The use of polyphase systems presents significant advantages over three-phase systems. For example, the total power circulating in the system can be distributed in all phases allowing decreasing currents flowing in each phase for the same total exploited power, which reduces the stress and requirements of power switching devices. Another advantage of polyphase systems is the possibility of operating with one or several phases at fault without having to stop the system. The goal of this paper is to present some advantages, features and applications of polyphase systems as well as to describe an input current control technique employed in the rectifier stage of frequency converters connected to polyphase isolated generators or polyphase distribution grids. This approach can be easily adapted to systems composed by M input phases, as well as three-phase systems. To validate the efficiency of the proposed technique, simulation results for a pentaphase system and a three-phase system, as well as experimental results for three-phase rectifier, are presented.