QUASI-RESONANT VOLTAGE DOUBLER WITH SNUBBER CAPACITOR FOR BOOST HALF-BRIDGE DC-DC CONVERTER IN PHOTOVOLTAIC MICRO-INVERTER

Abstract

This project proposes a quasi-resonant boost half-bridge DC-DC converter with high power conversion efficiency and a wide input voltage range for photovoltaic micro-inverter. The proposed converter has a combined structure of a boost integrated half-bridge converter on the primary side of the transformer and a voltage doubler with a snubber capacitor on the secondary side. By using the quasi-resonance techniques, it achieves zero-voltage switching (ZVS) turn-on and low turn-off losses for the switches, as well as ZVS turn-on for the diodes. In addition, the proposed converter has no DC-magnetizing current for the transformer due to the DC blocking capacitor, and it doubles the voltage gain with half the voltage stress of diodes through the voltage doubler. The effectiveness of the converter was verified with a 300-W prototype with input voltage range of 13 ~ 50 V, output voltage of 400 V, and switching frequency of 50 kHz. The experimental results show that the converter had more than 90.0% power conversion efficiency for the output power range of ~ 300 W, and its maximum power conversion efficiency was 97.5% for an output power of 160 W.

Existing System

In the existing system, non-isolation converters such as conventional LLC resonant converter for micro-inverters are used.

Proposed System

In this project, an improved quasi-resonant BHB converter with a voltage doubler is proposed to overcome the disadvantages of other BHB converters with the voltage doubler. The effectiveness of the converter was verified with a 300-W prototype, which was compared with other converters. The proposed converter has a combined structure of a boost integrated half-bridge converter on the primary side of the transformer and a voltage doubler with a snubber capacitor on the secondary side. The proposed converter uses the pulse-width modulation (PWM) control with a fixed switching period TS and the duty ratio D. It has seven distinct operating modes. A quasi-resonant boost half-bridge (BHB) DC-DC converter with high power conversion efficiency ηe and a wide input voltage range. The proposed converter uses the resonance techniques to achieve ZVS turn-on and low turn-off switching losses for the switches, and to achieve ZVS turn-on for the diodes. These soft-switching operations in the switches and diodes improve ηe. Moreover, the proposed converter had no DC-magnetizing current of the transformer, and the voltage gain was increased by using the voltage doubler with a snubber capacitor.

Architecture

The proposed converter.