New method for computing unstable equilibrium points of power systems with induction motors

The computation of the unstable equilibrium point (UEP) is a key step involved in stability region estimation of nonlinear dynamic systems. A new continuation-based method to compute the UEPs of a power system with induction motors is proposed. The mechanical torques of motors are changed to form a parameterized equation set. Then the solution curve of the equation set is traced by the continuation method from the stable equilibrium point to a UEP. The direction of mechanical torque change is varied to get multiple UEPs. The obtained UEPs are mostly type-1. Then fast assessment of induction motor stability is studied by approximating the stable manifolds of the UEPs. The method is tested in several systems and satisfactory results are obtained.