CN104917437A - Control method of asymmetric four-section SVPWM (space vector pulse width modulation) technology for three-phase motor - Google Patents

Abstract

The invention relates to a control method of an asymmetric four-section SVPWM (space vector pulse width modulation) technology for a three-phase motor. The three-phase motor comprises a three-phase motor body and six switching devices connected with the three-phase motor body, the six switching devices of the motor with three phases A, B and C have eight switching states 000, 001, 010, 011, 100, 101, 110 and 111 which are represented by eight vector voltages including U1, U2, U3, U4, U5, U6, U7 and U8 respectively, wherein the U1 and the U8 are zero vectors, and the rest U2-U7 are non-zero vectors. The six non-zero vector voltages are divided into vector spaces of six sectors I-VI. The vectors U1, U5 and U7 are used in the sector I, the vectors U1, U7 and U3 are used in the sector II, the vectors U1, U3 and U4 are used in the sector III, the vectors U1, U4 and U2 are used in the sector IV, the vectors U1, U2 and U6 are used in the sector V, and the vectors U1, U6 and U5 are used in the sector VI. The control method has the advantages that switching frequency can be decreased, switching loss is reduced, the maximum modulation ratio can be increased and the like.

Description

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

Technical field

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

Background technology

At present, SVPWM technology is most widely used modulation technique in Electric Machine Control.Conventional SVPWM can be divided into again five-part form and seven segmentations two kinds.The switching loss of five-part form and seven segmentation SVPWM is higher.In addition, the maximum modulation of five-part form SVPWM tri-resistor current sampling plan is about 99%; The maximum modulation of seven segmentation SVPWM tri-resistor current sampling plans is about 95%.Low at ask for something input voltage, the application scenario that motor output speeds is high, the maximum modulation of five-part form and seven segmentation SVPWM can not meet application requirement.

Summary of the invention

For the problems referred to above, the object of this invention is to provide one and both can reduce on-off times, reduce switching loss, the control method of the asymmetric four-part form SVPWM technology of maximum modulation can be improved again.

Realize technical scheme of the present invention as follows:

For a control method for the asymmetric four-part form SVPWM technology of three phase electric machine, comprise three phase electric machine

And coupled six switching devices, comprise the following steps;

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

Step 2: according to the voltage given under alpha-beta coordinate, calculates t1 and t2 and the sector at voltage vector place action time of two non-zero;

Step 3: according to sector, and t1 and t2 action time of two non-zero, calculate the comparison value of A, B, C two-levels three-phase PWM generator;

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

Note: Tpwm is the cycle of a PWM;

Step 4: overflow on the timer and upgrade the comparison value of two-levels three-phase PWM generator with the underflow point of interruption;

Step 5: the operating state carrying out selector switch device according to the comparative result of step 3 and step 4.

Have employed above-mentioned scheme, the present invention utilizes the comparison value of A, B, C two-levels three-phase PWM generator to carry out the using state of selector switch, to ensure can there be the sufficiently long time when sampling phase current, the result of such sampling is more accurate, the phase current of cannot sampling to prevent the time too short, even in higher modulation ratio, also has time enough to sample, also reduce the access times of the switching device within a PWM cycle simultaneously, reduce its loss.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the inventive method;

Fig. 2 be the inventive method in the same PWM cycle, the oscillogram of seven segmentation SVPWM, conventional five-part form SVPWM and asymmetric four-part form SVPWM;

Fig. 3 is the inventive method contrast table corresponding with Fig. 2;

Fig. 4 is the inventive method four-part form SVPWM oscillogram when 0 sector;

Fig. 5 is fundamental space voltage vector-diagram corresponding to the inventive method

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is further described.

Electric Machine Control needs the phase current using motor.In low-power machine controls, generally adopt resistance to obtain electric machine phase current.As shown in Figure 1, when switch Q4 opens, resistance R1 upper reaches overcurrent, on resistance R1, coating-forming voltage falls.This voltage drop and the proportional relation of motor A phase current.When in like manner switch Q5 opens, the voltage drop on resistance R2 and the proportional relation of B phase current; When switch Q6 opens, the voltage drop on resistance R3 and the proportional relation of C phase current.

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

Step 2: according to the voltage given under alpha-beta coordinate, gets 001 and 101 these two voltage vectors, and is respectively t1 and t2 the action time of these two voltage vectors within the PWM cycle of sector IV.

As Fig. 2 and Fig. 3, switch on the bridge oscillogram in seven segmentation SVPWM mono-PWM cycles.An one PWM periodic voltage vector sequence of operation is 000,001,101,111,101,001,000, and on-off times is seven times.

Switch on the bridge oscillogram in the conventional PWM cycle of five-part form SVPWM.An one PWM periodic voltage vector sequence of operation is 000,001,101,001,000, and on-off times is five times.

Switch on the bridge oscillogram in the PWM cycle of asymmetric four-part form SVPWM.An one PWM periodic voltage vector sequence of operation is 000,001,101,000, and on-off times is four times.

As can be seen from above contrast, asymmetric four-part form SVPWM will lack compared with seven segmentation SVPWM and conventional five-part form SVPWM on-off times within a PWM cycle, has the advantages that to reduce switching loss.

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

The phase current sampling time comprises the AD sampling time, dead band affects the sampling stand-by period, the bridge switch pipe ON time that cause and wait for time of current stabilization.Assuming that this phase current sampling time is ts.

When modulation ratio increases, the action time of Zero voltage vector shortens, and the action time of 000 voltage vector also shortens thereupon.When being less than ts the action time of the left side 000 voltage vector, just cannot sampling and obtaining phase current.

According to Fig. 2 and 3, the action time of the five-part form SVPWM left side 000 voltage vector is 2 times of seven segmentations.Therefore five-part form SVPWM can obtain higher modulation ratio.When modulation ratio continues to increase, now 000 voltage vector on the five-part form SVPWM left side is also less than ts action time, and cannot sample obtains phase current.At this moment need, at 001 sampling of voltage vector district A, B biphase current, then according to the formula of Ia+Ib+Ic=0, to calculate C phase current.For conventional five-part form SVPWM, the action time of its left side 001 voltage vector is t1/2, and the action time of its left side 001 voltage vector of asymmetric four-part form SVPWM is t1.Therefore asymmetric four-part form SVPWM can more high modulation than time, sampling obtains phase current.

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

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

Note: Tpwm is the cycle of a PWM;

Step 4: overflow on the timer and upgrade the comparison value of two-levels three-phase PWM generator with the underflow point of interruption;

Step 5: the operating state carrying out selector switch device according to the comparative result of step 3 and step 4.

Claims (1)

1., for a control method for the asymmetric four-part form SVPWM technology of three phase electric machine, comprise three phase electric machine and coupled six switching devices, it is characterized in that: comprise the following steps;

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

Step 2: according to the voltage given under alpha-beta coordinate, calculates t1 and t2 and the sector at voltage vector place action time of two non-zero;

Step 3: according to sector, and t1 and t2 action time of two non-zero, calculate the comparison value of A, B, C two-levels three-phase PWM generator;

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

Note: Tpwm is the cycle of a PWM;

Step 4: overflow on the timer and upgrade the comparison value of two-levels three-phase PWM generator with the underflow point of interruption;

Step 5: the operating state carrying out selector switch device according to the comparative result of step 3 and step 4.