Post on 03-Jun-2018
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DEPARTMENTOF
ELECTRONICS& INSTRUMENTATION ENGINEERINGA
PAPER PRESENTATIONON
Fuzzy Adaptive PID control of pitchsystem in var iable speed wind turbines
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CONTENTS Objective
Need for pitch control
Principle of operation of wind turbines
Cross-sectional view of wind turbine system
Blade and pitch system
Drive-train system
Block diagram of wind turbine model
Operation of wind turbine
Pitch actuator model
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Continued.. Mechanical model of drive-train
Simulink model of conventional PID controller
Simulink pitch output curve
Fuzzy adaptive PID control block of pitch system
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ObjectiveTo adjust the pitch angle of rotor blades of
wind turbines according to the changes in
wind speed.
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Pitch angle controlis commonly used in a variety of windturbines.
The output power of wind turbines changes constantly
depending on the speed and direction of the wind.
Due to change in wind speed, the pitch adjusting mechanism mustmove frequently.
This pitch adjusting mechanism of wind turbines generation system
has some delay to the reaction of wind speed.
When it is too late for the pitch adjusting mechanism to move ,it
causes the wind turbine to overload instantaneously which is notconducive to the operation of wind turbines and also it makes harm
to the grid.
So, pitch control plays a crucial role in affecting the output power of
wind turbine.
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The wind turbine is a device for conversion of kinetic
energy in the wind into electrical energy. Kinetic energy of wind is converted to rotational
energy and then to electrical energy.
The mechanical power of wind turbine is given by:
C i i i
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Cross-sectiona view o t e win
turbine system
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Blade and Pitch system This system is the entry point to the wind turbine
system.
The wind is the input to this system.
Ideally, positioning the blades to the direction of wind
optimizes the electrical power generated from the
wind in both low and high wind conditions.
The rotor generates a rotational force which serves as
an input to the drive train system.
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Drive-train system The drive train system is made up of low-speed shaft,
a high speed shaft and gear system.
The principle of operation of drive train is based on aspeed transmission mechanism.
This is done by gear system which boosts the speed
generated by low-speed shaft to a high- speed shaft.
This high speed shaft transmits torque and rotational
speed to the generator at a level required to generate
electric energy.
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Block diagram of wind turbine
model
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Operation of wind turbine A simple wind turbine controller is basically
switching between full load and partial load
controller based on wind speed measurement. Full load controller measures the generator
speed,Wg and acts on the pitch reference ,ref
in order to keep the generator speed at nominal value.
Partial load controllersets ref to the optimal pointto increase the generator speed in order to meet the
generator power set point, Po.
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The pitch actuator is used to turn blades along theirlongitudinal axis.
The actuator model describes a dynamic behavior
between a pitch demand ,dfrom the pitch controller
and measurement of pitch angle, .
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The change in pitch angle is given by:
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Mechanical model of drive-train
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Mechanical model parameters
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The dynamics of drive-train are described by following
differential equations:
Thus by using Newtons
Second Law of motion,
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Parameters of wind turbine
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Fuzzy adaptive PID control block of
pitch system
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Fuzzy adaptive PID control It is called adaptive since it auto tunes the PID
parameters.
These parameters are given as inputs to the PIDcontroller.
The output follows the changes in the input signalquickly.
The overshoot in conventional PID can be eliminated.
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Fuzzy control simulation diagram of
pitch system
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Fuzzy adaptive simulation diagram
of pitch system
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Membership functionsE and EC functions in range
[-5 5]
Kp, Ki and Kd functions inrange [0 1]
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Fuzzy regulars
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Fuzzy regulars for Kd
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Mamdani type FIS
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The Gaussian membership function with seven
fuzzy sets used for the input Error
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Rules are given in the Rule Editor
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Rule viewer is shown below:
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The response of the pitch system using a Fuzzy
controller is shown below:
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The response of the pitch system using a Fuzzy
adaptive PID controller is shown below:
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Comparing the two responses
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Comparison of Rise time and peak
time of the two responsesFOR FUZZY
CONTROLLER
FOR FUZZY PID
CONTROLLER
PEAK TIME 24 SEC 10.5 SEC
RISE TIME 10 SEC 7.5 SEC
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Advantages
This methodology involving a fuzzy PID controller
gives better performance in the rise time, peak time
than a Fuzzy controller.
There is zero steady state error.
It can better control a process when compared to the
conventional methods.
It incorporates the experts knowledge.
It is used to model both linear and non-linear systems.
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Disadvantages
Rules must be formed accurately while designingthe controller.
Choice of Membership function is dependent on
context.
As the number of fuzzy sets increases, complexityincreases.
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Conclusion
Fuzzy PID controller gives optimal performance when
compared to conventional Fuzzy controller.
Through the above simulation we can see that the
pitch angle can follow the input signal changesquickly and the output has no overshoot.
It eliminates the delay characteristics influence on the
system stability.
This technique is much better to realize the control of
pitch system and to guarantee the stability of wind
turbine output power.
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