【摘要】：采用小電流接地方式的模塊化多電平多端柔性直流輸電系統(tǒng)(MMC based multi-terminal HVDC,MMC-MTDC)發(fā)生直流線路單極接地后,所有非故障極線路電壓升高為額定值的2倍,威脅線路和設備安全,因此,需要快速識別并切除故障線路,以恢復MMC-MTDC系統(tǒng)的正常運行。而小電流接地方式的MMC-MTDC系統(tǒng)單極接地后,無穩(wěn)態(tài)故障電流,且各直流線路穩(wěn)態(tài)電壓基本相同,無法依靠穩(wěn)態(tài)電壓、電流量來識別故障線路。分析了MMC-MTDC單極接地時線路對地電容電流暫態(tài)變化特性,提出采用線路兩端的暫態(tài)差流作為區(qū)分故障線路和非故障線路的依據(jù);進一步通過計算線路兩端差流的短時能量來擴大故障線路和非故障線路的差異,減少暫態(tài)過程對故障線路識別的影響,達到可靠識別故障線路的目的。在PSCAD中搭建四端MMCMTDC系統(tǒng)進行仿真,結(jié)果表明故障線路兩端差流短時能量遠大于非故障線路兩端差流短時能量,并且該故障線路差動電流短時能量波動較小,能可靠識別接地線路。
[Abstract]:After unipolar grounding of DC line occurs in modularized multilevel flexible HVDC transmission system (MMC based multi-terminal HVDC,MMC-MTDC) with small current grounding mode, the voltage of all non-fault pole lines increases twice as high as the rated value. It is necessary to quickly identify and remove the fault lines in order to restore the normal operation of the MMC-MTDC system. However, there is no steady-state fault current after single-pole grounding in MMC-MTDC system with small current grounding mode, and the steady voltage of each DC line is basically the same, so it is impossible to identify the fault line by steady-state voltage and current. In this paper, the transient characteristics of line to ground capacitive current are analyzed when MMC-MTDC monopole is grounded, and the transient differential current at both ends of the line is proposed as the basis for distinguishing fault line from non-fault line. Furthermore, the difference between fault line and non-fault line can be enlarged by calculating the short time energy of differential current at both ends of line, and the influence of transient process on fault line identification can be reduced, and the purpose of reliable identification of fault line can be achieved. A four-terminal MMCMTDC system is built in PSCAD for simulation. The results show that the short time energy of differential current at both ends of fault line is much larger than that of non-fault line, and the short time energy fluctuation of differential current of fault line is small. Reliable identification of ground wiring.
【作者單位】： 新能源電力系統(tǒng)國家重點實驗室(華北電力大學);中國電力科學研究院;
【基金】：國家重點基礎研究發(fā)展計劃項目(973項目)(2012CB215206) 國家自然科學基金項目(51407067;51222703) 高等學校學科創(chuàng)新引智計劃資助(B08013)~~
【分類號】：TM721.1

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