Differential Flatness Controller for BLIL PFC Boost Rectifier

Abstract

Electric Vehicle uses AC/DC boost converters for charging high energy battery pack from the input AC supply. They incorporate a PFC controller to improve the input side power factor and also regulate the output voltage with reduced ripple. PFC converter is followed by DC /DC converter which provide high-frequency isolation from the battery bank. This paper presents a technique based on differential flatness principle to improve the power factor of the converter based on the input power. In this case, input power is taken as the reference instead of intermediate dc bus voltage, unlike the conventional ACM (ACM) control. This flatness approach improves the dynamic behavior of the converter with good load adaptive regulation. The converter is initially analyzed with ACM controller and compared with the flatness theory based controller. The front-end converter topology considered in this work is BLIL AC/DC converter and for the second stage, an isolated resonant DC/DC converter is preferred as it is best suited for charging applications. The results reveal that the differential flatness controller improves the dynamic response of the converter under varying load conditions and soft switching is achieved in the second stage converter which results in improving the overall converter efficiency.

Keywords: AC/DC Boost Converter, Resonant DC/DC Converter, Flatness Principle, Power Factor Correction, Acm Controller, Non- Linear Control, Plug-In Hybrid Electric Vehicles