Research On Distributed Robust Adaptive Control Of DC Microgrid Under Uncertain Structure

In recent years,the scale of DC microgrid has become larger and larger,and the proportion of DC load has also increased.Because of the few energy conversion links in DC microgrid,the utilization rate of electric energy is improved,and there are no control problems such as reactive power and frequency.Therefore,DC microgrid has gradually become a research hotspot at home and abroad.During the operation of the DC microgrid,it is often necessary to plug in or out the Distributed Generation Unit(DGU),which leads to changes in the system structure and affects voltage stability.In addition,due to load changes and external disturbances,the voltage fluctuations will also occur in DC microgrid,the research on voltage stability control of DC microgrid is of great significance.Considering a DC microgrid composed of multiple DGU interconnected,the system model is established based on Kirchhoff’s law.To solve the problem that the structural uncertainty caused by DGU Plug and Play affects the voltage stability of DC microgrid,a distributed robust H_∞ control is adopted to ensure the voltage stability of the microgrid.For a single DGU,the H_∞ state feedback controller is designed through Lyapunov stability analysis.In order to improve the dynamic response characteristics of the system,the regional pole configuration is used to constrain the controller parameters,and the poles of the closed-loop system are configured in the region D.The problem of the controller design is transformed into a robust optimization problem of linear matrix inequality(LMI).And each DGU is configured with a robust H_∞ controller,which can realize the distributed control of the DC microgrid.The design of the controller only needs the DGU and the line parameters connected to it,and does not require the entire microgrid parameters.In Matlab/Simulink,DC microgrid models based on Buck converters and Boost converters are built.The simulation show s,compared with PID control,H_∞ control is robust to disturbances and microgrid structural changes caused by DGU plug and play.In order to reduce the influence of structural uncertainty on the output voltage of DC microgrid,adaptive control is introduced on the basis of H_∞ control,so a distributed robust adaptive control method is proposed.According to the state error of the control object and the reference model,the parameter adaptation law is designed.Under the premise of ensuring the stability of the control system,the parameters of the H_∞ controller are adjusted in real time,s o that the adjustment mode of the controller changes with the changes in the operating conditions of the microgrid.Through LMI optimization solution,a robust controller with adaptive law is obtained.The proposed control method can not only effectively r ealize the stability of each DGU subsystem,but also can realize the stable operation of DGU interconnection.Through Lyapunov stability analysis,the stability of the distributed robust adaptive control syste m of the DC microgrid is proved.Based on the Matlab/Simulink platform,a robust adaptive control simulation model of DC microgrid based on different converters is built.The simulation results show that the proposed control method can improve the robustness of DC microgrid under structural uncert ain conditions.