Research On Harmonic Analysis And System Of Isolated Charging Pile

In view of the environmental pollution caused by fuel consumption,electric vehicles have been vigorously promoted and used as one of the main forms to alleviate this problem,and the charging pile's performance and design determine whether it is an important device for smooth implementation.Including nonlinear devices in the charging pile can generate power quality problems caused by harmonic currents,etc.At the same time,the design of the internal high-frequency transformer is also the key to reduce costs.This article has conducted some research and analysis.First of all,it is expatiated that under the APFC correction,the traditional current control strategy will cause the grid-side current to contain low-order harmonic components,resulting in a large distortion in the input current,making it difficult to further improve the power factor.On this basis,the mechanism of harmonic generation in the charging pile was analyzed,and a compensation strategy was proposed.Third harmonic compensation was added to the command current to further suppress the harmonics,and the third harmonic content compensation was given by calculation.According to the third harmonic current amplitude and phase adjustment,the best suppression effect is obtained.From the experimental results,it is known that the THD of the APFC circuit after adding the third harmonic compensation is reduced from 3.28% to2.02%.Among them,the third harmonic amplitude is reduced from 304.5 mA to 2.48 mA,and the harmonic amplitude is negligible for more than 5 times.The lower harmonics are effectively suppressed.At the same time,adjusting the third harmonic compensation amplitude and phase can improve the input current waveform.Secondly,after analyzing the circuit of the latter stage,it selects the resonant circuit and establishes the LLC resonant transformation model.Through the analysis of its parameters and performance,the parameters of the resonant network are given,and theresonant inductor and excitation inductance are calculated according to the calculation of the high frequency transformer.The transformer is designed by changing the gap between the core and the winding,and changing the tightness of the winding,the number of turns,and the shortness of the winding in the winding process.Finally,the overall system hardware circuit selection and software program flow design,after MATLAB simulation verification,and based on DSP 28335 experimental prototype,The experimental results show the feasibility of the design of this paper,and its practicality and correctness are verified from the principle and the experiment.