Wind power is generated when the earth orbits the sun daily, it receives light and heat. Across the earth there are areas with different temperatures, so this heat transfers from one area to another area. Due to heat differences wind is created. In warmer regions of the earth, the air is hot and the pressure will be high, compared with the air in colder regions, where it is low. Wind is the movement of the air from high pressure to low pressure. From this the idea of generating power from wind came to action.
When compared with conventional sources, wind energy offers great potential to generate electricity without the causing any pollution problems. Mechanical energy in wind has been used for thousands of years for numerous applications like in milling, pumping water and other mechanical power applications. But the use of wind energy as an electrical supply with free pollution what makes it attractive and takes more interest and used on a significant scale.
Wind Energy Conversion System (WECS) includes either an induction type or a synchronous generator within its structure. The permanent magnet synchronous generator is considered as best choice for wind turbines due to the simplicity of its generating mechanism and good power density.
2.2.2 Components of Wind Energy Conversion System
Figure 2.4 Components of wind system
Various components connected to the wind systems are as shown in figure 2.4. Each of the elements is described below
I. Wind turbines
Wind turbines produce electricity from kinetic energy of the wind to drive an electrical generator. Usually wind passes over the blades of turbine exerting a turning force over the blades. Inside the nacelle the rotating blades turn a shaft then goes into a gearbox. The gearbox helps in increasing the rotational speed for the operation of the generator and thus converts the rotational energy into electrical energy. Then the output electrical power is rectified by diode converters.
Power curve, which is a graph of power output versus wind speed is shown in figure 2.5
Figure 2.5 Power Speed Characteristics of Wind Turbine
II. Permanent Magnet Synchronous Generator (PMSG)
There are different types of generators are used for conversion of mechanical energy into electrical energy in wind system. But the most common is the permanent magnet generator.
III. Power Electronic Converter (AC-DC Recti?er )
It converts alternating current (AC) source to direct current (DC) source using power diodes or by controlling the ?ring angles of controllable switches. In this project, a three phase full wave AC- DC recti?er has been used connected to the output side of the wind model. It will convert the AC voltages generated by the wind model into DC voltage to make compatible with the DC side of the system.