| In recent years,due to the rising of new energy industries such as photovoltaics,DC power distribution technology has developed rapidly.In the DC power distribution system,the DC converter undertakes the important tasks of power flow control and system energy coordination,and has received extensive attention.Among them,the three-port active bridge converter(TAB)has the advantages of electrical isolation,two-way power transmission,and multi-voltage level conversion.It is not only suitable for energy interaction between multiple bus bars,but also in new energy access scenarios.Also played an important role.The current research on TAB focuses on steady-state operation optimization.However,the TAB port has strong coupling,which may cause other ports to face transient shocks in the event of a failure.The quit operation of the converter under a fault causes multiple ports to be paralyzed,blocking energy transmission.Therefore,it is of great significance to analyze the operating characteristics of TAB under internal and external faults,and to find fault-tolerant operating methods under faults.Taking TAB as the research object,this paper analyzes the transient characteristics of port short-circuit and power device open-circuit faults.For port short-circuit faults,a non-faulty port ride-through strategy based on phase-shift power compensation is proposed to maintain stable port transmission;for power device open-circuit faults,a fault-tolerant method based on the principle of symmetrical operation is proposed to eliminate internal DC bias.The specific work of the article is as follows:First,a non-faulty port traversal strategy for TAB under external port short-circuit faults is proposed.In order to distinguish different types of fault characteristics,the short-circuit conditions are divided into direct short-circuit and indirect short-circuit on the output side,analyze the transient characteristics of the port voltage and current under the fault state;calculate the high-frequency current inside the TAB under the fault condition,and explore the voltage drop duration The impact on the generation of DC bias;for the instantaneous voltage drop,calculate the DC bias generated by each port,according to the internal coupling principle of the converter,calculate the transient impact of the non-faulty port caused by the voltage drop of the faulty port;propose a The phase shift angle selection method based on power compensation is used to realize the fault ride-through of non-faulty ports,which is verified by simulation and experiment.Secondly,a TAB fault-tolerant operation method under open-circuit faults of power devices is proposed.Use the modal analysis method to analyze the internal current path after the device is open,and locate the fault according to the current and high-frequency voltage signals;analyze the current characteristics of the open circuit in different operating modes,and solve the DC bias of each winding.The influence of the open circuit of the power device on the transmis sion characteristics of the port is analyzed;based on the asymmetrical operating structure of th e TAB after the device is opened,a fault-tolerant operation method of blocking the switch tubes of the same bridge arm is proposed.This method can eliminate the DC bias to a certain extent.The above guarantees the stable operation of the power output po rt;finally,the port power transmission range under this method is deduced,and the feasibility of this method is verified by simulation and experiment.Finally,a TAB experimental prototype platform with a rated power of 5k W was built.Completed part of the hardware circuit design work,including the core board’s power supply,clock and other peripheral circuits,as well as the backplane’s power supply,sampling and conditioning circuit,and hardware protection circuit;the framework of the software main program was constructed,and based on the basic principles of soft start and fault protection Completed flow chart design and program implementation. |
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