A Relay Controller with Parallel Feed-forward Compensation for a Buck Converter Feeding Constant Power Loads

Abstract

A simple and efficient analog direct voltage control design for improving the performance and stability of a buck converter feeding constant power loads (CPLs) is the main aim of this article. One of the oldest and most spread approaches is to design a relay control system. In these systems, although the hysteretic relay adds non-linearity to the closed-loop system, an adequate controller design procedure will be presented using the locus of a perturbed relay system (LPRS) technique. This work shows how a designer can apply LPRS technique to a converter plant, in this case a buck converter feeding a mixed linear and constant power load (CPL), using a parallel feed-forward compensator (PFC) to obtain a suitable performance in the closed-loop system. That means to enlarge the range of stable behavior with respect to the power in the CPLs, in comparison with the open-loop case, and to regulate adequately the output voltage of the converter in front of input voltage and load power variations. The simulation results with the converter-load non-linear model show the good performance of the designed controller with respect to the above-mentioned disturbances and perturbations.