Structure Optimization And Research On Control Strategy In Wireless Charging System For Electric Vehicles

Under the background of the Chinese government vigorously implements the strategy of sustainable development, electric vehicles(EV) has been developed rapidly, but the existence of conventional charging device operability poor, low security area and other shortcomings, largely limited EV’s promotion. In contrast, wireless power transmission technology is safe, easy to operate, intelligence, etc., and therefore has a strong research value and broad application prospects based wireless power transmission technology for electric vehicle charging systems.Based on the principle of resonant magnetic coupling, energy transfer mechanism in WPT system is analyzed in this paper by using the theory of mutual inductance, and on this basis, it is designed to optimize the structure parameters of smaller size magnetic coupling mechanism, the medium-power wireless charging system for electric vehicles is designed.Firstly, from the Circuit mutual model of resonant WPT system, this paper explains the principles of WPT capacitance compensation system, explains the choice of rationality "PS-SS" compensation structure, and deduce the system parameters(transmission power, system efficiency) mathematical expressions; compare linear load and nonlinear load system parameters on the similarities and differences; quantitative analysis of the coupling coefficient, the impact of mutual value system parameters, presented the general conclusions of system optimization.Secondly complete the development of wireless charging platform, mainly include source inverter control circuit, signal detection and transform circuit, protection circuit and magnetic coupling mechanism, and finish the relevant characteristics experiments on the platform, including battery load characteristics, frequency, transmission shift characteristics and distribution of energy loss experiments. Finally the platform achieves 3.6k W power output, wherein the conversion efficiency is about 90%, and also has a certain offset capability.Finally, control strategies were studied on the WPT system, by changing the system frequency on the hardware platform controllable constant current to the battery charge is implemented. Through experimental results indicate the limitations of conventional nonlinear control algorithms in WPT system, and how fuzzy control algorithm in the WPT system should be applied in the future.