A Hybrid 2/3 Level Converter With Minimum Switch Count

Multilevel topologies have emerged as a viable technique for medium and high voltage inverters but in the low voltage range they have failed to attract much interest due to their increased cost associated with the additional components and complicated control. This paper proposes a new hybrid converter that combines features from both two- and three-level converters with a reduced number of extra semiconductors. It is shown that for a very wide modulation index this converter can switch the maximum and the minimum phase voltages as a three-level converter while the third phase voltage is switched as a two-level converter. Only for a very narrow band in the modulation index range this topology behaves as a two-level converter. The proposed approach is implemented on a 16-bit fixed point DSP (ADSP 21992) and tested on a three-phase 20 kW IGBT-based PWM inverter