摘要
介绍了模块化多电平换流器(MMC)的拓扑结构和工作原理。对MMC可以使用的几种调制策略进行了比较,当MMC用于直流输电这样的高压大功率场合时,需要的电平数很多,而最近电平逼近调制(NLM)正适用于这类情况。提出了NLM在MMC中的实现方法,给出了计算NLM基波和各次谐波幅值的解析表达式,绘出了NLM的基波分量和总谐波畸变率随电平数和调制波幅值的变化而变化的情况。指出了当系统进入严重过调制区时,NLM性能会明显恶化。利用PSCAD/EMTDC下搭建的仿真系统对NLM的基波和谐波特性进行了仿真。理论计算和仿真结果均表明使用NLM策略的MMC在较大的工作范围内都具有很好的调制波跟踪能力和较低的谐波水平。
This paper describes the circuit configuration and operation mechanism of MMC.The comparisons of some modulation methods for MMC show that NLM is the best for MMC in high-power high-voltage applications,such as high voltage direct current（HVDC）transmission.The NLM method for MMC is proposed,and the formulas to calculate the fundamental and harmonic components are given.The variations of the fundamental component and the voltage THD with the number of voltage levels and the amplitude of modulation wave are exhibited.The system performance will be deteriorated in the over modulation range,which need to be avoided.Simulation results obtained with PSCAD/EMTDC are consistent with the theoretical results.Both the calculation and simulation results show that the output voltage of NLM based MMC is a good approximation to the modulation wave and has low harmonic contents in a wide operation range.
出处
《电力系统自动化》
EI
CSCD
北大核心
2010年第2期48-52,共5页
Automation of Electric Power Systems
关键词
模块化多电平换流器
电压源换流器
高压直流输电
调制策略
最近电平逼近调制
谐波
总谐波畸变率
modular multilevel converter（MMC）
voltage sourced converter（VSC）
high voltage direct current（HVDC）
modulation methods
nearest level modulation（NLM）
harmonics
total harmonic distortion（THD）
