【摘要】：近年來,隨著直流輸電技術(shù)的進(jìn)步,柔性直流輸電因其可控性強(qiáng)、不存在換相失敗問題、易于構(gòu)建多端直流系統(tǒng)等優(yōu)點(diǎn)得到快速發(fā)展。模塊化多電平換流器(Modular Multilevel Converter,MMC)具有高度的模塊化結(jié)構(gòu)、可以擴(kuò)展到任何電壓等級(jí)、波形質(zhì)量高和故障處理能力強(qiáng)等特點(diǎn),在柔性直流輸電實(shí)際工程中得到廣泛應(yīng)用。隨著直流系統(tǒng)容量的增加,強(qiáng)耦合情況下的混合系統(tǒng)在電網(wǎng)調(diào)度、協(xié)調(diào)控制等方面存在許多新的問題。對(duì)于含MMC-HVDC的交直流混合系統(tǒng),其繼電保護(hù)的動(dòng)作機(jī)理和配置都與傳統(tǒng)交流系統(tǒng)存在較大區(qū)別。本文對(duì)這一問題開展研究,對(duì)現(xiàn)有繼電保護(hù)配置進(jìn)行總結(jié),在分析接入MMC-HVDC的交直流混合系統(tǒng)中存在的不正確動(dòng)作基礎(chǔ)上,提出保護(hù)改進(jìn)方案。本文首先按照保護(hù)對(duì)象的不同,將含MMC-HVDC的交直流混合系統(tǒng)劃分為不同的保護(hù)區(qū),對(duì)現(xiàn)有繼電保護(hù)配置進(jìn)行了總結(jié)。然后,從諧波影響、距離保護(hù)存在拒動(dòng)、零序電壓保護(hù)誤動(dòng)方面分析了接入MMC-HVDC的交直流混合系統(tǒng)中存在的不正確動(dòng)作問題。在諧波影響方面,研究了MMC電平數(shù)、交流系統(tǒng)參數(shù)與輸出諧波特性的關(guān)系,分析了由于諧波含量大和保護(hù)裝置選擇不合理而造成的誤動(dòng)。在此基礎(chǔ)上,提出了防范措施,避免誤動(dòng)的發(fā)生。在距離保護(hù)方面,深入研究了MMC-HVDC系統(tǒng)運(yùn)行方式對(duì)交流線路距離保護(hù)的影響,揭示了距離保護(hù)Ⅱ段發(fā)生拒動(dòng)的原因。從整定方法上出發(fā),提出了基于公共連接點(diǎn)處量測(cè)信息的自適應(yīng)距離保護(hù)方法能夠克服MMC-HVDC對(duì)距離保護(hù)Ⅱ段的影響。這樣可以避免出現(xiàn)因保護(hù)覆蓋下一線路過短時(shí),本線路末端短路故障引起的距離保護(hù)Ⅱ段保護(hù)拒動(dòng)的風(fēng)險(xiǎn),減小了故障的清除時(shí)間,對(duì)電力系統(tǒng)的穩(wěn)定運(yùn)行具有重要的意義。在零序電壓保護(hù)誤動(dòng)方面,建立了MMC平均值模型和零序等值網(wǎng)絡(luò),推導(dǎo)出MMC-HVDC系統(tǒng)的零序電壓關(guān)系式,著重分析了零序電壓保護(hù)誤動(dòng)的機(jī)理,并提出了保護(hù)改進(jìn)方案。最后通過仿真驗(yàn)證所做分析和所提改進(jìn)方案的有效性。
[Abstract]:In recent years, with the development of HVDC technology, flexible HVDC transmission has been rapidly developed due to its strong controllability, no commutation failure and easy to build multi-terminal HVDC system. Modular multilevel converter (Modular Multilevel Converter,MMC (Modular multilevel Converter), with its high modularization structure, can be extended to any voltage level, high waveform quality and strong fault handling capability. It has been widely used in the practical engineering of flexible DC transmission. With the increase of DC system capacity, there are many new problems in power network dispatching and coordination control of hybrid systems with strong coupling. For AC / DC hybrid system with MMC-HVDC, the action mechanism and configuration of relay protection are different from those of traditional AC system. This paper studies this problem and summarizes the existing relay protection configuration. On the basis of analyzing the incorrect action of AC / DC hybrid system connected to MMC-HVDC, the protection improvement scheme is put forward. In this paper, according to the different protection objects, the AC / DC hybrid system with MMC-HVDC is divided into different protected areas, and the existing relay protection configuration is summarized. Then, the problem of incorrect operation in AC / DC hybrid system connected to MMC-HVDC is analyzed from harmonic effect, distance protection and zero sequence voltage protection misoperation. In the aspect of harmonic effect, the relationship between MMC level, AC system parameters and output harmonic characteristics is studied, and the misoperation caused by large harmonic content and unreasonable selection of protection device is analyzed. On this basis, the preventive measures are put forward to avoid the occurrence of misoperation. In the aspect of distance protection, the influence of the operation mode of MMC-HVDC system on the distance protection of AC lines is deeply studied, and the reasons for the failure of distance protection in the second section of distance protection are revealed. Based on the tuning method, an adaptive distance protection method based on the measurement information at the common connection point is proposed, which can overcome the influence of MMC-HVDC on the distance protection stage 鈪，

本文編號(hào)：2442172