Research On Adaptive Control Method Of DC Converter With Nonlinear Loa

With the rapid development of new energy,the application and research of DC microgrid have received extensive attention.DC/DC converter is an important part of DC microgrid,which is used between energy and bus,bus and load for regulating and stabilizing the output voltage.Its working performance will directly affect the stability of the DC microgrid.The nonlinear and negative impedance characteristics introduced by the load,as well as the uncertainty introduced by the variable working environment,are important factors that affect its working performance.Consequently,considering the uncertainties such as parameter perturbation,input voltage and load fluctuation,this thesis carries out adaptive control research for DC/DC converters with nonlinear loads.The specific contents are as follows:(1)To solve the control problem of boost converter with constant power load,an adaptive finite-time controller is proposed.Firstly,the boost converter system is transformed into a linear system by feedback linearization technology,which solves the non-minimum phase characteristics of the boost converter and the nonlinear characteristics of the constant power load.Secondly,a non-singular terminal sliding mode controller is designed for the obtained linear system.Thirdly,a finite time observer is designed to estimate the input voltage.By introducing the observed value into the controller,an adaptive finite time controller is obtained.Then,the finite time stability of the closed loop system under the proposed controller is proved Finally,simulation results show that the proposed controller is effective and can effectively suppress the negative effect of input voltage disturbance on the system.(2)An observer based on reduced-order generalized parameter estimation is designed to solve the sensorless control problem of DC/DC buck converter with unknown constant power load.Firstly,based on dynamic dynamic extension,the state observation problem is transformed into parameter estimation problem.Secondly,borrowing dynamic regression extension and mixing technique,the unmeasured inductance current and unknown power load are simultaneously reconstructed.Thirdly,based on reconstructed information,a finite time observer is designed.Then,the observation items are introduced into the existing full information controller to realize the adaptive sensorless control scheme.Finally,the performance of the designed controller is evaluated by experiments.(3)An adaptive energy shaping controller is designed for DC/DC buck converter with ZIP load(a parallel combination of resistive load ‘Z’,constant current current load ‘I’ and constant power load ‘P’).Firstly,a state feedback controller is designed under the framework of port Hamiltonian system using energy shaping techniques.The implementation of the controller does not require ZIP load information.Secondly,based on the theory of immersion and invariance,an input voltage observer is designed.Thirdly,by substituting output of the observer into the above controller,an adaptive energy shaping control scheme is obtained.Then,a rigorous stability analysis of the closed-loop system is carried out.Finally,simulation and experimental results are presented to evaluate the performance of the designed controller.The control scheme has nice robustness against the perturbation of load and input voltage.