Design and analysis of time delay compensator for digital control of single-phase UPS

The time delay caused by the calculation time is unavoidable for the implementation of digital controller and also degrades the control performance. In order to cope with the time delay for the control of single-phase uninterruptible power supply (UPS), this paper proposes the time delay compensator based on the Smith-predictor for both voltage and current controller and also evaluates the usefulness of the compensator by analytic analysis and experimental results. Theoretically the compensator alleviates the effect of time delay for both voltage and current controller, but the compensation for the fast current control is usually sufficient from the practical point of view. The experimental results are presented to show the validity of the proposed design and analysis of the time delay compensator for single-phase UPS.