The student Iosu Marzo Elguero obtained an OUTSTANDING qualification with 'CUM LAUDE' mention
The student Iosu Marzo Elguero obtained an OUTSTANDING qualification with 'CUM LAUDE' mention
The student Iosu Marzo Elguero obtained an OUTSTANDING qualification with 'CUM LAUDE' mention
Thesis title: Modular Converter Structures for STATCOM Application under Unbalanced Conditions
Court:
- Chairmanship: Remus Teodorescu (Aalborg University)
- Vocal: Oriol Gomis-Bellmunt (Universitat Politécnica de Catalunya)
- Vocal: Salvador Ceballos Recio (Tecnalia Research and Innovation)
- Vocal: Juan José Valera García (Ingeteam)
- Secretary: Aritz Milikua Urzelai (Mondragon Unibertsitatea)
Abstract:
The current society is facing several challenges related to the field of energy, such as the high dependency on fossil fuels, the constant increment in the energy consumption, or the environmental problems caused by these factors. The integration of distributed generation systems, mainly based on renewable energy sources (RES), is the most interesting solution to address these issues.
However, the penetration of RES into the power grid implies certain challenges due to their non-dispatchable nature compared to conventional generation systems. Such systems often use power electronic converters for grid connection instead of synchronous generators, making power systems become converter-dominated. As the power electronic converter-based grid makes it increasingly necessary to count on power equipment with higher voltage and power rating, since their scalable attributes, multilevel Voltage Source Converters (VSC) based on modular structures are envisioned as the most promising alternatives for that purpose.
In this framework, Flexible AC Transmission System (FACTS) devices and in particular Static Synchronous Compensators (STATCOM) play a key role in the evolution of the modern power grids to the future smart grids. The STATCOM, especially that using multilevel VSCs based on modular structures, is applied in an increasingly wider variety of scenarios in which the operation under unbalanced conditions stands out.
From the power converter manufacturer point of view, it is not obvious which VSC topology should be used. That is why the purpose of the thesis is to contribute to the body of knowledge in the field of the design of VSCs, with the aim of facilitating the manufacturer to compare and select the most appropriate topology, to design it properly, or to adapt it in order to face the demanding operating requirements that a converter-dominated power grid implies. Among these, this work is mainly focused on the STATCOM application of multilevel VSCs based on modular structures operating under unbalanced voltage and/or current conditions.
In order to achieve this objective, the operation of the most commonly used high power VSC topologies and their main modulation strategies is first reviewed. Secondly, a methodology which provides valuable information that allows the converter manufacturer to compare and select the most appropriate VSC topology for any required application is proposed. Then, a comprehensive review about the operation of multilevel VSCs based on modular structures for different and equivalent unbalanced operating scenarios is presented, in which the STATCOM functionality is included. Having identified the research gap, the reactive power limits of different VSC topologies for STATCOM application operating under unbalanced voltage and/or current conditions are studied and compared. Finally, the control implementation of one of the most interesting topologies for the application under study is evaluated, comparing the performance of different controllers that could be employed. Experimental results obtained from a real-scale 100 kV prototype in a medium voltage laboratory validate the carried out studies.
In conclusion, this study balances theoretical contributions to the process of SD capability development in established service organisations with contributions to practice through a new model for measuring and managing SD. The validity of the results of both the longitudinal study and the new model are supported by data triangulation, thick descriptions, the prolonged engagement of the researcher with the case studies, and member checking.