New voltage sensorless approach for maximum constant power tracking of WECS based on a cascaded DFIG

The paper proposes a new control strategy of a grid connected variable speed wind turbine (WT), based on a cascaded doubly fed induction generator (CDFIG). The generating plant is carried to extract the maximum power relative to the predicted mean wind speed, thus eliminating the power fluctuations associated to high frequencies component. Moreover the system attempts to adjust the power factor of the generated power according to grid code requirements. This can be achieved by means of a bidirectional back to back PWM converter. A virtual flux oriented vector control is applied for the decoupled regulation of active and reactive powers, leading to grid voltage sensorless operation. The suggested method ensures high efficiency and enhances the energy quality by feeding constant power into the grid, regardless wind fluctuations.