Coupling analysis & preliminary MIMO control design for wide-area damping using HVDC

The high voltage direct current (HVDC) transmission line known as the Pacific DC Intertie (PDCI) has shown to be a potentially important actuator for retaining small-signal stability of the western North American Power System (wNAPS) for large contingencies. However, certain wNAPS damped oscillatory line flows and generator rotor speeds may be adversely affected by PDCI modulation subject to particular system configurations. Thus, a secondary, similar actuator is investigated to improve these characteristics, and potentially provide additional damping for burdensome contingencies. The Intermountain HVDC (IMDC) line provides less rated capacity than the PDCI, but has the ability to impact troublesome oscillatory modes insufficiently responsive to the PDCI, and is chosen as the secondary actuator for this reason. Inspection of Gershgorin bands of the loop transmission transfer matrix suggests coupling between the PDCI and IMDC channels, and thus care must be taken when introducing multi-input, multi-output (MIMO) feedback. Initial results for the IMDC closed-loop system are provided, as well as a MIMO controller employing a gain-adjusted compensator developed for the SISO PDCI approach.