【摘要】：PWM技術(shù)在變流器中得到越來越廣泛的應(yīng)用,該技術(shù)以固定的開關(guān)頻率控制開關(guān)器件的開通和關(guān)斷,變流器輸出的電壓電流在開關(guān)頻率處及開關(guān)頻率的整數(shù)倍附近含有豐富的高次諧波,這些不期望的諧波會降低PWM變流器的電磁兼容品質(zhì),產(chǎn)生很強的寬帶電磁發(fā)射源,導(dǎo)致電磁干擾。針對上述問題,本文以APF變流器為研究平臺,引入隨機PWM調(diào)制技術(shù)將集中在開關(guān)頻率處的高頻諧波連續(xù)均勻地分布在一個較寬的頻率范圍內(nèi),降低電磁干擾和減小LCL濾波器的體積。本文主要在以下幾方面開展了工作:首先,分析二極管中點箝位(Neutral Point Clamped,NPC)型三電平拓撲APF變流器的工作原理,建立數(shù)學(xué)模型,揭示了網(wǎng)側(cè)電流與交流側(cè)電壓之間的數(shù)學(xué)關(guān)系,分析了PWM調(diào)制在變流器的作用。其次,介紹了隨機PWM調(diào)制基本原理,重點介紹了隨機開關(guān)頻率PWM調(diào)制技術(shù),并通過一個周期PWM波形的傅里葉展開,得到了隨機SPWM調(diào)制輸出相電壓的頻譜分布,為后續(xù)LCL參數(shù)優(yōu)化設(shè)計提供基礎(chǔ)。進一步,本文給出隨機開關(guān)頻率PWM調(diào)制的設(shè)計和實現(xiàn)方法,并針對常規(guī)隨機頻率PWM調(diào)制技術(shù)存在的問題提出混合隨機開關(guān)頻率調(diào)制和基于馬爾科夫(Markov)鏈隨機開關(guān)頻率調(diào)制兩種改進型調(diào)制方法。再次,定性地分析了LCL濾波器各個參數(shù)對系統(tǒng)的濾波性能的影響,重點介紹了LCL濾波器各個參數(shù)設(shè)計方法,并針對固定開關(guān)頻率和隨機開關(guān)頻率SPWM調(diào)制的不同約束條件設(shè)計出對應(yīng)滿足并網(wǎng)要求的APF變流器LCL濾波器參數(shù)。最后,對固定、隨機和兩種改進型隨機開關(guān)頻率SPWM調(diào)制策略進行仿真,在得到相應(yīng)的輸出相電流頻譜后,對得到的不同相電流頻譜進行對比和分析,得出采用隨機開關(guān)頻率SPWM調(diào)制既可以將集中在開關(guān)頻率及其倍頻處的高次諧波連續(xù)均勻地分布在一定的范圍內(nèi),降低電磁干擾,又可以減小LCL濾波器的電感值,減小濾波器的體積和降低設(shè)備成本。
[Abstract]:PWM technology is more and more widely used in converters. The switching devices are switched on and off at a fixed switching frequency. The output voltage and current of the converter contain abundant high-order harmonics near the switching frequency and the integer multiple of the switching frequency. These undesirable harmonics will reduce the electromagnetic compatibility of the PWM converter. In this paper, the APF converter is used as the research platform, and the random PWM modulation technology is introduced to distribute the high frequency harmonics concentrated at the switching frequency in a wide frequency range continuously and evenly, so as to reduce the electromagnetic interference and reduce the volume of the LCL filter. The following work should be carried out: Firstly, the working principle of the three-level topology APF converter with diode-neutral-point-clamped (NPC) is analyzed, the mathematical model is established, the mathematical relationship between grid-side current and AC-side voltage is revealed, and the function of PWM modulation in the converter is analyzed. Secondly, the random PWM modulation base is introduced. In this paper, the random switching frequency PWM modulation technique is mainly introduced, and the spectrum distribution of the output phase voltage of the random SPWM modulation is obtained by the Fourier expansion of a periodic PWM waveform, which provides the basis for the subsequent optimization design of LCL parameters. The problems of machine frequency PWM modulation technology are pointed out. Two improved modulation methods are proposed, which are mixed random switching frequency modulation and Markov chain random switching frequency modulation. Thirdly, the influence of each parameter of LCL filter on the filtering performance of the system is qualitatively analyzed, and the design method of each parameter of LCL filter is emphatically introduced. According to the different constraints of SPWM modulation with fixed switching frequency and random switching frequency, the LCL filter parameters of APF converter are designed to meet the requirements of grid connection. By comparing and analyzing the current spectrum, it is concluded that SPWM modulation with random switching frequency can not only distribute the high-order harmonics concentrating on the switching frequency and its frequency doubling continuously and evenly in a certain range, reduce the electromagnetic interference, but also reduce the inductance value of LCL filter, reduce the size of filter and reduce the cost of equipment.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM46

【參考文獻】

相關(guān)期刊論文 前1條

1 陳國柱,呂征宇,錢照明;典型工業(yè)電網(wǎng)諧波及其混合有源濾波抑制[J];電網(wǎng)技術(shù);2000年05期

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