A two-stage bidirectional DC-DC converter system and its control strategy

Abstract

With the development of more-electric aircrafts, bidirectional DC-DC converter has been widely used in this field. In order to improve the voltage regulation range and stability of the bidirectional DC-DC converter system, a two-stage bidirectional DC-DC converter with some operation modes is used and analyzed in this paper. The converter is composed of a four-switch buck-boost circuit and an isolated CLLC resonant circuit, where all MOSFETs can realize soft switching action. The four-switch buck-boost circuit regulates the output voltage in a certain range through the duty cycle control, and the CLLC resonant circuit can control the output voltage by changing its switching frequency, where the two-stage bidirectional DC-DC converter adopts voltage closed-loop control strategy to realize the stable voltage output. Due to the existence of the intermediate part conversion voltage, the converter has three-port network characteristics, which makes it applicable to the working occasions with multiple voltage levels. The feasibility of this two-stage bidirectional DC-DC converter system combined with control strategy and its three-port operation used for more-electric aircraft power system are verified by simulation analysis.