Estimating Phase Angle Jump of Commutation Voltage and Suppressing Commutation Failure During Fault Recovery

The phase angle jump (PAJ) of the commutation voltage during fault is well-known to have significant impact on the commutation failure during fault recovery (CFFR) in line-commutated converter-based high voltage direct current (LCC-HVDC). However, the value of PAJ has been empirically determined in previous research without a theoretical foundation, leading to inaccurate estimation of its impact on CFFR and inappropriate control actions to mitigate CFFR. To address this issue, this paper theoretically shows how the Network Structure (NS) in different AC systems changes the level of PAJ of commutation voltage, demonstrating the decisive role of changing NS in evaluating CFFR. Specifically, a calculation method based on equivalent AC-DC system (EADSC) is proposed, showing that transient NS changes (TNSC) and transient DC power flow changes (TDPC) jointly contribute to the level of PAJ. Based on these findings, a PAJ-based firing angle compensation strategy (PAJ-ACS) is proposed for CFFR suppression. PAJ-ACS compensates for tracking error of the phase-locked loop (PLL-TE) caused by TNSC and TDPC, and prevents the saturation of the constant extinction angle controller (CEA) by using adaptive extinction angle reference values. Unlike existing methods, PAJ-ACS is designed based on proportional controllers and considers the most extreme PAJ, enabling rapid and targeted compensation with margin, effectively suppressing CFFR under a wide range of fault conditions. The accuracy of the proposed EADSC and the effectiveness of PAJ-ACS are validated using PSCAD/EMTDC simulations on the modified CIGRE LCC-HVDC benchmark system and the IEEE 39-bus system.