New Principle of Pilot Protection Based on Kendall’s Rank Correlation Coefficient

Abstract

Affected by the control strategy after MMC failure, the fault current on the converter side of the AC line interconnected with the MMC is significantly different from the fault characteristics of the traditional power supply in amplitude and phase. The new fault current characteristics lead to the inapplicability of the traditional longitudinal current phase differential protection. In order to solve the problem of the applicability of relay protection, a new principle of longitudinal protection based on Kendall’s rank correlation coefficient is proposed. After the AC line fails, the Kendall grade correlation coefficient of the calculated current on both sides is calculated to distinguish the internal and external faults. Simulations are carried out on the RTDS platform, and the results show that the proposed protection principle can reliably distinguish between internal and external faults and has the ability to withstand transition resistance under various control reference values.