A new modulation method for multilevel converters

This paper presents a simple method for modulation in multilevel converters, which is hardly affected with the number of levels. The method is based on a simple graph, whose x-axis is directly related to the extra degree of freedom associated with component γ (in the αβγ reference frame) of the desired reference vector. In the y-axis, the different possibilities for the phase averaged references are plotted. In this way, the degree of freedom is more explicit than in Space Vector Modulation (SVM) and it can be the basis of new algorithms to pursue additional control objectives such as voltage balancing or common-mode reduction, among others. A comparison with SVM based on examples is included, showing the benefits of the proposed modulation strategy.Ministerio de Economía y Competitividad. Unión Europe

A new controller for the inverted pendulum on a cart

This paper presents a complete solution to the problem of swinging-up and stabilization of the inverted pendulum on a cart, with a single control law. The resulting law has two parts: first, an energy-shaping law is able to swing and maintain the pendulum up. Then, the second part introduces additional control to stop the cart and it is based on forwarding control with bounded input. The resulting control law is the sum of both parts and does not commute between different laws although there exist switches inside the controller.MEC-FEDER DPI2006-0733

Modeling and Full Decoupling Control of a Grid-Connected Five-Level Diode-Clamped Converter

This paper presents a novel approach to deal with the regulation of the dc-link capacitor voltages and ac-side currents in a grid-connected five-level diode-clamped converter. Due to the controllability problems of this topology, guaranteeing a solid current control and, mainly, a correct dc-link voltage sharing, represents a complex technical challenge. With the purpose of coping with it, an averaged model that describes the system dynamics at both sides of the converter is presented, assuming that a modulation strategy is integrated in the system to generate the switching sequence. In order to derive the proposed model, no restriction concerning the use of only the three nearest vectors to the desired voltage reference is taking into account. Then, several changes of variables are carried out in the model equations to obtain control input decoupling for control purposes, while reducing the complexity of the model as well. Finally, the voltage and current controllers are designed separately using different control inputs in a straightforward way. Neither auxiliary hardware nor complicated mathematical calculations are required to achieve the control objectives. The effectiveness and good performance of the system under the proposed control approach is validated by simulation results, suggesting that the five-level diode-clamped converter can be a solid solution as an interfacing system connected to the utility grid for, e.g., industrial drives or renewable energy applications.Ministerio de Economía y Competitividad y Unión Europea : DPI2016-75294-C2-1-RMinisterio de Economía y Competitividad y Unión Europea : DPI2013-41891-

Representación narrativa de madres maduras: estudio de casos en la cinematografía española y japonesa

A pesar de que la población madura femenina constituye la mayoría de los envejecientes del primer mundo, los medios de comunicación muestran un rechazo social hacia la mujer mayor. Así, en el medio cinematográfico, la mujer que supera los cincuenta años suele aparecer caracterizada por su escasa relevancia y su vinculación a argumentos que giran en torno a las enfermedades, la soledad, la muerte, la angustia por el deterioro físico o la remembranza de otros tiempos. El presente artículo se centra en la figura de la mujer de edad avanzada como madre y en su relación con hijos o hijas adultos e independientes. Para ello, se estudian seis películas procedentes de dos filmografías tan dispares como la española y la japonesa en un intento de buscar similitudes y disimilitudes culturales, sociales y fílmicas entre estos personajes femeninos cuyos únicos nexos de intersección son la edad y la maternidad. Por parte del cine español se han elegido los filmes Solas (Benito Zambrano, 1999), Volver (Pedro Almodóvar, 2006) y La soledad (Jaime Rosales, 2007) para ser cotejados con tres películas japonesas de la última década: I just didn't do it (Masayuki Suo, 2006), Tokyo Tower: Mom and Me, and Sometimes Dad (Joji Matsuoka, 2007) y Still walking (Hirokazu Koreeda, 2008)

Integrated Control of Five-Level Diode-Clamped Rectifiers

This paper presents an approach for dealing with the control of five-level, diode-clamped rectifiers. The control of such converters is challenging since the voltage balancing among capacitors is not a trivial task. Some of the existing approaches that cope with this problem use specific modifications of one of the traditional modulation techniques such as using redundant vectors in SVM. The main feature of the proposed technique is that part of the modulation is considered in the system equations and, in this way, the voltage balance can be solved designing a specific controller for this problem. As a result, several levels are used within a switching period. Furthermore, it is shown that the proposed approach hardly affects the control of active and reactive powers and total dc-link voltage in such a way that the well-known direct power control (DPC) can be applied. As a consequence, the resultant modulation stage is simpler than other techniques based on, e.g., space vector modulation (SVM). The effectiveness and good performance of the system under the proposed control approach are validated by both simulation and experimental results.Ministerio de Economía y Competitividad y Unión Europea : DPI2016-75294-C2-1-

Stabilization of oscillations through backstepping in high-dimensional systems

This paper introduces a method for obtaining stable and robust self-sustained oscillations in a class of single input nonlinear systems of dimension n ≥ 2. The oscillations are associated to a limit cycle that is produced in a second-order subsystem by means of an appropriate feedback law. Then, the controller is extended to the full system by a backstepping procedure. It is shown that the closed-loop system turns out to be generalized Hamiltonian and that the limit cycle can be thought as born in a Hopf bifurcation after moving a parameter.Ministerio de Ciencia e Innovación (España

A family of smooth controllers for swinging up a pendulum

Es el primer envío que hago. Le agradeceré si me confirma que es todo correcto, especialmente el cumplimiento de los derechos de propiedad de la editorial. Mi email es [email protected] paper presents a new family of controllers for swinging up a pendulum. The swinging up of the pendulum is derived from physical arguments based on two ideas: shaping the Hamiltonian for a system without damping; and providing damping or energy pumping in relevant regions of the state space. A family of simple smooth controllers without switches with nice properties is obtained. The main result is that all solutions that do not start at a zero Lebesgue measure set converge to the upright position for a wide range of the parameters in the control law. Thus, the swing-up and the stabilization problems are simultaneously solved with a single, smooth law. The properties of the solution can be modified by the parameters in the control law. Control signal saturation can also be taken into account using the Hamiltonian approach.MCyT-FEDER DPI2006-0733

Asymptotic rejection of sinusoidal disturbances based voltage balance control in back-to-back power converters

This paper addresses the imbalance problem of the dc-link capacitor voltages in the three-level diode-clamped back-to-back power converter. In order to cope with it, a mathematical analysis of the capacitor voltage difference dynamics, based on a continuous model of the converter, is first carried out. It leads to an approximated model which contains explicitly several sinusoidal functions of time. In view of this result, the voltage imbalance phenomenon can be addressed as an output regulation problem, considering the sinusoidal functions as exogenous disturbances. Thus, a novel approach to deal with the mentioned problem in the back- to-back converter is presented. Then, the particular features of the disturbances are used to design several controllers. They all follow an asymptotic disturbance rejection approach. In this way, the estimations of the disturbances are used to apply a control law that cancels them while regulating the capacitor voltage balance as well. Finally, the performance of the proposed control laws is evaluated, presenting the simulation results obtained when the different controllers are implemented.MICINN-FEDER DPI2009-0966

A simple modulation approach for interfacing three-level Neutral-Point-Clamped converters to the grid

Datos suplementarios: https://ars.els-cdn.com/content/image/1-s2.0-S0360544220309427-mmc1.mp4Multilevel converters are nowadays an enabling key in the integration of electric power into the grid as they introduce less distortion and, thus, they are more compliant with the grid standards, among other benefits. A well-known topology is the three-level Neutral-Point-Clamped whose control requires to deal with the capacitors voltage unbalance. This paper presents a modulation approach where the injection of a common component in the modulated voltage is studied in order to achieve such voltage balance. An optimization problem that, apart from the voltage balance, aims the lowest number of commutations and can be solved very efficiently with up to five computations of the cost function is formulated. The main advantages of the proposed modulation strategy are its simplicity and its flexibility, since it is also valid for unbalanced grid conditions and, with little added complexity, for low (and even zero) power factor conditions. Simulation results under unbalanced grid conditions are provided in order to show its validity under this scenario. The strategy is evaluated and compared with a space-vector-based approach in an experimental setup, yielding similar total harmonic current distortion, a 30% reduction in the number of commutations, and better voltage balance performance for lower power factor conditions.Ministerio de Economía y Competitividad DPI2016-75294-C2-1-RJunta de Andalucía (Consejería de Economía y Conocimiento), Programa Operativo FEDER Andalucía 2014-2020, US-1264655

Hybrid Modelling and Control of a Class of Power Converters With Triangular-Carrier PWM Inputs

In this paper, a new control design procedure for a class of power converters based on hybrid dynamical systems theory is presented. The continuous-time dynamics, as voltage and current signals, and discrete-time dynamics, as the on- off state of the switches, are captured with a hybrid model. This model avoids the use of averaged and approximated models and includes the PWM as well as the sample-and-hold mechanism, commonly used in the industry. Then, another simplified hybrid system, whose trajectories match with the original one, is selected to design the controller and to analyse stability properties. Finally, an estimation of the chattering in steady state of the voltage and current signals is provided. The results are validated through simulation and experiments.MCIN/ AEI Project PID2019-105890RJ-I00MCIN/ AEI Project PID2019-109071RB-I0