Research On Wireless Heating Device For Power Lithium-ion Battery

With the continuous development of electric vehicles,lithium-ion batteries have been widely used because of their high power density and pollution-free advantages.However,under cold conditions,the capacity of lithium-ion batteries is severely attenuated.Therefore,it is necessary to heat the lithium-ion battery under low temperature conditions.However,most of the existing internal heating devices are non-isolated wired heating,which has problems such as easy leakage and mismatching of plugs and sockets.In addition,the currently studied heating device cannot flexibly adjust the amplitude and frequency of the heating current online,which reduces the heating speed of the battery.In response to the above problems,this article proposes a frequency-adjustable and amplitude-modulated wireless power transmission heating device,and derives the optimal heating frequency for lithium-ion batteries.The specific work is as follows:First of all,in view of the complicated operation steps of wired heating and potential safety hazards,this paper proposes an AC heating circuit with adjustable frequency and amplitude modulation for wireless power transmission.It focuses on the analysis of loosely coupled transformers and derives the effects of loosely coupled transformers.The control source equivalent model is designed and the corresponding compensation circuit is designed,the Buck circuit is modeled with small signal and the PI corrector is designed,and the method of adjusting the amplitude and frequency of the output AC current is explained.Next,the hardware and software design of the lithium-ion battery heating device.Carry out the main circuit design,drive circuit design,control circuit design,DSP28335 peripheral circuit design and device selection for the wireless heating circuit,write the PI voltage closed loop program of the Buck circuit in the main control chip,and the SPWM pulse width of the inverter circuit Modulation program and LCD module program.Finally,the optimal frequency of lithium-ion battery is deduced and the lowtemperature heating experiment is completed.Measure the electrochemical impedance spectroscopy of lithium-ion batteries at different temperatures to obtain a threedimensional model of the relationship between battery impedance,temperature and frequency,and determine the best heating frequency at different temperatures according to the thermal model of the lithium battery.Then,a low-temperature heating experiment was carried out for cylindrical lithium iron phosphate power batteries,and a control group was set up to conduct low-temperature heating experiments with multiple frequencies and variable amplitudes to verify the effectiveness of the AC heating strategy.