两电平VSC-HVDC系统直流侧接地方式选择  

DC Side Grounding Methodology for a Two-level VSC HVDC System

作　　者：管敏渊[1] 徐政[1] 

机构地区：[1]浙江大学电气工程学院,浙江省杭州市310027

出　　处：《电力系统自动化》2009年第5期55-60,共6页Automation of Electric Power Systems

基　　金：国家电网公司科技项目(SGKJ[2007]249)~~

摘　　要：基于开关函数法对两电平电压源换流器型高压直流(VSC-HVDC)系统进行了建模,分析了正弦脉宽调制(SPWM)时VSC的谐波特性,指出零序的载波频率次谐波电压、电流是VSC交流侧的主要谐波分量,推导了该零序谐波电流经开关函数中的基波分量作用后将在直流侧形成载波频率次不平衡谐波电流。发现了直流侧不平衡谐波电流流通路径与直流侧的接地方式密切相关,只有VSC-HVDC系统两端直流侧都接地,直流侧不平衡谐波电流才能通过本端直流侧接地点和交流侧高通滤波器接地点流通而被限制在本地,否则该高频谐波电流将在输电线路上流通,从而引发一系列危害。在PSCAD/EMTDC下搭建VSC-HVDC系统进行了仿真分析,验证了以上结果,提出了两电平VSC-HVDC系统需要采用两端直流侧都接地的拓扑结构。A mathematical model of two-level voltage sourced converter （VSC） HVDC system based on the switching function method is introduced. The paper analyzes the harmonic characteristics of VSC with sinusoidal pulse width modulation （SPWM）, points out that the zero sequence harmonics at the carrier frequency are the main harmonic component at the AC side. The zero sequence harmonic current is converted into unbalanced DC side harmonic currents at the same frequency by multiplying the fundamental component of the switching functions. The DC side grounding method is found to determine the path of the unbalanced DC side harmonic currents. With both DC sides of the VSC HVDC system grounded, the unbalanced DC side harmonic currents will circulate at local area via the DC side grounding point and the AC side high-pass filter grounding point. Otherwise, the unbalanced DC side harmonic currents will flow along the DC cables, and cause a series of problems. The results are verified by a test system established in PSCAD/EMTDC. It concludes that the DC sides of both terminals need to be grounded in a VSC HVDC system.

关 键 词：VSC-HVDC系统 两电平电压源型换流器 接地方式 开关函数 谐波 直流侧电流 

分 类 号：TM862[电气工程—高电压与绝缘技术]