CN112260601A - Low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method - Google Patents

Low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method Download PDF

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CN112260601A
CN112260601A CN202011049689.9A CN202011049689A CN112260601A CN 112260601 A CN112260601 A CN 112260601A CN 202011049689 A CN202011049689 A CN 202011049689A CN 112260601 A CN112260601 A CN 112260601A
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sampling
phase
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current
permanent magnet
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CN112260601B (en
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童怀
李志忠
黄国宏
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Guangdong University of Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/22—Current control, e.g. using a current control loop

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Abstract

The invention discloses a low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method, which comprises the following steps of: determining the minimum sampling time of single-resistor sampling, and calculating the change curves of the action time of two non-zero voltage vectors corresponding to each sector controlled by vector frequency conversion and the intersection point of the action time at a given low-speed operation node; the motor operates in a no-load mode at the lowest set rotating speed, and whether a low modulation unobservable region reconstructed by single resistance current exists is judged; if the low modulation unobservable region is not entered, obtaining enough sampling time by optimizing a pulse item shifting method; otherwise, increasing the back electromotive force coefficient of the permanent magnet synchronous motor for recalculation; and distributing the three-phase current according to the sector number of the current control iterative operation based on the result of the optimized pulse shift term. According to the method, the single-resistor sampling three-phase current reconstruction is ensured not to enter a low-modulation unobservable region through the optimization of the counter electromotive force coefficient of the motor, and the sampling precision of the three-phase current in the low-speed operation process is improved.

Description

Low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method
Technical Field
The invention relates to the field of motor control, in particular to a phase current reconstruction method of a low-speed running single-resistor sampling permanent magnet synchronous motor.
Background
The permanent magnet synchronous motor has the advantages of simple structure, wide speed regulation range, high power density, high motor efficiency and the like, and is widely applied to the fields of household appliances, fan and pump products and the like at present. The medium and small power permanent magnet synchronous motor driving system has higher requirement on product cost performance, the proportion of a current sampling circuit in the hardware cost of the whole machine cannot be ignored, and a common current sampling method adopts two current sensors to measure phase current, but the method has higher cost. The system structure can be simplified by using resistance sampling, the cost of a hardware circuit is reduced, and the current scheme which is more commonly used is a double-resistance sampling scheme. The single-resistor sampling scheme of the motor phase current can further simplify the hardware circuit layout and reduce the cost, and in recent years, the scheme is more and more emphasized by manufacturers, but the single-resistor sampling needs to reconstruct the three-phase current of the bus current of the driving system, and a blind area, namely an unobservable area, exists in the current reconstruction process, and can be generally divided into a low-modulation unobservable area, a sector transition unobservable area and a high-modulation unobservable area.
Regarding the single-resistor sampling current reconstruction method, when a low-modulation unobservable region and a sector transition unobservable region occur, the traditional pulse phase-shifting method is to fix the widest pulse phase to be unchanged, firstly, the second-time wider pulse phase is shifted backwards for a certain time, and then, on the basis, the narrowest pulse phase is shifted backwards for a certain time, so that two pulse phase shifts are usually needed to be carried out when a group of three-phase current is obtained through sampling, and the two pulse phase shifts cause the three-phase pulse to be seriously asymmetric, thereby causing the waveform of the three-phase current acquired under the low-speed running condition to be distorted.
A single-resistor sampling current reconstruction method is optimized, a single-resistor sampling permanent magnet synchronous motor phase current reconstruction strategy is provided by Huang Keyuan et al in electric power system and its automatic chemistry report (VOL.30, NO.9), measuring pulses are inserted into a low-modulation unobservable region and a medium-modulation unobservable region, and a voltage vector approximation method is adopted in a high-modulation unobservable region, but the method has the defects of long algorithm execution time and complex implementation process; saritha B et al, IEEE Trans on Industrial Electronics (VOL.54, No.5), use a sine curve fitting observer for the unobservable region to approximate the estimated current to the reference sinusoidal three-phase current, but this method relies on motor parameters and does not solve the low speed error problem.
In addition, the existing algorithm for improving the single-resistor sampling precision is complex, the time for the processor to execute the algorithm is long, and the scheme for inhibiting the phase current waveform distortion of the permanent magnet synchronous motor by optimizing the single-resistor sampling current reconstruction algorithm is difficult to implement in a low-cost microprocessor control system. The current waveform distortion of the permanent magnet synchronous motor and the low-speed noise caused by the current waveform distortion limit the popularization and application of a single-resistor sampling scheme.
Disclosure of Invention
The invention aims to provide a low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method, which is used for overcoming the problems existing in the existing single-resistor sampling scheme.
In order to realize the task, the invention adopts the following technical scheme:
a low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method comprises the following steps:
determining the minimum sampling time of single resistance sampling according to the parameters of a single resistance sampling permanent magnet synchronous motor driving system, calculating a change curve of two nonzero voltage vector action times corresponding to each sector controlled by vector frequency conversion at a given low-speed operation node, and calculating the intersection point of the two nonzero voltage vector action times;
the motor operates in a no-load mode at the lowest set rotating speed, and whether a low modulation unobservable region reconstructed by single resistance current exists is judged based on the action time of the two non-zero voltage vectors, the intersection point of the action time and the minimum sampling time;
if the single-resistor current reconstruction does not enter a low-modulation unobservable region, obtaining enough sampling time by optimizing a pulse shifting method; otherwise, the back electromotive force coefficient of the permanent magnet synchronous motor is increased and the method is re-executed;
and distributing the three-phase current according to the sector number of the current control iterative operation based on the result of the optimized pulse shift term.
Further, the determining whether there is a low modulation unobservable region reconstructed by the single resistance current includes:
when in use
Figure BDA0002709169260000021
At any moment, no time appears
Figure BDA0002709169260000022
While being less than TminIn the case of (1), the single-resistance current reconstruction does not have a low modulation unobservable region;
when in use
Figure BDA0002709169260000023
At certain times, certain time instants may occur
Figure BDA0002709169260000024
While being less than TminIn the case of (1), a low modulation unobservable region exists in the single-resistance current reconstruction;
wherein, T1、T2Representing the action time of two non-zero voltage vectors, TcrossIs T1、T2Point of intersection of, TminIs the minimum sampling time.
Further, the specific method for increasing the back electromotive force coefficient of the permanent magnet synchronous motor is as follows:
the number of turns of the motor winding is increased, the wire diameter of the winding is correspondingly reduced, and the back electromotive force coefficient of the permanent magnet synchronous motor is increased under the condition of maintaining the motor slot filling rate basically unchanged.
Further, if the single-resistance current reconstruction does not enter the low modulation unobservable region, the method for optimizing the pulse shift term to obtain the sufficient sampling time comprises the following steps:
when the running speed of the motor is higher than the lowest set rotating speed, the single-resistor current reconstruction can not enter a low-modulation unobservable region but only exists in a sector transition region unobservable region, sufficient sampling time is obtained by optimizing a pulse phase shifting method, the number of pulse shift and the asymmetry of three-phase pulses in the sampling process are reduced, and the reconstruction precision of the three-phase current in the low-speed running single-resistor sampling process is improved.
Further, the method for optimizing the pulse phase shift comprises the following steps:
determining which phase the widest pulse phase, the secondary wide pulse phase and the narrowest pulse phase in the three-phase pulse are respectively according to the sector number of the current control iterative operation;
when in use
Figure BDA0002709169260000031
The widest pulse phase shifts to the left, triggers in advance to obtain enough sampling time, triggers T at the widest pulse phaseminThen starting a first bus current sampling;
when in use
Figure BDA0002709169260000032
The narrowest pulse phase is shifted to the right, delayed triggering is carried out to obtain enough sampling time, and T is triggered in the second-time-width pulse phaseminAnd then starting the second bus current sampling.
Further, the allocating three-phase currents according to the sector number of the current control iterative operation based on the result of the optimized pulse shift term includes:
sampling value I of first-time bus currentad1And negative value-I of second time bus current sampling valuead2And distributing two phases of three-phase currents according to the sector number of the current control iterative operation, wherein the third phase current is a negative value of the sum of the distributed two-phase currents.
A controller comprises a processor, a memory and a computer program stored in the memory, wherein when the computer program is executed by the processor, the steps of the low-speed operation single-resistance sampling permanent magnet synchronous motor phase current reconstruction method are realized.
A computer readable storage medium, having stored thereon a computer program which, when executed by a processor, performs the steps of the low-speed operation single-resistor sampling permanent magnet synchronous motor phase current reconstruction method.
Compared with the prior art, the invention has the following technical characteristics:
the invention has been made by researchVector frequency conversion control two non-zero voltage vector action time T corresponding to each sector1、T2On one hand, the rule of the curve ensures that the single-resistor sampling three-phase current reconstruction does not enter a low-modulation unobservable region through the optimization of the back electromotive force coefficient of the motor, reduces the times of pulse shift in the current sampling process, and eliminates the current waveform distortion existing in the single-resistor sampling scheme; on the other hand, the invention finds out that the single-resistor three-phase current reconstruction only has the sector transition non-observable region but does not have T1[ 2 ] and T 22 is simultaneously less than TminThe method has the advantages that the pulse phase-shifting method is further optimized to obtain enough sampling time, the pulse shifting times and the asymmetry of three-phase pulses in the sampling process are reduced, and the reconstruction precision of three-phase current in the low-speed running single-resistor sampling process is improved.
Drawings
FIG. 1 is a schematic diagram of a single-resistor sampling permanent magnet synchronous motor three-phase current reconstruction;
FIG. 2 is a space voltage vector diagram of a permanent magnet synchronous motor;
FIG. 3 is a PWM waveform diagram of a three-phase current reconstruction observable region;
FIG. 4 is a three-phase current reconstruction shortest sampling time TminA schematic diagram;
FIG. 5 is a schematic diagram of a three-phase current reconstruction non-observable region, wherein (a) is a sector transition non-observable region and (b) is a low modulation non-observable region;
FIGS. 6 (a) and (b) are conventional pulse phase shifting methods;
FIG. 7 is T1、T2Curve simulation oscillogram;
FIGS. 8 (a) and (b) are
Figure BDA0002709169260000041
Shifting the phase of the widest pulse to the left;
FIGS. 9 (a) and (b) are
Figure BDA0002709169260000042
The narrowest pulse is shifted to the right in phase;
FIG. 10 is a control block diagram of a single resistance sampling PMSM system;
FIGS. 11 (a) and (b) shows T before and after Ke optimization1、T2Comparing the curve waveforms;
fig. 12 (a) and (b) are phase current waveforms compared.
Detailed Description
The basic principle of single-resistor sampling permanent magnet synchronous motor three-phase current reconstruction is to sample bus current at different moments in a PWM period and obtain each phase current through phase current reconstruction, as shown in fig. 1, which is a schematic diagram of single-resistor sampling permanent magnet synchronous motor three-phase current reconstruction. The motor controller is controlled by adopting SVPWM modulation mode, as shown in FIG. 2, the space voltage vector diagram corresponding to 7-segment SVPWM of permanent magnet synchronous motor vector control has 8 switch working states including six non-zero voltage vectors V1～V6And two zero voltage vectors V0、V7Which divides the voltage space plane into 6 sectors, each period TsWithin, an arbitrary target voltage vector V in each sectorrefThe non-zero voltage vector and the zero vector of the sector can be synthesized together, and the analysis of the current reconstruction unobservable region firstly needs to calculate the action time T of the non-zero voltage vector corresponding to each sector1、T2Taking sector 1 of fig. 2 as an example, T can be calculated according to the following formula1、T2：
Figure BDA0002709169260000051
Ts＝T0+T1+T2 (2)
Figure BDA0002709169260000052
Figure BDA0002709169260000053
Wherein, TsFor one vector control operation period, sector 1The non-zero voltage vector corresponding to the zone is V4、V6，T0Is a zero voltage vector V0、V7Sum of action times ofdcIs the bus voltage, θrefIs a voltage vector VrefAnd non-zero voltage vector V4The included angle therebetween.
The relationship between the DC bus current and the three-phase current is determined by the state of the instantaneous switching value, the two-phase current is sampled in one PWM period by taking sector 4 of FIG. 2 as an example, as shown in FIG. 3, and the reference voltage vector in FIG. 3 is decomposed into a basic voltage vector V1(001) And V3(011) At a voltage vector V1Bus current I sampled during actiondcCorresponding to the W phase current, at voltage vector V3Bus current I sampled during actiondcCorresponding to the U-phase current.
In practical systems, considering that the sampling of the bus current requires a sufficient sampling window, this requires that the non-zero voltage vector must last for a minimum sampling time Tmin. When the output voltage vector is in a low modulation region or near a non-zero voltage vector, the time that the non-zero voltage vector possibly acts in one PWM period is less than TminThis makes the sampled bus current meaningless, as shown in fig. 4, which is the shortest sampling time T in the actual situationminSchematic representation. T in FIG. 4minThe medicine consists of three parts: dead time TdBus current settling time TsetAnd AD conversion time Tconv，TminThe size is generally 3 mus to 5 mus, which is related as follows:
Tmin＝Td+Tset+Tconv (5)
from FIG. 3, it can be known that it is necessary to ensure that the non-zero voltage vector is in the first half sampling period T to complete the single-resistor sampling current reconstructionsInternal action time greater than TminThat is, it is required to satisfy:
Figure BDA0002709169260000061
the region in which different phase currents cannot be sampled in one PWM period is called an unobservable region, and in practical application, for convenience of processing, the space voltage vector hexagon is specifically divided into an observable region, a low modulation unobservable region, a sector transition unobservable region and a high modulation unobservable region.
In this scheme, when the low modulation unobservable region and the sector transition unobservable region are shown in fig. 5, and the sector transition unobservable region is shown in fig. 5 (a), the target voltage vector VrefWhen approaching one of the substantially non-zero voltage vectors in the sector, the other substantially non-zero voltage vector has a short duration of action, i.e. the time is short
Figure BDA0002709169260000062
Or
Figure BDA0002709169260000063
Low modulation unobservable region when the target voltage vector V is as shown in fig. 5 (b)refWhen the amplitude of (A) is small, form VrefBoth basic voltage vectors have a short action time, i.e.
Figure BDA0002709169260000064
And is
Figure BDA0002709169260000065
Neither can accurately sample the current.
In the early production practice process, for a fan product for indoor air purification, the phase current waveform distortion of a single-resistor sampling scheme in a low-speed area (500-800 rpm) is found to be obviously larger than that of a double-resistor sampling scheme. Further contrast research shows that when single-resistor sampling current reconstruction is carried out in a low-modulation unobservable region, the action time of a certain basic voltage vector state is very short, and the pulse needs to be translated in a PWM period to be staggered so as to obtain enough single-resistor sampling time, namely pulse phase shifting is needed, so that the waveform of PWM output is asymmetric, phase current harmonic components are increased, and the pulse phase shifting is the main reason of phase current waveform distortion of a single-resistor sampling scheme. On the other hand, the load is light when the low-speed operation is carried out, the phase current is small, the sampling error is not negligible relative to the amplitude of the phase current, and the waveform distortion generated by the phase current is aggravated by the sampling error.
Aiming at the problems in the prior art, the invention provides a low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method, which comprises the following steps of:
step 1, determining minimum sampling time T of single-resistor sampling according to parameters of a single-resistor sampling permanent magnet synchronous motor driving systemmin。
Step 2, calculating the action time T of two non-zero voltage vectors corresponding to each sector by vector frequency conversion control at a given low-speed operation node1、T2And calculating T1And T2Cross point of (T)crossThe size of (d); obtaining T according to the formulas (3) and (4)1、T2The curve simulates a waveform diagram, as shown in FIG. 7, of the key quantity TcrossIs T1And T2The intersection point of (a).
Step 3, setting the lowest rotating speed nset_minAnd (3) judging whether a low modulation unobservable region reconstructed by single resistance current exists or not when the motor runs in no-load mode:
with reference to FIG. 7, the following description will be made
Figure BDA0002709169260000071
When the space vector of the reference voltage is outside the low modulation unobservable region reconstructed by the single resistance current, the space vector of the reference voltage does not appear at any time
Figure BDA0002709169260000072
While being less than TminI.e. single resistance current reconstruction, there is no low modulation unobservable region.
When in use
Figure BDA0002709169260000073
At certain times, certain time instants may occur
Figure BDA0002709169260000074
While being less than TminThe situation of (1), i.e. the single resistance current reconstruction is lowThe non-observable area is modulated.
And 4, if the single resistance current reconstruction does not enter a low modulation unobservable region, directly turning to the step 5, otherwise, increasing the back electromotive force coefficient of the permanent magnet synchronous motor under the condition of maintaining the motor slot full rate basically unchanged by increasing the number of turns of the motor winding and correspondingly reducing the winding wire diameter, and returning to the step 1 for recalculation.
T is calculated in equations (5) and (6)1、T2Voltage vector V ofrefCan be controlled by a direct-axis voltage VdAnd quadrature axis voltage VqAnd (3) calculating:
Figure BDA0002709169260000075
and the steady state voltage equation of a permanent magnet synchronous motor is expressed as:
Figure BDA0002709169260000076
wherein id、iqD and q axis currents respectively; r is a stator resistor; l isd、LqD-axis and q-axis inductors respectively; omega is the electrical angular velocity; keIs the back electromotive force coefficient of the permanent magnet synchronous motor.
V can be derived from the above equations (7), (8)refAnd KeThe relationship of (1):
|Vref|∝Ke (9)
further, the following equations (3) and (4) can be derived
T1∝Ke，T2∝Ke (10)
T1、T2And back electromotive force coefficient KeIs proportional to the magnitude of TcrossIs T1And T2Of (a) thus TcrossAlso with KeIn direct proportion, increase KeCan achieve the purpose of
Figure BDA0002709169260000077
The purpose of (1).
According to the design principle of the motor, the back electromotive force coefficient K of the permanent magnet synchronous motor can be increased by increasing the number of turns of the motor winding and correspondingly reducing the wire diameter of the windingeIn actual operation, in order to ensure that the ampere-turns of the motor are not changed, the phase current of the motor can be properly increased, and the problem that the motor generates heat can not be caused by properly increasing the phase current under the conditions of low-speed operation and light motor load.
Step 5, setting the lowest set rotation speed n by the previous processingset_minWhen the motor is in no-load, the single-resistor current reconstruction does not enter a low-modulation unobservable region, so that the running speed n of the motor is increasedset＞nset_minIn the process, the single-resistance current reconstruction cannot enter a low-modulation unobservable region but only has a sector transition region unobservable region, the single-resistance current reconstruction cannot have a low-modulation unobservable region but only has a sector transition region unobservable region, and at the moment, the three-phase pulse has T1[ 2 ] and T 22 is not less than T simultaneouslyminThe method has the characteristics that the pulse phase shifting method can be optimized to obtain enough sampling time, the pulse shifting times and the asymmetry of three-phase pulses in the sampling process are reduced, and the reconstruction precision of three-phase current in the sampling process of low-speed running single resistor is improved, and the method specifically comprises the following steps:
and step 5.1, each phase current period comprises 6 sectors, corresponds to a space voltage vector diagram corresponding to 7-segment SVPWM shown in fig. 2, and can determine U, V, W which phase the narrowest pulse phase, the second-order wide pulse phase and the widest pulse phase in the three-phase pulse respectively according to the table 1 and the sector number of the current control iteration operation.
TABLE 1 correspondence between sector number and three-phase pulse width in FIG. 2
Sector number Narrowest pulse phase Sub-wide pulse phase Phase of widest pulse
1 W U V
2 V W U
3 W V U
4 U V W
5 U W V
6 V U W
Step 5.2, when
Figure BDA0002709169260000081
The widest pulse is shifted to the left and triggered in advance to obtain enough sampling timeTriggering T at the widest pulse phaseminThe first bus current sampling is then initiated as shown in fig. 8.
Step 5.3, when
Figure BDA0002709169260000082
The narrowest pulse phase is shifted to the right, delayed triggering is carried out to obtain enough sampling time, and T is triggered in the second-time-width pulse phaseminAnd then a second bus current sampling is initiated as shown in fig. 9.
Step 6, according to the table 2, sampling values I of the first-time bus currentad1And negative value (-I) of second time bus current sampling valuead2) The three-phase current I is distributed according to the sector number of the current control iterative operationu、Iv、IwThe third phase current is the negative value of the sum of the distributed two phase currents.
Table 2 correspondence between bus current sampling values and three-phase currents in fig. 2
Sector number Iad1 -Iad2
1 Iv Iw
2 Iu Iv
3 Iu Iw
4 Iw Iu
5 Iv Iu
6 Iw Iv
Examples
The principle experiment verifies that the adopted permanent magnet synchronous motor is an outer rotor fan motor applied to a household air purifier, wherein the parameters of the permanent magnet synchronous motor are as follows: rated voltage DC 24V, minimum operating speed nset_min500 revolutions per minute (rpm), maximum operating speed nset_max3000rpm, pole pair number p n2, stator resistance Rs1.6 omega, stator direct axis inductance LdQuadrature axis inductance L of 1.0mHq1.2mH, the front back emf coefficient k is optimizedeAnd the vector control PWM frequency is 16KHz at 3.0V/krpm. According to the system hardware parameters and the dead time setting of the power tube, the minimum sampling time T of single resistance samplingminSet to 4 μ s.
In the specific embodiment of the present invention, a single-resistance sampling permanent magnet synchronous motor system adopts position-sensorless vector control, and as shown in fig. 10, the system control block diagram includes units such as current sampling, rotor position estimation, Clarke and PARK transformation, maximum torque-to-current ratio control (MTPA), speed loop, dq-axis current loop, PARK inverse transformation, SVPWM calculation, and three-phase PWM inverter.
Counter potential coefficient k before optimizatione3.0V/krpm, T before Ke optimization as in FIG. 11 (a)1、T2Wave form, T1And T2Cross point of (T)cross7 mus, and minimum sampling time T min4 mus less thanFoot condition Tcross/2＞TminThis means that the single resistance current reconstruction may enter both the low modulation unobservable region and the sector transition region unobservable region, and in order to obtain sufficient sampling time, the control algorithm needs to perform frequent pulse phase shifting, which results in extremely asymmetric PWM output waveforms, greatly increasing phase current harmonic components, and increasing sampling errors.
According to the method of the invention, the back emf coefficient of the motor is changed from keIncrease to k at 3.0V/krpme4.2V/krpm, while experimental verification showed that the motor could also be run safely at 3000rpm, Ke optimized and T after deburring as in fig. 11 (b)1、T2Wave form, as shown in the figure T1And T2Cross point of (T)crossIncreases from 7 mus to 10 mus, when the condition T is satisfiedcross/2＞TminThe single resistance current reconstruction does not enter a low modulation non-observable region, but only enters a sector transition region non-observable region, and the frequency of pulse phase shifting can be greatly reduced through the processing.
FIG. 12 shows the motor at n before and after the optimization of the present inventionset_minAs a comparison of three-phase current waveforms at 500rpm, it can be seen from (a) of fig. 12 that there is distortion in the optimized front-phase current waveform, especially the current is not smooth at the phase current peak, and the phase current waveform has burrs due to frequent pulse phase shifting times; the phase current waveform after the current reconstruction optimization processing of the present invention is shown in fig. 12 (b), the distortion of the current waveform is greatly reduced, the current peak is smoother, and the number of pulse phase shifts is reduced, so the burrs in the phase current waveform are also reduced, and fig. 12 shows that the current reconstruction method proposed by the present invention is feasible.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims (8)

1. A low-speed running single-resistor sampling permanent magnet synchronous motor phase current reconstruction method is characterized by comprising the following steps:
determining the minimum sampling time of single resistance sampling according to the parameters of a single resistance sampling permanent magnet synchronous motor driving system, calculating a change curve of two nonzero voltage vector action times corresponding to each sector controlled by vector frequency conversion at a given low-speed operation node, and calculating the intersection point of the two nonzero voltage vector action times;
the motor operates in a no-load mode at the lowest set rotating speed, and whether a low modulation unobservable region reconstructed by single resistance current exists is judged based on the action time of the two non-zero voltage vectors, the intersection point of the action time and the minimum sampling time;
if the single-resistor current reconstruction does not enter a low-modulation unobservable region, obtaining enough sampling time by optimizing a pulse shifting method; otherwise, the back electromotive force coefficient of the permanent magnet synchronous motor is increased and the method is re-executed;
and distributing the three-phase current according to the sector number of the current control iterative operation based on the result of the optimized pulse shift term.
2. The method for reconstructing phase current of a low-speed running single-resistance sampling permanent magnet synchronous motor according to claim 1, wherein the step of judging whether a low modulation unobservable region reconstructed by single-resistance current exists comprises the following steps:
when in use
Figure FDA0002709169250000011
At any moment, no time appears
Figure FDA0002709169250000012
While being less than TminIn the case of (1), the single-resistance current reconstruction does not have a low modulation unobservable region;
when in use
Figure FDA0002709169250000013
At certain times, certain time instants may occur
Figure FDA0002709169250000014
While being less than TminIn the case of (1), a low modulation unobservable region exists in the single-resistance current reconstruction;
wherein, T1、T2Representing the action time of two non-zero voltage vectors, TcrossIs T1、T2Point of intersection of, TminIs the minimum sampling time.
3. The low-speed operation single-resistance sampling permanent magnet synchronous motor phase current reconstruction method according to claim 1, wherein the specific method for increasing the back electromotive force coefficient of the permanent magnet synchronous motor is as follows:
the number of turns of the motor winding is increased, the wire diameter of the winding is correspondingly reduced, and the back electromotive force coefficient of the permanent magnet synchronous motor is increased under the condition of maintaining the motor slot filling rate basically unchanged.
4. The method for reconstructing phase current of a low-speed running single-resistance sampling permanent magnet synchronous motor according to claim 1, wherein if the single-resistance current reconstruction does not enter a low modulation unobservable region, the method for optimizing pulse phase shift term is used for obtaining enough sampling time, and the method comprises the following steps:
when the running speed of the motor is higher than the lowest set rotating speed, the single-resistor current reconstruction can not enter a low-modulation unobservable region but only exists in a sector transition region unobservable region, sufficient sampling time is obtained by optimizing a pulse phase shifting method, the number of pulse shift and the asymmetry of three-phase pulses in the sampling process are reduced, and the reconstruction precision of the three-phase current in the low-speed running single-resistor sampling process is improved.
5. The method for reconstructing phase current of a low-speed running single-resistance sampling permanent magnet synchronous motor according to claim 1, wherein the method for optimizing pulse phase shift comprises the following steps:
determining which phase the widest pulse phase, the secondary wide pulse phase and the narrowest pulse phase in the three-phase pulse are respectively according to the sector number of the current control iterative operation;
when in use
Figure FDA0002709169250000021
The widest pulse phase shifts to the left, triggers in advance to obtain enough sampling time, triggers T at the widest pulse phaseminThen starting a first bus current sampling;
when in use
Figure FDA0002709169250000022
The narrowest pulse phase is shifted to the right, delayed triggering is carried out to obtain enough sampling time, and T is triggered in the second-time-width pulse phaseminAnd then starting the second bus current sampling.
6. The method for reconstructing the phase current of the low-speed running single-resistance sampling permanent magnet synchronous motor according to claim 1, wherein the step of distributing the three-phase current according to the sector number of the current control iterative operation based on the result of the optimized pulse shift term comprises the following steps of:
and distributing the negative values of the first bus current sampling value and the second bus current sampling value to two phases of three-phase currents according to the sector number of the current control iterative operation, wherein the third phase current is the negative value of the sum of the distributed two-phase currents.
7. A controller comprising a processor, a memory and a computer program stored in the memory, the computer program, when executed by the processor, performing the steps of the method according to any one of claims 1 to 6.
8. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 6.
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