Dual Active Bridge DC-DC Converter Research Articles

Circulating power flow restricted operation of the isolated bi-directional dual-active bridge DC-DC converter for battery charging applications

This paper presents the Non-Circulating Power Flow (NCPF) enabled Dual Active Bridge (DAB) converter controller strategy. The proposed DAB controller eliminates the non-circulating power flow for all the four conventional modulation algorithms, i.e., Single Phase Shift (SPS), Extended Phase Shift (EPS), Dual Phase Shift (DPS) and Triple Phase Shift (TPS) modulation schemes. This leads to lesser current stress and power loss across the DAB converter switches due to reduced peak inverse current. The proposed controller strategy finds various applications, such as in a Solid-State Transformer (SST) enabled microgrid, or for Electric Vehicle (EV) Energy Storage Unit (ESU: battery, supercapacitor) integrations, etc. The proposed NCPF operation reduces battery (and supercapacitor) current stress by upto 71.8 %, and improves operative environment, thus fostering its health and lifecycle. In NCPF mode, if the rating of installed switches (current and voltage ratings) remains unchanged, its power transfer capability is marginally reduced by mere 10.0 %. In addition to this, the operating range (i.e., controlling range of phase shift (Φ) and modulation index (m)) remains unaffected. This paper summarizes the DAB NCPF operation in restricted power flow mode as a function of Φ and m through 3-D and 4-D graphs. Finally, working of NCPF DAB is tested via both simulation and hardware platforms. Comparative results are shown for conventional and proposed modulation schemes on hardware platform, to showcase the elimination of circulating current in both forward and reverse DAB operating modes. It is inferred that proposed controller is worthy of real-world implementations.

Design and Implementation of Single-Phase Grid-Connected Low-Voltage Battery Inverter for Residential Applications

Integrating residential energy storage and solar photovoltaic power generation into low-voltage distribution networks is a pathway to energy self-sufficiency. This paper elaborates on designing and implementing a 3 kW single-phase grid-connected battery inverter to integrate a 51.2-V lithium iron phosphate battery pack with a 220 V 50 Hz grid. The prototyped inverter consists of an LCL-filtered voltage source converter (VSC) and a dual active bridge (DAB) DC-DC converter, both operated at a switching frequency of 20 kHz. The VSC adopted a fast DC bus voltage control strategy with a unified current harmonic mitigation. Meanwhile, the DAB DC-DC converter employed a proportional-integral regulator to control the average battery current with a dynamic DC offset mitigation of the medium-frequency transformer’s currents embedded in the single-phase shift modulation scheme. The control schemes of the two converters were implemented on a 32-bit TMS320F280049C microcontroller in the same interrupt service routine. This work presents a synchronization technique between the switching signal generation of the two converters and the sampling of analog signals for the control system. The prototyped inverter had an efficiency better than 90% and a total harmonic distortion in the grid current smaller than 1.5% at the battery power of ±1.5 kW.

Minimum current stress control strategy for three degree of freedom three-phase dual active bridge DC-DC converter

Compared to single-phase dual active bridge (1p-DAB) DC-DC converters, three-phase dual active bridge (3p-DAB) DC-DC converters have advantages such as high single machine power, high power density, small filtering capacitance, and are more suitable for high-voltage situations. Therefore, they have good application prospects in DC transmission and industrial high-power DC-DC converters. However, under traditional single-phase shift (SPS) control, especially in the low power range, there is a large reactive current and severe soft switch loss. This article adopts an asymmetric modulation strategy for its larger reactive power, which reduces its reactive power in the low power range with more degrees of freedom and improves the efficiency of power transmission. Taking current stress as the optimization objective, the KKT algorithm is used to solve, and the corresponding analytical solution is ultimately obtained. Finally, a simulation is built by using MATLAB software to verify the feasibility of the proposed solution.

Full power range DAB unified ZVS control strategy based on low current RMS

Inductive current RMS and soft switching are important performance indexes of dual active bridge DC-DC converter (DAB). This paper proposes a new optimal control strategy for the soft switching range based on the optimization of the effective value of the inductor current. This control strategy restricts the inductor current during switch action, ensuring a significant extension of the soft switching range across the entire power range, reducing switch losses, and achieving the accurate effective value of current, thereby further enhancing the efficiency of the DAB converter. Meanwhile, a new modulation method is proposed to achieve thermal balance between bridge arms. Finally, a simulation model is built and verified using Matlab.

Soft-switching dual active bridge converter-based bidirectional on-board charger for electric vehicles under vehicle-to-grid and grid-to-vehicle control optimization

Electric vehicles (EVs) are rapidly replacing conventional fuel vehicles, offering powerful, emission-free performance. This paper introduces an innovative three-phase bidirectional charger for grid-to-vehicle (G2V) and vehicle-to-grid (V2G) applications, strengthening the connection between EVs and the power grid. The charger employs a two-stage power conversion approach with advanced converters and a simplified dq-based charging control strategy. An efficient AC-DC converter facilitates smooth transitions between modes, responding to grid directives for active and reactive power. A soft-switching dual active bridge (SS-DAB) DC-DC converter optimally interfaces with the EV battery pack, while dual active LCL filters suppress harmonics, enhancing system performance. Simulated results confirm the charger’s effectiveness in a 3.5-kW prototype using MATLAB/Simulink. The proposed SS-DAB converter-based bidirectional on-board charger introduces a groundbreaking unified Voltage Source Converter (VSC) control approach, enabling efficient power transfer in both vehicle-to-grid (V2G) and grid-to-vehicle (G2V) modes. This innovation ensures rapid dynamic response, exceptional steady-state performance, and robustness against grid demand changes, optimizing EV integration.

Improved Dual Active Bridge DC–DC Converter With Symmetric Bipolar Output by Utilizing a Switched-Capacitor Circuit for Bipolar DC Distribution System

The bipolar dc distribution system is a promising solution due to its advantages in efficiency and reliability, but there are also challenges of pole voltage imbalance. By using a simple switched-capacitor circuit, this paper presents a semi-dual active bridge converter with symmetrical bipolar output characteristics. The converter is capable of single-stage power conversion, offering the advantages of low cost and high-power conversion efficiency. Moreover, the symmetrical bipolar output voltage can be achieved without an additional voltage balancer and feedback control under unbalanced load conditions, which reduces system cost and control system complexity. In addition, the proposed converter also has a significant advantage over existing solutions in terms of the number of semiconductor devices and magnetic components. A detailed analysis of the proposed converter is presented, including the operation principle, steady-state performance, soft-switching performance, voltage gain, voltage/current stresses, efficiency and loss analysis, and control method. Finally, a 1-kW prototype is developed and tested to verify the performance of the proposed converter.

Soft-switching dual Active Bridge Converter-based Bidirectional On-Board Charger for Electric Vehicles under Vehicle-to-Grid and Grid-to-Vehicle Control Optimization

Electric Vehicles (EVs) are rapidly replacing conventional fuel vehicles, offering powerful, emission-free performance. This paper introduces an innovative three-phase bidirectional charger for Grid-to-Vehicle (G2V) and Vehicle-to-Grid (V2G) applications, strengthening the connection between EVs and the power grid. The charger employs a two-stage power conversion approach with advanced converters and a simplified dq-based charging control strategy. An efficient AC-DC converter facilitates smooth transitions between modes, responding to grid directives for active and reactive power. A Soft Switching Dual Active Bridge (SS-DAB) DC-DC converter optimally interfaces with the EV battery pack, while dual active LCL filters suppress harmonics, enhancing system performance. Simulated results confirm the charger’s effectiveness in a 3.5kW prototype using MATLAB/Simulink.

Offset Current Modulation Technique for Wide ZVS Range in Dual Active Bridge (DAB) DC-DC Converter

Offset Current Modulation Technique for Wide ZVS Range in Dual Active Bridge (DAB) DC-DC Converter

Development of Dual Active Bridge DC-DC Converter to Achieve High Efficiency in Wide Voltage and Load Range and Application to V2H Systems

Development of Dual Active Bridge DC-DC Converter to Achieve High Efficiency in Wide Voltage and Load Range and Application to V2H Systems

Grid integrated multifunctional EV charging infrastructure with improved power quality

This paper presents a grid integrated multifunctional electric vehicle (EV) charging infrastructure to power the EV batteries and simultaneously improve grid power quality. The EV charger control function is designed to operate the charger in grid-to-vehicle (G2V), vehicle-to-grid (V2G), and proposed active-filtering-mode (AFM) operating modes. In AFM mode, the proposed self-tuning filter (STF) based control algorithm effectively compensates the grid current harmonic distortions arising from nonlinear charging station load. Furthermore, the charger controller uses STF to estimate the synchronizing voltage templates for reference current generation instead of conventional phase-locked-loop (PLL) and second-order generalized integrator (SOGI) to address the nonideal grid voltage conditions. The charger controller is designed to operate in AFM operating mode simultaneously with G2V and V2G operating modes. Furthermore, to achieve these multifunctional operations in a single charger, the power electronics circuitry of the charger is developed by using an AC/DC voltage source converter and a DC/DC dual active bridge (DAB) converter. The embedded isolation in the DAB converter ensures the safety of the EV batteries from the disturbance in the AC and DC side of the charger. Furthermore, a 3.6 kVA EV charger prototype is developed in the laboratory to show the effectiveness of the control techniques.

Mode analysis and fault-tolerant method of open-circuit fault for a three-level dual active bridge DC-DC converter

The three-level dual-active-bridge (TL-DAB) DC-DC converter is a promising dc-dc converter for high-voltage and high-power systems. Open-circuit faults on power switches are crucial issues for the TL-DAB dc-dc converters, resulting in various performance degradations such as dc bias and divided capacitor voltage imbalance. The mode analysis after fault is necessary for fault detection and fault-tolerant control. Subsequently, fault-tolerant control is essential to reduce or overcome these issues. In the proposed fault-tolerant method, when the primary side inner switch or the secondary side switch breaks down, the gate-driving signal of the complementary switch is recommended to block and the effects can be removed. Finally, experiment results demonstrate that the issues caused by open-circuit faults can be reduced significantly with the proposed fault-tolerant method.

Review of Modeling, Modulation, and Control Strategies for the Dual-Active-Bridge DC/DC Converter

This paper provides a comprehensive review of the existing research on the Dual Active Bridge (DAB) DC-DC converter, focusing on modeling methods, modulation strategies, optimization algorithms, and control methods. A comparative analysis of selected methods along with guidelines to assist engineers and researchers in their study of DAB is also presented. Firstly, a comprehensive review of modulation strategies for DAB is provided, ranging from classical phase-shift modulation to the popular asymmetric duty modulation. The intrinsic relationships among different modulation methods are summarized, and a comparison is made based on the difficulty of control and DAB operating characteristics. Secondly, the various modeling methods for DAB are described, including reduced-order modeling, generalized state-space averaging modeling, and discrete-time modeling methods. A comparison is made based on the suitability for different application scenarios, providing recommendations for the adoption of different modeling methods. Furthermore, a survey of optimization algorithms for modulation methods is presented, including classical algorithms, swarm intelligence optimization, and reinforcement learning algorithms. A number of criteria are proposed for different algorithms, and an analysis of the unresolved challenges and future prospects is provided. Finally, the advanced control methods for DAB are summarized based on control effectiveness and applicability. The article concludes with a summary and an outlook on future research directions is also provided.

Asymmetric Half-Frequency Modulation in DAB to Optimize the Conduction and Switching Losses in EV Charging Applications

Dual active bridge (DAB) DC-DC converters are used widely in electric vehicle (EV) charging systems with the advantage of high-power density, bidirectional power flow, and possibility of soft-switching. The Maximum converter efficiency of DAB-based EV chargers happens at unity voltage gain, while it degrades at the start of the charging cycle where the gain is lower. This paper presents a novel gate signal modulation method called asymmetric half-frequency modulation (AHFM) that modifies the duty ratio and switching frequency of the source bridge switches to achieve the higher converter efficiency at low gain operation. Generalized harmonic approximation (GHA) method is utilized to analyze the circuit operation with applied AHFM, and evaluation of zero voltage switching (ZVS) requirements is explained. Then, a loss optimization problem is developed with an objective to select the optimal set of phase shift control variables depending on the modulation method to minimize the sum of conduction and switching losses. Five modulation methods based on conventional modulation and proposed AHFM are compared in terms of resultant switching network efficiency at a wide gain/power range that gives an understanding of optimal method at a specific operating point. The proposed AHFM and loss optimization are applied to the EV battery charging profile to improve the converter efficiency during the whole charging cycle. A 1.1 kW-rated proof-of-concept DAB DC-DC converter has been developed to validate the performance of the proposed method.

Magnetizing Current Injection Based Push-Pull Dual Active Bridge Converter With Optimized Control to Achieve Full Load Range ZVS for the Distributed Generation System

To reduce greenhouse gas emissions, the distributed generation system is an approach worth investigating. With fewer switches, the push-pull circuits are suited for low-voltage and high-current applications, such as the distributed generation system. In this paper, a modified push-pull dual active bridge (PPDAB) dc-dc converter and its optimized control are proposed to achieve full load range zero voltage switching (ZVS). Considering the switch junction capacitors, the added current is injected by the magnetizing inductance to achieve full load range ZVS. Based on the RMS value of transformer current, the optimized control strategy is proposed to enhance the system efficiency with the precondition of achieving full load range ZVS of all switches. The working principles, ZVS region analysis, and design of key parameters are discussed in detail. Finally, the effectiveness of the proposed method for the PPDAB converter is verified by the results of a laboratory prototype.

Enhancing EV charger resilience with reinforcement learning aided control

This study aims to improve the performance of sustainable electric vehicle chargers in the face of unpblackictable/unpreventable disturbances. Over the past few years, Dual Active Bridge (DAB) DC-DC Converters are procuring substantial recognition for electric vehicle charging applications due to their superior characteristics such as higher power density, bidirectional mode of operation, and higher efficiency. Unexpected disturbances and fault scenarios at both source and load sides can deteriorate DAB converters’ performance. In this study, the performance of a single-phase shifted DAB converter is enhanced to achieve desiblack output current under several disturbance conditions for electric vehicle (EV) charging applications. A Reinforcement Learning (RL) based Deep Deterministic Policy Gradient (DDPG) algorithm is deployed to proactively tune control parameters when the DAB undergoes certain unexpected disturbances including short circuit faults at the source and battery sides. Results show that the RL-tuned PI controller improves the rate of current overshoot significantly compablack with the manually-tuned PI controller. The method and results are validated through simulations in MATLAB/Simulink environment.

Analysis of Common-Mode Noise and Design of a Reduced-Volume Concentric Choke for Dual Active Bridge dc–dc Converter With Integrated Magnetics

Dual active bridge (DAB) dc-dc converter with integrated transformer is explored in recent years due to its advantages of the low component count, high power density and high efficiency. Although the operational performance of the DAB converter is well reported, the common-mode (CM) noise with the integrated transformer is yet to be thoroughly analyzed. Hence, this paper presents a detailed analysis of the CM noise performance of the DAB converter employing integrated transformer. Moreover, the conventional CM chokes incorporated to mitigate the CM noise cause a deleterious impact on volume and power density of the converter. This paper proposes a concentric CM choke that occupies less volume compared to its equivalent conventional CM choke of the same CM impedance. The analysis and design guidelines for the proposed concentric CM choke are presented. The above-mentioned analyses of the integrated transformer and the concentric CM choke are experimentally validated on a DAB converter prototype.

Isolated Cascaded DAB DC-DC Converter to Boost Medium DC Voltage to HVDC

The offshore wind farms typically use ac system to collect power from each generator, with the voltage increased by means of high, heavy step-up transformers. DC collection grids have also recently been taken into consideration as solution to simplify and minimize the offshore windfarm platforms. DC collection grids offer an additional method to reduce complexity of offshore windfarms. However, to increase the DC voltage for HVDC transmission requires the development of high-power and high voltage converters, which presents a technical challenge. This research makes use of an isolated cascaded dual active bridge (DAB) DC-DC converter to boost medium DC voltage to HVDC. Isolated Cascaded DAB DC-DC Converters are connected in series on the output side and in parallel on the input side to obtain a high transformation ratio and high power. The bidirectional DAB DC-DC converters cab be designed with power densities in the variability of tens to hundreds of kilowatts, depending on the components used and the switching frequency at which the converters function most effectively. The input parallel output series (IPOS) topology, 225 kV HVDC can be generated from a 5 kV MVDC input by cascading DAB DC-DC up to 30 stages. This converter family is useful due to its scalability and flexibility, since the power and voltage ratings can be increased while still using the same cells. MATLAB Simulink simulations are performed and verified the elementary operating characteristics of the system.

Discrete Extended-Phase-Shift Control for Dual-Active-Bridge DC–DC Converter With Fast Dynamic Response

In this paper, a discrete extended-phase-shift (DEPS) control scheme is proposed to improve dynamic response of dual-active-bridge (DAB) dc-dc converter. The proposed DEPS control adjusts the transmission power of the DAB dc-dc converter by generating high and low power control pulses, which are preset to have discrete phase-shift ratios, rather than employing PWM control. Thus, it is simple and easy to implement in digital-signal processor or field-programmable gate array. Moreover, without error amplifier and corresponding compensation circuit, its dynamic response is fast and robust. Parameter design method considering the effect of equivalent resistance of the DAB dc-dc converter and dc-bias current elimination is also presented. Theoretical analyses, energy-balance-based iteration modeling and control performance of DEPS controlled DAB dc-dc converter are given, and they are verified by experiments on a 96V-48V, 50kHz (100kHz), 288 W DAB dc-dc converter.

High Efficiency Isolated 5-Level Dual Active DC–DC Converter Using Wide Band Gap Devices

In this paper a bidirectional isolated dc-dc converter is proposed for application in shipboard power systems. In this topology, an active 5-level T-type converter is used on the primary and secondary sides of a high-frequency transformer. The operation of the proposed converter is optimized based on minimizing power losses. For the optimization, the transformer core loss, reactive power, and rms current are considered. Wide band gap devices are used for minimization of semiconductor switching losses. A control method based on the Fourier series and decomposition theorem is proposed. The proposed converter features higher efficiency, fault tolerant capability and smaller filter size compared to the common dual active bridge dc-dc converters. To reduce voltage overshoot, a laminated dc-link is designed and a two-level turn-off method is used for operating frequencies around 75 kHz. Finally, the step-up and step-down operations of the proposed structure are verified through experiments.

High frequency isolated bidirectional dual active bridge DC-DC converters and its application to distributed energy systems: an overview

Among the DC-DC converters, an isolated bidirectional dual active bridge converter is a core circuit for high-frequency power converters in distributed energy system applications. These high-frequency power conversion systems attract academia and industry due to various advantages, such as high-power density, less weight, reduced noise, high efficiency, low cost and high reliability. First, the importance of power electronic converters in modern-day life is introduced. Second, a topological overview of voltage-fed and current-fed isolated bidirectional dual active bridge converters is presented with their importance in integrating hybrid power sources. Third, switching modes of isolated bidirectional DC-DC converters are also presented with a degree of freedom of control. Forth, performance evaluation of voltage-fed and current-fed isolated bidirectional converters has been presented with an example. Their suitability in integrating fuel cells and photovoltaics with energy storage systems in low to medium-power applications is presented.