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EFFECTIVE POWER MANAGEMENT FOR AUTONOMOUS OPERATIONS OF MICROGRIDS

Cingoz, Fatih
http://rave.ohiolink.edu/etdc/view?acc_num=akron1469038927

Abstract Details

2016, Doctor of Philosophy, University of Akron, Electrical Engineering.
Integration of distributed energy sources (DESs) into conventional power networks has gained significant interest due to benefits such as introducing environmentally friendly renewable sources and the improvement of power quality, reliability, and efficiency. The concept of the microgrid (MG) has been recently introduced as a small-scale power generation platform for DESs to be efficiently and reliably integrated into existing infrastructures. A microgrid is usually composed of various DESs, energy-storage devices, and loads that are localized in a small vicinity. An effective management of the components within the MG is performed as a single entity by implementing centralized/decentralized control techniques. Droop control is one of the most widely used techniques in MG to perform an autonomous power management among DESs without the need of a communication network. Conventionally, droop control settings are designed based on the power ratings of the sources to perform power sharing among the participating DESs in proportion to their rated output power. The proportional load sharing strategy is commonly practiced to avoid overstressing and aging of sources. Since this approach does not take the operating cost of the sources into account, it may not offer a cost-effective operations in islanded AC MGs. In addition, the conventional droop concept utilized in DC MGs degrades the current sharing accuracy as well as the bus voltage across the MG. This dissertation investigates alternative droop control techniques with improved droop settings design strategies to realize more effective power management for autonomous operation of AC and DC MGs. A nonlinear droop concept is introduced to achieve a cost-effective and reliable operation in islanded AC MGs. When the droop curve of the sources is allowed to vary nonlinearly, better performance could be achieved. However, these curves need to be designed properly to minimize the MG operating cost while maintaining the system stability. In this research, a new droop settings design approach is introduced to develop a nonlinear droop controller that carries out the required stabilization while introducing more economical power sharing and plug-and-play functionality for the sources. In addition, this research covers the area of a novel droop control design strategy to achieve more effective and reliable operations in islanded DC MGs. In AC MGs, the frequency is used as a universal signal to effectively share the loads among the participating sources; however, in a DC MG, no such signal exists. Therefore, to mitigate this limitation and realize an enhanced droop controller for DC MGs, this research proposes a novel design methodology in which the droop settings are selected by making use of all of the information such as MG topology, source locations and their proximity to loads, loading conditions and their variations in addition to current ratings. The droop controllers implemented with the droop settings obtained through the proposed design methodologies introduce relatively higher current sharing performance while maintaining minimal bus voltage degradations. For the AC and DC MGs considered in this thesis, the droop settings are designed through an optimization process. The optimization problems are formulated along with the necessary constrains that keep the operating variables within their acceptable ranges. The optimization problems are solved for various loading conditions to determine the optimized design settings for the droop controller. The effectiveness of droop control design strategies are analyzed through different case studies and the performance of the designed droop control techniques are verified by simulations and hardware experimentations. Hardware setups for AC and DC MGs have been established to verify the validity of the proposed method. Through a number of hardware experimentations, the effectiveness of the proposed methods has been successfully demonstrated and its advantage over the conventional droop setting approach has been verified. The simulation and experimental studies conducted for AC MGs have shown that the nonlinear droop controllers implemented with the droop settings obtained using the proposed design methodology minimize the MG operating cost more than the existing methods introduced in the literature. The simulation and experimental studies conducted for DC MGs have clearly shown that the enhanced droop controller proposed in this research offers improved current sharing performance with less bus voltage degradations compared to the conventional droop controller.
Yilmaz Sozer (Advisor)
Malik Elbuluk (Committee Member)
Alexis De Abreu-Garcia (Committee Member)
Siamak Farhad (Committee Member)
Kevin L. Kreider (Committee Member)
247 p.
Electrical Engineering

Recommended Citations

Citations

  • Cingoz, F. (2016). EFFECTIVE POWER MANAGEMENT FOR AUTONOMOUS OPERATIONS OF MICROGRIDS [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469038927

    APA Style (7th edition)

  • Cingoz, Fatih. EFFECTIVE POWER MANAGEMENT FOR AUTONOMOUS OPERATIONS OF MICROGRIDS . 2016. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1469038927.

    MLA Style (8th edition)

  • Cingoz, Fatih. "EFFECTIVE POWER MANAGEMENT FOR AUTONOMOUS OPERATIONS OF MICROGRIDS ." Doctoral dissertation, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469038927

    Chicago Manual of Style (17th edition)

akron1469038927
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© 2016, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.