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Modular Multilevel Converter Based High Voltage DC Protection

Lewis, Patrick (2015) Modular Multilevel Converter Based High Voltage DC Protection. Master's Thesis, University of Pittsburgh. (Unpublished)

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This thesis addresses the protection of a high voltage DC (HVDC) system that utilizes the modular multilevel converter (MMC) topology, a voltage sourced converter (VSC), and incorporates two transmission line sections, a cable and an overhead line. Protection for high voltage AC systems is mature in installation experience. On the other hand there are many avenues of research needs for the protection of the more modern technology, HVDC.

The avenue of system protection focused upon in this work is the system restart sequence post DC side faults. This restart sequence is simply the sequence of events that occur necessarily in order to restart the HVDC system after a specified fault is already isolated and diminished. This avenue of system protection is focused upon but not exclusively. Fault isolation and suppression are also protection topics noted and discussed. Ultimately a fault section identification protection method is required for restart of the HVDC system when there are two transmission line sections. Specific to the HVDC system design presented there is desire for no communication channel between the converter stations of the system. Additionally, recovery of the system to normal operation is preferably as fast as possible in order to maintain power delivery with minimal disturbance. Solutions to these challenges are investigated and proposed.

The first part of this thesis work involves the detailed modeling of the MMC-HVDC system in the PSCAD simulation environment. After providing the validation of the model, both a parameter sensitivity analysis and an in-depth fault case analysis are performed for the overall examination of protection needs of the HVDC design. The fault analysis evaluation brings to light the means for a unique protection coordination method for the system design during post-fault system restart. The protection method ensures that cable faults, assumed to be permanent faults, are not reclosed upon while for any non-permanent faults attempt of reclose is made. The protection coordination method proposed in this work is unique in that it utilizes a signal characteristic to the HVDC system design to implement protection coordination without the use of a communications channel between converter stations.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Lewis, Patrickptl7@pitt.eduPTL7
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairReed, Gregorygfr3@pitt.eduGFR3
Committee MemberMao, Zhi-Hongzhm4@pitt.eduZHM4
Committee MemberMcDermott, Tomtem42@pitt.eduTEM42
Date: 9 April 2015
Date Type: Publication
Defense Date: 24 November 2014
Approval Date: 9 April 2015
Submission Date: 25 November 2014
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 139
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Electrical and Computer Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Modular Multilevel Converter, High Voltage DC, Protection, Fault, Protective Relay Coordination, Modeling, Section Identification
Date Deposited: 09 Apr 2016 05:00
Last Modified: 09 Apr 2020 05:15


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