Modeling And Transient Operation Characteristic Analysis On Micro-grid

Since the beginning of the21st century, electric power system has developed in theform of centralized power generation, long distance transmission of large-scale interconnectedsystem gradually. With the grid size expanding gradually, however, drawbacks of large-scaleinterconnected system has become increasingly prominent, such as high cost, operationcontrol not flexibly, more and more difficult to meet the reliability requirements of users and avariety of power quality needs. Distributed generation technologies with less pollution, highreliability, low investment, good environment compatible emerged, however, its operationparallel to grid brings a lot of adverse effects, causing power quality and reliability issues.The problems of distributed generation parallel operation to grid are solved bymicro-grid perfectly. Micro-grid can be defined as a cluster of distributed generations, storagesystem, loads and control systems, which is viewed as a subsystem of distributed network.Micro-grid can operate either in grid connected mode or in islanded mode which can enhancethe power supply reliability. Distributed generations adopt power electronic interface to gridmostly, which make its steady state and transient operating characteristic different from thetraditional grid.The modeling and transient characteristics simulation is an important mean to study thedynamic characteristics of the micro-grid system. The detailed modeling of the distributedgeneration, storage system, controllers, etc. is not only needed, but also the switching ofpower electronic devices is needed. Electromechanical and electromagnetic transientsimulation can be made by the software DIgSILENT batch in a same environment perfectly.In this paper, according to the research on the mathematical model of each distributiongeneration and co-generation system, the simulation model of every distribution generationand co-generation system are built detailed and accurately. Simulation and testing are didoperating in parallel to grid and the control and operation characteristics are analyzed. Thentwo types of micro-grid are built which adopting the energy storage system as the mainfeature. One adopts the centralized storage system, and the other adopts the co-generation system. Comparative analyses of two micro-grids are investigated in different operationconditions, including intentional islanding, load changes under islanded operation, poweroutput of distributed generation changes, one distributed generation outage and islandedoperation mode to parallel mode.