Direct Power and Torque Control of AC/DC/AC Converter-Fed Induction Motor Drives

160 Pages·2006·7.53 MB·English

POLITECHNIKA
WARSZAWSKA
WARSAW UNIVERSITY OF TECHNOLOGY
Faculty of Electrical Engineering

ROZPRAWA DOKTORSKA
Ph.D. Thesis

Marek Jasiński, M. Sc.

Direct Power and Torque Control
of AC/DC/AC Converter-Fed Induction Motor Drives

WARSZAWA
2005

z
Warsaw University of Technology

Faculty of Electrical Engineering
Institute of Control and Industrial Electronics

Ph.D. Thesis

Marek Jasiński, M. Sc.

Direct Power and Torque Control
of AC/DC/AC Converter-Fed Induction
Motor Drives

Thesis supervisor
Prof. Dr Sc. Marian P. Kaźmierkowski

Warsaw – Poland, 2005
Acknowledgements
The work presented in the thesis was carried out during author’s Ph.D. studies at
the Institute of Control and Industrial Electronic at the Warsaw University of
Technology, Faculty of Electrical Engineering and grant of the Ministry of Science
and Information Society Technologies. Some parts of the work were realized in
cooperation with foreign Universities and scientific organization:

(cid:190) University of Aalborg at Institute of Energy Technology, Denmark (Prof.
Frede Blaabjerg)
(cid:190) Nordic Network for Multi Disciplinary Optimised Electric Drives,
Denmark (Prof. Ewen Ritchie)
(cid:190) Politecnico di Bari (Prof. Marco Liserre)

First of all, I would like to express gratitude Prof. Marian P. Kaźmierkowski for the
continuous support and help. His precious advice and numerous discussions
enhanced my knowledge and scientific inspiration.
I am grateful to Prof. Andrzej Sikorski from the Białystok Technical University
and Prof. Roman Barlik from the Warsaw University of Technology for their interest
in this work and holding the post of referee.
Furthermore, I thank my colleagues from the Intelligent Control Group in Power
Electronics for their support and friendly atmosphere. Especially, to Dr. Mariusz
Malinowski, Dr Marcin Żelechowski, Dariusz Świerczyński M.Sc., and Patrycjusz
Antoniewicz M.Sc.
Finally, I am very grateful for my wife Agnieszka, daughter Maja, and son Mateusz
for their love, patience and faith. I would also like to thank to my whole family,
particularly my parents for their care over the years.
Contents

Page
1. Introduction............................................................................................................1
1.1. AC/DC/AC Converters.....................................................................................1
2. Voltage Source Converters – VSC......................................................................11
2.1. Introduction.....................................................................................................11
2.2. Space Vector Based Description of VSC........................................................11
2.3. Operation of Voltage Source Converter – VSC..............................................12
2.4. Mathematical Model of the VSI - Fed Induction Motor (IM)........................14
2.4.1. IM Mathematical Model in Rotating Coordinate System with Arbitrary
Angular Speed....................................................................................................16
2.4.2. IM Model in Stationary αβ Coordinates................................................16
2.4.3. IM Model in Synchronous Rotating dq Coordinates - RFOC................18
2.4.4. IM Model in Synchronous Rotating xy Coordinates - SFOC.................19
2.5. Operation of Voltage Source Rectifier – VSR................................................22
2.5.1. Operation Limits of the Voltage Source Rectifier – VSR.......................24
2.5.2. VSR Model in Three-Phase ABC Coordinates........................................27
2.5.3. VSR Model in Stationary αβ Coordinates...............................................29
2.5.4. VSR Model in Synchronously Rotating xy Coordinates.........................30
2.6. Summary.........................................................................................................32
3. Vector Control Methods of AC/DC/AC Converter-Fed Induction Motor
Drives – A Review....................................................................................................33
3.1. Introduction.....................................................................................................33
3.2. Control Methods of VSI-Fed Induction Motor...............................................34
3.2.1. Field Oriented Control – FOC.................................................................34
3.2.2. Direct Torque Control – DTC..................................................................38
3.2.3. Direct Torque Control with Space Vector Modulation – DTC-SVM......43
3.3. Control Methods of VSR................................................................................45
3.3.1. Virtual Flux Oriented Control – V-FOC..................................................45
3.3.1.1. Line Current Controllers.......................................................................47
3.3.2. VF based Direct Power Control – VF-DPC.............................................52
3.3.3. Direct Power Control with Space Vector Modulator – DPC-SVM.........57
3.3.3.1. Line Power Controllers.........................................................................57
3.3.3.2. DC-link Voltage Controller..................................................................65
3.4. Conclusion......................................................................................................68
4. Direct Power and Torque Control with Space Vector Modulation – DPTC-
SVM...........................................................................................................................69
4.1. Introduction.....................................................................................................69
4.2. Model of the AC/DC/AC Converter-Fed Induction Motor Drive with Active
power feedforward.................................................................................................69
4.2.1. Analysis of the Power Response Time Constant.....................................71
Contents

4.2.2. Energy of the DC-link Capacitor.............................................................71
4.2.2.1. Transfer Function of the AC/DC/AC Converter-Fed IM Drive with DC-
link Voltage Feedback only – PF ....................................................................74
0
4.2.2.2. Transfer Function of the AC/DC/AC Converter-Fed IM Drive with DC-
link Voltage Feedback and Active Power Feedforward Calculated Based on
Mechanical Speed, Commanded Torque, and Power Losses – PF ................75
Ω
4.2.2.3. Transfer Function of the AC/DC/AC converter-Fed IM Drive with DC-
link Voltage Feedback and Active Power Feedforward Calculated From
Commanded Stator Voltage and Actual Stator Current - PF .........................75
UI
4.3. Simulation Study.............................................................................................76
4.3.1. Steady State Performances.......................................................................76
4.3.2. AC/DC/AC Converter-Fed IM Drive Operated with Closed Torque
Control Loop......................................................................................................79
4.3.3. AC/DC/AC Converter-Fed IM Drive Operated with Closed Speed
Control Loop......................................................................................................83
4.4. Conclusion......................................................................................................91
5. Passive Components Design – DC-link Capacitor............................................93
5.1. Introduction.....................................................................................................93
5.2. Selection of Filter Components.......................................................................93
5.2.1. Nominal Voltage of the DC-link Capacitor.............................................93
5.2.2. Ripple Current Consideration..................................................................95
5.2.3. Ratings of the DC-link Capacitor.............................................................97
5.2.3.1. Consideration of Operation with Reduced DC-link Capacitor...........102
5.3. Conclusion....................................................................................................104
6. Simulation an Experimental Results................................................................105
6.1. Introduction...................................................................................................105
6.2. Steady States Operation................................................................................105
6.3. Active and Reactive Power Controllers........................................................108
6.4. AC/DC/AC Converter-Fed IM Drive Operated with Closed Torque Control
Loop.....................................................................................................................109
6.5. AC/DC/AC Converter-Fed IM Drive Operated with Closed Speed Control
Loop.....................................................................................................................112
6.6. Conclusion....................................................................................................122
7. Summary and Conclusion.................................................................................123
References...............................................................................................................126
Symbols Employed.................................................................................................136
Main Symbols......................................................................................................136
Rectangular Coordinates System.........................................................................139
Indices..................................................................................................................140
Mathematical symbols.........................................................................................140
Abbreviations.......................................................................................................140
A. Appendices.........................................................................................................141
A.1. Space vector in coordinate systems..............................................................141
A.1.1. Fixed System of Coordinates - αβ.......................................................141
A.1.2. Rotating System of Coordinates............................................................141
A.1.3. Model of the Induction Motor in Natural ABC Coordinates................143
A.2. Coordinate Transformation..........................................................................145
A.2.1. Three-Phase to Two-Phase Conversion (ABC/αβ).............................145
A.2.2. Two-Phase to Three-Phase Conversion (αβ/ABC).............................145
II
Contents

A.2.3. Rectangular to Rectangular Coordinate Conversion (αβ/xy) and
(xy/αβ)............................................................................................................145
A.3. Apparent, Active, and Reactive Power........................................................146
A.3.1. Complex Representation of the Power..................................................146
A.4. Simulation Model and Laboratory setup......................................................148
A.4.1. Saber Model..........................................................................................148
A.4.2. Matlab Simulink Power Toolbox Model...............................................149
A.4.3. Laboratory setup....................................................................................150
A.4.4. List of Equipment..................................................................................154

III
Chapter 1
1. Introduction
1.1. AC/DC/AC Converters
AC/DC/AC converters are part of a group of AC/AC converters. Generally
AC/AC converters take power from one AC system and deliver it to another with
waveforms of different amplitude, frequency and phase. Those systems can be single
phase or three phase. The major application of voltage source AC/AC converters are
adjustable speed drives – ASD [15], [63], [65], [140].
The most used voltage source AC/AC converters utilize a DC-link between the
two AC systems as presented in Fig.1. 1a,b, and provide direct power conversion as
in Fig.1. 1c.
3~ 3~ 3~

Fig.1. 1. Chosen AC/AC converters for adjustable speed drives – ASD; a) with diode rectifier, b)
with voltage source rectifier – VSR, c) direct converter (matrix or cycloconverter) [67].
Where VSI – voltage source inverter, IM – induction motor, PWM – pulse width modulation [47]

In AC/DC/AC converter the input AC power is rectified into a DC waveform and
then is inverted into the output AC waveform. A capacitor (and/or inductor) in DC-
1. Introduction

link stores the instantaneous difference between the input and output powers. AC/DC
and DC/AC converters can be controlled independently.
The matrix converter (cycloconverter) avoids the intermediate DC-link by
converting the input AC waveforms directly into the desired output waveforms
(Fig.1. 1c) [21], [58].
Although a three-phase induction motor was introduced more than one hundred
years ago, the research and development – R&D in this area appears to be never-
stopping. Moreover, the new power semiconductor devices and power electronics
converters are developing in last twenty/thirty years even faster. The introduction of
IGBTs in the mid of 80s was an important milestone in the history of power
semiconductor devices. Similarly, digital signal processors – DSP developed in 90s
were a milestone in implementation and applications of advanced control strategies
for power converter drives [1], [15], [25], [27], [70], [98], [104], [131], [151]. As a
result ASD systems are widely used in applications such as pumps, fans, paper and
textile mills, elevators, electric vehicles and underground traction, home appliances,
wind generation systems, servo drives and robotics, computer peripherals, steel and
cement mills, ship propulsion, etc. [15]. Nowadays, most of ASD consist of
uncontrollable diode rectifier (Fig.1. 1a) or a line commutated phase controlled
thyristor bridge. Although both these converters offer a high reliability and simple
structure, they also have serious disadvantages. The DC-link voltage of the diode
rectifier is uncontrolled and pulsating; therefore bulky DC-link capacitor and usually
DC-choke are needed. Moreover, the power flow is unidirectional and the input
current (line current) is strongly distorted [36], [42], [43], [106], [135]. The last
drawback is very important because of standard regulation such as IEEE Std 519-
1992 in the USA and IEC 61000-3-2/IEC 61000-3-4 in UE. Even small power ASD
can cause a total harmonics distortion – THD problem for a supply line when a large
number of nonlinear loads are connected to one point of common coupling – PCC
[8], [54]. Tab. 1. 1 lists the harmonic current limits based on the size of a load with
respect to the size of line power supply. The ratio of I / I is the ratio of short-
SC Lm
circuit current I available at the PCC, to the maximum fundamental load current
SC
I . It is recommended that the load current I , should be calculated as the average
Lm Lm
current of the maximum demand over a year [54].

2
1. Introduction

Tab. 1. 1. Current Distortion Limits for General Distribution Systems (up to 69 kV) Where:
TDD – is the total demand distortion (root-sum-square – RSS) [54]

The recommended voltage distortion limits, usually expressed by THD index, is
shown in Tab. 1. 2. Where, THD – is total (root-sum-square – RSS) harmonic
voltage in percent of nominal fundamental frequency voltage. This term has come
into common usage to define either voltage or current distortion factor – DF (Eq.(1.
1)). The DF: is the ratio of the RSS of the harmonic content to the root-mean-square
– RMS value of the fundamental quantity, expressed as a percent of the fundamental
[54]:

50
∑U2
L(h)
THD = h=2 100% (1. 1)
U2
L(1)

Tab. 1. 2. Voltage distortion limits [54]

Some types of electronic receiver can be affected by transmission of AC supply
harmonics through the equipment power supply or by electromagnetic coupling of
harmonics into equipment components (electromagnetic interference – EMI
problem). Computers and associated equipment such as programmable controllers
frequently require AC sources that have no more distortion than a 5% THD, with the
largest single harmonic being no more than 3% of the fundamental. Higher levels of
harmonics result in erratic, sometimes subtle malfunctions of the equipment that can,
3
1. Introduction

in some cases, have serious consequences [108]. Also, instruments can be affected
similarly. Perhaps the most serious of these are malfunctions in medical instruments.
Consequently, many medical instruments are provided with special power electronics
devices (line-conditioners). Here is a wide application field, especially, for
AC/DC/AC converters, such as uninterruptible power supplies – UPS systems. Less
dramatic interference effects of harmonics can be observed in audio and video
devices [54].
Therefore, a lot of methods for elimination of harmonics distortion in the power
system are developed and implemented [100], [123]. Moreover, several blackouts in
recent years (USA and Canada (New York, Detroit, Toronto) in 08.2003, Russia
(Moscow) in 05.2005, USA (Los Angeles) 09.2005), and high prices of the oil shows
that the idea of “clean power” is more and more up-to-date.
Harmonics reduction methods can be divided into two main groups (Fig.1. 2):
a) passive filters and active filters – harmonics reduction of the already
installed nonlinear loads,
b) multi-pulse rectifiers and VSR (active rectifiers) – power-grid friendly
converters (with limited THD) [8], [73].

Fig.1. 2. Chosen harmonics reduction techniques; where CSR – is current source rectifier

Furthermore, the energy saving is important because, VSR assures regenerating
braking with energy saving capability [71] as well as after minor modification active
filtering function can be implemented [2], [3], [24], [154], [166].
Typical application of the VSR is like in Fig.1. 1b. Thanks to, systematical cost
reduction of the IGBTs and DSPs there have appeared on the market serially
produced VSR from few kVA up to MVA range. An individual VSR can provide the
4