LAUSR

Parallel operation of voltage source converters is widely accepted in industrial motor drive applications. However, the interleaving operation will inevitably generate phase circulating current (PCC) as well as zero-sequence circulating current (ZSCC) when converters share a common dc link, which will result in increased power losses and reduced system reliability. Traditional circulating current suppression strategies are either vulnerable to nonideal factors or complicated in parameter tuning. In this article, these challenges are solved by proposing an improved finite control set model predictive control, where two parallel-operated two-level converters are analyzed as a single three-level converter. In this article, a two-stage voltage vector preselection strategy is proposed to release the total calculational burden based on the deadbeat principle and dynamic behavior of the circulating currents. Hence, the number of candidate vectors is reduced from 64 to 7 in each control cycle. Moreover, both the ZSCC and PCC are suppressed simultaneously in a closed-loop form with better performance compared to the interleaving modulation scheme. Experimental results verify that the proposed method can achieve superior load current performance and suppress circulating current effectively.