The Fault Diagnosis Method of Photovoltaic DC Transmission Line Based on the Current Polarity Zero-Crossing Characteristics

When the large-scale photovoltaic power station adopts the method of DC step-up collection access system, the fault of DC transmission line needs to be identified quickly and accurately. By analyzing the fault characteristics of inter-pole short circuit of photovoltaic DC transmission line, a fault diagnosis method based on current polarity zero-crossing characteristics of fault current polarity is proposed. This method combines the zero-crossing times of fault current and its slope characteristics to construct a diagnosis method. The least square method is used to describe the slope characteristics of the fault current, and the number of zero-crossings is added to construct the criterion, so as to avoid the misjudgment caused by the single instantaneous current change rate and the damage to the DC system caused by the long discrimination time when the inter-pole short-circuit fault occurs. The simulation model of 1 MW / ±30 kV photovoltaic DC step-up access system is built by PSIM simulation software. The simulation results show that the method can quickly and accurately diagnose the fault section.