Research On Variable Universe Fuzzy Control And Application In Switching Converter

With the development of integrated circuits and intelligent control theory,low-power DC-DC switching power supplies are widely used in new energy electric vehicles,photo-voltaic power generation systems,green energy systems,and LED lighting equipment.DC-DC converter is the core component of energy conversion in switching power supply.Buck-Boost converter is a kind of nonlinear time-varying system which has the function of raising and lowering voltage at the same time.Non-linear behaviors such as period-doubling bifurcation,sub-harmonic oscillation,and quasi-periodic oscillation will occur during the process,which will affect the working quality and performance of the converter.At the same time,the Buck-Boost converter is a non-minimum phase system.The inevitable negative modulation can cause serious damage to the system.In view of the above situation,a variable universe fuzzy PID control strategy is proposed to compensate the stability of Buck-Boost converter.The corresponding advantages of the fuzzy PID control are inherited in Variable universe fuzzy PID control,and using expansion factor to break the fixed limitation of fuzzy control.Therefore,the variable universe fuzzy PID control strategy is essentially an optimization of fuzzy PID control,which improves the adaptability and stability of fuzzy PID control.The variable universe fuzzy PID control strategy applied to Buck-Boost converter will be introduced from the following aspects in this paper:Firstly,the several kinds of classification of the Buck-Boost converter and the characteristics of the non-minimum phase system are introduced.The basic working principle of the Buck-Boost converter and the calculation method of the related parameters are analyzed.The small signal mathematical model is established according to the circuit structure of different switch state.The advantages and disadvantages of traditional control strategies and intelligent control strategies applied in switching converter are analyzed.Secondly,according to the transfer function of Buck-Boost converter,the PID control parameters are designed by combining the bode diagram and the amplitude and phase margin compensation method.Combining with the characteristics of the actual system,the fuzzification,defuzzification part,and fuzzy rule library of fuzzy controller are designed reasonably.The structural characteristics and optimization principle of variable universe fuzzy PID control are analyzed.The scaling factor suitable for the controlled system is selected to complete the design of the variable domain structure.Thirdly,based on the Simulink simulation environment,the simulation model of the PID,fuzzy PID and variable universe fuzzy PID control strategy of the controlled system are built.Through the experimental simulation,it is proved that the method proposed in this paper is effective in the anti-interference ability,the suppression ability when the external parameters mutate and the system control accuracy is effectively improved.Finally,in order to further verify the superiority of variable universe fuzzy PID strategy in the control strategies of Buck-Boost converter,the actual circuit test platform is built based on STM32G474 chip,and the experimental test results are used to prove the optimization of variable universe fuzzy PID control system in response speed compared with fuzzy PID control system.