCC-HVDC transmission system is an effective scheme for long distance transmission of wind power. Commutation failure is a common fault for LCC-HVDC transmission system. During the commutation failure, the voltage of sending AC grid presents the first decreased then increased characteristic. In order to avoid the overvoltage under the commutation failure causing WPGS to separate from the power grid, it is necessary to suppress the overvoltage of sending AC grid under commutation failure. This paper quantitatively analyzes for the first time the transient voltage characteristics of the sending AC grid under commutation failure. The analysis indicates that the delay of the grid voltage detection part in the wind turbine is the significant influence factor on the overvoltage of sending AC grid. Based on the analysis results, this paper proposes the delay compensation control strategy of WPGS to suppress the over voltage of the sending AC grid with high penetration of wind power under commutation failure. The effectiveness of the strategy is verified by simulation and CHIL experiment, and it is also verified that the strategy is also applicable for conventional LVRT faults, which shows that the control strategy is univesal.