Frequency generated during ramp up of rpm

[Asif Khan]

We know what for variable speed wind turbines (utility scale), the rpm increase from cut-in speed to rated speed. How is the frequency maintained at 50 HZ(or 60HZ) by DFIG during this regime? Because the power converter of DFIG is not 100% rated. So can it accommodate all power generated during cut-in to rated speed regime?

[Rob Beckers]

Asif, the two types of alternators/generators I'm aware of for utility scale wind are either induction motors (used as a generator). Those run at a constant speed and therefore frequency. The other type is permanent magnet alternators. Those run over a wide RPM range and do not have a constant frequency. For permanent magnet alternators the output is rectified, and then converted to grid Voltage and frequency via an inverter.

-RoB-