摘要
针对柔性直流(VSC-HVDC)输电系统在交流电网电压不平衡情况下,功率产生2倍频波动分量的问题,首先通过分析不平衡电网电压下VSC换流器的数学模型,将引起系统2倍频功率波动的因素归结为电流因素分量和电压因素分量,推导并建立了不平衡电网电压下以系统2倍频功率为状态变量的控制方程;进而基于该控制方程提出了一种VSC-HVDC功率滑模变结构补偿策略,以同时抑制电流因素和电压因素引起的功率波动,以及VSC换流器输出电流的畸变,并提高了变工况状态下系统的动态响应性能。将该补偿策略引入到VSC-HVDC原有矢量控制环节中,当交流电网电压不平衡时,该控制策略能够单独对其中的2倍频分量进行有效控制,可以在不影响正常状态运行的同时又能抑制2倍频功率波动分量。通过在PSCAD/EMTDC中搭建两端VSC-HVDC仿真模型,证明了该策略抑制不平衡电网电压下系统2倍频功率和平衡交流侧电流的有效性。
Under the influence of unbalanced grid voltage,the double line-frequency ripple will appear in the output power of voltage source converter based high voltage direct current transmission(VSC-HVDC).In this paper,the mathematical model of VSC under unbalanced grid voltage is first analyzed,and the double line-frequency ripple of the VSC converter power is consequently ascribed to current factor and voltage factor.Then the double line-frequency power control equation is established,and a power sliding mode variable structure compensation control of VSC-HVDC is proposed to suppress the ripple power caused by current factor and voltage factor.In this case,the double line-frequency power fluctuation and the distorted output current can be suppressed at the same time,hence the system dynamic performance in variable operating conditions can be ensured.The compensation control is introduced into the original vector control and can separately control the double line-frequency component effectively under unbalanced grid voltage,which will not affect system normal operating.The proposed strategy is verified by the simulations of a two-terminal VSC-HVDC in PSCAD/EMTDC.
作者
刘子文
苗世洪
范志华
魏德华
涂青宇
Liu Ziwen;Miao Shihong;Fan Zhihua;Wei Dehua;Tu Qingyu(State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China)
出处
《电工技术学报》
EI
CSCD
北大核心
2018年第14期3296-3305,共10页
Transactions of China Electrotechnical Society
基金
国家重点研发计划(2017YFB0903601)
国家自然科学基金(51377068)资助项目
关键词
不平衡电网电压
柔性直流
2倍频波动
电流/电压因素分量
滑模变结构控制
Unbalanced grid voltage
VSC-HVDC
double line-frequency ripple
current factor and voltage factor
sliding mode variable structure control
