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1、 英文原文 无锡科技职业学院Frequency changerIn general inverter power electronic technology, micro computer technology and modern control theory developed based on intelligent electrical appliances. Its main function is to provide the variable frequency communication load of power. In recent years, inverter with
2、 excellent performance of speed adjustment and energy-saving ability in the field of electric power drag control won a wide range of applications. Here is a frequency converter to the relevant knowledge introduction.1.Converter working principle(1)OverviewMain circuit is provided for asynchronous mo
3、tor power surge FM power, and the inverter transform part of main circuit substantially can be divided into two classes: the voltage type is the dc voltage source inverter, the transformation as dc circuit communicate the filtering is capacitance. Current model is to transform into the dc current so
4、urce of converter, communicate the dc circuit filter is the inductance. It consists of three components, will work frequency power transformation for dc power rectifier, absorb the converter and inverter the resulting voltage ripple” flat wave loop ”and will transform into ac power dc power of inver
5、ter.(2)RectifierRecently the extensive use of the diodes converter, it is the industrial frequency power transformation for dc power supply. Also used two groups of transistor converter constitute reversible, because its power converter, can undertake renewable direction reversible operation.(3)Flat
6、 wave loopAfter rectifying the rectifier of dc voltage, contains six times the power supply voltage ripple frequency, moreover inverter produces the current ripple also make dc voltage fluctuant. In order to restrain voltage fluctuation, using inductance and capacitance absorption voltage ripple (cu
7、rrent). Device capacity hours, if the power and main circuit constitute devices have allowance, can save inductance using simple flat to wave circuits.(4)InverterContrary, inverter with rectifier is required by the power transformation for dc frequency ac power, to the fixed time make six switch dev
8、ice conduction, shut off can get 3 phase ac output. Voltage source PWM inverter with open for example shows voltage waveform and time.Control circuit is for asynchronous motor power supply (voltage, frequency adjustable) provides the main circuit of the loop control signals, it has frequency and vol
9、tage operation circuit, main circuit voltage, current detection circuit, motor speed detection circuit , the control signal will operation circuit to amplify drive circuit , and inverter and motor to protect circuit composition.operation circuit: will the external speed, torque, etc with measuring c
10、ircuit of instruction of current and voltage signal comparison operations, decided to inverter output voltage, frequency.voltage, electric current detection circuit: and main circuit potential isolation test voltage, current, etc.drive circuit: drive main circuit device circuit. It and control circu
11、it isolation make main circuit device conduction, shut off.Speed detection circuit: packed in asynchronous motor axis machine speed detector signal for speed signal, into operation circuit, according to instructions and computing can make the motor speed on command operation.Protection circuit: dete
12、ction main circuit of voltage, current, when happen overload or over voltage etc anomalies, in order to prevent inverter and asynchronous motor damage, make inverter to stop working or inhibit the voltage and current.2. Inverter roleThe high pressure high-power inverter integration transistor techno
13、logy and electronic control technology, widely used. The role of frequency converter is to change the ac motor power frequency and amplitude are changing its movement, and the magnetic field of the cycle, achieve the purpose of smooth control motor speed. The emergence of frequency converter, make c
14、omplex speed regulation control simplifies, use frequency converter + ac induction motor is a rat trap type replaced the most original combined with dc motor only completed work, reducing the volume, reduced maintenance rate, the transmission technology development to a new stage.Inverter can optimi
15、ze motor running, so can also play the role of synergistic energy saving. According to the global famous inverter production enterprise ABB calculate, is only the group worldwide production and installation of the inverter has been able to save each year 1150 billion kilowatt-hours of electricity, r
16、educed correspondingly 9,700 tons in carbon dioxide emissions a year, it has already surpassed the Finnish co2 emissions.3. Converter composed ofInverter usually consists of four parts: rectifier unit, high-capacity capacitor, inverter and controller.(1) rectifier unit will work frequency fixed ac c
17、onversion for direct current.(2) the high-capacity capacitor storage after conversion of electric power.(3) inverter composed by powerful switching transistors, electron switch dc current into different frequency, pulse width and amplitude.(4) controller set according to procedures work, control the
18、 output pulse amplitude and pulse width, make for approximate sine wave superimposition of alternating current, drive ac motor.4. Inverter control modeLow voltage general frequency output voltage for 380 0.75 650V, power output, working frequency for 400kW 0 400Hz, its main circuit USES pay - straig
19、ht - pay circuit. The control mode has experienced the following generations.(1) U/f = C sine pulse-width modulation (SPWM) control modeIts characteristic is the control circuit is simple in structure, low cost, mechanical properties hardness is better also, and can satisfy the requirements of the s
20、mooth general transmission speed in industry, has widely applied in various fields. But, this kind of control mode, because in low frequency output voltage, low torque pressure drop by the influence of the stator resistance notable, to make the output maximum torque reduction. In addition, its mecha
21、nical properties for dc hard, it ultimately didnt dynamic torque ability and static performance of speed are is unpleased, and the system performance is not high, control curve can follow load changes, torque response is slow, motor torque utilization rate is not high, low speed for stator resistanc
22、e and inverter dead zone effect exists and slow performance, stability become so poor. So people are also developed vector control variable frequency speed regulation.(2)Voltage space vector (SVPWM) control modeIt is the overall effect of three-phase waveform generated as the premise, and with the i
23、deal gas gap approximate motor circular rotating magnetic track for purpose, a generation three-phase modulating waveform cut polygon, within the control approach the way round. After practice after the use and improvements in frequency compensation, namely, can eliminate speed control error; Throug
24、h feedback estimate flux amplitude, eliminate the influence of the stator resistance speed; Will output voltage, current loop, in order to improve the accuracy and stability of dynamic. But control circuit link is more, and not introduced torque control, so the system performance didnt get the basic
25、 improvement.(3) Vector control (VC) wayThe practice of vector control variable frequency speed regulation in three-phase asynchronous motor is to coordinate the stator currents , through the three-phase - two phase transformation, equivalent to two phase static coordinate ac current Ia1 Ib1, again
26、through the press rotor field-oriented rotation transformation into an equivalent synchronization reference frame, the dc current Im1, It1 (Im1 for dc excitation current equivalent; and torque It1 is proportional to the equivalent of the armature current), and imitate the dc machines for dc control
27、method, the control signal obtained, through the corresponding coordinates transform, realize the control of induction motor. Its essence is equivalent to dc to ac motor respectively, the speed, motivation, an independent control field two components. Through controlling the rotor flux, then decompo
28、sed stator currents and obtain torque and magnetic field component, the two coordinate transformation, realize orthogonal or decoupling control. The vector control methods proposed epoch-making significance. But in practical applications, because the rotor flux hard accurate observation, the system
29、characteristics influenced by motor parameters, and on equivalent used in dc machines control process of vector rotation transformation is more complex, makes the actual control effect is difficult to achieve the ideal analysis results.(4) Direct torque control (DTC) wayIn 1985, the professor German
30、 Ruhr university offers the first direct torque control frequency conversion technology. This technology in largely solve this vector control deficiencies and, based on novel control thoughts, succinctly system structure, good dynamic and static performance have developed rapidly. At present, the te
31、chnology has been successfully used in the high-power electric locomotive ac drive traction. Direct torque control under directly on the stator coordinate system analysis, mathematical model of ac motor control motor magnetic linkage and torque. It doesnt need to ac motor is equivalent to the dc mot
32、ivation, and tell the vector rotation transformation calculation; many of the complex It does not need to imitate the control dc machines, also do not need for decoupling and simplified ac motor mathematical model.(5) Matrix into - straight - pay control modeVVVF inverter, vector control frequency c
33、onversion, direct torque control variable frequency are hand in hand in the straight - frequency - one. Its common shortcoming is the input power factor, the harmonic current low, dc circuit need big reserved capacitance, renewable energy and cant feedback is returned to power grid, namely quadrant
34、operation cannot carry out. Therefore, matrix into - pay variable frequency arises at the historic moment. Because matrix into frequency conversion into - saves the intermediate dc link, thereby eliminating the need for bulky, expensive electrolytic capacitors. It can realize the power factor, the i
35、nput current for l for sine quadrant operation and system, the power densities. Though the technology now is not yet, but still attracted many scholars in-depth research. Its essence is not the indirect control current and magnetic chain equivalent the torque, but by directly as the control signal t
36、o realize. Specific means is:Introduced the stator flux control, to realize the stator flux observer is speed sensor less mode;Automatic identification (ID) rely on accurate mathematical model of the motor and motor parameter automatic identification;Calculate the actual value of the stator resistan
37、ce and corresponding mutual inductance, magnetic saturation factors, such as the actual figure is rotary inertia of the stator flux linkage and torque, and real-time control; rotor speedBand - Band control realization by the flux and the torque control from the Band - Band of PWM signal, inverter sw
38、itch state control.Matrix into frequency conversion is fast into - the torque response ( 2ms), high speed precision (+ 2%, no PG feedback), high torque accuracy ( + 3%); Also has high starting torque and high torque accuracy, especially in low speed (including 0 speed), can output by 150% 200% torqu
39、e.5. Inverter historyFrequency conversion technology emerge background is ac motor step less speed regulations extensive demand. Traditional dc speed control technology for large size high failure rate applied limited.(1)Since 1960s, power electronics device generally applied the tryristor and upgra
40、de the product. But its speed control performance far cannot satisfy needs.(2)Starting in the 1970s, pulse width modulation (PWM voltage variable frequency speed - VVVF) the research get breakthrough, after 1980s microprocessor technology is perfect makes all sorts of optimization algorithm to easy
41、implementation.(3)In the mid 1980s, America, Japan, Germany, England and other developed countries, commodity practicalization frequency VVVF technology in market, can be widely used. The earliest converter may is Japanese bought British patent development. But the United States and Germany with ele
42、ctronic components production and electronic technology advantage, high-end product rapid preemption market.(4)Stepping into the 21st century, home-made frequency converter gradually rise, has been gradually preempted high-end market.6. Inverter classificationUnit series model converterThis is in re
43、cent years that it has developed a kind of circuit topology, it mainly consists of input transformer, power unit and control unit three major components. Modular design, because use the power unit are interconnected ways to solve the problem of the high pressure can be named, ac motor driven directl
44、y, without the output transformer, more do not need any form of filter.Set of inverter power unit is a total of 18 by 6 sets, each phase of the power unit in series, and composition Y shape connect, direct drive motor. Every stage of the power unit circuit, structure identical interchangeable, also
45、can, as spare.Converter input part is a phase shifting transformer, the original edge adopt Y shape connect, vice edge adopts border triangle connection, eighteen three-phase winding, respectively, vice per power unit power supply. They were divided into , , on average, each part three most small wi
46、nding with six vice three-phase, uniform phase offset between 10 degrees.This converter features below:using multi-PWM mode control, output voltage waveform near sine wave.the multiple rectifier circuit of pulse power factor number up to 36, high, input harmonic small.modular design, compact structu
47、re, convenient maintenance, enhance product interchangeability.direct high-pressure output, without the output transformer.very low dv/dt output, without any form of filter.by using optical fiber communication technology, improve the product of anti-jamming and reliability.power unit automatically,
48、can realize by electricity road fault non-stop function.With modern power electronic technology and computer control technology, promote the rapid development of electric drive technological revolution. Ac adjustable speed replace dc speed control, computer digital control replace analog control has
49、 become the development trend. Ac motor speed is the saving energy, improve the production process, improve product quality, and to improve the operation environment of a main instrument. Frequency control with its high efficiency, high power factor, and superior speed and rev brake can wait for a lot of advantage and be domestic grandpa think most promising speed