模块化多电平SVG负序补偿容量比较

Comparison of Negative Sequence Compensation Capacity Between SVGs Based on Modular Multilevel Converters

全桥单元作为子模块且主电路采用三角形连接的拓扑(single-delta bridge cells,SDBC)和半桥单元作为子模块且主电路采用双星形连接的拓扑(double-star chopper cells,DSCC)都可应用于负序电流的补偿,但两种拓扑负序电流补偿机理不同,哪种拓扑更具优势尚待研究。文中分别阐明了SDBC型静止无功发生器(static var generator,SVG)和双星形连接的拓扑(double-star chopper cells,DSCC)型SVG的负序补偿原理,对环流和桥臂电流进行了数学推导,并进行了仿真验证。对比分析了两种模块化多电平SVG的负序补偿特性,分析表明在相同的负序补偿情况下,DSCC型SVG的桥臂电流应力和安装容量均小于SDBC型SVG。所得结论为工程应用时合理选择负序补偿拓扑提供了理论依据。

Two kinds of SVGs based on modular multilevel converters can be applied to negative sequence current compensation, which are cascaded by bridge cells with delta configuration （SDBC） and cascaded by chopper ceils with double star configuration （DSCC）. The negative sequence current compensation mechanisms of SDBC converter and DSCC converter are different, it needs further study which kind of topology is more to identify. This paper expounded the negative sequence compensation principle of the SDBC-SVG and the DSCC-SVG, and deduced the circulation current and bridge arm currents mathematically. The correctness of the derivation was validated by PSIM simulation. Through contrastive analysis of bridge arm currents stress and the installed capacity of two kinds of modular multilevel SVGs, it was found that the negative sequence compensation characteristics of DSCC-SVG are superior to SDBC-SVG. The conclusion provides a theoretical reference for making reasonable selection of negative sequence compensation topology in engineering applications.