Low-voltage enhancement-mode Gallium Nitride high-electron mobility transistors (eGaN HEMTs) are a kind of promising devices to realize high efficiency and high power density conversion because of their fast switching speed, low conduction and switching losses. In order to get loss breakpoint of a converter and predict its power conversion efficiency, a complete and accurate switching analytical model is needed. Since the reverse conduction loss of eGaN HEMTs accounts for a large part of switching losses, it is of great importance to improve the traditional switching analytical model to predict the reverse conduction loss. In this paper, a complete and accurate switching analytical model of low voltage eGaN HEMTs are presented. And an accurate loss calculation method based on the proposed model is proposed including the reverse conduction loss. The accuracy of the proposed model is validated by comparing the predicted switching waveforms and the efficiency of a synchronous buck converter with the experimental results, respectively. Moreover, the effect of top switch (TS) gate resistance, power loop inductance, current ripple, bottom switch (BS) gate resistance, and dead time on the loss breakpoint is explored and some qualitative suggestions are given to improve the conversion efficiency based on these analyzing results.

Wide bandgap devices such as GaN devices are being widely used due to their low on-resistance and parasitic parameters that can improve system performance compared to Si MOSFETs. However, these advantages above can sometimes lead to unexpected behavior in practical systems, such as false triggering oscillation. False triggering oscillation may cause overshoot, electromagnetic interference (EMI), shoot-through, and even device damage, which seriously affects the performance of the system. In this paper, an RC snubber circuit is proposed to suppress false triggering oscillation in a half-bridge circuit and the design method of the RC parameters is proposed. Firstly, the double pulse circuit is used as an example to analyze false triggering oscillation and its high frequency equivalent circuit is obtained. Then, the RC region is established by scrutinizing the characteristic equations via root locus method. The RC snubber circuit has better oscillation suppression effect when the RC parameters are within the region rather than outside the region. Finally, the RC region designed by the proposed method is verified by simulation and experiment results and the proposed method indicates a substantial improvement of the switching characteristics of the controlled device at turn-off

Including “generalized integrators” for sinusoidal signals, multiple resonant control (MRSC) scheme which can accurately compensate selected sinusoidal signals, is widely used as a high-performance current control method for grid-connected converters. In this article, the plug-in digital plug-in MRSC scheme is proposed to provide a general framework for housing various MRSC schemes, which plugs the MRSC controller into a stable feedback control loop. It can take advantages of both controllers—the feedback controller provides fast response and good robustness, and the MRSC controller offers accurate compensation of the periodic signals. More critically, based on a new type of sinusoidal signal model, the sufficient stability criteria and the gain tuning rules are developed to offer a simple universal approach to the design of the digital plug-in MRSC schemes. An application case study on the digital plug-in MRSC of a 5-kVA three-phase four-wire grid-connected inverter with LCL filter is provided. Experimental results demonstrated that the proposed MRSC scheme can force the inverter to produce high-quality currents with high accuracy, fast transient response, and good robustness.

The hybrid distribution transformer (HDT) achieves a compromise between the low-frequency transformer (LFT) and the solid-state transformer. It combines the LFT's efficiency and reliability with the added advantage of partial power controllability via an integrated converter. However, the existing research on the HDT fault ride-through does not consider the coordination relationship with its own safe operation constraints, while few studies have considered capacity coordination between multiple converters. Therefore, this article proposes an improved hierarchical coordination control of integrated HDT (IHDT), considering grid fault and normal conditions. First, the IHDT topology is proposed, and the operation mechanism of IHDT to realize the voltage support and current compensation is clarified by analyzing the coupling mechanism between the converter and LFT. Furthermore, under complex conditions, the unified expressions of the IHDT winding voltage, current, and power are derived, the safe operation constraints of IHDT are analyzed, and a hierarchical coordination control strategy is proposed. Finally, the correctness and effectiveness of the IHDT topology and control strategy are demonstrated by simulation analysis and experimental verification.

A single-stage high frequency resonant AC/AC converter transfers ac-line input voltage into high frequency sinusoidal output voltage, which consists of two power conversion units, i.e., power factor correction unit and high frequency resonant DC/AC unit, and it can be used to derive a modular multi-channel constant current LED driver. By adopting a totem-pole bridgeless PFC boost rectifier to reduce conduction losses, a single-stage bridgeless high frequency resonant AC/AC converter is proposed in this paper. The operating principle is described and the performance analysis is presented in detail. Moreover, the quantitative parameter design method of the main circuit is presented, which is suitable for other single-stage ac input converters, such as single-stage PFC rectifier. Finally, a 130-W prototype has been built and tested to verify the correction of related theory analysis and parameter design .

Light-emitting diodes (LEDs) are widely used in street lighting, landscape lighting, liquid crystal display (LCD) backlighting, healthcare, etc. As an important part of LED lighting products, LED driver plays a vital role in maintenance costs reduction, energy saving and lifetime prolongation. In this paper, a single-stage LED driver is proposed, which is integrated by a totem-pole bridgeless power factor correction (PFC) unit and several modular LCL-T resonant rectifiers. The totem-pole bridgeless PFC unit and the LCL-T resonant rectifiers are integrated by sharing switches, which can simplify the circuit and reduce the system cost. The output current can be regulated by applying the variable inductor control. Constant duty cycle and fixed switching frequency operation can be achieved as well. The operating principle and the performance of the proposed converter are analyzed in this paper. In addition, a precise parameter design method is proposed by considering the high-order harmonics. At last, an experimental prototype is established to validate the proposed parameter design and variable inductor control method.