The Key Research Of Electric Vehicle Drive-charging Integrated System Based On Inteleaved DC-DC Converter

With the rapid development of new energy vehicles,the related technologies of electric vehicles are also constantly improving.All parts of electric vehicles are also developing in the direction of high efficiency and high power density.For the bidirectional DC-DC converter for electric vehicle driving,the interleaved parallel technology is adopted to improve the power density of the DC-DC converter.The degree of integration of can be greatly improved through reuse the interleaved parallel DC-DC circuit topology in the integrated drive mode to realize the charging function.The control strategy has an important influence on the performance of the system.Therefore,it is of great significance to study the control strategy of electric vehicle drive-charging integrated system based on interleaved parallel DC-DC in different modes.The paper focuses on solving the problem of efficiency optimization of integrated systems and the suppression of secondary voltage ripple of bus capacitors in charging mode.This paper first introduces the integration principle of the electric vehicle traction-charging integrated system,analyzes the working principle of the three-phase interleaved parallel DC-DC in the driving mode,and the working principle of the topology of the PWM rectifier + Buck converter in the charging mode.The signal modeling method establishes the mathematical model of the circuit in different modes,and then designs the control system.For the driving mode,the voltage outer loop + current independent inner loop are used to control the three-phase interleaved parallel DC-DC.For the charging mode PWM rectifier,the dq current decoupling control method and the parallel harmonic controller control method are used,and the rear-stage Buck adopts voltage and current double closed-loop control with input voltage feedforward.The simulation model under different modes of the system is constructed in the simulation software to verify the feasibility of the control strategy.Secondly,this paper analyzes the cause of the secondary voltage ripple on the DC bus capacitor,and analyzes the impact of the voltage ripple on the lifetime of the bus film capacitor.Then DC decoupling methods are used to The secondary ripple of DC bus voltage was suppressed,and a new type of differential converter was tried to suppress the secondary ripple of DC bus voltage.Finally,the simulation verifies that the methods used can suppress the secondary ripple.Finally,this paper studies the optimization strategy of the efficiency in different modes.In the driving mode,the frequency reduction method is used to improve the efficiency of the interleaved parallel DC-DC converter.And in order to improve the low efficiency of the converter under light load,a method of power-phase number distribution is proposed,which effectively improves the efficiency of the converter under light load.In the charging mode,the frequency reduction method is also used to improve the efficiency of the PWM rectifier.The effect of different modulation methods,bus voltage and other factors on the system efficiency is studied.Finally,the system efficiency is simulated by simulation software to verify The correctness of the efficiency improvement scheme adopted,and the Simulation software was used to simulate the temperature rise under the working state of the system.