Nonlinear Integral Backstepping Control of DFIGs-based Wind Farm under Unbalanced Electrical Grid Voltage

This paper proposes a modified and efficient control strategy for controlling a doubly fed induction generator (DFIG) based wind farm (WF) connected to an unbalanced electrical grid voltage. This strategy has two loops, the first is main and the second is auxiliary. The main loops control the positive sequence currents of the rotor and the grid side converter (GSC), while the auxiliary loops control the negative sequence currents. In this work, the positive and negative rotor current loops of each DFIG were controlled using a nonlinear integral backstepping control (IBSC) algorithm, while the positive and negative sequence current loops of each GSC were controlled using a proportional-integral (PI) controller. This study was validated by comparing the proposed strategy with the single-loop strategy through simulation in the Matlab/Simulink environment. The obtained results show that the proposed strategy allows to reduction of the oscillations in the active and reactive power generated by the WF, which reduces the oscillations in the DC bus voltage and reduces the total harmonic distortion.