A Comprehensive Survey on Different Control Strategies and Applications of Active Power Filters for Power Quality Improvement

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Power quality (PQ) has become an important topic in today’s power system scenario. PQ issues are raised not only in normal three-phase systems but also with the incorporation of different distributed generations (DGs), including renewable energy sources, storage systems, and other systems like diesel generators, fuel cells, etc. The prevalence of these issues comes from the non-linear features and rapid changing of power electronics devices, such as switch-mode converters for adjustable speed drives and diode or thyristor rectifiers. The wide use of these fast switching devices in the utility system leads to an increase in disturbances associated with harmonics and reactive power. The occurrence of PQ disturbances in turn creates several unwanted effects on the utility system. Therefore, many researchers are working on the enhancement of PQ using different custom power devices (CPDs). In this work, the authors highlight the significance of the PQ in the utility network, its effect, and its solution, using different CPDs, such as passive, active, and hybrid filters. Further, the authors point out several compensation strategies, including reference signal generation and gating signal strategies. In addition, this paper also presents the role of the active power filter (APF) in different DG systems. Some technical and economic considerations and future developments are also discussed in this literature. For easy reference, a volume of journals of more than 140 publications on this particular subject is reported. The effectiveness of this research work will boost researchers’ ability to select proper control methodology and compensation strategy for various applications of APFs for improving PQ.publishedVersio

Model predictive control of grid-connected voltage source converters

In this thesis, the main focus is on the design and implementation of an advanced control scheme, namely model predictive control (MPC) to the grid- connected voltage source converter (VSC) for a three phase system. MPC is a control paradigm that solves a mathematical optimization problem based on a dynamic model of the system. Due to the computationally demanding nature of MPC, the areas of applications have long been restricted to slow dynamical systems. However, with the recent advancement of microprocessor and simu- lation technologies, application of MPC is now even possible for the control of power electronics. With a very powerful concept such as on-line cost optimisation, input/output constraint handling and model-based design, MPC is able to offer the optimal actuation that allows one to achieve very fast dynamics, while also considering uncertainties such as system parameter variations and unknown disturbances. Furthermore, it is also possible to take advantage of the discrete nature of the power converters and choose from the possible switching states the optimal solution according to the minimization of a predefined cost.  Exploring these advantages of MPC and making them suitable for the control of power converters are the key focus of the thesis. The first part of the thesis investigates a multi-variable control scheme, namely a predictive voltage controller that controls both DC bus voltage and re- active current (i.e. q-axis current) in the synchronous reference frame. Explicit tuning methods of MPC are introduced to improve the closed-loop transient response as well as improving the robustness against the parameter variations such as the grid inductance. The second part of the thesis focuses on the predictive current control design. A predictive current controller for VSC with LCL (inductor-capacitor- inductor) input filter is first proposed with a robust control scheme that employs nominal and disturbance rejection control parts. The nominal control part is designed using the reduced-order model (i.e. L filter model) to control dominant dynamics of the LCL filter where as the disturbance rejection control part actively suppresses the disturbance due to unmodeled dynamics of LCL filter (i.e. resonance of the LCL filter). Following from this, a predictive resonant controller is presented to control the converter in the stationary frame axis. A resonant module with a grid frequency is embedded in the model to handle the periodicity in the measured states and the reference inputs. The proposed de- sign considers the periodic input constraints in the stationary frame as well as disturbances due to grid voltage distortion. The last part of the thesis investigates the stability aspect of a finite control set predictive control (FCS-MPC) method and presents a design framework to handle the imposed the output current constraints in the cost function. All of the presented control methods in this thesis are experimentally validated on a 1kW prototype converter that has been built by the author

Design and Control of Power Converters 2019

In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc

Model Predictive Control Techniques with Application to Photovoltaic, DC Microgrid, and a Multi-Sourced Hybrid Energy System

Renewable energy sources continue to gain popularity. However, two major limitations exist that prevent widespread adoption: availability and variability of the electricity generated and the cost of the equipment. The focus of this dissertation is Model Predictive Control (MPC) for optimal sized photovoltaic (PV), DC Microgrid, and multi-sourced hybrid energy systems. The main considered applications are: maximum power point tracking (MPPT) by MPC, droop predictive control of DC microgrid, MPC of grid-interaction inverter, MPC of a capacitor-less VAR compensator based on matrix converter (MC). This dissertation firstly investigates a multi-objective optimization technique for a hybrid distribution system. The variability of a high-penetration PV scenario is also studied when incorporated into the microgrid concept. Emerging (PV) technologies have enabled the creation of contoured and conformal PV surfaces; the effect of using non-planar PV modules on variability is also analyzed. The proposed predictive control to achieve maximum power point for isolated and grid-tied PV systems speeds up the control loop since it predicts error before the switching signal is applied to the converter. The low conversion efficiency of PV cells means we want to ensure always operating at maximum possible power point to make the system economical. Thus the proposed MPPT technique can capture more energy compared to the conventional MPPT techniques from same amount of installed solar panel. Because of the MPPT requirement, the output voltage of the converter may vary. Therefore a droop control is needed to feed multiple arrays of photovoltaic systems to a DC bus in microgrid community. Development of a droop control technique by means of predictive control is another application of this dissertation. Reactive power, denoted as Volt Ampere Reactive (VAR), has several undesirable consequences on AC power system network such as reduction in power transfer capability and increase in transmission loss if not controlled appropriately. Inductive loads which operate with lagging power factor consume VARs, thus load compensation techniques by capacitor bank employment locally supply VARs needed by the load. Capacitors are highly unreliable components due to their failure modes and aging inherent. Approximately 60% of power electronic devices failure such as voltage-source inverter based static synchronous compensator (STATCOM) is due to the use of aluminum electrolytic DC capacitors. Therefore, a capacitor-less VAR compensation is desired. This dissertation also investigates a STATCOM capacitor-less reactive power compensation that uses only inductors combined with predictive controlled matrix converter

Contribution à la commande robuste d’une GADA utilisée dans un système de conversion d’énergie éolienne

Cette thèse décrit la conception et la mise en oeuvre d'une commande directe des puissances pour une génératrice asynchrone à double alimentation (GADA). L’intérêt porté à la GADA est dû à sa capacité de fournir une puissance active par le stator et par le rotor selon son mode de fonctionnement. La topologie usuelle de la GADA adoptée dans ce travail consiste à connecter le stator directement au réseau, alors que le rotor se connecte par l’intermédiaire de deux convertisseurs triphasés à deux niveaux. Les deux convertisseurs sont identiques et sont connectés en cascade via un lien à courant continu (CC). La commande du convertisseur côté réseau assure la régulation de la tension du lien CC et la maîtrise du facteur de puissance côté réseau. Or, la commande du convertisseur côté machine permet de réguler les puissances active et réactive au stator de la GADA en tenant compte de la vitesse de rotation et du couple mécanique d’entraînement imposé sur la GADA. La commande vectorielle du convertisseur côté réseau est basée sur l’orientation de la tension de réseau en utilisant la transformation de Park pour assurer un découplage entre les puissances active et réactive côté réseau. Les régulateurs proportionnels-intégrales (PI) sont utilisés, en premier lieu, pour contrôler la tension du lien CC et le facteur de puissance à travers deux boucles de régulation imbriquées. En se basant sur l’orientation du flux statorique de la GADA, la structure et l’implémentation de la commande du convertisseur côté rotor est très similaire à la commande du convertisseur côté réseau. Par contre, cette commande consiste principalement à découpler les puissances active et réactive échangées avec le réseau au stator de la GADA. Également, on maîtrise la vitesse de rotation de la GADA, selon le mode de fonctionnement désiré, en utilisant des régulateurs PI. La commande robuste par mode glissant est proposée dans cette thèse comme alternative aux régulateurs PI. Ainsi, la commande dite directe des puissances par mode glissant est appliquée sur les deux convertisseurs afin d’améliorer le comportement de la GADA. Les stratégies de commande élaborées ont été simulées dans Matlab et implémentées expérimentalement sur un banc d’essai réalisé en laboratoire. Ceci a permis d'évaluer les techniques de contrôle des convertisseurs électroniques en laboratoire dans un contexte le plus réel possible, en apportant des contributions significatives. Les résultats obtenus montrent bien la validité de la démarche suivie. Ils montrent également que la stratégie de commande développée est bien adaptée aux problèmes de suivi de trajectoires, au respect des contraintes électromécaniques et à la robustesse vis-à-vis des incertitudes paramétriques. This thesis deals with the design and implementation of direct power control for doubly fed induction generator (DFIG). The interest in the DFIG is due to its ability to provide active power by the stator and the rotor according to its operation mode. In this work, the topology adopted for the DFIG is to connect the stator directly to the network, while the rotor is connected to the network through two three-phase back-to-back converters. Both converters are connected in cascade via a direct current (DC) bus. The grid side converter provides DC bus voltage regulation and controls of the power factor. While the rotor side converter control ensures the active and reactive power regulation on the stator of the DFIG, taking into account the rotational speed and the mechanical drive torque imposed on the DFIG. The vector control of the grid-side converter is based on the grid voltage orientation using the Park transformation to ensure a decoupling between the active and reactive powers on the network side. Proportional-Integral (PI) controllers are primarily used to control the DC bus voltage and power factor through two cascade control loops. Based on the stator flux orientation of the DFIG, the structure and the implementation of the rotor-side converter control are very similar to the grid-side converter control. However, the role of this control is mainly used to decouple the active and reactive powers exchanged with the network at the stator of the DFIG. In addition, the DFIG rotational speed is controlled according to the desired operating mode using PI regulators. A robust sliding mode control is proposed in this thesis as an alternative to PI controllers. This control method is used to control both converters in order to improve the behavior of the DFIG. The developed strategy was simulated on MATLAB, and implemented experimentally through a test bench realized in laboratory. The objective was to experimentally evaluate the control techniques of electronic converters as close to reality as possible. The obtained results show clearly the validity of the adopted methodology. They also show that the developed control strategy is well adapted to tracking trajectory problems, to electromechanical constraints limits, and to robustness regarding parametric uncertainties

Cálculo, diseño y simulación de una instalación fotovoltaica de 100 kW conectada a red.

En este TFG se propone modelar y diseñar el control de una planta fotovoltaica residencial de 100kW de potencia pico con conexión a red eléctrica CA, mediante la herramienta Matlab-Simulink. La instalación dispone de un convertidor CC-CC (corriente continua – corriente continua) elevador capaz de maximizar la potencia extraída fotovoltaica mediante un algoritmo de seguimiento de la máxima potencia (MPPT, maximum power point tracking) y cuenta con un inversor cuyo control permite adecuar la tensión CC a su consigna y evacuar la energía fotovoltaica a la red eléctrica CA con inyección nula de reactiva. Además, dicho inversor dispone de un filtro LCL en su salida, que permite la inyección de corriente a la red con contenido reducido en armónicos. El trabajo comienza con un análisis del proyecto Actur Barrio Solar, del que se extrae la idea de este TFG. Para encuadrar la instalación dentro del contexto normativo, se hace un breve repaso del Real Decreto 244/2019 de autoconsumo, aclarando las diferentes modalidades de autoconsumo de energía eléctrica que existen en España. En base a esto, se describe la modalidad en la que se encuadra la planta fotovoltaica de este TFG, siendo “autoconsumo conectado a la red con excedentes y compensación económica”. Posteriormente se hace una breve introducción de la normativa IEEE 1547, que nos proporciona los requisitos a cumplir para la inyección de energía a la red, de cara a la eliminación de los rizados de corriente y a tener un bajo contenido en armónicos. Después se analizan otros proyectos de autoconsumo fotovoltaico colaborativo ya implantados en algunas ciudades europeas. A continuación, se describen los objetivos del control de la instalación, tanto de su convertidor CC-CC elevador como de su inversor, el modelado de la instalación y se especifican los componentes que la conforman. Tras ello, se define un escenario base para demostrar que el control realizado cumple con las especificaciones propuestas ante un escalón de irradiancia, que son: seguimiento del punto de máxima potencia (MPPT), control de la tensión CC, inyección nula de potencia reactiva y contenido reducido en armónicos y en rizados de la corriente inyectada a la red CA. Una vez se comprueba que el control diseñado funciona correctamente ante dicho escalón de irradiancia, se analiza su funcionamiento ante diferentes escenarios adversos a los que se podría enfrentar la red. Concretamente se evalúa la respuesta del control ante variaciones en la potencia de cortocircuito de la red CA, presencia de huecos de tensión trifásicos y sobretensiones. También se evalúa el comportamiento frente a otros escenarios de variación de irradiancia. A través de las simulaciones se descubren los límites del control propuesto en otros escenarios, y se proponen mejoras y nuevas funcionalidades del control, así como líneas futuras de trabajo.<br /

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen