Upload
minh-hai
View
245
Download
0
Embed Size (px)
Citation preview
7/30/2019 Servo Motor(6)
1/17
Current control strategy of PMSM
Control of Servo Motors
Current control strategy of vector controlled PMSM- Control both the magnitude and phasor of stator current for vector control of PMSM
The d-axis & q-axis current are controlled independently
Current control strategy Hysteresis current control
Ramp comparison method
Space vector control
Current controlled PWM inverter- Converting DC voltage into three phase ac voltage
- To control three phase currents to their reference current
d-axis
q-axis
E
Vsiqs is=
d-axis
q-axis
E
e Lsidse Lsiqs-
Vs
ids
iqsis
PMSM
* Normal operation * Flux weakening control
7/30/2019 Servo Motor(6)
2/17
Hysteresis Current control of PMSM
Control of Servo Motors
Block diagram of hysteresis current control
d-axis current ids = 0
d-q axis current in synchronous reference framed-q axis current in stationary reference frame d-q axis current in stationary reference frame3-phase reference current
Hysteresis control
[1] Hysteresis current control
- 3-phase motor current : control within the hysteresis band at a centered reference currents
2
3
a*
ia ib ic
eje
e
ib*c*Iqs*
Ids*=0HysteresisController
E
idss
iqss
7/30/2019 Servo Motor(6)
3/17
Hysteresis Current control of PMSM
Control of Servo Motors
Operations of hysteresis current control
t
t1 t2
Ts
t
A
0.5E
-0.5E
Va
ia* ia+ ia
-
Ba
+
A-
Rs
Va
Vb
Vc
ia
ib
ic
Rs
Rs
L s
L
L
ea+ -
eb+ -
ec+ -
Vo
+-
+-0.5E
A+
s
s
B+ C+
A- B C--
0.5 E
Current controlled PWM Inverter
)(*
BHii aa
)(*
BHii aa
Upper switching device A+ is conducting Current is increased
Lower switching device A- is conducting Current is decreased
7/30/2019 Servo Motor(6)
4/17
Hysteresis Current control of PMSM
Control of Servo Motors
Advantage of hysteresis current control
Simple implementation
- a-phase voltage equation
* Inductance Ls a variation of current switching frequency
Hysteresis band switching frequency current ripple
Hysteresis band switching frequency current ripple
Fast current response & Inherent peak current limiting
Disadvantage of hysteresis current control
Switching frequency of PWM inverter is widely varied with motor speed & load
Problems to design the filter and select switching frequency (turn-off time)
aa
sasa edtdiLiRV
- Neglecting resistance voltage drop, a variation of current
s
aaa
L
eV
dt
di
* Motor speed motor EMF ea a variation of current switching frequency * Motor speed motor EMF ea a variation of current switching frequency
7/30/2019 Servo Motor(6)
5/17
Hysteresis Current control of PMSM
Control of Servo Motors
Simulation results
Motor current, reference current
with HB, and gating signal
Current ripple and switching frequency
with a variations of HB
(1) HB = 0.2A
7/30/2019 Servo Motor(6)
6/17
Hysteresis Current control of PMSM
Control of Servo Motors
Simulation results
Current ripple and switching frequency with a variations of HB
(2) HB = 0.3A (3) HB = 0.4A
Hysteresis band switching frequency current ripple Switching frequency is widely varied at one period
The current is mostly controlled within the hystersis band
The Hysteresis current control method is not applied to industrial applications
7/30/2019 Servo Motor(6)
7/17
Ramp Comparison Method of PMSM
Control of Servo Motors
Ramp comparison method
PWM pulses : Three-phase reference voltages arecompared with the triangular wave withconstant frequency and magnitude
Both the frequency and magnitude of reference three-phase voltages is adjusted for
controlling the output voltage of PWM inverter
LOCKOUT A
AVas
* ComparatorCIRCUIT
LOCKOUT B
BVbs
* ComparatorCIRCUIT
LOCKOUT C
C
Vcs* Comparator
CIRCUIT
* Vas* > Triangular waveform : Upper switching device is conducting
* Vas* < Triangular waveform : Lower switching device is conducting
* Dead time is required to prevent the arm short
C l f S M
7/30/2019 Servo Motor(6)
8/17
Control of Servo Motors
a-phase reference voltage, triangular waveform, and switching signal with a variation of motor speed
(1) Speed = 400 rpm (2) Speed = 800 rpm
(3) Speed = 1600 rpm
C t l f S M t
7/30/2019 Servo Motor(6)
9/17
Control of Servo Motors
a-phase reference voltage, triangular waveform, and stator current with a variation of switching frequency
(1) switching frequency= 1500Hz (2) switching frequency= 3000Hz
- Motor speed = 1500 rpm, load torque = 0.8[N.m]
Ramp Comparison Method of PMSM
Control of Servo Motors
7/30/2019 Servo Motor(6)
10/17
Control of Servo Motors
a-phase reference voltage, triangular waveform, and stator current with a variation of switching frequency
(3) switching frequency= 4500Hz
Ramp Comparison Method of PMSM
Switch frequency of PWM inverter = frequency of triangular waveform
Constant switching frequency
Both the frequency and magnitude of reference voltages
the frequency and magnitude of output voltage of PWM inverter
Current control performance < Current control performance of hysteresis control
PWM pulses : Three-phase current errors arecompared with the triangular wave
Control of Servo Motors
7/30/2019 Servo Motor(6)
11/17
Control of Servo Motors
Block diagram of space voltage vector method
Space Voltage Vector Method of PMSM
ej e
Vds
Vqs
P W M
Vdss
Vqss
Space
Voltage
Vector
Controller
c
b
a
v( 2)
v( 1)
v(3 )
v( 4)
v(5 )
v(k )v(7 )
v( 6)
v( 0)
IIIII
IV IVV
Vdc3
vB
vA ds-axis
qs-axis
Space voltage vector
- Six sectors
- Reference voltage vector Vref is locate at sector 1
- Voltage vector is divided into vector V1 and V2
2211 TVTVVref
* Voltage vectorV1 is applied at time T1
& Voltage vectorV2 is applied at time T2
* Zero voltage vector Vo at T0
T0 = Ts (T1+T2)
Control of Servo Motors
7/30/2019 Servo Motor(6)
12/17
Control of Servo Motors
Space Voltage Vector Method of PMSM
Three phase PWM signal at Sector 1
Ub
Ua
Uc
T T
Ts
1 2T02
T02
fs =12
Ts
T T
Ts
2 1T02
T02
Control of Servo Motors
7/30/2019 Servo Motor(6)
13/17
Control of Servo Motors
Space Voltage Vector Method of PMSM
Features for space voltage method
Constant switching frequency
Good current control performance
Complex implementation
d-q axis reference voltage
d-q axis stator current
No. of sector
V
S e c t o r
ds
s
Vqss
idss
iqss
Control of Servo Motors
7/30/2019 Servo Motor(6)
14/17
f
Closed loop control of PMSM
Position P controller
Position control of PMSM using the hysteresis current control method
2
3
ai*
ia ib ic
e
PMSM
je
e
ib*
ci*Iqs
*
Ids*
=0
Hysteresis
Controller
E
*r
r
idss
iqss*e
e
p
)(**
eePr K
Speed PI controller )()(**
rrI
PqsS
KKI
Control of Servo Motors
7/30/2019 Servo Motor(6)
15/17
f
Closed loop control of PMSM
Position control of PMSM using the ramp comparison method
+
-
3
2
ej-
PWM
Inverter
PMSM
i b
i a
i c
Vdss
Vqss
Iqse
i qss
i dss
Iqse
Idse
+
-
Vqse
Iqse
= 0Idse
+
-
Vdse
Idse
Comparator
TrianglerWave
eje
e
e
e
r
r 3
2Vas
Vbs
Vcs
E
p
+
-
e
e
e
Control of Servo Motors
7/30/2019 Servo Motor(6)
16/17
Closed loop control of PMSM
Speed control of PMSM with the ramp comparison method using current errors
Control of Servo Motors
7/30/2019 Servo Motor(6)
17/17
Closed loop control of PMSM
Position control of PMSM using the space voltage vector
+
-
3
2
ej-
PWM
Inverter
PMSM
ib
ia
ic
Vdss
VqssIqs
e
iqss
idss
Iqse
Idse
+
-
Vqse
Iqse
= 0Idse
+
-
Vdse
Idse
eje
e
e
e
r
r
E
p
+
-
e
e
e
Space Voltag Vector
Controller