Parallel connections of pulsewidth modulated NPC converters using current sharing reactors

A technique of parallel connection of power devices by using current sharing reactors for NPC-PWM inverters is reported in this paper, in which a certain modulation technique is discussed. This proposed modulation technique can not only increase current capacity and the output voltage level but also decrease the output harmonic contents. The output voltage waveforms of the proposed inverter have certain voltage levels during their half cycles, thus it is anticipated that it will be difficult to analyze the output waveforms. For such waveforms, a frequency analysis approach is described, whose results are verified by experiments.