Abstract ii
R´esum´e iii
Overzicht v
Acknowledgements vi
Contents viii
Acronyms xv
List of Figures xxi
List of Tables xxx
0 Introduction 2
0.1 Background . . . . 2
0.1.1 Global climate challenge . . . . 2
0.1.2 Evolution of wind energy sector . . . . 2
0.1.3 POWER Project . . . . 5
0.1.4 Evolution of electrical-vehicle sector . . . . 6
0.1.5 DeMoTest-EV Project . . . . 7
0.2 Motivation . . . . 9
0.2.1 Fault detection and isolation, with focus on DFIGs in WECS context . . . . . 9
0.2.2 NVH issues on SRMs with focus on EV applications . . . . 10
0.3 Structure and contributions of the thesis . . . . 10
0.3.1 Fault-tolerant DFIG drives for wind energy conversion systems . . . . 11
0.3.2 NVH aspects of electrical drives for EVs . . . . 11
I Fault-tolerant DFIG drives for wind energy conversion systems 13 1 Principles of wind energy conversion 14 1.1 Introduction . . . . 14
1.2 Characterization and modelling of the wind . . . . 15
1.2.1 Distribution of wind power potential around the world . . . . 15
1.2.2 Average and turbulent components of the wind speed . . . . 15
1.2.3 Wind-speed distribution . . . . 16
1.2.4 Wind profile along the altitude . . . . 17
1.2.5 Wind-turbulence model . . . . 18
1.3 Mechanical-energy extraction . . . . 18 viii
1.3.1 Principle and modelling of wind-power extraction . . . . 18
1.3.1.1 Equivalent wind speed and wind turbulence . . . . 18
1.3.1.2 Blade-element model . . . . 19
1.3.1.3 Actuator-disc model . . . . 21
1.3.2 Wind-power-extraction control . . . . 23
1.3.2.1 Fixed-speed wind turbines . . . . 23
1.3.2.2 Variable-speed wind turbines . . . . 23
1.4 Principal wind-turbine-drive configurations . . . . 25
1.4.1 Induction generator drives . . . . 25
1.4.1.1 Squirrel-cage induction generators (SCIGs) . . . . 25
1.4.1.2 Wound-rotor induction generators (WRIGs) with rotor-resistance vari- ation . . . . 26
1.4.1.3 Doubly-fed induction generators (DFIGs) . . . . 27
1.4.2 Synchronous-generator drives . . . . 28
1.4.2.1 Wound-rotor synchronous generators (WRSGs) . . . . 28
1.4.2.2 Permanent-magnet synchronous generators (PMSGs) . . . . 29
1.5 Summary . . . . 29
2 DFIG wind generator, power converter and grid connection – modelling and con- trol 31 2.1 Introduction . . . . 31
2.2 Doubly-fed induction generator (DFIG) . . . . 32
2.2.1 DFIG model . . . . 32
2.2.1.1 Equivalent circuit and hypotheses . . . . 32
2.2.1.2 Direct, inverse, homopolar components and Fortescue transformation 33 2.2.1.3 Equations of the DFIG . . . . 34
2.2.2 DFIG control . . . . 42
2.2.2.1 Vector control . . . . 42
2.2.2.2 Other control strategies for DFIGs . . . . 46
2.3 Power converter and acquisition systems . . . . 48
2.4 Grid connection . . . . 49
2.4.1 Grid connection requirements . . . . 49
2.4.2 Grid filter design . . . . 49
2.4.2.1 Grid configuration choice . . . . 49
2.4.2.2 Design of the LCL grid filter . . . . 51
2.4.3 Hypotheses and reference frame related to the control of the grid-side converter 52 2.4.4 DC-link voltage dynamics and power balance . . . . 53
2.4.5 Control of the grid-side converter . . . . 53
2.4.5.1 Detection of the phase of the grid voltage . . . . 53
2.4.5.2 Grid-side converter start-up procedure . . . . 54
2.4.5.3 Grid-side converter control after synchronization . . . . 54
2.5 Practical realization of the 3 kW DFIG test bench . . . . 57
2.5.1 Presentation of the test bench . . . . 57
2.5.2 Implementation of the control and emulation of the turbine . . . . 59
2.6 Summary . . . . 61
3 Theoretical background on reliability management and fault detection and isola- tion 63 3.1 Introduction . . . . 63
3.2 Reliability models . . . . 64
3.2.1 The bathtub curve . . . . 64
3.2.2 Basic terminology of reliability . . . . 65
3.2.3 Principal failure distributions . . . . 66
3.2.3.1 Exponential distribution . . . . 66
3.2.3.2 Truncated normal and lognormal distributions . . . . 67
3.2.3.3 Weibull distribution . . . . 67
3.3 Ways to improve reliability . . . . 68
3.3.1 Fault prevention . . . . 69
3.3.2 Fault removal . . . . 69
3.3.3 Fault forecasting . . . . 69
3.3.4 Fault tolerance . . . . 69
3.4 Overview of fault detection and isolation (FDI) techniques . . . . 70
3.4.1 Process-history-based FDI algorithms . . . . 71
3.4.1.1 Quantitative methods . . . . 72
3.4.1.2 Qualitative methods . . . . 72
3.4.1.3 General advantages and drawbacks of process-history-based methods 72 3.4.2 Model-based FDI . . . . 72
3.4.2.1 Quantitative methods . . . . 72
3.4.2.2 Qualitative methods . . . . 73
3.4.2.3 General advantages and drawbacks of model-based methods . . . . . 73
3.4.3 Combined FDI algorithms . . . . 73
3.5 Decision functions for quantitative model-based FDI . . . . 73
3.5.1 Basic tools: incidence table and log-likelihood ratio . . . . 73
3.5.2 Elementary decision algorithms . . . . 75
3.5.3 CUSUM algorithm . . . . 75
3.5.3.1 Fault detection . . . . 75
3.5.3.2 Fault isolation . . . . 76
3.5.4 GLR algorithm . . . . 77
3.5.4.1 Fault detection . . . . 77
3.5.4.2 Fault isolation . . . . 77
3.6 Summary . . . . 78
4 Causes of failures in WTs and potential faults in DFIG drives 79 4.1 Introduction . . . . 79
4.2 Failure occurrence and costs in wind turbines . . . . 79
4.2.1 Discussion on failure rates . . . . 80
4.2.2 Consideration of the downtime relative to each failure . . . . 83
4.3 Potential faults in DFIG drives . . . . 84
4.3.1 Generator faults . . . . 84
4.3.1.1 Mechanical faults . . . . 84
4.3.1.2 Electrical faults . . . . 85
4.3.2 Power-switch faults . . . . 86
4.3.3 DC-link-capacitor faults . . . . 86
4.3.4 Sensor faults . . . . 87
4.3.4.1 General sensor-fault types . . . . 87
4.3.4.2 Current-sensor faults . . . . 88
4.3.4.3 Voltage-sensor faults . . . . 88
4.3.4.4 Position-sensor faults . . . . 88
4.3.4.5 Temperature-sensor fault . . . . 89
4.4 Summary . . . . 89
5 Fault-tolerant DFIG drives for WECS 90 5.1 Introduction . . . . 90
5.2 Fault-tolerant configurations . . . . 91
5.2.1 Fault-tolerant generator . . . . 91
5.2.2 Fault-tolerant inverter . . . . 91
5.2.3 Fault-tolerant DC-bus . . . . 92
5.2.4 Fault-tolerant measurement system . . . . 93
5.2.4.1 Position and speed measurement . . . . 93
5.2.4.2 Current measurement . . . . 93
5.2.4.3 Voltage measurement . . . . 94
5.3 Combined fault-tolerant current and position measurement using available redundancies in DFIGs . . . . 94
5.3.1 State-of-the-art of the observers and sensor-FDI techniques on DFIGs . . . . . 94
5.3.1.1 Position observers . . . . 94
5.3.1.2 Current observers . . . . 95
5.3.1.3 Voltage observers . . . . 96
5.3.1.4 Combined observers . . . . 96
5.3.1.5 FDI techniques . . . . 96
5.3.2 Combined current and position observer . . . . 97
5.3.2.1 Computation of active and reactive power transferred via the air gap 97 5.3.2.2 Magnetic saturation model . . . . 98
5.3.2.3 Estimation of the rotor position . . . . 99
5.3.2.4 Estimation of the electromagnetic torque and power . . . 100
5.3.2.5 Stability analysis of the MRAS system . . . 101
5.3.2.6 Estimation of the rotor currents . . . 101
5.3.2.7 Robustness analysis . . . 101
5.3.2.8 Behaviour of the sensorless algorithm during DFIG startup . . . 107
5.3.3 Combined current and position FDI . . . 110
5.3.3.1 Residual generation . . . 111
5.3.3.2 Fault detection and isolation algorithm . . . 111
5.3.4 Experimental validation . . . 113
5.3.4.1 Detection of rotor-current-sensor faults . . . 113
5.3.4.2 Detection of encoder faults . . . 114
5.3.4.3 Detection of faults in transient state . . . 116
5.3.4.4 Behaviour of the FDI algorithm in case of unbalanced grid voltages . 119 5.4 Summary . . . 120
II NVH aspects of electrical drives for EVs 124 6 Principal drives for EV propulsion 125 6.1 Introduction . . . 125
6.2 General requirements for electrical drive trains used in vehicles . . . 126
6.3 Kinematic chains for electrical and hybrid vehicles . . . 126
6.3.1 Kinematic chains for full-electrical vehicles . . . 127
6.3.1.1 Single- versus multiple-motor topology . . . 127
6.3.1.2 Variable-gear versus fixed-gear versus gearless transmission . . . 127
6.3.1.3 System voltage . . . 127
6.3.2 Kinematic chains for hybrid vehicles . . . 127
6.3.2.1 Series hybrids . . . 128
6.3.2.2 Parallel hybrids . . . 128
6.3.2.3 Series-parallel hybrids . . . 129
6.4 Existing technologies for energy storage . . . 130
6.4.1 Batteries . . . 130
6.4.2 Supercapacitors . . . 132
6.4.3 Flywheels . . . 132
6.4.4 Fuel cells . . . 132
6.5 Mainly used motor types in EVs . . . 132
6.5.1 DC motors . . . 132
6.5.2 Induction motors . . . 132
6.5.3 Permanent-magnet synchronous motors . . . 133
6.5.4 Synchronous reluctance motors and permanent-magnet-assisted synchronous re- luctance motors . . . 133
6.5.5 Switched reluctance motors . . . 133
6.5.6 Other machine types . . . 134
6.6 Summary . . . 134
7 SRM drives for EVs: modelling and control 135 7.1 Introduction . . . 135
7.2 SRM model . . . 136
7.2.1 General working principle of SRMs . . . 136
7.2.2 Voltage and torque equations of the SRM . . . 138
7.2.2.1 Flux-linkage / current curves . . . 138
7.2.2.2 Expressions of the electromagnetic torque and power . . . 138
7.2.2.3 Interest of working with magnetic saturation . . . 141
7.2.2.4 Voltage equation of the SRM . . . 141
7.2.2.5 Ideal waveforms in SRMs . . . 142
7.2.3 Identification process of SRMs . . . 143
7.2.3.1 Computational methods . . . 143
7.2.3.2 Experimental methods . . . 144
7.3 SRM control . . . 145
7.3.1 General control structure . . . 145
7.3.2 SRM converter topologies, current control and chopping modes . . . 146
7.3.2.1 SRM converter topologies . . . 146
7.3.2.2 Current control techniques . . . 146
7.3.3 Torque control strategies . . . 150
7.3.3.1 Average torque control . . . 150
7.3.3.2 Instantaneous torque control . . . 152
7.4 Practical realization of the 15 kW SRM test bench . . . 158
7.4.1 Presentation of the test bench . . . 158
7.4.2 Implementation of the control . . . 158
7.4.3 Simulation model of the test bench . . . 159
7.5 Summary . . . 160
8 Investigation of NVH aspects of SRM drives 161 8.1 Introduction . . . 161
8.2 Main causes of NVH issues in SRMs . . . 162
8.2.1 Principal vibration sources . . . 162
8.2.1.1 Global mechanisms and modelling . . . 162
8.2.1.2 Spatial distribution . . . 163
8.2.1.3 Frequency content . . . 163
8.2.2 Main resonance modes . . . 164
8.2.2.1 Analytical computation of natural frequencies . . . 165
8.2.2.2 FE computation of natural frequencies and modes . . . 166
8.2.2.3 Experimental measurement of natural frequencies and modes . . . 167
8.2.2.4 Comparison of computation and measurement results on the investi- gated 8/6 SRM . . . 168
8.2.3 Interaction between vibration sources and eigenmodes . . . 169
8.2.4 Generation of acoustic noise . . . 170
8.2.5 Perception of acoustic noise by the human ear and sound metrics . . . 171
8.2.5.1 Characteristics of the human ear . . . 171
8.2.5.2 Definition of sound metrics . . . 172
8.3 Investigation of NVH aspects in SRMs in transient conditions . . . 175
8.3.1 Evolution with speed . . . 177
8.3.1.1 Reference-test results and global comments . . . 177
8.3.1.2 Higher-speed- and coasting-test results . . . 180
8.3.2 Evolution with torque and reference current . . . 182
8.3.3 Comparison of soft and hard chopping . . . 184
8.3.4 Evolution with converter DC-bus voltage . . . 187
8.3.5 Evolution with current-hysteresis bandwidth . . . 188
8.3.6 Evolution with hysteresis-controller sampling frequency . . . 192
8.3.7 Influence of faults . . . 196
8.4 Summary . . . 197
9 Conclusion 200 9.1 Summary and contributions . . . 200
9.1.1 Fault-tolerant DFIG drives for wind energy conversion systems . . . 200
9.1.2 NVH aspects of electrical drives for EVs . . . 201
9.2 Future work . . . 202
9.2.1 Fault-tolerant DFIG drives for wind energy conversion systems . . . 202
9.2.2 NVH aspects of electrical drives for EVs . . . 203
References 205 Appendices 228 A Main characteristics of the DFIG-test-bench components 229 A.1 Characteristics of the rotating machines . . . 229
A.2 Characteristics of the converters . . . 233
A.3 Grid and filter characteristics . . . 234
A.4 Main characteristics of the measurement chain . . . 235
A.5 Implementation of the control on dSPACE . . . 238
B Main characteristics of the SRM test-bench components 244 B.1 Characteristics of the rotating machines . . . 244
B.2 Characteristics of the converters . . . 246
B.3 Main characteristics of the measurement chain . . . 249
B.4 Implementation of the control . . . 252
B.5 Future upgraded version of the SRM test bench . . . 254
C Complementary information on FDI techniques 258 C.1 Process-history-based FDI algorithms . . . 258
C.1.1 Quantitative methods . . . 258
C.1.1.1 Statistical methods . . . 258
C.1.1.2 Neural networks . . . 259
C.1.2 Qualitative methods . . . 259
C.1.2.1 Expert systems . . . 259
C.1.2.2 Qualitative trend analyses . . . 259
C.2 Model-based FDI . . . 260
C.2.1 Quantitative methods . . . 260
C.2.1.1 Residual generation using observers . . . 260
C.2.1.2 Residual generation using parity equations . . . 261
C.2.1.3 Residual generation using Kalman filters . . . 262
C.2.2 Qualitative methods . . . 262
C.2.2.1 Causal algorithms . . . 262
C.2.2.2 Abstraction-hierarchy-based algorithms . . . 263
D List of publications 264 D.1 Papers published in the frame of part A of the present thesis . . . 264
D.1.1 Conference papers . . . 264
D.2 Papers published in the frame of part B of the present thesis . . . 264
D.2.1 Journal paper . . . 264
D.2.2 Conference papers . . . 265
D.3 Additional published papers . . . 265
D.3.1 Conference papers . . . 265
D.4 Additional published papers (co-author) . . . 265
D.4.1 Journal papers . . . 265
D.4.2 Conference papers . . . 266
