Harmonic analysis and output filter design of NPC multi-level inverters

In this paper, LC output filters are designed for a single phase multi-level inverter and harmonic analysis with respect to modulation index is performed. In general, since the multi-level inverter is adapted to high power application and operated with low switching frequency, it has a large amount of output harmonics. Thus it needs an output filter to reduce output harmonic components. An output filter of the NPC multi-level inverter system is designed and its characteristics are analyzed with simulation. The controller using DSP (TMS320C31) and the NPC multi-level inverter are built. Then the implemented system is verified through experiment