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Implementing Embedded Speed Control for AC Induction Motors
Yashvant Jani, Director of Applications Engineering Leonard Haile, Applications Engineer
Renesas Technology America, Inc. 450 Holger Way San Jose, CA 95134 USA
TEL: 408-382-7500 FAX: 408-382-7501E-mail: [email protected]
Web: www.renesas.com
Topics Outline
• Induction Motor principles– Physics of induction motors– Induction motor construction
• Control hardware – typical layout• Modulation techniques
– Sinusoidal, Quasi-sinusoidal & Space Vector• Control methods
– Open loop algorithms– Closed loop algorithms
• MCU performance benchmark• Summary
Physics of Induction Motors• Current passing through a conductor creates magnetic
field– Direction of magnetic field is determined by the
right hand rule• Changing magnetic field produces current in a
conductor– Direction of current is determined by right hand
rule• Electromagnetic Induction
– Changing current induces changing magnetic field around it.
– A conductor placed in this field has induced current and induced magnetic field
• Interaction between two magnetic fields and two currents in stator and rotors produce the torque
• Torque is proportional to the magnitude and frequency of the current in stators– Torque = K (E1/f1)2*s/R2
I Φ
dΦ/dt
dI
dIdΦ
-dφ
-di
dΦ/dtdI1 I2
Torque α mag & freq of I1
Induction Motors
• Motors operate on principle of Induction and hence the name “Induction Motors” is used
• Motors also known as AC motors because Alternating Current (AC) is required
• All AC motors are “brushless”– No mechanical contacts to wear– Requires AC source– If used, inverter creates desired freq and
magnitude of AC• AC induction motors for lower cost
applications– Single speed applications: fan, blower,
pump, compressor– No control, just start the AC power
source– Relays are used for ON/OFF
Stator Construction
• Stator has windings with lamination to– Create strong magnetic field– Maintain continuous flux
• Three phase motor windings are sinusoidal around the stator to produce a roughly sinusoidal distribution in flux
• When three phase AC voltages are applied to the stator windings, a rotating magnetic field is produced– The rotating magnetic field of the stator drags the
rotor around.
Stator
α
Rotor Construction
• Squirrel cage construction– Behaves like shorted 3-phase
windings– Rotor bars are often skewed to
prevent cogging– No magnets or windings
Rotor
Windings & Slip Angle
Y or StarConnection
Phase A Phase B
Phase CNeutral
iSa + iSb + iSc = 0
Sum of currents is zero
Phase A Phase B
Phase C
DeltaConnection
Vab + Vbc + Vca = 0
Sum of voltages is zero
• Stator has Sinusoidal Flux/Voltage Generation• Rotor rotates at the excitation speed minus slip s
• Stator has two types of connections
Voltage/FluxStator Cross section
A BC D
A
B
C
D
Rotor Cross section
Slip s =(ω-pωm)/ω
Slip S = 1 -Stator Speed
Rotor Speed
Motor Model Per Phase Equivalent Circuit
StatorResistance
Stator LeakageInductance
Stator MagnetizingInductance
Rotor LeakageInductance
RotorResistance
R1 L1
LM
L2
R2s
E1
IsIM I2
MagnetizingCurrent
IsIq
Id
Torque Producing Current
E1f1
( )2
Ks
R2Torque =
V/Hz Control
Torque = K ( i2 )2 R2/s
Torque = (3/2) (P/2) (λm Iq + (Ld – Lq) Iq Id)
• In vector formulation, Torque is proportional to the Magnetizing Flux and current in q-axis
Torque Speed Curve • At constant supply frequency
– The synchronous mechanical angular speed is: ωmSync=ω/p • where p number of pole pairs and ω electrical angular speed [2pf]
– When load is present the rotor speed is lower than the supplied frequency.
• ωm < ωmSync
– Slip: s=(ω-pωm)/ω
Constant Supply Frequency
Torq
ue
Speed (ωr)ωs
Open loopoperating point (stable)
~1.5-3 % S (or below ws)Startingtorque
No torque atsynchronous speed (ωs)
S = 0
Controlled operating point(unstable)
peak torque
motoring
generating S = 1
MaximumEfficiency~5-7% S
Braking
Example:ws = 60 HzS = 1.5 % giveswo = 59 Hz
Typical Control Hardware
MAC/DCIn
put F
ilter
ing
DC Filtering Output Power Stage
MCU
Set Values
DriversSensing
ConditioningFeedbackControl Algorithms
Converter Inverter Mixed VoltageHigh Voltage
VDC
A+
A-
B+
B-
C+
C-
For DC supply, bridge and motor are presented
Typical Motor Drive Configuration
MotorEncoder
Current Feedback
Hall Effect Absolute position feedback**
Absolute Position/Speed feedback
S1
S2
S3
S4
S5
S6
One Shunt
** Generally not used for Induction Motor
ACCT
MCRP Overview• This reference platform has two boards
LCD
MCU
Power supply connection
U, V, W 3-phaseMotor interface
Hall Sensor inputIntegrated Power Module with heat sinkEncoder input
One Shunt
Three LED showing PWM pulsing
SKP
Two DCCT
Built in Back EMF Circuit
Modulation Schemes
Modulation Schemes
• Sinusoidal wave– 180 deg vs. 120 deg drive
• Quasi- sinusoidal wave drive– Add 3rd harmonic for efficiency
• Space vector modulation
What is a 180° Drive?120°Drive & 180°Drive
W
U
V W
U
V
120°Drive 180°Drive
On two of the 3 coil wires, the electricity is always flowing. After every 120 degrees, the positive and the negative is connected to the power supply alternately.
The electricity is always flowing on every coil wires. After every 180 degrees, the positive and the negative change.
Item
NoiseRipple
120°Drive 180°Drive
△ YesTorque-Ripple Yes
◎ NOTorque-Ripple less
Phase detection(back EMF)
○ YesBecause of 60 degree of non-driventime, commutation is easy and simple
△ NOBecause of the dead time, the
commutation is difficult.
Power Usage Only 2 coils used All 3 coils used
W
U
V W
U
V W
U
V W
U
V W
U
V W
U
V
UUVVWW
Vu
Vv
Vw
Iu
Iv
Iw
U_ONU_ON
V_ONV_ONV_ON
W_ONW_ON
Back EMF
Switch pattern
0
0
0
0
0
0
120°PWM Control
UUVVWW
Vu
Vv
Vw
Iu
Iv
Iw
U_ONU_ON
V_ONV_ONV_ON
W_ONW_ON
W
U
V
0
0
0
0
0
0
W_ON
W
U
V W
U
V W
U
V W
U
V W
U
V
Back EMF
Switch Pattern
180°Electric Sinusoidal Wave Drive
180°Drive Operation
• Utilizes entire electrical rotation to rotate the motor vs. 120 deg uses only 2/3 rotation
• Requires dead time register to make sure two power devices do not conduct at the same time for a given phase – e.g. Up and Un do not turn on at the same time
• This operation generally can not use the back EMF signal to detect the rotor position
• Allows various modulation strategies including sine wave & pseudo sine wave
3-Phase Timer on M16C
Dead Time counter
TimerA1=UTimerA2=VTimerA4=W
TimerB2
Positive
NegativeOutput
Buffer Register for 3 Phase
P Signal(Internal)
N Signal(Internal)
Carrier
Di0=”0”,Di1=”1”DiB0=”1”,DiB1=”0”
Di0=”1”,Di1=”0”DiB0=”0”,DiB1=”1”
Di0=”0”,Di1=”1”DiB0=”1”,DiB1=”0”
※Output as Low Active
50 μsec
3-Phase Timer Capabilities • This timer generates complimentary PWM with dead time inserted
between transitions• Dead time to be programmed only one time
• 16-bit registers provide more than adequate resolution
Modulation schemes• 120 deg
• 60 or 120 deg• Upper/lower/both• One at a time
• 180 deg• Sinusoidal• Quasi-sinusoidal• SV-PWM• Custom
120 Deg 6-step modulation• Timer allows modulation during one step – up or down switch
(0,0) (1,0)(DU0,DU1)
Sine Wave Generation
Desired Voltage V0 & Frequency f Carrier wave (Frequency fc )
U = V0 sin θV = V0 sin (θ+120°) W = V0 sin (θ+240°)
θ(n) = θ(n-1)+ΔθΔθ = 2πf / fc
(1) Phase angle θ of a voltage in time t is calculated (2) Corresponding Sin θ value is found from the ROM table (3) Multiplying the sin θ value with modulation ratio a results in PWM values (4) These U, V, and W PWM counts are transferred to RAM.
(V and W phase differences are kept at 120 and 240 degrees to U, respectively.)
Steps for Sine Wave Generation• Three items required: carrier freq fc, Sine freq f and voltage
level Vdc [implying Vmax = Vdc and Vmin = 0]• Example: Fc = 10 kHz, f = 50 Hz, Vdc = 160 volts• Computation results
– Average voltage = (Vmax+Vmin)/2 = Vdc/2 = 160/2 = 80 volts– Vmax = Vdc = ½ Vdc + ½ Vdc * Sin 90 (Sine value is 1) – Vmin = 0 = ½ Vdc + ½ Vdc * Sin 270 (Sine value is -1)– Vpwm = ½ Vdc + ½ Vdc * Sin θn (Sine θn value from Table)– Δt = 1/fc = 1/10000 = 100 μs– Δθ = 2πf/fc = 360 * 50 / 10000 = 360 / 200 = 1.8 deg – This is the angle traversed in Δt time (every carrier frequency)– PWM is computed as:
• θn = θn-1 + Δθ, if θn > 360 θn = θn - 360, Vpwm = ½ Vdc + ½ Vdc * Sin θn• PWM counts @20 MHz is 20*100=2000, Timer B2 is half of this 1000. • 1st PWM for Timer A is PWM1 = 500 + V0*Sin θn & PWM2 = 1000 – PWM1
– V = Vdc/2 @0 deg, V = Vdc @90 deg, V = 0 @270 deg
Sine Wave Generation• One degree resolution results in a table with 360
entries• For integer math, sine values are scaled in 2^13
format (2^13=8192= 1.0 floating point)
IndexMid point
angle Sine valueSine in 2^13
format
Integer value for
Sin1 0.5 0.008726535 71.4877788 712 1.5 0.026176948 214.4415605 2143 2.5 0.043619387 357.3300213 3574 3.5 0.06104854 500.1096359 5005 4.5 0.078459096 642.7369122 6436 5.5 0.095845753 785.1684046 7857 6.5 0.113203214 927.3607272 9278 7.5 0.130526192 1069.270567 10699 8.5 0.147809411 1210.854696 121110 9.5 0.165047606 1352.069987 135211 10.5 0.182235525 1492.873425 149312 11.5 0.199367934 1633.222119 163313 12.5 0.216439614 1773.073317 177314 13.5 0.233445364 1912.384421 191215 14.5 0.250380004 2051.112993 205116 15.5 0.267238376 2189.216777 2189
Three sine waves at a time
-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
10000
1 41 81 121 161 201 241 281 321
angle
Sine
val
ue
Integer value for uInteger value for vInteger value for w
U phase W phase V phase
Sine Generation
• Lab activity• View the MCRP, motor and PC set-up
for testing• View the High-Performance Embedded
Workbench operation• See Sine wave, quasi-sine wave and
space vector wave on scope
Sinusoidal PWM drive
• Possible to improve control performance and efficiency
• Carrier frequency is preferred for complementary waveform, because it is necessary to keep the symmetry of the output voltage
This method requires a true 3-phase timer unit for proper operation
W
V
U
Inverter Output PWM
U-V
V-W
W-U
0 π 2π
Trapezoidal vs Sinusoidal Commutation
360°300°0° 60° 120° 180° 240°
S1
S2
S3
S4
S5
S6
VA
VB
VC
“BLDC” “PMAC”
Quasi Sinusoidal Modulation
Sinusoidal/Quasi-sinusoidal Wave Drive
⎭⎬⎫
⎩⎨⎧
+⎟⎠⎞
⎜⎝⎛ +=
⎭⎬⎫
⎩⎨⎧
+⎟⎠⎞
⎜⎝⎛ −=
⎭⎬⎫
⎩⎨⎧ +=
θπθ
θπθ
θθ
3sin61
32sin
32
3sin61
32sin
32
3sin61sin
32
Vw
Vv
Vu
⎟⎠⎞
⎜⎝⎛ +=
⎟⎠⎞
⎜⎝⎛ −=
=
πθ
πθ
θ
32sin
32sin
sin
Vw
Vv
Vu
0 10 20 30 40 50-2
-1
0
1
2U V W
time (ms)
mag
nitu
de
Sine curve
0 10 20 30 40 50-2
-1
0
1
2
mag
nitu
de
time (ms)
U V W
With 3rd Harmonic included
U-V phase
fc = 20kHz, f=50Hz
U-V phase
fc = 20kHz, f=50Hz
Comparison of Sine & Quasi-sine
Comparison of Sine & Quasi-sine waveforms
-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
10000
1 29 57 85 113 141 169 197 225 253 281 309 337
Angle
Inte
ger v
alue
Sine wave
Quasi sine wave
• Quasi- sine wave allows nearly 15% higher bus utilization• Torque is increased due to this high current
Space Vector Modulation
Basics of Space Vector• A 3 phase inverter is made by 6 switching devices.• The purpose is to calculate the output desired vector as a linear
combination [in the time domain] of 2 fundamental vectors.• Each fundamental vector is given by a fixed driving combination.
va vb vc
a
a’
Vdc
b
b’
c
c’α
β
U0 (1,0,0)
U60 (1,1,0)U120 (0,1,0)
U180(0,1,1)
U240 (0,0,1) U300 (1,0,1)
S0
S1
S2
S3 S4
S5
Fundamental Space VectorsInverter Structure
Unull=(000) Uall=)111)
SV PWM• When fixed carrier frequency is used, angle is
easy to calculate and also the ON time for each switch
Here a is the angle between one base vector to the applied U vector
A, B and C are the typical U, V & W values
Space Vector Output• Carrier Freq is 20kHz
Why Use Space Vector?• Improves DC bus utilization
– Instead of being able to create √2 /2 Sin() magnitude voltage we can create √3 /2 Sin() magnitude voltage
• Reduces EMI– Less transistors are switching.
• Reduces switching losses– Requires only two windings switching during
60 degree electrical portion of motion. Third winding can fixed high or low.
– Special firmware is necessary with special timer features
ACIM Control Methods
Modulation Schemes
• Modulation schemes– Sinusoidal wave drive (180 deg drive)– Quasi- sinusoidal wave drive– Space vector modulation
• Open loop control algorithms– V/f control
• Closed loop control algorithms– Sensor feedback: scalar, vector – Sensorless: scalar & vector control
180deg Sinusoidal Drive (M16C/28) a) V/f control (open loop)
• Without Pos. Sensor)
b) Scalar PI control (closed loop)• With Pos. Sensor)
Under development c) Vector Control (With Pos. & Current Sensor)
d) Sensor-Less Control (With Current Sensor)
e) Sensor-Less OSCD Control (Without Any Sensor)
ACIM Control Methods
Scalar controlScalar controlV/F controlV/F controlWay to control Open loop Feedback
Speed controlConstant torque control
Low accuracy High accuracy
Torque control
Others
Indirect – OK under certain conditions Indirect but better torque control
Dynamic control difficult Indirect torque control only
Micro Computercontrol
Output PWM pattern correspond to speedcommand value from Data table
Speed detected by sensor, closed loop Speed control, No Current control
• Simple configuration• Adjustment is easy
• Speed detect is necessary • Additional sensor cost
Inverter part
3 phase IM
MicroComputer
Driver
a) V/f Control a) V/f Control
Sinusoidal Wave
3phase IM Control Techniques (1)Inverter part
3 phase IM
MicroComputer
DriverTachometer(Speed)
b) Scalar Control b) Scalar Control
Vector ControlVector ControlV/F controlV/F controlWay to control Open loop Feedback – closed loopSpeed controlConstant torque control
Low accuracy High accuracy
Torque control
Others
OK under certain conditions Best among all
Dynamic control difficult Best among all
Micro Computercontrol
Output PWM pattern correspond to speedcommand value from Data table
MCU detects speed, measures currents using ADC, and makes adjustments for PWM
• Simple configuration• Adjustment is easy
• Speed & current detection is necessary • Additional cost for sensor & DCCT
Inverter part3 phase IM
MicroComputer
Driver
a) V/f Control a) V/f Control
Sinusoidal Wave
3phase IM Control Techniques (2)Inverter part
3 phase IM
MicroComputer
Driver
DCCT for Current
Encoder orTachometer for Speed
c) Vector Control c) Vector Control
Sensorless 2DCCT ControlSensorless 2DCCT ControlVector controlVector controlWay to control Closed loop Closed loop with estimationSpeed controlConstant torque control
Very High accuracy High accuracy
Torque control
Others
Best among all Very High
Best among all Very High
Micro Computercontrol
MCU detects speed, measures currents using ADC, and makes adjustments for PWM
MCU estimates (!) speed, measures currents using ADC, and makes adjustments for PWM for torque control
• Speed estimation requires more computing • Current detection is necessary • DCCT cost only, NO cost for position sensor
3phase IM Control Techniques (3)
Inverter part3 phase IM
MicroComputer
Driver
DCCT for Current
Encoder orTachometer for Speed
c) Sensorless 2DCCT Control c) Sensorless 2DCCT Control Inverter part
3 phase IM
MicroComputer
Driver
DCCT for Current
Encoder orTachometer for Speed
c) Vector Control c) Vector Control
X
• Speed & current detection is necessary • Additional cost for sensor & DCCT
Sensorless OSCD ControlSensorless OSCD ControlVector controlVector controlWay to control Closed loop Closed loop with estimationSpeed controlConstant torque control
Very High accuracy High accuracy
Torque control
Others
Best among all Very High
Best among all Very High
Micro Computercontrol
MCU detects speed, measures currents using ADC, and makes adjustments for PWM
MCU estimates (!) speed, measures currents using OSCD method & ADC, and makes adjustments for PWM for torque control
• Speed estimation & OSCD current measurement requires even more computing
• NO DCCT or position sensor cost
3phase IM Control Techniques (4)
Inverter part3 phase IM
MicroComputer
Driver
DCCT for Current
Encoder orTachometer for Speed
e) Sensorless OSCD Control e) Sensorless OSCD Control Inverter part
3 phase IM
MicroComputer
Driver
DCCT for Current
Encoder orTachometer for Speed
c) Vector Control c) Vector Control
X
• Speed & current detection is necessary • Additional cost for sensor & DCCT
X
Voltage/Frequency Motor Control• Control based on the following assumptions:
– The motor impedance increases when the frequency increases.– We want to have fixed current as much as possible.– So it is simple to increase the motor speed by increasing the
frequency and the related voltage.
Generally, wmin and wmax depend on the motor and wops is determined by the system configuration
No Load Resulting Current
100%
50%
wmin wops wmax
DC BusVoltage
Frequency
++ Operational Points
+ +
+
+ + ++
What accuracy is necessary?
V/F Motor Control
• Advantages– No current measurement required.– No speed measurement required.– Very simple algorithm.
• Weakness– No feedback on speed so:
• in case of variable load, a speed sensor must be added and the algorithm become more complex.
– No feedback on current so:• over-current condition is possible.
– No flux control so:• Low motor efficiency.• Low maximum torque achievable.
V/f Control without any Sensor
Sine VoltageCalculations
PWM
invertervu*,vv
*,vw*
6ω1
Speed Commandωr
* TBL Motor
Voltage & Freq determined from
table
TBL – Table Look Up for Freq and Voltage
• Simple to achieve with a true 3-ph Timer unit• Table stores sine values• Carrier freq 16-20 kHz range• Able to run V/f control without position sensor
Scalar Control with a Rotor Position Sensor
Sine VoltageCalculations
PWM
invertervu*,vv
*,vw*
6ω1
Speed command ωr*
ASR+-
ωr
Motor
input captureand
counter
Rotor position θdFor correction
Rotating speed ωr
Position sensor encoder or tacho
ASR - Auto Speed Regulator - PI Controller
• Simple to achieve with a true 3-ph Timer unit• Table stores sine values• Carrier freq 16-20 kHz range• Able to run closed loop PI control with position sensor
V/f Performance for M16C
• V/f open loop testing– without feedback and – with feedback of tacho pulse
• Two major interrupts– PWM output via TB2 timer channel– Tacho input via Timer S
• Frequency and voltage changes made only when the U phase is near zero angle.
PWM Interrupt Processing
• Carrier Frequency 16 kHz, interrupt time 62.5 ms– Can be easily changed to any value
• Four steps done in this PWM interrupt– Computing angle index– Calculating u, v and w using sine table (look-up)– Max-min checking– Loading the timers
• Peak voltage and desired frequency decided by a time based profile or another task
• Updates to desired speed & peak voltage is processed when U angle is near zero– Two flags are used to minimize processing
CPU Time Measurements
• Lab activity• Perform code review for measuring
execution time• Measure execution time for the PWM
interrupt via scope• View the scope pictures• CPU bandwidth analysis with the time
measurements performed
Performance Results (1)
• Interrupt execution time for this code is 33.56 μs– About 54% CPU usage,
still more than 40% left for other tasks
• Interrupt execution time remains the same at 20kHz carrier frequency– CPU bandwidth usage
about 66%
Performance Results (2)• Code optimization in
several areas– Sin(W) is computed from
Sin(U) and Sin(V) to avoid multiplication and table lookup
– Max-min checks are deleted (guarantee by design)
• Measured time now is 14.31 μs
• Standard code 33.56 μs vs optimized 14.31 μs– CPU usage only 23%– More than 50%
optimization
Sensor Processing (1)• Sensor interrupt
– Time depends on speed– Average of 8 speed measurements– Digital filtering capability of the Timer S is used for proper
measurements Performance of filter
0
2000
4000
6000
8000
10000
12000
14000
0 10 20 30 40 50 60
Time in units of T period
Cou
nts
div 64div 32div 32div 16
Sensor Processing (2)• Sensor measurement time = 3.7 μs• Closed loop control time = 2 μs• CPU bandwidth is speed dependent
– For example, at 100 Hz speed, it is 100 times per second
Sensor data processing Control function
CPU Bandwidth Analysis
• Interrupt Time ~ 15 μs (@16kHz freq)• Timer S measurement = 3.7 μs • Closed loop control = 2 ms (4 μs) • CPU usage time in 1 second
– 15 * 16000 = 240000 μs – This time is required for sure– This is the main time as shown below
Speed RPM
Speed Hz
Timer S time μs
Closed loop time μs
Total ms
6000 100 370 400 240770 μs or ~0.25 second
12000 200 760 800 241560 μs or ~0.25 second
18000 300 1130 1200 242330 μs or ~0.25 second
Questions & Answers
• For a short period
Control Example V/f - Control
• open loop V/f control
– sensorless• induction machine• fan• M16C, H8, R8C,
SH
• closed loop V/f control – Tach sensor– Encoder
• compressor, pump
• M16C, H8, R8C, SH
MPWMsin(wt)
wset
patternwset t
wset A
sin(wt)MPWM
pattern
PI
-
w
Vector Control with a Rotor Position Sensor
Iq*
Vqc*
Id* Vdc*
VoltageCalculation
dq
3ΦPWM
inverter
dq3Φ
P2
θd
vu*,vv
*,vw*
6
Idc
Iqc
ω1
ACR ++Idc
+
-
ACR
Iqc
+-
Speed commandωr
*
ASR+-
++
ωrIu
Iw
Motor
input capture/
counter
Rotor positionθd
Rotating speed ωr
A,B,Z
Position SensorEncoder
Current Sensor(DCCT)
ACR - Auto Current RegulatorASR - Auto Speed Regulator PI Controller
Id*
ω
Iq*
Vqc*
Id* Vdc*
VoltageCalculation
dq
3ΦPWM
inverter
dq3Φ
P2
θdc
vu*,vv
*,vw*
6
Idc
Iqc
ω1
ACR ++Idc
+
-
ACR
Iqc
+-
Speed commandωr
*ASR
+-
++
ωrIuIw
Motor
Position &Speed
Estimator
Estimatedposition θdc
Estimated speed ωr
Current sensor(DCCT)
IuIw
Vu
Vw
PositionSensor-less
× Gain adjustment is very difficult.(ASR, ACR×2,Estimator(several parameters))
Modern control theory・Observer・Kalman filter
↓Requires
Matrix Calculations
Vector Control with two DCCT
Id*
ω
OSCD vector control OSCD vector control
Iq*
Vqc*
Id* Vdc*
VoltageCalculation
dq
3ΦPWM
inverter
dq3Φ
P2
θdc
vu*,vv
*,vw*
6
Idc
Iqc
ω1
ACR ++Idc
+
-
ACR
Iqc
+-
Speed commandωr
*
ASR+-
++
ωrIuIw
Motor
Position &Speed
Estimator
Estimatedposition θdc
Estimated speed ωr
Shunt Resistance
IuIw
Vu
Vw
× Gain adjustment is difficult.(ASR, ACR×2,Estimator(several parameters))
Modern Control Theory・Observer・Kalman filter
↓Requires
Matrix Calculations
Current Meas
PositionSensor-less
Vector Control with OSCD
Id*
ω
Current / Flux-Control Examples
• Closed loop speed control– Hall/encoder sensor or
sensorless pos. feedback
– current sensor• Brushless DC• Washing machine,
general purpose drives• H8S and SH devices
• Feed forward flux control / vector control
– Sensor or sensorless• Induction machine (IM)• Industrial tools• SH devices
PI
I
Pattern
PI
ω
sin(ωt)
ωt
PWM Mωset
ω
iset iabcset
i
uabcsetPI PI
sin(ωSt)
ωSt
PWM Mωset
ω
iYset iabcset
ω
iabcuabcset
iYsetim TR
im
im
ω
ωS
ωRiYset : Torque commandωS : stator frequencyωR : rotor frequency, (slip)im : magnet. currentTR : rotor time const.
+
1 SHUNT ELECTRICAL CURRENT MEASURING FUNCTION1 SHUNT ELECTRICAL CURRENT MEASURING FUNCTION
U phase
V phase
W phase
CarrierWave
TB2underflow
AN0
AN1
S/H and A-D conversion timing
1) TB0 and TB1 are started in one-shot modewith TB2 underflow as the trigger.
2) S/H or A-D conversions are executed with TB0 and TB1 one-shot trigger.
TB0 one-shot timer
TB1 one-shot timer
PRELIMINARYNotice This is not a final specification. Some parametric limits are Subject to change.
• OSCD method
Summary
• Induction motor fundamentals, motor construction, modulation techniques and control methods are covered in this presentation
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