R Balamurugan FDP Electrical Drives and Control
Transcript of R Balamurugan FDP Electrical Drives and Control
1 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Faculty Development Programe on “Faculty Development Programe on “Faculty Development Programe on “Faculty Development Programe on “ELECTRICAL DRIVES AND CONTROLELECTRICAL DRIVES AND CONTROLELECTRICAL DRIVES AND CONTROLELECTRICAL DRIVES AND CONTROL””””
By
R. BALAMURUGAN Asst. Prof. – Electrical and Electronics Engineering
Anna University of Technology Coimbatore, Coimbatore
Anna University of Technology CoimbatoreAnna University of Technology CoimbatoreAnna University of Technology CoimbatoreAnna University of Technology Coimbatore
CoimbatoreCoimbatoreCoimbatoreCoimbatore
ELECTRICAL DRIVES CONTROLELECTRICAL DRIVES CONTROLELECTRICAL DRIVES CONTROLELECTRICAL DRIVES CONTROL
Date: 12Date: 12Date: 12Date: 12----07070707----2011 2011 2011 2011
Venue: Seminar Hall, School of Management Studies Venue: Seminar Hall, School of Management Studies Venue: Seminar Hall, School of Management Studies Venue: Seminar Hall, School of Management Studies
University Academic Campus University Academic Campus University Academic Campus University Academic Campus
2 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
1.1.1.1. IntroductionIntroductionIntroductionIntroduction
2.2.2.2. TypesTypesTypesTypes ofofofof DrivesDrivesDrivesDrives ControlControlControlControl
3.3.3.3. FieldFieldFieldField OrientedOrientedOrientedOriented ControlControlControlControl (FOC)(FOC)(FOC)(FOC)
4.4.4.4. DirectDirectDirectDirect TorqueTorqueTorqueTorque ControlControlControlControl (DTC)(DTC)(DTC)(DTC)
5.5.5.5. AdaptiveAdaptiveAdaptiveAdaptive ControlControlControlControl SchemesSchemesSchemesSchemes
Topics of DiscussionTopics of DiscussionTopics of DiscussionTopics of Discussion
3 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variable Frequency Drive SystemVariable Frequency Drive SystemVariable Frequency Drive SystemVariable Frequency Drive System
Figure: PWM VFD WaveformFigure: PWM VFD WaveformFigure: PWM VFD WaveformFigure: PWM VFD Waveform
Figure: VFD SystemFigure: VFD SystemFigure: VFD SystemFigure: VFD System
4 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Possible Possible Possible Possible parameter parameter parameter parameter variations controlled variations controlled variations controlled variations controlled electrical drive systemselectrical drive systemselectrical drive systemselectrical drive systems,,,,
Change of winding electromagnetic time constant due to the temperature rise or material deterioration
Change of the mechanical time constant due to moment of inertia changes of the drive
Change of the flux value, in drive with the field weakening operation
Change of the drive system structure (e.g., due to the transition from continuous to discontinuous armature current in a rectifier-fed DC motor drive)
5 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variable Speed Electric DriveVariable Speed Electric DriveVariable Speed Electric DriveVariable Speed Electric Drive
Common features - Require information on instantaneous rotor position (speed), - Closed-loop control operation - Machine is supplied from a power electronic converter Applications Robotics Machine tools Elevators Rolling mills Paper mills Spindles Mine winders Electric traction Electric and hybrid electric vehicles, and the like.
6 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variable Speed Electric DriveVariable Speed Electric DriveVariable Speed Electric DriveVariable Speed Electric Drive
Figure : Schematic outlay of a high-performance variable speed electric drive
7 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variable Speed Electric Drive Variable Speed Electric Drive Variable Speed Electric Drive Variable Speed Electric Drive ---- OperationOperationOperationOperation
Electromagnetic torque of an electric machine - Product of the flux-producing current and torque-producing current - Control system has two parallel paths - Flux-producing current reference (as a constant) - Torque-producing current (the output of the torque controller)
8 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variable Speed Electric Drive Variable Speed Electric Drive Variable Speed Electric Drive Variable Speed Electric Drive ---- OperationOperationOperationOperation
- Torque controller is usually not present in high-performance drives - Torque-producing current reference can be obtained directly from the reference torque by means of a simple scaling (or the output of the speed controller can be made to be directly the torque-producing current reference
- The torque and the torque-producing current - related through a constant. The control (when a high-performance control algorithm is applied)
- Control structure : Composed of cascaded controllers (typically of PID)
9 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Fundamentals of Induction Motor (IM) TheoryFundamentals of Induction Motor (IM) TheoryFundamentals of Induction Motor (IM) TheoryFundamentals of Induction Motor (IM) Theory
Case 1: Case 1: Case 1: Case 1: VoltageVoltageVoltageVoltage----ControlledControlledControlledControlled IMIMIMIM RepresentedRepresentedRepresentedRepresented inininin aaaa StatorStatorStatorStator----FixedFixedFixedFixed SystemSystemSystemSystem ofofofof CoordinatesCoordinatesCoordinatesCoordinates ((((α,,,, β))))
Case 2: Case 2: Case 2: Case 2: CurrentCurrentCurrentCurrent----ControlledControlledControlledControlled IMIMIMIM RepresentedRepresentedRepresentedRepresented inininin SynchronousSynchronousSynchronousSynchronous CoordinatesCoordinatesCoordinatesCoordinates (d,(d,(d,(d, q)q)q)q)
FigureFigureFigureFigure:::: VectorVectorVectorVector diagramdiagramdiagramdiagram ofofofof InductionInductionInductionInduction MotorMotorMotorMotor (IM)(IM)(IM)(IM) inininin stationarystationarystationarystationary α − β
andandandand rotatingrotatingrotatingrotating dddd − qqqq coordinatescoordinatescoordinatescoordinates
10 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Steady State CharacteristicsSteady State CharacteristicsSteady State CharacteristicsSteady State Characteristics
The The The The breakdown torque breakdown torque breakdown torque breakdown torque is is is is independent independent independent independent of the of the of the of the rotor resistancerotor resistancerotor resistancerotor resistance
The The The The breakdown slip frequency breakdown slip frequency breakdown slip frequency breakdown slip frequency is is is is proportional proportional proportional proportional to the to the to the to the rotor resistance rotor resistance rotor resistance rotor resistance
Under Under Under Under constant Us/constant Us/constant Us/constant Us/fsfsfsfs modemodemodemode, the , the , the , the breakdown torque breakdown torque breakdown torque breakdown torque remains remains remains remains constantconstantconstantconstant
The simplified The simplified The simplified The simplified KlossKlossKlossKloss formulaformulaformulaformula
where the breakdown torque iswhere the breakdown torque iswhere the breakdown torque iswhere the breakdown torque is
11 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Steady State CharacteristicsSteady State CharacteristicsSteady State CharacteristicsSteady State Characteristics
Figure: Torque-slip frequency characteristic obtained from the Kloss formula
12 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
IM Control CharacteristicsIM Control CharacteristicsIM Control CharacteristicsIM Control Characteristics
Figure: Control characteristics of IM in constant and weakened flux regions
General Classification of IM control MethodsGeneral Classification of IM control MethodsGeneral Classification of IM control MethodsGeneral Classification of IM control Methods
13 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Constant V/Hz control schemeConstant V/Hz control schemeConstant V/Hz control schemeConstant V/Hz control scheme
14 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Constant V/Hz control schemeConstant V/Hz control schemeConstant V/Hz control schemeConstant V/Hz control scheme (dashed lines show version with limited slip frequency (dashed lines show version with limited slip frequency (dashed lines show version with limited slip frequency (dashed lines show version with limited slip frequency Ωslcslcslcslc and speed control)and speed control)and speed control)and speed control)
15 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
16 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
VectorVectorVectorVector controlcontrolcontrolcontrol (also(also(also(also calledcalledcalledcalled FieldFieldFieldField----OrientedOrientedOrientedOriented ControlControlControlControl,,,, FOC)FOC)FOC)FOC) isisisis oneoneoneone methodmethodmethodmethod usedusedusedused inininin
variablevariablevariablevariable frequencyfrequencyfrequencyfrequency drivesdrivesdrivesdrives totototo controlcontrolcontrolcontrol thethethethe torquetorquetorquetorque (and(and(and(and thusthusthusthus finallyfinallyfinallyfinally thethethethe speedspeedspeedspeed)))) ofofofof
threethreethreethree----phasephasephasephase ACACACAC electricelectricelectricelectric motorsmotorsmotorsmotors bybybyby controllingcontrollingcontrollingcontrolling thethethethe currentcurrentcurrentcurrent fedfedfedfed totototo thethethethe machinemachinemachinemachine....
Vector ControlVector ControlVector ControlVector Control
PropertiesPropertiesPropertiesProperties
Speed or position measurement or some sort of estimation is needed
Torque and flux can be changed reasonably fast, in less than 5-10 milliseconds, by
changing the references
The step response has some overshoot if PI control is used
The switching frequency of the transistors is usually constant and set by the
modulator
The accuracy of the torque depends on the accuracy of the motor parameters
used in the control. Thus large errors due to for example rotor temperature
changes often are encountered.
Reasonable processor performance is required, typically the control algorithm
has to be calculated at least every millisecond.
17 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Field Oriented ControlField Oriented ControlField Oriented ControlField Oriented Controll (l (l (l (FOC)FOC)FOC)FOC)
1. Principle of the FOC - An analogy to the mechanically commutated DC
brush motor
2. Owing to separate exciting and armature winding,
Flux - Controlled by exciting current
Torque - Controlled independently by adjusting the armature current
3. Flux and torque currents - Electrically and magnetically separated
4. The cage-rotor IM
- Only a three-phase winding in the stator
- Stator current vector (Is) - Used for both flux and torque control
5. Coupled Currents - Exciting and armature currents
(Not separated) in the stator current vector
- Cannot be controlled separately
18 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Field Oriented ControlField Oriented ControlField Oriented ControlField Oriented Controll (l (l (l (FOC) Schemes FOC) Schemes FOC) Schemes FOC) Schemes
Direct FOCDirect FOCDirect FOCDirect FOC
19 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Field Oriented ControlField Oriented ControlField Oriented ControlField Oriented Controll (l (l (l (FOC) Schemes FOC) Schemes FOC) Schemes FOC) Schemes
Indirect FOCIndirect FOCIndirect FOCIndirect FOC
Variants of FOC control schemes Variants of FOC control schemes Variants of FOC control schemes Variants of FOC control schemes
for fieldfor fieldfor fieldfor field----weakened operation: (a) Indirect FOC weakened operation: (a) Indirect FOC weakened operation: (a) Indirect FOC weakened operation: (a) Indirect FOC
20 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
21 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variants of FOC control schemes Variants of FOC control schemes Variants of FOC control schemes Variants of FOC control schemes
for fieldfor fieldfor fieldfor field----weakened operation: (b) direct FOCweakened operation: (b) direct FOCweakened operation: (b) direct FOCweakened operation: (b) direct FOC
22 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
TTTTrrrr ---- Adaption based on model reference adaptive system (MRAS)Adaption based on model reference adaptive system (MRAS)Adaption based on model reference adaptive system (MRAS)Adaption based on model reference adaptive system (MRAS)
Parameter Adaptation - The critical parameter - Rotor time constant (Tr)
ConditionsConditionsConditionsConditions ofofofof ChangeChangeChangeChange ::::
Under the influence of temperature changes of rotor resistance (Rr) and
Changes brought about by the saturation effect (Rotor inductance (Lr) )
The temperature changes of Rr - VeryVeryVeryVery slow,slow,slow,slow,
The changes of Lr - veryveryveryvery fast,fast,fast,fast,
( i.e., Case of speed reversal when the motor)
23 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Variants of Variants of Variants of Variants of TTTTrrrr————Adaption AlgorithmsAdaption AlgorithmsAdaption AlgorithmsAdaption Algorithms
24 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Block scheme of NFO (Voltage Controlled SBlock scheme of NFO (Voltage Controlled SBlock scheme of NFO (Voltage Controlled SBlock scheme of NFO (Voltage Controlled S----FOC) FOC) FOC) FOC)
with optional outer torque control loop (dashed lines)with optional outer torque control loop (dashed lines)with optional outer torque control loop (dashed lines)with optional outer torque control loop (dashed lines)
Note: Note: Note: Note:
Natural field orientation(NFO)Natural field orientation(NFO)Natural field orientation(NFO)Natural field orientation(NFO)
---- Commercially available as Commercially available as Commercially available as Commercially available as
an ASICan ASICan ASICan ASIC
25 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Block scheme of NFO (Voltage Controlled SBlock scheme of NFO (Voltage Controlled SBlock scheme of NFO (Voltage Controlled SBlock scheme of NFO (Voltage Controlled S----FOC) FOC) FOC) FOC) with optional outer torque control loop (dashed lines)
26 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Vector Vector Vector Vector control scheme for a multiphase machinecontrol scheme for a multiphase machinecontrol scheme for a multiphase machinecontrol scheme for a multiphase machine
Figure : Basic vector control scheme for a multiphase machine with CC in the stationary reference frame
27 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Vector Vector Vector Vector control scheme for control scheme for control scheme for control scheme for PMSMPMSMPMSMPMSM
Figure : Vector control of a PMSM with surface-mounted magnets in the base
speed region (K1 = Pψm)
28 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
FieldFieldFieldField----Oriented Control of Oriented Control of Oriented Control of Oriented Control of
Multiphase Synchronous Multiphase Synchronous Multiphase Synchronous Multiphase Synchronous Reluctance MachinesReluctance MachinesReluctance MachinesReluctance Machines
Figure: FOC of a multiphase Syn-Rel using CC in the stationary reference frame
29 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
FieldFieldFieldField----Oriented Control of Oriented Control of Oriented Control of Oriented Control of
Multiphase Synchronous Multiphase Synchronous Multiphase Synchronous Multiphase Synchronous Reluctance MachinesReluctance MachinesReluctance MachinesReluctance Machines
Figure: Basic form of an RFOC scheme for a multiphase induction machine, with CC in the stationary reference frame (base speed region only)
30 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
FieldFieldFieldField----Oriented Control of Oriented Control of Oriented Control of Oriented Control of
Multiphase Synchronous Multiphase Synchronous Multiphase Synchronous Multiphase Synchronous Reluctance MachinesReluctance MachinesReluctance MachinesReluctance Machines
Figure: Indirect RFOC scheme for operation of an induction machine in the base speed region (p = Laplace operator; 1/p = integrator)
31 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
IRFOC scheme with compensation of magnetizing flux IRFOC scheme with compensation of magnetizing flux IRFOC scheme with compensation of magnetizing flux IRFOC scheme with compensation of magnetizing flux
dededede----saturation saturation saturation saturation for operationfor operationfor operationfor operation
Figure: IRFOC scheme with compensation of magnetizing flux de-saturation for operation in both base speed and field weakening region. Inverse magnetizing curve of the machine is embedded in the controller as ananalytical function in per unit form.
32 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)
In the FOC strategy, the torque is controlled by the stator current component (Isq), in accordance with equation
where δ is the torque angle between the rotor flux vector and the stator current vector
This makes the current-controlled PWM inverter very convenient for the implementation of the R-FOC scheme (Figure shown below) and torque is controlled by adjusting the stator current vector.
FigureFigureFigureFigure:::: InverterInverterInverterInverter outputoutputoutputoutput voltagevoltagevoltagevoltage
representedrepresentedrepresentedrepresented asasasas spacespacespacespace vectorsvectorsvectorsvectors
33 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)
In the case of voltage source PWM inverter–fed IM drives, Both the stator current and the torque are used as the control components
FigureFigureFigureFigure:::: VectorVectorVectorVector diagramdiagramdiagramdiagram ofofofof inductioninductioninductioninduction motormotormotormotor inininin statorstatorstatorstator----fixedfixedfixedfixed coordinatescoordinatescoordinatescoordinates α––––β
34 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)
FigureFigureFigureFigure:::: InverterInverterInverterInverter outputoutputoutputoutput voltagevoltagevoltagevoltage representedrepresentedrepresentedrepresented asasasas spacespacespacespace vectorsvectorsvectorsvectors
where
Eight voltage vectors (correspond to possible inverter states) – Equation shown
above
Six active vectors, U1–U6, and two zero vectors, U0 and U7
35 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)Direct Torque Control (DTC)
The stator flux vector can directly be adjusted by the inverter voltage vector
In six-step operation,
Inverter output voltage constitutes a cyclic and symmetric sequence of active vectors
The stator flux moves with constant speed along a hexagonal path (Figure : a).
The introduction of zero vectors stops the flux, but does not change its path.
In Sinusoidal PWM operation,
The inverter output voltage constitutes a suitable sequence of two active and zero vectors and the stator flux moves along a track resembling a circle (Figure: b).
Figure : a Figure : b
36 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Magnified part of the flux vector trajectoryMagnified part of the flux vector trajectoryMagnified part of the flux vector trajectoryMagnified part of the flux vector trajectory
Figure:
Forming of the stator flux trajectory by selection of appropriate voltage vectors
sequence
37 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Magnified part of the flux vector trajectoryMagnified part of the flux vector trajectoryMagnified part of the flux vector trajectoryMagnified part of the flux vector trajectory
In any case, the rotor flux rotates continuously at the actual synchronous speed along a near-circular path, since it is smoothed by the rotor circuit filtering action.
In the view of torque production, Relative motion of the two vectors
- Forms the torque angle δΨ (that determines the instantaneous motor torque)
The cyclic switching of active and zero vectors – Control of Motor torque
Field-weakening region,
No zero vectors
Torque control - Via a fast change of the torque angle, δΨ, by advancing (to increase the torque) or
retarding (to reduce it) the phase of the stator flux vector
38 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Generic Direct Torque Control (DTC)Generic Direct Torque Control (DTC)Generic Direct Torque Control (DTC)Generic Direct Torque Control (DTC)
The generic DTC scheme - Two hysteresis controllers
The stator flux controller - The time duration of the active voltage vectors,
(imposes) (move the stator flux along the commanded trajectory)
The torque controller - The time duration of the zero voltage vectors,
(determines) (The motor torque in the defined-by-hysteresis tolerance band)
At every sampling time - The voltage vector selection block chooses
- The inverter switching state (SA, SB, SC),
- which reduces the instantaneous flux and torque errors.
39 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Generic Direct Torque Control (DTC)Generic Direct Torque Control (DTC)Generic Direct Torque Control (DTC)Generic Direct Torque Control (DTC)
Figure: Block scheme of switching table based direct torque control (ST-DTC) method.
40 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Characteristics features of Generic Direct Torque Control (DTC)Characteristics features of Generic Direct Torque Control (DTC)Characteristics features of Generic Direct Torque Control (DTC)Characteristics features of Generic Direct Torque Control (DTC)
Nearly sinusoidal stator flux and current waveforms Harmonic content (Determination)
- By the flux- and torque-controller hysteresis bands, HΨ and HM Excellent torque dynamics Flux and torque hysteresis bands (Determination) - Inverter switching frequency, (which varies with the synchronous speed and load conditions)
41 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Sectors in the classical STSectors in the classical STSectors in the classical STSectors in the classical ST----DTC methodDTC methodDTC methodDTC method
42 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Sectors in the classical STSectors in the classical STSectors in the classical STSectors in the classical ST----DTC methodDTC methodDTC methodDTC method
Figure: Selection of the optimum voltage vectors for the stator flux vector
located in sector 1.
43 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Sectors in the classical STSectors in the classical STSectors in the classical STSectors in the classical ST----DTC methodDTC methodDTC methodDTC method
TABLE : Optimum Switching Table of Classical DTC
44 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DSC DSC DSC DSC –––– Block DiagramBlock DiagramBlock DiagramBlock Diagram
45 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DSC AlgorithmDSC AlgorithmDSC AlgorithmDSC Algorithm
Based on
the command stator flux, Ψsc, and
the actual phase components, ΨsA, ΨsB, and ΨsC,
the flux comparators generate
digital variables, dA, dB, and dC,
which correspond to active voltage vectors (U1–U6).
The hysteresis torque controller
- Generates signal dm,
-which determines zero states.
In the constant flux region, the control algorithm is as follows:
46 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DSC DSC DSC DSC –––– Characteristics Characteristics Characteristics Characteristics
Non-sinusoidal stator flux and current waveforms that, with the exception of
the harmonics, are identical for both PWM and the six-step operation
The stator flux vector moves along a hexagonal path also under the PWM
operation
No voltage supply reserve is necessary and the inverter capability is fully
utilized.
The inverter switching frequency is lower than in the ST-DTC scheme, because
PWM is not of sinusoidal type as it turns out by comparing the voltage
patterns
Excellent torque dynamics in constant and weakening field regions.
47 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DTCDTCDTCDTC----SVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with Closed----Loop Torque ControlLoop Torque ControlLoop Torque ControlLoop Torque Control
For torque regulation -> PI controller is applied
An increment in the torque angle, ΔδΨ
Produced by the output of PI controller (Figure 21.31).
Assuming that rotor and flux magnitudes are approximately equal,
the torque is controlled only by changing the torque angle, δΨ.
Figure: Vector diagram for DTC-SVC control scheme
48 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DTCDTCDTCDTC----SVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with Closed----Loop Torque ControlLoop Torque ControlLoop Torque ControlLoop Torque Control
Figure: DTC-SVM scheme with closed-loop torque control
49 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DTCDTCDTCDTC----SVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with Closed----Loop Torque and Flux ControlLoop Torque and Flux ControlLoop Torque and Flux ControlLoop Torque and Flux Control
The output of the PI flux and torque controllers is k interpreted as the
reference stator voltage components, Usdc and Usqc, in S-FOC (d − q).
DC voltage commands – Transformed into
Stationary coordinates (α − β), and
Commanded values, Usαc and Usβc,
- Delivered to the SVM block
DTCDTCDTCDTC----SVMSVMSVMSVM SchemeSchemeSchemeScheme withwithwithwith ClosedClosedClosedClosed----LoopLoopLoopLoop TorqueTorqueTorqueTorque ControlControlControlControl
DTCDTCDTCDTC----SVMSVMSVMSVM SchemeSchemeSchemeScheme withwithwithwith ClosedClosedClosedClosed----LoopLoopLoopLoop TorqueTorqueTorqueTorque andandandand FluxFluxFluxFlux ControlControlControlControl –––– LessLessLessLess SensitiveSensitiveSensitiveSensitive
Commanded voltage vector is generated by flux and torque controllers
50 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
DTCDTCDTCDTC----SVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with ClosedSVM Scheme with Closed----Loop Torque and Flux ControlLoop Torque and Flux ControlLoop Torque and Flux ControlLoop Torque and Flux Control
Figure: DTC-SVM scheme operated in stator flux Cartesian coordinates d–q.
51 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
SummarySummarySummarySummary
Scalar control is based on the IM equations at steady-state operating points
and is typically implemented in open-loop schemes keeping constant V/Hz.
However, such a scheme applied to a multivariable, coupled system like the
IM cannot perform decoupling between inputs and outputs, resulting in
problems of independent control of outputs, for example, torque and flux.
To achieve decoupling in high-performance IM drives, vector control, also
known as field oriented control as well as direct torque control, has been
developed. The FOC and DTC are now de facto standard, in highly dynamic IM
industrial drives.
52 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
SummarySummarySummarySummary
The R-FOC is easily implemented in combination with a current-controlled
PWM inverter.
For a good low-speed operation performance, indirect R-FOC with a
speed/position sensor is recommended. This scheme, however, is sensitive
to changes of the rotor time constant, which has to be adapted online.
DTC has a very fast torque response, a very simple structure, does not
require a shaft motion sensor, and is less sensitive to IM parameter changes
as in FOC.
For a speed-sensorless operation, the DTC or the direct R-FOC scheme can be
advised..
53 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
SummarySummarySummarySummary
To reduce torque ripple and fix the inverter switching frequency, the SVM has
been introduced into the DTC structure, resulting in a new scheme known as
DTC-SVM.
Basically, this is S-FOC without current control loops. However, the DTC-SVM
scheme combines advantages and eliminates disadvantages of classical DTC
and FOC schemes.
Therefore, it is an excellent solution for general-purpose IM (also PMSM)
drives.
54 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Overview of Main IM Control Strategies Overview of Main IM Control Strategies Overview of Main IM Control Strategies Overview of Main IM Control Strategies
((((in in in in Low and Medium Low and Medium Low and Medium Low and Medium Power)Power)Power)Power)
55 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Digital Digital Digital Digital control of a multiphase SPMSM drivecontrol of a multiphase SPMSM drivecontrol of a multiphase SPMSM drivecontrol of a multiphase SPMSM drive
Figure: Fully digital control of a multiphase SPMSM drive with CC in rotational reference frame.
56 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
The The The The three three three three classes of adaptive classes of adaptive classes of adaptive classes of adaptive control control control control systemssystemssystemssystems
Gain scheduling systems (GS)
Self-tuning regulators (STR)
Model reference adaptive systems (MRAS)
Figure: Block diagram of a system with gain scheduling.
57 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Adaptive Adaptive Adaptive Adaptive control control control control systemssystemssystemssystems
Figure : Block diagram of a system with an MRAS
Figure : Block diagram of STR
58 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Fuzzy Logic (FL) ControllerFuzzy Logic (FL) ControllerFuzzy Logic (FL) ControllerFuzzy Logic (FL) Controller
Figure: Structure Figure: Structure Figure: Structure Figure: Structure of adaptive speed control loop of adaptive speed control loop of adaptive speed control loop of adaptive speed control loop forforforfor
sensorlesssensorlesssensorlesssensorless DC drive with DC drive with DC drive with DC drive with FL FL FL FL controllercontrollercontrollercontroller
59 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
Figure: The internal structure of the FL controller
Figure: Membership functions
Figure: The rule base.
Fuzzy Logic (FL) ControllerFuzzy Logic (FL) ControllerFuzzy Logic (FL) ControllerFuzzy Logic (FL) Controller
60 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
REFERENCESREFERENCESREFERENCESREFERENCES
1. Bogdan M. Wilamowski J. david Irwin, The Industrial Electronics Handbook - Power
electronics and motor drives Edited by, Second Edition, CRC Press, 2011 by Taylor
and Francis Group, LLC.
2. Austin Hughes, Electric Motors and Drives - Fundamentals, Types and Applications,
Third edition, Newnes , published by Elsevier Ltd., 2006.
3. Bimal K. Bose, Modern Power Electronics and AC Drives, Prentice Hall PTR, 2002.
4. Bimal K. Bose, Power Electronics and Motor Drives-Advances and Trends, Academic
Press, Elseveir Group, 2006.
5. R. Krishnan, Electric Motor Drives: Modeling, Analysis and Control, Prentice Hall
Inc., 2002.
6. www.wikipedia.com
7. www.google.com
61 R. Balamurugan - FDP on “Electrical Drives & Control,” DEEE, Anna Univ. of Tech. Coimbatore : 12th July, 2011
THANKS FOR YOUR KIND ATTENTIONTHANKS FOR YOUR KIND ATTENTIONTHANKS FOR YOUR KIND ATTENTIONTHANKS FOR YOUR KIND ATTENTION