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.

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.

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.

Reliable fault diagnosis and identification are essential for permanent magnet synchronous motor (PMSM) drive systems with high-reliability requirements. Since open-switch fault and output current sensor fault both affect the residual of output phase current, it is difficult to identify them apart from each other. Thus, this article proposes an open-switch fault and output current sensor fault diagnosis and identification method for the matrix converter (MC)-based PMSM drive system. The finite control set-model predictive control (FCS-MPC) method is applied in the MC-based PMSM drive system. The fault identification method is proposed based on the extracted different faulty features of the open-switch fault and the output current sensor fault. After the open-switch fault is separated from the current sensor fault, an error-voltage-based open-switch fault diagnosis strategy is applied to locate the faulty switch. Hardware-in-the-loop tests are carried out to verify the effectiveness of the proposed method.

This paper proposes a single-phase power factor correction (PFC) rectifier to achieve high power factor, wide output voltage range, and ripple power decoupling without using electrolytic capacitors. It consists of two parts: PFC circuit and output voltage regulation circuit. The load side is involved in both parts, which is different from the regular two-stage conversion structure. The proposed rectifier can be directly applied to low voltage cases due to the wide output voltage range. And the decoupling capacitor voltage can be smaller than the peak grid voltage, which reduces the voltage stress. Besides, the low-frequency ripple power buffer is implemented without a dedicated power-buffering controller. This paper first introduces the circuit structure, operation principles, and control method. Then, the system design consideration is given. Finally, the effectiveness of the proposed topology is verified by the simulations and experimental results.