Dual Active Bridge Converter Research Articles

ANALYSIS OF A HYBRID CURRENT MODULATED DUAL ACTIVE BRIDGE PHOTOVOLTAIC DC/DC CONVERTER FOR UNIFORM IRRADIATION CONDITIONS

The energy of Photovoltaic (PV) modules can be connected to DC grid with high step-up ratio power electronics converters. Generally, two-stage isolated boost-based converters are used for this purpose. However, these types of converters consist of a high number of semiconductors which must withstand high voltage levels, and they utilize input inductance which has high value and large magnetic core size. To solve these problems, single-stage conversion-based Hybrid Current Modulated (HCM) isolated Dual Active Bridge (DAB) converter is proposed in the literature. However, this converter is designed for considering partial shading (PS), and PS rarely occurs in PV farms. In this study, the design methodology of DAB PV DC/DC converter is given for uniform irradiation (UI) conditions that is more suitable for PV farms. In addition, UI and PS designs of HCM DAB PV DC/DC converter are compared to each other. Analyses show that UI-based design has 3.88% smaller RMS2 current, 3.56% smaller peak current and 2.35% smaller core size than the PS-based design. Hence, UI-based design can be more efficient, cheaper, and smaller in size.

Spacecraft Medium Voltage Direct-Current (MVDC) Power and Propulsion System

This paper introduces a medium voltage direct-current (MVDC) system for large spacecraft megawatt-scale (MW) power and propulsion systems intended for interplanetary transport, including missions to the Moon and Mars. The proposed MVDC system includes: (i) A nuclear electric propulsion (NEP) that powers a permanent magnet (PM) generator whose output is rectified and connected to the MVDC bus. (ii) A solar photovoltaic (PV) source that is interfaced to the MVDC bus using a unidirectional boost DC-DC converter. (iii) A backup battery energy storage system (BESS) that connects to the MVDC bus using a bidirectional DC-DC boost converter. (iv) A dual active bridge (DAB) converter that controls the power to the spacecraft’s electric thruster. The NEP serves as the main power source for the spacecraft’s electric thruster, while the solar PV and BESS are intended to provide power for the payload and spacecraft’s low-voltage power system. The paper will (i) provide a review of the spacecraft MVDC power and prolusion system highlighting state-of-the-art main components, (ii) address the control of boost converters for the PV and BESS sources and the DAB converter for the thruster, and (iii) propose an uncertainty and disturbance estimator (UDE) concept based on current control algorithms to mitigate MVDC instability due to unpredictable factors and external disruptions. The proposed UDE can actively estimate and compensate for the system disturbance and uncertainty in real time, and thus, both the system tracking performance and robustness can be improved. Simulation studies have been conducted to substantiate the efficacy of the proposed schemes.

Variable Switching Frequency for ZVS over Wide Voltage Range in Dual Active Bridge

The Dual Active Bridge (DAB) converter is known for its advantageous characteristics, including bidirectionality, galvanic isolation, and soft-switching operation. However, achieving Zero Voltage Switching (ZVS) across the complete operation range is not guaranteed, particularly through a wide input–output voltage ratio. This paper explores the integration of the switching frequency as a control variable in the DAB converter to ensure ZVS operation across a wide voltage range, employing Single Phase Shift (SPS) modulation. The study evaluated the RMS and reactive currents under variable switching frequency, presenting the advantages of this approach. Moreover, it includes a design-oriented analysis of the ZVS limits and their relationship with the switching frequency, aiming to ensure ZVS at any operating point. Experimental results validated the theoretical analysis, while presenting the main advantages of variable switching frequency implementation.

Fractional order modelling and optimal control of dual active bridge converters

As the construction of new power systems centred around renewable energy gains traction, the installed capacity of new energy sources has experienced explosive growth. Research has shown that the actual external characteristics of inductors and capacitors in circuits exhibit fractional order characteristics. As a core device in dual active bridge converters, the non-integer order of inductors and capacitors has an important impact on their dynamic performance, frequency domain characteristics, and control system design. This paper conducts modelling and control research on dual active bridge converters based on fractional-order calculus theory. First, based on the definition of fractional-order calculus, according to the operating mode of the fractional-order dual active bridge converter and the characteristics of fractional-order components, The fractional-order state space average model was established, and the influence of the order of inductance and capacitance on the amplitude frequency characteristics, phase frequency characteristics and dynamic performance of the converter was analyzed. Secondly, the average model and circuit model were built on the MATLAB/Simulink simulation platform, and the simulation results under different fractional orders were compared. Finally, in order to further improve the control performance of the converter, a fractional-order P I λ control strategy is designed based on the established state space average model of the fractional-order dual active bridge converter and based on the transfer function from the control to the output of the fractional-order dual active bridge converter. The research results show that the fractional-order model can more accurately describe the actual characteristics of the converter. In addition, the fractional-order controller P I λ enables the fractional-order dual active bridge converter to obtain better robustness and improve the dynamic performance of the converter.

Composite Duty Modulation of Dual Active Bridge Converters to Minimize Output Voltage Ripples and Inductor RMS Currents

Composite Duty Modulation of Dual Active Bridge Converters to Minimize Output Voltage Ripples and Inductor RMS Currents

A Hybrid Data-Driven Power Loss Minimization Method of Dual-Active Bridge Converters

A Hybrid Data-Driven Power Loss Minimization Method of Dual-Active Bridge Converters

Small-signal modeling comparison of dual active bridge converter

The dual active bridge (DAB) converter is a versatile DC-DC converter, which has AC components in the high-frequency transformer within the converter topology as well as DC components at the input and output sides. These AC components are constructed from infinite sinusoids of multiples of the converter's switching frequency. Different approaches have been proposed to model the DAB converter. The generalized averaging modeling (GAM) includes only the first order harmonic of the inductor current with the DC components of the input and output voltages and currents. For better model accuracy, harmonic-domain models have been employed, where the model includes all the harmonics of all the model state variables up to an arbitrary harmonic index. While the harmonic model provides a systematic approach to include the harmonics, this increases the model complexity. To avoid this complexity, the flexible harmonic model is used where harmonics can be selected per each state variable without needing to be in successive order. The aforementioned modeling approaches have been implemented on the DAB converter. This paper aims to compare between the dynamic performance of GAM and the harmonic modeling approaches under different disturbances, where the GAM approach provided a simple model with acceptable results that can be used for controller design, while the LTP model provided a more complex model with better accuracy that is suitable for harmonic studies. The models have been validated and compared using simulations executed on MATLAB /Simulink environment.

Improved Adaptive Network-Based Fuzzy Inference System Approach for Power Flow Analysis in Interconnected DC Microgrid

High-performance power conversion needs are becoming more and more important for microgrid applications. In actuality, many contemporary DC distribution systems use isolated bidirectional dc-dc converters. Hence, in this paper, an Improved Adaptive Network-based Fuzzy Inference System (IANFIS)is developed to control the output power of the components and reduce the variation among the consumption and generation of the power while managing a constant DC bus voltage. This work proposes a power management control strategy that ensures the power balance of a stand-alone DC microgrid where DAB converters link the battery energy storage (BES) unit and the renewable energy source (RES). The generation side, or photovoltaic (PV) system and BES, is coupled to the storage systems and renewable energy sources. Furthermore, a DC microgrid is connected to the load demand. The load demand is compensated with the help of the storage and generation systems with the help of a dual active bridge converter. The DAB is connected with the dual DC microgrid system for managing power flow among the two DC microgrids. This dual active bridge converter is utilized to balance the power among Dual DC microgrids. The proposed methodology is developed to manage the power among generation and load demand management. The proposed method is evaluated on a dual active bridge converter connected microgrid system with the components of PV and BESS respectively.

Adaptive Extended State Observer for the Dual Active Bridge Converters.

The DC-DC dual active bridge (DAB) converter has become one of the essential units for bidirectional energy distribution and connecting various renewable energy sources. When it comes to regulating the converter's output voltage, integrating an extended state observer (ESO) offers the advantage of eliminating the need for a current sensor, thereby reducing system costs. The ESO with a high observer bandwidth tends to acquire a faster system convergence and greater tracking accuracy. However, its disturbance suppression performance will become poor compared to the ESO with a low observer bandwidth. Based on this, the adaptive ESO (AESO) is proposed in this study to make a compromise between tracking performance and disturbance suppression. When the system is subjected to a high voltage error, the observer bandwidth will increase to improve the tracking performance and decrease to enhance the disturbance suppression. In order to demonstrate that the proposed method is effective, it is compared to the ESO with a fixed observer bandwidth and the improved model-based phase-shift control (MPSC). These comparisons are made through simulation and experimental results in various operation scenarios.

Second‐harmonic current reduction of dual active bridge with triple‐phase shift in two‐stage single‐phase inverter system

AbstractThis article proposes a method to effectively suppress second‐harmonic current (SHC) of dual active bridge (DAB) converter, which adopts the triple‐phase shift (TPS) modulation strategy, in two‐stage single‐phase inverter system. Load current feedforward control with twice the output voltage frequency notch filter inserted is introduced to ensure the dynamic response performance. The averaged model of the system is established to analyse the influence of output impedance of front‐end DAB converter on SHC from the perspective of impedance. The proposed method does not need to consider the accuracy of the intermediate bus capacitance. Finally, an experimental prototype was established to verify the correctness and effectiveness of the proposed SHC reduction method.

AI-Based Design With Data Trimming for Hybrid Phase Shift Modulation for Minimum-Current-Stress Dual Active Bridge Converter

Dual active bridge (DAB) topology has been recognized as the key circuit for the next generation of high-frequency-link power conversion systems. In order to realize desired operating performance, DAB modulation strategies need to be selected carefully. Different modulation strategies have been considered and combined into a hybrid one, which is able to fully optimize performance. However, to develop a hybrid modulation strategy, the conventional methods including harmonic model and piecewise model have difficulty in balancing modeling accuracy and manpower burden. Although recent data-driven modulation approaches can automate the design process, the accuracy of data-driven models decreases nontrivially with the existence of outliers and without sufficient data. Hence, to alleviate human-dependence and improve modeling accuracy, this paper proposes an AI-based design with data trimming (AI-DT) for hybrid phase shift modulation. Two two-degree-of-freedom modulation strategies are considered for the sake of optimal current stress performance. AI-DT firstly adopts the one-class support vector machine (SVM) to exclude outliers. Second, the state-of-the-art extreme gradient boosting (XGBoost), which is insensitive to training data size, is adopted to build data-driven current stress models for the DAB converter. After that, differential evolution (DE) algorithm helps to choose modulation strategy and optimize modulation parameters for optimal current stress. Generally, the proposed AI-DT is developed in an automated fashion, which largely relieves manual computational complexity while exhibiting satisfactory modulation accuracy. The effectiveness of the proposed AI-DT approach has been experimentally verified with a 1kW hardware prototype, realizing optimal current stress under full operating conditions with more than 96.5% as peak efficiency.

Optimal Dual-Side Asymmetric Modulation Strategy for Dual Active Bridge Converter to Improve Efficiency Over a Wide Voltage Range

Optimal Dual-Side Asymmetric Modulation Strategy for Dual Active Bridge Converter to Improve Efficiency Over a Wide Voltage Range

Second harmonic reduction strategy for two‐stage inverter energy storage system with dual active bridge converter based on virtual LC series resonant circuit

SummaryThe second harmonic current (SHC) caused by the instantaneous power of downstream inverter will seriously deteriorate the performance of two‐stage inverter and shorten the life of energy storage device, which narrows the application prospect of two‐stage inverter energy storage system (TSIESS). To reduce the SHC in TSIESS, this paper proposes a strategy of virtual LC series resonant circuit with notch filter (NF‐VLCSRC). This strategy utilizes the virtual impedance technology to achieve the function of a LC series resonant circuit (LCSRC) paralleled to the intermediate DC bus capacitor of the TSIESS, so the output impedance of the DAB converter can become larger than the impedance of the DC bus capacitor at twice fundamental frequency and thus the SHC in the front‐end DAB converter can be reduced effectively without power loss problem caused by the internal resistance of the actual LCSRC. Then, in order to facilitate the implementation and avoid interference of parameter mismatches on system performance, the NF is adopted to realize the VLCSRC strategy based on the frequency characteristics of the introduced virtual impedance. Theory analysis and experimental results are presented to illustrate the effectiveness of the proposed control techniques.

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.

Phase Shift Angle Segmentation Modulation for Soft-Switching Medium-Voltage DAB Converter With Series-Connected SiC MOSFETs

Medium voltage (MV) dual active bridge (DAB) converter with series-connected SiC MOSFETs (S-SiC) is a promising solution for high power density isolated DC/DC converter. To improve the voltage sharing and reliability of S-SiC, relatively large snubber capacitors are connected in parallel with S-SiC. But this narrows the zero voltage switching-on (ZVS-on) range of S-SiC, and even reduces the efficiency and reliability of the entire converter. Adding non-optimized internal phase shift angle to the low-voltage (LV) side switching unit will result in excessive circulating power and still lead to low efficiency. In this paper, the phase-shift angle segmentation modulation (PSSM) scheme featuring soft-switching performance is proposed for a MV DAB converter with S-SiC. The proposed modulation scheme is based on a detailed derivation of the ZVS-on range and operation modes. Then, the changes in operation characteristics and the advantages brought by the proposed modulation scheme are analyzed in terms of transmission power, state transition process, switching current and device losses. Moreover, the introduced modes and ZVS-on characteristics are verified on the 4kV/1kV 200kW experimental prototype. As a result, the converter’s loss can be decreased by up to 75% under light load, validating the efficiency advantage of the proposed modulation scheme.

Dynamic Model of AC–AC Dual Active Bridge Converter Using the Extended Generalized Average Modeling Framework

Dynamic Model of AC–AC Dual Active Bridge Converter Using the Extended Generalized Average Modeling Framework

A Semi-Implicit Parallel Leapfrog Solver With Half-Step Sampling Technique for FPGA-Based Real-Time HIL Simulation of Power Converters

Field Programmable Gate Array (FPGA) based Hardware-in-the-loop (HIL) simulation is an effective tool to verify the performance of physical controllers and shorten the development cycle of power converters. In HIL simulations, sampling accuracy is of concern and is desired to be improved by reducing the step size. However, due to the cost of computational time, the step size is hard to reduce indefinitely to meet the requirements for high switching frequency applications. To improve the sampling accuracy and simulation performance of HIL simulation, this paper proposes a semi-implicit parallel leapfrog (SPL) solver with half-step sampling technique. In this solver, the switches and the rest part of the system are implemented to be computed parallel when the switch leg model operates in continuous current mode. Besides, the solver is formulated in leapfrog format to reduce computational costs and to compute at half-step as a minimum step-size. With this format, the half-step sampling technique can be employed to increase the sampling rate by onefold, even in cases where it is challenging to reduce the simulation step size further. A dual active bridge converter case is implemented on the FPGA board with a 12.5-ns sampling step-size, retaining the simulation accuracy while switched at 400 kHz. To further verify the advantages, the results are compared with other HIL method and experimental results.

Analysis and Design of Independent DC Bus Structure Multiport Power Electronic Transformer Based on Maximum Power Transmission Capability of Low-Voltage DC Ports

Owing to the diverse connection configurations of dual active bridge converters, a multiplicity of low-voltage DC port structures are anticipated to emerge in the independent DC bus structure multiport power electronic transformer (IDBS-MPET). An inadequate low-voltage DC port structure exacerbates the power imbalance in IDBS-MPET, presenting a risk of overmodulation even when transmitting relatively low levels of power. To overcome this limitation, a design scheme of IDBS-MPET topology based on the maximum power transmission capability of the low-voltage DC ports is proposed in this paper. Three topology design rules are derived from the maximum power transmission capability results of more than 80 typical IDBS-MPET topologies. The symmetrical triple cross-phase connection structure, the symmetrical double cross-phase connection structure and the single-phase connection structure are sequentially identified as the three most optimal structures of low-voltage DC ports. By employing the proposed design methodology, each low-voltage DC port achieves its maximum power transfer capability relative to other configurations. The effectiveness of the proposed design scheme is validated by an optimal designed IDBS-MPET topology with six low-voltage DC ports.

Moving Discretized Control Set Model Predictive Control with Dominant Parameter Identification Strategy for Dual Active Bridge Converters

The dual active bridge (DAB) converter has grown significantly as one of the most important units for energy distribution, connecting various types of renewable energy sources with the DC microgrid. For controlling the DAB converter, moving discretized control set model predictive control (MDCS-MPC) is considered one of the most effective methods because of its advantages, such as high dynamic performance and multiobjective control. However, MDCS-MPC strongly depends on the accuracy of system parameters. Meanwhile, the system parameters can be changed due to temperature drift, manufacturing tolerance, age, and operating circumstances. As a result, the steady-state performance of the output voltage of MDCS-MPC is affected. Motivated by this, this paper proposes MDCS-MPC combined with the parameter identification technique to improve the steady-state performance of the output voltage of the DAB converter. Then, analysis of the percentage of the steady-state error of the output voltage is defined on six model parameters, and sensitivity analysis of two dominant parameters is chosen. After that, a straightforward least-squares analysis (LSA) technique is used to identify the two parameters online. The proposed method is verified through simulation in several different operating scenarios to verify its effectiveness.

Phase shift control of dual active bridge DC‐DC converter based on feedforward compensation and transient optimization strategy

SummaryIn the context of the dual active bridge (DAB) bidirectional DC‐DC converter using the traditional dual‐phase‐shift (DPS) control method, a transient DC bias occurs during power co‐direction and commutation conversion. This bias negatively impacts the converter's transient performance and can lead to harsh effects, such as hard switching problems, resulting in power loss and excessive current stress. In a closed‐loop control system, poor transient response may destroy the stability of the converter. In this paper, the transient‐optimized‐dual‐phase‐shift (TODPS) control strategy is proposed to eliminate the transient DC bias and to maintain soft switching during transient states. It reduces power loss, eliminates excessive current stress, and allows for smooth transitions between single‐phase‐shift (SPS) and DPS control strategies without introducing DC bias. A closed‐loop control system based on TODPS control is established with feed‐forward compensation to adjust the primary‐side current and modify transmission power. This adjustment enhances the transient performance of the DAB converter. The proposed strategy is versatile and applicable to various power conversion scenarios involving DAB converters. It enables quick switching of the magnitude and direction of the primary‐side current during transient states, resulting in a smooth transient effect without noticeable overshoot or oscillation. The experiment results verify the effectiveness of the proposed transient optimization strategy.