induction generator for wind power generation by w5E7TAC

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									INDUCTION
 GENERATOR
   FOR
    WIND
      POWER
       GENERATION
               OUTLINES
   INTRODUCTION
   HISTORY
   WIND TURBINES
   TERMINOLOGIES USED
   WORKING
   CONTROLLING
   ADVANTAGES OF VARIABLE SPEED
    GENERATION
   WHY INDUCTION GENERATOR?
   ADVANTAGES & DISADVANTAGES OF WIND
    ENERGY
   APPLICATIONS
   CONCLUSION
            INTRODUCTION
Wind  turbines convert the kinetic energy present
in the wind into mechanical energy by means of
producing torque.
Large scale wind power projects are an attractive
alternative to conventional capacity expansion.
In the present scenario , most wind turbine
manufacturers now equip power generating units
by induction generators.
They are operated either at fixed speed or
variable speed.
Generators driven by fixed speed turbines can
directly be connected to grid.
Variable speed generators need a power
electronic converter interface for interconnection
with the grid.
Variable speed generation is preferred over fixed
speed generation.
HISTORY
          In 200 B.C., in ancient
          Persia , the earliest
          windmills were used to grind
          grain.
          These early devices
          consisted of one or more
          vertically-mounted wooden
          beams , on the bottom of
          which was a grindstone,
          attached to a rotating shaft
          that turned with the wind.
          Starting in the 11th century
          A.D. , European crusaders
          brought the concept and
          developed the DUTCH type
          wind mill.
The first automatically
operating wind turbine for
electricity generation.
It was built by Charles F.
Brush in 1887-1888 in his
backyard.
Charles’s 60 foot , 80,000
pounds turbine supplied 12
kW power to 350
incandescent lights.
Its rotor was 17 meters in
diameter.
                WIND TURBINES
Wind  turbines convert wind energy to electricity for
distribution.
Aerodynamic  modeling is used to determine the
optimum tower height, control systems, number of blades
and blade shape.
Wind   turbines are generally classified depending on
their axis of rotation as:
 -Horizontal axis type,
 -Vertical axis type.
The   horizontal axis types generally have better
performance.
A quantitative measure of the wind power available at
any location is called Wind Power Density(WPD).
Commercial  wind farms generally produce a WPD of 400
watts/square meter.
HORIZONTAL AXIS WIND TURBINE   VERTICAL AXIS WIND TURBINE




    AALBORG-TURBINE                 DARRIEUS-WINDMILL
 The ROTOR component : Its approx 20% of the wind turbine
  cost, includes the blade for converting wind energy to low
                  .



  speed rotational energy.

 The GENERATOR component : Its approx 34% of the wind turbine
  cost, includes electrical generator ,the control electronics and a
  gearbox.
    .

 The STRUCTURAL component : Its approx 15% of the wind turbine
  cost, includes the tower and yaw mechanism.
              TERMINOLOGIES USED



ANEMOMETER:     IT’S A WIND DIRECTION SENSOR WITH DIGITAL DISPLAY.
USED IN AREAS WHERE AC POWER IS NOT AVAILABLE. MONITORS WIND SPEED
AND STORE MAX AND AVERAGE VALUE.


YAW SYSTEM: THEY PERFORM THE TASK OF ORIENTING THE ROTOR IN THE
DIRECTION OF WIND.


NACELLE: IT IS STRUCTURE THAT HOUSES ALL OF THE GENERATING
COMPONENTS LIKE-GEARBOX, ROTOR SHAFT AND BRAKE ASSEMBLY ETC.



ROTOR BLADES: THE BLADES ARE THE SAILS OF THE SYSTEM ,
WHEN THE WIND FORCES THE BLADES TO MOVE   , IT HAS TRANSFERRED SOME
OF ITS ENERGY TO THE ROTOR.




                                                                      .
SHAFT SYSTEM:          THE WIND TURBINE SHAFT IS CONNECTED TO THE CENTRE
OF THE ROTOR , WHEN THE ROTOR SPINS THE SHAFT SPINS AS WELL.THUS ROTOR
TRANSFERS ITS MECHANICAL ROTATIONAL ENERGY TO THE SHAFT.




WIND VANE:    SMALL TURBINES ARE POINTED INTO THE WIND BY USING IT.


GEAR BOX: IT TURNS THE SLOW ROTATION OF THE BLADES INTO A QUICKER
 ROTATION THAT IS MORE SUITABLE TO DRIVE AN ELECTRICAL GENERATOR
                         WORKING

Aeroturbines convert wind energy into rotary mechanical energy.
A mechanical interface , consisting of a step –up gear and a
suitable coupling transmits the energy to an electrical generator.
The output of this generator is connected to the load or system
grid.
The controller senses the wind direction ,wind speed , power
output of the generator and other necessary performance
quantities of the system and initiates appropriate control signals to
take suitable corrective actions.

Several schemes for electrical generation have been developed.
These schemes can be broadly classified under these categories:
1. Constant speed generation system.
2. Variable speed generation system.

  As constant speed generation system suffer from a number of
   drawbacks hence variable generation system is preferred .
                        GEARING
           WIND           AND          ELECTRICAL
          TURBINE       COUPLING       GENERATOR

WIND        WT
            WT                GC             EG
                                                      TO LOAD
                                                      UTILITY GRID
                                   CONTROL    GEN.
       PITCH        YAW            SIGNAL     TEMP.
       CONTROL      CONTROL




                    SPEED          CONTROLLER




       COMPONENTS OF WIND ELECTRIC SYSTEM
VARIABLE SPEED WIND ENERGY CONVERSION SYSTEM


 In variable speed systems, the turbines rotor absorbs the mechanical
 power fluctuations by changing its speed.

 So the output power curve is smoother which greatly enhances the
 quality of power.

 However ,since variable speed operation produces a variable
 frequency voltage, a power electronic converter must be used to
 connect to the constant frequency grid

 It can be achieved by using:

 WECS with Squirrel cage induction generator.

 WECS with Wound rotor induction generator.

 WECS with Doubly-fed induction generator.
WECS with Squirrel cage induction generator




In this set up the stator of the squirrel cage induction generator will be
connected to the grid by the means of back to back connected power
electronic converter bridges.
Since the power converter has to convert all the stator power, the converter
size depends on the stator power rating.

 ADVANTAGE:
Ability to make the best use of available wind power.
It eliminates the need for a capacitor bank.

DISADVANTAGE:
Cost of power converter is high.
WECS with Wound rotor induction generator




The power converter size in the earlier system can be reduced by using it
on the rotor side of a wound rotor induction generator. Above fig shows a
variable speed system using a wound rotor generator. The power converter
is now connected between the rotor and grid , so it needs to carry only the
slip power.

ADVANTAGES:
For utility scale wind power generation it outweighs squirrel cage
machine.
             WECS with DFIG




Double-fed induction machines can be operated as a generator as well as a
motor in both sub-synchronous and super-synchronous speeds, thus giving
four possible operating modes.
Only the two generating modes at sub-synchronous and super-synchronous
speeds are of interest for wind power generation.
       BACK TO BACK CONNECTED POWER CONVERTER BRIDGES




Two power converter bridges connected back-to-back by means of a dc link can
accommodate the bidirectional rotor power flow in a DFIG.
 The purpose of the grid side converter is to maintain the dc link voltage constant.
 It has control over the active and reactive power transfer between the rotor and
the grid.
The rotor side converter is responsible for control of the flux, and thus, the stator
active and reactive powers .

ADVANTAGES:
Less cost of AC-AC converter.
Improved system efficiency.
WIND POWER DEVELOPED BY THE WIND TURBINE IS
GIVEN BY :


P=(Cp AρV^3)/2


Where
Cp: Power coefficient
A: Area swept by rotor blades
ρ: Air density
V: Velocity of wind
            CONTROLLING
Induction generator control:
Cage rotor induction generators can be made to operate over
a wider speed range by pole changing or pole amplitude
modulating the main winding.
A Wound rotor induction generator can be controlled by
varying the slip energy of the rotor circuit using following
methods : rotor resistance control , cascading etc
A bank of capacitors connected to the terminals can be used.
Transmission control:
By using silicon controlled rectifier device.
Conduction period of electronic devices can be controlled by
applying delayed trigger pulses.
Load control:
Using switched load resistors stepwise load approximation can
be made .
Operation within the maximum current loading of the
generator can be set.
ADVANTAGES OF USING VARIABLE
   SPEED GENERATION

   Better energy capture than fixed speed
   generation.

   Mechanical    stress reduction of turbine.

   Acoustic   noise reduction.

   Cost   effective and entirely feasible.
WHY INDUCTION GENERATOR?

Simple  and robust construction.
Can run independently.

Inexpensive.

Minimal maintenance.

Inherent overload protection.

At high speed, reduces size and weight of
machine(roughly 0.33m long, 0.5m diameter)
and filter components.
     Wind turbine data


The wind turbine is a MOD 5 type with the following data

Nominal values

Turbine                        1.8 MVA

Rated wind speed               7 m/s

Rotor radius                   40 m

Rotor swept area               5026.548 m2

Air density                    1.225 kg/m3

Gear box efficiency            0.979 pu

Gear ratio (machine/turbine)   120
ADVANTAGES OF WIND ENERGY


It   is a renewable source of energy.

Wind    power systems are non-polluting.

Wind energy systems avoid fuel provision and
transport.

On  a small scale upto a few kilowatt system is less
costly.
DISADVANTAGES OF WIND ENERGY


Wind   energy available is fluctuating in nature.

Wind    energy needs storage capacity because of
its irregularities.

Wind   energy systems are noisy in operation.

Windpower systems have a relatively high overall
 weight.
APPLICATIONS OF WIND ENERGY

Invarious industrial process like: food processing, textile
processing , production of inorganic chemicals like chlorine,
bromine etc

Wind   powered pump can be used to desalinate water.

   powerful turbines(50kW), are for operating irrigation
The
pumps , navigational signals and remote communication.

Inaqueduct system , large scale wind driven units can
provide power for the pumping of water from the main
reservoir to auxiliary reservoir.
               CONCLUSION

Wind  is one of the most flexible and tractable of all
energy sources, since the mechanical energy derived
directly from the wind can be readily and efficiently
converted to other forms of energy.

The  cost of power generation from wind farms has now
become lower than diesel power and comparable to
thermal power in several areas of our country especially
near the coasts.

Thus Wind power can be used in centralized utility
applications to drive synchronous AC electrical
generators.

								
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