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This paper provides a control system with an internal model principle based controller combined with a plant state feedback controller suitable to track sinusoidal references and to reject disturbances affecting the plant. The control design can be carried out by means of conventional and advanced state feedback techniques. In order to illustrate the applicability of the control system, three techniques are used here to control the voltage of an UPS system: the linear quadratic regulator, the pole placement and the H¿¿ control. Fast transient and low distortion of the output voltage for a typical nonlinear load are obtained for the closed-loop system with the proposed controllers, indicating good performance without using repetitive controllers or multiple resonant controllers to cope with cyclic loads, and also without using models for the load disturbance or more complex control algorithms.