Page 188 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

Small Wind Energy Systems 175

cylinders and turbine rotor. It is also possible that a fuzzy logic–based controller will perform really
well for a Magnus turbine coupled to a PMSG or an IG [20, 21].

7.8 SUMMARY

This chapter presents how a customized wind turbine has a typical operation for medium and low
wind velocity sites since the power of any wind generator is directly affected by the wind speed.
It is not possible to maintain a fixed speed of a generator always at a high efficiency level because
commercially available generators for low wind speeds (5–15 m/s) are not currently designed
to operate with their best efficiency over the whole speed range (typically from 3 to 25 m/s).
In addition, high towers for wind turbines increase the overall costs and the turbine exposure to
turbulences and wind gusts affects the generators performance.
Medium- or long-term statistics of wind resources must be taken into account to define the power
envelope for turbines, considering copper and iron losses for three PMSG designs considered and
the IG. In addition, a brief review of the IG and its advantages and disadvantages for small wind tur-
bines has been discussed. A PMSG-based system has been described in details too, and it has been
discussed how a low-speed electrical generator can be competitive and may be the best solution for
small-scale wind turbines, typically used in rural systems, small farms, and villages.
Data, instrumentation, and measurements are necessary for small wind energy systems in order
to approach the design and implementation for commercial and residential applications. In addi-
tion, it is necessary to manage the utility connection, assessing reactive power requirements, fault
ride through, and power quality monitoring. Some schemes can be implemented for an SEIG using
standard squirrel cage machines, and advanced control and signal processing system can be imple-
mented for PMSG wind energy systems connected to the grid.
Although large-scale wind turbines may have optimized speed control, the market for small-scale
wind turbines does not allow expensive solutions. Therefore, an optimized electric generator must
be designed to have the best efficiency for low wind velocities under cost constraints. It remains a
challenge, even today, to design a generator capable of operating at wind velocities less than 3.5 m/s
with a high efficiency and this is still an open-ended problem to be solved.

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