【作者】 张璞；

【导师】 王钢；

【作者基本信息】 华南理工大学 ， 电力系统及其自动化， 2010， 博士

【摘要】 近年来,我国加快了直流输电工程的建设。直流输电具有众多优点,同时也不可避免地给电网带来许多问题。其中,直流馈入对交流保护动作特性的影响是值得重点关注的问题之一。在交直流混合系统中,交流与直流系统间存在紧密的电气耦合关系,其相互作用的故障暂态过程必然将改变交流电网继电保护的运行环境而对交流保护的动作行为造成影响,严重时将造成其误动或拒动。目前,相关的研究成果仍不多见,更缺乏系统的理论分析和研究。为此,本文针对多直流馈入下受端交流电网的继电保护动作特性进行了深入的研究,主要研究内容有:1.在对直流系统换相失败特性深入研究的基础上,对不同受端交流电网故障所引发的直流系统换相失败等暂态过程特点进行了系统的分析。2.建立了适用于直流受端交流电网故障分析的直流系统等值工频变化量阻抗模型,利用该模型对不同故障情况下直流系统等值工频变化量阻抗特性进行了分析。在此基础上,结合输电线路工频变化量方向保护原理,通过对受端交流电网故障及其诱发的直流系统暂态过程中工频变化量方向元件动作特性的定量分析,揭示了直流馈入对其影响的机理。通过对直流换相失败暂态过程引发非故障线路方向元件感受的暂态功率方向突变问题的研究,并结合方向纵联保护不同的动作逻辑,研究了直流换相失败暂态过程造成非故障线路方向纵联保护误动行为。在上述研究的基础上,对多直流馈入环境下受端电网输电线路工频变化量方向纵联保护动作特性进行了分析研究。基于PSCAD/EMTDC仿真,全面系统地验证了理论分析的正确性。3.在分析研究了受端交流电网故障及其诱发的直流系统暂态过程中直流系统等值故障分量电流暂态特性的基础上,对直流馈入下受端交流电网输电线路电流差动保护故障分量判据和稳态量判据的动作特性进行了全面系统的理论分析与研究,揭示了直流馈入对电流差动保护影响的机理。在此基础上,对多直流馈入下输电线路电流差动保护动作特性进行了分析研究。基于PSCAD/EMTDC仿真,全面系统地验证了理论分析的正确性。4.在对受端交流电网故障及其诱发的直流系统暂态过程中直流系统等值工频量电流暂态特性分析研究的基础上,从距离保护测量阻抗变化的角度,对直流馈入下输电线路距离保护的动作特性进行了全面系统的理论分析与研究,揭示了直流馈入对输电线路距离保护影响的机理。在此基础上,对多直流馈入环境下输电线路距离保护动作特性进行了分析研究。基于PSCAD/EMTDC仿真,全面系统地验证了理论分析的正确性。本文研究工作得到了“十一五”国家科技支撑计划重大项目(2006BAA02A30) ,国家自然科学基金项目(50977032)和粤港关键领域重点突破项目(2009498B3201)的资助。更多还原

【Abstract】 In recent years, China has accelerated the construction of direct current transmission projects. HVDC system has many advantages, but also inevitably brings many problems to the network. Among them, the impact of the HVDC infeed on the the operation characteristics of the AC protections is one of the issues that should be focused. In the AC-DC interconnected system, there is a close electrical coupling relationship between AC system and HVDC system. The fault transient process of two systems’interaction will change the operation environment of the AC system protections inevitably, so that it will influence the actions of those protections. In the worst situation, it will lead to the malfunctions or rejecting operations of the AC protections. At present, relevant research results are still rare, but the lack of systematic and theoretical analysis and research. Therefore, this paper deep studies the operation characteristics of the receiving AC network’s protections under the situation of multi-infeed HVDC system. The main contents are decribed below:1. Based on the in-depth study of HVDC commutation failure characteristics, transient process of commutation failures caused by the different receiving AC network faults is analyzed systematically.2. The impedance model of HVDC equivalent power-frequency component variation is eatablished to analyze the AC-DC interconnected system faults. On this basis, considering the principle of power-frequency componet variation direction relay, the impacts of commutation failure on power-frequency component variation elements of the fault line are analyzed. And the factors leading to the rejecting operation of power-frequency component variation directional pilot protection are also analyzed quantitatively in different situations. The issue of the transient power direction sudden change of the non-fault line direction element caused by the commutation failure transient process is analyzed. And then, based on the different action logic of direction pilot protection, the malfunction operation of directional pilot proctection of the non-fault line caused by the commutation failure transient process is analyzed. Then the action characteristics of the directional pilot protection under the situation of multi-infeed HVDC system are analyzed. The validity of theoretical analysis is proved based on the PSCAD/EMTDC simulation at last.3. Based on the theoretical analysis of fault component criterion and steady state component criterion of transmission line current differential protection, considering the transient characteristics of HVDC equivalent fault current component under the different AC fault situations, the influence mechanisms of the infeed HVDC on the fault component criterion and steady state component criterion of transmission line current differential protection are analyzed comprehensively. The HVDC impacts on the fault component criterion and steady state component criterion of transmission line current differential protection are theoretically analyzed and compared in different operation situations.Then the action characteristics of transmission line current differential protection under the situation of multi-infeed HVDC system are analyzed. At last, the validity of theoretical analysis is proved based on the PSCAD/EMTDC simulation.4. Considering the characteristics of distance protection, the impacts of infeed HVDC system on the transmission line distance protection are analyzed from the point of measured impedance variation angle of distance protection caused by the infeed HVDC system. Based on the faults of receiving network and commutation failures caused by the faults of receiving network, the impacts of HVDC system on the transmission line distance protection are theoretically analyzed and compared under the different operation situations of receiving network. Then the action characteristics of distance protection are analyzed under the situation of multi-infeed HVDC system. At last, the validity of theoretical analysis is proved based on the PSCAD/EMTDC simulation.This dissertation is supported by Key Project of the National Eleventh-Five Year Research Program of China (2006BAA02A30) ,National Natural Science Foundation of China(50977032) and Guangdong-Hongkong Technology Cooperation Funding (2009498B3201) .更多还原