基于子模块电容电压分块的MMC直流均压控制法

Block modulation and voltage balance control of the sub-modules in modular multilevel converter direct-current

针对模块化多电平换流器在均压控制方面排序慢,开关动作次数多,以及换流器损耗大的问题,提出一种提高MMC的电容电压分块均压控制方法.依据桥臂电容电压极值来确定分块组合个数,用排序的复杂度和电压均衡效果来确定分块的多少,将不同大小的电容电压子模块放入不同的分块组合中,然后根据需要投入子模块的数目和电流方向进行优化排序,改变子模块的投入和切除状态.在PSCAD/EMTDC中21电平的MMC仿真结果显示,提出的均压方法加快了均压控制的排序,同时利用IGBT使换流器的开关损耗得到了降低.

A kind of high level of modular multilevel converter （MMC） capacitor voltage blocking balance control method is proposed to solve the problem, which the modular multilevel converter in equalizing control sorting slow, switching frequency, and the large inverter loss. Firstly, according to the extreme value of bridge arm capacitor voltage to determine the block combination, with the complexity of the sorting and the influence of voltage balance to determine how many combined number. Secondly, putting different sizes of capacitor voltage sub-modules in different block combinations, then according to the needs of input number of sub-modules and current direction to conduct optimized sorting, and change the sub-modules＇ input and resection status. The 21 levels MMC inverter is built in PSCAD/EMTDC and its simulation results show that the equalizing method can speed up the sorting of equalizing control, at the same time, the switching losses of the converter which use Insulated Gate Bipolar Transistor （IGBT） are reduced.