Generation Rate Constraints Physical Identification and Modeling in AGC of Multi-Area Power Systems

Abstract

In this article, generation rate constraints (GRCs) of power generating units are modeled accurately in transfer function modeling of automatic generation control (AGC) system. Typically, GRCs are used to restrict the rate of change of plant generating unit’s power output in order to mimic the realistic dynamic behavior of AGC system. Though, this practice of limiting plant generating unit’s response using GRCs was inferred from the IEEE committee report published in 1967. IEEE working group named as “power plant response” carried out investigations to study the maximum allowable rates of load changes for thermal, hydro and gas based power generating units. In this investigation, it was clearly stated that study is not intended to analyze the ability of plant generating units to cope with changing power system load. However, this study was misinterpreted and researchers started to use GRCs to restrict the rate of change of generating unit’s power outputs. This article rectifies the aforementioned anomaly and presents the accurate placement of GRCs in AGC transfer function model. The study is validated with the dynamic responses of actual 500 MW thermal generating unit and from the tripping tests performed by IEEE working groups in 2001.