Patent ID: 8759994

Claim:
A method of controlling a wind turbine generator, the wind turbine generator converting mechanical energy to electrical energy, the method comprising: determining an electromagnetic power reference representing the electromagnetic power generated by the wind turbine generator, wherein the electromagnetic power reference is determined based on a desired output of the wind turbine generator, controlling the electrical power generated by the wind turbine generator using a control signal, wherein the control signal is derived from the electromagnetic power reference and is modified in dependence on an inverse power function of the wind turbine generator such that non-linearity of the wind turbine generator is compensated; determining a first field power stator flux or stator current reference based on a first criterion and the electromagnetic power reference; determining a second field power stator flux or stator current reference based on a second criterion and the electromagnetic power reference; selecting one of the first field power stator flux or current reference and the second field power stator flux or stator current reference; and controlling a stator flux or current of the wind turbine generator based on the selected field power stator flux or current reference; wherein determining the second field power stator flux or stator current reference comprises: determining a first preliminary field power stator flux or stator current reference based on the electromagnetic power reference obtained at a partial field weakening speed (speed at which field weakening operation starts) of the wind turbine generator; determining a second preliminary field power stator flux or stator current reference based on the electromagnetic power reference obtained at a maximum speed of the wind turbine generator; and determining a weighted average of the first preliminary field power stator flux or stator current reference and the second preliminary field power stator flux or stator current reference in order to obtain the second field power stator flux or stator current reference.