Abstract：The common dc-link dual parallel three-phase converter-system would produce circulating current. To suppress circulating current, a method to expand the bandwidth of zero-sequence current loop was proposed. Restrictions to the bandwidth of zero-sequence current loop caused by the difference in parameters between inverters and the time delayed by the control system were analyzed based on the model of parallel system. The restrictions caused by parameter difference as well as different converter operating state was eliminated with the zero vectors feed-forward strategy. Dual current sampling and dual PWM duty update method combined with the zero vectors feed-forward strategy was proposed to expand the zero-sequence current bandwidth effectively. This method has fast dynamic response and good performance of circulating current suppression, without increase in switching frequency. Both the validity of the theoretical analysis and the effectiveness of the control strategy was confirmed by experimental results.
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2015, Vol. 30 
