Stability analysis and voltage control method based on virtual resistor and proportional voltage feedback loop for cascaded DC-DC converters

Abstract

This paper proposes a voltage control method based on virtual resistor and proportional voltage feedback loop for cascaded DC-DC converters. The closed-loop DC-DC converter would act as negative impedance load for the front-end converter and might lead to system instability. Based on the analysis of DC-DC converter with distributed parameters, a modified voltage control strategy based on virtual resistor is proposed which is to only add a proportional feedback of inductor current in the control block. Thus, no extra power loss would be generated. However, under some conditions, this method cannot achieve system stabilization. Then, an additional output voltage feedback loop is introduced which can not only stabilize the system under different cases but also improve system performance. Experimental results verified theoretical analysis and feasibility of the proposed control methods.