3 research outputs found
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
Design and Control of Power Converters 2019
In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc
Modulation and control strategies for multilevel five-phase open-end winding drives
Industrial and automotive trends clearly demonstrate an increased interest in medium- and high-power variable speed drives. Despite constant progress in the technology, the semiconductor characteristics are still the bottleneck in drive designs, due to their limitations to block high voltage (several kilovolts) and conduct high current (several hundreds of amperes per-phase). For this reason and numerous other advantages, solutions based on multilevel inverters and multiphase machines are considered in recent years.
The open-end winding drives are an alternative approach for drives construction. This thesis investigates carrier based pulse width modulation schemes for five-phase open-end winding drives. Two drive topologies, with isolated dc-links of two inverters, are considered. The first one consists of two two-level inverters and a five-phase machine. The second topology utilises one three- and one two-level five-phase inverter. It is shown that the same drive structure can produce a different number of phase voltage levels, when different dc-link voltages of two inverters are in use. Hence, dc-link voltage ratio is considered as an additional degree of freedom. An open-end winding structure that comprises of two two-level inverters offers harmonic performance equivalent to three- and four-level single-sided supply. The second drive structure under analysis is able to produce four, five and six voltage levels, depending on utilised dc-link voltage ratio.
Modulation schemes are classified in two categories. So-called coupled modulation schemes are developed under the assumption that open-end winding drives are equivalent to certain single-sided multilevel solutions. This enables the application of slightly modified modulation methods for multilevel inverters, to the open-end winding configurations. As a consequence, number of utilised voltage levels can be higher than the sum of two inverters’ number of levels. However, this boost in number of levels relies on simultaneous switching in two inverters’ legs connected to the same drive phase,which causes so-called dead-time spikes. The second group, referred to in this thesis as decoupled modulation schemes, rely on the separate modulation of two inverters, using voltage references obtained by splitting the overall phase voltage reference, proportionally to inverters’ dc-link voltages. Hence, this kind of modulation offers somewhat worse harmonic performance, when compared to coupled modulation schemes.
Special attention is paid to the stability of dc-link voltage levels, which is one of the most important figures of merits of quality for multilevel drives. Using a novel analysis approach, it is demonstrated that utilisation of optimal harmonic performance offered by coupled modulation methods leads to unstable dc-link voltages, but only in the cases where dc-link voltage ratio is used for increment of available number of voltage levels. Decoupled modulation methods offer stable dc-link voltages, regardless of drive configuration.
One of the drawbacks of the analysed open-end winding drives is the need for two isolated dc sources, which form dc-link voltages of two inverters. For that reason, a possibility to use only one dc-source in open-end winding drives with isolated inverters is considered. Analysis shows that both drive topologies can be operated using so-called bulk and conditioning inverter control, where bulk inverter is supplied from an active dc source, but operates in staircase mode, while conditioning inverter performs high-frequency pulse width modulation, in order to suppress low-order harmonic content. This kind of operation is investigated in details for two specific configurations in which two inverters never operate at the same time in PWM mode, when coupled modulation methods are used. Comparison of the results shows that topology which comprises from one three- and one two-level inverter is more suitable for this kind of control. Together with previously analysed configurations and modulation strategies, dynamic performance of this novel drive is tested under the closed-loop speed control. Experimental results show that open-end winding drives are suitable for a wide range of applications