Modulation strategy for minimizing commutations and capacitor voltage balancing in symmetrical cascaded multilevel converters

摘要

Multilevel inverters are suitable for power quality applications because the converter can be directly applied in medium voltage distribution systems. If the converter is not required to deliver active power to a load, a power source is not necessary, and the converter can operate only with capacitors on the DC side. This paper presents a strategy for the symmetrical cascade inverter that balances individual DC voltages and minimizes switching losses by eliminating useless commutations. If the converter has redundant modules to increase reliability, the duty-cycle and the losses of each module can be evenly distributed.