Key Technology Of Solid State DC Circuit Breaker With Current Limiting Capability

The flexible DC technology has attracted wide attention for its advantages of effectively reducing line losses,reducing power supply corridors and facilitating gridconnected new energy sources.However,flexible DC system is faced with many technical problems which need to be solved urgently.The large DC fault current,no natural zero-crossing and rapid development make DC fault isolation technology and fault current limiting technology one of the most concerned technical problems in the development of flexible DC system.Therefore,this paper studies the solid-state DC circuit breaker with adaptive current limiting capability and its key technologies.Based on the analysis of the control strategy and low voltage traversal control method of wind turbine connected to grid,the transient characteristics of the fault of flexible DC system connected to isolated islands of wind power are studied,and it is pointed out that the influence of voltage drop depth of wind power grid-connected point on transient process of DC system fault.In order to isolate DC faults quickly,the working mechanism and breaking capacity of different DC circuit breakers are studied in this paper.In order to effectively avoid the adverse effects of conventional current limiting reactance on the operation stability of DC system and the breaking speed of DC circuit breaker,a bridge solid-state DC circuit breaker with current limiting capability is studied,and its comprehensive advantages in fault current limiting,current breaking and fault recovery performance are comprehensively analyzed.Aiming at the serious short-circuit impact of bias DC power supply on solid-state DC circuit breaker when DC side faults occur,this paper designs three-phase half-wave bridge rectifier DC power supply and its over-current protection circuit by optimizing the topology of current-limiting solid-state circuit breaker,which effectively reduces the cost of bias power supply and avoids the impact of fault current on device.In addition,the voltage setting method of DC bias power supply is analyzed and studied in this paper,which reduces the operation loss on the premise of meeting the operation requirements of solid-state DC circuit breakers.Finally,through the prototype topology design,parameter configuration and controller development,an experimental prototype of adaptive current-limiting solid-state DC circuit breaker is constructed.A large number of experimental prototype tests and fault simulation examples prove the correctness of the design of solid-state DC circuit breaker and its DC bias power supply and the feasibility of its application in flexible DC distribution system.