Hybrid DC Circuit Breaker And Its Application Research

As our country attaches great importance to environmental protection,and the global coal,oil and other non-renewable energy sources are gradually depleted,the country has increased the development and utilization of renewable clean energy.The best way for these clean distributed energy sources to carry out long-distance power transmission is high-voltage direct current transmission.One of the main technical problems of HVDC transmission is HVDC short-circuit protection technology.As the key equipment for maintaining the safe operation of the DC grid,high-voltage DC circuit breakers are receiving more and more attention.Simultaneously,as China’s urban rail transit has completed the 13 th Five-Year Plan and entered the 14 th Five-Year development stage,realization of domestic key equipment and core technologies has become a task that be completed.The DC circuit breaker in DC power supply system is an extremely important protect equipment,so the research on the core technology of DC circuit breakers is of great significance.Compared with the traditional mechanical DC circuit breaker currently used in subways,hybrid DC circuit breaker has the advantages of mechanical DC circuit breaker,such as low conduction loss,and solid-state DC circuit breaker,such as fast switching speed,arc free operation.However,it does not have the disadvantages of arcing,poor reliability of mechanical DC circuit breaker and high conduction loss of solid-state DC circuit breaker.Hybrid DC circuit breaker meets the protection requirements in the power supply system of urban rail transit in the future.Therefore,this thesis takes the hybrid DC circuit breaker as the research object.Considering the control complexity and cost of the circuit breaker,a hybrid DC circuit breaker suitable for the subway catenary is designed.First,taking the high-voltage hybrid DC circuit breaker as the research object,theoretically analyze the working principle of the hybrid DC circuit breaker;a bootstrap driving circuit for cascaded IGBTs is introduced in detail,and the positive and negative voltage formulas for IGBT driving are deduced,and the driving voltage influence factors are obtained.In view of the large turn-off current characteristics of the hybrid high-voltage DC circuit breaker,an adaptive fault current limiter is designed,which can effectively suppress the increase of fault current,and can effectively reduce the amplitude of the fault current through the current limiting resistor and coupling inductance.The correctness of the design scheme is verified by simulation.Secondly,this thesis analyzes the working principle of the hybrid DC circuit breaker;the driving method of the cascaded SiC JFET devices is design,only a special driving circuit can drive all the cascaded SiC JFET devices,which simplifies the control circuit of the circuit breaker.The method of voltage balancing of the cascaded devices and the control method based on JK flip chip are designed and analyzed in detail.The simulation model is built to verify the performance of the hybrid DC circuit breaker and the effectiveness of the control strategy.In time,a hybrid DC circuit breaker based on SiC JFET devices suitable for subway catenary is proposed.Which can realize the normal power supply and fault protection of the traction power supply system in the small double-sided power supply mode and the large double-sided power supply mode,and also can realize the free switching between the small double-sided power supply mode and the large double-sided power supply mode.In addition,the three circuit breakers in this scheme share the transfer branch and the absorption branch,which can reduce the manufacturing cost of the circuit breaker.Based on the JK flip chip control method,a hybrid DC circuit breaker control suitable for the subway catenary is designed,which can meet the control requirements of circuit breakers working in different scenarios.A simulation model is built to verify the correctness of the proposed hybrid DC circuit breaker scheme suitable for subway catenary.Finally,the experimental sample is built.The experimental results show the feasibility of the proposed hybrid DC circuit breaker for subway catenary.