A Novel Voltage Clamping Circuit Based on Thyristor-Controlled MOV for Low-Voltage DC Solid-State Circuit Breaker

Metal oxide variable resistors (MOVs) are usually used in voltage clamping circuits of SSCBs to limit overvoltage and absorb energy. However, the clamping voltage of the MOV is 23 times of the rated DC system voltage, which results in high voltage requirement for main semiconductor devices. In this paper, a novel voltage clamp circuit based on thyristor-controlled MOV (TC-MOV) is proposed. A thyristor is connected in series with the MOV to share the DC voltage during off state. The snubber capacitor is first self-charged during the breaking transient. And then they are also used to inject counter-current for reliable turning off the thyristor. The working principles of TC-MOV are analyzed and the design criteria for the main parameters are given. In addition, a prototype rated at 375V/100A is built to validate the proposed topology. The results show that the TC-MOV voltage clamping circuit has a better overvoltage suppression performance. The turn-off overvoltage is reduced from 680V to 501V for a 375V DC system, which reduces the voltage requirement of the main switch and improves the efficiency of the SSCB.