Dual Active Bridge DC-DC Research Articles

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.

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.

Comparison and Validation of Five Modulation Strategies for a Dual Active Bridge Converter

This paper addresses the comparison and validation of different modulations for an isolated dc-dc dual active bridge converter (DAB), namely, Duty-Cycle Modulation, Single Phase Shift (SPS), Dual Phase Shift (DPS), Extended Phase Shift (EPS) and Triple Phase Shift (TPS). Given the DAB’s applicability in a wide variety of power electronics branches, several control strategies are being studied to improve its efficiency, by mitigating circulating currents and reactive power. Regardless of the chosen architecture, appropriate modulations must be adopted, assessing which one presents the better cost-benefit ratio. This simulation-based analysis aims to investigate the DAB performance when controlled by the above-mentioned modulations and operating with a nominal power of 3.6 kW. Thus, simulation results show that only SPS, DPS, and TPS are considered suitable, while Duty-Cycle Modulation has time limitations during power transfer and EPS is more appropriate for dynamic power applications.

Design and Development of Bidirectional DC-DC Dual Active Bridge Converter for Energy Storage Systems

The ever-increasing demand for renewable energy resources as compared to conventional means of energy generation has resulted in a growing demand for more efficient power storage systems and applications. However, this necessitates the use of different converters that must be employed to achieve efficient voltage conversions right from the generation stage to the point power is stored in the battery banks. To achieve efficient conversions of the voltage levels, Bidirectional DC-DC Dual-Active-Bridge (DAB) converters can be employed. Accordingly, this research work involves use of a closed-loop PI controller for controlling the outputs of a DC-DC converter and compensating for the load disturbances. The Simulink-derived results indicate the input & output characteristics of the converter to achieve the design of a controller that is capable of providing significant tracking reference command without undergoing steady-state error, thereby offering a fast transient response. Hence, by maximizing the performance of the converter, the controller resolves the issues identified in the output current. The system was also implemented on a 400W laboratory experimental model with a view to additionally validate its performance effectiveness. As a whole, a DAB system was successfully designed, simulated, implemented and analyzed for employing in various energy storage applications

Integral sliding mode based direct power control of isolated DC‐DC converter for improved voltage regulation

AbstractThis article presents an isolated bidirectional DC‐DC dual active bridge (DAB) converter with an integral sliding mode‐based direct power control (SM‐DPC). Maintaining the dc‐link stability and obtaining a robust control for the converter during sudden load change is a significant challenge. The sliding mode control is well known for its robustness, stability, and tracking performance. The sliding surface based on output voltage error is selected, while the proposed method utilizes the equivalent control approach to generate the power reference for the DAB converter. The direct power control provides an easy control method for the DAB converter as the output voltage depends on the transmitted power, governed by the phase shift angle of two H‐bridges of the converter. The proposed method enhances the steady‐state performance and renders a fast transient response under load change and input voltage variation. Moreover, the method avoids complicated converter modeling and utilizes the voltage dynamic equation and power transfer equation for the controller design. The controller performance and effectiveness are validated with experimental results for a 2‐kW DAB converter.

Comparison of First- and Second-Order Sliding-Mode Controllers for a DC-DC Dual Active Bridge

This paper compares four sliding-mode control strategies for a dual active bridge. The proposed control algorithms define different switching functions resulting in first-and second-order controllers, and using both discontinuous and continuous sliding-mode algorithms. The paper details the design stage and includes simulation and experimental tests to better compare the performance for each control scheme.

Control of a DC-DC Dual Active Bridge Converter in DC Microgrids Applications

In this paper, a control strategy for an isolated DCDC dual active bridge converter to adapt different voltage levels in a DC microgrid is proposed. The control strategy allows regulating the output voltage while maintaining in zero the mean value of the current in the high frequency transformer. The system is represented with a linearized version of its generalized average model and the controller is designed using classical techniques. The performance of the proposal is validated with simulations and experimental results.

Sliding mode and current observer‐based direct power control of dual active bridge converter with constant power load

This article presents a bidirectional isolated DC-DC dual active bridge (DAB) converter, with an improved control strategy under constant power load (CPL) conditions. Major applications of DAB are in solid-state transformers (SSTs), energy storage systems, dc-microgrid, and electric vehicle, where it feeds other converters, which act as a CPLs. CPLs have negative impedance characteristics, thereby, have a destabilizing effect and impact the dynamics and stability of power converters feeding them. Maintaining the dc-link stability and obtaining a robust control with enhanced dynamic performance is a significant challenge. This paper proposes a sliding mode control method for DAB feeding CPL in its output dc-link. A sliding mode controller is designed to employ direct power control and maintain a constant output voltage in dc-link for various loading conditions. Additionally, to remove the output current sensor, an output current observer is proposed for improving the reliability and decreasing the cost. The proposed method improves the transient performance, with robust control over parameter mismatch when CPL is connected to the dc-link. The transient performance and output voltage regulation with the proposed control technique are simulated with a 3 kW DAB converter in MATLAB/Simulink environment. Furthermore, the same proposed control scheme is validated experimentally with various loading conditions.

Dual Active Bridge (DAB) DC-DC converter for multilevel propulsion converters for electrical multiple units (EMU)

Semiconductor power devices made from silicon carbide (SiC) reached a level of technology enabling their widespread use in power converters. Two different approaches to implementation of modern traction converters in electric multiple units (EMU) have been presented in recent years: (i) 3.3-kV SiC MOSFET-based three-level PWM inverter with regenerative braking and (ii) 6.5-kV IGBT-based fourquadrant power electronic traction transformer (PETT). The former has successfully reached optimized dimensions and efficiency but still requires a bulky line frequency transformer for multisystem applications. The latter characterizes inherent galvanic isolation from AC traction, which is realized by cascaded system of power electronic cells containing medium frequency transformers (MFT). The downsizing of the 6.5-kV IGBT-based cells is, however, problematic. The present paper proposes a different approach, that involves the use of a fast switching 1.2-kV SiC MOSFETS. The SiC-based PETT proposed in the paper is dedicated first for the DC traction. For multi-system application the input voltage of the proposed PETT can be adjusted using weight-optimized adjusting autotransformer. Thanks to utilization of fast-switching SiCbased power modules the weight and size of the power electronic cells can be optimized in a convenient way.

DC-DC Dual Active Bridge 컨버터의 소신호 모델링 및 제어기 설계에 관한 연구

DC-DC Dual Active Bridge 컨버터의 소신호 모델링 및 제어기 설계에 관한 연구

Closed-Loop Control of DC–DC Dual-Active-Bridge Converters Driving Single-Phase Inverters

A solid-state transformer (SST) is a high-frequency power electronic converter that is used as a distribution power transformer. A common three-stage configuration of an SST consists of ac-dc rectifier, isolated dc-dc dual-active-bridge (DAB) converter, and dc-ac inverter. This study addresses the controller design issue for a dc-dc DAB converter when driving a regulated single-phase dc-ac inverter. Since the switching frequency of the inverter stage is much higher than that of the DAB stage, the single-phase inverter is modeled as a double-line-frequency (e.g., 120 Hz) current sink. The effect of 120-Hz current by the single-phase inverter is studied. The limitation of a PI-controller, low gain at 120 Hz, is investigated. Two methods are proposed to improve the regulation of the output voltage of DAB converters. The first one uses a bandstop filter and feedforward, while the second method uses an additional proportional-resonant controller in the feedback loop. Theoretical analysis, simulation, and experiment results are provided.

Generalized Average Modeling of Dual Active Bridge DC–DC Converter

Full-order continuous-time average modeling and dynamic analysis of bidirectional dc-dc dual active bridge (DAB) converters are studied. The transformer current in DAB converter is purely ac, making continuous-time modeling difficult. The proposed full-order continuous-time average model uses the dc terms and first order terms of transformer current and capacitor voltage as state variables, resulting in a third-order model, if capacitor equivalent series resistance (ESR) is not considered, and a sixth-order model if ESR is considered. A control-to-output-voltage transfer function is derived for DAB converters. Experimental results confirm that the proposed model correctly predicts the small-signal frequency response and an even more accurate prediction can be obtained if capacitor ESR is taken into account.

Dual Active Bridge Modulation with Complete Zero Voltage Switching Taking Resonant Transitions into Account

The paper proposes an optimized modulation scheme for the Dual Active Bridge (DAB) DC-DC converter topology, ensuring complete Zero Voltage Switching (ZVS) over the whole operating range. At first, ZVS limits for the modulation scheme in use are evaluated, taking the effect of resonant commutations into account. A strategy to achieve ZVS over the whole operating area is then proposed. A simple procedure to analytically calculate the switching pattern is presented, achieving high conversion efficiency without using complex loss models. Performance of the proposed control system is evaluated by actual measurements on a 2 kW DAB prototype, showing that complete ZVS is obtained over the whole operating range of the converter, resulting in high conversion efficiency even in the case of light load and buck/boost ratio considerably different from unity.