A new hybrid power filter using multilevel inverters

This paper proposes a transformerless power conversion system which consists of a three-phase diode rectifier and a shunt hybrid filter. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multilevel inverter. Compared with conventional active filters, transformers are not used and multilevel inverters are used. The LC filter works as not only a harmonic filter tuned at the 7th harmonic frequency but also a switching-ripple filter. The rating of the switching devices for the active filter decreases with use of a NPC type multilevel inverter. The simulation results confirm the validity of the system