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

USI

3

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

USI

4

Design controllerand identify

physical controller

USI

5

SinusRif.Imains

K LC

Umains

Imains

+++

-

Ideal controller for rectifier with given reference current

feedback term

feedforward term

controller

reference current

USI

6

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)

USI

7

Introduce model of various signal and

variable conversions

USI

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

USI

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

USI

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

USI

11

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)

USI

12

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)

USI

13

Group gains and offset,scaling variables

USI

14

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)

USI

15

Implement multiplicationsin fixed-point

representation

USI

16

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