A center-of-inertia transform applied to transient responses of nonlinear power systems

The authors describe a rotational transform that has been developed to reduce a large electrical power system into an equivalent system of reduced size. Any arbitrary group of nodes can be eliminated from a circuit, with each group being replaced by a single equivalent node. The significance of the transform is found in the usefulness of the equivalent nodes. The choice of the voltage phasor at each equivalent is an arbitrary one, and this choice is judiciously made to preserve nonlinear properties of the reduced regions of the circuit. The equivalent node is chosen to represent the center of inertia (COI) of the reduced region. The generators in the region are also reduced into a COI equivalent generator. The COI equivalent node and the COI equivalent generator replace each region´s nodes and generators during simulation of large transient disturbances. The application of the transform to a 17-generator power system is described