Think of it more that the battery sits on the side of the DC bus. Double conversation UPS are generally the highest end (rectified AC > DC > inverted AC) becau

Think of it more that the battery sits on the side of the DC bus. Double conversation UPS are generally the highest end (rectified AC > DC > inverted AC) because there's no switching time between the inverter taking power from the DC bus being supplied by the rectifier or the battery. It is always inverting. The power quality never changes too because of the always inverting setup.