Introduction of a new index for evaluating the effect of wind dynamics on the power of variable speed wind turbines

Abstract

The instantaneous wind speed variations are ignored in the wind turbine power curves. Hence, the output power of the wind turbines becomes a function of only the average wind speed. In the variable-speed wind turbines, the output power is a function of wind speed as well as the wind dynamics because in order to extract the maximum amount of electrical energy, the control system in these turbines will adjust the rotor speed and blades' pitch angle according to the instantaneous wind speed. Since the wind dynamics is not taken into account in the power curve, the power generated by the controllers is overlooked and therefore the turbine output power is not represented accurately by the power curve. In this paper, a new method is proposed using a new index called wind turbine controllability factor in order to make it possible to calculate precisely the output power of wind turbines based on the wind dynamics. In this method, the energy pattern factor is used as an indicator of the amount of instantaneous wind speed variations and power curve is modified corresponding to the values of the energy pattern factor.