Induction motor model for the study of transient stability in both balanced and unbalanced multi-machine networks

An induction motor model is presented that represents the motor as a constant equivalent impedance in series with a variable voltage source that is a function of slip. The model is based on that presented by M.A. Lahoud et al. (see Electr. Power Syst. Res., vol.7, no.1, p.53-63, 1984) for balanced systems using the full nonlinear two-axis equations, and it is adapted for use in unbalanced networks with phase-frame network representation. This model overcomes the need to update the [Y_bus ] matrix at every integration step and significantly reduces the computer execution time. In addition, the model takes into account the time rate of change of rotor flux linkages. Results show a reduction in computation time of between 31% for a 10-bus system and 73% for a 15-bus system