Research On Variable Frequency Current Source For AC Impedance Spectrum Detection Of Lithium Battery Module Based On SiC

The life cycle and resource utilization of retired lithium batteries can be maximized by recycling and then recycling.The detection and application of battery module level or even battery pack level can obtain higher efficiency and economic benefits than the battery core level.Battery’s status of health(SOH)is an important basis for screening and recombination,and AC impedance spectroscopy is an important means to evaluate SOH.In the AC impedance test system of lithium battery module,frequency conversion current source as excitation is particularly important.In this dissertation,the silicon carbide(SiC)MOSFET is taken as the main switch device,and the sinusoidal current output with variable frequency and adjustable amplitude is realized through the transformation of the rectifier circuit and inverter circuit.The main contents are as follows: three-phase uncontrolled rectifier circuit with capacitor filter is used in the rectifier,and single-phase full-bridge inverter circuit with inductor filter is used in the inverter.Through the comparison of several common control strategies,the incremental proportional regulation is adopted to control the current.The modulation method of the inverter is frequency doubling monopolar SPWM.According to the theoretical analysis,the hardware and software circuits of the whole power supply are designed.The hardware part completes the design of the main circuit,control circuit,and drive circuit.The main circuit design includes the switching devices,filter inductors,and soft-start resistances,the control circuit design includes A/D sampling,monitoring DC voltage,software over-current protection,hardware over-current protection,communication,and auxiliary power supply module.In the software part,the software design idea based on DSP is described,including the main program design idea,interrupt execution content,current tracking algorithm,and the communication logic between the host computer and the main control board.For the problem that the voltage and current oscillation of SiC MOSFET’s switch affect the circuit,the driving voltage spike and the drain-source voltage oscillation of SiC MOSFET are reduced by optimizing the driving resistance;A filter is added to the DC side of the inverter to suppress the DC voltage ripple and the output voltage spike of the inverter;the high-frequency clutter interference of the signal is reduced by optimizing the main control board PCB.The MATLAB simulation and experimental platform are built,and the results show that the power supply system achieves good output effects.