Patent ID: 7692321

Claim:
A method of operating a wind turbine comprising a generator that provides variable voltage at variable frequency and has a stator and a rotor, a turbine assembly including at least one blade for rotating the rotor of the generator, and a power converter that interfaces the generator to a supply network operating at nominally fixed voltage and nominally fixed frequency, the power converter including: a first active rectifier/inverter electrically connected to the stator of the generator and including a plurality of semiconductor power switching devices; a second active rectifier/inverter including a plurality of semiconductor power switching devices; a dc link connected between the first active rectifier/inverter and the second active rectifier/inverter; a filter connected between the second active rectifier/inverter and the supply network, the filter including network terminals; a first controller for the first active rectifier/inverter; and a second controller for the second active rectifier/inverter; wherein in response to a change in wind speed the method comprises the steps of: controlling the second active rectifier/inverter to change the level of power exported out of the dc link such that the dc link voltage changes from a desired level; and controlling the first active rectifier/inverter to import sufficient current into the dc link through the generator bridge from the generator to restore the dc link voltage to the desired level.