A simple smooth mode transition strategy for resonant converters with topology morphing control in renewable energy applications

Renewable energy sources require power converters with wide input voltage range operation capability. Resonant converters have gained popularity in these applications owning to its high efficiency operation characteristic. Nevertheless, the traditional frequency-controlled resonant converter has the disadvantages of wide switching frequency operation, high circulating current, and low conversion efficiency. The topology morphing control is proposed for LLC converter with multiple operations to tackle these problems. However, due to the large switching frequency mismatch at the mode transition point, there are large voltage transients during the mode transition. In this article, a simple smooth mode transition strategy is proposed. The large switching frequency mismatch and voltage transients are mitigated.