The control of unequal power losses distribution in three-level neutral-point-clamped VSC

The three-level neutral-point-clamped (3L-NPC) VSC is used to reduced the harmonics and to achieve high-voltage, high-power capability but the unequal power loss distribution among the semiconductor devices limits the maximum output power and switching frequency. Firstly, this paper is focused on calculating the each semiconductor power losses of SPWM 3L-NPC VSC under different loads, power factors and modulation indices to show the unequal power losses distribution. Secondly, a control strategy used in three-level active neutral-point-clamped (3L-ANPC) VSC is proposed, which is based on the relationship between load current and switching energy, conduction voltage. Some simulation results are shown to validate the analysis of the power losses distribution in 3L-NPC and the loss-balancing control in 3L-ANPC.