A method for suppressing speed fluctuation of memory motor based on quadrature-axis current reversal

Abstract

The present invention discloses a method for suppressing speed fluctuations of a memory motor based on cross-axis current reversal, and relates to the technical field of motor control. The present invention discloses a method for suppressing speed fluctuations of a memory motor based on cross-axis current reversal. Aiming at the problem that the electromagnetic torque of a high salient pole ratio memory motor is reversed during magnetization, which leads to large speed fluctuations, the method of the present invention measures the direct-axis current value corresponding to the torque reversal in advance, and when the actual direct-axis magnetic modulation current is within the current range corresponding to the torque reversal, the output of the speed controller is reversed as the cross-axis current reference value. This method can avoid negative torque (i.e. torque reversal) during magnetic modulation, reduce torque fluctuations, and thus greatly reduce speed fluctuations.

Description

Technical Field

[0001] The invention relates to the technical field of motor control, and in particular to a method for suppressing magnetic field modulation speed fluctuation of a memory motor based on quadrature-axis current reversal. Background Art

[0002] The memory machine (MM) has low coercive force permanent magnets placed inside. Its magnetization state (MS) can be changed by applying direct axis (d axis) pulse current, thereby changing the permanent magnet flux of the motor. Therefore, by flexibly adjusting the permanent magnet flux, the memory motor can operate in a variety of occasions. Usually, at low speed, the permanent magnet flux of the motor is increased to generate large torque; at high speed, the permanent magnet flux is reduced to achieve wide speed operation. However, when adjusting the magnetization state of the memory motor, it is necessary to apply d axis pulse current with a large amplitude, about 2-3 times the rated current, which will cause large speed fluctuations. For high salient pole ratio memory motors, the magnetic resistance torque component is large. When applying the magnetizing d axis current, the torque will inevitably drop to 0. The use of traditional control methods under load will cause very large speed fluctuations. Summary of the invention

[0003] The purpose of the present invention is to provide a method for suppressing speed fluctuation of a memory motor based on quadrature-axis current reversal, which can greatly reduce speed fluctuation by reversing the quadrature-axis q-axis current to ensure that the torque is not reversed and reduce torque fluctuation.

[0004] To achieve the above object, the present invention provides the following technical solution: A method for suppressing the fluctuation of the magnetic speed of a memory motor, comprising establishing a dq coordinate system, defining the direct axis in the memory motor as the d axis and the quadrature axis as the q axis, measuring the dq axis inductance of the memory motor when it is unloaded and recording it as L dn and L qn ;

[0005] Apply a constant positive q-axis current to the memory motor, and match it with the measured dq-axis inductance value of the memory motor when it is unloaded to determine whether the electromagnetic torque is reversed during magnetic adjustment, that is, whether the electromagnetic torque will change from positive to negative during magnetic adjustment. If the electromagnetic torque is not reversed during magnetic adjustment, the q-axis current reference value will not be reversed.

[0006] If the electromagnetic torque is reversed during magnetic adjustment, the d-axis current value i corresponding to the reverse electromagnetic torque is measured in advance. dr1 (current rising phase) and i dr2 (current falling phase);

[0007] During magnetic modulation, in the current rising stage, when the d-axis current is less than i dr1 , or in the current drop phase, when the d-axis current is less than i dr2When the speed controller directly outputs the q-axis current reference value; in the current rising stage, when the d-axis current is greater than i dr1 Or, in the current decreasing phase, when the d-axis current is greater than i dr2 When the speed controller output passes through the inverter, it is used as the q-axis current reference value.

[0008] Furthermore, it is determined whether the electromagnetic torque is reversed during magnetic modulation, specifically including the following:

[0009] The electromagnetic torque equation of the motor is:

[0010]

[0011] In the formula, i d and i q are the d-axis and q-axis currents, L d and L q are the d-axis and q-axis inductances, ψ PM is the variable permanent magnetic flux, p is the number of pole pairs, ψ t is the defined equivalent magnetic flux;

[0012] Substitute the measured no-load dq-axis inductance and the d-axis current value of the magnetic modulation into the above formula to determine the equivalent flux linkage ψ during the magnetic modulation process. t Will it change from greater than 0 to less than 0, that is, when i q Whether the electromagnetic torque is reversed while keeping the polarity unchanged.

[0013] Furthermore, the d-axis current value corresponding to the torque reversal is measured, as follows:

[0014] Install the motor on a test bench equipped with a torque sensor and lock the rotor;

[0015] Apply a constant positive i q , slowly increase i from 0 d (Current rising stage) until the magnetic modulation current amplitude is reached, and at the same time observe the torque sensor measurement value. When the torque changes from positive to negative, record the corresponding i when the torque is 0 d The current value is i dr1 ;

[0016] Keep constant positive i q , slowly reduce the amplitude of the magnetic current i d (current decrease phase) to 0, and observe the measured value of the torque sensor at the same time. When the torque changes from negative to positive, record the corresponding i when the torque is 0 d The current value is i dr2 ;

[0017] Change q The amplitude of i is repeated, and the above operation is finally obtained. qNext dr1 and i dr2 , and then fit to get i dr1 (i q ) and i dr2 (i q ) and stored in the controller.

[0018] The present invention has at least the following beneficial effects:

[0019] 1. When measuring the d-axis current corresponding to the torque reversal, the method of the present invention fully considers the influence of the q-axis current on the motor parameters, and the measurement is more accurate;

[0020] 2. Compared with the traditional method, the method of the present invention can greatly reduce the fluctuation of the magnetic modulation speed of the memory motor through the reverse control of the cross-axis current.

[0021] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the quadrature-axis current reverse control method of the present invention;

[0023] Figure 2 is a Simulink model of the quadrature-axis current reversal control method of the present invention;

[0024] Figure 3 is the current i corresponding to the torque reversal of the present invention dr1 and i dr2 Schematic diagram of the test scheme;

[0025] Figure 4 The invention adopts the conventional method to adjust the rotation speed and current waveform;

[0026] Figure 5 The invention discloses a rotation speed and a current waveform for adjusting magnetic field by adopting a cross-axis current reverse control method. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0028] See also Figure 1-5 The present invention provides a technical solution: a method for suppressing the speed fluctuation of a memory motor based on the reversal of the quadrature axis current, and the specific steps are as follows:

[0029] S1. Establish a dq coordinate system, define the direct axis of the memory motor as the d axis and the quadrature axis as the q axis, measure the dq axis inductance of the memory motor when it is unloaded and record it as L dn and L qn ;

[0030] S2, applying a constant positive q-axis current to the memory motor, and matching it with the measured dq-axis inductance value of the memory motor when it is unloaded, to determine whether the electromagnetic torque is reversed during magnetic adjustment, that is, whether the electromagnetic torque will change from positive to negative during magnetic adjustment. If the electromagnetic torque is not reversed during magnetic adjustment, the q-axis current reference value will not be reversed;

[0031] Furthermore, the step of determining whether the electromagnetic torque is reversed during magnetic modulation specifically includes the following steps:

[0032] S2.1, the motor electromagnetic torque equation is

[0033]

[0034] In the formula, i d and i q are the d-axis and q-axis currents, L d and L q are the d-axis and q-axis inductances, ψ PM is the variable permanent magnetic flux, p is the number of pole pairs, ψ t is the defined equivalent magnetic flux;

[0035] S2.2, Substitute the no-load dq-axis inductance measured by S1 and the d-axis current value of magnetic modulation into formula (1) to determine the equivalent flux linkage ψ during magnetic modulation. t Will it change from greater than 0 to less than 0, that is, when i q Whether the electromagnetic torque is reversed while keeping the polarity unchanged;

[0036] It should be noted that this phenomenon only occurs in memory motors with a large salient pole ratio. Since memory motors need to apply pulsed current, L d -L q Less than 0, and positive i d Very big, so (L d -L q )i d This term is less than 0 and its magnitude exceeds ψ PM , resulting in torque reversal;

[0037] S3. If the electromagnetic torque is reversed during magnetic adjustment, the d-axis current value i corresponding to the reverse electromagnetic torque is measured in advance. dr1 (current rising phase) and i dr2 (current falling phase);

[0038] like Figure 3As shown, measuring the d-axis current corresponding to the torque reversal in S3 specifically includes the following steps:

[0039] S3.1. Install the motor on a test bench equipped with a torque sensor and lock the rotor;

[0040] It should be noted that locking the rotor is to prevent the motor from running away and causing an accident when the q-axis current is applied;

[0041] S3.2, apply a constant positive i q , slowly increase i from 0 d (Current rising stage) until the magnetic modulation current amplitude is reached, and at the same time observe the torque sensor measurement value. When the torque changes from positive to negative, record the corresponding i when the torque is 0 d The current value is i dr1 ;

[0042] S3.3, keep the same as S3.2 q , slowly reduce the amplitude of the magnetic current i d (current decrease phase) to 0, and observe the measured value of the torque sensor at the same time. When the torque changes from negative to positive, record the corresponding i when the torque is 0 d The current value is i dr2 Usually dr1 and i dr2 There is a slight difference in the values, which is because the permanent magnet flux linkage is different in the rising stage of the magnetic modulation current and the falling stage of the current;

[0043] S3.4. Change i q Repeat steps S3.2 and S3.3 to obtain different i q Next dr1 and i dr2 , and then fit to get i dr1 (i q ) and i dr2 (i q ), stored in the controller for real-time call;

[0044] S4, when adjusting the magnetic field, in the current rising stage, when the d-axis current is less than i dr1 , or in the current drop phase, when the d-axis current is less than i dr2 When the speed controller directly outputs the q-axis current reference value; in the current rising stage, when the d-axis current is greater than i dr1 Or, in the current decreasing phase, when the d-axis current is greater than i dr2 When the speed controller output passes through the inverter, it is used as the q-axis current reference value.

[0045] Figure 4 The speed and current waveforms are shown in the figure when the magnetic field is adjusted by the traditional method.d Increase, motor L d Less than L q , the electromagnetic torque decreases and the speed decreases, so the speed controller outputs a larger q-axis current reference value to try to maintain a constant speed. However, when i d When it is larger, the total magnetic flux is reversed, the electromagnetic torque is negative, and i q Although the limit value is reached, the electromagnetic torque is still negative and the speed fluctuates greatly. It can be seen from the figure that the speed fluctuation reaches 250rpm (62.5% reference speed). Figure 5 The speed and current waveforms when the quadrature axis current reversal control method of the present invention is used for magnetic modulation. It can be seen from the figure that the torque fluctuation and speed fluctuation are reduced by the quadrature axis current reversal. The speed fluctuation of the method of the present invention is only about 20rpm (5% reference speed).

[0046] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0047] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on", "installed on", "fixed on" or "set on" another element, it can be directly on the other element or there can also be a centered element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and are not intended to be the only implementation method.

[0048] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0049] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A method for suppressing speed fluctuation of a memory motor based on quadrature-axis current reversal, characterized in that: include: Establish a dq coordinate system, define the direct axis of the memory motor as the d axis and the quadrature axis as the q axis, measure the dq axis inductance of the memory motor when it is unloaded and record it as L dn and L qn ; Apply a constant positive q-axis current to the memory motor, and match it with the measured dq-axis inductance value of the memory motor when it is unloaded to determine whether the electromagnetic torque is reversed during magnetic adjustment, that is, whether the electromagnetic torque will change from positive to negative during magnetic adjustment. If the electromagnetic torque is not reversed during magnetic adjustment, the q-axis current reference value will not be reversed. If the electromagnetic torque is reversed during magnetic adjustment, the d-axis current value i corresponding to the reverse electromagnetic torque is measured in advance. dr1 and i dr2 ; During magnetic modulation, in the current rising stage, when the d-axis current is less than i dr1 , or in the current drop phase, when the d-axis current is less than i dr2 When , the speed controller directly outputs the q-axis current reference value; In the current rising stage, when the d-axis current is greater than i dr1 Or, in the current decreasing phase, when the d-axis current is greater than i dr2 When , the output of the speed controller is used as the reference value of the q-axis current after passing through the inverter; Measure the d-axis current value corresponding to the torque reversal, as follows: Install the motor on a test bench equipped with a torque sensor and lock the rotor; Apply a constant positive i q , slowly increase i from 0 d Until the magnetic modulation current amplitude is reached, observe the torque sensor measurement value at the same time. When the torque changes from positive to negative, record the corresponding i when the torque is 0. d The current value is i dr1 ; Keep constant positive i q , slowly reduce the amplitude of the magnetic current i d to 0, and observe the measured value of the torque sensor at the same time. When the torque changes from negative to positive, record the corresponding i when the torque is 0 d The current value is i dr2 ; Change q Repeat the above operation to obtain different i q Next dr1 and i dr2 , and then fit to get i dr1 (i q ) and i dr2 (i q ) and stored in the controller.

2. The method for suppressing speed fluctuation of a memory motor based on quadrature-axis current reversal according to claim 1 is characterized in that: Determine whether the electromagnetic torque is reversed during magnetic modulation, specifically including the following: The electromagnetic torque equation of the motor is: In the formula, i d and i q are the d-axis and q-axis currents, L d and L q are the d-axis and q-axis inductances, ψ PM is the variable permanent magnetic flux, p is the number of pole pairs, ψ t is the defined equivalent magnetic flux; Substitute the measured no-load dq-axis inductance and the d-axis current value of the magnetic modulation into the above formula to determine the equivalent flux linkage ψ during the magnetic modulation process. t Will it change from greater than 0 to less than 0, that is, when i q Whether the electromagnetic torque is reversed while keeping the polarity unchanged.

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