Research On Dual Active Bridge Bidirectional DC-DC Converter Of All-electric Aircraft

As a new kind of single-power aircraft,all-electric aircraft compared to conventional hybrid system aircraft has obvious advantages,which can not only greatly reduce the aircraft pollution to the environment,but also can achieve the integration of energy.To a certain extent,the body weight of aircraft can be reduced,so that the aircraft is more flexible and easier to be controlled.As one of the core power conversion components of the all-electric aircraft power supply system,the bidirectional DC-DC converter plays an important role in the aircraft energy supply system.Therefore,it is of great significance to study bi-directional DC-DC converters for all-electric aircraft.In this paper,the working principles of dual active bridge bidirectional DC-DC converter,interleaved parallel coupled inductor bidirectional DC-DC converter and interleaved parallel forward-flyback bidirectional DC-DC converter are presented in detail,then verify the rationality of the analysis by simulation.According to the results,it can be seen that the interleaved parallel forward-flyback bidirectional DC-DC converter not only has a small output voltage overshoot,but also a small voltage regulator capacitor on the low side,which is very advantageous for the integration of the converter.Therefore,this paper chooses the interleaved parallel forward-flyback bidirectional DC-DC converter for hardware design.The drive signal of the converter is provided by the DSP2812 control chip.The experimental results show that the main parameters of the converter are consistent with the simulation results.Considering that the power consumption of the switch tube is directly related to the voltage,current and temperature,this paper implements a thermal model simulation in order to get the actual power consumption and temperature rise of the switch.The switch tube conduction and switching losses can be observed in real time by importing the thermal model into the electrical simulation.In order to ensure the safe operation of the converter,the maximum thermal resistance between the switch and the external environment can be determined according to the simulation results,which can be a reference for the design of the heat dissipation device.Finally,when the load changes in the half load and double load range,in order to ensure the output voltage is constant,this paper uses fixed-frequency sliding mode control strategy to design the converter closed-loop.According to the actual design requirements,this paper selects the output voltage error value,the voltage error value of the derivative and the voltage error of the integral as the closed-loop system state variables.For the purpose of reducing the adjustment time of the converter,a proportional integral part is added in the closed-loop system,which can not only greatly speed up the closed-loop regulation speed,but also can eliminate the system steady-state error to a certain extent.The simulation results show that the designed closed-loop controller fully meets the design requirements.