Design and Validation of a MVDC Isolated Active Voltage Injection Based HCB

Abstract

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 main DC line. The VIBB utilizes an E-core-based integrated magnetic structure for injection purpose. The core is unbiased during normal operation, which does not affect system response or add more inductance in the main DC line. Further, the injection circuit is isolated from the main circuit. Hence, any surge or fault current does not impact the injection circuit. The injection circuit comprises a SiC-based full bridge auxiliary converter, which provides fast (μs range) bidirectional fault clearing capability. Moreover, the EMS is opened under zero voltage and zero current, which increases EMS reliability and lifetime. Lastly, the design does not require bulky high rating energy absorption components such varistors due to miniscule post-fault interruption residual energy. A detailed design procedure is derived and validated through Finite Element Analysis using ANSYS Maxwell Transient solver. This is followed by experimental verification on a scaled down hardware prototype.