Wind plant electrical systems: electrical generation, machines, power electronics, and collector systems

One of the earliest nonanimal sources of power used by man was the wind turbine. Wind turbines have been in documented use for more than 1,000 years. The earliest wind-turbine designs were extremely simple; turbines were allowed to rotate at a rate proportional to the velocity of the wind. They were used to pump water, grind grain, cut lumber, and perform a myriad of other tasks. For these purposes, varying speed seldom impacted the effectiveness of the windmill enough to justify the complications of closely controlling rotational speed. Allowing the machines to run at variable speed was in fact highly advantageous as it greatly increased the total energy that could be extracted from the wind.