Mobile QR Code QR CODE : The Korean Institute of Power Electronics
Title Analysis and Control of Neutral Point Current Deviation in Grid Tied 3-Level NPC Converter under Various Grid Unbalanced Conditions
Authors Jaehoon Choi ; Yongsug Suh
DOI 10.6113/TKPE.2020.25.5.385
Page pp.385-394
ISSN 1229-2214
Keywords 3-level NPC (Neutral Point Clamped) converter; Unbalanced grid voltage; Neutral point current; Neutral point deviation
Abstract This study introduces an analysis and control method for the variation of neutral point current in a grid-tied three-level neutral point clamped (NPC) converter under various grid imbalance operating conditions. Various fault cases with unbalanced amplitude and phase are systematically categorized and described using a unified metric called the imbalance factor. The fundamental component of neutral point current is generated under grid imbalance cases. The pattern and behavior of this fundamental component of neutral point current highly depend on the imbalance factor regardless of the particular type of grid fault cases. The control scheme for regulating the negative sequential component of AC input current effectively reduces the size of the fundamental component of neutral point current under a wide range of grid imbalance cases. The control scheme will enable a grid-tied three-level NPC converter to operate reliably and stably under various types of grid faults.