Implementing Power Buffer Functionality in a Dc-Dc Converter by Geometric Control

Modern power electronics are capable of regulating loads with bandwidths so high that they essentially enforce constant power on millisecond time scales. These types of loads continue to grow in influence on electrical distribution systems. Most such loads, including motor drives, computer power supplies, and compact fluorescent lighting, serve to "isolate" the load dynamics from the utility grid. The unfortunate effect is that these loads exhibit negative impedance characteristics which tend to destabilize the supply system during a system transient, potentially contributing to voltage collapse. Active front-end control of such loads to implement a power buffer function has been shown to mitigate collapse but has relied on complicated hybrid control techniques. This paper introduces a geometric control surface based on a change of converter variables that simply and effectively implements a power buffer function. The formulation and implementation of the optimal surface is presented, in addition to experimental validation of the new power buffer control law