Current-fed Dual Active Bridge Research Articles

Model and Control of a Current-Fed Dual Active Bridge Based Ultrawide-Voltage-Range Auxiliary Power Module for 400 V/800 V Electric Vehicles

Model and Control of a Current-Fed Dual Active Bridge Based Ultrawide-Voltage-Range Auxiliary Power Module for 400 V/800 V Electric Vehicles

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

Parallel AC-Link Connection of Current-Fed Dual Active Bridge Converters

Parallel AC-Link Connection of Current-Fed Dual Active Bridge Converters

Effect of Phase Shift Definition on Power Characterization of Isolated DC–DC Converter Under PWM Plus Phase Shift Modulation

PWM plus phase shift (PPS) modulation is a popular modulation technique for the current fed dual active bridge (CFDAB) converter. Power transfer characteristics for any modulation technique are important for converters. However, in the literature, different power characteristics of CFDAB are presented for PPS modulation. This disparity in power transfer behavior creates confusion and ambiguity to the readers. This brief reveals the reason for such disparity. This is primarily due to the definition of the phase shift considered. When the phase shift is considered between the rising edges of high frequency voltages, asymmetric power transfer characteristics are obtained. On the contrary, symmetric power transfer characteristics are obtained if phase shift is considered between the mid point of high level of high frequency voltage signals. Thus the latter provides useful features and universal conditions for power reversal and peak power transmission individually. Steady state power under different modulation is obtained from unified model of CFDAB. The analytical results and experimental investigations are in agreement with each other.

Hybrid-Type Dual Active Bridge DC–DC Converter for Ultrawide Input-Voltage Range

This paper proposes a hybrid-type dual active bridge (H-DAB) topology and extended gain control (EG) method applied to the ultra-wide input-voltage range. The H-DAB is obtained by adding an auxiliary half-bridge to the conventional current-fed dual active bridge (CF-DAB) topology. The auxiliary half-bridge can assist the CF-DAB to achieve ZVS on the one hand, and further expand the voltage gain range on the other. The proposed extended gain control (EG) expands the input voltage range of ZVS for all switches by calculating the optimal intermediate bus voltage. In addition, the backflow power has also been drastically reduced. The proposed piecewise control strategy simplifies the complexity of control. The proposed topology and the control method are verified by the experimental results of a 500 W prototype. The input voltage range is 27 – 240 V and the output voltage is 375 V. The experimental results proved that the proposed scheme achieves ZVS of all switches in a wide input voltage range and power range, and the efficiency is improved.

Development of Current-Fed DAB Converter Applying Triangular Current Mode for Wide Voltage Applications

This paper proposes a control and modulation method for a Current-Fed Dual Active Bridge (DAB) converter to improve the conversion efficiency for wide voltage range applications. The current-fed DAB converter is preferred in battery applications owing to its high-power density and low current ripple. On the other hand, the high-conversion efficiency range is limited to close to the nominal DC voltage condition as the DAB converter. The proposed method provides Zero-Voltage-Switching (ZVS) in a wide DC voltage range by Triangular Current Mode (TCM). Furthermore, the proposed control reduces the inductor RMS current compared with the DAB converter to minimize the conduction loss. The validity of the proposed method is established by experimental results. According to the experiment using a 2-kW prototype, the conversion efficiency reached 97.2% when the input voltage was varied by 50% from the nominal DC voltage, then the conversion loss was reduced by 52.5% owing to the proposed control. Finally, the maximum power density of the current-fed DAB converter was improved by 38.1% compared to that of the DAB converter.

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.

H5-CFDAB: A Current-Fed Dual-Active-Bridge Converter for Application in Modular DC Solid-State Transformer

Isolated DC-DC converters in DC Solid-State Transformers (DCSSTs) must conform to stringent requirements such as high voltage conversion ratio, high efficiency, and reliable operation with grid fault handling capabilities. This paper proposes a novel current-fed Dual-Active-Bridge (CFDAB) converter, named H5-CFDAB, for modular DCSST application. Compared to the existing topologies, the proposed converter provides a single-stage power conversion with reduced component count and semiconductor Volt-Ampere (VA) rating. The proposed modulation scheme makes the pulse widths of the transformer winding voltages independent of the duty ratio. This allows further optimization of the high-frequency-link (HFL) characteristics like minimized HFL conduction losses and full range Zero-Voltage-Switching (ZVS) at turn ON for the switches, further increasing the converter efficiency. Several modules of the proposed H5-CFDAB converter connected in Input-Series-Output-Parallel (ISOP) configuration makes the system suitable for Medium-Voltage (MV) high-power applications. The operation of the proposed converter is analyzed in detail, including the HFL characteristics and derivation of the ZVS conditions for the switches. In addition, a closed-loop control scheme is proposed for achieving tight regulation of the converter outputs during transients. A 1.2 kW laboratory prototype is built to verify the effectiveness of the proposed converter, along with the control scheme.

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.

Soft Switched Current Fed Dual Active Bridge Isolated Bidirectional Series Resonant DC-DC Converter for Energy Storage Applications

This paper proposes a high-frequency isolated current-fed dual active bridge bidirectional DC–DC series resonant converter with an inductive filter for energy storage applications, and a steady-state analysis of the converter is carried out. The performance of the proposed converter has been compared with a voltage-fed converter with a capacitive output filter. The proposed converter topology is operated in continuous conduction mode with zero circulation current (ZCC), less current stress and high efficiency. The conditions required for soft switching are determined, and it is found that the converter operates with soft switching of all switches for a wide variation in load and input voltage without loss of duty cycle. Current-fed converters are suitable for low-voltage renewable energy applications because of their inherent boosting capability. An inductive output filter is chosen to make the output current ideal for fast charging and high-power-density battery storage applications. Simple single-phase shift control is used to control the switches. The performance of the converter is studied using PSIM simulation software. These results are confirmed by an experiment on a 135 W converter on an OPAL-RT real-time simulator. The maximum efficiency obtained in simulation is 96.31%. Simulation and theoretical results are given in the comparison table for both forward and reverse modes of operation. A breakdown of the losses of this converter is also presented.

Hybrid Inverter and Control Strategy for Enabling the PV Generation Dispatch Using Extra-Low-Voltage Batteries

This paper proposes a dispatchable photovoltaic (PV) hybrid inverter for output power tracking without any dependency on the converter’s efficiency and with no power closed loop. The system uses an extra-low-voltage battery energy storage system (BEES) based on a Li-ion battery pack to be applicable for use inside homes and other installations close to the end-user. A bidirectional isolated current-fed dual-active bridge (CF-DAB) converter associated with the batteries provides a wide conversion voltage ratio and ensures safety for the users. The proposed control system shares the DC bus voltage controller between the ac grid interfacing converter (AC-DC) and CF-DAB (DC-DC), eliminating the converter’s efficiency in the reference equations. When dispatchable power is not required, or according to the user’s request, the battery’s charge/discharge current can be specified. A disturbance rejection technique avoids low-frequency current ripple on the battery side. It contributes to the battery’s lifespan. Experimental results presenting the dc bus voltage control, current disturbance rejection, and power dispatching are included to validate the proposal.

Coupled-Inductor-Based Dual Active Bridge Converter With Soft Switching Capability and Low Component Count

A coupled-inductor-based dual active bridge (DAB) converter with soft switching capability and low component count is proposed in this article. Under wide-input voltage range application, it only utilizes four active switches to achieve voltage regulation and can behave like the current-fed DAB (CF-DAB) converter. In addition, three magnetic components, including the input dc inductor, the transformer, and the leakage inductor, can all be integrated into one coupled inductor, thus reducing the magnetic component count. With the coupled-inductor structure, the voltage of the half bridge capacitor at the output side can be automatically changed according to different duty cycle. Consequently, the voltage matching at the two ports of the equivalent leakage inductor will always be satisfied by controlling the input capacitor voltage with the adopted pulsewidth modulation (PWM). Based on the detailed analysis of the working modes, power transfer characteristics, and zero-voltage switching (ZVS) conditions, full load range ZVS can be mathematically obtained, which shows that the full load range ZVS capability is an intrinsic feature of the proposed converter and is not related to the converter inductance values. Furthermore, the magnetic integration and parameter design are analyzed in detail. Finally, experimental results are provided to demonstrate the effectiveness of the proposed solution.

A Direct Actual-Power Control Scheme for Current-Fed Dual-Active-Bridge DC/DC Converter Based on Virtual Impedance Estimation

High dynamic performance is an essential requirement for the dual-active-bridge (DAB) dc/dc converters. As dc voltage sources, they should maintain the desired output voltage instantly under all working conditions. However, the previous literature mainly focus on the dynamic control of the voltage-fed DAB converters, and the existing control schemes for the current-fed DAB converters achieve limited dynamic performance. Aiming at improving the dynamic performance, a direct actual-power control (DAPC) scheme based on virtual impedance estimation (VIE) is proposed for the current-fed DAB converters in this article. The proposed DAPC scheme is based on a parallel structure instead of the series structure of existing control schemes, and it realizes fast dynamic control through combining actual power control with the VIE method. The proposed DAPC scheme can obtain the fastest transient response for the output voltage without voltage overshoot in transient conditions, such as load step change, input voltage fluctuation, and the desired output voltage step change. Besides, a leakage inductor precharging method is integrated into the DAPC scheme to avoid the current mismatching. Finally, the proposed DAPC schemes are compared with two existing control schemes and tested in a scale-down experimental prototype. Experimental results verify the effectiveness of the proposed DAPC scheme.

A Graph-Modeling Approach to Topology Simplification in Power Converters

In this article, we propose a topology simplification method (TSM) for power converters, based on graph theory, to improve the converter design. In the proposed method, a directed graph is first established to model a converter circuits, from which the conceptually new converter adjacency matrix (CAM) is derived. Combined with the electrical features of power converters, a rule for electronics current paths is presented. Then, the redundant components are eliminated based on the proposed TSM and a new CAM is obtained, which is converted to a new directed graph and thus a new converter topology with reduced components. In the process, the integrity of the current paths is preserved and the new topology contains all the current paths of the original converter. With the proposed TSM, the derivations of the existing single-ended primary-inductor converter and current-fed dual active bridge converters are employed for theoretical verification. A novel single-phase boost push–pull converter topology is designed, which is validated by experiments.

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.

Dual Active Bridge Based Reduced Stage Multiport DC/AC Converter for PV-Battery Systems

Standalone power systems are significant for electrifying the remote areas where extending the grid connectivity is not feasible, either economically or logistically. Solar Photovoltaic (PV) systems with battery backup are among the most popular candidates to serve as an energy source in standalone systems. This article presents a novel multiport converter (MPC) for PV-battery systems powering standalone loads. The proposed converter is a reduced stage power converter based on current fed dual active bridge (CF-DAB) topology. CF-DAB offers galvanic isolation and a high voltage ratio without sacrificing efficiency. Switching losses are further reduced by a modified modulation scheme that reduces the average switching frequency of some of the switches. The proposed converter performs the functions of tracking maximum power point of the solar panel and regulating the load voltage while using fewer power conversion stages. This is done by sharing components among the various stages performing maximum power point tracking, voltage boosting, and dc/ac conversion. A small-signal model of the proposed MPC required for its closed-loop control is also proposed, which can also be utilized for other CF-DAB-based converters. A lab prototype of the proposed MPC has been fabricated and its operation has been validated under various static and dynamic conditions.

Design Considerations for PPS Controlled Current-Fed DAB Converter to Achieve Full Load Range ZVS and Low Inductor Current Stress

Current-fed dual active bridge dc–dc converters are suited for renewable energy systems such as solar photovoltaic and fuel cells, due to the advantages of small input current ripple and wide input voltage range. In this article, a current-fed dual active bridge dc–dc converter based on pulse width modulation plus phase shift control is studied. The working principle and zero-voltage switching (ZVS) conditions of the converter are analyzed in depth, and it is proved mathematically for the first time that all switches can naturally achieve ZVS independently of dc inductance and leakage inductance under a wide input voltage range within full load range. Based on maximum power transfer, peak current, and root mean square (RMS) current analysis, optimal dc inductance and leakage inductance design to obtain low inductor RMS current is proposed. In addition, the detailed loss breakdown was implemented by comparing it with the nonoptimized case. The effectiveness of the theoretical analysis and design method has been verified by experimental results.

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.