Research On Control Method Of Electric Vehicle Wireless Charging System Based On Z-Source Resonant Converter

The large-scale application of electric vehicles can effectively alleviate the energy crisis and environmental pollution.Among the factors that determine the large-scale promotion speed of electric vehicles,the convenience of supplementing electric energy is an important factor that affects the choice of electric vehicles by commercial and individual users.With the rapid development of charging technology,the charging mode of electric vehicles is no longer simply wired charging,wireless charging technology has also attracted extensive attention.In this paper,Z-Source Resonant Converter(ZSRC)is applied to the main circuit of the electric vehicle wireless charging system and the basic working principle,control method and charging control strategy are also studied.Firstly,the topological structure and working principle of electric vehicle wireless charging system based on ZSRC with magnetic coupling resonance mode for wireless power transmission are analyzed,the expression of output voltage and power of the topology and the regulation mode of PFC are given.In order to improve the efficiency of the wireless charging system,the asymmetric voltage control is improved and the Z-Source Asymmetrical Voltage Control(Z-AVC)is proposed to make it works in softswitching mode,then the optimal Z-AVC control strategy and the range of power regulation are derived.On the premise of realizing soft-switching,comparing with the relationship between output power,control Angle and switching frequency of conventional fixed-frequency phase-shift control and asymmetrical duty ratio control,and it is concluded that Z-AVC has excellent soft-switching characteristics and reduces switching loss of inverter.Finally,the correctness of the above theory is verified by Matlab simulation.Secondly,in terms of battery charging control strategy,the piecewise control strategy of the battery is analyzed.According to the characteristics of SS resonant network,the control strategy is improved,and the constant power charging phase is added in the constant current charging and constant voltage charging phases.At this stage,the charging voltage and current are increased as much as possible to keep the charging power constant in order to reduce the charging time.Combined with Z-source asymmetrical voltage control,the whole charging control strategy is proposed: piecewise frequency conversion control strategy.Finally,the simulation results of constant current phase,constant power phase,constant voltage phase and efficiency curve are given by using Pspice circuit simulation software,and the feasibility of the control strategy is verified.Finally,the experimental platform of electric vehicle wireless charging based on ZSRC is designed,including the calculation of Z-source network parameters,the design of main inverter and rectifier parameters,the hardware circuit design of each module of control system,control software design,and the design of magnetic coupling mechanism.The experiment verifies the Z-AVC can realize soft-switching in electric vehicle wireless charging system based on ZSRC.