Enhancing Current Sharing in Metal Oxide Varistors Using Dynamic U-I Characteristic Analysis

Metal oxide varistors (MOVs) are widely used as protective elements in power electronics (PEs) to clamp overvoltage and dissipate energy. However, the conflict between the increasing power capacity of PEs and the limited energy-handling capacity of single MOV valves leads to a multivalve parallel connection in the MOV devices, thus difficulties in current sharing. This article presents an investigation into the dynamic volt-ampere (U -I ) characteristic of MOVs under high-capacity PE switching off and proposes a strategy to improve current sharing performance between MOV valves. An experimental circuit is designed to simulate the working conditions, and a dynamic U -I curve extraction procedure is proposed. The Fréchet distance is utilized to evaluate the similarity of dynamic U -I curves, and a matching strategy is proposed to improve the current sharing performance.