Design and Implementation of Linear and Nonlinear Feedforward Controllers for High-Performance Power Factor Corrected Circuits

Abstract

This paper investigates the design and implementation of a linear feedforward controller, which creates the compensation duty cycle near zero-voltage crossing points for the power factor corrected (PFC) circuits, and a nonlinear feedforward controller, which is developed by using a linearization model of the high-performance PFC circuits. These two control approaches are proposed, compared and analysed. To address the discontinuous current near the zero-crossing point, two extra feedforward compensators with specific parameters are designed to refine the duty cycles of the switching devices. Experimental results and analytical results show that the proposed methods can provide a wider frequency range and flatter gain for the closed-loop PFC system. Furthermore, the proposed control methods have quicker recovery times and smaller voltage drops at the direct current (DC) output voltage than the traditional control method when the PFC is operated at a repetitive switching resistance load. Control algorithms were implemented and tested on a digital signal processor-based PFC circuit, which is a 500 W prototype with a single-phase alternating current input of 110 V and a DC output of 300 V to validate the feasibility and effectiveness of the proposed methods. Experimental results demonstrate that these feedforward control methods are superior to traditional proportional integral controllers, offering an improved input power factor, reduced harmonic currents, better performance under a repetitive switching resistance load and more straightforward implementation.