2020 Volume 9 Issue 3 Pages 291-297
This paper considers the application of series-connected press-pack Injection Enhanced Gate Transistors (IEGTs) as semiconductor breakers for hybrid DC circuit breakers (DCCBs) in multi-terminal HVDC transmission systems. In order to interrupt a large current equivalent to a fault current without parallel connection of a press-pack IEGT, a snubber circuit was applied. With the snubber circuit, surge voltages and switching losses can be reduced. In order to balance the voltages across each series-connected IEGT, their characteristics and circuit conditions should be similar, and the operation timings should be adjusted. The performance a prototype hybrid DCCB was evaluated. The semiconductor breaker of the hybrid DCCB prototype was composed of four series-connected IEGTs (4.5kV, 2.1kA) with the snubber circuit. The experimental results show that it successfully interrupted a current of 9.5kA. The peak voltage across the semiconductor breaker was 14.3kV. The variation in the voltage across each IEGT was less than 5%. This means that the peak voltage of each IEGT was suppressed to less than the withstand voltage of the IEGT.