Analysis of the Application of MOV-Based Voltage Balancing Circuit in Series-Connected IGBTs

In the field of high-voltage power conversion, the series connection of Insulated Gate Bipolar Transistor (IGBT) devices is the most direct method to increase the voltage and power levels of power electronic converters, offering advantages such as low cost, simple control, and improved reliability. However, uneven voltage distribution during switching transients in series-connected devices remains a major bottleneck limiting their application. The metal oxide varistor (MOV), a common protection device, can not only limit overvoltages across devices but also absorb the unbalanced energy caused by uneven voltage distribution, enhancing reliability. The use of MOVs in the protection of power electronic equipment has been increasing. This paper introduces the use of MOVs into series-connected converters as a protection circuit, analyzes their working principle and parameter design, and verifies the effectiveness and benefits of the proposed voltage balancing circuit through simulation.