INDUCTION GENERATOR FOR WIND POWER GENERATION

1
INDUCTION GENERATOR
FOR WIND POWER
GENERATION
2
OUTLINES

• INTRODUCTION
• HISTORY
• WIND TURBINES
• TERMINOLOGIES USED
• WORKING
• CONTROLLING
• ADVANTAGES OF VARIABLE SPEED GENERATION
• WHY INDUCTION GENERATOR?
• ADVANTAGES DISADVANTAGES OF WIND ENERGY
• APPLICATIONS
• CONCLUSION

3
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.

4

• 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.
5

• The first automatically operating wind turbine
  for electricity generation.
• It was built by Charles F. Brush in 1887-1888 in
  his backyard.
• Charless 60 foot , 80,000 pounds turbine
  supplied 12 kW power to 350 incandescent lights.
• Its rotor was 17 meters in diameter.

6
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.

7

• HORIZONTAL AXIS WIND TURBINE

VERTICAL AXIS WIND TURBINE
AALBORG-TURBINE
DARRIEUS-WINDMILL
8
.
Conventional horizontal axis turbines can be
divided into three components

• 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.

• .

.
9
Anemometer Its 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.

TERMINOLOGIES USED

• .

10
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
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.
11
Parts of a wind turbine
12
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
• Constant speed generation system.
• Variable speed generation system.
• As constant speed generation system suffer
  from a number of drawbacks hence variable
  generation system is preferred .

13
GEARING AND COUPLING
ELECTRICAL GENERATOR
WIND TURBINE
WTWT
WIND
GC
EG
TO LOAD UTILITY GRID
CONTROL SIGNAL
GEN. TEMP.
YAW CONTROL
PITCH CONTROL
CONTROLLER
SPEED
COMPONENTS OF WIND ELECTRIC SYSTEM
14
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.

15
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.

16
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.

17
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.
18
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.

19
WIND POWER DEVELOPED BY THE WIND TURBINE IS
GIVEN BY

• P(Cp A?V3)/2
• Where
• Cp Power coefficient
• A Area swept by rotor blades
• ? Air density
• V Velocity of wind

20
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.

21
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.

22
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.

23
Wind turbine data The wind turbine is
a MOD 5 type with the following data
Nominal values 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
24
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.

25
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.
• Wind power systems have a relatively high overall
  
• weight.

26
APPLICATIONS OF WIND ENERGY

• In various industrial process like food
  processing, textile processing , production of
  inorganic chemicals like chlorine, bromine etc
• Wind powered pump can be used to desalinate
  water.
• The powerful turbines(50kW), are for operating
  irrigation pumps , navigational signals and
  remote communication.
• In aqueduct system , large scale wind driven
  units can provide power for the pumping of water
  from the main reservoir to auxiliary reservoir.

27
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.

28
THANK YOU