Dual active bridge (DAB) converters are widely studied for applications requiring isolation, bidirectional power flow and high efficiency. To solve the problem of limited zero voltage switching (ZVS) range and achieve seamless transition for extended-phase-shift (EPS) control, the magnetizing current is utilized and an optimized control law is proposed in this article. With the injection of magnetizing current, the two ZVS regions under EPS control will be creatively intersected with a large region, instead of disconnected or just intersected at a particular point as in previous studies. The ZVS model considering switch junction capacitors, ZVS region analysis with magnetizing current injection and power transfer characteristics are analyzed. Based on these analyses, the optimized EPS control is proposed to achieve full load range ZVS, low root-mean-square current and maximum transmission power capability. A 250 kHz, 500 W GaN-based DAB prototype is built to verify the effectiveness of the proposed solution.

Dual-active-bridge (DAB) converter is an attractive topology to be used as a dc transformer (DCT) in the dc power distribution system. Because the voltage gain for dc transformer is relatively fixed, single-phase-shift (SPS) control is popularly adopted for the DAB converter to achieve simple power control. Aiming at increasing the light load efficiency of high-frequency DAB converter under SPS control, this letter proposes a concept to achieve full load range zero-voltage-switching (ZVS) with minimum rms current in certain voltage variation range. In the proposed method, the added magnetizing inductance creates the possibility to achieve ZVS for all power switches. The voltage gain of the converter is specially controlled by turns ratio, which is no longer the conventional unity voltage gain condition. The key parameters optimization, including the turns ratio, magnetizing inductance, and leakage inductance of the transformer, is introduced based on ZVS and current stress analysis. A 250 kHz, 400/48 V, 1000 W GaN-based DAB prototype is built, which shows performance improvements at light load.

For the high-power Li-Ion battery (LIB) Formation and Grading System using multi-stage conversion structure, bidirectional isolated DC-DC converter with high input voltage and large output current is needed to achieve isolation and relatively fixed voltage conversion gain. This paper proposes a modulation strategy and modifies the topology to achieve naturally bidirectional power transfer, automatic power sharing and power limitation for an Input-series-output-parallel (ISOP) LLC-DCX converter. Firstly, an active Pulse Width Modulation (PWM) strategy is proposed to avoid synchronous rectifier (SR) sensing and to achieve the nature bidirectional power flow for each sub-module. The resonant current always keeps discontinuous, and the conversion gain can keep constant if ignoring the conduction resistance. Secondly, clamping diodes are added in the conventional LLC converter to limit the inrush current during start-up, and to achieve constant power limitation under over load condition. Thirdly, with the proposed modulation, the power sharing of two-module ISOP LLC converter is analyzed and compared with the conventional ISOP LLC converter. Finally, experiments based on an 8kW (output:15V/533A) prototype composed of two-module ISOP LLC converter are conducted to verify the effectiveness of the proposed solution.

The traditional method for achieving misalignment tolerance using two detuned circuits depends on output sampling and communication between the primary and secondary sides. This paper proposes a self-adaptive dual-channel detuned compensation topology to achieve a stable output for wireless charging of autonomous underwater vehicles (AUVs). In the low coupling coefficient interval, power is transferred through both channels; in the high coupling coefficient interval, power is transferred through only one channel. The mode switching process occurs naturally without additional switches or control. Two sets of arc-shaped coils are employed as the two channels, forming dual arc-shaped coil sets, without cross-coupling between them. Due to the symmetrical magnetic couplers, the mutual inductances of the two channels respond similarly to both rotational and axial misalignment. A 1.6-kW experimental prototype for the AUV wireless charging is built to validate the feasibility of the proposal. The output voltage fluctuation of the system is 8% within the coupling coefficient interval of [0.2, 0.6]. The system can still maintain over 89% transmission efficiency in the worst case.

Dynamic wireless power transfer (DWPT) for electrical vehicles (EVs) is a promising technology that can alleviate mileage anxiety and address onboard battery capacity limitations. However, there are power fluctuation and interoperability problems in DWPT systems. In order to solve these two issues, this letter proposes a decoupling self-adaptive two-pole interoperable receiver. The receiver coils are decoupled by partial overlapping. During the EV movement, the receiver coil can automatically change its polarity according to the mutual inductance variation. In this way, the secondary-side rectifier presents a series or parallel connection and produces a smooth equivalent mutual inductance fluctuation within the moving range, thus achieving a smooth output. Meanwhile, the proposed receiver can be tolerant with the unipolar and bipolar transmitter coils, capable of outputting the same power level and high transmission efficiency. The experimental results validate the effectiveness of the proposed DWPT system.

The unipolar and bipolar coils are two most common coil structures used in inductive power transfer systems. However, they are decoupled from each other when fully aligned, indicating that they are not interoperable with each other. In order to solve the interoperability problem, an interoperable transmitter composed of two adjacent unipolar coils and a three-switch dual-output inverter is proposed in this letter. It can achieve compatibility with unipolar or bipolar coils through circuit configuration by alternating the current directions with efficient wireless power transmission. Two different operating modes are presented, and the mathematical models are established. An experimental prototype is established. Besides, the anti-offset has been tested. The calculated and experimental results have revealed that the proposed system can effectively improve interoperability and has great potential for development.