An Interleaved Bidirectional Coupled-Inductor Based DC-DC Converter with High Conversion Ratio for Energy Storage System

In this article, an interleaved coupled-inductor (CI) based bidirectional dc-dc converter (BDC) is proposed with a higher voltage conversion ratio (VCR). In this proposed interleave CI-based BDC (ICI-BDC), the CIs can operate as both a filter inductor and a transformer simultaneously, so that the power density is improved. Moreover, as a transformer, the turns ratio of CIs is used to improve the VCR with a voltage stress reduction purpose. Furthermore, the interleaved technique can well achieve the low current ripple and reduced current stress in this topology. To control ICI-BDC, the pulsewidth modulation plus phase-shift (PPS) control is employed, where the duty cycle is used to match the two side voltages, and the phase-shift angle is used to control the amount and direction of power flow. Uniquely, a difference value is set between the two side duty cycles, and the duty cycle of the high voltage side is smaller than that of the low voltage side by a fixed value. In this proposed control method, all the switches can achieve soft-switching even at light load condition, which can improve transmission efficiency. Experimental results obtained from a 1-kW prototype show a nearly high efficiency under all loading conditions, validating the viability of the proposed ICI-BDC topology and control method.