Research On The Network Structure Of Multi-microgrid And Its Coordinated Control Strategy

In recent years,in order to reduce the adverse impact caused by the energy crisis,distributed generation and microgrid technology have been developed vigorously,and the multi-microgrid system with multiple neighboring microgrids is formed to improve the energy efficiency and integrate the advantages of multiple microgrids.Due to different network structures can be formed in multi-microgrid system,and capacity of each sub-microgrid,composition of distributed generation,load changes are different,how to coordinate control the multi-microgrid system with different network structure has become a research focus.In this paper,the network structure of multi-microgrid system and its coordinated control strategy are studied.The main work is as follows:Firstly,the typical structure of micro-grid and the main control methods are studied in this paper,and the basic working principle and operation characteristics of several typical distributed generations in multi-microgrid system are analyzed,the corresponding simulation models are set up.At the same time,based on the architecture and operation characteristics of two independent sub microgrids in our school,the network structure of multi-microgrid system is designed so that two AC sub microgrids can be connected in series and parallel structure.On this basis,the operation mode of the multi-microgrid system and the corresponding mode switching trigger events are analyzed.Secondly,the three-layer control framework is designed for the multi-microgrid system with multiple network structures in this paper,and the main functions of the micro source control layer,the coordinated control layer and the central control layer are analyzed respectively.Aiming at the power sharing problem in microgrid system,an improved droop control strategy based on virtual impedance is proposed in this paper,and the corresponding simulation model is built by Matlab/Simulink,which verifies the effectiveness of the strategy.At the same time,based on the different network structure of multi-microgrid system,the power control problem of multi-microgrid system is analyzed when active grid-connected switching to island mode,passive grid-connected switching to island mode and island switching to grid-connected mode,and the corresponding coordination power control scheme of tie line is designed and implemented.Finally,a experimental platform of multi-microgrid system is built,which realizes the interconnection between two independent sub microgrids,and the corresponding hardware components,communication structure and software development environment of system are introduced.And the experimental verification of the multi micro network structure designed in this paper is carried out,based on the experimental platform,the power coordinationcontrol strategy of multi micronetwork system during mode switching is verified by experiments,which shows that the strategy can achieve the smooth switching of multi-microgrid system from grid-connected mode to island mode,and can effectively ensure the coordination of power generation power and power consumption.