在新能源发电占比不断提高的当下，一个具有高效率宽输入范围的大功率变换器的提出十分有必要。在现有研究的基础上，提出了由Buck-boost LLC和LLC-DCX两个变换器共同构成的Sigma结构变换器，能够很好地实现高效率、宽输入范围的需求。Buck-boost LLC通过桥臂集成能够有效地减少元器件同时降低损耗,但是其Buck-boost电感上流过的是全部输入电流，在大功率场合这会造成很大的损耗。因此采用Sigma结构和部分功率传输的理念,减小了Buck-boost LLC变换器所产生的损耗。最后实验证明了所提出拓扑优越的调压特性和高效率。
With the increasing proportion of new energy power generation, it is necessary to design a high-power converter with a high efficiency and a wide input range. In this paper, a Sigma converter composed of a Buck-boost LLC converter and an LLC based on DC trsnsformer(LLC-DCX) converter is proposed based on the existing research, which can meet the requirements of a high efficiency and a wide input range. The Buck-boost LLC converter can effectively decrease the number of components and reduce loss through bridge arm integration. However, all the input current flows through its Buck-boost inductor, which will cause a lot of loss in high-power scenarios. Therefore, the Sigma structure and the concept of partial power transmission are adopted to reduce the loss caused by the Buck-boost LLC converter. Finally, experimental results demonstrated the superior voltage regulation characteristics and high efficiency of the proposed topology.