Passivity-Based Control of Buck Converters with Constant-Power Loads

This paper studies the control of buck converters subjected to constant-power loads using a passivity-based technique. This technique allows for global analysis and avoids the limitations present in small-signal-based techniques. Passivity-based control in this application leads to a systematic derivation of a linear proportional-differential controller. It is also proved that the equilibrium point is only locally stable due to the infeasibility of duty ratio values larger than unity. The paper presents a method to obtain the region of attraction and shows that this region is not affected by controller gains. Experimental work is included to verify the analysis.