Dual Active Bridge Converter Research Articles

RMS Current Minimization in a SiC-Based Dual Active Bridge Converter Using Triple-Phase-Shift Modulation

This paper proposes an optimization approach targeting RMS current minimization in a dual active bridge (DAB) converter controlled by triple-phase-shift modulation. The proposed technique overcomes the drawbacks in the existing optimization solutions, namely, the high complexity of the time-domain optimization and low accuracy of the fundamental harmonic minimization. A finite-component harmonic model is employed in the optimization approach to calculate the current harmonic values in the converter. The total RMS current is approximated as the summation of dominant harmonics using the harmonic model. A numerical assessment technique is also proposed in this research that guarantees the accuracy of the adopted harmonic model. The proposed method ensures that the harmonic approximation error is less than a certain level over the operating range. The converter's optimal parameters are calculated through a standard nonlinear optimization procedure. The results are verified in the PLECS simulation environment and experimentally validated on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5\ kW$</tex-math></inline-formula> DAB converter. The prototype input and output voltage ranges are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$600\ V - 800\ V$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$200\ V - 450\ V$</tex-math></inline-formula> , respectively.

Closed-Form ZVS Boundaries for Three-Phase M-Level-to-N-Level DAB Converters With Different Winding Configurations

One of the essential characteristics of a three-phase dual-active-bridge (DAB) DC-DC converter is its inherent zero-voltage switching (ZVS) capability during the turn-on of the switches. This paper provides closed-form equations that identify the ZVS boundaries for an M-level-to-N-level DAB converter, where M and N can be any natural numbers. It is shown that the derived ZVS boundaries can be used for different converter topologies, including but not limited to: two-level full-bridge converter, three-level neutral-point-clamped converter, T-type converter, transition arm converter, modular multilevel converter, and controlled-transition-bridge converter. The effect of different winding configurations of the medium frequency transformer—YY, Y <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta \Delta$</tex-math></inline-formula> —is also considered in the study. Additionally, easy-to-implement simplified ZVS boundaries are provided, and the effects of the different number of levels, transition times, and dead times on the ZVS operation are quantified. An important result shown is that the converters with the YY and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta \Delta$</tex-math></inline-formula> windings lose ZVS at partial loads as soon as the transition time increases from zero, whereas the ones with the Y <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> configuration retain ZVS at partial loads and DC ratios close to unity, without any advanced modulation techniques. The derived analytical models are validated with MATLAB simulations and experiments.

Review of Dual-Active-Bridge Converters With Topological Modifications

Dual active bridge (DAB) converters inherit favorite features including zero voltage switching (ZVS) capability, wide voltage range, and natural bidirectional power flow. Facing different applications and high market requirements, conventional DAB topologies with various modulations are gradually inadequate, so topological modifications are emerged in literature to deal with these situations. Based on their characteristics of these modified DAB topologies, this paper provides a comprehensive review and classification, and the methodology to modify DAB topologies is proposed. Firstly, basic cells including input/output types, active bridges, transformers, and auxiliary high-frequency networks are introduced. Next, by combining these cells flexibly, modified DAB converters are derived, and they are classified in terms of structural characteristics and discussed in detail. Finally, the characteristics, merits, and demerits of the modified DAB converters are concluded. Evolvement history, future trends, and derivation of new topologies are also analyzed. This paper aims to present a clear picture of the general law and framework of the modified DAB topologies and give the inspiration to derive new DAB topologies to address specific requirements.

Optimal Components Selection for a DAB Model of CHB Converter

This paper proposes a sizing procedure for the cascaded H-bridge (CHB) converters integrating the battery energy storage system at the submodule level through a dual active bridge (DAB) converter. The suggested methodology considers different parameters, such as the adopted modulation strategies and the topology of the DAB converter employed. Three possible DAB configurations are considered: the one using only full-bridges (for both sides), the one using only half-bridges (for both sides) or a mixed configuration using half-bridge on one side and full-bridge on the other side. After determining the system parameters, the solution capable of reaching the required efficiency target at the minimum cost is obtained. The cost analysis and the efficiency evaluation are carried out considering a dataset containing almost 1000 semiconductor devices whose datasheets have been taken from the manufacturers' websites. The procedure has been developed in the framework of a collaboration with NHOA Energy and its effectiveness is demonstrated by sizing a 1 MW-CHB converter combined with energy storage systems at 11 kV.

Loss Balance and Transient DC-Bias Suppression Strategies in Three-Level DAB Converters Modulated With Five DoFs

In the three-level (3 L) neutral-point-clamped (NPC) dual-active-bridge (DAB) converter, both sides of the converter can adapt to higher DC bus voltage, and more control degrees of freedom (DoFs) are provided compared to the conventional DAB converter. In the PWM generating technique with 5 DoFs, loss imbalance may develop in inner switches and outer switches because the leading or lagging arm is introduced, affecting system reliability. In addition, the transient DC-bias issue may also arise in the 3L-NPC-DAB converter modulated with 5 DoFs, leading to the transformer saturation. In this paper, two strategies are proposed to suppress the loss imbalance and the transient DC-bias in the current stress and magnetizing branches. It is also general and applicable for SPS, DPS, and TPS modulations. Furthermore, the loss balance strategy and DC-bias suppression strategy are applied in the PWM generation technique simultaneously without additional components. With the proposed solutions, the loss imbalances of inner switches and outer switches are suppressed and DC-bias in the integral of voltages on both sides of the 3L-NPC-DAB converter is abolished. The effectiveness of the proposed strategies is validated by a series of experiments conducted under varying situations.

Solid-State Transformer Based on Naturally Cell Balanced Series Resonant Converter With Cascaded H-Bridge Cells Switched at Grid Frequency

This paper proposes a closed-loop control architecture for a three-stage (MV, isolated DC/DC, LV) Solid State Transformer (SST) system and a modulation technique for the MV stage that shows better performance over existing solutions in terms of control simplicity, semiconductor loss, and cost. A simple and effective closed-loop control architecture is proposed for the entire SST system using the natural cell balancing ability of the Series Resonant Dual Active Bridge (SRDAB) converters in the DC/DC stage. In order to reduce semiconductor losses and cost, Si IGBT and SiC MOSFET devices are introduced properly in the MV stage of the SST power architecture, and the proposed modulation technique switches these devices appropriately according to their merits. The proposed modulation scheme ensures more than 50% semiconductor loss reduction in the MV stage. A circulating logic is proposed to achieve equal power sharing among cells in the MV stage and associated components. Detailed dynamic modeling, closed-loop control architecture, and modulation scheme are discussed in this paper. The proposed control technique and modulation scheme are verified experimentally in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{600}~V/100~V, \text{5}~kW$</tex-math></inline-formula> SST system.

Modulation-Based DC-Bias Elimination of DAB Converter Under Second Harmonic

As a basic unit of solid-state transformer (SST), the single-phase system composed of H-bridge and dual-active-bridge (DAB) is becoming an exciting topic for its high-efficiency, flexible power flow. However, the inherent second-harmonic power brings dc-link voltage ripple and phase shift oscillation, especially for the back-to-back systems with bilateral harmonics. In this paper, the behavior of DAB's high-frequency link under second harmonic is modeled and described, revealing the inevitable dc-bias and current-stress increase. A modulation-based dc-bias eliminating strategy is presented, which uses two sawtooth carriers to generate a transitional period without any calculations. To reduce magnetic material's waste, a second-harmonic correction to transformer design is proposed. Moreover, the optimal inductance for single-phase shift (SPS) with minimal current stress and full-range ZVS is obtained. These strategies enhance the ripple immunity of DAB, enabling the reduction of dc-link capacitance. Comprehensive simulations and experiments are performed to validate the accuracy and effectiveness of these optimizations.

Model Predictive Controlled Dual Active Bridge Converter with Efficiency Optimization and Fast Dynamic Response

Model Predictive Controlled Dual Active Bridge Converter with Efficiency Optimization and Fast Dynamic Response

Impact of Parameter Mismatch on Three-Phase Dual-Active-Bridge Converters

Three-phase dual active bridge converters (DAB3) are a widely used topology in battery charging applications thanks to their numerous advantages, such as bidirectional power flow, galvanic isolation, low output current ripple, and inherent soft-switching. In such applications, three single-phase transformers are commonly employed as the AC-link to simplify manufacturing and reduce costs. These transformers’ leakage inductance can be utilized instead of the external leakage inductance to achieve high power density. However, the assumption of uniformity in these inductances is not always accurate as they can vary significantly during fabrication. This study presents a comprehensive analysis of the impact of transformer leakage inductance variation, which can deviate by up to 24% from the desired value. The effects of this variation are investigated from different perspectives, including power transfer, soft-switching range, root-mean-square (RMS) current, and the temperature rise of the transformer winding. Although the power transfer and total copper loss of transformers are changed insignificantly even under highly mismatched leakage inductance, the currents and thermal distribution among phases are considerably impacted. Based on statistical probability, a maximum leakage inductance variation threshold of 10–15% compared to the desired value is recommended to ensure the maximum acceptable temperature rise among phases. Experimental results are presented to validate the analysis.

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.

Over-Current Mechanism and Suppression Strategy of DC Transformer in Multiterminal Interconnected Flexible DC Distribution Network

Direct current (dc) transformers are an important component of the multiterminal interconnected flexible dc distribution network. However, it is apt to suffer from the inrush current, which can trigger the shutdown protection and threaten the reliability of the system and equipment. In this article, a 2-MW dc transformer is developed for a T-connected star type multiterminal flexible dc distribution network, where the dual active bridge (DAB) converter is one of the important components. The design of the key parameters is also presented. Based on the steady-state model of the dc transformer, the overcurrent mechanism is elaborated and a suppression strategy of H-bridge temporary blocking and DAB not blocking is proposed, which can automatically clear the fault current. Simulations and practical engineering tests are conducted to verify the effectiveness and practicability of the proposed method, which provides engineering practical value.

Analytical and Normalized Equations to Implement the Optimized Triple Phase-Shift Modulation Strategy for DAB Converters

A fully normalized algorithm to implement the optimal triple-phase shift (TPS) modulation strategy of the dual active bridge converter is proposed in this paper. The algorithm evaluates three simple expressions that fit the optimal solutions obtained in recent works, which allows the algorithm to be implemented in real-time and valid for the whole operating range. As a result, the converter operates under zero voltage switching conditions and minimizes conduction losses. In addition, the algorithm considers the minimum current required to guarantee zero voltage switching condition that faces undesired dead-band of switching devices effect. The proposal achieves soft transition between any operation region and fast closed-loop response with no stability concern, presenting robustness under leakage inductance deviation. Finally, the algorithm presented in this paper is verified with a 4 kW experimental prototype. Experimental results show that the algorithm proposed can be evaluated with less than 2.8 μs and allows soft transition between any operation region to be achieved. Besides, fast closed-loop changes of 750 μs through all the operating ranges, keeping minimum RMS current under zero voltage switching, are shown.

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.

An MV-Connected Ultra-Fast Charging Station Based on MMC and Dual Active Bridge with Multiple dc Buses

The diffusion of electric vehicles will be strongly related to the capacity to charge them in short times. To do so, the necessity of widespread fast charging stations arises. However, their intermittent demand represents a challenging load for grid operators. In order to relieve their impact on the electrical grid operation, integrating storage systems in the charging stations represents a potential solution, although it complicates the overall system management. Moreover, standard converter architectures for the MV grid interface require the installation of bulky transformers and filters. In order to cope with the mentioned problems, this paper proposes an ultra-fast charging station topology based on a modular multilevel converter (MMC) structure and dual-active bridge (DAB) converters. Thanks to the multilevel converter properties, the proposed charging station can be directly interfaced with the MV grid without requiring transformers or filters. Additionally, exploiting the degree of freedom in the converter control system, such as circulating components, offers uneven power distribution among the converter submodules that can be managed. Along with the MMC control strategy, the article addresses a straightforward methodology to select the main parameters of the DAB converter as a function of the involved grid power and circulating power contributions, with the primary goal of obtaining a trade-off between internal balancing performances and a broad soft-switching region without incurring in converter oversizing. The effectiveness of the proposed charging station is finally discussed through numerical simulations, where its behavior during a power demand cycle is analyzed.

AI-aided power electronic converters automatic online real-time efficiency optimization method

Energy losses during the conversion and supply of electric power are considered a significant issue and cannot be estimated. Improvement in the efficiency of energy conversion systems is highly restricted because of their internal nonlinearity and complexity. Thus, inspired by the successful utilization of robotic chemists, we demonstrate a pioneering concept of artificial intelligence (AI)-aided automatic online real-time optimization of a power electronics converter using a dual active bridge (DAB) converter as an example. An optimal modulation strategy was obtained through repeated automatic exploration experiments on a practical DAB converter platform. Specifically, the DAB experimental platform operated autonomously around the clock for approximately 71 h. It performed 120,000 consecutive experiments (12,000 episodes) within a six-variable experimental space driven by a deep deterministic policy gradient (DDPG) algorithm. The proposed AI-aided automatic online real-time optimization method achieved significantly improved efficiency of power conversion and supply. Consequently, zero carbon emissions may be obtained in the future.

Grid Interactive Solar PV and Battery Operated Air Conditioning System: Energy Management and Power Quality Improvement

The drop in solar panel cost over past decade has accelerated the usage of solar photovoltaic (SPV) in various applications. In tropical countries, air conditioning unit is extensively used for cooling comfort. In this paper, PV generation is utilized with a battery energy storage (BES) for an air conditioner to reduce the impact of energy consumption from utility grid. Recently, air conditioning units are adopted with variable speed drive (VFD) that creates peaky nature of the input grid current due to the AC-DC conversion. The diode bridge rectifier (DBR) used for such conversion, does not allow bidirectional current flow. In this paper, considering such facts and taking the benefit of the VFD technology, an energy management methodology is proposed using PV array and BES to reduce the power consumption of air conditioning unit as well as it feeds excess PV generation to the grid with improved power quality. The DC power produced by the PV panel and BES is fed to DC bus of the VFD directly with the help of dual active bridge (DAB) converter, that eliminates DC-AC conversion stage. A voltage source converter (VSC) is interfaced as a front-end converter of VFD, to feed PV generation to the grid when air conditioner is not operating. This system is useful from multistory buildings to small consumers where the air conditioners are extensively used and PV array is installed. The concept of the system is validated by implementing in a prototype in the laboratory scale. The system is investigated with different possible scenarios. Under all test conditions, the THD of the grid current is found within the limits of the IEC 6100-3-2 standard.

Ripple Voltage Suppression of Dual Active Bridge Converter in Electric Locomotive Using H∞ Loop Shaping Control Method

The next-generation electric locomotive drive system has the problem of double grid frequency ripple voltage in the DC side of a single-phase PWM rectifier. In this paper, the intermediate stage dual-active-bridge DC-DC converter is studied, and an H∞ loop shaping ripple voltage suppression control strategy is proposed to restrain the harmonic voltage and optimize the dynamic and robust performance of the closed-loop system. Firstly, the mathematical model of the DAB closed-loop control system with fluctuating input voltage is established. Then, based on the H∞ loop shaping control theory, the dynamic performance, the ability of ripple voltage suppression, and the robust performance of the system are analyzed in the frequency domain. According to the results, a reasonable compensator is selected to reconstruct the magnitude frequency characteristic curve of the nominal system. After reconstruction, the solution of the robust stability margin of the corrected object is transformed into the H∞ robust control problem under the coprime factor uncertainty. The suboptimal H∞ robust controller is solved to obtain the best robustness boundary of the constructed system. Finally, the H∞ loop shaping ripple voltage suppression controller is obtained by combining the H∞ controller with the compensator. The experimental environment is set up in MATLAB-Simulink software. Compared with the traditional voltage loop control method and the input voltage feedforward control method, the dynamic performance of the proposed control strategy is slightly improved, and while within the allowable robust boundaries of the system, it has better ripple voltage suppression performance. When the system magnitude frequency curve is outside the tolerant robust stability margin, the ripple voltage suppression performance fails, but the harmonic content of output voltage is still far less than the other two control methods. The experiment results also prove the correctness of the theoretical analysis and that the proposed control method is effective and proper.

단상 멀티 레벨 인버터의 출력 전력 전향 보상

This study proposes a feedforward compensation method based on output power estimation for 2-stage single-phase multilevel inverter-based solid-state transformer. The proposed method consists of the output power estimation by phase reference of DAB (Dual Active Bridge) converter and feedforward the d-axis current reference of AFE (Active Front-End) converter. Feedback controller for AFE and DAB converters is designed based on small signal model of each converter for verifying the proposed method. Simulations and experimental results are provided to confirm the effectiveness of the proposed method.

An improvement of stability and dynamic response in hybrid AC-DC microgrids using optimal power control management

Microgrid topologies enable more effective use of renewable resources as well as the autonomous process. Microgrids are effective frameworks for managing dispersed assets such as renewable structures with small-scale distributed generator supplies. Smart grids are adaptable electricity networks that have arisen as a result of the introduction of new technologies and features. It is suggested that a three-terminal AC/DC hybrid microgrid with DC two and AC one terminal be used. A two dual active bridge (DAB) with cascaded H-bridge (CHB) converter with AC grid link-based interactions that connect isolated two DC buses are included in the suggested structure. To minimise the energy generation stages and power devices, the DAB converters are intrinsically linked to the CHB of DC rails based on the structure-specific requirements. To present the unnecessary grid currents and DC rail voltage issues exist by this revised structure topology by simply two power alteration stages, a better solution is suggested that employs zero-sequence voltage (ZSV) injection in the CHB converters. The impacts of managed settings on structure stability and dynamic responsiveness are investigated in order to reduce conflicts among ZSV injection by structure voltage/current regulation. This paper compares the performance of a PI and a PR for DC voltage regulation. A comparison of simulation results for both control approaches is provided. The major difficulty is to normalise the system model in order to identify the appropriate controller settings for robust control. The findings are confirmed and compared to the conventional regulator PI. The suggested 3-Φ AC current and DC rail voltage regulating approach's universal efficacy is proved by MATLAB/Simulink analytical model from the three and five-terminal hybrid AC/DC power structures.

고밀도 배터리 충방전 시스템을 위한 낮은 높이를 갖는 500W급 양방향 DC-DC 컨버터

This study proposes a new bidirectional low DC-DC converter without a fan with a low height of 25 mm for direct connection between a battery and a bidirectional low DC-DC converter(BLDC). To implement the proposed BLDC, dual active bridge(DAB) converter and two interleaving buck converter are adopted. For BLDC with low height and high efficiency, the transformer of the DAB converter is separated into two series on the primary side and two parallel structures on the secondary side. Inputs and outputs are connected in parallel and interleaving control is applied in two interleaving buck converters. Finally, double heat sink structure is adopted for high heat dissipation performance. A prototype of 500 W with an input voltage of 650 V and an output voltage of 1–5 V is manufactured to verify the performance of operation, efficiency, and temperature in steady and transient states.