The dual-active-bridge (DAB) converters inherit favorite features including zero-voltage switching (ZVS) capability, wide voltage range, and natural bidirectional power flow. Facing different applications and high market requirements, conventional DAB topologies with various modulations are gradually inadequate, so topological modifications are emerged in the literature to deal with these situations. Based on their characteristics of these modified DAB topologies, in this article, we provide a comprehensive review and classification, and the methodology to modify DAB topologies is proposed. First, basic cells including input/output types, active bridges, transformers, and auxiliary high-frequency networks are introduced. Next, by combining these cells flexibly, modified DAB converters are derived, and they are classified in terms of structural characteristics and discussed in detail. Finally, the characteristics, merits, and demerits of the modified DAB converters are concluded. Evolvement history, future trends, and the derivation of new topologies are also analyzed. This article aims to present a clear picture of the general law and framework of the modified DAB topologies and give the inspiration to derive new DAB topologies to address specific requirements.

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.

This letter addresses the parameters design problem for converter-based virtual synchronous generators (VSGs), which is crucial for stable operation. Existing methods only consider performance optimization based on the small-signal model or qualitative analysis of large-signal stability. However, it remains to be elucidated on how to quantitatively design virtual inertia and damping to ensure transient stability. In this letter, sufficient conditions of VSG control parameters for transient synchronization stability are derived using Lyapunov direct method. Then, a systematic feasible parameters region is obtained that satisfies grid-code-based transient stability and rate-of-change-of-frequency (RoCoF) requirement under large disturbances. As a result, this letter provides a practical reference for control parameters design and engineering application of VSG. Control-hardware-in-the-loop (CHIL) experiment validates the designed control parameters region.

The active power-decoupling (APD) method is an effective solution to handle the inherent double-line frequency ripple power in single-phase power systems. It removes the bulky passive devices and facilitates the improvement of the system power density and even the reliability. This article provides a comprehensive review of the prior-art and state-of-the-art control strategies in APD. They are categorized into four groups according to the basic control ideas of “power balance,” “harmonic suppression,” “volt-second balance/charge balance,” and “virtual impedance.” And the specific control strategies under each control idea are discussed and compared. The pros and cons of each control idea are also presented . Finally, this article draws a sketch of the global trends in APD control.

The low coupling coefficient between the transmitter and receiver is the major constraint of a wireless power transfer (WPT) system. Although some approaches, such as increasing the quality factor and achieving precise impedance matching, can reduce the adverse impacts of the low coupling coefficient and improve the system performance, high leakage magnetic flux between the transmitter and receiver remains a problem. With the increase in transfer distance and the misalignment between the transmitter and receiver, the increasing leakage magnetic flux of nondirectional fields degrades the WPT system performance. This paper proposes an active field orientation method to shape the magnetic flux so as to minimize the leakage flux. The amplitude and phase angle of the magnetizing current are controlled, and a coil structure for minimizing the coupling among the transmitters and generating a three-dimensional magnetic field is proposed. This method realizes three-dimension full-range field orientation with adjustable magnitude and direction of B-field at an arbitrary point, and as a result the B-field is concentrated with reduced leakage magnetic flux. The proposed field orientation shaping technique is verified by theoretical analysis, simulation, and experimental results.

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.