IMPLEMENTATION OF A FAST MATRIX INVERSION METHOD IN THE ELECTRODYNAMIC SIMULATION PROGRAM

Abstract

This paper describes the imple!llentation of a fast matrix inversion algorithm that can be used efficiently in the electric network analysis. The ElectroDynamic Simulation (EDS) is an IBM PC based computer program for studying short and middle term dynamics of the electric power system. The electric network is modelled by quasi-stationary representation. EDS has an interactive menu system. The user can change the operating conditions like sending telecommands from a control center-or initiate simulation of disturbances. Simulation of some events requires changing the network matrices. The admittance matrix Y can be modified directly while the impedance matrix Z is updated by inverting the new Y. The conventional inversion is very time consuming and freezes the simulation for unacceptably long intervals. A new, faster method has been developed which takes into account that the change in the matrices due to the events is small and well-defined. In these cases the complete inversion is not needed, the impedance matrix can be updated directly, by the aid of the Sherman-IvIorrison theorem. The new method has been implemented in recent EDS versions and performs significantly faster than the conventional inversion.