Online estimation of power system actual frequency response characteristic

In power systems, the system frequency as well as the real power interchange between balancing authority areas must be maintained at the nominal value and the scheduled values, respectively. To this end, the area control error (ACE), which incorporates information about potential mismatches in the values of these two quantities, is calculated and fed to the automatic generation control (AGC) system, the goal of which is to drive the ACE to zero. The purpose of this paper is to present a systematic method to estimate, in real time, the actual frequency response characteristic (AFRC) and to use it in the ACE calculation. In such a case, the AGC system only reacts to internal disturbances and not to external ones. To do so, we use a simplified model to represent power system dynamics, and a sliding exponentially weighted window blockwise least squares algorithm for the estimation of the AFRC. The proposed methodology is illustrated in the 9-bus 3-machine WECC system model, and in a 140-bus 48-machine system.