Research On Parallel Current-average Technology Of High-power Charging Power Supply

With the rapid development of power electronic technology,the demand of power supply system is higher and higher.The reliability and redundancy of the system can not meet the requirement if single power supply is used.Multiple power modules can be connected in parallel to meet the demand of high power load.In fact,each power module is not allowed to be connected directly in parallel,and the current-average technology is required to divide the load current equaly.In this way,the reliability,safety and redundancy of high-power supply system can be improved.In this dissertation,several common current-average methods are analyzed and compared.The output impedance method has better current-average effect in the two parallel modules,which is suitable for high current-output applications,but the current-average effect in multiple parallel power modules is poor;the reliability of the master-slave setting method is good,but it is not suitable for high current-output applications;the maximum current method has better current-average performance in multi-parallel power modules.This dissertation adopts the maximum current method to control the current of charging power supply.A phase-shifted full-bridge ZVS converter is used as the main topology structure to design the main circuit.The output requirements of the high-power charging power supply 22 KW determine the parameters and perform selection of device.A small-signal model of a full-bridge converter is designed and the current-average control system is analysed.The current inner loop,the current sharing loop,and the voltage outer loop can be designed to verify the feasibility of the three-closed-loop control scheme.A high-efficiency charging power supply system is realized.Under the environment of MATLAB/Simulink,the simulation models of two-parallel module circuit without current-average and adopting output impedance method are established.And the simulation models of three-parallel module circuit with maximum current method,output impedance method and master-slave setting method are respectively established.Finally,the analyses under light load and heavy load are carried out in the charging power simulation model of the three-closed loop control mode.The simulation results show that the maximum current method has the best performance in the multi-parallel power module,and the current of each parallelmodule is smaller.The unbalanced degree of the output impedance method is less than5% in the circuit simulation of two-parallel module.When the maximum current method is adopted in the simulation model of the charging power supply under the three closed-loop control mode,the output currents of each parallel module are equal,and the current-average control can be realized.