發(fā)布時間：2018-09-11 21:05

【摘要】：模塊化多電平換流器(modular multilevel converter,MMC)的高壓直流輸電技術由于其換流器的結構特性,所以具有高度模塊化、諧波含量低及調控靈活的優(yōu)勢,因此,在電網領域中得到了廣泛的應用。目前,MMC-HVDC系統(tǒng)的交流側故障是國內外研究的側重點,而對于系統(tǒng)直流輸電線路的故障特性方面的研究較少。因此,本文主要內容是對MMC-HVDC系統(tǒng)直流輸電線路上的故障特性及其保護策略的研究分析,其內容結構如下:首先,敘述直流輸電技術的研究背景及現(xiàn)狀,可知柔性直流輸電技術對解決分布式能源并網、風電場并網、海上作業(yè)平臺供電、以及對偏遠無源地區(qū)等供配電場合的問題,具有較高的可行性和經濟性,對創(chuàng)建綠色、清潔的電網具有重要的價值和意義。其次,對MMC-HVDC系統(tǒng)的拓撲結構和工作原理、系統(tǒng)的調制方式、子模塊電容均壓控制和MMC-HVDC系統(tǒng)的控制體系結構進行研究分析,這為MMC-HVDC系統(tǒng)控制策略的分析及其系統(tǒng)的建模提供了理論基礎與依據(jù)。然后,針對MMC-HVDC系統(tǒng)的換流器級控制,依次對直接電流控制、啟動控制和相間環(huán)流控制,利用建立數(shù)學模型的方法對這三種控制策略作了理論的分析和研究。并在PSCAD/EMTDC的仿真軟件上,搭建了相應的控制器模型,由仿真結果表明系統(tǒng)控制策略及搭建模型的正確性。最后,針對直流輸電線路上的單極接地故障、雙極短路故障和斷線故障,從其故障機理進行分析和研究,對單極接地故障提出,通過設定不同的交直流側的保護定值和增大故障極線路的絕緣性的保護策略;對于雙極短路故障提出,故障時利用過電流抑制策略、閉鎖換流器和跳開交流斷路器的保護策略;對于斷線故障,提出通過改變換流站的控制方式的保護策略;最后通過仿真驗證其保護策略的有效性。
[Abstract]:The high voltage direct current (HVDC) transmission technology of modular multilevel converter (modular multilevel converter,MMC) has the advantages of high modularity, low harmonic content and flexible control, so it has been widely used in the field of power network. At present, the AC side fault of MMC-HVDC system is the focus of research at home and abroad, but the research on fault characteristics of HVDC transmission line is less. Therefore, the main content of this paper is to study and analyze the fault characteristics and protection strategies of HVDC transmission lines in MMC-HVDC system. The content structure is as follows: firstly, the background and current situation of HVDC transmission technology are described. It can be seen that flexible direct current transmission technology has high feasibility and economy to solve the problems of distributed energy grid, wind farm grid, offshore platform power supply, and remote and passive areas. Clean power grid has important value and significance. Secondly, the topology and working principle of MMC-HVDC system, the modulation mode of the system, the capacitive voltage sharing control of sub-module and the control system structure of MMC-HVDC system are studied and analyzed. This provides a theoretical basis for the analysis of the control strategy of MMC-HVDC system and the modeling of the system. Then, aiming at the converter level control of MMC-HVDC system, direct current control, startup control and interphase circulation control, the three control strategies are analyzed and studied theoretically by the method of establishing mathematical model. Based on the simulation software of PSCAD/EMTDC, the corresponding controller model is built. The simulation results show that the control strategy and the model are correct. Finally, according to the single pole grounding fault, bipolar short circuit fault and break line fault on HVDC transmission line, the fault mechanism is analyzed and studied, and the unipolar grounding fault is put forward. By setting different protection settings of AC / DC side and increasing insulation of fault pole line, for bipolar short circuit fault, overcurrent suppression strategy, locking converter and skip AC circuit breaker protection strategy are put forward in the case of bipolar short circuit fault. The protection strategy by changing the control mode of the converter station is proposed for the fault line break, and the effectiveness of the protection strategy is verified by simulation.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM721.1;TM755

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本文編號：2237837