Modeling and Overvoltage Suppression Analysis of Grid-connected Converter with VSG Control Strategy Under Commutation Failure

The line commutated converter based high voltage direct current (LCC-HVDC) system is a widely used long-distance power transmission system. The sending terminal grid of the DC transmission system exhibits the characteristics of a high proportion of power electronic equipment. The virtual synchronous generator (VSG) control strategy has been proved to be an effective technology to improve the stability of weak grids. Commutation failure is a common fault in the LCC-HVDC system, which causes the voltage amplitude of the sending terminal grid to decrease first and then increase. The mathematical model of the power electronic equipment adopting VSG control under commutation failure is established. Based on the mathematical model, an enhanced VSG control is proposed to suppress the overvoltage of the sending terminal grid voltage under commutation failure. The effectiveness of the enhanced VSG control strategy is verified by the simulation model of grid-connected converter connected to an LCC-HVDC transmission system based on Matlab/Simulink.