【摘要】：電力系統(tǒng)頻率是電能質(zhì)量的重要指標(biāo),其準(zhǔn)確測量有助于客觀反映電力系統(tǒng)的運行狀態(tài),具有重要的理論和實際意義。同步采樣情況下,采用快速傅里葉變換(Fast Fourier Transform,FFT)可以獲得高準(zhǔn)確度的頻率測量結(jié)果。然而,在電力系統(tǒng)中,信號頻率往往存在一定波動,且受到諧波等干擾的影響,使嚴(yán)格的同步采樣很難實現(xiàn)。在非同步采樣條件下,FFT固有的頻譜泄漏和柵欄效應(yīng)影響了頻率測量的準(zhǔn)確度。因此,如何克服非同步采樣偏差對頻率測量結(jié)果的影響,一直是國內(nèi)外學(xué)者研究的重點。本文提出并研究改進準(zhǔn)同步采樣電力系統(tǒng)頻率測量方法,提高了非同步采樣情況下的頻率測量精度,為電力系統(tǒng)頻率測量方法的發(fā)展與應(yīng)用提供了新思路。本文首先綜述了常用頻率測量方法的優(yōu)缺點,介紹了準(zhǔn)同步采樣算法的基本原理。準(zhǔn)同步采樣算法通過積分和迭代運算實現(xiàn)局部信號的頻譜計算,且允許信號存在一定的非同步采樣偏差,但該方法也存在計算量較大、準(zhǔn)確度不高等不足。其次,本文根據(jù)準(zhǔn)同步采樣算法實現(xiàn)過程中需要進行數(shù)值積分的特點,在基于復(fù)化矩形的準(zhǔn)同步采樣算法推導(dǎo)過程的基礎(chǔ)上,研究并推導(dǎo)了改進準(zhǔn)同步采樣頻率測量算法,包括基于復(fù)化梯形的準(zhǔn)同步采樣頻率測量算法和基于復(fù)化Simpson的準(zhǔn)同步采樣頻率測量算法,建立了改進準(zhǔn)同步采樣電力系統(tǒng)頻率測量實現(xiàn)流程,從理論上對比分析了常用的加窗插值FFT算法和改進準(zhǔn)同步采樣頻率測量算法的運算復(fù)雜度。本文研究結(jié)果表明:當(dāng)采樣頻率和采樣點數(shù)相同時,改進準(zhǔn)同步采樣頻率測量算法執(zhí)行過程中所需加法次數(shù)遠遠少于加窗插值FFT算法所需加法次數(shù)。由于基于復(fù)化矩形、復(fù)化梯形和復(fù)化Simpson三者僅在積分加權(quán)系數(shù)上不同,且準(zhǔn)同步采樣頻率測量算法的運算復(fù)雜度僅與采樣點數(shù)有關(guān),因此本文所研究的兩種改進準(zhǔn)同步采樣頻率測量算法的運算復(fù)雜度相同。隨后,本文通過仿真實驗對比分析了改進準(zhǔn)同步采樣頻率測量算法與加窗插值FFT算法的測量準(zhǔn)確度。本文選取了被廣泛應(yīng)用的基于4項3階Nuttall窗的插值FFT算法作對比,仿真分析了基波頻率波動、諧波干擾、白噪聲影響等不同情況下的頻率測量結(jié)果。仿真結(jié)果表明:與基于4項3階Nuttall窗的插值FFT算法相比,本文所研究的改進準(zhǔn)同步采樣頻率測量算法具有更高的頻率測量準(zhǔn)確度,且該算法可有效抑制白噪聲對電力系統(tǒng)頻率測量的影響。在兩種改進準(zhǔn)同步采樣頻率測量算法中,基于復(fù)化梯形的準(zhǔn)同步采樣頻率測量算法的性能略優(yōu)于基于復(fù)化Simpson的準(zhǔn)同步采樣頻率測量算法。最后,本文利用嵌入式系統(tǒng)平臺實現(xiàn)了本文所提出的改進準(zhǔn)同步采樣頻率測量算法,并根據(jù)GB/T 15945-2008、GB/T 19862-2005、DL/T 1028-2006的要求設(shè)計了電力系統(tǒng)頻率測量校準(zhǔn)方案。通過大量校準(zhǔn)前后頻率測量實驗,對比分析了校準(zhǔn)前后的電力系統(tǒng)頻率測量偏差,并分析了基波頻率不變時校準(zhǔn)后的電力系統(tǒng)頻率測量不確定度。實驗結(jié)果表明:校準(zhǔn)后的頻率測量偏差均能達到國標(biāo)規(guī)定的頻率偏差在±0.01Hz以內(nèi)的要求,這也驗證了本文所提出的改進準(zhǔn)同步采樣頻率測量算法在實際應(yīng)用中的的有效性和準(zhǔn)確性。
[Abstract]:Power system frequency is an important index of power quality. Its accurate measurement is helpful to reflect the operation state of power system objectively. It has important theoretical and practical significance. Under the condition of asynchronous sampling, the inherent spectrum leakage and fence effect of FFT affect the accuracy of frequency measurement. Therefore, how to overcome the influence of asynchronous sampling deviation on frequency measurement results has been a problem at home and abroad. This paper presents and studies the improvement of frequency measurement method of quasi-synchronous sampling power system, which improves the accuracy of frequency measurement under the condition of non-synchronous sampling. It provides a new idea for the development and application of frequency measurement method of power system. The quasi-synchronous sampling algorithm realizes the spectrum calculation of local signal by integral and iterative operation, and allows the signal to have some asynchronous sampling deviation, but this method also has the shortcomings of large amount of calculation and low accuracy. Secondly, the numerical product is needed in the implementation of quasi-synchronous sampling algorithm. Based on the derivation process of quasi-synchronous sampling algorithm based on complex rectangle, the improved quasi-synchronous sampling frequency measurement algorithm is studied and deduced, including the quasi-synchronous sampling frequency measurement algorithm based on complex trapezoid and the quasi-synchronous sampling frequency measurement algorithm based on complex Simpson. The improved quasi-synchronous sampling power system is established. The computational complexity of the commonly used windowed interpolation FFT algorithm and the improved quasi-synchronous sampling frequency measurement algorithm is theoretically compared and analyzed. The results show that the number of additions needed in the implementation of the improved quasi-synchronous sampling frequency measurement algorithm is much less than that of the addition algorithm when the sampling frequency and the sampling points are the same. Because the complex rectangle, complex trapezoid and complex Simpson are only different in integral weighting coefficients, and the computational complexity of the quasi-synchronous sampling frequency measurement algorithm is only related to the number of sampling points, the computational complexity of the two improved quasi-synchronous sampling frequency measurement algorithms studied in this paper is phase. Similarly, the accuracy of the improved quasi-synchronous sampling frequency measurement algorithm and the windowed interpolation FFT algorithm are compared and analyzed through simulation experiments. In this paper, the interpolation FFT algorithm based on 4-term 3-order Nuttall window is selected for comparison, and the fundamental frequency fluctuation, harmonic interference and white noise are simulated and analyzed. The simulation results show that the improved quasi-synchronous sampling frequency measurement algorithm has higher accuracy than the interpolation FFT algorithm based on 4-term 3-order Nuttall window, and the algorithm can effectively suppress the influence of white noise on power system frequency measurement. The performance of the quasi-synchronous sampling frequency measurement algorithm based on complex trapezoid is slightly better than that of the quasi-synchronous sampling frequency measurement algorithm based on complex Simpson. Finally, the improved quasi-synchronous sampling frequency measurement algorithm proposed in this paper is implemented by using embedded system platform, and according to GB/T 15945-2008, GB/T 19862-2005, DL/T 1028-2005. According to the requirement of 2006, a frequency measurement and calibration scheme for power system is designed. Through a large number of frequency measurement experiments before and after calibration, the power system frequency measurement deviations before and after calibration are compared and analyzed, and the uncertainty of power system frequency measurement after calibration is analyzed when the fundamental frequency is invariant. It can meet the requirement of the national standard that the frequency deviation is within (+0.01 Hz), which also verifies the effectiveness and accuracy of the improved quasi-synchronous sampling frequency measurement algorithm in practical application.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM935.1

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