| DC-DC converters are widely used in the field of power transmission and power conversion,and the traditional control method commonly uses the small signal linear model near the static operating point to design the controller.But for the power supply voltage or load changes in a large occasion,using such control method is difficult to guarantee the control performance of the system.What's more,some DC-DC converters have non-minimum phase characteristics,which results in overshoot,negative tone and slow dynamic response and other issues of the closed-loop control of the system composed of these converters.For the DC-DC converter with non-minimum phase characteristics,this paper proposes a variable universe fuzzy PID controller to study its control performance.This controller is composed of the variable universe fuzzy controller and the PID controller.The PID controller can effectively make the system work well near the static working point.The variable universe fuzzy controller not only extends the simple structure of fuzzy controller,but does not need the exact mathematical model of control object.At the same time,the steady-state control precision of the fuzzy controller is improved and the optimization process of the fuzzy rules is simplified.Considering the characteristics of DC-DC converters with variable non-minimum phase and variable universe fuzzy PID controller,it is possible to apply that control method to the closed-loop control of DC-DC converters.Firstly,the small-signal mathematical model of DC-DC converter with the non-minimum phase characteristics are built in this paper,then the Boost,Buck-Boost,Cuk,Sepic and Zeta converters are analyzed by their transfer function,which is the duty cycle to the output voltage.There are the zero point of the right half-plane of the S domain in these transfer functions,that is,these converters have non-minimum phase characteristics,and the system constituted by them is a non-minimum phase system.Secondly,the basic knowledge of fuzzy control and the basic principle of variable universe fuzzy control are discussed in next chapter.The role of the stretching factor in the variable universe fuzzy control is analyzed,which fulfills the high precision control of controller and makes that the fuzzy rules are no longer dependent on rigorous expert knowledge and engineering experience.Lastly,using the Boost and Sepic converters as example,the method of variable universe fuzzy PID control is applied to study the closed-loop control performance of the DC-DC step-up non-minimum phase control system.The closed-loop control parameters of Boost and Sepic converters are obtained by PID correction.The closed-loop simulation model and experimental platform of Boost and Sepic are established in MATLAB and Simulink environment.By comparing the simulation and experimental results of PID control,fuzzy PID control and variable universe fuzzy PID control,it is proved that the variable universe fuzzy PID control has better control performance. |
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