Research On Modeling And Control Method Of Buck Converter At High Temperature

With the development of power electronic technology, electronic circuits are widely used in industrial production, transportation, renewable energy systems and national defense science and technology. Many of these areas require the circuit to operate stably in high temperature environment, such as oil exploration, automotive industry and aerospace industry. The device parameters and characteristics will change at high temperature, which leads to the change of circuit model and efficiency. The control effect of the controller also changes with temperature, which designed based on the normal temperature parameter. Therefore, it is significant to study the device model, circuit characteristics and adaptive control algorithms at high temperature. The research object of this paper is the Buck converter.Firstly, this paper establishes the temperature model of the IGBT, aluminum electrolytic capacitor and magnetic element. The mathematical model of IGBT is detailed introduced and the relationship between the electrical characteristics and the internal parameters is found. The temperature characteristics of the semiconductor parameters are analyzed. On the basis of these analysis, the temperature model of IGBT is obtained. And then, the temperature characteristics of the aluminum electrolytic capacitor and the magnetic components are analyzed. Based on the equivalent circuit model of the aluminum electrolytic capacitor and the magnetic components, the temperature model of these devices are obtained.Secondly, based on the temperature model of the devices, this paper analyzes the effect of temperature on the output ripple and establishes the small signal model and loss model of Buck converter. On the basis of the above research, the influences of temperature change on the frequency characteristics and the partial loss of the converter are analyzed. In order to improve the efficiency of the converter at different temperature, this paper uses frequency optimization method. The frequency optimization control table is obtained by Matlab simulation. But the variation of switching frequency and device parameters leads the performance degradation of the fixed parameters PID controller. In order to improve the system control performance, this paper adopts selftuning control method to regulate controller parameters. The PSIM simulation result shows that, compared with the fixed parameters PID control, the self-tuning control method based on relay feedback makes the system have better dynamic characteristic. And with self-tuning control method the system has good adaptability to parameter variation and load disturbance.Finally, this paper designs and manufactures the hardware and write the control program based on TMS320F28035. The circuit board is placed in the heating box to carry out high temperature experiment. The experimental result shows the feasibility and correctness of the proposed control method.