Research On LLC Resonant Converter Based On Charge And Active Disturbance Rejection Control

With the development of power electronics technology,as an important part of power conversion,DC/DC converter is gradually developing towards high frequency and high power density,and is widely used in industrial and other electrical equipment.Usually,users not only require the DC/DC converter to have strong stability,but also have certain requirements for the dynamic performance after being disturbed.Such as some server power supply and other special occasions for the system’s dynamic requirements are increasing,so the research on the dynamic performance of the converter has certain engineering and practical significance.As a DC/DC converter,the half-bridge LLC resonant converter has the characteristics of isolation,high gain and soft switching,and is also one of the hotspots of researchers.However,In the voltage control mode,the transfer function of the system is easily affected by the change of the operating point.It is difficult to obtain a better control bandwidth.The control of the resonant capacitor voltage can realize the cycle-by-cycle charge control;the active disturbance rejection controller introduces the extended state observer in modern control theory to observe the output and uncertain disturbances in the system in real time,and then the disturbance is compensated and eliminated by the feedback control law,which has certain advantages in dealing with nonlinear and time-varying systems.In view of this,based on the half-bridge LLC resonant converter,charge control and active disturbance rejection control are applied in this thesis,in order to obtain better transient characteristics of the system when the system is disturbed by load.The main work of this thesis is as follows:(1)The current dynamic performance control strategy of LLC resonant converter is briefly summarized,and then the research status of charge control and linear active disturbance rejection is described.The modal analysis of the converter is analyzed in detail,and then the charge of the resonant network can be controlled by the resonant capacitor voltage in each cycle through mathematical derivation.The extended description function method is introduced into LLC resonant converter for small signal modeling,and the required transfer function is deduced,which is verified by the frequency sweep method in MATLAB.At the same time,the specific design process of resonant network parameters is given.(2)Based on the principle of ADRC,the transfer function of ADRC is derived,and the equivalent relationship between first-order and second-order ADRC and twodegree-of-freedom PID is analyzed.Then,the resonant capacitor voltage inner loop and output voltage outer loop controller are designed by frequency domain method.Finally,the parameters of voltage outer loop ADRC are tuned based on the equivalent relationship,and the initial tuning ADRC is optimized by particle swarm optimization.(3)Calculating the voltage and current stress of the power device of the converter,complete the calculation and selection of the transformer,and discretize the active disturbance rejection controller to facilitate digital control.In addition,in order to simplify the complexity of manual configuration of DSP registers,this thesis uses MATLAB/Simulink to build a model to configure the relevant registers of the digital controller.(4)The rationality of the designed controller is verified in Simulink.The TMS320F28377 D digital controller of Texas Instruments Company is used to verify the soft-switching characteristics of the experimental prototype,and then the cascade controllers of outer-loop ADRC and inner-loop PI controller,outer-loop PID and innerloop PI controller are verified.The results show that ADRC and PI cascade control show better dynamic characteristics when the system is disturbed by load.