CN106655915A - Method for acquiring compensating voltage restraining commutation torque pulsation device of brushless direct-current motor - Google Patents

Abstract

The invention belongs to the field of brushless direct-current motor control, and particularly relates to a method for acquiring compensating voltage restraining a commutation torque pulsation device of a brushless direct-current motor. In a non-commutation period, a first switch T1 is switched off, a second switch T2 is switched up, a power supply charges a boosting capacitor to enable the compensating voltage Uc=Ubus-Udc, and when charging is over, the second switch T2 is switched off, when commutation starts, the first switch T1 is switched on, a diode is switched off, the power supply and the capacitor are connected serially so as to supply power to the brushless direct-current motor until commutation is over, and when voltage of the capacitor drops and commutation is cover, bus voltage is equal to four times of a counter electromotive force amplitude, namely Ubus=4E. In a commutation period, a phase power device can be switched on without modulating the bus voltage by chopping, so that generation of direct-current bus voltage fluctuation caused by reverse bus current is avoided, switch loss and switch interference are reduced. The method for acquiring the compensating voltage restraining the commutation torque pulsation device of the brushless direct-current motor is low in data acquisition amount and has a certain engineering application value.

Description

It is a kind of to suppress the offset voltage of brshless DC motor commutation torque ripple device to obtain Method

Technical field

The invention belongs to brshless DC motor control field, and in particular to one kind suppresses brshless DC motor commutation torque arteries and veins The offset voltage acquisition methods of dynamic device.

Background technology

Brshless DC motor is because its is reliable, dynamic response is fast, efficiency high, little noise, the speed of service width the features such as quilt It is widely used in various industrial circles, such as automotive electronics, medicine equipment, industrial automation equipment and instrument and meter etc..But, Due to electric machine structure feature and uniqueness commutation control strategy cause motor torque pulsation occur in commutation, have impact on direct current without Application of the brush motor in high-performance field.

Machine winding is perceptual device, and electric current raising and lowering can not be completed instantaneously during commutation, cause ascending current and under Drop electric current reaches the Time Inconsistency of stable state, changes non-converting commutating current amplitude, so as to produce commutation torque ripple.

The method of DC brushless motor commutation torque ripple is suppressed to be broadly divided at present：Direct Torque, intelligent algorithm, switch Modulation method and switch converters method etc..Direct Torque method is with torque as controlled quentity controlled variable；Intelligent algorithm, obtains high precision, but obtains Taken amount is big；Switch modulation method is to use various modulator approaches to reduce torque pulsation, but when much modulation strategy can postpone commutation Between；Switch converters method is that switch converters are installed between power supply and inverter, and busbar voltage, commutation performance are improved during commutation It is good, but it is relatively costly.

The content of the invention

It is an object of the invention to provide a kind of suppress the offset voltage of brshless DC motor commutation torque ripple device to obtain Take method,

The object of the present invention is achieved like this：

During non-commutation, first switch T1 cut-off, second switch T2 conductings, power supply to boost capacitor charges to offset voltage U_c=U_bus-U_dc, after charging terminates, second switch T2 cut-offs；When commutation starts, the conducting of first switch T1, diode cut-off, electricity Supply power to commutation to motor after source and capacitances in series to terminate, capacitance voltage declines, at the end of commutation, busbar voltage be equal to 4 times it is anti- Electromotive force amplitude U_bus=4E；

Offset voltage acquisition methods are as follows

AC=U_A-U_C=U_bus-4E

Wherein, U_busFor busbar voltage, U_cFor offset voltage, U_dcFor supply voltage, E is back-emf, and I is phase current, t_fFor Commutation time, L is winding inductance.

The beneficial effects of the present invention is：

1st, in commutation process, phase power device is turned on without the need for chopping modulation busbar voltage, so will not produce by reverse mother The DC bus-bar voltage fluctuation that line current is caused.

2nd, switching loss and switch interference are reduced.

3rd, formula amount to obtain is little, with certain engineering application value.

Description of the drawings

Fig. 1 is brshless DC motor commutation torque ripple restraining device schematic diagram.

Fig. 2 is T2-ON, T1-OFF；T2-OFF, T1-OFF；T2-OFF, T1-ON fundamental diagram.

Fig. 3 offset voltages obtain schematic diagram.

Fig. 4 busbar voltages, phase current, bus current, torque profile figure (busbar voltage U_bus=345V).

Fig. 5 busbar voltages, phase current, bus current, torque profile figure (busbar voltage U_bus=391V).

Specific embodiment

Below in conjunction with the accompanying drawings the present invention will be further described：

Offset voltage is obtained according to the method for tangent trigonometric function, busbar voltage is anti-equal to 4 times electronic at the end of making commutation Gesture amplitude, converting commutating current reaches steady-state value simultaneously, reduces non-converting commutating current fluctuation, effectively suppresses commutation torque ripple.

The purpose of the present invention is realized by following technical proposal：

Operation principle：During non-commutation, T1 cut-offs, T2 conductings, power supply to boost capacitor charges to offset voltage U_c= U_bus-U_dc, after charging terminates, T2 cut-offs；When commutation starts, T1 conductings, diode cut-off, to motor after power supply and capacitances in series Supply power to commutation to terminate, capacitance voltage declines, at the end of commutation, busbar voltage is equal to 4 times of counter electromotive force amplitude (U_bus=4E).

Offset voltage acquisition methods are as follows, as shown in Figure 3.

AC=U_A-U_C=U_bus-4E (2)

By formula (1)-(3), shown in offset voltage such as formula (4).

Wherein, U_busFor busbar voltage, U_cFor offset voltage, U_dcFor supply voltage, E is back-emf, and I is phase current, t_fFor Commutation time, L is winding inductance.

By taking AC phases commutation to BC phases as an example.During non-commutation, T2 conductings, T1 cut-offs, according to formulaBoost capacitor is charged, shown in such as Fig. 2 (a)；After charging terminates, T2 cut-offs, meanwhile, Power supply is powered by VT1, VT2 to motor, such as shown in Fig. 2 (b).When commutation starts, T1 conductings, diode cut-off, capacitances in series Enter bus by powering to motor.A phases are turned off, by VD4, VT2 afterflow, until A phase currents decay to 0；B is conducted, and passes through VT2, VT3 to motor is powered, until C phase currents reach steady-state value I, shown in such as Fig. 2 (c).The commutation stage, under boost capacitor voltage Drop, when busbar voltage is equal to 4 times of counter electromotive force amplitudes, commutation terminates.

The embodiment of the present invention is used for explaining the present invention, rather than limits the invention, in the spirit and right of invention In the protection domain of requirement, any modifications and changes made to the present invention both fall within protection scope of the present invention.

Embodiment

Brshless DC motor is operated under conduction mode two-by-two, by taking AC commutations to BC as an example, during non-commutation, according to public affairs FormulaBoost capacitor is charged, during commutation, boost capacitor is motor with power sources in series Power supply, capacitance voltage declines, at the end of commutation, busbar voltage U_bus=4E, wherein U_bus=U_dc+U_c, U_busFor busbar voltage, U_dc For supply voltage, U_cFor capacitance voltage, E is back-emf, and I is phase current.

The present invention adopts the parameter of brshless DC motor：

According to formulaIdeal compensation voltage U_cFor 91V.

In Fig. 4, busbar voltage U during commutation_bus=345V, now boost capacitor offset voltage U_c=U_bus-U_dc=345-300 =45V, less than ideal compensation voltage 91V.Now, torque minimum of a value is 20N*m in commutation process, and average torque is 22N*m, is turned Square stability bandwidth is 9.1%.

In Fig. 5, busbar voltage U during commutation_bus=391V, now boost capacitor offset voltage U_c=U_bus-U_dc=391-300 =91V, is ideal compensation voltage.Now, torque minimum of a value is 21.5N*m in commutation process, and average torque is 22N*m, torque Stability bandwidth is 2.3%, with U_cThe non-ideal offset voltages of=45V are compared, and torque pulsation reduces 6.8%.

This method using tangent trigonometric function method obtain offset voltage, make in commutation process turn on phase power device without Need modulation, it is to avoid produce the DC bus-bar voltage caused by reverse bus current and fluctuate, reduce switching loss and switch interference, Amount to obtain is little, with good engineering application value.

Claims (1)

1. it is a kind of suppress brshless DC motor commutation torque ripple device offset voltage acquisition methods, it is characterised in that：

During non-commutation, first switch T1 cut-off, second switch T2 conductings, power supply to boost capacitor charges to offset voltage U_c= U_bus-U_dc, after charging terminates, second switch T2 cut-offs；When commutation starts, first switch T1 conducting, diode cut-off, power supply with Commutation is supplied power to after capacitances in series to motor to terminate, capacitance voltage declines, at the end of commutation, busbar voltage is anti-equal to 4 times electronic Gesture amplitude U_bus=4E；

Offset voltage acquisition methods are as follows

$\frac{AC}{CB}=tan\mathrm{\θ}=\frac{2(U_{bus}-E)}{3L}$

AC=U_A-U_C=U_bus-4E

$CB=t_f=\frac{3LI}{U_{bus}+2E}$

$U_c=E+I+\sqrt{9E^2+I^2}-U_{dc}$

Wherein, U_busFor busbar voltage, U_cFor offset voltage, U_dcFor supply voltage, E is back-emf, and I is phase current, t_fFor commutation Time, L is winding inductance.