Uninterruptible Power Supplies and Active Filters By Ali Emadi and Abdolhosein Nasiri And Stoyan B Bekiarov

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Uninterruptible Power Supplies and Active Filters By Ali Emadi and Abdolhosein Nasiri And Stoyan B Bekiarov

Preface

In recent years, with the increase of nonlinear loads drawing nonsinusoidal
currents, power quality distortion has become a serious problem in electrical
power systems. Active filters have been known as an effective tool for harmonic
mitigation as well as reactive power compensation, load balancing,
voltage regulation, and voltage flicker compensation. On the other hand,
uninterruptible power supply (UPS) systems provide uninterrupted, reliable,
and high-quality power for vital loads. They, in fact, protect sensitive
loads against power outages as well as overvoltage and undervoltage
conditions. UPS systems also suppress line transients and harmonic
disturbances. Applications of UPS systems include medical facilities, lifesupporting
systems, data storage and computer systems, emergency equipment,
telecommunications, industrial processing, and on-line management
systems. Generally, an ideal UPS should be able to deliver uninterrupted
power and, simultaneously, provide the necessary power conditioning for
the particular power application.
This book describes harmonic-producing loads, effects of harmonics, and
harmonic mitigation methods using active filters. Different topologies of
active filters and UPS systems, their applications, configurations, control
methods, modeling and analysis, and stability issues are also comprehensively
discussed.
Recent advancements in the area of power electronics have resulted in a
great variety of new topologies and control strategies for active filters and
UPS systems. The research has been focused mainly on improving the
performance and expanding application areas of these systems. The issue of
cost reduction has been attracting the attention of researchers. Reducing the
number of switches allows one of the most significant cost reductions. Adifferent
technique is replacing controlled switches such as IGBTs, MOSFETs,
and thyristors with diodes. Another approach for reducing cost is to develop
topologies that employ switches with lower reverse voltage stresses and
lower current ratings. This book addresses these new trends in detail.

Contents

1. Uninterruptible Power Supplies …………………………………………………………….1
1.1 Classification ………………………………………………………………………………..3
1.1.1 Static UPS …………………………………………………………………………3
1.1.1.1 On-Line UPS ……………………………………………………….4
1.1.1.1.1 Normal Mode of Operation ………………4
1.1.1.1.2 Stored-Energy Mode of Operation ……..5
1.1.1.1.3 Bypass Mode of Operation ………………..5
1.1.1.2 Off-Line UPS ……………………………………………………….6
1.1.1.2.1 Normal Mode of Operation ………………7
1.1.1.2.2 Stored-Energy Mode of Operation ……..7
1.1.1.3 Line-Interactive UPS …………………………………………..8
1.1.1.3.1 Normal Mode of Operation …………….10
1.1.1.3.2 Stored-Energy Mode of Operation ……11
1.1.2 Rotary UPS ……………………………………………………………………..12
1.1.3 Hybrid Static/Rotary UPS ………………………………………………13
1.2 Batteries for UPS Applications ……………………………………………………14
1.2.1 History …………………………………………………………………………….14
1.2.2 Valve-Regulated Lead–Acid Batteries ………………………………14
1.2.3 UPS Battery Features ……………………………………………………….15
1.2.4 Problems …………………………………………………………………………15
1.2.5 Charging Strategies …………………………………………………………17
1.2.6 Failure Category ………………………………………………………………18
1.2.7 Monitoring ……………………………………………………………………..18
1.3 Flywheels for UPS Applications ………………………………………………….19
1.3.1 Fundamentals ………………………………………………………………….19
1.3.2 Classification ……………………………………………………………………22
1.3.2.1 Low-Speed Flywheel Systems …………………………..22
1.3.2.2 High-Speed Flywheel Systems …………………………..22
1.3.3 UPS Applications of Flywheels ……………………………………….23
1.4 Comparative Analysis of Flywheels and Electrochemical
Batteries ……………………………………………………………………………………..26
1.5 Applications of UPS Systems ……………………………………………………..27
1.5.1 Distributed Approach ……………………………………………………..28
1.5.2 Centralized Approach ……………………………………………………..29
1.6 Parallel Operation ……………………………………………………………………….30
1.6.1 Configurations ………………………………………………………………..31
1.6.2 Fundamental Principles of Parallel Operation ………………..35
1.6.3 Control Strategies in UPS Parallel Operation ………………….36
1.6.3.1 Concentrated Control ……………………………………….36
1.6.3.2 Master–Slave Control ……………………………………….36
1.6.3.3 Distributed Control …………………………………………..37
1.6.3.4 Wireless Independent Control …………………………..37
1.7 Performance Evaluation of UPS Systems ……………………………………38
1.8 Power Factor Correction in UPS Systems ……………………………………39
1.8.1 Passive PFC Techniques ………………………………………………….40
1.8.2 Active PFC Techniques ……………………………………………………40
1.9 Control of UPS Systems ………………………………………………………………43
1.9.1 Single-Voltage Control Loop Strategy …………………………….43
1.9.2 Multiple Control Loops ……………………………………………………44
1.9.2.1 Hysteresis Current Control ………………………………..45
1.9.2.2 SPWM Current Control ……………………………………..45
1.9.2.3 Predictive Current Control ………………………………..46
1.10 Converters for UPS Systems ……………………………………………………….46
1.10.1 Rectifiers …………………………………………………………………………47
1.10.1.1 Uncontrolled Rectifiers ……………………………………..47
1.10.1.2 Controlled Rectifiers …………………………………………48
1.10.2 Inverters …………………………………………………………………………..52
1.10.2.1 Basic Principles of Operation …………………………….52
1.10.2.2 Pulse Width-Modulated Switching Scheme ……..53
1.11 Battery Charger/Discharger ……………………………………………………….56
References …………………………………………………………………………………………..58
2. Active Filters ……………………………………………………………………………………….63
2.1 Harmonic Definition ………………………………………………………………….65
2.2 Harmonic Sources in Electrical Systems ……………………………………..66
2.2.1 Fluorescent Lamps …………………………………………………………..66
2.2.2 Switching Power Supplies ………………………………………………67
2.2.3 Electric Furnace ………………………………………………………………67
2.2.4 High-Voltage DC Systems ………………………………………………67
2.2.5 Adjustable Speed Drives ………………………………………………….68
2.2.6 AC/DC Converters/Inverters …………………………………………69
2.2.7 Other Harmonic-Producing Loads ………………………………….69
2.3 Effects of Harmonics ………………………………………………………………….70
2.3.1 Disturbance to Electric and Electronic Devices ………………..70
2.3.2 Higher Losses ………………………………………………………………….70
2.3.3 Extra Neutral Current ……………………………………………………..71
2.3.4 Improper Working of Metering Devices …………………………71
2.3.5 De-Rating of Distribution Equipment …………………………….72
2.3.6 Resonance Problem …………………………………………………………72
2.4 Harmonic Mitigation Methods ……………………………………………………72
2.4.1 Harmonic Production Prevention ……………………………………73
2.4.3 Active Filters ……………………………………………………………………73
2.4.3.1 Applications ……………………………………………………..75
2.4.3.1.1 Adjustable Speed Drives ………………….76
2.4.3.1.2 DC Capacitor Cancellation ………………76
2.4.3.1.3 HVDC Systems ………………………………..76
2.4.3.1.4 High-Power Locomotives ………………..77
2.4.3.1.5 Remote Generations …………………………77
2.4.3.1.6 Commercial Loads …………………………..77
2.4.3.1.7 Other Applications …………………………..77
2.5 Classification of Active Filters ……………………………………………………78
2.5.1 Current Source Active Filters …………………………………………..78
2.5.2 Voltage Source Active Filters …………………………………………..80
2.5.3 Shunt Active Filters …………………………………………………………82
2.5.4 Series Active Filters …………………………………………………………84
2.5.5 Hybrid Active Filters ……………………………………………………….86
2.5.6 Unified Power Quality Conditioners ………………………………88
2.6 Active Filters for DC/DC Converters …………………………………………90
2.6.1 Active EMI Filters …………………………………………………………..90
2.6.2 Active Ripple Filters ……………………………………………………….92
2.6.2.1 Configurations ………………………………………………….92
2.7 Modeling and Analysis ………………………………………………………………95
2.7.1 Switching Function Model ………………………………………………95
2.7.2 DC Model ……………………………………………………………………….96
2.7.3 Analytical Model …………………………………………………………….97
2.7.3.1 Basic Equations ………………………………………………….97
2.7.3.2 Time Delay for Extraction of Reference
Current ………………………………………………………………99
2.7.3.3 Time Delay of Response for Current ………………..100
2.7.3.4 Control of DC Bus Voltage ………………………………100
2.8 Control Strategies ……………………………………………………………………..100
2.8.1 Reference Current/Voltage Detection Method ………………100
2.8.1.1 Time Domain Analysis ……………………………………101
2.8.1.1.1 High-Pass Filter Method ………………..101
2.8.1.1.2 Low-Pass Filter Method ………………….101
2.8.1.1.3 Instantaneous Reactive Power
Algorithm ……………………………………….101
2.8.1.1.4 Modified Instantaneous Reactive
Power Algorithm …………………………..103
2.8.1.1.5 Synchronous Reference Frame
Method…………………………………………….103
2.8.1.1.6 Modified Synchronous Reference
Frame Method ………………………………..104
2.8.1.1.7 Unity Power Factor Method …………..105
2.8.1.1.8 Sliding Mode Control ……………………..105
2.8.1.1.9 Passivity-Based Control ………………….105
2.8.1.1.10 PI Controller ………………………………….105
© 2005 by CRC Press LLC
2.8.1.1.11 Flux-Based Controller ……………………106
2.8.1.1.12 Sine Multiplication Method …………..106
2.8.1.2 Frequency Domain Analysis …………………………..106
2.8.2 Derivation of Switching Scheme ……………………………………107
2.9 Stability Assessment ………………………………………………………………….107
2.10 Conclusion ………………………………………………………………………………..110
References …………………………………………………………………………………………111
3. Unified Power Quality Conditioners ………………………………………………….117
3.1 Series–Parallel Configuration……………………………………………………..119
3.2 Current Control …………………………………………………………………………120
3.3 Voltage Control…………………………………………………………………………..123
3.4 Power Flow and Characteristic Power ……………………………………….126
References …………………………………………………………………………………………..131
4. Reduced-Parts Uninterruptible Power Supplies ………………………………..133
4.1 Concept of Reduced-Parts Converters Applied to
Single-Phase On-Line UPS Systems …………………………………………..134
4.2 New On-Line UPS Systems Based on Half-Bridge
Converters ………………………………………………………………………………..137
4.2.1 Reduced-Parts Single-Phase On-Line UPS System …………137
4.2.1.1 Description of the Proposed UPS System ……….137
4.2.1.2 Basic Principles of Operation …………………………..138
4.2.1.3 Design of a 1 kVA UPS System ……………………….144
4.2.1.4 Simulation Results …………………………………………..149
4.2.2 Single-Phase to Two-Phase On-Line UPS System …………..151
4.2.2.1 Basic Principles of Operation …………………………..151
4.2.2.2 Simulation Results …………………………………………..156
4.2.3 Single-Phase to Three-Phase On-Line UPS System ……….157
4.2.3.1 Basic Principles of Operation …………………………..157
4.2.3.2 Simulation Results …………………………………………..158
4.2.4 Performance Analyses and Cost Evaluation ………………….160
4.2.5 Conclusions ……………………………………………………………………163
4.3 New On-Line UPS Systems Based on a Novel
AC/DC Rectifier ……………………………………………………………………….164
4.3.1 Reduced-Parts Single-Phase On-Line UPS System …………164
4.3.1.1 System Description …………………………………………164
4.3.1.2 Basic Principles of Operation …………………………..165
4.3.1.3 Simulation Results …………………………………………..170
4.3.2 Single-Phase to Two-Phase On-Line UPS System …………..175
4.3.2.1 Basic Principles of Operation …………………………..175
4.3.2.2 Simulation Results …………………………………………..178
4.3.3 Single-Phase to Three-Phase On-Line UPS System ……….179
4.3.3.1 Basic Principles of Operation …………………………..180
4.3.3.2 Simulation Results …………………………………………..180
© 2005 by CRC Press LLC
4.3.4 Performance Analyses and Cost Evaluation ………………….180
4.3.5 Conclusions ……………………………………………………………………181
4.4 New Three-Phase On-Line UPS System with Reduced
Number of Switches ………………………………………………………………….183
4.4.1 System Description ……………………………………………………….185
4.4.2 Basic Principles of Operation …………………………………………186
4.4.3 Simulation Results …………………………………………………………188
4.4.4 Performance Analyses and Cost Evaluation ………………….194
4.4.5 Conclusions ……………………………………………………………………195
4.5 New Single-Phase to Three-Phase Hybrid
Line-Interactive/On-Line UPS System ……………………………………..195
4.5.1 System Description ……………………………………………………….196
4.5.2 Basic Principles of Operation …………………………………………197
4.5.3 Simulation Results …………………………………………………………200
4.5.4 Performance Analyses and Cost Evaluation ………………….203
4.5.5 Conclusions ……………………………………………………………………206
References …………………………………………………………………………………………209
5. Reduced-Parts Active Filters ………………………………………………………………211
5.1 Reduced-Parts Single-Phase and Three-Phase Active Filters ……212
5.2 Reduced-Parts Single-Phase Unified Power Quality
Conditioners …………………………………………………………………………….212
5.2.1 Single-Phase UPQC with Two Full-Bridge Converters ….213
5.2.1.1 Voltage Control ………………………………………………..215
5.2.1.2 Current Control ………………………………………………217
5.2.2 Single-Phase UPQC with Two Half-Bridge Converters ….218
5.2.3 Single-Phase UPQC with Three Legs …………………………….219
5.3 Reduced-Parts Single-Phase Series–Parallel Configurations ……..222
5.3.1 Single-Phase Configuration Based on Two Full-Bridge
Bidirectional Converters ………………………………………………..227
5.3.1.1 Bypass Mode ……………………………………………………227
5.3.1.1.1 Voltage Control ………………………………228
5.3.1.1.2 Current Control ………………………………229
5.3.1.2 Backup Mode ………………………………………………….229
5.3.2 Single-Phase Configuration Based on Two Half-Bridge
Bidirectional Converters ………………………………………………..230
5.3.3 Single-Phase Configuration Based on the Three-Leg
Topology ……………………………………………………………………….231
5.4 Reduced-Parts Three-Phase Series–Parallel Configurations ……..233
5.4.1 Bypass Mode ………………………………………………………………….234
5.4.1.1 Voltage Control ………………………………………………..235
5.4.1.2 Current Control ………………………………………………237
5.4.2 Backup Mode ………………………………………………………………..241
References …………………………………………………………………………………………242
6. Modeling, Analysis, and Digital Control…………………………………………….245
6.1 Systems Modeling Using the Generalized State Space
Averaging Method ……………………………………………………………………246
6.1.1 Fundamental Equations ………………………………………………..246
6.1.2 Generalized State Space Averaging Method ………………….249
6.1.3 Modeling of Single-Phase Active Filter System …………….249
6.1.4 Simulation Results …………………………………………………………251
6.1.5 Other Examples …………………………………………………………….253
6.2 Digital Control …………………………………………………………………………..259
6.2.1 Deadbeat Control Technique for a Single-Phase
Shunt Active Filter …………………………………………………………260
6.2.2 Deadbeat Control Technique for Series–Parallel
UPS System ……………………………………………………………………261
6.2.2.1 System Equations …………………………………………….261
6.2.2.2 Series Converter ………………………………………………263
6.2.2.3 Parallel Converter …………………………………………..264
6.2.2.4 Control of a Parallel Converter in
Backup Mode ……………………………………………………265
6.2.3 Digital Controller Implementation ………………………………..266
6.2.4 Analysis of Controller ……………………………………………………267
References …………………………………………………………………………………………271