A novel output LC filter design method of high power three-level NPC converter

For high power three-level Neutral Point Clamped (NPC) converter widely used in medium voltage speed regulation system, which has the characteristics of low switching frequency and complex harmonic distribution of output current waveform, output filter is needed in order to protect AC-side device. Normally, LC filter is used for its good performance. However, the low switching frequency and complex harmonic distribution lead to the design difficulties of the output LC filter. In this paper, on the basis of theoretical analysis, a novel design method of the output LC filter used in three-level NPC converter basing on minimum reactive power is proposed and the parameter design formula is deduced. Simulation results are given to demonstrate the validity of this new method.