Sheet motor single-phase short circuit fault-tolerant current reconstruction method for eliminating reverse magnetic potential

Abstract

The invention discloses a slice motor single-phase short-circuit fault-tolerant current reconstruction method for eliminating reverse magnetic potential, which adopts a six-tooth and one-pair-pole motor structure, and constructs five-phase current to eliminate the reverse magnetic potential by constructing a magnetic potential expression of residual-phase current in an air gap after single-phase short circuit, extracting the reverse magnetic potential and enabling the reverse magnetic potential to be equivalent to a magnetic vector. The method comprises the following specific steps: firstly, according to a magnetic potential calculation formula, extracting a reversal magnetic potential expression and enabling the reversal magnetic potential expression to be equivalent to a magnetic vector; secondly, five-phase current is constructed through the vector superposition principle, and it is ensured that reversal magnetic potentials are mutually counteracted; and finally, considering the influence of the short-circuit current on the reversal magnetic potential, correcting the adjacent tooth current of the short-circuit current phase, and further eliminating the reversal magnetic potential caused by the short-circuit current. According to the invention, by eliminating the reverse magnetic potential, stable suspension of the slice motor under a single-phase short-circuit fault is realized, suspension force pulsation is avoided, and the fault-tolerant performance and practicability of the slice motor are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bearingless motor control, and mainly relates to a single-phase short-circuit fault-tolerant current reconstruction method for a wafer motor that eliminates reverse magnetomotive force. Background Art

[0002] During the operation of a wafer motor, once an open-circuit fault occurs in the suspension winding, the suspension performance will be greatly reduced, resulting in unnecessary losses. Existing fault-tolerant methods for bearing motors cannot be fully applied to the open-circuit fault tolerance of the suspension winding of wafer motors. Existing short-circuit fault-tolerant methods for wafer motors do not start from the perspective of eliminating suspension pulsation and maintaining stable suspension of the wafer motor. Instead, based on the power-optimal constraint, the remaining current is solved by equations, and the influence of reverse magnetomotive force on the suspension force is ignored during the solution process. Although the reconstructed current can enable the motor to continue to suspend, the radial displacement of the rotor becomes larger and the suspension performance deteriorates.

[0003] The document "202411260114.X" proposes a fault-tolerant control algorithm under single-phase open-circuit fault, which can eliminate the reverse magnetomotive force problem under single-phase open-circuit fault, but does not consider the influence of short-circuit current and cannot be directly applied to short-circuit faults. Summary of the Invention

[0004] Object of the Invention: Aiming at the problems existing in the above background art, the present invention provides a single-phase short-circuit fault-tolerant control method that corrects the current of the short-circuited adjacent phase, eliminating the reverse magnetomotive force from two levels.

[0005] Technical Solution: To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A single-phase short-circuit fault-tolerant current reconstruction method for a wafer motor that eliminates reverse magnetomotive force, comprising the following steps:

[0007] Step 1: Adopt a motor structure with six teeth and one pair of poles to construct the magnetomotive force expression of the remaining-phase current in the air gap after single-phase short circuit;

[0008] Step 2: According to the magnetomotive force expression in Step 1, extract the reverse magnetomotive force expression and equivalent it to a magnetic vector;

[0009] Step 3: Based on the vector superposition principle, construct a five-phase current to ensure that the reverse magnetomotive forces cancel each other out;

[0010] Step 4: Consider the influence of short-circuit current on the reverse magnetomotive force, correct the relative tooth current of the short-circuit current phase, and further eliminate the reverse magnetomotive force caused by the short-circuit current;

[0011] Step 5: Through the corrected five-phase current, ensure the stable suspension of the wafer motor under single-phase short-circuit fault and avoid suspension force pulsation.

[0012] Preferably, in the step 1, the motor structure includes 6 L-shaped stators. Each L-shaped stator includes an axial stator yoke and a radial stator tooth, and surrounds the flaky rotor. 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 has one pair of poles, and the suspension winding has two pairs of poles, realizing suspension control and rotation control simultaneously; the bottoms of the L-shaped stators are connected by a core magnetic conduction ring; a pair of pole permanent magnets are attached to the outer side of the flaky rotor.

[0013] Preferably, in the step 2, the reverse magnetomotive force expression is extracted through the magnetomotive force calculation formula and is equivalent to two groups of ten vectors about one pair of poles and two pairs of poles.

[0014] Preferably, in the step 3, through the principle of vector superposition, a five-phase current is constructed to ensure that the phase difference between two vectors is 180° and they cancel each other out, and the remaining three vectors form an equilateral triangle and cancel each other out.

[0015] Preferably, in the step 4, considering the influence of the short-circuit current on the reverse magnetomotive force, the adjacent tooth currents of the short-circuit current phase are corrected, specifically including:

[0016] According to the reverse magnetomotive force of two pairs of poles generated by the short-circuit current in the air gap, the adjacent tooth currents of the short-circuit current phase are corrected;

[0017] Through the principle that the magnetic motive forces of two phases differ by 180° and cancel each other out, the reverse magnetomotive force caused by the short-circuit current is further eliminated.

[0018] Preferably, in the step 5, through the corrected five-phase current, the stable suspension of the flaky motor under the single-phase short-circuit fault is ensured, and the suspension force pulsation is avoided, specifically including:

[0019] By eliminating the reverse magnetomotive force, ensuring that the suspension force is consistent with the non-fault-tolerant situation;

[0020] Through the corrected five-phase current, ensuring that the suspension performance of the flaky motor is not affected by the single-phase short-circuit fault.

[0021] Specifically,

[0022] Taking the short-circuit phase as the initial phase with a mechanical angle of 0°, considering the combined magnetomotive force of one pair of poles and two pairs of poles, the specific combined magnetomotive force expressions of one pair of poles and two pairs of poles are shown in formula (1):

[0023]

[0024] 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 magnetomotive forces of one pair of poles and two pairs of poles of the five-phase winding respectively, A, B, C, D, and E are the phases of the five-phase current respectively, θ is the rotor position angle, and ω is the synchronous electrical angular frequency of the motor. is the amplitude of the reverse rotating magnetomotive force of two pairs of poles.

[0025] According to the synthetic magnetomotive force expressions of one pair of poles and two pairs of poles in formula (1), the extracted reverse rotating magnetomotive force expression can be expressed in the form of formula (2):

[0026]

[0027] In the formula, F 1Af , F 1Bf , F 1Cf , F 1Df , F 1Ef , F 2Af , F 2Bf , F 2Cf , F 2Df , F 2Ef are the reverse rotating magnetomotive forces of one pair of poles and two pairs of poles of the five-phase winding respectively.

[0028] According to the reverse rotating magnetomotive force expression in formula (2), the reverse rotating magnetomotive forces of one pair of poles and two pairs of poles are equivalent to two groups of ten vectors in total regarding one pair of poles and two pairs of poles, specifically as shown in formula (3):

[0029]

[0030] 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 vectors equivalent to the reverse rotating magnetomotive forces of one pair of poles and two pairs of poles of the five-phase winding respectively.

[0031] According to the superposition principle of vectors, in order to cancel out after the superposition of five vectors with equal amplitudes, there are two superposition methods. Method one is that the five vectors can form a regular pentagon and cancel each other out. Method two is that two of the vectors cancel each other out after a phase difference of 180°, and the remaining three vectors form an equilateral triangle and cancel each other out. The specific scheme is as Figure 1 shown.

[0032] Since there are two sets of reverse magnetomotive forces of one pair of poles and two pairs of poles that need to be cancelled, there are theoretically four options to choose from. For the example in this article, when one set of vectors cancels the reverse magnetomotive force in the way of forming an equilateral pentagon, no matter which method the other set of vectors adopts, it is impossible to make the vector sum zero. Therefore, Method 1 is not within the scope of consideration, and only Method 2 can be selected to cancel the two sets of reverse magnetomotive forces.

[0033] Based on the above principle, after constructing the current according to the Figure 2 cancellation process, the new five-phase current is shown in Equation (4):

[0034]

[0035] Considering the influence of the short-circuit current on the reverse magnetomotive force, when phase F is short-circuited, modify the amplitude and phase of the short-circuit current and the amplitude and phase of phase A current in Equation (4). The specific steps are as follows:

[0036] When the winding of phase F is short-circuited, the short-circuit current in the winding can be simplified as

[0037]

[0038] where I is the amplitude of the short-circuit current, is the phase. According to Equation (2), the reverse magnetomotive force of two pairs of poles generated by this current in the air gap is

[0039]

[0040] According to the principle that the magnetic potential difference between two phases cancels each other by 180°, the final five-phase current considering the influence of the short-circuit current on the magnetic potential is

[0041]

[0042] where,

[0043] A single-phase short-circuit fault-tolerant current reconstruction method for a thin-film motor based on the magnetic field modulation theory provided by the present invention has the following beneficial effects compared with the existing model:

[0044] (1) During the current reconstruction process, the reverse magnetomotive forces of one pair of poles and two pairs of poles are cancelled, the suspension force pulsation is eliminated, and a stable suspension force is obtained.

[0045] (2) Further eliminate the reverse magnetomotive force caused by the short-circuit current.

[0046] (3) 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.

[0047] (4) The current reconstruction process is simple, and the reconstructed current form is simple, facilitating the input of fault-tolerant current and motor control.

[0048] (5) The suspension performance remains unchanged before and after fault tolerance. Compared with existing fault-tolerant current reconstruction methods, the motor performance after fault tolerance is significantly improved. Description of the Drawings

[0049] Figure 1 is a schematic diagram of the superposition method in which the sum of five equal-amplitude vectors is zero provided by the present invention;

[0050] Figure 2 is a schematic diagram of the superposition process in which the sum of five equal-amplitude vectors is zero provided by the present invention;

[0051] Figure 3 is an axial sectional view of a six-tooth one-pole bearingless permanent magnet thin-sheet motor provided by the present invention;

[0052] Figure 4 is a suspension force simulation diagram when six-phase normal suspension current is applied in the simulation;

[0053] Figure 5 is a suspension force simulation diagram when five-phase fault-tolerant current is applied in the simulation;

[0054] Figure 6 is a fitting diagram of the suspension force before and after the fault-tolerant current is applied in the simulation. Detailed Embodiments

[0055] The present invention will be further described in detail below with reference to the drawings. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0056] The present invention uses a bearingless permanent magnet thin-sheet motor as shown in Figure 3 . The motor structure has six teeth and one pole, including 6 L-shaped stators 2. Each L-shaped stator 2 includes an axial stator yoke and a radial stator tooth, surrounding the thin-sheet 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 has one pole, and the suspension winding has two poles, realizing suspension control and rotation control simultaneously. The bottoms of the L-shaped stators are connected by a core magnetic conduction ring 3. A pair of pole permanent magnets are attached to the outside of the thin-sheet rotor 1.

[0057] Specifically, taking the open-circuit phase as the initial phase with a mechanical angle of 0°, considering the combined magnetomotive force of one pole and two poles, the specific expression of the combined magnetomotive force of one pole and two poles is as shown in Equation (1):

[0058]

[0059] In the formula, F 1A , F 1B , F 1C , F 1D , F 1E , F 2A , F 2B , F 2C , F 2D , F 2E are respectively the magnetomotive forces of one pair of poles and two pairs of poles of the five-phase winding, and A, B, C, D, and E are respectively the phases of the five-phase currents.

[0060] According to the synthetic magnetomotive force expressions of one pair of poles and two pairs of poles in formula (1), the extracted reverse magnetomotive force expression can be expressed in the form of formula (2):

[0061]

[0062] In the formula, F 1Af , F 1Bf , F 1Cf , F 1Df , F 1Ef , F 2Af , F 2Bf , F 2Cf , F 2Df , F 2Ef are respectively the reverse magnetomotive forces of one pair of poles and two pairs of poles of the five-phase winding.

[0063] According to the reverse magnetomotive force expression in formula (2), the reverse magnetomotive forces of one pair of poles and two pairs of poles are equivalent to two groups of ten vectors in total regarding one pair of poles and two pairs of poles, specifically as shown in formula (3):

[0064]

[0065] In the formula, F 1A , F 1B , F 1C , F 1D , F 1E , F 2A , F 2B , F 2C , F 2D , F 2E are respectively the vectors equivalent to the reverse magnetomotive forces of one pair of poles and two pairs of poles of the five-phase winding.

[0066] According to the superposition principle of vectors, in order to cancel out the five vectors with equal amplitudes after superposition, there are two superposition methods. Method one is that the five vectors can form an equilateral pentagon and cancel each other out. Method two is that the phase difference between two of the vectors is 180° and they cancel each other out, and the remaining three vectors form an equilateral triangle and cancel each other out. The specific scheme is as Figure 1as shown

[0067] Since there are two sets of reverse magnetomotive forces of one pair of poles and two pairs of poles that need to be cancelled, there are theoretically four options to choose from. For the example in this article, when one set of vectors cancels the reverse magnetomotive force in the way of forming an equilateral pentagon, no matter which method the other set of vectors adopts, it is impossible to make the vector sum zero. Therefore, Method 1 is not within the scope of consideration, and only Method 2 can be selected to cancel the two sets of reverse magnetomotive forces.

[0068] Based on the above principle, after constructing the current according to the cancellation process of Figure 2 , the new five-phase current is as shown in Equation (4):

[0069]

[0070] Considering the influence of the short-circuit current on the reverse magnetomotive force, when phase F is short-circuited, the amplitude and phase of the short-circuit current in Equation (4) are corrected, and the amplitude and phase of phase A current. The specific steps are as follows:

[0071] When the winding of phase F is short-circuited, the short-circuit current in the winding can be simplified as

[0072]

[0073] where I is the amplitude of the short-circuit current, is the phase. According to Equation (2), the reverse magnetomotive force of two pairs of poles generated by this current in the air gap is

[0074]

[0075] According to the principle that the magnetic potential difference between two phases is 180° for cancellation, the final five-phase current considering the influence of the short-circuit current on the magnetic potential is

[0076]

[0077] where

[0078] To verify whether the derivation is correct, in the MAXWELL simulation, the suspension forces before and after the motor is energized with the fault-tolerant current are simulated and compared respectively, so as to verify whether the theoretical derivation is correct.

[0079] Figure 4 is the suspension force simulation diagram when six-phase normal suspension current is applied in the simulation. After phase F is short-circuited, if the current in the file "202411260114.X" is applied, due to the reverse magnetomotive force of the short-circuit current not being cancelled, a large suspension force pulsation will be generated.

[0080] Figure 5 is the suspension force simulation diagram when the five-phase fault-tolerant current of the present invention is applied in the simulation, Figure 6It is the fitting diagram of the suspension force before and after the fault-tolerant current is applied in the simulation. From the comparison of several figures, it can be seen that the single-phase open-circuit fault-tolerant current reconstruction method of the thin-sheet motor based on the magnetic field modulation theory provided by the present invention to eliminate the reverse magnetomotive force

[0081] (1) After eliminating the reverse magnetomotive force, a stable suspension force can be obtained.

[0082] (2) The suspension force of the motor after fault tolerance is stable.

[0083] (3) Compared with the suspension force before fault tolerance, the suspension force after fault tolerance remains consistent in the x and y directions.

[0084] The A-phase current obtained by the present invention can change as follows:

[0085]

[0086] Wherein, The generated reverse magnetomotive force of two pairs of poles is It just cancels out the reverse magnetomotive force generated by the short-circuit current of the F phase.

[0087] In summary, compared with the existing fault-tolerant reconstructed current, the single-phase short-circuit fault-tolerant current reconstruction method of the thin-sheet motor based on the magnetic field modulation theory provided by the present invention enables the suspension force before and after fault tolerance to remain unchanged, and greatly improves the suspension performance after fault tolerance.

[0088] The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A single-phase short-circuit fault-tolerant current reconstruction method for a thin-film motor to eliminate reverse magnetomotive force, characterized in that, It includes the following steps: Step 1: Adopt a six-tooth one-pole motor structure to construct the magnetic potential expression of the remaining-phase current in the air gap after single-phase short circuit; Step 2: According to the magnetic potential expression in Step 1, extract the reverse magnetic potential expression and equivalent it to a magnetic vector; Step 3: Based on the vector superposition principle, construct five-phase current to ensure that the reverse magnetic potentials cancel each other out; Step 4: Considering the influence of the short-circuit current on the reverse magnetic potential, correct the relative tooth current of the short-circuit current phase to further eliminate the reverse magnetic potential caused by the short-circuit current; Step 5: Through the corrected five-phase current, ensure the stable suspension of the wafer motor under single-phase short-circuit fault and avoid suspension force pulsation.

2. The method according to claim 1, wherein In the said Step 1, the motor structure includes 6 L-shaped stators. Each L-shaped stator includes an axial stator yoke and a radial stator tooth, surrounding the wafer-shaped rotor. 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 one-pole, and the suspension winding is two-poles to achieve suspension control and rotation control simultaneously; the bottoms of the L-shaped stators are connected by a core magnetic conduction ring; a pair of pole permanent magnets are pasted on the outer side of the wafer-shaped rotor.

3. The method according to claim 1, wherein In the said Step 2, the reverse magnetic potential expression is extracted through the magnetic potential calculation formula and equivalent it to two groups of a total of ten vectors regarding one-pole and two-poles.

4. The method according to claim 1, wherein In the said Step 3, through the vector superposition principle, construct five-phase current to ensure that the phase difference between two of the vectors is 180° and then cancel each other out, and the remaining three vectors form an equilateral triangle and cancel each other out.

5. The method according to claim 1, characterized in that, In the said Step 4, considering the influence of the short-circuit current on the reverse magnetic potential, correct the adjacent tooth current of the short-circuit current phase, specifically including: According to the two-pole reverse magnetic potential generated by the short-circuit current in the air gap, correct the adjacent tooth current of the short-circuit current phase; Through the principle that the magnetic potentials of two phases differ by 180° and cancel each other out, further eliminate the reverse magnetic potential caused by the short-circuit current.

6. The method according to claim 1, wherein In the said Step 5, through the corrected five-phase current, ensure the stable suspension of the wafer motor under single-phase short-circuit fault and avoid suspension force pulsation, specifically including: By eliminating the reverse magnetic potential, ensure that the suspension force is consistent with that without fault tolerance; Through the corrected five-phase current, ensure that the suspension performance of the wafer motor is not affected by single-phase short-circuit fault.

7. The method according to claim 2, wherein Based on the said motor structure, taking the short circuit of Phase F as an example, the synthetic magnetic potential expressions of one-pole and two-poles are shown in Formula (1): Where, F 1A , F 1B , F 1C , F 1D , F 1E are the magnetomotive forces of a pair of poles of the five-phase winding, F 2A , F 2B , F 2C , F 2D , F 2E are the magnetomotive forces of two pairs of poles of the five-phase winding, A, B, C, D, E are the phases of the five-phase currents respectively, and the mechanical angles corresponding to the F phase, A phase, B phase, C phase, D phase, and E phase are 0°, 60°, 120°, 180°, 240°, 300° respectively, θ is the rotor position angle, ω is the synchronous electrical angular frequency of the motor, F φ1 is the amplitude of the magnetomotive force of a pair of poles in reverse rotation, is the amplitude of the magnetomotive force of two pairs of poles in reverse rotation.

8. The method according to claim 7, wherein According to the synthetic magnetic potential expressions of one-pole and two-poles in Formula (1), the extracted reverse magnetic potential expression is expressed in the form of Formula (2): where F 1Af , F 1Bf , F 1Cf , F 1Df , F 1Ef is the reverse magnetomotive force of a pair of poles of the five-phase winding, and F 2Af , F 2Bf , F 2Cf , F 2Df , F 2Ef is the reverse magnetomotive force of two pairs of poles of the five-phase winding; According to the reverse magnetic potential expression in Formula (2), the reverse magnetic potentials of one-pole and two-poles are equivalent to two groups of a total of ten vectors regarding one-pole and two-poles, specifically as shown in Formula (3): where, F 1A , F 1B , F 1C , F 1D , F 1E are vectors equivalent to the reverse magnetomotive force of a pair of poles of a five-phase winding, and F 2A , F 2B , F 2C , F 2D , F 2E are vectors equivalent to the reverse magnetomotive force of two pairs of poles of a five-phase winding.

9. The method according to claim 8, characterized in that, After the current is constructed according to the cancellation process in Step 3, the new five-phase current is shown in Formula (4):

10. The method according to claim 9, characterized in that, In Step 4, considering the influence of the short-circuit current on the reverse magnetic potential, when Phase F is short-circuited, correct the amplitude and phase of the current of Phase A in Formula (4), and the specific steps are as follows: When the winding of Phase F is short-circuited, the short-circuit current in the winding is simplified to where I is the amplitude of the short-circuit current, is the phase; the reverse magnetomotive force of two pairs of poles generated by the current in the air gap is According to the principle that the magnetic potentials of two phases differ by 180° and cancel each other out, the final five-phase current considering the influence of the short-circuit current on the magnetic potential is Among them,

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