CN114465535B - Commutation method and device for brushless direct current motor and brushless direct current motor system - Google Patents
Commutation method and device for brushless direct current motor and brushless direct current motor system Download PDFInfo
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Classifications
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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
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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
- H02P6/10—Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
Abstract
The invention relates to a commutation method and device of a brushless direct current motor and a brushless direct current motor system. The method comprises the following steps: acquiring a target phase counter electromotive force and a target phase current of the brushless direct current motor under a two-phase static coordinate system; filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a fundamental wave of the counter electromotive force of the phase and a fundamental wave of the current of the phase; constructing a commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave; and correcting the commutation of the brushless direct current motor according to the commutation error. The method can obtain more accurate commutation errors to correct commutation, thereby improving the precision of commutation.
Description
Technical Field
The disclosure relates to the technical field of brushless motors, and in particular relates to a commutation method and device of a brushless direct current motor and a brushless direct current motor system.
Background
The commutation method of the brushless direct current motor without the position sensor does not need to adopt three Hall signals or sensors such as encoders, avoids the introduction of commutation errors in the installation of the position sensor, and improves the reliability of a commutation system. However, in the implementation of the sensorless commutation technology, the use of a low-pass filter and delays in the software and hardware links may introduce commutation errors. The existence of the commutation error can reduce the precision of commutation control, increase the fluctuation of current, cause torque pulsation and seriously affect the operation efficiency of the motor, so that the commutation error needs to be accurately judged and extracted and compensated.
In the prior art, an integral or sampling method is adopted, voltage, current or integral deviation before and after a phase change point is used as feedback quantity of a phase change error, and error compensation is carried out; or integrating the flux linkage and the current, extracting a commutation error angle by using the pulse, and performing error compensation.
However, with the above method, a relatively accurate commutation error cannot be obtained, resulting in a decrease in the precision of commutation.
Disclosure of Invention
The present disclosure provides a commutation method and apparatus for a brushless dc motor and a brushless dc motor system, which can obtain a relatively accurate commutation error to correct commutation, thereby improving the accuracy of commutation.
In a first aspect, the present disclosure provides a commutation method of a brushless dc motor, comprising:
acquiring a target phase counter electromotive force and a target phase current of the brushless direct current motor under a two-phase static coordinate system;
filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a fundamental wave of the counter electromotive force of the phase and a fundamental wave of the current of the phase;
constructing a commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave;
and correcting the commutation of the brushless direct current motor according to the commutation error.
Optionally, before the step of obtaining the phase back electromotive force and the phase current of the brushless dc motor in the two-phase stationary coordinate system, the method further includes:
acquiring terminal voltages of three-phase windings in a three-phase static coordinate system, wherein the brushless direct current motor comprises the three-phase windings;
and determining the phase counter electromotive force of the three-phase winding according to the terminal voltage of the three-phase winding.
Optionally, the obtaining the target phase counter electromotive force of the brushless dc motor in the two-phase stationary coordinate system includes:
converting the phase counter electromotive force of the three-phase winding into the target phase counter electromotive force based on coordinate system transformation;
under the two-phase stationary coordinate system, the target phase current of the brushless direct current motor is obtained, and the method comprises the following steps:
based on the coordinate system transformation, phase currents of the three-phase windings in the three-phase stationary coordinate system are converted into the target phase currents.
Optionally, the constructing a commutation error of the brushless dc motor according to the phase back emf fundamental wave and the phase current fundamental wave includes:
based on a double phase-locked loop structure, determining a back electromotive force fundamental wave phase angle according to the phase back electromotive force fundamental wave;
determining a current fundamental phase angle from the phase current fundamental based on the double phase-locked loop structure;
and constructing the commutation error according to the counter electromotive force fundamental wave phase angle and the current fundamental wave phase angle.
Optionally, the correcting the commutation of the brushless dc motor according to the commutation error includes:
determining a commutation error compensation amount according to the integral, the integral coefficient, the commutation error and the gain coefficient of the commutation error;
determining a commutation signal according to the commutation error compensation amount and the zero crossing signal;
and controlling the commutation of the brushless direct current motor according to the commutation signal.
Optionally, the determining the back emf fundamental wave phase angle according to the phase back emf fundamental wave includes:
determining the back emf fundamental phase angle θ with zero as the following formula e ：
Wherein A is e1 For the fundamental wave of the phase back emf,an estimate of the back emf fundamental phase angle;
the determining a current fundamental phase angle according to the phase current fundamental wave comprises the following steps:
determining the current fundamental phase angle θ with zero as the following formula i ：
Wherein A is i1 For the fundamental wave of the current,is an estimate of the phase angle of the current fundamental wave.
Optionally, the constructing the commutation error according to the back emf fundamental phase angle and the current fundamental phase angle includes:
constructing the commutation error theta according to the following formula dif ：
θ dif ＝θ e -θ i
Wherein θ e For the back emf fundamental phase angle, theta i Is the current fundamental phase angle.
Optionally, the determining the commutation error compensation amount according to the integral, the integral coefficient, the commutation error and the gain coefficient of the commutation error includes:
determining the commutation error compensation amount theta according to the following formula com ：
θ com ＝k p (θ dif +k i ∫θ dif dt)
Wherein k is p Is the gain coefficient, k i Is an integral coefficient, θ dif Is the commutation error.
In a second aspect, the present disclosure provides a commutation apparatus for a brushless dc motor, comprising:
the acquisition module is used for acquiring the counter electromotive force and the current of the target phase of the brushless direct current motor under a two-phase static coordinate system;
the filtering extraction module is used for filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a phase counter electromotive force fundamental wave and a phase current fundamental wave;
the commutation error constructing module is used for constructing the commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave;
and the commutation correction module is used for correcting the commutation of the brushless direct current motor according to the commutation error.
In a third aspect, the present disclosure provides a brushless dc motor system comprising: brushless DC motor, three-phase full bridge and commutation device that the second aspect provided.
In the technical scheme provided by the disclosure, the counter electromotive force and the current of the target phase of the brushless direct current motor under a two-phase static coordinate system are obtained; filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a fundamental wave of the counter electromotive force of the phase and a fundamental wave of the current of the phase; constructing a commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave; according to the commutation error, the commutation of the brushless direct current motor is corrected, and the same-frequency extractor cannot influence the phases of the phase back electromotive force fundamental wave and the phase current fundamental wave, so that the commutation error obtained based on the same-frequency extractor is accurate, and the commutation correction is performed based on the commutation error, so that the commutation of the brushless direct current motor is accurate, and the commutation accuracy can be improved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the disclosure and together with the description, serve to explain the principles of the disclosure.
In order to more clearly illustrate the embodiments of the present disclosure or the solutions in the prior art, the drawings that are required for the description of the embodiments or the prior art will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
Fig. 1 is a schematic structural diagram of a brushless dc motor system provided by the present disclosure;
fig. 2 is a schematic flow chart of a commutation method of a brushless dc motor provided in the present disclosure;
fig. 3 is a schematic structural diagram of a common-frequency extractor provided in the present disclosure;
fig. 4 is a schematic flow chart of another commutation method of a brushless dc motor provided in the present disclosure;
fig. 5 is a schematic flow chart of a commutation method of a brushless dc motor provided in the present disclosure;
fig. 6 is a schematic flow chart of a commutation method of a brushless dc motor provided in the present disclosure;
fig. 7 is a schematic structural diagram of a dual phase-locked loop structure provided in the present disclosure;
fig. 8 is a schematic flow chart of a commutation method of a further brushless dc motor provided in the present disclosure;
fig. 9 is a schematic flow chart of a commutation method of a further brushless dc motor provided in the present disclosure;
fig. 10 is a schematic flow chart of a commutation method of a further brushless dc motor provided in the present disclosure;
fig. 11 is a schematic flow chart of a commutation method of a further brushless dc motor provided in the present disclosure;
fig. 12 is a schematic structural diagram of a commutation device of a brushless dc motor provided in the present disclosure.
Detailed Description
In order that the above objects, features and advantages of the present disclosure may be more clearly understood, a further description of aspects of the present disclosure will be provided below. It should be noted that, without conflict, the embodiments of the present disclosure and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure, but the present disclosure may be practiced otherwise than as described herein; it will be apparent that the embodiments in the specification are only some, but not all, embodiments of the disclosure.
Fig. 1 is a schematic structural diagram of a brushless dc motor system provided in the present disclosure, and as shown in fig. 1, a brushless dc motor system 100 includes: the brushless direct current motor 110 and the three-phase full-bridge 120 phase-change device 130, wherein the control end of the three-phase full-bridge 120 is electrically connected with the output end of the phase-change device 130, the three-phase full-bridge 120 is electrically connected with the brushless direct current motor 110, and the input end of the phase-change device 130 is electrically connected with the brushless direct current motor 110.
Illustratively, the three-phase full bridge 120 includes six switches, each of which is controlled by a commutation signal, and three output terminals of the three-phase full bridge 120 are electrically connected to three-phase windings of the brushless dc motor 110, respectively. The three-phase full bridge 120 can convert phase signals and control on-off of a switch of the full bridge, so that any two phases in the three-phase winding are conducted at the same moment, and one phase is suspended, thereby driving the brushless direct current motor 110 to operate.
The commutation apparatus 130 can be used to perform any of the method embodiments of the present disclosure, which are described in detail in several specific embodiments below:
fig. 2 is a schematic flow chart of a commutation method of a brushless dc motor provided in the present disclosure, as shown in fig. 2, including:
s101, acquiring the counter electromotive force and the current of the target phase of the brushless direct current motor under a two-phase static coordinate system.
The motor control field comprises a stationary coordinate system and a rotating coordinate system, wherein the stationary coordinate system comprises a two-phase stationary coordinate system and a three-phase stationary coordinate system, the two-phase stationary coordinate system is an alpha beta coordinate system, the three-phase stationary coordinate system is an ABC coordinate system, and the rotating coordinate system is a two-phase rotating coordinate system, namely a dq coordinate system. Based on different coordinate systems, different mathematical models can be established, so that motor control is convenient in different use scenes.
In a two-phase stationary coordinate system (alpha beta coordinate system), the brushless DC motor corresponds to alpha-phase back electromotive force e αh And beta-phase back electromotive force e βh I.e. the back emf of the target phaseAnd alpha-phase current i αh And beta-phase current i βh I.e. the target phase current. Illustratively, the alpha-phase counter electromotive force e can be determined based on the three-phase terminal voltage of the brushless DC motor in a three-phase stationary coordinate system (ABC coordinate system) αh And beta-phase back electromotive force e βh Three-phase current of brushless DC motor, determining alpha-phase current i αh And beta-phase current i βh . In other embodiments, the α -phase back electromotive force e may be determined based on the d-phase back electromotive force and the q-phase back electromotive force of the brushless dc motor in a two-phase rotation coordinate system (dq coordinate system) αh And beta-phase back electromotive force e βh D-phase current and q-phase current of brushless DC motor, determining alpha-phase current i αh And beta-phase current i βh 。
S102, filtering out multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a fundamental wave of the counter electromotive force of the phase and a fundamental wave of the current of the phase.
Illustratively, based on fourier decomposition, the target back emf can be expressed as equation (1):
wherein e αh For alpha-phase back EMF, e βh Is beta-phase back electromotive force A en N times of coefficients of the target phase counter electromotive force, wherein n is a positive integer greater than or equal to 1, and if n=1, the formula (1) is an expression of a phase counter electromotive force fundamental wave in the target phase counter electromotive force; if n is more than or equal to 2, the formula (1) is an expression of superposition of multiple harmonics of the phase counter electromotive force in the target phase counter electromotive force.
Illustratively, based on fourier decomposition, the target phase current may be expressed as equation (2):
wherein i is αh For alpha-phase current, i βh Is beta-phase current, A in N is a positive integer greater than or equal to 1 for n times of coefficients of the target phase current, and if n=1, the formula (2) is an expression of a phase current fundamental wave in the target phase current; if n is more than or equal to 2, the formula (2) is an expression of superposition of multiple harmonics of the phase current in the target phase current.
Fig. 3 is a schematic structural diagram of an on-channel extractor provided by the present disclosure, as shown in fig. 3, where if an input signal of the on-channel extractor is a target phase counter electromotive force/target phase current, an output signal is a phase counter electromotive force fundamental wave in the target phase counter electromotive force, and may be expressed as formula (3):
wherein f eα For an output signal corresponding to alpha-phase back electromotive force, f eβ Output signal corresponding to beta-phase back electromotive force e α Is an alpha-phase back electromotive force fundamental wave, e β Is beta-phase electromotive force fundamental wave.
If the on-channel extractor input signal is the target phase current, the output signal is the phase current fundamental wave in the target phase current, which can be expressed as formula (4):
wherein f iα For an output signal corresponding to the alpha-phase current, f iβ Output signal corresponding to beta-phase current, i α For the alpha-phase current fundamental wave, i β Is a beta-phase current fundamental wave.
Based on the above embodiments, the on-channel extractor can filter out multiple harmonics in the input signal, so that the output signal only includes the phase back emf fundamental wave and the phase current fundamental wave. In addition, the same-frequency extractor has no amplitude attenuation and no phase delay at the extracted frequency, so that the amplitude and the phase of the phase back electromotive force fundamental wave and the phase current fundamental wave can be kept, and further, the introduction of extra errors can be avoided, and more accurate phase-change errors can be obtained.
And S103, constructing a commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave.
The phase difference of the back electromotive force fundamental wave and the current fundamental wave can fundamentally reflect the superposition effect of various commutation errors, and the phase difference of the back electromotive force fundamental wave and the current fundamental wave, namely the commutation error, can be determined based on the phase back electromotive force fundamental wave and the phase current fundamental wave. Thus, the commutation error in the present disclosure includes a commutation error caused by an internal power factor angle, where the internal power factor angle refers to an included angle between a counter electromotive force and a current vector, and the electromagnetic torque is positively correlated with the counter electromotive force and the current, and when a certain included angle exists between the counter electromotive force and the current vector, the product value of the two vectors is reduced, so that the motor torque is reduced, and the maximum torque can be obtained only when the internal power factor angle is zero. Therefore, the obtained commutation error comprises the commutation error caused by various factors, so that the commutation error is accurate.
S104, correcting the commutation of the brushless direct current motor according to the commutation error.
According to the phase change error, a three-phase change signal, namely an A-phase change signal, a B-phase change signal and a C-phase change signal, can be obtained, and the brushless direct current motor can be controlled to perform phase change through a three-phase full bridge based on the A-phase change signal, the B-phase change signal and the C-phase change signal. Therefore, on the premise of considering the commutation error, the commutation control of the brushless direct current motor is realized, so that the commutation of the brushless direct current motor is more accurate.
In the embodiment, the counter electromotive force and the current of the target phase of the brushless direct current motor under a two-phase static coordinate system are obtained; filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a fundamental wave of the counter electromotive force of the phase and a fundamental wave of the current of the phase; constructing a commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave; according to the commutation error, the commutation of the brushless direct current motor is corrected, and the same-frequency extractor cannot influence the phases of the phase back electromotive force fundamental wave and the phase current fundamental wave, so that the commutation error obtained based on the same-frequency extractor is accurate, and the commutation correction is performed based on the commutation error, so that the commutation of the brushless direct current motor is accurate, and the commutation accuracy can be improved.
Fig. 4 is a schematic flow chart of another phase-change method of a brushless dc motor provided by the present disclosure, and fig. 4 is a flowchart of the embodiment shown in fig. 2, before executing S101, further including:
s201, acquiring terminal voltage of a three-phase winding and phase current of the three-phase winding under a three-phase static coordinate system.
The brushless direct current motor includes the three-phase winding.
Illustratively, a brushless DC motor includes an A-phase winding, a B-phase winding, and a C-phase winding. In a three-phase static coordinate system, the balance equation of the brushless direct current motor is as follows:
wherein L is equivalent phase inductance of the brushless direct current motor, R is phase resistance of the brushless direct current motor, e A Is the counter electromotive force of A phase, e B Is B-phase counter electromotive force, e C Is counter electromotive force of C phase, N is neutral point of winding in brushless DC motor, i A For phase A current, i B For B-phase current, i C Is C phase current, t is time, u A For the terminal voltage of the A-phase winding, u B Terminal voltage u of B phase winding C For the terminal voltage of the C-phase winding, u N Is the neutral point voltage of the three-phase winding.
S202, determining the phase counter electromotive force of the three-phase winding according to the terminal voltage of the three-phase winding.
The phase back emf can be derived according to equation (5), as shown in equation (6):
the inductance in the high-speed brushless direct current motor is very small, and the variation of phase current is very small during operation, so that the inductance term in the formula (6) can be ignored, and the counter electromotive force of the phase can be estimated by the difference value between the terminal voltage and the neutral point voltage of the three-phase winding, as shown in the formula (7):
when the A phase winding is suspended, the A phase current i A Is 0, u A -u N Equal to the counter-electromotive force e of phase A A When the B phase winding is suspended, B phase current i B Is 0, u B -u N Equal to the back electromotive force e of B phase B When the C-phase winding is suspended, the C-phase current i C Is 0, u C -u N Equal to the counter-electromotive force e of C phase C Thus, according to the A-phase terminal voltage u A B-phase terminal voltage u B Voltage u at C-phase terminal B And neutral point voltage u N Estimating the A-phase counter electromotive force e A Back electromotive force e of B phase B And a counter electromotive force e of C phase C 。
Fig. 5 is a flowchart of another commutation method of a brushless dc motor provided in the present disclosure, and fig. 5 is a specific description of one possible implementation manner when S101 is performed on the basis of the embodiment shown in fig. 4:
and S1011, converting the phase counter electromotive force of the three-phase winding into the target phase counter electromotive force based on coordinate system transformation.
Illustratively, based on the Clark (Clark) transform, the phase back EMF in the ABC coordinate system can be converted to the target phase back EMF in the αβ coordinate system according to equation (8):
wherein e αh For alpha-phase back EMF, e βh Is beta-phase back emf.
And S1012, converting phase currents of the three-phase windings in the three-phase static coordinate system into the target phase currents based on the coordinate system transformation.
Illustratively, based on the Clark (Clark) transform, the phase current in the ABC coordinate system can be converted to a target phase current in the αβ coordinate system according to equation (9):
wherein i is αh For alpha-phase current, i βh Is beta-phase current.
Fig. 6 is a flowchart of another commutation method of a brushless dc motor provided in the present disclosure, and fig. 6 is a specific description of one possible implementation manner when S103 is performed on the basis of the embodiment shown in fig. 2:
s301, based on a double phase-locked loop structure, determining a counter electromotive force fundamental wave phase angle according to the phase counter electromotive force fundamental wave.
Fig. 7 is a schematic structural diagram of a dual phase-locked loop structure provided by the present disclosure, and as shown in fig. 7, the dual phase-locked loop structure includes four input terminals for receiving an α -phase back emf fundamental wave, a β -phase back emf fundamental wave, an α -phase current fundamental wave, and a β -phase current fundamental wave, respectively. The double phase-locked loop structure determines a back emf fundamental phase angle based on the received alpha-phase back emf fundamental wave and the received beta-phase back emf fundamental wave.
As a specific description of one possible implementation when S301 is performed, as shown in fig. 8:
s301' determining the back EMF fundamental phase angle θ in the case where equation (10) is zero e ：
Wherein A is e1 For the fundamental wave of the phase back emf,as an estimate of the back EMF fundamental phase angle ε e Is the deviation of the estimated value of the phase angle of the back electromotive force fundamental wave and the phase angle of the back electromotive force fundamental waveAnd (3) difference. At epsilon e When the closed loop control is 0, the phase locking purpose is achieved,thus, the +.>I.e. as back emf fundamental phase angle.
S302, based on the double phase-locked loop structure, a current fundamental wave phase angle is determined according to the phase current fundamental wave.
The dual phase-locked loop structure may determine a current fundamental phase angle based on the received alpha phase current fundamental and the received beta phase current fundamental.
As a specific description of one possible implementation when S302 is performed, as shown in fig. 9:
s302' determining the current fundamental phase angle θ in the case where equation (11) is zero i ：
Wherein A is i1 For the fundamental wave of the phase current,epsilon is an estimate of the phase angle of the fundamental current i Is the deviation of the estimated value of the phase angle of the current fundamental wave from the phase angle of the current fundamental wave. At epsilon i When the closed loop control is 0, the purpose of phase locking is achieved, < + >>Thus, the +.>I.e. as the current fundamental phase angle.
And S303, constructing the commutation error according to the counter electromotive force fundamental wave phase angle and the current fundamental wave phase angle.
Based on the phase angle theta of the back electromotive force fundamental wave e And the phase angle theta of the current fundamental wave i That is, of a double phase-locked loop structureAnd->According to->And->Can obtain the phase difference between the phase angle of the back electromotive force fundamental wave and the phase angle of the current fundamental wave, and takes the phase difference as the phase change error of the brushless direct current motor, namely, the phase change error theta is constructed according to the formula (12) dif ：
Fig. 10 is a flowchart of another commutation method of a brushless dc motor provided in the present disclosure, and fig. 10 is a specific description of one possible implementation manner when S104 is performed on the basis of the embodiment shown in fig. 2, as follows:
s401, determining a commutation error compensation amount according to the integral of the commutation error, the integral coefficient, the commutation error and the gain coefficient.
The proportional integral (Proportional Integral, PI) controller is a linear controller that forms a control deviation from a given value and an actual output value, and forms a control quantity by linearly combining the proportional and integral of the deviation, thereby controlling a controlled object. Taking the commutation error as the control deviation, determining the coefficient of an integral term of the commutation error and the coefficient of the commutation error based on the gain coefficient and the integral coefficient, and linearly combining the integral of the commutation error and the commutation error based on the two coefficients to obtain the compensation quantity of the commutation error.
As a specific description of one possible implementation when S401 is performed, as shown in fig. 11:
s401' determining the commutation error compensation θ according to equation (13) com ：
θ com ＝k p (θ dif +k i ∫θ dif dt) (13)
Wherein k is p Is the gain coefficient, k i Is an integral coefficient, θ dif Is the commutation error.
S402, determining a commutation signal according to the commutation error compensation and the zero crossing signal.
Under the condition of no commutation error, the zero crossing signal delay pi/6 is the commutation point, but in the actual brushless direct current motor system, the commutation error exists, and the commutation point is the zero crossing signal delay theta com +pi/6, thus a new commutation signal can be obtained.
S403, controlling the brushless direct current motor to change the phase according to the phase change signal.
Based on a commutation logic control table, the commutation signals can control the on-off states of six switches in the three-phase full bridge, so that any two phases in the three-phase winding are conducted at the same time, one phase is suspended, and the brushless direct current motor is driven to perform commutation, and the operation of the brushless direct current motor is realized.
The disclosure further provides a commutation device of a brushless dc motor, and fig. 12 is a schematic structural diagram of the commutation device of a brushless dc motor provided by the disclosure, as shown in fig. 12, the commutation device includes:
the acquisition module 210 is configured to acquire a target phase back electromotive force and a target phase current of the brushless dc motor in a two-phase stationary coordinate system.
The filtering extraction module 220 is configured to filter out multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the on-channel extractor, so as to obtain a phase counter electromotive force fundamental wave and a phase current fundamental wave.
A commutation error constructing module 230, configured to construct a commutation error of the brushless dc motor according to the phase back emf fundamental wave and the phase current fundamental wave.
The commutation correction module 240 is configured to correct commutation of the brushless dc motor according to the commutation error.
Optionally, the collecting module 210 is further configured to obtain a terminal voltage of a three-phase winding in a three-phase stationary coordinate system, where the brushless dc motor includes the three-phase winding; and determining the phase counter electromotive force of the three-phase winding according to the terminal voltage of the three-phase winding.
Optionally, the collecting module 210 is further configured to convert a phase counter electromotive force of the three-phase winding into the target phase counter electromotive force based on coordinate system transformation; based on the coordinate system transformation, phase currents of the three-phase windings in the three-phase stationary coordinate system are converted into the target phase currents.
Optionally, the commutation error constructing module 230 is further configured to determine a back emf fundamental phase angle according to the phase back emf fundamental wave based on a double phase locked loop structure; determining a current fundamental phase angle from the phase current fundamental based on the double phase-locked loop structure; and constructing the commutation error according to the counter electromotive force fundamental wave phase angle and the current fundamental wave phase angle.
Optionally, the commutation correction module 240 is further configured to determine a commutation error compensation amount according to an integral of the commutation error, an integral coefficient, the commutation error, and a gain coefficient; determining a commutation signal according to the commutation error compensation amount and the zero crossing signal; and controlling the commutation of the brushless direct current motor according to the commutation signal.
Optionally, the commutation error constructing module 230 is further configured to determine the back emf fundamental phase angle θ if equation (10) is zero e The method comprises the steps of carrying out a first treatment on the surface of the Determining the current fundamental phase angle θ with equation (11) zero i 。
Optionally, the commutation error constructing module 230 is further configured to construct the commutation error θ according to formula (12) dif 。
Optionally, the commutation correction module 240 is further configured to determine the commutation error compensation θ according to equation (13) com 。
The phase change device provided in this embodiment is used to execute the steps of any one of the method embodiments, and is specifically described herein without further details by the corresponding functional modules and beneficial effects of the method embodiments.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is merely a specific embodiment of the disclosure to enable one skilled in the art to understand or practice the disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown and described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A commutation method for a brushless dc motor, comprising:
acquiring a target phase counter electromotive force and a target phase current of the brushless direct current motor under a two-phase static coordinate system;
filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a fundamental wave of the counter electromotive force of the phase and a fundamental wave of the current of the phase;
constructing a commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave;
correcting the commutation of the brushless direct current motor according to the commutation error;
the construction of the commutation error of the brushless DC motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave comprises the following steps:
based on a double phase-locked loop structure, determining a back electromotive force fundamental wave phase angle according to the phase back electromotive force fundamental wave;
determining a current fundamental phase angle from the phase current fundamental based on the double phase-locked loop structure;
and constructing the commutation error according to the counter electromotive force fundamental wave phase angle and the current fundamental wave phase angle.
2. The method of claim 1, wherein prior to obtaining the phase back emf and the phase current of the brushless dc motor in the two-phase stationary coordinate system, further comprising:
acquiring terminal voltages of three-phase windings in a three-phase static coordinate system, wherein the brushless direct current motor comprises the three-phase windings;
and determining the phase counter electromotive force of the three-phase winding according to the terminal voltage of the three-phase winding.
3. The method of claim 2, wherein the obtaining the target phase back emf of the brushless dc motor in the two-phase stationary coordinate system comprises:
converting the phase counter electromotive force of the three-phase winding into the target phase counter electromotive force based on coordinate system transformation;
under the two-phase stationary coordinate system, the target phase current of the brushless direct current motor is obtained, and the method comprises the following steps:
based on the coordinate system transformation, phase currents of the three-phase windings in the three-phase stationary coordinate system are converted into the target phase currents.
4. A method according to any one of claims 1-3, wherein said correcting commutation of said brushless dc motor based on said commutation error comprises:
determining a commutation error compensation amount according to the integral, the integral coefficient, the commutation error and the gain coefficient of the commutation error;
determining a commutation signal according to the commutation error compensation amount and the zero crossing signal;
and controlling the commutation of the brushless direct current motor according to the commutation signal.
5. The method of claim 1, wherein said determining a back emf fundamental phase angle from said phase back emf fundamental comprises:
determining the back emf fundamental phase angle θ with zero as the following formula e ：
Wherein A is e1 For the fundamental wave of the phase back emf,an estimate of the back emf fundamental phase angle;
the determining a current fundamental phase angle according to the phase current fundamental wave comprises the following steps:
determining the current fundamental phase angle θ with zero as the following formula i ：
Wherein A is i1 For the fundamental wave of the current,for the phase angle of the fundamental currentAnd (5) estimating a value.
6. The method of claim 1, wherein said constructing said commutation error from said back emf fundamental phase angle and said current fundamental phase angle comprises:
constructing the commutation error theta according to the following formula dif ：
θ dif ＝θ e -θ i
Wherein θ e For the back emf fundamental phase angle, theta i Is the current fundamental phase angle.
7. The method of claim 4, wherein said determining a commutation error compensation based on the integral of the commutation error, the integral coefficient, the commutation error, and the gain coefficient comprises:
determining the commutation error compensation amount theta according to the following formula com ：
θ com ＝k p (θ dif +k i ∫θ dif dt)
Wherein k is p Is the gain coefficient, k i Is an integral coefficient, θ dif Is the commutation error.
8. A commutation device for a brushless dc motor, comprising:
the acquisition module is used for acquiring the counter electromotive force and the current of the target phase of the brushless direct current motor under a two-phase static coordinate system;
the filtering extraction module is used for filtering multiple harmonics in the counter electromotive force of the target phase and multiple harmonics in the current of the target phase based on the same-frequency extractor to obtain a phase counter electromotive force fundamental wave and a phase current fundamental wave;
the commutation error constructing module is used for constructing the commutation error of the brushless direct current motor according to the phase back electromotive force fundamental wave and the phase current fundamental wave;
the commutation correction module is used for correcting the commutation of the brushless direct current motor according to the commutation error;
the commutation error constructing module is specifically configured to: based on a double phase-locked loop structure, determining a back electromotive force fundamental wave phase angle according to the phase back electromotive force fundamental wave; determining a current fundamental phase angle from the phase current fundamental based on the double phase-locked loop structure; and constructing the commutation error according to the counter electromotive force fundamental wave phase angle and the current fundamental wave phase angle.
9. A brushless dc motor system, comprising: brushless DC motor, three-phase full bridge and the commutation device according to claim 8.
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