Variable speed direct-drive concept with a full-scale power converter

learnedbawledΗλεκτρονική - Συσκευές

24 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

77 εμφανίσεις

Overview of different
wind
generator systems and
their
comparisons 2
-
4~2
-
7



陳昱希




Outline


Variable speed direct
-
drive
concept with
a full
-
scale power
converter


Variable speed single
-
stage
geared concept
with a
full
-
scale power converter


Variable speed multiple
-
stage
geared concept
with a
full
-
scale power
converter



Variable speed direct
-
drive concept with
a full
-
scale power converter


The full
-
scale power converter
can perform
smooth grid connection
over the
entire speed
range. However, it has a higher
cost and
a higher
power loss in the power
electronics, since
all the
generated power has to pass through
the power
converter

Types of direct
-
drive generators used in the

market can be classified into the electrically
excited synchronous generator (EESG) and the
PMSG.


Variable speed direct
-
drive concept with
a full
-
scale power converter


Direct
-
drive types V.S.

geared
-
drive


Lower generator rotor speed


H
igher
torque


L
arger size


Simplified
drive
train


Omitting the gearbox
.


Higher overall efficiency


H
igh
reliability

Electrically excited synchronous
generator (EESG)


The amplitude
and frequency of the voltage can
be fully
controlled by the power electronic at
the generator side.


The
EESG has the opportunities
of controlling
the flux for a
minimized
loss in
different power
ranges, because the excitation current can be

controlled by means of the power converter in
the rotor side.

PM synchronous generator

The advantages of PM
machines
over
EESG


Higher
efficiency


No
additional power supply for the magnet
field
excitation.

Disadvantages


High
cost of PM
material


Difficulties
to handle in
manufacture

PM synchronous generator

B
ased
on the direction of flux
penetration.


Radial
-
flux
PM
machines


Axial
-
flux PM
machines


Transversal
-
flux PM machines

Radial
-
flux PM
machines


The PMs of radial
-
flux
machines are
radically
oriented
.


Two
types of RFPM machines, the slotted
surface mounted PM
machine and the slotted
flux concentrating PM machine


Axial
-
flux PM machines


The axial
-
flux PM (
AFPM) machine
is a machine
producing magnetic flux in
the axial direction.


The
slotless

single stator double rotor is a
typical structure of
slotless

AFPM machines.


Axial
-
flux PM machines

AFPM V.S
RFPM

Advantages


Simple
winding


Short
axial length



Higher
torque/volume ratio.

D
isadvantages


L
ower
torque/mass ratio ,


Difficulty
to maintain air gap in large diameter


D
ifficulty
in production of stator core


Transversal
-
flux PM machines


The path
of the magnetic flux
is perpendicular
to
the direction of the rotor rotation
.


TFPM machines
have some advantages, such as
higher
force density
, considerably low copper
losses and
simple winding
.


TFPM machines have some
disadvantages
, such
as
the
electromagnetic structure is
much more
complicated ,


low power factor.

Variable speed single
-
stage geared

concept with a full
-
scale power converter

In this scheme, a variable speed pitch control
wind

turbine
is connected to a single
-
stage
planetary

gearbox
that increases the speed by a factor of
roughly10
and a low
-
speed permanent
-
magnet
generator
.

It
has
the

advantages
of a higher speed than the
direct
-
drive

concept
and a lower mechanical
component
than

the
multiple
-
stage gearbox
concept.

Variable speed multiple
-
stage geared
concept with a full
-
scale power converter


A PMSG system with a
multiple gearbox

is
used in
order to reduce the
generator’s volume
and
improve the generator efficiency
in variable
speed
wind turbine concepts with a
full
-
scale power
converter
.


PMSG
system compared
with the DFIG
system

A
dvantages


The
generator has a better efficiency.


The generator can be brushless
.

D
isadvantages


Larger


More
expensive converter


The losses in the converter are higher







Thanks
for
your listening