| Micro-grid can make better use of renewable energy,give play to the economical and environmental protection of solar energy,wind energy and other energy sources,and its characteristics can complement the distribution network,improve the flexibility and stability of power supply,and improve power quality.With the integration of high-permeability micro-grid into the distribution network,the research on the control strategy of micro-grid grid-connection and the switching control strategy of micro-grid into/off the distribution network has an important influence on the power supply stability of the power system.This thesis focuses on the analysis and control of various operating states of the micro-grid.This thesis takes the optical storage micro-grid system as the research objective.Firstly,it analyzes and understands the overall system structure of the optical storage micro-grid,explores the power generation characteristics of photo-voltaic solar cells in the micro-grid and the charge-discharge characteristics of the hybrid energy storage system,and further obtains the corresponding MPPT control strategy of photo-voltaic and the power divider control strategy of the hybrid energy storage system.Secondly,the working principle and characteristics of the inverter are studied.The grid-connected operation adopts PQ control,while the isolated island operation adopts V/f control strategy.At last,pre-synchronous processing is added in grid-connected operation of micro grid to effectively eliminate the impact of distribution network,amplitude tracking is increased when off-grid,voltage frequency fluctuation is reduced,and smooth switching of micro grid is realized.A system model of an optical storage micro-grid was built on the Matlab/Simulink simulation system platform.Through the switching of loads and changing the inverter output power,the simulation analysis of the micro-grid’s transient stable operation under various environments was simulated.The results show that the control strategy proposed in this thesis can achieve the purpose of stable operation and smooth switching. |
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