Patent ID: 9683551
Date: 2017-06-20
CPC Classifications: F03D,Y02E

Claim:
1. A method of operating a wind turbine at below rated power, comprising: sensing stall conditions using one or more stall condition sensors on wind turbine rotor blades; determining a stall margin based on the sensed stall conditions, wherein the determination of the stall margin comprises determining a stall event count using a stall event counter based on outputs from the one or more stall condition sensors, the stall margin being determined from the stall event count, wherein the stall event count is dependent on the time between detected stall conditions output by the at least one stall condition sensor; selecting a curve of tip to wind speed ratio against blade pitch angle according to the determined stall margin; and varying the blade pitch angle of at least one of the wind turbine blades in accordance with the selected curve.