IRJET- Fuzzy predictive control of Variable Speed Wind Turbines using Fuzzy Techniques

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 03 | Mar-2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 3566
Fuzzy predictive control of Variable Speed Wind Turbines Using Fuzzy
Techniques
D. Jyothirmayi 1, P. Navyasri2, N.Sudhakar3,A.Madhubabu4 ,S.Anil5 ,K.Saranya6
1,2,3,4,5,6 IV B tech student, RSR engineering college Dept of EEE ,R.S.R engineering college ,Kadanuthala
6 Assistant Professor ,Dept of EEE ,R.S.R engineering college ,Kadanuthala, Bogole (M) ,SPSR Nellore (Dst)
A.P state, India.
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Abstract -In this paper, a fuzzy logic controller is proposed
to fulfill the objective of maximum power extraction based on
a two mass model. One of the typical problems is that the
effective wind speed cannot be measured directly due to the
high disturbance of the wind speed and the high cost of
sensors. Three algorithms are used to estimate the effective
wind speed by solving power balance equations.Theestimated
wind speed is used to determine the optimal speed reference
for generator control system. The control performance of the
fuzzy logic controller is verified in the whole system
Simulation results are presented to illustrate the effectiveness
and robustness against parameter variations of the proposed
control design.
Key Words: Wind Power generation ,MPPT, LQR, Fuzzy
systems, Filtering algorithms
1. INTRODUCTION
DURING the last decades, the demand of clean and
renewable energy sourceshasbeen growing intensivelydue
to environment issues. Among the renewable energy
sources, such as wind turbines, Photovoltaic and fuel cells,
are expected Owing to the rapid progress in wind turbine
technology and its economic and safety properties, wind
power is considered as one of the most promising cleaner
and renewable sources among these renewable energy
sources [1]–[3]. One of the most prominent problems of
wind energy extraction is itslow efficiency.Therefore,under
the partial loaded operation condition, how to increase the
power extraction becomesof high importance.Awidelyused
control method is maximum power point tracking (MPPT)
control [4]–[8]. This control strategy aimsto adjusttherotor
speed according to the variations of wind speed, in order to
maintain the tip speed ratio at its optimal value, which
equivalently realizes MPPT. The principle obstacle of the
MPPT control design is the unavailability of the wind speed.
First, wind speed is a highly disturbed value whichcannotbe
easily measured using simple and portable measuring
device. Second, since the blade is a non-particle rigid body,
the measured wind speed only represents a single point in
the blade which is not applicative to other parts. Third, the
implementation of physical sensors will increase system
complexity, cost, space and reduce system reliability [9].
According to [10], the sensors failure and the consequent
control failures take up more than 40% of failures. As a
result, many research endeavors have been focused on the
wind speed estimation problem [11] such as power balance
estimator method [12], Kalman filter (KF)-based estimator
[13]–[15], disturbance accommodating control (DAC) [16],
unknown input observer (UIO) [17] and the immersion and
invariance (I&I) estimator [18]. In this paper, three
algorithms are used to estimate the effective wind speed by
solving power balance equations. The estimated windspeed
is used to determine the optimal speed reference for
generator control system. Several model based control
approaches have been studied for the wind turbine system,
such as linear-quadratic regulator (LQR), pole-placement
and PID, which provides convenience to implement such
controllers in practical applications [3], [19].
Sliding mode techniques have been widely used to control
the wind turbine systems [21], [22]. Especially, higherorder
sliding mode algorithms have better performance as
compared to classical sliding mode controllersbecausetheir
output is continuous and does not require any low pass
filters [23]–[25]. However, such methods require accurate
mathematical models of wind turbine system, which are
difficult to obtain.
In this paper, fuzzy logic control method is adopted [5].
Fuzzy logic is a part of artificial intelligence which
approximates the imprecise reasoning process in human
mind and largely enhanced the expert system technology.
Fuzzy logic control is based on the fuzzy if-then linguistic
rules and has the inherent robustness to uncertainties [27],
[28].
2. WIND SYSTEM
A wind turbine is a device that converts the wind's kinetic
energy into electrical power.
Wind turbines are manufactured in a wide range of vertical
and horizontal axis types. The smallest turbines are used for
applications such as battery charging for auxiliary power for
boats or caravans or to power traffic warning signs. Slightly
larger turbines can be used for making contributions to a
domestic power supply while selling unused power back to
the utility supplier via the electrical grid. Arrays of large
turbines, known aswind farms, are becominganincreasingly
important source of intermittent renewable energy and are
used by many countries as part of a strategy to reduce their
reliance on fossil fuel.

A quantitative measure of the wind energy available at any
location is called the Wind Power Density(WPD). It is a
calculation of the mean annual power available per square
meterof swept areaof a turbine, and is tabulatedfordifferent
heights above ground. Calculation of wind power density
includes the effect of wind velocity and air density.
Wind turbines can rotate about either a horizontal or a
vertical axis, the former being both older andmore common.
They can also include blades (transparent or not) or be
bladeless. Vertical designs produce less power and are less
common.
3. WIND TURBINE MODELING
Wind turbine system consists of four major parts,i.e., wind
turbine blades, gearbox and shaft, generator, and power
converters. The wind energy is captured through turbine
blades and converted into mechanical torque. Thegenerator
transforms the mechanical torque into electricity, which is
conveyed into the grid after been adjusted by the power
converters. This paper focuses on the modeling of the
mechanical and aerodynamic parts, which considers
comprehensive dimensions, such as gearbox and shafts
stiffness, viscous resistance, loading effect, losses, etc. A
two-mass model is adopted in this paper which is suitable
for control design. Fig. 1 shows the structural model of such
transmission system [20].
Fig1- Two-Mass Drive Train Model.
The rotator and low-speed shaft is modeled by a rotational
moment of inertia Jr, two viscous damper with damping
constant Br and Bls respectively and a spring which
represents shaft stiffness Kls. The generator and high-speed
shaft is modeled by a rotational moment of inertia Jg, and a
viscous damper with damping constant Bg. The gearbox is
modeled by a gearbox ratio ng, which is supposed to be
perfectly stiff.
4. FUZZY LOGIC CONTROL
Fuzzy logic is a part of artiﬁcial intelligence which
approximates the imprecise reasoning process in human
mind and largely enhanced the expert system technology.
The fuzzy controller consists of four parts: fuzzification,
fuzzy rule base, inference engine and defuzzification [4],
[27],[30]. Fuzzy logic control is based on the fuzzy if-then
linguistic rules and has the inherent robustness to
uncertainties [27], [28]. Compared to classical control
methods, fuzzy logic based controller can effectively avoid
the requirement of precise model of the control system. The
block diagram of MPPT control system is shown in Fig.2(a).
In the block diagram, the ωtopt and iqopt are the reference
value of rotor speed and generator current respectively,
while the ωt and iq are the measurement value derived from
the wind turbine system.
The block diagram of MPPT control system is shown in
Fig.2(a). In the block diagram, the ωtopt and iqopt are the
reference value of rotor speed and generator current
respectively, while the ω t and iq are the measurementvalue
derived from the wind turbine system.
Fig2- (a) MPPT Control System With Fuzzy Logic
Controller
(b) Structure Of Fuzzy Logic Controller
4.1 DESIGNING OF FUZZY SYSTEM:
Inorder to create a Fuzzy system for the model we have to
follow the given procedure.
1.Open the MATLAB File.
2.Enter Fuzzy in the matlab window.
3.Fuzzy toolbox will open.
4.Open file in the tool box.
5.Select Mandani model
6.Now open edit option and add required variables from
input and output.
7.Now open input and draw the membership functions for
the required range.
8.After drawing the membership functions now write down
the rules for the system.

9.Now SAVE the system with the nameXX.fis.
10.After saving the system now export it to the matlab
model.
In the case of fuzzification process for this system we have
taken two inputs input 1 is actual value of the error e ,input
2 is change of the error e and output 1 is∆u .For these
inputs we have taken the triangular membership functions
from the range -6 to 6.For the outputs we have taken the
triangular membership function for thr range -7 to 7.For
these member ship functions we have taken the rule base
sytem in 7X8 format .it means that totally we have created
56 rules. For the defuzzification method we use thecentroid
method.
For these inputs and output the linguistictermsareshownin
table 1.
TABLE-1: Fuzzy linguistic terms
The linguistic terms “NB”, “NM”, “NS”, “ZO”,“PS”, “PM”, “NB”
mean “negative big”, “negative medium”, “negative small”,
“zero”, “positive small”, “positive medium”, “positive big”,
respectively. The “NO” and “PO” mean “negative zero” and
“positive zero” respectively to improve control precision as
the variables approach zero. The universes of discourse of
the error e, the change of the error e and the output ∆u are
firstly determined by the range of predicted actual values.
These universes of discourse can be adjusted on the basis of
the controller performance by the scalingfactorsasshownin
Fig. 2(a).
Particularly, the triangle membership functions of all the
three signals have no overlap in order to simplify the
controller. The membership functions should not be set to
zero at the neighborhood of original to precludeoutputdead
zone.
The parameters of the membership function should be
slightly adjusted in order to improve the controller’s
performance. To fulfill the control objective that the
measurement value ωt track the optimal reference rotor
speed ωtopt , the following fifty-six fuzzy inference rulesare
adopted as illustrated in Table 2. In this fuzzy logic
controller, the inference method used is minimum and the
defuzzication used is based on the center of gravity method.
TABLE-2: FUZZY RULES
The fuzzy editor system and the surface viewer is shown in
the figure3 and 4.
Fig3- FIS editor system
Fig4-Surface viewer of fuzzy system
4.2 Advantages of fuzzy logic controllers
1. FLC controllers do not need an accurate mathematical
model it can work with imprecise inputs.
2.More robust.
3.Faster adjustment time.
4. High adaptability of fuzzy controller to nonlinear system.
5. The steady-state error of fuzzy logic control is minor.

5. SIMULNK DIAGRAM
Simulink model For Wind Turbine Using Fuzzy Logic
Controller Is Shown Below:
Fig4-Wind turbine using FLC
6. RESULTS:
Fig5- Wind Speed Estimation Of FLC Control
Fig6- Optimal Rotor Speed Tracking Of FLC Control
Fig7- Turbine Power Capture Of FLC Controller
Fig8- Actual Tip Speed Ratio Of FLC Controller
Fig9- Low Speed Shaft Torque Of FLC Controller

Fig10- Actual Power Coefficient Of FLC Control
CONCLUSION
This paper has proposed a fuzzy logic controller for
maximum wind power extraction based on a two-mass
model. The value of wind speed hasbeen estimated fromthe
available variables, i.e. the generator speed and turbine
torque using three numerical algorithms. The estimated
value has been used for sensor-less control design based on
fuzzy logic algorithm. The effectiveness and superiority of
the proposed estimation and control approaches have been
demonstrated by simulation results, as compared to PI
controller with its gains well-tuned.
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IRJET- Fuzzy predictive control of Variable Speed Wind Turbines using Fuzzy Techniques

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