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英文原文
1 Frequency Variation Speed Control
1.1 The Popularity and Prospect of Frequency Variation Speed Control
The 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 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 thought 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 and 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 big 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 technology 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 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 exchanges the velocity modulation foundation and the 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 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, 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%, 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 technology 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 controlling 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 the 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 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 speed 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 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 bottleneck 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.
1.2 Our Country’s Development Condition in Speed Controlled Technique
Our 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 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. 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 supposes advanced each, own develop the application 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 company'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 country’s electric power and electronic device aggregate level is very low, although the production of 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 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 frequency 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 remarkable achievement in each aspect. In power component aspect, high voltage、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. 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 flux 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 has 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 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 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 technique 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, 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 Mode
The alternating frequency conversion velocity modulation technique 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 microcomputer and large scale integrated circuit, and so on.
1) Vector Control Technique
Vector 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 solution 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 considerable development, and also obtained the widespread application.
2) Vector Control Without Velocity Generator Technique
Vector control without velocity generator technique abolish the problems that the environment compatibility、install and maintenance bring on, reduce the cost, enhance the system reliability, 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 refer 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 without 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 1987, and had promoted the product one after another. At 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 Technique
In1985, Germany's M. Depen-block proposes the direct torque control technique（DTC） 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 current，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 alternating frequency conversion velocity modulation technique after vector control technique in the nearly 10 years, this kind of control technique is insensitive to the electrical machinery parameter, not influence by the rotor parameter, easy and feasible, it has the broad development and the application prospect.
4) PWM (pulse width modulation) Control Technique
In1964, Germany's A. Schonung and some people took the lead to propose the pulse-duration modulation (PWM -pulse width modulation) frequency conversion thought, opened the recent development domain for the modern alternating velocity modulation system. The PWM control technique controls the inversion output alternating fundamental wave voltage peak-to-peak value by changing the rectangle pulse width, controls its output frequency through changing the modulation cycle, in order to carry on the output voltage peak-to-peak value and the frequency control on the inversion at the same time. The PWM technique simplified the inversion structure, can distinctly change the output wave shape of the frequency converter, reduces the overtone loss of electric motor, and reduces the torque pulsation, at the same time enhances the performance of dynamic response system. The PWM technique also may use in the rectifier controlling, can realize the input current which approaches the sine extremely. And may cause the electrical network power factor is 1. The PWM rectifier thus is called “the green converter”. At present, PWM technique has become the most widespread control technique applied in the frequency converter. The unceasingly velocity modulation performance of alternating current motor is as a result of the PWM technique unceasing progress enhancement in the very great degree. At present the widely applies is the optimizes PWM law which developing based on the regular sampling PWM foundation, that is Thrice Harmonic Superpose theory and voltage space vector PWM theory.
5) Numerical Control Technique
The digitalize in control technique is the key technique of static frequency conversion installment, also will be the next development tendency, at present in the market frequency conversion installment nearly comprehensively has realized the numerical control. Has realized the fast operation and the high accuracy control by using the DSP and the ASIC technique, and could gain a fine current wave, reduce the noise of the frequency converter in a large scale, and the scanning time also be reduced in a large scale, at present the electric current response is 0.1~0.7ms, the speed response is 2~4 ms, could satisfy the control request sufficiently in the transmission domain. At the same time, on account of the application of the micro electron and ASIC technique, the installment primary device quantity can be reduced in a large scale, thus, could make the frequency conversion equipment volume to be reduced, the reliability obtains the large scale enhancement. The entire numerical control way can make the information-handling capacity of frequency converter enhance greatly. The complex control has been realized in nowadays which could not be realized by simulation control mode, so that, the RAS which mean Reliability, Availability, Serviceability could be realized.
6) Self-setting Technique
The self-setting technique is widespread used in the frequency conversion velocity modulation system day by day, it may accord to the speed and the load to auto adjust the parameter of the control system, enable the system with rapid dynamic response. The self-setting technique divides into off-line and the on-line. The research results in the kind of off-line has been applied in the most production, before the system program operate, it operate a block self-setting program, recognize the correlation data, and amend the parameter of the system program that related, in order to gain a approved system control performance. Moreover, improve the control technique, enhance the robustness of the system, also have close relatives with self-setting technique.
2 PLC interference analysis
With the development of science and technology, the application in industrial control of PLC is more and more extensive. The dependability of PLC control system influences the safety in production and economical operation of the industrial enterprise directly; systematic anti-interference ability is the key to concerning the whole system and running reliably. All kinds of PLC used in the automated system, some install concentrated in the control room , some install in production scene and every electrical machinery equipment, they in strong electric circuit and strong electric abominable electromagnetic environment that equipment form mostly. Should improve PLC dependability of control systems, on one hand require PLC manufacturer to improve the anti-interference ability of the equipment; On the other hand, require engineering design, installation construct and use of maintaining causing paying close attention to, cooperate and perfect the problem of solving in many ways, strengthen systematic anti-interference performance effectively.
2.1 Sources of interference and interference with the general classification
It is like generally influencing the interference source of the industrial control equipment to influence the interference source of PLC control system, mostly producing the position in the electric current or violent change of voltage, these violent position that move of electric charge is the noise source, namely interfere the source.
Interfere type interfere the division different from wave form nature of the noise of the mode according to reason, noise produced to interfere usually. Among them: According to reason that noise produce being different, is it discharge noise, wave well up noise, high frequency shake noise, etc. to divide into; Different according to the wave form, nature of the noise, divided into a lasting noise, accidental noiseless.; It is different to interfere the mode according to the noise, is divided into mould interfering and difference mould interference altogether. It is a kind of commonly more used categorized method that the mould interferes interfering with the difference mould altogether. It is signal electric potential difference to place for mould not to interfere altogether, bunch enter, ground electric potential difference and space electromagnetic radiation reaction attitude (with direction) voltage is it is it form to add to change altogether at signal line by electric wire netting mainly. Mould voltage sometimes relatively heavy altogether, is it isolate performance mixing electric apparatus supply power in the room bad to adopt, changer output voltage generally relatively high mould altogether of signal, some can up to 130V to be the abo