Andrii Chub

A Review of Galvanically Isolated Impedance-Source DC–DC Converters

Impedance-source converters, an emerging technology in electric energy conversion, overcome limitations of conventional solutions by the use of specific impedance-source networks. Focus of this paper is on the topologies of galvanically isolated impedance-source dc-dc converters. These converters are particularly appropriate for distributed generation systems with renewable or alternative energy sources, which require input voltage and load regulation in a wide range. We review here the basic topologies for researchers and engineers, and classify all the topologies of the impedance-source galvanically isolated dc-dc converters according to the element that transfers energy from the input to the output: a transformer, a coupled inductor, or their combination. This classification reveals advantages and disadvantages, as well as a wide space for further research. This paper also outlines the most promising research directions in this field.

Galvanically Isolated Quasi-Z-Source DC–DC Converter With a Novel ZVS and ZCS Technique

This paper focuses on the galvanically isolated quasi-Z-source dc-dc converter with a novel zero voltage and zero current switching technique. The unique feature of the impedance network lies in combining the buck-boost operation capability with the short- and open-circuit immunity of transistors; at the same time, it can perform zero voltage and zero current switching on the primary side. The boundary conduction mode of the current in the second inductor of the quasi-Z-source network was used along with snubber capacitors in the two out of four transistors and a special control algorithm to achieve full zero-switching operation of the inverter. Simulation and experimental results prove the discussed ideas. Possible modifications of the algorithm and future applications are also described.

Quasi-Z-source half-bridge DC-DC converter for photovoltaic applications

This paper presents a novel quasi-Z-source halfbridge galvanically isolated DC-DC converter intended for the photovoltaic applications. The topology could be envisioned as an alternative to the boost half-bridge DC-DC converter but the benefit of its symmetric structure reduces the threat of transformer saturation due to the dc flux. The proposed converter features the continuous input current and could be used either with one or two input voltage sources.

Voltage Distortion Approach for Output Filter Design for Off-Grid and Grid-Connected PWM Inverters

This paper proposes a novel voltage distortion approach for output filter design based on the voltage transfer function for both off-grid and grid-connected Pulse Width Modulation (PWM) Inverters. The method explained in detail is compared to conventional methods. A comparative analysis is performed on an example of L and LCL-filter design. Simulation and experimental results for the off-grid and the grid-connected single phase inverter prove our theoretical predictions. It was found that conventional methods define redundant values of the output filter elements. Assumptions and limitations of the proposed approach are also discussed.

Feasibility study of Si and SiC MOSFETs in high-gain DC/DC converter for renewable energy applications

This paper presents an evaluative comparison of Si- and SiC-based MOSFETs, operating in a qZS-derived step-up DC/DC converter. Special attention is paid to switching behaviour and power dissipation. A range of experiments was performed to determine an optimal di/dt value during transients to minimise overvoltages and dynamic losses. Additionally, some particular properties such as gate driver requirements, housing types and price are discussed.

Full soft-switching bidirectional current-fed DC-DC converter

The focus is on a switching control strategy for the galvanically isolated bidirectional current-fed dc-dc converter. The converter under study employs the current-fed full-bridge stage at the low-voltage side and the voltage-fed half-bridge stage at the high-voltage side. The current-fed side of the converter utilizes four-quadrant switches comprised of two MOSFETs each. The switching sequence proposed enables soft-switching operation of all switches in both directions of energy transfer for a wide range of dc voltage gain and load variations. Moreover, it features natural clamping and thus eliminates voltage overshoot at the turn-off of switches at the current-fed side. Full zero-current switching is achieved in the current-fed side, while full zero-voltage switching is accommodated in the voltage-fed side. Theoretical predictions were verified with simulations in PSIM 9.

Experimental study of high step-up quasi-Z-source DC-DC converter with synchronous rectification

Quasi-Z-source DC-DC converters have attracted research interest due to their numerous advantages in emerging applications. However, they suffer from relatively low efficiency. This paper presents semiconductor loss breakdown of the quasi-Z-source DC-DC converter to show that conduction losses in semiconductors contribute most to overall losses. Synchronous rectification realized through replacement of diodes with N-channel MOSFETs was proposed to improve the converter efficiency in prior works. Our detailed experimental study of efficiency improvement with synchronous rectification was based on a 250 W prototype. Results were first obtained for replacement of diodes in the primary side only, then in the secondary side only. Finally, a converter that contains only controlled switches was evaluated. Efficiency curves measured were compared with those for the baseline diode-based topology. The experimental study was performed using operating points typical of photovoltaic module integrated converters.

Asymmetrical quasi-Z-source half-bridge DC-DC converters

This paper presents a novel quasi-Z-source half-bridge DC-DC converter family derived by a combination of the single-switch qZS DC-DC converter and the half-bridge galvanically isolated DC-DC converter. The novel topologies have only two active switches and are a cheaper alternative to the galvanically isolated quasi-Z-source DC-DC converters with a full-bridge switching stage. Such promising features as circuit simplicity, low cost, high efficiency, and high reliability are attributed to the new alternative solution. A 200W prototype was assembled and tested. Simulation and experimental results are presented to verify the step-up performance of the topology.

Impedance-source galvanically isolated DC/DC converters: State of the art and future challenges

Impedance-source switched mode converters are an emerging technology in electric energy conversion. They overcome limitations of conventional solutions by the utilization of specific impedance-source networks. Previous review papers cover impedance-source networks. Focus of this paper is on the topologies of the impedance-source galvanically isolated DC/DC converter. These converters are particularly appropriate for distributed generation systems with renewable or alternative energy sources which require input voltage regulation in a wide range. This paper presents a concise review of basic existing topologies for researchers and engineers. All the reviewed topologies of the impedance-source galvanically isolated DC/DC converter are classified by the element that transfers energy from the input to the output: a transformer or a coupled inductor. This classification undoubtedly reveals wide space for further research and the most promising research directions in this field.

Novel family of quasi-Z-source DC/DC converters derived from current-fed push-pull converters

This paper is devoted to the step-up quasi-Z-source dc/dc push-pull converter family. The topologies in the family are derived from the isolated boost converter family by replacing input inductors with the quasi-Z-source network. Two new topologies are proposed, analyzed and compared. Theoretical predictions are verified by means of simulations.