MMC模块化串并联扩容方法及在能源互联网中的应用

能源互联网可以实现大规模可再生能源的高效利用与远距离传输。基于模块化多电平技术的直流电网是构成能源互联网、实现可再生能源电能传输的重要组成部分与有效技术手段。但受限于现有电力电子技术的发展，单个模块化多电平换流器（modular multilevel converter，MMC）的额定电压和额定电流难以提高，难以实现跨国或者跨洲的大规模可再生能源电力传输。针对上述问题，研究了MMC的子模块串、并联，桥臂串、并联及换流站串、并联的拓扑结构，并对比分析了各种结构在大规模风电并网传输中应用的技术优缺点。为了综合MMC和相控换流器（line commutated converter, LCC）的技术优势，并适应未来能源互联网的需要，还研究了MMC与LCC的串、并联结构。最后，仿真研究了串联结构的均压问题和并联结构的均流问题。通过对各种串并联扩容方法的对比研究，得出了MMC串联及MMC与LCC串联在高压大功率场合中更具技术优势的结论。研究结果可以为大功率换流站的构成方法与工程应用提供参考。

Capacity Enlarging Method of Series and Parallel MMC and Its Application in Energy Internet

Energy internet technology can achieve the efficient utilization and long-distance transmission of large-scale renewable energy. The DC grid based on modular multilevel converter （MMC） technology is an important component and effective technical mean of energy internet and renewable energy transmission. However, limited to the existing development of power electronic technology, the rated voltage and rated current of single MMC are hard to increase, which will hamper the large-scale renewable energy transmission over countries or over states. To solve the above challenges, the topological structures of MMCs sub-modules, arms and converters in series and parallel were studied, whose technology advantages and disadvantages applied in large-scale wind power integration transmission were analyzed. Moreover, in order to combine the advantages of line commutated converter （LCC） and MMC and meet the need of future energy internet, the series, parallel structures of LCC and MMC were also studied. At last, the voltage balancing problem for series structure and current balancing problem for parallel structure were simulated and analyzed. Through the comparison on the capacity enlarging methods of various series, parallel structure, it can be concluded that either the series of MMC or the series of MMC and LCC is applicable for high voltage and power application. The research results can provide reference for the construction method and engineering application of high-power converter station.