畢業(yè)論文-基于pwm技術(shù)的三相橋式逆變電路性能研究(編輯修改稿)
2025-02-08 12:39 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 了三相無(wú)源型逆變器的構(gòu)建方式及其內(nèi)部結(jié)構(gòu)。同時(shí)也簡(jiǎn)要介紹了正弦波脈寬調(diào)試的技術(shù)。通過(guò)應(yīng)用 Matlab 軟件，構(gòu)建一個(gè)無(wú)源型三相逆變電路供電的系統(tǒng)，并進(jìn)行仿真，再對(duì)仿真波形進(jìn)行分析，定性討論了逆變器的兩個(gè)主要參數(shù)：參考波頻率（正弦波）和調(diào)制波（三角波）不同負(fù)載對(duì)系統(tǒng)仿真結(jié)果的影響，獲得以下結(jié)論： （一） 在電壓輸出頻率和正弦波頻率一定的情況下，三角波頻率的大小決定了每個(gè)周期內(nèi)的仿 真脈沖個(gè)數(shù) ,也決定了正弦波形的仿真質(zhì)量。 （二） 在電壓輸出頻率和正弦波頻率一定的情況下，三角波頻率的大小決定了三相交流電的脈沖寬度和波形清晰度。 （三） 在電壓輸出頻率和三角波頻率一定的情況下，正弦波頻率的大小決定了三相交流電的脈沖寬度和波形清晰度。 23 [參考文獻(xiàn) ] [1] 丁道宏．電力電子技術(shù) [M]．北京：航空工業(yè)出版社 ， 1992． [2] 王兆安，劉進(jìn)軍．電力電子技術(shù) [M]．北京：機(jī)械工業(yè)出版社 ， ． [3] 張立．電力電子技術(shù) [M]．科學(xué)出版社， 1995． [4] 尹克寧．電力工程 [M]．北京：中國(guó)電力出版社 ， 1997． [5] 周明寶．電 力電子技術(shù) [M]．第一版 .機(jī)械工業(yè)出版社 ， 1997． [6] 林渭勛．現(xiàn)在電力電子電路 [M]．第二版 .浙江大學(xué)出版社 ， 2022． [7] 邱關(guān)源．電路 [M]．北京：高等教育出版社 ， 1999． [8] 趙可斌，陳國(guó)雄 .電力電子變流技術(shù) [M]．上海：上海交通大學(xué)出版社， 1993． [9] 張立．趙永健 .現(xiàn)代電力電子技術(shù) [M]．北京：科學(xué)出版社， 1992． [10] 趙良炳．現(xiàn)代電力電子技術(shù)基礎(chǔ) [M]．清華大學(xué)出版社， 1995． 24 請(qǐng)刪除以下內(nèi)容， O(∩ _∩ )O 謝謝?。?！ The origin of taxation in the United States can be traced to the time when the colonists were heavily taxed by Great Britain on everything from tea to legal and business documents that were required by the Stamp Tax. The colonists39。 disdain for this taxation without representation (socalled because the colonies had no voice in the establishment of the taxes) gave rise to revolts such as the Boston Tea Party. However, even after the Revolutionary War and the adoption of the . Constitution, the main source of revenue for the newly created states was money received from customs and excise taxes on items such as carriages, sugar, whiskey, and snuff. Ine tax first appeared in the United States in 1862, during the Civil War. At that time only about one percent of the population was required to pay the tax. A flatrate ine tax was imposed in 1867. The ine tax was repealed in its entirety in 1872. Ine tax was a rallying point for the Populist party in 1892, and had enough support two years later that Congress passed the Ine Tax Act of 1894. The tax at that time was two percent on individual ines in excess of $4,000, which meant that it reached only the wealthiest members of the population. The Supreme Court struck down the tax, holding that it violated the constitutional requirement that direct taxes be apportioned among the states by population (pollock v. farmers39。 loan amp。 trust, 158 . 601, 15 S. Ct. 912, 39 L. Ed. 1108 [1895]). After many years of debate and promise, the sixteenth amendment to the Constitution was ratified in 1913, providing Congress with the power to lay and collect taxes on ine without apportionment among the states. The objectives of the ine tax were the equitable distribution of the tax burden and the raising of revenue. Since 1913 the . ine tax system has bee very plex. In 1913 the ine tax laws were contained in eighteen pages of legislation。 the explanation of the tax reform act of 1986 was more than thirteen hundred pages long (Pub. L. 99514, Oct. 22, 1986, 100 Stat. 2085). Commerce Clearing House, a publisher of tax information, released a version of the Internal Revenue Code in the early 1990s that was four times thicker than its version in 1953. Changes to the tax laws often reflect the times. The flat tax of 1913 was later replaced with a graduated tax. After the United States entered world war i, the War Revenue Act of 1917 imposed a maximum tax rate for individuals of 67 percent, pared with a rate of 13 percent in 1916. In 1924 Secretary of the Treasury Andrew W. Mellon, speaking to Congress about the high level of taxation, stated, The present system is a failure. It was an emergency measure, adopted under the pressure of war necessity and not to be counted upon as a permanent part of our revenue structure…. The high rates put pressure on taxpayers to reduce their taxable ine, tend to destroy individual initiative and enterprise,
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