A fuzzy PID control strategy for buck converter system of double closed loop circuits

A novel fuzzy PID control strategy of Buck converter system with double closed loop structures is proposed to solve problems that complex control objects are difficult of modeling and the artificial tuning experiences are lack, etc. The voltage and current loop structures are designed to improve both the anti-disturbance performance and the following performance of the system. A membership function that combines the Gauss function and the triangular function is selected to enhance the sensitivity of the controller to small error. Three sub inference devices are designed based on the PID parameters and the rule base of expert experiences, and the fuzzy rule of Buck converter is developed to make the designed controller independent of the precise mathematical model of Buck converter. So that it overcomes the high percent overshoot, oscillation and other shortcomings of the output voltage caused by traditional PID controls. A new Buck converter system of double closed loop circuits is designed, and the fuzzy PID control strategy is applied to control the quantities with rapid change and small time delay by making use of STM32. Experimental results show that the fuzzy PID control strategy not only improves the tracking accuracy of the output voltage, but also effectively suppresses the load disturbance and parameter perturbation, and that the overshoot of the output voltage is less than 10% and the adjustment time is less than 3 ms under the step to start. A comparison with the traditional PID system show that the designed system's output voltage ripple, maximum dynamic voltage drop and recovery time under the disturbance are reduced by one order of magnitude.