基于算法优化的MMC子模块降频均压策略研究

Frequency Reduction and Voltage Equalization Strategy of MMC Submodules Based on Algorithm Optimization

伴随着应用电压等级不断升高,模块化多电平换流器子模块级联数目大幅增长,各子模块间的电容电压均衡问题尤为明显.高效的排序算法是作用于子模块电压均衡过程的核心模块,降低排序算法的时间复杂度可以有效减轻硬件控制器设计难度,提高系统可靠性.基于快速排序的Top K算法,在原有子模块投切策略基础上每轮排序只提取需要的前K个模块,并将有助于MMC均压的开关降频策略引入Top K算法进行深度优化,非全排序降频算法能够大幅减少排序次数,有效缩减程序仿真运算量.在多电平双端背靠背互联系统Simulink仿真模型中,验证算法封装子模块排序和降频实验效果良好.

With the improvement of application voltage level,the number of cascades of MMC sub-modules increases greatly,especially the voltage balancing problem of sub-module capacitors.Efficient sorting algorithm is the core module of capacitor voltage balancing control of sub-module.Reducing the time complexity of sorting algorithm can effectively reduce the difficulty of hardware controller design and improve the system reliability.Based on the Top K algorithm of fast sorting,only the front K modules are extracted for each round of sorting on the basis of the original sub module switching strategy,and the switch frequency reduction strategy which is helpful for MMC voltage sharing is introduced into the Top K algorithm for depth optimization.The incomplete sorting frequency reduction algorithm can significantly reduce the times of sorting and effectively reduce the amount of simulation calculation.In the simulation model of MMC-HVDC system,both sorting improvement and frequency reduction experiments in the encapsulated submodules are validated well.