Souhir NOUALI
Abderrazak OUALI
J. Electrical Systems 7-3 (2011): 343-357
Regular paper
Modelling and Control Strategy of
a Wind Energy Conversion System
based on a Doubly-Fed Twin
Stator Induction Generator
In this paper, we present a model and a control strategy of new Wind Energy
Conversion Systems (WECS) including the wind turbine, the gearbox, the Doubly Fed
Twin Stator Induction Generator (DFTSIG) driven by back to back power converters
which are connected to the grid via a filter. Between them, a capacitor is placed as a
voltage DC bus. This topology is used for great power production. It is characterized
by a better exploitation of the kinetic energy of the wind. It allows us to maximize the
capturing of energy and to improve quality of the powers forwarded to the grid.
Compared to the topology using Doubly Fed Induction generator (DFIG), the new
one is more economical since it allows us to reduce maintenance and installation
cost. The control device is established by considering a simplified model with the
orientation of power machine stator flux. It is decomposed into two parts. The first
one is the DFTSIG control. It is vector based on the orientation of the power
machine stator flux, and used to maximize energy captured from the wind turbine for
each wind speed. The second part is the control of the active and reactive powers
injected into the grid via the converters connected to the control machine stator.
Simulation results demonstrate the control device excellent performances using
Matlab/simulink.
Keywords: WECS, DFTSIG, PWM converter, PI controller, vector control, power control.
1. INTRODUCTION
Wind energy is the fastest growing energy technology in terms of percentage of yearly
growth of installed capacity per technology source [1]. Various types of aero-generators are
introduced. Those which have Squirrel cage induction generators are widely used because
of their lower cost, reliability, construction and simplicity of maintenance [2] and [3]. But
when the aero-generator is directly connected to a grid, which imposes the frequency, the
speed must be set to a constant value by a mechanical device on the wind turbine [2].
Another problem is that when we have a high value of wind speed, the totality of the
theoretical power can not be extracted. To overcome this issue, a converter, which must be
dimensioned for the totality of the power exchanged, should be placed between the stator
and the network [2] and [3]. Another type of aero-generator is the one which disposes a
doubly-fed induction generator (DFIG). The latter provides access to the rotor windings;
hence the rotor voltage can be impressed. By using power converter connected to the rotor
side, the independent control of the active power and reactive one can be obtained ensuring
a good performance at both low losses and low cost [2] and [3]. The disadvantage
associated with the DFIG is that the slip rings and carbon brushes have to be systematically
maintained. To cure this disadvantage, more research has been developed about the
DFTSIG [4, 5, 6].This machine combines the great advantages of a DFIM with a high
reliability and low maintenance requirement; avoiding the use of slip ring and brushes
[ 5,6,7,8,9,10,11,12,13,14,15and 16]. DFTSIG is composed of two doubly fed induction
machines called power machine (PM) and control one (CM). They are used with the rotors
Corresponding author: souhir.nouali@laposte.net
Advanced Control and Energy Management Research Unit
University of Sfax, National School of Engineering, Department
of Electrical Engineering BP W, 3038, Sfax, Tunisia
Copyright © JES 2011 on-line : journals/esrgroups.org/jes
S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
mechanically and electrically coupled. As all variable-speed constant-frequency generators
the BDFTSIG can be controlled to maximise the system efficiency by capturing maximum
wind power at the rotor speed tuned according to the wind speed (maximal power
tracking)[8,10].The active and reactive power of the power machine can be controlled via
the rotors from the control machine stator [8,10]. For that, DFTSIG have been proposed to
apply in renewable energy generation systems i.e. small hydropower plants, windmills,
shaft generators of vessels and embedded applications [13,11,12].
Over recent years, various DFTSIM control strategies have been reported. For example,
in [10,14,15,16] a different vector control schemes have been attempted. In [11] the control
of an autonomous cascaded doubly fed induction generator, operating in a variable speed
constant frequency mode, has been presented. A modeling methodology based on
dynamical equivalent circuits is given in this paper for the design of the DFTSIM
controller. The control of a small distributed generation system with cascaded doubly fed
induction generator and back-to-back converter is discussed in [17].
In this paper, we propose a model and a control strategy of new Wind Energy Conversion
Systems (WECS) based on a DFTSIG. The WECS under study is presented in figure1. It is
based on a DFTSIG where the power machine stator is directly connected to the power
system grid while the control machine stator is connected to a PWM rectifier; allowing an
optimal power extraction by the use of an M.P.P.T algorithm. A PWM inverter ensures the
injection of the produced power to the AC grid .Between the tow converters, a capacitor is
used as a voltage DC bus .This system is connected to the grid via a filter to reduce the
higher-frequency components[12].
The remaining part of the paper is organized as follows: Section (2) focuses on the
modelling of each component of the WECS which are presented in fig1. Section (3)
describes the control strategies of the WECS. The latter constitutes of two parts: The
DFTSIG control, which is placed to maximize energy captured from the wind turbine for
each wind speed. The second part is the control of the active power and reactive one
injected into the network via converters. Section (4) presents the simulation results and
section (5) is the conclusion.
wind
Ωt
G
CM
Psp, Qsp
isp1
isp2
PM
ig1
ig2
ig3
isp3
Ωmec
Psc, Qsc
isc1
irec iinv
isc2
isc3
Uc
urecd urecq
rf
:
uind uinq
Fig.1. WECS Composition
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GRID
(vg,wg)
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1.
WECS Modelling
2.1. Wind Turbine Modelling
The wind power acting on the swept area of the blade S is a function of the air density ρ
and the wind velocity v . The transmitted power P is generally deduced from the wind
power using the power coefficient Cp.
1
C p ρ π R 2v 3
(1)
2
The power coefficient is a non-linear function of the tip speed-ratio λ , which depends on
P=
the wind velocity and the rotation speed of the shaft Ω t .
Ωt R
v
There is a value of
λ=
(2)
λ = λopt for
which C p is maximized [18], where the wind turbine
captures the maximum wind power.
The aerodynamic torque is given by
P
v3
1
= Cp ρπ R2
Ωtη 2
Ωt
where: η is the gear ratio .
Tw =
(3)
Fig. 2. The wind turbine output power characteristics
Fig. 2 gives the wind turbine output power characteristics for several wind speeds. It is
obvious that for each wind speed, there exists a specific point in the wind generator power
characteristic, called maximum power point (MPP), where the output power is maximized
[19].
2.2. DFTSIG Modelling
The model of the DFTSIG can be derived from the models of two DFIG connected as
shown in figure 1. Different pole pairs for power and control machine are possible, but for
approximately the same torque rating of the control and power machines pp should be equal
to pc [10]. And To make DFTSIG exhibit synchronous behaviour, the frequency of the
current induced in both the power machine rotor and the control machine rotor must be the
same. Under such conditions we can duduce that:
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S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
(ω p − p p Ωmec ) = −(ωc − pc Ωmec )
(4)
where
ωc and ω p are the control and power machine stator frequency ,respectively; Ωmec is the
mechanical speed and pp and pc are the power and control machine pole pairs, respectively.
Power Machine Modelling
The power machine model placed in (d,q) reference frame, which is synchronized with the
power machine stator flux rotates at the angular speed ω p = ωg ( d axis is aligned to the
flux space vector), expressed in the space vector notation :
⎧d
⎪⎪ dt Φ spn = − rslp I spn − jω g Φ spn + Vgn
⎨
⎪ d Ψ = −r I
rp rpn − j (ω g − ( p p + pc )Ω mec ) Ψ rpn + Vrpn
⎪⎩ dt rpn
(5)
where
⎧⎪Φ spn = (lsp + l ) I spn + lmp I rpn
⎨
⎪⎩ Ψ rpn = lrp I rpn + lmp I spn
and
(6)
⎡ispd ⎤
⎡φspd ⎤
⎡ vgd ⎤
⎡ vrpd ⎤
⎡irpd ⎤
⎡ψ rpd ⎤
; Vgn = ⎢ ⎥
; ispn = ⎢ ⎥ ; Φ spn = ⎢
Vrpn = ⎢ ⎥ ; I rpn = ⎢ ⎥ ; Ψ rpn = ⎢
⎥
⎥
⎣ ispq ⎦
⎣φspq ⎦
⎣ vgq ⎦
⎣ vrpq ⎦
⎣ irpq ⎦
⎣ψ rpq ⎦
Φ spn = Ψ spn + l I spn , rslp = r + rsp
Vrpn, Irpn, Ψrpn , rrp are the power machine rotor voltage, current, flux and resistor
;respectively, placed in the (d,q) reference frame
Ispn , Ψspn ,Ispn and rsp are the power machine stator current, flux and resistor ,respectively;
placed in the (d,q) reference frame
r, l and Vgn are the grid resistor, inductance and voltage magnitude, respectively.
l sp , l m p and l rp are the power machine stator, mutual, and rotor inductance , respectively
and d, q is the direct and quadrature components ;respectively.
Control Machine Modelling
The control machine model placed in (d,q) reference frame expressed in the space vector
notation :
⎧d
⎪⎪ dt Ψscn = −rsc I scn − j(ωg − ( p p + pc )Ωmec )Ψ scn + Vscn
⎨
⎪ d Ψ = −r I − j (ω − p Ω )Ψ + V
rc rcn
g
p mec
rcn
rcn
⎪⎩ dt rcn
where :
⎧⎪Ψ scn = lsc I scn + lmc I rcn
⎨
⎪⎩Ψ rcn = lrc I rcn + lmc I scn
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and
⎡iscd ⎤
⎡ψ scd ⎤
⎡vscd ⎤
⎡ vrcd ⎤
⎡ircd ⎤
⎡ψ rcd ⎤
Vrcn = ⎢ ⎥ ; I rcn = ⎢ ⎥ ; Ψ rcn = ⎢
⎥ ; I scn = ⎢i ⎥ ; Ψ scn = ⎢ψ ⎥ ; Vscn = ⎢ v ⎥
v
i
ψ
⎣ rcq ⎦
⎣ rcq ⎦
⎣ rcq ⎦
⎣ scq ⎦
⎣ scq ⎦
⎣ scq ⎦
Vrcn, Ircn, Ψrcn , rrc are the control machine rotor voltage, current, flux and resistor
;respectively, placed in the (d,q) reference frame.
Vscn , Iscn , Ψscn , rsc are the control machine stator voltage, current, flux and resistor
,respectively; placed in the (d,q) reference frame.
lsc , lmc and lrc are the control machine stator, mutual, and rotor inductance , respectively.
Taking into account the connection between the two rotors, the power machine and
control machine currents and voltages, placed in d,q reference frame, are related as:
*
⎧⎪Vrpn = Vrcn
⎨
*
⎪⎩ I rpn = − I rcn = I rn
(8)
By taking into account the following equation (8), the rotor current model of the DFTSIG
placed in d,q reference frame, expressed in the space vector notation can be written:
rr I rn +
d
Ψrn + j (ωg − p pΩmec )Ψrn = 0
dt
(9)
where
Ψ rn = Ψ rpn − Ψ *rcn and rr = rrp + rrc
Mechanical Equation
The mechanical equation is given by:
J
d Ω m ec
= T w − Tem
dt
(10)
where : T em = T emp + T emc
3
*
Temp = p p imag ( I spn Ψspn
)
2
3
*
Temc = − p c imag ( I scn Ψ scn
)
2
and Tem is electromagnetic torque, Temp and Temc are the power an control machine
electromechanically torque, respectively and J is the total inertia which appears on the shaft
of the generator (kg.m2).
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S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
We deduce, from (5), (7) and (9) and (10), that the DFTSIG model placed in (d,q)
reference frame, which is synchronized with the power machine stator flux rotates at the
angular speed, expressed in the space vector notation:
d
Φ spn = − rslp I spn − jω g Φ spn − V gn
dt
(11)
d
Ψrn = −rr I rn − j (ω g − p p Ω mec )Ψrn
dt
(12)
d
Ψ scn = − rsc I scn − j( ω g − ( p p + pc )Ω mec )Ψ scn + Vscn
dt
j
(13)
d Ω m ec
= T w − Tem
dt
(14)
where
Φ spn = lspl I spn + lmp I rn
(15)
Ψ rn = l mp I spn + l r I rn − l mc I scn
(16)
Ψ scn = lsc I scn − lmc I rn
(17)
and l r = l rp + l rc
2.3. Converters Modelling
The converters are modelled in the d-q reference frame according to the switching
function concept [20].
The rectifier provides the voltages Vscn = vscd vscq T from the capacitor voltage Uc and the
[
]
modulated current i rec :
⎛ v scd ⎞ U c
⎜
⎟
⎜v ⎟ = 2
⎝ scq ⎠
⎛ u recd ⎞
⎜
⎟
⎜u ⎟
⎝ recq ⎠
and
irec =
1
(u recd i scd + u recq i scq )
2
(18)
where (urecd,urecq) are the rectifier switching functions.
The inverter yields the inverter voltages vinvn = vinvd vinvq T from the capacitor voltage and
[
]
[
]
the inverter modulated current i inv from the line currents I fn = i fd i fq T :
⎛ v invd ⎞ U c
⎟
⎜
⎜v ⎟ = 2
⎝ invq ⎠
⎛ u invd ⎞
⎟
⎜
⎜u ⎟
⎝ invq ⎠
and
i inv =
1
(u invd i fd + u invq i fq )
2
(19)
where (uinvd,uinvq) are the inverter switching functions
The DC bus voltage is given by the following differential equation:
d
U c = i rec − iinv
dt
where C represents the capacitance of the DC bus.
C
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J. Electrical Systems 7-3 (2011):343-357
It is assumed that the filters of the converter reduce the higher-frequency components [21].
In the d-q reference frame, the voltage balance across the filter inductors and resistors is:
v invd − v gd = r f i fd + l f
d
i fd − l f ω g i fq
dt
d
v invq − v gq = r f i fq + l f
i fq + l f ω g i fd
dt
2. WECS Control strategy
(21)
The control strategy of the studied WECS consists of two parts:
• The DFTSIG control is vector based on the orientation of the power machine
stator flux, to maximize energy captured from the wind turbine for each wind
speed, and to control the reactive power injected to the grid via the power machine
stator.
• The control of the active and reactive power injected into the grid via converter.
3.1. DFTSIG control vector
3.1.1
Control description
The WECS includes the wind turbine; the DFTSIG and the rectifier (see Fig.2). The
latter is used to control the control machine stator currents. By such doing, active and
reactive power, speed and torque of the generator can be controlled [21]. MPPT block
wind, based on knowledge of the WECS dynamics and power characteristics, is used to set the
torque reference on the optimal wind torque corresponding to the maximum wind power of
each wind speed [21]. This Block provides the value iscq _ ref . In this study, the vector
control strategy, applied to the DFTSIG and based on the orientation of the power machine
stator flux, consists in imposing a reference of the forward current i scd _ ref .This latter is set
from desired reactive power reference (Qsp_ref=0) . The d- and q-axis reference voltages
v scd _ ref and v scq _ ref are given by the d- and q-axis reference currents applied to two PI
regulators and two decoupling stages. The control strategy of the DFTSIG, previouslydescribed, is illustrated in figure 3.
Fig.3. block diagram of the DFTSIG control
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S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
3.1.2
Simplified model of the DFTSIG
To elaborate the adequate control device allowing us to follow the wind speed random
variations, it is very important to reduce the order of the aero-generator model.
By choosing a d-q reference-frame which synchronizes with the power machine stator
flux rotates at the angular speed ωp ,and setting the power machine stator flux vector
aligned with d-axis, we can write:
Φ spn = φ spd + jφ spq = φ spd + j 0
Neglecting the per-phase power machine stator resistance R spl (that's the case for
medium power machines used in wind energy conversion systems WECS) and supposing
that the permanent state is reached, the amplitude and frequency of the network voltage (of
infinite power) is fixed [3], we have:
⎧⎪vgd = 0
d
and φspd = 0
(22)
⎨
ω
φ
V
=
0
+
jv
=
j
dt
gq
g spd
⎪⎩ gn
The rotor current can be found from (21) as:
Φ spn − lsp I spn
(23)
I rn =
lmp
By using (30) Irn can be eliminated from (22) as follows:
Ψ rn = ( lmp −
lr lsp
lmp
)I spn +
lr
Φ spn − lmc I scn
lmp
(24)
By using (30), and (31) I rn and Ψrn can be eliminated from (18) as follows:
0 = −(lr −
2
lmp
lmclmp d
d
l d
r
I scn
) I spn − rr I spn + r
ϕ spd + r φspd −
lsp dt
lsp dt
lsp
lsp dt
2
⎡
⎤
lmp
lmclmp
l
I scn ⎥
+ j (ω g − p pωr ) ⎢ −(lr −
) I spn + r φspd −
lsp
lsp
lsp
⎢
⎥
⎣
⎦
(25) if
the imaginary part equals to zero, we can deduce the power machine stator current as
shown in the following equation:
I spn = k1
where
φ spd
l sp
k1 =
− k 2 I scn
(26)
2
l l
lr ; ' l 'r ; '
τr ;
l mp
and k 2 = mc mp
=
τ
τr =
lr = lr −
r
'
rr
τr
rr
l sp l r'
l sp
The rotor current can be found by using (30) and (33):
I rn = −k 3
where k 3 =
φ spd
l sp
−
l mc
l r'
I scn
l mp
l r'
The control machine stator flux can be found by using (23) and (34):
Ψ scn = l sc' I scn + k 2φ spd
(28)
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J. Electrical Systems 7-3 (2011):343-357
2
where l sc' = l sc + l mc
lr
By substituting (35) in equation (19), and decomposing this latter into real and imaginary
parts, the simplified DFTSIG model which will be considered later for elaboration of the
control device is:
d
1
(29)
iscd = ' ⎡⎣vscd − rsc iscd − ed ⎤⎦
dt
lsc
d
1
iscq = ' ⎡⎣ vscq − rsc iscq − eq − eφ ⎤⎦
dt
lsc
j
d Ω mec
= T m − T em
dt
(30)
(31)
where
'
ed = −lsc
(ω g − ( p p + pc )Ω mec )iscq
eq = lsc' (ωg − ( p p + pc )Ωmec )iscd
eφ = k2 (ω g − ( p p + pc )Ω mec )φspd
Showing the control machine quadrature component current, the expression of the
electromagnetic torque reduces itself to:
3
(32)
Tem = − k2 ( p p + pc )φspd iscq
2
We note from (39) that DFTSIG behaves as an equivalent induction machine with the flux
equals to φ spd and number of pole pairs equals to ( p p + p c ) .
The active and reactive powers injected to the grid via the power machine stator can written
as follows:
(33)
Psp = − k2 iscq vgq
Qsp =
k1
φspd v gq − k2 iscd v gq
lsp
3.1.3
(34)
Control device Establishment
When we impose an electro mechanic torque and reactive power reference, we can
determine the control machine current references as follows:
iscq _ ref = −
Tem _ ref
2
3 k2 ( p p + pc )φspd
iscd _ ref = −
Qsp _ ref
k 2 vgq
−
k1
φspd
lsp k2
The control device introduces two new decoupling voltages vd and vq expressed as follows:
⎧
' d
⎪⎪v d = lsc dt iscd + rsc iscd
(35)
⎨
⎪v = l ' d i + r i
⎪⎩ q sc dt scq sc scq
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S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
The vector control allows fixing the (d-q) control machine stator voltage refernces as
follows:
⎧⎪ v scd − ref = v d − ref + e d − ref
⎨
⎪⎩ v scq − ref = v q − ref + eq − ref + eΦ − ref
(36)
where
vd _ ref = ( k p +
vq _ ref = ( k 'p +
ki
)(iscd _ ref − iscd )
p
ki'
)(iscq _ ref − iscq )
p
ki, kp, ki’, kp’ are the regulators parameters
ed _ ref = −l sc' (ω g − ( p p + p c )Ω mec )i scq _ ref
eq − ref = l sc' (ω g − ( p p + p c )Ω mec )i scd _ ref
eΦ _ ref = k 2 (ω g − ( p p + p c )Ω mec )φ spd _ ref
where φ spd _ ref is the power machine stator flux value imposed by the grid .After an
inversion of equation (24), we obtain the rectifier voltage references given by :
⎛ urecd _ ref ⎞
2 ⎛ vscd _ ref ⎞
⎜
⎟ =
⎜
⎟
⎜ urecq _ ref ⎟ U c ⎜ vscq _ ref ⎟
⎝
⎠
⎝
⎠
Fig.4 Show the DFTSIG model and the currents control proposed in this section.
1 / l’sc s+rsc
1 / l’sc s+rsc
Fig. 4. Block diagram of the currents control and the model of the DFTSIG
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3.2. Active and reactive power control
Fig. 5. Block diagram of the active and reactive power control
The aero generator is connected to the DC bus and then to the load via the inverter and a
line. This converter allows us to control the continuous voltage and the active and reactive
powers exchanged with the grid [22].
The power control is illustrated in Fig.6. This latter consists of:
• An outer regulation loop consists of a DC voltage regulator and generates an
active power reference Pfref.
• Inner current regulation loops consist of a current regulator whose references are
set from desired active and reactive power references on the filter side. We chose
the unity power factor strategy; i.e. the reactive power is set to zero (Qf_ref =0).
The power control is illustrated in Fig. 5.
Currents control
When we impose an active and reactive power reference, we can determine the line current
references as follows:
Pf _ ref v gd − Q f _ ref v gq
⎧
⎪if dref =
2
2
v gd + V gq
⎪
⎨
Pf _ ref v gq + Q f _ ref v gd
⎪if
=
2
2
⎪ qref
v gd + v gq
⎩
We can deduce from (27) that the control of the
different actions shown in Fig.6:
-The closed loop current control:
⎧⎪v bd _ ref = C i (i fd _ ref − i fd )
⎨
⎪⎩v bq _ ref = C i (i fq _ ref − i fq )
- The compensation of a grid voltage:
⎧⎪e fd = l f ω g i fq
⎨
⎪⎩e fq = l f ω g i fd
- The currents decoupling:
(38)
i fd and i fq currents leads to three
(39)
(40)
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S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
⎧⎪v invd _ ref = v bd _ ref + v gd − e fd
⎨
⎪⎩v invq _ ref = v bq _ ref + v gq + e fq
(41)
Fig.6. block diagram of the line currents control
The continuous bus Control:
To ensure the regulation of the transits power, it is paramount to use the regulation loop to
maintain the DC bus voltage as constant as possible.The output of the DC voltage regulator
is the reference current:
icref = C v ( U cref − U c )
(42)
In order to generate and send a current to the grid, the DC bus voltage U cref must be higher
than the peak value of the voltage appearing on the filter side. So U cref f 2 3 Vrms , where
Vrms is the rms value of the simple voltage appearing side of the filter.
4.
Simulation results
We present the simulation of the DFTSIG, which is connected directly to the network
through the power machine stator, and controlled by the control machine stator through a
back to back converter. Results of simulations are obtained with reactive power references
Qsp_ref = 0 and Qf_ref=0. Figure 7 shows the wind speed which is ranged between 6 and 12
m/s with an average value of 9 m/s. Figure 8 shows the rotor speed. The latter varies
according to the wind turbine speed change to extract the maximum wind power for each
wind speed. Figure 9 presents wind power. The reference electromechanical torque,
presented in figure 10, accords with the MPPT algorithm. The voltage of DC bus is
represented in figure 11, which demonstrates that this voltage is perfectly constant, and
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J. Electrical Systems 7-3 (2011):343-357
proves the effectiveness of the established regulators. The d and q components of line
currents are given respectively in figure12 and 13. It is noticed that the control allows them
to maintain their references values. Figure 14 presents the total active power injected into
the grid (Pg=Psp +Pf). This cuve shows that PR varies over time in accordance with wind
variation and presents fluctuations compared to the maximum wind power, shown in the
figure (9).The total reactive power injected in the grid Qg (Qg =Qf+Qsp) is presented in
figure 15. Obviously, reactive power is kept at 0 VAR, which coincides with the imposed
power reference thanks to the currents regulation loop. Figure 16 shows the control
machine stator voltages whose values are remained in the acceptable limits of functioning
despite important wind speed fluctuations.
Fig. 7. Wind speed
Fig. 9. Wind power
Fig. 11. DC bus voltage
Fig. 13. q-component of the line current
Fig. 8. Rotor speed
Fig. 10. Output torque of the wind turbine
Fig. 12. d-component of the line current
Fig. 14. active power
355
S. NOUALI et al: Control Strategy of a Wind Energy Conversion System
Fig. 15. reactive power
5.
Fig. 16. control machine stator voltages
Conclusion
The work presented in this paper is devoted to modelling, control and simulation of a
WECS using a Doubly-Fed twin Stator Induction Generator connected to the grid. We have
established a two-phase mathematical WECS model. The latter contains representations of
a wind turbine, DFTSIG and the converters. The control strategy of the studied WECS
consists of two parts: the first one is the DFTSIG control which is vector based on the
orientation of the power machine stator flux. The second presents the control powers. The
obtained simulation results demonstrate the robustness of the control device whose
objective is to maximize energy captured from the wind turbine for each wind speed and
the control of the active power and reactive one injected into the grid via converters.
6. Appendice
The parameters describing the WECS under study are given by :
- Power machine Parameters: lsp=0.0073H ;lrp =0.0061H; lmp =0.0062H; rsp = 0 Ω;
rrp=0.0073 pp=1;wp=wg=100*pi rad ; j = 4kg.m2
- Control machine Parameters: lsc=0.0073H ; lrc =0.0061H; lmc =0.0062H; rsc =0.0073 Ω
Ω ; rrc =0.0073 Ω; pc=1
- DC bus and line parameters: rf=0,0002Ω; lf=5 μH; Uc=600V ; C=4400 μF.
- Grid parameters: Vg=220V; ωg=100*pi rad
7.
[1].
[2].
[3].
[4].
[5].
[6].
[7].
[8].
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