模块化多电平换流器的分频均压控制策略

Frequency dividing control of capacitor voltage balance for modular multilevel converter

随着模块化多电平换流器(MMC)子模块个数的增多,传统基于排序的均压方法存在开关频率偏高和排序计算量偏大的问题。为此提出了分频均压控制策略,使电容电压排序频率远小于触发控制频率,并从理论上给出了此控制策略的排序频率选取方法。通过厦门柔性直流输电示范工程的电磁暂态仿真算例验证了所提出的分频均压控制策略在一定范围内减小排序频率时,可以在满足MMC的运行性能及安全性的前提下,明显减小开关频率和减轻排序计算负担。

With the increase of the sub-module number of MMC（Modular Multilevel Converter）,the traditional capacitor voltage balancing method has two problems,i.e.high switching frequency and large computation amount.In order to solve these problems,the frequency dividing control strategy of capacitor voltage balance is proposed,which makes the sorting frequency far less than the trigger control frequency.The selection method for sorting frequency in proposed control strategy is given theoretically.The electromagnetic transient simulative results based on Xiamen flexible DC project verify the proposed control strategy reduces the sorting frequency in a certain range,which can meet the running performance and the safety of MMC,and significantly reduce the switching frequency and the computational burden of sorting.