Environmental Engineering Reference
In-Depth Information
Figure 4-3. Schematic diagram of a dump circuit for switching excess wind power to
nonessential loads on small grids.
Turbine Control
Variable-pitch turbines are more expensive but offer power and speed control advan-
tages over fixed-pitch stall-regulated machines when it is necessary to match power from
fluctuating winds to the fluctuating demand of the electrical grid. The potential for greater
control with variable-pitch turbines allows higher penetration on small grids. Coupled with
an asynchronous generator, blade pitch control can regulate frequency as well as power, act-
ing more like a conventional power plant.
Recent advancements in variable-speed constant-frequency generating systems allow
rotor speed to vary ± 50 percent as it tracks the wind speed while the generator produces a
constant 60 Hz frequency. With variable speed asynchronous machines, the output voltage,
frequency, and power factor to the grid can be managed to provide both real and reactive
power as needed.
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