Interconnection Model Update in Real-Time

Abstract

Characteristic of advanced system operation control (SOC) centers is the real-time implementation of security functions which include interconnection modelling and tie-line flow matching. This paper is an outcome of such an effort at The Cleveland Electric Illuminating Company (CEI). It is imperative, from the security point of view, that the effect of the nonobservable system, either external or internal, be properly taken into account. The resulting model should, therefore, reflect the prevailing operating conditions as closely as possible so that the security predictions made would be dependable for real-time operation. One approach is to develop an interconnection model off-line and adjust the boundary injections on-line so that the resulting tie-line flows match the actual MW and MVAR measurements. A possible method of interconnection model update was discussed in Reference 1. This paper presents a new algorithm called Calibration Load Flow (CALF) based on the Fast Decoupled Load Flow (FLF) with necessary modifications to make the boundary injection adjustments. The unique feature of the method is that one CALF solution provides a real-time base case for the use by the Contingency Analysis program. This technique has been in real-time operation for the interconnection model used at CEI’s SOC center for over one year. Generalization of this method has some potential application in State Estimation and also in emergency generation control to correct overloads.