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Research On Reactive Power Sharing Control Strategy In AC Microgrids

Posted on:2015-09-30Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiuFull Text:PDF
GTID:2272330431499335Subject:Electrical engineering
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Abstract:The security, stability and economic operation of a grid are an important role in national life. However, with the shortage of global energy and the growing demand for user loads, the vulnerability of centralized power systems is gradually presented. So it is difficult for the traditional power system which has the characteristic of large units and high voltages to meet the reliability demand and diverse requirements of power the supply users. Based on the above issues, distributed generation has cased widespread attention. Then the microgrid makes use of the values and benefits of the distributed energy, and intergrates energy storage devices, power electronics, and monitoring and protection devices.Compared with the traditional centralized power system, the power electronic devices as the interface of distributed power (Distributed Generation, DG), is the core of the AC microgrid. When the AC microgrid operates islanding mode, due to the property of line impedance and other factors in microgrid, reactive power supplied by distributed generation units could not be shared accurately. Then it will lead to circulated current between the DG unit, seriously affect the power quality and system stability. Therefore, how to make a reasonable power sharing between the DG unit, has become a research hotspot of AC microgrid. So this paper will presents a study of the active and reactive power sharing in islanding mode for AC microgrid.Specifically, the paper can be divided into the following areas:(1) This paper analyses the mechanism and the influence factors of circulated current generation. Then the paper also research on the three kinds of the power sharing control strategy. They are the control strategy based communications, the droop control strategy, and the method combined communication and droop control respectively.(2) Base on the mechanism of the droop control, an improved droop control strategy is proposed. The method with low bandwidth communication is employed to obtain the reactive power values of DG units. Then the local reative power values can adapt to adjust the voltage bias of reactive power-voltage droop characteristic, so that the reactive power sharing accuracy can be improved obviously.(3) In order to further reduce the communication cost, a novel reactive power-voltage droop control based on the synchronous comensation is presented. The proposed method is realized through the sharing error reduction operation and the voltage recovery operation based on the conventional droop control. So the method not only improves the reactive power sharing accuracy, but also increases the PCC voltage level.(4) Based on the two novel reactive power-voltage droop control, this paper established the MATLAB/Simulink platform, and built the experimental platform of the two parallel DG units. Simulations and experimental results show that the effectiveness and feasibility of the proposed reactive power sharing method.
Keywords/Search Tags:AC Microgrid, Reactive power sharing, Improved droop control, Low-bandwidth communication, Synchronous compensation
PDF Full Text Request
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