A Novel Solid-State Switch Scheme With High Voltage Utilization Efficiency by Using Modular Gapped MOV for DC Breakers

Metal oxide varistors (MOV) is often used to limit the overvoltage generated by the current breaking of dc breaker to protect power electronic device from breakdown. However, while suppressing overvoltage, the MOV also causes the degradation of continuous operating voltage capability. This letter proposes a novel solid-state switch scheme with high voltage utilization efficiency by using modular gapped-MOV (MG-MOV) for dc breakers. The breakable gap is first applied to the protection of power electronic devices. By using the gap to share the voltage in the static-state and be broken down in the dynamic state, the overvoltage and continuous operating voltage of the solid-state switch can be decoupled. Moreover, based on the modular scheme, the instability of the gap discharges and the voltage imbalance of the series devices can be solved well. The working mechanism, voltage-balance and stability issue of the MG-MOV are discussed in detail in this letter, and a 15-kA prototype is developed to verify the feasibility of the novel solid-state switch scheme. The experiment under results show that voltage utilization efficiency can be increased from 44.4% to 72.0% by using MG-MOV.