•© UMN 2010

First Course onElectric Drives

Power Processing Unit (PPU)fixed

form

measured speed/ position

speed /

position

Motor

Electric Drive

Load

input command

(speed / position)

Power

Signal

adjustable

formElectric Source

(utility)

Sensors

Controller

• Harnessing Wind Energy

• Electric and Hybrid-Electric Vehicles

•© UMN 2010

Windmills: Example of an Integrated System

0 69010 60

VHz

34.5kV

161kV

Power ElectronicsConverters

V

Time0

60Hz

Low-VoltageRide-Through

Generator

690V

•© UMN 2010

Course Objectives• Analyze

• Control

• System Design (not machine design)

Two Common Principles

emf Bi

(a) (b)add

subtract

external fieldB

emf

add

subtract

external fieldB

emf

resultant

emf

resultant

emf

(c)

i

emf

B

i

emf

B

e B uqf

u

(into paper)B

qf

u

(into paper)B

(b)(a)

qf

qf

u

(into paper)B

qf

qf

u

(into paper)B

•© UMN 2010

Use of Space Vectors

(a) (b)

axisc

axisa

axisb

N

S

bi

ai

ci

m

( )m t

( )rB t

axisa

Similar to use of Phasors

(a) (b)

( )i t

ˆV V 0

L

R

C

I

Lj L j X

R

C

1j j X

C

ˆv( t ) V cos( t )

( )i t

ˆV V 0

L

R

C

I

Lj L j X

R

C

1j j X

C

ˆv( t ) V cos( t )

Im

Z

cjX

R

LjX

Re0

Im

Z

cjX

R

LjX

Re0

(c)

Imaginary

Real

Positiveangles

I I

V V 0

Imaginary

Real

PositiveanglesPositiveangles

I I

V V 0

•© UMN 2010

(a) (b)

rB

m

axisa

si

N

S

ˆsI

magnetic axis of

equivalent

winding

axisc

axisa

axisb

N

S

bi

ai

ci

m

rB

o90

'a

a

si

at t

o90

.

. .

ˆ ˆ( ) cos cos2

sem r s

cond lengthflux density at

no of cond in d

NdT r B I d

/ 2 / 2

2

/ 2 / 2

ˆ ˆ ˆ ˆ2 ( ) 2 cos ( )2 2

s sem em r s r s

N NT dT r B I d r B I

Physics-Based Analysis

•© UMN 2010

Topics• Designing for the Mechanical Load

• DC Motor Drives

• Permanent Magnet AC Drives

• Induction Motor Drives: Steady State and V/f Control

• Stepper and Switched-Reluctance Drives

• Feedback Control

• Power Quality Considerations

Textbook

• Presentation Slides

• Solutions Manual

•© UMN 2010

Electric Drives Lab

Drives Board for Motor and Active Load (Generator) 42- V Motor Set

• Low-cost; 42-V no Shock Hazard!

• DSP Controlled; easy to use

• Active Load Allows Experiments otherwise not possible

• Very Popular with students!

•© UMN 2010

Graduate-Level Course

d-q axes control

Applications in windmills, hybrid and electric vehicles,

robotics and factory automation

Control of Drives in Windmills

Kpp

+ Kip/s

+

+-

Pord

Pelec

Trip

flagPitch Control

1

____

1+ sTp

Pmech

1

____

2H

Paccel 1

____

s

ref

Wind

Power

Model

Wind

speed

+

-

+

-

Pitch

Anti-windup on

Pitch Limits

min

& d /dt min

Kpfreq

+ Kifreq

/s

Torque ControlPmax

Pelec +

Kpc

+ Kic/s

Pmax

-

Pmax

Pitch

Compensation

X1

____

1+ sTpc

P min

Anti-windup on

Power Limits

Over/Under

Speed Trip

Logic:

if

speed > max

or

speed < min

then

set trip flag = true

endif

Power Order

cmd

err

max & d /dt

max

•© UMN 2010

t

t0

0

Load Torque

Seamless Transition to Dynamic Control and

Encoderless Operation

Speed

•© UMN 2010

a axis

b axis

c axis

m

ia

ib

ic

iA

iC

iB

A axis

B axis

C axis

m

a axis

b axis

c axis

m

ia

ib

ic

iA

iC

iB

A axis

B axis

C axis

m

•© UMN 2010

Mutual Inductance Between dq

Windings on Stator and Rotor

a axisstator

A axisrotor

d axis

m

isd

isq

q axisat t

i rq

ird

m

is

ir

3

2isd

3

2isq

3

2irq 3

2ird

d

d

da

dA

3

2sN

3

2sN

3

2sN

Figure 3-3 Stator and rotor mmf representation by

equivalent dq winding currents.

a axisa axisstator

A axisA axisrotor

d axisd axis

m

m

isdisd

isqisq

q axisq axisat tat t

i rqi rq

irdird

m

m

is

is

ir

ir

3

2isd

3

2isd

3

2isq

3

2isq

3

2irq

3

2irq 3

2ird

3

2ird

d

d

da

dA

3

2sN

3

2sN

3

2sN

Figure 3-3 Stator and rotor mmf representation by

equivalent dq winding currents.Figure 3-3 Stator and rotor representation by equivalent dq winding currents. The

dq winding voltages are defined as positive at the dotted terminals.

Note that the relative positions of the stator and the rotor current

space vectors are not actual, rather only for definition purposes.

sd s sd m rdL i L i

sq s sq m rqL i L i

rd r rd m sdL i L i

rq r rq m sqL i L i

•© UMN 2010

Drives Board for Motor and Active Load (Generator) 42- V Motor Set

Graduate

Level Course

• Low-cost

• 42-V no Shock Hazard!

• DSP Controlled; easy to use

• Active load allows experiments not

otherwise possible