Fault Diagnostic System for Cascaded H-Bridge Multilevel Inverter ...

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is ideal where a source of ac voltage is available, such as in a hybrid electric vehicle. The cascaded MLID is the focus of this dissertation. 1.2.1 Cascaded H- bridge multilevel inverter drives A single-phase structure of an m-level cascaded inverter is illustrated in Figure 1.1. Each separate dc source (SDCS) is connected to a single-phase full-bridge, or H-bridge, inverter. Each inverter level can generate three different voltage outputs, +Vdc, 0, and –Vdc by connecting the dc source to the ac output by different combinations of the four switches, S1, S2, S3, and S4. To obtain +Vdc, switches S1 and S4 are turned on, whereas –Vdc can be obtained by turning on switches S2 and S3. By turning on S1 and S2 or S3 and S4, the output voltage is 0. The ac outputs of each of the different full-bridge inverter levels are connected in series such that the synthesized voltage waveform is the sum of the inverter outputs. The number of output phase voltage levels m in a cascade inverter is defined by m = 2s+1, where s is the number of separate dc sources. Cascaded inverters have also been proposed for use as the main traction drive in electric vehicles, where several batteries or ultracapacitors are well suited to serve as SDCSs [1]. The cascaded inverter could also serve as a rectifier/charger for the batteries of an electric vehicle while the vehicle was connected to an ac supply as shown in Figure 1.2. Additionally, the cascade inverter can act as a rectifier in a vehicle that uses regenerative braking. The main advantages and disadvantages of multilevel cascaded H-bridge converters are as follows [1]. 6
Advantages: • The number of possible output voltage levels is more than twice the number of dc sources (m = 2s + 1); • The series of H-bridges makes for modularized layout and packaging. This will enable the manufacturing process to be done more quickly and cheaply. Disadvantages: • Separate dc sources are required for each of the H-bridges. This will limit its application to products that already have SDCSs readily available. v a va[(m-1)/2] n v a[(m-1)/2-1] v a2 v a1 S 1 S 3 S 1 S 3 S 1 S 3 S 1 S 3 7 S 2 S 4 S 2 S 4 S 2 S 4 S 2 S 4 V dc V dc V dc V dc + - + - + - + - SDCS SDCS SDCS SDCS Figure 1.1. Single-phase structure of a multilevel cascaded H-bridges inverter.
Page 1 and 2: To the Graduate Council: I am submi
Page 3 and 4: Copyright © by Surin Khomfoi All R
Page 5 and 6: ACKNOWLEDGEMENTS There are many peo
Page 7 and 8: ABSTRACT A fault diagnostic and rec
Page 9 and 10: TABLE OF CONTENTS CHAPTER PAGE 1. I
Page 11 and 12: LIST OF FIGURES FIGURE 1.1. SINGLE-
Page 13 and 14: FIGURE 5.21. SIMULATION RESULTS OF
Page 15 and 16: 1. INTRODUCTION 1.1 Background In r
Page 17 and 18: Multilevel inverters provide more p
Page 19: • Common-mode (CM) voltage: Multi
Page 23 and 24: VCA C C5 C4 C3 C2 120 o C1 A A5 A4
Page 25 and 26: times the level of an unbalanced vo
Page 27 and 28: then, if the probability of a singl
Page 29 and 30: It is possible that AI-based techni
Page 31 and 32: Va n v a2 v a1 A + S A - S B- S A +
Page 33 and 34: 2. SURVEY OF PREVIOUS WORKS 2.1 Int
Page 35 and 36: vehicle. It would be better if one
Page 37 and 38: Several research papers on fault de
Page 39 and 40: technology would reduce the impleme
Page 41 and 42: The vector in the d-q frame can als
Page 43 and 44: iβ iβ iβ Fault @ S 1 iα phase a
Page 45 and 46: As can be seen in Figure 2.5, the t
Page 47 and 48: Current beta (A) Current beta (A) 1
Page 49 and 50: 2.3.2 Control signal observer appro
Page 51 and 52: Current phase A (A) 25 20 15 10 5 0
Page 53 and 54: As can be seen, two binary bits are
Page 55 and 56: As illustrated in Table 2.4, most d
Page 57 and 58: system or training a neural network
Page 59 and 60: Murphy [33] presented a fault diagn
Page 61 and 62: Vdc Vdc Current (A) n 15 10 5 0 -5
Page 63 and 64: 2.4.3 Cascaded H-bridges MLID Fault
Page 65 and 66: 2.5 A promising support for AI-base
Page 67 and 68: waveforms. It is evident that the u
Page 69 and 70: Figure 2.16 (b) shows an example of
Page 71 and 72:
technique methodology of fault diag
Page 73 and 74:
3.2 Structure of fault diagnostic s
Page 75 and 76:
The modulation index (ma) is the ra
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The simulation model is illustrated
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Normal Fault A+ Fault A- Fault B+ F
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(a) (c) Figure 3.8. Experiment of o
Page 83 and 84:
3.4 Feature extraction system Simul
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Normal Fault A+ Fault A- Fault B+ F
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X1 X2 X3 X4 X5 Xn Data PCA Scores t
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Selecting a reduced subset (PCs kep
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The collected data from both simula
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Score PC1 Score PC1 -2 -4 -6 4 6 4
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population created from multiple in
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• Encoded input PCs: the PCs to b
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andomly selects a crossover point w
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Loadings on PC#13 Scores on PC#13 L
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3.6 Neural network classification A
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As a comparison among transformatio
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Reselect training set Table 3.2. Ta
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[42], is used to simulate the targe
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The second category of testing resu
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4. RECONFIGURATION TECHNIQUE 4.1 In
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4.3 Reconfiguration method The reco
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Amplitude (pu.) 1 0.8 0.6 0.4 0.2 0
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traction motor only at half load co
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% Relative to fundamental component
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Van Vbn Vcn Vab Vbc Vca 100 0 -100
Page 125 and 126:
4.5 Summary The reconfiguration tec
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5.2 Fault Diagnostic technique for
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will be trained with short circuit
Page 131 and 132:
5.2.3 Principal component selection
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5.3 Simulation validation Several S
Page 135 and 136:
The principal component analysis (P
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1 p{1} a{1} Input 1 p{1} Subsystem
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INV_A INV_B INV_C Showing the sub-s
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Fault creating circuit RT-LAB comma
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Figure 5.13. Obviously, the loss of
Page 145 and 146:
For the short circuit validation, t
Page 147 and 148:
Starting current Fault start (a) Fa
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As can be seen, the simulation and
Page 151 and 152:
Loss of gate drive signal fault Rea
Page 153 and 154:
Starting current Fault start Fault
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Fault start Fault clear Fault start
Page 157 and 158:
Table 5.3. Performance investigatio
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5mV/1A (2A/Div) Real open circuit f
Page 161 and 162:
The Opal-RT system needs a few cycl
Page 163 and 164:
6. CONCLUSIONS AND RECOMMENDATIONS
Page 165 and 166:
their locations. Also, a genetic al
Page 167 and 168:
6.2 Contributions This dissertation
Page 169 and 170:
technique for tracking the current
Page 171 and 172:
• S. Khomfoi, L. M. Tolbert, “A
Page 173 and 174:
Chapter 1 [1] L. M. Tolbert, F. Z.
Page 175 and 176:
Characteristics,” IEEE Transactio
Page 177 and 178:
[28] S. Nandi, H. A. Toliyat, X. Li
Page 179 and 180:
[43] D. Zhang, H. Li, “A Low Cost
Page 181 and 182:
[58] J. Fieres, A. Grubl, S. Philip
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