628 research outputs found
Lead pursuit control of multiphase drives
Los accionamientos multifásicos, compuestos por una máquina eléctrica de más de tres
fases alimentada por un convertidor de potencia, han atraído recientemente un importante
interés en la comunidad investigadora debido a las ventajas que presentan frente a las
máquinas trifásicas convencionales. Este es el caso de la mejor distribución de potencia
por fase, la menor producción de armónicos en el convertidor de potencia y, la más
importante, la tolerancia a fallos, lo cual significa que la máquina multifásica puede seguir
funcionando cuando una o varias fases se pierden, siempre que el número restante de fases
sea igual o mayor que tres. Debido a esta alta fiabilidad, los accionamientos multifásicos
son especialmente adecuados para aplicaciones relacionadas con los vehículos eléctricos
(terrestres, marítimos y aéreos) y las energías renovables por razones de seguridad y/o
económicas.
El uso de controladores avanzados y de alto rendimiento en accionamientos multifásicos
es particularmente relevante, ya que las estrategias de control convencionalmente aplicadas
a los accionamientos trifásicos no terminan de alcanzar un estándar en su extensión al caso
multifásico. La razón es la mayor complejidad y número de variables a controlar. En este
contexto, los controladores predictivos han encontrado un interesante nicho de aplicación
en convertidores de potencia y accionamientos multifásicos debido a su formulación
intuitiva y flexible: un modelo del sistema es usado para calcular las predicciones de las
variables controladas, que luego se comparan con las referencias impuestas dentro de
una función de coste. Esta estrategia permite incorporar varios objetivos de control y
restricciones en el proceso de control a través de la función de coste. Sin embargo, es
bien sabido que este tipo de controlador sufre de un alto coste computacional y contenido
armónico de corriente que limita su aplicación en los accionamientos multifásicos.
La investigación desarrollada en esta Tesis se centra en la mitigación de las limitaciones
citadas siguiendo dos objetivos principales:
• La incorporación de observadores de corrientes rotóricas en el controlador predictivo
para mejorar así la precisión del modelo predictivo y, consecuentemente,
el rendimiento del sistema de control, principalmente en términos de contenido
armónico y pérdidas por conmutación en el convertidor de potencia. Un observador de Luenberger es construido para este propósito utilizando una estrategia innovadora
de posicionamiento de polos en su diseño.
• La introducción de un grado de libertad adicional en el controlador predictivo
basado en tiempos de muestreo variables e implementado usando el concepto de
lead pursuit. El resultado es un controlador novedoso que conduce a una resolución
en los tiempos de conmutación más fina en comparación con las técnicas predictivas
más convencionales, lo que proporciona una reducción importante en el contenido
armónico.
Las estrategias de control propuestas son validadas mediante simulación y experimentación
utilizando un accionamiento compuesto por una máquina de inducción de cinco
fases como caso de ejemplo. Los resultados y conclusiones derivadas de esta investigación
han sido presentados en cinco trabajos principales publicados en revistas internacionales
de alto impacto, los cuales constituyen las contribuciones de esta Tesis por compendio de
artículos. Sin embargo, otros trabajos relacionados con la línea de investigación han sido
también publicados en artículos de revista y conferencia y en un capítulo de libro.Multiphase drives, constituted by an electric machine with more than three phases
fed by a power converter, have recently attracted an important interest in the research
community due to the advantages that they present over the conventional three-phase ones.
This is the case of the better power distribution per phase, the lower harmonic production
in the power converter, and the most important one, the fault-tolerant capability, which
means that the multiphase machine can still be operated when one or several phases are
missing, provided that the number of remaining phases is equal or greater than three. Due
to this high reliability, multiphase drives are specially well suited for applications related
to electric vehicles (terrestrial, maritime and aerial) and renewable energies for safety
and/or economical reasons.
The use of advanced and high-performance controllers in multiphase drives is particularly
relevant, since the control strategies conventionally applied to three-phase drives do
not reach a standard in their extension to the multiphase case. The reason is the greater
complexity and number of variables that must be controlled. In this context, predictive
controllers have found an interesting niche of application in power converters and multiphase
drives due to their intuitive and flexible formulation: a model of the system is
used to compute predictions of the controlled variables, which are later compared with the
imposed references in a cost function. This strategy permits incorporating several control
objectives and constraints in the control process through the cost function. However, it is
well known that this type of controller suffers from a high computational cost and current
harmonic content that limit its application in multiphase drives.
The research developed in this Thesis work is focused on the mitigation of the cited
limitations following two main goals:
• The incorporation of rotor current observers in the predictive controller in order to
improve the accuracy of the predictive model and, consequently, the control system
performance, principally in terms of harmonic content and commutation losses in
the power converter. A Luenberger observer is constructed for that purpose using
an innovative pole-placement strategy in its design.
• The introduction of an additional degree of freedom in the predictive controller
based on variable sampling times and implemented using the lead-pursuit concept. The result is a novel controller that leads to a finer resolution in the commuting
times in comparison with more conventional predictive techniques, which provides
an important reduction in the harmonic content.
The proposed control strategies are validated by simulation and experimentation using a
five-phase induction machine drive as case example. The results and conclusions derived
from this research have been presented in five main works published in high-impact
international journals, which constitute the contributions of this article compendium Thesis.
Nevertheless, other related works have also been published in journal and conference papers
and a book chapter
Predictive current control in electrical drives: an illustrated review with case examples using a five-phase induction motor drive with distributed windings
The industrial application of electric machines in variable-speed drives has grown in the last decades thanks to the
development of microprocessors and power converters. Although three-phase machines constitute the most common case, the
interest of the research community has been recently focused on machines with more than three phases, known as multiphase
machines. The principal reason lies in the exploitation of their advantages like reliability, better current distribution among phases
or lower current harmonic production in the power converter than conventional three-phase ones, to name a few. Nevertheless,
multiphase drives applications require the development of complex controllers to regulate the torque (or speed) and flux of the
machine. In this regard, predictive current controllers have recently appeared as a viable alternative due to an easy formulation
and a high flexibility to incorporate different control objectives. It is found however that these controllers face some peculiarities
and limitations in their use that require attention. This work attempts to tackle the predictive current control technique as a viable
alternative for the regulation of multiphase drives, paying special attention to the development of the control technique and the
discussion of the benefits and limitations. Case examples with experimental results in a symmetrical five-phase induction machine
with distributed windings in motoring mode of operation are used to this end
Min-Max Predictive Control of a Five-Phase Induction Machine
In this paper, a fuzzy-logic based operator is used instead of a traditional cost function for
the predictive stator current control of a five-phase induction machine (IM). The min-max operator
is explored for the first time as an alternative to the traditional loss function. With this proposal,
the selection of voltage vectors does not need weighting factors that are normally used within
the loss function and require a cumbersome procedure to tune. In order to cope with conflicting
criteria, the proposal uses a decision function that compares predicted errors in the torque producing
subspace and in the x-y subspace. Simulations and experimental results are provided, showing how
the proposal compares with the traditional method of fixed tuning for predictive stator current control.Ministerio de Economía y Competitividad DPI 2016-76493-C3-1-R y 2014/425Unión Europea DPI 2016-76493-C3-1-R y 2014/425Universidad de Sevilla DPI 2016-76493-C3-1-R y 2014/42
Model predictive MRAS estimator for sensorless induction motor drives
Ph. D. ThesisThe project presents a novel model predictive reference adaptive system (MRAS) speed
observer for sensorless induction motor drives applications. The proposed observer is based
on the finite control set-model predictive control principle. The rotor position is calculated
using a search-based optimization algorithm which ensures a minimum speed tuning error
signal at each sampling period. This eliminates the need for a proportional integral (PI)
controller which is conventionally employed in the adaption mechanism of MRAS observers.
Extensive simulation and experimental tests have been carried out to evaluate the
performance of the proposed observer. Both the simulation and the experimental results show
improved performance of the MRAS scheme in both open and closed-loop sensorless modes
of operation at low speeds and with different loading conditions including regeneration. The
proposed scheme also improves the system robustness against motor parameter variations and
increases the maximum bandwidth of the speed loop controller.
However, some of the experimental results show oscillations in the estimated rotor speed,
especially at light loading conditions. Furthermore, due to the use of the voltage equation in
the reference model, the scheme remains sensitive, to a certain extent, to the variations in the
machine parameters. Therefore, to reduce rotor speed oscillations at light loading conditions,
an adaptive filter is employed in the speed extraction mechanism, where an adaptation
mechanism is proposed to adapt the filter time constant depending on the dynamic state of the
system. Furthermore, a voltage compensating method is employed in the reference model of
the MP-MRAS observer to address the problems associated with sensitivity to motor
parameter variation. The performance of the proposed scheme is evaluated both
experimentally and by simulation. Results confirm the effectiveness of the proposed scheme
for sensorless speed control of IM drives
Finite control set and modulated model predictive flux and current control for induction motor drives
The paper presents a new implementation of direct flux and current vector control of an induction motor drive using the techniques of model predictive control. The advantages offered by predictive control are used to enhance the dynamics of direct flux vector control. To minimize the problems of variable switching frequency inherent to finite control set predictive control, an alternative approach using pulse width modulation is studied for command execution as occurs in the so-called modulated model predictive control. A comparison between finite control set and modulated model predictive control is presented and the results are also compared with the control implementation through traditional proportional-integral regulators to highlight the advantages and drawbacks of predictive control based strategies. Apart from a greater harmonic content in stator currents, the predictive control can offers control dynamics comparable with proportional-integral control while maintaining immunity against machine parameter variations and excluding the need for controller tunin
Advances in Rotating Electric Machines
It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines
On-line estimation of rotor variables in predictive current controllers: a case study using five-phase induction machines
Predictive current control has been recently proposed like an alternative to conventional PI-PWM current control techniques. Implemented solutions are based on inaccurate estimation of the rotor electrical variables to reduce the computational cost of the method. In this work, the utility and computational cost of predictive current control with different methods for the on-line estimation of the rotor variables are studied. Experimental results are provided to characterize the obtained benefits and drawbacks, using a five-phase induction machine as a case example
Online estimation of rotor variables in predictive current controllers: A case study using five-phase induction machines
Predictive current control (PCC) has been recently proposed like an alternative to conventional PI-PWM current control techniques. Implemented solutions are based on inaccurate estimation of the rotor electrical variables to reduce the computational cost of the method. In this study, the utility and computational cost of PCC with different methods for the online estimation of the rotor variables are studied. Experimental results are provided to characterize the obtained benefits and drawbacks, using a five-phase induction machine as a case example.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI
Full predictive cascaded speed and current control of an induction machine
This paper presents and experimentally validates a new control scheme for electrical drive systems, named cascaded predictive speed and current control (PSCC). This new strategy uses the model predictive control concept. It has a cascaded structure like that found in field-oriented control or direct torque control. Therefore the control strategy has two loops, external and internal, both implemented with model predictive control. The external loop controls the speed, while the inner loop controls the stator currents. The inner control loop is based on Finite Control Set Model Predictive Control (FCS-MPC), and the external loop uses MPC deadbeat, making full use of the inner loop‘s highly dynamic response. Experimental results show that the proposed strategy has a performance that is comparable to the classical control strategies but that it is overshoot-free and provides a better time response
Deadbeat control based on a multipurpose disturbance observer for permanent magnet synchronous motors
© The Institution of Engineering and Technology 2018. Robustness against parameter mismatches and position-sensorless operation are two important research topics for permanent magnet synchronous motor (PMSM) drives. Usually, the existing observers are designed for achieving a specific function. While here, both the above two functions are integrated into the proposed sliding-mode disturbance observer: (i) if a position sensor is equipped, accurate current regulation can be achieved by deadbeat predictive current control despite mismatched motor parameters; (ii) if the position sensor is not equipped but with a good estimation of motor parameters, the observer can serve as a back electromotive force estimator. Then, the rotor position can be extracted for position-sensorless control. Usually, a low-pass filter is required to suppress high-frequency noises in the conventional sliding-mode observer. This inevitably leads to phase delay in the estimation. By comparison, a complex coefficient filter is inherently embedded in the proposed method, which can provide accurate estimation without phase delay or magnitude error. Experimental results obtained from a 2.4 kW PMSM drive platform indicate that high-performance current control can be achieved with good robustness for position sensor-based operation. Also, rotor position can be accurately estimated with good steady and dynamic performance for position-sensorless operation
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