A configuration concept of solid state switch for 2kV class DC circuit breaker

In the HVDC grid hybrid circuit breakers are adopting stack of solid state SW (S/S) has the capability to break the fault current. The S/S of the circuit breaker comprise several semiconductors which are connected in series. The importance of large capacity of S/S has been shaping up in the HVDC circuit breaker. However, the rated capacity of power semiconductor at S/S is not enough to overcome the high voltage generated by blocking the fault current. In this reason, the serial connection of a number of semiconductor switches is necessary. However, when the semiconductor switches are connected by serially, unbalanced voltage could be appeared at each semiconductor switches due to the difference in semiconductor´s turn-off time. Despite the same model of manufacturer, the turn off time could be different in accordance with the temperature. As a result, the S/S should be designed in order the unbalanced voltage not to exceed the breakdown voltage of the semiconductor by taking into account the turn-off time. To solve this problem, the configuration concept for balancing of breaking voltage between semiconductors is proposed in this paper. In addition, the experimental results of voltage distribution at 2kV class S/S are presented to verify the procedure.