Improved Load Flow Model for Induction Generators Differentiating Stator and Rotor Circuits

In existing load flow model of induction generators, the magnetizing path is moved to the stator terminal, parallel to the shunt capacitor, yielding the same stator and rotor currents. The power output is equal to the mechanical power input. The stator resistance and the machine loss are ignored. It can not provide the initial condition for the dynamic and control schemes requiring the exact stator and rotor parameters. In this paper, an improved load flow model is proposed for the induction generators. The configuration of the stator and rotor is preserved. Instead of including the inner bus into the admittance matrix, its power constraints are introduced directly to load flow model. So together with the torque balance, there are 3 additional constraints for a wind-farm bus. The numerical results on IEEE RTS test system and a regional power system are provided. The calculation time and iteration steps are quantified to validate the efficiency. The relative error of the simplified model is quantified for the electrical parameters of the induction generators, i.e. the power output, the slip, and the equivalent impedance.