Abstract
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 stresses 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.
Highlights
Nowadays, the growing demand for energy from fossil fuels causes air pollution, global warming, and other environmental concerns. These problems motivate research communities to find alternative or clean energy sources. Renewable energy sources such as solar energy and wind energy are the best response to these growing demands
High step-up dc-dc converters are commonly used to step-up the PV array voltage to the grid voltage level
The high step-up dc-dc converters are widely used in many applications such as fuel cells, batteries, servo motors, etc. [5]-[8]
Summary
The growing demand for energy from fossil fuels causes air pollution, global warming, and other environmental concerns. To increase the converter voltage gain, decrease the voltage stress across the semiconductors, reduce the switching losses, and add another designing freedom degree, an HF transformer is added to the converter and combined with the diode capacitor voltage multiplier stages [22]. In addition to the mentioned techniques, to further increase the converter voltage gain and the designing freedom degrees and decrease the voltage stress across the semiconductors, coupled inductors can be utilized instead of inductors In this technique, the coupled inductors are combined with the HF transformer and diode-capacitor voltage multiplier cells to provide three designing freedom degrees. By adding two auxiliary switch-capacitor voltage multiplier cells, the leakage inductances of the coupled inductances and HF transformer can be utilized to provide ZVS for the power switches, ZCS for the power diodes, and increase the converter voltage gain significantely.
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