An Ultraefficient DC Hybrid Circuit Breaker Architecture Based on Transient Commutation Current Injection

Protection against circuit faults represents a major technical challenge in the emerging dc transmission and distribution power networks. A popular prior-art dc hybrid circuit breaker (HCB) using a series load commutation switch (LCS) offers an excellent solution with arcless operation but suffers from a high conduction power loss associated with the LCS. This article proposes a new HCB architecture that relies on a switching-mode transient commutation current injector (TCCI) circuit instead of the LCS. The TCCI in the electronic path remains in a standby mode with near-zero power loss under normal conditions, but can rapidly generate a pulse current matching the fault current, and therefore facilitate current commutation from the mechanical to the electronic path. It completely eliminates the conduction power loss associated with the LCS, and delivers ultrahigh transmission efficiency. The TCCI circuit provides a near-zero voltage and a small high-frequency ac ripple current condition for the mechanical contacts to separate arclessly. A 600-V/20-A HCB prototype based on a two-phase current source buck converter topology and a high-voltage vacuum relay has experimentally validated the HCB concept, and demonstrated a mechanical to electronic commutation time of 7.2 μs, a total active response time of 310 μs, and a peak interrupted fault current of 89 A at a dc bus voltage of 400 V. The new HCB architecture can be applicable in medium voltage direct current (MVDC) (>5 kV) and high voltage direct current (HVDC) (>100 kV) applications as well.