A low-vibration fault-tolerant current calculation method for six-phase permanent magnet motor with phase loss fault

Abstract

The present invention discloses a low-vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase-loss fault. When the six-phase permanent magnet motor adopts a full-bridge power supply mode, if a phase-loss fault occurs, the vibration performance of the motor in the phase-loss operation will deteriorate sharply. Among them, the phase-loss fault types include single-phase phase loss, two adjacent phases loss, two non-adjacent phases loss and at most three phases loss. In order to suppress the deterioration of the vibration response of the motor after the phase-loss fault occurs, the residual phase magnetomotive force is reconstructed according to the reverse magnetomotive force in the residual phase synthetic magnetomotive force under different phase-loss fault types, and the residual phase current is adjusted to maintain the normal vibration response. Compared with the traditional phase-loss fault-tolerant current algorithm, the present invention mainly solves the problem of deterioration of vibration response in the operation process of the six-phase permanent magnet synchronous motor with a phase-loss fault. At the same time, while improving the vibration performance of the motor under a phase-loss fault, the torque performance of the motor under a phase-loss fault is guaranteed.

Description

Technical Field

[0001] The invention relates to a low-vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase-loss fault, and belongs to the technical field of low-vibration and high-reliability driving of multi-phase permanent magnet motors such as aerospace, electric vehicles, and ships. Background Art

[0002] Compared with the traditional three-phase permanent magnet motor, the six-phase permanent magnet motor has a more significant advantage in driving freedom. The multi-phase drive scheme can not only improve the output torque performance, but also reconstruct the residual phase magnetomotive force by adjusting the fault-tolerant algorithm when the motor has a phase failure, thereby maintaining the torque output capacity of the motor under the phase failure. Therefore, multi-phase permanent magnet motors are increasingly widely used in aerospace, electric vehicles, ships and other applications that require high reliability and low vibration. However, the current phase failure fault-tolerant current algorithm only focuses on how to improve the motor torque quality under fault operation, or maintain the stability of the motor heat dissipation temperature rise under phase failure operation. These fault-tolerant control methods do not consider the vibration performance of the motor under phase failure fault-tolerant operation. Deteriorated vibration performance will damage the life of the motor bearing and even destroy the stability of the motor system. Therefore, while ensuring the fault-tolerant operation of the motor under phase failure, how to design a low-vibration fault-tolerant current calculation method has become a problem that needs to be solved urgently.

[0003] The literature Third harmonic current injection in fault-tolerant five-phase permanent-magnet motor drive [J]. IEEE Transactions on Power Electronics, vol. 33, no. 8, pp. 6970-6979, Aug. 2018. proposed a method of injecting the third harmonic of the remaining phase fault-tolerant current after a phase failure to improve the torque pulsation. However, this method injects new current harmonics, which will inevitably introduce new winding magnetomotive force harmonics, thereby deteriorating the vibration performance of the motor in the fault-tolerant state. Therefore, it is impossible to achieve the joint optimization of torque performance and vibration performance.

[0004] China's invention patent publication number CN113364364A authorizes a six-phase permanent magnet motor open-circuit fault-tolerant control method with adjustable torque fluctuation. This invention solves the problem of balanced compensation of torque derating and torque fluctuation in six-phase permanent magnet motors under open-circuit faults when facing different power requirements. However, in the fault-tolerant current waveform, the reconstructed fault-tolerant phase current has poor symmetry, and the current amplitude is inconsistent, which cannot achieve complete cancellation of the fundamental wave reversal magnetomotive force, thereby failing to suppress zero-order vibration to the greatest extent and improve vibration performance under fault-tolerant operation. Summary of the invention

[0005] The purpose of the present invention is to improve the shortcomings of the existing six-phase permanent magnet motor fault-tolerant control technology, and propose a low-vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase-loss fault. The method has strong standardization and is applicable to six-phase permanent magnet motors with different slot-pole combinations. When the motor is running with a phase-loss fault, the fault-tolerant current calculation method is used, and the vibration performance of the motor is significantly improved. In addition, the structure can further optimize the torque pulsation after the phase-loss fault, optimize the electromagnetic performance, take into account vibration suppression and torque performance improvement, and greatly improve the stability of the motor's operation with a phase-loss fault.

[0006] The present invention is implemented by adopting the following technical solution: a low vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase failure, and the specific steps are as follows:

[0007] Step 1, establish a motor electromagnetic simulation model, simulate the torque, magnetomotive force distribution and radial force distribution of the six-phase permanent magnet motor under rated working conditions and healthy operation, and detect the vibration response of the motor;

[0008] Step 2, classify the six-phase permanent magnet motor into different phase loss fault types, simulate the torque and magnetomotive force distribution of each motor after each phase loss fault, simulate and calculate the radial force distribution under different phase loss fault types, and simulate and verify the vibration response of the motor when running under different phase loss fault types;

[0009] Step 3, according to the difference in magnetomotive force distribution under different fault types, design and reconstruct the residual phase synthetic magnetomotive force under each phase-loss fault type;

[0010] Step 4, according to the residual phase synthetic magnetomotive force reconstruction scheme, determine the residual phase current phase angle and solve the low vibration fault-tolerant current expression;

[0011] Step 5, substitute the calculated low vibration fault-tolerant current expression, simulate the radial force distribution under fault-tolerant operation, and simulate and verify the improvement of vibration response under fault-tolerant operation.

[0012] The present invention has the following benefits:

[0013] 1. The application object of the present invention is a six-phase permanent magnet motor. The permanent magnet motor has unique advantages such as high efficiency, high power density, and low vibration. In recent years, it has been widely used in aerospace, electric vehicles, ships and other applications; at the same time, the use of a multi-phase winding structure improves the degree of freedom of drive control and enhances the reliability of motor operation.

[0014] 2. The driving mode of the motor of the present invention adopts a full-bridge driving structure, which realizes the electrical isolation between the control of each phase winding, and ensures that when a phase failure occurs in one or several phases, the current phase of the remaining phase windings is not affected, which is very beneficial for the implementation of fault-tolerant control of multi-phase permanent magnet motors.

[0015] 3. The present invention designs a fault-tolerant current calculation method for various types of phase loss faults, and is applicable to various types of phase loss faults, including four types: single-phase phase loss fault, adjacent two-phase phase loss fault, non-adjacent two-phase phase loss fault, and three-phase phase loss fault.

[0016] 4. The fault-tolerant current driving method designed for phase-loss fault in the present invention achieves optimal vibration performance under fault-tolerant operation and ensures the operation stability under motor phase-loss fault.

[0017] 5. The fault-tolerant current driving method designed for phase-loss fault in the present invention has a very obvious improvement effect on output torque pulsation compared with the torque pulsation under phase-loss fault operation.

[0018] 6. When the motor in the present invention is driven by a low vibration fault-tolerant current, its average output torque is consistent with its corresponding average output torque under a phase-loss fault operation, thereby achieving the stability of the motor's output torque capacity.

[0019] In summary, the low-vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase-loss fault of the present invention can not only be applied to a variety of phase-loss fault types, improving the vibration performance of the multi-phase permanent magnet motor under fault-tolerant operation, but also takes into account the improvement of torque pulsation under phase-loss fault, ensuring the torque output capacity under phase-loss fault, and overcoming the limitation of the single application effect of the traditional phase-loss fault-tolerant current calculation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the electromagnetic effective part of the six-phase permanent magnet motor in the present invention;

[0021] Figure 2 It is the spatial phase vector distribution diagram of the six-phase permanent magnet motor in the present invention;

[0022] Figure 3 This is a structural diagram of the external drive circuit of the six-phase permanent magnet motor in the present invention;

[0023] Figure 4 This is a waveform diagram of the rated torque of the six-phase permanent magnet motor in the present invention under healthy operation;

[0024] Figure 5 It is a Fourier decomposition diagram of the winding magnetomotive force under healthy operation of the six-phase permanent magnet motor of the present invention;

[0025] Figure 6 This is a vibration acceleration distribution diagram of the six-phase permanent magnet motor in the present invention under healthy operation;

[0026] Figure 7 (a)(b)(c)(d) are the rated torque waveforms of the six-phase permanent magnet motor before and after the application of the low vibration fault-tolerant current in the present invention;

[0027] Figure 8 A comparison diagram of the armature fundamental wave reversal magnetomotive force per unit value before and after the application of the low vibration fault-tolerant current of the six-phase permanent magnet motor in the present invention;

[0028] Fig. 9 A comparison diagram of the zero-order radial force before and after the application of the low-vibration fault-tolerant current of the six-phase permanent magnet motor in the present invention;

[0029] Fig.10 (a)(b)(c)(d) are low-vibration fault-tolerant current waveforms of the six-phase permanent magnet motor for different phase-loss faults in the present invention;

[0030] Fig.11 (a)(b)(c)(d) are comparison diagrams of the vibration acceleration effects before and after the application of the low vibration fault tolerance current in the present invention;

[0031] Fig.12 A low-vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase-loss fault is disclosed;

[0032] In the figure: 1- stator winding, 2- stator core, 3- rotor core, 4- rotor permanent magnet. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In order to more simply and clearly illustrate the beneficial effects of the present invention, a detailed description is given below in conjunction with a specific six-phase permanent magnet motor.

[0034] Attached Figure 1 The meaning of each structure is: 1. stator winding, 2. stator core, 3. rotor core, 4. rotor permanent magnet. In this embodiment, the permanent magnet motor adopts a slot-pole combination of 72 slots and 12 poles. The stator winding 1 is embedded in the stator core 2 in a distributed winding winding manner, and the rotor permanent magnet 4 is embedded in the rotor core 3. When the motor is running under load, a six-phase sinusoidal current is passed through the stator winding 1, and the motor is driven in a full-bridge drive mode.

[0035] The present invention provides a low-vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase-loss fault, and the specific steps are as follows:

[0036] Step 1, see attached Figure 2In the present invention, the six-phase winding distribution of the permanent magnet motor is uniformly distributed in the slot space according to 0, 60°, 120°, 180°, 240°, and 300°. In order to ensure that the phase angle of the remaining phase current is not affected when a phase failure occurs in one or more phases, a full-bridge drive method with high electrical isolation is used for inverter power supply.

[0037] See attached Figure 3 Establish the electromagnetic finite element simulation model of the motor and simulate the torque of the motor under healthy operation. Figure 4 As shown. At this time, the rated torque of the motor is 100Nm, the rated torque pulsation is only 7%, and the torque output capacity under healthy operation is good. The torque, magnetomotive force and radial force distribution simulation under rated working conditions are numerically calculated using electromagnetic finite element simulation software.

[0038] The magnetomotive force under healthy operation is expressed as the product of the motor's fundamental winding function and current function. Among them, the motor's fundamental winding function is expressed as:

[0039]

[0040] The current function of the motor is expressed as:

[0041]

[0042] The single-phase fundamental magnetomotive force function of the motor is expressed as:

[0043]

[0044] And the fundamental wave synthetic magnetomotive force function of the motor is expressed as:

[0045]

[0046] Among them, n A,B,C。。。 (θ) is the fundamental winding function from phase A to phase F, N is the number of stator winding turns, C p represents the calculation coefficient of the fundamental wave winding function, p represents the number of rotor pole pairs, k represents the digital representation of phase A to phase F, and phase A to phase F are staggered by 60°, 120°, 180°, 240°, 300° and 360° spatial phase angles respectively. A,B,C… is the current function from phase A to phase F, θ represents the mechanical position angle, I m represents the current amplitude, and ω represents the electrical angular velocity. 0 is the six-phase composite magnetomotive force, f k It represents the single-phase fundamental winding magnetomotive force, of which the first half represents the fundamental forward magnetomotive force component, and the second half represents the fundamental reverse magnetomotive force component. Figure 5 As shown, in the armature magnetomotive force distribution under healthy operation, the harmonic content other than the fundamental positive magnetomotive force component is relatively small.

[0047] The radial force component that mainly contributes to vibration under healthy operation is the 12th-order 2nd-frequency radial force. The vibration response verified by simulation is mainly the vibration acceleration response. The specific simulation verification method is as follows:

[0048] First, the established finite element motor model is simulated and solved, and the radial force data of the motor stator tooth surface is collected. Secondly, the structural finite element calculation software is used to simulate the structural finite element modal parameters of the motor and obtain the modal natural frequency data of each order of the motor. Finally, in the motor harmonic response calculation software, the known radial force data and finite element modal parameters are imported, and the vibration acceleration response of the motor is coupled and calculated to verify the relationship between the radial force and the vibration acceleration, and to clarify the radial force component that plays a major role in the vibration acceleration.

[0049] See attached Figure 6 As shown in the figure, the main vibration acceleration under healthy operation is located at the 2nd frequency, which is consistent with the main radial force frequency under healthy operation.

[0050] Step 2, respectively simulate the torque, magnetomotive force and radial force distribution of the motor under each phase failure. The torque and magnetomotive force simulation of the motor is numerically calculated using electromagnetic finite element simulation software. Compare the fundamental forward magnetomotive force value and average torque value under different phase failures. The fundamental forward magnetomotive force value and average torque expression of the motor under phase failure are:

[0051]

[0052] Among them, f fau_forward Indicates the fundamental wave forward magnetomotive force value after a phase failure, f 0_forward Indicates the fundamental positive magnetomotive force value under healthy operation, T fault Indicates the average torque value after a phase failure, T e It indicates the rated torque value under healthy operation, and m indicates the number of phases in the phase failure.

[0053] Phase loss fault types include single-phase phase loss fault, adjacent two-phase phase loss fault, non-adjacent two-phase phase loss fault, and three-phase phase loss fault. Figure 7 As shown in the figure, under different phase failure types, the average torque and torque pulsation of the motor output are different.

[0054] The magnetic motive force distribution of the phase failure obtained by analysis simulation is shown in the attached Figure 8As shown in Table 1, fundamental reverse magnetic motive force components will be generated in single-phase loss, adjacent two-phase loss, non-adjacent two-phase loss and some three-phase loss faults, and the magnitude of fundamental reverse magnetic motive force components generated by different phase loss fault types are inconsistent. Among them, the three-phase loss is quite special, with a total of 20 combinations (any combination of 3 phases out of 6 phases), and a total of eight combinations of three-phase loss will not generate fundamental reverse magnetic motive force components, as shown in Table 1. Therefore, the vibration response will not deteriorate under these eight three-phase loss combinations. In the remaining twelve three-phase loss situations, fundamental reverse magnetic motive force can be generated, thereby deteriorating the vibration response.

[0055] Table 1 8 three-phase missing combinations that do not produce reverse magnetomotive force

[0056] (Phase A, Phase B, Phase C) (Phase A, Phase B, Phase F) (Phase A, Phase E, Phase C) (Phase A, Phase E, Phase F) (Phase D, Phase B, Phase C) (D phase, B phase, F phase) (Phase D, Phase E, Phase C) (Phase D, Phase E, Phase F)

[0057] The magnetomotive force distribution under different types of phase loss faults is divided into four cases for calculation. Since the windings of each phase are evenly and symmetrically distributed in space, the typical working conditions of the four phase loss faults can be selected for magnetomotive force calculation, which is specifically shown as follows:

[0058] Taking phase A failure as an example to represent a single-phase failure, its synthetic magnetic motive force is expressed as:

[0059]

[0060] Among them, f q1 is the remaining five-phase composite magnetomotive force, f B 、f C 、f D 、f E 、f F They are the single-phase magnetomotive force of phase B, phase C, phase D, phase E and phase F respectively;

[0061] Take phase A and phase B as an example to represent the adjacent two-phase failure. q_ad2 is the remaining four adjacent phases composite magnetomotive force, which is expressed as:

[0062]

[0063] Take phase A and phase D as an example to represent the non-adjacent two-phase failure. q_nonad2 is the remaining non-adjacent four-phase composite magnetomotive force, which is expressed as:

[0064]

[0065] Take phase A, phase B and phase D as an example to represent a three-phase phase failure. q3 is the remaining three-phase composite magnetomotive force, which is expressed as:

[0066]

[0067] The radial force distribution after the phase failure is further simulated. According to Maxwell stress equation, the fundamental reverse magnetomotive force interacts with the forward magnetomotive force, and the distorted zero-order radial force component excites the zero-order vibration, thereby deteriorating the vibration response. See Appendix Fig. 9 As shown in the figure, the radial force distribution characteristics under the phase failure fault are consistent with the magnetomotive force distribution characteristics under the phase failure fault.

[0068] Among them, the zero-order vibration excited by the zero-order radial force mainly contributes to the vibration response of the motor under the phase failure. Specifically, the ratio of the zero-order vibration displacement excited by the unit zero-order radial force to the vibration displacement excited by the original unit lowest-order radial force is:

[0069]

[0070] Among them, Y s＝0 represents the zero-order vibration displacement, Y s＝2p represents the vibration displacement excited by the lowest order radial force, R y Indicates the average radius of the stator yoke. In the motor of the embodiment, R y 200mm, T y Indicates the average thickness of the stator yoke. In the motor of the embodiment, T y The ratio is calculated to be 17. Therefore, the effect of zero-order vibration is huge.

[0071] Step 3: Reconstruct the residual phase synthetic magnetic force according to the difference in magnetic force distribution under various types of phase loss faults to improve the vibration response under phase loss operation. The principle of reconstructing the fundamental magnetic force is to ensure the maximum amplitude of the fundamental forward armature magnetic force and eliminate the amplitude of the fundamental reverse armature magnetic force to the greatest extent. Four typical phase loss conditions are selected to further design a low-vibration magnetic force reconstruction method and determine the phase angle of the reconstructed residual phase current.

[0072] Take phase A failure as an example to represent a single-phase failure. Since the remaining five-phase windings are symmetrically distributed about the D-phase winding, it is assumed that the phase angle between phase B and phase F is -ɑ 1 and 1 , the phase angles of phase C and phase E are -β 1 and β 1 , then the residual phase reconstruction fundamental magnetomotive force is expressed as:

[0073]

[0074] Among them, f' A 、f' B 、f' C 、f' D 、f' E 、f' FThey are the reconstructed magnetomotive force expressions of phase B, phase C, phase D, phase E and phase F respectively;

[0075] The reconstructed five-phase composite magnetomotive force is expressed as:

[0076]

[0077] After calculation, when 1 is 45°, β 1 When it is 135°, the fundamental wave forward magnetomotive force is the largest and the fundamental wave reverse magnetomotive force is zero, realizing the reconstruction of single-phase missing phase low-vibration magnetomotive force.

[0078] Take the phase loss of phase A and phase B as an example to represent the phase loss fault of two adjacent phases. Since phase C and phase F are symmetrically distributed, and phase D and phase E are symmetrically distributed in the remaining four-phase windings. Assume that the phase angle between phase C and phase F is -ɑ 2 and 2 , the phase angles of phase D and phase E are -β 2 and β 2 , then the remaining four phases reconstruct the fundamental magnetomotive force are expressed as:

[0079]

[0080] Reconstruction of the four-phase composite magnetomotive force f' q_ad2 It is expressed as:

[0081]

[0082] After calculation, when 2 is 60°, β 2 When it is 180°, the fundamental forward magnetomotive force is the largest and the fundamental reverse magnetomotive force is zero, realizing the reconstruction of low-vibration magnetomotive force between two adjacent phases.

[0083] Take the phase loss of phase A and phase D as an example to represent the non-adjacent two-phase phase loss fault. Since phase B and phase F are symmetrically distributed, and phase C and phase E are symmetrically distributed in the remaining four-phase windings. Assume that the phase angle between phase B and phase F is -ɑ 3 and 3 , the phase angles of phase C and phase E are -β 3 and β 3 , then the remaining four phases reconstruct the fundamental magnetomotive force are expressed as:

[0084]

[0085] Reconstruction of the four-phase composite magnetomotive force f' q_nonad2 It is expressed as:

[0086]

[0087] After calculation, when 3is 30°, β 3 When it is 150°, the fundamental forward magnetomotive force is the largest and the fundamental reverse magnetomotive force is zero, realizing the reconstruction of low-vibration magnetomotive force between two non-adjacent phases.

[0088] Take phase A, phase B and phase D as an example to represent the adjacent three-phase phase failure. In the remaining three-phase windings, it is assumed that phase C and phase F are symmetrically distributed with respect to phase E, and the phase angle between phase C and phase F is -ɑ 4 and 4 , the phase angle of phase E is 150°, then the remaining three phases reconstruct the fundamental wave magnetomotive force are expressed as:

[0089]

[0090] Reconstruction of three-phase synthetic magnetomotive force f' q3 It is expressed as:

[0091]

[0092] After calculation, when 4 When it is 30°, the fundamental wave forward magnetomotive force is the largest, and the fundamental wave reverse magnetomotive force is zero, realizing the reconstruction of the low-vibration magnetomotive force in the absence of three phases.

[0093] Step 4: After solving the reconstructed current phase angle, the low-vibration fault-tolerant current expression can be obtained, still taking four typical phase-loss conditions as examples.

[0094] Take phase A as an example to represent a single-phase phase failure. At this time, the remaining five phases are rotating forward to synthesize the magnetic motive force f 5 (θ,t) is expressed as:

[0095] f 5 (θ,t)=0.25C p NI m ·4.86cos(ωt-pθ) (18)

[0096] Remaining five-phase low vibration fault-tolerant current I con and the initial current amplitude I m The relationship is:

[0097]

[0098] Therefore, the expression of the remaining five-phase low-vibration fault-tolerant current is:

[0099]

[0100] Among them, I' B , I' C , I' D , I' E , I' FThey are the low vibration fault-tolerant current expressions of phase B, phase C, phase D, phase E and phase F respectively;

[0101] Take phase A and phase B as an example to represent the adjacent two-phase failure. At this time, the remaining four phases are rotating forward to synthesize the magnetic motive force f 4 (θ,t) is expressed as:

[0102] f 4 (θ,t)=0.25C p NI m ·3.46cos(ωt-pθ) (21)

[0103] The remaining four-phase low vibration fault-tolerant current I con and the initial current amplitude I m The relationship is:

[0104]

[0105] The expression of the remaining four-phase low-vibration fault-tolerant current is:

[0106]

[0107] Take phase A and phase D as an example to represent the non-adjacent two-phase failure. At this time, the remaining four phases are rotating forward to synthesize the magnetic motive force f 4 (θ,t) is expressed as:

[0108] f 4 (θ,t)=0.25C p NI m ·3.46cos(ωt-pθ) (24)

[0109] The remaining four-phase low vibration fault-tolerant current I con and the initial current amplitude I m The relationship is:

[0110]

[0111] The expression of the remaining four-phase low-vibration fault-tolerant current is:

[0112]

[0113] Take the A, B and D phases as an example to represent the three-phase phase failure. At this time, the remaining three phases are forward rotating to synthesize the magnetic motive force f 3 (θ,t) is expressed as:

[0114] f 3 (θ,t)=0.25C p NI m ·2cos(ωt-pθ) (27)

[0115] Remaining three-phase low vibration fault-tolerant current I con and the initial current amplitude I m The relationship is:

[0116]

[0117] The expression of the remaining three-phase low-vibration fault-tolerant current is:

[0118]

[0119] See attached Fig.10 , based on the expression, the low vibration fault-tolerant current waveforms under four typical working conditions are plotted.

[0120] Step 5, substitute the calculated low-vibration fault-tolerant current expression as the armature excitation, and use electromagnetic finite element simulation software to numerically calculate the torque waveform, reverse magnetomotive force distribution, and radial force distribution.

[0121] See attached Figure 7 As shown in the figure, after using low vibration fault-tolerant current, the torque pulsation under the four types of phase loss faults is very well suppressed. The torque pulsation under single-phase phase loss fault is reduced by 32.3%, the torque pulsation under adjacent two-phase phase loss fault is reduced by 42.8%, the torque pulsation under non-adjacent two-phase phase loss fault is reduced by 83.4%, and the torque pulsation under three-phase phase loss fault is reduced by 83.3%.

[0122] See attached Figure 8 As shown in the figure, after using low vibration fault-tolerant current, the reversal magnetomotive force under the four types of phase loss faults is very well suppressed. The reversal magnetomotive force amplitude is suppressed by 87% under single-phase phase loss fault, 82% under adjacent two-phase phase loss fault, 82.5% under non-adjacent two-phase phase loss fault, and 90% under three-phase phase loss fault.

[0123] See attached Fig. 9 As shown in the figure, when low vibration fault-tolerant current is adopted, the zero-order radial force distribution amplitude under the four phase loss fault types is significantly reduced. The zero-order radial force amplitude under single-phase phase loss fault is suppressed by 86.2%, the zero-order radial force amplitude under adjacent two-phase phase loss fault is suppressed by 82.6%, the zero-order radial force amplitude under non-adjacent two-phase phase loss fault is suppressed by 82%, and the zero-order radial force amplitude under three-phase phase loss fault is suppressed by 91%.

[0124] The vibration acceleration simulation of the motor model after adopting the low vibration fault tolerance current is further carried out to verify the improvement effect of the vibration acceleration. Fig.11As shown, the vibration amplitude at the 2 times frequency under a single-phase loss fault decreased by 71.4%, the vibration amplitude at the 2 times frequency under an adjacent two-phase loss fault decreased by 69.6%, the vibration amplitude at the 2 times frequency under a non-adjacent two-phase loss fault decreased by 74.1%, and the vibration amplitude at the 2 times frequency under a three-phase loss fault decreased by 77.8%.

[0125] The detailed process of all the above steps is attached. Fig.12 , mainly includes three main parts: fault category judgment, low vibration fault tolerance current algorithm calculation and low vibration fault tolerance effect verification.

[0126] Although the present invention has been disclosed as above with preferred embodiments, the embodiments are not intended to limit the present invention. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention shall fall within the scope of protection defined by the appended claims of this application.

Claims

1. A low vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase failure, characterized in that: The specific steps are as follows: Step 1, establish a motor electromagnetic simulation model, simulate the torque, magnetomotive force distribution and radial force distribution of the six-phase permanent magnet motor under rated working conditions and healthy operation, and detect the vibration response of the motor; Step 2, classify the six-phase permanent magnet motor into different phase loss fault types, simulate the torque and magnetomotive force distribution of each motor after each phase loss fault, simulate and calculate the radial force distribution under different phase loss fault types, and simulate and verify the vibration response of the motor when running under different phase loss fault types; Step 3, according to the difference in magnetomotive force distribution under different fault types, design and reconstruct the residual phase synthetic magnetomotive force under each phase-loss fault type; Step 4, according to the residual phase synthetic magnetomotive force reconstruction scheme, determine the residual phase current phase angle and solve the low vibration fault-tolerant current expression; Step 5, substitute the calculated low vibration fault-tolerant current expression, simulate the radial force distribution under fault-tolerant operation, and simulate and verify the improvement of vibration response under fault-tolerant operation; The vibration response in step 1 is mainly the vibration acceleration response. The specific steps of detecting the vibration response of the motor are as follows: Step 1.1, simulate and solve the established finite element motor model, and collect the radial force data of the motor stator tooth surface; Step 1.2, using structural finite element calculation software to simulate the structural finite element modal parameters of the motor and obtain the natural frequency data of each order modal of the motor; Step 1.3, in the motor harmonic response calculation software, import the known radial force data and finite element modal parameters, couple and calculate the vibration acceleration response of the motor, verify the relationship between the radial force and the vibration acceleration, and identify the radial force component that plays a major role in the vibration acceleration; In step 2, the torque and magnetomotive force distribution after each phase failure of the simulated motor are numerically calculated using electromagnetic finite element simulation software, and the fundamental forward magnetomotive force value and the average torque value under different phase failures are compared, wherein the fundamental forward magnetomotive force value and the average torque expression of the motor under the phase failure are: Among them, f fau_forward Indicates the fundamental wave forward magnetomotive force value after a phase failure, f 0_forward It indicates the fundamental forward magnetomotive force value under healthy operation, Tfault indicates the average torque value after a phase failure, Te indicates the rated torque value under healthy operation, and m indicates the number of phases under phase failure. The radial force distribution under different phase failure types in step 2 is: Phase loss fault types include single-phase phase loss fault, adjacent two-phase phase loss fault, non-adjacent two-phase phase loss fault, and three-phase phase loss fault. Among them, single-phase phase loss, adjacent two-phase phase loss fault, and non-adjacent two-phase phase loss fault will generate fundamental reversal magnetomotive force components. According to Maxwell stress equation, the radial force harmonic component generated by the interaction between this component and the forward magnetomotive force will change the original radial force distribution, excite zero-order vibration, and thus deteriorate the vibration response. The three-phase phase loss fault is quite special. There are a total of eight combinations of three-phase phase loss faults that will not generate fundamental reversal magnetomotive force components. The vibration response will not deteriorate under these eight three-phase phase loss combinations. In the remaining twelve three-phase phase loss situations, fundamental reversal magnetomotive force can be generated, thereby deteriorating the vibration response. The eight three-phase phase loss combinations that do not generate fundamental reversal magnetomotive force components are as follows: Table 1 8 three-phase missing combinations that do not produce fundamental reversal magnetomotive force components The vibration response of the motor when running under different phase failure types in step 2 is specifically: The zero-order vibration excited by the zero-order radial force mainly contributes to the vibration response of the motor under the phase failure. Specifically, the ratio of the zero-order vibration displacement excited by the unit zero-order radial force to the vibration displacement excited by the original unit lowest-order radial force is: Among them, Ys=0 represents the zero-order vibration displacement, Ys=2p represents the vibration displacement excited by the lowest-order radial force, Ry represents the average radius of the stator yoke, and Ty represents the average thickness of the stator yoke; The magnetomotive force distribution under different types of phase loss faults is divided into four cases for calculation. Since the windings of each phase are evenly and symmetrically distributed in space, the typical working conditions of the four phase loss faults can be selected for magnetomotive force calculation, which is specifically shown as follows: If the phase A is missing to represent a single-phase missing fault, the synthetic magnetic motive force is expressed as: Where N is the number of stator winding turns, Cp is the fundamental wave winding function calculation coefficient, Im is the current amplitude, ω is the electrical angular velocity; fq1 is the remaining five-phase composite magnetomotive force, f B 、f C 、f D 、f E 、f F They are the single-phase magnetomotive force of phase B, phase C, phase D, phase E and phase F respectively; If phase A and phase B are missing, it represents a two-phase missing fault. q_ad2 is the remaining four adjacent phases composite magnetomotive force, which is expressed as: If the phase A and phase D are missing to represent the non-adjacent two-phase missing fault, f q_nonad2 is the remaining non-adjacent four-phase composite magnetomotive force, which is expressed as: If phase A, phase B and phase D are missing, it represents a three-phase missing fault. q3 is the remaining three-phase composite magnetomotive force, which is expressed as: The specific process of step 3 is as follows: For various types of phase-loss faults, the residual phase synthetic magnetomotive force is reconstructed and designed to improve the vibration response under phase-loss operation. The principle of fundamental magnetomotive force reconstruction is to ensure the maximum fundamental forward armature magnetomotive force amplitude and eliminate the fundamental reverse armature magnetomotive force amplitude to the greatest extent. Four typical phase-loss conditions are selected to further design a low-vibration magnetomotive force reconstruction method and determine the reconstructed residual phase current phase angle. If the A phase is missing to represent a single-phase missing fault, since the remaining five-phase windings are symmetrically distributed about the D phase winding, assuming that the phase angles of the B phase and the F phase are -ɑ1 and ɑ1, and the phase angles of the C phase and the E phase are -β1 and β1 respectively, then the fundamental wave magnetomotive force reconstructed by the remaining phases can be expressed as: Where, N represents the number of stator winding turns, C p represents the fundamental wave winding function calculation coefficient, p represents the number of rotor pole pairs, f' A 、f' B 、f' C 、f' D 、f' E 、f' F They are the reconstructed magnetomotive force expressions of phase B, phase C, phase D, phase E and phase F respectively; Reconstruction of the five-phase composite magnetomotive force f' q1 It is expressed as: According to calculation, when ɑ1 is 45° and β1 is 135°, the fundamental wave forward magnetomotive force is the largest and the fundamental wave reverse magnetomotive force is zero, thus realizing the reconstruction of single-phase missing phase low-vibration magnetomotive force. If the phase loss of phase A and phase B represents the phase loss fault of two adjacent phases, since phase C and phase F are symmetrically distributed, and phase D and phase E are symmetrically distributed in the remaining four-phase winding, assuming that the phase angles of phase C and phase F are -ɑ2 and ɑ2, and the phase angles of phase D and phase E are -β2 and β2 respectively, then the reconstructed fundamental magnetomotive force of the remaining four phases is expressed as: Reconstruction of the four-phase composite magnetomotive force f' q_ad2 It is expressed as: According to calculations, when ɑ2 is 60° and β2 is 180°, the fundamental wave forward magnetomotive force is the largest and the fundamental wave reverse magnetomotive force is zero, thus realizing the reconstruction of low-vibration magnetomotive force between two adjacent phases. If the phase loss of phase A and phase D represents the phase loss fault of two non-adjacent phases, since the phases B and F are symmetrically distributed, and the phases C and E are symmetrically distributed in the remaining four-phase windings; assuming that the phase angles of phase B and phase F are -ɑ3 and ɑ3, and the phase angles of phase C and phase E are -β3 and β3 respectively, then the reconstructed fundamental magnetomotive force of the remaining four phases is expressed as: Reconstruction of the four-phase composite magnetomotive force f' q_nonad2 It is expressed as: According to calculation, when ɑ3 is 30° and β3 is 150°, the fundamental wave forward magnetomotive force is the largest and the fundamental wave reverse magnetomotive force is zero, thus realizing the reconstruction of low-vibration magnetomotive force between two non-adjacent phases. If phase A, phase B and phase D are missing to represent the adjacent three-phase missing phase fault, in the remaining three-phase winding, it is assumed that phase C and phase F are symmetrically distributed with respect to phase E, the phase angles of phase C and phase F are -ɑ4 and ɑ4, and the phase angle of phase E is 150°, then the reconstructed fundamental magnetomotive force of the remaining three phases is expressed as: Reconstruction of three-phase synthetic magnetomotive force f' q3 It is expressed as: According to calculation, when ɑ4 is 30°, the fundamental wave forward magnetomotive force is the largest and the fundamental wave reverse magnetomotive force is zero, thus realizing the reconstruction of the low-vibration magnetomotive force without three phases. The specific process of step 4 is as follows: After solving the reconstructed current phase angle, the low vibration fault-tolerant current expression can be obtained, assuming four typical phase-loss conditions; If phase A is missing to represent a single-phase missing fault, the low-vibration fault-tolerant current expression of the remaining five phases is: Among them, I m represents the current amplitude, ω represents the electrical angular velocity, I' B , I' C , I' D , I' E , I' F They are the low vibration fault-tolerant current expressions of phase B, phase C, phase D, phase E and phase F respectively; If phase A and phase B are missing to represent the adjacent two-phase missing fault, the expression of the remaining four-phase low-vibration fault-tolerant current is: If phase A and phase D are missing to represent a non-adjacent two-phase missing fault, the expression of the remaining four-phase low-vibration fault-tolerant current is: If phase A, phase B and phase D are missing to represent a three-phase phase loss fault, the expression of the remaining three-phase low-vibration fault-tolerant current is:

2. A low vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase failure according to claim 1, characterized in that: The six-phase permanent magnet motor adopts a full-bridge drive mode to supply power to each phase, has high electrical isolation, and is conducive to fault-tolerant control under motor failure. The permanent magnet motor includes a stator core, an armature winding, a rotor core and a permanent magnet. The stator core and the rotor core are made of silicon steel sheets, and the permanent magnet material is a high remanence neodymium iron boron material. The permanent magnet arrangement can adopt a pole surface mounting type or a built-in structure.

3. The low vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase failure according to claim 1 is characterized in that: In the step 1, the torque, magnetomotive force distribution and radial force distribution simulation under rated working condition and healthy operation are numerically calculated using electromagnetic finite element simulation software; for a six-phase permanent magnet motor, the radial force component that mainly contributes to vibration under healthy operation is the pole logarithm order 2-fold frequency radial force; The magnetomotive force under healthy operation is expressed as the product of the motor's fundamental winding function and the current function, where the motor's fundamental winding function is expressed as: The current function of the motor is expressed as: The single-phase fundamental magnetomotive force function of the motor is expressed as: And the synthetic magnetomotive force function of the motor is expressed as: Among them, n A,B,C… (θ) is the fundamental winding function from phase A to phase F, N is the number of stator winding turns, C p represents the calculation coefficient of the fundamental wave winding function, p represents the number of rotor pole pairs, k represents the digital representation of phase A to phase F, and phase A to phase F are staggered by 60°, 120°, 180°, 240°, 300° and 360° spatial phase angles respectively; i A,B,C… is the current function from phase A to phase F, θ represents the mechanical position angle, I m represents the current amplitude, ω represents the electrical angular velocity; f0 is the six-phase composite magnetomotive force, f k It represents the single-phase fundamental winding magnetomotive force, where the first half represents the fundamental forward magnetomotive force component, and the second half represents the fundamental reverse magnetomotive force component.

4. The low vibration fault-tolerant current calculation method for a six-phase permanent magnet motor with a phase failure according to claim 1 is characterized in that: The specific process of step 5 is: substituting the calculated low-vibration fault-tolerant current expression as the armature excitation, and using finite element simulation software to perform numerical calculations on the radial force distribution; comparing the difference in radial force distribution under low-vibration fault-tolerant operation and under phase-loss fault operation, verifying the radial force improvement effect after magnetomotive force reconstruction, and further comparing the vibration acceleration simulation under the low-vibration fault-tolerant current expression to verify the vibration acceleration response improvement effect.

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