A novel polymorphic topology with hybrid control strategy based LLC resonant converter for ultra-wide input voltage range applications

To realize effective utilization of renewable energy sources, a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper. By combining the merits of a full bridge LLC resonant converter, three-level half bridge LLC resonant converter, and variable frequency control mode, the converter realizes an intelligent estimation of input voltage by automatically changing its internal circuit topology. Under this control strategy, different input voltages determine different operation modes. This is achieved in full bridge LLC mode when the input voltage is low. If the input voltage rises to a certain level, it operates in three-level half bridge LLC mode. These switches are digital and entirely carried out by the DSP (Digital Signal Processor), which means that an auxiliary circuit is unnecessary, where a simple strategy of software modification can be utilized. Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92% are developed to verify feasibility and practicability. This type of converter is suitable for applications with an ultra-wide input voltage range, such as wind turbines, photovoltaic generators, bioenergy, and other renewable energy sources. © 2021, Tech Science Press. All rights reserved.