Nine-switch current source driven double three-phase motor single-phase open-circuit fault-tolerant control method

Abstract

The application discloses a nine-switch current source driven double three-phase motor single-phase open circuit fault-tolerant control method, and belongs to the field of motor control. The application is used for solving the problems of flux linkage distortion, large current harmonics and serious torque ripple after the system single-phase open circuit fault. The application comprises the following steps: S1, taking maintaining the circular fundamental flux linkage unchanged after the fault as the target, performing order reduction and zero sequence compensation correction on the normal working condition Clarke conversion matrix to obtain a modified coordinate conversion matrix suitable for the single-phase open circuit fault; S2, constructing a rotating coordinate system mathematical model of the motor under the single-phase open circuit fault based on the modified coordinate conversion matrix, and solving the fault-tolerant current reference value of each non-fault phase according to a preset current constraint; S3, eliminating the fault phase corresponding vector, reconstructing the inverter current vector space and dividing the sectors; selecting three adjacent effective vectors in each sector, so that the synthesized vector of the vector combination in the harmonic subspace is zero; and solving the action time of each vector and generating a switching time sequence by simultaneously solving the vector projection relationship, and driving the motor.

Description

Technical Field

[0001] This invention belongs to the field of motor control, specifically relating to a single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source. Background Technology

[0002] Dual three-phase permanent magnet synchronous motors (DTP-PMSMs) are widely used in high-end fields such as aerospace servo systems due to their high power density, high efficiency, and superior fault-tolerant operation. When one or two phases fail, the redundant winding structure of the dual three-phase motor allows the system to maintain continuous and stable operation of the motor by properly controlling the remaining healthy phases. Open-circuit faults are among the most common electrical faults in motor drive systems, and short-circuit faults can also be converted into open-circuit faults by fuses. Therefore, research on fault-tolerant control for open-circuit faults has significant theoretical and engineering value.

[0003] When a single-phase open-circuit fault occurs in a DTP-PMSM, the system symmetry is disrupted. To achieve fault-tolerant operation, existing technologies mainly face the following challenges: the coordinate transformation matrix during normal operation is no longer applicable, making it impossible to maintain the circular fundamental flux linkage, which severely affects the motor's operating performance; the space vector modulation method during normal operation fails, requiring reconstruction of the current vector space and design of corresponding fault-tolerant modulation methods; the open-circuit fault introduces a large number of odd harmonics (such as the 3rd and 5th harmonics) into the non-faulty phase currents, which manifest as even harmonics (such as the 2nd and 4th harmonics) in the dq coordinate system, leading to electromagnetic torque pulsation.

[0004] Currently, most fault-tolerant control research focuses on motor systems driven by voltage-source inverters. In contrast, current-source inverters (CSI) offer significant advantages such as high output current quality and strong short-circuit protection, demonstrating great potential in applications such as motor drives. Nine-switch CSI, as a novel inverter topology, reduces three power switches compared to the traditional twelve-switch CSI, lowering system cost and size while retaining all the advantages of CSI.

[0005] Therefore, there is an urgent need for a single-phase open-circuit fault-tolerant control method suitable for a nine-switch CSI-driven DTP-PMSM, which can both ensure the circularity of the fundamental flux linkage and effectively suppress harmonics, thereby improving the fault tolerance capability and operational stability of the system. Summary of the Invention

[0006] To address the problems of flux distortion, large current harmonics, and severe torque ripple after a single-phase open-circuit fault in the system, this invention provides a single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source.

[0007] The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to the present invention includes the following steps:

[0008] S1. Coordinate transformation matrix correction steps: With the goal of maintaining the circular fundamental flux after the fault, the Clarke transformation matrix under normal operating conditions is reduced in order and zero-sequence compensation is performed to obtain the corrected coordinate transformation matrix adapted to single-phase open circuit fault.

[0009] S2. Fault modeling and fault-tolerant current solution steps: Based on the modified coordinate transformation matrix, construct a rotating coordinate coefficient mathematical model of the motor under single-phase open-circuit fault, and solve the fault-tolerant current reference value of each non-faulty phase according to the preset current constraint.

[0010] S3, Fault-tolerant space vector modulation steps: Using the fault-tolerant current reference value obtained in step S2 as the control target, eliminate the corresponding vectors of the fault, reconstruct the inverter current vector space and divide it into sectors; select three adjacent effective vectors in each sector so that the combined vector in the harmonic subspace is zero; solve the action time of each vector by combining the vector projection relationship and generate the switching sequence, synthesize the reference current vector, and realize the fault-tolerant operation control of the motor.

[0011] Preferably, step S1 specifically includes:

[0012] The column elements corresponding to the faults in the Clarke transform matrix under normal operating conditions are deleted, and the order of the harmonic subspace is reduced to obtain the reduced order Clarke transform matrix.

[0013] By using the zero-order subspace flux linkage component to compensate and correct the corresponding row elements of the fundamental subspace within the reduced-order Clarke transform matrix, the fundamental flux linkage distortion caused by the fault is eliminated, ensuring that the fundamental flux linkage remains circular after the fault, consistent with that before the fault.

[0014] Preferably, when the single-phase open-circuit fault is the W-phase open-circuit fault of the dual three-phase permanent magnet synchronous motor;

[0015] The reduced-order Clarke transformation matrix is:

[0016] ;

[0017] The modified Clarke transformation matrix is:

[0018] .

[0019] Preferably, the rotating coordinate coefficient mathematical model in step S2 includes: the stator voltage equation and electromagnetic torque equation of the rotating coordinate system derived based on the modified coordinate transformation matrix.

[0020] Preferably, in step S2, the reference values ​​of the fault-tolerant current for each non-faulty phase are solved based on the preset current constraints. Specifically, given the quadrature axis current of the rotating coordinate system, the direct axis current, the zero-sequence subspace current, and the harmonic subspace current are all set to zero. The reference values ​​of the current for each non-faulty phase are solved by the inverse matrix operation of the modified coordinate transformation matrix.

[0021] Preferably, the process of reconstructing the inverter current vector space in step S3 is as follows: all vectors coupled with the fault in the normal current vector space are removed, the reconstructed vector space contains multiple valid vectors and multiple zero vectors, and the reconstructed vector space is divided into multiple sectors.

[0022] Preferably, in step S3, three adjacent effective vectors are selected in each sector to make the harmonic subspace composite vector zero. Specifically, three adjacent effective vectors with spatially adjacent positions are selected in each sector to form a vector combination. The vector combination is superimposed in the harmonic subspace to form a composite vector of zero, thereby suppressing harmonic current.

[0023] Preferably, step S3, which involves solving for the action time of each vector, includes: obtaining the projection components of three adjacent effective vectors and the zero vector in the fundamental subspace and harmonic subspace, establishing a set of equations in conjunction with the target reference current vector, and solving for the action time of each effective vector and the zero vector.

[0024] Preferably, the system of equations for solving the vector action time is as follows:

[0025] ;

[0026] In the formula, , , The selected number A vector in axis, Projection components on the x-axis and z-axis, , These represent the durations of action of three adjacent effective vectors. The duration of action of the zero vector. For the switching cycle, The reference current vectors are respectively at axis, Components on the x-axis and z-axis.

[0027] Preferably, step S3 further includes switching timing generation: calculating the vector switching time based on the action time of each effective vector and zero vector obtained by solving, and outputting the on / off switching timing of each power switch in the nine-switch current source inverter to drive the motor to operate in a fault-tolerant manner.

[0028] The beneficial effects of this invention are:

[0029] 1. The fundamental subspace row of the reduced-order Clarke transformation matrix is ​​corrected by using the flux linkage component of the zero-order subspace to ensure that the fundamental flux linkage remains circular after the fault, and the mathematical model of the motor remains consistent in the fundamental subspace before and after the fault.

[0030] 2. The proposed adjacent three-current-vector fault-tolerant SVPWM method effectively utilizes the non-uniformly distributed current vector after the fault, and while accurately synthesizing the fundamental current vector, it effectively suppresses the current components in the harmonic subspace and reduces the current harmonic distortion rate.

[0031] 3. Through simulation and experimental verification, the proposed method shows superior performance in maintaining the fundamental flux linkage vector to rotate in space after the fault, the sinusoidal current of the non-faulty phase, and harmonic suppression. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the dual three-phase permanent magnet synchronous motor system driven by the nine-switch current source inverter described in this invention after a W-phase open circuit fault.

[0033] Figure 2 This is the normal operating state of the dual three-phase permanent magnet synchronous motor described in this invention. Fundamental subspace current vector distribution diagram;

[0034] Figure 3 This is a diagram showing the z-harmonic subspace current vector distribution under normal operating conditions of the dual three-phase permanent magnet synchronous motor described in this invention.

[0035] Figure 4 This invention relates to the W-phase open-circuit fault in the dual three-phase permanent magnet synchronous motor. Fundamental subspace current vector distribution diagram;

[0036] Figure 5 This is a vector distribution diagram of the z-harmonic subspace current after a W-phase open-circuit fault in the dual three-phase permanent magnet synchronous motor described in this invention.

[0037] Figure 6 This is the first sector after the W-phase open-circuit fault described in this invention. Schematic diagram of vector synthesis of fundamental subspace currents;

[0038] Figure 7This is a schematic diagram of the vector synthesis of the z-harmonic subspace current in sector I after a W-phase open-circuit fault as described in this invention.

[0039] Figure 8 This is the timing diagram of the switching sequence of sector I after a phase W open-circuit fault as described in this invention;

[0040] Figure 9 This is the FFT harmonic analysis diagram of the non-faulty phase current after the W-phase open-circuit fault-tolerant control described in this invention;

[0041] Figure 10 This is a comparison diagram of the six-phase current waveforms before and after the W-phase open-circuit fault described in this invention;

[0042] Figure 11 This is the W-phase open circuit fault before and after the present invention. Comparison chart of shaft current trajectories;

[0043] Figure 12 This is a comparison diagram of the q-axis current response before and after the W-phase open-circuit fault described in this invention;

[0044] Figure 13 This is a comparison diagram of the electromagnetic torque response before and after the W-phase open-circuit fault described in this invention;

[0045] Figure 14 This is a flowchart of the single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source as described in this invention. Detailed Implementation

[0046] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0047] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0048] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; and the term "one embodiment" means "at least one embodiment". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0049] It should be noted that the terms "one" and "more" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0050] The names of the messages or information exchanged between the multiple devices in the embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0051] In related technologies, dual three-phase permanent magnet synchronous motors (DTP-PMSMs) are widely used in high-end fields such as aerospace servo systems due to their high power density, high efficiency, and superior fault-tolerant operation. When one or two phases fail, the redundant winding structure of the dual three-phase motor allows the system to maintain continuous and stable operation of the motor by properly controlling the remaining healthy phases. Open-circuit faults are among the most common electrical faults in motor drive systems, and short-circuit faults can also be converted into open-circuit faults for handling by fuses. Therefore, research on fault-tolerant control for open-circuit faults has significant theoretical and engineering value.

[0052] During normal operation of the DTP-PMSM, the six-phase currents are symmetrically distributed in space, and the combined magnetomotive force generates a circular rotating magnetic field in the air gap. The stator current vector is... The components undergo uniform circular motion in the fundamental subspace, and cancel each other out in the z-harmonic subspace and the zero-sequence subspace. This symmetry is based on two fundamental premises: first, the six-phase windings are spatially symmetrically distributed; second, the six-phase currents have equal amplitudes and phases differing by 60° electrical degrees. When a single-phase open-circuit fault occurs, the current in that phase is forced to zero, and the system degenerates from a six-phase symmetrical state to a five-phase asymmetrical state. At this time, the remaining five non-faulty phase currents no longer satisfy the conditions of equal amplitudes and 60° phase differences, the original current constraint space is destroyed, and the six-phase Clarke transformation matrix under normal conditions is no longer applicable.

[0053] The Clarke transformation matrix under normal conditions maps the six-phase natural coordinate system to a six-dimensional mathematical space, where The fundamental subspace corresponds to the fundamental flux linkage, and the z-harmonic subspace corresponds to the 5th and 7th harmonics. and The zero-sequence subspace corresponds to the zero-sequence component. The row vectors of the Clarke transform matrix form an orthonormal basis in six-dimensional space, ensuring power invariance before and after the transform. When an open-circuit fault occurs in a phase, the current in that phase is always zero, equivalent to adding a zero-value constraint hyperplane to the six-dimensional current space. Under this constraint, any current vector in the original six-dimensional space is restricted to move within a five-dimensional subspace. However, the Clarke transform matrix in its normal state does not consider this constraint; the projection of its fundamental subspace row vectors onto the five-dimensional constraint subspace fails to satisfy the circular flux linkage condition, resulting in distortion of the transformed fundamental flux linkage.

[0054] The distribution of the fundamental flux linkage generated by the permanent magnet in the six-phase windings is determined by the winding function. The flux linkages in each phase are sinusoidal quantities with equal amplitude and a phase difference of 60°. When any phase (e.g., phase W) is open-circuited, the flux linkage information in the winding of the open-circuit fault phase is lost. When transforming using a reduced-order Clarke transform matrix... A pulsating component appeared in the shaft flux linkage. This pulsating component caused the remaining five-phase windings to have an asymmetrical spatial distribution after the fault, making the equivalent two-phase windings in the rotating coordinate system no longer orthogonal. The shaft winding couples with pulsating information from the rotor position angle. A circular fundamental flux linkage is the fundamental guarantee for the motor to generate constant electromagnetic torque. Once the flux linkage trajectory degenerates from circular to elliptical, harmonic magnetic field components with opposite rotational directions will appear in the air gap magnetic field. These harmonic magnetic fields interact with the rotor permanent magnet magnetic field, generating torque pulsations dominated by the sixth fundamental frequency, while simultaneously increasing core losses and exacerbating motor temperature rise.

[0055] After a single-phase open-circuit fault, the current path for the faulty phase is lost. To maintain the fundamental flux linkage amplitude, the currents of the other five phases must be redistributed. This redistribution process results in the current amplitudes of the non-faulty phases no longer being equal and the phases no longer being uniformly distributed, introducing a large number of odd harmonics (mainly the 3rd, 5th, and 7th harmonics) into the current waveform. Under the traditional coordinate transformation framework, these harmonic currents appear as even harmonics (2nd, 4th, etc.) in the dq coordinate system, which cannot be effectively suppressed by conventional PI controllers, further deteriorating the tracking performance of the current loop and the output torque quality.

[0056] During normal operation, the current vector space of a nine-switch current source inverter consists of 12 effective vectors and 3 zero vectors. The conduction time of the vectors is determined by the reference current vector. The projection in the fundamental subspace determines that the sectors are divided into 12, each sector being 30°. When phase W is open-circuited, all vectors that make the phase W current non-zero become unavailable, reducing the number of effective vectors from 12 to 8. The remaining current vectors are... The distribution in the fundamental subspace and the z-harmonic subspace is no longer uniform. At this point, the traditional two-vector synthesis method (selecting two adjacent vectors to synthesize a reference vector) cannot simultaneously meet the control requirements of the fundamental and harmonic subspaces, which will lead to the generation of non-zero components in the z-harmonic subspace. These harmonic components will further aggravate current distortion and torque ripple.

[0057] In summary, existing technologies face three interconnected core problems when handling single-phase open-circuit faults in DTP-PMSM driven by nine-switch CSI: first, the failure of the coordinate transformation matrix leads to fundamental flux distortion; second, a large number of harmonics are generated in the non-faulty phase current, resulting in a sharp increase in torque ripple; and third, the traditional SVPWM method cannot simultaneously consider fundamental synthesis and harmonic suppression in the reconstructed vector space. These three problems correspond to the mathematical foundation of the control system, current reference value calculation, and PWM modulation, respectively. Deficiencies in any one of these areas will lead to failure of fault-tolerant operation. This invention proposes solutions for each of these three areas, forming a systematic fault-tolerant control technology system.

[0058] To address the problems existing in the aforementioned related technologies, this embodiment provides a single-phase open-circuit fault-tolerant control method for a dual three-phase permanent magnet synchronous motor based on a nine-switch current source inverter.

[0059] like Figure 1 As shown, the nine-switch current source inverter consists of nine power switching transistors. The circuit consists of a diode connected in series with each switching transistor to ensure unidirectional current conduction and prevent reverse current from flowing through the transistor. A large inductor is connected in series on the DC side. As a current source, it provides a stable DC current input to the inverter; a filter capacitor is connected in parallel to each phase on the AC side (output side). This is used to filter out AC side current ripple and improve system stability. The nine power switches are arranged in three bridge arms: the first bridge arm contains the switching transistors... The second bridge arm includes The third bridge arm includes ,in This is the upper bridge arm switch (connected to the positive terminal of the DC bus). For the intermediate bridge arm switch transistor, The lower bridge arm switch is connected to the negative terminal of the DC bus. The inverter output has a six-phase connection, which is respectively connected to the six-phase windings A, B, C, U, V, and W of the dual three-phase permanent magnet synchronous motor (DTP-PMSM). The dual three-phase permanent magnet synchronous motor in this invention adopts a double Y-shift 30° structure, meaning that the two sets of three-phase windings (A, B, C) and (U, V, W) are spatially 30° electrically different. This structure effectively reduces torque ripple and harmonic content.

[0060] When an open-circuit fault occurs in phase W, the electrical connection between the phase W winding and the inverter is severed, the phase W current remains constant at zero, and the inverter continues to drive the motor only through the remaining five phase windings (A, B, C, U, V). Compared to the traditional twelve-switch CSI, the nine-switch CSI reduces three power switching transistors, effectively lowering system cost and size, while retaining the inherent advantages of CSI, such as high output current quality and strong short-circuit protection. Figure 1 In, the current in each phase , , , , , The current flows through the corresponding six-phase windings, with phase W open-circuited. =0. Electrical angle Position data is acquired in real time via position sensors (such as resolvers or encoders) mounted on the motor rotor, and is used for coordinate transformation and vector control. The DC side current is the bus current. After being modulated by the SVPWM of the nine-switch CSI, the signal is distributed to the windings of each non-faulty phase.

[0061] The fault-tolerant control method of this invention is based on Figure 1 The topology shown achieves the following: after detecting an open circuit fault in phase W, by correcting the coordinate transformation matrix, solving for the fault-tolerant current reference value, reconstructing the current vector space, and designing a fault-tolerant SVPWM strategy, the on / off timing of the nine power switches is finally controlled, so that the motor can still be driven to operate smoothly and fault-tolerantly even when phase W is open.

[0062] Combination Figure 1 and Figure 14 As shown in the embodiment of the present invention, the single-phase open-circuit fault-tolerant control method for a dual three-phase permanent magnet synchronous motor based on a nine-switch current source inverter includes the following steps:

[0063] S1. Coordinate transformation matrix correction steps: With the goal of maintaining the circular fundamental flux after the fault, the Clarke transformation matrix under normal operating conditions is reduced in order and zero-sequence compensation is performed to obtain the corrected coordinate transformation matrix adapted to single-phase open circuit fault.

[0064] Specifically, after a single-phase open-circuit fault occurs, the system degenerates from a six-phase symmetrical operating state to a five-phase asymmetrical operating state, and the Clarke transformation matrix under normal conditions is no longer applicable. This step aims to maintain the circular fundamental flux linkage. It obtains a corrected coordinate transformation matrix adapted to the single-phase open-circuit fault through two stages: order reduction and zero-sequence compensation correction of the Clarke transformation matrix under normal operating conditions. The order reduction stage removes redundant information from the faulty phase to match the dimensions of the five-phase physical system, while the zero-sequence compensation stage uses the zero-sequence subspace flux linkage component to compensate for the fundamental subspace row, eliminating the fundamental flux linkage distortion caused by the phase loss. The corrected coordinate transformation matrix ensures that... In the fundamental wave subspace, the fundamental wave flux still maintains a standard circular trajectory, providing a correct coordinate transformation basis for the subsequent establishment of the fault mathematical model. The core value of this matrix correction lies in the fact that it is not a simple deletion of columns based on the original matrix, but rather a compensation correction that enables the row vectors of the fundamental wave subspace to re-satisfy the orthogonality and circular flux conditions in the five-dimensional constrained subspace, thus mathematically reconstructing a coordinate transformation framework that matches the physical system after the fault.

[0065] S2. Fault modeling and fault-tolerant current solution steps: Based on the modified coordinate transformation matrix, construct a rotating coordinate coefficient mathematical model of the motor under single-phase open-circuit fault, and solve the fault-tolerant current reference value of each non-faulty phase according to the preset current constraint.

[0066] Specifically, after obtaining the corrected coordinate transformation matrix, it is concatenated with the Park transformation matrix to derive the stator voltage equation and electromagnetic torque equation in the dq rotating coordinate system. Since the corrected matrix ensures that the fundamental flux linkage is circular, the voltage and torque equations are formally consistent with those under normal operation, using only the d-axis and q-axis currents as variables. This facilitates the use of a conventional vector control strategy. Based on this, the control strategy adopted is as follows: given the quadrature-axis current to generate electromagnetic torque, the direct-axis current, harmonic subspace current, and zero-sequence subspace current in the fundamental subspace are all set to zero. Substituting the above current given values ​​into the inverse matrix obtained by concatenating the corrected Clarke transformation matrix and the Park transformation matrix, the current reference values ​​of each non-faulty phase in the natural coordinate system can be solved in reverse. These current reference values ​​have clear physical meaning: they can guarantee the direct-axis current... Under the control conditions, the motor outputs a given electromagnetic torque while keeping the fundamental flux linkage circular and the harmonic and zero-sequence subspace currents zero, thereby eliminating the root cause of harmonic current generation at the current level.

[0067] S3, Fault-tolerant space vector modulation steps: Using the fault-tolerant current reference value obtained in step S2 as the control target, eliminate the corresponding vectors of the fault, reconstruct the inverter current vector space and divide it into sectors; select three adjacent effective vectors in each sector so that the combined vector in the harmonic subspace is zero; solve the action time of each vector by combining the vector projection relationship and generate the switching sequence, synthesize the reference current vector, and realize the fault-tolerant operation control of the motor.

[0068] Specifically, after obtaining the fault-tolerant current reference values ​​for each non-faulty phase, the continuous current reference values ​​need to be converted into actual switching signals using the space vector pulse width modulation (SVPWM) of the nine-switch current source inverter. During normal operation, the current vector space of the nine-switch current source inverter consists of 12 valid vectors and 3 zero vectors, each vector corresponding to a specific set of switching combinations. When an open-circuit fault occurs in phase W of the motor, the current in phase W must be zero. Therefore, all vectors in the normal vector space that make the current in phase W non-zero are unusable, and these vectors coupled to the fault phase need to be removed from the vector space. After removal, the number of usable vectors decreases, and the remaining current vectors... The distribution in the fundamental and z-harmonic subspaces is no longer uniform, and the original 12-sector symmetric structure is destroyed. This invention reclassifies the remaining effective and zero vectors and, based on their... The spatial angular positions in the fundamental subspace are re-divided into sectors. Within each sector, three adjacent effective vectors are selected to form a vector combination, ensuring that the synthesized vector in the harmonic subspace is zero. This allows for the accurate synthesis of the fundamental current vector while actively suppressing harmonic currents. Finally, a system of equations is established by simultaneously defining the projection relationships of the vectors in the fundamental and harmonic subspaces. The action times of each effective vector and the zero vector are solved to generate the switching sequence of each power switch in the nine-switch current source inverter. This achieves accurate synthesis of the reference current vector, enabling the drive motor to operate smoothly and fault-tolerantly under open-circuit fault conditions.

[0069] Further, step S1 specifically includes:

[0070] The column elements corresponding to the faults in the Clarke transform matrix under normal operating conditions are deleted, and the order of the harmonic subspace is reduced to obtain the reduced order Clarke transform matrix.

[0071] By using the zero-order subspace flux linkage component to compensate and correct the corresponding row elements of the fundamental subspace within the reduced-order Clarke transform matrix, the fundamental flux linkage distortion caused by the fault is eliminated, ensuring that the fundamental flux linkage remains circular after the fault, consistent with that before the fault.

[0072] Specifically, the dual three-phase permanent magnet synchronous motor under normal conditions uses a six-phase Clarke transformation matrix to map physical quantities in the six-phase natural coordinate system to a coordinate system containing two fundamental subspace axes. ), two harmonic subspace axes ( ) and two zero-order subspace axes ( In the six-dimensional space of the Clarke transform matrix, when a single-phase open-circuit fault occurs, the fault phase current is always zero. The physical quantity of this phase does not provide any effective information in the six-dimensional space. However, the column elements corresponding to this phase in the Clarke transform matrix still contribute non-zero values ​​during the transform operation. This contribution actually originates from mathematical operations rather than physical signals, leading to spurious components in the transform result. Therefore, it is necessary to remove the column elements corresponding to the fault from the Clarke transform matrix to eliminate this spurious contribution. Simultaneously, since the effective physical quantities decrease from six to five after the fault, the harmonic subspace degenerates from two dimensions to one dimension. The dimension of the harmonic subspace needs to be reduced accordingly (the axis is denoted as the z-axis). After the order reduction process, the fundamental flux linkage of the rotor permanent magnet is transformed using the reduced-order Clarke transformation matrix, and it is found that... A pulsating component appears in the axial flux linkage, and the fundamental flux linkage trajectory degenerates from a circle to an ellipse. The root cause of this phenomenon is that the order reduction operation only completes the dimensional matching, but the projection of the row vectors of the reduced fundamental subspace onto the five-dimensional constrained subspace no longer satisfies the circular flux linkage condition. This invention compensates and corrects the row elements of the fundamental subspace in the reduced-order matrix by extracting the zero-order subspace flux linkage component, so that the corrected fundamental subspace row vectors re-satisfy the circular flux linkage condition in five-dimensional space, thereby ensuring that the fundamental flux linkage after the fault remains completely consistent with that before the fault.

[0073] In a preferred embodiment, when the single-phase open-circuit fault is the W-phase open-circuit fault of the dual three-phase permanent magnet synchronous motor, the last column of elements related to the W-phase in the normal Clarke transform matrix is ​​deleted, and the dimension of the harmonic subspace is reduced to obtain the reduced-order Clarke transform matrix as follows:

[0074] ;

[0075] The rotor fundamental flux linkage is transformed using a reduced-order Clarke transform matrix to obtain... The magnetic flux linkage in the coordinate system (stationary coordinate system) is:

[0076] ;

[0077] In the formula, The rotor permanent magnets are respectively open-circuited after the W phase of the motor. axis, axis, z-axis, axis, The flux linkage component generated on the shaft; These are the magnetic flux linkages of phases A, B, C, U, and V after the W phase of the motor is opened. Each is the motor during normal operation axis, The fundamental flux linkage component generated on the axis, This represents the fundamental flux linkage amplitude of the rotor permanent magnet. The electrical angle between the d-axis of the motor rotor and the axis of the A-phase winding. This is the reduced-order Clarke transformation matrix (a reduced-order transformation from a five-phase stationary coordinate system to a two-phase stationary coordinate system).

[0078] From the above equation, it can be seen that after phase W is open-circuited, the fundamental flux linkage is... A pulsating component appeared on the axis. This pulsating component originates from the loss of W-phase flux linkage information, which will cause the fundamental flux linkage to no longer maintain a circular shape, directly resulting in a pulsating component in the electromagnetic torque.

[0079] Using the circular fundamental flux linkage as the correction target, zero-sequence components are injected into the first two rows of the reduced-order Clarke transform matrix to keep the fundamental flux linkage consistent before and after the open circuit, resulting in the corrected Clarke transform matrix:

[0080] ;

[0081] The flux linkage is transformed using the modified Clarke transformation matrix to obtain... The flux linkage in the coordinate system is:

[0082] ;

[0083] In the formula, To correct the Clarke transformation matrix.

[0084] at this time, The fundamental flux linkage in the coordinate system is restored to a circle, which is completely consistent with the flux linkage form during normal operation. Comparing the reduced-order matrix and the corrected matrix, it can be found that the elements in the second row, fourth column and fifth column of the corrected matrix change from 1 / 2 to 3 / 2, which is precisely the mathematical manifestation of the injected zero-sequence compensation.

[0085] Furthermore, the rotating coordinate coefficient mathematical model in step S2 includes: the stator voltage equation and electromagnetic torque equation of the rotating coordinate system derived based on the modified coordinate transformation matrix.

[0086] Specifically, the modified Clarke transformation matrix solves the problem of fundamental flux distortion after a fault, laying the foundation for establishing a unified rotating coordinate coefficient mathematical model. After obtaining the modified Clarke transformation matrix, it needs to be concatenated with the Park transformation matrix to achieve a complete transformation from the stationary five-phase natural coordinate system to the rotating dq coordinate system. The Park transformation matrix will... The AC quantities in the fundamental subspace are converted into DC quantities on the d-axis and q-axis, which is the basis for achieving field-oriented control. When deriving the stator voltage equation in the dq coordinate system based on the modified coordinate transformation matrix, due to the injection of zero-sequence compensation into the modified matrix, the voltage equation in the zero-sequence subspace... An electromotive force component related to the rotor position will appear on the shaft. This is a unique phenomenon generated by the remaining five-phase asymmetrical windings in the rotating magnetic field after a fault. The electromagnetic torque equation is derived using the virtual displacement method, and its form is consistent with the torque equation during normal operation, with only the q-axis current and d-axis current as variables. This characteristic ensures that the same vector control framework can be used after a fault as during normal operation, without the need to redesign a complex torque observer or nonlinear controller, significantly reducing the difficulty of implementing fault-tolerant control.

[0087] In a preferred embodiment, the Park transformation matrix is:

[0088] ;

[0089] The equation for the motor stator voltage in the dq coordinate system (rotating coordinate system) is as follows:

[0090] ;

[0091] In the formula, For the motor W phase after open circuit, the d-axis and q-axis in the dq coordinate system are... axis, axis, Stator voltage component of the shaft, The stator resistance is in the dq coordinate system. For the motor W phase after open circuit, the d-axis, q-axis, and z-axis in the dq coordinate system are... axis, Stator current components of the shaft, The rotor's electric angular velocity, Let the inductances of the motor's W phase be the d-axis and q-axis in the dq coordinate system after the W phase is open-circuited. This is the equivalent leakage inductance.

[0092] The electromagnetic torque equation in the dq coordinate system is:

[0093] ;

[0094] In the formula, This represents the number of pole pairs of the motor. This represents the electromagnetic torque. The electromagnetic torque equation is identical to that under normal operation, depending only on the d-axis and q-axis currents. This characteristic indicates that by properly controlling the d and q-axis currents, precise control of the electromagnetic torque can be achieved after a fault, meaning that the goal and means of torque control remain consistent before and after the fault.

[0095] Furthermore, in step S2, the reference values ​​of the fault-tolerant current for each non-faulty phase are solved based on the preset current constraints. Specifically, given the quadrature axis current of the rotating coordinate system, the direct axis current, the zero-sequence subspace current, and the harmonic subspace current are all set to zero. The reference values ​​of the current for each non-faulty phase are solved by the inverse matrix operation of the modified coordinate transformation matrix.

[0096] Specifically, after establishing the mathematical model in the dq coordinate system after the fault, it is necessary to determine the reference values ​​of the fault-tolerant current for each non-faulty phase. This step uses... The vector control strategy sets the harmonic subspace current and zero-sequence subspace current to zero. This is because these current components do not generate effective electromagnetic torque, only increasing losses and producing pulsations. Setting them to zero eliminates the excitation of harmonic torque pulsations at the current source. After determining the current setpoint in the dq coordinate system, it can be directly used as the setpoint signal for the inner current loop, controlling the inverter to output corresponding pulses and drive the motor to output the corresponding current. Furthermore, by correcting the inverse matrix obtained by cascading the Clarke and Park transformation matrices, the current reference values ​​of each non-faulty phase in the natural coordinate system can be solved in reverse to verify the accuracy of the simulation results. This method transforms the current control problem of a five-phase asymmetrical system after a fault into a conventional dq-axis current control problem, significantly reducing the design difficulty of the controller.

[0097] In a preferred embodiment, a given reference value is used during fault-tolerant operation. The control method, making ( (Given the q-axis current reference value for fault-tolerant operation), then the fault-tolerant current reference value for the non-faulty phase is:

[0098] ;

[0099] In the formula, This is the reference value for the q-axis current given during fault-tolerant operation. , , , , These are the reference values ​​for the fault-tolerant currents of phases A, B, C, U, and V after a phase W open-circuit fault, and the current of the faulty phase W. , This is the Park transformation matrix.

[0100] As can be seen from the above formula, after phase W is opened, the amplitude and phase of the remaining five-phase currents undergo regular changes. The fault-tolerant current amplitude of phase A is equal to... Phase is The fault-tolerant current amplitude of phase B is Phase is The fault-tolerant current amplitude of phase C is Phase is The fault-tolerant current amplitude of phase U is Phase is The amplitude of the V-phase fault-tolerant current is Phase is The phase relationship between the fault-tolerant currents of each phase is no longer a uniform 60° electrical angle, but rather exhibits a specific non-uniform distribution. This is the current distribution scheme necessary to maintain the circular fundamental flux linkage in a five-phase asymmetrical system.

[0101] Furthermore, the process of reconstructing the inverter current vector space in step S3 is as follows: all vectors coupled with the fault in the normal current vector space are removed, the reconstructed vector space contains multiple valid vectors and multiple zero vectors, and the reconstructed vector space is divided into multiple sectors.

[0102] Specifically, when the nine-switch current source inverter is operating normally, its current vector space consists of 12 effective vectors and 3 zero vectors. The correspondence between each current vector and the conducting switch is shown in Table 1. Figure 2 For the normal operation of a nine-switch current source inverter Fundamental subspace current vector distribution diagram, Figure 3 This is a diagram showing the z-harmonic subspace current vector distribution during normal operation. From... Figure 2 and Figure 3 It can be seen that the 12 effective vectors are in The vectors are uniformly distributed on the plane, with an angle of 30° between adjacent vectors and equal vector magnitudes, forming a complete regular dodecagonal vector space. These 12 effective vectors are divided into two groups based on their spatial position—the upper effective vectors (…). ) and the lower effective vector ( ), each corresponding to the switching combination of different bridge arms of the inverter; 3 zero vectors ( Located at the origin, corresponding to a switching state where the six-phase output current is zero. During normal operation, any reference current vector can be synthesized from the two adjacent valid vectors and the zero vector of its sector. The sector division rule is 12 sectors, each sector being 30°.

[0103] When an open-circuit fault occurs in phase W, all vectors that make the current in phase W non-zero become unusable, and all vectors coupled to phase W must be removed from the normal vector space. Figure 4 After opening the path for phase W Fundamental subspace current vector distribution diagram, Figure 5 This is a vector distribution diagram of the z-harmonic subspace current after phase W is open-circuited. From Figure 4 It can be seen that the remaining effective vectors are in The distribution in the fundamental subspace is no longer uniform; the angular spacing of some sectors increases, and vector loss leads to the destruction of symmetry; from Figure 5It can be seen that the projection of the effective vector in the z-harmonic subspace is also non-uniformly distributed, which is the fundamental reason why the traditional two-vector synthesis method cannot simultaneously take into account fundamental wave synthesis and harmonic suppression. The reconstructed current vector space contains 8 effective vectors and 3 zero vectors, reducing the number of effective vectors by 4 and the number of sectors from 12 to 8.

[0104] Table 1 Current vectors and corresponding on-state switches of a nine-switch current source inverter

[0105]

[0106] Furthermore, in step S3, three adjacent effective vectors are selected in each sector to make the harmonic subspace composite vector zero. Specifically, three adjacent effective vectors with spatially adjacent positions are selected in each sector to form a vector combination. The vector combination is superimposed in the harmonic subspace to form a composite vector of zero, thereby suppressing harmonic current.

[0107] Specifically, the reconstructed current vector space exhibits a non-uniform distribution. Traditional two-vector synthesis methods (selecting two adjacent vectors to synthesize a reference vector) can only control the synthesis result in the fundamental subspace and cannot consider the harmonic subspace. This is because any single effective vector in… The projections in the fundamental and z-harmonic subspaces are coupled. While a linear combination of only two vectors can accurately synthesize the fundamental reference vector, the synthesis result in the harmonic subspace will be uniquely determined and cannot be independently controlled. When the synthesized vector in the harmonic subspace is not zero, the actual output current will contain harmonic components, leading to current distortion and torque ripple. The adjacent three-vector synthesis principle proposed in this invention achieves decoupled control of the fundamental and harmonic subspaces by adding a degree of freedom to the vector: the linear combination of the three vectors, while satisfying the synthesis objective of the fundamental subspace, can also make the synthesized vector in the harmonic subspace zero by adjusting the action time ratio of the three vectors. The essence of this principle is to use the full-rank condition of the 3×3 matrix formed by the projections of the three vectors in the two-dimensional fundamental and one-dimensional harmonic subspaces to independently control the fundamental and harmonic components.

[0108] Figure 6 After opening the circuit for phase W, sector I Schematic diagram of fundamental subspace current vector synthesis. Figure 7 This is a schematic diagram of the vector synthesis of the z-harmonic subspace current in sector I after phase W is open-circuited. Figure 6 and Figure 7 It can be seen that the three adjacent effective vectors selected in sector I , , exist In the fundamental subspace, reference current vectors are synthesized in their respective directions. Simultaneously, in the z-harmonic subspace, the projected components of the three vectors cancel each other out to zero after superposition. This synthesis process intuitively demonstrates how adjacent three vectors can achieve complete suppression of harmonic subspace current components while accurately synthesizing the fundamental reference vector. The selection of adjacent vectors also takes into account minimizing switching losses, because switching between adjacent vectors involves only a few state changes of the switches, avoiding the simultaneous operation of multiple switches that may be caused by switching between non-adjacent vectors.

[0109] Furthermore, step S3, which involves solving for the action time of each vector, includes: obtaining the projection components of three adjacent effective vectors and the zero vector in the fundamental subspace and harmonic subspace, establishing a system of equations in conjunction with the target reference current vector, and solving for the action time of each effective vector and the zero vector.

[0110] Specifically, after determining the three adjacent effective vectors used in each sector, it is necessary to calculate the duration of each vector so that, within one switching cycle, the weighted sum of these vectors equals the reference current vector obtained in step S2. This calculation is based on the volt-second balance principle: decomposing the reference current vector into... In the fundamental and z-harmonic subspaces, the projected components of the three effective vectors in each subspace are known quantities, while their durations are unknown. Simultaneously, to maintain current continuity and satisfy the time constraint of one switching cycle during vector switching, a zero vector is introduced to fill the remaining time. Thus, the four unknowns (the durations of the three effective vectors and the duration of the zero vector) correspond to four equations— Shaft component balance, The balance of the axial components, the balance of the z-axis component (set to zero), and the total time equal to the switching cycle constitute a system of four linear equations with a unique solution. The coefficient matrix of this system of equations is composed of the projected components of the selected vector. In different sectors, the projected components of the selected vector are different, so it is necessary to call the corresponding coefficient matrix according to the sector number to solve the problem.

[0111] In a preferred embodiment, the equation for calculating the vector action time is:

[0112] ;

[0113] In the formula, , , The selected number A vector in axis, Projected components on the x-axis and z-axis, superscript Indicates the index of the selected vector. These represent the durations of action of three adjacent effective vectors. The duration of action of the zero vector. For the switching cycle, The reference current vectors are respectively at axis, The components on the x-axis and z-axis. Among them, For three adjacent valid vectors, Corresponding to the zero vector.

[0114] In a preferred embodiment, combined with Figure 6 , Figure 7 As shown, taking sector I as an example, the equation for calculating the vector action time is:

[0115] ;

[0116] In the formula, For the three selected adjacent valid vectors, Effective vectors The corresponding duration of action.

[0117] Solving the equation, we can obtain the effective vector duration of sector I as follows:

[0118] ;

[0119] In the formula, This represents the bus current.

[0120] The effective vector action time for each sector is shown in Table 2.

[0121] Table 2 Effective Vector Activation Time for Each Sector

[0122]

[0123] In the table, , , , Intermediate variables designed to simplify writing are calculated using the following formulas:

[0124] , , , .

[0125] Furthermore, step S3 also includes switching timing generation: calculating the vector switching time based on the action time of each effective vector and zero vector obtained by solving, and outputting the on / off switching timing of each power switch in the nine-switch current source inverter to drive the motor to operate in a fault-tolerant manner.

[0126] Specifically, after calculating the duration of each vector, these time values ​​need to be converted into drive signals for the actual power switches. The core of this conversion process is designing a reasonable switching sequence that maps the duration of each vector to the on / off state of the power switches on the time axis. During vector switching, the current source inverter must ensure the continuity of the DC-side current path, meaning that at any given time, at least one upper bridge arm switch and one lower bridge arm switch are on, with the middle bridge arm switch following the upper or lower bridge arm switch. To this end, this invention employs a symmetrical switching sequence design: zero vectors are evenly distributed at the beginning, end, and middle of the switching cycle, and effective vectors are symmetrically inserted between the zero vectors, ensuring that the vector switching times are symmetrical about the midpoint of the cycle within a single switching cycle. This symmetrical design reduces harmonic content in the output current, lowers switching losses, and ensures the balance of the six-phase output current. After determining the vector switching times, the on / off switching sequence of the power switches in the nine-switch current source inverter is generated based on the corresponding combinations of on switches for each vector, enabling the drive motor to operate with fault tolerance under open-circuit fault conditions.

[0127] In a preferred embodiment, taking sector I as an example, its switching sequence is as follows: Figure 8 As shown, the three adjacent valid vectors selected in sector I are , , The zero vector is , In the first half of the switching cycle Within, the vectors act on the inverter in the following order: zero vector First, it acts as a function, then it switches to the effective vector in sequence. , , Finally, it returns to the zero vector. In the second half of the switching cycle Inside, from the zero vector Begin reverse action. The action times for each vector are as follows: , , , (in zero vector , The total duration of action, with each zero vector acting separately. ), and satisfy .

[0128] To generate the symmetric switching sequence, four vector switching time points are defined. , , , The duration of action of the zero vector After dividing the circuit into four equal parts, the parts are placed at the beginning, end, and middle of the switching cycle. The calculation formulas for the four time points are as follows:

[0129] ;

[0130] After determining the switching times of each vector, the switching transistor combinations corresponding to each vector (zero vector) are used as shown in Table 1. Corresponding switching transistor On; zero vector Corresponding switching transistor Conductivity; Effective Vector Corresponding switching transistor Conductivity; Effective Vector Corresponding switching transistor Conductivity; Effective Vector Corresponding switching transistor (Conduction), generating power switches for each of the nine-switch current source inverters. The switching timing is controlled to control the inverter to output the corresponding current vectors in sequence, synthesize the required reference current vector within one switching cycle, and drive the motor to operate smoothly and fault-tolerantly under open circuit fault conditions.

[0131] FFT (Fast Fourier Transform) analysis after phase W is open: Figure 9 As shown, after fault-tolerant control, the Total Harmonic Distortion (THD) decreased to 0.64%, and the harmonic components of the non-faulty phase current were suppressed. Figure 10 This demonstrates that after phase W is opened, the non-faulty phase current rapidly transitions to a new stable sinusoidal state, and the phase and amplitude of the waveform are consistent with the theoretical analysis. (The text then repeats the description of phase W before and after the open circuit.) The axis current trajectory is as follows Figure 11 As shown, it can be seen that after adopting the coordinate transformation matrix given by theoretical analysis, after fault tolerance... The q-axis current trajectory remains circular. The q-axis current and electromagnetic torque before and after the W-phase is open-circuited are as follows: Figure 12 , Figure 13 As shown, after fault tolerance, the q-axis current and electromagnetic torque still follow the given parameters, with a steady-state ripple of 0.24A for the q-axis current and 0.50A for the torque. The steady-state fluctuations only increased slightly compared to before the fault, indicating good tracking and control performance.

[0132] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source, characterized in that, Includes the following steps: S1. Coordinate transformation matrix correction steps: With the goal of maintaining the circular fundamental flux after the fault, the Clarke transformation matrix under normal operating conditions is reduced in order and zero-sequence compensation is performed to obtain the corrected coordinate transformation matrix adapted to single-phase open circuit fault. S2. Fault modeling and fault-tolerant current solution steps: Based on the modified coordinate transformation matrix, construct a rotating coordinate coefficient mathematical model of the motor under single-phase open-circuit fault, and solve the fault-tolerant current reference value of each non-faulty phase according to the preset current constraint. S3, Fault-tolerant space vector modulation steps: Using the fault-tolerant current reference value obtained in step S2 as the control target, eliminate the corresponding vectors of the fault, reconstruct the inverter current vector space and divide it into sectors; select three adjacent effective vectors in each sector so that the combined vector in the harmonic subspace is zero; solve the action time of each vector by combining the vector projection relationship and generate the switching sequence, synthesize the reference current vector, and realize the fault-tolerant operation control of the motor.

2. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 1, characterized in that, Step S1 specifically includes: The column elements corresponding to the faults in the Clarke transform matrix under normal operating conditions are deleted, and the order of the harmonic subspace is reduced to obtain the reduced order Clarke transform matrix. By using the zero-order subspace flux linkage component to compensate and correct the corresponding row elements of the fundamental subspace within the reduced-order Clarke transform matrix, the fundamental flux linkage distortion caused by the fault is eliminated, ensuring that the fundamental flux linkage remains circular after the fault, consistent with that before the fault.

3. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 2, characterized in that, When the single-phase open circuit fault is the W-phase open circuit fault of the dual three-phase motor; The reduced-order Clarke transformation matrix is: The modified Clarke transformation matrix is: 。 4. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 1, characterized in that, The rotating coordinate coefficient mathematical model in step S2 includes: the stator voltage equation and electromagnetic torque equation in the rotating coordinate system derived based on the modified coordinate transformation matrix.

5. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 1, characterized in that, In step S2, the reference values ​​of the fault-tolerant current for each non-faulty phase are solved based on the preset current constraints. Specifically, given the quadrature axis current of the rotating coordinate system, the direct axis current, the zero-sequence subspace current, and the harmonic subspace current are all set to zero. The reference values ​​of the current for each non-faulty phase are solved by the inverse matrix operation of the modified coordinate transformation matrix.

6. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 1, characterized in that, The process of reconstructing the inverter current vector space in step S3 is as follows: remove all vectors coupled with the fault in the normal current vector space, the reconstructed vector space contains multiple valid vectors and multiple zero vectors, and divide the reconstructed vector space into multiple sectors.

7. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 6, characterized in that, In step S3, three adjacent effective vectors are selected in each sector to make the harmonic subspace composite vector zero. Specifically, three spatially adjacent effective vectors are selected in each sector to form a vector combination. The vector combination is superimposed in the harmonic subspace to form a composite vector of zero, thereby suppressing harmonic current.

8. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 7, characterized in that, Step S3, which involves solving for the action time of each vector, includes: obtaining the projection components of the three effective vectors and the zero vector in the fundamental subspace and harmonic subspace, establishing a set of equations in conjunction with the target reference current vector, and solving for the action time of each effective vector and the zero vector.

9. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 8, characterized in that, The system of equations for solving the vector action time is as follows: In the formula, , , The selected number A vector in axis, Projection components on the x-axis and z-axis, , These represent the durations of action of the three effective vectors. The duration of action of the zero vector. For the switching cycle, The reference current vectors are respectively at axis, Components on the x-axis and z-axis.

10. The single-phase open-circuit fault-tolerant control method for a dual three-phase motor driven by a nine-switch current source according to claim 8, characterized in that, Step S3 further includes switching timing generation: calculating the vector switching time based on the action time of each effective vector and zero vector obtained by solving, and outputting the on / off switching timing of each power switch in the nine-switch current source inverter to drive the motor to operate in a fault-tolerant manner.

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