Excitation controller design using H^∞ -control based on multirate output applied to a hydro-unit-system

In this paper an H^∞ -control technique is presented and applied to the design of optimal multirate-output controllers. The technique is based on multirate-output controllers (MROCs) having a multirate sampling mechanism with different sampling period in each measured output of the system. It relies mainly on the reduction, under appropriate conditions, of the original H^∞ -disturbance attenuation problem to an associated discrete H^∞ -control problem for which a fictitious static state feedback controller is to be designed, even though some state variables are not available (measurable) for feedback purposes. The proposed H^∞-control technique is applied to the discrete linear open-loop system model which represents a linear speed governor (mechanical-hydraulic type), a hydroturbine ideal version for rated speed, head etc. and a rotational dynamic part with inertia H.