In order to investigate the causes of DC voltage blocking event during the STATCOM transient start–up under the power grid asymmetric faults

and to solve the DC overvoltage problem

the DC voltage control strategy of STATCOM must be analyzed and optimized. Through analyzing the device level control strategy

we pointed out the capacitor voltage was mainly determined by the PI parameters of PI DC voltage control link and phase –locked loop phase angle. Moreover

we proposed the way of optimizing the DC voltage control loop proportional integral coefficient and increasing the phase compensation. Based on the actual parameters of Dongguan substation STATCOM

the power grid simulation model of Dongguan substation STATCOM was built in PSCAD/EMTDC. By simulation

the levels of DC over voltage under different PI parameters were compared

and the levels of DC before and after phase compensation were also compared. Simulation results show that both PI parameters optimization and phase compensation can reduce the DC over-voltage level. A way of combining the PI parameter optimization and the phase compensation is adopted

which can decrease the DC overvoltage level from 121% to 113%. With the DC voltage control strategy optimization

the problem of STATCOM DC overvoltage is effectively solved.