Research On The Modeling And Control Strategy Of Isolated DC Microgrid

With the integration of distributed power sources into the DC microgrid,the stability of bus voltage can be maintained by the main network.The voltage fluctuations caused by the loss of main network support during the operation of isolated DC microgrids need to be eliminated through control technology based on establishing a reasonable constraint model.The modeling and control technology research of isolated DC microgrids has become a hot topic in the field of DC microgrids.Therefore,this article takes the isolated DC microgrid as the research object,focusing on the regulation of DC bus voltage,to achieve stable operation of the isolated DC microgrid.The main content is as follows:(1)A fixed time controller is designed to address the secondary voltage regulation problem of isolated DC microgrids with input delay.The designed controller aims to achieve bus voltage regulation and current distribution and improve the convergence rate.Considering the existence of input delay in the secondary control,the time-delay system is simplified into a time-delay free ordinary differential equation through feedback linearization method and Artstein transform.Based on the simplified model,Lyapunov functional method is used to analyze the stability of fixed time and ensure accurate convergence.Finally,the effectiveness of the proposed control scheme is verified through simulation and comparison with relevant control methods.(2)A distributed secondary control strategy based on fuzzy adaptive control is designed to address the dynamic control parameters of isolated DC microgrids in bus voltage secondary regulation.This control strategy constrains the secondary control signal and adopts fuzzy PID logic to achieve voltage regulation and current distribution,while adaptively selecting secondary control parameters to improve the dynamic response ability of the controller.In addition,sufficient conditions for the system to achieve stability are provided based on the control scheme.Finally,the effectiveness of the control scheme is verified through simulation.(3)A distributed collaborative control strategy based on consistency is designed to address the voltage regulation of isolated DC microgrids under communication constraints and the balance of State of Charge(So C)of batteries.This control strategy aims to adjust the voltage of the isolated DC microgrid bus to the expected value in communication networks with time delay and noise interference,and achieve So C balance among battery energy storage systems(BESS).By using Lyapunov Krasovskii functional method and stochastic differential equation theory,the stability of the system is analyzed,and the sufficient conditions for the upper bound of delay are given.Finally,the effectiveness of the control scheme was verified through simulation.(4)The stability problem of isolated DC microgrids with multi port converters in a networked control system environment was studied.Considering the non independence of delay in digital communication networks and the high integration of multi port converters,an observer based stable control scheme was designed.In this scheme,the sensor to controller(S/C)delay and controller to actuator(C/A)delay are described by Bernoulli sequence,and the island DC microgrid closed-loop time-delay system model is obtained.The Lyapunov stability theory is used to give the necessary and sufficient conditions for the stability of the island DC microgrid closed-loop timedelay system,and a feasible solution is obtained by solving the minimization problem with linear matrix inequality(LMI).Finally,the effectiveness of the proposed scheme is verified through simulation.