【摘要】：隨著全球化石能源的開采,能源問題日益嚴(yán)峻。據(jù)統(tǒng)計,2050年左右,全球的石油資源將開采殆盡,屆時依賴傳統(tǒng)能源的國家將深受其害。因此,積極發(fā)展可再生能源,降低化石能源的使用率,提高太陽能等可再生能源的使用成為全球大部分國家解決能源危機(jī)的關(guān)鍵因素。光伏發(fā)電是太陽能使用的一個重要途徑,光伏并網(wǎng)逆變器的研究將成為光伏發(fā)電的研究重點。光伏并網(wǎng)逆變器必須具備孤島檢測功能,因此本文重點研究基于逆變器的光伏系統(tǒng)孤島檢測方法。 本文選取了移頻式孤島檢測方法和基于電網(wǎng)阻抗的孤島檢測方法作為研究對象,研究了這兩種方法各自的檢測性能并提出了改進(jìn)的新算法。首先研究了光伏系統(tǒng)控制策略,并對孤島檢測主動式方法中的頻率偏移法進(jìn)行了深入研究,從物理性質(zhì)層面分析了影響移頻式孤島檢測失效的原因及相關(guān)參數(shù),并針對低電壓穿越時Sandia頻率偏移法的檢測性能進(jìn)行了分析,根據(jù)以上研究結(jié)果提出了改進(jìn)算法；之后分析了基于電網(wǎng)阻抗的孤島檢測方法并提出了新的阻抗孤島檢測算法。具體的創(chuàng)新點如下： (1)提出了基于SFS的自適應(yīng)孤島檢測算法,利用系統(tǒng)頻率的變化自適應(yīng)整定初始階段系數(shù)cf0,該算法提高了孤島檢測性能,同時降低了光伏系統(tǒng)并網(wǎng)運(yùn)行時的諧波畸變率。 (2)分析了鎖相環(huán)在非對稱條件下鎖相不準(zhǔn)的原因,并在模型中使用了改進(jìn)的SPLL方法; (3)提出了新的基于電網(wǎng)阻抗變化電容孤島檢測技術(shù),利用雙閥值、分層投切電容的方式實現(xiàn)了快速準(zhǔn)確檢測孤島,并能有效避免出現(xiàn)偽孤島時誤判。 本文在MATLAB/Simulink平臺上搭建了光伏發(fā)電系統(tǒng)模型,并在仿真模型中嵌入所提出的孤島檢測新算法,驗證方法的有效性。分析結(jié)果表明,本文提出的方法與原算法比較,能快速檢測孤島,且對電網(wǎng)電能質(zhì)量影響較小。
[Abstract]:With the exploitation of fossil energy in the world, the energy problem is becoming more and more serious. According to statistics, around 2050, the world's oil resources will be exhausted, when countries relying on traditional energy will suffer. Therefore, developing renewable energy actively, reducing the utilization rate of fossil energy and increasing the use of renewable energy such as solar energy become the key factors to solve the energy crisis in most countries in the world. Photovoltaic power generation is an important way to use solar energy. The research of grid-connected photovoltaic inverter will become the focus of photovoltaic power generation. Photovoltaic grid-connected inverter must have islanding detection function, so this paper focuses on the research of photovoltaic system islanding detection method based on inverter. In this paper, the method of moving frequency island detection and the detection method of isolated island based on grid impedance are selected as the research object. The detection performance of the two methods is studied and a new improved algorithm is proposed. First of all, the control strategy of photovoltaic system is studied, and the frequency offset method in active detection of isolated island detection is deeply studied. The reasons that affect the failure of frequency shift islanding detection and related parameters are analyzed from the aspect of physical properties. The detection performance of Sandia frequency offset method for low voltage traversing is analyzed, and an improved algorithm is proposed based on the above research results. Then, the detection method of isolated island based on grid impedance is analyzed and a new detection algorithm of impedance island is proposed. The specific innovations are as follows: (1) an adaptive islanding detection algorithm based on SFS is proposed. The algorithm improves the detection performance of islanding by adaptive tuning initial phase coefficient cf0,. At the same time, the harmonic distortion rate of photovoltaic system is reduced. (2) the reason of phase-locked loop is analyzed under asymmetric condition, and the improved SPLL method is used in the model. (3) A new detection technique of capacitive isolated island based on impedance variation of power network is proposed. The method of double threshold and layer switching capacitor is used to detect the isolated island quickly and accurately, and the false island can be avoided effectively. In this paper, a photovoltaic system model is built on MATLAB/Simulink platform, and a new islanding detection algorithm is embedded in the simulation model to verify the effectiveness of the method. The analysis results show that compared with the original algorithm, the proposed method can detect isolated islands quickly and has little effect on power quality.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM464

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