Windmill construction and its working principles

Windmill control system and its working principles.

1. WINDMILL CONTROL SYSTEM

2. What is Wind Turbine? W ind turbines use wind to make electricity. The wind turns the blades, which in turn spins a generator to create electricity. The principle behind wind turbines is very simple: the energy in the wind turns the blades around a rotor. The rotor is connected to the shaft, which spins a generator to create electricity.

3. Major Parts of Wind Turbine A simple wind turbine consists of three main parts, the blades, shaft and generator 1)  Blades :  The blade acts as barriers to the wind. When the wind forces the blade to move, some of the wind energy is transferred to the rotor. 2)  Shaft:  When the rotor spins, the shaft also spins, and transfers the mechanical energy into rotational energy. 3) Generator :   A generator uses the difference in electrical charge to produce a change in voltage. Voltage is actually electrical pressure, the force that moves an electrical current. The voltage drives the electrical current (alternating current power) through power lines for distribution.

4. Major Parts of Wind Turbine

5. How Wind Turbine Works? When the wind flows across the blade, the air pressure on one side of the blade decreases. The difference in air pressure across the two sides of the blade creates both lift and drag. The force of the lift is stronger than the drag and this causes the rotor to spin. The rotor is connected to the generator, either directly (if it's a direct drive turbine) or through a shaft and a series of gears (a gearbox) that speed up the rotation and allow for a physically smaller generator. This translation of aerodynamic force to rotation of a generator creates electricity.

6. Device in Wind Turbine 1.   Nacelle 2.Rotor Blades-27 m 3.Hub –Rotor Hub to Shaft 4.Low Speed Shaft -Receive 19 to 20 RPM 4.Gearbox – Gives 1500 RPM 5.High Speed Shaft With Its Mechanical Brake 6.Electrical Generator 7.Yaw Mechanism –  to turn the nacelle with the rotor against the wind.  8.Electronic Controller 9.Hydraulics System

7. Device in Wind Turbine 10.Cooling Unit –Cooling oil and Fan 11.Tower -50 to 80m-Tubular and lattice Towers 12.Anemometer and Wind Vane- The electronic signals from the anemometer are used by the wind turbine's electronic controller to start the wind turbine when the wind speed reaches approximately 5 metres per second (10 knots). The computers stops the wind turbine automatically if the wind speed exceeds 25 metres per second (50 knots) in order to protect the turbine and its surroundings. The wind vane signals are used by the wind turbine's electronic controller to turn the wind turbine against the wind, using the yaw mechanism

8. Control Systems in Wind Turbine To enable automatic operation. Keep the turbine aligned with the wind. To Engage and disengage the generator. To govern the rotor speed. To protect the turbine from over speed. To sense malfunctions and warn operators.

9. Control Systems in Wind Turbine Types: Passive Control-own sensing and actuation Active Control-use mechanical, electrical, pneumatic or other combination Active control used transducer. Too much control add extra hardness to the machine to run.

10. RPM Control Start the rotor turning based on wind velocity. Set the pitch angle to a run position. Control RPM to prevent the rotor from overpowering the generator. Protect the rotor and system from high wind-velocity damage.

11. Electronic Controls Sensor- RPM,Vibration,Power , Blade pitch angle Computer Pitch Actuators Rotor

12. Electronic Controls Primary Control System failed Backup over speed control system works based on tip brakes or spoilers to stall the blade pitch angle.

13. Additional RPM C ontrol Techniques A tail vane to rotate the rotor edgewise to the wind direction. Blade tip plates that extended to cause braking . In VAWT(Vertical Axis Wind Turbine) an axis control system. Mechanical methods and M icro switch connected with the generator is unreliable. Rotor shaft coupling failure causes high current in slip rings

14. Electrical Cut-in In DC generators have a very low power output at low RPM. In AC generator design condition is more difficult to meet, first of all synchronous frequency is meet for rotor shaft and generator. In case when the power to the computer is gone and blade pitch servo actuators is also gone this is very dangerous situation.

15. Power Collection System MCCB-Detect over load of generators Molded Case Circuit Breaker ( MCCB ) is a circuit breaker and trip device assembled in a mould case. Also it can automatically cut off electric power in case of overload and short circuit. It is meant for higher rated current and is commonly used in Industrial applications. Its usual range is 250A-800A . Individual turbines has its own transformer

16. Earthing of Wind Farms

17. Earthing of Wind Farms Minimize Shock hazards to personnel. Establish low impedance path. Improve protection from lightning. Prevent large potential difference.

18. Lightning Protection Wind turbines are made up of conducting materials if we prefer carbon fiber is used to reinforce blades, additional precautions needed. Lightning Flashes – 1. Downward inception, negative and positive polarity. 2. Upward inception, negative and positive polarity.

19. Lightning Protection Downward inception, negative and positive polarity are the most common. Downward flashes a high amplitude burst of current lasting for a few microseconds followed by current of few hundred amperes. Peak current of lightning is 200 KA, charge transfer are 400C and specific energy 20 MJ/ohm

20. Effects of Various aspects of lightning on a wind turbine

21. Wind power integration into grid Short term measures-grid management procedure and addition of some tie lines. Long term measures-existing grid network operating at high voltage for long distance transmission. The large percentage of wind power affects the stability of grid network. Variability: Short term variability-scheduling of generation units. Long term variablility-sesonal meteorological patterns

22. Impact of variability can be ove rcome Frequency regulation by automatic generation. Load follow up unit commitment schedule can take place in a period of few minutes to a couple of hours. Unit commitment based on load profile prediction.

23. Cluster of Wind Turbines Combining ancillary power plants-gas turbine or oil fired power plant with wind farm. Using hydro storage reserves. Interconnection with other grids will improve The reliability of intermittancy management.