A digital control of a single-phase UPS inverter for robust AC-voltage tracking

This paper presents a digital controller for a single phase UPS inverter under two main considerations: (i) the overall system shall keep very low AC-voltage tracking error as well as no phase delay over different load conditions, and (ii) the digital controller shall be employed at a fixed sampling time. It is shown that the first requirement can be achieved by the proposed controller using the error-state approach. Due to the fixed sampling rate, the digital-control design using the emulation method may place a constraint on the speed of time response. We propose that such a problem can be dealt with by the so-called characteristic ratio assignment (Y.C. Kim et al., 2003).