本文選題：光伏并網(wǎng)逆變器　切入點(diǎn)：單位功率因數(shù)　出處：《中國(guó)礦業(yè)大學(xué)》2014年碩士論文

【摘要】：光伏并網(wǎng)發(fā)電系統(tǒng)主要由光伏陣列、并網(wǎng)逆變器和電網(wǎng)組成，三者都有可能發(fā)生故障，其中的并網(wǎng)逆變器單個(gè)開關(guān)管開路故障診斷與孤島檢測(cè)則是本文要進(jìn)行深入研究的內(nèi)容。 并網(wǎng)逆變器能否可靠運(yùn)行影響到其本身與電網(wǎng)的安全。并網(wǎng)逆變器主電路是由若干開關(guān)器件組合而成，而開關(guān)器件存在短路和開路故障。本文對(duì)單管開路故障特征量進(jìn)行分析并根據(jù)光伏并網(wǎng)逆變器特點(diǎn)，給出一種三相光伏并網(wǎng)逆變器開關(guān)器件開路故障診斷方法。逆變器開關(guān)器件發(fā)生開路故障時(shí)電網(wǎng)中性點(diǎn)與直流側(cè)負(fù)極之間的電壓與正常工作時(shí)的電壓不同，將該電壓作為特征量。結(jié)合光伏并網(wǎng)逆變器單位功率因數(shù)并網(wǎng)特點(diǎn)，以電網(wǎng)電壓矢量角度為參考，對(duì)開路器件進(jìn)行診斷。仿真和硬件實(shí)驗(yàn)結(jié)果表明，該方法可以在一個(gè)電流周期內(nèi)準(zhǔn)確定位開路故障器件。 孤島效應(yīng)是所有分布式發(fā)電系統(tǒng)都要面臨的一個(gè)問題，孤島效應(yīng)發(fā)生時(shí)，可能會(huì)給電網(wǎng)設(shè)備和人員帶來(lái)不利影響。本文介紹了常用的被動(dòng)式和主動(dòng)式孤島檢測(cè)方法的原理。采用P×Q坐標(biāo)系對(duì)被動(dòng)式孤島檢測(cè)算法的檢測(cè)盲區(qū)進(jìn)行分析。針對(duì)P×Q坐標(biāo)系的不足，采用Qf0×Cnorm坐標(biāo)系對(duì)基于頻率的孤島檢測(cè)算法的檢測(cè)盲區(qū)進(jìn)行分析。 針對(duì)孤島檢測(cè)算法中的主動(dòng)頻率偏移法進(jìn)行深入研究，詳細(xì)給出單相與三相主動(dòng)頻率偏移法的實(shí)現(xiàn)過程。由于傳統(tǒng)的主動(dòng)頻率偏移法會(huì)造成逆變器輸出電能質(zhì)量惡化，本文給出一種變反饋系數(shù)主動(dòng)頻率偏移法。在電網(wǎng)頻率波動(dòng)小的時(shí)候，采用小反饋系數(shù)；在電網(wǎng)頻率波動(dòng)大的時(shí)候，采用大反饋系數(shù)。仿真和硬件實(shí)驗(yàn)結(jié)果證明該方法在逆變器正常并網(wǎng)時(shí)對(duì)輸出電流的影響較小，當(dāng)孤島效應(yīng)發(fā)生時(shí)檢測(cè)能力比較突出，在孤島檢測(cè)的時(shí)間上也符合國(guó)家相關(guān)標(biāo)準(zhǔn)的規(guī)定。
[Abstract]:The photovoltaic grid-connected generation system is mainly composed of photovoltaic array, grid-connected inverter and power grid, all of which are likely to have faults. The open circuit fault diagnosis and islanding detection of grid-connected inverter are the contents of this paper.Whether the grid-connected inverter can run reliably will affect the security of itself and the power grid.The main circuit of grid-connected inverter is composed of several switching devices, which have short circuit and open circuit faults.According to the characteristics of photovoltaic grid-connected inverter, an open-circuit fault diagnosis method for switching devices of three-phase photovoltaic grid-connected inverter is presented in this paper.The voltage between the neutral point and the negative electrode of DC side is different from the voltage in normal operation when the switching device of inverter occurs open circuit fault, and this voltage is regarded as the characteristic value.Combined with the characteristics of grid-connected photovoltaic inverter with unit power factor, the open circuit device is diagnosed based on the voltage vector angle of the grid.Simulation and hardware experiments show that this method can accurately locate the open circuit fault devices in a current cycle.Islanding effect is a problem that all distributed generation systems have to face. When the islanding effect occurs, it may bring adverse effects to power grid equipment and personnel.This paper introduces the principle of passive and active island detection methods.The blind spot of passive isolated island detection algorithm is analyzed in P 脳 Q coordinate system.Aiming at the deficiency of P 脳 Q coordinate system, Qf0 脳 Cnorm coordinate system is used to analyze the blind spot detection of isolated island detection algorithm based on frequency.The active frequency migration method in islanding detection algorithm is studied in detail, and the realization process of single-phase and three-phase active frequency migration method is given in detail.Since the traditional active frequency offset method will cause the deterioration of the output power quality of the inverter, a variable feedback coefficient active frequency offset method is presented in this paper.The small feedback coefficient is used when the frequency fluctuation is small, and the large feedback coefficient is used when the frequency fluctuation is large.The results of simulation and hardware experiments show that the method has little effect on the output current when the inverter is grid-connected normally, and the detection ability is more prominent when the islanding effect occurs, and the detection time of the islanding detection is in accordance with the relevant national standards.
【學(xué)位授予單位】：中國(guó)礦業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM464

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