A 3X and X/3 voltage conversion‐based bidirectional CuK converter for supercapacitor‐assisted electric vehicles

Abstract

In this paper, a high‐gain bidirectional DC–DC converter is presented for electric vehicles where low terminal voltage source like a supercapacitor is used along with the battery. The supercapacitor provides or absorbs large amount power during acceleration and deacceleration and extends the life of main energy source, that is, battery. The supercapacitor terminal voltage varies considerably during charging and discharging activities; hence, a bidirectional DC–DC converter with a high‐voltage conversion ratio must be used to connect the lower supercapacitor voltage to the higher DC‐link voltage. Such application requires steep voltage conversion ratio along with continuous gain‐based bidirectional DC–DC converters. In this study, a typical CuK converter is employed to produce a voltage gain of 3X and X/3 with the ability to transmit power in both directions. The suggested bidirectional converter has a continuous current on both the low‐ and high‐voltage sides, which reduces the requirement for filter capacitance and increases the lifespan of the supercapacitor and DC‐link capacitor. Further, inherent inrush current safety is provided by the proposed converter as the inclusion of an inductor in the path of capacitor charging or discharging. Both in the charging and discharging phases, a detailed steady‐state analysis of the proposed circuit was performed. Moreover, a deep discharge analysis of the supercapacitor and its implication on the performance of the converter is also investigated.