Modeling Of Micro-grid And Research Of Its Control Strategy In Island Operation

The distributed generation (DG) which based on renewable energy gets awide range of application with deteriorating of the global environment andincreasingly exhausted of the natural resources, and with the deepening of theresearch of the DG technology, the Micro-grid which take DG and load as anentirety and controllable unit become the central issue at home and abroad. TheMicro-grid not only contain the DG which grid to power system through rectifierinverter, but also contain the DG which parallel to power system in form ofsynchronous generators. There are big difference between different type of DG incontrol strategy and dynamic characteristic, when Micro-grid by paralleloperation to island operation, there are many problem in the management ofvoltage and frequency, in the energy balance between supply and demand and inthe power quality.The Micro-grid was researched in this paper that includes two types of DG,the control strategy of Micro-grid was studied and the models of every DG wererespectively established. For synchronous generator, its speed control system andexcitation system was mainly analyzed, combine with the governor andexcitation system which widely used in the current, electronic governor andphase compound excitation AC brushless excitation system was choosed as thespeed control system and excitiation system of synchronous generator, and themathematical model of prime mover and its speed control system andsynchronous generator and its excitation system was established according to itsstructure and control principle. For the inverter DG, the mathematical model ofPWM inverter was established and the control strategy of it was studied. Thus,the simulation model of two types DG was established in MATLAB/Simulinkaccording to their mathematical model and the simulation model of Micro-grid was established coordinates its integral control strategy with join the simplifiedmodel of load.At last, the experiment was made when Micro-grid in typical workingconditions, the results accurately reflect the dynamic characteristics of the systemunder various conditions and verify the correctness of the Micro-grid and controlstrategy. According to the results, synchronous generator can provide thebraceing of voltage and frequency when Micro-grid in island operation; theinverter can tracking the reference current well and stable output with gooddynamic performance; the problem of Micro-grid was discussed and the solutionwas proposed in this paper.The study in this paper has important theoreticalsignificance and practical value in promoting the reasearch of Micro-grid.