Research On Control Technology For Electric Vehicle Charger

Nowadays,considering environmental protection and reduce energy consumption,various countries are vigorously developing electric vehicles.As corollary equipment of electric vehicles,GETC-EVDC has received wide attention and is developing towards the direction of high frequency,high power density,convenience and intelligentization.However,there are still massive problems during the process of scientific research,high frequency and high density would increase the switching loss,decrease the efficiency of switching power supply,and even lead to serious consequences.All these problems during the development of GETC-EVDC are needed to be solved urgently.In order to reduce the power factor correction topology switching losses,soft switching technology has been widely used and become an advanced research hot-spot in domestic and overseas.Through the establishment of small-signal model,integrating logic gate and average current control mode to carry out the research on APFC topology.The design processes of current controller,voltage controller and PI controller are given,and the feed-forward control method is adopted to solve the problem of current network measurement so as to ensure the power factor on grid recommend.Meanwhile,considering the grid voltage fluctuation and uncertain load variations,full load range of the cutting load simulation has been done,then theoretically verify the practicability of the topology.The rationality and feasibility of the design can be verified by experiment based on the hardware platform.In this paper,the charging device is a series two-stage topology,and we should also consider the ability of one-stage as a whole.As the second-stage topology,the Buck circuit is analyzed through the establishment of small-signal model,the design process of current controller,voltage controller and PI controller.In order to reduce the effection on APFC circuit,additional control strategy has been applied,verified by simulation of variable input,at the same time,the full load range of variable load the simulation is made to verify the topology of wide load range.Considering the effect of the traditional charging methods of lithium ion battery charging is not ideal,and comprehensively considering battery characteristics of lithium ion battery,battery principle and problems in the process of charging,the solution of multi-stage charging mode has been put forward.Based on the single current closed-loop PI controller and double closed-loop PI controller based on current voltage control,according to the charge curve selected set of each phase switching threshold,which is used to complete the charging process.To verify the whole process through simulation,and then to complete the corresponding hardware experiments on the experimental platform.According to the input and output indicators of the converter,the system based on the core of digital controller STM32F407 is designed.On this basis,the prototype of the 3kW is made.Through the detailed analysis on the experimental waveform,we can find out that power factor correction topology could realize soft switching,GETC-EVDC can be controlled by the preset charging curve,power factor meter as well as the transmission efficiency of GETC-EVDC all could meet the requirements.