【摘要】：由于大規(guī)模非線性元件以及設(shè)備再電力系統(tǒng)的廣泛應(yīng)用,導(dǎo)致大量的諧波注入電網(wǎng),嚴(yán)重影響了電網(wǎng)的電能質(zhì)量,因此諧波治是非常必要的。但無論是諧波責(zé)任認(rèn)定還是諧波的治理,都依賴于諧波的特性。快速傅里葉變換(FFT)是諧波分析常用的方法。但電力系統(tǒng)的諧波并非精確50Hz,且存在大量的間諧波,故導(dǎo)致信號非同步采樣,并且由于柵欄效應(yīng)、混疊效應(yīng)、截斷效應(yīng),導(dǎo)致無法精確的估計出信號的幅值、頻率和相位。另一方面,FFT的每個譜峰都不可避免的受到泄露的影響,故定量的給出每個譜峰的可信度也是一個關(guān)鍵問題�？紤]到諧波是時變或者瞬時性的信號,無法進(jìn)行較長時段的采樣,故直接使用FFT,導(dǎo)致信號分析的頻率分辨率低。本文針對這三個問題展開,詳細(xì)的闡述了在減小計算量的同時,如何有效的提高參數(shù)估計的精度和可靠性。研究了譜峰可信度的一些性質(zhì)。針對傳統(tǒng)的譜峰可信度判斷方法的缺陷,本文借助一族偏差公式給出商集,通過比較這些商與1的接近程度,進(jìn)而給出更精確的譜峰可信度;提出了一種基于狀態(tài)空間模型的諧波參數(shù)估計方法。首先建立了諧波信號的狀態(tài)空間模型,為了提高參數(shù)估計對噪聲的魯棒性,通過分析將參數(shù)估計的魯棒性問題轉(zhuǎn)化成一個求酉矩陣的過程,最后通過求該酉矩陣特征值即可高精度的估計出諧波頻率值。幅值和相位則可以通過最小二乘法或者其他優(yōu)化方法得到。另外還研究了狀態(tài)空間法和Prony法的聯(lián)系以及有效奇異值選取問題;針對同時含有諧波和間諧波的諧波分析問題,采用基于FFT和狀態(tài)空間法的諧波分析方法。為了提高算法的效率和可靠性,先通過判斷FFT的譜峰的譜間干擾程度分離出能用FFT分析的頻譜分量,進(jìn)而借助能量重心法估計出對應(yīng)的分量的參數(shù);接著利用狀態(tài)空間法估計出剩下諧波參數(shù)。在此基礎(chǔ)上又提出了兩種降維技術(shù)以提高算法的實用性。
[Abstract]:Due to the extensive application of large-scale non-linear components and equipment re-power system, a large number of harmonics are injected into the power grid, which seriously affects the power quality of the power grid. Therefore, harmonic treatment is very necessary. However, whether it is the recognition of harmonic responsibility or the treatment of harmonic, it depends on the characteristics of harmonic. Fast Fourier transform (FFT) is a common method for harmonic analysis. But the harmonic of power system is not accurate 50Hz, and there are a lot of inter-harmonics, so the signal is not synchronous sampling, and because of fence effect, aliasing effect and truncation effect, it is impossible to accurately estimate the amplitude, frequency and phase of the signal. On the other hand, each peak of FFT is inevitably influenced by leakage, so it is a key problem to give the credibility of each peak quantitatively. Considering that harmonics are time-varying or transient signals can not be sampled for a longer period of time. Therefore the direct use of FFT, leads to low frequency resolution of signal analysis. In view of these three problems, this paper expounds in detail how to improve the accuracy and reliability of parameter estimation while reducing the computational complexity. Some properties of the reliability of spectral peaks are studied. Aiming at the defect of traditional spectral peak reliability judgment method, this paper gives the quotient set by a family of deviation formulas. By comparing these quotient with 1, the more accurate spectral peak reliability is given. A harmonic parameter estimation method based on state space model is proposed. In order to improve the robustness of parameter estimation to noise, the robustness of parameter estimation is transformed into a unitary matrix. Finally, the harmonic frequency can be estimated with high precision by calculating the eigenvalues of the unitary matrix. Amplitude and phase can be obtained by least square method or other optimization methods. In addition, the relationship between the state space method and the Prony method and the selection of the effective singular value are also studied, and the harmonic analysis method based on FFT and the state space method is adopted to solve the harmonic analysis problem which contains both harmonics and inter-harmonics. In order to improve the efficiency and reliability of the algorithm, the spectral components which can be analyzed by FFT are separated by judging the interspectral interference of the spectral peaks of FFT, and then the parameters of the corresponding components are estimated by means of the energy center of gravity method. Then the state space method is used to estimate the remaining harmonic parameters. On this basis, two dimension reduction techniques are proposed to improve the practicability of the algorithm.
【學(xué)位授予單位】：湖北工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM711

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