Coupled Inductor-Based Zero Current Switching Hybrid DC Circuit Breaker Topologies

This paper proposes a coupled inductor-based hybrid dc circuit breaker topology with zero current switching for fast fault interruption in dc systems. A series resonant circuit comprising of the secondary winding of a two-winding coupled inductor and a charged capacitor (commutation capacitor) is switched on during fault to inject a counter-current pulse, and, consequently, force a zero crossing of fault current. Proposed solution facilitates arcless breaking for a mechanical circuit breaker due to zero current turn-OFF. The proposed circuit breaker exhibits fast fault response (~30 μs), and the response time is programmable based on the design of the coupled inductor and commutation capacitor. Furthermore, presented solution mitigates the requirement of energy-absorbing elements for demagnetizing the dc network following fault interruption, in contrast to conventional dc breakers. The paper also presents two modified circuit-breaker topologies to achieve unipolar voltage profile on the capacitor, which will enable the use of electrolytic capacitors for commutation so that the capacitor stack size is reduced in high-voltage applications. Detailed analysis and design equations are presented to explain the operation of the proposed topologies. Functionality of the proposed circuit breakers is verified through simulation, and experimental results are based on two laboratory prototypes.

I. Introduction

Direct current (dc) power distribution architectures have generated significant attention in numerous applications, such as offshore and subsea power systems [1], transportation [2], distributed generation, and grid energy storage [3]. However, the principal challenge in the growth of dc power market is the lack of reliable protection against short-circuit faults. A fault in a dc system results in fast ramp up of the fault current. Moreover, dc fault current does not experience any natural zero-crossing. Therefore, dc circuit breakers (DCCB) should be capable of fast fault quenching in order to prevent damage to the dc system and maintain grid resiliency [4]. Additionally, a DCCB should operate with minimal power loss as a closed switch.