pitch control of wind turbine

8/12/2019 pitch control of wind turbine

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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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pitch control of wind turbine

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