Research On Predictive Control Of DC-DC Converter With Constant Power Load

With the progress of The Times,the modernization of smart power grid and new energy industry is developing rapidly.Researchers are increasingly interested in new energy DC distributed power systems.In this system,the DC-DC converter is one of the main processing units,and is widely used in many fields,such as aircraft,electric vehicles,microgrids,aerospace and shipbuilding.In general,DC converters are regulated using closed-loop control.However,when the input to the DC converter is used as a Load converter,the system will exhibit a Constant Power Load(CPL)characteristic.When the power supply system is connected to CPL,the system shows negative impedance and nonlinear characteristics.Due to the influence of input voltage and load disturbance,the traditional control strategy is no longer suitable for this complex control system,and the DC converter based on the nonlinear control method is needed to achieve high performance requirements.Therefore,scholars are more and more interested in the application of nonlinear control methods in DC converter modeling and control.In this paper,the nonlinear control theory is used to model and control the DC converter,and the nonlinear control strategy is proposed.The precise feedback linearization and Romberg observer are combined with the model predictive control respectively,in order to improve the stability of the DC converter system with CPL and solve the problem of wide input range.The research content of this paper includes the following aspects:Firstly,the negative impedance characteristics,large signal model and small signal model of CPL are analyzed,and the mechanism of its influence on the system stability is explained in detail.The mathematical models of DC-DC Boost converter and Buck-Boost converter with CPL and resistive load are established respectively,and their working principles are analyzed,and they are transformed into predictive models.Secondly,the principle of accurate feedback linearization is introduced.The affine nonlinear model of DC-DC Boost converter with CPL and resistive load is established by differential geometry theory,and the exact linearization of input and output of the system is realized by using state feedback exact linearization technique.In order to solve the problem of CPL stability,the predictive control strategy is used as the control algorithm in this paper,and the effectiveness of the control strategy and the robustness of the control system are verified by simulation experiments.Finally,model prediction controllers are designed respectively for three operating modes of Buck-Boost DC converter.In order to further improve the stability of the two-tube Buck-Boost DC converter with CPL and resistive loads and solve the problem of wide input range,Romberg observer is introduced and fused into the control system to deal with input and output disturbances,thus improving the robustness of the control system.The effectiveness of the proposed method is verified by simulation experiments.