A robust coordinated control of the doubly-fed induction machine for wind turbines: a state-space based approach

A novel control methodology is proposed for the doubly-fed induction machines used for variable-speed windpower plants. The machine speed and its reactive power are controlled in a coordinated manner using a linear state-space representation. The regulator is synthesized for the machine model linked to an infinite bus through an external equivalent reactance. The grid to which the machine is connected is thus taken into account in the control model by the infinite bus voltage and the external reactance values. The short-term voltage stability is improved on the wind farm side of the grid connection point especially in case of failure events in the external power system. The controller gains can be easily tuned in order to achieve a performance/robustness trade-off. This regulator is tested in comparison with the vector control approach by dynamic simulations using EUROSTAG software.