An Improved Neutral-Point Voltage Control Method for Ten-Switch Three-Phase Three-Level Inverter Using Virtual Space Vector Modulation

This paper briefly reviews the neutral-point voltage control (NPVC) method for ten-switch three-phase three-level inverter (TP-TLI). Then, an improved NPVC method based on virtual space vector modulation, named as (IVSVM) is proposed for ten-switch TP-TLI. By analyzing vector synthesis principle in each region, a new control degree is explored to improve the NPVC capability. It preferentially distributes the duty ratio to the virtual small vector which can provide more average NP current in a switching cycle. Analysis results show that the available NP current provided by the proposed IVSVM is about 2.75 times at most than that provided by traditional VSVM. Besides, by adjusting the duty ratios of redundant small vectors, an active NPVC method is presented to eliminate the dc offset and ac ripples in NPV. Experimental results are carried out to verify the effectiveness and advantages of the proposed IVSVM.