Distributed Secondary Control of Hybrid ac/dc Microgrids

This thesis focuses on studying hybrid ac/dc-microgrids, composed of an ac-microgrid and a dc-microgrid, connected by Interlinking Converters (ICs). Specifically, this work is focused on developing distributed secondary controllers that consider the hybrid microgrid as a single entity and not as three independent systems interacting with each other. The main goal of the secondary controller is augmented with one of the following objectives: (i) achieving active power consensus between ac-DGs and dc-DGs (and ICs), or (ii) minimizing the operation cost of the microgrid. The additional control task is performed with information from the nearest neighbours from both sides of the microgrid. Two analytical closed-loop models for a hybrid microgrid are obtained in this thesis. The first one considers the consensus-based distributed control strategy proposed for active power consensus. In contrast, the second one considers the strategy proposed for minimizing the operation cost of the microgrid. The closed-loop models are used to perform several analyses of the control systems proposed. Several tests are carried out to validate the performance of the proposed control strategies in two different topologies: a 24kW prototype with a single IC and a 33kW prototype with multiple ICs

Self-tuning resonant control of a 7-leg back-to-back converter for interfacing variable speed generators to 4-wire loads

This paper considers the control of a 7-leg back-to-back Voltage Source Inverter (VSI) arrangement feeding a 4-wire load from a 3-phase Permanent Magnet Synchronous Generator (PMSG) operating at variable speed. The PMSG is controlled using a sensorless Model Reference Adaptive System (MRAS) to obtain the rotor position angle. The 7-leg converter is regulated using Resonant Controllers (RCs) at the load side and self-tuning resonant controllers at the generator side. The control system is augmented by a feed-forward compensation algorithm which improves the dynamic performance during transients. Experimental results, obtained from a prototype, are presented and discussed

Implementación y validación del método 5540-C para la determinación de surfactantes aniónicos como sustancias activas al azul de metileno (SAAM) en muestras de aguas residuales y superficiales

Implementar y validar una modificación al método normalizado 5540 – C, método fotométrico para la cuantificación de surfactantes aniónicos como sustancias activas al azul de metileno, de acuerdo con los procedimientos que se establece la política OGA-GEC-016, así determinar los límites de cuantificación y detección, la exactitud y sesgo en la mediación del contenido y realizar un análisis de reproducibilidad y repetitividad para la modificación propuesta

Distributed Control Strategies for Microgrids: An Overview

There is an increasing interest and research effort focused on the analysis, design and implementation of distributed control systems for AC, DC and hybrid AC/DC microgrids. It is claimed that distributed controllers have several advantages over centralised control schemes, e.g., improved reliability, flexibility, controllability, black start operation, robustness to failure in the communication links, etc. In this work, an overview of the state-of-the-art of distributed cooperative control systems for isolated microgrids is presented. Protocols for cooperative control such as linear consensus, heterogeneous consensus and finite-time consensus are discussed and reviewed in this paper. Distributed cooperative algorithms for primary and secondary control systems, including (among others issues) virtual impedance, synthetic inertia, droop-free control, stability analysis, imbalance sharing, total harmonic distortion regulation, are also reviewed and discussed in this survey. Tertiary control systems, e.g., for economic dispatch of electric energy, based on cooperative control approaches, are also addressed in this work. This review also highlights existing issues, research challenges and future trends in distributed cooperative control of microgrids and their future applications

Single-phase consensus-based control for regulating voltage and sharing unbalanced currents in 3-wire isolated AC microgrids

A distributed control strategy is proposed to share unbalanced currents in three-phase threewire isolated AC Microgrids (MGs). It is based on a novel approach where, rather than analysing the MG as a three-phase system, it is analysed as three single-phase subsystems. The proposal uses a modified single-phase Q - E droop scheme where two additional secondary control actions are introduced per phase. The first control action performs voltage regulation, while the second one achieves the sharing of negative sequence current components between the 3-legs power converters located in the MG. These secondary control actions are calculated online using a consensus-based distributed control scheme to share negative sequence current components, voltage regulation, and regulating the imbalance at the converters' output voltage to meet the IEEE power quality standards. The proposed methodology has the following advantages over other distributed control solutions, such as those based on the symmetrical components or those based on the Conservative Power Theory: (i) it achieves sharing of unbalanced currents, inducing smaller imbalances in the converters' output voltages than those of other methods, and (ii) the sharing of the unbalanced currents is simultaneously realised in both the sequence domain and the a-b-c domain. The latter is difficult to achieve using other solutions, as will be demonstrated in this work. Extensive experimental validation of the proposed distributed approach is provided using a laboratory-scale 3-wire MG

An integrated converter and machine control system for MMC-based high power drives

The Modular Multilevel Converter (MMC) is a promising topology for high power drive applications. However, large voltage fluctuations are produced in the floating capacitors when the machine is operating with high stator currents at low rotational speed. To compensate these oscillations, relatively large mitigation currents are required to keep the capacitor voltages within an acceptable range. In this paper, a new integrated control scheme is discussed to regulate the voltage fluctuations. The strategy is based on closed-loop vector-control of the voltage fluctuations, maintaining them inside a pre-defined threshold. The proposed control system is also augmented using flux weakening operation of the machine at low rotational speeds. An experimental prototype composed of eighteen power cells, feeding a vector-controlled induction machine in the whole speed range, is used to validate the effectiveness and feasibility of the proposed control strategies

Monitoring attentional processes for intelligent channelling of educational tasks

Aims: - Detection of attention: Map a lexicon of body postures to binarizedattentionallevels (Experiment I). - Attribution of attention: Identify postural features leading to appreciation of attention by third parties (e.g. educators) (Experiment II).Panel ACE.Ibero-American Science and Technology Education Consortium (ISTEC