CN111064396A - Brushless direct current motor power factor correction method based on virtual neutral point voltage - Google Patents

Brushless direct current motor power factor correction method based on virtual neutral point voltage Download PDF

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CN111064396A
CN111064396A CN201911343929.3A CN201911343929A CN111064396A CN 111064396 A CN111064396 A CN 111064396A CN 201911343929 A CN201911343929 A CN 201911343929A CN 111064396 A CN111064396 A CN 111064396A
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neutral point
virtual neutral
point voltage
voltage
power factor
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CN111064396B (en
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赵冬冬
王西坡
皇甫宜耿
夏磊
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Northwestern Polytechnical University
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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
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
    • H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
    • 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
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/14—Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, 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
    • H02P2203/00—Indexing scheme relating to controlling arrangements characterised by the means for detecting the position of the rotor
    • H02P2203/09—Motor speed determination based on the current and/or voltage without using a tachogenerator or a physical encoder
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)

Abstract

The invention relates to a method for correcting the power factor of a brushless direct current motor based on virtual neutral point voltage, which integrates the differential pressure between the virtual neutral point voltage of non-follow current time and 1/2 bus voltage with respect to time aiming at the virtual neutral point voltage waveform, and when the integral value is zero, the position error is corrected. The invention can simply and quickly realize the power factor correction and the position error correction of the motor.

Description

Brushless direct current motor power factor correction method based on virtual neutral point voltage
Technical Field
The invention belongs to the technical field of automation, relates to a brushless direct current motor power factor correction method, and particularly relates to a brushless direct current motor power factor correction method based on virtual neutral point voltage.
Background
The brushless direct current motor has the advantages of simple control, high power density and the like, and is widely applied to the aspects of aerospace, industry and civilian use, for example, a high-precision gyroscope, a robot arm, a fan, a compressor, an electric vehicle and the like are driven by the brushless direct current motor. In certain high temperature, humid application environments, the position sensor often fails, reducing the reliability of the system. Therefore, the position-less sensor becomes a research hotspot of the brushless direct current motor, and in addition, the volume and the weight of the brushless direct current motor can be reduced.
The back-emf zero-crossing method is the most widely used method in engineering due to simplicity and reliability, and comprises a terminal voltage method, a line voltage method, a virtual neutral point method and the like. The three methods are all to obtain the counter potential zero crossing point through a hardware circuit and simple calculation, delay the counter potential zero crossing point by 30 electrical angles to obtain a phase change signal, and realize the normal operation of the motor. The detection circuit, the filter circuit, the complex calculation and the like can generate signal delay, so that the detected position and the actual position have deviation, the installation of the position sensor can have larger errors, and the errors can cause the counter potential and the phase current of the motor to be out of phase, thereby reducing the power factor of the motor, further influencing the performance of the motor, and even damaging the motor in serious cases. Document 1(Park J S, Lee kd. online advanced angle adjustment method for sinusoidal BLDC motors with chemically synthesized Hall sensors [ J ]. IEEE Transactions on Power Electronics,2017,32(11):8247 and 8253.) proposes that the optimal lead time is half of the phase change follow current time, and achieves the purpose of Power factor correction by calculating the follow current time, but the follow current time is influenced by multiple factors such as voltage, rotating speed, inductance, current and the like, and the calculation is complex and has large calculation deviation. Document 2(Tan B, Wang X, ZHao D, et al. A Lag angular dependence stress of Phase Current for High-Speed BLDC Motors [ J ]. IEEEAccess,2018,7:9566-9574.) analyzes the Phase relationship between the back electromotive force and the Current to derive the relationship between the lead angle and the Current, but many variables are omitted in the simplification process, and the error between the calculated result and the actual result is large. Document 3(Song X, HanB, Wang k. sensorless Drive of High-speed BLDC Motors Based on visual 3rd-harmonic Back-EMF and High-precision comparison J. IEEE Transactions on power Electronics,2018.) obtains the optimum lead time by making the angle between the permanent magnet flux linkage and the current 90 electrical degrees, but this method requires multiple voltage current sensors and is also relatively complex to calculate.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a power factor correction method of a brushless direct current motor based on virtual neutral point voltage.
Technical scheme
A brushless direct current motor power factor correction method based on virtual neutral point voltage is characterized in that aiming at the virtual neutral point voltage waveform, the differential pressure between the virtual neutral point voltage of non-follow current time and 1/2 bus voltage is integrated with time, and when the integral value is zero, a position error is corrected; the method comprises the following specific steps:
step 1: when the virtual neutral point voltage is
Figure BDA0002332841690000021
When the area integral coefficient is set to 1; the U isdIs the bus voltage;
step 2: virtual neutral point voltage begins to be less than
Figure BDA0002332841690000022
Starting to integrate the voltage of the virtual neutral point;
and step 3: when the virtual neutral point voltage is
Figure BDA0002332841690000023
Stopping integration, recording the integral value as S1, setting the area integral coefficient as-1, performing PI control on S1 to make the area integral coefficient approach zero, and outputting the PI controller as a power factor correction angle;
and 4, step 4: when the virtual neutral point voltage begins to be greater than
Figure BDA0002332841690000024
Starting to integrate the voltage of the virtual neutral point;
and 5: when the virtual neutral point voltage becomes
Figure BDA0002332841690000025
Stopping integration, recording the integral value as S2, setting the area integral coefficient as 1, performing PI control on S2 to make the area integral coefficient approach zero, and outputting the PI controller as a power factor correction angle;
step 6: and (5) repeating the steps 2-5, and finally correcting the power factor.
Advantageous effects
The method for correcting the power factor of the brushless direct current motor based on the virtual neutral point voltage can simply and quickly realize the correction of the power factor of the motor and the correction of the position error. The invention has the following characteristics:
1. only one voltage sensor is required and no current sensor is required.
2. The method is independent of speed and is suitable for steady-state and dynamic working conditions.
3. Position correction is simultaneously achieved while power factor correction is achieved.
4. Power factor correction can be achieved for both position sensor and sensorless motors.
Drawings
FIG. 1 illustrates back-emf and phase current waveforms before and after correction
FIG. 2 virtual neutral Voltage waveforms before and after correction at Steady State
FIG. 3 virtual neutral voltage waveform at dynamic time
FIG. 4 is a graph of a current waveform and a virtual neutral voltage waveform before correction
FIG. 5 is a graph of corrected phase current waveforms and virtual neutral point voltage waveforms
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
it is first demonstrated that when the lead angle is half the commutation freewheel time, the midpoint of the non-conducting phase current is exactly coincident with the back-emf zero-crossing, which is exactly in phase with the phase current. In FIG. 1, Δ t is the freewheel time, O is the back emf zero crossing, ω is the electrical angular velocity of the motor, ia、ibTo correct the pre-A, B phase current, ia' for corrected A-phase current, eaFor A opposite potential, the uncorrected AO time interval is
Figure BDA0002332841690000031
BO time interval of
Figure BDA0002332841690000032
It is obvious that the inductance causes Δ t1＜Δt2And therefore the phase current is not in phase with the back-emf. When adding lead angle time of half of freewheel time
Figure BDA0002332841690000033
Point a leads to point a ', and point B leads to point B'. When the A' O time interval is
Figure BDA0002332841690000034
B' O time interval of
Figure BDA0002332841690000035
Since the motor is in steady state and the angular velocity is ω, then the electrical angle between a 'O and B' O is also equal, i.e. the phase current is in phase with the back-emf.
The relationship of the voltage waveform of the virtual neutral point when the added lead time is half of the freewheel time is analyzed below. U in FIG. 2shIs the virtual neutral point voltage before correction and the 1/2 bus voltage waveform us′hAre the corrected virtual neutral voltage and 1/2 bus voltage waveforms. From the above proof, t before correctionAO＜tBOThus the triangular area SAOM<SBONAnd after correction tA′O＝tB′OThus the triangular area SA'OM'＝SB'ON'. The above-mentioned proofs are all the results when the motor speed is at steady state, and it is proved below that the method is still effective when the motor is in dynamic regulation.
Fig. 3 is a waveform of the virtual neutral point voltage and 1/2 bus voltage changing with time during the motor speed increasing process, and O is a counter potential zero crossing point. Suppose that the angular velocity of the motor at point A is ω1Counter potential amplitude of E1＝Ceω1At point B, the angular velocity of the motor is ω2Counter potential amplitude of E2＝Ceω2. The slope of M' O can be expressed as
Figure BDA0002332841690000041
The slope of N' O can be expressed as
Figure BDA0002332841690000042
Since the motor speed is increasing, then time tA′O＞tB′OAssuming now that the back-emf and current are in phase, the electrical angle through which the motor passes between A 'O and B' O is equal and is not set to
Figure BDA0002332841690000043
Wherein
Figure BDA0002332841690000044
The electric angle passed by the motor during freewheeling under the current working condition. Therefore, it is not only easy to use
Figure BDA0002332841690000045
Then it is easy to obtain the area of the triangle A' OM
Figure BDA0002332841690000046
Similarly, the area of triangle B 'ON' is
Figure BDA0002332841690000047
Namely SA′OM′＝SB′ON′. So that, regardless of the steady-state or dynamic process, as long as the motor back electromotive force is in phase with the corresponding phase current, SA′OM′＝SB′ON′. The PI controller can be designed based on the error of the area of two triangles, so that the error approaches to zero, and the optimal lead angle of the motor is obtained. Because the areas of the two triangles are unequal due to the position error, the method can simultaneously realize the calibration of the position error, and the method can be used for eliminating the error no matter the error is caused by the inaccurate installation of the position sensor or the error is caused by no position sensor, and the motor works in the optimal state.
By analyzing the voltage waveform of the virtual neutral point, the power factor is corrected when the voltage integral value of the virtual neutral point is zero, and the brushless direct current motor works in the optimal state.
The technical scheme adopted by the invention is as follows: for the virtual neutral point voltage waveform, the differential pressure between the virtual neutral point voltage of the non-free-wheeling time and the 1/2 bus voltage is integrated with respect to time, and when the integrated value is zero, the position error is corrected. Namely, the differential pressure between the virtual neutral point voltage and the 1/2 bus voltage is integrated in the non-free-wheeling time period, and the error is recalculated in each time period, so that the accumulated error generated by the integral term of the PI controller is avoided.
When the free-wheeling time is over, the voltage difference between the virtual neutral point voltage and the 1/2 bus voltage is integrated with time, and a PI controller is designed based on the integration value, so that the integration value tends to zero, and the power factor and position error correction is realized. By means of the analysis circuit, the virtual neutral point voltage is always equal to
Figure BDA0002332841690000051
Or
Figure BDA0002332841690000052
This voltage threshold can therefore be used as a signal for us to start and end integration. When not corrected, in one period of the virtual neutral point voltage, the half-period integral value is found to be positive and the half-period integral value is found to be negative, and for the sake of closed-loop adjustment, the integral value is added with an integral coefficient of 1 or-1 according to the voltage threshold value. The specific implementation steps are as follows:
[1]when the virtual neutral point voltage is
Figure BDA0002332841690000053
When, the area integral coefficient is set to 1.
[2]Virtual neutral point voltage begins to be less than
Figure BDA0002332841690000054
Starting to integrate the voltage of the virtual neutral point;
[3]when the virtual neutral point voltage is
Figure BDA0002332841690000055
Stopping integration, recording the integral value as S1, setting the area integral coefficient as-1, performing PI control on S1 to make the area integral coefficient approach zero, and outputting the PI controller as a power factor correction angle;
[4]when the virtual neutral point voltage begins to be greater than
Figure BDA0002332841690000056
Starting to integrate the voltage of the virtual neutral point;
[5]when the virtual neutral point voltage becomes
Figure BDA0002332841690000057
Stopping integration, recording the integral value as S2, setting the area integral coefficient as 1, performing PI control on S2 to make the area integral coefficient approach zero, and outputting the PI controller as a power factor correction angle;
[6] repeating the steps (2) to (5), and finally correcting the power factor;
then, modeling simulation is carried out on the power factor correction method provided by the invention, and fig. 4 and 5 show simulation results. Fig. 4 shows the current waveform and the virtual neutral point voltage waveform before correction, and it can be seen that the virtual neutral point voltage waveform before correction is severely asymmetric, and the peak-to-peak value of the phase current is 12.81A. Fig. 5 shows the corrected phase current waveform and the virtual neutral point voltage waveform, and it can be seen that the virtual neutral point voltage waveform is completely symmetrical after correction, and the peak-to-peak value of the phase current is 12.02A. Before and after the correction, the current was reduced by 6.2%, and thus the method was effective.

Claims (1)

1. A brushless direct current motor power factor correction method based on virtual neutral point voltage is characterized in that aiming at the virtual neutral point voltage waveform, the differential pressure between the virtual neutral point voltage of non-follow current time and 1/2 bus voltage is integrated with time, and when the integral value is zero, a position error is corrected; the method comprises the following specific steps:
step 1: when the virtual neutral point voltage is
Figure FDA0002332841680000011
When the area integral coefficient is set to 1; the U isdIs the bus voltage;
step 2: virtual neutral point voltage begins to be less than
Figure FDA0002332841680000012
Starting to integrate the voltage of the virtual neutral point;
and step 3: when the virtual neutral point voltage is
Figure FDA0002332841680000013
Stopping integration, recording the integral value as S1, setting the area integral coefficient as-1, performing PI control on S1 to make the area integral coefficient approach zero, and outputting the PI controller as a power factor correction angle;
and 4, step 4: when the virtual neutral point voltage begins to be greater than
Figure FDA0002332841680000014
Starting to integrate the voltage of the virtual neutral point;
and 5: when the virtual neutral point voltage becomes
Figure FDA0002332841680000015
Stopping integration, recording the integral value as S2, setting the area integral coefficient as 1, performing PI control on S2 to make the area integral coefficient approach zero, and outputting the PI controller as a power factor correction angle;
step 6: and (5) repeating the steps 2-5, and finally correcting the power factor.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117811423A (en) * 2024-02-29 2024-04-02 深圳市唯川科技有限公司 Motor control method, control device and motor

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CN104767435A (en) * 2015-04-27 2015-07-08 山东大学 Real-time sensorless brushless motor phase change phase correction method based on voltage of neutral points
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EP2403123A2 (en) * 2010-06-30 2012-01-04 Kabushiki Kaisha Yaskawa Denki Three-level inverter, power conditioner, and power generating system
CN104767435A (en) * 2015-04-27 2015-07-08 山东大学 Real-time sensorless brushless motor phase change phase correction method based on voltage of neutral points
CN107749725A (en) * 2017-10-20 2018-03-02 哈尔滨工程大学 A kind of commutation bearing calibration of position-sensor-free DC brushless motor
CN110212819A (en) * 2019-05-28 2019-09-06 天津大学 A kind of commutation error compensating method for high-speed brushless DC electromotor
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