The design and construction of the rotor (as the propellers are called) control system for wind turbines is an ingenious series of devices, largely copied form the basic pitch control for propeller driven aircraft.
The rotor needs to operate at an optimum speed regradless of the wind speed. The maximum speed of the wind that can efficiently be utilized without structural danger to the entire rig is about 30 mph. In the event the wind speed increases a sensing device measure the electrical output several times per second and sends a signal to a dvice that controls the pitch of the rotor/propeller blades. The pitch is the degree of flatness of the blades to the oncoming wind. The blades can be made to twist or rotate on its axis with the rotor hub. A fully flexed rotor would have the leading or sharp edge, if you will, turned directly into the wind... called feathered in aviation terms. This allows the rotor to nearly fully stop even in high winds. To fully stop the blade or stop it in an emergency a dynamic brake is incorporated in the driven shaft leading to the generator turbine.
Blades can "ice up" in inclement weather and become dangerously out of balance... enough so that it can destroy the tower on which it's mounted.
All you ever wanted to know, I'm sure.
A wind turbine farm near Palm Springs, California has over 4,000 towers already installed.
A huge turbine/rotor system has been installed here in the U.S., whose blades are nearly 100 yards long (each). It's said it has the potential of producing enough elecrticity to power 1500 homes...