SELECTIVE HARMONIC ELIMINATION PWM STRATEGY FOR THREE-LEVEL NPC INVERTERS UNDER FAULT-TOLERANT OPERATION

To improve the reliability in high voltage and high power applications, the fault-tolerant control of three-level neutral-point-clamped (3L-NPC) inverter has been deeply studied. In this paper, the eight-switch three-phase inverter (ESTPI) is selected as the fault-tolerant topology of 3L-NPC inverter, and the synchronous modulation strategy of ESTPI is discussed for some particular application situation working at low switching frequency. The harmonic distribution of the ESTPI is analyzed firstly under synchronous modulation. To eliminate the specific low-order harmonics including the frequency tripling harmonics, the selective harmonic elimination pulse-width modulation (SHEP WM) based synchronous modulation strategy for the ESTPI is proposed in this paper, which can ensure a good performance of output voltage for 3L-NPC inverter under fault-tolerant operation. The effectiveness and feasibility of the proposed method are verified by the experimental results.