Thesis
Enhanced static voltage stability and short circuit monitoring performance and optimization of future onshore AC power systems
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16623
- Person Identifier (Local)
- 201651239
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This thesis presents several techniques focussed on improving characterisation, estimation and optimization of various factors associated with future power system strength and stability, that are markedly changing as the transition to renewable energy-dominated power systems continues. Changing systems strength in transmission and distribution networks are presenting unique regional challenges limiting the integration of low carbon technologies due to various constraints imposed on the network. These include fault level headroom constraints in MV distribution networks and steady state stability limits in transmission networks during periods of high power transfer. Specifically, a perturbation-coefficient based recursive least square (RLS) passive fault current estimation method, impedance matching bus-based and line-based static stability indices and voltage stability-constrained optimal power flow (VSCOPF) models are presented to facilitate enhanced system performance in future lowinertia/strength power systems. Alternative to model-based strategies for conducting short circuit studies, measurement based short circuit monitoring has presented effective means to facilitate active fault level management functions and support flexible distributed generation connections in MV distribution networks. The application of passive and active fault level estimation is presenting alternative means to support embedded generation connections in fault level constrained regions. This research therefore proposes a perturbation coefficient-based technique for passive short circuit estimation utilising RLS based methodologies. This improves existing OLS processes in fault current estimation as parameter estimates are continuously updated via gain vectors with the sum of square of errors recursively minimised with additional load perturbation events identified. Enhancements in the accuracy of the proposed estimation method are demonstrated utilizing extensive simulation-based studies relative to conventional estimation methods. Declining system strength presents several challenges in monitoring and managing future networks with increased risks of classical voltage instability in weak networks identified as an emerging challenge. Novel static line-based and bus-based voltage stability indices are developed based on the ratio of load current flowing in a line to the expected fault current flowing in the line and are based on impedance matching concepts during maximum power transfer. The proposed approach models shunt branch parameters, which have been historically neglected in two-bus equivalents and hence illustrate enhanced performance during stressed system conditions. Simulation based studies on multiple test networks have demonstrated improved detection capability of the developed stability indicator against several bespoke static line stability assessment methods. Index characterization considering solid state transformer (SST), constant voltage and constant power factor DG models are also presented to illustrate stability performance in future system conditions. The developed line index is incorporated into existing optimisation procedures for optimal generation dispatch with the inclusion of voltage stability criteria via voltage stability-constrained optimal power flow (VSCOPF). The proposed VSCOPF models incorporate the novel line stability indicator as part of an objective function in a multi-objective OPF formulation and as an inequality constraint. The proposed VSCOPF solution procedures demonstrate enhanced capability in increasing critical loadability, improved voltage performance, enhanced active/reactive generation dispatch and reduction in system losses relative to existing methods via simplified and robust calculation of proximity to collapse using static analysis techniques.
- Advisor / supervisor
- Campbell, Booth
- Resource Type
- DOI
- Date Created
- 2022
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PDF of thesis T16623 | 2023-06-20 | Public | Download |