A method for suppressing open-circuit fault torque ripple of a multiphase permanent magnet motor

Abstract

The application belongs to the technical field of electric machines, and discloses a method for suppressing open-circuit fault torque ripple of a multiphase permanent magnet motor, comprising the following steps: constructing a target function of a tracking current reference value and a set of virtual voltage vectors in a normal operating state, and selecting a virtual voltage vector that minimizes the target function value of the tracking current reference value as an optimal virtual voltage vector; calculating a duty cycle of the optimal virtual voltage vector; compensating the duty cycle of the optimal virtual voltage vector based on a PI regulator to obtain a final action time of the optimal virtual voltage vector. The method of the application does not require fault diagnosis and software reconstruction, and uses a unified control program and algorithm before and after a fault, has no additional influence when the motor system is normally operated, and automatically suppresses torque ripple after the motor system has an open-circuit fault.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a method for suppressing torque pulsation caused by an open-circuit fault of a multi-phase permanent magnet motor. Background Art

[0002] Multiphase permanent magnet motor drive systems have been widely researched in recent years. Compared to three-phase drive systems, multiphase drive systems offer additional degrees of freedom, enabling fault-tolerant operation after a fault without requiring additional hardware circuitry or downtime for maintenance. Consequently, they are often used in high-reliability applications such as electric aircraft, electric vehicles, and marine electric propulsion. However, control program switching within the software algorithm following a fault is unavoidable.

[0003] Among various fault types in multiphase permanent magnet motors, open-circuit faults are the most common. Model predictive control (MPC) has been used to handle fault-tolerant control of multiphase permanent magnet motor systems under open-circuit faults due to its simple structure, ease of implementation, and ease of handling nonlinear constraints.

[0004] Fault-tolerant operation based on model predictive control involves several aspects, including fault diagnosis, fault location, and control algorithm reconstruction. First, an open-circuit fault is diagnosed, the faulty phase is located, and then the corresponding control algorithm for that phase open circuit is selected from pre-stored programs. For example, with the goal of maintaining the circular shape of the rotating magnetomotive force after a fault, a fault-tolerant program is pre-designed using the minimum copper loss standard. The reduced-order coordinate transformation matrix for the phase open circuit is derived, the corresponding virtual voltage vector is designed, and the objective function is modified to ultimately achieve fault-tolerant operation.

[0005] While existing technologies can achieve good fault tolerance, they require tailored fault tolerance solutions for each specific fault scenario. These solutions involve new mathematical models, a new set of candidate voltage vectors, new reference currents, and new objective functions. Different control algorithms are required for different fault phases. After a fault occurs, a series of diagnostic measures are required to determine the fault phase and determine and select the correct fault tolerance solution. This leads to significant computational and storage burdens, as well as issues such as fault diagnosis delays.

[0006] Therefore, how to provide a method for suppressing torque pulsation caused by open-circuit fault of a multi-phase permanent magnet motor without fault diagnosis and software reconstruction is an urgent problem to be solved. Summary of the Invention

[0007] Embodiments of the present invention provide a method for suppressing torque ripple after an open-circuit fault in a multiphase permanent magnet motor, addressing the control hysteresis issue in the prior art. To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is provided below. This summary is not intended to be a comprehensive review, identify key or important elements, or delineate the scope of these embodiments. Its sole purpose is to present some concepts in a simplified form, serving as a prelude to the detailed description that follows.

[0008] According to a first aspect of an embodiment of the present invention, a method for suppressing torque pulsation due to an open-circuit fault in a multi-phase permanent magnet motor is provided.

[0009] In one embodiment, the method for suppressing torque pulsation due to an open-circuit fault in a multi-phase permanent magnet motor comprises the following steps:

[0010] Constructing an objective function and a set of virtual voltage vectors for tracking the current reference value under normal operating conditions, and selecting a virtual voltage vector that minimizes the objective function value for tracking the current reference value as the optimal virtual voltage vector;

[0011] Calculate the optimal virtual voltage vector duty cycle;

[0012] The duty cycle of the optimal virtual voltage vector is compensated based on the PI regulator to obtain the final action time of the optimal virtual voltage vector.

[0013] Optionally, the objective function of constructing the normal operating state is specifically:

[0014]

[0015] in and are the reference values ​​of the fundamental quadrature and direct axis currents at time k+2, and are the predicted values ​​of the fundamental dq axis current at time k+2 respectively.

[0016] Optionally, the step of calculating the optimal virtual voltage vector duty cycle is specifically:

[0017]

[0018] Among them, γ opt is the optimal virtual voltage vector duty cycle; t opt is the action time of the optimal virtual voltage vector; s opt is the q-axis current slope when outputting the optimal virtual voltage vector; s0 is the q-axis current slope when outputting the zero vector; is the quadrature-axis current component under the fundamental wave plane at time k+1; T s For the control cycle.

[0019] Optionally, the q-axis current slope when outputting the zero vector is calculated as follows:

[0020]

[0021] Among them, L q1 is the fundamental plane quadrature axis inductance; R s is the stator resistance; is the rotor electrical angular velocity at time k+1; is the direct axis current component under the fundamental wave plane at time k+1; ψ f is the permanent magnet flux.

[0022] Optionally, the q-axis current slope when outputting the optimal virtual voltage vector is calculated as follows:

[0023]

[0024] in, is the q-axis fundamental voltage component of the optimal virtual voltage vector.

[0025] Optionally, the input signal of the PI regulator is the duty cycle error e k , the calculation formula is as follows:

[0026]

[0027] in, is the quadrature and direct axis current component under the fundamental wave plane at time k; is the reference value of the fundamental quadrature-axis current at time k+2; s0 is the slope of the q-axis current when the output vector is zero; T s For the control cycle.

[0028] Optionally, the discrete mathematical model of the PI regulator is:

[0029]

[0030] Among them, d δ is the duty cycle compensation of the optimal virtual voltage vector, K c is the anti-saturation feedback coefficient, is the saturation error at time k-1; K p is the proportional coefficient of the PI regulator; e k is the duty cycle error at time k; is the accumulated integral value at time k-1; K i is the integral coefficient of the PI regulator.

[0031] Optionally, the saturation error e sat The calculation formula is:

[0032] e sat =sat(d δ )-d δ

[0033] sat(d δ ) is the saturation value.

[0034] According to a second aspect of an embodiment of the present invention, a computer device is provided.

[0035] In some embodiments, the computer device includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0036] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0037] The method of this application incorporates a PI regulator into duty cycle optimization. The output of the PI regulator is superimposed on the duty cycle calculation result to determine the action time of the optimal virtual voltage vector. The PI regulator and the duty cycle calculation are in a "parallel" relationship, so it has no additional impact during normal operation before a fault. After a fault, the duty cycle error corresponding to the control error is corrected. Furthermore, because of the "parallel" relationship, the PI regulator does not affect the response speed of the current loop.

[0038] The method of the present application does not require fault diagnosis and software reconstruction. A unified control program and algorithm are used before and after a fault. There is no additional impact when the motor system operates normally. When an open-circuit fault occurs in the motor, torque pulsation suppression is automatically performed.

[0039] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0041] Figure 1 is a flow chart showing a method for suppressing torque pulsation due to an open-circuit fault in a multi-phase permanent magnet motor according to an exemplary embodiment;

[0042] Figure 2 is a block diagram of a system control principle of a multi-phase permanent magnet motor according to an exemplary embodiment;

[0043] Figure 3 is a schematic diagram of a PI regulator according to an exemplary embodiment;

[0044] Figure 4is a schematic diagram of current control within a sampling period during normal operation before a fault according to an exemplary embodiment;

[0045] Figure 5 is a schematic diagram showing a control deviation caused by performing calculations according to a normal state even when a fault occurs, according to an exemplary embodiment;

[0046] Figure 6 is a schematic diagram showing the control effect after compensation using the method of the present application according to an exemplary embodiment;

[0047] Figure 7 is the value of i before PI regulator compensation according to an exemplary embodiment. q1 Waveform diagram;

[0048] Figure 8 is a schematic diagram showing a duty cycle compensation amount output by a PI regulator according to an exemplary embodiment;

[0049] Figure 9 According to an exemplary embodiment, the compensation correction method of the present application is used. q1 Waveform diagram;

[0050] Figure 10 The figure is a schematic diagram showing the structure of a computer device according to an exemplary embodiment. DETAILED DESCRIPTION

[0051] The following description and accompanying drawings sufficiently illustrate the specific embodiments herein to enable those skilled in the art to practice them. Portions and features of some embodiments may be included in or substituted for portions and features of other embodiments. The scope of the embodiments herein includes the entire scope of the claims, including all available equivalents thereof. Herein, the terms "first," "second," and the like are used solely to distinguish one element from another and do not require or imply any actual relationship or order between these elements. In practice, the first element can also be referred to as the second element, and vice versa. Furthermore, the terms "comprise," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a structure, device, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such structure, device, or apparatus. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of other identical elements in the structure, device, or apparatus comprising the element. The various embodiments herein are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. Similar or identical parts between the various embodiments can be referenced to each other.

[0052] The terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used herein to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are intended only to facilitate the description of this document and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In the description herein, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, they can be mechanical or electrical connections, or they can be internal connections between two elements, they can be directly connected, or they can be indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0053] As used herein, unless otherwise specified, the term "plurality" means two or more.

[0054] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0055] In this article, the term "and / or" is used to describe the association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0056] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0057] Figure 1 An embodiment of the method for suppressing torque ripple due to an open-circuit fault of a multi-phase permanent magnet motor according to the present invention is shown.

[0058] In this optional embodiment, the method for suppressing torque pulsation due to an open-circuit fault of a multi-phase permanent magnet motor includes the following steps:

[0059] Step S1, constructing an objective function and a virtual voltage vector set for tracking a current reference value under normal operating conditions, and selecting a virtual voltage vector that minimizes the value of the objective function for tracking the current reference value as the optimal virtual voltage vector;

[0060] Step S2, calculating the optimal virtual voltage vector duty cycle;

[0061] Step S3: Compensating the duty cycle of the optimal virtual voltage vector based on the PI regulator to obtain the final action time of the optimal virtual voltage vector.

[0062] For multi-phase permanent magnet motors, the mathematical model using the virtual voltage vector method only needs to consider the fundamental wave plane.

[0063] The multi-phase permanent magnet motor model is discretized to obtain the fundamental wave planar motor discrete model, as follows:

[0064]

[0065] in, and is the quadrature and direct axis current component under the fundamental wave plane at time k; and is the quadrature and direct axis current component in the fundamental wave plane at time k+1; and is the DC-axis voltage vector in the fundamental wave plane at time k; L q and L d is the DC-axis inductance; T s To control the cycle; is the rotor electrical angular velocity at time k; R s is the stator resistance; ψ f is the permanent magnet flux.

[0066] The current prediction model is obtained based on the motor discrete model, as follows:

[0067]

[0068] The current prediction model performs delay compensation for the first-order beat, specifically:

[0069]

[0070] Since the rotor electrical angular velocity can be regarded as a constant in adjacent control cycles,

[0071] Therefore, the objective function of tracking the current reference value under normal operating conditions is constructed:

[0072]

[0073] in, and They are the reference values ​​of the fundamental AC and DC axis currents at time k+2, and the permanent magnet motor uses i d =0 control, This is the speed loop output. and are respectively the predicted values ​​of the fundamental wave dq axis current at time k+2. According to the prior art, a virtual voltage vector set under normal operation is designed, and the virtual voltage vector with the smallest j value is selected as the optimal virtual voltage vector.

[0074] Optionally, the above step of calculating the optimal virtual voltage vector duty cycle is specifically as follows:

[0075] Inserting the zero vector v0 changes the optimal virtual voltage vector duty cycle. The optimal virtual voltage vector duty cycle is calculated as follows:

[0076]

[0077] Among them, γ opt is the optimal virtual voltage vector duty cycle; t opt is the action time of the optimal virtual voltage vector; s opt is the q-axis current slope when outputting the optimal virtual voltage vector; s0 is the q-axis current slope when outputting the zero vector.

[0078] The q-axis current slope s0 at zero vector is calculated as follows:

[0079]

[0080]

[0081] In the formula is the q-axis fundamental voltage component of the optimal virtual voltage vector; L q1 is the fundamental plane quadrature-axis inductance.

[0082] In order to enable the system to automatically suppress the torque ripple caused by the open circuit fault, it is necessary to set the optimal virtual voltage vector duty cycle γ opt To this end, a PI regulator is added to the duty cycle calculation to track the control error in real time. The system control principle block diagram of the multi-phase permanent magnet motor is shown in the figure. Figure 2 shown.

[0083] Figure 3 An embodiment of a PI regulator is shown.

[0084] The input signal of the PI regulator is the duty cycle error e k , the calculation formula is as follows:

[0085]

[0086] in, is the quadrature and direct axis current component under the fundamental wave plane at time k; is the reference value of the fundamental quadrature-axis current at time k+2; s0 is the slope of the q-axis current when the output vector is zero; T s For the control cycle.

[0087] In order to avoid integral saturation, the PI regulator introduces feedback inhibition to prevent saturation. The discrete mathematical model of the PI regulator is:

[0088]

[0089] d δis the duty cycle compensation of the optimal virtual voltage vector, K c is the anti-saturation feedback coefficient, is the saturation error at time k-1; K p is the proportional coefficient of the PI regulator; e k is the duty cycle error at time k; is the accumulated integral value at time k-1; K i is the integral coefficient of the PI regulator; e sat is the saturation error.

[0090] e sat The calculation formula is:

[0091] e sat =sat(d δ )-d δ

[0092] sat(d δ ) is the saturation value.

[0093] Before the open circuit fault occurs, the system operates normally and the calculation result of the duty cycle has no deviation. Figure 4 Figure 2 shows the current control diagram for one sampling period during normal operation before a fault occurs. At this time, the input to the PI regulator is approximately zero, so the PI regulator has no impact on system operation before the fault occurs.

[0094] After an open circuit fault occurs, the amplitude of the virtual voltage vector output by the system decreases. However, due to the lack of a fault diagnosis and software reconstruction environment, all voltage vectors are stored offline in the processor. Therefore, when calculating the duty cycle, the control algorithm still calculates the voltage amplitude under normal conditions. The duty cycle result obtained at this time is no longer accurate, resulting in control deviation, such as Figure 5 shown.

[0095] At this point, the PI regulator starts to work and q1 The deviation is converted into the duty cycle deviation according to the calculation formula of the duty cycle error, and tracking compensation is performed on it. The duty cycle compensation output by the PI regulator is superimposed on the duty cycle result obtained by the optimization calculation to determine the final action time of the optimal virtual voltage vector. The control effect after compensation is as follows Figure 6 shown.

[0096] According to the motor torque calculation formula:

[0097]

[0098] Among them, n is the number of motor phases, n p is the number of pole pairs. When the permanent magnet motor adopts i d1 =0 control mode, the output torque can be determined by i q1 Decision, therefore, for iq1 The stable control can suppress the torque ripple of the response.

[0099] Figure 7 i before PI regulator compensation q1 waveform; Figure 8 It is the duty cycle compensation output by the PI regulator; Figure 9 i after compensation correction using the method of this application q1 waveform.

[0100] This application proposes a torque pulsation suppression method that eliminates the need for fault diagnosis and software reconfiguration while suppressing the additional torque pulsation caused by the fault. This method is highly robust and versatile against open-circuit faults. It uses the same control algorithm before and after the fault occurs, eliminating the need for switching control programs or performing fault diagnosis and location. After an open-circuit fault occurs, it automatically suppresses the additional torque pulsation caused by the fault, giving the system self-healing capabilities.

[0101] The method of this application incorporates a PI regulator into duty cycle optimization. The output of this PI regulator is superimposed on the duty cycle calculation result to determine the action time of the optimal virtual voltage vector. This PI regulator is in parallel with the duty cycle calculation, so it has no additional impact during normal operation before a fault. After a fault, the duty cycle error corresponding to the control error is corrected. Furthermore, because of this parallel relationship, the PI regulator does not affect the response speed of the current loop.

[0102] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Figure 10 As shown. The computer device includes a processor, a memory, and a network interface connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store static information and dynamic information data. The network interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, the steps of the above-mentioned method embodiment are implemented.

[0103] Those skilled in the art will understand that Figure 10 The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present invention and does not constitute a limitation on the computer device to which the solution of the present invention is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0104] In one embodiment, a computer device is further provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiment when executing the computer program.

[0105] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above method embodiment are implemented.

[0106] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided by the present invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0107] The present invention is not limited to the structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for suppressing torque pulsation during an open-circuit fault of a multi-phase permanent magnet motor, characterized in that: The following steps are involved: Constructing an objective function and a set of virtual voltage vectors for tracking the current reference value under normal operating conditions, and selecting a virtual voltage vector that minimizes the objective function value for tracking the current reference value as the optimal virtual voltage vector; Calculate the optimal virtual voltage vector duty cycle; The optimal virtual voltage vector duty cycle is compensated based on the PI regulator to obtain the final action time of the optimal virtual voltage vector. The input signal of the PI regulator is the duty cycle error e k , the calculation formula is as follows: in, is the quadrature and direct axis current component under the fundamental wave plane at time k; is the reference value of the fundamental quadrature-axis current at time k+2; s0 is the q-axis current slope when the output vector is zero; T s For the control cycle.

2. A method for suppressing torque ripple due to an open-circuit fault in a multi-phase permanent magnet motor according to claim 1, characterized in that: The objective function of constructing the normal operation state is specifically: in and are the reference values ​​of the fundamental quadrature and direct axis currents at time k+2, and are the predicted values ​​of the fundamental dq axis current at time k+2 respectively.

3. A method for suppressing torque ripple due to an open-circuit fault in a multi-phase permanent magnet motor according to claim 2, characterized in that: The step of calculating the optimal virtual voltage vector duty cycle is specifically as follows: Among them, γ opt is the optimal virtual voltage vector duty cycle; t opt is the action time of the optimal virtual voltage vector; s opt is the q-axis current slope when outputting the optimal virtual voltage vector; s0 is the q-axis current slope when outputting the zero vector; is the quadrature-axis current component under the fundamental wave plane at time k+1; T s For the control cycle.

4. A method for suppressing torque ripple due to an open-circuit fault in a multi-phase permanent magnet motor as claimed in claim 3, characterized in that: The calculation method of the q-axis current slope when the zero vector is output is as follows: Among them, L q1 is the fundamental plane quadrature axis inductance; R s is the stator resistance; is the rotor electrical angular velocity at time k+1; is the direct axis current component under the fundamental wave plane at time k+1; ψ f is the permanent magnet flux.

5. The method for suppressing torque ripple due to open-circuit fault of a multi-phase permanent magnet motor according to claim 4, characterized in that: The calculation method of the q-axis current slope when outputting the optimal virtual voltage vector is as follows: in, is the q-axis fundamental voltage component of the optimal virtual voltage vector.

6. The method for suppressing torque ripple due to open-circuit fault of a multi-phase permanent magnet motor according to claim 1, characterized in that: The discrete mathematical model of the PI regulator is: Among them, d δ is the duty cycle compensation of the optimal virtual voltage vector, K c is the anti-saturation feedback coefficient, is the saturation error at time k-1; K p is the proportional coefficient of the PI regulator; e k is the duty cycle error at time k; is the accumulated integral value at time k-1; K i is the integral coefficient of the PI regulator.

7. A method for suppressing torque ripple due to an open-circuit fault in a multi-phase permanent magnet motor according to claim 6, characterized in that: The saturation error e sat The calculation formula is: e sat =sat(d δ )-d δ sat(d δ ) is the saturation value.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

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