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1、变频技术1.1 变频技术的普及前景电机交流变频调速技术是当今节电、改善工艺流程以提高产品质量和改善环境、推动 技术进步的一种主要手段。变频调速以其优异的调速和起制动性能,高效率、高功率因数 和节电效果,广泛的适用范围及其它许多优点而被国内外公认为最有发展前途的调速方 式。电气传动控制系统通常由电动机、控制装置和信息装置 3 部分组成,电气传动关系到 合理地使用电动机以节约电能和控制机械的运转状态, 实现电能 -机械能的转换,达到优质、 高产、低耗目的。电气传动分成不调速和调速两大类,调速又分交流调速和直流调速两种 方式。不调速电动机直接由电网供电,但随着电力电子技术的发展这类原本不调速的机械
2、越来越多地改用调速传动以节约电能 (节约 15%20%或更多 ),改善产品质量,提高产量。 在我国 60%的发电量是通过电动机消耗的,因此调速传动是一个重要行业,已经得到国家 重视,目前已有一定规模。近年来交流调速中最活跃、发展最快的就是变频调速技术,变频调速是交流调速的基 础和主干内容。上个世纪变压器的出现使改变电压变得很容易,从而造就了一个庞大的电 力行业。长期以来,交流电的频率一直是固定的,变频调速技术的出现使频率变为可以充 分利用的资源。这 10 年来,变频技术的应用在我国有很大的发展,并取得了良好的效果可以说,变频 技术已为大多数用户所接受,但是不能不指出,我国在变频技术的应用方面,
3、与发达国家 的水平尚有很大差距,目前,我国在用的交流电动机使用变频调速运行的仅6%左右,而下业发达国家已达 (60%70%),日本在风机、 水泵上变频调速的采用率已达 10% ,而我国还 不足 0.01%.在日本,空调器的 70%采用了变频调速, 而我国才刚刚起步。 从这个现实出发, 变频技术尚有很大的发展空间,应该锲而不舍地做好推广应用工作。而且随着控制技术和控制手段的不断提高,变频调速又由变压变频控制的变频调速发 展到了矢量控制变频调速,通过控制交流电动机里相当于并励直流电动机励磁绕组的磁通 变化,提高变频器的恒转矩输出范围和动静态特性,使得交流电动机变频调速系统的性能 超过了直流电动机调
4、压调速系统的性能。为了简化控制系统,减少设备故障率,在矢量控 制变频调速的基础上又发展了无速度传感器的矢量控制变频调速。在一些对动静态特性要 求不太高的应用中,无速度传感器的矢量控制变频调速己完全可以和有速度传感器的矢量 控制变频调速相媲美。矢量控制对交流电机调速具有划时代的意义。变频调速是电机调速的最佳方式,是企业技术改造和产品更新换代的理想设备,是工 业自动化系统必不可少的组成部分,是实现生产过程和管理自动化的前提,也是信息化发 展的先决条件。在我国传统产业中,采用直流电机拖动的调速系统约占调速系统总量的 85%90%,而交流调速系统仅占 10%15%。效率低、质量差、消耗大、故障率高己成
5、为 制约企业发展的瓶颈。因此,必须积极推广先进的交流变频调速技术,用先进的设备武装 传统产业,促进自动化、工业化和信息化的进一步发展。1.2 变频调速发展趋势 如果说以第一个晶闸管的出现作为交流电动机变频调速的起点,可以认为它的发展历 史己 40 多年了。而变频调速技术真正高速发展时期, 应该是在 PWM 调制技术的出现和微 机控制技术发展之后。特别是最近 20 年来,随着交流调速技术的应用普及,交流变频调 速在化工、火电厂、矿山、油田、机械制造、城市建设、水处理、甚至家电等行业己经全 面推广使用,一般主要用于节能及控制。随着变频技术的普及和深入,以及国际、国内电 器设备使用的有关标准意识的强
6、化,电力系统行业和用户对变频技术的质量要求也越来越 高。变频调速的发展趋势主要围绕下面几个方而展开。1) 高性能的智能控制变频器380V 系统的低压变频器是国内的主要研究对象, 应用交流调速的基本理论, 结合神经 网络控制、 鲁棒控制、模糊控制,或其他智能控制等手段, 实现电机运行参数的自动辨识, 以期达到自适应、自调整的最优控制。这方面己有一定的研究成果。2) 速度传感器研究 从前面所述的各种变频调速的理论可知,一般系统都要用到转速传感器。在实际使用 中,由于变频设备和被控电动机有一定的距离,而高精度的转速传感器都要使用专门的电 源,被控电动机有的是在户外,运行工况非常恶劣,要保证速度反馈的
7、准确性,有时不得 不采取特别措施,因此也会增加额外费用,运行的可靠性和控制精度也会因此受到影响。 无速度传感器的变频调速系统,是通过现场采集的电流电压量,以及控制的实施策略,综 合出被控电机的实际转速。这种控制方案要求计算机的控制速度较高,并有足够的精度。3) 针对功率因数提高和谐波污染的研究 低压变频调速系统的控制虽然己经是非常成熟了,但目前国际、国内的产品,一般都 是矢量控制和直接转矩控制,重点放在电机变频控制理论的实现和完善上,而对变频器的 输出波形、功率因数,以及谐波污染等问题还没有引起足够的重视。最近 10 多年来,国 外在这一领域己有较深入的研究。有的针对功率因数,有的强调输出波形
8、。多重化技术就 是为了解决输出波形问题。 最近几年的研究表明, 利用 PWM 输出控制解决谐波输出问题, 是比较理想的方法,它可以省去多重化中的变压器,或过多的开关元器件,使变频器的体 积和重量减少,但这种方法不能解决所有谐波的消除问题,只能部分消除特定谐波。这方 面的研究论文还不多,也还没有成熟的类似低压变频器的产品出现。4) 高压变频器的研究 变频器的主要作用之一是节能。而高压电动机的节能效果是比较明显的,大功率的风 机和水泵用电动机一般都是高压电动机。国内,高压变频调速和它的节能控制还是一个比 较薄弱的环节 .它主要是针对 610kV 的交流电动机进行变频调速控制。这种高压电动机广 泛应
9、用于火力发电厂的送风机和引风机上。同样也可用于其他如石油化工、矿山、冶炼、 机械制造等行业的变频节能控制。从某种意义上讲,由于目前国内还不能完全生产高质量 的合格电力电子器件,而且,国外低压变频器的性能价格比也比国内自己研究的变频器高 得多。因此 ,在这方面还有许多研究工作要做。随着电力电子技术最近 20 多年的飞速发展,功率半导体器件的成本逐年下降,技术 工艺和性能也得到不断改善 .电力电子器件的应用己从传统的直流调速、 直流屏、斩波器等 领域延伸到交流调速和电力系统的质量控制领域.并正朝着高电压、大功率的方向发展 .这也是千年之交和世纪之交我国电力电子技术应用的发展趋势。5) 无换向器同步
10、电机的变频调速无换向器电动机也是在 20世纪 70年代发展起来的新型调速系统。它是一种变频调速 同步电动机 .也可以认为是一种用半导体电子开关线路代替换向器和电刷作用的直流电动 机。根据采用的控制方式不同 .可分为直流无换向器电动机和交流无换向器电动机。 直流无 换向器电动机采用交 -直-交或直 -交变频控制系统 ;交流无换向器电动机采用交 -交变频控制 系统。近 10 年来.国内外杂志上有许多相关的研究论文。而且,也有一定的成果出现。1.3 变频调速控制方式交流变频调速技术在 20 世纪得到了迅速发展。这与一些关键性技术的突破性进展有 关,它们是交流电动机的矢量控制技术、直接转矩控制技术、
11、PWM 技术以及微型计算机 和大规模集成电路为基础的全数字化控制技术、自整定技术等。1) 矢量控制技术矢量变换控制技术是西门子公司于 1971 年提出的一种新的控制思想和控制理论。它 是以转子磁场定向,采用矢量变换的方法实现定子电流励磁分量和转矩分量之间的解藕, 达到对交流电动机的磁链和电流分别控制的目的,从而获得了优良的静、动态性能。迄今 为止,矢量控制技术己经获得了长足的发展,并得到了广泛应用。2) 无速度传感器矢量控制技术 无速度传感器控制技术免去了传感器带来的环境适应性、安装维护等问题,降低了成 本,提高了系统的可靠性,同时结合矢量控制,具有矢量控制的优良性能。无速度传感器 技术中速度
12、估算的方法,除了根据数学模型计算电动机转速外,目前应用较多的有模型参 考自适应法和扩展卡尔曼滤波法。此外全维转子磁通观测器,齿谐波电势(RSH)等理论也出现在无速度传感器技术中。从 1983 年提出无速度传感器矢量控制策略以来,一直受到 学术界和产业界的高度重视,日立、安川电机等公司在 1987 年分别发表了研究成果,并 相继推出了产品。目前,无速度传感器矢量控制变频器的调速范围为 1:50 左右,个别厂商 有 1:75 甚至更高的产品。3) 直接转矩控制技术1985年.德国的M . Depen-block首次提出直接转矩控制技术(DTC)。 DTC控制直接在 定子坐标系下分析交流电动机的数学
13、模型。采用定子磁场定向而无需解藕电流,直接控制 电动机的磁链和转矩,以使转矩得到快速响应,从而获得高效的控制性能。直接转矩控制技术是近 10 年继矢量控制技术之后发展起来的又一种新型的高性能交 流变频调速技术,这种控制技术与矢量控制技术相比,对电机参数不敏感,不受转子参数 的影响,简单易行,具有广阔的发展和应用前景。4) PWM 控制技术1964年,德国的A. Schonung等率先提出了脉宽调制(PWM -pulse width modulation)变 频的思想,为近代交流调速系统开辟了新的发展领域。 PWM 控制技术通过改变矩形脉冲 的宽度来控制逆变器输出交流基波电压的幅值,通过改变调制
14、周期来控制其输出频率,从 而在逆变器上同时进行输出电压幅值和频率的控制。 PWM 技术简化了逆变器的结构,能 够明显的改善变频器的输出波形,降低电动机的谐波损耗,并减小转矩脉动,同时提高了 系统的动态响应性能。 PWM 技术还可用于整流器的控制,能够实现输入电流非常接近正 弦。并可使电网功率因数为1。PWM整流器因而被称为“绿色”变流器。目前,PWM技 术己成为变频器中应用最为广泛的控制技术。交流电机调速性能的不断提高在很大程度上 是由于 PWM 技术的不断进步。目前广泛应用的是在规则采样 PWM 的基础上发展起来的 准优化 PWM 法,即三次谐波叠加法和电压空间矢量 PWM 法。5) 数字化
15、控制技术 控制技术的数字化是静止变频装置的核心技术,也是今后的发展趋势。目前市场上的变频装置几乎全面实现了数字化控制。采用DSP和ASIC技术实现了快速运算和高精度控 制,可以得到良好的电流波形,使变频器的噪音大幅度降低,并且扫描时间大幅度缩短, 目前电流响应为0.10.7ms,速度响应为24 ms足以满足传动领域的控制要求。同时由于 应用微电子技术和 ASIC 技术,装置的元器件数量得以大幅度减少,从而使变频装置的体 积减小,可靠性得到大幅度提高。全数字控制方式使变频器的信息处理能力大为增强。采 用模拟控制方式无法实现的复杂控制在今天都己成为现实,从而所谓的RAS概念即可靠性 (Reliab
16、ility)、可操作性(Availability)、可维修性(Serviceability)得以充实。6) 自整定技术 自整定技术在变频调速系统中的应用日益广泛,它可以根据速度和负载的变化自动调整控制系统的参数, 使得系统具有快速的动态响应。 自整定技术分为离线式和在线式两种。 离线式的研究成果己经在相当多的产品中应用,它是在运行系统程序之前通过运行一段自 整定程序,辨识相关数据,并修改系统程序的相关参数,以期获得良好的系统控制性能。 另外,改进控制技术,提高系统鲁棒性也和自整定技术紧密相联系。外文文献1 Frequency Variation Speed Control1.1 The Pop
17、ularity and Prospect of Frequency Variation Speed ControlThe electrical machinery exchange frequency conversion velocity modulation technology is the electricity saving, the improvement technical process improves the product quality and the improvement environment, the impetus technology advancement
18、 one main method now The frequency conversion velocity modulation by its outstanding velocity modulation and the braking quality, the high efficiency, the high power factor and the electricity saving effect, the widespread applicable scope and other many merits by the domestic grandfather was though
19、t most has the development future velocity modulation way. The electrical transmission control system usually by the electric motor, the control device and the information installs 3 parts to be composed, the electrical transmission relates uses the electric motor by to save the electrical energy an
20、d to control the machinery reasonably the operating condition, the realization electrical energy - mechanical energy transformation, achieves, the high production, the low consumption goal high quality. The electrical transmission divides into does not modulate velocity and modulates velocity two bi
21、g kinds, the velocity modulation is divided the exchange to modulate velocity and to direct current modulates velocity two ways. The variable speed motor directly does not supply power by the electrical network But the machinery which does not modulate velocity along with electric power electronic t
22、echnology development this kind of original manuscript more and more many changes to the velocity modulation transmission by to save the electrical energy The improvement product quality, enhances the output Therefore the velocity modulation transmission is an important profession, already obtained
23、the country to take, at present had certain scale.In recent years exchanged in the velocity modulation most to be active, to develop quickest is the frequency conversion velocity modulation technology, the frequency conversion velocity modulation is exchangesthe velocity modulation foundation and th
24、e branch content. The last century transformer appearance causes the change voltage to become very much easy, thus has accomplished a huge electric power profession. Since long ago, the alternating current frequency always is fixed, the frequency conversion velocity modulation technology appearance
25、causes the frequency to become may the full use resources.In this recent 10 years, the frequency conversion technology application has the very big development in our country, and obtained the good effect to be possible to say, the frequency conversion technology has accepted for the majority users,
26、 but had no alternative but to point out, our country in frequency conversion technology application aspect, with developed country level Shang You very big disparity. At present, the AC motors we are using now use frequency variation speed control only about 6%, but the developed country is 60%70%,
27、 Japan on air blower, water pump frequency conversion velocity modulation use rate is 10%, but our country is less than 0.01%, In Japan air-conditioner using frequency variation technique rate is 70%, but our country's only then just started Embarks from this reality, frequency conversion techno
28、logy remain have the very big development space, we should complete the promoted application work doggedly.And with the constant development of control technique and control avenue, frequency variation speed controlled has developed the vector controlled frequency variation velocity modulation, by c
29、ontrolling the AC motor inside act for shunt DC motor field coper's flux, to enhance the permanent torque output scope and static and dynamic character, make the AC motor frequency variation speed controlled system superior to DC motor voltage variation speed controlled system. For simplifying t
30、he control system, reducing the fault rate, there has developed a vector controlled frequency variation speed control without speed sensor which based on the vector controlled frequency variation speed control. In some application which have low require , vector controlled frequency variation speed
31、control without speed sensor could completely compare with the vector controlled frequency variation speed control that have speed sensor. The vector control has the epoch-making significance to the AC current motor velocity modulation.Frequency variation speed control is the best way in the motor s
32、peed modulation, it is the perfect gear in the company's technical reform and product renewal, it is the essential composition in the industrial automatic system, it is the assumption of realizing the automatic of product proceed and management, it is also the precondition in the development of
33、informationization. In our country's traditional estate, using the DC motor speed control actuation account about 85%90% in the speed controlled system, but the AC speed controlled system account about 10%15%. Low efficiency, bad quality, large cost, high fault rate have already been the bottlen
34、eck that restrain the development of the company. So, we must promote the advanced AC frequency variation speed control technique positively, arms the traditional industry with the advanced equipment, promote a further development in the automation, the industrialization and the informationization.1
35、.2 Our Country ' s Development Condition in Speed Controlled TechniqueOur country is a developing country, so many product's research ability has behind the developed countries. From now on, the product of frequency variation speed controlled that ourselves made only act for last century 90s
36、 in the international. With the reform and opening, rapid development of economic, forms a large market, it opens to the country companies, also the foreign companies. Many products are exported from the developed countries, and runs well in our country, satisfied our need in fabrication and living.
37、 Many co-partership companies in our country make the international advanced products. The domestic complete department independently is designing the manufacture in the complete set installment to use the foreign import company and the joint venture supposesadvanced each, own develop the applicatio
38、n software, can provide the first-class electrical transmission control system for the domestic and foreign important engineering project. Although obtains very many result, but should see because domestic develops, the production product ability voluntarily is weak, is serious to the overseas compa
39、ny's dependence.As early as in the country "85" technical attack plan, the alternating velocity modulation technique was listed as the key technical attack project, but because our countrys elec'tric power and electronic device aggregate level is very low, although the production o
40、f IGBT 、GTO component has introduced the overseas technique, it has not formed the economies of scale benefit, almost does not have the independent development ability of new frequency converter production, this has affected the domestic frequency conversion velocity modulation technique development
41、 in the certain degree. In the high efficiency AC-AC frequency convert technique、 the motors without commutator technique and so on, the domestic product also has the suitable disparity in the digitization and the system reliable aspect compares with the overseas level, in the medium efficiency freq
42、uency convert technique, nearly all productions use ordinary V/F control inland, few adopt the vector control technique, and can not satisfied the market requirement in the variety and quality. But in overseas, the frequency conversion technique obtains the full development, and has obtained the rem
43、arkable achievement in each aspect. In power component aspect, high voltag、e the appearance of SCR、GTO、IGBT 、IGCT with high current capacity and the using in series and parallel, the high-pressured and high efficiency frequency converter production obtains the production and the promoted application
44、. In microelectronic technique aspect, 16bit and 32bit high speed microprocessors as well as the fast development of DSP and ASIC technique, provided the hardware method in realizing the frequency converter which with high accuracy multi-purpose. In theory aspect,the vector control, the magnetic flu
45、x control, the torque control, the intelligent control, the new control theory and so on have provided the related rationale for the high performance frequency converter development, we may see that, in the overall, the alternating frequency conversion velocity modulation technique in our country ha
46、s big disparity compares with international level.Therefore, the AC frequency variation speed control technique has the following sides:1) The basic research of control strategy in frequency converter has a large gap compares with the foreign level.2) The technical level of the whole machine is low
47、in the frequency converter, although we had input certainly people, material resources, but because of the disperse power, did not form a certainly technique and production scale.3) All the semiconductor power device product in the frequency converter is blank.4) Correlative Industries and relative
48、Industries drop behind.5) Few production and sale, low reliable and technological standards.With the development and improvement in the power electronic technique, power divert based on power electronic circuit technique and various control technique, the AC frequency variation speed controlled tech
49、nique is mature day by day, and sure to be the main way in the future. With the constant development of power electronic technique, reliable character, well adoption, cheap price that the frequency converter have will become true. This technique will gain widely, popularity application .At present,
50、foreign developed countries 'frequency convert technique towards to the miniaturization, high reliability, defend with harm, more function, high character, and our country is coming on now.1.3 Frequency Variation Speed Controlled ModeThe alternating frequency conversion velocity modulation techn
51、ique obtained the rapid development in 20th century. This is related with some crucial technical which gain unprecedented progress, they are Motor vector control technique, Direct torque control technique, PWM technique, Entire numerical control technique and self-setting technique which based on mi
52、crocomputer and large scale integrated circuit, and so on.1) Vector Control TechniqueVector transformation control technique is a one kind of new control thought and control theory which posed by SIEMENS CO. in 1971. It is realizing the stator current excitation component and the torque component so
53、lution lotus root by rotor magnetic field direction detection, and vector transformation, achieved the goal that separately control the motor flux linkage and the electric current, as a result, obtain finely static, dynamic performance. Until now, the vector control technique has obtained the consid
54、erable development, and also obtained the widespread application.2) Vector Control Without Velocity Generator TechniqueVector control without velocity generator technique abolish the problems that the environment compatibility 、install and maintenance bring on,reduce the cost, enhance the system rel
55、iability, at the same time, union vector control,has the fine performance of vector control. The speed estimate method in vector control technique without velocity generator, besides basis mathematical model computation electric motor rotational speed,at present the more applied are the model to ref
56、er auto-adapted method and expands the Kalman filtering law. In addition, entire Uygur rotor magnetic flux sight, tooth overtone electric potential, such as this theory and so on, also appearance in the vector control without velocity generator technique. Since 1983 proposed the vector control witho
57、ut velocity generator technique control strategy, receives the academic circles and the industrial field continuously highly focused all the time. Hitachi company and Sichuan electrical machinery and so on had published the research results separately in 19a8n7d, had promoted the product one after a
58、notherA. t present, vector control without velocity generator technique in frequency converter controlling in the velocity modulation scope is about 1:50,some individual merchant has 1:75 or even higher product.3) Direct Torque Control TechniqueIn1985, Germany's M. Depen-block proposes the direc
59、t torque control techniq(ueDTC) for the first time, The direct torque control technique analyzes the motor mathematical model directly under the stator coordinate system.Uses the stator magnetic field direction detection but not to need the solution lotus root electric curren,t directly control the electric motor flux linkage and torque, enable the torque to obtain the fast response,in order to obtain the highly effective control performance.Direct torque control technique is another kind of new、high performance alter
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