Design and performance comparisons of two multi-drive systems with unity power factor

From economical aspects, the multi-drive systems are a promising application area for the converters, where the cost and size of the converters are shared by multiple inverter-motors. Given terminal constraints of unity power factor in grid line and independent multiple motor controls in output ports, two multi-drive topologies are possible: one with single PWM-VSR feeding inverters through the common dc bus, and the other using a diode rectifier and an active power filter with its own load. Despite several publications for two systems, the features and advantages of the two systems have not been clearly explained. This paper, in detail, presents the theoretical analyses and systematic comparisons of the two multi-drive topologies, from converter kVA ratings, dc-link voltage requirements, switch ratings, semiconductor losses and reactive component designs point of views.