Stability Optimization Method Based on Virtual Resistor and Nonunity Voltage Feedback Loop for Cascaded DC–DC Converters

This paper proposes a stability optimization method based on virtual resistor and nonunity voltage feedback loop for cascaded dc-dc converters. Oscillating phenomenon or instability would occur occasionally with two or more closed-loop dc-dc converters in series. The virtual resistor and nonunity voltage feedback are used to modify the feedback loop instead of only a direct voltage feedback to improve stability and get rid of oscillating behavior. Based on the stability analysis of dc-dc converters with distributed parameters, several cases have been derived. After that, relative to different cases, two modified methods based on virtual resistor and nonunity voltage feedback loop are proposed to stabilize the overall system. With these methods, no extra power loss would be generated, and it is easy to embed them into any conventional control system. Experimental results verified the theoretical analysis and feasibility of the proposed control methods.