Maximum Power Point Tracking of Wind Turbine Conversion Chain Variable Speed Based on DFIG

International Journal of Power Electronics and Drive System (IJPEDS)
Vol. 9, No. 2, June 2018, pp. 527~535
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v9.i2.pp527-535  527
Journal homepage: http://iaescore.com/journals/index.php/IJPEDS
Maximum Power Point Tracking of Wind Turbine Conversion
Chain Variable Speed Based on DFIG
H. Becheri1
, I. K. Bousarhanne2
, A. Harrouz3
, H. Glaoui4
, T. Belbekri5
1,2,4,5
Department of Technologie, Faculty of Techologie, University of Bechar, Algeria
3
Department of Hydrocarbon and Renewable Energy, Faculty of Science and Technology, University of Draïa, Algeria
Article Info ABSTRACT
Article history:
Received Oct 8, 2017
Revised Dec 10, 2017
Accepted Jan 23, 2018
Wind energy has many advantages, it does not pollute and it is an
inexhaustible source. However, the cost of this energy is still too high to
compete with traditional fossil sources. The yield of a wind turbine depends
on three parameters: the power of the wind, the turbine power curve and the
ability of the generator to respond to fluctuations in the wind. This article
presented the MPPT of a wind turbine system equipped with an
asynchronous generator has dual power under Matlab Simulink program, in
the first time we simulated all the conversion chain with complete model of
DFIG and vector control in second step then applied the extracted maximum
power MPPT strategists, this command is effective and has several
advantages it offered to kept the maximum power delivered to network
despite all the parameter is change.
Keyword:
DFIG
Fifth keyword
MPPT
Power supply
Vector control Copyright © 2018 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Houcine Becheri,
Departement of Technologie, Faculty of Techologie,
Tahri Mohamed University,
University Tahri Med, Street Knadssa, Bechar 08000, Algeria
Email: houcine.becheri@gmail.com
1. INTRODUCTION
Electrical energy is crucial to any socio-economic development [1]. The demand for electricity is
very important to this dilemma, it is necessary to appeal to new energy sources that will be without
consequence for man and environment. Wind energy represents a sizeable potential for bearing damping
demand increasingly rampant, after centuries of evolution and further research in recent decades and some
wind power projects developed by major central wind turbines provide electricity in parts of the world at a
competitive price than the energy produced by conventional plants [2].
Today, the development and proliferation of wind turbines have led researchers in Electrical
Engineering to conduct investigations in order to improve the efficiency of electromechanical conversion and
quality of the energy supplied [3]. It is in this context that this paper describes that we present a study on the
use of asynchronous machines has dual power in a wind system. Initially modeling and conversion system
simulation (turbine and asynchronous generator dual feed)
Then the vector control in stator active and reactive powers are proposed in a last step And
improved the system study and extract maximum power presents MPPT strategists and the simulation results.
The objective of this paper is to develop a novel combined MPPT-pitch angle control system of a variable
speed wind turbine.

 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 9, No. 2, June 2018 : 527 – 535
528
2. MODELLING WIND POWER SYSTEM
2.1. Model of the wind turbine
The wind turbine collects the kinetic energy of the wind and converts it into a torque, which turns
the blades of the rotor [3]. In our study, this system used a wind turbine based on DFIG, which supplies to
generate the torque required to the load in Figure 1.
Figure 1. Schematic of the wind turbine
2.1.1. Wind modeling
In our case, the wind speed will be modeled as a sum of several harmonics [5]:
(1)
2.1.2. Aaerodynamic power
(2)
Which is defined by: (3)
The coefficient of power Cp represents the aerodynamic efficiency of the wind turbine. We will use
an approximate expression of the power coefficient given by [6]:
(4)
The simulation of the power coefficient is shown in Figure 2:
Figure 2. Cp (λ,ß) Characteristics for various values of pitch angle ß
The aerodynamic torque is expressed as follows:
(5)

Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Maximum Power Point Tracking of Wind Turbine Conversion Chain Variable… (H. Becheri)
529
For the mechanical part can thus lead to a more simple mechanical model [7 and 14] (Figure 3). The
dynamic behavior of the generator can be represented by the following equation:
w
f
T
T
dt
dw
J m
em
e 

 (6)
Where Jt is the rotational moment of inertia of the rotor and the generator kg.m², ω is the angular
velocity of the rotor in red / s, Te is the mechanical torque applied to the alternator shaft in Nm, Tem is the
electromagnetic torque developed by the generator in Nm and fm is the viscous friction coefficient in Nm.
Figure 3. Mechanical model of turbine
2.2. DFIG Modeling
We modeled the DFIG with the implementation of the transformation of the park following
Repository related rotating field This repository is called system of axes (X, Y), it rotates with the speed of
the electromagnetic field is obtained [9]:
The stator: (7)
The rotor: (8)
The equations of flow and after the simplification are:
(9)
Also for the rotor and in the same way are:
(10)

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Doubly-Fed Induction Generator model of the landmark Park in the form of state:
Where: is the dispersion coefficient.
The expression of the electromagnetic torque of the DFIG in reference Park [10]. The general form
of electromagnetic torque is:
(11)
2.3. Power Modeling DFIG
2.3.1. Modeling of phase rectifier diodes
If we neglect the effect of encroachment, the rectifier output voltage will be defined as following:
(12)
2.3.2. Modeling of DC bus
To reduce the ripple of the voltage source adding a low pass filter LC Their operation is governed
by the following equations:
(13)
2.3.3. VDC Association to DFIG
We will have the following system:
(14)
In our case, the control of the switches of the inverter is performed by use of the command
modulation or PWM pulse width.
3. MAXIMUM POWER EXTRACTION TECHNIQUE
The goal of the (MPPT) strategy is to pick up the maximum power from the wind; it involves the
following of the power curve shown in Figure 4, given by in equation (15):
3
1
1
( )
2
opt
opt p opt
P C AV
   (15)

531
Figure 4. MPPT and power characteristics in function of mechanical speed
An erroneous speed measurement therefore inevitably leads to degradation of the power captured by
the first extraction technique. This is why most wind turbines are controlled without control of the speed.
This second control structure based on the assumption that the wind speed varies very little steady state.
4. APPLICATION VECTOR CONTROL WITH THE ORIENTATION FLOW STATOR
We consider the DFIG works in hypersynchronous mode, the principle is to direct the stator flux
along the axis of the rotating frame [9].
So we have: and we have: Relations between current stator and rotor currents:
The technical guidance of stator flux is applying on the couple become:
(16)
If neglecting the resistance of the stator winding R_S, voltage expressions become:
(17)
If neglecting the resistance of the stator winding R_S, voltage expressions become:
(18)
(19)
From this equation, we can write the equations linking the stator currents to the rotor currents:
(20)
Relations between the stator and rotor currents powers:
(21)
The adaptation of these equations axis system chosen and the simplifying assumptions made in this
case given:
(22)

 ISSN: 2088-8694
532
By replacing the stator currents by their values we get the expressions:
(23)
Relations between rotor and rotor currents tensions:
One could express the rotor voltages depending on rotor currents, we can write:
(24)
In steady state, the terms involving derivatives disappear, we can write:
(25)
Vector control in stator wind power system based on a PI controller [13,14]:
4.1. Direct Vector Control
This control mode ensures proper decoupling between flux and torque but the problem this
disadvantage by the sensor. We neglect the terms of coupling between the two axes of control because of the
low value of the slip. We are getting as shown in Figure 5.
Figure 5. Block diagram of the direct control
4.2. Vector control indirectly
The flow is controlled in open loop. It is not measured or estimated. The quantities (voltage or
current) ensuring the flow direction and are evaluated `decoupling from the equations of the machine
transient.
The values of the rotor voltages depending on power and found we calculate:
(26)
The Figure 6 shown the isolation carried at the outputs of regulators in rotor currents without any
return to the system.

533
Figure 6. Iindirect command without power loop Figure 7. Iindirect control with power loop
The Figure 7 shown the method of control with power. In this method, the isolation is carried out at
the outputs of the current regulators rotor with a return of the system.
5. RESULTS
To evaluate and test the indirect control technique with power loop of active and reactive power by
the PI controllers, a simulation was performed under the MATLAB / Simulink. In this case, the gains of the
PI controllers are based to method of design, which is based on the compensation of the time constant of the
regulator with that of the process of the quantity to be regulated, and were refined after simulation:
a. For the power loop: k_p = 75.75; K i = 5354.55.
b. For the current loop: k_p = 75.75; K_i = 5354.55.
Figure 8. Stator current Figure 9. Rotor current
Figure 10. Speed wind Figure 11. Rotor Speed

 ISSN: 2088-8694
534
Figure 12. Stator active power Figure 13. Stator reactive power
Figure 14. Comparison between Wr and Wr with MPPT
6. DISCUSSION
We obtained good results in dynamic handling and response to regulations imposed and reactive
power. The fluctuations in the power due to the PWM inverter and the dependence of these powers slip. The
figure 7 and 8 shown the results of the stator current and rotor current that have the same paces with the trend
of the wind and the power. Are sinusoidal, implying a clean energy without harmonics supplied or absorbed
by the DFIG.
The results obtained in Figure 12, 13 and 14, we can conclude that this type of control is more
efficient than direct control in terms of a variable speed operation, since it is able to provide a decoupled
control of active power and responsive regardless of the drive speed.
7. CONCLUSION
This paper present the modelling of the various components of a wind system for distributed
generation of electricity and the study of different double-fed asynchronous machine control systems (DEIG)
representing generator for production this energy. In the second part, we have begun the maximum power
extraction technique in the operation of the wind; this method proves and gives good results for the
maximum generated power to the grid. Subsequently, we developed vector of control reactive power in the
stator level, the proper follow instructions for the two powers by the real powers debited by the stator of the
machine showed the effectiveness of the applied control.
NUMENCLATURE
DFIG Doubly Fed Induction Generator
ρ Air density

535
S turbine area
v Wind Speed
PC power extraction coefficient
s (R) index of the stator (rotor)
d, q indices Park repository
V (I) voltage (current)
P (Q) active power (reactive)
Φ Magnetic flux
Cem (Cr)electromagnetic torque (mechanical)
R Resistance
L (M) Inductance (mutual)
σ Coefficient leaks, σ = 1 - M 2 / LsLr
θr (θs) Position of the rotor (stator)
ωr (ωs) electric speed rotor (stator)
Ω Mechanical speed
g Slip
f Friction
J Inertia
P Number of pole pairs
Parameters of system:
R =35.25 m; G= 90 m; J=0.1Kg.m2
.
Vs=220/381; Vr=18/31 V; f=50 Hz; fr=14 Hz.
R=0.3 ; L=0.014 H; = 2 e-3 F;
=620 V; = 85 ; E=220 V.
REFERENCES
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Metering System of Fluids”, International Journal of Power Electronics and Drive System (IJPEDS), ISSN: 2088-
8694, Vol. (3) No.4, Dec 2013, pp. 450-458.
[3] Hachemi Glaoui, Harrouz Abdelkader, Ismail Messaoudi, Hamid Saab, “Modeling of Wind Energy on Isolated
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