最近电平逼近调制的基波谐波特性解析计算  

Analytical Calculation of Fundamental Wave and Harmonic Characteristics for Nearest Level Modulation

作　　者：管敏渊[1] 徐政[1] 潘伟勇[1] 屠卿瑞[1] 

机构地区：[1]浙江大学电气工程学院,杭州310027

出　　处：《高电压技术》2010年第5期1327-1332,共6页High Voltage Engineering

基　　金：国家"十一五"科技支撑计划重大项目(2006BAA02A21)~~

摘　　要：随着模块化多电平换流器(modular multilevel converter,MMC)型直流输电工程的出现,高电平数换流器将在电力系统中得到越来越多的应用。最近电平逼近调制(nearest level modulation,NLM)是一种适合高电平数换流器的阶梯波调制策略,其实时控制触发方式用于理论研究,而其等间隔控制触发方式适合用于数字实现。为此推导了阶梯波调制的通用Fourier级数解析表达式,在PSCAD/EMTDC下搭建了基于NLM的两端MMC直流输电仿真系统。利用解析计算和仿真两种方法研究了实时控制触发和等间隔控制触发下NLM的基波和谐波特性。理论计算和仿真研究表明,间隔时间越大,阶梯波对调制波逼近的延迟越大。这会造成阶梯波的基波幅值偏差和总谐波畸变率变大,并且使系统的连续调节能力变差。基波幅值偏差过大会导致控制系统不稳定,因此在条件允许的前提下,等间隔控制触发选用适当小的间隔时间是有必要的。Since the emergence of modular multilevel converter （MMC） based high voltage direct current transmission（HVDC） project,more and more multilevel converters will be utilized in power system.Nearest level modulation（NLM） is a staircase modulation method fit for converters with high number of voltage levels.Its real time controlled firing scheme is used for theoretical analysis,and the equidistant controlled firing scheme is suitable for digital implementation.The generic Fourier series representation of stepped waveform was derived,and a simulation system of MMC based HVDC using NLM was implemented in PSCAD/EMTDC.The fundamental wave and harmonic characteristics of NLM with different control intervals were analytically calculated and simulated.The results show the tracking performance and the continuous regulating ability of NLM are deteriorated at a large control interval,which leads to large deviation in the amplitude of fundamental wave and high THD.Thus,an adequate small control interval is necessary for the equidistant controlled firing scheme of NLM.

关 键 词：模块化多电平换流器 电压源换流器型直流输电 阶梯波调制 最近电平逼近调制 谐波 FOURIER级数 

分 类 号：TM46[电气工程—电器] TM744