Reactive Power Coordinated Control for Improving Transient Characteristics of DC Side of LCC-HVDC Using Parallel VSC-HVDC

In order to mitigate the DC overcurrent and the AC transient voltage on the rectifier side of the LCC-HVDC (line commutated converter based HVDC) caused by commutation failures, a transient reactive power coordinated control scheme is proposed for a hybrid multi-infeed HVDC system in which the rectifier side of the LCC-HVDC and the VSC-HVDC (voltage source converter based HVDC) are in parallel. The transient characteristics caused by commutation failures of the hybrid multi-infeed HVDC system are analyzed. Based on the characteristics of the LCC-HVDC with constant DC current control and the VSC-HVDC with AC voltage control, a transient reactive power coordinated control module is designed for the hybrid multi-infeed HVDC system to mitigate overcurrent and transient voltage caused by commutation failure, including the quick response module of trigger angle, the quick response module of reactive power and the fault monitoring module. A hybrid multi-infeed HVDC system model is built in the PSCAD/EMTDC for a comparative simulation analysis. The simulation results show that the control performance of the proposed transient reactive power coordinated control scheme is superior to that of the VSC-HVDC with constant reactive power control and constant AC voltage control.