WEEK 8 - RESEARCH

Objective: To identify and research about the Wind Turbine and DC Motor Generator

Analysis/Discussion :

Wind Turbine

Wind turbine is an important element in a wind power system to generate electricity. A large wind turbine is able to generate up to megawatts (MW) of electricity. A small wind turbine is producing electricity less than 100kW, which is suitable to be used as backup source. A very small wind turbine is generating around 20 to 500 watts of electricity, and is normally used for batteries charging purpose. The wind turbine captures the wind’s kinetic energy in a rotor which consists of two or more blades mechanically coupled to an electrical generator and it is mounted on tall tower to enhance the energy capture. Currently two types of configuration for wind turbine exist, which is the vertical-axis configuration and the widely used horizontal-axis configuration.

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable. It is also an advantage when the turbine is integrated into a building because it is inherently less steerable. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance.

DC Motor (Generator)

A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter. Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using power rectification devices (vacuum tube or more recently solid state) is effective and usually economic.

The dynamo uses rotating coils of wire and magnetic fields to convert mechanical rotation into a pulsing direct electric current through Faraday's law of induction. A dynamo machine consists of a stationary structure, called the stator, which provides a constant magnetic field, and a set of rotating winding called the armature which turn within that field. The motion of the wire within the magnetic field causes the field to push on the electrons in the metal, creating an electric current in the wire. On small machines the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils.



Buck-Boost Circuit


The buck–boost converter is a type of DC-to-DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude. It is equivalent to a flyback converter using a single indutor instead of a transformer. Two different topologies are called buck–boost converter. Both of them can produce a range of output voltages, from an output voltage much larger (in absolute magnitude) than the input voltage, down to almost zero. Figure 4 shows the basic circuit of buck boost circuit.

A buck (step-down) converter combined with a boost (step-up) converter The output voltage is typically of the same polarity of the input, and can be lower or higher than the input. Such a non-inverting buck-boost converter may use a single inductor which is used for both the buck inductor and the boost inductor, it may use multiple inductors but only a single switch as in the SEPIC and CUK topologies.

Conclusion:

Based on the 3 research that I have done, I am fully understand on how the wind turbine works and how the DC generator works. Lastly, I can conclude that which circuit do I need to use for this project to boost the voltage.