Don Quixote in his madness tilted at windmills but wind turbines also exhibit their own kind of capricious behavior. In a wind gust they spin away, churning kilowatts of electricity. But in a breeze they turn slowly, eking out a fraction of that output.

If you sent such variable power straight to your house, your lights would go out and your fuse box would be ruined.

Luckily, this does not happen. The technology that precisely adjusts the voltage and electrical frequency of renewable power, like wind and solar, before it flows into the grid is called power conversion.

Last week, GE Energy launched its new Power Conversion business. The new unit builds on a century of expertise gathered by Converteam, a French expert in the field, which GE acquired for $3.2 billion last year.

At its heart, power conversion turns variable mechanical motion (think wind turbines) into useable power (electricity in your home socket), and vice versa. The technology has been around for decades, relying on mechanical systems with gears and crankshafts.

But GE is replacing this machinery with high-tech electrical motors, generators, and advanced electronic convertors. Compared to its mechanical counterparts, the electrical systems are more energy efficient and reliable, and require less maintenance.

The field where power conversion finds applications is vast. It ranges from renewable power, to ship propulsion, the steel industry, mining and elsewhere. Take ship propulsion.

A ship propeller is essentially a wind turbine turned on its head and attached to the bottom of a ship. Captains use a power conversion application called dynamic positioning when they need their vessels to stay in a fixed place on heaving seas, like when they unload supplies next to an oil platform, or move along a predetermined course, like when they lay undersea cables.

A suite of sensors from the compass and GPS to laser range finders and orientation sensors that track the roll and the pitch of the ship supply data to an onboard computer that creates a mathematical model of the ship. The computer sends orders to the electric engines powering the propellers and rudders to keep the ship in the right place.

Approximately 25 percent of electricity produced globally is used to power electric motors. Power conversion could help improve their energy efficiency by a third. GE's acquisition of Converteam will help the company take a large part of the $30 billion power conversion business.