Control of multi-terminal VSC-HVDC systems for combined AC/DC systems to improve power system dynamic performance

dc.contributor.advisor James D. McCalley
dc.contributor.author Zhang, Qian
dc.contributor.department Electrical and Computer Engineering
dc.date 2020-09-23T19:12:16.000
dc.date.accessioned 2021-02-25T21:37:20Z
dc.date.available 2021-02-25T21:37:20Z
dc.date.copyright Sat Aug 01 00:00:00 UTC 2020
dc.date.embargo 2021-08-28
dc.date.issued 2020-01-01
dc.description.abstract <p>Renewable energy resources are being integrated into power systems around the world and replacing conventional generators to reduce carbon emission. Voltage source converter based multiterminal HVDC (VSC-MTDC) is identified to be a promising technology to facilitate the integration and utilization of large amounts of renewable energy resources across large geographic areas. Many challenges exist in operating such a combined AC-MTDC power system under a high renewable future. This dissertation addresses three challenging problems in terms of improving dynamic performance of an AC-MTDC system, which are AC system frequency control, DC voltage control, and implementation of VSC-MTDC controls on practical large scale systems.</p> <p>The first part of this dissertation focuses on designing frequency control for VSC-MTDC to provide frequency support among asynchronous AC systems for AC side events. A global frequency control scheme is designed and is shown to have superior performance to the traditional local frequency droop scheme with improved frequency nadir and reduced impact to the DC voltage profile. Consequently, the amount of load shedding and the need of total online spinning reserves are reduced. In the second part of this dissertation, an adaptive DC voltage droop control strategy is developed for converter outages taking both DC voltage deviation and power sharing into consideration. The proposed control enables accurate power sharing based on converter operating conditions, with the capability to differentiate the outage of a rectifier from that of an inverter. As a result, converter overloading is avoided and transient DC voltage profiles are improved. Moreover, the proposed control has the flexibility to adjust the strength of DC voltage regulation. In the last part of our work, in order to investigate the effectiveness of the designed frequency and DC voltage controls on practical large scale systems, a six terminal VSC-MTDC system is modeled into a 100k bus North American power system with an HVDC overlay, with which the advantages of the developed controls are demonstrated. With the proposed control strategies for VSC-MTDC systems, the reliability of the overall AC-MTDC system is improved in terms of both AC and DC side contingencies.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/18256/
dc.identifier.articleid 9263
dc.identifier.contextkey 19236861
dc.identifier.doi https://doi.org/10.31274/etd-20200902-175
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/18256
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/94408
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/18256/Zhang_iastate_0097E_18611.pdf|||Fri Jan 14 21:39:15 UTC 2022
dc.subject.keywords continental HVDC overlay
dc.subject.keywords DC voltage control
dc.subject.keywords droop control
dc.subject.keywords primary frequency support
dc.subject.keywords VSC-MTDC
dc.title Control of multi-terminal VSC-HVDC systems for combined AC/DC systems to improve power system dynamic performance
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication a75a044c-d11e-44cd-af4f-dab1d83339ff
thesis.degree.discipline Electrical Engineering(Electric Powerand Energy Systems)
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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