Design and analysis of an LC trap/LCR output filter for a single-phase NPC three-level inverter

This article presents a filter design approach and the efficiency analysis of a single-phase Neutral Point Clamped (NPC) three-level inverter with a combined LC trap and LCR filter system. The multilevel inverter system using NPC type inverter is suitable for high-power application. The single-phase NPC three-level inverter operates normally at low switching frequency. The proposed LC trap filter is comprised of a conventional LCR output filter. By adding an LC trap filter, the need for a low-value damping resistor and low LC cut-off frequency is eliminated. Use of the high-value damping resistor increases the efficiency of the output filter system. The controller used is DSP (TMS320C31). The effectiveness of the proposed system is verified by SPICE simulation and experimental results.