Analytical method to calculate transient responses of induction motor load

An analytical method to calculate the transient responses of induction motors (IMs) following power system symmetrical and asymmetrical voltage sags is developed based on circuit and machine analysis theory. The derived calculation models and algorithm are composed of a series of algebraic formulae. The slip, transient voltage, stator current, and electrical power of the perturbed IM can be computed. Compared with electromagnetic transient simulation results using the PSCAD/EMTDC software package, the accuracy of the proposed method is proved. Applying the proposed method to calculate the transient responses of power system IM composite load shows that the approach not only has the advantage in computing speed but also improve the accuracy of power system electromechanical transient time domain simulations under unbalanced faults caused voltage sag.