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International Review of Electrical Engineering - February 2006 -
Preface and
acknowledgments
Preface and acknowledgments
by Santolo MEO
Vol. 0. n. 0, pp. 1-2
International Review of Electrical Engineering - Papers
Modelling, Analysis and Control of a DC-connected Wind Farms to Grid
by F. Iov, A. D. Hansen, P. Sørensen, F. Blaabjerg
Vol. 0. n. 0, pp. 3-13
Abstract
- Nowadays, there is an increasing trend to connect large MW wind farms to the
transmission system. Requirements that focus on the influence of the farms on
the grid stability and power quality, and on the control capabilities of wind
farms have already been established. The main trends of modern wind
turbines/farms are clearly the variable speed operation and a grid connection
through a power electronic interface, especially using doubly-fed induction
generators. Using power electronics the control capabilities of these wind
turbines/farms are extended and thus the grid requirements are fulfilled.
However, the traditional squirrel-cage generators based wind turbines/wind farms
directly connected to the grid have less control capabilities. These wind
turbines/farms cannot regulate their production and contribute to power system
stability. A DC transmission system for connection of the active stall wind
farms to the grid can provide these features and also maximize the produced
power especially at low wind speeds by using variable voltage/frequency for the
wind farm. The focus in this paper is in studying the variable speed operation
for the active stall wind farms using a voltage source converter based DC
transmission system.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: wind
power, active stall wind farms, DC transmission system, variable frequency
operation.
Winding functions theory and Maxwell's equations coupled analytical modeling of
an axial flux PM synchronous machine
by N. Adbelkarim, J. Azzouzi, G. Barakat
Vol. 0. n. 0, pp. 14-22
Abstract
- In this paper, a complete analytical model of an axial flux permanent magnet
synchronous machine (AFPMSM) is investigated. This modeling is based on an exact
2D solution of the magnetic field in the machine derived from the Maxwell's
equations and coupled with the winding function theory to calculate the back emf,
the self and mutual inductances. The developed analytical model is then used to
simulate a 10 kW / 130 rpm, 28-poles, AFPMSM dedicated to wind energy
application (WEA). According to the simulation results, it is possible to
evaluate the performance of the AFPMSM with reasonable accuracy via the
developed analytical model.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Disc-type
machine, Permanent magnet, magnetic field, analytical method.
Adaptive Speed Observers for Sensorless Control of Induction Motors : a New
Criterion of Stability
by E. Etien, N. Bensiali, C. Chaigne, G. Champenois
Vol. 0. n. 0, pp. 23-26
Abstract
- A new criterion of stability for the study of adaptive speed observer is
presented. It proves to be a good alternative to the classical transfer function
analysis and allows to simplify the determination of the regions of stability
and to provide a power full tool for observer design.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Induction
motor drive, adaptive observer, regenerating mode, stability analysis.
Stator Faults Diagnosis
In Induction Machines
by S. Bachir, S. Tnani, G. Champenois
Vol. 0. n. 0, pp. 27-35
Abstract
- In this paper, authors proposes a new monitoring technique of inter turns
short circuit windings under fixed speed. This method is based on introduction
of sinusoidal extra-signals to input voltage delivered by power inverter. For
diagnosis, we propose a model of squirrel cage induction motors under stator
faults. This model takes into account the effects of inter turn faults resulting
in the shorting of one or more circuits of stator phase winding. Experimental
test results show the good agreement between the real faults and their
estimations.
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Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Induction
motor, Estimation technique, Modelling, Excitation system, Diagnostics.
by J. Ahola, E. Vartiainen, T. Lindh, V. Särkimäki, R. Tiainen
Vol. 0. n. 0, pp. 36-43
Abstract
- The estimation of load impedance spectrum is required in the research and
applications of electrical engineering. Some of the current applications are the
grid impedance estimation of active filters, the research of the
propagation of EMI (Electro Magnetic Interference) and power line communication.
The direct measurement of load impedance, in the frequency range in question,
requires synchronous voltage and current measurement, which can be difficult.
Compared to the direct impedance spectrum measurement, the measurement of
impedance amplitude spectrum is a simple and low-cost method since e.g. only
peak or RMS (Root-Mean-Square) value of current and voltage for each measured
frequency is required. This article presents a method and a tool based on the
method that allows one to compute the phase spectrum estimate for the impedance
amplitude spectrum. The method is based on the maximum entropy model (MEM). The
applicability of the tool is demonstrated with input impedance measurements of a
low voltage power cable and a low voltage electric motor, where both the
amplitude and the phase spectrum of input impedance were measured in the
frequency range of 100 kHz – 30 MHz.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Impedance
measurements, phase retrieval, load impedance, active filters, power line
communication, electromagnetic interference.
Analysis of non-Linear Inductors with the Use of Generalized Rayleigh Relations
by Z. Włodarski, A. Brykalski, J. Włodarska
Vol. 0. n. 0, pp. 44-48
Abstract
- Evaluation of currents in circuits containing ferromagnetic cores involves
troublesome graphical or numerical procedures. For materials with narrow
hysteresis loops satisfactory good results may be obtained by the use of
inductance determined from the analytical approximation of main magnetization
curve based on the generalized Rayleygh relations. Extension of this formula to
hysteresis loops enables further improvement of computed characteristics.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Modeling,
Magnetization Curves, Non-Linear circuits, Hysteresis.
Speed Synchronized Control of Permanent Magnet Synchronous Motors distributed
system with
field-weakening capability
by L.
Samaranayake, Y.K. Chin
Vol. 0. n. 0, pp. 49-56
Abstract
- A vast amount of attentions has been given to permanent magnet synchronous
motors (PMSMs) in a variety of automotive applications as these motors present
higher efficiency, power factor and better dynamic performance than asynchronous
motors without sacrificing reliability. It has also been shown that they can be
operated over a wide constant power speed range (CPSR) with the field weakening
capability. This paper presents a theoretical study on speed synchronized
control of the permanent magnet synchronous motors (PMSMs) in both the constant
torque and the field-weakening (or constant power) operation regions. Promising
applications of this can be found in aero dynamic, naval, material processing
etc., industries.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords:
Field-weakening, Permanent Magnet Synchronous Motor, Speed Synchronization.
A
Novel Three-Phase UPS System with a Single-Phase Resonant HF Link
by M. K. Darwish
Vol. 0. n. 0, pp. 57-65
Abstract
- This paper presents a new three-phase uninterruptible power supply (UPS)
system based on a single-phase resonant high frequency (HF) link and a
single-phase transformer. The three-phase output voltage is constructed and
regulated from a three-phase cycloconverter fed from the constant amplitude,
constant frequency link voltage. The generation of a novel switching stategy for
the three-phase cycloconverter is presented. The simulation of the proposed
system is carried out and verified with experimental results.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: UPS, PWM
converters, Resonant inverters, HF transformers.
Linear model
and H∞ Control of Shunt Active Power Filter
by T. Al Chaer, J.P. Gaubert, L. Rambault, C. Dewez
Vol. 0. n. 0, pp. 66-73
Abstract
- This paper presents a shunt active power filter which is intended for
eliminating the unwanted harmonics generated by non-linear loads in power
distribution systems. An original linear model of a three phase network with a
parallel active filter is described as a complex state space representation.
Next, the objective of this work is to synthesize a robust static feedback
controller for controlling this three phase shunt active power filter. The
synthesis of such controller is realized by using H∞ robust control based on a
Linear Matrix Inequality (LMI) approach. Theoretical analyses and a complete
simulation of the system are presented to confirm the validity of the proposed
technique.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Active
filters, Harmonics, H Control, Linear model, State space representation.
Characteristics and Comparison of Output Voltage Non-Idealities of Direct and
Indirect Matrix Converters
by M. Jussila, M. Eskola, H. Tuusa
Vol. 0. n. 0, pp. 74-82
Abstract
- This paper compares the voltage transfer characteristics of direct and
indirect matrix converter topologies. Knowledge of the real voltage transfer
capability of a converter is essential, especially in sensorless motor drives.
The comparison is based on the analysis of non-idealities caused by real
semiconductor devices and safe commutation methods. The effects of on-state
voltage losses and commutation methods are modeled with equations. The analysis
is verified in measurements and simulations. The direct matrix converter follows
the reference more accurately than the indirect matrix converter. Thus direct
topology is also found to be a more suitable converter solution for sensorless
motor drives if no compensation methods of voltage inaccuracies are used. The
results show that analysis of voltage transfer inaccuracies in direct and
indirect matrix converter topologies can be used as a basis to develop the
compensation methods needed in high performance motor drives without speed
sensors.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Matrix
converter, Output voltage non-ideality, PMSM drive.
Redundancy and basic switching rules in multilevel converters
by Ó. López, J. Doval-Gandoy, C. M. Peñalver, J. Rey, F. D. Freijedo
Vol. 0. n. 0, pp. 83-89
Abstract
- This paper studies the per-phase redundancy in three basic multilevel
topologies: diode-clamped converter, flying capacitor converter and cascaded
bull-bridge converter. Redundancy in switching states provides some flexibility
in multilevel systems and may be used to achieve some control objectives:
capacitors voltage balancing, current control of dc-sources, switches power
looses balancing, fault tolerant systems, etc. This study gives the basic
switching rules for each topology taking advantage of redundancy. The
similarities between these rules allow the design of a general switching
generator useful for these three topologies. The implementation of a switching
strategy for the achievement of certain goals consists on adding constrains to
these basic rules. The knowledge of the number of different redundant switches
states for each level facilitates this implementation. The design of controllers
in accordance with the rules proposed in this paper increase the reliability of
multilevel converters without adding new devices.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords:
Multilevel converter, per-phase redundancy, switching generator.
A new single phase single stage high frequency AC-DC converter with CPLD
controller
by S. Mekhilef, A. M. Omar, K. S. Muhammad
Vol. 0. n. 0, pp. 90-96
Abstract
- A new single phase single stage high frequency AC-DC converter with CPLD
controller is presented. The digital controller is developed using Complex
Programmable Logic Devices (CPLD). The proposed system utilizes a single-phase
AC input supply. The power switching devices in the controlled bridge are
controlled by the multiple-pulse Pulse Width Modulation (PWM) switching
technique to minimize the low order harmonics present on the AC side of the
converter. A low pass filter is incorporated in the circuit to filter out
unwanted harmonics and provide a sinusoidal AC supply current. A high frequency
transformer with 1:1 ratio is used in the design to provide galvanic isolation
for better circuit performance and protection. The optimum operation of
transformer core in four quadrant of B-H curve is also considered in the
proposed converter topology. A laboratory prototype of the converter is
developed and tested. Experimental results are compared with the simulation
results to illustrate the effectiveness of the proposed technique.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: AC-DC
converter, CPLD controller, digital controller, multiple-pulse PWM.
Frequency converter
control in single FPGA circuit
by O. Laakkonen, K. Rauma, A. Penttinen, T. Härkönen, J. Luukko, O. Pyrhönen
Vol. 0. n. 0, pp.
97-103
Abstract
- Modern frequency converters use ASIC (Application Specific Integrated Circuit)
circuits to handle fastest operations and microprocessors or DSPs (Digital
Signal Processor) for slower operations. By using FPGA (Field Programmable Gate
Array) circuits it is possible to implement a powerful microcontroller inside
the FPGA circuit and replace the combination of ASIC and microprocessor with a
single chip solution. The FPGA implementation allows more flexible modification
of the used algorithms and control methods. Single chip implementation of the
control algorithms needs efficient and modular architecture to be used in
industrial applications. A novel control electronics architecture for frequency
converters is presented in this paper. The architecture consists of a single
FPGA circuit which consists of a software processor, IP-blocks (Intellectual
Property) and an internal bus connecting the IP-blocks. A modern small DC-link
capacitor frequency converter is used as a test case. The whole control
structure and measurements with a prototype are presented.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Field
programmable gate array, RTOS, Frequency converter, single chip, control system,
bus architecture.
Modeling Ferrite
Core Losses in Power Electronics
by A. Van den Bossche, V. C. Valchev
Vol. 0. n. 0, pp.
104-111
Abstract
- The paper summarizes the research of the authors dedicated to ferrite core
losses under conditions specific for Power Electronics. Models named NSE and
DNSE and models of the losses with DC bias are fully presented and validated.
The models are checked with measurements on two different ferrite grades, with
square voltage waves with a large variation in duty ratio. The model NSE is
extended and improved to DNSE (Double Natural Steinmetz Extension). The
dependency of the core looses in half bridge and full bridge configurations of
the waveforms are well modeled using a hysteresis part and a part dependent on
dB/dt. A model for ferrite loss under DC bias was proposed It is found the
relative sensitivity to DC bias is mainly present in the low frequency component
of the losses and that the higher frequency losses show an almost quadratic loss
dependency on the peak induction.
©
Copyright 2006 Praise Worthy Prize - All rights reserved
Keywords: Ferrite
core losses, Modeling and measuring core losses.
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