A Modified Z-Source DC Circuit Breaker for Power Electronic Converter Load Application

The protection of the DC system is a major concern due to the absence of natural current zero crossing during breaker operation. The Z-source DC circuit breaker utilizes passive components such as inductors and capacitors to create current zero crossing through the main line switch in order to isolate the fault from the system. It is a type of solid state DC circuit breaker with inherent fault detecting capability without use of any sensing circuitry and can clear the fault in microseconds. The breaker employs an SCR as a main line switch. It is to be ensured that the current through the SCR should be maintained above its holding current during steady state, so as to prevent any false tripping of the breaker. Power electronic converter loads such as buck converter, draws discontinuous current from the source. Application of breaker for protecting such loads will result into discontinuous current through the SCR and undesired commutation of SCR during steady state condition. This paper presents failure analysis of the Z-source DC circuit breaker in protecting the power electronic converter loads and proposes modified Z-source DC circuit breaker which avoids discontinuous current through the SCR during steady state condition, in order to make it function for power electronic converter loads with discontinuous input current.