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This paper introduces eight novel interleaved non-isolated dc-dc converters with ultra-high step-up and zero voltage switching (ZVS) capabilities for renewable energy systems. To increase the voltage gain, the proposed converters benefit coupled inductors, high-frequency (HF) transformer, and voltage multiplier (VM) techniques. In comparison to other converters, which just benefit coupled inductors or HF transformers, these combinations of the techniques make an additional degree of freedom to achieve high voltage gains (more than 25 without extreme duty cycle). Besides, two active clamp circuits, including two stages of switch-capacitor VM cells, not only increase the voltage gain of the proposed converters but also act as an auxiliary circuit to provide ZVS. Moreover, the stored energy in the leakage inductances is absorbed and passed to the output by the clamp capacitors. The input current ripple is reduced by applying the interleaved technique. The voltage stress es across the power switches are clamped to lower values and can be controlled by the turn ratios of the coupled inductors and the HF transformer. The theoretical performance of the proposed converters is fully explained. Also, the proposed converters are compared with more than twenty latest interleaved high step-up and ultra-high step-up dc-dc converters. Finally, a 1 kW, 20 V/500 V laboratory prototype is built to prove the advantages of the proposed converters.INDEX TERMS Interleaved structure, dc-dc converter, ultra-high step-up converter, zero-voltage switching

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