System and method for searching optimal harmonic injection current of electric drive

Abstract

The invention discloses a system and a method for searching an electric drive optimal harmonic injection current. The system comprises a noise test module and a harmonic calculation module, the noise acquisition module is used for injecting test harmonic current with set magnitude and direction into the motor for multiple times, and measuring a noise result under the corresponding test harmonic current; and the harmonic calculation module is used for calculating an original system harmonic current according to the noise result under the corresponding test harmonic current and the linear relationship between the current harmonic content and the vibration noise, and obtaining an optimal injection harmonic current according to the original system harmonic current. According to the method, the optimal injection harmonic current can be efficiently found based on fewer tests.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicle powertrain control, and specifically refers to a system and method for finding the optimal harmonic injection current for electric drive. Background Art

[0002] Electric vehicles have the advantages of zero emissions and intelligence, and are being accepted by the world. At present, new energy vehicle technology is in a stage of rapid development, and the popularity of electric vehicles is also getting higher and higher, which puts higher requirements on the electric drive performance of our electric vehicles, especially NVH (vibration and noise). Since the electric drive system is not an ideal model, for example, the IGBT that converts direct current into three-phase alternating current is also not an ideal model, so the converted three-phase current is not a perfect sine wave and there are current harmonic components; due to the existence of harmonics, the motor torque will also have harmonics, which will cause relatively large vibration noise and bring a poor driving experience to the vehicle driver. In order to reduce the vibration noise of the electric drive, it is necessary to add reverse harmonic current to the current to cancel the original harmonics and achieve the purpose of suppressing vibration noise. Specifically, how much reverse harmonic current to inject has become the main additional problem to be solved at the present stage.

[0003] The existing technology generally uses the exhaustive method to exhaust different harmonic currents, writes each harmonic current into the program, tests the change of vibration noise, and finds the optimal harmonic current amplitude and phase according to the comparison of vibration noise. Due to the use of the exhaustive method, a large number of experiments are required to verify the effectiveness of each exhaustive point, and manual comparison is used to find the optimal one. This will waste a large amount of human and material resources and cannot be solidified for program automation testing. Summary of the Invention

[0004] The purpose of the present invention is to provide a system for finding the optimal harmonic injection current for electric drive on the one hand, and a method for finding the optimal harmonic injection current for electric drive on the other hand. The system and method can efficiently calculate the optimal injected harmonics based on fewer tests, greatly reducing the test cost and shortening the project cycle.

[0005] To achieve this purpose, a system for finding the optimal harmonic injection current for electric drive designed by the present invention includes a noise test module and a harmonic calculation module;

[0006] The noise acquisition module is used to inject test harmonic currents with set magnitudes and directions into the motor multiple times and measure the noise results corresponding to the test harmonic currents;

[0007] The harmonic calculation module is used to calculate the original system harmonic current according to the noise results corresponding to the test harmonic currents and the linear relationship between the current harmonic content and the vibration noise, and obtain the optimal injected harmonic current according to the original system harmonic current.

[0008] Further, the method of injecting test harmonic currents of a set size and direction into the motor multiple times includes: injecting four test harmonic currents with an amplitude of d and different directions respectively, and obtaining the latest system harmonic currents based on the injected test harmonic currents and the original system harmonic currents.

[0009] Further, four test harmonic currents with an injection direction difference of 90 degrees are set, and the test harmonic current vectors are (d, 0), (0, d), (-d, 0), and (0, -d) respectively. The latest system harmonic currents after injecting the test harmonic currents are:

[0010]

[0011] Among them, (d, 0) is the injected test harmonic current, (a, c) is the original system harmonic current, (a + d, c) is the latest system harmonic current after injecting the test harmonic current (d, 0), and the corresponding noise result measured for the latest system harmonic current after injecting the test harmonic current (d, 0) is y1; (0, d) is the injected test harmonic current, (a, c) is the original system harmonic current, (a, c + d) is the latest system harmonic current after injecting the test harmonic current (0, d), and the corresponding noise result measured for the latest system harmonic current after injecting the test harmonic current (0, d) is y2; (-d, 0) is the injected test harmonic current, (a, c) is the original system harmonic current, (a - d, c) is the latest system harmonic current after injecting the test harmonic current (-d, 0), and the corresponding noise result measured for the latest system harmonic current after injecting the test harmonic current (-d, 0) is y3; (0 - d) is the injected test harmonic current, (a, c) is the original system harmonic current, (a, c - d) is the latest system harmonic current after injecting the test harmonic current (0 - d), and the corresponding noise result measured for the latest system harmonic current after injecting the test harmonic current (0 - d) is y4.

[0012] Further, the noise results under the corresponding test harmonic currents are directly measured by a noise measuring device.

[0013] Further, the linear relationship between the current harmonic content and the vibration noise is y = kx + b, where y is the noise performance, x is the amplitude of the latest system harmonic current, k is the constant coefficient, and b is the constant term.

[0014] Further, the expression is calculated based on the noise results under the corresponding test harmonic currents and the linear relationship between the current harmonic content and the vibration noise:

[0015]

[0016] By simultaneously solving the above four equations for the original harmonic (a, c) of the system, we can obtain:

[0017]

[0018] Among them, Y1 = (y1 - b)^2, Y2 = (y2 - b)^2, Y3 = (y3 - b)^2, Y4 = (y4 - b)^2, and K > 0.

[0019] Furthermore, after calculating the original system harmonic currents (a, c), the optimal injected harmonic currents can be obtained as the reverse harmonic currents (-a, -c) of the original system harmonic currents. After injecting the reverse harmonic currents (-a, -c) into the original system harmonic currents (a, c), the latest system harmonic currents obtained are 0.

[0020] Furthermore, the optimal injected harmonic currents are the reverse harmonic currents (-a, -c) of the original system harmonic currents, and the amplitude phase

[0021] Even further, based on the method for finding the optimal harmonic injection current for an electric drive in the system for finding the optimal harmonic injection current for an electric drive, it includes:

[0022] Injecting test harmonic currents with set magnitudes and directions into the motor multiple times, and measuring the noise results corresponding to the test harmonic currents;

[0023] Calculating the original system harmonic currents based on the noise results corresponding to the test harmonic currents and the linear relationship between the current harmonic content and the vibration noise, and obtaining the optimal injected harmonic currents based on the original system harmonic currents.

[0024] Advantages of the present invention: In the prior art, generally, different harmonic currents are exhausted by the exhaustive method, and each harmonic current is manually written into the program to test the change of vibration noise. According to the comparison of vibration noise, the optimal harmonic current amplitude and phase are found. Using the exhaustive method, a large number of experiments are required to verify the effectiveness of each exhaustive point, and the optimal injected harmonic currents are manually compared and found, which will waste a large amount of human and material resources and cannot be solidified for program automated testing. By using several selected experimental results as inputs, the present invention can solve for the optimal harmonic current amplitude and phase, greatly saving the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a structural schematic diagram of the present invention;

[0026] Figure 2 is a superimposed diagram of the system harmonic currents of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following further elaborates the present invention in detail in conjunction with the accompanying drawings and specific embodiments:

[0028] As Figure 1 shown, a system for finding the optimal harmonic injection current of an electric drive includes a noise test module and a harmonic calculation module;

[0029] The noise acquisition module is used to inject test harmonic currents with set magnitudes and directions into the motor multiple times and measure the noise results corresponding to the test harmonic currents;

[0030] The harmonic calculation module is used to calculate the original system harmonic current based on the noise results corresponding to the test harmonic currents and the linear relationship between the current harmonic content and the vibration noise, and obtain the optimal injection harmonic current based on the original system harmonic current.

[0031] When the motor product leaves the factory, since the electric drive system is a non-ideal model, for example, the conversion of DC to three-phase alternating current by IGBT is a non-ideal model, resulting in the three-phase current obtained by conversion not being a perfect sine wave and having current harmonic components. The harmonic current caused by the non-ideality of the electric drive system is the original system harmonic. The reasons for generating the original system harmonic are complex and diverse, making it difficult to directly measure the original system harmonic. In this solution, test harmonic currents with set magnitudes and directions are artificially injected into the motor multiple times, and the noise results generated after injecting the test harmonic currents with set magnitudes and directions are directly measured by a noise test device. The original system harmonic current is calculated inversely using the linear relationship between the noise results and the current harmonic content and the vibration noise. After obtaining the original system harmonic current, the anti-phase harmonic current of the original system harmonic current is used as the optimal injection harmonic current to cancel the influence of the original system harmonic current.

[0032] In the above technical solution, the method of injecting test harmonic currents with set magnitudes and directions into the motor multiple times includes: injecting four test harmonic currents with an amplitude of d and different directions respectively. If the value of the amplitude d is too large or too small, it will cause the test results to be distorted. Based on past test experience, the value range of the amplitude d includes 2% - 4% of the effective current under the current torque of the motor.

[0033] When different test harmonic currents are injected, the vibration and noise generated during the operation of the motor will also be different. The methods of injecting test harmonic currents include directly writing the test harmonic currents into the motor control software. The current loop inside the motor automatically emits the written test harmonic currents according to the current in the motor control software. When injecting four test harmonic currents with an amplitude of d and different directions, each harmonic current needs to be rewritten into the motor control software. After each time the test harmonic current is written into the motor control software, the motor is run on the test bench, and the noise results corresponding to each test harmonic current are measured. When injecting test harmonic currents, the control software of the motor controller can also be read by a computer, and the test harmonic currents can be written online into the control software of the motor controller to avoid repeatedly refreshing the motor control software. When the motor is run on the test bench, both the test bench equipment and the motor are placed in a semi-anechoic chamber, and the noise is measured by vibration and noise measuring equipment such as microphones. The microphone is placed beside the running motor. After the microphone collects the noise data, the noise value generated during the operation of the motor is obtained by the noise data analysis equipment connected to the microphone.

[0034] There are four unknown parameters to be solved for the calculation of the optimal injected harmonic current. The number of times of injecting test harmonic currents into the motor is greater than or equal to four. Four equations can be obtained by injecting four test harmonic currents with different directions, which are used to solve the four unknown parameters related to the optimal injected harmonic current. This method can calculate the optimal injected harmonic current with the least number of experiments.

[0035] By adding the injected harmonic currents to the harmonic currents of the original system during the operation of the motor, and then detecting the corresponding noises respectively, the number of times of injecting harmonic currents is determined according to the number of unknowns. In some embodiments, four test harmonic currents with an injection direction difference of 90 degrees are set, and the harmonic test current vectors are (d,0), (0,d), (-d,0), and (0,-d) respectively. The latest system harmonic current after injecting the test harmonic currents is:

[0036]

[0037] Among them, (d, 0) is the injected test harmonic current, (a, c) is the harmonic current of the original system, (a + d, c) is the latest system harmonic current after injecting the test harmonic current (d, 0), and the corresponding noise result measured from the latest system harmonic current after injecting the test harmonic current (d, 0) is y1; (0, d) is the injected test harmonic current, (a, c) is the harmonic current of the original system, (a, c + d) is the latest system harmonic current after injecting the test harmonic current (0, d), and the corresponding noise result measured from the latest system harmonic current after injecting the test harmonic current (0, d) is y2; (-d, 0) is the injected test harmonic current, (a, c) is the harmonic current of the original system, (a - d, c) is the latest system harmonic current after injecting the test harmonic current (-d, 0), and the corresponding noise result measured from the latest system harmonic current after injecting the test harmonic current (-d, 0) is y3; (0, -d) is the injected test harmonic current, (a, c) is the harmonic current of the original system, (a, c - d) is the latest system harmonic current after injecting the test harmonic current (0, -d), and the corresponding noise result measured from the latest system harmonic current after injecting the test harmonic current (0, -d) is y4.

[0038] (a, c) is the vector representation of the harmonic current of the original system. As Figure 2 shown, a is the component in the id direction, and c is the component in the iq direction. The generation of the harmonic current of the original system is multi-faceted, including but not limited to the fact that the change in air-gap permeance caused by the stator and rotor slots of the motor will generate harmonics; the conversion of DC to three-phase alternating current by IGBT is a non-ideal model, resulting in the converted three-phase current not being a perfect sine wave and having current harmonic components, making it difficult to measure the harmonic current of the original system. However, the vibration noise caused by harmonics can be directly measured. By injecting four test harmonic currents with a phase difference of 90 degrees and measuring the corresponding noise results, the vector of the harmonic current of the original system can be obtained through the noise results and the known injected test harmonic currents. It should be noted that any four test harmonic currents with different directions can be selected for calculating the harmonic current of the original system. Selecting four test harmonic currents with a phase difference of 90 degrees is more simple and convenient in calculation.

[0039] In some embodiments, for further optimization of the above technical solution, the detection of noise in the embodiments; the noise result under the corresponding test harmonic current is directly measured by a noise measuring device.

[0040] In some embodiments, for further optimization of the above technical solution, the key of the present invention is to determine the linear relationship between the current harmonic content and the vibration noise as y = kx + b, where y is the noise performance, x is the amplitude of the latest system harmonic current, k is a constant coefficient, and b is a constant term. Based on the basic situation that the higher the current harmonic content, the greater the vibration noise, it is assumed that the current harmonic content and the vibration noise are linearly related.

[0041] In some embodiments, for further optimization of the above technical solution, in one embodiment, an expression is calculated according to the noise results corresponding to the test harmonic current and the linear relationship between the current harmonic content and the vibration noise:

[0042]

[0043] By simultaneously solving the above four equations for the original harmonics (a, c) of the system, we can obtain:

[0044]

[0045] where Y1 = (y1 - b)^2, Y2 = (y2 - b)^2, Y3 = (y3 - b)^2, Y4 = (y4 - b)^2, and K > 0.

[0046] The higher the current harmonic content, the greater the vibration noise indicates that the current harmonic content and the vibration noise are positively correlated, and the constant coefficient K must be greater than zero. According to the expression characterizing the noise results corresponding to the test harmonic current and the linear relationship between the current harmonic content and the vibration noise, the vector component values of the original harmonics (a, c) of the system, the constant coefficient K, and the constant term b in the linear relationship between the current harmonic content and the vibration noise can be obtained. Based on the vector component values of the original harmonics (a, c) of the system, the constant coefficient K, and the constant term b, the amplitude and phase of the optimal input harmonic current can be obtained.

[0047] In some embodiments, for further optimization of the above technical solution, in one embodiment, after calculating the original system harmonic current (a, c), the optimal injected harmonic current can be obtained as the reverse harmonic current (-a, -c) of the original system harmonic current. After injecting the reverse harmonic current (-a, -c) into the original system harmonic current (a, c), the latest system harmonic current becomes 0. After calculating the original system harmonic current (a, c), only by injecting the reverse harmonic current (-a, -c) of the original system harmonic current can the influence of the original system harmonic current (a, c) be offset, making the latest system harmonic current 0, as Figure 2 shown.

[0048] In the above technical solution, the optimal injected harmonic current is the reverse harmonic current (-a, -c) of the original system harmonic current, and the amplitude of the optimal injected harmonic current (-a, -c) Phase The amplitude and phase can be calculated through the vector values of the reverse harmonic currents (-a, -c).

[0049] In a certain embodiment: Since the motor is a non-ideal model, there are original system harmonic currents (a, c) in the entire motor system; based on the phenomenon that the higher the current harmonic content, the greater the vibration and noise, it is assumed that there is a linear relationship between the current harmonic content and the vibration and noise. y = kx + b, where y is the noise performance, x is the amplitude of the harmonic current, k is the constant coefficient, and b is the constant term;

[0050] Based on the fact that the value range of the measured harmonic current amplitude d includes 2% - 4% of the effective current under the current torque of the motor, four test harmonic currents with an amplitude of 3 amperes and a phase difference of 90 degrees are respectively injected for calibration testing. The vectors of the four test harmonic currents are (3,0), (0,3), (-3,0), and (0,-3). After the four test harmonic currents are injected into the motor system, the corresponding measured noise results are 49.0 dB(A), 54.0 dB(A), 55.3 dB(A), and 50.9 dB(A).

[0051] According to the linear relationship between the harmonic content and the vibration and noise, the following expression is obtained:

[0052]

[0053]

[0054] By solving the above four equations simultaneously, the original system harmonics (a, c) = (-0.78, 0.39) are obtained

[0055] The optimal injected harmonic current is the reverse harmonic current of the original system harmonic current, that is, (0.78, -0.39). Its amplitude A = 0.87, phase

[0056] When using the original exhaustive method to calibrate the optimal harmonic current, by exhausting different test harmonic currents and manually injecting different test harmonic currents multiple times, finally the test harmonic current with the best effect of eliminating the original system harmonics is selected as the optimal injected harmonic current. The amplitude of the optimal injected harmonic current calibrated by the original exhaustive method is A = 0.95 amperes, and the phase θ = 335°. The amplitude error between the optimal injected harmonic current solved by this scheme and the optimal injected harmonic current calibrated by the traditional exhaustive method is only 8%, and the phase error is only 2°. The calibration steps of this scheme are simpler and faster than the traditional exhaustive method calibration steps, and the error is very small, greatly reducing the calibration time and labor costs.

[0057] Embodiment 2

[0058] In a specific embodiment, the value range of the measured harmonic current amplitude d is 2% to 4% of the effective current at the current torque of the motor (the effective current at the current torque can be obtained by measurement and calculation, but is not limited thereto). Four test harmonic currents with an amplitude of 3 amperes and a 90-degree phase difference are injected for calibration testing. The vectors of the four test harmonic currents are (3, 0), (0, 3), (-3, 0), and (0, -3). Write the test harmonic current (3, 0) into the motor software. After downloading the motor control software to the motor, run the motor on the test bench, and both the test bench equipment and the motor are placed in a semi-anechoic chamber. Place the microphone beside the running motor, measure the noise and record the noise results. The noise results of the test harmonic currents (0, 3), (-3, 0), and (0, -3) are measured in the above method in sequence.

[0059] The corresponding measured noise results after injecting the four test harmonic currents into the motor are 49.0 dB(A), 54.0 dB(A), 55.3 dB(A), and 50.9 dB(A).

[0060] According to the linear relationship y = kx + b between the harmonic content and the vibration noise, where y is the noise performance, x is the harmonic current amplitude of the latest system, k is the constant coefficient, and b is the constant term. The harmonic current of the original system is (a, c), and the following expression is obtained:

[0061]

[0062] By manually or using a computer to solve the above four equations simultaneously, the original harmonic of the system (a, c) = (-0.78, 0.39) is obtained.

[0063] The optimal injected harmonic current is the reverse harmonic current of the original system harmonic current, that is, (0.78, -0.39). Its amplitude A = 0.87, and the phase

[0064] The amplitude of the optimal injected harmonic current calibrated by using the original exhaustive method is A = 0.95 amperes, and the phase θ = 335°. The amplitude error between the optimal injected harmonic current solved by this solution and the optimal injected harmonic current calibrated by the traditional exhaustive method is only 8%, and the phase error is only 2°. This solution only needs to inject four test harmonic currents and is supplemented by easily measurable noise results to obtain the optimal injected harmonic current, and the error is very small, greatly reducing the calibration time and labor costs.

[0065] Embodiment 3

[0066] The present invention also includes a computer program product, including a computer program / instructions. When the computer program / instructions are executed by a processor, the steps of the method for finding the optimal harmonic injection current of the electric drive are implemented.

[0067] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. A system for finding the optimal harmonic injection current for electric drive, characterized by: It includes noise test module and harmonic calculation module; The noise acquisition module is used to inject test harmonic currents of set magnitude and direction into the motor multiple times, and measure the noise results under the corresponding test harmonic currents; The harmonic calculation module is used to calculate the original system harmonic current according to the noise result under the corresponding test harmonic current and the linear relationship between the current harmonic content and the vibration noise, and obtain the optimal injected harmonic current according to the original system harmonic current.

2. A system for finding the optimal harmonic injection current for electric drive according to claim 1, characterized in that: The method of injecting test harmonic currents of set magnitude and direction into a motor multiple times includes: injecting four test harmonic currents with amplitude d and different directions respectively, and obtaining the latest system harmonic current according to the injected test harmonic currents and the original system harmonic current.

3. A system for finding the optimal harmonic injection current for electric drive according to claim 2, characterized in that: Set four test harmonic currents with injection directions 90 degrees apart. The test harmonic current vectors are (d, 0), (0, d), (-d, 0), and (0, -d). The latest system harmonic current after injecting the test harmonic current is: Wherein, (d,0) is the injected test harmonic current, (a,c) is the original system harmonic current, (a+d,c) is the latest system harmonic current after the test harmonic current (d,0) is injected, and the corresponding noise result of the latest system harmonic current after the test harmonic current (d,0) is injected is y1; (0,d) is the injected test harmonic current, (a,c) is the original system harmonic current, (a,c+d) is the latest system harmonic current after the test harmonic current (0,d) is injected, and the corresponding noise result of the latest system harmonic current after the test harmonic current (0,d) is y 2; (-d, 0) is the injected test harmonic current, (a, c) is the original system harmonic current, (ad, c) is the latest system harmonic current after the test harmonic current (-d, 0) is injected, and the corresponding noise result tested by the latest system harmonic current after the test harmonic current (-d, 0) is injected is y3; (0-d) is the injected test harmonic current, (a, c) is the original system harmonic current, (a, cd) is the latest system harmonic current after the test harmonic current (0-d) is injected, and the corresponding noise result tested by the latest system harmonic current after the test harmonic current (0-d) is y4.

4. A system for finding the optimal harmonic injection current for electric drive according to claim 1 or 3, characterized in that: The noise result under the corresponding test harmonic current is directly measured by a noise measuring device.

5. A system for finding the optimal harmonic injection current for electric drive according to claim 1, characterized in that: The linear relationship between the current harmonic content and the vibration noise is y=kx+b, wherein y is the noise performance, x is the latest system harmonic current amplitude, k is a constant coefficient, and b is a constant term.

6. A system for finding the optimal harmonic injection current for electric drive according to claim 3 or 5, characterized in that: The expression is calculated based on the noise results under the corresponding test harmonic current and the linear relationship between the current harmonic content and the vibration noise: Solving the above four equations simultaneously to obtain the original harmonics (a, c) of the system, we can get: Among them, Y1=(y1-b)^2, Y2=(y2-b)^2, Y3=(y3-b)^2, Y4=(y4-b)^2, K>0.

7. A system for finding optimal harmonic injection current for electric drive according to claim 1, characterized in that: After calculating the original system harmonic current (a, c), the optimal injected harmonic current can be obtained as the reverse harmonic current (-a, -c) of the original system harmonic current. After the original system harmonic current (a, c) is injected into the reverse harmonic current (-a, -c), the latest system harmonic current is 0.

8. A system for finding the optimal harmonic injection current for electric drive according to claim 7, characterized in that: The optimal injected harmonic current is the reverse harmonic current (-a, -c) of the original system harmonic current. The amplitude of the optimal injected harmonic current (-a, -c) is Phase 9. A method for finding an optimal harmonic injection current for electric drive based on the system for finding an optimal harmonic injection current for electric drive according to any one of claims 1 to 8, characterized in that: Inject test harmonic currents of set magnitude and direction into the motor multiple times, and measure the noise results under the corresponding test harmonic currents; The original system harmonic current is calculated based on the noise result under the corresponding test harmonic current and the linear relationship between the current harmonic content and the vibration noise, and the optimal injected harmonic current is obtained based on the original system harmonic current.

10. A computer program product, comprising a computer program / instruction, which implements the steps of the method according to claim 9 when executed by a processor.

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