本文選題：模塊化多電平換流器　切入點(diǎn)：環(huán)流抑制　出處：《山東大學(xué)》2017年碩士論文

【摘要】：隨著電力電子器件技術(shù)的進(jìn)步和控制技術(shù)的發(fā)展,新型全控性半導(dǎo)體器件IGBT開始應(yīng)用于高壓直流輸電領(lǐng)域。自從1997年世界上首個(gè)使用電壓換流技術(shù)的直流工程——赫爾斯揚(yáng)實(shí)驗(yàn)工程投入運(yùn)行以來,目前已有多個(gè)柔性直流工程應(yīng)用于可再生能源并網(wǎng)、大功率電機(jī)驅(qū)動(dòng)、分布式發(fā)電并網(wǎng)、城市電網(wǎng)供電等方面。模塊化多電平換流器(Modular Multilevel Converter,MMC)是電壓源換流器拓?fù)渲械囊环N。與其他拓?fù)浣Y(jié)構(gòu)相比,MMC具有諧波含量低、輸出波形質(zhì)量高、擴(kuò)展性好、冗余備份簡單等優(yōu)點(diǎn)。但是由于自身拓?fù)浣Y(jié)構(gòu)固有的缺陷,MMC具有其他傳統(tǒng)兩電平、三電平拓?fù)錄]有的環(huán)流問題;并且當(dāng)系統(tǒng)發(fā)生故障時(shí),由于存在反并聯(lián)的續(xù)流二極管,MMC無法通過自身結(jié)構(gòu)阻斷直流側(cè)電流。故研究MMC環(huán)流問題及故障下控制策略問題具有重要的理論意義和實(shí)際價(jià)值。之前對于MMC環(huán)流的研究主要集中在穩(wěn)態(tài)下的情況,且對于電網(wǎng)電壓不平衡時(shí)的控制較復(fù)雜,需要引入多個(gè)控制器。本文對以上兩點(diǎn)進(jìn)行了深入研究,主要研究內(nèi)容包括以下幾點(diǎn):(1)提出了一種MMC-HVDC在電網(wǎng)電壓不平衡狀態(tài)下的內(nèi)環(huán)電流計(jì)算方法和環(huán)流抑制方法。在αβ坐標(biāo)系中設(shè)計(jì)了一個(gè)基于非理想PR控制器的內(nèi)環(huán)電流控制方法。與現(xiàn)有的正序、負(fù)序分別控制的方法相比,該控制方法更為精確。同時(shí)對于電網(wǎng)電壓不平衡時(shí)環(huán)流分量進(jìn)行了細(xì)致分析,分析結(jié)果顯示該情況下的環(huán)流將由正序、負(fù)序、零序分量構(gòu)成。為了抑制以上各分量,設(shè)計(jì)了相應(yīng)的準(zhǔn)PR環(huán)流抑制控制器,該控制器不僅具有良好的控制效果,還可以適應(yīng)電網(wǎng)頻率的波動(dòng)。(2)提出了 MMC-HVDC一種改進(jìn)的控制方法。為了有效控制MMC-HVDC,交流側(cè)電流、環(huán)流以及子模塊電容電壓需要綜合考慮,其中交流側(cè)電流為基頻分量,環(huán)流為二倍頻負(fù)序分量�，F(xiàn)有的方法是將交流分量、環(huán)流分量分開控制;然而當(dāng)電網(wǎng)電壓不平衡時(shí),交流側(cè)電流包含正序、負(fù)序分量,環(huán)流包括二倍頻正序、負(fù)序、零序分量,分開控制會導(dǎo)致控制器設(shè)計(jì)復(fù)雜,系統(tǒng)穩(wěn)定性降低。因此,本文中提出的方法不需要分離以上各分量,能有效控制交流正序、負(fù)序分量及環(huán)流中各分量,降低了控制器設(shè)計(jì)的數(shù)量和難度。(3)本文提出的各方法都在仿真環(huán)境中得到了驗(yàn)證,證明了本文分析的正確性和控制策略的有效性,證明本文提出的改進(jìn)控制策略可以應(yīng)用于實(shí)踐。
[Abstract]:With the development of power electronic device technology and control technology, A new type of fully controlled semiconductor device (IGBT) has been applied to HVDC transmission. Since 1997, the world's first DC project using voltage commutation technology, the Hulse project, has been put into operation. At present, many flexible DC projects have been applied to the grid connection of renewable energy, the drive of high power motor, and the grid connection of distributed generation. Modularized multilevel converter (Modular Multilevel converter MMC) is one of the voltage source converter topologies. Compared with other topologies, MMC has lower harmonic content, higher output waveform quality and better expansibility. Redundant backup is simple, but due to the inherent defects of its own topology, MMC has other traditional two-level, three-level topology has no circulation problem, and when the system failure, Due to the existence of anti-parallel recurrent diodes, the DC current can not be blocked by its own structure. Therefore, it is of great theoretical and practical value to study the MMC circulation problem and the control strategy under the fault. The former is of great theoretical and practical value for the MMC circulation. Most of the research is focused on the steady-state situation. And the control of voltage imbalance in power network is more complex, so it is necessary to introduce multiple controllers. In this paper, the above two points are deeply studied. The main research contents are as follows: 1) this paper presents a method to calculate the inner loop current and reduce the circulation of MMC-HVDC under the condition of voltage imbalance in the power system. An inner loop based on the non-ideal PR controller is designed in the 偽 尾 coordinate system. Current control methods-positive sequence with existing, The negative sequence control method is more accurate than the negative sequence control method. At the same time, the circulation component is analyzed carefully when the voltage is unbalanced. The results show that the circulation in this case will be positive sequence, negative sequence, In order to suppress the above components, the corresponding quasi-PR loop suppression controller is designed, which not only has good control effect, but also has good control effect. In order to effectively control MMC-HVDC, AC side current, circulation and capacitor voltage of submodule need to be considered comprehensively, in which AC side current is the fundamental frequency component. The current method is to control the AC component and the circulation component separately. However, when the voltage of the grid is unbalanced, the AC side current contains the positive sequence, the negative sequence component, the circulation includes the second harmonic positive sequence, the negative sequence, the zero sequence component. Separate control will lead to the complexity of controller design and the decrease of system stability. Therefore, the method proposed in this paper does not need to separate the above components, and can effectively control the ac positive sequence, negative sequence components and components in the circulation. The number and difficulty of controller design are reduced. (3) all the methods proposed in this paper are verified in the simulation environment, and the correctness of the analysis and the effectiveness of the control strategy are proved. It is proved that the improved control strategy proposed in this paper can be applied to practice.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM46;TM732

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本文編號：1673547