Stability analysis of modern power systems
(English) The massive installation of converter-based resources, such as wind and solar photovoltaic power plants and High Voltage Direct Current (HVDC) systems, is resulting in a profound transformation of power systems and their operation. In this context of modern power-electronics-dominated powe...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/421130 |
| Acceso en línea: | https://hdl.handle.net/2117/421130 https://dx.doi.org/10.5821/dissertation-2117-421130 |
| Access Level: | acceso abierto |
| Palabra clave: | 621.3 Àrees temàtiques de la UPC::Enginyeria elèctrica |
| Sumario: | (English) The massive installation of converter-based resources, such as wind and solar photovoltaic power plants and High Voltage Direct Current (HVDC) systems, is resulting in a profound transformation of power systems and their operation. In this context of modern power-electronics-dominated power systems, the converters’ control will play a key role in their performance and stability. This thesis focuses on the stability analysis of converter-dominated power systems, encompassing both small-signal and transient stability, aiming to understand the fundamental operation and limitations of such modern power systems. First, the two most extended Voltage Source Converter’s (VSC) control approaches, grid-following (GFOL) and grid-forming (GFOR), are compared via time domain simulations under different disturbances to identify the main characteristics and potential limitations of both control strategies. Regardless of the converter’s control selected, power system stability must always be ensured, both for small-signal and transient disturbances. In this work, thorough fundamental small-signal analysis are conducted to understand the principles governing network stability in converter-dominated power systems. For this purpose, a methodology to build accurate EMT linear state-space models of large power systems has been implemented. Using these models, a detailed analysis is developed to identify the stability limits of grid-following operation in an essential system, investigating the influence of the VSC’s controllers on the system stability, revealing the main mechanisms of interaction and identifying the minimum synchronous generation to ensure system stability. This work is later extended to a larger power system with several generators in presence of an HVDC link. To this end, an index-based methodology has been developed, which determines the steady-state, small-signal and transient analysis regions of stability. Additionally, previous publications have proved that grid-forming operation can improve power system stability for high penetrations of converters. In this thesis, a comprehensive study of frequency dynamics in modern low-inertia power systems is provided, revealing that the VSC’s dominance can be an opportunity to shape frequency dynamics, which can be designed to follow the desired response. However, considering the GFOR converter’s limitations can lead to synchronisation loss. Therefore, this work analyses the risk of synchronisation loss during frequency excursions for droop-based GFOR converters when active power limitations are considered. In addition, a control modification is proposed to extend the operation frequency range of GFOR converters. Finally, a transient stability study is performed for a future HVDC system that will connect the Balearic power system to the Spanish peninsula. In this realistic scenario, both GFOL and GFOR operation modes are studied, considering several contingencies in the system, such as faults in different locations and line disconnections. |
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