Optimization of Impedance-Source Galvanically Isolated DC–DC Converters With Reduced Number of Switches

Naser Fakhri,Seung-Ryle Oh,Soroush Aghili,Mohammad Salay Naderi,Saeid Gholami Farkoush,Adel Khoshdel,Sang-Bong Rhee,Seung Kil Choi

doi:10.1109/access.2021.3139948

Abstract

In this study, a new type of Z-source converter comprising galvanic isolation transformers is introduced based on classical non-isolated Z-source converters, which are promising devices for renewable applications. Compared to the typology of conventional converters with isolation transformers, the proposed converter topology has a simpler structure with fewer power switches and lower costs. Considering the lower number of switching devices required in the proposed typology, these efficiency and reliability of the presented converters are higher than those of the conventional ones. As only one switch is used in the developed structure, voltage stresses on the Z-source converter decreases in each period, which maintains voltage stress low and steady across the switch. Another desirable feature of the proposed topology is reduced converter size and volume with a maximum theoretical and practical efficiency of 97 to 94.05%, respectively. Moreover, these converters need low input voltage and provide the required amount of output voltage in small duty cycles. The theoretical and operational analysis of the designed converter and its comparison with other counterpart converters (e.g., isolated Z-source converters) is presented. The simulation and experimental results confirm the applicability of the proposed system.

Highlights

Because of the ever-growing demand for renewable energy resources, such as photovoltaic systems, wind turbines, and fuel cells, considerable attention has been directed to such resources
This study introduces an optimized structure for Z-source DCDC converters based on galvanically isolation transformers with a reduced number of switches and diodes as an alternative to conventional isolated Z-source DC-DC converters
These results show that despite the discontinuous input current, IL1 and IL2 operate in the continuous conduction mode (CCM)

Summary

INTRODUCTION

Because of the ever-growing demand for renewable energy resources, such as photovoltaic systems, wind turbines, and fuel cells, considerable attention has been directed to such resources. The technology of these typologies has been widely investigated and recognized, they have a fairly large size, impose high costs, and yield low efficiency owing to their single structure in complex applications [1],[2] To eliminate these problems and boost their efficiency, DC-DC converters with HV gains should be utilized [3]; Z-source (ZS) networks have been considered. The switches in these converters might undergo intense voltage pressures owing to the leakage inductance of transformers [14] To overcome this problem, a resistive capacitive diode is required [15]; it boosts power loss and declines efficiency. By reducing voltage stress on the elements of the Z-source network, a fewer number of constituents (e.g., switches and diodes) are needed, voltage tension on active elements decreases, and using double-winding isolation transformers becomes feasible. The proposed impedance-source isolated dc-dc converter with an output voltage of 206 V is located in the range of 200 to 600 V before being connected to the network of 110, 230, and 400 V AC [21],[22].the proposed converter is a promising device for photovoltaic panels, fuel cells, and wind turbines

CONVENTIONAL DC-DC CONVERTERS WITH ISOLATION TRANSFORMERS

INDUCTOR

SIMULATION AND EXPERIMENTAL RESULTS

SIMULATION RESULTS

Findings

CONCLUSION