CN103580575A - Dynamic PWM algorithm SDPWM based on speed - Google Patents
Dynamic PWM algorithm SDPWM based on speed Download PDFInfo
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- CN103580575A CN103580575A CN201310458758.5A CN201310458758A CN103580575A CN 103580575 A CN103580575 A CN 103580575A CN 201310458758 A CN201310458758 A CN 201310458758A CN 103580575 A CN103580575 A CN 103580575A
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Abstract
The invention discloses a modulation algorithm for output of a frequency converter. The modulation algorithm for output of the frequency converter is named as SDPWM (Speed Discrete Pulse Width Modulation). According to the modulation algorithm for the output of the frequency converter, overshoot factors related to the speed are introduced, the modulation mode that the output can be dynamically adjusted by the frequency converter according to different speeds is adopted, peak current of a motor stator winding is prevented from generating through control over the range of the overshoot factors, and a motor is effectively protected. The modulation algorithm for the output of the frequency converter has the advantages that good control performance can be achieved by the frequency converter within the range of the design speed, third harmonic is eliminated, EMC performance is improved, the frequency of opening and closing an IGBT is reduced to the maximum extent, and the temperature rise of the IGBT is effectively controlled so that the service life of the frequency converter can be prolonged, the size of a cooling fin can be reduced, and efficiency of the frequency converter can be improved. Therefore, the modulation algorithm for the output of the frequency converter has good practicability.
Description
Technical field
The present invention relates to the modulation way of output of frequency converter, frequency converter generally uses the electronic power switch devices such as IGBT to control as output, and its modulation output intent is directly connected to the control performance of frequency converter, the heating of electronic device, life-span, EMC performance, also can have influence on the insulation property of motor simultaneously.The modulation output intent of frequency converter can be divided into pulse amplitude modulation (Pulse Amplitude Modulation according to its cardinal principle, be called for short PAM) and two kinds of modulation systems of pulse width modulation (Pulse Width Modulation is called for short PWM).The algorithm of mentioning in the present invention belongs to a kind of of PWM, and called after SDPWM (speed discrete pulse width modulated, Speed Discrete Pulse Width Modulation) below is all used it to be called for short SDPWM.
Background technology
Frequency converter is power application electronic technology and microelectric technique, the Electric Drive equipment of controlling alternating current motor by changing the frequency of machine operation power supply and the mode of amplitude.In order to make the waveform of frequency converter output AC voltage be approximately sinusoidal wave, make the output torque of motor steady, thereby obtain outstanding service behaviour, inverter in modern universal frequency converter is all to consist of full-control type power electronic switching device, adopt PWM mode to control, application the earliest and what as PWM, control basis is sinusoidal pulse width modulation (Sinusoidal Pulse Width Modulation is called for short SPWM).Along with the raising to Frequency Converter Control performance requirement, and the requirement that harmonic wave is suppressed, derived again space vector pulse width modulation (Space Vector Pulse Width Modulation is called for short SVPWM).The cardinal principle of SVPWM is that while take the power supply of three-phase symmetrical sine voltage, three-phase symmetrical motor stator sub-ideal magnetic linkage track is normative reference, with the different switching modes of three-phase inverter, do suitable switching, thereby form PWM ripple, with formed actual flux linkage vector, follow the trail of its accurate magnetic linkage track.Traditional SPWM method, from the angle of power supply, generates the sine-wave power of a Frequency Adjustable pressure regulation, and SVPWM method does inversion system and asynchronous machine as a wholely to consider, model is fairly simple, is also convenient to the real-time control of microprocessor.
Common three phase full bridge is three half-bridges that consist of six switching devices.These six switching devices combine (the upper and lower brachium pontis signal of same phase is contrary) have the on off state of 8 kinds of safety: wherein 000,111 (meaning the on off states of three upper brachium pontis here) these two kinds of on off states can not produce effective electric current in motor drives, and are therefore called zero vector.Other six kinds of on off states are respectively six effective vectors, and they are divided into sector of 60 degree by the voltage space of 360 degree, and totally six sectors, utilize these six basic effectively two zero vectors of vector, can synthesize any vector in 360 degree.
In the time will synthesizing a certain vector, first by this resolution of vectors to from its nearest two basic effectively vector, then with these two basic effectively vectors, go to represent, and each basic effectively effect size of vector just utilizes action time length to go to represent.With voltage vector, according to different time scales, remove synthetic needed voltage vector, thereby guarantee that the voltage waveform generating is similar to sine wave.
When driving variable-frequency motor, direction vector is continually varying, so we need constantly compute vectors action time.For the convenience that computer is processed, when synthetic, be generally regularly to go to calculate (as every 0.1ms calculates once).As long as it is just passable that we calculate in 0.1ms time of two basic effectively vector effects like this.Because the sum totals of two times that calculate may not be 0.1ms (but being less than or equal to 0.1ms), and the remaining time is just inserted suitable zero vector by situation.Waveform after processing is like this referred to as the PWM based on space vector of voltage, is called for short SVPWM, and Fig. 1 is the waveform schematic diagram of a wherein phase.
The advantage of SVPWM has:
1. the doubly harmonic component for several times of having eliminated 3 times and 3 times, has improved EMC performance.
2. the voltage that inverter output line voltage first-harmonic maximum is DC side is higher by 15% than general SPWM inverter output voltage.
Yet the on-off times of SVPWM is comparatively frequent, larger on the life-span impact of switching device, SDPWM algorithm of the present invention, guaranteeing, under the prerequisite of control performance, to have reduced on-off times, has improved the life-span of switching device greatly, can dwindle frequency converter volume simultaneously.
Summary of the invention
The object of the invention is to propose a kind of new dynamic inverter modulation output intent, improve the overall performance of frequency converter.In the actual use of frequency converter, have many changing factors, so this algorithm provides the variable that can adjust according to actual conditions for user equally:
1. user can adjust two speed points, changes the rate of change of the overshoot factor;
2. user can adjust the limits value of the overshoot factor, and this value need to calculate according to the switching frequency of frequency converter and in conjunction with two speed points above-mentioned, hereinafter can introduce in detail its computational methods.
Accompanying drawing explanation
Fig. 1 is the oscillogram of SVPWM.
Fig. 2 is the change curve of overshoot coefficient.
Fig. 3 is the upper and lower brachium pontis switching waveform of the not homophase figure of SDPWM.
Fig. 4 is the limits value change curve of overshoot coefficient.
The oscillogram of SDPWM when Fig. 5 is low speed.
The oscillogram of SDPWM when Fig. 6 is middling speed.
The oscillogram of SDPWM when Fig. 7 is high speed.
Embodiment
Following content by reference to the accompanying drawings, is elaborated to algorithm.
In the PWM modulation system of frequency converter output, SVPWM has plurality of advantages, and SDPWM be take the waveform of SVPWM as basis, adds dynamic overshooting, to reach the object that reduces on-off times.
1. SVPWM discrete sheet
As shown in the SVPWM oscillogram of Fig. 1, output U, the V of frequency converter, W can add respectively, subtract 120 degree according to the phase angle of the phase SVPWM waveform in Fig. 1 and calculate, here SVPWM from [0,2 π] 1024 parts of deciles, form the discrete sheet (below representing this table with TabSVPWM) of a SVPWM, Fig. 1 is the oscillogram drawing according to this discrete sheet with MATLAB, and following calculating will realize based on this discrete sheet.
2. the calculating of amplitude modulation coefficient
At present, the main flow control algolithm of frequency converter has voltage-frequency than control, vectorial control, flux regulator and direct torque control, wherein first three plants control mode finally all needs to modulate output, here control algolithm is not repeated, only emphasize when using SDPWM, control algolithm needs output voltage vector Us, needs sampling to obtain the voltage U dc of DC bus simultaneously, and amplitude modulation coefficient (representing with ModIndex here) just can calculate by following formula so:
ModIndex = Us/Udc;
And need ModIndex to limit here, make it be less than or equal to 1, if the ModIndex that above formula calculates is greater than 1, force it to equal 1.
3. the calculating of overshoot coefficient
Overshoot coefficient is the piecewise function of a velocity correlation, generally when speed is low-down, is not suitable for using overshoot, and this slow door limit value is designated as SpeedL here; When speed is during higher than certain value, be applicable to using full overshoot, this high-speed door limit value is designated as SpeedH here, and SpeedH will be greater than SpeedL all the time.These two threshold values need to arrange according to concrete use occasion and the loading condition of frequency converter, such as, the low weight application scenario of load when frequency converter low speed, it is lower that SpeedL can suitably arrange; If low speed duty ratio heavier (such as occasions such as liftings), it is higher that this value can suitably arrange.In addition, according to the type of load motor, these two threshold values also need to adjust, if load motor is permagnetic synchronous motor, what these two threshold values all should arrange so is higher.
Overshoot coefficient represents with OverModIndex, and the maximum of overshoot coefficient represents with OverModLimit, and the f for function (Speed) of overshoot coefficient and speed represents, is below the content of this function:
OverModIndex = f (Speed);
Temp = 1+(OverModLimit–1) *((Speed–SpeedL) / (SpeedH-SpeedL));
F (Speed) is a piecewise function, divides following three sections:
f (Speed) = 1; (Speed < SpeedL)
f (Speed) = Temp; (SpeedL =< Speed < SpeedH)
f (Speed) = OverModLimit; (Speed >= SpeedH)
Fig. 2 gets the curve chart that OverModLimit is the function f (Speed) of 1.15 o'clock.
4. the restriction of overshoot coefficient
In calculating above, used the threshold limit value OverModLimit of overshoot coefficient, in general application, overshoot coefficient KB limit can be taken as following constant:
OverModLimit = 1/sin(π/3);
Yet, when being taken as above-mentioned constant, when the alternate upper and lower brachium pontis of difference cuts out or cuts from overshoot interval, 2 multiple differential pressures that can occur moment on the winding of motor, cause motor stator winding to occur peak current, this peak current is very large to the insulating properties injury of motor, has a strong impact on the life-span of motor.As shown in Figure 3, wherein Up, Vn, Wn are respectively the lower brachium pontis of upper brachium pontis, V and the W phase of U phase.Can see, L1 and L2 be respectively U phase overshoot interval incision and cut out a little, as we can see from the figure, L1 just in time overlaps with cutting out of the overshoot interval of Vn, and L2 point just in time overlaps with the cutting point in the overshoot interval of Wn.
The peak current that overlaps and cause for fear of switching point, following algorithm is avoided the generation of this situation by revising OverModLimit value.In principle, say, as long as putting forward previous switch periods cuts out overshoot interval and can avoid this situation, be below the computational methods of OverModLimit, the calculating of this value is relevant with speed (representing with Fspeed) to switching frequency (representing with Fswitch).
Ws = 2*π*Fspeed;
T = 1/Fswitch;
Theta = π/3 + Ws*T;
OverModLimit = 1/sin(Theta);
Wherein Ws is that time, Theta that angular speed, T represent a switch periods are the interval angles of overshoot.As shown in Figure 4, this figure is the situation when switching frequency is 8000Hz to the function curve of the overshoot coefficient limits value OverModLimit calculating.
Obtain after the function curve of OverModLimit, the function f of above-described OverModIndex (Speed) also can be optimized for;
OverModIndex = f (Speed);
Temp = 1 + ((1/sin(π/3)) –1) *((Speed–SpeedL) / (SpeedH-SpeedL));
F (Speed) is a piecewise function, divides following three sections:
f (Speed) = 1; (Speed < SpeedL)
f (Speed) = Min(OverModLimit, Temp); (SpeedL =< Speed < SpeedH)
f (Speed) = OverModLimit; (Speed >= SpeedH)
Wherein function Min () is the meaning getting the small value.
5. the calculating of SDPWM centrifugal pump
Finally, we need to calculate SDPWM centrifugal pump, and the U of below take calculates as example mutually, and V, W add respectively, subtract 120 degree on the basis of U phase.
Usdpwm(Theta) = ModIndex*OverModIndex*TabSVPWM(Theta);
SDPWM_Limit = 0.5 * ModIndex;
Wherein, Usdpwm (Theta) is the function of SDPWM, the amplitude limit that SDPWM_Limit is SDPWM.
Finally limit the value of Usdpwm (Theta), if Usdpwm (Theta) > is SDPWM_Limit, force Usdpwm (Theta)=SDPWM_Limit; If Usdpwm (Theta) is <-SDPWM_Limit, force Usdpwm (Theta)=-SDPWM_Limit.
Because OverModIndex is the function of velocity correlation, so the waveform of Usdpwm is also with velocity variations, shown in Fig. 5, be the 3 phase SDPWM oscillograms of speed during lower than SpeedL, Fig. 6 is the 3 phase SDPWM oscillograms of speed between SpeedL and SpeedH, and Fig. 7 is that speed is higher than the 3 phase SDPWM oscillograms of SpeedH.
Finally, the good balance of SDPWM the control performance of frequency converter when friction speed and the problem of switching loss, greatly improved life-span and the efficiency of frequency converter, can dwindle frequency converter fin volume, and then reduce the cost of frequency converter simultaneously.
Claims (3)
1. in frequency converter, the method of conventional modulation output has SPWM, SVPWM, 60 degree PWM etc., these modulator approaches respectively have pluses and minuses, in order to fully utilize the advantage of these modulator approaches, avoid shortcoming, the present invention introduces speed as variable, invent a kind of discrete type PWM that dynamically adjusts modulation system according to speed, in literary composition, be called SDPWM (Speed Discrete Pulse Width Modulation), it is characterized in that when frequency converter is modulated output, this variable of introducing speed, according to the difference of speed, dynamic adjustments modulation system, to reach the direct voltage that utilizes to greatest extent frequency converter, and minimizing harmonic wave, reduce again the on-off times of IGBT simultaneously, so both improved the life-span of frequency converter, improved again the performance of frequency converter.
2. the description based on above claim, another feature of this invention is to change modulation system according to overshoot coefficient, thereby reduce the on-off times of IGBT, and overshoot coefficient and velocity correlation, avoid like this gamut to reduce in a large number the low speed control performance that on-off times causes poor, in low regime limited range, under the prerequisite that guarantees control performance, suitably reduced again the on-off times of IGBT simultaneously.
3. the description based on above claim; the 3rd feature of this invention is by restriction overshoot coefficient; the phase conversion impact electric current of having avoided the switching over of the different alternate upper brachium pontis of IGBT and lower brachium pontis to cause; this impulse current is very large to the insulating properties injury of motor; can motor damage when serious, this feature has effectively been protected motor.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106797189A (en) * | 2014-08-29 | 2017-05-31 | 日产自动车株式会社 | Variable magnetization machine controller |
| CN106782689A (en) * | 2016-11-21 | 2017-05-31 | 中国核动力研究设计院 | A kind of linear motor type CRDM control method |
| CN111669105A (en) * | 2020-06-11 | 2020-09-15 | 上海有个机器人有限公司 | Motor rotating speed control method and device and storage medium |
| CN111756306A (en) * | 2019-03-28 | 2020-10-09 | 广州汽车集团股份有限公司 | SVPWM modulation zero vector distribution method and device for motor and electric vehicle |
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| CN1747318A (en) * | 2004-09-03 | 2006-03-15 | 通用汽车公司 | Delay compensation for stable current regulation when using variable-delay random PWM switching |
| CN101235758A (en) * | 2007-01-30 | 2008-08-06 | 通用汽车环球科技运作公司 | Purge flow control to reduce air/fuel ratio imbalance |
| US20110084638A1 (en) * | 2009-10-12 | 2011-04-14 | Gm Global Technology Operations, Inc. | Methods, systems and apparatus for dynamically controlling an electric motor that drives an oil pump |
| CN102384118A (en) * | 2011-08-31 | 2012-03-21 | 中联重科股份有限公司 | Electro-hydraulic proportional valve speed regulation control method, device, system and engineering mechanical equipment |
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Patent Citations (4)
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| CN1747318A (en) * | 2004-09-03 | 2006-03-15 | 通用汽车公司 | Delay compensation for stable current regulation when using variable-delay random PWM switching |
| CN101235758A (en) * | 2007-01-30 | 2008-08-06 | 通用汽车环球科技运作公司 | Purge flow control to reduce air/fuel ratio imbalance |
| US20110084638A1 (en) * | 2009-10-12 | 2011-04-14 | Gm Global Technology Operations, Inc. | Methods, systems and apparatus for dynamically controlling an electric motor that drives an oil pump |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106797189A (en) * | 2014-08-29 | 2017-05-31 | 日产自动车株式会社 | Variable magnetization machine controller |
| CN106782689A (en) * | 2016-11-21 | 2017-05-31 | 中国核动力研究设计院 | A kind of linear motor type CRDM control method |
| CN106782689B (en) * | 2016-11-21 | 2018-03-06 | 中国核动力研究设计院 | A kind of linear motor type CRDM control method |
| CN111756306A (en) * | 2019-03-28 | 2020-10-09 | 广州汽车集团股份有限公司 | SVPWM modulation zero vector distribution method and device for motor and electric vehicle |
| CN111669105A (en) * | 2020-06-11 | 2020-09-15 | 上海有个机器人有限公司 | Motor rotating speed control method and device and storage medium |
| CN111669105B (en) * | 2020-06-11 | 2022-04-01 | 上海有个机器人有限公司 | Motor rotating speed control method and device and storage medium |
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