ABSTRACT
WRIGs provide constant or controlled voltage Vs and frequency f1 power through the stator, while the rotor is supplied through a static power converter at variable voltage Vr and frequency f2, the rotor circuit may absorb or deliver electric power. As the number of poles of both stator and rotor windings is the same at steady state. Therefore, according to the frequency theorem, the speed ωm is as follows:
w w w wm m R p= ± = ×1 2 1; W (1.1)
where p1 is the number of pole pairs ΩR is the mechanical rotor speed
The positive (+) sign in Equation 1.1 indicates that the phase sequence in the rotor is the same as in the stator and ωm < ω1, that is, subsynchronous operation. The negative (–) sign in Equation 1.1 corresponds to an inverse phase sequence in the rotor when ωm > ω1, that is, supersynchronous operation.
