Z‐source‐based isolated high step‐up converter

Abstract

Continuous input currents and high step-up ratios are desired from the dc-dc converters that work with renewable energy sources such as photovoltaic panels and fuel cells. Most dc-dc converters use transformers to have high step-up ratios. There is another type of converters that use coupled inductors, but they need to operate at high duty cycles to increase the gain. These converters suffer from low efficiency values because of the leakage inductance values and long reverse recovery times of the diodes. A new dc-dc converter based on Z-source topology is proposed in this study. It uses coupled inductors to increase the step-up ratio. Its main features are high step-up ratios, continuous input currents, high efficiency and galvanic isolation between input and output. Simulation and experimental results are given for a prototype converter that converts 25-400 V dc at 300 W with over 91% efficiency.

A Fully Soft-Switched Single Switch Isolated DC–DC Converter

“…Isolated dc-dc converters with one main switch and one clamp switch achieves ZVS turn on of switches, but switches are turned off with hard switching [14]- [17]. Isolated single switch dc-dc converters are more attractive to achieve low cost [18]- [26]. Zsource converter [18], [19] and flyback converter [20]- [23] are hard switched at both turn-on and turn-off instants.…”

“…Isolated single switch dc-dc converters are more attractive to achieve low cost [18]- [26]. Zsource converter [18], [19] and flyback converter [20]- [23] are hard switched at both turn-on and turn-off instants. Frequencycontrolled flyback converter [24] and series-connected forward-flyback converter [25] achieve zero-current switching (ZCS) turn-on of switch, but the switch is hard switched at turn-off instant.…”

Galvanically isolated quasi-Z-source DC-DC converters with combined energy transfer for renewable energy sources integration

“…5. This topology has been derived as a superposition of the converters proposed in [14] and [20]. It has low input current ripple due to discrete implementation of the input inductor.…”

Non-isolated high step-up DC–DC converter adopting auxiliary capacitor and coupled inductor

“…To overcome the respective disadvantages of quasi-Zsource network and coupled inductor, some isolated high step-up DC-DC converters combining quasi-Z-source network and coupled inductor are proposed in [29,30]. However, due to the isolation, the energy stored in the leakage inductor of the primary winding is difficult to be transferred to the output.…”