39 research outputs found
Advances in dual-three-phase permanent magnet synchronous machines and control techniques
Multiphase electrical machines are advantageous for many industrial applications that require a high power rating, smooth torque, power/torque sharing capability, and fault-tolerant capability, compared with conventional single three-phase electrical machines. Consequently, a significant number of studies of multiphase machines has been published in recent years. This paper presents an overview of the recent advances in multiphase permanent magnet synchronous machines (PMSMs) and drive control techniques, with a focus on dual-three-phase PMSMs. It includes an extensive overview of the machine topologies, as well as their modelling methods, pulse-width-modulation techniques, field-oriented control, direct torque control, model predictive control, sensorless control, and fault-tolerant control, together with the newest control strategies for suppressing current harmonics and torque ripples, as well as carrier phase shift techniques, all with worked examples
Control of synchronous motor drives with an LC filter
Electric motors can experience voltage stress over the motor terminals due to the short rise time of the voltage pulse at the inverter output and the impedance mismatch between the lead cables and the motor. This overvoltage degrades the motor insulation, thus reducing the motor lifespan. The problems can be avoided by using a sinusoidal LC filter in the inverter output, limiting the overvoltage and dampening high-order harmonics. However, the existing control methods for LC-filtered synchronous motors are infeasible for plug-and-play drives, in which the motor data or user input are not required. This is because the methods either contain several cascaded control loops, require cumbersome parameter tuning, are sensitive to parameter errors, or the range of operating speeds is limited. Nevertheless, recently developed observer-based volts-per-hertz control shows advantages through relatively low sensitivity to parameter errors, simplicity and generality of the control algorithm, and reliance on common control gains for all synchronous motor types. These attributes indicate that the observer-based volts-per-hertz control can be used for medium-performance drives ensuring robust and stable operation at a wide range of speeds. This thesis develops observer-based volts-per-hertz control for synchronous motor drives with an LC filter. The two designed methods are based on two different observer types (reduced-order and full-order) with two state feedback control laws. The methods are further linearized by means of small-signal linearization, the control strategies are simulated in Simulink, and experimental measurements validate the simulations. The measurement results show a satisfactory performance of the permanent magnet synchronous motor with both methods. However, the control performance of the synchronous reluctance motor is poor when the full-order observer is used. The thesis subsequently provides several suggestions for future work improvements
The investigation of electromagnetic radial force and associated vibration in permanent magnet synchronous machines
The rising public awareness of climate change and urban air pollution has been one
of the key drivers for transport electrification. Such trend drastically accelerates the
quest for high-power-and-torque-density electric drive systems. The rare-earth permanent
magnet synchronous machine, with its excellent steady-state and dynamic
characteristics, has been the ideal candidate for these applications. Specifically, the
fractional-slot and concentrated-winding configuration is widely adopted due to its
distinctive merits such as short end winding, low torque pulsation, and high efficiency.
The vibration and the associated acoustic noise become one of the main
parasitic issues of high-performance permanent magnet synchronous drives. These
undesirable features mainly arise from mechanical connection failure, imperfect assembly,
torque pulsation, and electromagnetic radial and axial force density waves.
The high-power-and-torque-density requirement will only be ultimately fulfilled by
the reduction of both electromagnetic active material and passive support structure.
This results in inflated electromagnetic force density inside the electric machine.
Besides, the sti.ness of the machine parts can be compromised and the resultant
natural frequencies are significantly brought down. Therefore, the vibration and
acoustic noise that are associated with the electromagnetic radial and axial force
density waves become a burden for large deployment of these drives.
This study is mainly dedicated to the investigation of the electromagnetic radial
forced density and its associated vibration and acoustic noise in radial-flux permanent
magnet synchronous machines. These machines are usually powered by voltage
source inverter with pulse width modulation techniques and various control strategies.
Consequently, the vibration problem not only lies on the permanent magnet
synchronous machine but also highly relates to its drive and controller. Generally,
the electromagnetic radial force density and its relevant vibration can be divided
into low-frequency and high-frequency components based on their origins. The
low-frequency electromagnetic radial force density waves stem from the magnetic
field components by the permanent magnets and armature reaction of fundamental
and phase-belt current harmonic components, while the high-frequency ones are
introduced by the interactions between the main low-frequency and sideband highfrequency
magnetic field components.
Both permanent magnets and armature reaction current are the main sources of
magnetic field in electric machines. Various drive-level modeling techniques are first reviewed, explored, and developed to evaluate the current harmonic components
of the permanent magnet synchronous machine drive. Meanwhile, a simple
yet e.ective analytical model is derived to promptly estimate the sideband current
harmonic components in the drive with both sinusoidal and space-vector pulse
width modulation techniques. An improved analytical method is also proposed to
predict the magnetic field from permanent magnets in interior permanent magnet
synchronous machines. Moreover, a universal permeance model is analytically developed
to obtain the corresponding armature-reaction magnetic field components.
With the permanent magnet and armature-reaction magnetic field components, the
main electromagnetic radial force density components can be identified and estimated
based on Maxwell stress tensor theory.
The stator tooth structure has large impacts on both electromagnetic radial force
density components and mechanical vibration behaviors. The stator tooth modulation
e.ect has been comprehensively demonstrated and explained by both finite
element analysis and experimental results. Analytical models of such e.ect are developed
for prompt evaluation and insightful revelation. Based on the proposed
models, multi-physics approaches are proposed to accurately predict low-frequency
and high-frequency electromagnetic radial vibration. Such method is quite versatile
and applicable for both integral-slot and fractional-slot concentrated-winding
permanent magnet synchronous machines. Comprehensive experimental results are
provided to underpin the validity of the proposed models and methods.
This study commences on the derivations of the drive parameters such as torque angle,
modulation index, and current harmonic components from circuit perspective
and further progresses to evaluate and decouple the air-gap magnetic field components
from field perspective. It carries on to dwell on the analytical estimations of
the main critical electromagnetic radial force density components and stator tooth
modulation e.ect. Based on the stator mechanical structure, the corresponding electromagnetic
radial vibration and acoustic noise can be accurately predicted. Various
analytical models have been developed throughout this study to provide a systematic
tool for quick and e.ective investigation of electromagnetic radial force density,
the associated vibration and acoustic noise in permanent magnet synchronous machine
drive. They have all been rigorously validated by finite element analysis and
experimental results. Besides, this study reveals not only a universal approach for
electromagnetic radial vibration analysis but also insightful correlations from both
machine and drive perspectives
Prädiktive Regelung und Finite-Set-Beobachter für Windgeneratoren mit variabler Drehgeschwindigkeit
This dissertation presents several model predictive control (MPC) techniques and finite-position-set observers (FPSOs) for permanent-magnet synchronous generators and doubly-fed induction generators in variable-speed wind turbines. The proposed FPSOs are novel ones and based on the concept of finite-control-set MPC. Then, the problems of the MPC techniques like sensitivity to variations of the model parameters and others are investigated and solved in this work.Die vorliegende Dissertation stellt mehrere unterschiedliche Verfahren der modellprädiktiven Regelung (MPC) und so genannte Finite-Position-Set-Beobachter (FPSO) sowohl für Synchrongeneratoren mit Permanentmagneterregung als auch für doppelt gespeiste Asynchrongeneratoren in Windkraftanlagen mit variabler Drehzahl vor und untersucht diese. Für die Beobachter (FPSO) wird ein neuartiger Ansatz vorgestellt, der auf dem Konzept der Finite-Control-Set-MPC basiert. Außerdem werden typische Eigenschaften der MPC wie beispielsweise die Anfälligkeit gegenüber Parameterschwankungen untersucht und kompensiert