Research On Droop Control Strategy For Microgrid Inverter

With the energy crisis and environmental problem getting worse, the distributed powergeneration (DG) is undergoing a significant development all around the world. Although thedistributed power generation has many advantages, there are still a lot of problems, for example: thehigh cost of stand-alone access and control difficulties. In addition, as an uncontrollable powerinterface, the DG unit will produce some negative effects on the stable operation of the grid.Microgrid is proposed in this case, aiming to solve the contradiction between the grid and distributedpower, and take advantage of distributed generation systems in large-scale. As a basic powerelectronic interface unit in microgrid, the reasonable and effective control of the microgrid inverterdetermines directly the safe and stable operation of the microgrid.According to the requirement that the microgrid need to not only operate in both island mode andgrid connected, but also transfer smoothly between these two modes. The droop control basedmicrogrid inverter control strategy is studied in the thesis.The mathematical modeling of three phasevoltage source microgrid inverter based on droop control has been derived firstly, and the double closecontrol loops including outer voltage loop and inter inductor current loop in the control system aredesigned. The operation principle and the design method of the control parameter of the power controlloop are also introduced, and the stability of power loop is analyzed in quantity by mathematicmodeling. Then the operating characteristic in both island and grid-connected modes of microgridinverter are depicted, and a novel pre-synchronizing control strategy is proposed for the microgridinverter to transfer smoothly between two different modes. Finally, based on Matlab/Simulinksoftware, the simulation model of microgrid is built to verify the effectiveness of droop controlstrategy for microgrid inverter.Finally, an experimental platform of three-phase microgrid inverterbased on digital controller TMS320F2812is designed and built, and a variety of experimental resultsare presented and analyzed so as to evaluate the design of droop control based microgrid controlstrategy, including the stable operation of microgrid in both island mode and grid-connected mode,and the seamless shifting process between two modes.