Modified Modulation Strategy for Nine-Level Packed E-Cell Converter

Multilevel inverter topologies are known for their inherent ability to produce high power quality, yet this can only be achieved with proper control and modulation. In this paper, an improved modulation for a nine-level single-phase inverter called Packed E-Cell Converter is proposed. Previously the topology has been found to suffer from adverse commutation effects during the dead times between the switching operations. This is due to the lack of appropriate freewheeling current paths for certain commutation loops. The proposed modulation strategy allows the elimination of the most severe voltage spikes with an amplitude up to DC link voltage at the zero-crossings of the modulated output voltage. The proposed modulation is simulated and the superior performance is demonstrated in comparison to the original pulse-width modulation.