Modelling, Simulation and Implementation of a Fault Tolerant Permanent Magnet AC Motor Drive with Redundancy

Transcription

1 HE UNIVERSIY OF ADELAIDE Australia Modelling, Simulation and Implementation of a Fault olerant ermanent Magnet AC Motor Drive with Redundancy Jingwei Zhu Submitted to the Faculty of Engineering, Computer and Mathematical Sciences for the degree of Doctor of hilosophy School of Electrical and Electronic Engineering he University of Adelaide August 2008

2 Copyright 2008 Jingwei Zhu All Right Reserved

3 Contents Abstract Declaration... v... vii Acknowledgements... ix List of Figures... xi List of ables... xvii Symbols and Abbreviations... xix Chapter 1 Introduction roject Motivation Literature Review Fundamental aspects and fault modes in electric motor drives Fault tolerant motor design Inverter circuit fault analysis and possible topologies Fault detection and identification Fault tolerant control and torque ripple minimization Gaps and Contributions Gaps and objectives Main contributions Outline of the hesis Chapter 2 Fundamentals of Fault olerant Brushless M Motor Drives and Control Introduction Conventional Brushless M Motor Drives Classification Electrical model orque model Inverter circuit Control structure Fault olerant Brushless M Motor Drives Winding arrangement Inverter circuit i

4 2.4 Fault olerant M Motor Drives with Redundancy Fault olerant Brushless M Motor Drive Control Current control scheme orque control and torque ripple Conclusions...39 Chapter 3 Fault Analysis and Fault Remedial Strategy Investigation Introduction otential Faults and Fault Classification otential faults in motor drives Fault classification Mathematical Model of Reference Current Calculation Fault Analysis in Fault olerant Motor Drives Winding open-circuit fault analysis Switch open-circuit fault analysis Winding short-circuit fault analysis Switch short-circuit fault analysis Investigation of Fault Remedial Strategies Introduction Increasing average current fault remedial strategy Doubling current fault remedial strategy Zero torque ripple with minimum copper loss fault remedial strategy Comparison of different fault remedial strategies Conclusions...67 Chapter 4 Simulation Study of Fault olerant MAC Motor Drives With Redundancy Introduction Dual Module Fault olerant Motor Drive Setups Four-pole fault tolerant motor drive setup pole fault tolerant motor drive setup Efficiency rediction of 48-pole Motor Drive Setup Open-circuit power loss test Copper loss calculation Efficiency prediction of the dual fault tolerant motor drive Simulation Studies of Motor Drive Efficiency Simulation study of predicted efficiency...78 ii

5 4.4.2 Fault effect on motor drive efficiency Simulation Studies of 48-pole Motor Drive Setup Simulation of healthy operating condition One phase open-circuit fault simulation wo different phase open-circuit fault simulation wo same phase open-circuit fault simulation Simulation of one motor module complete open-circuit fault One phase short-circuit fault simulation Conclusions Chapter 5 Implementation of Fault olerant MAC Motor Drives with Redundancy Introduction Structure and Function of Motor Drive System Details of Hardware Implementation Current measurement circuit Motor controller and interface circuit Inverter and drive circuit Fault Detection and Identification Introduction he principle of electrical fault detection Fault identification Software Development Software development tools Software structure Synchronization of the rotor position Hysteresis current control implementation Look-up ables for Reference Current Calculation Look-up tables for one-phase open-circuit fault Look-up tables for two phase open-circuit fault Reference current calculation for one phase short-circuit fault Conclusions Chapter 6 Experimental Verification of Fault olerant MAC Motor Drives with Redundancy Introduction of the Experimental ests Healthy Operation Experiment iii

6 6.3 One hase Open-Circuit Fault Operation Experiment Four-pole motor drive experimental results Dual 48-pole motor drive experimental results Comparison of the experimental results wo Different hase Open-Circuit Fault Experiment Explanation of the experiment Analysis and comparison of the experimental results wo Same hase Open-Circuit Fault Experiment One Motor Complete Open-Circuit Fault Experiment One hase Short-Circuit Fault Experiment Motor Drive Efficiency est Conclusions Chapter 7 General Conclusions and Future Work General Conclusions Analytical investigation of fault tolerant motor drive Investigation of fault remedial strategies erformance investigation and simulation study of fault tolerant M motor drives Implementation and experimental verification of fault tolerant motor drives Future Work Appendix A List and Abstracts of ublications A.1 List of ublications A.2 Abstracts of ublications References iv

7 Abstract Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. his thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. hree fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. wo practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. he computer simulation studies using the MALAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. he efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. he effect of faults on the drive efficiency was investigated as well. he entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. he experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple. v

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9 Declaration he work in this thesis is based on research carried out at School of Electrical and Electronic Engineering, he University of Adelaide, Australia. his work contains no material which has been accepted for the award of any other degree or diploma in any university or other tertiary institution and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made in the text. I give consent to this copy of my thesis, when deposited in the University Library, being made available for loan and photocopying, subject to the provisions of the Copyright Act Signed: Date: vii

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11 Acknowledgements I am especially grateful to my supervisor Dr. Nesimi Ertugrul for his guidance, insightful conversations and endless encouragement throughout the duration of this research. It has been very stimulating and enjoyable to work with him. I am also sincerely grateful to my co-supervisor Dr. Wen L Soong for his consistent support and invaluable advice for finishing this work. I would like to thank all the technical staff for their help and assistance during my research in the power projects and in the instrumentation laboratories. I would also like to thank Dr. Ameen Gargoom and Ms Yongyong Jiang who help me in LABVIEW and dsic programming. I am grateful to the Australian Government and the University of Adelaide awarding me with the International ostgraduate Research Scholarship (IRS) and University of Adelaide Scholarship (UAS) during my studies. My thanks also go to all the staffs at the School of Electrical and Electronic Engineering of the University of Adelaide who were very helpful and friendly during my study in Australia. his thesis would not have been possible without the love and support of my wife, Mrs. Yujie Dong. I am grateful to her and appreciate her continuous encouragement and understanding during my studies. Jingwei Zhu August 2008, Adelaide. ix

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13 List of Figures 1.1 Fault modes in fault tolerant motor drives Classification diagram of the brushless M motors Sample cross sections of M motors based on magnet position Sample cross sections of M motors based on rotor position ypical single phase back-emf waveforms in brushless M motors Equivalent circuit of the standard three-phase brushless M motor opology of a three-phase brushless M motor inverter circuit hree-phase M motor drive current regulated torque control diagram Winding arrangement of fault tolerant brushless M motors hree phase fault tolerant brushless M motor drive inverter circuits rincipal diagram of dual fault tolerant motor drive configuration Inverter circuits of a dual fault tolerant motor drive rinciples of a hysteresis current control scheme WM current control scheme A sample measured phase currents and torque waveforms Structure of the fault tolerant M motor drive Graphical representations of the possible short-circuit fault in hase Relative output torque waveform in single motor drive when winding opencircuit fault occurred in hase 1 without remedial strategy Relative output torque waveform in dual motor drive when winding opencircuit fault occurred in hase 6 without remedial strategy Relative output torque waveform in the single motor drive under switch opencircuit fault without remedial strategy adopted Relative output torque waveform in the dual motor drive under switch opencircuit fault without remedial strategy adopted Equivalent circuit of winding and switch short-circuit faults Calculated per-unit short-circuit current curves as a function of rotor speed under winding short-circuit fault condition Calculated per-unit drag torque curves as a function of rotor speed under winding short-circuit fault condition xi

14 3.10 Calculated per-unit copper loss curves versus rotor speed under winding shortcircuit fault condition Simulated back-emf voltage and current waveforms under winding and switch short-circuit fault conditions Simulated back-emf voltage and drag torque waveforms under winding and switch short-circuit fault conditions Relationships between RMS short-circuit current and average drag torque with speed under winding and switch short-circuit faults Simulated results of dual motor drive under one phase open-circuit fault and fault remedial strategy Simulated results of single motor drive under hase 3 open-circuit fault with fault remedial strategy Simulated results of dual motor drive under hase 3 open-circuit fault condition with fault remedial strategy Simulated results of dual motor drive under hases 2 and 3 open-circuit fault condition with fault remedial strategy Dual 4-pole three phase fault tolerant motor drive setup Measured 4-pole motor back-emf voltages hotes of 48-pole fault tolerant motor drive setup and motor structure Measured back-emf waveforms of 48-pole fault tolerant motor hoto and block diagram for motor open-circuit power loss tests Measured open-circuit torque loss versus rotor speed he estimated power and the efficiency curves versus rotor speed he estimated efficiency contours of dual fault tolerant motor drive Dual motor drive simulation block diagram with speed control he estimated and simulated efficiency characteristics versus rotor speed under three load torques Changes in the coefficient of copper loss as a function of the number of opencircuit phase faults Dual motor drive simulation block diagram for torque control Simulated efficiency characteristics in healthy and faulty cases Simulated motor module 1 phase current and total torque waveforms under healthy operation xii

15 4.15 Simulated phase current waveforms of motor module 1 under different DC link voltages and same peak reference current value Simulated total output torque waveforms under different DC link voltages and same peak reference current value Simulation torque waveforms under one phase open-circuit fault Simulated phase current waveforms under one hase open-circuit fault with remedial strategy Simulated torque waveforms under two different phase open-circuit faults without and with fault remedial strategies 1, 2 and Simulated phase current waveforms under two different phase open-circuit faults with fault remedial strategy Simulated torque waveforms under two same phase open-circuit faults without and with fault remedial strategies 1 and Simulated phase currents and torque waveforms under one motor complete open-circuit fault with fault remedial strategy he characteristics of the drag torque and the phase current increment for compensating the drag torque in different rotor speed Simulated torque waveforms under hase 4 short-circuit fault at lower speed without fault remedial strategy was adopted Simulation results under hase 4 short-circuit fault at lower speed with fault remedial strategy Simulation results under hase 4 short-circuit fault at lower speed with fault remedial strategy Simulated torque waveforms under phase 4 short-circuit fault at higher speed without fault remedial strategy Simulation results under hase 4 short-circuit fault at higher speed with fault remedial strategy Block diagram of the dual motor module fault tolerant drive Current transducer and signal conditioning circuit hoto of CB board for three phase current test A simplified diagram of the microcontroller in the drive system he photo of motor controller CB board he simplified diagram of an Inverter and drive circuits he photo of the inverter circuit CB board xiii

16 5.8 est results of the optocoupler circuits in different resistance values Measured waveforms of controller output signal, optocoupler output signal, low side switch drive output signal, and inverter output signal A high side switch and its driver circuit with fault detection circuit Switch 1, 2 drive input, output and ERR waveforms in healthy operation Switch 1, 2 driver input, output and ERR waveforms in over-current operation Switch 1, 2 driver input, output and ERR waveforms in 2 open-circuit fault operation he fault identification subroutine flow chart Flow chart of the main program Synchronization of the rotor positions in a 4-pole M motor drive Flow chart of the phase 1 update state subroutine Measured phase voltage and current waveforms in the hysteresis current control scheme Reference current coefficient waveforms for fault remedial strategy 3 operation under one phase open-circuit fault Reference current coefficient waveforms for the fault remedial strategy 3 operation under two phase open-circuit faults Measured and calculated short-circuit current and phase difference in 48-pole fault tolerant motor drive versus rotor speed A functional diagram of the motor control system Block diagram of 48-pole dual motor drive experimental setup Block diagram of 4-pole dual motor drive experimental setup he photo of 48-pole dual motor module drive experimental setup he photo of 4-pole dual motor module drive experimental setup est results of dual 48-pole motor drive under healthy operation est results of dual 4-pole motor drive under healthy operation est results of dual 4-pole motor drive under one phase open-circuit fault condition without fault remedial strategy Dual 4-pole motor drive experimental results under one phase open-circuit fault operation with fault remedial strategy xiv

17 6.9 Dual 4-pole motor drive experiment results under one phase open-circuit fault operation with fault remedial strategy est results of dual 48-pole motor drive under one phase open-circuit fault without fault remedial strategy est results of dual 48-pole motor drive under one phase open-circuit fault with fault remedial strategy est results of dual 48-pole motor drive under one phase open-circuit fault with fault remedial strategy est results of dual 48-pole motor drive under one phase open-circuit fault with fault remedial strategy est torque waveforms of dual 48-pole motor drive under two different phase open-circuit fault without fault remedial strategy est results of dual 48-pole motor drive under two different phase open-circuit fault with fault remedial strategy est results of dual 48-pole motor drive under two different phase open-circuit fault with fault remedial strategy est results of dual 48-pole motor drive under two different phase open-circuit fault with fault remedial strategy he estimated output torque curves of dual 48-pole motor drive under two same phase open-circuit fault without fault remedial strategy est results of dual 48-pole motor drive under two same phase open-circuit fault with fault remedial strategy Estimated torque waveforms of dual 4-pole motor drive under two same phase open-circuit fault without fault remedial strategy est results of dual 4-pole motor drive under two same phase open-circuit fault with fault remedial strategy Experimental results of dual 48-pole motor drive under one complete motor module open-circuit fault with fault remedial strategy Experimental results of dual 48-pole motor drive under one phase short-circuit fault without fault remedial strategy Experimental results of dual 48-pole motor drive under short-circuit fault with fault remedial strategy Relationship between the short-circuit current (peak values) and the drag torque as a function of the rotor speed he power flow chart of the dual 48-pole motor drive setup xv

18 6.27 he dual 48-pole motor drive efficiency test results Relative copper loss versus torque ripple under different operating modes xvi

19 List of ables 3.1 otential electrical faults and their representations in hase he features of the fault remedial strategy 1 in different fault modes Feature comparison of different fault remedial strategies arameters of the 4-pole MAC Motor Modules pole motor parameters Feature comparisons of different fault remedial strategies for one phase opencircuit fault operation at higher speed Feature comparisons of different fault remedial strategies for two different phase open-circuit fault operations in higher speed Feature comparisons of different fault remedial strategies for two same phase open-circuit fault operations in higher speed Feature comparison of different fault remedial strategies for one phase opencircuit fault operation in 4-pole single motor module fault tolerant drive Feature comparison of different fault remedial strategies under one phase opencircuit fault operation in 48-pole dual motor module fault tolerant drive Feature comparison of different operating modes under two different phase open-circuit fault condition in the 48-pole dual fault tolerant motor drive Experiment results of motor drive under two same phase open-circuit fault xvii

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21 Symbols and Abbreviations Abbr. B Variable Name Damping coefficient e hase back-emf voltages 1, 2, 3, 4, 5, 6 e1, 2, 3, 4, 5, 6( θ e) hase back-emf functions E m I in I m Amplitude of back-emf voltage Input phase current of current sensor eak phase current in a dual module motor drive I m0 eak phase current in a single module motor drive i measured Measured current I mrs I R eak phase current in a dual module motor drive after the fault remedial strategy is adopted Current in the rheostat i reference Reference current I SCm eak value of short-circuit current I SCpu er unit value of short-circuit current i hase currents 1, 2, 3, 4, 5, 6 J Moment of inertia k e, e1 k, k e2 Back-EMF constant K ( θ ), K ( θ ) 1 e K ( θ ) 3 e 2 e K ( θ ), K ( θ ) 4 e K ( θ ) 6 e K ( θ e ) k j K ( θ e ) L k l j 5 e Coefficients for reference current calculation when one phase open-circuit fault with fault remedial strategy 3 Coefficients for reference current calculation when two different phase open-circuit fault with fault remedial strategy 3 hase j reference current coefficient when hase k suffers open-circuit fault with fault remedial strategy 3 hase j reference current coefficient when hases k and l suffer open-circuit fault with fault remedial strategy 3 Equivalent winding inductance xix

22 L 11, L 22, L 33 Self-inductances in phases 1, 2, and 3 L pu er unit the inductance m he number of phase with open-circuit fault M12 M 23 M 31 Mutual inductances between phases 1, 2, and 3 n N p otal number of phase in the motor drive Number of pole pairs ave Average copper loss in a dual module motor drive cu Instantaneous copper loss of a dual motor module cu0 Instantaneous copper loss of a single motor module curelative0 Relative copper loss in a single motor module drive curelative Relative copper loss in a dual motor module drive curs Copper loss of a dual motor module under a fault remedial strategy cusc Copper loss in a short-circuit winding cuscpu er unit copper loss in a short-circuit winding in0 otal input power of a single module motor drive in otal input power of a dual module motor drive mech0 Mechanical power of a single module motor drive openloss Open-circuit power loss in a dual motor module drive out Output power of a dual motor module drive R Equivalent winding resistance R pu er unit winding resistance 0 Electromagnetic torque of a single module motor drive Electromagnetic torque of a dual module motor drive ave Average torque in a dual module motor drive avedrag Average drag torque in a short-circuit winding avedragpu er unit average drag torque xx

23 F 0 F Output torque of a single module motor drive under faulty condition Output torque of a dual module motor drive under faulty condition L0 Load torque of a single module motor drive L Load torque of a dual module motor drive max, min Maximum and minimum total instantaneous torque values openloss0 Open-circuit torque loss in a single motor module drive openloss Open-circuit torque loss in a dual motor module drive ripple orque ripple factor RS 0 RS Output torque of a single module motor drive under a fault remedial strategy Output torque of a dual module motor drive under a fault remedial strategy v Instantaneous values of phase voltages 1, 2, 3, 4, 5, 6 V DC1, 2 DC link voltage V in Current sensor output voltage V out Amplifier output voltage of phase current measurement V phase hase voltage for Hysteresis current control V R Voltage of the rheostat h Bandwidth of the hysteresis current control i Current error between the reference current and measured current Integration time η Efficiency of the motor drive ψ hree phase flux linkages of the rotor permanent magnets pm1, pm2, pm3 θ e Electrical rotor position θ r Mechanical rotor position ω m Mechanical angular speed xxi

24 ω pu er unit value of the mechanical angular speed ω r ω e φ Electrical angular speed Electrical angular speed he phase difference between the back-emf voltage and the short-circuit current ψ otal values of the phase flux linkages 1, 2, 3, 4, 5, 6 F OC RS SC Fault Open-circuit fault Remedial strategy Short-circuit fault Superscript denoting reference values xxii