PHOTOVOLTAIC DC TRANSMISSION LINE FAST PROTECTION METHOD BASED ON CURRENT POLARITY DISTRIBUTION

In order to ensure the safe and stable operation of large- scale photovoltaic power stations through DC boost convergence access system，the protection device needs to accurately distinguish the short- circuit fault between the DC transmission lines. By analyzing the fault characteristics of the photovoltaic DC transmission line，a fast protection scheme based on the characteristics of the polarity change of the fault current at both ends of the line is proposed. The method uses the principle of two-dimensional mapping to distribute the polarity characteristics of the converters at both ends of the line before being blocked in the two-dimensional coordinate system，and construct the protection criterion in the form of probability description，so as to avoid the misjudgment caused by the instantaneous value when there is a polarity ride- through process in the short circuit fault between the poles. The 1 MW/± 30 kV photovoltaic DC boost output simulation model is built through the PSIM simulation platform for verification. The results show that this method can quickly and accurately identify the fault section，and has the ability to withstand higher transition resistance，distributed capacitance，noise interference and communication delay. © 2023 Science Press. All rights reserved.