One general linear power equalization scheme for asymmetric cascaded H-bridge multilevel inverters

In order to solve the problem of unbalanced power distribution between cascade units due to the different DC-side power supply voltages of each cascaded unit of asymmetric cascaded H-bridge multilevel inverter, a general linear power equalization modulation scheme was proposed. By constraining the conduction angle of the high-voltage unit and the modulation strategy of longitudinal cyclic reconstruction of the carrier of the low-voltage unit, in the power equalization modulation scheme the effect was realized that the inverter can maintain the output power balance of the linkage units at all levels under the full modulation system when the power supply voltage on the DC side of each cascade unit is different. And when the number of cascading elements is increased in the topology, the modulation strategy also shows excellent versatility. At the same time, the carrier reconstruction of the low-voltage unit in this scheme can also make the switch loss of each low-voltage unit consistent, so that the switch tube of each H-bridge has a closer temperature rise, which is conducive to the inverter to choose the appropriate radiator. Finally, effectiveness of the scheme was proved by simulation and experiment. © 2023 Editorial Department of Electric Machines and Control. All rights reserved.