Multiple 3-phase Fault Tolerant Permanent Magnet Machine Drives E-Book

Bo Wang

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 429

Veröffentlichungsjahr: 2024

Beschreibung

Groundbreaking analysis of a fully functional fault-tolerant machine drive

Electrical machine drives have become an increasingly important component of transportation electrification, including electric vehicles, railway and subway traction, aerospace actuation, and more. This expansion of electrical machine drives into safety-critical areas has driven an increasingly urgent demand for high reliability and strong fault tolerance. Machine drives incorporating a permanent magnet (PM)-assisted synchronous reluctance machine drive with a segregated winding have shown to exhibit notably reduced PM flux and correspondingly enhanced fault tolerance.

Multiple 3-Phase Fault Tolerant Permanent Magnet Machine Drives: Design and Control offers one of the first fully integrated accounts of a functional fault-tolerant machine drive. It proposes a segregated winding which can be incorporated into multiple machine topologies without affecting performance and brings together cutting-edge technologies to manage these crucial drives in both healthy and fault conditions. The result is a must-own for engineers and researchers alike.

Readers will also find:

• Advanced modeling techniques for different operation conditions
• Detailed discussion on topics including fault detection techniques, postfault tolerant control strategies, and many more
• An authorial team with immense experience in the study of fault-tolerant machine drives

Multiple 3-Phase Fault Tolerant Permanent Magnet Machine Drives: Design and Control is ideal for researchers and graduate students in engineering and related industries.

Leseprobe

Table of Contents

Cover

Table of Contents

Title Page

Copyright

Dedication

About the Authors

Preface

1 Introduction to Fault-Tolerant Machine Drives

1.1 Background of Fault-Tolerant Machine Drives

1.2 Frequent Faults in Electric Drives

1.3 Design Requirements of Fault-Tolerant Machine Drives

1.4 Current State-of-the-Art Techniques of Fault-Tolerant Machine Drives

1.5 Scope and Outline of This Book

References

2 Multiple 3-Phase Fault-Tolerant Machine Drive with Segregated Windings

2.1 Introduction

2.2 PMA-SynRM with Segregated Windings

2.3 Fault-Tolerant Capability Assessment

2.4 Analysis of Fault Operation Behavior

2.5 Summary

References

3 Design Optimization of Multiple 3-Phase Fault-Tolerant Machine

3.1 Introduction

3.2 Design Specifications

3.3 Design Optimization Process

3.4 Selected Design Alternatives and Performance Comparison

3.5 Test Setup of Fault-Tolerant Machine Drives

3.6 Test Under Healthy Conditions

3.7 Test Under Fault Conditions

3.8 Summary

References

Notes

4 General Modeling Technique for Multiple 3-Phase Machine Drive

4.1 Introduction

4.2 General Modeling Technique for 3-Phase Winding Sets

4.3 Study on Model Accuracy and Computational Efficiency

4.4 General Modeling of Turn Fault

4.5 Study on Model Accuracy and Computational Efficiency Under Turn Fault

4.6 Model Validation by Experimental Tests

4.7 Summary

References

5 Fault Detection Techniques for the Multiple 3-Phase Machine Drive

5.1 Introduction

5.2 Analysis of Fault Signal Under Open Circuit of an Inverter Switch

5.3 Open-Circuit Fault Detection Design

5.4 Experimental Validation on Open-Circuit Fault Detection

5.5 Analysis of Turn Fault Signature

5.6 Turn Fault Detection Design

5.7 Experimental Validation on Turn Fault Detection

5.8 High-Frequency Signal-Based Turn Fault Detection Techniques

5.9 Summary

References

6 Postfault Control Strategies for Fault-Tolerant Machine Drives

6.1 Introduction

6.2 Postfault Optimal Torque Control Strategies for Multiphase FSCW PM Machines

6.3 Simulation Validation on the Optimal Torque Control Strategy

6.4 Turn Fault Mitigation by Current Injection

6.5 Simulation Validation on the Current Injection Technique

6.6 Experimental Validation on the Current Injection Technique

6.7 Summary

References

7 Novel Segregated Windings with Enhanced Fault Tolerance for Multiple 3-Phase Machine

7.1 Introduction

7.2 Multiple 3-Phase Machines with Four Alternative Segregated Windings

7.3 FE Analysis of Machines with Five Segregated Winding Configurations

7.4 Experimental Assessments of Machines with Five Segregated Winding Configurations

7.5 Summary

References

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 Potential faults occurring in an electric drive.

Chapter 2

Table 2.1 Specifications of the PMA-SynRM.

Table 2.2 Summary of the faults in the machine drives.

Chapter 3

Table 3.1 Machine specifications.

Table 3.2 Leading parameters and losses of the initial sample.

Table 3.3 Design constraints of the machine.

Table 3.4 Parameters to be optimized.

Table 3.5 Key features of samples A and B.

Table 3.6 Performance comparison of samples A and B.

Table 3.7 Design parameters of samples A and B.

Chapter 5

Table 5.1 Faulty synthesized vector in six sub-sectors.

Table 5.2 Diagnostic rule.

Chapter 6

Table 6.1 Parameters of 5-phase fault-tolerant PM machine.

Table 6.2 Injected currents and resultant turn fault currents in six differe...

Table 6.3 Copper loss comparison between current injection, denoted as CJ, a...

Table 6.4 Peak-to-peak value of residual flux linkage.

Chapter 7

Table 7.1 Comparisons of winding factors with star, delta, and star-delta co...

Table 7.2 Machine specification and leading parameters.

Table 7.3 Performance comparison at rated healthy operation.

Table 7.4 Torque comparison under fault conditions

Table 7.5 Turn fault current, copper loss, and hotspot temperature.

Table 7.6 Overall performance comparison.

List of Illustrations

Chapter 1

Figure 1.1 Illustration of a typical electric drive system.

Figure 1.2 Fault distribution in electrical drives: (a) machine side and (b)...

Figure 1.3 3-Phase fault-tolerant machine drive: (a) full bridge with DC mid...

Figure 1.4 3-Phase machine using open-end winding drive (a) with independent...

Figure 1.5 Multiphase (5-phase for illustration) fault-tolerant machine driv...

Figure 1.6 Multiple 3-phase fault-tolerant machine drive: (a) dual 3-phase a...

Figure 1.7 SRM machine drive.

Figure 1.8 Multiphase FSCW fault-tolerant machine drive.

Figure 1.9 Multiple 3-phase FSCW fault-tolerant machine drive.

Figure 1.10 Open-circuit fault illustration: (a) switch open-circuit fault a...

Figure 1.11 Fault-tolerant control diagram of seven-phase motor.

Chapter 2

Figure 2.1 PMA-SynRM with conventional overlapped windings.

Figure 2.2 PMA-SynRM with segregated windings.

Figure 2.3 Torque and spectrum in healthy condition: (a) torque waveform and...

Figure 2.4 Flux distribution in healthy condition.

Figure 2.5 Flux density distribution in healthy condition.

Figure 2.6 Phase flux linkages in healthy condition.

Figure 2.7 Efficiency map under rated power operation region.

Figure 2.8 Torque with set ABC open-circuited (a) torque waveforms and (b) t...

Figure 2.9 Flux distribution with set ABC open circuited.

Figure 2.10 Faulty phase flux linkages with set ABC open circuited.

Figure 2.11 Healthy phase flux linkages with set ABC open circuited.

Figure 2.12 Short-circuit phase currents.

Figure 2.13 Flux distribution with set ABC short circuited.

Figure 2.14 Faulty phase flux linkages with set ABC short circuited.

Figure 2.15 Healthy phase flux linkages with set ABC short circuited.

Figure 2.16 Torque with set ABC short-circuited (a) torque waveforms and (b)...

Figure 2.17 Illustration of intraphase turn fault.

Figure 2.18 Coil location of the fault turn.

Figure 2.19 Turn fault current in coil B2 with 120 A load current at 4000 rp...

Figure 2.20 Flux distribution with turn fault in coil B2.

Figure 2.21 Variations of RMS turn fault currents in six coils with load cur...

Figure 2.22 Turn fault current and phase currents in ABC with turn fault in ...

Figure 2.23 Flux distribution in turn fault condition after TSC.

Figure 2.24 Comparison of torque waveforms under healthy and turn fault cond...

Figure 2.25 Variations of RMS turn fault currents in six coils with load cur...

Figure 2.26 Phase-to-phase insulation in the overhang region.

Figure 2.27 Interphase turn fault illustration.

Figure 2.28 Illustration of interphase fault (a) at the terminal end and (b)...

Figure 2.29 Interphase faults at the neutral end with TSC mitigation action....

Figure 2.30 Short-circuit currents of the interphase turn faults (a) phases ...

Figure 2.31 Schematic of TN grounding system of an electric drive.

Figure 2.32 Schematic of IT grounding system of an electric drive.

Figure 2.33 Ground fault current path caused by single point breakdown of ph...

Figure 2.34 Line back-emf at max speed 19,200 rpm.

Figure 2.35 Illustration of loss of inverter synchronization.

Figure 2.36 PM demagnetization BH curve.

Figure 2.37 Output torque after demagnetization fault.

Figure 2.38 Turn functions of the nine-phase winding coils.

Figure 2.39 Winding function of coil A1.

Figure 2.40 MMFs produced by each 3-phase set.

Figure 2.41 MMF produced by set ABC.

Figure 2.42 MMF in set ABC open-circuit condition.

Figure 2.43

dq

0 axis flux linkages of set DEF with set ABC open circuited.

Figure 2.44 Torque waveform with set ABC open circuited.

Figure 2.45 MMF and abs(MMF) offset component of set DEF when set ABC open c...

Figure 2.46

dq

axis currents of set DEF with set ABC open circuited.

Figure 2.47

dq

axis voltages of set DEF with set ABC open circuited.

Figure 2.48 Short-circuit currents in set ABC.

Figure 2.49 Positive and negative sequence components of the short-circuit c...

Figure 2.50 Phase flux linkages of set ABC when it is terminal short circuit...

Chapter 3

Figure 3.1 Required torque speed operation envelope.

Figure 3.2 Flow chart of SSO optimization process.

Figure 3.3 Flux maps of

ψ

d

and

ψ

q

versus

i

d

and

i

q

.

Figure 3.4 Flow chart of full machine model integration.

Figure 3.5 Illustration of spiral cooling jacket.

Figure 3.6 Evaluated temperature rise in Motor-CAD.

Figure 3.7 Lumped parameter thermal model of the machine.

Figure 3.8 Lumped parameter thermal model for turn fault.

Figure 3.9 Geometry parameter definitions of the PMA-SynRM.

Figure 3.10 Efficiencies of the design samples during design iteration.

Figure 3.11 Cross sections of samples A and B.

Figure 3.12 Stator and rotor stack: (a) stator stack and (b) rotor stack. Wa...

Figure 3.13 Machine windings and terminal leads: (a) segregated windings and...

Figure 3.14 Terminal connection of the three 3-phase sets: (a) set ABC, (b) ...

Figure 3.15 Real test bench: (a) 9-phase PMA-SynRM with dyno and (b) 9-phase...

Figure 3.16 Comparison of phase back-emf waveforms at 4000 rpm.

Figure 3.17 Comparison of line back-emf waveforms at 4000 rpm: (a) line back...

Figure 3.18 Phase currents of set ABC at 4000 rpm with three 3-phase sets sh...

Figure 3.19 Phase currents of set ABC at 4000 rpm in healthy condition,

x

-ax...

Figure 3.20 9-phase currents at 4000 rpm in healthy condition.

Figure 3.21 Illustration of current vector and gamma angle

γ

.

Figure 3.22 Torque variations with current magnitude and gamma angle.

Figure 3.23 Torque comparison in healthy condition.

Figure 3.24 Reluctance torque ratio against the current magnitude.

Figure 3.25 Measured machine efficiency map up to 12,000 rpm.

Figure 3.26 Comparison of measured and predicted machine efficiency at 4000 ...

Figure 3.27 Thermal test results with 120 A at 4000 rpm in healthy condition...

Figure 3.28 Healthy phase currents at 4000 rpm with set ABC open circuited....

Figure 3.29 Torque comparison with set ABC open circuited.

Figure 3.30 Illustration of TSC in the inverter side.

Figure 3.31 Torque comparison with set ABC short circuited.

Figure 3.32 Short-circuit phase currents at 4000 rpm.

Figure 3.33 Healthy phase currents at 4000 rpm with set ABC short circuited....

Figure 3.34 Test setup of interturn short-circuit fault: (a) cable leads and...

Figure 3.35 Turn fault current with 80 A load current at 1000 rpm.

Figure 3.36 Turn fault current variations in coil B2 and A1 at 1000 rpm in m...

Figure 3.37 Turn fault current in coil B2 and phase currents of set ABC with...

Figure 3.38 Healthy phase currents with turn fault in coil B2 when load curr...

Figure 3.39 Turn fault current variations in coil B2 and A1 at 4000 rpm in m...

Figure 3.40 Thermal test results under single-turn fault in coil B2 with 120...

Chapter 4

Figure 4.1 Illustration of turn fault location in a slot and phase winding....

Figure 4.2 MMF produced by set ABC.

Figure 4.3 MMFs produced by sets DEF and GHI.

Figure 4.4 One 3-phase module and its MMF in the air gap.

Figure 4.5 General modeling diagram.

Figure 4.6 Full machine model for 4D table generation.

Figure 4.7 General model integrated with voltage equations and current contr...

Figure 4.8 Comparison of predicted torque by two models in healthy condition...

Figure 4.9 Comparison of predicted phases ABC flux linkages by two models in...

Figure 4.10 Comparison of predicted torques by two models in open-circuit co...

Figure 4.11 Comparison of predicted flux linkages of healthy DEF set by two ...

Figure 4.12 MMF offset component of set ABC under open-circuit condition.

Figure 4.13 Comparison of predicted torques by two models in short-circuit c...

Figure 4.14 Comparison of predicted short-circuit currents by two models.

Figure 4.15 Comparison of predicted flux linkages in the short-circuit set b...

Figure 4.16 Comparison of predicted flux linkages in healthy DEF set by two ...

Figure 4.17 MMF offset component under short-circuit condition.

Figure 4.18 Comparison of predicted flux linkages of set ABC by two models....

Figure 4.19 Comparison of predicted torque in unbalanced current operation b...

Figure 4.20 Comparisons of

dq

-axis quantities of (a) flux linkages and (b) t...

Figure 4.21 Comparisons of

dq-axis

quantities with 50% increase in phase res...

Figure 4.22 Schematic circuit for set ABC with turn fault in phase B.

Figure 4.23 MMF phasors of phase B.

Figure 4.24 Derivation process of flux linkage of fault turn.

Figure 4.25 Flux linkage distribution induced by the MMF offset component.

Figure 4.26 AC component phasors of flux linkages.

Figure 4.27 Illustration of the slot position and leakage flux of the fault ...

Figure 4.28 General model integrated with turn fault model.

Figure 4.29 Illustration of turn fault simulation in FE: (a) set ABC without...

Figure 4.30 Comparison of predicted turn fault current when it occurs in coi...

Figure 4.31 Comparison of predicted phase flux linkages when it occurs in co...

Figure 4.32 Comparison of predicted torques when it occurs in coil B2 withou...

Figure 4.33 Comparison of predicted turn fault current when it occurs in coi...

Figure 4.34 Comparison of predicted turn fault current when it occurs in coi...

Figure 4.35 Comparison of predicted phase currents with turn fault in coil B...

Figure 4.36 Comparison of predicted torques with turn fault in coil B2 with ...

Figure 4.37 Comparison of predicted turn fault current when it occurs in coi...

Figure 4.38 Comparison of predicted phase currents of faulty set with fault ...

Figure 4.39 Comparison of measured and predicted currents in healthy mode.

Figure 4.40 Comparison of measured and predicted voltages in healthy mode.

Figure 4.41 Comparison of measured and predicted torques in healthy conditio...

Figure 4.42 Comparison of measured and predicted currents in open-circuit mo...

Figure 4.43 Comparison of measured and predicted

dq

voltages in open-circuit...

Figure 4.44 Comparison of measured and predicted torques in open-circuit con...

Figure 4.45 Comparison of measured and predicted short-circuit currents.

Figure 4.46 Comparison of measured and predicted currents in healthy DEF set...

Figure 4.47 Comparison of measured and predicted voltages in healthy DEF set...

Figure 4.48 Comparison of measured and predicted torques in short-circuit co...

Figure 4.49 Comparison of measured and predicted phase currents in set ABC u...

Figure 4.50 Comparison of measured and predicted voltages under unbalanced c...

Figure 4.51 Comparison of measured and predicted turn fault currents when a ...

Figure 4.52 Comparison of measured and predicted phase currents in fault set...

Figure 4.53 Comparison of measured and predicted

dq

-axis control voltages in...

Figure 4.54 Comparison of measured and predicted phase currents in healthy D...

Figure 4.55 Comparison of measured and predicted

dq

-axis control voltages in...

Figure 4.56 Measured and predicted turn fault current variations with health...

Figure 4.57 Comparison of measured and predicted turn fault currents at 50 A...

Figure 4.58 Comparison of measured and predicted turn fault current variatio...

Figure 4.59 Comparison of measured and predicted turn fault currents with tu...

Figure 4.60 Comparison of measured and predicted short-circuit phase current...

Figure 4.61 Comparison of measured and predicted phase current in DEF health...

Figure 4.62 Comparison of measured and predicted control output voltages in ...

Figure 4.63 Comparison of measured and predicted rms turn fault current vari...

Figure 4.64 Comparison of measured and predicted turn fault currents when it...

Figure 4.65 Comparison of measured and predicted rms turn fault current vari...

Chapter 5

Figure 5.1 One 3-phase module with

T

1

open-circuit fault.

Figure 5.2 Current flow paths under healthy condition and

T

1

open-circuit fa...

Figure 5.3 Space vectors in healthy condition and

T

1

open circuit: (a) healt...

Figure 5.4 The relative

αβ

coordinate systems with respect to the ...

Figure 5.5 Fault detection waveforms when

T

1

is open circuited: (a) phase cu...

Figure 5.6 Fault detection waveforms when

T

4

is open circuited: (a) phase cu...

Figure 5.7 Fault detection waveforms during a step increase in load current:...

Figure 5.8 Fault detection waveforms during a step decrease in load current:...

Figure 5.9 Influence of machine parameters on the voltage residuals during d...

Figure 5.10 Integrated test with fault mitigation strategy: (a) phases ABC c...

Figure 5.11 Schematic circuit for set ABC with turn fault in phase A.

Figure 5.12 Simplified

dq

-axis current control loops in a 3-phase drive.

Figure 5.13 Comparison of 2nd harmonics in IAP and IRP: (a) motoring mode an...

Figure 5.14 Comparison 2nd harmonics of faulty and healthy sets: (a) IRP in ...

Figure 5.15 Fault detection diagram in motoring mode.

Figure 5.16 Turn fault current when the drive operates at 1000 rpm and 100 A...

Figure 5.17 Measured currents and voltages before and after turn fault: (a)

Figure 5.18 IAP and IRP before and after turn fault: (a) instantaneous value...

Figure 5.19 Measured IAP and IRP in generating mode: (a) instantaneous value...

Figure 5.20 Detection ratio at 500 and 1000 rpm in motoring (M500, M1000) an...

Figure 5.21 Detection zone under (a) motoring mode and (b) generating mode....

Figure 5.22

i

dq

response and 2nd harmonic of IRP in transient (a)

i

dq

(b) 2n...

Figure 5.23

i

dq

response and 2nd harmonic of IRP in transient with turn faul...

Figure 5.24 Current responses during fault detection and mitigation test: (a...

Figure 5.25 Scheme of HF voltage injection.

Figure 5.26 Diagnosis process of turn fault under different operating condit...

Chapter 6

Figure 6.1 Schematic of 5-phase 10s12p fault-tolerant FSCW PM machine.

Figure 6.2 Measured and predicted waveforms of phase back-emf and cogging to...

Figure 6.3 Output torque under open-circuit and short-circuit conditions wit...

Figure 6.4 Current, voltage, back-emf, and torque waveforms under a short-ci...

Figure 6.5 Current, voltage, emf, and torque waveforms under a short-circuit...

Figure 6.6 Phasors of the subcoils in phase A.

Figure 6.7 MMF produced by the healthy set currents.

Figure 6.8 MMF produced by the fault set currents.

Figure 6.9 MMF AC and offset components in the fault set.

Figure 6.10 Illustration of current injection used in FE simulation of turn ...

Figure 6.11 Fault current waveforms with current inject technique when a sin...

Figure 6.12 Residual flux linkages under TSC application.

Figure 6.13 Residual flux linkages under current injection.

Figure 6.14 Illustration of the slot position of the fault turn.

Figure 6.15 Turn fault currents when the fault occurs in two different slot ...

Figure 6.16 Turn fault currents with four different numbers of faulted turns...

Figure 6.17 Output torques under different mitigation strategies considering...

Figure 6.18 Torque contribution of different set regions under two mitigatio...

Figure 6.19 Simulated turn fault current in coil A1 at 19,200 rpm under curr...

Figure 6.20 Schematic of the proposed current injection control diagram.

Figure 6.21 Fault current and phase currents in set ABC (a) with TSC and (b)...

Figure 6.22 Phase currents in sets DEF and GHI (a) with TSC and (b) with cur...

Figure 6.23 Rms turn fault current variation with healthy set currents with ...

Figure 6.24 Variations of torques with the load currents at 4000 rpm in diff...

Figure 6.25 Fault current and phase currents: (a) fault current and phase cu...

Figure 6.26 Rms turn fault current variations with healthy set currents with...

Figure 6.27 Variations of postfault torque with healthy set currents with tu...

Figure 6.28 Current waveforms from integrated test of turn fault injection, ...

Chapter 7

Figure 7.1 Triple redundant 3-phase PMA-SynRM with star-connected windings a...

Figure 7.2 Phase flux linkages in phases A, B, and C after TSC application: ...

Figure 7.3 Flux linkages of six subcoils in ABC set after TSC.

Figure 7.4 Star-delta winding connection, W3.

Figure 7.5 Triple redundant 3-phase PMA-SynRM with mixed-pitch windings, W4....

Figure 7.6 Turn functions of the six coils in the ABC set of W4.

Figure 7.7 MMF profile produced by ABC set of W4.

Figure 7.8 Triple 3-phase PMA-SynRM with concentric windings, W5.

Figure 7.9 Space vectors of the six coils in phases ABC (a) W1 and (b) W5.

Figure 7.10 Comparison of no-load phase flux linkages of W1 and W5 configura...

Figure 7.11 Comparison of no-load coil flux linkages of W1 and W5 configurat...

Figure 7.12 Line currents and induced zero-sequence currents.

Figure 7.13 Comparison of torque waveforms of the five machines in rated hea...

Figure 7.14 Comparison of torque waveforms of the five machines in open-circ...

Figure 7.15 Open-circuit fault in phase A winding for delta configuration (W...

Figure 7.16 Phase current vectors in healthy and phase A open-circuited cond...

Figure 7.17 Comparison of torque waveforms of the five machines in short-cir...

Figure 7.18 Induced short-circuit currents for the five machines, from top t...

Figure 7.19 Variations of turn fault current with load current and fault loc...

Figure 7.20 Variations of turn fault current with load current and fault loc...

Figure 7.21 Variations of turn fault current with load current and fault loc...

Figure 7.22 Variations of turn fault current with load current and fault loc...

Figure 7.23 Variations of turn fault current with load current and fault loc...

Figure 7.24 Turn fault current waveforms of the worst cases for the five win...

Figure 7.25 Thermal distribution prediction of the five machines: (a) W1, (b...

Figure 7.26 Stators and winding ptototypes of the five machines: (a) W1 and ...

Figure 7.27 Established experimental test platform of the five machines: (a)...

Figure 7.28 Measured phase back-emfs of the machines with winding configurat...

Figure 7.29 Measured torque variations with current magnitude and gamma angl...

Figure 7.30 Output torque variations with load current under MTPA operation ...

Figure 7.31 Measured torque waveforms of five machines at 10 rpm with rated ...

Figure 7.32 Measured line currents of the five machines: (a) W1, (b) W2, (c)...

Figure 7.33 Measured currents under rated healthy operation: (a) phase curre...

Figure 7.34 Measured line currents of the five machines with winding configu...

Figure 7.35 Measured currents when phases ABC are open circuited: (a) curren...

Figure 7.36 Variations of the output torques with the load currents for the ...

Figure 7.37 Measured line currents of five machines with winding configurati...

Figure 7.38 Measured currents when ABC phases are short circuited: (a) phase...

Figure 7.39 Variations of the output torques with the load currents for the ...

Figure 7.40 Measured line currents and turn fault current in five machines w...

Guide

Cover

Table of Contents

Title Page

Copyright

Dedication

About the Authors

Preface

Begin Reading

Index

End User License Agreement

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IEEE Press445 Hoes LanePiscataway, NJ 08854

IEEE Press Editorial BoardSarah Spurgeon, Editor-in-Chief

Moeness Amin

Jón Atli Benediktsson

Adam Drobot

James Duncan

Ekram Hossain

Brian Johnson

Hai Li

James Lyke

Joydeep Mitra

Desineni Subbaram Naidu

Tony Q. S. Quek

Behzad Razavi

Thomas Robertazzi

Diomidis Spinellis

Multiple 3-Phase Fault Tolerant Permanent Magnet Machine Drives

Design and Control

Bo Wang

Southeast University

China

Jiabin Wang

The University of Sheffield

United Kingdom

Copyright © 2025 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

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To all our colleagues and collaborators, past and present, who contributed to and supported the research of fault-tolerant machine drives.

About the Authors

Bo Wang received a Bachelor’s degree and a Master’s degree, in Electrical Engineering, from Nanjing University of Aeronautics and Astronautics, Nanjing, China, in 2009 and 2012, respectively, and a PhD in Electronic and Electrical Engineering from the University of Sheffield, Sheffield, United Kingdom (UK), in 2018.

From 2012 to 2014, he was a Senior Engineer at Delta Electronics Co. Ltd, Nanjing, China. From 2017 to 2018, he was a Research Associate at the Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield, UK. Since 2018, he has joined the School of Electrical Engineering, Southeast University, Nanjing, China, and now he is a full professor. From 2020 to 2022, he joined Hong Kong Polytechnical University, Hong Kong, China under the Hong Kong Scholar program.

He received several awards from the Xiaomi Young Scholarship, Hong Kong Scholarship, and Zhishan Young Scholarship funding programs. He is, currently, an editor of several technical journals, including IET Power Electronics, Power Electronics and Drives, Chinese Journal of Electrical Engineering, CES Transactions on Electrical Machines and Systems. His research interests include permanent magnet machine drives, electric traction, and fault-tolerant systems.

Jiabin Wang graduated with a Bachelor of Engineering degree in 1982 and a Master of Engineering degree in 1986 from Jiangsu University, Zhengjiang, China, and a PhD from the University of East London, London, United Kingdom (UK), in 1996, all in electrical and electronic engineering.

Since February 2023, he has been an emeritus professor in Electrical Engineering at the University of Sheffield, Sheffield, UK. From 1986 to 1991, he was with the Department of Electrical Engineering at Jiangsu University, where he was appointed a lecturer in 1987 and an associated professor in 1990. He was a postdoctoral research associate at the University of Sheffield, Sheffield, UK, from 1996 to 1997, and a senior lecturer at the University of East London from 1998 to 2001. In 2002 he joined the Electrical Machines and Drives Research group at the University of Sheffield as a senior lecturer, became a reader in 2007, and a professor in Electrical Engineering in 2010.

His research encompasses novel rotary and linear electrical machines and drives, advanced control techniques for electrical drives, electrical power trains, and “more-electric” technologies, with a particular focus on high integrity, fault-tolerant, and high-efficiency electric drives and associated condition-monitoring techniques for applications in aerospace, automotive, and renewable energy systems.

He is a fellow of the Institute of Engineering and Technology, UK, and a senior member of the Institute of Electrical and Electronics Engineers, USA.

Preface

Due to their high efficiency, zero-emission, good controllability, simple and flexible physical layout, electrical machine drives are increasingly used in transportation electrification, such as electric vehicles, railway traction, marine and aerospace propulsion, and their actuations. However, electronic and electrical components and cable interconnections are susceptible to adverse operation conditions and environmental stresses, such as high temperatures, and high levels of mechanical vibration and chemical erosion. The failures are usually abrupt and may lead to catastrophic consequences and considerable economic losses. Thus, high reliability and fault tolerance are essential for electrical machine drives in safety-critical applications.

To achieve high reliability and desirable fault tolerance, many novel machine topologies, such as multiphase machines and multiple 3-phase machines with innovative stator and rotor configurations and power electronic control, have been developed to cope with various electric faults, such as open-circuit faults, short-circuit faults, and winding interturn short-circuit faults as a result of insulation breakdown. Comprehensive and computationally efficient fault modeling techniques have also evolved to gain an in-depth understanding of various fault behaviors and to facilitate the development of fault detection and postfault control strategies. In this regard, effective fault detection is essential to identify the fault type, isolate it, and enable an appropriate mitigation action for continued postfault operations.

However, very few materials exist in the literature, which present a comprehensive and integrated treatment of the design and control of fault-tolerant machine drives, including the selection of fault-tolerant machine topology, fault modeling, fault detection, and post-fault control considering failures in both the machine and power inverter. The existing body of knowledge on fault-tolerant machine drives is fragmented, mainly in numerous technical journals and conference papers, which makes it difficult to apply them effectively in engineering designs and further developments. Thus, this book aims to fill this knowledge gap and address the pertinent issues on the design, operation, modeling, and control of fault-tolerant machine drives, including fault detection and mitigation, in a comprehensive and integrated manner.

While various fault-tolerant machine drive topologies and technologies are reviewed and discussed, this book focuses on the design and control of multiple 3-phase fault-tolerant permanent magnet machine drives. The conventional overlapped distributed 3-phase winding is reconfigured as multiple nonoverlapped 3-phase winding modules, each driven by a standard 3-phase inverter. Due to the segregated winding configuration and independent drive for each 3-phase module, physical, electrical, and thermal isolations are obtained in the multiple 3-phase subsystems of the electrical drive. As a result, a failure in one 3-phase subsystem does not significantly affect the operation of other healthy 3-phase subsystems. The modular approach minimizes the risk of fault propagation to the other subsystems, providing tolerance to various electric faults. By exploiting reluctance torque in a permanent magnet machine with a multilayer rotor topology, high torque density and the ability to tolerate short-circuit faults can be achieved. This book introduces the fault-tolerant machine drive system, analyses various fault behaviors, and presents comprehensive design and fault modeling techniques, including fault detection, postfault control, and alternative winding configurations for further reduction in short-circuit currents. The methods and approaches described in the book also apply to developing other fault-tolerant machine drives.

The authors have worked on developing fault-tolerant machine drive technologies at Southeast University and the University of Sheffield for more than 20 years and published over 50 SCI/EI-indexed papers on this topic. This book organizes a selected collection of the research outcomes and is arranged into seven chapters as outlined below.

Chapter 1 introduces the background knowledge and current state-of-the-art fault-tolerant machine drives.

Chapter 2 describes the multiple 3-phase permanent magnet-assisted synchronous reluctance machine with segregated windings and its ability to tolerate various electric faults. It also analyzes the mutual magnetic coupling among the 3-phase subsystems in the machine.

Chapter 3 presents the global design optimization process of the fault-tolerant machine drive to achieve performance requirements in healthy operations and the ability to tolerate worst-case fault scenarios, namely inter-turn short circuits, which lead to the largest possible fault current.

Chapter 4 establishes a general modeling technique for operations in healthy and various fault conditions and outlines the key characteristics of fault behaviors.

Chapter 5 develops fast and reliable fault detection techniques, particularly focusing on the detection of inter-turn short circuits at low speed.

Chapter 6 devises post-fault control strategies for fault-tolerant machine drives to minimize torque ripple and fault current in worst-case conditions.

Chapter 7 proposes several alternative winding configurations for the multiple 3-phase machine drive to reduce fault current in worst-case conditions further.

The authors thank professors Cheng Ming, Hua Wei, Deng Fujin, Antonio Griffo, and Zhao Wenxiang for their valuable suggestions on this book. The authors also thank postgraduate researchers Mr. Feng Xiaobao and Mr. Wei Zihan for their support in preparing this book.

Finally, the authors thank their families for their love and support in the research and writing of this book.

Bo Wang

Nanjing, China

Jiabin Wang

Sheffield, United Kindom

1Introduction to Fault-Tolerant Machine Drives

1.1 Background of Fault-Tolerant Machine Drives

Advanced electric drive systems are increasingly being used in a wide range of applications from industrial automation, household appliances, and transportation to oil and gas, mining, and renewable energy industries, where efficient and reliable electric-to-mechanical energy conversion or vice versa is essential. Extensive research activities on electrical drives have been undertaken in both academic and industrial organizations [1]. A typical electric drive is composed of a power converter, a control unit, and an electric motor, generally known as an electric machine, as shown in Fig. 1.1. The power converter contains typically power electronic devices (i.e. Insulate Gate Bipolar Transistor (IGBT), Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), SiC, and diode), gate drives, and passive components (capacitor and damping resistors, etc.), which are responsible for driving the motor. The control unit consists mainly of microprocessor and its associated electronic circuitry in addition to various sensors. The electric motor delivers controllable torque to a mechanical payload by converting electrical power into mechanical power or vice versa.

As advances emerge fast in the areas of materials, electric machine design and manufacturing, power electronics, microprocessors, and sensing, electrical drives are capable of delivering desirable features such as high-power density, high efficiency, low emission, and good controllability, compared to other counterparts, namely, mechanical, hydraulic, or pneumatic drive/actuation systems [2]. Aircraft employing electrical actuators, electrical propulsion, and power generation in the form of more electric, hybrid, and full-electric aircraft can leverage the merits of weight saving, economical fuel consumption, low CO2 emission, increased functionality, and less maintenance [3]. Another emerging example is the electric vehicle (EV) replacing traditional internal combustion engine (ICE) for low CO2 and low harmful pollutant emissions [4, 5]. However, high reliability is also an essential requirement for these safety critical applications, which should be addressed at the system design stage [6].

Figure 1.1 Illustration of a typical electric drive system.

In the aforementioned safety critical applications, the electrical drives are expected to continue operation if a fault occurs, or at least being fail-safe without catastrophic damage [7]. Otherwise, the unexpected fault may cause casualties and huge economic losses [8]. Thus, fault tolerance should be considered to attain the reliability requirement for the targeted applications.

Fault tolerance means that the system is capable of performing at a satisfactory level of operation in the presence of fault. It is a common requirement that has been investigated in various areas, such as fault-tolerant computing systems [9], distributed power systems [10], and high availability internet servers. In the scope of electrical drives, the fault tolerance mainly means it is capable of maintaining the original or an acceptable output torque or power level after a fault. The acceptable level defines the minimum output, which should be considered at the primary design stage of such systems.

1.2 Frequent Faults in Electric Drives

An electrical drive is a complex electromechanical system composed of an electronic controller, a power converter, an electric motor, and sensors. These components are exposed to electrical, thermal, mechanical, and environmental stresses as well as chemical corrosion. Fault may occur in each of these components. Studies in [11, 12] have been carried out to investigate the failure distribution of electric machines. The results of the survey show the bearing faults account for the majority of the failures, as much as 51%, followed by stator winding faults, up to 25%. Other faults such as rotor bars and end rings in induction machines, shafts, and other unidentified failures take up the remaining percentage in Fig. 1.2(a). The investigation data in [13] also illustrates that electrical winding failures amount to a failure rate of 1.4 × 10−7 failures per hour in military-grade machines and 1.0 × 10−6 in industrial machines. Since these surveys are mainly focused on induction machines, permanent magnet (PM) failure in permanent magnet synchronous machines (PMSMs) is not included. In fact, partial demagnetization is a frequent fault for PM machines due to a strong armature reaction field, overheating, and excessive mechanical stress and vibration [14].

Figure 1.2 Fault distribution in electrical drives: (a) machine side and (b) converter side.

A similar industry survey was conducted on failures in converters in [15]. The survey indicates that the most vulnerable component is the switching devices, followed by capacitors and gate drive circuitry. Open circuit in one phase due to device and connection failures is also a frequent fault. Failures associated with resistors and inductors are quite rare and only observed in a few applications, as shown in Fig. 1.2(b). The survey result shows most IGBT/MOSFET device failures result from thermal and power cycling, with a typical failure rate of 2.78 × 10−6 failures per hour. Additionally, the controller and sensors may also experience faults during operation. Nevertheless, it should be noted that the probability of the microcontroller and sensor faults is much lower.

As mentioned above, many potential faults may occur in the system. In this chapter, the principal device and electromagnetic faults under consideration that may occur within an electric drive are shown in Table 1.1.

On the machine side, the winding insulation degrades gradually due to electrical, thermal, and mechanical stresses and finally develops into open-circuit or short-circuit failure. The short-circuit failure can be classified as interphase and intraphase short circuit, which occur between phases or within a single phase, respectively. The intraphase fault is usually caused by turn-to-turn insulation failure. In particular, an intraphase fault involving a few turns, also known as a turn fault, is reported as the worst-fault scenario since only a few turns are short circuited. The resultant fault current is massive and the excessive hotspot temperature may lead to catastrophic failure. Partial demagnetization is another common fault in PM machines due to the excessive armature reaction field, overheating, and a high level of mechanical stress and vibration. It may cause torque reduction and increased torque ripple, etc.

Table 1.1 Potential faults occurring in an electric drive.

Machine side

Drive side

Winding open circuit

Switch device open circuit

Winding interphase short circuit

Switch device short circuit

Winding intraphase short circuit

DC-link capacitor failure

Demagnetization

Controller/sensor failure

Uncontrolled generation failure at high speed

On the drive side, the switch device is also subjected to open-circuit and short-circuit failure due to electric and thermal–mechanical stress during repeated switching on and off operations. DC-link capacitor is exposed to combined electrical and thermal stress during inverter operation and hence contributes to a considerable failure rate in electric drives [16]. Gate drive failure gives rise to similar consequences of switching device failures and may be incorporated into the switch device fault mechanism.

Besides, another possible fault is the uncontrolled generation, particularly for PM machines. If the power converter fails when the machine is rotating at high speed, the electromotive force (emf) may be much higher than the DC-link voltage and consequently cause uncontrolled rectification via the freewheeling diodes in the power converter. This may damage the DC-link components if the generated power is excessive and cannot be absorbed [17, 18].

So far, most of the fault-tolerant electrical drives focus on the faults described above [8, 13], since the most frequent bearing failure can be significantly reduced by regular maintenance, online monitoring, and replacement, whereas the controller and sensor faults are less likely.

1.3 Design Requirements of Fault-Tolerant Machine Drives

The requirements for the fault-tolerant systems in distributed power systems have been investigated in [10]. The methodology for fault-tolerant electrical drives follows relatively similar principles. The principal guideline is one fault in the system should be isolated in a subunit and has limited effect on the remaining healthy part, which can be in place to maintain uninterrupted operation. As extensively discussed in literature, four design criteria for fault-tolerant electrical drives are summarized.

Partitioning and Redundancy:

A fundamental specification for fault-tolerant system is that a single fault would not disrupt the whole system. Therefore, the fault must be confined to a relatively independent subsystem. This implies the system should be partitioned into several subunits. A fault would only disable the fault module, which would not cause malfunction of the whole system. Then, the remaining healthy modules could continue operation to meet the output requirement in the faulty condition. The trade-off between the redundancy number and cost is often debated at the design stage

[3]

.

Fault Isolation:

Partitioning alone is not enough to prevent the system breakdown from a faulty module, since certain types of fault may affect the remaining healthy subunits or even propagate to the whole system. It may lead to more severe consequences. Thus, many measures are employed to achieve fault isolation. Specifically, magnetic, electrical, thermal, and physical isolations are required for ideal fault-tolerant electrical drives to accommodate fault

[19]

.

Fault Detection:

On one hand, fault detection can help the electrical drive to isolate fault by taking appropriate fault mitigation action while on the other hand, continued operation needs information on fault type and location to perform appropriate postfault control. Fault must be detected before severe consequences occur. Indeed, fault detections are core techniques for fault-tolerant machine drives and require extensive and in-depth investigations.

Postfault Control:

After a fault, the machine drive changes its physical behaviors and the control law under healthy conditions may lose its effectiveness. For example, new voltage harmonics and excessive fault current may arise, and consequently, the current tracking quality with conventional control techniques deteriorates significantly, resulting in excessive torque pulsation, etc. Thus, a new postfault control strategy should be in place to protect the system and maintain its operation for continued functionality.

In summary, the above four requirements should be taken into consideration to design an integrated fault-tolerant electric machine drive system. However, current research on the fault-tolerant machine drive is quite fragmented, and most literatures only focus on one of them.

1.4 Current State-of-the-Art Techniques of Fault-Tolerant Machine Drives

To achieve an integrated fault-tolerant machine drive, a number of effective techniques have been developed, which include fault-tolerant machine drive topology, fault modeling, fault detection, and postfault control. These techniques are essential to accommodate various failures by transferring the machine drive from healthy operation to postfault operation in a reliable manner. The fault-tolerant machine drive topology enables the fault isolation and postfault operation while the fault modeling technique assesses machine performance in both healthy and faulty conditions and also aids in fault detection. Fault detection can identify and classify the faults and consequently trigger appropriate mitigation actions. After the fault, the previous control law becomes invalid since the machine has changed its physical behaviors. It requires a new postfault control strategy to accommodate the fault and suppress excessive and undesirable fault current if present. Subsequently, these key techniques are reviewed and the main challenges are highlighted.

1.4.1 Fault-Tolerant Machine Drive Topologies

Various fault-tolerant machine topologies have been reported and investigated in literature. The most straightforward approach is to adopt two or more redundant machine drive modules either in series or in parallel [7, 20]. In case of a failure in one module, the fault is isolated and the other module can continue its operation. However, the use of multiple machine modules for redundant operation occupies large space and necessitates additional accessories to guarantee operation, resulting in low power density and bulky size. Therefore, this approach becomes less attractive.

Alternatively, some level of fault tolerance may be achieved on a typical 3-phase machine drive by employing a neutral connection of the 3-phase winding to the midpoint of the DC link or to a fourth inverter leg as shown in Fig. 1.3(a) and (b) [21], respectively. It can cope with an open-circuit fault either in the inverter or in the 3-phase windings. By employing the neutral connection, the two remaining phase currents can be controlled independently. Zero-sequence current is utilized to generate the equivalent rotating magneto-motive force (MMF) in the machine if one phase is open circuited.

Figure 1.3 3-Phase fault-tolerant machine drive: (a) full bridge with DC midpoint and (b) four-leg inverter.

Figure 1.4 3-Phase machine using open-end winding drive (a) with independent power supplies and (b) with single power supply.

Another common fault-tolerant approach for 3-phase machines is to employ open-end winding drives as shown in Fig. 1.4. Both terminals of a 3-phase winding are available (opened) for connections to dual 3-phase inverters. The dual drives can share one DC link or use independent power supplies [22]. In addition to better fault-tolerant capability, they also bring the merits of 3-level voltage output, lower DC-link voltage for a given rated voltage of the machine and high efficiency. In case of a switch failure in one inverter, drive operation can be sustained by appropriate control of the healthy side inverter.

The access to the neutral point in Fig. 1.3 can be eliminated by employing more than three phases in a single machine as shown in Fig. 1.5 [23, 24]. Depending on the number of phases, a multiphase machine is capable of continuous operation when one or more than one phase has failed. Multiphase machine is initially investigated for high-power applications. By dividing the required power between multiple phases, higher power levels can be realized with specific rated power electronic converter modules. It can also reduce torque pulsation and lower DC-link harmonic current. As described above, a neutral point connection is required for a 3-phase machine after one phase is open circuited so that the current in the remaining two phases can be controlled independently. However, it is possible to take advantage of the additional degrees of freedom in a multiphase machine where the number of phases is greater than 3. With appropriate control of the power converter, a multiphase machine can continue its operation in case of an open-circuit fault without connecting the neutral point. Five-phase, six-phase, and seven-phase machines are most extensively investigated for both induction machines and PM machines [25–27