The circuit-level decoupling modulation strategy for three-level neutral-point-clamped (TL-NPC) inverter

In this paper, a circuit-level decoupling modulation strategy is proposed for the three-level (TL) neutral-point-clamped (NPC) inverters. With the proposed modulation scheme, the TL-NPC inverter can be decoupled into two three-level Buck converters in each defined operating section, which makes the controller design much simpler. The decoupling principle including the driving signal synthesis and the neutral point potential variation are analyzed detailed. It is found that switching losses can be reduced by one third and the voltage balance between the dividing dc link capacitors can be achieved without any feedback control. The simulation results show the validity of theoretical analysis.