CN108270380B - Speed control method for frequency converter without speed encoder - Google Patents
Speed control method for frequency converter without speed encoder Download PDFInfo
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- CN108270380B CN108270380B CN201711482962.5A CN201711482962A CN108270380B CN 108270380 B CN108270380 B CN 108270380B CN 201711482962 A CN201711482962 A CN 201711482962A CN 108270380 B CN108270380 B CN 108270380B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
- H02P23/14—Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2205/00—Indexing scheme relating to controlling arrangements characterised by the control loops
- H02P2205/01—Current loop, i.e. comparison of the motor current with a current reference
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- Control Of Electric Motors In General (AREA)
Abstract
The invention discloses a speed control method when a frequency converter has no speed encoder, which relates to the speed control of the frequency converter and comprises the following steps: resetting the motor static torque P278 parameter; slowly increasing the parameter value of the static torque P278 until the field motor stops under the condition of slight rotation; slowly reducing the parameter value of the static torque P278 until the motor is not moved; readjusting the value of the parameter P279 of the dynamic torque of the motor; the motor is powered on to run in no-load; during the operation of the motor, the value of the parameter P279 of the dynamic torque is slowly reduced, the given current waveform and the actual current waveform of the frequency converter are checked, and the adjustment of the value of the parameter P279 of the dynamic torque is stopped when the given current waveform and the actual current waveform of the frequency converter are overlapped. After the method is implemented, the time for recovering production after the motor encoder is damaged is greatly shortened, and the workload of rush repair of field equipment is reduced.
Description
Technical Field
The invention relates to the technical field of speed control of frequency converters, in particular to a speed control method of a frequency converter without a speed encoder.
Background
The requirement on the operation precision of the main motor on site is very high, so that the main motor is required to have quick response capability and instant large torque output, and cannot have large current over-temperature, and therefore, a speed feedback encoder is added at the motor end at the beginning of the design, and the speed feedback encoder is used for feeding the actual speed of the motor back to the frequency converter when the motor operates and adjusting the given speed in real time after comparing the actual speed with the given speed of the frequency converter, so that the speed closed-loop control is realized, and the purpose of accurate control is achieved. However, in actual work, because the field working condition is poor, and the encoder for speed feedback is a relatively precise device, the damage rate of the encoder is still relatively high in the actual production process. The time of production stop is longer when the encoder is directly replaced after being damaged, if the control mode of the frequency converter is directly changed into open loop or current closed loop, production can be temporarily recovered, and the problems of frequent triggering of overcurrent and overtemperature alarm caused by speed mismatching during production cannot be solved.
Disclosure of Invention
The invention aims at the technical problems, overcomes the defects of the prior art, and provides a speed control method for a frequency converter without a speed encoder.
In order to solve the above technical problem, the present invention provides a speed control method when a frequency converter has no speed encoder, wherein the frequency converter is a siemens 6SE70 frequency converter, and the method comprises the following steps:
s1, firstly, resetting a motor static torque P278 parameter, and setting the value of the static torque P278 parameter within the range of 5-10%;
s2, slowly increasing the parameter value of the static torque P278 until the static torque stops when the field motor rotates slightly;
s3, slowly reducing the parameter value of the static torque P278 until the motor is not moved, observing the static current, and keeping the value within the range of 10-40%;
s4, readjusting the parameter value of the dynamic torque P279 of the motor, and setting the parameter value of the dynamic torque P279 within the range of 10-30%;
s5, supplying power to the motor to enable the motor to run in an idle load mode;
and S6, slowly reducing the value of the parameter P279 of the dynamic torque during the running process of the motor, simultaneously checking the given current waveform and the actual current waveform of the frequency converter, and stopping adjusting the value of the parameter P279 of the dynamic torque when the given current waveform and the actual current waveform of the frequency converter are overlapped.
The technical scheme of the invention is further defined as follows:
further, the magnitude of the static torque P278 parameter is increased by 40% in step S2.
Further, after step S6, a P471 parameter device for inverter torque pre-control is added.
Furthermore, the numerical value of P471 parameter equipment for torque pre-control of the frequency converter is increased to 30-80% according to different field motor loads and different field motor loads.
The invention has the beneficial effects that: the invention is mainly used for rapidly recovering the accurate control of the frequency converter on the speed of the on-site motor under the condition of not replacing the encoder after the on-site motor speed encoder is damaged. Meanwhile, P471 parameter equipment for torque pre-control of the frequency converter is added, so that the response speed of the motor is improved, and overcurrent is avoided. Therefore, the invention has timely response during operation, torque meeting the requirement, actual speed matching, current control of the frequency converter within a reasonable range and no overcurrent and overtemperature alarm; after the motor encoder is used, the time for recovering production after the motor encoder is damaged is greatly shortened, and the workload of rush repair of field equipment is reduced.
Drawings
FIG. 1 is a schematic diagram of the present embodiment;
fig. 2 is a schematic diagram of the encoder speed feedback waveform of the present embodiment.
Detailed Description
In the speed control method for the frequency converter without the speed encoder provided by the embodiment, the frequency converter is a siemens 6SE70 frequency converter, and the method comprises the following steps:
s1, firstly, resetting a motor static torque P278 parameter, and setting the value of the static torque P278 parameter within the range of 5-10%;
s2, slowly increasing the value of the static torque P278 parameter, wherein the value of the static torque P278 parameter is increased by 10-40% until the static torque P278 parameter stops when the field motor slightly rotates;
s3, slowly reducing the parameter value of the static torque P278 until the motor is not moved, observing the static current at the moment, and keeping the value within the range of 40%;
s4, readjusting the parameter value of the dynamic torque P279 of the motor, and setting the parameter value of the dynamic torque P279 within the range of 10-30%;
s5, supplying power to the motor to enable the motor to run in an idle load mode;
s6, in the running process of the motor, slowly reducing the parameter value of the dynamic torque P279, simultaneously checking the given current waveform and the actual current waveform of the frequency converter, and stopping adjusting the parameter value of the dynamic torque P279 when the given current waveform and the actual current waveform of the frequency converter are overlapped;
and S7, adding P471 parameter equipment for torque pre-control of the frequency converter, and increasing the numerical value of the P471 parameter equipment for torque pre-control of the frequency converter to 30-80% according to different field motor loads.
The working principle is as follows:
in order to reduce the failure frequency of the motor, the spare part cost of the encoder and the labor cost, other control modes are used for replacing the closed-loop control of the speed of the encoder, and the encoder is finally cancelled, so that the failure point with the highest failure frequency on site is reduced.
The control is carried out in an open-loop mode by using the frequency converter, and the actual experiment shows that the instantaneous overcurrent alarm shutdown can be caused by urgent acceleration and urgent deceleration due to high dynamic requirements of field equipment under the open-loop control. The frequency converter current closed-loop control is adopted, the current control is good during rapid acceleration and rapid deceleration, but the whole current is overlarge during the operation of the motor and is close to an overcurrent threshold, if the field load is slightly changed, overcurrent and overtemperature alarm caused by long-time heavy current can occur, and the operation is extremely unstable. However, current closed-loop control is the only possible method for replacing encoder speed closed-loop control by the frequency converter at present. Therefore, the main solution in the test process is to reduce the current output under static and dynamic conditions when the equipment is loaded, and to meet the load requirement when the field motor operates.
The static current and the dynamic current are reduced mainly by reducing the static and dynamic output torques of the frequency converter so as to achieve the purpose of reducing the current.
As shown in fig. 2, after a series of parameter settings and optimizations, a frequency converter control mode P100 is changed to current closed-loop control, and an actual output speed waveform, a speed given waveform and an encoder speed feedback waveform not participating in control for a test of the frequency converter under the current closed-loop control are detected, wherein: 2 is speed set, 3 is frequency converter actual speed output, and 4 is field encoder speed feedback, and the three speeds are kept consistent.
Working example:
and in 2017, the speed of a pinch roll at a coiling inlet of a medium-thickness plate coil factory in 10 months is abnormal, and the speed feedback whole line of an encoder and the encoder are checked and found to have faults. The method is implemented as follows:
s1, firstly, resetting a motor static torque P278 parameter, and setting the value of the static torque P278 parameter within the range of 5-10%;
s2, slowly increasing the value of the static torque P278 parameter, wherein the value of the static torque P278 parameter is increased by 10-40, and the static torque P278 parameter is stopped until the field motor slightly rotates;
s3, slowly reducing the parameter value of the static torque P278 until the motor is not moved; at this time, P278=19, the static current was observed to be kept around 120A;
s4, readjusting the parameter value of the dynamic torque P279 of the motor, and setting the parameter value of the dynamic torque P279 within the range of 10-30%;
s5, supplying power to the motor to enable the motor to run in an idle load mode;
s6, in the running process of the motor, slowly reducing the parameter value of the dynamic torque P279, simultaneously checking the given current waveform and the actual current waveform of the frequency converter, and stopping adjusting the parameter value of the dynamic torque P279 when the given current waveform and the actual current waveform of the frequency converter are overlapped; at this time, P279 is reduced from original 36 to 27, and the current is kept within 300A when the load operates;
and S7, increasing the P471 parameter device of the frequency converter torque pre-control, and gradually increasing the numerical value of the P471 parameter device of the frequency converter torque pre-control until P471=47%, wherein the current and speed waveforms are the most gentle when the motor is started.
Finally, after a series of parameter setting and optimization, the coiling pinch roll motor normally and stably runs under the condition that an encoder is not used, the pinch roll encoder at the outlet of the coiler furnace in 11 months in 2017 is damaged, and the stable control of the speed precision under the condition of no encoder speed feedback is realized by the same method.
The invention has the following application prospect and economic benefit:
the method is characterized in that the fault time is saved for 24 hours each year, the steel yield per hour is 200 tons, and the one-ton benefit is calculated by 500 yuan: 24 x 200 x 500=240 ten thousand yuan; saving 10 encoder spare parts per year, on average 1 calculated as 3 ten thousand dollars: 10 x 3=30 ten thousand yuan. Thus, the implementation of the invention can achieve the total annual benefit: 240+30=270 ten thousand yuan.
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (4)
1. A speed control method when a frequency converter has no speed encoder is provided, the frequency converter is a Siemens 6SE70 frequency converter, and the method is characterized by comprising the following steps:
s1, firstly, resetting a motor static torque P278 parameter, and setting the value of the static torque P278 parameter within the range of 5-10%;
s2, slowly increasing the parameter value of the static torque P278 until the static torque stops when the field motor rotates slightly;
s3, slowly reducing the parameter value of the static torque P278 until the motor is not moved, observing the static current, and keeping the value within the range of 10-40%;
s4, readjusting the parameter value of the dynamic torque P279 of the motor, and setting the parameter value of the dynamic torque P279 within the range of 10-30%;
s5, supplying power to the motor to enable the motor to run in an idle load mode;
and S6, slowly reducing the value of the parameter P279 of the dynamic torque during the running process of the motor, simultaneously checking the given current waveform and the actual current waveform of the frequency converter, and stopping adjusting the value of the parameter P279 of the dynamic torque when the given current waveform and the actual current waveform of the frequency converter are overlapped.
2. The method for controlling the speed of a frequency converter without a speed encoder as claimed in claim 1, wherein: the magnitude of the static torque P278 parameter in step S2 is increased by 40%.
3. The method for controlling the speed of a frequency converter without a speed encoder as claimed in claim 1, wherein: after the step S6, a P471 parameter device for pre-control of the inverter torque is added.
4. The method for controlling the speed of a frequency converter without a speed encoder as claimed in claim 3, wherein: and increasing the numerical value of P471 parameter equipment for torque pre-control of the frequency converter to 30-80% according to different field motor loads.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201711482962.5A CN108270380B (en) | 2017-12-29 | 2017-12-29 | Speed control method for frequency converter without speed encoder |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201711482962.5A CN108270380B (en) | 2017-12-29 | 2017-12-29 | Speed control method for frequency converter without speed encoder |
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| CN108270380A CN108270380A (en) | 2018-07-10 |
| CN108270380B true CN108270380B (en) | 2020-10-27 |
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| IL124932A0 (en) * | 1998-06-16 | 1999-01-26 | Mea Motor Inspection Ltd | Method and apparatus for testing rotating machines |
| CN104065318B (en) * | 2014-06-26 | 2016-08-31 | 中冶南方（武汉）自动化有限公司 | A kind of converter closed-loop vector redundancy control method during high-speed cruising |
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