Experimental comparison of DPC and VOC control of a three-level NPC grid connected converter

This paper presents the principle of Direct Power Control (DPC) and Voltage Oriented Control (VOC) for a three-level Neutral point clamped (NPC) grid connected inverter. Considering balancing of the neutral point, a switching table with neutral point voltage control is derived for DPC. The two control algorithms are successfully implemented in a test bench, and an experimental comparison is conducted including dynamic performance and harmonics analysis in steady state. The equivalent switching frequency concept is introduced for DPC to guarantee a switching frequency comparable to VOC.