Method and device for modulating overall vehicle noise

Abstract

The application discloses a method for modulating whole vehicle noise, and proposes a harmonic current control scheme combining feedforward control and closed-loop control, and then harmonic voltage injected into a system is obtained according to required 5th, 7th, 11th and 13th harmonic current given values, and is superposed with fundamental wave voltage together to serve as output of control current. The harmonic current control method has very good effect in whole vehicle noise suppression.

Description

Technical Field

[0001] This invention relates to the field of automobile manufacturing technology, and in particular to a method and apparatus for modulating vehicle noise. Background Technology

[0002] With continuous economic development, automobiles have become commonplace in households, a necessity for people's travel, and people's demands for the driving experience are also increasing. The overall vehicle NVH performance is a crucial performance indicator affecting the driving experience; only by continuously improving NVH performance can current market demands be met. Overall vehicle NVH performance refers to the performance of a vehicle in terms of noise, vibration, and sound roughness during use. In new energy vehicles, defects in motor design and motor torque pulsation can damage NVH performance, resulting in a poor driving experience and weakened product competitiveness. Therefore, automakers and related component companies are currently investing heavily in NVH performance to improve the NVH performance of their products.

[0003] Existing methods for NVH performance optimization mainly include motor design optimization and software harmonic current control. However, optimizing motor design is costly, and there are few areas for optimization in mature motor designs, making it difficult to achieve the desired NVH performance improvement. Therefore, software algorithm-based harmonic current control is a more commonly used method. The paper "Harmonic Suppression Strategy for Permanent Magnet Synchronous Motors" published in the *Journal of Electrical Engineering Technology* elaborates on harmonic current suppression strategies from the perspectives of multi-rotation PI control, complex vector PI control, and repetitive control. The paper "A Harmonic Current Suppression Algorithm for Permanent Magnet Synchronous Motors" published in *Power Electronics Technology* extracts harmonic currents using a current closed-loop algorithm and calculates compensation voltages for harmonic suppression, thereby reducing torque ripple and optimizing the motor's NVH performance. The paper "Coupling Model and Feedforward Control of Harmonic Voltage and Current in Permanent Magnet Synchronous Motors" published in the *Journal of Electrical Engineering Technology* calculates the feedforward compensation voltage using the harmonic voltage equation to achieve harmonic suppression. The paper "Research on Harmonic Suppression of Permanent Magnet Synchronous Motor Current in Electric Vehicles" published in Automotive Technology extracts the harmonic current and performs harmonic control in the corresponding order dq coordinate system, suppressing harmonics through closed-loop control.

[0004] In terms of software harmonic current control, existing technologies mainly fall into two categories. One is to achieve harmonic suppression by performing closed-loop control in a higher-order dq coordinate system through harmonic extraction; the other is to perform harmonic control by compensating the voltage through feedforward compensation.

[0005] The paper "Research on Harmonic Suppression of Permanent Magnet Synchronous Motor Current in Electric Vehicles" published in Automotive Technology describes a method that converts the three-phase current to a 5th / 7th order dq coordinate system and then extracts the harmonic current using a second-order low-pass filter, thereby controlling the harmonic current components to zero in the 5th / 7th order dq coordinate system. While this method can suppress harmonic currents to zero, it has certain shortcomings in practical applications. First, using a second-order low-pass filter results in poor system real-time performance and lag in closed-loop control. Second, controlling the harmonic current to zero does not necessarily optimize the system's NVH performance. Furthermore, when the signal-to-noise ratio of the three-phase current is low, it is difficult to accurately extract the harmonic current, leading to inaccurate closed-loop control.

[0006] The paper "Coupling Model and Feedforward Control of Harmonic Voltage and Current in Permanent Magnet Synchronous Motors," published in the Journal of Electrical Engineering, constructs a harmonic voltage model for permanent magnet synchronous motors in a multi-synchronous rotating coordinate system. By adding a feedforward harmonic voltage calculation module to a traditional vector control system, the NVH (Noise, Vibration, and Harshness) performance is improved through feedforward compensation voltage. This method can achieve harmonic current tracking across the entire torque range, demonstrating good adaptability to various operating conditions. However, since it only controls the harmonic current component through feedforward, it cannot guarantee that the harmonic current will be truly controlled within the ideal range in practical applications.

[0007] In summary, this invention combines closed-loop harmonic suppression algorithm and feedforward harmonic suppression algorithm to solve the problems of poor real-time performance of current closed-loop harmonic suppression algorithm, poor control accuracy when current signal-to-noise ratio is low, and poor harmonic control accuracy of feedforward harmonic suppression algorithm, thereby improving the NVH performance of the system. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a method and apparatus for modulating vehicle noise, which solves the problems of poor real-time performance of current closed-loop harmonic suppression algorithms, poor control accuracy when the current signal-to-noise ratio is low, and poor harmonic control accuracy of feedforward harmonic suppression algorithms, thereby improving the NVH performance of the system.

[0009] A method for modulating vehicle noise, the method comprising:

[0010] Harmonic currents are extracted from three-phase currents;

[0011] Based on the harmonic current, determine whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation according to the current signal-to-noise ratio; calculate the α-axis and β-axis voltages of the waveform generated by open-loop feedforward modulation or closed-loop harmonic injection modulation, and obtain the closed-loop harmonics.

[0012] Feedback closed-loop harmonic injection modulation method is used for closed-loop feedback.

[0013] Furthermore, the extraction of harmonic current from the three-phase current includes:

[0014] The three-phase current is extracted by a second-order generalized integrator to obtain the harmonic three-phase current with only harmonic components. Then, the harmonic three-phase current is transformed into a rotating dq coordinate system of several orders, and the d-axis and q-axis harmonic currents of several orders are extracted by a first-order low-pass filter.

[0015] Furthermore, the conversion of the harmonic three-phase current to several rotating dq coordinate systems specifically includes: converting the harmonic three-phase current to 5th, 7th, 11th, and 13th rotating dq coordinate systems.

[0016] Furthermore, the extraction of several d-axis and q-axis harmonic currents through a first-order low-pass filter specifically includes: extracting 5th, 7th, 11th, and 13th d-axis and q-axis harmonic currents through a first-order low-pass filter.

[0017] Furthermore, the method of determining whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the current signal-to-noise ratio according to the harmonic current, and determining whether the vehicle noise modulation method is enabled before that;

[0018] The method for determining whether the vehicle noise modulation is enabled specifically includes: determining whether to enable vehicle noise modulation based on the rotational speed. When the rotational speed is higher than the rotational speed threshold but lower than the turning speed, vehicle noise modulation is allowed to be enabled; otherwise, vehicle noise modulation is not allowed to be enabled. The turning speed is the full-power turning speed point of the permanent magnet synchronous motor, and the turning speed = peak power * 9550 / peak torque.

[0019] Furthermore, the step of determining whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the harmonic current and the current signal-to-noise ratio specifically includes:

[0020] When the three-phase current is below the current threshold, open-loop feedforward modulation is used and closed-loop harmonic injection modulation is turned off; when the three-phase current is above the current threshold, closed-loop harmonic injection modulation is used and open-loop feedforward modulation is turned off.

[0021] Furthermore, the calculation of the α-axis and β-axis voltages of the generated waveform in the open-loop feedforward modulation mode or the closed-loop harmonic injection modulation mode specifically includes:

[0022] The open-loop feedforward modulation method calculates the required d-axis and q-axis voltages based on the torque; the closed-loop harmonic injection modulation method obtains the required harmonic id / iq current values ​​based on the torque, and then uses PI control to obtain the d-axis and q-axis voltages.

[0023] The obtained 5th, 7th, 11th, and 13th order d-axis and q-axis voltages are obtained by coordinate transformation to obtain their d-axis and q-axis voltages in the fundamental wave dq coordinate system. After being added to the fundamental wave, the final α-axis and β-axis voltages used for wave generation are obtained by inverse Park transformation.

[0024] Furthermore, the feedback closed-loop harmonic injection modulation method specifically includes:

[0025] The three-phase current is collected by sensors and fed back to the closed-loop harmonic injection modulation method for closed-loop feedback.

[0026] A device for modulating vehicle noise includes: a harmonic current unit, a closed-loop harmonic unit, and a feedback unit.

[0027] Harmonic current unit, used to extract harmonic current from three-phase current;

[0028] The closed-loop harmonic unit is used to determine whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the harmonic current and the current signal-to-noise ratio; it calculates the α-axis and β-axis voltages of the waveform generated by the open-loop feedforward modulation or closed-loop harmonic injection modulation, and obtains the closed-loop harmonics.

[0029] The feedback unit is used to provide feedback on the closed-loop harmonic injection modulation method, and is used for closed-loop feedback.

[0030] Furthermore, the harmonic current unit is specifically used for:

[0031] The three-phase current is extracted by a second-order generalized integrator to obtain the harmonic three-phase current with only harmonic components. Then, the harmonic three-phase current is transformed into a rotating dq coordinate system of several orders, and the d-axis and q-axis harmonic currents of several orders are extracted by a first-order low-pass filter.

[0032] The present invention has at least the following beneficial effects:

[0033] This invention proposes a method combining open-loop feedforward modulation and closed-loop control of harmonic currents, solving the problem of fixed-order noise in vehicles caused by harmonic currents. Since this method uses only software algorithms for harmonic current optimization, it requires no modification to the existing hardware, making implementation simple and convenient, and incurring no additional hardware maintenance costs.

[0034] This invention explores the possibilities of NVH performance optimization at the software level, proposing a harmonic injection method that combines open-loop and closed-loop approaches for complementary advantages. However, harmonic injection only effectively suppresses electromagnetic noise generated by torque pulsation, and its effectiveness is limited for poor NVH caused by motor design flaws. Furthermore, to avoid affecting motor system efficiency, harmonic injection becomes unsuitable after the turning point speed. Therefore, when using this harmonic injection method, targeted optimization design for other issues such as motor defects should be considered. Additionally, software algorithms such as random frequency dithering and variable carrier frequency can be used to optimize system NVH performance at speeds after the turning point.

[0035] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a method according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the device according to an embodiment of the present invention;

[0039] Figure 3 This is a block diagram of a vehicle noise modulation system according to an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In the automotive manufacturing field, existing technologies suffer from problems such as poor real-time performance of closed-loop harmonic suppression algorithms, poor control accuracy when the current signal-to-noise ratio is low, and poor harmonic control accuracy of feedforward harmonic suppression algorithms.

[0042] Therefore, the present invention proposes a method and apparatus for modulating vehicle noise, including a method for modulating vehicle noise and an apparatus for modulating vehicle noise.

[0043] Firstly, such as Figure 1 As shown, a method for modulating vehicle noise includes:

[0044] Harmonic currents are extracted from three-phase currents;

[0045] Based on the harmonic current, determine whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation according to the current signal-to-noise ratio; calculate the α-axis and β-axis voltages of the waveform generated by open-loop feedforward modulation or closed-loop harmonic injection modulation, and obtain the closed-loop harmonics.

[0046] Feedback closed-loop harmonic injection modulation method is used for closed-loop feedback.

[0047] In this embodiment, the extraction of harmonic current from three-phase current includes:

[0048] The three-phase current is extracted by a second-order generalized integrator to obtain the harmonic three-phase current with only harmonic components. Then, the harmonic three-phase current is transformed into a rotating dq coordinate system of several orders, and the d-axis and q-axis harmonic currents of several orders are extracted by a first-order low-pass filter.

[0049] In this embodiment, the conversion of the harmonic three-phase current to several rotating dq coordinate systems specifically includes: converting the harmonic three-phase current to the 5th, 7th, 11th, and 13th rotating dq coordinate systems.

[0050] In this embodiment, the extraction of several d-axis and q-axis harmonic currents through a first-order low-pass filter specifically includes: extracting 5th, 7th, 11th, and 13th d-axis and q-axis harmonic currents through a first-order low-pass filter.

[0051] In this embodiment, the step of determining whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the harmonic current and the current signal-to-noise ratio is performed before determining whether the vehicle noise modulation method is enabled.

[0052] The method for determining whether the vehicle noise modulation is enabled specifically includes: determining whether to enable vehicle noise modulation based on the rotational speed. When the rotational speed is higher than the rotational speed threshold but lower than the turning speed, vehicle noise modulation is allowed to be enabled; otherwise, vehicle noise modulation is not allowed to be enabled. The turning speed is the full-power turning speed point of the permanent magnet synchronous motor, and the turning speed = peak power * 9550 / peak torque.

[0053] In practice, the speed threshold is set to 500 rpm.

[0054] In this embodiment, the step of determining whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the harmonic current and the current signal-to-noise ratio specifically includes:

[0055] When the three-phase current is below the current threshold, open-loop feedforward modulation is used and closed-loop harmonic injection modulation is turned off; when the three-phase current is above the current threshold, closed-loop harmonic injection modulation is used and open-loop feedforward modulation is turned off.

[0056] In practice, the current threshold is set to 30A.

[0057] In this embodiment, the calculation of the α-axis and β-axis voltages of the generated waveform in the open-loop feedforward modulation mode or the closed-loop harmonic injection modulation mode specifically includes:

[0058] The open-loop feedforward modulation method calculates the required d-axis and q-axis voltages based on the torque; the closed-loop harmonic injection modulation method obtains the required harmonic id / iq current values ​​based on the torque, and then uses PI control to obtain the d-axis and q-axis voltages.

[0059] The obtained 5th, 7th, 11th, and 13th order d-axis and q-axis voltages are obtained by coordinate transformation to obtain their d-axis and q-axis voltages in the fundamental wave dq coordinate system. After being added to the fundamental wave, the final α-axis and β-axis voltages used for wave generation are obtained by inverse Park transformation.

[0060] In this embodiment, the feedback closed-loop harmonic injection modulation method specifically includes:

[0061] The three-phase current is collected by sensors and fed back to the closed-loop harmonic injection modulation method for closed-loop feedback.

[0062] Secondly, such as Figure 2 As shown, a device for modulating vehicle noise includes: a harmonic current unit, a closed-loop harmonic unit, and a feedback unit.

[0063] Harmonic current unit, used to extract harmonic current from three-phase current;

[0064] The closed-loop harmonic unit is used to determine whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the harmonic current and the current signal-to-noise ratio; it calculates the α-axis and β-axis voltages of the waveform generated by the open-loop feedforward modulation or closed-loop harmonic injection modulation, and obtains the closed-loop harmonics.

[0065] The feedback unit is used to provide feedback on the closed-loop harmonic injection modulation method, and is used for closed-loop feedback.

[0066] In this embodiment, the harmonic current unit is specifically used for:

[0067] The three-phase current is extracted by a second-order generalized integrator to obtain the harmonic three-phase current with only harmonic components. Then, the harmonic three-phase current is transformed into a rotating dq coordinate system of several orders, and the d-axis and q-axis harmonic currents of several orders are extracted by a first-order low-pass filter.

[0068] In specific implementation, the implementation process of the device for modulating vehicle noise and the method for modulating vehicle noise of the present invention correspond one-to-one, and will not be described in detail here.

[0069] To enable those skilled in the art to better understand the present invention, the principles of the present invention are explained below in conjunction with the accompanying drawings:

[0070] To address the issues of poor real-time performance, poor control accuracy under low current signal-to-noise ratio, and poor harmonic control accuracy of current closed-loop harmonic suppression algorithms, and to improve the NVH performance of the system, this invention provides a method for modulating vehicle noise. The system block diagram is shown below. Figure 1 This method uses a generalized second-order integrator to extract the d / q axis currents of the corresponding orders in the 5th, 7th, 11th, and 13th order rotating coordinate systems. It then uses closed-loop control to bring the harmonic current to a value that minimizes the overall vehicle noise. Combined with feedforward harmonic suppression, this method is improved to enhance its adaptability to different operating conditions, thereby achieving vehicle noise modulation across a wider range of speeds and torque conditions.

[0071] A method for modulating vehicle noise includes the following steps:

[0072] Step 1: Extracting Harmonic Currents. The three-phase currents are extracted by passing them through a second-order generalized integrator to obtain the harmonic three-phase currents with only harmonic components. Then, the harmonic three-phase currents are converted to the 5th, 7th, 11th, and 13th order rotating dq coordinate systems, and the d-axis and q-axis harmonic currents of the 5th, 7th, 11th, and 13th orders are extracted by passing them through a first-order low-pass filter.

[0073] Step 2: Determine the activation conditions for vehicle noise modulation. Determine whether vehicle noise modulation should be activated based on the engine speed. Vehicle noise modulation is permitted when the engine speed is above 500 rpm but below the turning point (i.e., the full-power turning point of the permanent magnet synchronous motor; turning point = peak power * 9550 / peak torque). Otherwise, vehicle noise modulation is not permitted.

[0074] Step 3: Determine which modulation mode to enable based on the current signal-to-noise ratio. When the current is below 30A, use open-loop feedforward modulation and disable closed-loop harmonic injection modulation; when the current is above 30A, use closed-loop harmonic injection modulation and disable open-loop feedforward modulation.

[0075] Step 4: Obtaining d-axis and q-axis voltages. The open-loop feedforward modulation method calculates the required d-axis and q-axis voltages based on the torque; the closed-loop harmonic injection modulation method obtains the required harmonic id / iq current values ​​based on the torque, and then uses PI control to obtain the d-axis and q-axis voltages. The d-axis and q-axis voltages obtained by the feedforward modulation method and the closed-loop harmonic injection modulation method are added together according to their order to obtain the 5th, 7th, 11th, and 13th order d-axis and q-axis voltages, which are used for the next step of obtaining the α-axis and β-axis voltages.

[0076] Step 5: Obtaining α-axis and β-axis voltages (Uα and Uβ). The 5th, 7th, 11th, and 13th d-axis and q-axis voltages obtained in Step 4 are transformed to obtain their d-axis and q-axis voltages in the fundamental dq coordinate system. These are then added to the fundamental wave and subjected to an inverse Park transformation to obtain the α-axis and β-axis voltages used for wave generation, encompassing open-loop harmonic feedforward modulation, closed-loop harmonic injection modulation, and the fundamental wave.

[0077] Step 6: Closed-loop current feedback. The three-phase current Iabc is collected by sensors and fed back to the closed-loop harmonic injection modulation mode for closed-loop feedback.

[0078] Step 7: Use of open-loop feedforward. When the conditions for enabling the vehicle noise modulation method in Step 2 and the conditions for enabling the open-loop feedforward modulation method in Step 3 are met, the relevant calculations for open-loop feedforward are used to disable the relevant calculations for closed-loop harmonic control; otherwise, the relevant calculations for closed-loop harmonic control are used to disable the relevant calculations for open-loop feedforward.

[0079] like Figure 3 As shown, open-loop feedforward harmonic injection, closed-loop harmonic injection and fundamental wave control respectively obtain the α-axis and β-axis voltages. The sum of the three gives the α-axis and β-axis voltages (Uα and Uβ) used for SVPWM and other algorithms to generate waves. Then, the permanent magnet synchronous motor (PMSM) is finally controlled through the SVPWM module and the inverter module.

[0080] This invention, based on harmonic current closed-loop control, organically combines it with feedforward control to achieve the following functions:

[0081] 1) Using a second-order generalized integrator to extract harmonic currents ensures the accuracy of harmonic current extraction and the real-time performance and stability of harmonic current control.

[0082] 2) A closed-loop harmonic injection algorithm was used to achieve precise control of harmonic current;

[0083] 3) When the current signal-to-noise ratio is low, the open-loop harmonic injection algorithm is used to avoid the error of closed-loop harmonic injection when the current signal-to-noise ratio is low.

[0084] 4) At higher speeds, an open-loop harmonic injection algorithm is used to compensate for the inability to use the closed-loop bandwidth at higher speeds.

[0085] In summary, this invention combines open-loop harmonic injection with closed-loop harmonic injection and uses a second-order generalized integrator to improve the accuracy and speed of harmonic current extraction, thereby achieving harmonic injection across the entire torque range in the speed range before the turning point without affecting the fundamental frequency, thus improving the system NVH performance under the applicable operating conditions of this invention.

[0086] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for modulating vehicle noise, characterized in that, The method includes: Harmonic currents are extracted from three-phase currents; Based on the harmonic current, determine whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation according to the current signal-to-noise ratio; calculate the α-axis and β-axis voltages of the waveform generated by open-loop feedforward modulation or closed-loop harmonic injection modulation, and obtain the closed-loop harmonics. Feedback closed-loop harmonic injection modulation method, used for closed-loop feedback; The decision to enable open-loop feedforward modulation or closed-loop harmonic injection modulation is based on the current signal-to-noise ratio, specifically including: When the three-phase current is below the current threshold, the open-loop feedforward modulation mode is used and the closed-loop harmonic injection modulation mode is turned off; when the three-phase current is above the current threshold, the closed-loop harmonic injection modulation mode is used and the open-loop feedforward modulation mode is turned off. Calculate the α-axis and β-axis voltages of the generated waveform using open-loop feedforward modulation or closed-loop harmonic injection modulation, specifically including: The open-loop feedforward modulation method calculates the required d-axis and q-axis voltages based on the torque; the closed-loop harmonic injection modulation method obtains the required harmonic id / iq current values ​​based on the torque, and then uses PI control to obtain the d-axis and q-axis voltages. The obtained 5th, 7th, 11th, and 13th order d-axis and q-axis voltages are obtained by coordinate transformation to obtain their d-axis and q-axis voltages in the fundamental wave dq coordinate system. After being added to the fundamental wave, the final α-axis and β-axis voltages used for wave generation are obtained by inverse Park transformation.

2. The method for modulating vehicle noise according to claim 1, characterized in that, The extraction of harmonic current from three-phase current includes: The three-phase current is extracted by a second-order generalized integrator to obtain the harmonic three-phase current with only harmonic components. Then, the harmonic three-phase current is transformed into a rotating dq coordinate system of several orders, and the d-axis and q-axis harmonic currents of several orders are extracted by a first-order low-pass filter.

3. The method for modulating vehicle noise according to claim 2, characterized in that, The process of converting the harmonic three-phase current to a number of rotating dq coordinate systems specifically includes converting the harmonic three-phase current to 5th, 7th, 11th, and 13th rotating dq coordinate systems.

4. The method for modulating vehicle noise according to claim 2, characterized in that, The extraction of several d-axis and q-axis harmonic currents through a first-order low-pass filter specifically includes: extracting 5th, 7th, 11th, and 13th d-axis and q-axis harmonic currents through a first-order low-pass filter.

5. The method for modulating vehicle noise according to claim 1, characterized in that, Based on harmonic current, the system determines whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation according to the current signal-to-noise ratio, and before that, it determines whether the vehicle noise modulation method is enabled. The method for determining whether the vehicle noise modulation is enabled specifically includes: determining whether to enable vehicle noise modulation based on the rotational speed. When the rotational speed is higher than the rotational speed threshold but lower than the turning speed, vehicle noise modulation is allowed to be enabled; otherwise, vehicle noise modulation is not allowed to be enabled. The turning speed is the full-power turning speed point of the permanent magnet synchronous motor, and the turning speed = peak power * 9550 / peak torque.

6. The method for modulating vehicle noise according to claim 1, characterized in that, The feedback closed-loop harmonic injection modulation method specifically includes: The three-phase current is collected by sensors and fed back to the closed-loop harmonic injection modulation method for closed-loop feedback.

7. A device for modulating vehicle noise, characterized in that, include: Harmonic current unit, closed-loop harmonic unit, and feedback unit; Harmonic current unit, used to extract harmonic current from three-phase current; The closed-loop harmonic unit is used to determine whether to enable open-loop feedforward modulation or closed-loop harmonic injection modulation based on the harmonic current and the current signal-to-noise ratio; it calculates the α-axis and β-axis voltages of the waveform generated by the open-loop feedforward modulation or closed-loop harmonic injection modulation, and obtains the closed-loop harmonics. Feedback unit, used for feedback of closed-loop harmonic injection modulation mode, for closed-loop feedback; The decision to enable open-loop feedforward modulation or closed-loop harmonic injection modulation is based on the current signal-to-noise ratio, specifically including: When the three-phase current is below the current threshold, the open-loop feedforward modulation mode is used and the closed-loop harmonic injection modulation mode is turned off; when the three-phase current is above the current threshold, the closed-loop harmonic injection modulation mode is used and the open-loop feedforward modulation mode is turned off. Calculate the α-axis and β-axis voltages of the generated waveform using open-loop feedforward modulation or closed-loop harmonic injection modulation, specifically including: The open-loop feedforward modulation method calculates the required d-axis and q-axis voltages based on the torque; the closed-loop harmonic injection modulation method obtains the required harmonic id / iq current values ​​based on the torque, and then uses PI control to obtain the d-axis and q-axis voltages. The obtained 5th, 7th, 11th, and 13th order d-axis and q-axis voltages are obtained by coordinate transformation to obtain their d-axis and q-axis voltages in the fundamental wave dq coordinate system. After being added to the fundamental wave, the final α-axis and β-axis voltages used for wave generation are obtained by inverse Park transformation.

8. The device for modulating vehicle noise according to claim 7, characterized in that, The harmonic current unit is specifically used for: The three-phase current is extracted by a second-order generalized integrator to obtain the harmonic three-phase current with only harmonic components. Then, the harmonic three-phase current is transformed into a rotating dq coordinate system of several orders, and the d-axis and q-axis harmonic currents of several orders are extracted by a first-order low-pass filter.

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