Introduction of wind stand-alone system

Introduction of wind stand-alone system:

There are two types of energy sources in the world i.e. renewable energy source and conventional energy sources. Renewable energy sources are the type of energy sources which are plenty in quantity and are derived from earth. Wind energy, solar energy, geo thermal and bio mass are different types of renewable energy sources. These resources are inexhaustible in nature. The known advantages of renewable energy sources are its clean nature, abundant in quantity and most importantly it is eco-friendly unlike non-renewable energy sources. 

Now days more research is going on the enhancement of technology which can efficiently convert the renewable energy sources into useful electrical energy sources. Though the literal conversion efficiency of renewable energy sources is lower than that of conventional energy source, the technology is developed and improvised on daily basis to improve its efficiency above 90%. On the other hand, conventional sources of energy are contributing towards pollution; it’s depleting in quantity and exhaustible. Because of several disadvantages renewable energy sources can be used as alternatives to it.

Among different types of renewable sources of energy, wind energy is the cleanest and the efficient source of energy. The major advantages of wind energy are wind-generated electricity doesn’t pollute the water, air or soil. It doesn’t contribute towards global warming. It doesn’t consume large amount of water needed by other energy sources. It is caused by every day solar radiation. Its supply is abundant unlike solar power during bad weather condition and night time. 

The price of electricity generation by wind power plant is comparatively lesser than other modes of generation. It contributes towards the economy of middle class and low-class communities. It also creates employment opportunities for highly skilled workers. It’s very fast and easy to install. 

In a year many large utility scale wind power plants are installed. 

There are several types of generators used such as Self-excited induction generator (SEIG), doubly fed Induction generator (DFIG) and permanent magnet synchronous generator (PMSG). Among these generators, PMSG has several advantages which make it very usable for WECS. 

It doesn’t require an additional dc supply for excitation circuit. By eliminating the excitation, energy savings of 20% can be had by simply using magnets. 

It doesn’t use slip rings, so it is simpler and maintenance free. The condensers are not required for power factor maintenance unlike in induction generator. It is also advantageous over geared driven segment IG system. Induction generator requires leading reactive power to build up terminal voltage. On other hand DFIG has shorter range of operation unlike PMSG.

In the recent years, Wind energy conversion systems (WECS) have become a focal point in the research of renewable energy sources. This is due to the rapid advances in the size of wind generators as well as the development of power electronics and their applicability in wind energy extraction. 

The higher target is to achieve 12% of the world’s electricity from wind power by 2020.The induction generators are commonly used for low and medium power generations in such generation schemes it is found that 25% of overall turbine downtime is due to gear box failures further the gearbox requires frequent maintenance and it also increases the weight of system and increases the cost. 

The above drawbacks can be overcome in the direct driven wind energy conversion systems (WECS) by replacing mechanical gearbox systems with power electronic converters. By eliminating the need for a gearbox between the turbine and generator, these systems are less expensive and also require less maintenance. Nowadays Permanent Magnet Synchronous Generators (PMSG’s) are more attractive for direct driven wind energy schemes. Further the 
PMSG has several advantages such as, 

·        Higher efficiency

·        Additional power supply is not needed for the magnet field excitation.

·        Higher reliability due to the absence of mechanical components such as slip rings.

In the case of wind energy conversion systems (WECSs), the interest is also focused on small units, used to provide electricity supply in remote areas that are beyond the reach of an electric power grid or cannot be economically connected to a grid [2]. WECSs are the most favoured alternatives for supplying electricity in stand-alone cases at this moment due to the fact that wind energy is relatively easily harnessed, the maintenance required by the wind turbine generators is reasonable, and there is no fuel cost. PMSGs are particularly interesting in low-power wind energy applications, due to their small size and high power density