Design And Realization Of High-power Wireless Charging System For Electric Bicycles

On the premise of steady socio-economic development,relevant measures are taken actively in various industries,which contribute to achieve ‘Carbon peak and neutral’ as scheduled,by improving the substitution of electric energy and decreasing demand for fossil fuels.With the advantages of cost-effective,flexibility and environmental protection,electric bicycles are well received by the public,which are important object to improve the substitution of electric energy for transportation industry.However,traditional cable charging method weakens the flexibility and increase potential security hazard for electric bicycles,which is solved effectively by wireless power transfer(WPT)technology.Organic combination of WPT technology and electric bicycles is a systematic work,whose industrialization is faced with some problems,such as lack of universal solutions,high-cost and low integration level of system.Therefore,in order to promote the industrialization of electric bicycle WPT systems,the paper proposes a universal solution for electric bicycle high-power WPT systems,which is established from magnetic coupler,compensation and DC/DC topology,closed-loop control system and prototype implementation.Firstly,existing solutions of magnetic coupler for electric bicycle WPT systems are classification introduced.The advantages and disadvantages of existing solutions are analyzed and the optimal solution is decided.On the premise of the performance that meets demand,the magnetic coupler is designed to reduce costs by Maxwell finite element analysis software,whose parameters are decided.Designed magnetic coupler is established and the transmitting performance is tested,which verifies the effectiveness of designed parameters for magnetic coupler.Secondly,the circuits of SS and LCC/S compensation topology are given,and their transmitting characteristics are derived and analyzed.Based on their transmitting characteristics,the component stress of two compensation topologies is compared at rated transmitting power,which shows that LCC/S compensation topology has smaller component stress.Then the effect of DC/DC topology on WPT systems is analyzed,and the scheme combining LCC/S compensation topology and BUCK topology is selected.The mathematical model of electric bicycle WPT systems are developed,and mathematical expressions of output voltage and output current are derived.Besides,the closed-loop demands are taken a deep dive into constant current(CC)output and constant voltage(CV)output of electric bicycle WPT systems,which verify the effectiveness of 300 W charging power and design a 6A/54 V CC/CV charging curve.And the protection circuits are designed to provide insurance for the closed-loop section and abnormal operating conditions.In order to ensure that the WPT systems supply power for load following the preset charging curve,the BUCK closed-loop section is designed.And the feasibility of designed closed-loop section is verified through simulation and experiment,which meets the needs of WPT systems with efficiency more than 96 percent.Finally,for the sake of further verifying the proposed scheme,the circuits of electric bicycle WPT systems are designed and a 300 W electric bicycle WPT prototype platform is established.The following experiments are carried out:(1)open-loop tests are carried out respectively under misaligned and variable load conditions,which ensures reliable voltage is obtained for closed-loop section under specified conditions;(2)closed-loop tests are carried out respectively under misaligned and variable load conditions,the CC/CV output data and energy efficiency indexes are respectively measured.The experiments show that the established prototype platform meets design requirements: the output accuracy of platform respectively up to 1.33 percent in CC mode and 1.28 percent in CV mode;the maximum transmitting power of platform is 324 W,and the maximum transmitting efficiency is 87.1 percent;the maximum transmitting distance of platform is 9.8cm,the tolerable misaligned distance under 8cm transmitting distance is 10 cm in single direction and 7cm*7cm in 45° direction,which means that the tolerable misaligned area reaches 7cm*7cm on the work plane.