Application Research Of Fractional Order PI~? Controller In Bidirectional DC-DC Converter

The DC energy storage scheme based on bidirectional DC-DC converter overcomes the energy waste of traditional elevator braking scheme and harmonic pollution of grid-connected inverters.It has emerged in the field of elevator energy saving in recent years,and has important research value and broad application prospects.Therefore,this paper will design a bidirectional DC-DC converter with perfect functions and excellent performance,and improve the control effect of the system through the improvement of the control algorithm.First,the basic structure of the elevator energy-saving system is introduced,the functional index of the converter according to the actual application environment is determined,and the bidirectional full-bridge topology is selected as the main topology of the system.Aiming at the key problems of the topology in practical application,a corresponding improvement scheme is given.According to the control structure and modeling method of the system,and the double closed-loop control structure of anglog peak current inner loop combined with digital voltage outer loop is determined.According to the closed-loop bandwidth difference between the current loop and the voltage loop of the system,the current loop is modeled by discretization method.The stability problem of the current loop is analyzed.The slope compensation technique is used to suppress the subharmonic oscillation phenomenon.The voltage loop is modeled by the state-space averaging method.The frequency domain characteristics of the closed-loop small-signal model are analyzed to guide the controller design.In order to improve the system control performance,the theory of fractional order PI~?D~? control is studied.Under the same design principle of frequency domain constraints and time domain evaluation index,the control parameters of the fractional order PI~?controller and integer order PI controller in two energy directions are set.Aiming at the problem that the traditional Oustaloup indirect discretization method has low out-of-band fitting precision and limited low-frequency gain,the method of configuring the integral link for the rational approximation function is used to improved the discretization realization precision of the fractional-order PI~?controller.The control performance of the two kinds of controllers is compared by MATLAB/Simulink simulation platform.The results show that the fractional order PI~?controller has better flexibility and robustness than the integer order PI controller,which improves the control performance of the system.Finally,the design of the system hardware circuit and software program is completed,a bidirectional DC-DC converter system platform is built,and the experimental schemes of current loop and voltage loop are designed.The experimental results show that the control performance of the bidirectional DC-DC converter is good,and the fractional order PI~?controller improves the control performance of the system.