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Review and Simulation of Voltage Source Converters for HVDC Grid Development
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- Author / Creator
- Alyami, Hadi
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For over a century, the electric energy generation, transmission, distribution and utilization patterns have been essentially based on Alternating Current (AC), throughout time the AC technologies have been pushed into their thermal and/or technical limitations. The Direct Current (DC) technologies have as a result and mean of support been recurred. This reappearance of the DC technologies has resulted in a volume of knowledge that is counterpart in some cases and complementary in others. Therefore, this thesis concerns with reviewing the latest knowledge of High-voltage DC (HVDC) technologies, and thereafter draws a critical comparison by putting a variety of the related promising and common exercises into PSCAD/EMTDC® simulations. With a particular focus on the Voltage Source Converters (VSCs) in HVDC application, the review is shaped to induce a critical reference that groups and classifies the growing scope, thereby providing an insightful evaluation of where the VSC-HVDC technology stands and is heading. Subsequently, the review is augmented by arguing the staged-development practice for the realization of MTDC grid. A number of HVDC project developers are supposedly ascertained that the possibility of erecting an MTDC grid shall occur in stages by interlinking the existing point-to-point HVDC systems. However, the transition requirements can differ greatly in one sense, and function in synchronism in another. Thus, a vital staging analysis of HVDC with Modular Multilevel Converters (MMC) is applied to show how the classical point-to-point structure (stage-1) can be a stepping-stone towards a radial structure (stage-2), after which a DC grid can be established (stage-3). The key focus upon each stage transition is the individual and cooperative performance of the interlinked MMC terminals. In stage-1 and stage-2, the performance of the interconnected MMC terminals is implemented with the master-slave based strategies. Stage-3 comprises one offshore windfarm and three ring-linked onshore AC systems, forming an MTDC grid. In many DC voltage coordination studies addressing MTDC grids, droop methodology is seemingly the primary option to redistribute the power unbalance, thereby precluding the onshore MMCs from hunting each other. Although droop method is effective; especially in damping the dynamics, it is not optimum for controlling VDC. Incorporating one MMC terminal to tightly control VDC and upon its outage or when it runs out of capacity, the other MMC terminals take over VDC regulation ensures a better VDC coordination. Thus, in stage-3, the master-slave concept is adopted in normal operation conditions and combined with droop control that is only active in disturbed operation conditions, where the transition boundaries dictate by the dead-band P/VDC characteristics.
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- Graduation date
- Spring 2018
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.