Line interactive UPS with the DSP based active power filter

A digital signal processor (DSP) based active power filter to compensate load harmonic current for a low cost, line interactive UPS is presented in this paper. The UPS full bridge switch mode power converter is used as an active power filter to compensate load harmonic current when electric utility line voltage is within the UPS´s input voltage range. As the effectiveness of an active power filter depends on the quality of harmonic reference waveform, a DSP is used to realize a high quality, low distortion notch filter, resulting in a good performance of active power filter. Both computer simulation and experimental implementation show a excellent result of the system