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This study proposes an estimation method of flux density in high‐frequency transformers of three‐phase dual‐active‐bridge transformers. The steady‐state analysis shows that the flux in the converter is different in Buck and Boost modes and depending on load and voltage gain condition. From that, a closed‐form formula is proposed to estimate the flux swing in the core. Unlike the conventional estimation technique, the proposed one represents the flux as a function of input and output voltages and the phase shift value. Finite element analysis confirms that the proposed formula can predict the flux with less than 4% error. The proposed formula can also help to improve the prediction of temperature profile of the transformers with a high accuracy of less than 1 degree Celsius in the mid‐ to high‐power range as validated in experiments. The proposed flux estimation method can be used in designing the converter or in predicting the converter behaviour under critical conditions such as load changing or starting, and so forth, to help protect the transformers from saturation or DC bias.
Duy‐Dinh Nguyen; Takuya Goto; Kazuto Yukita; Akinori Katou; Shinji Yoshida. A flux estimation method for three‐phase dual‐active‐bridge DC/DC converters. IET Power Electronics 2021, 14, 1102 -1110.
AMA StyleDuy‐Dinh Nguyen, Takuya Goto, Kazuto Yukita, Akinori Katou, Shinji Yoshida. A flux estimation method for three‐phase dual‐active‐bridge DC/DC converters. IET Power Electronics. 2021; 14 (6):1102-1110.
Chicago/Turabian StyleDuy‐Dinh Nguyen; Takuya Goto; Kazuto Yukita; Akinori Katou; Shinji Yoshida. 2021. "A flux estimation method for three‐phase dual‐active‐bridge DC/DC converters." IET Power Electronics 14, no. 6: 1102-1110.
In this paper, design and optimization method of a three-phase dual-active-bridge DC/DC converter is discussed. Three single phase transformers connected in star-star configuration were designed with large leakage inductance aiming to eliminate the need for external inductors. Switching frequency, peak flux density, number of turns, number of layers, etc., were optimized using non-linear programming technique for minimizing the overall converter loss. Experimental results on a 10 kW prototype show that the optimized converter can operate efficiently an efficacy of up to 98.65% and a low-temperature rise of less than 70 degrees Celsius on both transformers and semiconductor devices.
Duy-Dinh Nguyen; Ngoc-Tam Bui; Kazuto Yukita. Design and Optimization of Three-Phase Dual-Active-Bridge Converters for Electric Vehicle Charging Stations. Energies 2019, 13, 150 .
AMA StyleDuy-Dinh Nguyen, Ngoc-Tam Bui, Kazuto Yukita. Design and Optimization of Three-Phase Dual-Active-Bridge Converters for Electric Vehicle Charging Stations. Energies. 2019; 13 (1):150.
Chicago/Turabian StyleDuy-Dinh Nguyen; Ngoc-Tam Bui; Kazuto Yukita. 2019. "Design and Optimization of Three-Phase Dual-Active-Bridge Converters for Electric Vehicle Charging Stations." Energies 13, no. 1: 150.
In Dual-Active-Bridge converter control system, high frequency terminal current is usually measured then fed-back to the current mode controller. However, the measurement requires wide bandwidth sensors, fast and precise operational amplifier, and high sampling rate Analog to Digital conversion. This paper proposes a Proportional Integral Observer to estimate such the current to eliminate the need of current sensors. A combined feedforward-feedback control system is then developed to enhance the system dynamics and to regulate the output voltage. The control system needs only the information of terminal voltages. Simulation and experiment results show that the observer performs fast and accurately with acceptable observation error; and the output voltage is well regulated regardless of load changes.
Duy-Dinh Nguyen; Dinh-Hoa Nguyen; Minh C. Ta; Goro Fujita. Sensorless Feedforward Current Control of Dual-Active-Bridge DC/DC Converter for Micro-Grid Applications. IFAC-PapersOnLine 2018, 51, 333 -338.
AMA StyleDuy-Dinh Nguyen, Dinh-Hoa Nguyen, Minh C. Ta, Goro Fujita. Sensorless Feedforward Current Control of Dual-Active-Bridge DC/DC Converter for Micro-Grid Applications. IFAC-PapersOnLine. 2018; 51 (28):333-338.
Chicago/Turabian StyleDuy-Dinh Nguyen; Dinh-Hoa Nguyen; Minh C. Ta; Goro Fujita. 2018. "Sensorless Feedforward Current Control of Dual-Active-Bridge DC/DC Converter for Micro-Grid Applications." IFAC-PapersOnLine 51, no. 28: 333-338.
When controlling a Dual-Active-Bridge (DAB) DC/DC converter, the high frequency terminal current is usually measured for use in the current feedback controller. In order to measure that current, a wide bandwidth sensor accompanied with high-speed amplifiers are required. Furthermore, a high Analog-to-Digital sampling rate is also necessary for sampling and processing the measured data. To avoid those expensive requirements, this paper proposes an alternative control method for the DAB converter. In the proposed method, the terminal current is estimated by a reduced-order proportional integral observer. A technique is also proposed to reduce the phase drift effect when the voltages at two terminals are not matched. Afterwards, a combined current feedforward—voltage feedback control system is developed to enhance the system dynamics and to regulate the output voltage. This control system needs only the information of the terminal voltages and no current sensor is required. Experimental results show that the observer can estimate the terminal current very quickly with the accuracy of more than 98% . In addition, the output voltage is well regulated with a fluctuation of less than ±2.6% and a settling time of less than 6.5 ms in the presence of a 30% load change.
Duy-Dinh Nguyen; Dinh-Hoa Nguyen; Toshihisa Funabashi; Goro Fujita. Sensorless Control of Dual-Active-Bridge Converter with Reduced-Order Proportional-Integral Observer. Energies 2018, 11, 931 .
AMA StyleDuy-Dinh Nguyen, Dinh-Hoa Nguyen, Toshihisa Funabashi, Goro Fujita. Sensorless Control of Dual-Active-Bridge Converter with Reduced-Order Proportional-Integral Observer. Energies. 2018; 11 (4):931.
Chicago/Turabian StyleDuy-Dinh Nguyen; Dinh-Hoa Nguyen; Toshihisa Funabashi; Goro Fujita. 2018. "Sensorless Control of Dual-Active-Bridge Converter with Reduced-Order Proportional-Integral Observer." Energies 11, no. 4: 931.
An observer-based control (OBC) strategy for dual-active-bridge converters is proposed in this paper. The target is not only to handle the active power transferring between two terminals, but also to regulate the phase difference between the primary voltage and current around specific minimum value. The value is chosen to reduce the conduction loss in the system. A reduced-order observer is developed to estimate the direct and quadrature components of the transmission current for use in a decoupled current control system. Since the dc terminal current is the only input of the observer, a low sampling frequency is enough to ensure an acceptable precision. Experiment results show that the proposed OBC strategy can help improve the dynamic performance compared with that when using a single loop voltage mode system. Furthermore, at the high power range, the efficiency obtained when employing the OBC method is improved by up to 7.2%.
Duy-Dinh Nguyen; Goro Fujita; Quang Bui-Dang; Minh Cao Ta. Reduced-Order Observer-Based Control System for Dual-Active-Bridge DC/DC Converter. IEEE Transactions on Industry Applications 2018, 54, 3426 -3439.
AMA StyleDuy-Dinh Nguyen, Goro Fujita, Quang Bui-Dang, Minh Cao Ta. Reduced-Order Observer-Based Control System for Dual-Active-Bridge DC/DC Converter. IEEE Transactions on Industry Applications. 2018; 54 (4):3426-3439.
Chicago/Turabian StyleDuy-Dinh Nguyen; Goro Fujita; Quang Bui-Dang; Minh Cao Ta. 2018. "Reduced-Order Observer-Based Control System for Dual-Active-Bridge DC/DC Converter." IEEE Transactions on Industry Applications 54, no. 4: 3426-3439.