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WIND ENERGY COMPARISON SYSTEMS

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Presented by
SOWMYA.M
4SM05EE030
Dept. of E&E

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CONTENTS
INTRODUCTION

¢ Wind or air in motion contains the kinetic energy,which is converted into mechanical power by means of a wind turbine.
¢ wind strikes in wind turbine blade as shown the fig-1.
¢ The wind turbine is connected to a generator
for producing electricity.
¢ The potential for wind energy is immense,and
experts suggest wind power can supply up to
20% of world electricity
¢ Betz™ law


WHY WIND ENERGY IS REQUIRED
1.The Cheapest source of electrical energy
2. Wind Turbine Technology is available which is technically feasible.
3. No marketing risks, as the product is Electrical energy.
4. Wind Energy is considered as an important input for the economic development of any country.
5. This led to a search for environmental friendly renewable Energy sources.
6. Wind mill can be constructed near the load centre.
7. Wind mill can be immediately erected with in one month.
8. Can supply up to 20% of electricity demand.
POWER IN THE WIND
power is equal to energy per unit time.
energy available is the kinetic energy of the wind.
The kinetic energy of any particle is equal to one half its mass times the square of its velocity or ½ mV*V .
Amount of air passing in unit time ,through an area ËœAâ„¢, with velocity â„¢Vâ„¢, is A*V, and its mass Ëœmâ„¢, is equal to its volume multiplied by its density Ëœrâ„¢ of air , i.e. m= rAV.
An aeroturbine with a large swept area has higher power than a smaller area machine.
There fore available wind power Pa= 1/2 rAV^3.
BASIC COMPONENTS OF WECS
The main components of WECS are shown in the below block diagram form.
Aero turbines convert energy in moving air to rotary mechanical energy. In general, they require pitch control proper operation. A mechanical interface consisting of a step up gear and a suitable coupling transmits the rotary mechanical energy to an electrical generator.
THE TECHNICAL ANALYSIS:
Induction Generator:
The electrical power by the induction generator and is transmitted to grid by the stator winding.
The stator winding is connected to the grid by the wind turbine.
The pitch angle is controlled in order to limit the generator out put power to its nominal value for high wind speeds.
But the speed variation is typically so small that the wind turbine induction generator is considered to be a fixed speed wind generator.
The reactive power absorbed by the induction generator is provided by the grid or by the some devices like capacitor banks, SUC, STATCOM or synchronous condenser.
It acts like load of its rated power at time of starting the flow this energy conversion

Working principle of induction Generator
¢ When wind changes its direction wind wane senses direction of wind and sends the signal to controller. Then it sends signal to the yaw motor. Yaw motor will bring the wind turbine blades perpendicular to the flow of wind. Output of turbine is connected to high speed generator through the low speed shaft and gear mechanism.
¢ When wind velocity is less than minimum velocity required to run the turbine and greater than maximum permissible velocity, then pitch control turns the blades parallel to the wind direction, then wind turbine will shutdown.

THE TECHNICAL ANALYSIS:
Induction Generator:
The electrical power by the induction generator and is transmitted to grid by the stator winding.
The stator winding is connected to the grid by the wind turbine.
The pitch angle is controlled in order to limit the generator out put power to its nominal value for high wind speeds.
But the speed variation is typically so small that the wind turbine induction generator is considered to be a fixed speed wind generator.
The reactive power absorbed by the induction generator is provided by the grid or by the some devices like capacitor banks, SUC, STATCOM or synchronous condenser.
It acts like load of its rated power at time of starting the flow this energy conversion



Advantages AND Disadvantages:
Advantages:
1. Can generate more than rated o/p power
2. It is a self-starting type machine.
3. Mechanical interface can be easily attached.
4. It is robust in construction & maintenance is easy.
Disadvantages:
1.Works at low p.f.
2. It draws magnetizing current from the grid.
3. Power factor improvement equipment must be connected with it.
Needs gear and coupling mechanism.
5. Once the problem occurs in the gear system, maximum time is required for maintenance
6. Interruption of supply
7. Cost of maintain is more.
SYNCHRONOUS GENERARATOR:
Wind turbine which uses synchronous generator normally use electromagnet in the rotor, which are fed by direct current from the grid. Since the grid supplies alternating current, they first have to convert ac to dc, before sending it into the coil windings around the electromagnets in the rotor. The electromagnets are connected to the current by using brushes &slip rings on the shaft of the generator.
Figure-4: Block Diagram of a wind Electric system for Gearless machine
Working principle
Yaw drives controls the rotation of the turbine depending upon the wind velocity and pitch drives controls the blades position depending upon the wind direction.
Turbine is directly coupled to the generator, when D.C excitation is supplied to the rotor Winding flux will be produced. E.m.f will be induced in the stator of the generator, when flux cut by the stator conductors as shown below in figure
SYNCHRONOUS MACHINE WITHOUT GEAR
1.Rotor blade
2.Wind measurement device
3.Synchronous Generator
4.Winch
5.Nacelle control cabinet
6.Yaw drives
7.Blade adapter
8.Pitch drive
a). Single-line diagram of Synchronous machine connected to grid
Figure-6: Single-line diagram of Synchronous machine connected to grid.
Advantages AND Disadvantages:
Advantages:
1. Draw less power from grid at time of starting.
2. Work at leading and lagging p.f.
3. Helps grid in p.f. Improvement.
4. Can generate power at low wind speed.
5. No gear and coupling mechanism required.
Disadvantages:
1. Cannot generate more than its rated o/p.
2. Maintenance is difficult.
3. It is costlier
4. Most of the problems occur at electronic interface.
CONCLUSION:


But the main disadvantage with induction machine is it acts as a load of same rating at the time of start and hence draw huge amount of reactive power and works at low power factor and main problem occur in the gear system of induction machine where as synchronous machine draws very less amount of power at the time of starting for excitation and works on the leading power factor.
Hence synchronous machine is grid friendly, Both the machines need grid supply for generating power, when ever grid fails not possible to generate power even when required wind is available. But if we use permanent magnet generator we can generate power without grid supply there fore permanent magnet generator is more suitable for wind machine compare to the above two wind energy conversion systems