模块化多电平换流器子模块级联数量优化设计方法

An Optimized Design Method of Cascade Number for Sub-modules in Modular Multilevel Converters

针对模块化多电平换流器(MMC)直流电压等级可能会与交流侧电网电压等级不匹配的问题,提出了一种桥臂级联子模块数量的优化设计方法。通过该方法,可以在换流器直流侧电压和交流侧电压不匹配时直接将换流器接入较低电压等级的交流电网,减少桥臂所需的子模块级联数目,同时避免使用交流变压器,以降低换流站成本和占地。通过设计实例说明了所述方法所带来的优势,并通过PSCAD/EMTDC仿真验证了采用所提出优化设计方法时的MMC在调制方法和电压平衡控制策略上的可行性。

In some applications, the DC side voltage may do not match with AC-side voltage o{ modular multilevel converter （MMC）. To solve this problem, an optimized design method is proposed to determine the number of cascade sub modules in an arm of MMC. With the proposed design method, MMC can be integrated into the AC grid of lower voltage even when the DC side voltage does not match the AC side voltage, so that the number of sub modules in MMC can be reduced and without using transformer. Therefore, the size and the cost of MMC can be significantly reduced. An simulation module is built in PSCAD/ EMTDC to verify the proposed method.