SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

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Organization This report is organized into the following chapters and appendices. Chapter 2 – “Fundamentals of Electric Motors” – presents some fundamentals of electric motors and their models, eventually narrowing the focus to the brushless permanent magnet (BPMS) motor that is the subject of this report. The basics of motor structure and terminology are discussed, followed by a fundamental examination of the physical laws that govern motor operation; this leads to the general per-phase electrical model for a winding that will be used throughout the report. In addition, the derivation provides a foundation for understanding inductance in a motor winding and demonstrates the significance of the magnet’s leakage permeance on the magnetic circuit. Then torque production and back-EMF generation are investigated on a per-phase basis. This forms a basis for understanding polyphase motor operation and enables the full phase-variable electromechanical model of the polyphase motor to be developed. In the last section, the two theoretical types of BPMS motors are discussed and torque and back-EMF are then investigated for these two motors. This examination of torque production forms a natural introduction to current commutation. Chapter 3 – “Sinusoidal BPMS Motors” – is the most important chapter and comprises the bulk of the report. Its ultimate purpose is to develop a space vector model for the sinusoidal BPMS motor because that model and its understanding (reference frame theory) are the basis for all modern motor modeling and control schemes. In order to achieve this goal the chapter is split into three parts. In Part I the standard analysis of sinusoidal synchronous machines is presented in the time and phasor domains. Part II introduces and discusses the space vector definition, notation, and interpretation by building on the understanding of the synchronous machine presented in Part I. Finally, Part III applies the space vector concepts from Part II to the modeling material from Part I to yield the space vector model of a BPMS motor. Chapter 4 – “Inverters and Space Vector Modulation” –reviews inverter topologies and basic principles, concentrating on the voltage-source inverter (VSI). Space vector modulation (SVM) is introduced by building on the six-step 180° squarewave inverter. The 6
elationship between SVM and other PWM methods is discussed and some detailed aspects of SVM are presented. Chapter 5 – “Field Oriented Control of BPMS Motors” – develops the concept of field oriented control as applied to the brushless PM synchronous motor. The concept is introduced by building on the per-phase torque production described in Chapter 2. It is then shown that FOC implements current regulation in the synchronous frame. The stationary and synchronous regulators are compared, then the synchronous regulator is studied in greater detail and decoupling control is introduced. Chapter 6 – “Sensorless Techniques” – describes some techniques used to achieve control of a synchronous machine without using physical shaft sensors. Chapter 7 – “Concluding Remarks” – makes some final comments regarding the topics investigated in this report. Appendix A – “Elementary Electromagnetics” – reviews some basic electromagnetic concepts of a general machine in order to clarify terms that are sometimes incorrectly defined in the literature. Then the general case is specialized for the permanent magnet brushless motor in order to define the terminology used in this report. Appendix B – “Phase-variable BPMS Motor Model” – derives the phase-variable model of a BPMS motor. Particular attention is given to the concepts of magnetizing, leakage, and synchronous inductance of a three-phase machine and the influence of the wye connection on the phase-variable model. Appendix C – “Sinusoidal and Nonsinusoidal Motors” – elaborates the distinction between sinusoidal and nonsinusoidal motors. Appendix D – “Three-Phase Concepts and Transformations” – is a collection of various topics related to three-phase systems that appear throughout the report. Topics include harmonics, sequence components, the method of symmetrical components, the relationship between the Clarke and αβ0 transforms, the linear dependence of the phases 7
Page 1 and 2: SENSORLESS FIELD ORIENTED CONTROL O
Page 3 and 4: Table of Contents List of Figures..
Page 5 and 6: CHAPTER 5 - Field Oriented Control
Page 7 and 8: List of Figures Figure 2.1 - Radial
Page 9 and 10: Figure 3.29 - Arbitrary space vecto
Page 11 and 12: Figure 4.44 - ZS components of some
Page 13 and 14: Figure C.13 - Single-turn full-pitc
Page 15 and 16: List of Symbols Symbol Meaning Unit
Page 17 and 18: Abbreviations ACIM AC induction mot
Page 19 and 20: Superscripts * commanded value ref
Page 21 and 22: CHAPTER 1 - Introduction Historical
Page 23 and 24: vector theory to model a machine, w
Page 25: publications and magazines, and Int
Page 29 and 30: CHAPTER 2 - Fundamentals of Electri
Page 31 and 32: Preliminaries In reading the litera
Page 33 and 34: Taxonomy of Motors There is any num
Page 35 and 36: characteristics (the DC load curren
Page 37 and 38: torque component, sturdily construc
Page 39 and 40: Figure 2.7 - Cross sections of some
Page 41 and 42: draw the line between the solenoida
Page 43 and 44: These texts generally attribute the
Page 45 and 46: N B A B Y x(t) (2.6) The induc
Page 47 and 48: extended to the rotational case lat
Page 49 and 50: present analysis). When this is tru
Page 51 and 52: Figure 2.16 - Components of total f
Page 53 and 54: As aforementioned a spatial analysi
Page 55 and 56: clear the meaning, but the reader i
Page 57 and 58: Figure 2.20 - Elementary brushless
Page 59 and 60: called the per-phase torque functio
Page 61 and 62: Expressing bEMF in terms of the bEM
Page 63 and 64: Equation (2.44) is the component of
Page 65 and 66: d R( r) ke( r) kt( r) sin( r) (2.
Page 67 and 68: General Electromechanical Models Th
Page 69 and 70: Figure 2.28 - Phase-variable simula
Page 71 and 72: Trapezoidal and Sinusoidal BPMS Mot
Page 73 and 74: Figure 2.29 - Back-EMF and drive cu
Page 75 and 76: Figure 2.31 - Back-EMF and drive cu
Page 77 and 78:
3 KT Ke 2 (sinusoidal) K 2 K (tra
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control scheme must keep sinusoidal
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with misconceptions. The primary is
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Part I - Sinusoidal BPMS Motors wit
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grounded-neutral wye or delta conne
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N e f A ( ) i 2 N e f B ( ) i 2
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Figure 3.7 - Developed view at zero
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Figure 3.9 - Developed view showing
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Although Equations (3.6) or (3.7) a
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direction. The contributions always
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sinusoidal electrical variable will
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Figure 3.14 - Cross section of two
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3 N e (3.6): f ( , t) I p cos(
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In the previous chapter the per-pha
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peak value is represented as an upp
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Figure 3.21 - Time relationship bet
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another and thus could be placed in
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more widely understood theory (such
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other methods, although it has clos
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The SV as a Vector The first facet
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j0 j0 j0 aˆ 1 0 1 bˆ j e e e
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j j ee 1 cos( ) (3.45) 2 3 j t x
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Notice that the amplitude of the MM
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Figure 3.27 - Equivalent MMF produc
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Ne 1 jj f , t i e i * e 2 2
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distribution that is cosinusoidal i
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3 Ne j t f Ie p 2 2 . This
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j set θ to anything. Taking the re
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epresent any physically-distributed
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lumped-parameter model in this repo
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x kCx (3.75) abc The set of varia
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phase variable axes; three axes in
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The component MMFs act away from th
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common choice is to force the power
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As an example, find the SV that cor
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the same magnitude, the projection
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Figure 3.32 - Arbitrary SV referenc
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universal and the choice of convent
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stator’s perspective and at R fr
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The potential discrepancy (p.108) w
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x cos( r) sin( r) xd x sin(
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It must be emphasized that we have
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in relative time like an oscillogra
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Part III - SV Theory Applied to Sin
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In Equation (3.135) Z has elements
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to use SV theory. It may be helpful
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Figure 3.42 - Coupling between d- a
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R R d R R v Ri Li j Li dt s
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current does not influence the valu
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d v Ri L i e dt d v Ri L i e
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Figure 3.47 - Simulation diagram fo
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e je ), and (2) it was demonstrate
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Overview of Voltage Source Inverter
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In addition to measuring voltages w
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then there would be periods during
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Figure 4.9 - Gating and POLE voltag
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Figure 4.11 - Ideal voltage wavefor
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inverter is called sine-triangle co
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and it offers the fastest dynamic r
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Figure 4.18 - Fundamental gain and
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In the literature this is called th
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voltage will be below (above) the b
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Figure 4.24 - Instantaneous phase-A
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Figure 4.26 - Base SVs showing the
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Figure 4.27 - Transformed voltage w
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also correspond to six-step squarew
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was fed to the SVM inverter as a SV
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Figure 4.31 - Temporal limit of inv
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Figure 4.34 - SVM overmodulation re
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Checking sextant s 23 again for thi
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SVM Implementation The block diagra
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has been made of using THI in the S
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different triplen signal would be i
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Similarly, when the modulation inde
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Summary and Conclusion The two-leve
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CHAPTER 5 - Field Oriented Control
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torque production; this is called d
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Figure 5.3 - Torque control of sinu
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obviously a change in perspective.
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Figure 5.9 - Comparison of referenc
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variables to the stationary referen
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Figure 5.13 - Torque control of sin
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To analyze a salient machine one mu
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Figure 5.16 - Torque functions: (a)
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Figure 5.19 - Buried permanent magn
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Figure 5.21 - Flux weakening in the
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appears that this is very much rela
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Stationary and Synchronous Regulato
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stationary regulator had. For compl
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This coupling can be mitigated by m
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educes to two independent circuits,
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D, some of the 120° methods are ap
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d d v Ri Ls i R dt dt The r
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section a state-space model for the
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Figure 6.6 - Full state feedback (o
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State-Space Model of BPMS Motor A s
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Figure 6.9 - FOC block diagram. The
Page 271 and 272:
loop). A second way to implement th
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knowing the rotor position from ini
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[11] E. Clarke, Circuit analysis of
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Control Systems, Linear Analysis [4
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[77] J.M.D. Murphy, F.G. Turnbull,
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Machine Modeling, Analysis [103] J.
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THI, SVM, SPWM [127] J.A. Houldswor
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Wisconsin-Madison. [Online]. Availa
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Angle Tracking [175] D. Morgan, “
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Appendix A - Elementary Electromagn
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L i (A.8) S SS S SR S SS SR (A.9
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First the self-flux-linkage of an i
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vAN R iA LM iA eA d v R i
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Figure B.3 - One-half of the flux p
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Equations (B.27) and (B.28) are for
Page 301 and 302:
Fundamental Relationships Figure C.
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Figure C.3 - Sinusoidal winding den
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manufactured compared to the steppe
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phase winding of Figure C.4 will ha
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Distributed N Fp i 2 (C.5) Figu
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alanced machine only odd harmonics
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sinusoidal windings with a sinusoid
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0, and since the direction of inte
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That the rotor-stator flux linkage
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Figure C.17 - Summary of rotor-stat
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Figure C.19 - Amplitudes of harmoni
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triangle with an amplitude whose nu
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Returning to Figure C.18 it is clea
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torque will describe the torque pro
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However, Equation (D.2) is incorrec
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the same order as the PS set (arran
Page 333 and 334:
Implications of the ZS Component Th
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Figure D.6 - Neutral voltage of loa
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3v 3e 3v v v v v v v 3v AM BM CM A
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components of source voltage sum to
Page 341 and 342:
Equation (D.25) and instantaneous q
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If a ZS component could possibly be
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xA X1cos( t) X3cos(3 t) X5cos(5 t)
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Figure D.11 - 3-D base vectors of 1
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the Clarke transform is used. Howev
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Appendix E - Park Transforms This a
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Appendix F - Useful Mathematical Re
Page 355:
335
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