Hybrid posicast controller for a DC-DC buck converter

A new Posicast compensated hybrid controller for the DC-DC Buck converter is investigated. Posicast is a feed forward compensator, which eliminates the overshoot in the step response of a lightly damped system. However, the traditional method is sensitive to variations in natural frequency. The new method described here reduces this undesirable sensitivity by using Posicast within the feedback loop. Design of the Posicast function is independent of computational delay. The new controller results in a lower noise in the control signal, when compared to a conventional PID controller

Filtrado analógico en instrumentación para acondicionamiento de señales de pulsos en procesos industriales utilizando la técnica posicast

Maestría en IngenieríaFiltration is essential in industrial environments for eliminating noise and interference that are combined with signals from sensors. To perform such a function there are analog filters, which can be active or passive. In the case of industrial instrumentation, the active filters are the most used, because the inductors can be dispensed with when high-order implementations are required. The filter approach that shows the best performance against noise is Tchebyshev. But it presents the problem of the introduction of distortions in the signal due to the over-shot. That is, there is a compromise between noise suppression and distortion, and the limits the frequency of pulse signals that can be filtered due to establishment time. Less distortion implies a lower performance against noise. It is proposed to use the techniques of elimination of over-impulses provided by the control engineering, in combination with the filters of better performance against the noise, it’s possible to get a new approach to the design of analog filters for conditioning of signals of pulses, which does not alter the shape of the pulse signal. Of the techniques of elimination of over-impulses, Posicast emerges, taking into account its good performance in applications of industrial electronics, electrical machines and microelectronics. This project focuses on low pass filters, which are used in the conditioning of pulse signals to eliminate high frequency noise, using two specific approaches: Bessel and Tchebyshev, because these represent the two extremes in relation to the Over-impulse in the temporal response of the filters. When combined with the proposed approaches, Posicast proves to be a suitable technique to eliminate distortion caused by filters with better performance in the frequency response.El filtrado es fundamental en ambientes industriales para la eliminación del ruido y la interferencia que se combinan con las señales provenientes de sensores. Para realizar tal función existen los filtros analógicos, que pueden ser activos o pasivos. Para el caso de la instrumentación industrial, los filtros activos son los más utilizados, debido a que se puede prescindir de los inductores cuando se requieran implementaciones de alto orden. Las aproximaciones de filtros que presentan mejor desempeño frente al ruido son Tchebyshev. Pero presentan el problema de la introducción de distorsiones en la señal por cuenta del sobre impulso. Es decir, existe un compromiso entre la eliminación de ruido y la distorsión, y esta última limita la frecuencia de las señales de pulsos que se pueden filtrar debido al tiempo de establecimiento. Mayor eliminación de ruido implica mayor distorsión; menor distorsión implica un desempeño inferior frente al ruido. Ante esto, se propone la utilización de las técnicas de eliminación de sobre-impulsos provistas por la ingeniería de control, en combinación con los filtros de mejor desempeño frente al ruido, buscando una nueva aproximación al diseño de filtros analógicos para acondicionamiento de señales de pulsos que no altere o alterando lo menos posible, la forma de la señal de pulsos. De las técnicas de eliminación de sobre-impulsos, Posicast emerge como opción altamente viable, teniendo en cuenta su buen desempeño en aplicaciones de electrónica industrial, máquinas eléctricas y microelectrónica. Este trabajo se centra en filtros paso-bajo, que son utilizados en el acondicionamiento de señales de pulsos para eliminar el ruido de alta frecuencia, utilizando dos aproximaciones específicas: Bessel y Tchebyshev, debido a que estas representan los dos extremos en lo relacionado con el sobre impulso en la respuesta temporal de los filtros. Al combinarse con las aproximaciones propuestas, Posicast demuestra ser una técnica adecuada para eliminar la distorsión provocada por los filtros con mejor desempeño en la respuesta en frecuencia, impactando positivamente el acondicionamiento de señales de pulsos usadas en instrumentación

Robust active damping in LCL-filter based medium-voltage parallel grid-inverters for wind turbines

LCL-filter based grid-tie inverters require damping for current-loop stability. There are only software modifications in active damping, whereas resistors are added in passive damping. Although passive damping incurs in additional losses, it is widely used because of its simplicity. This article considers the active damping in medium-voltage parallel inverters for wind turbines. Due to cost reasons, only minimal software changes are allowed and no extra sensors can be used. The procedure must be robust against line-inductance variations in weak grids. Double-update mode is needed so the resonance frequency is under the Nyquist limit. The bandwidth reduction when using active damping is also required to be known beforehand. Moreover, the design procedure should be simple without requiring numerous trial-and-error iterations. In spite of the abundant literature, the options are limited under these circumstances. Filter-based solutions are appropriate and a new procedure for tuning the notch-filter is proposed. However, this procedure requires that the resistance of the inductors is known and a novel filter-based solution is proposed that uses lag-filters. The lag-filters displace the phase angle at the resonance frequency so that the Nyquist stability criterion is fulfilled. Simulations and experiments with a 100 kVA prototype validate the analysis

Facilitating the transition to an inverter dominated power system : experimental evaluation of a non-intrusive add-on predictive controller

The transition to an inverter-dominated power system is expected with the large-scale integration of distributed energy resources (DER). To improve the dynamic response of DERs already installed within such a system, a non-intrusive add-on controller referred to as SPAACE (set point automatic adjustment with correction enabled), has been proposed in the literature. Extensive simulation-based analysis and supporting mathematical foundations have helped establish its theoretical prevalence. This paper establishes the practical real-world relevance of SPAACE via a rigorous performance evaluation utilizing a high fidelity hardware-in-the-loop systems test bed. A comprehensive methodological approach to the evaluation with several practical measures has been undertaken and the performance of SPAACE subject to representative scenarios assessed. With the evaluation undertaken, the fundamental hypothesis of SPAACE for real-world applications has been proven, i.e., improvements in dynamic performance can be achieved without access to the internal controller. Furthermore, based on the quantitative analysis, observations, and recommendations are reported. These provide guidance for future potential users of the approach in their efforts to accelerate the transition to an inverter-dominated power system

Reduction of Torsional Vibrations Excited by Electromechanical Interactions in More Electric Systems

This paper studies the excitation of torsional vibrations by electromechanical interaction after the connection of electrical loads. Electrical generation and power system in aircraft are becoming of key importance, especially considering the current roadmap for aerospace systems’ electrification. However, since the drivetrain which links electrical generators to the main engine is relatively flexible in most aircraft structures, torsional vibrations can be excited by the sudden connection or disconnection of electrical loads, thus increasing the drivetrain’s fatigue and reducing its reliability and lifetime. Because of the increased amounts of intermittent electrical loads on aircraft systems, which excite torsional vibrations through electromechanical interactions, the electrical load connections are investigated in this paper. Specifically, a method for reducing torsional vibrations in aircraft drivetrains is proposed to extend their lifespan. This method is applied directly to the load being connected and it proposes the connection of the electrical loads following a pulsating pattern, for which the pulse connection time is determined as a function of the drivetrain vibration modes. Simulations results show that the proposed method provides a significant reduction in the drivetrain shaft torsional vibrations. Experimental results validate the simulation data showing the benefits this method can provide in drivetrain reliability, weight reduction and cost

Posicast applications to electronic design: a conceptual revision

Se presenta una revisión conceptual generalizada de los conformadores de entrada de sistemas de control como herramientas para eliminar vibraciones en la salida de los sistemas. Se desarrollan los diferentes tipos de conformadores como versiones mejoradas de Posicast, el conformador original. Luego se presentan las aplicaciones de Posicast en el desarrollo de sistemas electrónicos, específicamente, en circuitos de potencia y en circuitos microelectrónicosThis work is a generalized conceptual revision of the control system input shapers. The input shapers are used to eliminate vibrations at the output of the systems. The different types of shapers are developed as improved versions of Posicast, or the original shaper. Then, Posicast applications are presented in the development of electronic systems, specifically in power circuits and microelectronic circuit

Analysis of feedback control applied with command shaping to minimize residual vibration

Joint flexibility is a physical trait that affects all robotic systems to some degree. This characteristic has been shown to be very detrimental to the performance of these robotic systems when implementing fast point-to-point motion. During such motion, the robot will induce vibrations in its structure that will extend past the completion of the move. Many techniques have been applied over the years in order to minimize these residual vibrations. One such method is known as command shaping, which will construct the input profile so as to avoid exciting the natural frequencies of the system. This work seeks to extend this by analyzing how the feedback controller interacts with the input signal. Since a robotic manipulator is inherently nonlinear, this investigation is begun using a linear three-mass system that mimics the important dynamics of a two-link flexible-joint robot. A model of this three-mass system is derived and simulated in order to provide a new testbed for analyzing the problem of reducing residual vibration. It is shown that by appropriately designing the feedback controller so as to minimize the level of energy at the natural frequencies, lower residual vibration amplitudes are achieved. However, in some instances, these vibrations may take longer to settle out, which is directly correlated to the closed-loop damping of the system. This provides guidelines on how to appropriately construct a feedback controller so as to minimize residual vibration. Using this better understanding of the influence of the feedback, several different controllers are then tested on a two-link flexible-joint robot. The results of these experiments show correlation with the results obtained from the linear system analysis completed, and the trends are now better understood by applying the knowledge gained from the three-mass system. With the influence of the feedback controller on the level of residual vibration that ensues from fast point-to-point motion identified, the separate problems of command shaping and feedback control are tied together so as to achieve even lower levels of residual vibration

Active gate switching control of IGBT to improve efficiency in high power density converters

Insulated gate bipolar transistor (IGBT) power semiconductors are widely employed in industrial applications. This power switch capability in high voltage blocking and high current-carrying has expanded its use in power electronics. However, efficiency improvement and reducing the size of products is one of main tasks of engineers in recent years. In order to achieve high-density power converters, attentions are focused on the use of fast IGBTs. Therefore, for achieving this desire the trend is designing more effective IGBT gate drivers. In gate drive (GD) controlling, the main issue is maintaining transient behavior of the MOS-channel switch in well condition; when it switches fast to reduce losses. It is well known that fast switching has a direct effect on the efficiency improvement; meanwhile, it is the major reason of appearing electromagnetic interference (EMI) problems in switched-mode power converters. Nowadays the most expectant of an active gate driver (AGD) is actively adjusting the switching transient through simple circuit implementation. Usually its performance is compared with the conventional gate driver (CGD) with fixed driving profile. As a result a proposed AGD has the capability of increasing the switching speed while minimizing the switching stress. Different novel active gate drivers (as feed-forward and closed-loop topologies) have been designed and analysed in this study. To improve the exist trade-off between switching losses and EMI problem, all effective factors on this trade-off are evaluated and considered in proposed solutions. Theoretical developments include proposed controlling methods and simulated efficiency of IGBTs switching control. The efficiency improvement has been pursued with considering EMI study in the proposed active gate controller. Experimental tests have been conducted to verify the design and validate the results. Beside technical aspects, cost study has also considered in the closed-loop GD. The proposed gate drivers are simple enough to allow its use in real industrial applications.Los semiconductores de potencia (IGBT) se emplean ampliamente en aplicaciones industriales. La capacidad de este interruptor de bloqueo en alta tensión y conducción de alta corriente ha ampliado su uso en la electrónica de potencia. Sin embargo, la mejora de la eficiencia y la reducción del tamaño de los convertidores de potencia es una de las tareas principales de los ingenieros de diseño. Para lograr convertidores de potencia de alta densidad y eficiencia, se requiere el uso de IGBT rápidos. Por lo tanto, la tendencia es diseñar controladores de puerta para IGBT más efectivos. En el control de la unidad de puerta (GD), el problema principal es mantener el comportamiento transitorio del conmutador del canal MOS bajo control, cuando conmuta a lata frecuencia para reducir las pérdidas. Es bien sabido que la conmutación rápida tiene un efecto directo en la mejora de la eficiencia; Sin embargo, la alta frecuencia de conmutación es la razón principal de la aparición de problemas de interferencia electromagnética (EMI) en los convertidores de potencia de modo conmutado. En la actualidad, la acción más directa para un controlador de puerta activo (AGD) consiste en el ajuste activo del transitorio de conmutación a través de la implementación de un circuito simple. Para evaluar su eficiencia, su rendimiento se compara con el controlador de puerta convencional (CGD) con perfil de conducción fijo. Los resultados muestran que la propuesta de AGD tiene la capacidad de aumentar la velocidad de conmutación mientras minimiza el stress. En este estudio se han diseñado y analizado diferentes controladores de puerta activa novedosos (como topologías de control en avance y de bucle cerrado). Para mejorar el balance existente entre la reducción de pérdidas y los problemas de EMI, todos los factores que afectan a las pérdidas y la EMI se evalúan y se consideran en las soluciones propuestas. Los desarrollos teóricos incluyen el análisis y desarrollo de los métodos de control propuestos, la simulación de la operación del control de conmutación del IGBT, y la validación experimental. Además de los aspectos técnicos de eficiencia y emisiones electromagnéticas, el estudio de costes también se ha considerado en los análisis de AGD. Los resultados muestran que los controladores de puerta propuestos son lo suficientemente eficientes y económicos como para permitir su uso en aplicaciones industriales realesPostprint (published version

Advancements in Real-Time Simulation of Power and Energy Systems

Modern power and energy systems are characterized by the wide integration of distributed generation, storage and electric vehicles, adoption of ICT solutions, and interconnection of different energy carriers and consumer engagement, posing new challenges and creating new opportunities. Advanced testing and validation methods are needed to efficiently validate power equipment and controls in the contemporary complex environment and support the transition to a cleaner and sustainable energy system. Real-time hardware-in-the-loop (HIL) simulation has proven to be an effective method for validating and de-risking power system equipment in highly realistic, flexible, and repeatable conditions. Controller hardware-in-the-loop (CHIL) and power hardware-in-the-loop (PHIL) are the two main HIL simulation methods used in industry and academia that contribute to system-level testing enhancement by exploiting the flexibility of digital simulations in testing actual controllers and power equipment. This book addresses recent advances in real-time HIL simulation in several domains (also in new and promising areas), including technique improvements to promote its wider use. It is composed of 14 papers dealing with advances in HIL testing of power electronic converters, power system protection, modeling for real-time digital simulation, co-simulation, geographically distributed HIL, and multiphysics HIL, among other topics

Travelling Wave Control of Stringed Musical Instruments

PhDDespite the increasing sophistication of digital musical instruments, many performers, composer and listeners remain captivated by traditional acoustic instruments. Interest has grown in the past 2 decades in augmenting acoustic instruments with sensor and actuator technology and integrated digital signal processing, expanding the instrument’s capabilities while retaining its essential acoustic character. In this thesis we present a technique, travelling wave control, which allows active control of the vibrations of musical strings and yet has been little explored in the musical instrument literature to date. The thesis seeks to demonstrate that travelling wave control is capable of active damping and of modifying the timbre of a musical string in ways that go beyond those available through the more conventional modal control paradigm. However, we show that travelling wave control is highly sensitive to nonlinearity, which in practical settings can lead to harmonic distortion and even instability in the string response. To avoid these problems, we design and build a highly linear optical string displacement sensor, and investigate the use of piezoelectric stacks to actuate the termination point of a string. With these components we design and build a functioning travelling wave control system which is capable of damping the vibrations of a plucked string without adversely affecting its timbre. We go on to show that by deliberately adding nonlinearity into the control system, we are able to modify the timbre of the string in a natural way by affecting the evolution of the modal amplitudes. The results demonstrate the feasibility of the concept and lay the groundwork for future integration of travelling wave control into future actuated musical instruments