【摘要】：隨著非線性設(shè)備的廣泛應(yīng)用,尤其是近年來新能源并網(wǎng)工程的大量投用,電力系統(tǒng)中的諧波污染日趨嚴重。對電力諧波參數(shù)進行準確、實時的測量是治理諧波污染的前提和重要技術(shù)手段�；诳焖俑道锶~變換(FFT)的諧波測量方法由于計算速度快、易于工程實現(xiàn)等優(yōu)勢,在電力諧波在線監(jiān)測中得到了廣泛的應(yīng)用。然而,風電、光伏等新能源發(fā)電的有功輸出功率具有不確定性,可能造成發(fā)電與負荷不平衡,從而導(dǎo)致電網(wǎng)頻率偏移,甚至發(fā)生頻率寬范圍波動和頻率崩潰等現(xiàn)象。在頻率動態(tài)過程中,由于非同步采樣造成的頻譜泄漏等問題的存在,基于FFT的電力諧波測量方法存在較大的誤差,甚至可能測量失敗。非同步采樣下的改進測量方法,從采樣方式上分為兩類:定速率采樣與自適應(yīng)采樣。定速率采樣方法的采樣頻率恒定,通過時域或頻域上的插值等算法來減小非同步采樣的影響。自適應(yīng)采樣方法通過實時跟蹤電網(wǎng)頻率,自適應(yīng)調(diào)整采樣頻率,使實際采樣序列接近理想同步采樣序列,包括硬件同步和軟件準同步。考慮頻率動態(tài)過程,分別對定速率采樣方法與自適應(yīng)采樣方法進行改進。對于定速率采樣方法,考慮了頻率動態(tài)過程中的頻率變化率,以相位差校正法為例,推導(dǎo)了基于頻率變化率修正的歸一化頻率校正量公式,提高了頻率動態(tài)過程中的諧波參數(shù)連續(xù)測量精度;對于自適應(yīng)采樣方法,在連續(xù)測量中根據(jù)前次測得的基波頻率與前次計算所得的頻率變化率來預(yù)測電網(wǎng)的實時基波頻率,從而實時調(diào)整采樣頻率以跟蹤變化的電網(wǎng)頻率,減小了頻率動態(tài)過程產(chǎn)生的頻譜泄漏。對采用不同頻率變化模型的電網(wǎng)信號進行仿真分析,并考慮互感器精度對測量系統(tǒng)的總誤差進行評價。結(jié)果表明,本文所提出的改進方法較原方法具有更高的測量精度與實時性,更適用于頻率動態(tài)過程中的諧波測量,實用性較高。
[Abstract]:With the wide application of non-linear equipment, especially in recent years, a large number of new energy grid-connected projects, harmonic pollution in the power system is becoming more and more serious. Accurate and real-time measurement of power harmonic parameters is the premise and important technical means to control harmonic pollution. The harmonic measurement method based on Fast Fourier transform (FFT) has been widely used in power harmonic on-line monitoring due to its advantages of fast computing speed and easy engineering realization. However, the active output power of new energy such as wind power, photovoltaic and so on is uncertain, which may cause the imbalance between power generation and load, thus lead to the frequency offset of the power grid, and even occur the phenomenon of wide range of frequency fluctuation and frequency collapse. In the frequency dynamic process, due to the existence of spectrum leakage caused by asynchronous sampling, the measurement method of power harmonic based on FFT has a large error and may even fail to measure. The improved measurement method based on asynchronous sampling can be divided into two types: constant rate sampling and adaptive sampling. The sampling frequency of the constant-rate sampling method is constant, and the influence of non-synchronous sampling is reduced by interpolation in time-domain or frequency-domain. The adaptive sampling method tracks the power network frequency in real time and adaptively adjusts the sampling frequency to make the actual sampling sequence close to the ideal synchronous sampling sequence including hardware synchronization and software quasi-synchronization. Considering the frequency dynamic process, the constant rate sampling method and the adaptive sampling method are improved respectively. For the constant rate sampling method, the frequency change rate in the frequency dynamic process is considered. Taking the phase difference correction method as an example, the normalized frequency correction quantity formula based on the frequency change rate correction is derived. The continuous measurement accuracy of harmonic parameters in frequency dynamic process is improved. For the adaptive sampling method, the real-time fundamental frequency of the power network is predicted according to the fundamental frequency measured earlier and the frequency change rate obtained from the previous calculation in continuous measurement, so that the sampling frequency can be adjusted in real time to track the changing power network frequency. The frequency spectrum leakage caused by frequency dynamic process is reduced. The power system signals with different frequency variation models are simulated and analyzed, and the total error of the measurement system is evaluated considering the accuracy of the transformer. The results show that the improved method is more accurate and real-time than the original method, and is more suitable for harmonic measurement in frequency dynamic process.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM935

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