-
Vector Controlled Doubly Fed Induction
Generator for
Wind Applications
Dr. Ani Gole, Dept. of
Electrical and Computer Eng.,
University of Manitoba.
This document discusses the theory of
operation behind the doubly fed generator
case developed by Ani Gole (Univ. of
Manitoba, Canada) and Om Nayak (Nayak
Corporation, Princeton, NJ). The
controller concept is based on the paper by
Pena et al [1].
Description of Rotor Current Generation
Circuit (Generator PWM Converter and
Controls)
转子电流产生电路的描述（发电机脉宽调制转换器及其控制）
CTRL
GENERATOR
PWM Converter
& Controls
a
b
c
W
S
TL
a
b
c
I M
ira,irb,irc
A
Isa
B
Isb
C
Isc
13.8 kV, 500 HP
INDUCTION GENERATOR
a
GRID
PWM
Converter
b
c
&
Controls
A
Va
B
Vb
C
Vc
Fig 1: Doubly
Fed Induction Generator
双馈感应发电机
The
Doubly
fed
induction
generator/motor
allows
power
output/input
into
the
stator winding as well
as the rotor winding of an induction machine with
a wound
rotor
winding.
双馈式感应发电机
/
电动机通过绕线转子绕组将功率
输出
/
输入感应电
机的定子绕组和转子
绕组。
Using
such
a
generator
it
is
possible
to
get
a
good
power
factor even when the machine speed is quite
different from synchronous
speed.
使用这样发电机即使在机器转速完全不同于同步速度时也可以得到一个好
的
功
率
因
数
。
Such
machines
can
therefore
operate
without
the
need
for
excessive shunt compensa
tion.
这种发电机不需要过度的并联补偿。
The rotor currents
(ira,irb,irc) of the machine can be resolved into
the well known
direct and quadrature
components i
d
and
i
q
.
双馈感应发电机的转子电流
(ira,irb,irc)
可以分解为直接和正交分量
id
和
iq
。
The component id
produces a flux in the air
gap which is
aligned with the rotating flux vector linking the
stator; id
部分在空气
间隙处产生磁通，这与连
结定子的旋转磁通量是一致的。
whereas the component
i
q
produces flux
at right angles to this vector.
而
iq
产生的磁通与
id
产生
的垂直。
The torque in the machine is the
vector cross product of these two vectors, and
hence only the component i
q
is contributes to the machine torque
and hence to
the power.
机器的转
矩是这两个向量的向量积，因此，只有
iq
与机械转矩变化有<
/p>
关，进而导致功率的变化。
The component id
then controls the reactive power
entering the machine.
id
控制输入机器的无功功率。
If id and iq
can be controlled
precisely, then so
can the stator side real and reactive powers.
如果
iq
和
id
能被
精准控制，于是定子侧的实际功率和无功功率就能被准确控制。<
/p>
The procedure
for ensuring that the correct values of id and iq
flow in the rotor is
achieved by
generating the corresponding phase currents
references ira_ref, irb
_ref and
irc_ref, and then using a suitable voltage sourced
converter (VSC) base
d current source to
force these currents into the rotor.
确保
id
和
iq
正
确的值流入
转子侧的方法是产生相电流参考值
ira_ref, irb_ref
和
irc_ref
，然后用一个基于电流
源的合适的电压转换器促使这些电流流入转子侧。
The latter action is
straightforw
ard and can be achieved
using current-reference pulse width modulation
(CRPW
M) or other technique.
后面的过程就很直接了，用当前参考脉冲宽度调制
(CRPW
M
)
或者其他的相应的装置就可以实现。
The crucial
step is to obtain the instantane
ous
position of the rotating flux vector in space in
order to obtain the rotating refer
ence
frame.
最关键的一步是获得空间里旋转磁通向量的瞬时位置，从而确定旋转
参考系。
This can be achieved by
realizing that on account of Lenz’s law of
electr
omagnetism, the stator voltage
(after subtracting rotor resistive drop) is simply
th
e deriva
a
as in
eqn. (1) which is written for phase
a.
这点可以这样获得
:
根据楞次定律，定
子电压（减去转子电阻上压降后）是定子
磁链
a
的导数，如下式所写：
v
a
?
i
a
R
a
?
d
?
a
…….(1)
dt
The control structure shown in Fig. 2
can thus be used to determine the location
(
?
s
)
of the rotating flux vector.
因而图
2
所示的控制结构能够决定旋转磁通的位置。
Identification
of main stator flux by integrating stator
voltage
after removal of resistive drop.
The washout filter removes any
dc
component from the integrated flux without
significantly
ffecting the phase
1
sT
phisx
X
Y
Y
Isa
*
0.467
D
+
-
Va
C
A
alfa
D
+
-
Vb<
/p>
C
D
+
-
Vc
C
Valfa
B
3 to 2
Transform
b
eta
Vbeta
C
Isa
*
0.467
*
0.46
7
1
sT
?
?
?
?
G
sT
1 +
sT
G
sT
1 +
sT
r to p
X
mag
Vsmag
phi
phis
phsmag
Isa
phisy
Ve
ry important signal -
present location
==>
of rotating stator
flux
phis
Ra
rotor_
angle
C
+
D
-
in
Angle
out
Resolver
slpang
determi
ning the relative difference between
stator flux and rotor position for
resolving the
rotor currents
Fig 2: Determination of
rotating mag. Flux vector location
In Fig. 2, the three phase
stator voltages (after removal of resistive
voltage drop)
are
converted
into
the
Clarke <
/p>
(
?
and
?<
/p>
)
components
v
??
and
v
?
,
which
are
orthogonal in the balanced steady
state.
在图
2
中，三项定子
电压
Va
、
Vb
、
Vc
（已去除电阻电压降）被转换成
v
?
和
v
?
，
v
?
和
v
?
处于正交平衡的稳定状态。
This
transformation is given
by:
转换公式如下
:
?
v
?
?
?
v
?
?
?
v
?
?
1
?
1/
2
?
1
/
2
?
?
a<
/p>
?
?
v
?
?
?
?
2
/
3
?
?
0
?
?
b
?
……(2)
3
/
2
?
3
/
2
?
?
?
?
v
?
?<
/p>
c
?
Integrating
v
?
and
v
?
, we obtain
?
?
?
?
, the Clarke
components of stator
flux.
给
v
?
和
v
?
积分
,
我们得到
?
?
和
?
?
以及定子磁通
Converting
to polar form
转化为极坐标形式
|
?
|
?
< br>?
?
2
?
?
?
2
,
?
s
?
tan
(
?
?
/
?
?
)
?
1
……(3)
The
angle
?
s
gives
the
instantaneous
location
of
the
stator’s
rotating
magnetic
field.
角
?
s
给出了定子磁场的瞬时位置
.In
practical
control
circuits,
as
in
Fig.
2,
some
filtering is required in order to rid the
quantities
?
?
and
?
?
of any
residual
dc component introduced in the
integration process.
在实际电路中，如图
2
所示，
为了减少集成过程中引入的残余直流分量
(
?
?
和
?
?
)
，需要对其进行一些过滤。
Now the rotor itself is rotating and is
instantaneously located at angle
?
r
(labeled
“rotor angle” in
th
e figure).
既然，转子本身旋转，且瞬时位置
由角
?
r
（标记为转角图）体现。
Thus,
with
a
reference
frame
attached
to
the
rotor,
the
stator’s
magnetic
field
vector
is
at
?
s
-
?
r
,
which we refer to the “slip angle”
?
slip.
因此，给转子加一个参考
系，定子磁场磁通在位置
?
s
-
?
r
处，这就是所谓的偏离角
?
slip.
。
The
instantaneous
values
for
the
desired
rotor
currents
can
then
be
readily
calculated using the
inverse dq transformation, with respect to the
slip angle, as
shown in Fig. 4.
对于偏离角
,
如图
4
所示，使用逆
dq
变换可以很容易计算出所需
的转子电流的瞬时
值。
The equations for
all transformations are shown in the appendix.
所有转换方
程见文档末尾附录部分。
Generation of current references
slpang
alfa
D
Rotor
to Stator
Q
beta
D and Q
reference currents
A
alfa
2 to 3
B
Transform
beta
C
Ira_ref
Iraa
Irb_ref
Irbb
Irc_ref
Ircc
Fig. 4: Final step in generation of
rotor phase reference
currents
Once
the
reference
currents
are
determined,
they
can
be
generated
using
a
voltage sourced converter operated with
a technique such as current reference
pulse width modulation (CRPWM) as shown
in Fig. 5.
一旦参考电流确定，
他们
使
用图
5
所示的参考电流脉
冲调制控制的电压转换器产生。
The
Appendix
gives
a
short
introduction
to
C
RPWM.
附录部分对参考电流脉冲调制（
CRPWM
）作了简
要说明。
T1
D1
T1
T3
T1
D1
T5
T1
D1
CR-PWM
based
Rotor-side converter
BRK
Ecapref
T2
D2
T4
T6
T2
D2
T2
T2
D2
V
1
.
0
E
r
b
E
r
a
I
r
a
I
r
b
I
r
c
E
r
c<
/p>
Ira
E
Ira_ref
10000.0
Ecap
GA
Current-Reference PWM Controls. Hysteresis band
can be
adjusted
GB
GC
C
C
Irb
-
+
C
Irc
-
+
T1
T1
T3
-
+
C
E
T5
<
/p>
ira_ref
E
Irb_ref
E
Irc_ref
T4
T6
hysband
10
CPane
l
T2
ira_ref
hy
*
-1
+
+
nhy
0
0.1
C
E
+
-
hy
hy
Fig. 5: CRPWM
Converter and Controller for rotor
currents
Grid PWM Converter and Controls
< br>:
电网脉冲调制转换控制：
As
can be
seen
from Fig.
5,
the
rotor side VSC converter
requires
a
dc
power
supply.
如图<
/p>
5
所示，转子侧
VSC
< br>转换器需要直流供电。
The dc voltage is usually
generated
using
another voltage
sourced
converter
connected
to
the
ac
grid
at
the
generator stator terminals.
用连接到交流电网的电压
源换流器产生直流电压，
电压源换流器位于发电机定子终端。
A
dc
capacitor
is
used
in
order
to
remove
ripple
and keep the dc bus voltage relatively smooth.
用直流电容器来滤波且保证
直流母线电压相对稳定。
This grid PWM Converter is operated so as to keep the
dc voltage on the capacitor at
a constant value.
电网脉冲调制转换器保障了电容器
两端直流电压的稳定。
In
effect,
this
means
that
the
Grid
side
converter
is
supplying the real power demands of the
rotor side converter.
事实上，这意味着
网侧变流器提供的有用功率由转子侧变流器控制。
It is possible to operate this
converter using a current reference approach used
for
the
rotor
side
converter.
用针
对转子侧变流器的参考电流法是可以来控制网侧
变流器的。
However, as mentioned earlier, CRPWM has the
drawback that the
switching frequency
and hence the losses are not predictable.
然而，如前面所提
到的那样，参考电流脉冲调制有如下缺点：开关频率的损失是无法
预估的。
Therefore, a feedback controller is
used in which the error between the desired
and
ordered
currents
is
passed
through
a
proportional-integral
controller
which
controls the output voltage of a
conventional Sinusoidal PWM Converter.
因此，
需要运用一个反馈控制器
让故障电流通过比例积分控制器。比例积分控制器是用
来控制传统的
正弦脉冲调制转换器的。
The
advantage
of
the
SPWM
controller
is
that the number of switchings in a
cycle is fixed, and so the losses can be easily
estimated
a-priori.
正弦脉宽调制控制器的好处是一个周期的开关次数是固定的，
因此损耗易被估算。<
/p>
It is possible
to control the d axis current by controlling the
d-component of the
SPWM output waveform
and the q axis current via the q component.
通过控制正弦脉宽调制的
d
部分输出波形
进而控制
d
轴的电流
，同理
q
轴电流由
q
< br>部分控制。
However,
this
leads
to
a
poor
control
system
response,
because
attempting to change
id also causes iq to change transiently.
然而这会导致不良
的控制系统响应，因为试图改变
id
时也会导致
iq
暂时改变。
Hence,
modifications
have
to
be
made
to
the
basic
P-I
controller
structure
so
that
a
decoupled
response is
possible, and a request to change id changes id
and not iq; and vice-
versa.
因
此，需要对导出控制器作出修改，进而产生解耦响应。并且改变
id
的请求
改变
id
而不是
iq,
反之亦然。
If
a
voltage
sourced
converter
with
constant dc
bus
voltage
is
connected
to
an
ac
grid
through
a
(transformer)
inductance
L
and
resistance R, it can be shown that that
:
如果电压源转换器和恒定直流总线电压，
通过电阻（
R
）和电感
(L)
连接
到交流电网中，那么可以如下表示：
R
–
-
-
-
d
id
L
d
t<
/p>
iq
=
–
?
R
–
-
-
-
0
1
id
-
-
-
vd
–
ed
L
x1
+
L
=
R
< br>iq
–
eq
R
< br>x2
–
-
-
-
0
–
-
-
-
L
L
?<
/p>
eq
x2
=
–<
/p>
-
-
-
-
-
–
?
iq
L
vd
–
ed
x1
=
-
-
-
-
-<
/p>
-
-
-
-
-
-
-
-
-
-
-
-
+
?
id
L
< br>ed
=
–
L
x1
+
vd
+
?
Lid
…
eq
=
–<
/p>
Lx2
–
?
Li
q
….(4)
Here
v=vd
is
the
voltage
of
the
ac
grid,
and
because
this
is
chosen
as
the
reference, vq is by definition,
zero.
这里
v=vd
指的是交流
电网的电压，因为这里的
V
被选为参考值，
vq
被定义为
0.
Ed
and
eq
are
the
d
and
q
components
of
the
generated
VSC
voltage.
Ed
和
eq
是
VSC
电压的
dq
部分。
Eqn.
4
clearly
shows
that attempting to change id using ed
will also cause a transient change in iq.
< br>从
等式
4
中不难看出，用
ed
改变
id
的值的
同时也会导致
iq
值的瞬间变化。
If
instead, we use the quantities Lx1 and
Lx2 to control the currents, the resulting
equations are decoupled.
如果换
个说法，我们用
Lx1
和
Lx2
的数量来控制电流，
最终的方程式是解耦的。
Using feedback PI control, we let the error in
the id loop
affect L x1 and in the iq
loop, L x2 as shown in Fig. 6.
如图
6
所示，用反馈
PI
控
制，我们可以让
id
部分的故障影响
Lx1,iq
部分的影响
Lx2
。
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