Salient pole synchronous motor synchronous modulation method and system for torque ripple suppression

Abstract

The invention relates to the technical field of motor synchronous modulation, and discloses a torque ripple suppression salient pole synchronous motor synchronous modulation method and system, and the method comprises the steps: improving the scalar relation between the current harmonic amplitude of a motor and the switching angle of an inverter into a vector relation according to the electrical parameter information of the motor; a torque current harmonic balance equation is introduced, and difference analysis of influences of d-axis and q-axis currents of the synchronous coordinate system on torque pulsation is carried out; a weighting coefficient is introduced and a cost function is designed to transfer a current harmonic wave from a q axis to a d axis, so that the sinusoidal property of the phase current is kept and the torque ripple is effectively suppressed. By introducing a weighting coefficient, current harmonics on a q axis are transferred to a d axis, and effective suppression of torque pulsation is realized. And two-dimensional variables are converted into single variables, so that the complexity and dimensionality of solving the switching angle are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of motor synchronous modulation, and in particular to a torque pulsation suppressed salient pole synchronous motor synchronous modulation method and system. Background Art

[0002] Synchronous motors are one of the most widely used motors in modern industry. Taking permanent magnet synchronous motors as an example, they have high energy conversion efficiency and high torque density and are widely used in various fields. Since the synchronous optimal pulse width modulation method has low switching frequency requirements, it is a potential way to reduce losses.

[0003] In order to suppress current harmonic distortion, synchronous optimal pulse width modulation proposes to use the minimum current harmonic as the cost function, calculate and optimize the inverter switching angle, and store the switching angle in a table. However, the influence of the saliency of the synchronous motor on the current harmonics has not been taken seriously. In addition, in the process of optimizing the inverter switching angle, torque pulsation, as an important performance indicator of motor control, has not been considered in the cost function. Therefore, the application and development of synchronous modulation methods that take into account both current harmonic suppression and torque pulsation suppression in the field of motor control still needs to be studied. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: the existing synchronous modulation method of synchronous motor has large loss, and how to consider the optimization problem of torque pulsation.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a synchronous modulation method of a salient pole synchronous motor with torque pulsation suppression, comprising: According to the electrical parameter information of the motor, the scalar relationship between the motor current harmonic amplitude and the inverter switching angle is improved into a vector relationship; The torque current harmonic balance equation is introduced to analyze the difference between the influence of the d-axis and q-axis currents on the torque ripple in the synchronous coordinate system. By introducing the weighting factor A cost function is designed to transfer current harmonics from the q-axis to the d-axis, thereby effectively suppressing torque ripple while maintaining the sinusoidality of phase current.

[0007] As a preferred solution of the synchronous modulation method of a salient-pole synchronous motor with torque pulsation suppression described in the present invention, the vector relationship includes: based on a two-level voltage source inverter, a synchronous optimal pulse width modulation method with half-wave symmetry is adopted to eliminate even harmonic components, and the phase of the harmonics is adjustable; In the three-phase stationary coordinate system, the phase voltage output by the inverter is expressed by the Fourier series: , , , in, , , They are the ABC three-phase voltages of the motor respectively; For voltage The angle between the vector and the A axis in the stationary ABC coordinate system, The voltage vector representing the synthesis of three-phase voltages; Represents the Fourier expansion cosine term coefficient of the nth harmonic component, represents the Fourier expansion sinusoidal coefficient of the nth harmonic component, Indicates sum.

[0008] As a preferred solution of the torque pulsation suppression synchronous modulation method of the salient pole synchronous motor of the present invention, wherein: the Fourier coefficient of the harmonic component can be expressed as the inverter switching angle Function: , in, is the DC bus voltage, l is the number of switching angles in a half cycle, represents the switching angle of the i-th inverter.

[0009] As a preferred solution of the synchronous modulation method of a salient-pole synchronous motor with torque pulsation suppression described in the present invention, wherein: Can be expressed as the electrical angle of the motor and the voltage vector angle of the dq axis sum: , , in, represents the q-axis voltage, represents the d-axis voltage, Represents the inverse function of tan.

[0010] As a preferred solution of the synchronous modulation method of a salient pole synchronous motor with torque pulsation suppression described in the present invention, the torque current harmonic balance equation includes: the voltage value in the dq multi-synchronous coordinate system and The relationship between them can be expressed as: , Let k be a positive integer. When k is 1, it represents -5th and 7th harmonics. , The sub-dq axis voltage harmonics are: , , Among them, for the built-in permanent magnet synchronous motor, the relationship between the flux and the current is expressed as: , L d , L q is the motor dq axis inductance, , is the dq axis - (6k-1) times magnetic flux , is the 6k+1 magnetic flux of the dq axis; by inverse solution, we can obtain , The secondary dq axis current is: , Transform the current to the 6k-times dq synchronous coordinate system: , in, , , , They are the 6kth harmonic current of the d and q axes in the dq synchronous coordinate system. The amplitude of the term and the sin term; The 6th harmonic current of the dq axis in the dq synchronous coordinate system can be analyzed as the switching angle Function of Rewriting the torque equation using the current harmonic analytical expression yields: , in, as well as Respectively represent the average torque and torque harmonics, i d0 and q0 It represents the DC current of dq axis, is the motor flux, is the number of motor pole pairs.

[0011] As a preferred solution of the torque pulsation suppression synchronous modulation method of the salient pole synchronous motor of the present invention, wherein: the weighting coefficient Including, the coefficient of torque ripple generated by q-axis current harmonics and d-axis current harmonics per ampere is: , We can get: .

[0012] As a preferred solution of the torque pulsation suppression synchronous modulation method of the salient pole synchronous motor of the present invention, wherein: the transfer of the current harmonics from the q-axis to the d-axis includes: As a weight coefficient, it is multiplied by the q-axis current harmonic and substituted into the cost function for solving the optimal switching angle: , , , In the formula, is the modulation system, and its range is .

[0013] The system of the synchronous modulation method of the salient-pole synchronous motor with torque pulsation suppression of the present invention comprises: A conversion unit, which improves the scalar relationship between the motor current harmonic amplitude and the inverter switching angle into a vector relationship according to the electrical parameter information of the motor; The analysis unit introduces the torque current harmonic balance equation to analyze the difference between the influence of the d-axis and q-axis currents on the torque ripple in the synchronous coordinate system; Control unit, by introducing weighting coefficients A cost function is designed to transfer current harmonics from the q-axis to the d-axis, thereby effectively suppressing torque ripple while maintaining the sinusoidality of phase current.

[0014] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein: the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0015] A computer-readable storage medium stores a computer program, wherein: when the computer program is executed by a processor, the steps of any one of the methods of the present invention are implemented.

[0016] Beneficial effects of the present invention: Compared with the prior art, the synchronous modulation method of a salient-pole synchronous motor with torque pulsation suppression provided by the present invention has the following advantages: 1. Due to the presence of permanent magnets in the built-in permanent magnet synchronous motor, the current harmonics on the d-axis and q-axis have different effects. The present invention improves the modeling method of the scalar relationship between the harmonic current amplitude and the switching angle into a vector-based representation, which can effectively reflect the impact of the current harmonic phase on the motor performance.

[0017] 2. The present invention studies the torque and current harmonic balance equation and finds that the current harmonics on the d-axis have little effect on the torque ripple. By introducing the weighting coefficient , the current harmonics on the q-axis are transferred to the d-axis, achieving effective suppression of torque pulsation.

[0018] 3. The torque ripple caused by current harmonics is different at different current operating points on the d-axis and q-axis. Therefore, the optimization of the switching angle is highly dependent on these operating points. The present invention converts the two-dimensional variable into a single variable, reducing the complexity and dimensionality of solving the switching angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0020] Figure 1 A control block diagram of a synchronous modulation method for a salient-pole synchronous motor with torque pulsation suppression provided by a first embodiment of the present invention; Figure 2 A voltage vector diagram of a Fourier plane and a dq multi-synchronous reference system in a synchronous modulation method for a salient-pole synchronous motor with torque pulsation suppression provided by the first embodiment of the present invention; Figure 3 A synchronous modulation method for a salient-pole synchronous motor with torque pulsation suppression provided by a second embodiment of the present invention is provided for solving the off-line optimization switching angle solution; Figure 4 A comparison diagram of current harmonics and torque harmonics experiments of a salient-pole synchronous motor synchronous modulation method for torque pulsation suppression provided in the second embodiment of the present invention; wherein (a) represents the current harmonic performance of the traditional method, (b) represents the current harmonic performance of the method described in the present invention, (c) represents the torque pulsation suppression performance of the traditional method, and (d) represents the torque pulsation suppression performance of the method described in the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0022] Example 1, reference Figure 1 and Figure 2 , which is an embodiment of the present invention, provides a synchronous modulation method for a salient-pole synchronous motor with torque pulsation suppression, comprising: S1: According to the electrical parameter information of the motor, the scalar relationship between the motor current harmonic amplitude and the inverter switching angle is improved to a vector relationship.

[0023] Based on the two-level voltage source inverter, the half-wave symmetrical synchronous optimal pulse width modulation method is adopted to eliminate the even harmonic components and adjust the phase of the harmonics. In the three-phase stationary coordinate system, the phase voltage output by the inverter can be expressed by the Fourier series: , , in, , , They are the ABC three-phase voltages of the motor respectively; For voltage The angle between the vector and the A axis in the stationary ABC coordinate system; and is the Fourier coefficient of the nth harmonic component, which can be expressed as the inverter switching angle Function: , Where udc is the DC bus voltage and l is the number of switching angles in a half cycle.

[0024] Can be expressed as the electrical angle of the motor and the voltage vector angle of the dq axis The sum, such as Figure 2 , expressed by the following formula: , , in, represents the q-axis voltage, represents the d-axis voltage.

[0025] S2: Introduce the torque current harmonic balance equation to analyze the difference in the impact of the d-axis and q-axis currents on the torque pulsation in the synchronous coordinate system.

[0026] Furthermore, the voltage vector in the stationary coordinate system can be decomposed into the nth harmonic synchronous rotating a(n)-b(n) coordinate system through the vector angle relationship, and the voltage value in the dq multi-synchronous coordinate system is and The relationship between them can be expressed as: , Considering the convenience of solving current in synchronous coordinate system, , Subharmonics all consider negative sequence conditions. , The sub-dq axis voltage harmonics are: , , Taking the built-in permanent magnet synchronous motor as an example, the relationship between magnetic flux and current can be expressed by the following formula: , in , is the motor dq axis inductance, , is the dq axis - (6k-1) times magnetic flux , It is the 6k+1 magnetic flux on the dq axis.

[0027] Furthermore, the current is obtained by inversely solving equation (7): , Transforming the current into the 6k-order dq synchronous coordinate system, we can obtain: , In the formula , , , They are the 6k+1 and -(6k-1) sub-current harmonics of the d and q axes in the dq synchronous coordinate system. The magnitude of the term and the sin term.

[0028] Furthermore, the combined equations (6), (7), (8), and (9) can be used to resolve the 6th harmonic current of the dq axis in the dq synchronous coordinate system into the switching angle function.

[0029] Rewriting the torque equation using the current harmonic analytical expression yields: , In the formula as well as They represent the average torque and torque harmonic respectively, id0 and iq0 represent the DC current of dq axis, is the motor flux, is the number of motor pole pairs.

[0030] S3: By introducing weighting coefficients A cost function is designed to transfer current harmonics from the q-axis to the d-axis, thereby effectively suppressing torque ripple while maintaining the sinusoidality of phase current.

[0031] In general, since the harmonic component and the DC component are not in the same order of magnitude, the product of the two harmonic components in equation (12) can be ignored. And from the above equation, it can be observed that the influence of the current harmonics on the dq axis on the torque pulsation is different, and changes with the steady-state operating point. Therefore, a coefficient can be introduced to quantify this influence, which can optimize the torque pulsation by reasonably distributing the current harmonics. Define, the coefficient of the torque pulsation generated by the q-axis current harmonic and the torque pulsation generated by the d current harmonic per ampere is: , Substituting into formula (12) we can get: , Analysis shows that the q-axis current harmonic has a greater impact on the torque ripple, so As a weight coefficient, it is multiplied by the q-axis current harmonic and substituted into the cost function for solving the optimal switching angle: , , , In the formula, is the modulation system, and its range is . is the DC bus voltage.

[0032] On the other hand, this embodiment also provides a salient pole synchronous motor synchronous modulation system with torque pulsation suppression, which includes: The conversion unit improves the scalar relationship between the motor current harmonic amplitude and the inverter switching angle into a vector relationship according to the electrical parameter information of the motor.

[0033] The analysis unit introduces the torque current harmonic balance equation to analyze the difference in the impact of the d-axis and q-axis currents on the torque pulsation in the synchronous coordinate system.

[0034] Control unit, by introducing weighting coefficients A cost function is designed to transfer current harmonics from the q-axis to the d-axis, thereby effectively suppressing torque ripple while maintaining the sinusoidality of phase current.

[0035] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program code.

[0036] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0037] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0038] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0039] Example 2, reference Figure 3-Figure 4 , which is an embodiment of the present invention, provides a synchronous modulation method for a salient-pole synchronous motor with torque pulsation suppression. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0040] Verification work is carried out on the test bench, such as Figure 3 As shown in the figure, the test bench consists of a motor to be tested, a dynamometer, a flexible coupling and a high-precision torque sensor.

[0041] Referring to the total harmonic distortion (THD) value of current harmonics, the torque THD value is introduced to quantitatively evaluate the quality of torque. Torque THD is calculated by the ratio of total harmonics to DC components: , For the synchronous modulation optimization method proposed in the present invention, it is necessary to obtain the optimized switch angle table offline, and then calculate the optimal switch angle table according to the three input variables modulation degree m, voltage vector angle and weighting coefficients The inverter switching angle is retrieved. The method used in the offline calculation of the switching angle is the Newton method of the constrained optimization problem. The optimized switching angle obtained in the embodiment is as follows: Figure 3 As shown in Figure 2, the number of inverter switching angles is set to 8, and the switching frequency of the inverter is proportional to the number of pulses.

[0042] In order to verify the advantages of the present invention, the conventional method and the method proposed in the present invention were experimentally verified under the same working conditions. In the experiment, the motor under test was operated in the torque control mode, and the motor speed was controlled by the dynamometer. The higher the speed, the greater the noise during the torque pulsation measurement, so the test conditions were carried out at low and medium speeds to ensure the validity of the test results. Figure 4This is the experimental result diagram of the traditional method and the method proposed in the present invention. The test condition is set at a torque of 25 N·m, a motor speed of 1600 rpm, and a switching frequency of 720 Hz. By comparing the current harmonics and torque pulsation of the two methods, it can be seen that the current harmonic performance of the two methods is similar, but the torque pulsation suppression performance of the method proposed in the present invention is better, reducing from 22.89% to 18.03%.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A synchronous modulation method for a salient pole synchronous motor with torque pulsation suppression, characterized in that: include: According to the electrical parameter information of the motor, the scalar relationship between the motor current harmonic amplitude and the inverter switching angle is improved into a vector relationship; The torque current harmonic balance equation is introduced to analyze the difference between the influence of the d-axis and q-axis currents on the torque ripple in the synchronous coordinate system. By introducing the weighting factor And a cost function is designed to transfer the current harmonics from the q-axis to the d-axis, thereby effectively suppressing the torque ripple while maintaining the sinusoidality of the phase current; The vector relationship includes, based on a two-level voltage source inverter, using a half-wave symmetrical synchronous optimal pulse width modulation method so that even harmonic components are eliminated and the phase of the harmonics is adjustable; In the three-phase stationary coordinate system, the phase voltage output by the inverter is expressed by the Fourier series: ， ， ， in, Indicates the A voltage of the motor, Indicates the B voltage of the motor, Indicates the C voltage of the motor; For voltage The angle between the vector and the A axis in the stationary ABC coordinate system, The voltage vector representing the synthesis of three-phase voltages; Represents the Fourier expansion cosine term coefficient of the nth harmonic component, represents the Fourier expansion sinusoidal coefficient of the nth harmonic component, Indicates sum.

2. A synchronous modulation method for a salient pole synchronous motor with torque ripple suppression as claimed in claim 1, characterized in that: The Fourier coefficients of the harmonic components are expressed as the inverter switching angle Function: ， in, is the DC bus voltage, l is the number of switching angles in a half cycle, represents the switching angle of the i-th inverter.

3. A synchronous modulation method for a salient pole synchronous motor with torque pulsation suppression as claimed in claim 2, characterized in that: Can be expressed as the electrical angle of the motor and the voltage vector angle of the dq axis sum: ， ， in, represents the q-axis voltage, represents the d-axis voltage, Represents the inverse function of tan.

4. A synchronous modulation method for a salient pole synchronous motor with torque pulsation suppression as claimed in claim 3, characterized in that: The torque current harmonic balance equation includes: voltage value in dq multi-synchronous coordinate system and The relationship between them can be expressed as: ， Let k be a positive integer. When k is 1, it represents -5th and 7th harmonics. , The sub-dq axis voltage harmonics are: ， ， Among them, for the built-in permanent magnet synchronous motor, the relationship between the flux and the current is expressed as: ， L d is the motor d-axis inductance, L q is the motor q-axis inductance, is the d-axis-(6k-1)th magnetic flux, is the q-axis-(6k-1)th magnetic flux; is the d-axis 6k+1 magnetic flux, is the 6k+1 magnetic flux on the q axis; by inverse solution, we can obtain , The secondary dq axis current is: ， Transform the current to the 6k-times dq synchronous coordinate system: ， in, Indicates the 6kth harmonic of the d-axis current in the d synchronous coordinate system Item Amplitude, represents the amplitude of the 6kth harmonic sin term of the d-axis current in the d synchronous coordinate system, Indicates the 6kth harmonic of the q-axis current in the q-synchronous coordinate system Item Amplitude, It represents the amplitude of the 6kth harmonic sin term of the q-axis current in the q-synchronous coordinate system; The 6th harmonic current of the dq axis in the dq synchronous coordinate system can be analyzed as the switching angle Function of Rewriting the torque equation using the current harmonic analytical expression yields: ， in, represents the average torque, represents the torque harmonic, i d0 represents the d-axis current DC, i q0 represents the q-axis current DC, is the motor flux, is the number of motor pole pairs.

5. A synchronous modulation method for a salient pole synchronous motor with torque ripple suppression as claimed in claim 4, characterized in that: The weighting coefficient Including, the coefficient of torque ripple generated by q-axis current harmonics and d-axis current harmonics per ampere is: ， We can get: 。 6. A synchronous modulation method for a salient pole synchronous motor with torque ripple suppression as claimed in claim 5, characterized in that: The transferring of the current harmonics from the q-axis to the d-axis includes: As a weight coefficient, it is multiplied by the q-axis current harmonic and substituted into the cost function for solving the optimal switching angle: ， ， ， In the formula, is the modulation system, and its range is .

7. A synchronous modulation system for a salient-pole synchronous motor with torque pulsation suppression, using a synchronous modulation method for a salient-pole synchronous motor with torque pulsation suppression as claimed in any one of claims 1 to 6, characterized in that: include: A conversion unit, which improves the scalar relationship between the motor current harmonic amplitude and the inverter switching angle into a vector relationship according to the electrical parameter information of the motor; The analysis unit introduces the torque current harmonic balance equation to analyze the difference between the influence of the d-axis and q-axis currents on the torque ripple in the synchronous coordinate system; Control unit, by introducing weighting coefficients A cost function is designed to transfer current harmonics from the q-axis to the d-axis, thereby effectively suppressing torque ripple while maintaining the sinusoidality of phase current.

8. A computer device comprising: Memory and processor; The memory stores a computer program, wherein the processor implements the steps of any one of the methods of claims 1 to 6 when executing the computer program.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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