0885-8993 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TPEL.2016.2637506, IEEE Transactions on Power Electronics > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract— Isolated bidirectional DC-DC converters (IBDCs) with high efficiency and high power density demand for complete zero voltage switching (ZVS) of all active devices for its entire operating range. This paper presents a comprehensive analysis and optimization problem formulation of a triple phase shift (TPS) controlled inductive link based voltage fed - dual active bridge (VF-DAB) converter. Limitation on natural ZVS range for the TPS controlled inductive link based VF-DAB is presented. To extend the ZVS range in a TPS controlled VF-DAB converter, passive auxiliary inductors are connected in parallel (LLL tank) to the primary and secondary sides of the high frequency (HF) transformer. Analysis and subsequent numerical solutions for the TPS controlled VF-DAB with auxiliary inductors shows complete ZVS of all the MOSFETs for the entire operating range. Experi- mental results confirm complete ZVS of all MOSFETs under various voltage gains and load conditions. A comparative loss breakdown for the TPS controlled LLL tank VF-DAB and the conventional inductive link VF-DAB at various operating condi- tions show the necessity of the additional auxiliary inductors in the conventional design for increasing optimal switching fre- quency of the IBDC. Index Terms—Isolated bidirectional DC-DC converter (IBDC), Voltage fed - dual active bridge (VF-DAB), High frequency (HF) transformer, Triple phase shift (TPS), Zero Voltage Switching (ZVS) I. INTRODUCTION HE research in the area of dual active bridge (DAB) based isolated bidirectional DC/DC Converter (IBDC) has gained momentum in recent years due to the advancements in the fields of electrified transportation, integration of energy storage elements due to the intermittent nature of the distribut- ed renewable energy generation and other applications. The main focus of research has been to achieve high power densi- ty, higher efficiency, superior dynamic performance and im- proved reliability of the DAB converters [1]-[4]. Various forms of DABs are presented in the literature and are mainly classified based on the filter network, active switching net- work and high frequency (HF) reactive network [1], [2]. Manuscript received July 27, 2016; revised October 17, 2016; accepted November 28, 2016. The authors are with the Department of Electrical and Computer Engineer- ing, National University of Singapore (NUS), Singapore 117583 (e-mail: a0103321@u.nus.edu, kanakesh.vk@bears-berkeley.sg, eleprdas@nus.edu.sg, eleskp@nus.edu.sg). The Dual Active Full Bridge (DAFB) converter with an in- ductive type reactive tank as shown in Fig. 1 has now become the most popular DAB based IBDC for medium voltage and low voltage applications due to its additional control freedom and symmetric control on bi-directional power flow. The con- trol strategy for the DAFB based IBDC with the inductive type reactive tank to improve the soft switching range and reduce the circulating current in the converter is one of the important research directions for this topology. The full bridge configuration can achieve three levels of pole voltages de- pending upon the switching states. The dual full bridge con- figuration with 50% duty on each switch and constant switch- ing frequency offers three degrees of freedom to control power transferred by the converter as follows: • , the phase shift between the pole voltages of the two active bridges where − ߨ<< ߨin radians; • ܦ ଵ , the duty ratio of the primary bridge pole voltage ݒ ஺ ᇲ ஻ ᇲ where 0< ܦ ଵ <1, and • ܦ ଶ , the duty ratio of the secondary bridge pole voltage ݒ ஼஽ where 0< ܦ ଶ <1. ܦ ଵ and ܦ ଶ represent intra-bridge phase shift and can be varied by controlling the phase shift between the two legs of its cor- responding active bridges.  represents inter-bridge phase shift. Single phase-shift (SPS) control based modulation which uses only one degree of control freedom is the most conven- tional modulation scheme for DAB [5]-[9]. The bidirectional power transfer in the SPS control is achieved by adjusting the phase-shift,  between pole voltages of the active bridges while keeping ܦ ଵ and ܦ ଶ as 1. However, SPS controlled DAB suffers from drawbacks due to loss of soft switching and high circulating currents for wide variations in the terminal voltag- es and load. The drawbacks of the SPS control are severe, especially when the voltage conversion ratio is not close to the Triple Phase Shift Control of LLL Tank Based Bidirectional Dual Active Bridge Converter Shiva S.M., Student Member, IEEE, Kanakesh V.K., Pritam Das, Senior Member, IEEE and Sanjib Kumar Panda, Senior Member, IEEE T + - 1 : n Secondary side active bridge A’ B’ vA’B’ + - vAB C D LR iL C o + - V o S5 S6 S 7 S8 + - Vin Cin Primary side active bridge I o I in vCD + - S1 S 2 S3 S4 Tx D xCx Sx Fig. 1. Voltage fed - Dual active bridge (VF-DAB) converter topology