Design On DC/DC Converter And Research On Control Strategy For Fuel Cell Vehicle Based On SiC Device

The main power source of fuel cell electric vehicles(FCEV)is provided by the fuel cell system.It has the advantages of zero pollution and zero emission.However,its output characteristics are relatively soft,the dynamic response time of the load is slow,and the environment is hard to adapt the changing conditions.The DC/DC converter can compensate for the above-mentioned shortcomings of the fuel cell system,according to boosting and regulating the low output voltage so as to control the entire vehicle energy flow.This is one of the key components of the FCEV.First of all,with the development of the DC/DC converters for FCEVs,in this paper a non-isolated boost topology of interleaving in parallel is selected in order to improve the converter’s conversion efficiency and energy efficiency.Based on ripple analysis deeply,the two-phase topology of interleaving in parallel is finally selected as the converter structure,and its working mode is also further analyzed.Then,the control strategy of the converter is studied.Through the small signal analysis method,the nonlinear converter system is converted into a linear mathematical model.And the open-loop transfer function of the converter is determined.According to the classical control theory and the discrete PI control algorithm,the output voltage and the inductor current are taken as the feedback signals to design the double closed-loop compensation network.According to the application and power requirements,SiC power devices that can operate at high frequency and high temperature and filter capacitors are calculated and selected.An integrated inductor is designed,and hardware and software are designed based on theoretical calculations.The driving circuits of new SiC module is designed.A prototype of a two-phase interleaved parallel boost converter with a power level of 24 k W based on DSP is prototyped.The paper builds a simulation model based on Si and SiC power devices in the simulation environment,estimating the power loss and efficiency of the converter at different loads and frequencies.The power loss and efficiency of the device are compared and analyzed.Through the simulation results,the new SiC power device can significantly improve the conversion efficiency of the converter.The designed converter can achieve good dynamic response characteristics and stability.Finally,the control strategy of the converter is verified by the prototype test.And the PWM pulse drive signal is tested at the frequency of 25 k Hz,which proved the effectiveness of the double closed-loop control strategy of the DC/DC converter in practical application.