摘要
模块化多电平换流器(modular multilevel converter,MMC)因其模块化设计易于扩展、开关频率低等特点,在中高压大功率系统中得到越来越多的应用;而最近电平调制(nearest level modulation,NLM)作为一种实时阶梯波调制方式,常用于上百个电平数的场合。首先对MMC的基本结构和最近电平调制的运行机理进行分析,推导出该调制策略所存在的固有缺陷;在此基础上,提出了改进的最近电平调制策略。通过引入调制波与阶梯波间偏差,有效避免了在电平数较低情况下电容电压波动、环流等问题。最后在PSCAD/EMTDC中搭建了MMC仿真模型,对改进前后的最近电平调制策略进行了比较分析。仿真结果表明该改进调制策略可以提高系统的稳态运行特性,对子模块电容电压波动和环流产生抑制作用。
Modular multilevel converter can be easily applied to higher voltage and large-scale capacity with good expansibility and low switching frequency.And the optimized nearest level modulation is used for modular multilevel converter under low-level conditions.The reason of unbalanced voltage with nearest level control method.Under low-level modular multilevel converter,nearest level control method have problems such as sub-module capacitor voltages balancing and circulating currents were analyzed.Then propose an optimized control method considering inaccuracy of integral function.The effectiveness of the proposed controlling method is verified through simulation results using PSCAD/EMTDC and a comparison between traditional and optimized nearest level control is also included.
出处
《科学技术与工程》
北大核心
2017年第30期63-68,共6页
Science Technology and Engineering
基金
国家电网公司科技项目(52130415000 M)资助
关键词
模块化多电平换流器
最近电平调制
电压均衡
环流
子模块
modular multilevel converter nearest level modulation voltage balancing circulatingcurrent sub modules
