Accurate Linearization Sliding Mode Variable Structure Control Of Three-level Supercapacitor Energy Storage Converter

DC microgrid is an important part of intelligent power distribution system of the future,which has a simple structure,without regard to the frequency and phase synchronization,high conversion efficiency,and lower cost.However,distributed new energy generation is vulnerable to the impact of weather and other natural environment,so it needs to be connected to energy storage devices to stabilize the power fluctuation in the system.In this paper,a charge and discharge system for a three-level supercapacitor energy storage converter is designed for DC microgrid,and its control strategy is studied.First,the working principle of non-isolated thee-level bidirectional DC/DC converter is introduced in detail,and its working mode under different duty cycle is analyzed.Combined with the equivalent circuit model of DC microgrid,the mathematical model of three-level super capacitor energy storage converter is established,and the converter parameters are designed,and the capacity of super capacitor is configured.Secondly,an accurate linearized sliding mode variable structure controller is designed for three-level supercapacitor energy storage converter,which reduces the strong dependence of the precise linearization on the mathematical model,enhances the system robustness and improves the dynamic response speed.The influence of the parameters of the linear sliding mode surface on the control performance of the system is analyzed.An improved method of piecewise linear sliding mode surface is adopted,and the switching error points of the piecewise linear sliding mode surface are designed.The simulation shows that DC bus voltage overshoot can be effectively suppressed by this method in the dynamic process of the system,the tracking accuracy of the system is improved at the stable time,and the recovery time of system is reduced by heavy load interference.Finally,on the experimental platform of the three-level super capacitor energy storage converter,the charge and discharge experiments of the system are completed,and the control algorithm is proved to be correct and feasible.