A Predictive Method of LCC-HVDC Continuous Commutation Failure Based on Threshold Commutation Voltage Under Grid Fault

Line-commutated converter based high-voltage direct-current (LCC-HVDC) has been extensively applied in power system. LCC-HVDC is prone to continuous commutation failure (CCF), which consequently causes numerous active and reactive impacts, thereby resulting in various power system security and stability issues. Given that there is no CCF predictive method at present, the effect of CCF suppression measure is still limited, and the control margin of DC commutation station and power grid cannot be fully applied, so that the negative impact of CCF is difficult to reduce through advance control. In view of this situation, this paper aims at proposing a predictive method of LCC-HVDC CCF, which occurs again during the first CF recovery process. First, the predictability of CCF is demonstrated, and the idea for predicting CCF by comparing commutation voltage is proposed; Second, the calculation equation of CCF threshold voltage is derived by analyzing the CF process; Third, a predictive method of CCF based on threshold commutation voltage is proposed; Finally, the correctness of the theoretical analysis and predictive method is verified through the CIGRE HVDC standard system. Simulation results show that the proposed method has high accuracy and can provide sufficient time margin for emergency control to suppress the LCC-HVDC CCF.