Research On High Voltage Hybrid DC Circuit Breaker And Its Key Technologies

In the context of energy interconnection,long-distance high-power multi-terminal flexible HVDC transmission will achieve energy time difference complementation,seasonal complementarity and regional complementarity.While improving the penetration rate of new energy,it can effectively solve the intermittent and solar energy and wind power generation.Randomness to maximize the potential of renewable energy.Among them,one of the key technologies for the engineering application of the DC transmission and distribution network is the development of DC circuit breakers.DC’s hard-to-reach arc has always been a difficult point in DC circuit breaker research.With the large-scale development of new energy sources and long-distance transmission,DC breakers need to further improve their breaking current in the case of reducing their own operating losses;The damping of the DC system is lower than that of the AC system.When the DC fault occurs,the fault current rises quickly.Therefore,it is necessary to quickly disconnect the faulty line.For this reason,the DC breaker needs to have a fast breaking capability,and the mechanical switch breaking speed is proposed.High requirements.In view of the high cost,large floor space,complicated control,large on-state loss and low voltage level of arc voltage shutdown,two new topologies are proposed for the current hybrid DC circuit breaker: based on low voltage capacitor suppression Arc high-voltage hybrid DC circuit breaker,secondary commutated high-voltage hybrid DC circuit breaker,two topologies are based on the current forced commutated hybrid DC circuit breaker for improvement,based on the voltage across the capacitor can not be abrupt to suppress the mechanical switch The initial arcing is disconnected;The first type is to connect the mechanical switch and the capacitor bank in parallel to replace the forced commutation of the power electronic module.The conduction loss is low,the control is simple,and the breaking speed is fast.The second type is the power electronic module and the mechanical switch and capacitor.The three groups are connected in parallel,which replaces the forced commutation of the power electronic module.Compared with the first type,the breaking capacity is stronger and the cost is lower,but the breaking time is increased.In this paper,the key technologies involved in the two topologies are introduced,and the advantages and disadvantages of the topology are compared.The differential control is proposed for the high-voltage hybrid DC-circuit breaker topology based on low-voltage capacitors.The two control strategies are controlled by linkage,and the pre-shutdown control strategy is proposed for the topology of the secondary commutated high-voltage hybrid DC circuit breaker.The mathematical theory analysis is carried out on the parallel mechanical switch of the capacitor bank to suppress the breaking and arcing.Based on the PSCAD/EMTDC simulation software,the proposed hybrid DC circuit breaker based on low voltage capacitor suppression arcing and quadratic commutated high voltage hybrid DC circuit breaker are simulated and verified,and the feasibility of the proposed topology is verified.It embodies the characteristics of the proposed topology.