Wind turbine modeling using pitch controller

Presentation on Wind turbine modeling using pitch controller

OBJECTIVES
  1. Modeling of a wind turbine where pitch angle is a control variable.
  2. At the high wind speed the pitch controller will automatically active to maintain the output power at the rated level.
PITCH ANGLE AS A CONTROL VARIABLE
  1. The amount of energy that is extracted from wind and converted into mechanical energy is depending on the radial force acting on the blade. The formation of the force depends on particular profile design and dimension.
  2. The Cp (λ, β) characteristic gives us a power coefficient, that depends on the tip speed ratio λ and the pitch angle β .
  3. For blade profiles two forces are generally used to describe the characteristics, lift force component (FLIFT ) and a drag component (FDRAG) which resulting as FTOTAL.
  4. The FLIFT component and a FDRAG together are transformed into a pair of axial FTHRUST force and rotor's directions FTORQUE components, where only the FTORQUE produces the driving torque around the rotor shaft. By varying the pitch angle, β the size the direction of FTOTAL components can be changed.
  5. The axial forces FTHRUST has no driving effect but puts stress on rotor blades and furthermore, leads to a thrust on the nacelle and on tower.
AERODYNAMIC FORCES AND VELOCITIES AT ROTOR BLADE
AERODYNAMIC FORCES AND VELOCITIES AT ROTOR BLADE
POWER COEFFICIENT VS TIP SPEED RATIO CURVE WITH DIFFERENT VALUE OF PITCH ANGLE
POWER COEFFICIENT VS TIP SPEED RATIO CURVE WITH DIFFERENT VALUE OF PITCH ANGLE
Power coefficient surface
clip_image006
Where,
Lamda = Tip speed ratio
Beta = Pitch angle
Cp = Rotor power coefficient
NEED OF PITCH CONTROLLER
  1. Because of the fluctuating nature of the wind speed the output of the wind turbine varies.
  2. At the high wind speed, fatigue damage can be occurred to the mechanical parts of the wind turbine.
  3. By controlling the pitch angle the output power can be limited as the wind turbine rotor power coefficient decreases with the increase of pitch angle.
  4. At the high wind speed the automatically activated pitch controller keep the output power within rated level by increasing the value of pitch angle.
BLOCK DIAGRAM
Wind turbine scheme with pitch controller
Wind turbine scheme with pitch controller
BLOCK DIAGRAM
Pitch actuator system
Pitch actuator system
OPERATIONAL WAVE SHAPE
OPERATIONAL WAVE SHAPE
MATHMATICAL EXPRESSIONS
The mechanical output power equation is given by,
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And the expression for power coefficient is given by,
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Where,
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MODEL SPECIFICATIONS
The specifications of the wind turbine VESTAS-V52 are given in the following table.
Rotor diameter
52m
Area swept
2124m2
No of blades
3
Power regulation
Pitch/opti speed
Air brake
Full blade pitch
Cut-in wind speed
4m/s
Nominal wind speed
16m/s
Cut-out wind speed
25m/s
Nominal output
850kw
METHODOLOGY
Wind turbine modeling using pitch controller
SIMULINK BLOCK OF WIND TURBINE MODEL FOR VESTAS V52
SIMULINK BLOCK OF WIND TURBINE MODEL FOR VESTAS V52
SIMULINK MODEL OF PI CONTROLLER
SIMULINK MODEL OF PI CONTROLLER
SIMULINK MODEL OF PITCH ACTUATOR
SIMULINK MODEL OF PITCH ACTUATOR
SIMULATION RESULT
The simulation results obtained from the MATLAB/SIMULINK wind turbine model are given below(for various wind speed)
Wind speed(m/s)
Pitch angle
(degree)
Cp
Power(pu)
16(rated)
0
0.1595
1
17
6.22
0.1138
1
19
12.98
0.11
1
RESULT ANALYSIS
From simulation result, we observed that, at rated wind speed pitch angle is zero i.e. pitch controller remains inactive and above rated wind speed the pitch controller is activated and keep the output power at rated value by changing the value of pitch angle.
By using pitch controller the output power has been limited at high wind speed and wind turbine can operate safely. The simulation results has been shown that at the wind speed above the rated speed of the turbine the pitch controller automatically activate and limiting the output power by increasing the pitch angle.
Submitted by- Sudipta Dey and Md. Mazedul Huq
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