Passive Clamping Circuit for Reduced Switch Count in Solid State Circuit Breakers

DC Solid-State Circuit Breakers (SSCB) play an important role in the protection of DC and hybrid AC/DC systems. As they operate mostly in on-state, the use of wide-bandgap devices, with low conduction losses, is an attractive solution. These devices need to be selected based on the rare occasion of fault breaking, with associated overcurrent and overvoltage intervals. In this work a novel clamping circuit, consisting in its simplified form of Metal-Oxide Varistors and capacitors, is proposed to be used in a DC SSCB. This circuit has the objective to reduce the breaker overvoltage during protection, enabling a lower number of required semiconductors in series and consequent overall reduced losses. An analysis of the idea and operation principle of the system is presented, alongside its stages of operation and defining equations. To evaluate its benefits, the system is compared with one typical passive solution. At the end a scaled prototype is tested, validating the benefits and theoretical analysis of the proposed approach.


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