1,613 research outputs found
Direct torque control for dual three-phase induction motor drives
A direct torque control (DTC) strategy for dual three-phase induction motor drives is discussed in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The DTC strategy is based on a predictive algorithm and is implemented in a synchronous reference frame aligned with the machine stator flux vector. The advantages of the discussed control strategy are constant inverter switching frequency, good transient and steady-state performance, and low distortion of machine currents with respect to direct self-control (DSC) and other DTC schemes with variable switching frequency. Experimental results are presented for a 10-kW DTC dual three-phase induction motor drive prototype
Assessment of a Universal Reconfiguration-less Control Approach in Open-Phase Fault Operation for Multiphase Drives
Multiphase drives have been important in particular industry applications where reliability is
a desired goal. The main reason for this is their inherent fault tolerance. Di erent nonlinear controllers
that do not include modulation stages, like direct torque control (DTC) or model-based predictive
control (MPC), have been used in recent times to govern these complex systems, including mandatory
control reconfiguration to guarantee the fault tolerance characteristic. A new reconfiguration-less
approach based on virtual voltage vectors (VVs) was recently proposed for MPC, providing a natural
healthy and faulty closed-loop regulation of a particular asymmetrical six-phase drive. This work
validates the interest in the reconfiguration-less approach for direct controllers and multiphase drives
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
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
Model Predictive Control based on Dynamic Voltage Vectors for Six-phase Induction Machines
Model predictive control (MPC) has been recently
suggested as an interesting alternative for the regulation of
multiphase electric drives because it easily exploits the inherent
advantages of multiphase machines. However, the standard
MPC applies a single switching state during the whole sampling
period, inevitably leading to an undesired x y voltage production.
Consequently, its performance can be highly degraded when the
stator leakage inductance is low. This shortcoming has been,
however, mitigated in recent work with the implementation
of virtual/synthetic voltage vectors (VVs) in MPC strategies.
Their implementation reduces the phase current harmonic
distortion since the average x y voltage production becomes
null. Nevertheless, VVs have a static nature because they are
generally estimated offline, and this implies that the flux/torque
regulation is suboptimal. Moreover, these static VVs also present
some limitations from the point of view of the dc-link voltage
exploitation. Based on these previous limitations, this article
proposes the implementation of dynamic virtual voltage vectors
(DVVs), where VVs are created online within the MPC strategy.
This new concept provides an online optimization of the output
voltage production depending on the operating point, resulting
in an enhanced flux/torque regulation and a better use of the
dc-link voltage. Experimental results have been employed to
assess the goodness of the proposed MPC based on DVVs.Ministerio de Ciencia, Innovación y Universidades RTI2018-096151-B-100
Extension of Finite-Control Set Model-Based Predictive Control Techniques to Fault-Tolerant Multiphase Drives: Analysis and Contributions
Las máquinas eléctricas son una de las principales tecnologías que hacen posible las energías renovables y los vehículos eléctricos. La necesidad constante de incrementar la capacidad de potencia para generar más energía o para impulsar vehículos cada vez más grandes, ha motivado la investigación y el desarrollo en el área de las máquinas multifásicas las cuales, gracias a su número de fases, permiten no sólo manejar más potencia con menos pulsaciones de par y contenido armónico en la corriente que las máquinas trifásicas convencionales, sino que también permiten obtener una mayor tolerancia a fallos, aumentando el interés de su implementación en aplicaciones donde la fiabilidad juega un papel importante por razones económicas y de seguridad.
La investigación más reciente en el área de sistemas multifásicos se centra en el desarrollo de técnicas que permitan explotar las características específicas y especiales de las máquinas multifásicas, viendo el incremento en el número de fases no como un aumento en la complejidad de implementación, sino como un mayor número de grados de libertad tanto en el diseño como en el control, permitiendo mejorar sus prestaciones y fiabilidad, haciéndolas más atractivas para su uso en aplicaciones industriales. Es así como se han desarrollado técnicas de control que permitan operar a alta velocidad o alto par, tolerancia a diferentes tipos de fallos y máquinas con diferentes conexionados de devanados o con sistemas formados por múltiples variadores y máquinas.
El objetivo de esta tesis doctoral es la extensión del control predictivo para máquinas multifásicas (específicamente el control predictivo de estados finitos basado en modelo o FCS-MPC por sus siglas en inglés) a la operación tolerante a fallos, aprovechando la capacidad de tolerancia a fallos que las máquinas multifásicas poseen, asegurando su funcionamiento de una manera eficiente y controlada.
Con este fin se estudió el modelo matemático de la máquina en condiciones de pre- y post- falta considerando diferentes tipos de faltas, permitiendo establecer el efecto que las condiciones de fallo tienen en el comportamiento del sistema. Se desarrollaron modelos de simulación de una máquina de inducción de cinco fases, considerando faltas de fase abierta y en el disparo de los IGBT’s de una fase, permitiendo el diseño y validación del controlador FCS-MPC tolerante a fallos, cuyos resultados obtenidos fueron presentados en diversos congresos internacionales. La posterior implementación y validación experimental del control tolerante a fallos propuesto dio lugar a la publicación de dos de los artículos científicos presentados en esta tesis. Del mismo modo, se desarrolló un control tolerante a fallos basado en controladores lineales (de tipo resonante), teniendo en cuenta los esquemas propuestos en publicaciones científicas recientes y se realizó una comparativa entre el control tolerante a fallos basado en FCS-MPC y el controlador resonante ante un fallo de fase abierta, mediante resultados de simulación y experimentales, dando lugar a la publicación en un congreso internacional y en un artículo de revista científica.
Las contribuciones de esta tesis doctoral se han publicado en la revista científica IEEE Transactions on Industrial Electronics entre los años 2013/2015
Model predictive control of six-phase induction motor drives using virtual voltage vectors
The most serious and recent competitor to the standard field oriented control for induction motors (IM) is the finite control set model predictive control (FCS-MPC). Nevertheless, the extension to multiphase drives faces the impossibility to simultaneously regulate the flux/torque and the secondary current components (typically termed x − y in the literature). The application of a single switching state during the whole sampling period inevitably implies the appearance of x − y voltage/currents that increase the system losses and deteriorate the power quality. These circulating currents become intolerably high as per the unit x − y impedance and the switching frequency diminish. Aiming to overcome this limitation, this work suggests the integration of virtual voltage vectors (VVs) into the FCS-MPC structure. The VVs ensure null x − y voltages on average during the sampling period and the MPC approach selects the most suitable VV to fulfill the flux/torque requirements. The experimental results for a six-phase case study compare the standard FCS-MPC with the suggested method, confirming that the VV-based MPC maintains the flux/torque regulation and successfully improves the power quality and efficiency
Recent advances in model predictive and sliding mode current control techniques of multiphase induction machines
Multiphase machines have attracted the attention of the research and industrial communities due to their advantages, namely better power distribution and fault-tolerant capabilities without extra hardware. However, the multiphase machine requires high-performance control strategies to take advantage of these features. From this perspective, the field-oriented control with the inner current control loop that uses using an explicit modulation stage has been considered the benchmark solution thanks to the reduced harmonic distortion obtained with this regulation strategy. Nevertheless, nonlinear controllers, thanks to their inherent nature, allow exploiting the extra multiphase capabilities in a simplified manner. Consequently, this paper aims to concentrate and discuss the latest developments on nonlinear current control of two of the most popular multiphase electric drive configurations, five-phase and six-phase. Then, this paper covers mainly finite-control-set model predictive control and their variations. Moreover, sliding-mode control is also explained. Finally, this paper includes experimental assessments of the most recent nonlinear current control techniques considering steady-state and transient conditions, stability and performance analysis.Agencia Estatal de Investigación | Ref. PID2019-105612RB-I0
Novel control techniques in multiphase drives: direct control methods (DTC and MPC) under limit situations.
Premio Extraordinario de Doctorado U
Experimental stability study of modulated model predictive current controllers applied to six-phase induction motor drives
Modulated model predictive current control techniques are considered an interesting option to control multiphase
drives due to their control flexibility and fast dynamic response.
However, a practical stability study of those techniques is still
missing. This article presents an experimental stability study, to
quantify the limits of stability, to modulated predictive current controllers applied to an asymmetrical six-phase induction machine.
Experimental results are presented to verify the theoretical analysis
results in terms of stability ranges regarding sampling frequency
and rotor speedCONACYT-Paraguay | Ref. POSG16-05Agencia Estatal de Investigación | Ref. PID2019-105612RB-I0
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