本文關(guān)鍵詞： 非線性現(xiàn)象 穩(wěn)定性 變換器 電網(wǎng)阻抗　出處：《華中科技大學(xué)》2014年博士論文　論文類型：學(xué)位論文

【摘要】：三相高頻整流器被廣泛應(yīng)用于分布式電力系統(tǒng)及各種工業(yè)設(shè)備中,并且得到了廣泛的研究,而其非線性行為研究頗為少見。本文主要對(duì)這種變換器的非線性行為進(jìn)行了定義和分析。隨著微網(wǎng)及分布式發(fā)電的迅猛發(fā)展,電網(wǎng)不在應(yīng)該被認(rèn)為是理想電壓源,而被認(rèn)為是一種含有內(nèi)部阻抗的非理想電壓源。因此,連接在這樣的弱電網(wǎng)上的三相高頻整流器則不能被認(rèn)為是一個(gè)獨(dú)立的系統(tǒng),而是一個(gè)能夠和非理想電網(wǎng)相互影響的子系統(tǒng)。關(guān)于此系統(tǒng),本文將展示一些特別的非線性現(xiàn)象,并且通過(guò)分岔分析來(lái)定義有關(guān)非線性現(xiàn)象。而后,本文將通過(guò)基于設(shè)計(jì)的分析,得出系統(tǒng)各關(guān)鍵參數(shù)的穩(wěn)定邊界以及區(qū)分不同運(yùn)行狀態(tài)的區(qū)域,給設(shè)計(jì)者提供設(shè)計(jì)思路。 首先,當(dāng)本地電阻性負(fù)載與三相整流器同時(shí)連接在非理想電網(wǎng)的相同節(jié)點(diǎn)時(shí),變換器的一種不可逆分岔現(xiàn)象將發(fā)生。而此系統(tǒng)模型是作為實(shí)際應(yīng)用中非�，F(xiàn)實(shí)的一種模型。由于在此模型中,非理想電網(wǎng)提供給變換器的有功功率被限制住了,當(dāng)變換器不能得到它所需要的有功功率時(shí),變換器的輸出直流電壓將會(huì)下跌。此時(shí),變換器吸收的無(wú)功功率會(huì)瞬時(shí)增大,并且?guī)缀豕ぷ髟诹愎β室驍?shù)模式下。變換器的這種工作模式可以稱之為“不正常運(yùn)行”。本章將應(yīng)用大信號(hào)模型分析了此物理現(xiàn)象的基本原理,并且通過(guò)基于設(shè)計(jì)的分析方法把此系統(tǒng)的關(guān)鍵參數(shù)的穩(wěn)定邊界劃定出來(lái)。同時(shí),本章也通過(guò)實(shí)驗(yàn)驗(yàn)證了此現(xiàn)象的存在。 其次,在三相高頻整流器連接在非理想電網(wǎng)時(shí)發(fā)生的Hopf分岔現(xiàn)象,本章將會(huì)重點(diǎn)描述。當(dāng)三相變換器所連接的非理想電網(wǎng)自身的內(nèi)部阻抗足夠大時(shí)候,變換器的直流輸出電壓將會(huì)出現(xiàn)明顯的低頻振蕩,或者被稱之為Hopf分岔。本章應(yīng)用三相變換器的平均模型和時(shí)域分析方法來(lái)預(yù)測(cè)Hopf分岔現(xiàn)象的發(fā)生。同時(shí),一些參數(shù)的穩(wěn)定區(qū)間及其邊界也得到了分析。最后,本章也通過(guò)實(shí)驗(yàn)驗(yàn)證了此現(xiàn)象的發(fā)生。 最后,本文將介紹兩個(gè)或多個(gè)并網(wǎng)變換器同時(shí)連接在同一非理想電網(wǎng)的節(jié)點(diǎn)時(shí)發(fā)生的Hopf分岔現(xiàn)象。當(dāng)單個(gè)變換器連接在非理想電網(wǎng)上能夠穩(wěn)定運(yùn)行時(shí),連接在同一非理想電網(wǎng)的相同節(jié)點(diǎn)的兩個(gè)變換器則會(huì)相互影響而可能導(dǎo)致不穩(wěn)定運(yùn)行。由于其相互影響,兩個(gè)或多個(gè)變換器輸出電壓會(huì)出現(xiàn)低頻振蕩或者Hopf分岔現(xiàn)象。本章將利用變換器的阻抗模型和廣義奈圭斯特判據(jù)來(lái)判別此種不穩(wěn)定現(xiàn)象。而后,通過(guò)基于設(shè)計(jì)的分析,尋找到系統(tǒng)關(guān)鍵參數(shù)并得到系統(tǒng)的穩(wěn)定區(qū)域劃分以及參數(shù)變化對(duì)穩(wěn)定裕度的影響。并且,本章的研究充分說(shuō)明了并網(wǎng)變換器的穩(wěn)定性問(wèn)題不再是一個(gè)獨(dú)立系統(tǒng)的穩(wěn)定性問(wèn)題,而是要根據(jù)所連接的系統(tǒng)環(huán)境來(lái)判斷的系統(tǒng)級(jí)穩(wěn)定性問(wèn)題。
[Abstract]:Three-phase high-frequency rectifier is widely used in distributed power system and various industrial equipment, and has been widely studied. In this paper, the nonlinear behavior of this converter is defined and analyzed. With the rapid development of microgrid and distributed generation, the power grid should not be considered as an ideal voltage source. Therefore, a three-phase high-frequency rectifier connected to such a weak network cannot be considered an independent system. It's a subsystem that can interact with a non-ideal grid. For this system, we will show some special nonlinear phenomena and define the nonlinear phenomena by bifurcation analysis. Through the analysis based on design, the stable boundary of the key parameters of the system and the region of distinguishing different running states will be obtained, and the design ideas will be provided to the designers. First, when the local resistive load is connected to the same node as the three-phase rectifier at the same time as the non-ideal grid, An irreversible bifurcation will occur in the converter, and the system model is a very practical model in practical application. In this model, the active power provided by the non-ideal power grid to the converter is limited. When the converter fails to get the active power it needs, the output DC voltage of the converter will fall. In this case, the reactive power absorbed by the converter will increase instantaneously. And it almost works in zero power factor mode. This operation mode of converter can be called "abnormal operation". In this chapter, the basic principle of this physical phenomenon is analyzed by using large signal model. The stable boundary of the key parameters of the system is delineated by the Design-based analysis method. At the same time, the existence of this phenomenon is verified by experiments in this chapter. Secondly, when the three-phase high-frequency rectifier is connected to the non-ideal power network, the Hopf bifurcation will be described in this chapter. When the internal impedance of the non-ideal power network connected by the three-phase converter is large enough, The DC output voltage of the converter will appear obvious low-frequency oscillation, or called Hopf bifurcation. In this chapter, the average model of three-phase converter and the time-domain analysis method are used to predict the occurrence of Hopf bifurcation. The stability interval and its boundary of some parameters are also analyzed. Finally, the occurrence of this phenomenon is verified by experiments. Finally, this paper introduces the phenomenon of Hopf bifurcation when two or more grid-connected converters are connected to the same node in the same non-ideal power network at the same time. When a single converter is connected to a non-ideal power network, it can operate stably. Two converters connected to the same node in the same non-ideal grid will interact with each other and may lead to unstable operation. The output voltage of two or more converters will appear low frequency oscillation or Hopf bifurcation. In this chapter, the impedance model of the converter and the generalized Nigel criterion will be used to judge the instability. The key parameters of the system are found and the stable region partition of the system and the influence of the parameter variation on the stability margin are obtained. Furthermore, the research in this chapter fully shows that the stability problem of grid-connected converter is no longer a stability problem of an independent system. It is a system-level stability problem to be judged by the connected system environment.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM46

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