Keywords: wind power, variable structure control, nonlinear system, modelling, simulation, robust control, wind turbines, wind energy, vector control theory, sliding mode control, SMC, stability analysis, disturbances, parameter uncertainty
Robust vector control strategy for variable speed wind turbines
The efficiency of the wind power conversions systems can be greatly improved using an appropriate control algorithm. In this work, a robust control for variable speed wind power generation that incorporates a doubly feed induction generator is described. The electrical systems incorporate a wound rotor induction machine with back–to–back three phase power converter bridges between its rotor and the grid. In the presented design, it is applied the so called vector control theory. The proposed control scheme uses stator flux–oriented vector control for the rotor–side converter bridge control and grid voltage vector control for the grid–side converter bridge control. The proposed robust control law is based on a sliding mode control theory that, as it is well–known, presents a good performance under system uncertainties. The stability analysis of the proposed controller under disturbances and parameter uncertainties is provided using the Lyapunov stability theory. Finally, simulated results show, on the one hand, that the proposed controller provides high–performance dynamic characteristics, and on the other hand, that this scheme is robust with respect to the uncertainties that usually appear in the real systems.