摘要
特高压混合级联直流输电系统结合了电网换相换流器(line commutated converter,LCC)和模块化多电平换流器(modular multilevel converter,MMC)的优势,具有很好的工程应用前景。该文建立整流侧为双12脉动LCC,逆变侧为一个LCC与3个并联MMC串联的特高压混合级联直流输电系统,针对其逆变站多个并联MMC站之间不平衡电流的问题进行研究,分析不平衡电流的产生机理,并提出一种基于不平衡电流进行功率补偿的电流均衡控制策略。该控制策略首先获得MMC换流站间的电流不平衡量,再转化为功率偏差量补偿至定有功功率控制MMC站的外环有功功率控制环节中,由此实现对MMC换流器间不平衡电流的均衡控制。基于PSCAD/EMTDC搭建特高压混合级联直流输电系统的仿真模型,在逆变侧LCC降压运行和交流侧故障导致LCC换相失败2种工况下,对比研究未投入/投入均衡控制策略时系统的动态响应特性,结果表明,所提出的控制策略不仅可有效均衡多个MMC换流器之间的不平衡电流,而且可显著加快系统的恢复速度,因此具有一定的工程应用价值。
The hybrid cascaded ultra-high voltage direct current(UHVDC) transmission system combines the advantages of the line commutated converter(LCC) and the modular multilevel converter(MMC), and has a good engineering application prospect. This paper established a hybrid cascaded UHVDC transmission system, whose rectifier side is a dual 12-pluse LCC and inverter side is an LCC connected in series with three paralleled MMCs. This paper investigated the unbalanced current issue among multiple paralleled MMCs at the inverter side in the hybrid cascaded UHVDC system, analyzed the mechanism of unbalanced current, and then purposed a balancing control strategy by compensating the active power based on the unbalanced current.The proposed control strategy first obtains the unbalanced current value among the MMC stations, and then generates the compensated active power to the outer loop of the active power control of power-controlled MMC stations, thereby realizes the current balance. The hybrid cascaded UHVDC transmission system was built in the PSCAD/EMTDC simulation environment. Under the two conditions, i.e. DC voltage step-down of LCC inverter and commutation failure of LCC inverter caused by faults on the AC side, the dynamic responses of the system with/without the proposed balancing control strategy are compared and investigated. The results show that the proposed control strategy not only can effectively balance the unbalanced current among multiple MMCs, but also can significantly speed up the recovery of the system, thus has certain engineering application value.
作者
郭春义
吴张曦
赵成勇
GUO Chunyi;WU Zhangxi;ZHAO Chengyong(State Key Laboratory for Alternate Electrical Power System With Renewable Energy Sources(North China Electric Power University),Changping District,Beijing 102206,China)
出处
《中国电机工程学报》
EI
CSCD
北大核心
2020年第20期6653-6662,共10页
Proceedings of the CSEE
基金
国家自然科学基金(面上项目)(51877077)。
关键词
特高压混合级联直流输电系统
电网换相换流器
模块化多电平换流器
不平衡电流
均衡控制策略
hybrid cascaded ultra-high voltage direct current transmission system
line commutated converter
modular multilevel converter(MMC)
unbalanced current
balancing control strategy
