MA Hongyue, LI Yan, ZHANG Tao, et al. 光伏电站接入柔性直流系统的交流侧不对称故障稳态特征研究[J]. Power System Protection and Control, 2025, (24). DOI: 10.19783/j.cnki.pspc.250119.
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.