| Step response is an important index to investigate the output dynamic response performance of DC converter.The traditional DC / DC control strategy generally adopts linear PID controller.As long as the parameters are set properly,the DC / DC converter can quickly restore stability under step load.However,with the emergence of plasma generator,aircraft,power battery and other applications,the response performance of DC / DC converter under pulse load is required.The power of pulse load changes periodically,which has the characteristics of high pulse power and low average power.Due to the limited capacity of the energy storage element at the output side of the converter,the pulse load with a certain frequency and duty cycle may cause the output voltage oscillation of the converter,which seriously affects the normal operation of the pulse load.In this paper,the output response characteristics of DC / DC converter under different pulse loads are analyzed in detail.Aiming at the possible problems of the converter under power pulse loads,the DC / DC controller is optimized,and the effect of the controller optimization design is verified by comparison.The main contents of this paper are as follows(1)The topology and control strategy of DC / DC converter are summarized and classified.Taking half bridge bidirectional DC / DC converter as an example,the small signal models of peak current loop and average current loop are established,the control parameters are optimized,and the stability of the control loop is analyzed and compared;The mathematical model of the pulse load is established,and the influence of the main parameters of the pulse load on the output response of the converter with different control strategies is analyzed in detail.(2)A variable universe fuzzy adaptive PI controller is designed.By optimizing the control precision of fuzzy control with variable universe,the principle and design steps of variable universe fuzzy PI control are described in detail,and the fuzzy rules are formulated according to the control requirements.The simulation results show that the variable universe fuzzy PI control can effectively reduce the output voltage fluctuation caused by pulse load,but it still takes a long time to restore the steady state.(3)A fuzzy active disturbance rejection controller is designed.The principle of ADRC is discussed in detail,and the setting method of corresponding control parameters is given.The combination of fuzzy control and nonlinear feedback improves the adaptive performance of ADRC.The simulation results show that the fuzzy ADRC has fast transient response to pulse load and effectively shortens the recovery time of output voltage.(4)A 500 W experimental prototype is developed.The main program and interrupt program flow are introduced.The step response of peak current control and average current control are compared in experiment.The step response and pulse load response of variable universe fuzzy PI control and fuzzy active disturbance rejection control are compared in simulation.The adaptability of the designed controller to pulse load is verified. |
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