Abstract:To address the issue that the AC-side fault characteristics of photovoltaic (PV) power plants integrated into VSC-HVDC differ significantly from those of traditional AC systems due to the influence of power electronic devices at both ends, a steady-state fault characteristic analysis method is proposed that incorporates system topology and converter fault control strategies, in order to clarify the sequence-component coupling among devices. First, steady-state fault characteristics of AC-side asymmetric faults in PV power plants connected to VSC-HVDC are analyzed. The results reveal the controllable nature of the output currents from power electronic devices at both ends, as well as the relationship of sequence-component coupling between converter’s grid-connected point voltage and its output current. Then, it is emphasized that when the PV power plants adopt the negative-sequence current suppression strategy, the HVDC converter becomes the sole source of negative-sequence current in the system. It is further concluded that, under single-phase-to-ground faults and phase-to-phase faults, the fault phase current differences exhibit a quantitative relationship with the negative-sequence current of the HVDC converter. It is also noted that the negative-sequence current limiting of the converter significantly alters the system’s sequence-component characteristics. Finally, the correctness of the steady-state fault characteristic analysis is verified through electromagnetic transient simulations of a large-scale PV power plant integrated into a VSC-HVDC system, providing theoretical and technical support for the research of protection principles in power electronics dominated new power systems.