Detection of possible voltage collapse buses in stressed power systems based on information from multiple solutions in load flow calculations

Abstract

Conventionally, most voltage stability indices, including the voltage instability proximity index (VIPI), have been formulated for the overall system. Voltage instability phenomena, however, can occur locally and then cause cascade collapses throughout the system. Therefore, it is of some importance to establish an index that can locate the possible voltage collapse buses in power systems efficiently. In this paper, we describe the local properties of the information of multiple solutions in load flow calculation and their use in voltage instability assessment. It should be noted that this kind of information is formatted in the voltage space rather than in the specified value space. Therefore, it is difficult to obtain information in the specified value space, and the qualitative property in a simple one-machine one-load (two-bus) power system may not be generalized for multimachine multiload power systems. We present our investigation by considering several model systems and quantitatively comparing them with the two-bus power system. Taking advantage of the power flow formulation, it can be concluded that the localization of the voltage variation vector that indicates the initial direction of the voltage collapse will provide exact information for identifying problem buses in the system. The nose curves of problem buses can be obtained for monitoring purposes at the same time. With the application of these results and VIPI, an emergency countermeasure is suggested for monitoring and delaying possible voltage collapse in stressed power systems. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(1): 45–54, 1997