CN116317719B - Method for restraining magnetic regulating transient torque fluctuation of variable flux motor by quadrature axis current compensation - Google Patents
Method for restraining magnetic regulating transient torque fluctuation of variable flux motor by quadrature axis current compensation Download PDFInfo
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- 230000004907 flux Effects 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 25
- 230000001052 transient effect Effects 0.000 title claims abstract description 17
- 230000000452 restraining effect Effects 0.000 title claims abstract description 10
- 230000001105 regulatory effect Effects 0.000 title claims description 9
- 230000005347 demagnetization Effects 0.000 claims abstract description 60
- 229910000828 alnico Inorganic materials 0.000 claims abstract description 50
- 230000005415 magnetization Effects 0.000 claims description 15
- 230000008859 change Effects 0.000 claims description 7
- 230000009471 action Effects 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 5
- 229910052796 boron Inorganic materials 0.000 claims description 3
- 238000004364 calculation method Methods 0.000 claims description 3
- 238000004804 winding Methods 0.000 description 6
- 229910001172 neodymium magnet Inorganic materials 0.000 description 5
- 238000004088 simulation Methods 0.000 description 5
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 description 4
- 230000004888 barrier function Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- -1 aluminum nickel cobalt Chemical compound 0.000 description 2
- 230000001808 coupling effect Effects 0.000 description 2
- 238000006880 cross-coupling reaction Methods 0.000 description 2
- 230000005389 magnetism Effects 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
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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
- H02P6/10—Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
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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
- H02P21/05—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation specially adapted for damping motor oscillations, e.g. for reducing hunting
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
Abstract
The invention provides a method for restraining transient torque fluctuation of magnetic regulation of a variable flux motor by means of quadrature axis current compensation considering the passive demagnetization influence of a permanent magnet, which comprises the following steps: acquiring and analyzing influence data of the compensation quadrature axis current on the flux density of the Alnico permanent magnet; based on the obtained influence data, a permissible range for allowing the permanent magnet to be influenced by the passive demagnetization difference value is prepared; on the premise of ensuring that the magnetic flux density of the permanent magnet with low coercivity is the same before and after the compensation of the quadrature axis current after demagnetization, the quadrature axis current compensation flow is formulated based on the influence of the quadrature axis current on the passive demagnetization of the permanent magnet. On the premise of ensuring that the magnetic flux densities of the permanent magnets with low coercive force before and after the cross current Is compensated after demagnetization are the same, the cross current compensation flow Is formulated by taking the influence of the cross current on the passive demagnetization of the Alnico permanent magnets as a basis, and the distribution of the cross current and the demagnetization current Is changed by controlling the synthesized stator current with the amplitude of Is and the internal power factor angle gamma, so that the purpose of reducing torque fluctuation in the magnetic regulation period Is achieved.
Description
Technical Field
The invention relates to the technical field of motors and control, in particular to a method for restraining transient torque fluctuation of a variable magnetic flux motor by compensating and restraining quadrature axis current by considering the influence of passive demagnetization of a permanent magnet.
Background
The permanent magnet of the armature winding magnetism-regulating type variable magnetic flux memory motor usually adopts low-coercivity permanent magnet materials such as Alnico, the magnetization state of the materials can be changed in a short time by applying magnetizing magnetomotive force or demagnetizing magnetomotive force, and the magnetization level of the materials can be memorized. The weak magnetic expansion is realized by setting the quadrature axis current component to zero while the magnetization state of the low-coercivity permanent magnet is regulated by the direct axis current component. However, the quadrature axis current component is set to zero, so that the output torque of the motor is 0 at the moment, and the motor is still loaded at the moment of magnetic modulation, so that larger torque fluctuation and mechanical vibration are generated.
In order to reduce transient torque fluctuation of magnetic regulation, a quadrature current compensation method is generally adopted to reduce torque fluctuation at the moment of applying direct current component demagnetization, but due to the cross coupling effect among permanent magnets, certain influence is generated on the magnetic density amplitude of the low-coercivity permanent magnet after the quadrature current component is compensated, so that the inside of a motor is influenced to heat and the torque output performance of the motor is influenced. Therefore, the method has great significance in compensating the cross-axis current to inhibit the transient torque fluctuation of the magnetic regulation on the premise of considering the passive demagnetization influence of the permanent magnet.
Disclosure of Invention
In order to achieve the purpose of reducing the magnetic regulating transient torque fluctuation of the variable flux motor, the invention provides a method for restraining the magnetic regulating transient torque fluctuation of the variable flux motor by taking the influence of the passive demagnetization of a permanent magnet into consideration, and under the premise of ensuring that the magnetic flux densities of low coercive force permanent magnets before and after the compensation of the cross current after the demagnetization are the same, the cross current compensation flow Is formulated by taking the influence of the cross current on the passive demagnetization of an Alnico permanent magnet as a basis, and the distribution of the cross current and the demagnetization current Is changed by controlling the synthesized stator current with the amplitude Is and the internal power factor angle gamma so as to achieve the purpose of reducing the torque fluctuation during the magnetic regulating.
The invention adopts the following technical means:
a method for restraining transient torque fluctuation of magnetic regulation of a variable flux motor by using quadrature axis current compensation considering the passive demagnetization influence of a permanent magnet comprises the following steps:
acquiring and analyzing influence data of the compensation quadrature axis current on the flux density of the Alnico permanent magnet;
based on the obtained influence data of the compensation quadrature axis current on the flux density of the Alnico permanent magnet, an allowable range for allowing the permanent magnet to be influenced by the demagnetization difference value is prepared;
on the premise of ensuring that the magnetic flux density of the permanent magnet with low coercivity is the same before and after the compensation of the quadrature axis current after demagnetization, a quadrature axis current compensation flow is formulated based on the influence of the quadrature axis current on the passive demagnetization of the permanent magnet.
Further, the acquiring and analyzing the data for compensating the influence of the quadrature current on the flux density of the Alnico permanent magnet specifically includes:
when the motor Is demagnetized, the same demagnetizing current Is applied, the amplitude of the quadrature axis current Is changed by changing the internal power factor angle gamma and the stator current Is, and the change of the magnetic density value of the Alnico permanent magnet Is observed, so that the conclusion that the existence of the quadrature axis current can cause the permanent magnet to be demagnetized passively Is obtained, and under the action of the same demagnetizing current, the larger the quadrature axis current Is, the more obvious the demagnetizing effect Is;
the demagnetizing current and the quadrature axis current with different magnitudes are respectively applied to the motor, and the magnetic density B of the Alnico permanent magnet and the internal power factor angle gamma and the demagnetizing current I are fitted through a surface fitting tool d The relation is as follows:
wherein z=3.28338, a 1 ＝-0.00338，a 2 ＝1.67246e-4，a 3 ＝-1.96503e-7，a 4 ＝-1.34498e-7，a 5 ＝1.2909e-9；b 1 ＝-0.21999；b 2 ＝0.00762；b 3 ＝-1.27545e-4；b 4 ＝1.03523e-6；b 5 ＝-3.26441e-9。
Further, the method for preparing the permissible range for influencing the passive demagnetization difference value of the permanent magnet based on the obtained influence data of the compensation quadrature current on the flux density of the Alnico permanent magnet specifically comprises the following steps:
defining uncompensated quadrature axis current, and only applying demagnetizing current to demagnetize the corresponding Alnico permanent magnet with magnetic density of B 0 . When the same demagnetizing current is applied, the magnitude of the compensating quadrature current is I q When the demagnetizing is carried out, the corresponding Alnico permanent magnet density is B 1 The variation of the magnetic flux density difference before and after the compensation of the cross current is delta B, and the variation delta B of the magnetic flux density difference of the permanent magnet before and after the demagnetization of the compensation of the cross current is not more than the magnetic flux density B of the permanent magnet after the demagnetization of the uncompensated cross current 0 3% of (3%), namely:
ΔB≤3％B 0
definition T rip The integral torque fluctuation coefficient before and after demagnetizing the motor is that:
wherein T is ave For the torque average before demagnetization, T mag A torque average value during the period of applying the magnetizing and demagnetizing current;
further, on the premise of ensuring that the magnetic flux densities of the permanent magnets with low coercive force before and after the compensation of the quadrature axis current after demagnetization are the same, a quadrature axis current compensation flow is formulated based on the influence of the quadrature axis current on the passive demagnetization of the permanent magnets, and specifically comprises the following steps:
step 1, determining the magnetic flux density B of the required Alnico permanent magnet, and enabling an initial internal power factor angle gamma to be the same 0 90 °;
step 2, according to the magnetic density B and the demagnetizing current I of the Alnico permanent magnet d Relational computation I d0 I.e. calculate the demagnetizing current I required for magnetization to the desired magnetization state without compensating the quadrature current d0 ；
Step 3, calculating Δb according to Δb=3%b, and then demagnetizing current I d0 B-DeltaB is substituted into the magnetic density B and the internal power factor angle gamma of the Alnico permanent magnet, and the demagnetizing current I d The relation is that the internal power factor angle gamma is solved, namely the internal power factor angle gamma corresponding to the maximum quadrature axis current value which can be compensated under the passive demagnetization allowable range is calculated, and the quadrature axis current corresponding to the internal power factor angle gamma is I q0 ；
Step 4, substituting the internal power factor angle gamma and the required magnetic flux density B calculated in the step 3 into the Alnico permanent magnet magnetic flux density B and the internal power factor angle gamma, and demagnetizing current I d Relational calculation of the quadrature current I q0 Demagnetizing current I corresponding to magnetization state B needed when present d1 ；
Step 5, simulating demagnetizing current I d1 And outputting a torque result under the action of an internal power factor angle gamma, and calculating a torque fluctuation coefficient;
step 6, if the torque fluctuation coefficient is greater than 0, obtaining corresponding demagnetizing current I under the quadrature axis current compensation strategy d1 And a value of a power factor angle gamma; if the torque ripple factor is smaller than 0, it means that the applied quadrature current is too large, resulting in the quadrature current overcompensation, and according to the torque ripple result, the internal power factor angle which is as small as possible and does not overcompensate the current is reselected within the (gamma, 90 °) interval, and the above step 5 is performed back.
Compared with the prior art, the invention has the following advantages:
according to the method for restraining the transient torque fluctuation of the magnetic regulation of the variable flux motor by the quadrature axis current compensation taking the passive demagnetization influence of the permanent magnet into consideration, the quadrature axis current compensation flow is formulated based on the influence of the quadrature axis current on the passive demagnetization of the permanent magnet, and the transient torque fluctuation of the magnetic regulation of the variable flux motor is reduced by the method on the premise that the magnetic density of the permanent magnet is unchanged before and after the compensation of the quadrature axis current.
Based on the reasons, the invention can be widely popularized in the fields of motors, control and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.
Fig. 1 is a block diagram of a variable flux motor according to the present invention.
Fig. 2 is a graph of the magnetic density relationship between the demagnetizing current and the Alnico permanent magnet according to the present invention.
Fig. 3 is a graph showing the torque change during demagnetization according to the present invention.
Fig. 4 is a graph showing the relationship between the magnetic density and the quadrature current of an Alnico permanent magnet under the action of different demagnetizing currents.
FIG. 5 is a graph showing the angular relationship between the magnetic density and the demagnetizing current of the Alnico permanent magnet according to the present invention.
FIG. 6 is a flow chart of the quadrature current compensation of the present invention.
Fig. 7 is a graph showing the contrast of the magnetic density change of the Alnico permanent magnet before and after the quadrature axis current compensation according to the present invention.
Fig. 8 is a graph comparing torque output before and after quadrature current compensation in accordance with the present invention.
In the figure: 1. an Alnico permanent magnet; 2. an armature winding; 3. a stator; 4. a magnetic isolation bridge; 5. NdFeB permanent magnets; 6. magnetic barriers.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be clear that the dimensions of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
In the description of the present invention, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present invention: the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.
Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.
In order to achieve the purpose of reducing the magnetic regulating transient torque fluctuation of the variable magnetic flux motor, the invention provides a quadrature current compensation method which reduces the magnetic regulating transient torque fluctuation by compensating the quadrature current at the moment of applying demagnetizing current pulse to regulate magnetism of the variable magnetic flux motor. In addition, the invention analyzes the passive demagnetization effect of the applied quadrature current on the low-coercivity permanent magnet, and prepares a flow for compensating the quadrature current to inhibit torque fluctuation by taking the influence of the quadrature current on the passive demagnetization of the Alnico permanent magnet as a basis. Finally, a variable flux motor finite element model is established by using JMAG software, and the feasibility of the method for restraining the transient torque fluctuation of the magnetic regulation by the quadrature axis current compensation is verified through simulation.
The technical solutions in the examples of the present invention will be clearly and completely described below with reference to the accompanying drawings in the examples of the present invention.
In the dq-axis coordinate system, the stator current I is synthesized s The angle to the q-axis is alternatively referred to as the internal power factor angle gamma, i.e. the angle between the no-load back emf and the resultant stator current. In motor vector control, the d-axis and q-axis currents and the stator resultant current Is are related as follows:
I d ＝-I s sinγ
I q ＝I s cosγ
thus, in motor control, the resultant stator current I is controlled by s The magnitude of dq-axis current can be controlled by the magnitude of the internal power factor angle gamma and the magnitude of the internal power factor angle gamma.
As shown in FIG. 1, which is a structure diagram of a variable magnetic flux motor, a finite element simulation model is built in a JMAG, the invention adopts an 8-pole 48-slot built-in variable magnetic flux memory motor, and an armature winding is arranged on a stator. The rotor core adopts two permanent magnet materials of aluminum nickel cobalt and neodymium iron boron, and V-shaped low-coercivity permanent magnet grooves and radial grooves are uniformly and alternately arranged along the circumferential direction. In order to reduce the cross coupling effect between the two permanent magnets, the motor is provided with a magnetic barrier, and an aluminum nickel cobalt permanent magnet is arranged in a low-coercivity permanent magnet groove; the radial slot is provided with the neodymium-iron-boron permanent magnet and the magnetic barrier, when the magnetization level of the alnico permanent magnet is reduced by applying the direct-axis demagnetization pulse current in the armature winding, the magnetic flux of the neodymium-iron-boron permanent magnet is short-circuited through the magnetic barrier, and the problem that the alnico permanent magnet is easy to be reversely magnetized by the neodymium-iron-boron permanent magnet after being positively magnetized is avoided. Besides, two ends of the coercive force permanent magnet groove are provided with magnetism isolating bridges to limit the magnetic leakage phenomenon of the alnico permanent magnet.
In order to obtain the influence change of the demagnetizing current on the magnetic density of the Alnico permanent magnet, ensuring that the quadrature axis current applied to the stator winding of the variable flux motor is 0A, gradually increasing the magnitude of the demagnetizing current to simulate to obtain the relationship curve of the magnetic density and the demagnetizing current of the Alnico permanent magnet shown in figure 2, and fitting the magnetic density B and the demagnetizing current I of the Alnico permanent magnet d The relationship is shown in formula 2.
Wherein a is 0 ＝0.83088，a 1 ＝-0.00409，a 2 ＝5.43728e-4，a 3 ＝-2.12765e-5，a 4 ＝2.51657e-7，a 5 ＝-9.86643e-10。
The demagnetization simulation is carried out on the variable magnetic flux motor, a demagnetization current pulse is applied to the armature winding, the quadrature current is guaranteed to be zero when the demagnetization current is introduced, the change of the transition time in the demagnetization process is shown in fig. 3, and as can be seen from fig. 3, the zero-setting of the quadrature current can cause the motor torque to generate great fluctuation during the period of applying the demagnetization current pulse for 0.01-0.02 s.
Based on the defects, the invention provides a quadrature current compensation method which reduces the transient torque fluctuation of magnetic regulation by compensating the quadrature current at the moment of applying the demagnetizing current to regulate the magnetic regulation of a variable magnetic flux motor. The method flow is formulated based on the fact that the compensated quadrature axis current does not have too much influence on the magnetic density passive demagnetization of the Alnico permanent magnet. The method specifically comprises the following steps:
s1, in the demagnetization process, the permanent magnet can still be subjected to passive demagnetization due to the fact that the cross-axis current is applied by the cross saturation effect. In order to obtain the influence of the cross-axis current on the magnetic density of the permanent magnet, the same demagnetizing current is applied, and different cross-axis currents are applied by changing the internal power factor angle to observe the change of the magnetic density amplitude of the Alnico permanent magnet. Fig. 4 shows that the magnetic density of the Alnico permanent magnet changes along with the cross-axis current when different demagnetizing currents are applied, and the result shows that the existence of the cross-axis current can cause the permanent magnet to perform passive demagnetization, and the smaller the internal power factor angle is, the larger the cross-axis current is, the more obvious the passive demagnetization effect is.
Applying different demagnetizing currents to the motor respectively, changing the magnitude of an internal power factor angle under the corresponding demagnetizing current, and fitting the magnetic density and the internal power factor angle of the Alnico permanent magnet, wherein a three-dimensional curved surface diagram of the demagnetizing current is shown in fig. 5, and it can be seen that the magnetic density of the Alnico permanent magnet is reduced along with the increase of the demagnetizing current; the internal power factor angle is reduced, that is, the quadrature axis current is increased, and the magnetic density of the Alnico permanent magnet is reduced. Fitting the magnetic density B and the internal power factor angle gamma of the Alnico permanent magnet and the demagnetizing current I by using a curved surface fitting tool d The relation is shown as 3
Wherein z=3.28338, a 1 ＝-0.00338，a 2 ＝1.67246e-4，a 3 ＝-1.96503e-7，a 4 ＝-1.34498e-7；a 5 ＝1.2909e-9；b 1 ＝-0.21999；b 2 ＝0.00762；b 3 ＝-1.27545e-4；b 4 ＝1.03523e-6；b 5 ＝-3.26441e-9。
S2, according to simulation experiments of the influence of the cross-axis current on the flux density of the Alnico permanent magnet, the internal power factor angle gamma is too small, namely the q-axis current compensation value is too large to produce passive demagnetization on the permanent magnet, uncompensated cross-axis current is set, and only demagnetization current I is applied d The magnetic density of the corresponding Alnico permanent magnet after demagnetization is B 0 . When the same demagnetizing electricity is appliedStream I d At the same time, compensating the magnitude of the quadrature axis current to be I q When the demagnetizing is carried out, the corresponding Alnico permanent magnet density is B 1 The variation of the magnetic flux density difference before and after the compensation of the quadrature axis current is delta B, and the variation delta B of the magnetic flux density difference of the permanent magnet before and after the demagnetization of the compensation quadrature axis current is not more than the magnetic flux density B of the permanent magnet after the demagnetization of the uncompensated q axis current 0 3% of (3%), namely:
ΔB≤3％B 0
definition T rip The integral torque fluctuation coefficient before and after demagnetizing the motor is that:
wherein T is ave For the torque average before demagnetization, T mag The torque average value during the period of applying the magnetizing and demagnetizing current.
And S3, on the premise of ensuring that the magnetic flux densities of the permanent magnets with low coercive force before and after the compensation of the quadrature axis current after demagnetization are the same, the quadrature axis current compensation flow is formulated based on the influence of the quadrature axis current on the passive demagnetization of the permanent magnets. The flow chart of the quadrature current compensation method is shown in fig. 6.
From the relation between d-axis and q-axis currents and stator resultant current Is, the motor Is loaded with current of the same magnitude, and the distribution I can be changed by changing the internal power factor angle gamma d 、I q The magnitude of the current value. Thus, the stator current I will be synthesized s And the internal power factor angle gamma is used as a variable, and the relation between the magnetic flux density and the demagnetizing current of the fitted permanent magnet and the internal power factor angle is obtained through the simulation, so that the corresponding synthetic stator current I can be calculated s And an internal power factor angle gamma value, the calculation process is as follows:
s31, determining a needed magnetization state B, and enabling an initial internal power factor angle gamma to be 0 90 °;
s32, according to the magnetic density B and the demagnetizing current I of the Alnico permanent magnet d Relational computation I d0 I.e. calculate the demagnetizing current Id required for magnetization to the desired magnetization state without compensating the quadrature current 0 ；
S33, calculating Δb from Δb=3%b, and applying a demagnetizing current I d0 Substituting B-DeltaB into formula 2 to solve an internal power factor angle gamma, namely calculating the internal power factor angle corresponding to the maximum quadrature current value which can be compensated under the passive demagnetization allowable range, wherein the quadrature current corresponding to the internal power factor angle gamma is Iq 0 ；
S34, substituting the calculated internal power factor angle gamma and the required magnetization state B into the formula 2, and recalculating the quadrature axis current Iq 0 Demagnetizing current I corresponding to magnetization state B needed when present d1 ；
S35, simulated demagnetizing current I d1 And outputting a torque result under the action of an internal power factor angle gamma, and calculating a torque fluctuation coefficient;
s36, if the torque fluctuation coefficient is greater than 0, obtaining the corresponding demagnetizing current I under the quadrature axis current compensation strategy d1 And a value of a power factor angle gamma; if the torque ripple coefficient is less than 0, it indicates that the applied quadrature current is too large, resulting in the quadrature current being overcompensated. At this time, based on the torque fluctuation result, the internal power factor angle which is as small as possible and does not overcompensate the current is reselected within the (γ,90 °) interval, and the above-described step S34 is repeated.
The invention takes 20A load current and 50A demagnetizing current as examples, and calculates and compensates the transient torque fluctuation condition of the magnetic modulation before and after the quadrature axis current. Fig. 7 is a graph comparing the flux density of an Alnico permanent magnet when the compensating quadrature current after demagnetization and the uncompensating quadrature current after demagnetization, and it can be seen that the compensating quadrature current after demagnetization and the uncompensating quadrature current both demagnetize the permanent magnet to the same flux density. The requirements of the same magnetic flux density before and after the quadrature axis current compensation are met. FIG. 8 is a graph comparing output torque when compensating for cross current with output torque when not compensating for cross current, wherein the torque fluctuation coefficient before compensating for cross current is 0.99, the torque fluctuation coefficient after compensating for cross current is 0.11, which is obviously improved compared with the torque fluctuation coefficient before compensating for cross current.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (1)
1. A method for restraining the magnetic regulating transient torque fluctuation of a variable flux motor by quadrature axis current compensation is characterized by comprising the following steps:
the method for acquiring and analyzing the influence data of the compensation quadrature axis current on the flux density of the Alnico permanent magnet specifically comprises the following steps:
when the motor Is demagnetized, the same demagnetizing current Is applied, the amplitude of the quadrature axis current Is changed by changing the internal power factor angle gamma and the stator current Is, and the change of the magnetic density value of the Alnico permanent magnet Is observed, so that the conclusion that the existence of the quadrature axis current can cause the permanent magnet to be demagnetized passively Is obtained, and under the action of the same demagnetizing current, the larger the quadrature axis current Is, the more obvious the demagnetizing effect Is;
the demagnetizing current and the quadrature axis current with different magnitudes are respectively applied to the motor, and the magnetic density B of the Alnico permanent magnet and the internal power factor angle gamma and the demagnetizing current I are fitted through a surface fitting tool d The relation is as follows:
wherein z=3.28338, a 1 ＝-0.00338，a 2 ＝1.67246e-4，a 3 ＝-1.96503e-7，a 4 ＝-1.34498e-7，a 5 ＝1.2909e-9；b 1 ＝-0.21999；b 2 ＝0.00762；b 3 ＝-1.27545e-4；b 4 ＝1.03523e-6；b 5 ＝-3.26441e-9；
Based on the obtained influence data of the compensation quadrature axis current on the flux density of the Alnico permanent magnet, the allowable range for allowing the influence of the passive demagnetization difference of the permanent magnet is formulated, and the method specifically comprises the following steps:
defining uncompensated quadrature axis current, and only applying demagnetizing current to demagnetize the corresponding Alnico permanent magnet with magnetic density of B 0 When the same demagnetizing current is applied,at the same time compensate the magnitude of the quadrature axis current as I q When the demagnetizing is carried out, the corresponding Alnico permanent magnet density is B 1 The variation of the magnetic flux density difference before and after the compensation of the cross current is delta B, and the variation delta B of the magnetic flux density difference of the permanent magnet before and after the demagnetization of the compensation of the cross current is not more than the magnetic flux density B of the permanent magnet after the demagnetization of the uncompensated cross current 0 3% of (3%), namely:
ΔB≤3％B 0
definition T rip The integral torque fluctuation coefficient before and after demagnetizing the motor is that:
wherein T is ave For the torque average before demagnetization, T mag A torque average value during the period of applying the magnetizing and demagnetizing current;
on the premise of ensuring that the magnetic flux density of the permanent magnet with low coercivity is the same before and after the compensation of the quadrature axis current after demagnetization, the quadrature axis current compensation flow is formulated based on the influence of the quadrature axis current on the passive demagnetization of the permanent magnet, and specifically comprises the following steps:
step 1, determining the magnetic flux density B of the required Alnico permanent magnet, and enabling an initial internal power factor angle gamma to be the same 0 90 °;
step 2, according to the magnetic density B and the demagnetizing current I of the Alnico permanent magnet d Relational computation I d0 I.e. calculate the demagnetizing current I required for magnetization to the desired magnetization state without compensating the quadrature current d0 ；
Step 3, calculating Δb according to Δb=3%b, and then demagnetizing current I d0 B-DeltaB is substituted into the magnetic density B and the internal power factor angle gamma of the Alnico permanent magnet, and the demagnetizing current I d The relation is that the internal power factor angle gamma is solved, namely the internal power factor angle gamma corresponding to the maximum quadrature axis current value which can be compensated under the passive demagnetization allowable range is calculated, and the quadrature axis current corresponding to the internal power factor angle gamma is I q0 ；
Step 4, substituting the internal power factor angle gamma and the required magnetic flux density B calculated in the step 3 into the Alnico permanent magnet magnetic flux density B and the internal power factor angle gamma, and demagnetizing current I d Relational calculation of the quadrature current I q0 Demagnetizing current I corresponding to magnetization state B needed when present d1 ；
Step 5, simulating demagnetizing current I d1 And outputting a torque result under the action of an internal power factor angle gamma, and calculating a torque fluctuation coefficient;
step 6, if the torque fluctuation coefficient is greater than 0, obtaining corresponding demagnetizing current I under the quadrature axis current compensation strategy d1 And a value of a power factor angle gamma; if the torque ripple factor is smaller than 0, it means that the applied quadrature current is too large, resulting in the quadrature current overcompensation, and according to the torque ripple result, the internal power factor angle which is as small as possible and does not overcompensate the current is reselected within the (gamma, 90 °) interval, and the above step 5 is performed back.
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Application publication date: 20230623 Assignee: Zhengzhou Light Electric Technology Research Institute Co.,Ltd. Assignor: Dalian Maritime University Contract record no.: X2024210000012 Denomination of invention: A Method for Suppressing Transient Torque Fluctuations in Variable Flux Motors with Quadrature Axis Current Compensation Granted publication date: 20230815 License type: Common License Record date: 20240201 |