1、本科毕业设计(论文)开题报告题目： 基于软开关投切的无功补偿技术的研究课 题 类 型： 科研 论文 模拟 实践学 生 姓 名： 学 号： 专 业 班 级： 系 别： 指 导 教 师： 开 题 时 间： 1、 毕业设计内容及研究意义设计内容：无功功率补偿装置在电系统中所承担的作用是提高电网的功率因数，降低供电变压器及输送线路的损耗，提高供电效率，改善供电环境。所以无功功率补偿装置在电力供电系统中处在一个不可缺少的非常重要的位置。合理的选择补偿装置，可以做到最大限度的减少网络的损耗，使电网质量提高。反之，如选择或使用不当，可能造成供电系统，电压波动，谐波增大等诸多因素。软开关是电器回路中用于连通和
2、切断负载的一种方式和装置，这种方式系指负载的切断和接通不是瞬间突然地完成，而是逐渐地由小到大完成接通过程，逐渐地由大到小完成切断过程。本文就是研究如何将软开关技术引用到电网系统中进行无功补偿。研究意义：交流电在通过纯电阻的时候,电能都转成了热能,而在通过纯容性或者纯感性负载的时候,并不做功.也就是说没有消耗电能,即为无功功率。然而电网系统中实际负载,不可能为纯容性负载或者纯感性负载,一般都是混合性负载,这样电流在通过它们的时候,就有无功功率,此时的功率因素小于 1,为了提高电能的利用率,就要进行无功补偿。无功补偿的意义：补偿无功功率，可以增加电网中有功功率的比例常数。减少发、供电设备的设计容量
3、，减少投资。降低线损，减少设计容量，减少投资，增加电网中有功功率的输送比例。而软开关技术的引入可以使电流的接入更加的和缓,减少接通的瞬时电流,延长使用寿命,减少能量消耗。2、 毕业设计研究现状和发展趋势研究现状：补偿技术一直备受人们关注。无功补偿有很多方法,主要有同步调相机；静止无功补偿器 SVC(staticvarcompensator)；静止无功发生器SVG(staticvargenerator)；功率因数校正装置 PFC(powfactorcorrector)；既可以治理谐波又可以进行无功补偿的有源滤波装 APF(activepowerfilter) 和并联电容器。在这些无功补偿方案中,
4、同步调相机由于其本身所固有的缺点(噪声大,损耗大)已经过时；SVG 虽然具有各种优越的性能,但它控制复杂,价格昂贵,短期内难以在我国电力系统推广使用；PFC 是针对某一种拓扑的改进(一般是整流器),是针对新产品开发的方案,不是单独对电网的；APF 一般说来控制比较复杂,且价格也比较昂贵,因此我国现行使用的无功补偿装置主要是并联投切电容器和晶闸管控制电抗器与固定电容的组合。用投切电容方式进行无功补偿,由于电容的投切是分级进行的,故产生的补偿电流也是阶跃式的,一段运行期内(例如白天和夜间)不是过补偿就是欠补偿,无法使电网无功功率得到恰当的实时补偿“另外,目前电容的投切多采用MSC(mechanic
5、allyswitchedcapacitor),开关是机械式交流接触器,其接点间容易拉弧粘连,工作寿命短,响应速度慢,且投切过程还对系统产生冲击电流和冲击电压“一些电容投切装置改用无触点的固态继电器,但它成本高,在流过大补偿电流时将产生较大的额外损耗“。发展趋势：APF(activepowerfilter)的确正逐步的在我国普及使用，但是现有的无功补偿装置大多是并联投切电容器和晶闸管控制电抗器与固定电容的组合。而软开关切投技术的引用不仅避免了切投时对电网与电容的冲击，且使开关使用寿命从电寿命上升到机械寿命，二者相差可达 10 倍以上。无论是经济性还是实用性,都有广阔的前景。三、毕业设计研究方案及
6、工作计划研究方案： 无功补偿的基本原理是：把具有容性功率负荷的装置与感性功率负荷并联接在同一电路，能量在两种负荷之间相互交换。这样，感性负荷所需要的无功功率可由容性负荷输出的无功功率补偿。用电容并联和可调式电压源作为无功补偿装置并用二级拓扑结构实现软开关投切。如图：当系统接入电网后，如果电网需要增加无功，则先让可调电压源电压 U v=U ，然后合开关 SW1，使补偿电容 C1 在零电流条件下接入电网（ZCSON） ，随后可根据所需补偿的无功，使 Uv 逐步减小，C1 提供的容性无功将逐步增加。当Uv=0 时，第一支路补偿达到最大值，此时如果仍需要提供无功，则使 SW3 在零电压条件下接通，同时
7、断开 SW1。在 SW1 断开后使 Uv 又迅速增到 U，闭合SW2，使电容 C2 在零电流条件投入，减小 Uv 可连续增大第二支路偿补电流大小，直到无功得到恰当的补偿。同理减少无功可通过增大可调电压源的电压来实现，具体操作方法则与增加无功相反，以上工作模式可通过改变 C1,C2 或增加电容推广到更多级，以适应多类负载环境。工作重点及难点： 如何实现连续可调的电压源；系统的仿真与验证;拟定解决方案：考虑到软开关下的并联电容式补偿可应用到多类负载场合，故可调电压源拟采用电力电子电路搭建或自耦变压器实现。而系统的仿真和验证用民用 220V 电压做电网电源，家用小电器做负载进行模拟测试。四、设计进度
8、计划：第一至四周，接收毕业设计任务书，了解设计内容，查相关资料。第五周，写开题报告和计划进度表。第六周，学习所查到的资料，清楚软开关的工作原理以及无功补偿的原理。第七周，考虑可行的补偿装置。第八周，根据相关资料论证并完善总体设计方案。第九周，进一步查阅与现有的无功补偿开关如复合线性开关的相关资料，研究可调电压源的方案。第十周，完善系统的总体电路的搭建。第十一周，对上述设计工作进行整理和完善。第十二周，根据论文撰写规范写出论文框架，撰写论文并自己检查修改。第十三至十六周，根据老师指导，改善不足之处，完善论文。第十七至十八周，完成论文。并查阅资料，找出知识点，准备答辩。3、 主要参考文献（不少于
9、10 篇，期刊类文献不少于 7 篇，应有一定数量的外文文献，至少附一篇引用的外文文献（3 个页面以上）及其译文）参考文献:1.周谦之开关 T 线性复合功率变换技术展望U2 第七届中国电力电子与传动控制学术会议论文集，电气传动自动化,（增刊）2.凌志斌, 邓超平, 郑益慧, 叶芃生 . 新型连续无功调节控制器的研制J. 电工技术杂志, 2003, 1(8) : 48-51.3.Zhibin Ling, Chaoping Deng, Pengshen Ye . A New King of Shunt Compensation .Capacitor Linked CompensatorJ . EPE
10、, 2003：56-594.周谦之, 李 定, 张捍东 . 开关线性复合功率变换技术机理和实效J. 电工技术学报, 2002, 17(4) : 75-79.5.许海斌, 许 敏, 周谦之 . 基于开关线性复合功率变换技术的新型无功补偿装置J. 电气传动自动化, 2004, 26(1) : 39-42.6.李旭, 谢运祥 PWM 技术实现方法综述J . 电源技术应用, 2005, 8 (2) : 51- 557.B R L in , T Y Yang. Single 2 phase half 2b ridge rect if ier w ith pow er facto r co rrect i
11、on J .IEEE P roc. 2Elect r. Pow er App l. , 2004 , 151 (4) 443- 450.8.余勇, 张兴等, Cu rren t sou rce SV PWM rect if ier based on DSP J. A dv. Tech. of Elec. Eng. 2.Maanshan Iron harmonic suppression; continuous variable voltage sourceIntroduction With the rapid development of science and technology to p
12、ower electronic devices based non-linear load has been an unprecedented range of applications, to the production and life of the earth-shaking changes. However, it also makes extensive use of the power of harmonic pollution and low power factor problems have become more prominent, or even seriously
13、affected the quality of power supply and network security. In this research, the reactive power compensation and harmonic suppression technique is a combination of one very important trend. Currently, reactive power compensation and harmonic suppression methods are LC filters, static var compensator
14、 SVC (Static Var Compensator), advanced static var generator ASVG (Adcanced Static Var Generator) and active power filter APF (Active Power Filter). LC filter with harmonic suppression which mainly take into account reactive power compensation, but not continuously. SVC is itself divided into many t
15、ypes, some can not be continuous reactive power compensation, such as the thyristor switched capacitor TSC (Thyristor Switching Capacitor), some compensation in a continuous reactive power injection at the same time a large number of harmonics You Xiang, such as crystal gate control reactor TCR (Thy
16、ristor Controlled Reactor) + Fixed capacitors FC (Fixed Capacitor). ASVG can continuously adjust the inductive or capacitive reactive power, but control complex, expensive and has its own frequency switching devices used by the restrictions, can not suppress harmonics. APF can compensate the dynamic
17、 suppression of harmonics and reactive power, but also control the complexity, high cost and limited capacity in the short term limits are widely used 1. In view of these several reactive power compensation and harmonic suppression device characteristics, in line with the technical and economic poin
18、t of view, containing harmonics of the power grid, a continuous compensation of reactive power can further inhibit new ideas harmonic.Basic principles The filtering device to meet the requirements of general reactive power compensation using two methods. First, to design filtering devices by filteri
19、ng, as its reactive capacity Does not meet the requirements, the installation of shunt capacitors; the second is the filtering capacity, to meet the requirements of reactive power compensation. Both will have been completed or less up the possibility of problems resulting voltage is too high. Progra
20、m used in this paper is the first method, based on the realization of a continuous variable reactive power compensation, power factor to ensure stability in the set value, does not appear due to fill or too up. This filter compensator is mainly passive filter circuit (PPF) and the continuously adjus
21、table reactive power compensation circuit composed of two parts. To simplify, a single-phase example to illustrate the basic principles, shown in Figure 1.U-grid voltage; UV - adjustable voltage source; In-harmonic current source; QC - adjustable reactive; Q f - PPF compensation of fundamental react
22、ive.Figure 1:The new reactive power compensation and harmonic suppression schematic.LC filter theory Such devicehas a simple structure, equipment investment, high reliability, easy maintenance and so, use it to achieve harmonic suppression. LC filter is a filter capacitor, inductor, and resistor app
23、ropriate combination of the structure shown in Figure 2. The filter is essentially for the circuit to provide a free path to the harmonic, or fundamental Ershi reserved harmonic short circuit. Meanwhile, due to the structural characteristics of its own apart from the filtering function for it can ta
24、ke into account fundamental reactive power compensation needs.Figure 2:Principle of single-tuned filter and impedance frequency characteristics.The filter to harmonic have impedance f(t)nsnwCnwLjRZssfnf 1Where: f(t)subscript represents the first time N single tunable filter. At the resonance point ;
25、 ; CwLnss1fnfssSlip on the fundamental terms of which were capacitive, so that the output filter branch of fundamental reactive power capacity :21111 ULUIQsssff LC single-tuned harmonic filter is mainly used for filtering the main features of harmonic source. For example, the harmonic source for the
26、 six-phase rectifier device, can be set 5 times, 7 times, 11 second-class single-tuned filter, if it needs to filter out higher frequency harmonics, can set a group of high-pass filter. For non-features of the three harmonics, the installation of filter should be based on the size of the 3rd harmoni
27、c current, and the installation of other filters that may occur after the 3rd harmonic is determined.Continuous reactive power compensation principleFigure 1, continuously adjustable reactive power compensation circuit as follows: grid voltage U, AC adjustable voltage source for the UV, C is capacit
28、ance, frequency and phase of UV required grid voltage U with the same power UV by changing the adjustable C on the amplitude can change the size of reactive current, reactive power compensation to achieve a continuous variable. Obviously, this part of the total generated reactive power QC as follows
29、: wUZUQsVCVCWhen the UV = U when, QC = 0; when UV = 0 when the shows with UV in the U 0 continuously changes between the reactive power in the continuous change between 0 .It is noteworthy that the non-adjustable voltage power QV 2wsissued as follows: CwCwUZI sVsVCVV 2214When the adjustable voltage
30、source voltage is half the grid voltage, the output of the maximum reactive power QV: 42maxsVQUClearly, the capacity of the adjustable voltage source compensation capacity only 1 / 4.Continuously adjustable voltage source to achieve Generation and grid voltage with frequency, with phase, amplitude o
31、f the voltage source is continuously adjustable to achieve that part of the key. Reactive power compensation on the dynamic response of the lower power requirements, can be generated by auto transformer, auto transformer secondary side voltage magnitude as continuously adjustable voltage source, the
32、 primary power directly connected to the Internet, can guarantee the secondary voltage in phase with the grid voltage, but also has a reliable, convenient and low cost characteristics. Through appropriate control circuitry to change the auto-sliding contact voltage regulator location can get the var
33、iable voltage. On the control precision and real time requires high, adjustable voltage source can be used with SLH AC chopper voltage regulator. Because Switch-Linearity Hybrid SLH 4 (Switch-Linearity Hybrid) Power Conversion basic structure (shown in Figure 3) is added after the filter circuit in
34、the switch-level output device a radio to follow the linear unit, the technology After the class is characterized by the linear circuit in the output device-level power control radio work in the critical partial linear saturated side of the special status (see Figure 3), that is, after filtering for
35、 switching power supply ripple voltage US and base-level input signal Ui synchronization and amplitude was slightly higher than it is. This entire circuit while maintaining low loss characteristics of the switch circuit, but also take into account the strong linear circuit load adaptability, robustn
36、ess and rapid rigid reference signal tracking ability, just to satisfy the adjustable voltage source of technical performance indicators requirements, the specific circuit shown in Figure 4.Figure 3 SLH basic structure and the working state of power transistorFigure 4 adjustable voltage source circu
37、it diagramAdjustable voltage source of input directly from the power grid voltage, the rectifier bridge are two half-wave rectifier, chopper regulator circuit with BUCK and filtered to obtain the duty cycle proportional to the amplitude of the “bread ripple“ for the After the class of linear power i
38、nverter module, the posterior pole of the two complementary conduction switch emitter follower output, by push-pull transformer, cascade compensation branch, shown in Figure 4, M2 turns on output is half-wave, M3 turns on the negative half-wave output. Here emphasize that the pre-amplifier output le
39、vel increases at the gate of the drive signal, is added in the collector than the “bread ripple“ small few large voltage signal V, so that switching on the power amplification, the output to follow drive signal, the ripple voltage to drop in push-pull switch on.一种新型的电网无功补偿及谐波抑制技术陈乐柱 1，孟樱 1,高绪松 2(1.安
40、徽工业大学 电气信息学院，安徽 马鞍山 243002 ; 2.马鞍山钢铁股份有限公司, 安徽 马鞍山 243002)摘 要：提出了一种新型的电网无功连续补偿及谐波抑制思路，介绍了其基本原理并对该思路的核心技术提供了实现方案。最后进行了仿真分析和实验验证。关键词：无功功率补偿；谐波抑制；连续可调电压源中图分类号：TM714 文献标识码：B引言随着科学技术日新月异的发展，以电力电子装置为主的非线性负荷得到了空前广泛的应用，给生产和生活带来了翻天覆地的变化。然而，它的广泛应用也使得电网中谐波污染和低功率因素问题日趋突出，甚至严重地影响了供电质量和电网安全。在这一研究领域，将无功补偿和谐波抑制技术相结
41、合是十分重要的发展趋势之一。目前，无功补偿和谐波抑制的方法主要有 LC 滤波器、静止无功补偿器 SVC(Static Var Compensator) 、先进静止无功发生器 ASVG（Adcanced Static Var Generator）和有源电力滤波器 APF（Active Power Filter） 。其中 LC 滤波器以谐波抑制为主，兼顾无功补偿，但不能连续调节。SVC 本身又分为许多种，有的不能连续补偿无功功率，如晶闸管投切电容器 TSC（Thyristor Switching Capacitor） ，有的在连续补偿无功的同时又向电网注入大量谐波，如晶闸管控制电抗器 TCR（Th
42、yristor Controlled Reactor）+固定电容器 FC（Fixed Capacitor） 。ASVG 可连续地调节感性或容性无功，但它控制复杂、价格昂贵且自身又受所用开关器件频率的限制，不能抑制谐波。APF 能动态抑制谐波和补偿无功功率，但同样控制复杂、成本高、容量有限等限制了在短期内被广泛推广应用1。鉴于上述几种无功补偿和谐波抑制装置的特点，本着从技术和经济的角度出发，对含有谐波的电网，提出了一种既可连续补偿无功功率又可抑制谐波的新思路。 1 基本原理使滤波装置满足无功补偿的要求一般采用两种方法。一是按滤波要求设计滤波装置，如其无功容量不满足要求，加装并联电容器；二是加大滤
43、波容量，使其满足无功补偿的要求。两者都会有过补或欠补的可能，致 使 电 压 过 高 等 问 题 出 现 。文中所采用的方案是在第一种方法的基础上，将实现无功功率的连续可调补偿，确保功率因数稳定在设定值，不会出现欠补或过补。此滤波补偿装置主要是由无源滤波电路（PPF）和连续可调无功补偿电路两部分组成。为简化起见，以单相为例来说明其基本原理，如图 1 所示。U 电网电压 ; UV 可调电压源 ; In 谐波电流源 ; QC 可调无功 ; Q f PPF 补偿的基波无功图 1 新型的无功补偿及谐波抑制原理图1.1 LC 滤波器原理 1此类装置具有结构简单、设备投资少、运行可靠性高、维护方便等优点，用
44、它来实现谐波抑制。LC 滤波器是由滤波电容器、电抗器和电阻器适当组合而成，结构如图 2 所示。其滤波实质上是为电路中的谐波提供一条释放路径，即保留基波而使谐波短路。同时，由于其自身的结构特点使其除了起滤波作用外还能兼顾基波无功功率补偿的需要。 图 2 单调谐滤波器原理及阻抗频率特性滤波器对 次谐波（ ）的阻抗为 f(t)nsnwCnwLjRZssfnf 1式中：下标 表示第 次单调谐滤波器。在谐振点处f; ; Lss1fnfRZss1一般 很小， 次谐波电流主要通过 分流，很少流入电网中，起到滤除该次谐波fnRfn的目的。对基波而言该条支路呈电容性，这样滤波支路输出的基波无功容量 为：fQ21
45、111 UnCwLUIQsssff LC 单调谐滤波器主要用于滤除谐波源中的主要特征谐波。例如，谐波源为六相整流装置时，可设 5 次、7 次、11 次等单调谐滤波器，若还需滤除更高频率的谐波，可设一组高通滤波器。对于非特征的 3 次谐波，装设滤波器应根据 3 次谐波电流的大小，以及装设其它滤波器后是否可能发生 3 次谐振来决定。1.2 连续无功补偿原理如图 1 中连续可调无功补偿电路所示：电网电压为 U，交流可调电压源为 UV，C 为电容，要求 UV的频率和相位与电网电压 U 相同，通过改变可调电源 UV的幅值就可以改变 C 上无功电流的大小，从而实现无功补偿的连续可调。显然，此部分产生总的无
46、功功率 QC为： wZQsCVC当 UV=U 时， QC=0；当 UV=0 时， ，可见随着 UV在 U0 之间连续变化时，2ws无功功率在 0 之间连续变化。值得注意的是，可调电压源发出的无功 QV为：2ws CZI ssVCV 2214式中，当 即可调电压源电压为电网电压的一半时，其输出的无功功率 QV最大为： 21U42maxCsVQwU显然，该可调电压源 2的容量只需要补偿容量的 1/43。2 连续可调电压源的实现产生与电网电压同频、同相、幅值大小连续可调的电压源是该部分实现的关键。对无功补偿动态响应要求较低的电网，可通过自耦变压器产生，自耦变压器的副边作为电压幅值连续可调的电压源，原
47、边直接接在电网上，既能保证副边电压与电网电压同相位，又具有可靠、方便、成本低廉的特点。通过合适的控制电路来改变自耦调压器滑动触头的位置即可获得所需的可变电压。对控制精度和实时性要求较高的场合，可调电压源可以采用带有 SLH 的交流斩波调压器。由于开关线性复合 SLH4 （Switch -Linearity Hybrid）功率变换技术的基本结构（如图 3 所示）是在开关滤波电路之后增加一级射级输出器型线性跟随单元，该技术的特点在于后级线性电路中的射级输出器功率管工作在临界饱和偏线性一侧的特殊状态（见图3） ，即让开关电源滤波之后的纹波电压 US与基级输入信号 Ui 同步且幅值略高于它。这样整个电
48、路既保持了开关电路的低损耗特性，又兼顾了线性电路较强的负载适应性、鲁棒性和对参考信号的快速刚性跟踪能力，恰好满足了可调电压源对技术性能指标的要求，具体电路如图 4 所示。图 3 SLH 基本结构及功率管的工作状态 图 4 可调电压源电路结构图 可调电压源的输入直接取自电网电压，经整流桥整流得到 2 个半波，采用 BUCK 电路斩波调压和滤波后，得到幅值与占空比成正比的“馒头纹波” ，为后级线性逆变单元供电，后极的二个互补导通开关的射极跟随输出，经推挽变压器，直接串接在补偿支路中，如图 4所示，M 2导通时输出正半波，M 3导通时输出负半波。此处强调的是前置级放大电路输出的加于栅极的驱动信号，是比加于集电极的“馒头纹波”小几伏的大电压信号，使开关工作于放大状态，其输出跟随驱动信号，这些纹波电压就降在推挽的开关上。
