基于快速排序法的MMC电容电压均衡控制策略

Capacitance-Voltage Balancing Control Method for the Submodule of Modular Multilevel Converter Based on the Rapid Sequencing Method

摘要: 随着基于模块化多电平换流器的柔性直流输电工程容量和直流侧电压等级的提高，对子模块电容平衡控制提出了更高的要求。为降低众多子模块均压排序的计算量及MMC开关损耗，提出一种基于分治思想和快速排序算法的改进子模块电容电压均衡控制策略。根据每个控制周期的投切控制指令和桥臂充放电状态，将待投切子模块电容电压值进行两轮分组，然后根据具体投切数量在最小范围内选取与额定电容电压差值较大的子模块进行投切操作，从而避免对所有子模块进行重复排序。最后，通过在PSCAD/EMTDC中搭建MMC模型对本文方法进行了验证，结果表明该策略可以有效减小排序计算量并降低MMC开关损耗。

Abstract: With the improvement of the engineering capacity and the DC voltage level of FACTS based on modular multilevel converter (MMC), it is putting forward higher requirement for capacitor bal-ance control issue of MMC sub-modules (SMs). In order to reduce the computational complexity of voltage balancing sorting of SMs and switching dissipation of MMC, a new voltage balancing control improved algorithm based on Quick Sort method and divided conquer was presented in this paper: dividing into groups twice according to the switching control instruction as well as charging and discharging active status of bridge arms in each control cycle; then choosing the SMs which have large difference with rated voltage within the minimum range on the basis of specific switching number; avoiding the prophecy of collating all SMs repeatedly. A MMC model has been set up on the PSCAD. Finally, the effectiveness of the design control method was verified. The results show that this voltage balancing method can be realized effectively under low switching dissipation and low ranking calculation.