Improved Synchronized Space Vector PWM Strategy for Three-Level Inverter at Low Modulation Index

Aimed at reducing the switching loss and common-mode voltage amplitude of high-power medium-voltage three-level inverter under low modulation index conditions, an improved synchronous space vector PWM strategy is proposed in this paper. The switching times in each fundamental period are reduced by the re-division of small regions and the full use of the redundant switching state. The sum of switching algebra is introduced as an evaluation index and the switching state with the minimum value of the sum of switching algebra are adopted. Then, the common mode voltage amplitude is reduced. The theoretical analysis and experimental results show that the improved modulation strategy proposed in this paper can effectively reduce the switching loss and common-mode voltage amplitude of the inverter under the condition of the low modulation index. Moreover, the neutral-point voltage ripple is also reduced simultaneously.