CN101599738A - The universal pulse width duty ratio of three-phase AD motor PWM control is determined method - Google Patents

Abstract

A kind of universal pulse width duty ratio that is used for three-phase AD motor PWM (pulse width modulation) control is determined method, comprises step: the normalization three-phase current set-point I that determines three-phase alternating-current motor _a, I _b, I _cAccording to normalization three-phase current set-point I _a, I _b, I _cCalculate every biphase current difference I _Ab, I _Bc, I _CaCalculate the maximum max{|I of the absolute value of every biphase current difference _Ab|, | I _Bc|, | I _Ca|; According to max{|I _Ab|, | I _Bc|, | I _Ca| three kinds of situations determine three-phase pulse duty ratio k by arithmetic _a, k _b, k _cThis method and conventional six sector resolution of vectors methods determine that the three-phase pulse duty ratio relatively, come to the same thing, but because process is simple and avoided complicated sector to judge and trigonometric function operation, the code amount is few, it is few to take hardware resource, the computational efficiency height, and can realize comprising the multiple PWM control mode of SPWM (sinusoidal pulse width modulation) and SVPWM (space vector pulse width modulation) control mode, be specially adapted to the high accuracy SVPWM control of three-phase alternating-current motor.

Description

The universal pulse width duty ratio of three-phase AD motor PWM control is determined method

Technical field

The present invention relates to definite method of the universal pulse width duty ratio of a kind of three-phase AD motor PWM (pulse width modulation) control, particularly relate to and a kind ofly avoid complicated sector to judge and resolution of vectors, and can realize comprising definite method of the universal pulse width duty ratio of SPWM (sinusoidal pulse width modulation) mode and SVPWM (space vector pulse width modulation) mode.

Background technology

At present, need to realize that in Switching Power Supply, Electric Machine Control etc. in the device of power inverting function, PWM control has become most widely used control mode.The theoretical foundation of PWM control is the impulse conservation law principle in the sampled-data control theory, that is: when the equal and variform burst pulse of momentum affacted on the inertial element, its effect was basic identical.The PWM control technology is a foundation with this principle exactly, by according to certain rule, controls the turn-on and turn-off of semiconductor switch device, obtains a series of constant amplitudes and not wide pulse.If control the width of these pulses according to sinusoidal rule, so, it is applied to as on the inertial elements such as motor, will obtain action effect as sine wave.

In three phase electric machine PWM control principle circuit diagram shown in Figure 1, the PWM controller applies control signal to the switch triode of the upper and lower brachium pontis of three phase inverter bridge of DC power supply inverter respectively, make three phase inverter bridge to the controlled three-phase pulse of threephase motor M output width, drive motors is with the direction and the speed rotation of appointment.

In fact,, be subjected to the restriction of power electronic device performance though the basic principle of PWM control proposes for a long time, before the eighties 20th century of last century, always can extensive use on engineering.Since the eighties in 20th century, along with the appearance of all-controlling power electronics device and develop rapidly, the raising of microprocessor performance, the PWM control technology has just really had the ample scope for abilities and has obtained unprecedented development.

At present, in the digital control of PMSM (three-phase permanent magnet synchronous motor), the PWM control mode has become only choosing.PWM control method at PMSM had developed into present SVPWM control method already from the SPWM control method that begins.

Compare with SPWM, the advantage of SVPWM is to make the utilization ratio of DC power supply to improve 15.47%, but, because the needs of resolution of vectors are divided into six sectors with the three-phase vector space, as shown in Figure 2, Vr among the figure promptly needs the reference vector that decomposes, will judge at first which sector Vr is in, selection vector then is decomposed into the pairing effect vector component in this sector (V among Fig. 2 for example with Vr ₁' and V ₂'), also to calculate and determine its action time of T (pulse duration) and sampling period T by the size of each vector component _sRatio (duty ratio), wherein sector is judged and resolution of vectors need be carried out trigonometric function and antitrigonometric function computing, algorithm complexity not only, the programming code amount is big, and amount of calculation is also big, its cost is higher to the operational capability requirement of processor.Usually the chip arithmetic speed and the memory space that are adopted of PWM controller is all limited, therefore, realize that the PWM High Accuracy Control must simplify the PWM control algolithm, to reduce EMS memory occupation and raising operation efficiency.

Summary of the invention

The objective of the invention is to provide a kind of definite method of pulse duration duty ratio of simple general-purpose for three-phase AD motor PWM control, make it both be applicable to the SPWM control mode, also be applicable to the SVPWM control mode, avoid complicated sector to judge and resolution of vectors simultaneously.Technical problem to be solved is the size by the absolute value of the difference of every biphase current of more given three-phase current, determines three-phase current pulse duration duty ratio according to the electric current difference of absolute value maximum.

Of the present inventionly be used for three-phase AD motor PWM control, can realize that the universal pulse width duty ratio that comprises SPWM control mode and SVPWM control mode determines method, may further comprise the steps:

Determine the normalization three-phase current set-point I of three-phase alternating-current motor _a, I _b, I _c(1≤I _a, I _b, I _c≤ 1);

According to normalization three-phase current set-point I _a, I _b, I _cCalculate every biphase current difference I of normalization three-phase current according to formula (1) _Ab, I _Bc, I _Ca

I _ab＝I _a-I _b

$I_{\mathrm{bc}}=I_b-I_{c_c}---\left(1\right)$

I _ca＝I _c-I _a

Calculate every biphase current difference I of normalization three-phase current _Ab, I _Bc, I _CaAbsolute value | I _Ab|, | I _Bc|, | I _Ca| maximum max{|I _Ab|, | I _Bc|, | I _Ca|;

As maximum max{|I _Ab|, | I _Bc|, | I _Ca| be A, B biphase current difference I _AbAbsolute value | I _Ab| the time, by formula (2) calculate three-phase pulse duty ratio k _a, k _b, k _c:

$k_a=p\frac{I_{\mathrm{ab}}}{2}$

k _b＝-k _a (2)

$k_c=p\frac{{3\mathrm{<figure-callout\; id="2"\; label="I\; c"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">I</figure-callout>}}_c}{2}$

As maximum max{|I _Ab|, | I _Bc|, | I _Ca| be B, C biphase current difference I _BcAbsolute value | I _Bc| the time, by formula (3) calculate three-phase pulse duty ratio k _a, k _b, k _c:

$k_b=\mathrm{<figure-callout\; id="2"\; label="p\; I\; bc"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">p</figure-callout>}\frac{I_{\mathrm{bc}}}{}\frac{{}_{}}{2}$

k _c＝-k _b (3)

$k_a=p\frac{{3I}_{\mathrm{<figure-callout\; id="2"\; label="a"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">a</figure-callout>}}}{2}$

As maximum max{|I _Ab|, | I _Bc|, | I _Ca| be C, A biphase current difference I _CaAbsolute value | I _Ca| the time, by formula (4) calculate three-phase pulse duty ratio k _a, k _b, k _c:

$k_c=p\frac{I_{\mathrm{ca}}}{2}$

k _a＝-k _c (4)

$k_b=p\frac{{3\mathrm{<figure-callout\; id="2"\; label="I\; b"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">I</figure-callout>}}_b}{2}$

In formula (2), (3) and (4), p is a proportionality coefficient, $1\&le;p\&le;\frac{2}{\sqrt{3}}.$

Further:

Universal pulse width duty ratio of the present invention is determined method, when adopting the SPWM control mode, and the proportionality coefficient p=1 in formula (2), (3) and (4).

Universal pulse width duty ratio of the present invention is determined method, when adopting the SVPWM control mode, and the proportionality coefficient in formula (2), (3) and (4) $p=\frac{2}{\sqrt{3}}.$

Further:

Universal pulse width duty ratio of the present invention is determined method, and three-phase alternating-current motor wherein can be a turning motor.

Universal pulse width duty ratio of the present invention is determined method, and three-phase alternating-current motor wherein can be a linear motor.

Universal pulse width duty ratio of the present invention determines that method has following beneficial effect:

1. can realize the PWM control mode of different-effect by the size that changes the proportionality coefficient p in the formula (2), for example when the P value is 1, be equivalent to conventional SPWM control mode, when the P value is

The time, promptly realize the SVPWM control mode.

2. when adopting the SVPWM control mode, the control effect of the inventive method is identical with conventional six sector resolution of vectors methods, but owing to replace the sector in the resolution of vectors method to judge definite effect vector with the order of magnitude that compares the three-phase current difference, and directly draw the three-phase pulse duty ratio with simple arithmetic, avoided trigonometric function and antitrigonometric function computing complicated in the resolution of vectors process, result of implementation shows, the executable code length that realizes the inventive method have only conventional six sector resolution of vectors methods determine duty ratio executable code length 1/4, operational efficiency improves 17%, therefore can reduce the performance of processors requirement, improve arithmetic speed, help realizing high accuracy SVPWM control.

3. the PWM modelling by mechanism realizes owing to the calculating of this method duty ratio is based on, the switching value of its solution procedure and PWM control there is no directly gets in touch, therefore universal pulse width duty ratio of the present invention determines that method can also expand other field that is applied to naturally, for example the control of control of DC, multi-level inverse conversion power supply etc.

Description of drawings

Fig. 1 is a three phase electric machine PWM control principle circuit diagram;

Fig. 2 is a resolution of vectors schematic diagram between six sector null in the conventional SVPWM control method;

Fig. 3 is three phase alternating current motor stator current I _a, I _b, I _cWith every biphase current difference I _Ab, I _Bc, I _CaChange curve in one-period (0 °～360 °);

Fig. 4 is a three phase alternating current motor stator winding equivalent electric circuit;

Fig. 5 is the flow chart that the resolution of vectors method is determined the three-phase duty ratio between SVPWM control employing six sector null;

Fig. 6 is that SVPWM control adopts method of the present invention to determine the flow chart of three-phase duty ratio.

Embodiment

Before introducing embodiments of the present invention, at first introduce design of the present invention.

The objective of the invention is according to known three-phase electricity flow valuve, avoid complicated sector to judge and the space vector decomposition, directly determine the three-phase duty ratio.As can be seen from Figure 3, if with three phase alternating current motor stator current I _a, I _b, I _cA period of change be divided into 6 phase angle intervals of 0 °～60 °, 60 °～120 °, 120 °～180 °, 180 °～240 °, 240 °～300 ° and 300 °～360 °, these 6 phase angle intervals are successively corresponding to sector I, sector II, sector III, sector IV, sector V and the sector VI of space vector shown in Figure 2.

At first, every biphase current difference I of three-phase current _Ab, I _Bc, I _CaThough in these 6 phase angle intervals, change difference, the maximum max{|I of its absolute value _Ab|, | I _Bc|, | I _Ca| variation but have regularity, promptly

In 0 °～60 ° and 180 °～240 ° phase angle intervals | I _Ca| maximum all the time;

In 60 °～120 and 240 °～300 ° phase angle intervals | I _Bc| maximum all the time;

In 180 °～240 ° and 300 °～360 ° phase angle intervals | I _Ab| maximum all the time.

So only, just three-phase current can be limited in two phase angle intervals, for example as if | I by judging the maximum of every biphase current difference absolute value _Bc| maximum, the phase angle interval that can judge the three-phase current place are 60 °～120 ° or are 240 °～300 °.

Secondly, in each phase angle interval, the positive and negative of the difference between current of absolute value maximum also is thick-and-thin, and 180 ° of the phase phasic differences in two intervals that maximum limited of difference between current absolute value, and each phase current and every biphase current difference are anti-phase fully in these two intervals.Promptly

| I _Ca| all the time in Zui Da two anti-phase each other phase angle intervals, I _CaIn 0 °～60 ° intervals all the time less than 0, in 180 °～240 ° intervals all the time greater than 0;

| I _Bc| all the time in Zui Da two anti-phase each other phase angle intervals, I _BcIn 60 °～120 ° intervals all the time greater than 0, in 240 °～300 ° intervals all the time less than 0;

| I _Ab| all the time in Zui Da two anti-phase each other phase angle intervals, I _AbIn 120 °～180 ° intervals all the time less than 0, in 300 °～360 ° intervals all the time greater than 0.

So just can be according to the difference between current of absolute value maximum positive and negative, unique definite three-phase current I _a, I _b, I _cThe phase angle interval at place, for example if | I _Bc| maximum and I _Bc＜0, the phase angle interval that can judge the three-phase current place is 240 °～300 °.Determine the phase angle interval at three-phase current place, also just be equivalent to determine the sector at three-phase current space vector place shown in Figure 2.

The method of definite three-phase duty ratio that below will describe in detail is exactly according to every biphase current difference I _Ab, I _Bc, I _CaThe maximum of absolute value is determined the value of three-phase duty ratio in three kinds of situations in inphase angle interval not, the size of the duty ratio of this two-phase that the biphase current difference of absolute value maximum is limited is directly proportional with this biphase current difference, the size of an other phase duty ratio is directly proportional with this other phase current, and each phase duty ratio positive and negative depended on the positive and negative of this biphase current difference or this other phase current, determined three-phase current I shown in Figure 2 in fact fully _a, I _b, I _cThe sector at space vector place and in this sector the size of each vector component, but method is simply many.

Now determine method with the digital example detailed description universal pulse width duty ratio of the present invention that is controlled to be of PMSM (three-phase permanent magnet synchronous motor).

Fig. 4 shows PMSM three-phase stator winding model.Among the figure, three phase windings are represented with symbol A, B, C respectively, U _a, U _b, U _cExpression is added to the phase voltage of A, B, C three phase windings respectively; I _a, I _b, I _cThe phase current of A, B, C three phase windings is flow through in expression respectively, and its positive direction is defined as the inflow winding; Z _a, Z _b, Z _cRepresent the impedance of A, B, C three phase windings respectively, be made as three-phase symmetric winding, Z is arranged _a=Z _b=Z _c=Z.According to voltage-current relationship, can set up following equation:

$I_a=\frac{2U_a-U_b-U_c}{3Z}$

$I_b=\frac{{2U}_b-U_a-U_c}{3Z}---\left(5\right)$

$I_c=\frac{{2U}_c-U_a-U_b}{3Z}$

If voltage-source type DC power supply busbar voltage is from U to-U,, have according to impulse principle

U _a＝Uk _a

U _b＝Uk _b

(6)

U _c＝Uk _c

-1≤k _a，k _b，k _c≤1

In the formula, k _a, k _b, k _cBe respectively the duty ratio of three phase inverter bridge, then equation (5) can turn to

$I_a=\frac{{2k}_a-k_b-k_c}{3}\&CenterDot;\frac{U}{Z}$

$I_b=\frac{{2k}_b-k_a-k_c}{3}\&CenterDot;\frac{U}{Z}---\left(7\right)$

$I_c=\frac{{2k}_c-k_a-k_b}{3}\&CenterDot;\frac{U}{Z}$

With the three-phase current I in the formula (7) _a, I _b, I _cWith U/Z normalization, can get

$I_a=\frac{{2k}_a-k_b-k_c}{3}$

$I_b=\frac{{2k}_b-k_a-k_c}{3}$

$I_c=\frac{{2k}_c-k_a-k_b}{3}$

-1≤I _a，I _b，I _c?≤1

The purpose of this method is according to given motor phase current, determines three-phase voltage duty ratio k _a, k _b, k _cCan get by formula (8)

k _a＝I _a-I _b+k _b＝I _ab+k _b

k _b＝I _b-I _c+k _c＝I _bc+k _c (9)

k _c＝I _c-I _a+k _a＝I _ca+k _a

According to given phase current, the group of solving an equation (9) can get each phase duty ratio k _a, k _b, k _cBecause the three-phase current sum is zero, equation group (9) is by three unknown number k of two equation solutions in essence _a, k _b, k _c, exist no array to separate.For example, a kind of simple method for solving is to make k _a=I _a, k _b=I _b, k _c=I _c, traditional SPWM method that Here it is.But also just because of k _a, k _b, k _cHave or not array to separate, wherein must have one group to be optimum.

According to the PMSM stator current is the three-phase sine-wave of 120 ° of phase phasic differences

I _a＝cos(ωt)

$I_b=\cos (\mathrm{\&omega;t}-\frac{2\mathrm{\&pi;}}{3})---\left(10\right)$

$I_c=\cos (\mathrm{\&omega;t}-\frac{4\mathrm{\&pi;}}{3})$

Can get

$I_{\mathrm{ab}}=I_a-I_b=\sqrt{3}\cos (\mathrm{\&omega;t}+\frac{\mathrm{\&pi;}}{6})$

$I_{\mathrm{bc}}=I_b-I_c=\sqrt{3}\cos (\mathrm{\&omega;t}+\frac{9\mathrm{\&pi;}}{6})---\left(11\right)$

$I_{\mathrm{ca}}=I_c-I_a=\sqrt{3}\cos (\mathrm{\&omega;t}+\frac{5\mathrm{\&pi;}}{6})$

The every phase current that formula (10) and (11) are represented and the change curve of every biphase current difference are as shown in Figure 3.

According to formula (8), in order to bring into play the utilance of DC power supply, k _a, k _b, k _cThe three should be not simultaneously for just or simultaneously for negative, and should make its absolute value big as much as possible.Based on this,, can select I by formula (9) _Ab, I _Bc, I _CaOf absolute value maximum, maximum thus one begins to calculate each duty ratio.

For example, establish max{|I _Ab|, | I _Bc|, | I _Ca|=| I _Ab|, then can select k _b=-k _a, can get by formula (9)

$k_a=\frac{{\mathrm{<figure-callout\; id="2"\; label="I\; ab"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">I</figure-callout>}}_{\mathrm{ab}}}{2}$

k _b＝-k _a (12)

$k_c=\frac{{3I}_{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">c</figure-callout>}}}{2}$

With formula (12) substitution formula (8), can get three-phase current and equate with set-point, the three-phase duty ratio that draws thus is equivalent to traditional SPWM method.

But by formula (11) as can be known, $\left|I_{\mathrm{ab}}\right|\max =\sqrt{3},$ Therefore $\left|k_a\right|\max =\frac{\sqrt{3}}{2}<1,$ In order to improve the voltage utilization of dc inverter, should make | k _a| max=1, the three-phase duty ratio that is about to formula (12) multiply by proportionality coefficient respectively $p=\frac{2}{\sqrt{3}},$ Promptly

$k_a=\mathrm{<figure-callout\; id="2"\; label="p\; I\; ab"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">p</figure-callout>}\frac{I_{\mathrm{ab}}}{}\frac{{}_{}}{2}=\frac{2}{\sqrt{3}}\frac{{\mathrm{<figure-callout\; id="2"\; label="I\; ab"\; filenames="A2009100889510019H1.png,A2009100889510020H1.png"\; state="\{\{state\}\}">I</figure-callout>}}_{\mathrm{ab}}}{2}=\frac{I_{\mathrm{ab}}}{\sqrt{3}}$

k _b＝-k _a (13)

$k_c=p\frac{{3I}_c}{2}=\frac{2}{\sqrt{3}}\frac{{3I}_c}{2}=\sqrt{3}{I}_c$

In like manner, if max{|I _Ab|, | I _Bc|, | I _Ca|=| I _Bc|, then select the three-phase duty ratio

$k_b=\frac{I_{\mathrm{bc}}}{\sqrt{3}}$

k _c＝k _b (14)

$k_a=\sqrt{3}{I}_a$

If max{|I _Ab|, | I _Bc|, | I _Ca|=| I _Ca|, then select the three-phase duty ratio

$k_c=\frac{I_{\mathrm{ca}}}{\sqrt{3}}$

k _a＝-k _c (15)

$k_b=\sqrt{3}{I}_b$

So handle, the dc inverter voltage utilization can be risen to original $\frac{2}{\sqrt{3}}=1.1547$ Doubly.In this sense, the three-phase duty ratio that draws thus is equivalent to the SVPWM method.

Only comprise arithmetic in all computing formula of said method, its realization flow determines that with resolution of vectors between six sector null that Fig. 5 represents the computing formula of three-phase duty ratio compares with realization flow as shown in Figure 6, and is simply many.

Adopt resolution of vectors method and method of the present invention between six sector null to implement the SVPWM control of three-phase permanent magnet synchronous motor respectively, the hardware environment that two kinds of methods are implemented is identical, is

Hardware environment: TMS320F2812, dominant frequency 150MHz;

Programming language: C language;

Development environment: CCS3.1 (Code Composer Studio).

Provide the code of the inventive method below respectively and based on the SVPWM duty ratio Accounting Legend Code of resolution of vectors method between six sector null, for reference.Both call parameters are all A phase, the B phase current I of motor _a, I _b, result of calculation is the SVPWM duty ratio.

The code of the inventive method:

struct{

_iq?Ta；

_iq?Tb；

_iq?Tc；

}PWM；

void?mysvgen(_iq?Ia，_iq?Ib，PWM*v)

{

_iq?Va，Vb，Vc；

_iq?m；

Vc＝-Ia-Ib；

v-＞Ta＝Ia-Ib；

v-＞Tb＝Ib-Vc；

v-＞Tc＝Vc-Ia；

Va＝_IQabs(v-＞Ta)；

Vb＝v-＞Ta；

m＝0；

if(Va＜_IQabs(v-＞Tb))

{

Va＝_IQabs(v-＞Tb)；

Vb＝v-＞Tb；

Vc＝Ia；

m＝1；

}

if(Va＜_IQabs(v-＞Tc))

{

Vb＝v-＞Tc；

Vc＝Ib；

m＝2；

}

Vb＝_IQmpy(Vb，_IQ(0.57735026918963))；

Va＝-Vb；

Vc＝_IQmpy(Vc，_IQ(1.73205080756887))；

if(m＝＝0)

{

v-＞Ta＝Vb；

v-＞Tb＝Va；//v-＞Ta；

v-＞Tc＝Vc；

}

else?if(m＝＝1)

{

v-＞Tb＝Vb；

v-＞Tc＝Va；//v-＞Tb；

v-＞Ta＝Vc；

}

else

{

v-＞Tc＝Vb；

v-＞Ta＝Va；

v-＞Tb＝Vc；

}

}

SVPWM duty ratio Accounting Legend Code based on resolution of vectors method between six sector null:

struct{

_iq?Ta；

_iq?Tb；

_iq?Tc；

}PWM；

void?svgen_sector(_iq?Ia，_iq?Ib，PWM*v)

{

_iq?Va，Vb，Vc，t1，t2；

_iq?sector＝0；

Va＝_IQmpy(Ia，_IQ(0.57735026918963))+_IQmpy(Ib，_IQ(1.15470053837926))；

Vb＝_IQmpy(Ia-Ib，_IQ(0.57735026918963))；

Vc＝-Va-Vb；

/ * 60 degree sectors judgement */

if(Va＞_IQ(0))

{

sector＝1；

}

if(Vb＞_IQ(0))

{

sector＝sector+2；

}

if(Vc＞_IQ(0))

{

sector＝sector+4；

}

If (sector==1)/* sector 1*/

{

t1＝-Vb；

t2＝-Vc；

v-＞Tb＝_IQmpy(_IQ(0.5)，(_IQ(1)-t1-t2))； /*tbon＝(1-t1-t2)/2*/

v-＞Ta＝v-＞Tb+t1； /*taon＝tbon+t1*/

v-＞Tc＝v-＞Ta+t2； /*tcon＝taon+t2*/

}

Else if (sector==2)/* sector 2*/

{

t1＝-Vc；

t2＝-Va；

v-＞Ta＝_IQmpy(_IQ(0.5)，(_IQ(1)-t1-t2))； /*taon＝(1-t1-t2)/2*/

v-＞Tc＝v-＞Ta+t1； /*tcon＝taon+t1*/

v-＞Tb＝v-＞Tc+t2； /*tbon＝tcon+t2*/

}

Else if (sector==3)/* sector 3*/

{

t1＝Vb；

t2＝Va；

v-＞Ta＝_IQmpy(_IQ(0.5)，(_IQ(1)-t1-t2))； /*taon＝(1-t1-t2)/2*/

v-＞Tb＝v-＞Ta+t1； /*tbon＝taon+t1*/

v-＞Tc＝v-＞Tb+t2； /*tcon＝tbon+t2*/

}

Else if (sector==4)/* sector 4*/

{

t1＝-Va；

t2＝-Vb；

v-＞Tc＝_IQmpy(_IQ(0.5)，(_IQ(1)-t1-t2))； /*tcon＝(1-t1-t2)/2*/

v-＞Tb＝v-＞Tc+t1； /*tbon＝tcon+t1*/

v-＞Ta＝v-＞Tb+t2； /*taon＝tbon+t2*/

}

Else if (sector==5)/* sector 5*/

{

t1＝Va；

t2＝Vc；

v-＞Tb＝_IQmpy(_IQ(0.5)，(_IQ(1)-t1-t2))； /*tbon＝(1-t1-t2)/2*/

v-＞Tc＝v-＞Tb+t1； /*tcon＝tbon+t1*/

v-＞Ta＝v-＞Tc+t2； /*taon＝tcon+t2*/

}

Else if (sector==6)/* sector 6*/

{

t1＝Vc；

t2＝Vb；

v-＞Tc＝_IQmpy(_IQ(0.5)，(_IQ(1)-t1-t2))； /*tcon＝(1-t1-t2)/2*/

v-＞Ta＝v-＞Tc+t1； /*taon＝tcon+t1*/

v＞Tb＝v-＞Ta+t2； /*tbon＝taon+t2*/

}

else

{

v-＞Ta＝_IQ(0.5)；

v-＞Tb＝_IQ(0.5)；

v-＞Tc＝_IQ(0.5)；

}

v-＞Ta＝_IQmpy(_IQ(2)，(v-＞Ta-_IQ(0.5)))；

v-＞Tb＝_IQmpy(_IQ(2)，(v-＞Tb-_IQ(0.5)))；

v-＞Tc＝_IQmpy(_IQ(2)，(v-＞Tc-_IQ(0.5)))；

}

Two kinds of comparisons of calculating SVPWM duty ratio method: result of implementation shows, the three-phase pulse duty cycle that draws under the identical condition of given motor phase current is identical, it is identical promptly to control effect, but the executable code length that realizes the inventive method has only 1/4 of conventional six sector resolution of vectors methods, operational efficiency has but improved 17%, the hardware resource of being saved takies and can be used to improve the SVPWM control performance, has objectively played the effect that improves the system hardware performance.Like this, method of the present invention uses common dsp processor can obtain high-precision SVPWM control.

Claims (5)

1. one kind is used for three-phase AD motor PWM (pulse width modulation) control, can realize that the universal pulse width duty ratio that comprises SPWM (sinusoidal pulse width modulation) control mode and SVPWM (space vector pulse width modulation) control mode determines method, comprises step:

Determine the normalization three-phase current set-point I of described three-phase alternating-current motor _a, I _b, I _c(1≤I _a, I _b, I _c≤ 1);

It is characterized in that also comprising step:

According to described normalization three-phase current set-point I _a, I _b, I _cCalculate every biphase current difference I of normalization three-phase current according to formula (1) _Ab, I _Bc, I _Ca

I _ab＝I _a-I _b

$I_{\mathrm{bc}}=I_b-I_{c_c}---\left(1\right)$

I _ca＝I _c-I _a

Calculate every biphase current difference I of described normalization three-phase current _Ab, I _Bc, I _CaAbsolute value | I _Ab|, | I _Bc|, | I _Ca| maximum max{|I _Ab|, | I _Bc|, | I _Ca|;

As described maximum max{|I _Ab|, | I _Bc|, | I _Ca| be described A, B biphase current difference I _AbAbsolute value | I _Ab| the time, by formula (2) calculate described three-phase pulse duty ratio k _a, k _b, k _c:

$k_a=p\frac{I_{\mathrm{ab}}}{2}$

k _b＝-k _a (2)

$k_c=p\frac{3I_c}{2}$

As described maximum max{|I _Ab|, | I _Bc|, | I _Ca| be described B, C biphase current difference I _BcAbsolute value | I _Bc| the time, by formula (3) calculate described three-phase pulse duty ratio k _a, k _b, k _c:

$k_b=p\frac{I_{\mathrm{bc}}}{2}$

k _c＝-k _b (3)

$k_a=p\frac{{3I}_a}{2}$

As described maximum max{|I _Ab|, | I _Bc|, | I _Ca| be described C, A biphase current difference I _CaAbsolute value | I _Ca| the time, by formula (4) calculate described three-phase pulse duty ratio k _a, k _b, k _c:

$k_c=p\frac{I_{\mathrm{ca}}}{2}$ (4)

k _a＝-k _c

$k_b=p\frac{3I_b}{2}$

In described formula (2), (3) and (4), p is a proportionality coefficient, $1\&le;p\&le;\frac{2}{\sqrt{3}}.$

2. determine method according to the universal pulse width duty ratio of claim 1, it is characterized in that when adopting described SPWM control mode the proportionality coefficient p=1 in wherein said formula (2), (3) and (4).

3. determine method according to the universal pulse width duty ratio of claim 1, it is characterized in that when adopting described SVPWM control mode the proportionality coefficient in wherein said formula (2), (3) and (4) $p=\frac{2}{\sqrt{3}}.$

4. determine method according to the universal pulse width duty ratio of each claim in the claim 1 to 3, it is characterized in that wherein said three-phase alternating-current motor is a turning motor.

5. determine method according to the universal pulse width duty ratio of each claim in the claim 1 to 3, it is characterized in that wherein said three-phase alternating-current motor is a linear motor.

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