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Modeling, Analysis and Mitigation of Sub-Synchronous Interactions between Full- and Partial-Scale Voltage-Source Converters and Power Networks Open Access


Other title
pulse-width-modulated (PWM) voltage-source converters (VSCs)
active damping control
subsynchronous interaction
electrical damping
input impedance
Type of item
Degree grantor
University of Alberta
Author or creator
Alawasa, Khaled Mohammad
Supervisor and department
Co-supervisor: Xu, Wilsun (Electrical and Computer Engineering)
Mohamed, Yasser A.-R. I. (Electrical and Computer Engineering)
Examining committee member and department
Khajehoddin, S. Ali (Department of Electrical and Computer Engineering)
Mohamed, Yasser A.-R. I. (Department of Electrical and Computer Engineering)
Yazdani, Amirnaser (Department of Electrical and Computer Engineering, Ryerson University)
Xu, Wilsun (Department of Electrical and Computer Engineering)
Salmon, John (Department of Electrical and Computer Engineering)
Department of Electrical and Computer Engineering
Power Engineering and Power Electronics
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Voltage-source converters (VSCs) have gained widespread acceptance in modern power systems. The stability and dynamics of power systems involving these devices have recently become salient issues. In the small-signal sense, the dynamics of VSC-based systems is dictated by its incremental output impedance, which is formed by a combination of ‘passive’ circuit components and ‘active’ control elements. Control elements such as control parameters, control loops, and control topologies play a significant role in shaping the impedance profile. Depending on the control schemes and strategies used, VSC-based systems can exhibit different incremental impedance dynamics. As the control elements and dynamics are involved in the impedance structure, the frequency-dependent output impedance might have a negative real-part (i.e., a negative resistance). In the grid-connected mode, the negative resistance degrades the system damping and negatively impacts the stability. In high-voltage networks where high-power VSC-based systems are usually employed and where sub-synchronous dynamics usually exist, integrating large VSC-based systems might reduce the overall damping and results in unstable dynamics. The objectives of this thesis are to (1) investigate and analyze the output impedance properties under different control strategies and control functions, (2) identify and characterize the key contributors to the impedance and sub-synchronous damping profiles, and (3) propose mitigation techniques to minimize and eliminate the negative impact associated with integrating VSC-based systems into power systems. Different VSC configurations are considered in this thesis; in particular, the full-scale and partial-scale topologies (doubly fed-induction generators) are addressed. Additionally, the impedance and system damping profiles are studied under two different control strategies: the standard vector control strategy and the recently-developed power synchronization control strategy. Furthermore, this thesis proposes a simple and robust technique for damping the sub-synchronous resonance in a power system
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
K. Alawasa, Y.A.-R.I. Mohamed, and W. Xu, "Modeling, Analysis, and Suppression of the Impact of Full-Scale Wind-Power Converters on Subsynchronous Damping," IEEE Systems Journal, , vol.7, no.4, pp.700-712, Dec. 2013. K. Alawasa, Y.A.-R.I. Mohamed, and W. Xu, "Active Mitigation of Subsynchronous Interactions Between PWM Voltage-Source Converters and Power Networks," IEEE Transactions on Power Electronics, , vol.29, no.1, pp.121-134, Jan. 2014

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