An LLC Topology Suitable for Renewable Energy System Applications

Wide range operation dc/dc converters are required in renewable energy system applications. For example, for photovoltaic (PV) system, the output voltage of the PV ranges from 20 V to 60 V, which requires a dc/dc converter has a wide voltage gain range of 3. LLC resonant converters are popular due to their high efficiency characteristic. However, when traditional LLC converters are adopted in wide voltage range applications, the converter efficiency and power density performances are degraded due to the wide switching frequency operating range. In this article, a novel LLC topology, which has different operation modes, is proposed for renewable energy system applications, is proposed to satisfy the voltage gain requirement. By operating the proposed converter in three different operation modes, namely dual full-bridge, single full-bridge, and single half-bridge, the system normalized voltage gain can be varied from double to half. The operational principles, design considerations, and experimental validations are presented in this paper.