In the present work an H∞ -control technique is presented in concise form and applied to the design of discrete optimal multirate-output controllers. The technique used is based on multirate-output controllers having a multirate sampling mechanism with different sampling period in each measured output quantity of the system. It relies mainly, under appropriate conditions, on the reduction 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 may not be available (measurable) for feedback purposes. The discrete linear open-loop system model under consideration (which includes a disturbance term) is systematically derived from the associated continuous 3th-order MIMO linearized open-loop model of a practical power system, having an 160ΜVΑ synchronous generator supplying power to an infinite grid through a step-up transformer and an appropriate transmission line. Through the obtained pertinent simulation results the validity and practical usefulness of this design control technique is assessed.