A Novel Pilot Protection Scheme for AC Power Grid with Energy Router Interconnection

Abstract

A high proportion renewable energy regional power grid is interconnected with the large power grid through the energy router (ER), which is conducive to the safe consumption of renewable energy sources (RES), while the fault characteristics of RES deteriorate the traditional protection performance. Based on the engineering practice of county-level high proportion renewable energy grid, this paper analyzes the short-circuit current characteristics of ER and RES. On this basis, the pilot protection principle based on dynamic time warping distance comparison and the comprehensive protection scheme combined with ratio-restrained differential protection principle are proposed. In the case of controlled short-circuit current of the whole network, the internal and external faults are identified by using the Euclidean distance of the current sampling sequence on both sides of the line to improve the sensitivity of the protection. When ER is out of running and the regional power grid is directly interconnected with the power grid, the ratio-restrained characteristic is automatically switched under the condition of large short-circuit current by comparing the amplitude of short-circuit current, so as to prevent CT saturation from causing maloperation of pilot protection based on Euclidean distance comparison. The simulation results show that the proposed protection principle and scheme is suitable for different operating requirements of high-proportion new energy system, and has good operating performance, which meets the requirements of engineering application.