• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.95-100
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• 2022

In this paper, a power loss analysis technique of a high-frequency transformer of a bidirectional DAB (Dual Active Bridge) converter is reported. To miniaturize the transformer of the dual active bridge converter, a resonant inductor was designed with an air gap included low-coupled rate state core to combine leakage inductor with the resonant inductor which is required for soft-switching. In this paper, leakage inductance and magnetizing inductance, core material, type of winding and winding method are included in the dual active bridge transformer loss analysis process to enable optimal design at the initial design stage. Transformer loss analysis for dual active bridge with a switching frequency of 200 kHz and maximum output of 5 kW was executed, and elements necessary for design based on the number of turns on the primary side were graphed while maintaining the transformer turns ratio and window area. In particular, it was possible to determine the optimal number of turns and thickness of the transformer, and ultimately, the total loss of the transformer could be estimated.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.310-311
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• 2018

본 논문은 배터리팩 테스터에 적용되는 3상 전류원 기반의 Dual Active Converter(DAB)의 효율 향상 기법에 대해 제안한다. 기존의 1, 2차 측 스위치의 위상차를 통해 컨버터의 출력을 제어하는 경우, 변압기 1, 2차 측 전압 차이에 의해 스위치에 순환 전류가 커지고 도통 손실이 증가하는 문제가 있다. 본 논문에서는 3상 전류원 기반의 DAB 컨버터의 1, 2차 측 스위치의 위상과 시비율을 동시에 제어함으로써 스위치 도통 손실을 저감할 수 있는 방식을 제안한다. 제안하는 제어방법은 시뮬레이션 및 실험을 통해 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.82-89
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• 2021

This study proposes a DAB two-stage series structure with insulated bidirectional DC-DC converter for two-way power transfer between the renewable energy of high voltages (1 kV and above). The proposed circuit transforms the existing DAB converter into a two-stage series structure to reduce the pressure in the switch. The problem of power imbalance occurring in the design of the DAB converter second-stage series is improved by applying the cell balancing method circuit and the common mode coupled inductor using an external flying capacitor instead of reflecting the existing improvement measures, voltage balance control, and inductor current control. In addition, a no-load supercharging sequence is proposed in high voltages and high-speed switching by using the fixed duty output method. This study presents the analysis results through the structure of the proposed circuit, the principle of improving the power imbalance problem, and simulations. Prototypes were manufactured to meet the specifications of input/output voltage of 1700 V, maximum load of 65 kW, and switching frequency of 51kHz, and the validity of the topology was verified using the experimental results and efficiency data.

• Journal of Power Electronics
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• v.18 no.1
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• pp.45-55
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• 2018

It is usually difficult for dual-active-bridge (DAB) dc-dc converters to operate efficiently at light loads. This paper presents an in-depth analysis of a DAB with triple-phase-shift (TPS) control under the light load condition to overcome this problem. A kind of operating mode which is suitable for light load operation is analyzed in this paper. First, an analysis of the zero-voltage-switching (ZVS) constraints for the DAB converter has been carried out and a reasonable dead-band setting method has been proposed. Secondly, the basic operating characteristics of the converter are analyzed. Third, under the condition of satisfying the ZVS constraints, both the reactive power and the root mean square (RMS) value of the current are simultaneously minimized and a particle swarm optimization (PSO) algorithm is employed to analyze and solve this optimization problem. Lastly, both simulations and experiments are carried out to verify the effectiveness of the proposed method. The experimental results show that the converter can effectively achieve ZVS and improved efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.336-344
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• 2017

This paper presents the three-port DC-DC converter modeling and controller design procedure, which is part of the solid-state transformer (SST) to interface medium voltage AC grid to bipolar DC distribution network. Due to the high primary side DC link voltage, the proposed converter employs the three-level neutral point clamped (NPC) topology at the primary side and 2-two level half bridge circuits for each DC distribution network. For the proposed converter particular structure, this paper conducts modeling the three winding transformer and the power transfer between each port. A decoupling method is adopted to simplify the power transfer model. The voltage controller design procedure is presented. In addition, the output current sharing controller is employed for current balancing between the parallel-connected secondary output ports. The proposed circuit and controller performance are verified by experimental results using a 30 kW prototype SST system.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.498-506
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• 2022

This study proposes a design methodology for bidirectional, series-resonant, dual-active bridge (SRDAB) converters. The circuit parameters of the SRDAB converters are designed by considering the output power and efficiency of the converter. The proposed method can be used to design a high-power, high-efficiency SRDAB converter. A voltage controller is employed to manipulate the output voltage of the converter, and the controller gains are selected using the transfer function and frequency response of the controller. Simulation results show that the output power of the designed SRDAB converter is 2 kW per converter module as designed. In addition, the performance of the voltage controller is evaluated using the simulation and experimental results. The output voltage follows the reference voltage within 10 ms under the step change of the reference command. The output voltage also follows the reference voltage under the step load change. The efficiency of the designed SRDAB converter is 95.6%.

• Journal of Power Electronics
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• v.19 no.2
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• pp.431-442
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• 2019

This paper proposes a unified high-frequency bipolar buck-boost (UHFBB) control strategy for a dual-active-bridge (DAB), which is derived from the classical buck and boost DC/DC converter. It can achieve optimized current stress of the switches and soft switching in wider range. The UHFBB control strategy includes multi-control-variables, which can be achieved according to an algorithm derived from an accurate mathematical model. The design method for the parameters, such as the transformer turns ratio and the inductance, are shown. The current stress of the switches is analyzed for selecting an optimal inductor. The analysis is verified by the experimental results within a 500W prototype.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.385-386
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• 2020

최근, 에너지저장장치를 활용하여 태양광-ESS 하이브리드 시스템이 도입되고 있다. 태양광-ESS 하이브리드 시스템은 구성방식에 따라 다양한 전력변환장치를 활용한다. 그중 DAB 컨버터는 절연형이며, 양방향 전력전달이 가능하므로 스위칭 기법, 토폴로지 개발 등 연구가 활발히 진행되고 있다. 본 논문에서는 태양광-ESS 하이브리드 시스템에 적용되는 대표적인 벅-부스트 컨버터와 DAB 컨버터에 대해 리뷰한다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.6-7
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• 2019

본 논문에서는 양방향 전력 전송을 가능케 해주는 Dual-active-bridge (DAB) 컨버터에서, 고주파 변압기 대신 무선 전력 전송 코일을 이용한 시스템을 제안한다. 기존의 DAB 컨버터에서 주로 사용되는 고주파 변압기는 Core-type 또는 shell-type으로 만들어지며, 1차 측 권선과 2차 측 권선이 자기적으로 강하게 결합되어 높은 전력 전달 효율을 가지도록 만든다. 이런 DAB 컨버터를 직/병렬 연결해 MV-DC to LV-DC로 변환하는 반도체 변압기 등을 구성할 때, 1차 측 권선과 2차 측 권선 사이에는 절연 문제와 1차 측 스위치 회로와 2차 측 스위치 회로, 그리고 고주파 변압기가 각각 따로 절연해야 하는 문제점이 있다. 본 논문에서 제안하는 DAB 컨버터는 1차 측과 2차 측이 수 cm 이격되어 있어 1차 측과 2차 측 사이의 자기적 결합이 굉장히 약하다. 따라서 1차 측과 2차 측 코일을 커패시터로 공진시켜 전력을 전달하는 무선전력전송(Loosely Coupled Inductive Wireless Power Transfer)을 이용한다. 무선전력전송의 공진 topology는 Parallel-Series로 선택했고, impedance transformation 회로를 추가했다.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1650-1660
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• 2016

This paper proposes a compensator to eliminate the DC bias of inductor current. This method utilizes an average-current sensing technique to detect the DC bias of inductor current. A small signal model of the DC bias compensation loop is derived. It is shown that the DC bias has a one-pole relationship with the duty cycle of the left side leading lag. By considering the pole produced by the dual active bridge (DAB) converter and the pole produced by the average-current sensing module, a one-pole-one-zero digital compensation method is given. By using this method, the DC bias is eliminated, and the stability of the compensation loop is ensured. The performance of the proposed compensator is verified with a 1.2-kW DAB converter prototype.