Abstract:

This paper proposes a mathematical model for analyzing the transient voltage stability of power systems whose load is presented by a three-order induction motor paralleling constant impedance model, and gives a practical scheme to choose the initial point when the Newton method is used to compute the control＇ling unstable equilibrium point （CUEP） corresponding to the instability mode of system voltage. In this scheme, the controlling load bus of a given fault is identified, the Thevenin equivalent circuit is used to represent the rest of. the system in the state of post-disturbance stable equilibrium point, the steady equivalent circuit is adopted to describe the induction motor in a composite load, and a point near the CUEP is obtained based on the torque characteristics of the induction motor and is then taken as the initial iteration point. Moreover, a method to obtain the initial iteration point closer to the CUEP is proposed, by which the CUEP can be computed more reliably. Computation results of the IEEE 9-bus and the 39-bus systems show that the proposed method is reliable and effective.

Key words: power system, transient voltage, voltage stability, controlling unstable equilibrium point, induction motor, Newton method