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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]

This article proposes a three-phase six-switch switching-cell current source inverter (H6-SC-CSI) and a modified switching scheme of space vector pulsewidth modulation (SVPWM). Compared to the conventional three-phase six-switch current source inverter, the H6-SC-CSI has no open-circuit possibility, thus, the inverter reliability is greatly enhanced. In addition, the overlap-time can be minimized; hence, the output waveform quality can be considerably improved. Due to the presence of switching-cell capacitors, a conventional switching sequence of the SVPWM is modified for the inverter to operate properly. A 2.2 kW hardware prototype is built and tested to verify the effectiveness of the proposed PWM. [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 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]

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. [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]

A dual-buck inverter (DBI) possesses no shoot-through worries and can boost efficiency by using power mosfet s. The main drawback of a DBI is the use of more inductors than in a traditional full-bridge inverter. This greater number of inductors decreases the power density and increases system cost. In this paper, a modified cascaded full-bridge DBI is proposed. It retains all the advantages of the conventional cascaded full-bridge DBI, possesses no shoot-through issues, and can be operated with no pulse-width-modulation dead-times. It can be implemented with power mosfet without reverse recovery issues of a body diode to boost efficiency. The cascaded modules in the proposed inverter share current limiting inductors. Therefore, the number of inductors and inductor footprints, the complexity of the circuit layout, required inductance, and magnetic volume can all be decreased. To show the advantages of the proposed inverter, detailed theoretical analysis and experimental results are provided. [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]

To regulate an output ac voltage in inverter systems having wide input dc voltage variation, a buck–boost power conditioning system is preferred. This paper proposes a novel high-efficiency quasi single-stage single-phase buck–boost inverter. The proposed inverter can solve current shoot-through problem and eliminate PWM dead time, which leads to greatly enhanced system reliability. It allows bidirectional power flow and can use MOSFET as switching device without body diode conducting. The reverse recovery issues and related loss of the MOSFET body diode can be eliminated. The use of MOSFET contributes to the reduction of switching and conduction losses. Also, the proposed inverter can be operated with simple pulse width modulation (PWM) control and can be designed at higher switching frequency to reduce the volume of passive components. The detailed experimental results are provided to show the advantages of the proposed inverter. Efficiency measurement shows that using simple PWM control the proposed inverter can obtain peak efficiency of 97.8% for 1.1-kW output power at 30-kHz switching frequency. [ABSTRACT FROM AUTHOR]

In this paper, the switching cell concept is extended to isolated ac–ac converters, and a highly reliable double step-down ac–ac converter is proposed with high-frequency transformer (HFT) isolation. By using the switching cell structure and coupled inductors, the proposed converter has no commutation problem as it is immune from both short-circuit and open-circuit problems, even when all the switches are turned on or turned off, simultaneously. Therefore, it does not require pulse width modulation dead times along with bulky and lossy RC snubbers or voltage-sensing circuitry to implement soft-commutation strategies, resulting in high reliability and high quality output waveforms. The HFT in the proposed converter provides electrical isolation and safety which is required in applications such as dynamic voltage restorer (DVR), solid-state transformer (SST), etc., without the need for external bulky line frequency transformer. Moreover, all the passive components experience twice the switching frequency; therefore, their size can be reduced. The proposed converter is very suitable for application as DVR, to compensate both voltage sags and swells, owing to its ability to provide both inverting and noninverting outputs. A detailed theoretical analysis and operation of the proposed ac–ac converter are provided, and its applications as DVR and SST are also discussed. Experimental results with scaled-down prototype are also provided to verify its performance. [ABSTRACT FROM AUTHOR]

This paper proposes single-phase direct pulsewidth modulation (PWM) buck-, boost-, and buck–boost-type ac–ac converters. The proposed converters are implemented with a series-connected freewheeling diode and MOSFET pair, which allows to minimize the switching and conduction losses of the semiconductor devices and resolves the reverse-recovery problem of body diode of MOSFET. The proposed converters are highly reliable because they can solve the shoot-through and dead-time problems of traditional ac–ac converters without voltage/current sensing module, lossy resistor–capacitor (RC) snubbers, or bulky coupled inductors. In addition, they can achieve high obtainable voltage gain and also produce output voltage waveforms of good quality because they do not use lossy snubbers. Unlike the recently developed switching cell (SC) ac–ac converters, the proposed ac–ac converters have no circulating current and do not require bulky coupled inductors; therefore, the total losses, current stresses, and magnetic volume are reduced and efficiency is improved. Detailed analysis and experimental results are provided to validate the novelty and merit of the proposed converters. [ABSTRACT FROM AUTHOR]

This paper presents a novel dc–dc converter incorporating a distributed impedance-source network ( Z-source network, or Z-network) to achieve the buck (step-down) and boost (step-up) function of a transformer-isolated dc–dc converter. In this paper, the distributed impedance source network composed of an array of inductors and capacitors is coupled between power source and main switching devices. The great and unique feature about the distributed impedance source network dc–dc converter is that unlike the traditional V-source or I-source converters, it can be open- and short-circuited without damaging switching devices. Therefore, the desired buck and boost function can be achieved. Moreover, converter reliability can be greatly improved. A dc–dc converter using this proposed concept is built and tested. Its performances are verified with experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a novel buck–boost ac–ac converter is proposed. The basic switching unit of the proposed converter is a unidirectional buck circuit; therefore, it has no shoot-through worries. It can achieve safe commutation without using RC snubbers or soft commutation strategies. It can be implemented with power MOSFETs without their body diodes conducting and, for current freewheeling external diodes, can be used to minimize the reverse recovery issues and related loss. It has a bipolar voltage gain with both inverting and non-inverting operations. The non-inverting operation can be used to compensate voltage sag, and inverting operation can be used to compensate voltage swell. Therefore, the proposed converter as a dynamic voltage restorer is capable of compensating for both voltage sag and swell in a wide range. The detailed theoretical analysis followed by detailed experimental results of a 300-W prototype converter is provided. [ABSTRACT FROM AUTHOR]

In this paper, two single-phase single-stage split-inductor buck–boost inverters are proposed: type-I and II. The proposed type-I is unity power factor inverter, while the proposed type-II inverter is suitable for any power factor. Both topologies remove the shoot-through problem. Furthermore, the reverse recovery issues for all switches are eliminated; therefore, mosfets are used to obtain higher efficiencies. The proposed inverters operated at higher switching frequencies confer the additional benefit of smaller passive components. The current stresses of the two switches in the proposed type-I and II inverters are lower of the conventional boost inverter. The dead time can be eliminated at both the high and line switching frequencies. In addition, the inductor conduction loss is minimized to improve efficiency. Moreover, the voltage stresses of the two switches in the type-I inverter can be much lower of its counterpart boost inverter. Most importantly, unlike the conventional high-reliability inverters, the magnetic volume of the proposed high-reliability type-I and II inverters is same of its counterpart boost inverter. The experimental results obtained for 500 W, 110 Vrms, 60 Hz hardware prototypes verify the analysis. [ABSTRACT FROM AUTHOR]