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A novel beta-quasi-Z-source (β-qZS) converter is proposed for an isolated dc–dc converter with the buck (step-down) and boost (step-up) functions. The β-qZS isolated dc–dc converter addresses the common challenges such as components stresses, reliability, suppression of switch voltage overshoot, size, and power derating in the existing impedance source-based isolated dc–dc converter applications. In addition, the proposed topology dealt with operating duty cycle constraint and loss of duty cycle phenomenon in the Z/qZS galvanically isolated dc–dc converters. This article describes the configuration and provides the principle of operation for the proposed β-qZS converter topology. A laboratory prototype is developed, and the experimental results satisfy the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this article, two configurations of the quadratic quasi-Z-source (Q-qZS) isolated dc–dc converters are presented, namely continuous input current and discontinuous input current configurations. The operating principles and steady state of the continuous input current topology analyzed in this article is characterized with the following features: 1) wider operating range due to buck and boost functions in a single stage; 2) draws continuous input current; 3) low input current ripple compared with other qZS-based isolated dc–dc converters; 4) better reliability and good immunity against EMI noise; 5) common ground between the input source and the inverting bridge; and 6) continuous control over the entire operating range. Compared with other qZS-based isolated dc–dc converters, lower current stresses on active and passive components used are realized. Hence, the total magnetic volume/energy required by the proposed converter is reduced with the potential of achieving high power density. A prototype of 40–140 V input voltage, 300 V output, and 550 W rated power is developed to validate the performance of the proposed converter presented. [ABSTRACT FROM AUTHOR]

This article proposes a single-phase five-level current source inverter with an inductor cell based on the switching-cell (SC) structure. Compared to the conventional inverter, the proposed structure has no open-circuit problem; thus, its reliability is greatly enhanced. The overlap-time inserted in the driving signals can also be minimized to improve the output waveform quality. The proposed inverter's operation is analyzed herein, and the design guideline of SC capacitors is discussed. In addition, the SC extension for the n-level topology is provided. A 1-kW prototype is built and tested to validate the effectiveness of the proposed structure. [ABSTRACT FROM AUTHOR]

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

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, dual-buck structured single-stage buck–boost inverters that use power MOSFETs to achieve high efficiency are presented. The proposed inverters require fewer switches, and half of the switches have reduced current stresses. They have no shoot-through problem; therefore, high system reliability can be obtained. The dead-time in PWM signals can be minimized or eliminated, which improving the quality of the output ac voltages and increasing the efficiency. In the proposed inverters, MOSFETs can be used without reverse-recovery issues of their body diodes to boost the efficiency and increase the switching frequency. To further improve the efficiency and stability of the proposed single-phase inverter, PWM strategies combining high- and low-frequency modulation are presented. A hardware prototype of the single-phase inverter was built and tested using resistive, inductive, and nonlinear loads. Experimental results for a 300-W prototype inverter show a 97.4% peak efficiency with a 25 kHz switching frequency. [ABSTRACT FROM AUTHOR]

In this paper, a new nonisolated high-voltage-gain boost converter is proposed. The proposed converter is constructed by adding an additional inductor to a conventional three-level-boost (TLB) converter. When compared with the conventional boost and TLB converters, the proposed converter can achieve higher voltage conversion ratio with reduced voltage and current stresses in the switches. In particular, the proposed converter can reduce the losses of active devices by reducing the current of the switch compared to conventional converters, thus, can achieve high efficiency. In addition, the proposed converter automatically balances the output voltages for an unbalanced load without the need for any additional control strategy or auxiliary circuit. A 2-kW prototype converter was built and tested to verify performances of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper proposes a new bidirectional direct pulse width modulation (PWM) three-phase buck-boost ac–ac converter. It requires six switches and three inductors and can provide wide range buck-boost voltage operation. It has high reliability due to no short-circuit and open-circuit risks in the converter. Therefore, it solves the commutation problem without using lossy snubber circuits, soft commutation strategies, and coupled inductors. It can be designed with metal–oxide–semiconductor field-effect transistors (MOSFETs) without their body diodes conducting, which eliminate reverse recovery issues and losses of body diodes. In addition, to reduce the ripples in input and output voltages and currents, the proposed converter can be operated with a PWM strategy-II. The PWM strategy-II is a type of interleaved PWM strategy with dead- and overlap-times operating modes. To validate the effectiveness of the proposed converter extensive analysis followed by detailed experimental results are provided. [ABSTRACT FROM PUBLISHER]

In this paper, a new type of matrix converter (MC) also called a single-phase high-frequency transformer isolated (HFTI) buck MC is proposed. The proposed converter can provide step-down operation of the input voltage with various types of output voltages such as in-phase and out-of-phase output voltages, rectified (or positive) output voltage, and output voltage with step-changed frequency. By incorporating HFT isolation, the proposed MC saves an extra bulky line frequency transformer, which is required for the conventional MCs to provide electrical isolation and safety, when used in application such as dynamic voltage restorers, etc. Two different circuit variations of the proposed HFTI MC are presented with and without continuous output currents, with the latter having less passive components. The safe-commutation strategy is also employed for the proposed HFTI MC to provide current path for the inductor during dead-time, which avoids switch voltage spikes without adding any snubber circuits. The operation principle and circuit analysis of the proposed MC are presented, and switching strategies are also developed to obtain various output voltages. Moreover, a prototype of the proposed MC is fabricated, and experiments are performed to produce in-phase/out-of-phase and rectified output voltages, and output voltage with step-changed frequency. [ABSTRACT FROM PUBLISHER]

A single-phase inverting buck–boost ac–ac converter is proposed in this paper. The proposed converter has no shoot-through and dead-time problems and, like conventional dc–dc converters, it can be operated with simple pulse width modulation (PWM) control. It offers high frequency and high efficiency operation because high speed mosfet can be used as switching device without the reverse recovery issues and losses of its body diode. The proposed converter features quasi-continuous input and output currents, high input power factor, low total harmonic distortion of input and output currents, and high efficiency. A 460 W laboratory prototype was constructed and tested with interleaved and complementary PWM controls using a resistive and inductive load. Detailed experimental results are provided to show the novelty of the proposed converter. Experimental results confirmed that the proposed converter can obtain 93.8% efficiency at 60 kHz switching frequency. [ABSTRACT FROM PUBLISHER]

In this paper, a family of three-phase direct pulse-width modulated (PWM) ac–ac converters consisting of buck, boost, and buck–boost converters is proposed. The proposed converters have no commutation problem even if all of the switches are turned on or off simultaneously. They do not use lossy snubbers and do not sense the voltage polarity for commutation, and produce high-quality output voltage waveforms. The proposed converters allow the use of power MOSFETs and fast recovery freewheeling diodes independently. The use of power MOSFETs as active switches and freewheeling diodes with extremely fast recovery features lower the switching losses and enable us to reduce the volume of passive components by increasing switching frequency. The input (or output) filter inductor experiences twice of the converter switching frequency and thus can be designed with minimum size. To increase power density of the proposed converters, a three-phase three-limb coupled inductor is proposed. Three-phase coupled inductor integrates three separate coupled inductors of the proposed converters in one three-limb core. In comparison with separate coupled inductors, the three-phase coupled inductor has a smaller size with large current-handling capability. Experimental results obtained for the boost-type converter show the robustness of the proposed three-phase ac–ac converters. [ABSTRACT FROM AUTHOR]

In this article, a single-phase bipolar buck–boost direct pulsewidth-modulated ac–ac converter is proposed, comprised of six insulated-gate bipolar transistors, a small film capacitor, and input/output LC filters. The converter can provide discrete noninverting buck (NIBu) and boost (NIBo) operations with voltage gains of D and 1/(1 – D), respectively. Moreover, it provides symmetric noninverting buck–boost (NIBB) and inverting buck–boost (IBB) operations with voltage gains of D/(1 – D) and –D/(1 – D), respectively. It supplies both continuous input/output currents, and it is well suited for reactive loads. It is immune from the commutation problem, and thus, has enhanced the reliability. The various modes of operation of the proposed converter make it suitable for diverse applications, including the following: 1) application as a direct ac voltage regulator when operating in NIBu and NIBo modes; 2) IBB operation can be utilized along with NIBu/ NIBo or NIBB operation to compensate both voltage sag and swell, when used as dynamic voltage restorer; and 3) symmetric NIBB/IBB operations can provide step-changed frequency output, similar to the single-phase matrix converters, for applications as induction motor drive or high-gain ac–dc rectifier. Extensive circuit analysis, component design guidelines, and appropriate comparisons are provided, followed by experimental results obtained using a laboratory prototype. [ABSTRACT FROM AUTHOR]