Multi-level inverters, especially dual inverters

Abstract

A multi-level inverter 103, in particular a dual inverter, has a first level for generating at least one first AC voltage and a second level for generating at least one second AC voltage with finer steps than the first AC voltage. The inverter 103 has a current-controlling zero-point connection 151 on a capacitive voltage divider circuit 149 and is equipped per phase with two semiconductor switches T115, T115I, T115I, T116, T116I, T116II for a first assembly for generating the first AC voltage and with at least four semiconductor switches T101, T101I, T101II, T102, T102I, T102II, T103, T103I, T103II, T104, T104I, T104II for a second assembly for generating the second AC voltage. Due to the design of the semiconductor switch, the four semiconductor switches of the second assembly have a lower voltage withstand rating than the two semiconductor switches of the first assembly.An inverter control 131 enables a switching of an operating state I, II between the first AC voltage and the second AC voltage in response to a load current I1, I2, I3 on ​​at least one of the phases 115, 115I, 115II.