Introducing the Natural Switching Surface for reference frame systems: Three-phase boost PFCs

This paper presents the boundary control of three-phase boost rectifiers, bringing unprecedented dynamic response to reference frame based systems. A novel approach using the Natural Switching Surface (NSS) in the normalized αβ domain is introduced, providing superior dynamic performance and low input harmonic distortion. The derivation of the natural trajectories in the aforementioned domain is first performed to gain insight into the behavior of the system, yielding a generalized analysis that is valid for any possible combination of converter parameters. The target operating trajectory produced by the varying references is also described and characterized. Based on the previous analysis, the control laws that rule the behavior of the active rectifier are proposed, achieving constant-frequency operation as part of the control scheme. The resulting strategy provides excellent transient behavior, reverting to steady state in a few switching cycles when the PFC is subject to sudden load disturbances. Experimental and simulation results of a small scale 50W converter are presented to verify the enhanced properties of the NSS.