This paper proposes three high step-up Z-source (ZS)-based DC-DC converters through integrating the conventional ZS network with switched-capacitor (SC) cells. The proposed converters offer a simple structure with a smooth input current, a high-voltage gain, and low voltage stress on the semiconductor devices. In addition, the proposed converters, unlike some existing ZS-based topologies in the literature, do not impose any limitation on the duty cycle of the power switch. These characteristics make the proposed converters excellent candidates to interface a low-voltage solar photovoltaic (PV) panel with a high-voltage DC bus in PV applications. Among the proposed three converters, the operating principles and steady-state analysis of the one with more components are presented in detail. However, the steady-state voltage and current relationships are also tabulated for two other proposed converters. In addition, design considerations are presented. The performance of the proposed converters is compared against similar existing high step-up DC-DC converters with regards to the component count, normalized voltage stress on the power switch and diodes, and voltage gain. Finally, the theoretical analyses and calculations are validated through experimental results using a 400 W/400 V laboratory prototype.

In this article, two single-switch quadratic boost converters based on a three-winding coupled inductor (CI) are proposed. These converters provide a high voltage gain in a low duty cycle, reduced voltage stress on the power switch, continuous input current with a low di/dt, higher design flexibility, and limited current falling rate on the voltage multiplier diodes to minimize the reverse recovery loss. Moreover, the first proposed converter has two capacitors in the output reducing the need for a bulky output capacitor, while the second proposed converter has higher utilization of the CI and is able to provide a higher voltage gain. The operation principle and theoretical analysis, such as voltage stress, current stress, effect of leakage inductances on the voltage gain, and design considerations are presented in this article. Furthermore, the superiority of the proposed converters over the competitive high step-up quadratic converters are justified through a comparison study. Finally, a 300-W, 30- to 400-V laboratory experimental setup is implemented to validate the theoretical analysis.

This paper proposes an interleaved high step-up DC-DC converter with the coupled inductor (CI) and built-in transformer (BIT) for renewable energy applications. Two double-winding (2W) CIs and one triple-winding (3W) BIT are integrated with the switched-capacitor (SC) voltage multiplier cells (VMCs) to achieve high-voltage gains without extreme duty cycles. The CIs and BIT turns-ratios provide two other degrees of freedom—in addition to the duty cycle—to adjust the voltage gain that leads to increased design flexibility. The diodes turn off naturally under the zero-current switching (ZCS) conditions because their current falling rates are controlled by the leakage inductances of the CIs and BIT; therefore, the diodes’ reverse-recovery problems are alleviated. Moreover, employing passive diode-capacitor clamp circuits, the voltage stresses of the switches are limited to a low value far less than the output voltage. Additionally, the leakage inductances energies are recycled and transferred to the output to further extend the voltage gain. Furthermore, due to the interleaved structure, the input current ripple and current stresses of the components are reduced. The proposed converter is analyzed in detail and then compared with similar converters that employed two 2W CIs and one 3W BIT along with passive clamp circuits for the MOSFETs. Finally, to verify the feasibility of the proposed converter, the experimental results of a 200 W prototype with output voltage of 400 V and voltage gain of 25 are presented.

A new high step-up DC-DC converter for renewable energy applications is proposed in this paper. Employing an interleaved quadratic structure, two two-winding coupled inductors (CIs), and voltage multiplier cells (VMCs), the proposed converter can provide high-voltage gains, continuous input current with low ripple, reduced voltage stresses on semiconductors, common ground between input and output sides, and low numbers of components. In addition, diode-capacitor lossless clamp circuits are utilized to limit the voltage stresses of the power switches and further extend the voltage gain. The operating and steady-state analyses, design considerations, and a comparison with other previously published high step-up converters are presented. Lastly, experimental results of a 400 W prototype with 400 V output voltage are illustrated to verify the theoretical analysis and the functionality of the proposed converter.

In this article, an interleaved high-voltage gain dc–dc converter is proposed for use with photovoltaic (PV) systems. By integrating two three-winding coupled inductors (CIs) with switched capacitor cells, the voltage gain is further extended. Through passive diode-capacitor clamp circuits, the energy stored in the leakage inductances is absorbed; additionally, the voltage stress of the power switches is clamped to a value far lower than the output voltage, which enables designers to select switches with low-voltage ratings. Due to the interleaved structure of the proposed converter, the input current has a small ripple, which leads to the increased lifespan of the PV panels. In addition, the current stress on the components is reduced. Thanks to the leakage inductances of the CIs, the zero-current switching condition is intrinsically provided for the diodes; accordingly, the adverse impact of the diodes’ reverse-recovery is alleviated. The operating principles, steady-state analyses, and design considerations of the proposed converter are presented in this article. A comparison with other similar converters is carried out to verify the merits of the proposed converter. Finally, the theoretical analyses are confirmed through the experimental results of a 400-W prototype with an output voltage of 400 V.

This paper proposes a new high step-up DC-DC converter for photovoltaic (PV) applications. A dual-switch structure with a three-winding coupled inductor (3WCI), whose secondary and tertiary windings are integrated with switched-capacitor (SC) cells, is adopted to achieve a high-voltage gain with a small duty cycle, thus avoiding an extremely high duty cycle. The input current is continuous, and the voltage gain could be adjusted by two parameters: the switches' duty cycle and 3WCI's turns-ratio, thus increasing the design flexibility of the proposed converter. In addition, low-voltage-rated MOSFETs with small ON-state resistances are selected, and their losses are reduced due to the low voltage stress and small duty cycle of the switches. Moreover, the current-falling rates of most diodes are controlled by the 3WCI's leakage inductances. The operating modes, detailed analyses, and design considerations for the proposed converter are presented. Additionally, comparisons with other high step-up converters are provided. A 200-W laboratory prototype with an output voltage of 400 V is fabricated and tested using various input voltages to validate the theoretical analyses.