Design and analysis of a linear quadratic regulator with repetitive controller for AC power supplies

This paper presents a discrete-time controller for uninterruptible power supplies applications. The proposed technique is able to guarantee good stability margins and to reduce errors from eventual or periodical disturbances through the combination of a discrete linear quadratic regulator with a repetitive controller. A Kalman filter is used to observe the plant state variables, considering only the measurement of the output voltage. Stability and performance analysis are carried out through simulation and experimental results, illustrating the efficiency of the proposed scheme for uninterruptible power supplies as well as its suitability for AC power sources applications.