Current-fed Dual Active Bridge Converter Research Articles

Design and implementation of a current-fed dual active bridge converter for an AC battery

Abstract Home battery has become more and more popular in which the AC battery is a trending product along with the AC-coupled system. The energy conversion of an AC battery commonly consists of a two-stage power converter to flexibly connect to the wide-range input battery voltage and different grid or load types. This study specifically concentrates on the DC/DC stage which plays an important role in transferring power with the battery. In addressing the need for isolation, bidirectional power flow, and limited battery current ripple, the Current-fed Dual Active Bridge (CFDAB) structure is chosen for this stage. This paper presents a comprehensive design for the CFDAB converter for an AC battery application, especially a technical solution focusing on zero voltage switching is applied to increase the efficiency of the converter. Finally, an experimental prototype is carried out to validate the performance of the CFDAB converter in both two modes of the power flow.

Current-Fed Dual Active Bridge Converter With Asymmetric Three-Phase Transformer

Current-Fed Dual Active Bridge Converter With Asymmetric Three-Phase Transformer

Dead-Time Optimization and Magnetizing Current Design for a Current-Fed Dual Active Bridge DC–DC Converter to Secure Full Load Range ZVS in Wide Voltage Range

Current-fed dual active bridge (CF-DAB) converters are widely used because of the small input current ripple and high power density. This paper proposes the dead-time optimization methods and the magnetizing current design for a CF-DAB converter under the pulse-width plus phase-shift (PPS) control to achieve full load range zero-voltage-switching (ZVS) in a wide voltage range. In the ZVS analysis, the influence of junction capacitance and dead time is considered, including the dead-time effect on leakage inductance current, which can effectively explain that the CF-DAB converter under PPS control is difficult to achieve ZVS at light load in practice. Based on the analysis, it is first revealed that the CF-DAB converter under PPS control is not sufficient to achieve ZVS only by adjusting the dead time. Based on the new ZVS model and analysis of the dead-time effect, the magnetizing inductance design and dead-time optimization without adding extra control degrees of freedom and auxiliary components are proposed to achieve the full load range ZVS and improve the overall efficiency of the converter in a wide voltage range. Besides, to obtain the low root-mean-square (RMS) current, the design of DC inductance and leakage inductance are also investigated. Finally, a 1 kW prototype is built to verify the effectiveness of the proposed solution.

Open-Circuit Fault-Tolerant Control for a Three-Phase Current-Fed Dual Active Bridge DC–DC Converter

Fault-tolerant methods have been recognized for improving the reliability of multiphase bidirectional dc–dc converters, including current-fed and voltage-fed dual active bridge converters. Fault-tolerant research for voltage-fed dual active bridge converters has caught much attention recently. In this article, a new fault-tolerant method for current-fed dual active bridge (CF-DAB) converters with blocking capacitors is proposed. The operation of the CF-DAB converter when an open-circuit fault occurs is comprehensively presented and analyzed. A frozen-phase fault-tolerant method with additional blocking capacitors on both sides of the transformer is proposed. The aim of the use of blocking capacitors is to block the dc current component of the high-frequency transformer, which could avoid the core saturation of the transformer. Also, the dc blocking capacitors help isolate the faulty phase when a frozen-phase fault-tolerant method is applied. The proposed method is shown to be a practical, simple, low loss, and effective solution for not only open-circuit fault isolation but also for shedding capability of the multiphase converter. The proposed concept could be applied for general multiphase current-fed converters. The experiment of a 6-kW prototype is implemented to confirm the proposed concept.

Characterization of ZVS Behavior and Optimum Control Point Determination for Three-Port Current-Fed Dual Active Bridge Converter

Current-fed dual active bridge converter offers multiport structure and can be used in applications, such as renewable energy systems, hybrid electric vehicles, etc. Dual pulsewidth modulation plus phase shift control provides three degrees of freedom for power control, which include duty ratios of primary and secondary side bridges ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and the phase difference between them ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ</i> ). Converter operation at the optimum point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_1^{\text{opt}}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_2^{\text{opt}},\ $</tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sup> ) can help achieve multiple objectives, such as achieving zero voltage switching (ZVS) and minimizing current stress along with controlling the power flow. When a CF-DAB is operated as a multiport converter, the optimal control point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_1^{\text{opt}}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_2^{\text{opt}},\ $</tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sup> ) depends on the voltages and currents at different ports, and determining it online is a challenge. In this article, ZVS behavior and current stress of CF-DAB converter are analyzed under various operating conditions pertaining to different source voltages/currents and load power. Based on the analysis, an algorithm has been proposed for determining ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_1^{\text{opt}}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$d_2^{\text{opt}},\ $</tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sup> ) for the given operating condition. Experimental results on a laboratory prototype have been presented, which validate the theoretical analysis and the proposed algorithm.

A Novel Modeling and Control Design of the Current-Fed Dual Active Bridge Converter under DPDPS Modulation

This paper proposes a novel control design for a Current-Fed Dual Active Bridge (CFDAB) converter in boost mode. The Double PWM plus Double Phase Shifted (DPDPS) modulation is applied to the converter due to its considerable merits. A small-signal model is developed to control the output voltage stably in boost mode. Simulations of the control design for the CFDAB converter were conducted to verify the proposed model. The results show that the system can achieve high performance, not only in the dynamic response but also in the steady-state.

Secondary Side Cascaded Winding-Coupled Bidirectional Converter With Wide ZVS Range and High Conversion Gain

In this article, a secondary side cascaded bidirectional dc-dc converter (SSC-BDC) is proposed with the winding-coupled structure for the bidirectional operations of power flow, which features high voltage gain, full range of soft switching, low current ripple in low voltage side, and extended duty cycle range. Derived from a current-fed dual active bridge converter, the interleaved buck/boost circuit in the primary side is cascaded with the secondary side of full-bridge circuit through the winding coupled inductor to achieve high voltage gain. The differential voltage is designed to generate the bias current to realize soft switching of the eight power switches within a wide range of load variation. Meanwhile, pulse width modulation (PWM) plus phase-shift modulation is used to eliminate backflow power and increase conversion efficiency. The operation principle, steady-state analysis, and comparison result are presented in detail. Finally, a 1-kW experimental prototype is constructed to verify the feasibility of the SSC-BDC, and the correctness of the theoretical analyses is validated by experimental results.

PI Control of Current-Fed Dual Active Bridge Converter for DC Microgrid

A detailed modelling of soft-switching isolated current-fed dual active bridge (CFDAB) DC/DC converter is presented. This converter is suitable for an interface between two DC buses in a microgrid but is not controlled. The model of the converter is derived with the help of state space averaging method. Based on this modelling, the PI controller designed to improve the operation of the CFDAB converter. Simulation results using MATLAB/Simulink with controller design to verify the stability of the converter and validated performance of the system used for DC microgrid applications of between two buses. The effectiveness of the controller has justified in terms of line, load variation and tracking the reference values.

A Control Strategy for Bidirectional Isolated 3-Phase Current-Fed Dual Active Bridge Converter

This paper examines the characteristics of the zero voltage switching (ZVS) and zero voltage transition (ZVT) soft-switching applied in the 3-phase current fed dual active bridge (3P-CFDAB) converter, which combines the advantages of the dual active bridge (DAB) converter and current-fed full bridge (CFFB) converter. When an active clamp circuit is added to the CFFB converter, the circuit configuration of the DAB converter is shown in part of the entire circuit. This allows the use of pulse width modulation (PWM) techniques which combine the PWM techniques of both the DAB converter and CFFB converter. The proposed converter performs both duty and phase control at the same time in order to reduce the circulating current and ripple current of the output capacitor, which are the disadvantages of the CFFB converter and DAB converter. In addition, the ZVS and ZVT soft switching areas were analyzed by means of the phase current and leakage inductor current in each transformers. To verify the principle and feasibility of the proposed operation techniques, a simulation and experiment were implemented with the 3P-CFDAB.

3상 전류원 듀얼-능동 브릿지 컨버터의 효율 최적화 제어기법에 관한 연구

3상 전류원 듀얼-능동 브릿지 컨버터의 효율 최적화 제어기법에 관한 연구

High-Efficiency Current-Fed Dual Active Bridge DC–DC Converter With ZVS Achievement Throughout Full Range of Load Using Optimized Switching Patterns

For current-fed dual active bridge bidirectional dc-dc converters, all the possible switching patterns are summarized in view of the combinations of both side pulse-width modulation duty cycles and phase-shift angle. A control strategy is proposed for the current-fed dual active bridge converter to operate with the optimized patterns. The equivalent duty cycle of the secondary side is smaller than that of the primary side by a fixed value, which is optimized based on the soft-switching achievement and the circulating current minimization. The closed-loop control is easy to be implemented since there are only two independent variables, one-side duty cycle and the phase-shift angle. With the proposed control, zero-voltage switching can be achieved for all power switches throughout full range of load even at no-load condition. The typical working modes with the proposed control are given. The optimal design of the system parameters including the fixed time delta and dead time is illustrated. The converter has a very good performance, not only under steady states but also in transients. The conversion efficiency is high. The effectiveness of the proposed control is verified by the experimental results of a 1-kW laboratory prototype.

Utility Direct Interfaced Charger/Discharger Employing Unified Voltage Balance Control for Cascaded H-Bridge Units and Decentralized Control for CF-DAB Modules

A bidirectional high-frequency isolated ac–dc converter for utility direct interfaced electric vehicle charger with vehicle-to-grid (V2G) capability is presented in this paper. This type of charger can achieve the direct utility interface with medium voltage input. It is composed of multilevel cascaded H-bridge ac–dc converter as the first stage and modular current-fed dual active bridge dc–dc converters as the second stage. For the cascaded H-bridge converter, a unified control to balance the cascaded H-bridge dc voltages is proposed for both charging and discharging modes. For the second dc–dc isolation stage, the current-fed dual active bridge converter is used in facing of the wide conversion gain in battery charging application and also to reduce the charging current ripple. Meanwhile, to improve the system flexibility and reliability, decentralized control is utilized for individual current-fed dual active bridge converters in view of the battery charging profile. The proposed method along with the presented topology can achieve voltage balance in spite of the power flow direction, simplification of the controller for the dc–dc modules and can also bear unbalanced power flow. The simulation and experimental results have been presented to show the effectiveness of the proposed control.

Small-Signal Analysis of Naturally Commutated Current-Fed Dual Active Bridge Converter and Control Implementation Using Cypress PSoC

A detailed small-signal analysis and a closed-loop control design of a naturally commutated bidirectional current-fed dual active bridge (CFDAB) dc/dc converter are presented. The proposed converter is suitable for a fuel cell vehicle (FCV) between a traction inverter and batteries. State-space averaging technique is used to derive the small-signal model. Based on the derived small-signal model, a closed two-loop controller is designed and implemented on mixed signal (analog and digital) processor Cypress programmable system-on-chip (PSoC) 5. A complete design procedure is presented. Simulation results using PSIM 9.0.4 and experimental waveforms from a 250-W prototype with the designed controller are shown to verify the stability of the control system. Experimental results for step changes in load clearly show satisfactory transient performance of the converter and validate the closed two-loop design. It is suitable for energy storage, interfacing two dc buses of different voltages in a microgrid and a solar photovoltaic power system to boost a low-voltage panel up to the peak of the utility voltage.

Optimized Operation of Current-Fed Dual Active Bridge DC–DC Converter for PV Applications

The current-fed dual active bridge (CF-DAB) dc–dc converter gains growing applications in photovoltaic (PV) and energy storage systems due to its advantages, e.g., a wide input voltage range, a high step-up ratio, a low input current ripple, and a multiport interface capability. In addition, the direct input current controllability and extra control freedom of the CF-DAB converter make it possible to buffer the double-line-frequency energy in grid-interactive PV systems without using electrolytic capacitors in the dc link. Therefore, a PV system achieves high reliability and highly efficient maximum power point tracking. This paper studies the optimized operation of a CF-DAB converter for a PV application in order to improve the system efficiency. The operating principle and soft-switching conditions over the wide operating range are thoroughly analyzed with phase-shift control and duty-cycle control, and an optimized operating mode is proposed to achieve the minimum root-mean-square transformer current. The proposed operating mode can extend the soft-switching region and reduce the power loss, particularly under a heavy load and a high input voltage. Moreover, the efficiency can be further improved with a higher dc-link voltage. A 5-kW hardware prototype was built in the laboratory, and experimental results are provided for verification. This paper provides a design guideline for the CF-DAB converter applied to PV systems, as well as other applications with a wide input voltage variation.