| In recent years,in order to further promote the concept of sustainable development,the government has launched various policies to promote the development of electric vehicles.As a result,the production capacity of electric vehicles increases,and the demand for charging of electric vehicles is also increasing.Compared with the traditional Power supply mode,Wireless Power Transfer(WPT)technology has the advantages of safety,flexibility,reliability,easy maintenance,etc.,and it can also achieve dynamic Wireless charging of electric vehicles to improve the range,making it an ideal charging mode for electric vehicles.Constant voltage and constant current power supply by closed-loop control is the basic demand for EV charging.The secondary side control method is more close to the control object,has a small feedback delay,and does not need to add additional wireless communication equipment,so it has higher research value.In this paper,a novel semibridgeless active rectifier is adopted to realize the short-circuit decoupling control.By studying the single and double tube control strategy and the working mode of the soft-switching,the soft-switching is realized to reduce the switch tube stress and switch loss.Firstly,starting from the principle and structure of the wireless charging system of electric vehicle based on short-circuit decoupling,the advantages and disadvantages of several common inverters and harmonic network topologies are analyzed.Full-bridge inverters suitable for high-power applications and LCC-LCC resonant network topologies with high offset resistance and constant current characteristics are selected.The principle of short-circuit decoupling using controllable short-circuit rectifier bridge is expounded and divided into two parts.The soft switching can be realized.Secondly,the specific scheme of the decoupling control of the secondary side short circuit is analyzed,and the working principle of the single-tube and double-tube control,half-soft switching and full-soft switching modes is expounded.The equivalent impedance model is established by Fourier analysis,and the charging current model is established by circuit averaging method.The switching problem of the single-tube semi-soft switching mode at 50% current point is explained.Based on theoretical analysis and comparison,the effects of different operating modes on power factor,switching loss,control complexity and output characteristics of the system are illustrated,and the applicable scenarios of different operating modes are described.Thirdly,different closed-loop control methods are selected according to the characteristics of different working modes,PI control is adopted for the semi-soft switching mode,variable speed integral PI control is adopted to solve the problem of integral saturation,sliding mode variable structure control is adopted for the full-soft switching mode,charging circuit model is established,its phase trajectory is drawn,and the switching function is obtained.The switching problem of 50% current critical point is discussed.The control strategy of critical point switching mode is proposed.Finally,the overall design of the system is carried out,and some key peripheral hardware circuits and software control processes are presented.The control effect of the corresponding closed-loop control method under different working modes is verified by simulation on MATLAB/Simulink platform.In the simulation process,the improved control strategy of integral compensation at 50% current point is further proposed,and the feasibility and effectiveness of the scheme are further verified by setting up an experimental device. |
