US Patent 9976539 Control method and system for wind turbine

A control method and a control system for a wind turbine are disclosed. The control method comprises measuring wind turbine blade pitch angles; obtaining a wind turbine rotor acceleration value; determining whether a blade pitch runaway fault condition is occurring; and during the blade pitch runaway fault condition, adjusting a pitch angle command based at least in part on the rotor acceleration value, a pitch angle of at least one faulted blade and a pitch angle of a healthy blade; and controlling wind turbine blades based at least in part on the adjusted pitch angle command.