Multivariable loop-shaping control design for stability augmentation and oscillation rejection in wide-area damping using HVDC

•Weighting functions emphasizing feedback provide high gain controllers.•2×2 design using multivariable techniques may yield high performance WADCs.•Basic loop-shaping techniques complicate off-diagonal compensation substantially.•Appropriately designed WADCs reject forced disturbances system-wide. Two high-voltage DC (HVDC) transmission lines known as the Pacific DC Intertie and Intermountain DC line operate in the western North American Power System. These HVDC lines have the potential to be capable actuators in both single-input, single-output (SISO) and multivariable wide-area damping controllers. Implementation of a multivariable design is investigated and compared to two SISO controllers implemented simultaneously using these actuators. Control synthesis is executed using a robust multivariable auto-synthesis methods with modifications based on closed-loop behavior. Sensitivity weighting functions which result in controllers that emphasize feedback at troublesome frequencies while meeting prescribed bandwidth restrictions are applied. Performance criteria include transient responses to large contingency events and disturbance rejection. A forced oscillation is used to perturb the system at an eigenfrequency of interest to determine the effectiveness of each controller in rejecting oscillatory disturbances system-wide.