Research On The Definition Of Turning-off Area And Bidirectional Switching Function Of Γ-source Dc Solid-state Circuit Breaker

DC has no natural zero-crossing point,and DC circuit breakers have become a key technology for the promotion and application of DC systems.The Γ-source DC circuit breaker(ΓDCCB)uses the straight-through mode of operation to break short-circuit faults.It is a new type of micro-level self-shutdown solid-state circuit breaker,which solves the traditional Z-source circuit breaker’s non-common ground,power circulation,load mutation error action and input resonance and other issues.This paper focuses on the key issues ofΓDCCB bidirectional power flow breaking,shut-off area definition and safe reclosing,in order to optimize the performance of the DC circuit breaker.Aiming at the problem that the traditional Z-source circuit breaker in the bidirectional DC system cannot realize the bidirectional power flow separation,the comparison and combination method is used to construct the bidirectional Z-source circuit breaker and the conduction loss is the constraint condition to reconstruct the electrical network,and puts forward two topologies of bidirectional Γ-source DC circuit breaker.In view of the ambiguity of the short-circuit shut-off range,the difficulty of defining the regional boundary,and the internal connection of multi-dimensional parameters of the Γ-source circuit breaker,this article gives the selection boundary of shut-off parameters of ΓDCCB through theoretical derivation,and then combines its nonlinear simulation and experiment to fit the accurate shut-off region,and puts forward a method to define nonlinear failure region ofΓDCCB three-dimensional graph,and obtains the definition criterion of self-turn-off failure region.In view of the problem that the Z-source circuit breaker cannot be safely reclosed and re-broken,this paper proposes three solutions based on the construction of the virtual non-through mode before and after reclosing:a reverse repetitive energy-feeding reclosing method,a thyristor phase-shift control reclosing method,a ю-source DC solid-state circuit breaker and its control method,which can realize infinite safe reclosing and re-breaking of DC circuit breaker,and at the same time reduce the impact of fault current.The scheme is verified by simulation,and an experimental prototype of Г-source DC solid-state circuit breaker is built at the same time.It’s designed the hardware circuit and software algorithm,and the above functions of the circuit breaker are verified on the experimental platform.The experimental results showed that:the proposed Г-source DC circuit breaker can effectively break under bidirectional power flow,which verifies the accuracy of the self-turn-off area definition criterion mentioned in this paper,and demonstrates the feasibility and superiority the feasibility and superiority of the extended application of Г-source network in circuit breaker field.