A frequency adaptive resonant controller for fixed point digital implementation at high sampling frequency

For applications with high sampling frequency and word length limitation, this paper presents a robust resonant (R) controller. The proposed R controller is derived by transforming the representation of conventional R controller to the polar coordinates. The transformed equations entail trigonometric operations similar to a phase-locked loop (PLL) system which results in another inherent advantage of such systems which is frequency adaptiveness. Feasibility and robustness of the proposed controller is illustrated by comparing its performance with a delta-domain implementation of the conventional R controller, which is conventionally used for high sampling frequency applications with fixed point calculations. The validity of the proposed controller is verified using a laboratory prototype of a single-phase uninterruptable power supply (UPS) system operating at high switching frequency.