CN104852599A - Optimized PWM control method of cascaded high-voltage frequency converter - Google Patents
Optimized PWM control method of cascaded high-voltage frequency converter Download PDFInfo
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- CN104852599A CN104852599A CN201510274756.XA CN201510274756A CN104852599A CN 104852599 A CN104852599 A CN 104852599A CN 201510274756 A CN201510274756 A CN 201510274756A CN 104852599 A CN104852599 A CN 104852599A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
Abstract
The invention discloses an optimized PWM control method of a cascaded high-voltage frequency converter. The method is advantaged in that control is simple, and the method can reduce loss, improve system efficiency and prolong device life through circulation dormancy. The cascaded high-voltage frequency converter uses V/f control. The method comprises: firstly, according to system rated frequency F, each phase of cascade number n and output frequency f, calculating the least number A of units and carrier phase-shifting angle [theta] of each phase under the working condition , the units needing to operate, at the time, the A units operating, the upper (or the lower) bridge arm of the (n-A) units being connected at the same time and output being in short circuit, and the (n-A) units being in a relative dormant state, and A operating and sleeping according to a certain time sequence in the n, so as to ensure use degree of all power units is consistent; and then according to up-frequency (or down-frequency), rounding upward through n*f/F, to determine whether one more (or less) power unit is needed to satisfy output capacity at the time, if an adjusting condition is satisfied, calculating the phase-shifting angle again according to the adjusted unit number A, and adjusting modulation ratio m.
Description
Technical field
The present invention relates to a kind of optimization PWM control method of cascaded high-voltage frequency converter, belong to cascaded high-voltage frequency converter PWM control technology field.
Background technology
Along with high voltage converter is in the power-saving technology extensive use of the occasions that count for much such as electric power, metallurgy, oil, chemical industry,, unit little with its harmonic wave by the tandem type high voltage converter of several independently power unit cascades can fast and easy exchange, can be mass, the advantage such as easy to maintenance, receive domestic and international every profession and trade more and more to favor, show wide promotion prospect.
Current general cascade high voltage transformer adopts V/F opened loop control usually, triangular carrier phase-shift PWM modulator approach, namely according to output frequency Serial regulation modulation ratio m, unit at different levels to compare with triangular carrier at different levels according to unified modulating wave and exports PWM ripple, export after superposition again, all power cells are switch under same modulation ratio all, but the power device used because cascade connection type is topological is a lot, and in order to safety, all protective circuit is configured with to all power devices, and a frequency converter inherently electromagnetic interference source, therefore there will be the situation of protective circuit misoperation chaser in actual use unavoidably.On the other hand because power device can produce extra loss in switching process, and we are desirably under the prerequisite not affecting output harmonic wave, switching frequency is the smaller the better, and modulation ratio is larger, the harmonic wave of output voltage is less, and at present in the occasion using high-voltage high-power frequency transformator, its actual running frequency is general all only between 20-38Hz, its modulation ratio m is relatively low like this, and therefore switching frequency can not be selected too low.
For these reasons; therefore the optimization PWM control method of establishing a kind of cascaded high-voltage frequency converter is necessary; under the prerequisite not affecting frequency converter performance; the equivalent switching frequency of reduction system; thus reduction system loss; the quantity reducing power device work reduces the number of times of protection misoperation, improves the useful life of Whole Equipment simultaneously.
Summary of the invention
The invention provides a kind of optimization PWM control method of cascaded high-voltage frequency converter, can system loss be reduced, improve Whole Equipment useful life simultaneously.
In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:
An optimization PWM control method for cascaded high-voltage frequency converter, comprises the following steps,
Step one, according to the frequency f of the rated frequency F of system, each phase concatenation unit number n and current output voltage, to be rounded up number=A by formula n*f/F;
Step 2, according to the A of step one, determine under this frequency f, respectively the unit number working in PWM on off state is needed to be A mutually, all the other n-A unit export short circuit and are in relative dormancy state, simultaneously minimum in order to ensure harmonic wave of output voltage, phase-shifting carrier wave angle when recalculating A cell operation between each unit is 180 °/A, and each phase A unit is according to certain sequential periodic duty and dormancy;
Step 3, according to actual operating mode, to be rounded up number by formula n*f/F, judge that whether the unit number now put into operation is suitable, number=the A+1 if n*f/F rounds up, illustrate and need to drop into a cell operation again in PWM on off state to ensure enough fan-out capabilities, adjust modulation ratio is m=m*A/ (A+1) simultaneously, number=the A-1 if n*f/F rounds up, illustrate that now frequency conversion is in frequency reducing load shedding, can reduce by a power cell under present operating mode makes its dormancy still can ensure enough fan-out capabilities, adjust modulation ratio is m=m*A/ (A-1) simultaneously, to prevent and the now unmatched ovennodulation of operating mode or undermodulation,
Step 4, makes A equal step 3 and to be rounded up the value A+1 that calculates of number or A-1 by formula n*f/F, return step 2 and cover A value, and carry out cycle criterion.
Described in step 3, the method for adjustment modulation ratio m is in time, the number=A+1 if n*f/F rounds up, modulation ratio m=m*A/ (A+1), the number=A-1 if n*f/F rounds up, modulation ratio m=m*A/ (A-1).
N-A described in step 2 unit exports short circuit and is in relative dormancy state, specifically comprise upper (or under) conducting simultaneously short circuit by unit two inverter bridge legs, simultaneously in order to ensure the useful life of power device, upper and lower bridge arm takes equal time circulation conducting (shutoff) mode.
Described in step 2, each phase A unit is according to certain sequential periodic duty and dormancy, and its cycle period need be adjusted according to the power grade of high voltage converter reality and applying working condition, to guarantee that in equipment, the whole service life of power device is the longest.
The invention has the beneficial effects as follows: under the prerequisite not affecting frequency converter performance; reduce the equivalent switching frequency of system; thus reduction system loss; the quantity of power device work is decreased by circulation dormant technology; thus reduce the number of times of protection misoperation, improve the useful life of Whole Equipment simultaneously.
Accompanying drawing explanation
Fig. 1 is cascaded high-voltage frequency converter circuit topological structure figure.
Fig. 2 is power cell topological diagram.
Fig. 3 is that conventional P WM controls lower 5 grades of cascade 30Hz output voltage waveforms.
Fig. 4 is the optimization PWM control flow chart of cascaded high-voltage frequency converter of the present invention.
Fig. 5 is the change curve of control method of the present invention 5 grades of cascade modulation ratios.
Fig. 6 is each power cell circulation dormancy schematic diagram under the lower 5 grades of cascade 30Hz operating modes of control method of the present invention.
Fig. 7 is the lower 5 grades of cascade 30Hz output voltage waveforms of control method of the present invention.
Embodiment
Below in conjunction with Figure of description, simultaneously for convenience of explanation with 5 grades of cascades, adopt V/F Linear Control, be example during output voltage 30Hz, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.
As shown in Figure 1, be cascaded high-voltage frequency converter circuit topological structure figure.Primarily of inlet wire Multiple coil phase shifting transformer, be respectively in series power cell form.Power cell topological diagram as shown in Figure 2.Fig. 3 is that conventional P WM controls lower 5 grades of cascade 30Hz output voltage waveforms, and all power cells are all operated in PWM on off state.
As shown in Figure 4, be the optimization PWM control flow chart of cascaded high-voltage frequency converter of the present invention.Specific implementation comprises the following steps:
Step one, according to the frequency f of the rated frequency F of default, each phase concatenation unit number n and current output voltage, to be rounded up number=A, A≤n by formula n*f/F;
Step 2, according to the A of step one, determine under ongoing frequency f, respectively the unit number working in PWM on off state is needed to be A mutually, all the other n-A unit export short circuit (conducting), are in relative dormancy state, simultaneously minimum in order to ensure harmonic wave of output voltage, phase-shifting carrier wave angle θ when recalculating A cell operation between each unit is 180 °/A, and each phase A unit is according to certain sequential periodic duty and dormancy;
Step 3, according to actual operating mode, to be rounded up number by formula n*f/F, judge that whether the unit number now put into operation is suitable, number=the A+1 if n*f/F rounds up, illustrate that needing to drop into a power cell again works in PWM on off state to ensure enough fan-out capabilities, adjust modulation ratio is m=m*A/ (A+1) simultaneously, number=the A-1 if n*f/F rounds up, illustrate that now frequency conversion is in frequency reducing load shedding, can reduce by a power cell under present operating mode makes its dormancy still can ensure enough fan-out capabilities, adjust modulation ratio is m=m*A/ (A-1) simultaneously, to prevent and the now unmatched ovennodulation of operating mode or undermodulation.0 < modulation ratio m < 1.
When n gets 5, optimize PWM control method modulated than m2 value change curve as shown in Figure 5, be compared to the modulation ratio m1 curve under traditional control method, m2>m1 under same output frequency, then when not affecting output performance, equivalent switching frequency can be reduced.
Step 4, makes A equal step 3 and to be rounded up the value A+1 that calculates of number or A-1 by formula n*f/F, return step 2 and cover A value, and carry out cycle criterion.
As shown in Figure 6, be each power cell circulation dormancy time diagram under the lower 5 grades of cascade 30Hz operating modes of control method of the present invention.In figure, PWM represents at this interval power cell work and PWM on off state, and PP represents that in power cell inverter side as shown in Figure 2, brachium pontis two devices are simultaneously open-minded, and NN represents that lower brachium pontis two devices of Fig. 2 power cell inverter side are simultaneously open-minded.By carrying out circulation dormancy according to the sequential of regulation, the utilization rate ensureing all power cells is all consistent, thus can the whole service life of extension device.
As shown in Figure 7, be the lower 5 grades of cascade 30Hz output voltage waveforms of control method of the present invention.Single switching cycle T=0.05s, each power cell is ined succession 3 T cyclings and PWM on off state, then 2 T cycles of ining succession are in relative dormancy state, unit circulates in this manner, and being in relative dormancy state power unit like this has PP state to switch to the cycle of NN state also to equal T.
In sum; take the optimization PWM control method of cascaded high-voltage frequency converter of the present invention; under the prerequisite not affecting frequency converter performance; reduce the equivalent switching frequency of system; thus reduction system loss; decrease the quantity of power device work thus the number of times of minimizing protection misoperation by circulation dormant technology, improve the useful life of Whole Equipment simultaneously.
More than show and describe general principle of the present invention, principal character and advantage.The technical staff of the industry should understand; the present invention is not restricted to the described embodiments; what describe in above-described embodiment and specification just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.Application claims protection range is defined by appending claims and equivalent thereof.
Claims (5)
1. an optimization PWM control method for cascaded high-voltage frequency converter, is characterized in that: comprise the following steps,
Step one, according to the frequency f of the rated frequency F of system, each phase concatenation unit number n and current output voltage, to be rounded up number=A by formula n*f/F;
Step 2, according to A value, determine under this frequency f, respectively the unit number working in PWM on off state is needed to be A mutually, all the other n-A unit export short circuit and are in relative dormancy state, phase-shifting carrier wave angle when recalculating A cell operation between each unit is 180 °/A, and each phase A unit is according to certain sequential periodic duty and dormancy;
Step 3, according to actual operating mode, to be rounded up number by formula n*f/F, judge that whether the unit number now put into operation is suitable, number=the A+1 if n*f/F rounds up, then raising frequency, then drop into a power cell and work in PWM on off state, the number=A-1 if n*f/F rounds up, then frequency reducing, under present operating mode, reduce by a power cell make its dormancy, simultaneously when adjusting module work number, correspondingly adjust modulation ratio m;
Step 4, makes A equal step 3 and to be rounded up the value A+1 that calculates of number or A-1 by formula n*f/F, return step 2 and cover A value, and carry out cycle criterion.
2. the optimization PWM control method of a kind of cascaded high-voltage frequency converter according to claim 1, is characterized in that: the method adjusting modulation ratio m in step 3 is, the number=A+1 if n*f/F rounds up, modulation ratio m=m*A/ (A+1).
3. the optimization PWM control method of a kind of cascaded high-voltage frequency converter according to claim 1 and 2, is characterized in that: the method adjusting modulation ratio m in step 3 is, the number=A-1 if n*f/F rounds up, modulation ratio m=m*A/ (A-1).
4. the optimization PWM control method of a kind of cascaded high-voltage frequency converter according to claim 1, it is characterized in that: n-A described in step 2 unit exports short circuit and be in relative dormancy state, specifically comprise by conducting short circuit in power cell two inverter side or while lower brachium pontis, upper and lower brachium pontis takes the mode of equal time circulation conducting or shutoff.
5. the optimization PWM control method of a kind of cascaded high-voltage frequency converter according to claim 1, it is characterized in that: described in step 2, each phase A unit is according to certain sequential periodic duty and dormancy, and its cycle period is adjusted according to the power grade of high voltage converter reality and applying working condition.
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| CN101604956A (en) * | 2009-07-06 | 2009-12-16 | 山东雷奇电器有限公司 | A kind of method and device thereof that produces three-phase sine-wave |
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| CN103986356A (en) * | 2014-05-13 | 2014-08-13 | 湖南大学 | Control system and method of cascaded multi-level inverter |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101604956A (en) * | 2009-07-06 | 2009-12-16 | 山东雷奇电器有限公司 | A kind of method and device thereof that produces three-phase sine-wave |
| CN102290828A (en) * | 2011-08-12 | 2011-12-21 | 广州智光电气股份有限公司 | Cascaded photovoltaic grid-connected inverter and control method |
| CN103986356A (en) * | 2014-05-13 | 2014-08-13 | 湖南大学 | Control system and method of cascaded multi-level inverter |
Non-Patent Citations (1)
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| 李兴鹤，等: "基于Matlab 的级联型高压变频器VF 控制仿真平台研究", 《大功率变流技术》 * |
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Effective date of registration: 20170818 Address after: Nanjing City, Jiangsu province 210032 Spark Road, Pukou hi tech Development Zone No. 8 Patentee after: NANJING SAC NEW ENERGY TECHNOLOGY CO., LTD. Address before: 210009 Gulou District, Jiangsu, Nanjing new model road, No. 38 Patentee before: Nanjing Automation Co., Ltd., China Electronics Corp. |