Five-level nested inverter with neutral point connection

Multilevel inverter technology has been a well-established concept especially in medium voltage drives. This paper presents a new five-level nested inverter topology, that has a neutral point connection and two flying capacitors per phase. Compared to five-level topologies presented previously, the proposed topology has the same switch count, but fewer of the switching devices are rated at half of the DC link voltage. The operation of the topology is demonstrated with system level and thermal loss simulations. The simulations show that the topology produces an ideal five-level pulse width modulated output voltage without any unnecessary commutations. The loss simulations show the trending and the distribution of power losses for the phase-leg semiconductor devices as a function of output frequency with a linear u/f curve.