Analysis of Active and Reactive Power Coupling Characteristics of the Feeder System under DC Faults

This study investigates the active-reactive power interaction coupling under commutation failure (CF) following high-voltage direct current (HVDC) faults. First, the coupling mechanism between the rectifier power characteristics (transmitted active power and consumed reactive power) under DC faults is analyzed. Next, the dynamic interaction between active and reactive power at the sending-end system after CF at the inverter side is examined. The variation patterns and underlying mechanisms of DC voltage, DC current, active power, and reactive power under varying fault severity levels are elucidated. Finally, simulations based on the CIDRE HVDC benchmark test system in PSCAD/EMTDC validate the theoretical analysis. This work provides critical references for enhancing traditional stability control strategies in sending-end grids.