A Sliding Mode Disturbance Observer-Based Approach for Grid Connected Wind Energy Systems

An observer based-sliding mode approach is proposed in this paper for a (DFIG)-based wind energy system directly connected to the grid. The design aims at maintaining the current fluctuations resulting from grid faults within acceptable ranges and ensuring robustness to system uncertainties. An integral terminal sliding mode disturbance observer (ITSMDO) was designed first to estimate system uncertainties. Then an ITSMC approach was derived to steer the rotor currents to their desired values. A fuzzy logic approach was considered to auto-tune the controller gains. System stability and finite time convergence were established using the Lyapunov theory. The effectiveness of the proposed approach was validated under severe grid faults and in the presence of parameter variations.