摘要
为了实现系统功率双向传输控制、有功无功解耦控制、故障隔离等目标,2个交流微电网通过背靠背结构的电压源型变流器(VSC)进行直流互联。在功率双向流动系统中,定功率控制模式下变流器作为功率负载时,其直流或交流端口阻抗会呈负阻抗特性,进而减小系统阻尼,容易让系统失去稳定。针对该问题,提出一种多阻抗优化控制方法,不仅将该变流器直流和交流端口的负阻抗优化为正阻抗,还对定直流电压模式下的变流器直流端口阻抗进行优化,减小两侧阻抗的相位差,多角度增强系统的稳定性。首先,对系统的结构和控制进行了简单介绍。其次,对优化前两侧变流器多个端口阻抗的特性进行分析。然后,分析了多阻抗优化控制的工作机理,并得到优化后的端口阻抗模型。依据最小环路比和奈奎斯特稳定判据,对比分析了优化前后系统的稳定性。结果表明:提出的多阻抗优化控制方法能对系统中多个端口阻抗进行优化,不仅可以将原交、直流侧的阻抗特性从负优化为正,还可以减小直流侧阻抗间的相位差,使系统保持更大的稳定裕度。最后通过Matlab/Simulink仿真对所提控制方法的有效性进行了验证。
The two AC microgrids are DC interconnected through back-to-back structured VSC converters.Usually one side converter adopts DC voltage control,and the other side converter adopts constant active power control.Under bidirectional power flow,when the power-controlled converter mode is used as a power load,its DC or AC port impedance will show negative impedance characteristics,reducing system damping and stability.To solve this problem,a multi-impedance optimization control is proposed,which not only optimizes the negative impedance to positive impedance,but also reduces the phase difference on DC side,enhancing the stability of the system completely.First,the structure of the AC micro-grid DC interconnected converter system,the topology and control of the converter are briefly introduced.Secondly,small-signal modeling was modelled of the multiple ports of the converters on both sides before the optimization,and the impedance characteristics were analyzed.Then,the working mechanism of multi-impedance optimization control is analyzed,and the optimized port impedance is re-modeled.The results show that the proposed multi-impedance optimization control can optimize the impedance of multiple ports in the system.It can not only optimize the negative impedance of the original AC and DC sides to positive impedance,but also reduce the phase difference between the impedances of the DC side,maintaining a larger stability margin and greatly improving system stability.
作者
刘振国
金铭
于海
陈文涛
杨定乾
LIU Zhenguo;JIN Ming;YU Hai;CHEN Wentao;YANG Dingqian(Electric Power Research Institute,State Grid Xinjiang Electric Power Co.,Ltd.,Urumqi 830013,China)
出处
《中国电力》
CSCD
北大核心
2023年第2期93-101,156,共10页
Electric Power
基金
国家电网公司总部科技项目(5230DK180015)。
关键词
交流微电网
变流器
小信号建模
稳定性分析
优化控制
AC microgrid
current converter
small signal modeling
stability analysis
coordinative control
