Hybrid DC Circuit Breaker With Fault Current Limiting Capability Research On Topology And Control Method

With the emergence of new high-power power electronic switches,DC transmission can meet the control requirements technically,and it also has the ability to compete with AC transmission economically.Different from AC transmission,the DC transmission system has weak damping characteristics.After a short-circuit fault occurs,the fault current rises rapidly,and the peak value is large,which poses a threat to the safe and stable operation of the DC system.It is of great significance to the safe and stable operation of the DC system to develop a DC circuit breaker that can quickly break the fault current.This paper analyzes the working principle and electrical stress of a hybrid DC circuit breaker（HCB）,and proposes two types of hybrid DC circuit breakers with current limiting capability combined with its advantages and disadvantages.In this paper,the topology,working principle,advantages and existing problems of typical hybrid DC circuit breakers are analyzed,and it is concluded that HCB has the advantages of low on-state loss and easy control,and has become the mainstream direction of the development of DC circuit breaker equipment.HCB still has problems such as difficulty in arc extinguishing,slow breaking speed and large energy dissipation.The breaking principle and electrical stress analysis at different stages involved in the development and application of HCB are expounded,which lays a theoretical foundation for the design of the topology structure.Aiming at the problems existing in the breaking process of HCB,combined with its topological advantages,a pre-charge hybrid DC circuit breaker（PH-DCCB）topology is proposed.The negative pressure circuit can be put into operation quickly after the fault occurs to suppress the rising rate of the fault current,and reduce the peak value of the breaking current of the circuit breaker through the current limiting branch.In addition,an improved coupled hybrid DC circuit breaker（CH-DCCB）topology is proposed based on the topology of PH-DCCB,which optimizes the topology without affecting the breaking performance of the circuit breaker.With the control method,the coupled inductance part is introduced,and the fault current rising rate is reduced after the current limit is switched on.After the open circuit part operates,the non-fault side inductance energy is released through the discharge circuit,which reduces the energy absorbed by the arrester and shortens the fault breaking time.Aiming at the two proposed current-limiting topological structures,the topological structures and working principles are introduced,the breaking process is theoretically deduced,and the selection of main device parameters is given.On the PSCAD/EMTDC simulation platform,build a DC system grounding short-circuit simulation experimental model.The simulation results show that the PH-DCCB can effectively limit the rising rate of the fault current after the fault occurs,which can enable the circuit breaker to complete the breaking process at a lower current level and reduce the use of fully controlled power electronic devices.The manufacturing cost is about 55.3%of conventional DC circuit breakers.Under the premise that the improved CH-DCCB hardly affects the breaking performance of the circuit breaker,compared with the PH-DCCB before the improvement,the energy absorption value of the arrester is reduced by 50.1%,and the time required for fault breaking is shortened further.DC fault interrupting requirements.