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1、 大庆师范学院本科生毕业设计基于PWM技术的三相桥式逆变电路性能研究院 （系） 机电学院 专 业 自动化 学 生 姓 名 学 号 指导教师姓名 指导教师职称 2015年 5月 25日 摘 要本文讲述了逆变电路的工作原理，以及逆变电路的分类。在三相桥式逆变电路中，PWM技术的应用，可以使得输出的波形更加的优质。PWM技术意思是脉冲宽度调制技术,可以对其脉冲宽度和整体面积进行对比，其实是相等幅度而宽度不相等的脉冲，形成的波形。控制电路中正弦波和三角波的参数，可以对输出的波形进行控制，从而实现在PWM技术的控制下三相桥式逆变电路的性能研究。关键词：PWM控制；逆变；三相桥式目 录第一章 前言11.1
2、 研究背景11.2 前景及应用1第二章 PWM波形的工作原理22.1 PWM控制的基本原理22.2调制方式22.3采样法32.4 脉宽调制逆变电路32.4.1基于PWM的单相桥式逆变电路32.4.2基于PWM的三相桥式逆变电路4第三章 三相桥式逆变电路的主要应用技术53.1逆变电路原理53.2逆变电路电压型53.3逆变电路电流型6第四章 基于PWM的三相桥式逆变电路的仿真研究84.1 仿真模块参数设定84.2 仿真电路134.3 仿真波形13第五章 结论22参考文献23谢 辞24 26第一章 前言1.1 研究背景PWM逆变技术，它可以把直流输入经过脉冲的变化，从得到需要的交流电输出。它需要参考
3、波（如正弦波、梯形波等）和调制波（如三角波）的比较，从而在用开关量代替模拟量，来对逆变电路进行控制，实现把直流变成交流1。PWM逆变技术也被叫做脉宽调制逆变技术，它可以构成多种多样的交流电源，应用于生活中的各个角落。1.2 前景及应用 在人类社会的的与时俱进和生产生活中，逆变电路的应用变的更加的广泛和实用。比如说我们普通家庭使用的空调和家庭影院以及洗衣机和冰箱。它也应用于轮船制造、宇宙探索等领域。逆变电路对于现今社会来讲，已经得到充分的利用。在普通家庭中它应用于各种电源，照相机等；而在国家的设施中，特别是火力发电设备、风力发电、太阳能电池等设备都有广泛的应用2。随着电力电子技术的发展，以及计算
4、机技术和各种新技术的研发，这个技术应用得到了有效的利用和发展，其器件变的更加小巧和实用，效率和性能上有了更宽广的提高3。 第二章 PWM波形的工作原理2.1 PWM控制的基本原理PWM变换器其实就是用来控制逆变器开关器件的通断次以及时间分配得到相应规律，等幅和宽度可调的矩形方波都来自变换器输出端4。我们可以根据抽样理论的观点控制，当脉冲等不同应用系统的惯性的窄脉冲的形状，这是几乎相同的输出响应，和较窄的脉冲，然后之间差异较小的输出。这充分证明惯性系统的输出响应是受到系统冲量的影响。当它是一个窄脉冲信号时，作用于相同的惯性系统，分别和输出响应的波形几乎是相同的5。2.2调制方式调制方式可以有同步
5、调制类型，它的成因是因为，输入的载波信号的载波比，与另一个调制信号的同步进行，其中载波比为常数。我们想要做到异步调制，那就必须在载波信号输入时，令调制信号与其不同，以此来得出。然而我们在三相电路中，为了使三相输出对称。我们可以选取一个三角波，用它作为信号的载体，此时的N是3的整数倍。在异步调制中，我们可以看到许多的参数，比如半个周期内，来调节可控制输出的波形，因此在这个电路中，我们会得到许多数据和参数都会是不固定的， 其中PWM的脉冲个数，还有它的相位都包括在其中。它也有不对称的地方，比正负半周期的脉冲信号和前后四分之一周期的脉冲信号6。在同步调制中，N应该为整数，方便调制。想要调制三相PWM
6、波形，应使N=9。三相PWM同步调制波形如图2-1。 图2-1 三相PWM同步调制波形2.3采样法利用正弦波和三角波的自然交叉点时刻，通过控制功率开关的通和断，来产生SPWM波形。这其实就是自然采样法。在实际应用中，我们大多还是用三角波来做载波进行规则采样7。其得到的数据来讲，都可以使其得到的最后波形几乎是相差不多的。2.4 脉宽调制逆变电路2.4.1基于PWM的单相桥式逆变电路单极性逆变电路可分为双极和单极性控制。电路原理图如图2-2所示。图2-2 基于PWM的单相桥式逆变电路原理图单极性PWM控制方式：输入正弦的调制信号，载波形成的三角波与调制信号的正负半周期有关，正半周期是正极性，负半周
7、期是负极性。在信号波的正半周，需要保持V1处于导通的状态以及V2处于断开的状态。当uruc时使V4导通，V3关断，uo=Ud。当uruc时使V4关断，V3导通，uo=0。而在信号波的负半周期运行的时候，我们则需要保持V1处于断开的状态以及V2处于导通的状态。当uruc时使V3关断，V4导通，uo=0。波形如图2-3所示。图2- 3单极性PWM控制方式电压波形双极性PWM控制方式：当uruc时，V1和V4导通，V2和V3关断，这时如io0，则V1和V4通，如io0，则VD1和VD4通，不管哪种情况都是uo=Ud。当uruc时，V2和V3导通，V1和V4关断，这时如io0，则VD2和VD3通，不管
8、哪种情况都是uo=-Ud。波形图如图2-4所示。图2-4双极性PWM控制方式电压波形2.4.2基于PWM的三相桥式逆变电路电路图如图2-5所示。我们可以采用双极性的PWM控制，来控制三相桥式逆变电路。其三个相的PWM控制我们一般会用同一个三角波为载波，即为uc，它的的调制信号urU、urV和urW依次相差一百二十度8。其工作原理与单相桥式逆变电路基本箱相同，这里不再阐述说明其工作的运行原理。它的波形图如图2-6所示。图2-5基于PWM的三相桥式逆变电路图图2-6 三相桥式PWM逆变电路波形图第三章 三相桥式逆变电路的主要应用技术3.1逆变电路原理逆变电路它可以把直流输入经过脉冲的变化，经过相同
9、的冲量面积，等效结果后从得到需要的交流电输出。在我们生活中，它的应用也普遍体现在工业生产和生活的各个角落。比如家用的充电器，就体现了整流电路在生活中小小地方的应用，而在街道上可以随处可见的是大型的变压器，为人们生活用电提供了方便的条件。在桥式逆变电路中，社会的进步使得我们越来越多的完善和改进，使得这逆变可以切换开关的频率来体现9。总之在逆变电路中，直流变交流的过程的具体实现，依靠电路中晶闸管的通断状态来实现。随着二极管和晶闸管以及IGBT等元器件的不断产生，更加提高了整流电路的应用在我们生活中越来越充当了不可替代的地位10。3.2 逆变电路电压型图3-1为半桥电路，其负载是阻感（当负载中感抗w
10、L和电阻R比较来说不能忽略时）。三极管导通时过的时间，负载上的电流和电压有同样的方向，能量是从只留测到负载；VD1或VD2通时，io和uo的方向相反，能量的走向为从电感中贮能到直流侧。VD1、VD2称为反馈二极管,它的存在时负载电流连续。图3-1 单相半桥型逆变电路的工作原理图图3-2为全桥电路。图中两对桥臂为一组，每组导通180o，每组之间交替导通。图3-2 单相全桥型逆变电路结构图图3-3为三相桥式逆变电路的电路原理结构图。其负载是阻感（当负载中感抗wL和电阻R比较来说不能忽略时）。它的工作方式是一百八十度导电方式。在V、W三个相中各相每次通过程中，其两个桥臂不能够一起交替导电工作，U、V
11、、W的工作相互之间都有着一百二十度的差别。其中每次都是纵向换流。因此uUN就会是Ud/2的矩形波（Ud为电源电压），V、W两相和U一样，只是相位相差一百二十度。图3-3 三相桥式逆变电路结构图3.3 逆变电路电流型我们在实际工作的过程中，负载参数会随时间的变化而变化，当然我们的工作频率必须去适应负载的变化，并且自动调整，这就是自励方式。他励方式我们可以在电路工作前，来设定需要的固定频率，使得系统进入工作状态。我们需要先用他励方式，等到系统开始工作后再转入自励方式（克服自励方式的缺陷）。其连接如图3-4所示。图3-4单相电流型逆变电路图在120o导电工作方式下进行横向换流。电路图如图3-5所示。
12、图3-5 三相电流型逆变电路第四章 基于PWM的三相桥式逆变电路的仿真研究4.1 仿真模块参数设定控制电路： 图4-1控制电路图由三个Sine wave正弦波发生装置产生正弦波，以及一个三角波发生器Repeating Sequence Interpolated产生三角波，通过Relational operator 和Logical operator组成控制电路来进行脉宽调制。其中正弦波发生装置Sine wave的参数设置如下图。图4-2正弦波参数模块图三角波发生装置Repeating Sequence Interpolated的参数设置如下图。图4-3三角波模块参数比较器Relational
13、Operator 的参数设定如图4-4。图4-4比较器模块参数图反相器模块的参数设定如图4-5。图4-5反相器模块参数图控制电路产生的控制信号输出，一个结果输入到示波器模块Scope1；一个结果给后面的电路由IGBT和二极管组成的逆变电路。逆变电路：图4-6逆变电路仿真图其中IGBT模块的参数设置如图4-7。图4-7 IGBT模块参数图二极管模块的参数设置如图4-8，图4-8二极管模块参数图再经过滤波电路进行滤波，以及负载，通过示波器模块Scope得出波形。滤波电路和负载输出电路图如图4-9所示。 图4-9滤波电路和负载输出电路图其中各各模块的参数设定如下。阻感负载如图4-10所示。图4-10
14、阻感负载的模块参数图滤波电路中的电感模块参数如图4-11，电容模块参数如图4-12。图4-11滤波电路中的电感模块参数图图4-12滤波电路中的电容模块参数图4.2 总仿真电路图2-13系统中的仿真电路图4.3 仿真波形当正弦波参数不变，更改三角波的模块的参数时。各个模块的参数介绍如下。 图4-14三角波模块的参数图 图4-15正弦波模块的参数图Scope图4-16示波器 Scope的波形图Scope图4-17示波器模块Scope的波形图更改三角波模块参数后的参数如图4-18所示。图4-18三角波模块的参数图 Scope图4-19示波器模块Scope的波形图Scope1图4-20示波器模块Sco
15、pe1的波形图再次更改三角波模块参数如图4-21所示。 图4-21三角波模块参数图Scope图4-22示波器模块Scope的波形图Scope图4-23示波器模块Scope1的波形图当三角波模块的参数不变，更改正弦波模块的参数时。各个模块的参数介绍如下。图4-24三角波模块参数图图4-25正弦波模块参数图Scope图4-26示波器模块Scope的波形图Scope1图4-27示波器模块Scope1的波形图更改三角波模块参数后如图4-28所示。图4-28正弦波模块参数图Scope图4-29示波器模块Scope的波形图Scope1图4-30示波器模块Scope1的波形图第五章 结论本文通过对逆变器的概
16、念、设计技术分类等方面的介绍，简要描述了三相无源型逆变器的构建方式及其内部结构。同时也简要介绍了正弦波脉宽调试的技术。通过应用Matlab软件，构建一个无源型三相逆变电路供电的系统，并进行仿真，再对仿真波形进行分析，定性讨论了逆变器的两个主要参数：参考波频率（正弦波）和调制波（三角波）不同负载对系统仿真结果的影响，获得以下结论：（一） 在电压输出频率和正弦波频率一定的情况下，三角波频率的大小决定了每个周期内的仿真脉冲个数,也决定了正弦波形的仿真质量。（二） 在电压输出频率和正弦波频率一定的情况下，三角波频率的大小决定了三相交流电的脉冲宽度和波形清晰度。（三） 在电压输出频率和三角波频率一定的情
17、况下，正弦波频率的大小决定了三相交流电的脉冲宽度和波形清晰度。参考文献1 丁道宏电力电子技术M北京：航空工业出版社，19922 王兆安，刘进军电力电子技术M北京：机械工业出版社，2009.053 张立电力电子技术M科学出版社，19954 尹克宁电力工程M北京：中国电力出版社，19975 周明宝电力电子技术M第一版.机械工业出版社，19976 林渭勋现在电力电子电路M第二版.浙江大学出版社，20027 邱关源电路M北京：高等教育出版社，19998 赵可斌，陈国雄.电力电子变流技术M上海：上海交通大学出版社，19939 张立赵永健.现代电力电子技术M北京：科学出版社，199210 赵良炳现代电力电
18、子技术基础M清华大学出版社，1995请删除以下内容，O(_)O谢谢！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 colonists disdain for this taxation without r
19、epresentation (so-called 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 U.S. Constitution, the main source of revenue for the newly created states was money rece
20、ived from customs and excise taxes on items such as carriages, sugar, whiskey, and snuff. Income 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 flat-rate income tax was imposed in 1867. The i
21、ncome tax was repealed in its entirety in 1872. Income tax was a rallying point for the Populist party in 1892, and had enough support two years later that Congress passed the Income Tax Act of 1894. The tax at that time was two percent on individual incomes in excess of $4,000, which meant that it
22、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. farmers loan & trust, 158 U.S. 601, 15 S. Ct. 912, 39 L. Ed. 1108 1895). A
23、fter many years of debate and compromise, the sixteenth amendment to the Constitution was ratified in 1913, providing Congress with the power to lay and collect taxes on income without apportionment among the states. The objectives of the income tax were the equitable distribution of the tax burden
24、and the raising of revenue. Since 1913 the U.S. income tax system has become very complex. In 1913 the income 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. 99-514, Oct. 22, 1986, 100 Stat. 20
25、85). 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
26、the United States entered world war i, the War Revenue Act of 1917 imposed a maximum tax rate for individuals of 67 percent, compared 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 syst
27、em 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 income, tend to destroy individual initiative and enterprise, and seriou
28、sly impede the development of productive business. Ways will always be found to avoid taxes so destructive in their nature, and the only way to save the situation is to put the taxes on a reasonable basis that will permit business to go on and industry to develop. Consequently, the Revenue Act of 19
29、24 reduced the maximum individual tax rate to 43 percent (Revenue Acts, June 2, 1924, ch. 234, 43 Stat. 253). In 1926 the rate was further reduced to 25 percent. The Revenue Act of 1932 was the first tax law passed during the Great Depression (Revenue Acts, June 6, 1932, ch. 209, 47 Stat. 169). It i
30、ncreased the individual maximum rate from 25 to 63 percent, and reduced personal exemptions from $1,500 to $1,000 for single persons, and from $3,500 to $2,500 for married couples. The national industrial recovery act of 1933 (NIRA), part of President franklin d. roosevelts new deal, imposed a five
31、percent excise tax on dividend receipts, imposed a capital stock tax and an excess profits tax, and suspended all deductions for losses (June 16, 1933, ch. 90, 48 Stat. 195). The repeal in 1933 of the eighteenth amendment, which had prohibited the manufacture and sale of alcohol, brought in an estim
32、ated $90 million in new liquor taxes in 1934. The social security act of 1935 provided for a wage tax, half to be paid by the employee and half by the employer, to establish a federal retirement fund (Old Age Pension Act, Aug. 14, 1935, ch. 531, 49 Stat. 620). The Wealth Tax Act, also known as the R
33、evenue Act of 1935, increased the maximum tax rate to 79 percent, the Revenue Acts of 1940 and 1941 increased it to 81 percent, the Revenue Act of 1942 raised it to 88 percent, and the Individual Income Tax Act of 1944 raised the individual maximum rate to 94 percent. The post-World War II Revenue A
34、ct of 1945 reduced the individual maximum tax from 94 percent to 91 percent. The Revenue Act of 1950, during the korean war, reduced it to 84.4 percent, but it was raised the next year to 92 percent (Revenue Act of 1950, Sept. 23, 1950, ch. 994, Stat. 906). It remained at this level until 1964, when
35、 it was reduced to 70 percent. The Revenue Act of 1954 revised the Internal Revenue Code of 1939, making major changes that were beneficial to the taxpayer, including providing for child care deductions (later changed to credits), an increase in the charitable contribution limit, a tax credit agains
36、t taxable retirement income, employee deductions for business expenses, and liberalized depreciation deductions. From 1954 to 1962, the Internal Revenue Code was amended by 183 separate acts. In 1974 the employee retirement income security act (ERISA) created protections for employees whose employer
37、s promised specified pensions or other retirement contributions (Pub. L. No. 93-406, Sept. 2, 1974, 88 Stat. 829). ERISA required that to be tax deductible, the employers plan contribution must meet certain minimum standards as to employee participation and vesting and employer funding. ERISA also a
38、pproved the use of individual retirement accounts (IRAs) to encourage tax-deferred retirement savings by individuals. The Economic Recovery Tax Act of 1981 (ERTA) provided the largest tax cut up to that time, reducing the maximum individual rate from 70 percent to 50 percent (Pub. L. No. 97-34, Aug.
39、 13, 1981, 95 Stat. 172). The most sweeping tax changes since world war ii were enacted in the Tax Reform Act of 1986. This bill was signed into law by President ronald reagan and was designed to equalize the tax treatment of various assets, eliminate tax shelters, and lower marginal rates. Conserva
40、tives wanted the act to provide a single, low tax rate that could be applied to everyone. Although this single, flat rate was not included in the final bill, tax rates were reduced to 15 percent on the first $17,850 of income for singles and $29,750 for married couples, and set at 28 to 33 percent o
41、n remaining income. Many deductions were repealed, such as a deduction available to two-income married couples that had been used to avoid the marriage penalty (a greater tax liability incurred when two persons filed their income tax return as a married couple rather than as individuals). Although t
42、he personal exemption exclusion was increased, an exemption for elderly and blind persons who itemize deductions was repealed. In addition, a special capital gains rate was repealed, as was an investment tax credit that had been introduced in 1962 by President john f. kennedy. The Omnibus Budget Rec
43、onciliation Act of 1993, the first budget and tax act enacted during the Clinton administration, was vigorously debated, and passed with only the minimum number of necessary votes. This law provided for income tax rates of 15, 28, 31, 36, and 39.6 percent on varying levels of income and for the taxa
44、tion of social security income if the taxpayer receives other income over a certain level. In 2001 Congress enacted a major income tax cut at the urging of President george w. bush. Over the course of 11 years the law reduces marginal income tax rates across all levels of income. The 36 percent rate
45、 will be lowered to 33 percent, the 31 percent rate to 28 percent, the 28 percent rate to 25 percent. In addition, a new bottom 10 percent rate was created. Since the early 1980s, a flat-rate tax system rather than the graduated bracketed method has been proposed. (The graduated bracketed method is the one that has been used since graduated taxes were introduced: the percentage of tax differs based on the amount of taxable income.) The flat-rate system would i