An inrush current reduction technique for multiple inverter-fed transformers

This paper introduces a transformer inrush current reduction technique for the conventional double-conversion UPS feeding multiple loads and their transformers. As these loads are engaged or dis-engaged, their transformers are also connected or dis-connected from the power lines. To avoid the inrush current, a closed-loop flux linkage control is proposed to maintain the flux of transformers which are already engaged, and of the transformer which is switched-in. The proposed method can utilize the existing voltage and current sensors feedback of the UPS, and it can be seamlessly integrated with the voltage and current control. Experimental test results are provided to validate the effectiveness of the proposed method.