Research On Key Technologies Of Electric Vehicles Charging And Discharing Stations

With the rapid development of the industry, as well as traditional fossilfuels dwindling, worldwide environmental pollution and energy shortage havebecome significantly restrictive factors to build a harmonious society. Electricvehicles leads the direction of the automotive industry in the future to somedegree in that they use electrical energy as power source and avoid pollutingthe environment. Besides, the corresponding facilities-charging anddischarging station has also raised widespread concern among scientificresearch.This paper is based on several key technologies of electric vehiclescharging and discharging station, including harmonic control of chargingstations, fast charging and discharging technology, charging stationconnecting-to-grid technology and electric vehicle charging station withphotovoltaic power. The details are as follows:Firstly, after analyzing characteristics of the charging machine, animproved filtering method has been proposed based on principle offundamental resonance and fundamental magnetic flux compensation, andcontraction with traditional passive filter. According to theoretical analysis andsimulation results about single and multi-charger harmonic control, thefollowing filtering method can effectively eliminate grid current and voltageharmonic which decrease the total distortion rate to less than5%(current) and1%(voltage) respectively.Secondly, the topology of charging and discharging machine is designed,consisting of a reversible bi-DC PWM rectifier and a plurality of parallel/DCconverter. With passive damping method to eliminate resonant,controlstrategy of feed-forward decoupling control based on LCL filtering is appliedto PWM rectifier while several control strategies about charging mode areproposed for the design of DC/DC converters, including current control,voltage control and double-closed-loop control. In addition, the mode ofpulse-charging and constant current discharging is simulated in the MATLABand the results verify that the charging and discharging machine has gooddynamic and stable performance and meet the demand of rapid charging and discharging for electric vehicles.Thirdly, according to the technology of V2G, with the object ofstudy-grid inverter, several methods about how electric vehicles connect togrid are raised in order to control micro-power grid-connected inverter.Basically, equivalent PQ control model of inverter is built. The simulationresults indicate that the controller has a good follow ability to connect to gridsuccessfully when the electric vehicle discharges.At last, in consideration of electric vehicle charging station withphotovoltaic power, relations between every subsystems is studied and threecontrol system of charging station is designed. The Droop Control theory ishighlighted with reference to islanded operation of charging station. This paperdesigns a kind of droop controller and Matlab/simulink model is built inconditions of charging station load mutates and micro power drops to verifythe control methods mentioned preciously. It turned out that the droopcontroller has fast response and good stability which significantly meet thedemand of islanded operation of electric vehicle charging station withphotovoltaic power.