Observer based Primary Control Structure without Wind Speed Measurement for Variable Speed Wind Turbines

When increasing the number of renewable energy sources coupled to the grid, the number of conventional power plants is decreased. To prevent higher frequency gradients and nadirs in the future grid, wind turbines (WT) have to provide inertial and primary power. For the last one a WT has to keep power reserves by overspeeding the drive train or pitching the blades. To avoid unnecessary losses in this operation point, the maximal available power must be determined accurately. An opportunity is to use the current wind speed value, whereby the measurement at the roof of the nacelle is usually not precise enough. Therefore in this paper a novel method to reconstruct the wind speed value by using a disturbance observer and an iterative algorithm is shown. Its robustness to measurement delays and model uncertainties is investigated. This wind reconstruction is included in a total control structure with primary and inertia controller for the grid support.