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Hierarchical Control of Inverter-Based Microgrids

Chang, Chin-Yao
http://rave.ohiolink.edu/etdc/view?acc_num=osu1471815065

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
Electric power grid is experiencing a major paradigm shift toward a more reliable, efficient, and environmentally friendly grid. The concept of microgrid is introduced to integrate distributed renewable generation in proximity to demands for both environmental and power-efficient promises. A microgrid can be disconnected, or "islanded", from the main grid and operates on its own, providing energy to remote areas or during faults of the main grid for better reliability. Islanded microgrids inherit several different properties from traditional power grids, including uncertain and limited generation, mixed R/X ratio lines, and lack of power inertia from synchronous generators. Those properties pose new challenges for the stable operation of islanded microgrids. The dissertation is dedicated to addressing the control challenges of islanded microgrids. The contribution is twofolds. First, we propose a polynomial time optimal power flow (OPF) solver which finds an optimal operating point for the inverters of the distributed energy resources. The proposed algorithm can account for the cost functions on the reactive generation that are common in microgrids. It also brings new understanding on the conjectures of exact semidefinite programming (SDP) convex relaxation on the OPF problem. Furthermore, we show that without the load over-satisfaction assumption usually seen in the literature, a near global optimum can be found for the OPF problem with arbitrary convex quadratic cost functions. The results are important to both microgrids and the classical OPF problem. Our second major contribution is developing a novel distributed controller that addresses the control challenges originated from limited generation, mixed R/X ratio lines, and lack of power inertia properties of islanded microgrids. The proposed controller can ensure proportional active and reactive power sharing and frequency synchronization while respecting the voltage constraints. Variances of the distributed controller are proposed to further relax the communication infrastructure requirements or add compatibility between the real time distributed controller and the OPF solution. An important feature of the proposed OPF solver and the distributed controller is that they can be applied to mesh microgrids with mixed R/X ratio lines. Both the OPF algorithms and the distributed controller are shown effective through simulation studies.
Wei Zhang (Advisor)
Kevin Passino (Committee Member)
Andrea Serrani (Committee Member)
Krishnaswamy Srinivasan (Other)
131 p.
Electrical Engineering; Mechanical Engineering
Distributed control, droop control, hierarchical control, microgrid control, optimal power flow problem, semidefinite programming convex relaxation, near global optimum algorithm

Recommended Citations

Citations

  • Chang, C.-Y. (2016). Hierarchical Control of Inverter-Based Microgrids [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471815065

    APA Style (7th edition)

  • Chang, Chin-Yao. Hierarchical Control of Inverter-Based Microgrids. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1471815065.

    MLA Style (8th edition)

  • Chang, Chin-Yao. "Hierarchical Control of Inverter-Based Microgrids." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471815065

    Chicago Manual of Style (17th edition)

osu1471815065
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© 2016, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.