Research On Power Module Control Of DC Charging Pile Power Supply

With the increasing number of electric vehicles in China,the shortage of charging infrastructure has become an important factor restricting the development of electric vehicle industry.The state has issued a large number of preferential policies to encourage the construction of charging piles.Compared with the AC charging pile,the DC charging pile has high power and fast charging speed,but the harmonics generated in the charging process will interfere with the power grid,and there will be more energy loss during high-power and fast charging.The DC charging pile power module studied in this paper has the characteristics of high working efficiency and high power density.It can effectively suppress the generation of harmonics and reduce the loss of energy in the charging process.It is of great significance to improve the quality of power grid and save energy.Firstly,according to the working characteristics of the DC charging pile,the topology of the front stage power factor correction circuit is given,the working principle of the front stage power factor correction circuit is introduc ed,and a twophase static structure is constructed αβ mathematical model in coordinate system.In order to stably and reliably output the DC voltage required by the later stage and realize low harmonic and high power factor operation,a double closed-loop control system with sliding mode variable structure control voltage outer loop and model predictive control power inner loop is designed.In order to solve the complex problem of calculating the basic vectors of three-level space vector pulse width modulation,the three-level space vector pulse width modulation is converted into two-level space vector pulse width modulation by vector translation,which reduces the complexity of three-level space vector pulse width modulation.At the same time,the corresponding control strategy is studied for the balance of the neutral point potential of the output capacitor.Secondly,in order to realize the high-efficiency output of DC voltage and current required by electric vehicle by the post stage DC-DC converter,the post stage of DC charging pile adopts the structure of full bridge LLC resonant converter.According to the influence of different resonator parameters on gain control in underresonant region,the resonator parameters are optimized.Aiming at the problem that it is difficult to realize soft switching of full bridge LLC resonant converter under low voltage and light load,a multi-modal hybrid control strategy suitable for low loss and wide range output of DC charging pile is designed.In addition,the application of Si C devices in full bridge LLC resonant converter is researched.The Si C devices and other main power devices are selected according to the design objectives,and the suitable circuit for sampling and drive protection are devised.Finally,the simulation model of DC charging pile power module is builded in Simulink.The feasibility and correctness of this research are verified by the analysis of experimental results.