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Distributed Robust Adaptive Droop Control for DC Microgrids

Title: Distributed Robust Adaptive Droop Control for DC Microgrids.
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Name(s): Vu, Tuyen Van, author
Edrington, Christopher S., 1968-, professor directing dissertation
Clark, Jonathan E., university representative
Foo, Simon Y., committee member
Moss, Pedro L., committee member
Florida State University, degree granting institution
College of Engineering, degree granting college
Department of Electrical and Computer Engineering, degree granting department
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2016
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (125 pages)
Language(s): English
Abstract/Description: The increase of electric power demand for advanced weapons and combat systems in all-electric ships (AES) including electrical propulsions, electromagnetic rail-guns, lasers, radars, and sensors relies on future advanced integrated power systems. The U.S. Navy has predicted that future integrated shipboard power systems will be DC power distribution systems (DC microgrids). To achieve the system’s objectives or missions, power flows among distributed resources (DR) and load devices in these systems have to be properly regulated. Therefore, the main objective of this dissertation is to control the power flows among distributed devices in DC microgrids. Control of the power flows in DC microgrids involves controlling the current sharing among DR and stabilizing the DC bus voltage. To fulfill these control objectives, voltage droop control has been utilized. However, there is a tradeoff between current sharing among DR and DC bus voltage stability when droop control is used in DC microgrids, as current sharing approaches set points, bus voltage deviation increases. Previous studies have suggested using secondary control utilizing linear controllers to overcome the drawbacks of droop control. However, linear control design depends on an accurate model for systems. In many other applications, where the parameters of systems are known, the linear control techniques are superior. Nevertheless, the derivation of such an accurate model is challenging in DC microgrids because the noise and disturbances caused by the coupling between sources, loads, and switches in microgrids are under-represented. This under-representation makes linear modelling and control insufficient. Hence, the adaptive control is a worthy choice because of its ability to deal with the model uncertainty. The robust adaptive control method developed and utilized in the Dissertation is based on model reference adaptive control (MRAC) because it provides DC microgrids the ability to deal with the uncertainty and ensures the system's stability. However, the main problem of the conventional adaptive method is that the high-speed adaptation results in a high oscillation of the transient response in adaptive systems. The limitations in the conventional method limit itself from applications. Thus, a new class of adaptive method based on the closed-loop reference models (CRM) has been suggested in literature to minimize the oscillatory effect of the conventional method, specifically for aircraft systems. Yet, the CRM with fixed adaptation gain still finds challenges in dealing with different operating points and is sensitive to noise and disturbance. Therefore, this research proposes a modified CRM for a robust response in the system. The first modification made is the integration of the normalization technique and parameters projection algorithm in the CRM. The next modification made is scheduling the adaptation gain for various operating points in the system. These modifications are proved to be stable following Lyapunov. Finally, the application of the developed robust adaptive method in a distributed control framework to adjust the droop characteristics to satisfy both current sharing and DC bus voltage stability criteria in DC microgrids is proposed and analyzed. Simulation results and experimental validation on a 400 VDC microgrid show that the adaptive method precisely shares current between two DR and maintains the nominal bus voltage in various scenarios of islanded mode and grid-connected mode.
Identifier: FSU_2016SU_Vu_fsu_0071E_13340 (IID)
Submitted Note: A Dissertation submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Degree Awarded: Summer Semester 2016.
Date of Defense: June 30, 2016.
Keywords: Adaptive Control, Distributed Control, Droop Control, Microgrids, Ship Power Systems
Bibliography Note: Includes bibliographical references.
Advisory Committee: Chris S. Edrington, Professor Directing Dissertation; Jonathan Clark, University Representative; Simon Y. Foo, Committee Member; Pedro Moss, Committee Member.
Subject(s): Electrical engineering
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_2016SU_Vu_fsu_0071E_13340
Owner Institution: FSU

Choose the citation style.
Vu, T. V. (2016). Distributed Robust Adaptive Droop Control for DC Microgrids. Retrieved from http://purl.flvc.org/fsu/fd/FSU_2016SU_Vu_fsu_0071E_13340