Transient Response Analysis and System Fault Ride-Through Capability Optimization of HVDC Based on Hybrid Commutated Converter

Modifying the inverter of line-commutated converter- based high-voltage direct current (LCC-HVDC) to hybrid commutated converter (HCC) is currently a highly effective solution for mitigating the risk of commutation failure (CF). This paper investigates the transient performance of HCC from five perspectives while retaining the LCC-HVDC control system. Since constant extinction angle (CEA) controller leads to significant reduction in power transmission, constant voltage (CV) controller is considered a more appropriate choice as the main controller during AC faults. In addition, the extreme case of insufficient forced commutation capacity leading to CF is considered. It is revealed for the first time that the voltage clamping effect of the arrester will cause a new CF phenomenon. There will be no short circuit on the DC side and the fault current is greatly reduced. This leads to insufficient regulation capability of the CV controller, resulting in continuous CFs. Given the limited fault ride-through capability of the selected CV controller, this paper proposes an adaptive order regulation control (AORC) based on expected reactive power. It can adjust the DC current and voltage in a targeted manner according to AC faults, and determine the maximum allowable upper limit of the firing angle. This improves the reliability of HCC in resisting CF. Under extreme cases, it also effectively prevents the continuous CFs. The simulation results in PSCAD/EMTDC verify the theoretical analyses and the proposed control method.