Current Transfer Characteristics Study Of DC Micro-Grid Hybrid Circuit Breaker

As a protection unit of DC micro-grid and micro-grid network, the safe and reliable operation performance of DC micro-grid hybrid circuit breaker has become one of the most important factors for distributed power development. Hybrid DC circuit breaker constituted by mechanical switch and power electronic device, combines the advantages of both traditional mechanical switch and solid state circuit breaker, its fast breaking performance provide a guarantee for the development of DC micro-grid and the distributed power. The current transfer characteristics study of hybrid DC breaker in breaking micro-grid fault current is based on the internal parameters, then some reasonable current transfer characteristics conclusions and some better design solutions are got by the analysis of the current transfer characteristics, which can also provide a theoretical basis and reliable reference solution for future fast breaking DC micro-grid hybrid circuit breaker.At first, a simulation model of hybrid DC circuit breaker is build in Matlab/Simulink, using Mayr arc model, IGBT, RCD snubber circuit and surge arrester, which can fulfill the requirement of the study, then some theoretical support current transfer characteristics conclusions are got according the analysis of simulation waveform under different external circuit parameters and different transfer slip parameters. The conclusions not only verify the accuracy of the simulation model but also provide a reasonable and effective reference for designing and testing a DC micro-grid hybrid circuit breaker prototype.Under the guidance of the current transfer characteristics conclusions from simulation results, a hybrid DC circuit breaker prototype withstand breaking overvoltage 1200V, breaking current 150A is designed. The prototype use a rapid vacuum switch as a mechanical switch, which is repulsion breaking, permanent magnet repulsion maintain, power electronics IGBT as breaking unit, RCD buffer circuit and ZnO arrester as protection part. The rapid vacuum switch has a high breaking speed, which lays a solid foundation for the study of current transfer characteristics of hybrid circuit breaker.At last, a testing platform for the self-designed prototype of hybrid DC circuit breaker is designed, which can use to simulate DC short-circuit fault of Micro-grid voltage level (400V), and make breaking tests with different fault currents (below 200A) and different line inductance. The current transfer characteristics conclusions same as the simulation are got which verifies the effectiveness of the prototype and the accuracy of the current transfer characteristics conclusions with different parameters, these conclusions also provide reasonable bases and references for future faster micro-grid hybrid DC breaker design.