基于故障电流预测的柔性直流电网自适应限流策略  

Adaptive Current Limiting Strategy for Flexible DC Power Grid Based on Fault Current Prediction

作　　者：王渝红[1] 杜婷[1] 廖建权 史云翔 郭春生 王强钢[2] WANG Yuhong;DU Ting;LIAO Jianquan;SHI Yunriang;GUO Chunsheng;WANG Qianggang(College of Electrical Engineering,Sichuan University,Chengdu 610065,China;State Key Laboratory of Power Transmission Equipment&.System Security and New Technology(Chongqing University),Chongqing 400044,China)

机构地区：[1]四川大学电气工程学院,四川省成都市610065 [2]输配电装备及系统安全与新技术国家重点实验室(重庆大学),重庆市400044

出　　处：《电力系统自动化》2023年第20期134-142,共9页Automation of Electric Power Systems

基　　金：国家自然科学基金青年科学基金资助项目(52207126);国家自然科学基金联合基金集成项目(U22B6006)。

摘　　要：故障限流是保证柔性直流电网安全运行的关键技术。然而,现有基于故障限流器(FCL)的限流策略未考虑与故障严重程度的匹配,增加了FCL在轻微故障下非必要启动的次数及保护拒动的风险。针对上述问题,提出一种基于人工神经网络(ANN)预测故障电流的柔性直流电网自适应限流策略。该策略能在线评估故障严重程度并据此灵活选择加速投入、正常投入或不投入FCL,提升了FCL的限流效率。首先,分析了自适应限流及故障在线预测的必要性,并阐述了基于ANN预测故障电流的流程。在此基础上,结合差模电流积分比和故障电流瞬时值形成故障严重程度分级指标,并基于故障电流及其预测值在线评估故障严重程度。针对极严重故障、严重故障、轻微故障及区外故障分别采取相应时序的限流策略,进而形成匹配故障严重程度的柔性直流电网自适应限流策略,在避免FCL非必要启动的同时降低直流断路器开断容量需求。最后,在PSCAD/EMTDC环境中搭建了四端柔性直流电网仿真模型,以直流断路器开断电流为评估指标,对比验证了所提自适应限流策略在各故障工况下的灵敏性和有效性。Fault current limiting is a key technology to ensure the safe operation of flexible DC power grids.However,existing current limiting strategies based on fault current limiters(FCLs)do not consider matching with the severity of faults,increasing the times of unnecessary startup of FCL under minor faults and the risk of protection failure.A flexible DC power grid adaptive current limiting strategy based on artificial neural network(ANN)prediction of fault current is proposed to address the above issue.This strategy evaluates the severity of faults online and flexibly chooses the accelerated putting-in,normal putting-in,or no putting-in of FCL based on the severity,improving the current limiting efficiency of the FCL.First,the necessity of adaptive current limiting and online fault prediction is analyzed,and the process of predicting fault current based on the ANN is elaborated.On this basis,a fault severity grading indicator is formed by combining the differential mode current integral ratio and the instantaneous value of fault current,and the fault severity is evaluated online based on the fault current and its predicted value.Corresponding time series current limiting strategies are adopted for extremely severe faults,severe faults,minor faults,and external faults,in order to form an flexible DC power grid for adaptive current limiting strategy that matches the severity of the fault,avoiding unnecessary startup of FCL and reducing the demand for DC circuit breaker breaking capacity.Finally,a four-terminal flexible DC power grid simulation model is built in the PSCAD/EMTDC environment,and the sensitivity and effectiveness of the proposed adaptive current limiting strategy under various fault conditions are compared and verified using the DC circuit breaker breaking current as an evaluation indicator.

关 键 词：柔性直流电网 故障电流 故障限流器 自适应限流策略 人工神经网络 

分 类 号：TM721.1[电气工程—电力系统及自动化] TM471