Research On Parallel Control Strategy Of Microgrid Energy Storage Inverter Based On SOC Collaboration

AC microgrid contains a large amount of renewable energy,and its power generation has volatility and randomness.During island operation,Energy storage inverters with batteries as energy storage units are often connected to provide stable energy output for the microgrid,while stabilizing system voltage and frequency.In order to achieve capacity expansion and efficiency enhancement of the microgrid,multiple energy storage inverters are often connected in parallel to the microgrid for operation,enhancing the reliability and redundancy of the entire microgrid power supply,and meeting the diverse power consumption needs of users.However,between energy storage inverters,the line impedances connected to the microgrid are generally different,and using traditional droop control cannot achieve accurate reactive power allocation.At the same time,due to the different operation time and aging degree of the energy storage inverter connected to the system,the state of charge(SOC)and capacity of its battery are generally different.In order to improve the operational efficiency of microgrids and extend the work cycle of energy storage systems,it is important to study the control methods for the coordinated operation of multiple energy storage inverters(SOC)in isolated island microgrids for large-scale applications in the future.This paper focuses on the coordinated control of multiple energy storage inverters in parallel and the coordinated operation of SOC in the isolated island state of AC microgrid.The main research contents are as follows: Firstly,the mathematical models of the storage battery and inverter in the energy storage inverter are established,and the filter capacitance,inductance,and closed-loop control parameters in the inverter are designed in detail.Analyze the characteristics of different inverter control schemes,and select droop control as the basic control strategy.Further establish a parallel operation model of multiple energy storage inverters.Aiming at the problem of different line impedances leading to differences in output reactive power,an adaptive virtual impedance improved droop control strategy is proposed to suppress system circulation and improve the accuracy of reactive power distribution in the system.A MATLAB/Simulink simulation model is built,and the results verify the effectiveness of the proposed adaptive virtual impedance control.Secondly,aiming at the problem of SOC coordination in parallel with multiple energy storage inverters,a collaborative control scheme based on multiplication factor and exponential factor is proposed,which combines adaptive virtual impedance control to achieve dynamic SOC balance in the system.Compared with conventional collaborative control schemes,the proposed exponential factor control strategy has the characteristics of small frequency offset and fast collaborative speed.The small signal model of the proposed control strategy is established,and the stability of the control scheme is analyzed in detail,providing theoretical guidance for the selection of collaborative parameters.Introducing multi agent technology and adopting consistent algorithms to achieve information exchange in parallel systems without a central controller ensures the system’s plug and play performance.Finally,a model is built on the MATLAB/Simulink simulation platform to verify the proposed improved SOC collaborative control strategy.The relationship between the size of collaborative control parameters and collaborative speed is analyzed and discussed.Simulation results verify the effectiveness and scalability of the proposed control strategy.