Theses - Group of Electronic Engineering Applied to Renewable Energy Systems
 

Group of Electronic Engineering Applied to Renewable Energy Systems

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Publications PhD. Thesis

Theses

  • Optimización del comportamiento de un convertidor de tres niveles NPC conectado a la red eléctrica

     

    Research Area

    Power Electronics
     
  • Sistema de supervisión tolerante a fallos para mejorar la seguridad en entornos ferroviarios

     
     
  • Sistema de navegación global aplicado al guiado de un vehículo autónomo terrestre en entornos exteriores parcialmente conocidos

     

    Research Area

    Embedded Systems
     
  • Arquitectura para silla de ruedas con guiado autónomo

     
     
  • Medida de temperatura sin contacto con alta velocidad de respuesta

     

    Research Area

    Acquisition System
     
  • Optimization and Analysis of the Current Control Loop of VSCs Connected to Uncertain Grids through LCL Filters

     

    Research Area

    Power Electronics
     
  • Aplicación de técnicas de identificación y control multivariable en convertidores en fuente de tensión conectados a la red eléctrica

     

    Research Area

    Power Electronics
     
  • Control contributions to the universal operation of wind turbines

     

    Research Area

    Uncategorized
     

    The continuously growth of the energy consumption is taking the current electric system close to certain limits where the power supply reliability is seriously affected by voltage interruptions. Besides, some factors like the downturn in the economy and the drive of developing countries (i.e. China and India) have forced the companies to extend their products to weaker power systems, where the power quality has not been treated with a strong regulation yet.

    This Thesis is framed in the improvement of the power supply reliability through the isolated operation of Wind Turbines. The concept of Universal Operation addresses the island operation of Wind Turbines when the connection to the grid is not longer required after a voltage interruption. In constrast with other tendencies, the peculiarity resides on avoiding the use of expensive external storage devices. This concept is just proposed in the low and medium power level scenarios of on-shore Wind Turbine to face power interruptions of minutes.

    With the general objective of extending the island operation to cover the most of the interruption, this work approaches the main challenges of the Universal Operation from the control point of view: regulation of the island power mismatch by means of the inherent storage and dissipation capacities, transition between the island and grid-connected modes, power sharing, etc. On the other hand, an important research line of this Thesis is focused on the optimization of the system response under unbalanced conditions. The proposed control enhancements deal with the oscillating power and the distortion of control references caused by unbalanced conditions.

  • Contributions to cascade linear control strategies applied to grid-connected voltage-source converters

     

    Research Area

    Uncategorized
     

    Among the existing techniques for implementing the current control for harmonic compensation, two of the most used are resonant and repetitive controllers both in stationary and synchronous reference frames. A thorough study of different existing structures to implement them is carried out, showing the frequency-adaptive algorithm for each of these structures and analyzing their computational load. Basic guidelines for the programming of such controllers are given. The current control scheme is studied and characterized in order to establish a comparison among the different structures.

    After studying in depth the current control of a grid-connected VSC, the second control to analyze is the PCC voltage controller. The presence of an unbalanced voltage at the PCC results in the appearance of a negative sequence current component, which deteriorates the control performance when applying conventional control techniques. STATCOMs are wellknown to be a power application capable of carry out the PCC voltage regulation in distribution lines that may suffer from grid disturbances. This Thesis proposes a novel voltage controller in synchronous reference frame to compensate an unbalanced PCC voltage by means of a STATCOM, allowing an independent control of both positive and negative voltage sequences. Several works have been proposed in this line but they were not able to compensate an unbalance in the PCC voltage. Furthermore, this novel controller includes aspects as antiwindup and droop control to improve the control-system performance.

    Several experimental tests have been carried out to analyze the performance of the current controllers discussed in the Thesis. All of them have been tested under the same conditions of power, voltage and current. These tests aim at characterizing the transient response, steadystate response, behavior under frequency jumps and computational load of the current controllers.

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