Hysteretic control of grid-side current for a single-phase LCL grid-connected voltage source converter

© 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/This paper proposes a new approach to control the grid-side current of LCL-grid connected voltage source converters using hysteretic relay feedback controllers. The closed loop system is stabilized by designing a local feedback around the relay element. The compensator allows the use of relay feedback controllers by making the controlled plant almost strictly positive real. The article proposes the use of the locus of the perturbed relay system as analysis and design tool and studies orbital stability for several plant and controller conditions. The approach is validated by means of simulation testing.Postprint (author's final draft

A relay controller with parallel feed-forward compensation for a buck converter feeding constant power loads

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.A simple and efficient analog direct voltage control design for improving the performance and stability of a buck converter feeding constant power loads (CPLs) is the main aim of this article. One of the oldest and most spread approaches is to design a relay control system. In these systems, although the hysteretic relay adds non-linearity to the closed-loop system, an adequate controller design procedure will be presented using the locus of a perturbed relay system (LPRS) technique. This work shows how a designer can apply LPRS technique to a converter plant, in this case a buck converter feeding a mixed linear and constant power load (CPL), using a parallel feed-forward compensator (PFC) to obtain a suitable performance in the closed-loop system. That means to enlarge the range of stable behavior with respect to the power in the CPLs, in comparison with the open-loop case, and to regulate adequately the output voltage of the converter in front of input voltage and load power variations. The simulation results with the converter-load non-linear model show the good performance of the designed controller with respect to the above-mentioned disturbances and perturbations.Postprint (author's final draft

Contribución a la identificación de sistemas dinámicos mediate métodos conexionistas

El presente trabajo de tesis doctoral propone una clase de modelos, con estructura de red neuronal con dinámica aditiva evolucionando en tiempo continuo, para la identificación de sistemas dinámicos.Para la clase de modelos propuesta se efectúa, utilizando herramientas del dominio frecuencial, un estudio de estabilidad absoluta obteniéndose una serie de condiciones suficientes para esta en función de los parámetros del modelo.Asimismo, se desarrollan dos métodos de adaptación de parámetros para llevar a cabo la identificación en línea:uno basado en técnicas de gradiente y análisis de sensibilidad, y el otro en técnicas de control óptimo e inmersión invariante.La generación de los modelos y los algoritmos de adaptación se efectúa automáticamente mediante el uso de técnicas de cálculo simbólico, lo cual permite iterar de forma rápida en el proceso de identificación. Tanto los modelos como los algoritmos de adaptación de parámetros han sido probados frente a plantas dotadas de funciones no lineales estándar y frente a un conjunto de datos reales. Asimismo, se han evaluado sus prestaciones en comparación a la identificación de estos mismos casos mediante modelos neuronales estáticos, que constituyen, actualmente, una técnica tan establecida que permite su uso como marco de referencia.El trabajo de tesis se ha realizado bajo una óptica unificadora entre la teoría de control y la teoría de redes neuronales. Se ha puesto especial énfasis en tratar con herramientas y visión de la teoría de control las redes neuronales que se usan, desde el punto de vista de control, para identificar un sistema y, desde el punto de vista de la neurociencia, para aprender un determinado comportamiento. En particular, la clase de modelos de identificación se formula de forma compacta usando productos de Kronecker, técnica habitual en teoría de sistemas y el estudio de estabilidad de los modelos

Modelling and simulation of a magnetically coupled multiport dc-dc converter

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper present two different approaches for modelling a magnetically coupled multiport dc-dc converter. First, from the magnetic coupling equations, the instantaneous dynamic model is obtained. Secondly, a behavioural dynamic model, based on averaging the power flowing among the ports, is derived. Some numerical simulations compare the temporal evolutions with the two obtained modelsPeer ReviewedPostprint (author's final draft

A local stability condition for dc grids with constant power loads

Currently, there are an increasing number of power electronics converters in electrical grids, performing the most diverse tasks, but most of them, work as constant power loads (CPLs). This work presents a sufficient condition for the local stability of dc linear time-invariant circuits with constant power loads for all the possible equilibria (depending on the drained power) of the systems. The condition is shown as a method with successive steps that should be met. Its main step is expressed as a linear matrix inequality test which is important for easiness of verification reasons. The method is illustrated with two examples: a single-port RLC circuit connected to a CPL and a two-port linear dc circuit connected to two CPLs.Postprint (published version

A repetitive controller for discrete-time passive systems

This work proposes and studies a new repetitive controller for discrete-time systems which are required to track or to attenuate periodic signals. The main characteristic of the proposed controller is its passivity. This fact implies closed-loop stable behaviour when it is used with discrete-time passive plants. The work also discusses the energetic structure, the frequency response and the time response of the proposed controller structure. Some examples are included to illustrate its practical use

Phase-Locked Loop using a comb filter with fractional delay

A Phase Locked Loop is a feedback system combining a Voltage Controlled Oscillator and a Phase Comparator These are connected so that the oscillator maintains a constant phase angle relative to a reference signal. Phase locked loops can be used, for example to generate stable output frequency signals from a fixed frequency signal. A Comb Filter is a kind of Notch Filter (Non Recursive Filter) that is normally used to remove the harmonic terms from a particular signal. In this Design, a PLL is implemented using a Comb Filter because the main frequencies that are considered noise in the PLL loop are the harmonics of the fundamental frequency. There are 2 objectives of this project report, 1. Implementing Comb Filter Using Fractional Delay 2. Comparision of Frame Based and Typical Discrete Sample Based Implementation of a Comb FilterPostprint (published version

Duino-Based Learning (DBL) in control engineering courses

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis document presents a project to develop freely redistributable materials to conduct educational lab projects with MATLAB, Simulink, Arduino and low-cost plants. This work materials introduce the fundamentals of Control Engineering through exercises and videos. Along with all this, the most important steps and issues appeared in the project are explained, so anyone interested on doing a project can have a starting point instead of starting a project from scratch, which most of times this results hard to implementPeer ReviewedPostprint (author's final draft

Output voltage regulation of a high-efficiency high step-up DC-DC power converter

Step-up dc-dc power converters are needed in many applications. Depending on the voltage conversion ratio, one or another structure should be chosen, usually leading to efficiency vs. conversion ratio trade-offs. Recently, a new class of switchmode dc-dc power converters has been introduced into the literature. These new converters show high efficiency levels at high conversion ratios, making them attractive to applications where efficiency is a major concern. Due to the complexity of the structure, mathematical models of the system have not been developed up to now, making the closed-loop control of these devices a challenging task. In this paper, an output voltage regulation control scheme is proposed and tested in simulation. The system is decomposed in subsystems, whose models are identified within the different control stages.Peer Reviewe

Transient analysis of RF cavities under beam loading

The conventional electrical model analogy of a RF cavity is a shunt RLC circuit supplied by two current sources representing the RF amplifier and the beam. In the literature, the impedance of the cavity is often calculated in the Fourier domain. This type of cavity modelling has two drawbacks: First, it assumes a perfect matching between the cavity and the amplifier therefore it neglects the reflected voltage. And, second, it does not provide any information about the cavity transient response, for example at start-up or upon beam arrival, while this information can be very important for the design of the regulation loops. In this work we will remove these drawbacks by calculating the cavity impedance in Laplace domain taking the reflected voltage into account. We will then modify our model so that it also includes the influence of the beam on the cavity. For transient RF simulations, though, a typical problem is the long simulation time due to the relatively slow transient response compared to the RF period. To overcome this problem, finally, we will use a mathematical method to map the cavity frequency response from RF to baseband to reduce the simulation time significantly.Peer ReviewedPostprint (author’s final draft