Abstract
Solid-state circuit breakers (SSCBs) are designed to interrupt fault currents typically several orders faster than its electromechanical counterparts. However, such an ultrafast switching operation would produce a dangerous overvoltage which might cause damages to SSCBs and other circuit elements in the system. This paper proposes a novel snubber circuit for suppressing the overvoltage. It takes the advantages of both resistor-capacitor-diode (RCD) snubbers and metal oxide varistors (MOVs). Its operating process is analysed before the proposed snubber circuit for 400V DC SSCBs is designed. Pspice simulator is employed for simulating the operating process and a prototype SSCB with the proposed snubber is built and tested in a lab-scale DC system. The results of simulation and experiment validate the effectiveness of the proposed snubber.
Highlights
DC distribution networks are gaining popularity in data centres, commercial buildings and transport power systems [1,2,3,4] because in comparison to traditional AC systems, they demonstrate higher efficiency and more readiness for integrating with various local renewable power sources and ever-increasing DC electronic loads
The results demonstrate the overvoltage across solid-state circuit breakers (SSCBs) can be effectively suppressed less than twice of the supply voltage with the proposed snubber
The increase of metal oxide varistors (MOVs) clamping voltage can reduce the response time whereas the response time would increase in concert with the rising of snubber capacitance, system inductance and trip current level
Summary
DC distribution networks are gaining popularity in data centres, commercial buildings and transport power systems [1,2,3,4] because in comparison to traditional AC systems, they demonstrate higher efficiency and more readiness for integrating with various local renewable power sources and ever-increasing DC electronic loads. Solid-state circuit breakers (SSCBs) have been intensely researched as promising candidates to replace mechanical circuit breakers for DC protection due to its ultrafast switching speeds [5,6,7,8] Such a fast switching operation would produce an unacceptably high voltage across SSCBs because of the rapid fall of fault current and small system inductance [9]. To start with, the operating process of both conventional RCD snubber circuits and MOVs are reviewed and their pros and cons are discussed. A novel snubber circuit combining a RCD with a MOV is proposed and analysed before the proposed snubber for 400V DC SSCBs is designed and its components are selected. ∙ The impact factors involved in the snubber on the response time of SSCBs have been identified to optimise the snubber design to meet different application requirements
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