An Isolated Voltage Injection Based Hybrid Circuit Breaker for MVDC Applications

A MVDC hybrid circuit breaker (HCB) is proposed in this paper that consists of an electro-mechanical switch (EMS) in series with a voltage injector building block (VIBB). The VIBB-HCB does not employ any semiconductor devices in the line current path and utilizes a magnetic structure for injecting purpose that is unbiased in the normal operation, not interfering in line power path and without loss except the negligible winding copper losses. The EMS is being opened under zero voltage and zero current which makes the structure more reliable and the design of energy absorber easier. The injection circuit is isolated from the line. Hence, any surge or fault current does not impact the injection circuit. Also, by employing full bridge in the auxiliary converter, bidirectional fault clearing option is achieved for the proposed structure. Further, the design does not require large pre-charged capacitors for interrupting the fault. The proposed concept is validated through Finite Element Analysis, followed by experimental verification on a scaled down hardware prototype.