Zero-Sequence Voltage Modulation Strategy for Multiparallel Converters Circulating Current Suppression

A zero-sequence circulating current (ZSCC) is typically generated among the multiparallel converters that share the common dc link and ac side without isolated transformers under the space vector modulation (SVM), due to the injected third-order zero-sequence voltage (ZSV). This paper analyzes SVM techniques, studies the effects of the ZSV on the ZSCC control loop in detail, and then proposes an improved SVM scheme to suppress the impact of the ZSV on the ZSCC. The proposed strategy can effectively realize the ZSCC suppression, even though the parallel converter modules have asymmetrical current references and filter inductances. The simulation and experimental results based on the parallel converters clearly verify the effectiveness of the proposed control.