Research On Non-Fragile Robust Control Method For AC/DC Hybrid Microgrid Interface Voltage

In recent years,energy and environmental issues have become increasingly prominent,power load has gradually increased,and grid technology has been continuously innovated,prompting the development of power systems in a more efficient and sustainable direction.As a form of microgrid that effectively integrates different types of distributed power sources and loads—AC/DC hybrid microgrid,it can reduce the use of power converters,reduce system harmonic pollution,and achieve green energy conversion.In the AC/DC hybrid microgrid,the bidirectional AC/DC converter connected to the AC subnet and the DC subnet constitutes an AC/DC interface system,which plays an important role in realizing power transfer between multiple regions,stabilizing the bus voltage and improving the flexibility of the grid.In this paper,based on the structure and operation characteristics of the bidirectional AC/DC converter,the robust control method of the AC/DC interface converter with the purpose of stabilizing the bus voltage is studied.The main research work is as follows:Firstly,the basic theory and application methods of linear matrix inequalities(LMI)in robust control are introduced.The index function of quantitative system performance and the corresponding constraints are given.A design method of system state feedback control law is given for a class of system with norm bounded parameter uncertainties.At the same time,in order to improve the dynamic response quality of the system,the regional pole placement technology is introduced.Secondly,based on the analysis of the working mode of the AC/DC interface converter,considering the bus voltage fluctuation caused by the randomness of the intermittent power supply output and the model parameter perturbation caused by the aging of the system components,to establish the the norm-bounded uncertain model including voltage disturbance and the model parameter perturbation.At the same time,a non-fragile robust controller is employed,taking into account gain perturbation caused by controller parameter variations.Then the above uncertainty is transformed into the mathematical problem of the optimization norm.In order to balance the dynamic response characteristics of the system,the closed-loop poles of the control system are arranged in a pre-selected area.A stable controller is obtained by solving the convex optimization problem with multiple performance index constraints such as asymptotic stability,interference suppression performance and regional stability performance of the closed-loop system.Finally,the non-fragile robust control law is solved by LMI toolbox,and the simulation model is built.The simulation results are used to compare and analyze the control effects of the non-fragile robust control method and the traditional PI method.The former has better control performance under the condition of model parameters,and external disturbance and controller gain perturbation,and meets the requirements of stability,robustness and high precision control of hybrid microgrid AC/DC interface system.