A method of maximum power point tracking for a variable speed wind turbine system

The paper presents a hill climbing method of maximum power point tracking control for a variable-speed wind turbine energy conversion system. The method does not require knowledge on the turbine parameters, power coefficient characteristics C-p(lambda) nor air speed and density. The algorithm searches for the generator peak power by varying the angular speed and observing if it results in increment or decrement of the output power. The operation is repeated iteratively in the direction of the power growth until the peak power point dP/d omega=0 on the P(omega) curve is reached. The speed reference calculated by the algorithm is used to modify the generator reference torque. The main difficulty is that P(omega) curve and the peak power point vary with the wind speed so the algorithm may wrongly recognize current position on the power curve. Illustrative Matlab/Simulink simulations carried out for a 40 kW fixed pitch wind turbine data are presented to verify the presented algorithm.