【摘要】：隨著風(fēng)力發(fā)電技術(shù)的發(fā)展，風(fēng)電場的規(guī)模越來越大，而風(fēng)電具有間歇性、不可控等特性，采用交流輸電需要大量無功補償裝置、采用傳統(tǒng)直流輸電需要投入大量濾波裝置而且容易發(fā)生換相失敗，，研究更適合于風(fēng)電場的并網(wǎng)方式具有重要意義�；谀K化多電平換流器的柔性直流輸電技術(shù)具有容量大、獨立控制有功無功、穩(wěn)定交流母線電壓、隔離故障和容易構(gòu)成多端直流系統(tǒng)等優(yōu)點，非常適合于大型風(fēng)電場并網(wǎng)，將在其風(fēng)電并網(wǎng)連接中有廣泛的應(yīng)用。 本文首先對交流輸電、高壓直流輸電、柔性直流輸電三種并網(wǎng)輸電方式進行了綜合比較，并對在風(fēng)電并網(wǎng)中具有技術(shù)優(yōu)勢的柔性直流輸電技術(shù)的研究現(xiàn)狀、工程實例進行了介紹，接著對風(fēng)電場的低電壓穿越技術(shù)進行了綜述，并介紹本文的主要工作。 分析了模塊化多電平換流器（MMC，modular multilevel converter）的拓?fù)浣Y(jié)構(gòu)、工作原理、調(diào)制方法、電壓平衡方法的原理。研究了MMC的數(shù)學(xué)模型，在此基礎(chǔ)上分析直接電流控制的內(nèi)外環(huán)控制策略，設(shè)計風(fēng)電場側(cè)和交流電網(wǎng)側(cè)換流器的控制策略。設(shè)計風(fēng)電場向交流系統(tǒng)輸送功率的兩端MMC-HVDC系統(tǒng)，搭建了鼠籠式異步風(fēng)力發(fā)電機模型和永磁直驅(qū)風(fēng)力發(fā)電機模型，利用等值技術(shù)形成風(fēng)電場。進行了從MMC-HVDC的空載啟動、風(fēng)電場并網(wǎng)及風(fēng)速波動過程的仿真研究。將風(fēng)電場聯(lián)接交流電網(wǎng)兩端MMC-HVDC系統(tǒng)的啟動策略和控制策略應(yīng)用于多端柔性直流輸電系統(tǒng)，設(shè)計了兩個風(fēng)電場向交流系統(tǒng)送電的三端直流系統(tǒng)，仿真驗證了控制策略的可行性。 對受端交流系統(tǒng)連接點發(fā)生不同類型故障的故障特性進行分析，針對三相故障提出了直流側(cè)接耗能電阻的控制方法，維持故障階段風(fēng)電場出口的電壓穩(wěn)定；針對不對稱故障提出基于負(fù)序電壓前饋的雙序控制方法，抑制故障負(fù)序電流分量的影響。最后對MMC-HVDC的隔離干擾能力和本文提出的故障控制策略進行了仿真驗證。
[Abstract]:With the development of wind power generation technology, the scale of wind farm becomes larger and larger, and wind power has the characteristics of intermittent, uncontrollable, etc. Traditional DC transmission needs a large number of filter devices and is prone to commutative failure. It is of great significance to study the grid-connected mode which is more suitable for wind farms. The flexible DC transmission technology based on modularized multilevel converter has the advantages of large capacity, independent control of active and reactive power, stable AC bus voltage, isolation of fault and easy construction of multi-terminal DC system. It will be widely used in wind power grid connection. In this paper, three grid-connected transmission modes, namely AC transmission, high voltage direct current transmission and flexible direct current transmission, are firstly compared, and the research status of flexible direct current transmission technology which has technical advantages in wind power grid connection is also discussed. The engineering example is introduced, and then the low voltage traversing technology of wind farm is summarized, and the main work of this paper is introduced. The topology, working principle, modulation method and voltage balance method of modular multilevel converter (MMC,modular multilevel converter) are analyzed. The mathematical model of MMC is studied and the internal and external loop control strategy of direct current control is analyzed. The control strategy of wind farm side and AC power grid side converter is designed. The MMC-HVDC system for transmitting power from wind farm to AC system is designed. The model of squirrel-cage asynchronous wind generator and permanent magnet direct drive wind generator is built. The equivalent technology is used to form wind farm. The simulation study of no-load startup of MMC-HVDC, grid connection of wind farm and fluctuation process of wind speed is carried out. The start-up strategy and control strategy of the MMC-HVDC system connected to the AC power grid are applied to the multi-terminal flexible DC transmission system. The three-terminal DC system of two wind farms to the AC system is designed. The feasibility of the control strategy is verified by simulation. This paper analyzes the fault characteristics of different types of faults in the connection point of AC system at the receiving end, and puts forward the control method of the DC side energy dissipation resistance for the three-phase fault, which maintains the voltage stability of the wind farm outlet in the fault stage. A double sequence control method based on negative sequence voltage feedforward is proposed to suppress the influence of the negative sequence current component of the fault. Finally, the isolation interference ability of MMC-HVDC and the fault control strategy proposed in this paper are simulated and verified.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM614

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