CN104917437B - A kind of control method of asymmetric four-part form SVPWM technologies for three phase electric machine - Google Patents

Abstract

The present invention relates to a kind of control method of the asymmetric four-part form SVPWM technologies for three phase electric machine, including three phase electric machine and coupled six switching devices, the on off state of six switching devices of the motor with A, B, C three-phase has 000,001,010,011,100,101,110,111 8 kind, represented respectively with eight vector voltages of U1, U2, U3, U4, U5, U6, U7, U8, wherein U1 and U8 is zero vector, remaining six U2 U7 is non-zero；Six non-zero voltages are divided into the vector space of I VI 6 sectors within an electric cycle, vector used in I sector is U1, U5, U7, vector used in II sector is U1, U7, U3, vector used in III sector is U1, U3, U4, vector used in IV sector is U1, U4, U2, vector used in V sector is U1, U2, U6, and vector used in VI sector is U1, U6, U5；The present invention has the features such as can both reducing on-off times, reducing switching loss, and can improve maximum modulation.

Description

A kind of control method of asymmetric four-part form SVPWM technologies for three phase electric machine

Technical field

The present invention relates to motor control technology field, more particularly to a kind of asymmetric four-part form for three phase electric machine The control method of SVPWM technologies.

Background technology

At present, SVPWM technologies are most widely used modulation techniques in motor control.Common SVPWM can be divided into again Two kinds of five-part form and seven segmentations.The switching loss of five-part form and seven segmentation SVPWM are higher.In addition, tri- resistance of five-part form SVPWM is electric The maximum modulation of sampling plan is flowed 99% or so；The maximum modulation of seven segmentation SVPWM, tri- resistor current sampling plans exists 95% or so.Require input voltage low at some, the high application scenario of motor output speeds, five-part form and seven segmentation SVPWM's Maximum modulation can not meet application requirement.

The content of the invention

In view of the above-mentioned problems, can both reduce on-off times the object of the present invention is to provide a kind of, switching loss is reduced, again The control method of the asymmetric four-part form SVPWM technologies of maximum modulation can be improved.

Realize that technical scheme is as follows：

A kind of control method of asymmetric four-part form SVPWM technologies for three phase electric machine, including three phase electric machine

And six coupled switching devices, comprise the following steps；

Step 1：The on off state of six switching devices of the motor with A, B, C three-phase has 000,001,010,011, 100th, 101,110,111 8 kind, represented respectively with eight vector voltages of U1, U2, U3, U4, U5, U6, U7, U8, wherein U1 and U8 For zero vector, remaining six U2-U7 is non-zero；Six non-zero voltages are divided into I-VI six fan within an electric cycle The vector space in area, an electric cycle is 360 °, and each sector is 60 °, and only uses U1 and 2 non-null vector in each sector Amount, vector used in I sector is U1, U5, U7, and vector used in II sector is U1, U7, U3, and vector used in III sector is U1, U3, U4, Vector used in IV sector is U1, U4, U2, and vector used in V sector is U1, U2, U6, and vector used in VI sector is U1, U6, U5；

Step 2：Given according to the voltage under alpha-beta coordinate, calculate the action time t1 and t2 and voltage of two non-zeros Sector where vector；

Step 3：According to sector, and the action time t1 and t2 of two non-zeros, calculate A, B, C three-phase PWM and occur The fiducial value of device；

The fiducial value of the generator of each sector is as follows：

Note：Tpwm is the cycle of a PWM；

Step 4：The fiducial value to overflow on the timer with underflow point of interruption renewal two-levels three-phase PWM generator；

Step 5：According to the comparative result of step 3 and step 4 come the working status of selecting switch device.

Above-mentioned scheme is employed, the present invention is using the fiducial value of A, B, C two-levels three-phase PWM generator come the use of selecting switch State, to ensure can there is the sufficiently long time when sampling phase current, the result so sampled is more accurate, to prevent the time It is too short and phase current can not be sampled, even in the modulation ratio of higher, also there is time enough to be sampled, also reduce at the same time The access times of switching device in a PWM cycle, reduce its loss.

Brief description of the drawings

Fig. 1 is the schematic diagram of the method for the present invention；

Fig. 2 is the method for the present invention in same PWM cycle, seven segmentation SVPWM, routine five-part form SVPWM and four sections asymmetric The oscillogram of formula SVPWM；

Fig. 3 is the method for the present invention and the corresponding contrast tables of Fig. 2；

Fig. 4 is the method for the present invention four-part form SVPWM oscillograms at 0 sector；

Fig. 5 is the corresponding fundamental space voltage vector-diagram of the method for the present invention

Embodiment

The present invention is further described with specific embodiment below in conjunction with the accompanying drawings.

Motor control needs to use the phase current of motor.Motor is generally obtained using resistance in low-power machine control Phase current.As shown in Figure 1, when switching Q4 and opening, resistance R1 upstream overcurrent, forms voltage drop on resistance R1.The voltage drop Relation proportional to motor A phase currents.When similarly switch Q5 is opened, the voltage drop relation proportional to B phase currents on resistance R2； When switch Q6 is opened, the voltage drop relation proportional to C phase currents on resistance R3.

Step 1：We represent that upper bridge turns off with numeral 0 now, and numeral 1 represents that upper bridge is open-minded.The Shang Qiao of each phase is with The complementary conducting of bridge.Such as Fig. 5, the on off state with six switching devices of the motor of A, B, C three-phase has eight kinds, uses U1 respectively (000), (111) eight U2 (001), U3 (010), U4 (011), U5 (100), U6 (101), U7 (110), U8 vector voltmeters Show, wherein U1 and U8 are zero vector, remaining six U2-U7 is non-zero；Six non-zero voltages are within an electric cycle It is divided into the vector space of I-VI six sector, an electric cycle is 360 °, and each sector is 60 °, and is only made in each sector With U1 (000) and 2 non-zeros, vector used in I sector is U1, U5, U7, and vector used in II sector is U1, U7, U3, and III fans Vector used in area is U1, U3, U4, and vector used in IV sector is U1, U4, U2, and vector used in V sector is U1, U2, U6, VI sector Vector used is U1, U6, U5；

Step 2：Given according to the voltage under alpha-beta coordinate, 001 and 101 the two electricity are taken in the PWM cycle of sector IV Vector is pressed, and the action time of the two voltage vectors is respectively t1 and t2.

Such as Fig. 2 and Fig. 3, switch on the bridge oscillogram in seven PWM cycles of segmentation SVPWM mono-.One PWM cycle voltage is sweared It is 000,001,101,111,101,001,000 to measure sequence of operation, and on-off times are seven times.

Switch on the bridge oscillogram in conventional mono- PWM cycle of five-part form SVPWM.One PWM cycle voltage vector acts on Order is 000,001,101,001,000, and on-off times are five times.

Switch on the bridge oscillogram in asymmetric mono- PWM cycle of four-part form SVPWM.One PWM cycle voltage vector is made It is 000,001,101,000 with order, on-off times are four times.

Asymmetric four-part form SVPWM exists compared with seven segmentation SVPWM and routine five-part form SVPWM it can be seen from contrast more than On-off times will lack in one PWM cycle, have the characteristics that to reduce switching loss.

We are typically chosen in 000 action time of voltage vector section, the phase current of sample motor.Because in the section, lower bridge Three switching tubes it is all open-minded, can be with the phase current of sampling three-phase.

Sampling stand-by period, bridge switch pipe are led caused by the phase current sampling time includes the AD sampling times, dead band influences Logical time and the time for waiting electric current to stablize.It is assumed that the phase current sampling time is ts.

When modulation ratio increase, the action time of Zero voltage vector shortens, and the action time of 000 voltage vector also becomes therewith It is short.When the action time of 000 voltage vector of the left side being less than ts, can not just sample to obtain phase current.

According to Fig. 2 and 3, the action time of 000 voltage vector of the five-part form SVPWM left sides is 2 times of seven segmentations.Therefore Five-part form SVPWM can obtain the modulation ratio of higher.When modulation ratio continues to increase, 000 voltage on the five-part form SVPWM left sides at this time Vector action time again smaller than ts, can not sample to obtain phase current.At this moment need to sample A, B two in 001 voltage vector area Phase current, then according to the formula of Ia+Ib+Ic=0, is calculated C phase currents.For conventional five-part form SVPWM, its left side The action time of 001 voltage vector is t1/2, and the action time of asymmetric four-part form SVPWM its 001 voltage vector of left side is t1.Therefore asymmetric four-part form SVPWM can be sampled in higher modulation ratio and obtain phase current.

Step 3：Such as Fig. 4 to 5, according to sector, the fiducial value of A, B, C two-levels three-phase PWM generator is calculated；

The fiducial value of the generator of each sector is as follows：

Note：Tpwm is the cycle of a PWM；

Step 4：The fiducial value to overflow on the timer with underflow point of interruption renewal two-levels three-phase PWM generator；

Step 5：According to the comparative result of step 3 and step 4 come the working status of selecting switch device.

Claims (1)

1. a kind of control method of asymmetric four-part form SVPWM technologies for three phase electric machine, including three phase electric machine and and its Six connected switching devices, it is characterised in that：Comprise the following steps；

Step 1：The on off state of six switching devices of the motor with A, B, C three-phase has 000,001,010,011,100, 101st, 110,111 8 kind, represent that wherein U1 and U8 are zero with eight vector voltages of U1, U2, U3, U4, U5, U6, U7, U8 respectively Vector, remaining six U2-U7 are non-zero；Six non-zero voltages are divided into I-VI six sector within an electric cycle Vector space, an electric cycle is 360 °, and each sector is 60 °, and U1 and 2 non-zero is only used in each sector, I Vector used in sector is U1, U5, U7, and vector used in II sector is U1, U7, U3, and vector used in III sector is U1, U3, U4, and IV fans Vector used in area is U1, U4, U2, and vector used in V sector is U1, U2, U6, and vector used in VI sector is U1, U6, U5；

Step 2：Given according to the voltage under alpha-beta coordinate, calculate the action time t1 and t2 and voltage vector of two non-zeros The sector at place；

Step 3：According to sector, and the action time t1 and t2 of two non-zeros, A, B, C two-levels three-phase PWM generator are calculated Fiducial value；

The fiducial value of the generator of each sector is as follows：

Note：Tpwm is the cycle of a PWM；

Step 4：The fiducial value to overflow on the timer with underflow point of interruption renewal two-levels three-phase PWM generator；

Step 5：According to the comparative result of step 3 and step 4 come the working status of selecting switch device.