Research on the improved hybrid DC circuit breaker with voltage-limiting and current-limiting capability

The DC circuit breaker (DCCB) is a critical device that ensures the safe and reliable operation of the DC transmission system. As the level of DC voltage and transmission power increases, the flexible DC grid will need more and more opening capacity of the DCCB, as well as the burden of high costs. To solve the problem of excessive voltage and current stresses in existing DCCBs during DC fault current opening, an Improved Hybrid DCCB with the capacity of current-limiting and voltage-limiting is proposed, which crucially adds current-limiting and voltage-limiting branches. The current limiting branch can be activated 2 ms earlier in a fault circuit, significantly reducing the number of diodes and IGBTs required for branch transfer. In addition, overvoltage problems can be greatly reduced by properly designing the parameters of the current limiting branch. These improvements significantly increase the open ability, safety, reliability, and economy of the DCCB. The improved hybrid DCCB is shown to be effective and feasible by a large number of simulation and experimental test results.