Research On Frequency Modulation And Resonating Of Induction Powered Trams

In recent years,with the advantages of safety,reliability,non-contact spark and flexible power supply,wireless power transfer(WPT)technology has solved the problems of wire breaking and arc scraping,contact spark,lightning strike and power failure in traditional catenary power supply,and has gradually become a new power supply option for modern trams.However,due to the difference of parameters of different vehicle pick-up coils,the deviation of relative position of coils,and the change of intrinsic circuit parameters caused by long-term operation,the inherent resonance frequency of the system will drift,which will lead to the system un-resonating and the transmission power and efficiency of electric energy will be greatly reduced.Therefore,it is necessary to adjust the working frequency of the system in real time to make the system work in resonance state,that is to say,it is of great significance to study the method of frequency modulation and resonating for the efficient and stable power transmission of WPT system.This paper first introduces the composition of modern tram WPT system,analyzes its working principle and working process,and conducts a detailed study on the ground converter,electromagnetic coupling mechanism and on-board converter,and selects the full bridge inverter and SS compensation topology suitable for tram.Using the mutual inductance equivalent model to model SS topology,the circuit characteristics of the system in resonance state and un-resonance state are studied respectively,which lays a theoretical foundation for the subsequent frequency modulation tuning based on the transmitter loop.Secondly,this paper make clear the structure of the tram,analyze the causes of the system un-resonance,study the divergence and convergence of the inherent circuit parameters,determine the frequency modulation range of the system,and analyze the feasibility of the frequency modulation principle based on the impedance angle of the transmitter.Then,this paper proposes a frequency modulation control strategy based on the impedance angle of the transmitter and variable step size,and give the specific frequency modulation flow chart of variable step size tracking.The simulation model of the system is built and simulated in MATLAB?/Simulink? to verify the validity of the control strategy.Finally,the influence of the system frequency on the coil self induction is studied,and the design of each component module of the low-power frequency modulation resonating experimental platform is described in detail.The platform is built and relevant experiments are carried out,including output voltage regulation experiment and frequency regulation experiment.The experimental conclusions are drawn,which provide reference for the frequency modulation resonating of actual trams.