摘要
电压源型变流器技术发展日臻成熟,电压等级及容量不断提高,已成功用于柔性直流输电系统,并展现出高电压、大容量和多端柔性直流输电系统应用的发展态势。本文结合世界首个多端柔性直流输电工程,针对多端柔性直流输电系统应用中存在的强非线性和多端协调等技术难点,提出采用改进下垂控制方法,即通过多个换流站同时采用定电压控制方式运行,暂态过程中,采用定电压控制的换流站退出时系统仍能正常运行,保持直流网络功率平衡。通过检测直流网络电压和动态改变平滑切换控制器输出值,即由切换控制器选择定功率控制输出有效或定电压控制器输出有效,在无需站间通信情况下,实现定电压控制换流站和定功率控制换流站之间的相互转换,相对于传统采用单点电压控制的多端系统,具有较好的灵活性。此外,针对采用定电压控制的换流站完全退出的极端工况,设计反步电压控制器,有效地减小了暂态过电压程度,与下垂控制策略结合,能较好地实现系统直流电压的稳定控制,充分发挥其多端协调功能,提高系统抗干扰性能。仿真结果证明了所采用方法的正确性和有效性。
With the voltage source converter(VSC)technology continues improving,the development orientations of high-voltage direct current based voltage source converter(VSC-HVDC)system are high-voltage,large capacity and multi-terminal.For the technical difficulties of strong nonlinearity and multi-terminal coordination in VSC-HVDC system,an improved droop control method is proposed based on the first multi-terminal VSC-HVDC project of the world.In this method,multiple constant voltage control stations are in operation at the same time,thus during transient process,the system can continue to run when the voltage control stations exit.This can maintain the DC network power balance.Conversion between constant voltage control stations and power control stations can be realized by measuring DC voltage and changing controller output value dynamically.Namely,the switching controller selects power controller output or DC voltage controller output,without inter-station communication.Compared with the traditional single-point voltage-controlled multiterminal VSC-HVDC system,it has better flexibility.In addition,the back stepping controller of DC voltage is designed for extreme conditions that voltage control stations fail completely.It can reduce transient overvoltage level effectively.Combined with droop control strategy,its multi-terminal coordinated control function is manifested and the immunity performance is improved.The simulations have verified the proposed methods.
作者
吴杰
王志新
Wu Jie;Wang Zhixin(School of Electrical Engineering Shanghai Jiaotong University Shanghai 200240 China)
出处
《电工技术学报》
EI
CSCD
北大核心
2017年第20期241-250,共10页
Transactions of China Electrotechnical Society
基金
国家自然科学基金(51377105)
上海市教育发展基金(2015LM11)
上海市闵行区重大产业技术攻关计划(2015MH103)资助项目
关键词
高压柔性直流输电
下垂控制
反步法
协调控制
Voltage source converter-HVDC
droop control
backstepping method
coordinated control
