Control Method for HVDC System with STATCOM

In order to reduce the probability of commutation failure in HVDC transmission system equipped with STATCOM, we developed an improved control strategy of STATCOM and HVDC system. When a fault occurs, based on the constant AC voltage control of STATCOM, a regulation function for AC voltage reference value is applied to STATCOM. Meanwhile, additional DC current and extinction angle control functions are applied to HVDC system. Simulation in PSCAD/EMTDC shows that the proposed constant AC voltage control of STATCOM can mitigate commutation failure when the levels of single phase fault at inverter busbar are 23.08% and 84.24%, and the additional DC current and extinction angle control functions can prevent continuous commutation failure when the fault level gets higher, such as 120.34%. Hence, the proposed control method can improve HVDC systems in both commutation failure immunity and operation performance.