Efficiency-Optimized High-Current Dual Active Bridge Converter for Automotive Applications

Abstract

An efficiency-optimized modulation scheme and design method are developed for an existing hardware prototype of a bidirectional dual active bridge (DAB) dc/dc converter. The DAB being considered is used for an automotive application and is made up of a high-voltage port with port voltage V 1 , 240 V ≤ V 1 ≤ 450 V, and a low-voltage port with port voltage V 2 , 11 V ≤ V 2 ≤ 16 V; the rated output power is 2 kW. A much increased converter efficiency is achieved with the methods detailed in this paper: The average efficiency, calculated for different voltages V 1 and V 2 , different power levels, and both directions of power transfer, rises from 89.6% (conventional phase shift modulation) to 93.5% (proposed modulation scheme). Measured efficiency values, obtained from the DAB hardware prototype, are used to verify the theoretical results.Index Terms-Battery chargers, circuit optimization, dc-dc power conversion, design methodology, digital systems. NOMENCLATURE D 1Duty cycle used for the HV full bridge. D 2 Duty cycle used for the LV full bridge. ϕPhase angle between v T1 and v T2 . f S Switching frequency. i T1 Transformer current, HV side. i T2 Transformer current, LV side. I S1,sw,min Minimum HV MOSFET current needed to achieve low switching losses, HV side. I S2,sw,opt LV MOSFET current needed to achieve minimum switching losses on the LV side. L DAB converter inductance. n Transformer turns ratio. P 1 HV port power. P 2 LV port power. P out Converter output power. P out,d Designated output power (mod. scheme). P ,a,maxMaximum power of the modified triangular current mode modulation for V 2 ≤ V 2,lim .Maximum power of the modified triangular current mode modulation for V 2 ≥ V 2,lim . P ,V2 lim,max Maximum power of the modified triangular current mode modulation at V 2 = V 2,lim . P opt,a,min Minimum power of the high-power mod. scheme for V 2 ≤ V 2,lim (P opt,a,min > P ,a,max ).P opt,b,min Minimum power of the high-power mod. scheme for V 2 ≥ V 2,lim (P opt,b,min > P ,b,max ). P opt,a,hi Transition power level with D 1 = D 2 = 0.5 for V 2 ≤ V 2,lim (P opt,a,hi > P opt,a,min ). P max Maximum output power of the DAB. T S Switching period,Defines the boundary between different operating modes of the DAB. v T1 AC volt. generated by the HV full bridge. v T2 AC volt. generated by the LV full bridge.

Reactive Power and Soft-Switching Capability Analysis of Dual-Active-Bridge DC-DC Converters with Dual-Phase-Shift Control

“…It shows that the efficiency improvement using the DPS is not as good as expected. The effect of the DPS in in terms of efficiency improvement is also undervalued in other studies [6], [8], [19], [20]. The possible reasons may include:…”

“…magnitude of the transformer primary voltage v T1 transient value of the transformer primary voltage V T2 magnitude of the transformer secondary voltage v T2 transient value of the transformer secondary voltage I S1 rms current produced by V S1 I L_rms rms current flowing through the inductor L V L_rms rms voltage across the inductor L Q L reactive power produced by the inductor L I peak peak current of the inductor L I peak_min minimum value of I peak I rms_min minimum value of I L_rms I peak_min_G global minimum value of I peak I peak_min_L local minimum value of I peak INTRODUCTION Originally proposed in [1] for aerospace power applications, the topology of a dual active bridge (DAB) converter became popular in battery chargers [2], hybrid wind-photovoltaic systems [3], solid-state transformers (SSTs) [4], micro grids [5], and hybrid electric vehicles [6]. Compared with other isolated dc-dc topologies, the DAB converter shows many advantages, such as bi-directional power flow, inherent soft-switching capability, power controllability and high efficiency [7].…”

“…4) The complexity for implementation: the study in [6] demonstrates that the 2-D solving problem of the DPS, which is regarded as too complex to be optimized when compared with 1-D PWM strategies. However, like PSPWM [10], the efficiency optimization with the DPS is essentially a 1-D problem.…”

Combined Pulse-Width Modulation of Dual Active Bridge DC-DC Converter to Increase the Efficiency of Bidirectional Power Transfer

“…Although (13) stated that the phase must be negative, the phase is set to zero to avoid a discontinuous modulation strategy (26) . Therefore, the hard-switching will still occur in the interval 1.…”

High-Performance AC-DC Power Electronic Converter Generator for Hybrid-Solar Vehicles

“…In fact, at the end of driving the final SOC (state of charge) is required to be low enough to allow full storage of solar energy captured in the next parking phase, D DAVID PUBLISHING whereas, the adoption of an unnecessary constantly low value of final SOC would give additional energy losses and compromise Ch-E/E-Ch storage battery life-time. The optimal management of Ch-E/E-Ch storage battery would therefore require a previous knowledge of the SE to be captured in next parking phase that can be achieved through real-time access to weather forecast [9][10][11][12]. The impact of PhPs can be significantly improved by adopting suitable MPPT (maximum power point tracking) techniques, whose role is more critical here than in fixed plants.…”