Transfer function lowering device and power system modeling device

摘要

A power system modeling system in which a frequency response of admittance of a power system viewed from a specified joint point is inputted and an estimated transfer function Y(s) in an n-order mode represented by such a rational function form that minimizes the square error for that frequency response is calculated (step S11), and the order of the n-order estimated transfer function Y(s) thus calculated is further lowered (step S12). The lowering of order of a transfer function at step S12, is done such that a mode influence index Ini is calculated in the following expression, only a higher-order mode is selected out of it and then a transfer function including only the selected mode is generated. Ini=||1/Re(lambdai)||x||Ri||, where Ri is the residue of i-th mode, and Re(lambdai) is the real part of an eigenvalue.