Modeling And Simulation Of Microgrid Operation And Control

In recent years, large-area power outages occured so frequently that fully exposed the vulnerability of traditional grid. Under the double presure of energy demand and evironmental protection, people begin to fix their eyes on the distributed generation (DG), which is environment friendly, high efficiency and flexible. As an effective complement of the centralized power generation, Using DGs is able to solve the problem of energy shortage and serious environment pollution, improve the reliability of present power systems. With the increase of the permeability of distributed generations, many problems occurred. The output power of DGs such as solar energy and wind energy is random, so they are considered as uncontrollable source of the large grid. The restriction and isolation measurements taken to DGs limit their full efficiency. With the development of smart grid. in order to coordinate the contradictions between DGs and large grid and fully excevate value and benefits brought by DGs to users and grid, people proposed the concept of "Microgrid".Microgrid is a standalone power system with DGs,controllable loads,energy storage devices and controllers. It runs flexible and changeable, having a high request for control strategy. So studying on operation and control of Microgrid is beneficial to promote its development and application.The thesis introduced related technologies of microgrid from three aspects of modeling of micro power, grid connected and the comprehensive operation of Microgrid. Chief research achievements are as follows.(1)Considering the voltage output model, thermodynamic model, double charge layer model and gas supply model, dynamic model of PEMFC is presented with Matlab/Simulink.PEMFC polarization characteristics are also analysised. And the use of load current changes, simulate the output voltage, power and efficiency characteristics of fuel cell.(2)Give the general model of photovoltaic using Matlab/Simulink, analysis the output characristics under different environments.And achieved MPPT of of photovoltaic with traditional Perturbation and Observation (P&O) method.(3)Introduced the single-phase grid-connected control strategy with photovoltaic as an example.Proposed boost-based two-level grid-connected photovoltaic inverter system.by which the MPPT and unity power factor grid-connected was achieved. Introduced the three-phase grid-connected control strategy with PEMFC as an example.Achieved unity power factor grid-connected by the three-phase grid-connected inverter system based on grid voltage vector orientation. (4)Researched the principle of PQ, U/f and Droop control strategy and designed examples to verify the effectiveness of each control strategy.Simulated the connected mode, disconnected mode and switch the two mode of Microgrid, as well as cutting or increasing load and DG in islanding mode.Simulation results showed that the control strategy proposed can made the Microgrid work reliably under different operation conditions.