Small Signal Modelling for Variable Frequency Control With Maximum Efficiency Point Tracking of DAB Converter

Abstract

Dual active bridge (DAB) converters have experienced a boom thanks to the demands of new applications where bidirectional energy transfer, galvanic isolation and high efficiency are essential. In order to improve the efficiency of the stage without losing sight of the converter advantages, previous works have proposed complex forms of control that are not always applicable. This paper proposes the use of a variable frequency control strategy plus an additional control loop to find the point of maximum efficiency. Therefore, in this paper, the generalized state space average model is developed in depth to obtain in an analytical way a new small-signal model between the switching frequency and the output voltage, which is used to design the digital variable frequency control. In addition, to increase efficiency, reduce losses and ensure zero voltage switching, a second loop based on perturb and observe methodology is presented. The results obtained in the analysis of this control are validated and contrasted by simulation and experimentally with a 1kW prototype.

Keywords

• Dual active bridge
• digital control
• GSSAM