A fault location method for internal faults of inverter in offshore wind HVDC system based on temporal characteristics of AC current

• Defines non - zero conduction width of AC minimum current characteristic quantity to capture fault temporal characteristics. • Analyzes temporal characteristics of AC minimum current for different fault types. • Proposes fault location method based on AC minimum current temporal characteristics. • Identifies fault type and locates fault quickly & accurately via the proposed method. The LCC inverter is the core equipment in the offshore wind HVDC system. Identifying the fault types and locating the fault locations in the inverter area are crucial for inverter safety. Due to the fault form is complex and diverse, this paper proposes a fault location method based on the temporal characteristics of the three-phase AC minimum current in the HVDC inverter area to identify the fault types and locate the fault locations. Firstly, it is found that there are zero and non-zero characteristics in the temporal characteristics of the AC minimum current, and the temporal characteristics of the AC minimum currents of internal faults have apparent differences. Secondly, based on the inverter topology and the difference of the non-zero conduction width of AC minimum current characteristic quantity in single bridge or double bridge, it is proposed to identify the fault types and locate the fault locations. Thirdly, affected by the waveform, the high-voltage bridge short-circuit to ground fault on the DC side and the high-voltage bridge short-circuit to ground fault on the valve side may be misjudged after the fault location is determined, so it is proposed to correct the fault location using amplitude characteristics of AC current. Finally, the simulation results verify the validity of the proposed fault location method. Moreover, the location method is not affected by the fault occurrence moment, the short circuit ratio, and the signal-to-noise ratio, which verifies the adaptability of the proposed method.