Research On Predictive Functional PID Control Of DC/DC Converter Based On Hybrid System

The interaction between on-off switching devices and continuous dynamic systems makes DC/DC converters exhibit non-linear characteristics.Traditional modeling methods mostly adopt state space averaging method,and use linear relation approximation to replace the non-linear relationship between variables to obtain small signal model.Although the small signal model is simple and practical,it ignores the inherent characteristics of the converter and has great limitations in the non-linear system.At present,most of the researches on DC/DC converter control adopt linear control based on small signal model.When the system is disturbed by large signal,the robustness and dynamic performance can hardly meet the requirements.Therefore,it is of great significance to select appropriate modeling methods and control strategies to study DC/DC converter in depth and improve its robustness and dynamic performance under large signal disturbances.Aiming at the hybrid switching characteristics of DC/DC converters,the hybrid system theory is used to analyze the dynamic behavior of DC/DC converters in detail,and a more precise piecewise affine model is built in this research.Based on piecewise affine model and predictive function PID control algorithm,the control system of a single DC/DC converter and a parallel DC/DC converter is designed.Furthermore,the dynamic performance of the system in the case of load jump is studied.The specific contents are as follows:(1)This thesis briefly introduce the basic theory of hybrid system and predictive function PID control algorithm,and analysis the hybrid characteristics of the converter.Combined with predictive function PID control algorithm,the expression of optimal control quantity is deduced,and the predictive function PID control system of Buck converter is designed.(2)MATLAB software is used to simulate the predictive function PID control system of a single Buck converter,verifying the robustness and dynamic performance of the system with this model and control strategy in response to load disturbances.(3)For the parallel Buck converter,the predictive function PID control algorithm is combined with the master-slave current sharing method,and the predictive function PID master-slave current sharing control system is designed.In addition,the system is simulated according to MATLAB software,and system performance in response to load disturbance is tested.(4)The control system designed in this research is experimentally studied on a hardware platform by using digital control chip FPGA.The flow charts of predictive function PID algorithm,voltage and current double closed-loop PI algorithm,parallel Buck predictive function PID master-slave current sharing algorithm and double closed-loop master-slave current sharing algorithm are introduced in detail.Experimental studies show that the control system designed in this thesis is effective.