Research On Predictive Control Of Two-switch Buck-Boost Converter

With the continuous development of power electronics,the application o f wide-range input DC-DC converters has become more and more widely used.The two-switch Buck-Boost converter is one of them.Compared to other wide-range input converters,it has a lower switching pressure.Its input and output voltage have same polarity,so it has gradually gained the attention of many researchers.Model predictive control was originally applied to slow systems,and its application in chemical and other process control areas was extensive.However,in applications where power electronics,motor control,etc.require real-time control and large amounts of computation,the processing speed of the CPU is not enough.In recent years,with the continuous development of microprocessors,the model predictive control has been widely applied in the vector control of the motor,and r esearch in the field of DC/DC has also attracted the attention of researchers.In this paper,starting from the working characteristics of the two-switc h Buck-Boost converter,a three-mode operation mode including Buck mode,Boost mode and Buck-Boost mode is used to establish a state space model for different operating modes under continuous inductor current conditions.On the basis of the state space model,the establishment of a prediction model is performed.Considering that the model predictive control needs sufficient prediction accuracy to ensure the accuracy of the prediction result,the v-step discrete method is further adopted,so that under the same sampling frequency,the prediction model constructed based on the state space model can achieve higher accuracy requirements.Based on the prediction model of the completed converter,the off-line control law in the prediction algorithm of different working states under different working modes is designed by taking the output voltage as the optimal cost function and solving the cost function.Part of the derivation work.The on-line calculation and scroll optimization of the duty cycle are performed on the basis of completion of the offline derivation of the control law,and an effective control of the co nverter is achieved.Corresponding simulations were performed in Matlab,and the expected simulation results were obtained.Based on the prediction algorithm,a prototype with an input voltage in the range of 18 V to 72 V and an output voltage of 36 V was bui lt.And write a software program to use DSP to process the data collected from the system and perfor m online calculations.Through the experiments,the feasibility and effectiveness of the model predictive control method applied to the two-switch Buck-Boost converter was verified.