A study on the single-phase NPC multilevel power converters for active power injection

In medium and high voltage industrial applications multilevel converters are widely employed due to their capability to achieve both, high quality output voltages, as well as input currents. In particular, the neutral point clamped (NPC) converter highlights as a valuable choice. Hence, in this paper, the properties of single-phase NPC converters are studied. The analysis is focused on the active power injection property of a single-phase five level (5L-NPC) converter. The control scheme of this converter is based on a current tracking loop, which includes a proportional resonant (PR) scheme. Furthermore, the switching harmonic content is evaluated and compared to the three-level NPC (3L-NPC) counterpart. Moreover an efficiency analysis for both topologies is performed. Experimental validation in 2 kW single-phase 3L-NPC and 5L-NPC prototypes is provided to assess the performance of the controlled systems.