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Conventional dual-active-bridge dc-dc converters require dedicated voltage balancer or feedback control if they are used for a bipolar LVDC distribution system. This paper proposes a dual-active-half-bridge (DAHB) converter with voltage balancing capability. The proposed converter is composed of a conventional DAHB converter with additional inductor and capacitor voltage balancer (LCVB). The LCVB is added between transformer and output of the DAHB converter. Although the LCVB increases switch current, it can balance the two output voltages without additional active switching device and feedback control under unbalanced load condition. In addition, when compared with the conventional DAHB converter, the LCVB can increase zero-voltage-switching range of the DAHB converter and has no detrimental effect on the operation modes and performance. A 2.8-kW prototype was built and tested to verify the performances of the proposed converter.

In this letter, an asymmetrical PWM scheme is proposed to solve the output voltage unbalance and voltage gain issues of the input-parallel output-series (IPOS) converter when < .With the proposed scheme, the natural output voltages balancing and high step-up conversion ratio can be extended when < .As a result, combined with the conventional PWM scheme, the duty cycle limitation of the IPOS converter is completely eliminated without any extra components or dedicated control. A 2-kW prototype of the IPOS converter was built and tested to verify the performance of the proposed PWM scheme.

This article presents a novel two-channel light emitting diode (LED) current balancing method using current-fed (CF) quasi-Z-source (qZS) dc–dc converter. The proposed LED driver is simple in structure and requires minimal number of component counts. Currents flowing through the two LED strings are automatically balanced owing to charge (amp–sec) balance condition on capacitors in the CF–qZS network. Since current balancing is achieved automatically by passive components, current control of the proposed converter is very simple. In addition, the proposed circuit uses only one active switch and one diode. The operating principle and characteristics of the proposed two-channel LED driver are analyzed in detail. To verify validity of the proposed converter, 80 W prototype is built and tested.

This article presents current-fed (CF) full-bridge (FB) isolated dc–dc converter using quasi-Z-source network. Owing to its inherent buck–boost and clamping function, the proposed converter can effectively eliminate start-up and switch voltage overshoot problems. In addition, when compared with the conventional CF-FB converter with active clamp, switch current stress is much reduced and less active switches are required. Operation principles of the proposed converter are analyzed in detail. The simulation and experimental results with 1-kW prototype are also provided to verify theoretical analysis.

In this article, a current balancing coupled inductor (CBCL) based asymmetrically configured quad-active-bridge (QAB) converter is proposed. The QAB converter provides high-frequency isolation for a dc–dc stage of a solid state transformer (SST), as well as provides a modular solution to the SST medium-voltage (MV) dc link. The proposed CBCL ensures current balancing among/three active H-bridges without using any dedicated controller and without expensive sensors when transferring equal power from MV to low-voltage side. The proposed CBCL is the integration of three inductors of the active H-bridges required for power transfer and zero-voltage-switching and does not require an extra magnetic volume. Experimental results are presented to validate the performance.

Conventional current source inverter (CSI) suffers from open-circuit problem during switch transition. Thus, overlap-time should be inserted in the gate signals for safe commutation. The overlap-time distorts output current waveforms and increases total harmonic distortion of output current. Moreover, it reduces the current source utilization of the inverter. To solve these problems, this article proposes a new three-phase four-leg switching-cell (SC) CSI, abbreviated as H8-SC-CSI. With the help of the SC structure, the reliability of the proposed inverter is greatly enhanced as open-circuit concerns are eliminated. In addition, with the intrinsic voltage clamping action of the SC structure, switch voltage overshoot at turn- off is mitigated. In the proposed CSI, the switch overlap-time can be minimized or eliminated because the inductor current can flow through the SC capacitors. A 1.2 kW prototype inverter is designed and tested to verify the feasibility of the circuit.

Like conventional two-switch leg converters, the three-switch leg converters also have short-circuit risks and dangerous shoot-through current is generated if switches of the same leg are turned-on simultaneously. In this article, a new dual-buck structure is proposed for three-switch leg converters. The proposed structure is reliable because of no shoot-through concerns and high quality of output waveforms can be obtained due to the reduction in pulsewidth modulation (PWM) dead-time. Unlike the conventional dual-buck three-switch leg which uses many passive components such as four current limiting inductors and three external diodes, the new dual-buck three-switch leg uses only one current limiting inductor with two external diodes. To verify the performance, the proposed three-switch legs are used in single-phase dual-output inverter and detailed theoretical analysis, simulation, and experiments are performed. Both continuous and discontinuous modulation schemes are applied and it has been figured out that discontinuous modulation scheme can improve the dc-link voltage utilization in the common-frequency mode of operation.

In this article, a novel single-phase single-stage transformerless inverter is proposed for grid-tied and standalone applications. The proposed inverter has low leakage current and can perform both buck and boost functions. Furthermore, compared to the conventional state-of-the-art buck–boost inverters, it can achieve high power density because the magnetic volume is reduced significantly. In addition, high power conversion efficiency can be realized because only one switch operates at a high frequency. Moreover, there is no need for inserting high-frequency dead-time between the switches because only one switch receives high frequency and all other switches receive line frequency signals. In order to verify the performance of the proposed topology, a laboratory prototype is designed for 500 W, and the experimental results are provided as well.

In this letter, an asymmetrical pulsewidth modulated (PWM) scheme is proposed to solve the inductor current unbalance and nonlinear voltage gain issues of the series-capacitor (SC) high-conversion-ratio (HCR) converter when $D > 0.5$ . With the proposed scheme, the converter can achieve both current balancing and high step-down conversion even for $D > 0.5$ . As a result, combined with the conventional PWM scheme, the duty cycle limitation of the SC-HCR converter is completely eliminated. A 2-kW prototype SC-HCR converter was fabricated and tested to validate the performance of the proposed PWM scheme.

Unlike voltage-source inverters (VSI), the power decoupling element in current-source inverters (CSI) is inductor. Inductor has a long lifetime and makes the CSI more reliable. However, the traditional CSIs suffer from open-circuit problem and dangerous voltage spikes are generated if the input inductor current is intermitted. Therefore, to avoid the voltage spikes, overlap-time should be inserted in the gate signals. But these intervals distort the output currents and reduce the current source utilization. To address these issues, a novel three-phase CSI is proposed in this article. The proposed inverter is originated from the conventional seven-switch CSI named CSI7 by adding only two small film capacitors. The film capacitors along with the pre-existing diodes of the CSI7 ensure that there is always a path for the inductor current, and thus the open-circuit issue is resolved. The elimination of open-circuit issue enhances the reliability and allows to minimize the overlap-time. This will improve the quality of output currents as well. Moreover, simulation and experimental results are provided at the output power of 950 W to verify the effectiveness of the proposed inverter.

In this article, a novel high-reliability single-phase dual-output current source inverter is presented. By using the switching-cell (SC) structure in the proposed topology, the overlap-time between switching transition can be minimized or eliminated. This improves the quality of ac output currents, efficiency, and dc-source utilization. Additionally, the capacitors in SC structure can help to reduce dv / dt of power switches and clamp the overshoot voltage under open-circuit problems, thus improving reliability. Two modes of common and different frequency operations are considered and detailed pulsewidth modulation schemes are presented. A 650-W hardware prototype was built and tested to verify the performance of the proposed inverter, and the results are compared with conventional single-phase dual-output current source inverters.

This paper presents a dynamic voltage restorer to solve the voltage sag problem that causes the most serious economic loss among various grid accidents. The proposed method, which uses a direct AC–AC converter, consists of a simple controller unlike methods using a voltage source inverter that is controlled using complex operations. Unlike the energy storage type, there is no additional energy storage device, which reduces system cost. In addition, unlike the back-to-back type, energy conversion loss is reduced by one stage conversion. A switching cell-structured direct AC–AC converter that solves the rectification problem without a separate sensor is a reliable structure that reduces the volumes of the passive filters by increasing the switching frequency. In addition, using interphase voltages, it can take a wide range of voltage compensations to compensate for most of the voltage sag in various situations. In this paper, the background of the study is revealed and the operating principles and control schemes of the proposed system are analyzed. Then, the validity of this study is confirmed through simulation and experiment results.