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Extra info for Analysis, modeling and control of doubly-fed induction generators for wind turbines

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In addition, the variables and the parameters in Fig. 5 will also be explained. 1 Machine Model Due to its simplicity for deriving control laws for the DFIG, the Γ representation of the IG model will be used. Note, that from a dynamic point of view, the rotor and the stator leakage inductance have the same effect. Therefore, it is possible to use a different representation of the Park model in which the leakage inductance is placed in the rotor circuit, the so-called Γ representation of the induction machine .

1 Introduction In this section, different aspects of designing and implementing control systems for doublyfed induction generators (DFIGs) are treated. 1 Space Vectors The idea behind space vectors is to describe the induction machine with two phases instead of three. Space vectors were originally invented to describe the spatial flux of an ac machine . A three-phase stator winding, which is supplied with three-phase currents, forms a rotating flux in the air gap. The same rotating flux could also be formed with only two phases, as seen in Fig.

Therefore, addition of an inner feed-back loop, see Fig. 3, can improve the disturbance rejection. 18) is changed to GEi (p) = p G(p) p 1 = . 20) GEi (p) = K (p + α)2 38 iref + F (p) v + v + E(p) + G(p) i − − R Fig. 3. ” where K is a constant. This means that a load disturbance E is damped with the same time constant as the control loop. ” “Active damping” has been used for the cage-bar induction machine to damp disturbances, such as varying back EMF [18, 41]. 21) where i is the state (current), v is the input signal (applied voltage), and e is a load disturbance (back emf).