Research On Control Strategy Of Enhanced Bidirectional Z Source Inverter

The vigorous development of new energy power generation technologies and energy storage systems has brought a clean and environmentally friendly,never-depleted electric energy production model,and has put forward higher requirements for inverters in distributed power generation systems.The Z-source inverter solves the problem that the traditional voltage and current inverters have no boosting capability,and the upper and lower arms cannot be connected directly,and there is no need to add a boosting module and a dead time control module.However,there are still limitations such as limited boosting capacity,abnormal working conditions and inability to realize energy feedback,which is not suitable for application in energy storage systems.Therefore,the introduction of switch inductance technology and fully controlled switch tube enhanced bidirectional Z-source inverter has far-reaching significance for the development of distributed grid energy storage application technology.Firstly,comparative analysis of various derived flutter structures and their advantages and disadvantages of Z-source inverter,based on which,an enhanced bidirectional Z-source inverter is obtained.Based on Kirchhoff's voltage and current laws,the mathematical relationship between the 7 current working modes and 2voltage working states of the enhanced bidirectional Z-source inverter is analyzed in detail.The spatial state averaging method is used to build a small signal model of the enhanced bidirectional Z-source inverter,and the mathematical transfer function relationship between variables in the topology is derived.Secondly,in view of the fact that the traditional seven-segment SVPWM modulation will cause the switching frequency of the fully controlled switch in this topology to be too high,a three-segment SVPWM modulation strategy based on fast implementation is proposed;Of the transfer function contains the zero point of theright half plane,there is a problem of non-minimum phase characteristics,an auto disturbance rejection controller with short transition process,no overshoot,and no dependence on the mathematical model is selected,and the nonlinear Based on the function fal function,an improved lfal function is proposed to avoid high-frequency chattering and accelerate the system gain reduction rate under large error conditions,in order to design and improve the auto disturbance rejection controller.Finally,in order to verify the correctness of the proposed theory,a simulation platform based on MATLAB / Simulink is built,and the advantage of the enhanced bidirectional Z-source inverter is that it has stronger boosting capability and can achieve bidirectional flow of energy;Three-stage SVPWM modulation strategy can reduce the switching frequency of the switch to reduce losses;improved auto-immunity control can enhance the robustness of the DC link voltage control.