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Research On Modeling And Control For Microgrid With Multiple Distributed Energy Resources

Posted on:2014-11-08Degree:MasterType:Thesis
Country:ChinaCandidate:J LiFull Text:PDF
GTID:2252330401458886Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
Under both energy crisis and environment pollution pressure, distributed generation (DG)technologies, which are environmentally friendly, efficient and flexible, have arousedwidespread attention and interest in recent years. However, output power of distributed energyresources (DERs), such as wind power, is random and intermittent due to weather conditionconstraints, which poses negative impact on the utility network. As a feasible option to solvethis problem, Microgrid can coordinate the contradiction between DERs and the utilitynetwork and fully exploit the value of DERs.Microgird owns functions of control, protection and management, which makes it anautonomous system. It can operate in grid-connected mode or islanded mode and henceincreases the reliability of power supplies by disconnecting from the grid in the case ofnetwork faults. In order to ensure safe and stable operation, rapid and effective controlstrategies are needed. Taking into consideration the generation characteristics of DERs,control schemes have been studied in the two modes based on the mathematical models ofDERs in this thesis.Firstly, this thesis gives an overview of Microgrid demonstrations around the worldfocusing on definitions, structures, characteristics and development trend.Secondly, it is illustrated that generation principles, structures and mathematical modelsof DERs including small hydro generation, doubly-fed induction wind power generation andthe supercapacitor energy storage system, which provides theoretical basis for the design andanalysis of the corresponding controllers. It is noted that energy storage devices play animportant role in Microgrid, the functions of which are summarized in detail. Then aMircogrid topology is put forward, on which following research will be conducted.Thirdly, three typical control methods for DERs and three integrated coordinated controlstrategies for Microgrid are identified. Then considering the DERs’ characteristics in thisthesis, the master-slave control strategy is proposed for Microgrid. Based on the foregoingmathematical models, PQ controllers are designed for small hydro units and wind powergenerations, and PQ and V/f controllers for the supercapacitor in grid-connected and islanded modes, respectively.Finally, simulation model of the Microgrid is established in Matlab/Simulinkenvironment. Simulation tests are performed to investigate the effects of each controller bothin grid-connected mode and islanded mode. In addition, transient responses of the Microgridwith sudden change of load are analyzed. The results verified the feasibility and validness ofthe proposed control strategies.
Keywords/Search Tags:distributed energy resource, Microgrid, mathematical model, PQ control, V/fcontrol
PDF Full Text Request
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