Research On The Double Input DC-DC Converter Of Fuel Cell Electric Vehicles

Nowadays, our country is striving to develop the new energy policy towards some situation like the energy crisis due to the traditional fossil fuel’s constant drain and the severe pollution caused by the huge emission of the automobile exhaust. The distributed energy, as a utilization pattern of the new energy, has many features of environment protection, resource saving, emission reduction and so on. It’s the key technology to solve the problem. The FC, as the main utilization of the distributed energy and also the main energy part of the FC car, it plays a significant role in the new energy automobile field. In that, the research towards the FC automobile has an important scientific significance.The system studied the DC-DC converter the FC automobile needed inside. First of all, it proposed a new topology structure of DC-DC converter in accordance with the weakness of the traditional one. The converter is composed by two parallel Buck-Boost converters and it uses the FC and the BU as the double input power to realize the bi-direction power flow. In this case, the automobile can feed excess energy back to the BU during the process of downhill, breaking, and slow down. Secondly, the system use the state-space average method to built a mathematical model of the DC-DC converter on both BU and FC. Then, it raised a control policy to control the voltage ring of the BU and the current loop of the FC to get a double-loop controlling parameter. Then the system used the Matlab/Simulink software to adapt a dynamic simulation on the charging and discharging mode of both BU and FC. By observing the system’s output voltage, SOC, charging current and the simulation waveform of armature current of motor, the system is proved to be feasible and stable. At last, the system use the DSP2812 to build an experimental platform with both hardware and software parts. The hardware part includes the design on the main control unit, power unit and detective protection unit. The software part used the C programming language to design a DSP control system to read the data sample of the output voltage Uo and input voltage Io. It will pass the data to execute on the PI closed loop program and send the result to its own control register. It will realize the control towards the closed loop of system by controlling the duty cycle of PWM.The experiment and the simulation result indicate that the system’s output voltage, the battery charge and current and the motor armature current can all realize a stable output; The relative error ratio of the steady-state current and voltage detected under the situation of no-load, normal operation and regenerative braking is in the normal range. The research of the system laid a foundation for solving the energy crisis, decreasing the environment pollution and boosting the auto industry’s development.