摘要
级联型混合直流输电系统具有能抑制换相失败、传输大容量功率的优势。但当级联型混合直流低端模块化多电平换流器(MMC)采用主从控制时,若系统发生交直流故障或负荷突增,可能会产生电流不平衡问题,导致受端交流侧功率出现大范围反向传输及电压支撑能力下降。为解决该问题并增强受端电网的稳定性,针对级联型混合直流输电系统,提出一种基于统一潮流控制器(UPFC)的柔性潮流协调控制策略。研究了基于柔性交流输电(FACTS)设备统一潮流控制器(UPFC)的级联型混合直流系统柔性潮流控制特性,针对系统故障及大扰动时出现的功率返送及电压稳定性问题,提出基于UPFC的频率支撑策略和基于动态限幅的电压支撑策略。该策略将送端侧故障带来的功率扰动转移到受端交流系统UPFC所在线路,利用UPFC功率补偿能力进行协调,同时基于动态限幅控制策略,采用无功优先控制方式提高换流站无功输出能力。最后,在PSCAD–EMTDC平台搭建了含受端交流系统的级联型混合直流输电系统模型。首先,仿真了LCC直流电流指令值下降过程,结果表明,本文所提基于UPFC的协调控制策略可以有效地减小交流系统频率波动,抑制功率返送现象;其次,仿真了系统负荷突增过程,验证了动态限幅控制策略能更好地提升MMC对交流系统的电压支撑能力;最后,仿真了连锁故障过程,结果表明,所提协调控制策略能有效地实现对系统频率和电压支撑,抑制功率波动,提高了级联型混合直流系统及受端电网的稳定性。因此,本文提出的级联型混合直流与UPFC的柔性潮流协调控制策略具有有效性和可行性。
The cascaded hybrid DC transmission system offers advantages in restraining commutation failure and transmitting large capacity power.However,when the downside MMC inverter of the cascaded hybrid HVDC employs master-slave control,AC/DC faults or sudden load increases can lead to a current imbalance problem.This results in large-scale power reverse transmission on the AC side and a decrease in voltage support ability.To enhance the stability of the receiving end power grid,this paper introduces a flexible power flow coordination control strategy based on UPFC for cascaded hybrid DC transmission systems.The article investigates the power flow control characteristics of a cascaded hybrid DC system with UPFC connected nearby.To address issues such as inverse power transmission and voltage support stability during faults and large disturbances,the paper proposes a frequency support strategy based on UPFC and a voltage support strategy based on dynamic limiting.This strategy redirects the power disturbance caused by the sending side fault to the UPFC line of the receiving AC system,leveraging UPFC’s power compensation ability for coordination.Additionally,the dynamic limiting control strategy enlarges reactive power output capacity.Sub-sequently,the paper establishes a model of the cascaded hybrid DC transmission system with the receiving AC system using PSCAD-EMTDC software.Firstly,the simulation demonstrates the decrease in LCC DC current command value,showing that the coordinated control strategy based on UPFC effectively reduces frequency fluctuations in AC systems and suppresses power backflow phenomena.Secondly,the simulation of a sudden increase in system load verifies that the dynamic limiting control strategy enhances the voltage support capability of MMC for the AC system.Finally,the paper simulates the cascading fault process,revealing that the proposed coordinated control strategy effectively supports sys-tem frequency and voltage.It suppresses power fluctuations,thereby improving the stability of the cascaded hybrid DC system and the receiving power grid.In conclusion,the results demonstrate the effectiveness and feasibility of the flexible power flow coordination control strategy pro-posed in this paper for cascaded hybrid DC and UPFC.
作者
黑玉鹏
张英敏
李保宏
江琴
张婉欣
张敏
王腾鑫
HEI Yupeng;ZHANG Yingmin;LI Baohong;JIANG Qin;ZHANG Wanxin;ZHANG Min;WANG Tengxin(School of Electrical Eng.,Sichuan Univ.,Chengdu 610065,China;State Grid Shanxi Electric Power Research Inst.,Taiyuan 030002,China)
出处
《工程科学与技术》
EI
CAS
CSCD
北大核心
2024年第2期80-90,共11页
Advanced Engineering Sciences
基金
国家电网总部科技项目(5100–202199274A–0–0–00)。
