直流故障下基于交流侧馈能的MMC换流站主动限流策略  

Active current limiting strategy of an MMC converter station based on AC side energy feedback under a DC fault

作　　者：唐欣[1] 黄晟 潘一彬 李珍 TANG Xin;HUANG Sheng;PAN Yibin;LI Zhen(College of Electrical and Information Engineering,Changsha University of Technology,Changsha 410000,China)

机构地区：[1]长沙理工大学电气与信息工程学院,湖南长沙410000

出　　处：《电力系统保护与控制》2023年第9期56-64,共9页Power System Protection and Control

基　　金：国家自然科学基金项目资助(51977013)。

摘　　要：模块化多电平换流器(modular multi-level converter,MMC)直流侧发生接地短路时,故障电流具有上升快、峰值高的特点。为减小断路器开断应力,从能量角度出发,对子模块和桥臂动态过程进行分析,建立考虑交流侧功率影响的直流故障下MMC等效放电模型,推导出了故障电流表达式。提出一种基于交流侧馈能的主动限流策略,通过引入前馈控制,对含物理限流电阻的控制框图进行变换,等效增大直流侧限流电阻。并对其参数进行整定,进而将故障时电容部分能量馈入交流侧,达到了降低故障时电流上升率和电流峰值的目的。该控制方式不仅抑制交流侧电源向故障点放电,而且减小了直流电容向故障点的放电电流。最后,在PSCAD/EMTDC中建立了四端环状MMC输电网模型,验证了所提方案的可行性。When a grounding short circuit occurs on the DC side of a modular multi-level converter(MMC),the fault current has the characteristics of fast rise and high peak value.To reduce the breaking stress of the circuit breaker,the dynamic process of the sub-module and the bridge arm is analyzed from the point of view of energy.An equivalent discharge model of an MMC under DC fault considering the influence of AC power is established,and the expression of fault current is derived.An active current limiting strategy based on AC side feeding is proposed.By introducing feed-forward control,the control block diagram with physical current limiting resistance is transformed,and the DC side current limiting resistance is increased equally,and its parameters are adjusted.Then part of the energy of the capacitor during the fault is fed to the AC side,so as to reduce the current rise rate and peak current during the fault.This control method not only suppresses the discharge from the AC side power supply to the fault point,but also reduces the discharge current from the DC capacitor to the fault point.Finally,a four-terminal ring MMC transmission network model is established in PSCAD/EMTDC to verify the feasibility of the proposed scheme.

关 键 词：MMC 过电流 等效放电模型 虚拟电阻 主动限流 

分 类 号：TM721.1[电气工程—电力系统及自动化] TM46