Asymmetric Load Control Method for Individual Pitch of Horizontal Axis Marine Current Turbine

Due to the turbulence of current and effects of shear flow, there exists large asymmetric load on the turbine. Taking a 120 kW turbine as an example, a fuzzy-PID based individual pitch control method for asymmetric load reduction is proposed. The rotating blade coordinate and the fixed hub coordinate are established, and loads acted on blades are transferred to the hub to get tilt moment and yaw moment. Linearized loads being Coleman transformed, the blade root bending moments are transformed into d-q coordinate, so tilt moment and yaw moment on the turbine are decoupled, and the pitch control system is simplified into SISO system. The Fuzzy-PID pitch controller outputs a pitch angle signal in the d-q coordinate, and after Coleman inverse transformation, it is given to the pitch actuator to realize the pitch angle change. System model is established in Matlab/Simulink and the control strategy is simulated. The simulation results show that the proposed load control method can effectively reduce the asymmetric load of the turbine.