Tip-speed ratio

It is generally assumed to be a function of both tip-speed ratio and pitch angle.

This has the benefit that the rotor speed in the generator is constant, so that the frequency of the AC voltage is fixed.

By extension, the efficiency of the wind turbine is a function of the tip-speed ratio.

Ideally, one would like to have a turbine operating at the maximum value of Cp at all wind speeds.

Therefore, direct connection to a transmission system for a variable speed is not permissible.

Variable-speed wind turbines cannot be directly connected to a transmission system.

One of the drawbacks of this is that the inertia of the transmission system is reduced as more variable-speed wind turbines are put online.

This can result in more significant drops in the transmission system's voltage frequency in the event of the loss of a generating unit.