Modeling And Simulation Of Distributed Generator In Micro-grid System

Accompanied by the emergence of energy issues and people increasingly highdemand for power quality, security and reliability, the drawback of tranditonallarge-scale centralized grid has increasingly apparent. In contrast, the micro-gridhas obvious environmental and social benefits, so it has become a hot point ofresearch around the world in recent years. To research the micro-grid system mustto give a study on its core component----distributed generator at first. So this paperfocus on in-depth studying the model and grid-connected control strategy of somedistributed generators which are main used in the micro-grid, such as: FuelCell(FC), Photovoltaic(PV) and Wind generation.The main research contents are asfollows:1) FC generation system: In this article, solid oxide fuel cell (SOFC) has beentaken as the research object. Based on the energy balance, material balance and thevoltage output equation, with the full consideration to the changes of thetemperature, partial pressure of each substance and polarization loss voltage duringthe power generation process, a dynamic mathematical model of SOFC has beenestablished. Then under the PSCAD/EMTDC software environment, we have built adetailed SOFC simulation model, and the accuracy of this model is verified byanalyzing the result of the simulation. Finally, by simulating the step change of theload current and the fuel flow, the characteristics of SOFC electrical outputresponses are simulated and analyzed, the result effectively reflect the dynamicperformance of SOFC.2) PV generation system: Based on the theory of the PV generation, theexternal characteristic equivalent mathematic model of PV array has beenestablished. Then carried out a detailed description of the necessity for maximumpower point tracking (MPPT) in the PV system, and two MPPT methods are mainlyelaborated: Newton Raphson method and incremental conductance method. Whenthe three-phase PV power system directly connected to the grid, the “MPPT-Unitpower factor” grid-connected control strategy has be applied. During thegrid-connected process, this control strategy can ensure not only the maximumpower output of PV, but also the unit power factor output of the grid-connectedinverter. Finally, a grid-connected PV generation system model has been created by using the PSCAD/EMTDC simulation software, and the result of the simulationconfirms the effectiveness of the model and the control strategy used in this article.3) Wind generation system: According to the basic theory of wind generationand the knowledge of electric machinery, the wind speed model, the wind turbinemodel, the shaft model of mechanical transmission part, the model of PMSG andDFIG are respectively constructed. Carried out a detailed description of the basicprinciple of maximum wind energy capture, and then the corresponding pitch anglecontrol strategy is established. On the basis of the grid-connected control principlesof PMSG and DFIG wind generation system are specifically analyzed respectively,the corresponding control strategys of grid-side converter and machine-sideinverter are designed. At last, grid-connected wind generation system model ofPMSG and DFIG are respectively set up under the PSCAD/EMTDC environment,and the result of the simulation has confirmed the effectiveness of the models andthe control strategys which posed in this article.