Three-layer Model Predictive Control For Optical Storage DC Microgrid

In the past ten years,the DC microgrid has received high attention in academia and industry.As an effective means for distributed energy to connect to the AC grid,microgrid is of great significance for improving the efficient use of energy and reducing greenhouse gas emissions.Firstly,this article introduces the domestic and foreign development history,research status and power coordinated control technology of DC microgrid,expounds the development status of energy storage system(ESS)in DC microgrid.It also summarizes the development of frontier control technology of energy storage system in recent years,and introduces the application background and the latest research status of model predictive control(MPC)mainly studied in this paper.Secondly,according to the mathematical model of the photovoltaic cell,the single variable method is used to analyze the characteristics of the output of the photovoltaic panel under different light intensity and temperature,and the disturbance observation method is selected to track the maximum output power of the photovoltaic power generation system;then the energy storage system is established mathematical model,analysis of the working principle of the bidirectional DC-DC converter,in view of the difficulty of parameter setting and difficult adjustment in traditional PI double closed-loop control,drawing on the model predictive control method commonly used in synchronous motors,combining the concept of sequence structure,and putting forward a three-level model predictive power control(MPPC)method to eliminate the weight factor of the objective function.In the objective function of traditional power control,two limiting items of switching frequency and charge are added to optimize it,and then the objective function is decomposed into three separate control items.By analyzing all possible three-level sequence structures,the stability of the system performance and rapidity are used as the criteria for judging,and the optimal sequence structure is selected.This method avoids the design of weighting factors while reducing switching losses,and the system can still maintain good dynamic performance,simple operation,and small amount of calculation;model predictive control is performed on the grid-connected inverter in the dq coordinate system to realize the smooth connection of distributed power sources and the grid.Finally,on the basis of the above theoretical analysis and simulation,an experimental platform is built and control programs are written,the hardware and software parts of the DC microgrid are designed,open-loop and closed-loop experiments are performed,it was completed after several debugging experiments,which proved that the control method proposed in this paper is correct and effective.