Voltage sharing between mechanical switch and IGBT in a hybrid DC circuit breaker

Hybrid DC circuit breakers have the advantages of fast fault current interruption with the solid-state semiconductor devices and low conducting loss with the mechanical switches. Therefore it is suitable to be used in the multi-terminal DC transmission system. The objective of this paper is to determine a voltage sharing between the mechanical switch and the IGBTs in a proposed topology of hybrid DC circuit breaker during the current interruption process. In the proposed topology, IGBTs and a mechanical switch is in series, then the series circuit is paralleled with a capacitor. A prototype of the proposed hybrid DC circuit breaker is built up. The voltage sharing between the IGBTs and the mechanical switch is measured with a variation of the parallel capacitance. The experiment results show that the IGBT bears almost no voltage while mechanical switch bears nearly all voltage during the current interruption process. As the parallel capacitance increases, the voltage on the IGBT decreases even more. Therefore it is possible to use low rated voltage of IGBTs to interrupt DC current in a high voltage circuit, which decreases the cost.