Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Alternators in windmill

705 views

Published on

Types of Alternators used in windmills

Published in: Engineering
  • Be the first to comment

  • Be the first to like this

Alternators in windmill

  1. 1. Alternators in windmills Presented by, R.Vasanthan – 14E113 V.Sai Krishna – 14E95 P.Vinith – 14E123 S.Padmanathan – 14E82
  2. 2. Fundamentals • Wind Power o Harnessed by using wind flow as the driving force of the generator in order to create a torque on the rotor and in effect produce electricity. o Wind is Uncontrollable => Special generators are needed o For constant rotor speed: some wind turbines have motors/controllers that drive the blades when the wind is not strong enough
  3. 3. Planetary gear set arrangement
  4. 4. Types of generators • Induction Generator • Permanent Magnet Synchronous Generators
  5. 5. Wind Turbines Generation System Wind Turbine Permanent magnet synchronous generator Rectifier Boost Controller Inverter
  6. 6. Wind turbine  The wind turbine is playing a cardinal role in the entire system as it is responsible for the generation of mechanical power needed to drive the generator.  The primary factors on which the wind turbine performance depend are:  Wind speed  Direction of wind  Blade size  Pitch angle  Mechanical gears involved in its design
  7. 7. Mathematical model of wind turbine  The wind turbine can be represented in terms of a mathematical equation, which governs its generated power. Pm=mechanical output power of the turbine Cp=D the air density [kg/m3], cp the performance coefficient or power coefficient, λ the tip speed ratio vt/vw, ( the ratio between the blade tip speed vt and the wind speed upstream the rotor vw [m/s]) Ѳ the blade pitch angle [deg], and Ar the area swept by the rotor [m2].
  8. 8. Model For Wind turbine  Wind turbine extracts portion of wind and converts it into mechanical Power.  It has three inputs  Generator Speed  The Blade Pitch Angle  Wind speed.  One Output  Torque
  9. 9. Generator  The prime mover rotor of the (PMSG) is driven by Wind turbine mechanical Power.  We have selected PMSG (5kW) because for small scale level PMSG is considered as best type of generator.  better reliability, less maintenance and  more effective  No external dc excitation is needed.  Less losses and improved efficiency
  10. 10.  The mechanical power of wind turbine provide torque to the generator shaft.  The output generated by PMSG is variable in magnitude and Frequency because of the fluctuating wind speed.  The output of the generator is fed via stator into the rectifier block to convert it into dc and smoothen it
  11. 11. Rectifier and controlled boost Converter  For controlling the Ac output to a constant magnitude and frequency .  Convert the AC (Variable Frequency and Voltage) from generator to a DC using Rectifier.  The boost converter then converts the DC rectified value into a constant DC value
  12. 12. Inverter  Finally the inverter is used to convert the constant dc Voltage into Ac with Constant frequency and Voltage Magnitude
  13. 13. Permanent Magnet Synchronous Generator Advantages  Don't require external excitation => Less power dissipation.  Space is not needed for windings => smaller  machine size (30% reduction in weight) and some cases cheaper.  Smooth stator structure unlike their salient pole structure in conventional dc machines.  Power ratings ranging from few watts to 100kW or more. Disadvantages  Risk of demagnetization due to excessive currents in the motor windings or due to overheating the magnet.  Limited air gap flux density that permanent magnets can produce.
  14. 14. Squirrel Cage Induction Generator  Stator of the SCIG is connected to grid through back to back power electronic converter bridges  The slip, and hence the rotor speed of a squirrel cage induction generator varies with the amount of power generated.  These rotor speed variations are, however, very small, approximately 1 to 2 per cent.  Therefore, this wind turbine type is normally referred to as a constant speed or fixed speed turbine.
  15. 15. SQUIRREL CAGE INDUCTION GENERATOR  Advantages To make best use of wind energy available It is only used in large scale applications.  Disadvantage Expensive A squirrel cage induction generator always consumes reactive power. So capacitor is needed to control the reactive power.
  16. 16. Wound Rotor Induction Generator  Power Convertor size reduced by using it on rotor side of WRIG  This is 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.
  17. 17. WRIG Advantages and Disadvantages  For utility scale wind power generation it outweighs squirrel cage machine.  Offers a lot of flexibility for wide range of speed control  Used in high power applications in which a large amount of slip power could be recovered  Speed of WRIM was changed by mechanically varying external rotor circuit resistance(simplest way)  Major disadvantage is low efficiency due to additional loses in resistor connected in the rotor circuit.
  18. 18. DOUBLY FED INDUCTION GENERATOR  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 .
  19. 19. ADVANTAGES AND DISADVANTAGES  Operation at variable rotor speed while the amplitude and frequency of the generated voltages remain constant.  Optimization of the amount of power generated as a function of the wind available up to the nominal output power of the wind turbine generator.  Virtual elimination of sudden variations in the rotor torque and generator output power.  Generation of electrical power at lower wind speeds.  Complicated  Maintainence
  20. 20. HTSWTG High Temperature Superconducting Wind Turbine Generators  HIGH CURRENT DENSITY  HIGH MAGNETIC FIELD  REDUCTION IN MASS AND SIZE  INCREASED EFFICIENCY  HIGHER PARTIAL LOAD EFFICIENCY  POWER RATING 5-10 MW  USED SPECIALLY IN OFFSHORE
  21. 21. ADVANTAGES  Increase machine efficiency beyond 99%, reducing losses by as much as 50% over conventional generators  Energy savings  Reduced pollution per unit of energy produced  Lower life-cycle costs  Enhanced grid stability  Reduced capital cost  Reduced installation expenses
  22. 22. REFERENCES  http://www.scribd.com/doc/27428761/Wound-Rotor-Induction-Motor  http://cdn.intechopen.com/pdfs/14821/InTech- High_temperature_superconducting_wind_turbine_generators.pdf  http://www.labvolt.com/downloads/download/86376_F0.pdf  http://www.azom.com/article.aspx?ArticleID=1083  http://www.taplondon.co.uk/bwea_offshore/pdf/JohnHill.pdf

×