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In this paper, a harmonic elimination of grid and stator currents of doubly fed induction generator (DFIG) in case of grid fault without line voltage sensors is proposed . This can be achieved by compensating power based on virtual flux voltage sensorless technique. Direct power control with space vector modulation (DPC-SVM) is used to control both grid-side (GSC)and rotor-side converters (RSC). To achieve the control objective, compensated active and reactive powers are calculated based on virtual flux technique with balanced and harmonic free current as a control target. A theoretical analysis of active and reactive powers under unbalanced voltage source is clearly demonstrated and the effect of grid fault on the performance of DFIG is profoundly discussed. Simulation results verified the effectiveness of the modified control strategy.

The present work focuses on modelling of sensor-less Direct Power Control based on Virtual Flux (DPC-VF) for three levels AC/DC converter for wind power system in the case of grid abnormality. As a fact, when an unbalance appears in the grid, the negative sequence affects the quality of Dc-link at the output of the converter and makes deterioration in grid current. In order to improve the behaviour of the converter under grid abnormality, the grid currents and Virtual Flux are decomposed in separating positive and negative sequence using double second order generalized integrator Direct Power Control (DSOGIFLL) then compensating active and reactive powers are calculated according to the control objective and injected in the referencing one. The proposed controller ensures voltage balance in DC-link capacitors by using redundant vectors in a space vector modulation block without needing additional components. In order to test the effectiveness of the control scheme, a numerical simulation is performed using the Matlab-Simulink software. The results prove the validity of the proposed control algorithm.