Research And Design Of Charging Pile For High Power Density Charging Vehicle

As the depletion of natural resources such as oil and environmental pollution are becoming more and more serious,electric vehicles,as environmentally friendly vehicles,have received much attention from many aspects.How to solve the charging problem is an important factor in the popularization of electric vehicles.In this paper,two-stage structure is used to design charging pile,three-phase three-level VIENNA rectifier is used as power factor correction(PFC)circuit,full-bridge LLC resonant converter is used as rear stage,and three-phase three-level VIENNA rectifier makes switching devices less,voltage stress lower and structure simpler.Firstly,the working principle of VIENNA rectifier is described in detail,and the circuit states under different switching states and current polarities are analyzed.On this basis,the mathematical model and equivalent circuit of the rectifier in abc,A-beta and d-q coordinates are derived and established.Three-level SVPWM is used to convert three-level SVPWM into equivalent two-level SVPWM for easy calculation.Secondly,the advantages and disadvantages of current feed-forward decoupling control and deadbeat power predictive control in VIENNA rectifier inner loop are compared and analyzed.Because of the predictive error,the improved algorithm predicts the power at K+2 time and executes ahead of time at K+1 time,which reduces the influence of delay and delay.MATLAB simulation is built to verify the reliability of the algorithm.The working state of the LLC resonant circuit is analyzed,which is helpful to derive the equivalent circuit by the fundamental approximation method.The equivalent voltage gain of the resonant circuit is deduced.The division of the working area of the circuit,the steady state of the circuit and the calculation of the resonant cavity parameters are analyzed,and the reliability of the circuit is verified by simulation.Finally,according to the selected charging pile design scheme,an experimental platform is built.The circuit parameters,sampling and conditioning circuit and isolation driving circuit are calculated and designed.The flow chart of software design is given,and it is verified that the input and output of the circuit meet the relevant requirements under the design index.The THD value can be reduced to 5%when the output voltage is greater than 500 V.The maximum output power can reach15 kw.