Research On Robust LQR Control Of Super Capacitor Energy Storage System

In recent years,energy storage technology has played an important role in the flexible peak regulation of micro-grids.It is not only the key technology to ensure the stable operation of the micro-grids,but also plays a positive role in promoting the widespread application of distributed power technology in the micro-grids.At present,the carriers of energy storage devices are mainly lithium batteries and super capacitors.In particular,energy storage devices of using super capacitors as components have been widely used,because of they have advantages such as high energy storage density and long cycle life under high power charge and discharge conditions.In addition,to a large extent,the development of energy storage technology is depending on the control of DC / DC converters.Therefore,this paper focuse on the control of bidirectional DC / DC converters with super capacitors as energy storage devices,and use robust control method to control bidirectional DC/DC converter with two uncertain parameters of super capacitor terminal voltage and load.This paper is organized as follows:At first,the research status of energy storage technology and DC / DC converter control are discussed.Apart from this,the development history of robust control theory and linear matrix inequality(LMI)technology are summarized.At the same time,the related concepts and theoretical knowledge of LMI that need to be applied in the design are introduced,Providing theoretical support for the subsequent design of robust controller in this article.Secondly,based on the selected bidirectional DC / DC converter circuit structure,the working principle of the DC / DC converter is analyzed.The state space averaging method is used to model the super capacitor bidirectional DC / DC converter system,and the small signal model of the system is linearized at different static operating points.Considering the variation characteristics of the super capacitor terminal voltage and load,the convex optimization theory is used to establish a multicellular model with uncertain factors to represent uncertain time-varying systems.Thirdly,based on the established multicellular model with two uncertain parameters of terminal voltage and load,a robust LQR controller is designed that takes into account the parameter uncertainty.At the same time,in order to reflect the performance of the designed controller,a traditional double closed-loop PI controller is designed based on the system model.At last,in order to verify the research content,with the help of MATLAB/Simulink simulation platform,a corresponding simulation model was built,and the simulation results of the robust LQR controller applied in the control system and the simulation results of PI controller were compared.According to the simulation results,there are found that the robust LQR controller based on the mathematical model proposed in this paper can make the system have good dynamic performance and stability.At the same time,when the super capacitor terminal voltage changes in a wide voltage range,the load changes or even there is external interference,the DC bus voltage can be stabilized faster and better,and the control effect is better than the traditional double closed-loop PI control.