【摘要】：電力電子變壓器是一種新型智能變壓器,具有一次、二次側(cè)電能靈活傳輸變換的特點,能滿足現(xiàn)代和未來電力系統(tǒng)的很多新要求,其安全可靠運行是電網(wǎng)穩(wěn)定運行的重要保障。電力電子變壓器絕緣長期承受高頻電應(yīng)力和熱應(yīng)力等因子的綜合作用,運行環(huán)境惡劣,容易發(fā)生絕緣的過早失效,其破壞機(jī)理較傳統(tǒng)的工頻正弦模式更為復(fù)雜。因此,本文在工頻下絕緣材料老化研究的基礎(chǔ)上,以環(huán)氧樹脂絕緣為對象,詳細(xì)研究了高頻電熱聯(lián)合作用下絕緣老化失效問題,為揭示高頻應(yīng)力作用機(jī)理和提高電力電子變壓器的運行可靠性奠定基礎(chǔ)。文中構(gòu)建了一套高頻正弦電壓的絕緣老化實驗裝置,模擬電力電子變壓器對絕緣材料進(jìn)行老化實驗。并設(shè)計了一套由高頻電流傳感器和示波器等構(gòu)成的局部放電檢測裝置。根據(jù)實際測量信號特征,研究了局部放電信號的提取方法。具體包括：首先,構(gòu)造FIR高通濾波器濾除信號的低頻干擾,并利用小波變換方法進(jìn)行信號分解、閾值降噪和信號重構(gòu)處理,以濾除高頻噪聲干擾；然后,通過選取合適的時間窗長度獲取有效的放電信號。為研究電力電子變壓器絕緣的老化特性,開展了高頻絕緣老化試驗,并基于局部放電的發(fā)展變化規(guī)律,從各個不同老化階段中提取出局部放電特征參量,以分析絕緣高頻老化特征及其老化表征參量。研究結(jié)果表明,高頻電壓作用下局部放電相位分布超過90°,相位分布譜圖中容易出現(xiàn)“兔耳狀”和“三角狀”放電。局部放電相位和偏斜度能反應(yīng)絕緣老化程度,隨著老化時間的增大,放電相位向兩端擴(kuò)展,偏斜度逐漸減小。采用加速老化實驗方法,開展了大量的壽命實驗,計算絕緣材料在各工況下的Weibull統(tǒng)計特征壽命值。通過最小二乘法擬合壽命數(shù)據(jù),分析了單因子老化壽命模型。研究結(jié)果表明,電壓幅值與老化壽命呈指數(shù)衰減關(guān)系,電壓頻率和溫度與老化壽命呈冪函數(shù)衰減關(guān)系。并根據(jù)多元統(tǒng)計分析方法,構(gòu)建了多因子作用下的絕緣老化壽命評估模型。
[Abstract]:Power electronic transformer is a new type of intelligent transformer. It can meet many new requirements of modern and future power system with the characteristics of flexible transmission and transformation of primary and secondary side power. Its safe and reliable operation is an important guarantee for the stable operation of power network. The insulation of power electronic transformer is subjected to the comprehensive action of high frequency electric stress and thermal stress for a long time, and its operating environment is bad, so it is prone to premature failure of insulation, and its failure mechanism is more complex than the traditional power frequency sinusoidal mode. Therefore, on the basis of the study on aging of insulation materials at power frequency, the aging failure of insulation under the combined action of high frequency electrothermal treatment was studied in detail, taking the insulation of epoxy resin as the object. It lays a foundation for revealing the mechanism of high frequency stress and improving the reliability of power electronic transformer. In this paper, a high frequency sinusoidal voltage insulation aging test device is constructed to simulate the insulation material aging experiment of power electronic transformer. A set of PD detection device composed of high frequency current sensor and oscilloscope is designed. According to the characteristics of actual measured signals, the extraction method of partial discharge signals is studied. The main contents are as follows: firstly, FIR high-pass filter is constructed to filter the low-frequency interference of the signal, and wavelet transform is used to decompose the signal, reduce the threshold noise and reconstruct the signal to filter the high-frequency noise interference. Then, the effective discharge signal is obtained by selecting the appropriate time window length. In order to study the aging characteristics of insulation in power electronic transformers, high frequency insulation aging tests were carried out. Based on the development and variation of partial discharge, the characteristic parameters of partial discharge were extracted from different aging stages. The high frequency aging characteristics of insulation and its aging characterization parameters were analyzed. The results show that the phase distribution of partial discharge exceeds 90 擄under the action of high frequency voltage, and the "rabbit ear" and "triangle" discharge are easy to appear in the phase distribution spectrum. Partial discharge phase and deflection can reflect the aging degree of insulation. With the increase of aging time, the discharge phase extends to both ends and the deflection decreases gradually. In this paper, a large number of life tests were carried out to calculate the Weibull characteristic life of insulating materials under different working conditions. The single factor aging life model was analyzed by using the least square method to fit the life data. The results show that the voltage amplitude is exponentially attenuated with the aging life, and the voltage frequency and temperature have a power function attenuation relationship with the aging life. According to the multivariate statistical analysis method, a multi-factor model for evaluating the aging life of insulation is constructed.
【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】：2015
【分類號】：TM41

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相關(guān)期刊論文 前1條

1 趙曉輝;楊景剛;路秀麗;袁鵬;王頌;李彥明;;油中局部放電檢測脈沖電流法與超高頻法比較[J];高電壓技術(shù);2008年07期

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本文編號：2418526