Abstract
The size and complexity of power systems increases greatly and the operating points of power system are liable to be close to the limitation of capacity of equipments in power systems. Small signal instability may occur under these situations. The eigen values obtained from a set of the state equations representing dynamics of power systems are useful for stability check.
The authors developed two programs computing eigen values: one is based on the S-method [1] and the other Iterative-inverse approach[2, 3] (IIA method). In order to reduce computation time, elements are stored in Linked-list form in which the structure of the list is formed so that the fill-in data can be stored with less computation time and the selection of elements used for computation can be performed efficiently. In order to check stability when the operating condition is changed gradually, the computations of eigen values under these changed conditions will be required. Several number of eigen values near the instable states can be calculated by using the program based on S-method. Then these values are used for initial values and new eigen values under the changed operating condition are obtained by using the program based on IIA method.
