Using MIMO system identification for modal analysis and global stabilization of large power systems

This paper applies a state-space system identification technique to first derive a large-scale small-signal model of the Hydro-Quebec power system. This linearized MIMO model is then used to design global stabilizing controllers which achieve supplementary modulation of voltage regulators, based on wide-area phasor measurements. Following a detailed SVD and modal analysis of the system dynamic interactions, five control sites consisting of four generators and one synchronous condenser were paired with remote phasor measuring units (PMU), geographically spread over nine electrically coherent areas. Four dominant natural loops were identified, each associated with a significant open-loop natural mode at 0.06, 0.43, 0.7 and 0.95 Hz respectively. These two-loop PSSs have a speed sensitive local loop operating in the usual way, and a wide-area measurement based global loop which involves a single differential frequency signal between two suitably selected areas. The tuning and coordination technique for these complex multiple controllers is described. Their impacts on the system is assessed using small-signal analysis