Maximum output power control of wind generation system considering loss minimization of machines

This paper proposes a maximum output control of wind power generation system considering loss minimization of machines. The wind turbine has its own optimum rotational speed which produce the maximum power conversion for the given dimension and wind speed. Even at this optimum speed, the generator cannot produce the maximum output power due to the useless machine loss. In general, the machine loss can be reduced by the decreasing the flux level, resulting in the significant reduction of the core loss. For the vector-controlled induction machine drives, the d-axis current controls the excitation level and the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power. The generator reference speed is adjusted according to the optimum tip-speed ratio. The generated power flows into the utility grid through the back-to-back PWM converter. The grid-side converter controls the dc link voltage and the line-side power factor by the q-axis and the d-axis current control, respectively. Experimental results are shown to verify the validity of the proposed scheme.