Research On The DC/DC System And Control For Fuel Cell Vehicles

As a key research field of new energy vehicles,fuel cell vehicles have the advantages of zero emissions,diverse fuel sources,long mileage and fast fuel replenishment.However,the output characteristics of the fuel cell are soft,the dynamic response is slow,and the adaptability of the working condition is poor.These shortcomings make the fuel cells unable to meet the needs of the vehicle.As a key component of the fuel cell vehicle power system,the DC/DC converter can make up the above disadvantages of fuel cells and improve the durability of fuel cells.Firstly,in view of the problems of large input current ripple and low energy conversion efficiency of the current vehicle DC/DC converter,this thesis proposes a new DC/DC converter configuration with low input current ripple.This configuration adds an input filter inductor to the three-phase interleaved Boost type circuits.The addition of the filter inductor can effectively reduce the input current ripple of the DC/DC converter,that is,the fuel cell output current ripple.Secondly,a comprehensive analysis of the topology reveals that the system is prone to oscillation.Therefore,this thesis analyzes the DC/DC system transfer function deeply,and selects the appropriate input side capacitance,inductance parameters,operating frequency and control mode to effectively solve the problem of oscillation.At the same time,the input current ripple of the DC/DC converter with or without input filter inductor is compared by simulation,and the effectiveness of the topology increasing the input filter inductor to reduce the input current ripple is verified.Then,for the DC/DC converter designed in this thesis,the input and output dual control method and the multi-phase alternate drive control strategy for improving efficiency are proposed,and the hardware and software design of the DC/DC controller is carried out.The Infineon AURIX^TM TC275 is adopted as the main control chip,which fully utilizes its advantages of high frequency,multi-core CPU,etc.So that the DC/DC converter not only has a suitable output voltage,but also can make the fuel cell output current change smoothly,effectively improve the working environment of fuel cells and realize DC/DC maximizes conversion efficiency at various operating points.Finally,the DC/DC converter experimental platform was built to test the performance of the DC/DC converter experimental prototype.The experimental results show that the DC/DC designed in this thesis can meet the suitable voltage output of the vehicle under various working conditions,and also has the characteristics of small input current ripple and high conversion efficiency.The DC/DC converter can control the input current ripple coefficient within 1%over the entire output power range,so that the output current stability of the fuel cell is optimized to the maximum.The converter effectively improves the working environment of the fuel cell,which is of great significance for prolonging the life of the fuel cell.The efficient working area with conversion efficiency greater than 93%can reach nearly 100%,and the highest efficiency can reach 98.60%,which improves the economy of fuel cell vehicles.