Abstract: Aiming at the disadvantage of the unbalanced output power of four units of Cascaded H-bridge (CHB) nine-level inverter under traditional carrier amplitude shift modulation, an improved power equalization strategy is proposed based on carrier reconstruction in this paper, which can effectively reduce the number of carriers. Through the secondary power equalization process, the output power equalization among the four units of the cascaded H-bridge nine-level inverter is realized. First, the power balance between the four units is realized by the carrier reconstruction method, and then the actual drive signal of the switch tube is obtained by performing a 1/4 cycle logic interchange of the drive signal of the switch tube, to realize the power balance of the whole unit under full modulation Simulation and experimental results show that this strategy can achieve a power balance of four cascaded H-bridge units based on effectively reducing the number of carriers.

Key words: multilevel Inverter, carrier reconstruction, pulse swap, power equalization, modulation optimization