CN102856884A - Heat accumulation based frequency converter overload method - Google Patents
Heat accumulation based frequency converter overload method Download PDFInfo
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- CN102856884A CN102856884A CN2012103435129A CN201210343512A CN102856884A CN 102856884 A CN102856884 A CN 102856884A CN 2012103435129 A CN2012103435129 A CN 2012103435129A CN 201210343512 A CN201210343512 A CN 201210343512A CN 102856884 A CN102856884 A CN 102856884A
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Abstract
The invention discloses a heat accumulation based frequency converter overload method including the steps: (1) computing data including heat dissipation potential, heat balance periods and overload capacity and conforming to actual hardware conditions according to hardware design; (2) performing integral computation for heat accumulation of all current in each latest heat balance period based on power consumption and temperature increase by a sliding window method; (3) making correction computation for an overload threshold according to the overload capacity obtained by actual testing; and (4) comparing a heat accumulation value in a heat balance period obtained by computing with a corrected overload threshold, and deeming as overload if the heat accumulation value exceeds the corrected overload threshold. Protective control of frequency converter overload is achieved by the steps. By means of computing heating and heat dissipation of hardware and current heat effect accumulation values within one heat balance period, the overload capacity of a specific frequency converter can be reflected accurately, and the hardware of the frequency converter is effectively protected from being damaged due to overload.
Description
Technical field
The present invention relates to the overload protection technology of frequency converter, particularly relate to a kind of frequency converter overload method based on heat accumulation.
Background technology
Along with developing rapidly of modern power electronics technology and Computer Control Technology, frequency converter has been widely used in the stepless speed regulation of alternating current motor.Ac motor speed control by variable frequency is current saves energy, improves the technological process of production, improve the quality of products, and a kind of Main Means that improves running environment.Frequency control is with its high-frequency, and High Power Factor, and excellent speed governing and open the plurality of advantages face such as braking ability and thought the most promising mode of speed regulation both at home and abroad are widely used in the industry-by-industries such as iron and steel, chemical industry, weaving, mechanical electric power, papermaking.
General frequency converter has certain overload capacity, because how many electric currents all can have certain fluctuation range in the use procedure, the situation that electric current surpasses rated current more or less all can appear, if short-term operation is under overload situations, its degree can not cause damage to frequency converter or load equipment immediately, if surpass its rated current but the system of leaving works long hours, though be the insulation or the mechanical strength of each parts all will reduce rapidly, wearing out of accelerating system, and mechanical performance, the reduction of electrical contact performance provides possibility can for again the fault of other type, brings very large destruction to equipment.So overload protection is an important defencive function of frequency converter.But owing to varying of load type, the load variations mode is varied, and the overload protection algorithm is difficult to effectively be solved.
At present, overload algorithm domestic and Japanese frequency converter all is that overload magnification is larger according to inverse-time curve of heat definition basically, and overload time is shorter.In the control flow, judge at first whether electric current satisfies overload condition, then carry out timing according to overload time and process, if before overload fault is quoted, current reduction, then overload time is reduced.This method is just transshipped Mathematical Modeling, only be described in electric current and the relation of the inverse time lag between operate time under the overload situations, do not consider the heat radiation cycle, that does not also consider to dispel the heat under different electric currents and the condition is different, can not correctly reflect the thermal effect of non-overload and critical overload current to the impact of inverse time-delay operation time, may cause hardware to burn out but overload fault is not quoted.
Summary of the invention
Technical problem to be solved by this invention is: provide a kind of frequency converter overload method based on heat accumulation, the defective that exists to overcome above-mentioned prior art.
The present invention solves its technical problem and adopts following technical scheme:
Frequency converter overload method based on heat accumulation provided by the invention, its step comprises:
(1) calculates the data that comprise heat-sinking capability, heat balance cycle and overload capacity that meet the hardware physical condition according to hardware designs;
(2) use the way of sliding window, by each up-to-date heat balance of integral and calculating in the cycle all electric currents based on the heat accumulation of power consumption and temperature rise;
The result of the overload capacity that (3) test obtains according to reality makes corrected Calculation to overload threshhold;
Heat accumulation value and corrected overload threshhold in the heat balance cycle that (4) will calculate compare, and surpass then to think overload;
Through above-mentioned steps, realize the protection control to the frequency converter overload.
The method of performing step of the present invention (1) can be: thermal losses value during according to power model characteristic and the specified and different overload of structure apparent size calculating; Be no more than under 40 ℃ of conditions of power model temperature rise in assurance, in conjunction with CAE emulation and calculated value, formulate overload capacity and heat balance cycle.
The method of performing step of the present invention (2) can be: the real-time sampling current effective value is also done data in the 1s and to be deposited array in after average value filtering is processed, and calculates its I
2The t value, and calculate the I of accumulation in the current heat balance cycle
2T value and overload threshhold compare judgement; When Cumulative Elapsed Time surpasses all after dates of a heat balance, gather each second and calculate new current value, then replace the current value of earliest time with new current value, and calculate its I
2T value, thereby the I of assurance accumulation
2The t value is the last look in current this heat balance cycle all the time, guarantees the real-time of overload protection.
The method of performing step of the present invention (3) can be: do the overload experiment by the load that adds different multiples to frequency converter, obtain the experimental data of a series of frequency converter actual overload capabilities, according to experimental result overload threshhold is done certain corrected Calculation, so that last program execution result really satisfies the actual hardware condition.
In the described step (4), in the situation that overload, the operator is according to user's setting, can select to be failure to actuate, to report to the police or reports disorderly closedown to block.
The present invention compared with prior art has following major advantage:
One. take into full account heating and the heat-sinking capability of particular hardware; be fit to the arbitrary load electric current; solved anti-time limit characteristic curve commonly used and only be described in electric current and the relation of the inverse time lag between operate time under the overload situations, thereby the thermal effect that can not correctly reflect non-overload and critical overload current causes effectively protecting the problem of hardware on the impact of inverse time-delay operation time.
They are two years old. by calculating to the calculating of hardware heating heat radiation and to the accumulated value of heat balance thermal effect of electric current in the cycle; the overload capacity that can accurately reflect concrete frequency converter; classical inverse time limit overload algorithm can't effectively be protected the problem of hardware when having solved the frequent overload of inverter load electric current and non-overload, effectively protects simultaneously frequency converter hardware not damage because of overload.
After design work is finished; the overload experiment is done in the load that we have added different multiples for each power section frequency converter; and frequent switch load size of current; because specially reserved certain surplus in the design, when the power model temperature rise reached 38 ℃ of left and right sides, frequency converter namely can be reported overload at every turn; this sufficient proof the overload algorithm be fit to the arbitrary load electric current; and meet the actual heating of hardware heat radiation situation, can accurately reflect the overload capacity of frequency converter, and real effectively protection hardware does not damage because of overload.
In a word, the present invention can accurately reflect the overload capacity of frequency converter, namely makes frequency converter have stronger overload capacity under the condition that hardware allows, and effectively protection frequency converter hardware does not damage because of overload simultaneously.
Description of drawings
Fig. 1 is the typical underloading overlond running cycle of the present invention.
Fig. 2 is the typical heavily loaded overlond running cycle of the present invention.
Fig. 3 is program flow diagram of the present invention.
Embodiment
The invention will be further described below in conjunction with specific embodiment.
The essential characteristic of overload is that temperature rise surpasses specified temperature rise, and the purpose of overload protection is that hardware is not burnt out because of overheated.
Theoretical foundation of the present invention is for to carry out I to output current
2T calculates, and this value has reflected the accumulation of frequency converter power consumption and temperature rise.
Its theoretical formula is as follows:
Wherein,
I (t) is the function of time of frequency converter output current effective value;
I
RatedIt is the output-current rating of frequency converter;
K
DIt is the electric current derating factor;
T is a heat balance cycle.
When actual coding, calculate for simplifying, above formula has been carried out the discretization processing, use n constant-current phase to be worth as an alternative.Concrete computing formula is simplified as follows:
Wherein,
I
1-I
nOutput current for frequency converter each time point in heat radiation cycle;
I
RatedOutput-current rating for frequency converter;
T
1-T
nBe the duration of each output current;
T is a heat balance cycle, and being calculated according to the hardware designs condition by the heat dissipation design personnel provides;
K
DBeing derating factor, also is to be calculated according to the hardware designs condition by the heat dissipation design personnel to provide.
The present embodiment is take the frequency converter EC550 series of Wisdri (Wuhan) Automation Co., Ltd. research and development as example, and its specified temperature rise is defined as 40 ℃, goes out power model temperature rise under the rated power by the CAE simulation calculation
Temperature rise when then overload time is t:
In the formula:
Thermal time constant for power model.
Heat radiator thermal resistance,
It is the radiator thermal capacitance.
By transient thermal impedance
,
,
,
The temperature rise of overload time when being t
It is the temperature rise under the rated power
Function calculation according to following formula overload power consumption and time relationship goes out overload capacity and heat balance cycle T.
K
DSetting numerical value be to calculate gained by hot simulation software and power consumption calculation software, then carried out certain correction with reference to final test data.This value is relevant with ambient temperature, height above sea level and pulse frequency.Use its value to be taken as 1 in the situation that do not need derate.
For guaranteeing the accuracy of overload protection, consider simultaneously the EMS memory occupation amount of dsp and the change curve of electric current, real-time sampling current effective value and the mean value got in its 1s deposit array in the program, calculate its I
2The t value, and calculate the I of accumulation in the current heat balance cycle
2T value and overload threshhold compare judgement.In whole program, adopt the mode of sliding window, when Cumulative Elapsed Time surpasses all after dates of a heat balance, gather each second and calculate new current value, then replace the current value of earliest time with new current value, and calculate its I
2T value, thereby the I of assurance accumulation
2The t value is the last look in current this heat balance cycle all the time, has guaranteed the real-time of overload protection.
Because the hardware designs of every money different capacity frequency converter is more or less all had any different; in order to reflect the most effectively the overload capacity of frequency converter; we do the overload experiment by the load of adding different multiples for each power section frequency converter; obtain the experimental data of a series of frequency converter actual overload capabilities; according to experimental result overload threshhold has been done certain corrected Calculation; guarantee that last program execution result can reflect the actual overload capabilities of frequency converter the most truly, and effectively protect hardware.
The EC550 Series Frequency Converter of described Wisdri (Wuhan) Automation Co., Ltd. independent research, it is powerful, and topology layout is reasonable.This frequency converter mainly is comprised of power amplifier board, radiator, reactor and control box, wherein: power amplifier board dispels the heat separately by the aluminum profile heat radiator of customization, radiator is placed on independently in the air channel, with 24V axial flow double fan to its heat radiation of directly drying, reactor is placed on the radiator front end simultaneously, can allow reactor keep lower temperature.Control board and power amplifier board layering are placed, control board is assemblied in the special control box, completely cut off external heat source, in the control box independently exhausting system is arranged simultaneously, stopped the possibility of heat accumulation in the control box, effectively reduce the control board temperature, prolonged device lifetime, improved the stability of a system and reliability.
By above-described embodiment as can be known; the present invention takes into full account heating and the heat-sinking capability of particular hardware; be fit to the arbitrary load electric current; solve anti-time limit characteristic curve commonly used and only be described in electric current and the relation of the inverse time lag between operate time under the overload situations; can not correctly reflect the thermal effect of non-overload and critical overload current to the impact of inverse time-delay operation time, thereby cause effectively to protect the problem of hardware.
Claims (5)
1. frequency converter overload method based on heat accumulation is characterized in that adopting the method that may further comprise the steps:
(1) calculates the data that comprise heat-sinking capability, heat balance cycle and overload capacity that meet the hardware physical condition according to hardware designs;
(2) use the way of sliding window, by each up-to-date heat balance of integral and calculating in the cycle all electric currents based on the heat accumulation of power consumption and temperature rise;
The result of the overload capacity that (3) test obtains according to reality makes corrected Calculation to overload threshhold;
Heat accumulation value and corrected overload threshhold in the heat balance cycle that (4) will calculate compare, and surpass then to think overload;
Through above-mentioned steps, realize the protection control to the frequency converter overload.
2. the frequency converter overload method based on heat accumulation according to claim 1 is characterized in that the method for performing step (1) is: thermal losses value during according to power model characteristic and the specified and different overload of structure apparent size calculating; Be no more than under 40 ℃ of conditions of power model temperature rise in assurance, in conjunction with CAE emulation and calculated value, formulate overload capacity and heat balance cycle.
3. the frequency converter overload method based on heat accumulation according to claim 1 is characterized in that the method for performing step (2) is: the real-time sampling current effective value is also done data in the 1s and to be deposited array in after average value filtering is processed, and calculates its I
2The t value, and calculate the I of accumulation in the current heat balance cycle
2T value and overload threshhold compare judgement; When Cumulative Elapsed Time surpasses all after dates of a heat balance, gather each second and calculate new current value, then replace the current value of earliest time with new current value, and calculate its I
2T value, thereby the I of assurance accumulation
2The t value is the last look in current this heat balance cycle all the time, guarantees the real-time of overload protection.
4. the frequency converter overload method based on heat accumulation according to claim 1, the method that it is characterized in that performing step (3) is: do the overload experiment by the load that adds different multiples to frequency converter, obtain the experimental data of a series of frequency converter actual overload capabilities, according to experimental result overload threshhold is done certain corrected Calculation, so that last program execution result really satisfies the actual hardware condition.
5. the frequency converter overload method based on heat accumulation according to claim 1 is characterized in that in the described step (4), in the situation that overload, the operator selects to be failure to actuate according to user's setting, reports to the police or the blockade of newspaper disorderly closedown.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105790677A (en) * | 2016-04-15 | 2016-07-20 | 郑州宇通客车股份有限公司 | Motor controller overload protection method and system |
| CN110867820A (en) * | 2019-11-15 | 2020-03-06 | 陕西航空电气有限责任公司 | Alternating current intelligent contactor system adaptive to multi-specification load current |
| CN114083989A (en) * | 2021-12-24 | 2022-02-25 | 天津英捷利汽车技术有限责任公司 | Current inverse time limit protection method for pure electric vehicle |
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| CN101123348A (en) * | 2007-09-14 | 2008-02-13 | 西安理工大学 | AC motor unbalanced protection method based on unbalanced accumulation |
| CN101132129A (en) * | 2007-08-10 | 2008-02-27 | 西安理工大学 | AC motor over-load inverse time-lag protection method based on heat accumulation |
| US20100007998A1 (en) * | 2008-07-14 | 2010-01-14 | International Business Machines Corporation | Apparatus, system, and method for detecting a power system component failure |
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2012
- 2012-09-17 CN CN201210343512.9A patent/CN102856884B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101132129A (en) * | 2007-08-10 | 2008-02-27 | 西安理工大学 | AC motor over-load inverse time-lag protection method based on heat accumulation |
| CN101123348A (en) * | 2007-09-14 | 2008-02-13 | 西安理工大学 | AC motor unbalanced protection method based on unbalanced accumulation |
| US20100007998A1 (en) * | 2008-07-14 | 2010-01-14 | International Business Machines Corporation | Apparatus, system, and method for detecting a power system component failure |
Non-Patent Citations (3)
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105790677A (en) * | 2016-04-15 | 2016-07-20 | 郑州宇通客车股份有限公司 | Motor controller overload protection method and system |
| CN110867820A (en) * | 2019-11-15 | 2020-03-06 | 陕西航空电气有限责任公司 | Alternating current intelligent contactor system adaptive to multi-specification load current |
| CN114083989A (en) * | 2021-12-24 | 2022-02-25 | 天津英捷利汽车技术有限责任公司 | Current inverse time limit protection method for pure electric vehicle |
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