They don't, there are brakes in the nacelle which is a part of the wind turbine. When there is no wind the brakes are on so that the rotors don't turn. In other words TURBINES DON'T MAKE ENERGY WHEN...
Wind energy is converted into electricity by spinning wind turbine. Any electric motor that is powered by electricity will generate electricity if you spin it yourself very fast.
Wind contains kinetic energy. When the wind enters the turbine, the kinetic energy is converted to mechanical energy. Then the energy goes through a generator that makes it into electrical energy...
Just like power plants. Each Wind Turbine has a generator. The generator has a magnet with a type of wires wrapped the are in a spiral tube. The Magnet is on a axle, the axle spins from the wind...