本文選題：二極管箝位式拓?fù)浣Y(jié)構(gòu) + 三電平逆變器�。� 參考：《沈陽工業(yè)大學(xué)》2017年碩士論文

【摘要】：光伏中點(diǎn)箝位型并網(wǎng)逆變器的原理是利用太陽能電池板儲存的直流電能轉(zhuǎn)化為可以直接并網(wǎng)使用的交流電,對其性能的有嚴(yán)格的要求。本文深入分析了NPC型三電平并網(wǎng)逆變器,著重解決其存在于調(diào)制方法的和中點(diǎn)電位波動中的兩個問題。首先,本文前期參閱了許多的國內(nèi)外有關(guān)書籍資料,綜述了光伏發(fā)電的背景和意義,國內(nèi)外的研究現(xiàn)狀以及光伏系統(tǒng)的分類,詳細(xì)闡述了NPC型逆變器的調(diào)制策略和中點(diǎn)波動問題的研究現(xiàn)狀。其次,重點(diǎn)分析了逆變器的幾種重要的拓?fù)浣Y(jié)構(gòu),對結(jié)構(gòu)不同的逆變器的特點(diǎn)進(jìn)行了比較分析,并且總結(jié)出逆變器的數(shù)學(xué)模型。為了達(dá)到降低開關(guān)損耗同時保證低的諧波畸變和輸出電壓的質(zhì)量的目的,深入分析了七段式調(diào)制和五段式調(diào)制各自的特點(diǎn)以及不足,七段式調(diào)制的優(yōu)點(diǎn)是能夠保證輸出電壓穩(wěn)定,五段式的特點(diǎn)為可以降低開關(guān)頻率。結(jié)合兩者的優(yōu)點(diǎn),根據(jù)五段式斷續(xù)調(diào)制策略開關(guān)停滯區(qū)間為120°,按照開關(guān)動作次數(shù)更少,且每次開關(guān)動作時只允許一個橋臂動作,推導(dǎo)出斷續(xù)混合調(diào)制策略,即一個基波周期內(nèi)的相鄰30°扇區(qū)采用不同的調(diào)制方法,并且通過計(jì)算將兩電平作用時間修正為三電平,簡化了計(jì)算過程,歸納出斷續(xù)混合調(diào)制策略的實(shí)現(xiàn)方法。最后,針對二極管箝位式拓?fù)浣Y(jié)構(gòu)的固有中點(diǎn)電位波動問題,在斷續(xù)混合調(diào)制策略的方法下提出了一套中點(diǎn)電位控制方案,將兩電容的差值不斷與標(biāo)準(zhǔn)值進(jìn)行比較,通過判斷差值的大小,以反比例調(diào)整正負(fù)半周斷續(xù)脈寬的寬度,改變小矢量的作用時間。如果正半周箝位的部分延長,其保持高電平狀態(tài)的時間也相應(yīng)的延長,因此高電平狀態(tài)下的小矢量作用時間增加。同時負(fù)半周箝位的部分縮短,低電平狀態(tài)小矢量作用時間縮短。正負(fù)半周斷續(xù)部分的反比例調(diào)整,保證了一個周期內(nèi)箝位角度是固定的,避免了斷續(xù)部分與其他相的重疊。
[Abstract]:The principle of grid-connected photovoltaic inverter is to convert the stored DC energy from solar panels to AC which can be directly connected to the grid, which has strict requirements for its performance. In this paper, NPC three-level grid-connected inverter is deeply analyzed, and two problems existing in modulation method and neutral point potential fluctuation are emphatically solved. First of all, this paper reviewed many domestic and foreign books, summarized the background and significance of photovoltaic power generation, domestic and foreign research status and photovoltaic system classification. The modulation strategy and midpoint fluctuation of NPC inverter are described in detail. Secondly, several important topology structures of the inverter are analyzed, the characteristics of the inverter with different structure are compared and analyzed, and the mathematical model of the inverter is summarized. In order to reduce switching loss and ensure the quality of harmonic distortion and output voltage, the characteristics and shortcomings of seven-segment modulation and five-segment modulation are analyzed. The advantage of seven-segment modulation is that the output voltage is stable and the five-segment modulation can reduce the switching frequency. Combining the advantages of the two methods, according to the five-segment intermittent modulation strategy, the switching stagnation range is 120 擄, according to the number of switching actions is less, and only one bridge arm is allowed for each switching operation, the intermittent mixed modulation strategy is deduced. In other words, different modulation methods are used in the adjacent 30 擄sector of a fundamental wave period, and the two-level action time is corrected to three-level by calculation, which simplifies the calculation process and induces the realization method of intermittent mixed modulation strategy. Finally, aiming at the inherent midpoint potential fluctuation of diode clamped topology, a set of midpoint potential control scheme is proposed under intermittent mixed modulation strategy. The difference between the two capacitors is constantly compared with the standard value. By judging the magnitude of the difference, the width of positive and negative half-cycle intermittent pulse width is adjusted in inverse proportion, and the action time of small vector is changed. If the partial length of the positive half-cycle clamping is extended, the time of holding the high level state is also prolonged accordingly, so the time of small vector action in the high level state is increased. At the same time, the negative half cycle clamping part is shortened, and the low level state small vector operation time is shortened. The inversely proportional adjustment of the positive and negative half-cycle intermittent parts ensures that the clamping angle is fixed in a period and avoids the overlap between the intermittent parts and other parts.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM464

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