Design and implementation of a high-efficiency bidirectional DC-DC Converter for DC micro-grid system applications Huang-Jen Chiu*, Yu-Kang Lo, Shu-Wei Kuo, Shih-Jen Cheng and Feng-Tsuen Lin Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology. Taiwan ABSTRACT This paper studies the design and implementation of a non-isolated dual-half-bridge bidirectional DC-DC converter for DC micro-grid system applications. High efficiency can be achieved under wide-range load variations by the zero-voltage-switching features and an adaptive phase-shift control method. A three-stage charging scheme is designed to meet the fast-charging demand and prolong the lifetime of LiFePO 4 batteries. A digital-signal-processing control IC is used to realize the power flow control, DC-bus voltage regulation, and battery charging/ discharging of the studied bidirectional DC-DC converter. Finally, a 10 kW prototype converter with Enhanced Controller Area Network communication function is built and tested for micro-grid system applications. A light-load efficiency over 96% and a rated-load efficiency over 98% can be achieved. Copyright © 2013 John Wiley & Sons, Ltd. Received 6 November 2012; Revised 25 December 2012; Accepted 21 February 2013 KEY WORDS: bidirectional DC-DC converter; micro-grid system; zero-voltage-switching; adaptive phase- shift control; three-stage charging; E-CAN communication 1. INTRODUCTION From the background of improving technologies and ecology aspects, renewable energies such as solar energy, wind energy, and fuel cell have become global trends [1–5]. In distributed electric power system, independent power generation system or large-scale power system in parallel is a trend. The idea is not replacing the centered power system, but according to different load requirement from different areas, a more reliable and economic power system is introduced [6–8]. A DC micro-grid system shown in Figure 1 is sited mainly at residents, social environments, and isolated islands. DC-load power demands can be achieved from renewable energy sources such as solar cells or wind energy, otherwise from parallel mains grid for AC-load demands or re-transfer, thus re-sell, the energy to power company. Each renewable energy method has problems of variations in energy capacity and response speed, and does not have their own energy storage function, so rechargeable batteries are needed for this application [9–12]. In a DC micro-grid system, a bidirectional DC-DC converter is always necessary to transfer the excessive energy from renewable energy resources to the batteries as DC-load power demand can be fulfilled and provide the energy from batteries to DC load as the renewable energy resources cannot fully supply the load demand [13–17]. This paper studies a non-isolated zero-voltage-switching (ZVS) dual-half-bridge bidirectional DC-DC converter with an adaptive phase-shift control design. High conversion efficiency performance can be achieved. *Correspondence to: Huang-Jen Chiu, Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology. Taiwan. † E-mail: hjchiu@mail.ntust.edu.tw Copyright © 2013 John Wiley & Sons, Ltd. INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS Int. J. Circ. Theor. Appl. 2013 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/cta.1910