Pilot Protection Method for Flexible DC Distribution Network Based on Quadratic Integration Value of Reference Voltage

Flexible DC distribution network is an important development direction of the future distribution network because it has good renewable accommodation capability. The control response speed of power electronic devices is fast, which leads to the fast switching of each stage after the fault and different fault characteristics, and brings the challenges to the rapidity and adaptability of the protection methods. On the basis of analyzing the fault characteristics of each stage after the fault of flexible DC distribution lines, this paper proposes a pilot comparison protection method for flexible DC distribution networks, which is applicable to the whole fault process. In this method, the quadratic integration value of the voltage at the corresponding reference point is calculated by the electrical quantities at the measuring point. According to the positive and negative polarity of the quadratic integration value, it is judged whether the fault point is between the measuring point and the reference point, which is used as the fault judgment result of the protection unit. The pilot protection can judge the internal and external faults of the protected line by comparing the fault judgment results of the protection units on both ends. The fault simulation model of the flexible DC distribution network is built using PSCAD/EMTDC, and the correctness of the proposed method is verified by setting different fault locations. The simulation results show that the proposed method can accurately judge the internal and external faults in the whole fault process, and has high reliability, good applicability and strong resistance to transition resistance. It also has a good ability to deal with the calculation errors caused by distributed capacitance and noise interference. © 2023 Automation of Electric Power Systems Press. All rights reserved.