Single-phase open-circuit fault-tolerant current reconstruction method for slice motor

Abstract

The invention discloses a thin-sheet motor single-phase open circuit fault-tolerant current reconstruction method for eliminating reverse magnetic potential based on a magnetic field modulation theory. A motor structure with six teeth and one pair of poles is adopted. The method comprises the following steps: firstly, according to a calculation formula of magnetic potential, writing a magnetic potential expression of residual-phase current in an air gap after single-phase open circuit; according to the obtained magnetic potential expression, extracting a reverse magnetic potential expression in the magnetic potential expression; the expression of the reverse magnetic potential is equivalent to a magnetic vector, and the magnetic vector is divided into two groups, namely ten vectors; after the phase difference between two vectors is 180 degrees, the residual phase current counteracts each other, and the remaining three vectors form an equilateral triangle to counteract each other; the five-phase current meeting the conditions simultaneously meets the condition that the reverse magnetic potential is 0, the suspension force is kept consistent with that when fault tolerance is not carried out, and suspension force pulsation does not exist. According to the invention, the defect that the reconstruction current after the traditional single-phase open circuit is applied to the slice motor is overcome, the suspension performance of the slice motor after fault tolerance is improved, and the practicability is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of bearingless motor control, and mainly to a single-phase circuit breaker fault-tolerant current reconstruction method for a thin-film motor based on magnetic field modulation theory to eliminate reverse magnetic potential. Background Art

[0002] During the operation of the thin-film motor, once the suspension winding has a short circuit fault, the suspension performance will be greatly reduced, causing unnecessary losses. The existing fault-tolerant methods for bearing motors are not fully applicable to the short circuit fault tolerance of the suspension winding of thin-film motors. The existing short circuit fault-tolerant methods for thin-film motors do not start from the perspective of eliminating suspension pulsation and maintaining stable suspension of thin-film motors. Instead, they solve the equations for the residual current based on the power optimal constraint. In the solution process, the influence of the reverse magnetic potential on the suspension force is ignored. Although the reconstructed current can make the motor continue to suspend, the radial displacement of the rotor becomes larger and the suspension performance is reduced. Summary of the invention

[0003] Purpose of the invention: In view of the problems existing in the above-mentioned background technology, the present invention provides a single-phase circuit breaker fault-tolerant control method based on magnetic field modulation theory to offset the reverse magnetic potential during the current reconstruction process. Compared with the traditional circuit breaker reconstruction current, the reconstructed current of the present invention offsets the reverse magnetic potential and eliminates the pulsation of the suspension force, which is more suitable for circuit breaker fault-tolerant control of thin-film motors.

[0004] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A single-phase circuit-breaking fault-tolerant current reconstruction method for a thin-film motor based on magnetic field modulation theory to eliminate reverse magnetic potential adopts a six-tooth one-pole motor structure; it includes six L-shaped stators; each L-shaped stator includes an axial stator yoke and radial stator teeth, which surround the thin-film rotor, and the radial stator teeth are flush with the rotor. Each axial stator yoke is respectively wound with a suspension winding and a torque winding, the torque winding is a pair of poles, and the suspension winding is two pairs of poles, and suspension control and rotation control are realized at the same time; the bottom of the L-shaped stator is connected through an iron core magnetic ring; a pair of permanent magnets are attached to the outside of the thin-film rotor; based on this motor structure, the magnetic potential formed in the air gap by the residual phase current after a single-phase circuit breaker is constructed; specifically,

[0006] Taking the open circuit phase as the initial phase with a mechanical angle of 0°, considering the synthetic magnetic potential of one pole pair and two pole pairs, the specific synthetic magnetic potential expression of one pole pair and two pole pairs is shown in formula (5):

[0007]

[0008] In the formula, F 1A 、F 1B 、F 1C 、F1D 、F 1E 、F 2A 、F 2B 、F 2C 、F 2D 、F 2E are the magnetic potentials of one pole and two pole pairs of the five-phase winding, and A, B, C, D, and E are the phases of the five-phase current.

[0009] According to the composite magnetic potential expression of one pair of poles and two pairs of poles in formula (5), the extracted reversal magnetic potential expression can be expressed in the form of formula (6):

[0010]

[0011] In the formula, F 1Af 、F 1Bf 、F 1Cf 、F 1Df 、F 1Ef 、F 2Af 、F 2Bf 、F 2Cf 、F 2Df 、F 2Ef They are the reverse magnetic potentials of one pole pair and two pole pairs of the five-phase winding respectively.

[0012] According to the reversal magnetic potential expression of formula (6), the reversal magnetic potential of one pair of poles and two pairs of poles is equivalent to two groups of ten vectors related to one pair of poles and two pairs of poles, as shown in formula (7):

[0013]

[0014] In the formula, F 1A 、F 1B 、F 1C 、F 1D 、F 1E 、F 2A 、F 2B 、F 2C 、F 2D 、F 2E They are the vectors equivalent to the reverse magnetic potentials of one pair of poles and two pairs of poles of the five-phase winding.

[0015] According to the principle of vector superposition, in order to make five vectors of equal amplitude cancel each other out after superposition, there are two superposition methods. The first method is that the five vectors can form an equilateral pentagon and cancel each other out. The second method is that two of the vectors have a phase difference of 180° and then cancel each other out. The remaining three vectors form an equilateral triangle and cancel each other out. The specific scheme is as follows: Figure 1 shown.

[0016] Since the two sets of reverse magnetic potentials of one pair of poles and two pairs of poles need to be offset, there are four theoretical options. In the example of this article, when one set of vectors uses an equilateral pentagon to offset the reverse magnetic potential, the other set of vectors cannot achieve a vector sum of zero no matter which method is used. Therefore, method one is not within the scope of consideration, and only method two can be used to offset the two sets of reverse magnetic potentials.

[0017] Based on the above principles, Figure 2 After the current is constructed by the offset process, the new five-phase current is shown in formula (8):

[0018]

[0019] The present invention also provides a thin-film motor. When the motor phase F is disconnected, the remaining five phases are injected with the reconstructed current shown in formula (4) to eliminate the reverse magnetic potential and reduce the pulsation of the suspension force.

[0020] The accurate mathematical model of unbalanced magnetic pull taking into account the influence of stator slotting provided by the present invention has the following beneficial effects compared with the existing models:

[0021] (1) During the current reconstruction process, the reverse magnetic potentials of one pair of poles and two pairs of poles are offset, the pulsation of the suspension force is eliminated, and a stable suspension force is obtained.

[0022] (2) The air gap magnetic potential remains unchanged before and after fault tolerance, the suspension force remains stable and unchanged, and the entire control system remains unchanged.

[0023] (3) The current reconstruction process is simple and the reconstructed current form is simple, which is convenient for fault-tolerant current input and motor control.

[0024] (4) The suspension performance before and after fault tolerance remains unchanged. Compared with the existing fault-tolerant current reconstruction method, the motor performance after fault tolerance is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a superposition method of five equal-amplitude vectors provided by the present invention in which the sum of the superposition vectors is zero;

[0026] Figure 2 It is a schematic diagram of the superposition process of five equal-amplitude vectors provided by the present invention, wherein the sum of the superposition vectors is zero;

[0027] Figure 3 This is an axial cross-sectional view of a six-tooth one-pole bearingless permanent magnet thin-film motor provided by the present invention;

[0028] Figure 4 is a fitting diagram of the unbalanced magnetic pull force x-axis component in the simulation and the calculated value of the unbalanced magnetic pull force x-axis component with the slotting effect neglected and the slotting effect considered provided by the present invention;

[0029] Figure 5 is a fitting diagram of the unbalanced magnetic pull force y-axis component in the simulation and the calculated value of the unbalanced magnetic pull force y-axis component with the slotting effect neglected and the slotting effect considered provided by the present invention;

[0030] Figure 6 It is a fitting diagram of the unbalanced magnetic pull in the simulation and the calculated value of the unbalanced magnetic pull with the slotting effect neglected and the slotting effect considered provided by the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention adopts Figure 3 The bearingless permanent magnet thin-film motor shown adopts a six-teeth-one-pole motor structure, including six L-shaped stators 2. Each L-shaped stator 2 includes an axial stator yoke and radial stator teeth, which surround the thin-film rotor. The radial stator teeth are flush with the rotor. Each axial stator yoke is respectively wound with a suspension winding 4 and a torque winding 5. The torque winding is a pair of poles, and the suspension winding is two pairs of poles, so that suspension control and rotation control are realized at the same time. The bottom of the L-shaped stator is connected through an iron core magnetic ring 3. A pair of permanent magnets with poles are attached to the outside of the thin-film rotor 1.

[0033] Specifically, taking the open circuit phase as the initial phase with a mechanical angle of 0°, considering the synthetic magnetic potential of one pole pair and two pole pairs, the specific synthetic magnetic potential expression of one pole pair and two pole pairs is shown in formula (9):

[0034]

[0035] In the formula, F 1A 、F 1B 、F 1C 、F 1D 、F 1E 、F 2A 、F 2B 、F 2C 、F 2D 、F 2E are the magnetic potentials of one pole and two pole pairs of the five-phase winding, and A, B, C, D, and E are the phases of the five-phase current.

[0036] According to the composite magnetic potential expression of one pair of poles and two pairs of poles in formula (9), the extracted reversal magnetic potential expression can be expressed in the form of formula (10):

[0037]

[0038] In the formula, F 1Af 、F 1Bf 、F 1Cf 、F 1Df 、F 1Ef 、F 2Af 、F 2Bf 、F 2Cf 、F 2Df 、F 2Ef They are the reverse magnetic potentials of one pole pair and two pole pairs of the five-phase winding respectively.

[0039] According to the reversal magnetic potential expression of formula (10), the reversal magnetic potential of one pair of poles and two pairs of poles is equivalent to two groups of ten vectors related to one pair of poles and two pairs of poles, as shown in formula (11):

[0040]

[0041] In the formula, F 1A 、F 1B 、F 1C 、F 1D 、F 1E 、F 2A 、F 2B 、F 2C 、F 2D 、F 2E They are the vectors equivalent to the reverse magnetic potentials of one pair of poles and two pairs of poles of the five-phase winding.

[0042] According to the principle of vector superposition, in order to make five vectors of equal amplitude cancel each other out after superposition, there are two superposition methods. The first method is that the five vectors can form an equilateral pentagon and cancel each other out. The second method is that two of the vectors have a phase difference of 180° and then cancel each other out. The remaining three vectors form an equilateral triangle and cancel each other out. The specific scheme is as follows: Figure 1 shown.

[0043] Since the two sets of reverse magnetic potentials of one pair of poles and two pairs of poles need to be offset, there are four theoretical options. In the example of this article, when one set of vectors uses an equilateral pentagon to offset the reverse magnetic potential, the other set of vectors cannot achieve a vector sum of zero no matter which method is used. Therefore, method one is not within the scope of consideration, and only method two can be used to offset the two sets of reverse magnetic potentials.

[0044] For a pair of pole reversal magnetic potentials, when B = A + 120°, the phase difference between the reversal magnetic potential vector generated by the A-phase current and the reversal magnetic potential vector generated by the A-phase current is 180°, and the two cancel each other out; when C = A - 120° and D = A - 60°, and E = A, the phase difference between the reversal magnetic potential vector generated by the C-phase current, the reversal magnetic potential vector generated by the D-phase current and the reversal magnetic potential vector generated by the E-phase current is 120°, and the three cancel each other out, such as Figure 2 As shown in (a); for the two-pole reversal magnetic potential, when B = A + 120° and E = A, the phase difference between the reversal magnetic potential vector generated by the A-phase current, the reversal magnetic potential vector generated by the B-phase current and the reversal magnetic potential vector generated by the E-phase current is 120°, and the three cancel each other out; when C = A - 120° and D = A - 60°, the phase difference between the reversal magnetic potential vector generated by the C-phase current and the reversal magnetic potential vector generated by the D-phase current is 180°, and the two cancel each other out, as shown in Figure 2 (b) as shown.

[0045] Based on the above principles, Figure 2 After the current is constructed by the offset process, the new five-phase current is shown in formula (12):

[0046]

[0047] In order to verify whether the derivation is correct, the suspension force before and after the fault-tolerant current is passed into the motor is simulated in the MAXWELL simulation, and the results are compared to verify whether the theoretical derivation is correct.

[0048] Figure 4 This is the simulation diagram of the suspension force when six-phase normal suspension current is passed through the simulation. Figure 5 This is the suspension force simulation diagram when five-phase fault-tolerant current is passed through the simulation. Figure 6 It is a fitting diagram of the suspension force before and after the fault-tolerant current is introduced in the simulation. From the comparison of several pictures, it can be seen that the single-phase circuit-breaking fault-tolerant current reconstruction method of the thin-film motor based on the magnetic field modulation theory to eliminate the reverse magnetic potential provided by the present invention is

[0049] (1) After eliminating the reverse magnetic potential, a stable suspension force can be obtained.

[0050] (2) The motor suspension force is stable after fault tolerance.

[0051] (3) Compared with the suspension force before fault tolerance, the suspension force after fault tolerance remains consistent in the x and y directions.

[0052] In summary, compared with the existing fault-tolerant reconstruction current, the single-phase circuit breaker fault-tolerant current reconstruction method of the thin-film motor based on the magnetic field modulation theory to eliminate the reverse magnetic potential provided by the present invention keeps the suspension force unchanged before and after fault tolerance, thereby greatly improving the suspension performance after fault tolerance.

[0053] The present invention also provides a thin-film motor. When the motor phase F is disconnected, the remaining five phases are injected with the reconstructed current shown in formula (12) to eliminate the reverse magnetic potential and reduce the pulsation of the suspension force.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A single-phase circuit-breaking fault-tolerant current reconstruction method for a thin-film motor, wherein the motor adopts a six-teeth-one-pole motor structure, characterized in that: The method comprises the following steps: firstly, writing the magnetic potential expression of the residual phase current in the air gap after the single-phase circuit breaker according to the calculation formula of the magnetic potential; extracting the reverse magnetic potential expression according to the obtained magnetic potential expression; making the reverse magnetic potential of one pair of poles and two pairs of poles equivalent to two groups of ten vectors about one pair of poles and two pairs of poles; reconstructing the phase of the residual current so that the vector sum of the five vectors of the reverse magnetic potential about one pair of poles is zero, and at the same time making the vector sum of the five vectors of the reverse magnetic potential about two pairs of poles is zero, after the reconstructed current is injected into the motor, the motor does not have the reverse magnetic potential, and the suspension force pulsation is reduced.

2. A single-phase circuit-breaking fault-tolerant current reconstruction method for a thin-film motor according to claim 1, characterized in that: The motor structure includes 6 L-shaped stators; each L-shaped stator includes an axial stator yoke and radial stator teeth, which are surrounded by a thin-film rotor, and the radial stator teeth are flush with the rotor. Each axial stator yoke is wound with a suspension winding and a torque winding respectively, the torque winding is a pair of poles, and the suspension winding is two pairs of poles, and suspension control and rotation control are achieved simultaneously; the bottom of the L-shaped stator is connected through an iron core magnetic ring; a pair of permanent magnets are attached to the outside of the thin-film rotor.

3. A single-phase circuit-breaking fault-tolerant current reconstruction method for a thin-film motor according to claim 2, characterized in that: Based on the motor structure, the method comprises the following steps: Taking the open circuit phase as the initial phase with a mechanical angle of 0°, considering the synthetic magnetic potential of one pole pair and two pole pairs, the specific synthetic magnetic potential expression of one pole pair and two pole pairs is shown in formula (1): In the formula, F 1A 、F 1B 、F 1C 、F 1D 、F 1E 、F 2A 、F 2B 、F 2C 、F 2D 、F 2E are the magnetic potentials of one pole and two poles of the five-phase winding, A, B, C, D, E are the phases of the five-phase current, F Φ1 is the amplitude of the composite magnetic potential of a pair of poles, F Φ2 is the auxiliary of the synthetic magnetic potential of two pairs of poles, θ is the rotor phase angle, ωt is the rotor electrical angular frequency; According to the composite magnetic potential expression of one pair of poles and two pairs of poles in formula (1), the extracted reversal magnetic potential expression is expressed in the form of formula (2): In the formula, F 1Af 、F 1Bf 、F 1Cf 、F 1Df 、F 1Ef 、F 2Af 、F 2Bf 、F 2Cf 、F 2Df 、F 2Ef They are the reverse magnetic potentials of one pole and two poles of the five-phase winding respectively; According to the reversal magnetic potential expression of formula (2), the reversal magnetic potential of one pair of poles and two pairs of poles is equivalent to two groups of ten vectors related to one pair of poles and two pairs of poles, as shown in formula (3): In the formula, F 1A 、F 1B 、F 1C 、F 1D 、F 1E F is the vector equivalent to the reverse magnetic potential of a pair of poles in the five-phase winding; 2A 、F 2B 、F 2C 、F 2D 、F 2E It is the vector equivalent to the reverse magnetic potential of two pairs of poles of the five-phase winding; The phases of the five residual currents are reconstructed so that the vector sum of the five vectors of the reversal magnetic potential about a pair of poles is zero, and the vector sum of the five vectors of the reversal magnetic potential about two pairs of poles is zero. After the reconstructed current is injected into the motor, there is no reversal magnetic potential in the motor, and the suspension force pulsation is reduced.

4. A single-phase circuit-breaking fault-tolerant current reconstruction method for a thin-film motor according to claim 3, characterized in that: According to the principle of vector superposition, the way to make five vectors of equal amplitude cancel each other out after superposition is that two of the vectors have a phase difference of 180° and then cancel each other out, and the remaining three vectors form an equilateral triangle and cancel each other out.

5. A single-phase circuit-breaking fault-tolerant current reconstruction method for a thin-film motor according to claim 4, characterized in that: After the current is constructed by the vector superposition and cancellation process, the new five-phase current is shown in formula (4):

6. A sheet motor, characterized in that: When the motor phase F is disconnected, the remaining five phases are injected with the reconstruction current shown in formula (4) in claim 5 to eliminate the reverse magnetic potential and reduce the pulsation of the suspension force.

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