usi 1 scaling of a controller for an active filter
TRANSCRIPT
USI
1
Scaling of a controller for an active filter
USI
2
Procedure
• Design controller and identify physical controller
• Introduce model of various signal and variable
• Group gains and offsets, scaling variables• Implement multiplications with shift operator
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A rectifier
Umains
Imains
UDC/2
UDC/2
Given:Umains sinusoidal
Objective:Imains sinusoidal in phase with Umains and with given amplitude
Measurements:Imains and Umains
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Design controllerand identify
physical controller
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SinusRif.Imains
K LC
Umains
Imains
+++
-
Ideal controller for rectifier with given reference current
feedback term
feedforward term
controller
reference current
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DSP code Physical system
SinusRif.Imains
LC
Umains
Imains
++
Ref.I.
+
-
MU
1
K LC
Ideal controller with reference currentproportional to mains voltage (UM is maximal allowable voltage)
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7
Introduce model of various signal and
variable conversions
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8
SinusRif.IRETE
LC
Umains
Imains
++
Ref.I.
+
-
LEM
M
U
I
M
LEM
I
U
MU
1
LEM
K LC
Introduce gain of Hall sensor (LEM) givingend-scale voltage ULEM for end-scale current IM
conversiongain from
sensor
inverse gain
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9
SinusRif.Imains
LC
Umains
Imains
++
Ref.I.
+
-
LEM
M
U
I
DSP
LEM
U
U
LEM
DSP
U
U
M
LEM
I
U
MU
1
DSP
M
U
U
M
DSP
U
U
LEM
K LC
Introduce gain of analog electronics adapting output voltage range of sensor (2*ULEM) to input voltage range of AD converter (2*UDSP), same for voltage measurement
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10
SinusRif.Imains
LC
Umains
Imsina
++
Ref.I.
+
-
LEM
M
U
I
DSP
LEM
U
U
LEM
DSP
U
U
M
LEM
I
U++
UDSP
MU
1
DSP
M
U
U
M
DSP
U
U
LEM
Interface board
Interface board
K LC
Introduce offset of analog electronics adapting output voltage level of sensor (-ULEM ULEM) to input voltage level of AD converter (02*UDSP), same for voltage measurement
+-
UDSP
+-
UDSP
++
UDSP
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SinusRif.Imains
LC
Umains
Imsina
++
Ref.I.+- + +
+++-
+
-
LEM
M
U
I
DSP
LEM
U
U
LEM
DSP
U
U
M
LEM
I
UDSP
IN
U
BIT
2IN
DSP
BIT
U2
UDSP U
DSP
UDSP U
DSP
MU
1
DSP
M
U
U
M
DSP
U
UIN
DSP
BIT
U2
DSP
IN
U
BIT
2
AD LEM
Interface board
Interface board
AD
K LC
Introduce AD conversion from DSP inputvoltages (0 2*UDSP ) to AD register values (0BITIN)
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SinusRif.Imains
LC
Umains
Imains
++
+
+
Ref.I.+- + +
+++-
+
-
LEM
M
U
I
DSP
LEM
U
U
LEM
DSP
U
U
M
LEM
I
UDSP
IN
U
BIT
2IN
DSP
BIT
U2
UDSP U
DSP
UDSP U
DSP
+-
2OUTBIT
2OUTBIT
DC
OUT
U
BIT
2 OUT
DC
BIT
U2
MU
1
DSP
M
U
U
M
DSP
U
UIN
DSP
BIT
U2
DSP
IN
U
BIT
2
AD LEM
PWM-DSP
Interface board
Interface board
AD
K LC
Add PWM gain from register range (0 BITout) to average output voltage range (-UDC UDC) and add offset of register (BITout/2)
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Group gains and offset,scaling variables
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SinusRif.Imains
K LC
Umains
Imains
++
+
+
Ref.I.+- + +
++
+
-
LEM
M
U
I +-IN
DSP
BIT
U2
UDSP
DSP
LEM
U
U
LEM
DSP
U
U
M
LEM
I
UDSP
IN
U
BIT
2
UDSP
UDSP U
DSP
+-
2OUTBIT
2OUTBIT
DC
OUT
U
BIT
2 OUT
DC
BIT
U2
MU
1
DSP
M
U
U
M
DSP
U
UIN
DSP
BIT
U2
DSP
IN
U
BIT
2
AD LEM
PWM-DSP
interface board
interface board
AD
+-IN
DSP
BIT
U2
2INBIT
+-IN
DSP
BIT
U2
2INBIT
INBIT
2 IM
INBIT
2 UM
MU
Ref.I.
INBIT
IM 2
2 IM UM
BITIN Ref.I.
2 IM UM
BITIN Ref.I.
INBIT
2 UM
INBIT
2 UM
IM
Ref.I.
2 UMINBIT
IM 2 BITIN 2 UM
BITINDC
OUT
U
BIT
2BITIN
OUTBITUM
K
Choose signed integer format, leave offset close to converters, move gains to maintain variable sizes as much as possible as size of measurement (registers range)
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Implement multiplicationsin fixed-point
representation
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Use shift operator
Operation
Y=X*0.51= (X*0.51*1024)/1024 (X*522)/1024
implemented as
Y= (X*522) >> 10
because 1024=210