CN103178851B - A kind of novel sampling method producing SPWM control signal - Google Patents
A kind of novel sampling method producing SPWM control signal Download PDFInfo
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- CN103178851B CN103178851B CN201310082565.4A CN201310082565A CN103178851B CN 103178851 B CN103178851 B CN 103178851B CN 201310082565 A CN201310082565 A CN 201310082565A CN 103178851 B CN103178851 B CN 103178851B
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Abstract
The invention discloses a kind of novel sampling method producing SPWM control signal, construct virtual sampled point according to the mode of mathematically linear combination, to reduce the number of sampled point in reality; Adopt the operation method of linear extrapolation to ask for the approximation in carrier wave and modulating wave nature intersection point moment, thus obtain higher pulse width control precision; Complete according to the rule of sine each power tube in rectification (inversion) device is opened, the control of off state.The sampled point number of this method of sampling and the consistent of conventional symmetrical regular sampling, but the precision of its pulse width control is higher than traditional regular sampling and existing common Variable Polarity rule sampling, two point form rule sampling, four-point rule sampling, linear combination sampling and linear extrapolation sampling method etc., the harmonic content of its output voltage is less, and be easy to programming during hardware designs based on DSP, man-machine interaction is good, can modify to program neatly, to meet the demand under various occasion, be mainly used in rectifier and inverter.
Description
Technical field
The present invention relates to a kind of field of power electronics, be specifically related to a kind of novel sampling method producing SPWM control signal.
Background technology
In recent years, along with the development of Microprocessor technology, computer technology and power electronic technology, based on digital signal processor (DigitalSignalProcessor, be called for short DSP) pulse-width modulation (PulseWidthModulation, be called for short PWM) technology be widely applied among the systems such as three phase electric machine control, frequency converter, rectifier and inverter.In various PWM control mode, sinusoidal pulse width modulation (SinusoidalPWM, be called for short SPWM) technology because its algorithm is simple, be easy to hardware implementing, revise the advantage such as amplitude and frequency and be widely used to the less and dynamic of harmonic content.
The basic modulation principle of SPWM modulation technique be according to " the equal and variform burst pulse of momentum be added in there is inertia link on time; its effect is substantially identical " principle, make frequency converter produce the not wide squared pulse trains of constant amplitude and sine wave equivalence, regulated amplitude and the frequency of frequency converter output voltage by the amplitude and frequency size changing modulating wave.So far, existing many forefathers are studied the SPWM waveform generator based on DSP, its common sampling type production method has: natural sampling method, symmetric regular-sampled method, asymmetric regular sampling method, improvement type Unsymmetric Regular sample, peak value type rule sampling, first kind tangent sampling, Equations of The Second Kind tangent sampling, the 3rd class tangent sampling, secant sampling, Variable Polarity rule sampling, two point form rule sampling, four-point rule sampling, linear combination sampling and linear extrapolation sampling method etc.The most traditional sampling method has:
Natural sampling method: the switching instant being determined switch by the intersection point of high frequency triangular carrier and sinusoidal modulation wave, it is a kind of method of sampling producing SPWM ripple best at present, but its sampled point and switching over point overlap, sampled point can not pre-determine, need the method Real-time solution transcendental equation by iterative numerical, be not easy to Digital Realization.
Symmetric regular-sampled method: sample at the trough times offset of sinusoidal modulating wave of each carrier cycle, utilizes sampled value to generate the sine wave of a notch cuttype crossing with triangular carrier, by the switching instant of intersection point determination switching point.This method of sampling sampled point number is few, numerically equals the value N of carrier wave ratio, and algorithm is simple, but accuracy is not high.
Asymmetric regular sampling method: sample at the crest of each carrier cycle and the equal offset of sinusoidal modulating wave of trough times, utilizes sampled value to generate the sine wave of a notch cuttype crossing with triangular carrier, by the switching instant of intersection point determination switching point.This method of sampling sampled point number is 2*N, and algorithm is simple, and accuracy is higher than traditional symmetric regular-sampled.
Afterwards, forefathers also proposed a lot of method of sampling improved, and the various method of sampling is relative to the switching time grade of errors of natural sampling method and the more as shown in table 1 of sampled point number, and table breaker in middle moment error is less, then number of degrees is larger, supposes that carrier wave ratio is N.
| The method of sampling | Grade of errors | Sampled point number | The method of sampling | Grade of errors | Sampled point number |
| Symmetric regular-sampled | 2 | N | Half complete period rule sampling | 5 | 2N |
| Unsymmetric Regular sample | 1 | 2N | Linear extrapolation sampling method | 7 | 2N |
| The asymmetric sampling of improvement type | 5 | 2N | Secant sampling method | 9 | 2N |
| Peak value type rule sampling | 3 | N | Variable Polarity rule sampling | 4 | N |
| First kind tangent sampling | 8 | N | Two point form rule sampling | 5 | 2N |
| Equations of The Second Kind tangent sampling | 9 | N | Four-point rule sampling | 6 | 3N 1 --> |
| Linear combination is sampled | 1 | N | Combination linear extrapolation sampling | 10 | N |
Summary of the invention
The object of the invention is to the above problem overcoming prior art existence, provide a kind of novel sampling method producing SPWM control signal, the present invention is easy to Digital Realization, and save DSP hardware resource, pulse-triggered time error is little.
For realizing above-mentioned technical purpose, reach above-mentioned technique effect, the present invention is achieved through the following technical solutions:
Produce a novel sampling method for SPWM control signal, comprise the following steps:
Step 1) detects input signal, obtains frequency of modulated wave f by outside input
s, modulation degree m
a, carrier wave ratio N and the time t that dies
sparameter, and accumulative value sin (the ω t preserving adjacent two " carrier wave peak value sampling points "
a) and sin (ω t
b);
Step 2) according to adjacent two sampled value sin (ω t of step 1 gained
a) and sin (ω t
b), by the linear combination method of mathematics, construct value sin (the ω t of virtual " carrier wave valley sampled point "
c), sin (ω t
c)=Asin (ω t
a)+Bsin (ω t
b), t
b=t
c+ T
c/ 2=t
a+ T
c, T
cfor carrier cycle time value, solve A=B=
, and use this three " sampled point " to calculate to send as an envoy to DSP to export the register comparison value of SPWM waveform, form the low and high level jumping moment table in one and half modulating wave cycles, be kept in the internal memory of DSP;
Step 3) produces three-phase symmetrical SPWM ripple, the low and high level jumping moment table in the half modulating wave cycle using step 2 to obtain, and according to the symmetry of sinusoidal modulation wave and the phase difference character of three-phase symmetrical sine wave, produces the SPWM control signal waveform of three-phase symmetrical.
Further, in described step 1), sample range is the positive half cycle in each modulating wave cycle.
Further, in described step 3), phase difference is 360 ° of ways divided by SPWM ripple.
The invention has the beneficial effects as follows:
1, take full advantage of the advantage of DSP fast operation, decrease the A/D sampling work of low speed, improve the real-time of system;
2, derive the formula of compute switch moment point, simplify writing of program, be easier to this new method Digital Realization;
3, compared with common with other method of sampling, output waveform harmonic wave is little, and hree-phase symmetry is good, and precision is high, and frequency conversion is convenient.
Above-mentioned explanation is only the general introduction of technical solution of the present invention, in order to better understand technological means of the present invention, and can be implemented according to the content of specification, coordinates accompanying drawing to be described in detail as follows below with preferred embodiment of the present invention.The specific embodiment of the present invention is provided in detail by following examples and accompanying drawing thereof.
Accompanying drawing explanation
Accompanying drawing described herein is used to provide a further understanding of the present invention, and form a application's part, schematic description and description of the present invention, for explaining the present invention, does not form inappropriate limitation of the present invention.In the accompanying drawings:
Fig. 1 is combination linear of the present invention extrapolation sampling method schematic diagram.
Embodiment
Below with reference to the accompanying drawings and in conjunction with the embodiments, describe the present invention in detail.
With reference to shown in Fig. 1, a kind of novel sampling method producing SPWM control signal, comprises the following steps:
Step 1) detects input signal, obtains frequency of modulated wave f by outside input
s, modulation degree m
a, carrier wave ratio N and the time t that dies
sparameter, and accumulative value sin (the ω t preserving adjacent two " carrier wave peak value sampling points "
a) and sin (ω t
b);
Step 2) according to adjacent two sampled value sin (ω t of step 1 gained
a) and sin (ω t
b), by the linear combination method of mathematics, construct value sin (the ω t of virtual " carrier wave valley sampled point "
c), sin (ω t
c)=Asin (ω t
a)+Bsin (ω t
b), t
b=t
c+ T
c/ 2=t
a+ T
c, T
cfor carrier cycle time value, solve A=B=
, and use this three " sampled point " to calculate to send as an envoy to DSP to export the register comparison value of SPWM waveform, form the low and high level jumping moment table in one and half modulating wave cycles, be kept in the internal memory of DSP;
Step 3) produces three-phase symmetrical SPWM ripple, the low and high level jumping moment table in the half modulating wave cycle using step 2 to obtain, and according to the symmetry of sinusoidal modulation wave and the phase difference character of three-phase symmetrical sine wave, produces the SPWM control signal waveform of three-phase symmetrical.
Further, in described step 1), sample range is the positive half cycle in each modulating wave cycle.
Further, in described step 3), phase difference is 360 ° of ways divided by SPWM ripple.
The operation principle of the present embodiment is as follows:
1) principle of mathematically linear combination is used to utilize the sampling point value of crest (or trough) to construct the sampling point value of virtual trough (or crest): to be located in K and K+1 triangular carrier cycle that carrier cycle is Ts, peak point moment Ta, Tb offset of sinusoidal modulating wave of carrier wave is sampled, and sampled point is for some A and put B; Algebraic relation formula between the virtual sampled point C of structure valley point moment Tc and some A, some B:
sin(ω·t
c)=A·sin(ω·t
a)+B·sin(ω·t
b)（1）
In above formula, A, B are coefficient undetermined, known T
s=
and T
b=T
c+ T
s/ 2=T
s+ T
a, N is the value of carrier wave ratio.(1) formula of substitution solves:
A=B=
=
（2）
Generally, when carrier wave ratio N value is larger, π <<N, then COS (π/N) → 1, therefore has A=B=0.5, and (1) formula of substitution obtains:
sin(ω·T
c)=[sin(ω·T
a)+sin(ω·T
b)]/2（3）
The equivalent error of this numerical value convergence is analyzed, when N>=12, | (
-
) |/
≤ 3.5276%, therefore, when carrier wave ratio N value is enough large, the sampled value of actual valley point just can be equivalent to completely by the virtual sampled value of valley point of (3) formula calculating gained, eliminate the actual samples step to valley point, thus make the number of times of sampling decrease half fully, save CPU operation time, improve the real-time of system.
2) as shown in Figure 1, the operation method of linear extrapolation is adopted to ask for the approximation in carrier wave and modulating wave nature intersection point moment: to be located in K-1, K and K+1 triangular carrier cycle that carrier cycle is Ts, the peak point moment T of carrier wave
k-1, T
kand T
k+1offset of sinusoidal modulating wave is sampled, and sampled point is A
k-1, A
kand A
k+1(value of sampled point also correspondence is expressed as A
k-1, A
kand A
k+1), use the principles of construction of above-mentioned linear combination to go out T
k-1-Band T
k+1-Bthe sampled point B in valley point moment
k-1and B
k(value of sampled point also correspondence is expressed as B
k-1and B
k, wherein T
k-1<T
k-1-B<T
k<T
k+1-B<T
k+1), then B
k-1a
kextended line must with triangular carrier compared to point (T
k-on, SK-on), this point is just as the moment point of switch device conductive; And B
ka
kextended line must with triangular carrier compared to point (T
k-off, SK-off), this point is just as the moment point that switching device turns off; So analogize, can determine that the rule that switch device conductive turns off is as follows: the turn-on instant of each crest sampled point and its previous reverse extending line of " virtual trough sampled point " and the intersection point determination switching device of triangular carrier, with the shutoff moment of the reverse extending line of thereafter " virtual trough sampled point " and the intersection point determination switching device of triangular carrier.Set up coordinate system, row write that math equation can separate:
(4) this equation formula needs to make into foregoing type, and can not be placed on this with the pattern of similar picture illustration, other places are revised.
Utilize the interrupt on overflow of DSP, can determine and identify T
kand T
k+1moment, so the switch on and off moment T of each carrier cycle
k-onand T
k+1-offcan determine one by one and produce corresponding SPWM control waveform.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (3)
1. produce a method of sampling for SPWM control signal, it is characterized in that: comprise the following steps:
Step 1) detects input signal, obtains frequency of modulated wave f by outside input
smodulation m
acarrier wave ratio N and the time t that dies
sparameter, and accumulative value sin (the ω t preserving adjacent two " carrier wave peak value sampling points "
a) and sin (ω t
b);
Step 2) according to adjacent two sampled value sin (ω t of step 1) gained
a) and sin (ω t
b), by the linear combination method of mathematics, construct value sin (the ω t of virtual " carrier wave valley sampled point "
c), sin (ω t
c)=Asin (ω t
a)+Bsin (ω t
b), t
b=t
c+ Tc/2=t
a+ Tc, Tc are carrier cycle time value, solve A=B=
, and use this three " sampled point " to calculate to send as an envoy to DSP to export the register comparison value of SPWM waveform, form the low and high level jumping moment table in one and half modulating wave cycles, be kept in the internal memory of DSP;
Step 3) produces three-phase symmetrical SPWM ripple, use step 2) the low and high level jumping moment table in half modulating wave cycle that obtains, according to the symmetry of sinusoidal modulation wave and the phase difference character of three-phase symmetrical sine wave, produce the SPWM control signal waveform of three-phase symmetrical.
2. a kind of method of sampling producing SPWM control signal according to claim 1, is characterized in that: in described step 1), sample range is the positive half cycle in each modulating wave cycle.
3. a kind of method of sampling producing SPWM control signal according to claim 1, is characterized in that: in described step 3), phase difference is 360 divided by the way of SPWM ripple.
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Families Citing this family (8)
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| CN104124858B (en) * | 2014-05-29 | 2017-01-04 | 浙江大学 | A kind of suppressing method of Sinusoidal Pulse Width Modulation PWM logic competition |
| CN104298107B (en) * | 2014-08-26 | 2017-02-15 | 苏州科技学院 | Combined local frequency multiplication sampling algorithm for generating SPWM waves |
| CN104375003B (en) * | 2014-11-10 | 2017-06-06 | 千江（上海）信息科技有限公司 | The method that sampled point is lifted in zero pressure drop equipment |
| CN106208784A (en) * | 2016-07-26 | 2016-12-07 | 中国科学院等离子体物理研究所 | A kind of converter controls the control method of operating lag |
| KR20180047517A (en) * | 2016-10-31 | 2018-05-10 | 삼성전기주식회사 | Wireless power transmitter and method for controlling sampling in wireless power transmitter |
| CN109818512B (en) * | 2019-03-08 | 2020-10-30 | 四川大学 | Multi-sampling method for single-phase cascaded H-bridge multi-level converter |
| CN114257102B (en) * | 2020-09-24 | 2023-07-18 | 苏州爱科赛博电源技术有限责任公司 | Double-sampling single-refreshing method based on three-phase two-level topological structure |
| CN113258909A (en) * | 2021-05-25 | 2021-08-13 | 福州大学 | Sine pulse width modulation method based on average value of sampling values |
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| EP1376877A1 (en) * | 2002-06-27 | 2004-01-02 | Pioneer Corporation | Pulse width modulator and pulse width modulation method |
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