Design and Optimization of an Efﬁcient (96.1%) and Compact (2 kW/dm3) Bidirectional Isolated Single-Phase Dual Active Bridge AC-DC Converter

Jordi Everts

doi:10.3390/en9100799

Abstract

The growing attention on plug-in electric vehicles, and the associated high-performance demands, have initiated a development trend towards highly efﬁcient and compact on-board battery chargers. These isolated ac-dc converters are most commonly realized using two conversion stages, combining a non-isolated power factor correction (PFC) rectiﬁer with an isolated dc-dc converter.This, however, involves two loss stages and a relatively high component count, limiting the achievable efﬁciency and power density and resulting in high costs. In this paper, a single-stage converter approach is analyzed to realize a single-phase ac-dc converter, combining all functionalities into one conversion stage and thus enabling a cost-effective efﬁciency and power density increase. The converter topology consists of a quasi-lossless synchronous rectiﬁer followed by an isolated dual active bridge (DAB) dc-dc converter, putting a small ﬁlter capacitor in between. To show the performance potential of this bidirectional, isolated ac-dc converter, a comprehensive design procedure and multi-objective optimization with respect to efﬁciency and power density is presented, using detailed loss and volume models. The models and procedures are veriﬁed by a 3.7kW hardware demonstrator, interfacing a 400Vdc-bus with the single-phase 230V,50Hz utility grid. Measurement results indicate a state-of-the-art efﬁciency of 96.1% and power density of 2 kW/dm3, conﬁrming the competitiveness of the investigated single-stage DAB ac-dc converter.

Highlights

Single-phase utility-interfaced ac-dc converters with power factor correction (PFC) and galvanic isolation cover a wide range of applications such as chargers for plug-in hybrid electrical vehicles (PHEVs) and battery electric vehicles (BEVs) [1,2], interfaces for residential dc distribution systems and energy storage systems [3,4], and inverters for photovoltaic modules
As these designs are located in the corner point of the so called “Pareto Front”, they are an optimal trade-off between efficiency and power density
A single-stage (1-S) converter approach is analyzed to realize a single-phase, bidirectional, isolated ac-dc converter, combining all functionalities into one conversion stage and enabling a cost-effective efficiency and power density increase compared to traditional dual-stage (2-S)

Summary

Introduction

Single-phase utility-interfaced ac-dc converters with power factor correction (PFC) and galvanic isolation cover a wide range of applications such as chargers for plug-in hybrid electrical vehicles (PHEVs) and battery electric vehicles (BEVs) [1,2], interfaces for residential dc distribution systems and energy storage systems [3,4], and inverters for photovoltaic modules. The above mentioned isolated ac-dc converters are most commonly realized using a dual-stage (2-S) approach, involving a non-isolated power factor correction (PFC) rectifier, followed by a dc-link to which a high-frequency (HF) isolated dc-dc converter is connected. An extensive review of uni- and bidirectional single-phase PFC rectifier topologies with improved power quality is presented in [7], including some variants with galvanic isolation. Examples of soft-switched, single-phase, Energies 2016, 9, 799; doi:10.3390/en9100799 www.mdpi.com/journal/energies

Methods

Results

Conclusion