부산대학교 도서관

This paper describes a combination of robust control techniques applied to an offset-free robust tracking control of a three-phase dc–ac inverter with an output $LC$ filter for application to uninterruptible power supply (UPS). The control law, which employs state feedback and integration of the tracking error, is described in a synchronous $dq$ frame and is implemented using a space vector modulation technique. The controller is designed by a linear matrix inequality (LMI)-based optimization so that the convergence rate to the steady state is maximized in the presence of the uncertainties in the $LC$ filter. These uncertainties are expressed as possible ranges of the capacitor and inductor values. In the absence of uncertainties, the designed controller will become a deadbeat controller, whereas in the presence of uncertainties, it provides the shortest possible settling time. Thus, the proposed design method provides a systematic tool to combine the robustness to model uncertainties with the deadbeat control. The use of a one-step-ahead predictor is considered to compensate for the computation delay, and an LMI-based method to obtain an optimal gain of the state estimator is also proposed. The efficacy of the proposed approach was experimentally confirmed on a three-phase 10-kVA prototype UPS system.