Research On Coordinated Control Strategy Of Multi-microgrid With Hierarchical Structure

With the continuous improvement of new energy power generation technology,the scale of microgrid access to distribution network has been continuously expanded,and many multi-microgrid systems have gradually formed.Multi-micro-grids have the functions of coordinated control,internal autonomous operation of micro-grids,overall optimization management,and micro-source energy complementation,and have the advantages of rapid stability and economic controllability.But at the same time,due to the complex components of the multi-micro-grid system and the variety of control methods,how to effectively realize the coordinated operation of the multi-micro-grid system,the smooth integration of the multi-micro-grid system and the smooth interaction with the distribution network have become the key technologies that need to be solved urgently.This article focuses on several important aspects such as distributed micro-sources,tie-line power and synchronous grid connection in a multi-micro-grid system,including the following research contents:1.The typical composition structure of multi-micro-grid system,the main control method of micro-grid and distributed power supply are researched.The three-layer hierarchical control structure of the multi-microgrid is analyzed and the functions of each layer are divided in detail.On the basis of this three-layer hierarchical control structure,the Coordination control strategy between sub-microgrids in different modes,distribution network and multi-microgrid are studied.2.In the process of multi-micronet coordinating the sub-micronet to connect to the network,the control strategy of the micro-source in the sub-micronet is traditional.On the basis of the dynamic and insufficient accuracy of droop control,an improved droop optimization control strategy with virtual impedance added to the droop control is proposed as the control strategy for the transition process of multi-microgrid grid-connected operation.The correctness of the proposed improvement strategy is verified through simulation.3.According to the characteristics of the multi-micro-grid system tie line in this paper,the power control strategy of the multi-micro-grid system tie line is studied.It realizes that the sub-micronet cooperates to adjust and control the power of the tie line.Aiming at the synchronization problem in the process of multi-microgrid connection,the grid-connected synchronous coordinated control strategy is studied.The central control layer measures the difference.The sub-micronet cooperates with the adjustment of the difference between the two sides of the grid-connecting switch according to the received control instructions the network system is smoothly connected to the network.4.Use Matlab/Simulink to build a multi-micro-grid simulation model.Through the multi-grid system running on the grid.The simulation of the unified tie line control strategy verifies that when the power grid and the multi-micronet need to interact with each other,the sub-micronet is used as the unit to coordinate and issue the corresponding power according to the instruction to achieve smooth control of the tieline power.According to the conditions of multi-microgrid synchronous grid connection,through simulation,it was verified that the multi-microgrid can be synchronized with the large power grid quickly.The multi-microgrid is connected to the grid and the voltage and current of the microgrid have no major impact on the system during the transition process.