Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

Increased demand of battery energy storage systems, has increased the need of bidirectional DC-DC converters with galvanic isolation. For high power density, compact size, less weight and low cost, Power Conversion Systems with High Frequency tie connection are most likely be preferable. Dual Active Bridge (DAB) Isolated Bidirectional DC-DC converter (IBDC) is the core circuit of High Frequency Power Conversion Systems. Most common topology of dual active bridge converter has two full bridge converters connected through a high frequency transformer. Bi-directional power flow capability, high power density, high efficiency, innate soft switching, low number of passive components and galvanic isolation are some attributes of DAB attracting industry. This paper discusses the application of Dual Active Bridge (DAB) Isolated Bi-directional DC-DC (IBDC) converter in Uninterrupted Power Supplies (UPS), also compares the Dual Phase Shift (DPS) control with the Single Phase Shift (SPS) control in parameters like voltage, current and VA stress, and inductor peak current. The MATLAB & SIMULINK simulation results for both charging and discharging mode are shown for closed loop control of the two control strategies viz., SPS and DPS control using PI controller by varying the load in two steps.

This paper proposes an isolated bidirectional dc-dc converter (IBDC) without a cooling fan with a low profile for a direct connection between a battery and the IBDC. To implement the low-profile IBDC, a dual active bridge (DAB) and two interleaved buck/boost converters are adopted in the proposed system. For the IBDC with a low profile and high efficiency, two transformers in the DAB converter are separated in series on their primary side and in parallel on their secondary side. In addition, in two interleaved buck/boost converters, their inputs and outputs are connected in parallel, and interleaving control is applied for a small total of inductor current ripple. Finally, a double heat sink is designed for excellent heat dissipation performance. A 500 W low-profile and fanless prototype with 650 V input and 1 (60 W)~5 V (500 W) output was made to verify its performance of operation, efficiency, and saturation temperature.

In a medium voltage (MV) solid state transformer(SST), the isolated bidirectional DC/DC converter (IBDC) is the core circuit for controlling power flow and galvanic isolation. Current research works on MV single-cell IBDC mainly focus on two directions: resonant and non-resonant topologies. However, for different scenarios with various voltage regulation ranges and power ranges, which topology should be adopted to achieve better efficiency performance is unclear. To effectively illustrate the two IBDCs’ respective benefits, a comparison between the two IBDCs is conducted in this study along with the optimization design method. For resonant IBDC, a complex objective optimization-based parameter design strategy is developed to realize rapid automatic design under various operating conditions. For non-resonant IBDC, a multi-phase modulation scheme aimed at minimizing the current stress under different voltage and power ranges is introduced. The optimal operating range of the two IBDCs has been derived. A 4 kV/1 kV 200 kW non-resonant IBDC experimental prototype has been built and its efficiency is tested under various operating conditions. The test data were compared with the established power loss model to derive the converter's full range efficiency, and the efficiency of the converter over a wider power range could then be projected.

Isolated bidirectional dc/dc converters (IBDDCs) are widely used in the renewable energy systems such as solar energy and wind power as the power interfaces. Dual active bridge (DAB) converters show many advantages compared with other IBDDCs, such as high power density and easy in control implementation. Nowadays, many advanced controls with multiple phase-shift variables such as triple phase-shift (TPS) control have been proposed to improve the efficiency for a wider output power range. In order to ensure the system reliability, the fault diagnosis is essential to identify the faulty devices quickly and avoid the system collapse. In this paper, three common operation modes are analyzed and an open-circuit diagnosis strategy is proposed for DAB converters under the advanced TPS control. Main simulation and experimental results are provided to validate the proposed fault diagnosis method.

The Dual Active Bridge (DAB) is one of the most promising topologies among bidirectional isolated DC-DC converters, especially in interfaces to batteries. It is recently gaining interest due to its versatile features. The investigative studies are progressing to inspect, control and improve the overall performance of the DAB converter. Currently, there are challenges regarding the control of DAB. It has complex nonlinear properties and also has to attain multiple aims (e.g. regulating power flow, achieving zero voltage switching (ZVS) and minimizing current stresses).This has resulted in the requirement to investigate with different abstraction levels in DAB design process, e.g. ideal behavior (steady-state, dynamics), losses analysis, optimization of parameters and control. In this paper, an accurate analytical model is presented which makes the design of voltage controller simple and independent of the operating conditions. The analytical developments presented, based on the superposition principle, allow obtaining the waveforms of inductor and output current using a simple and fast closed-form procedure. This allows to apply optimization methods for the selection of the operating point or during the design stage (e.g. for selecting inductance and frequency values). Moreover, the novel fully analytical model describes the output current vs. phase-shifts relation. As a study-case, the Single Phase-Shift (SPS) is used for regulating the output current (average) in an open-loop control (by linearizing the control of DAB output voltage. Simulations in PLECS Blockset validate the theoretical results.

The increase of electrical energy consumption in modern aircrafts stimulates manufactures to install a 540V DC bus in future aircrafts, together with the existing 270V and 28V DC buses. Energy transferred between the high voltage DC bus (HVDC, 270V) and the low voltage DC bus (LVDC, 28V) is made by bidirectional isolated DC-DC converters. A performing topology for these types of converters is the Dual Active Bridge (DAB) given its soft switching properties and the low number of components, which allow the converter to be highly compact. This paper introduces a new topology of DAB (named DABRSP) which uses only 4 switches at the high voltage (HV) side and can be used in 270V and 540V DC buses without oversizing switches. Oversizing is observed if regular Full Bridge (FB) or Neutral Point Clamped (NPC) converters are used in the HV side of the DAB. The proposed topology allows Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) the same way as in a typical DAB converter and it makes uses of a particular transformer to "magnetically" sum up 2-level voltages.

This paper describes a bidirectional isolated dc-dc converter considered as a core circuit of 3.3-kV/6.6-kV high-power-density power conversion systems in the next generation. The dc-dc converter is intended to use power switching devices based on silicon carbide (SiC) and/or gallium nitride, which will be available on the market in the near future. A 350-V, 10-kW and 20 kHz dc-dc converter is designed, constructed and tested. It consists of two single-phase full-bridge converters with the latest trench-gate insulated gate bipolar transistors and a 20-kHz transformer with a nano-crystalline soft-magnetic material core and litz wires. The transformer plays an essential role in achieving galvanic isolation between the two full-bridge converters. The overall efficiency from the dc-input to dc-output terminals is accurately measured to be as high as 97%, excluding gate drive and control circuit losses from the whole loss. Moreover, loss analysis is carried out to estimate effectiveness in using SiC-based power switching devices. Loss analysis clarifies that the use of SiC-based power devices may bring a significant reduction in conducting and switching losses to the dc-dc converter. As a result, the overall efficiency may reach 99% or higher

This paper proposes a triangular modulation with zero current switching (ZCS) for a hybrid Si-SiC isolated bidirectional DC-DC converter (IBDC). Three of the four legs in the IBDC operate at ZCS and use Si IGBTs, while the fourth operates at zero voltage switching (ZVS) and uses SiC MOSFET. In that case, the turn-off switching losses are concentrated regardless of the direction of the power. The main contribution of this paper resides in the proposed dead-band compensation mechanism. This dead-band compensation is crucial when addressing ZCS modulation and improves the overall efficiency of the full operating range. As a co-benefit, the proposed mix of semiconductor technologies can result in an effective cost reduction compared with a full SiC IBDC. The paper contains a detailed explanation of the implemented modulation applied to an IBDC. The paper contributes to deploy a theoretical implementation where the effect of parasitic capacitance on semiconductors during the dead-band is analytically considered. The presented method results are validated on a laboratory set-up using a 20 kW - 40 kHz hybrid Si-SiC IBDC.

A prototype bi-directional isolated DC-DC converter with 3.6 kW output power, operating at the maximum frequency of 400 kHz, using GaN-HEMTs was developed and evaluated. Typical circuits for bidirectional isolated DC-DC converters are the LLC resonant converter and the dual active bridge (DAB), both of which have the disadvantage of low efficiency at light loads. In this study, loss reduction by zero-voltage switching using the excitation current of the transformer and natural commutation was performed for DAB. As a result of the efficiency comparison between LLC resonant converter and DAB under the same components and input/output conditions, higher efficiency was obtained in DAB under most conditions. The maximum efficiency was 98.6%.

<p><span>The research work proposes a Gallium Nitride (GaN) based dual active bridge (DAB) converter for electric vehicle (EV) charging applications. The wide bandgap semiconductor device, GaN is implemented in the DAB topology of an Isolated Bidirectional DC-DC converter (IBDC). GaN-based DC-DC converters lead to higher efficiency, smaller size, faster charging, and reduced heat generation improving the overall performance of the EV charging system. The performance characteristics of GaN based DAB converter is analyzed both in simulation and hardware for EV charging application. The same analysis is extended to a Si based DAB converter and comparative results are presented. A 14.25 kW GaN based DAB and <br /> 10.5 kW Si based DAB is designed and evaluated using LTspice XVII software and a scaled-down prototype of 0.612 kW GaN based DAB and 0.25 kW Si based DAB is presented for experimental validation. Result analysis under similar operating conditions indicated an improvement of 36% more output power transfer on the GaN based DAB over the traditional Si based DAB. The developed prototype showcased improved levels of power, voltage, and current under same operating conditions. The power transmission in the developed DAB based IBDC topology is controlled using the single-phase-shift (SPS) control strategy.</span></p>

Solid-state transformer (SST) is a developing technology that is widely used in distribution systems for integrating renewable energy sources. Out of the numerous topologies available for SST, a Dual Active Bridge (DAB) converter based SST is the most commonly utilized one due to its control efficiency. DABs are isolated bidirectional DC DC converters (IBDC) which has soft switching capabilities, high power density, bidirectional power flow, galvanic isolation, etc. When the SST is connected to the grid, it requires a monolithic platform for the fast controlling, reliable operation and protection enhancement of the converters of the SST. In this paper, Xilinx System Generator (XSG) platform is used for the rapid prototyping of the SST that directly generates the HDL code for the target control board. The different control strategies of DAB such as Single Phase Shift (SPS), Extended Phase Shift (EPS) and Dual Phase Shift (DPS) are studied and compared with XSG which is developed in MATLAB simulation platform. In this work, XSG based Hardware in the Loop (HIL) simulation of the three control strategies is done in XSG, and the results are verified.

With the development of power electronics technology, compared with AC and DC power distribution network, the energy router has tremendous potential for its obvious advantage and make a significant contribution to the energy internet. Firstly the key devices of the energy router is discussed and the network framework of the small energy router in user layer is proposed. Then the research status of isolated bidirectional DC/DC converter(IBDC) is reviewed systematically. Subsequently the circuit topology of dual-active-bridge(DAB) and resonant full-bridge are analyzed in detail, the corresponding control strategies are studied and the characteristics of above mentioned converters are also summarized. Finally the key issues of the power electronic transformer(PET) or solid state transformer(SST) to be solved urgently are also pointed for energy router application. Conclusions will provide essential theoretical and practical basis for industry application of future energy router.

This research thoroughly examines control strategies for the isolated dual active bridge (DAB) isolated bidirectional dc-dc converter (IBDC), introducing an advanced switching method designed to optimize performance. The proposed method’s effectiveness is validated through a comprehensive evaluation involving theoretical analysis, simulations, and experimental testing. This article addresses the limitations of conventional phase shift techniques, notably their issues with circulating currents and current stress, by developing a technique offering a 3° flexibility, thereby significantly reducing circulating currents. This reduction leads to lower power losses and substantially improves efficiency beyond what traditional phase shift controls achieve. In addition, the research pioneers a method for enabling smoother switching within the DAB system, similar to DPS, effectively widening the zero voltage switching (ZVS) range. This innovative control strategy’s practical application and superiority are decisively proven through experimental validation on a 2.4 kW DAB prototype, showcasing its potential to redefine bidirectional dc-dc converter efficiency.

In this paper, the basic principle and control strategy of a 110V/3kW two-stage dual-active-bridge-based battery energy storage power conversion system are introduced. The parameter design of its control loop is provided in detail. Meanwhile, a small-signal impedance model of power conversion system is established to analyze the stability under the condition of weak grid. In the end, the simulation and experimental results are given to confirm the feasibility of designed control loop and the correctness of proposed impedance model.

This work demonstrates a method to build and operate hybrid battery systems, which can serve the need for Long-Duration Energy Storage (LDES). LDES systems have to provide energy at different timescales to compensate for the intermittency of renewable resources, supply peak power, support black-start, and serve loads with variable power factor. It is cost prohibitive to use a single battery technology to provide both high power and energy services. Therefore, integration of hybrid technologies is essential. Here, a scalable and flexible method is proposed to build such a hybrid system, where DC-DC converters are integrated between battery packs and a DC-AC converter. The DC-DC converters implement battery-specific charging/discharging protocols, and the DC-AC converter establishes the DC bus voltage and synchronizes with the grid. A hardware-software testbed has been built for operating Lead-Acid battery cells by integrating a commercial DC-AC power conversion system (PCS) with a custom-built Dual Active Bridge (DAB) DC-DC converter. The results validate this method's effectiveness in controlling hybrid battery strings and preventing battery degradation. The authors plan to make the software and hardware design available to the power electronics and battery community, and add support for other DC-DC converter topologies and battery technologies.