| The DC microgrid has the advantages of no reactive power components,easy to achieve seamless switching of multiple power sources,and good DC load compatibility,which has attracted wide attention from experts and scholars.However,the DC microgrid system has low impedance and small moment of inertia.When a short-circuit fault occurs,the short-circuit current rises quickly,which is likely to cause serious harm to the stable operation of the DC microgrid.Therefore,there is an urgent need to quickly locate and remove short-circuit faults.Because of its fast and flexible breaking characteristics,solid-state circuit breakers are very suitable for the application scenarios of DC microgrid short-circuit protection.According to the fault characteristics of the DC microgrid and the design requirements of the DC solid-state circuit breaker,this paper proposes two new solid-state circuit breaker topologies,the resistance segment current-limiting solid-state circuit breaker and the capacitive two-way DC solid-state circuit breaker,and analyzes and verifies them.Fast blocking performance of DC short-circuit current.First of all,this article reviews the current research status of DC microgrid protection,analyzes the operating principles of various protection devices,and according to the fault characteristics of the DC microgrid,it is concluded that the DC solid-state circuit breaker should have a fast breaking speed when breaking to ensure Performance requirements for the safety of the breaking process.Second,according to the topology and grounding method of the DC microgrid,the fault types of the DC microgrid are analyzed,and the fault characteristics of the common short-circuit faults and single-pole grounding faults in the DC microgrid are theoretically analyzed.According to the characteristics of rapid fault current change,the existing fault current limiting technology and fault ride-through technology are studied,and the design requirements of DC solid-state short-circuit devices are analyzed.Third,the topological structure of the resistance segmented current-limiting solid-state circuit breaker is proposed,the fault blocking process is analyzed,and the key parameters such as current-limiting resistance and blocking capacitance are theoretically analyzed and formula deduced.The pair of current-limiting components is explored.The influence law of fault performance is simulated and verified in combination with its control strategy.The results show that the topology can block the fault short-circuit current in sections quickly,and the overvoltage generated at both ends of the switch tube is low.Fourth,the topological structure of the capacitive bidirectional DC solid-state circuit breaker is proposed,its working principle is studied,the working process of its fault blocking is analyzed,and the key parameters affecting its blocking performance are theoretically analyzed and formula deduced.Combined with the current differential control strategy,the simulation verification is carried out in Saber software.The simulation results show that the fault blocking time is faster and can be adjusted according to the capacitance parameters.Fifth,an experimental platform for capacitive bidirectional DC solid-state circuit breakers was built.The blocking performance of the prototype DC solid-state circuit breaker was tested under the condition of 220 V DC voltage.The experimental results show that the circuit can block the short-circuit current within 4.2ms,and the blocking time can be adjusted according to the blocking capacitance. |
