Inverter control device and inverter control method for electric vehicle

Abstract

Provided are an inverter control device and an inverter control method for an electric vehicle. The inverter control device comprises: an inverter for converting direct current power applied from a battery into alternating current power by using a pulse width modulation scheme and transmitting the converted alternating current power to a motor; a noise detection unit for detecting noise generated by the motor; and a control unit for controlling an update period of a duty value of the pulse width modulation on the basis of the noise detected by the noise detection unit.

Description

Inverter control device and inverter control method for electric vehicles

[0001] The present invention relates to an inverter control device for an electric vehicle and a control method thereof, and more particularly, to an inverter control device for an electric vehicle and a control method thereof capable of reducing motor noise in an electric vehicle equipped with an inverter using a pulse width modulation (PWM) method.

[0002] As we enter the era of electric vehicles, the number of engine-less vehicles is increasing. With the elimination of engines, the primary contributor to vehicle noise, vehicle noise levels are decreasing overall. Consequently, small noises that were previously unproblematic in engine-powered vehicles are beginning to be audible, and noise regulations from Original Equipment Manufacturers (OEMs) are also becoming more stringent.

[0003] In particular, high-frequency noise, although small and inaudible, can be quite annoying in quiet environments. However, motor control requires an inverter, and inverters drive the motor using PWM switching techniques, constantly generating high-frequency signals. These high-frequency signals affect the current waveform flowing through the motor, and this current can induce high-frequency noise.

[0004] Accordingly, the need for technology that can reduce noise generated from motors is emerging.

[0005] The problem to be solved by the present invention is to provide an inverter control device for an electric vehicle and a control method thereof capable of reducing motor noise.

[0006] Another problem to be solved by the present invention is to provide an inverter control device for an electric vehicle and a control method thereof that can selectively reduce noise of a specific frequency.

[0007] The tasks of the present invention are not limited to the technical tasks mentioned above, and other technical tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0008] An inverter control device according to one embodiment for solving the above problem is an inverter control device that converts direct current power supplied from a battery into alternating current power using a pulse width modulation method and controls an inverter that transmits the converted alternating current power to a motor, the inverter control device including: a noise detection unit that detects noise generated from the motor; and a control unit that controls an update cycle of a duty value of the pulse width modulation based on the noise detected by the noise detection unit.

[0009] The control unit may change the update cycle to a second cycle different from the preset first cycle when noise is detected by the noise detection unit.

[0010] The above update cycle may be a multiple of the cycle of the pulse width modulation.

[0011] The control unit calculates a frequency band of the noise, and can change the update cycle if the frequency band is within a preset frequency band range corresponding to the update cycle.

[0012] After changing the update cycle, the control unit can check whether the waveform of the phase current driving the motor has changed according to the change in the update cycle, and determine whether noise continues to occur in the frequency band of the noise.

[0013] The above control unit can change the update cycle when the size of the noise detected by the noise detection unit is greater than a preset value.

[0014] The above control unit can change the update cycle when the noise detected by the noise detection unit is within a specific frequency band.

[0015] An inverter control method according to one embodiment for solving the above problem is a control method for controlling an inverter for an electric vehicle that converts direct current power supplied from a battery into alternating current power using a pulse width modulation method and transmits the converted alternating current power to a motor, the control method including a step of determining whether noise has occurred; and a step of controlling an update cycle of a duty value of the pulse width modulation based on the noise if it is determined that noise has occurred.

[0016] Before changing the above update cycle, the step of changing the above update cycle may include a step of changing the update cycle to a second cycle different from the preset first cycle if it is determined that noise is occurring.

[0017] The above update cycle may be a multiple of the cycle of the pulse width modulation.

[0018] The above inverter control method may further include a step of calculating a frequency band of the noise when it is determined that noise is generated; and a step of determining whether the calculated frequency band is within a preset frequency band range corresponding to an update cycle of a duty value of pulse width modulation.

[0019] The above inverter control method may further include a step of checking whether the waveform of the phase current driving the motor has changed according to the change in the update cycle after changing the update cycle; and a step of determining whether noise continues to occur in the frequency band of the noise.

[0020] The above inverter control method may further include a step of determining whether the size of the noise is greater than a preset value.

[0021] The above inverter control method may further include a step of determining whether the noise is within a specific frequency band.

[0022] Specific details of other embodiments are included in the detailed description and drawings.

[0023] According to embodiments, an inverter control device for an electric vehicle capable of reducing motor noise and a control method thereof can be provided.

[0024] According to embodiments, an inverter control device for an electric vehicle and a control method thereof capable of selectively reducing noise of a specific frequency can be provided.

[0025] The effects according to the embodiments are not limited to those exemplified above, and more diverse effects are included in this specification.

[0026] Figure 1 is a block diagram of an inverter control device for an electric vehicle according to one embodiment.

[0027] Figure 2 is a flowchart of an inverter control method for an electric vehicle according to one embodiment.

[0028] FIG. 3 is a diagram illustrating the relationship between the period of pulse width modulation and the update period of the pulse width modulation duty value according to one embodiment.

[0029] FIG. 4 is a diagram illustrating FFT (Fast Fourier Transform) waveform graphs of motor driving phase current before and after changing the update cycle according to one embodiment.

[0030] FIG. 5 is a graph showing measured noise levels before changing the update cycle according to one embodiment.

[0031] FIG. 6 is a graph showing measured noise levels after changing the update cycle according to one embodiment.

[0032] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined solely by the scope of the claims.

[0033] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, it should be understood that a "first" component referred to below may also be a "second" component within the technical scope of the present invention.

[0034] Hereinafter, specific embodiments will be described with reference to the attached drawings.

[0035] Figure 1 is a simplified block diagram of a drive unit for an electric vehicle according to one embodiment.

[0036] A drive unit (1) for an electric vehicle may include a motor (40), a battery (50), an inverter (10) that converts the direct current power of the battery into alternating current power and supplies it to the motor (40), and an inverter control device that controls the inverter (10).

[0037] The inverter (10) converts the direct current power of the battery (50) into alternating current power to control the speed of the motor (40). The inverter (10) converts the direct current power supplied from the battery (50) into alternating current power using the pulse width modulation (PWM) method and can transmit the converted alternating current power to the motor (40). The amount of power transmitted to the motor (40) may vary depending on the duty of the PWM supplied to the inverter (10), and thus the speed of the motor (40) can be controlled using this.

[0038] According to one embodiment of the present invention, the inverter control device may include a control unit (30) and a noise detection unit (20).

[0039] The noise detection unit (20) detects the noise of the motor (40). In the motor (40) of an electric vehicle, various types of noise (for example, noise generated by the motor (40) may include mechanical noise, noise due to unbalancing of the motor (40), noise due to bearings, electromagnetic noise, and combinations thereof) may be generated due to various causes, and the noise detection unit (20) may detect such noise.

[0040] In some embodiments, the noise detection unit (20) may include a microphone capable of picking up noise from the motor (40) and / or an input device capable of receiving user input.

[0041] The control unit (30) can control the operation of the inverter (10). The control unit (30) can include a processor. The control unit (30) can further include a memory for data storage. In FIG. 1, the control unit (30) is depicted separately from the inverter (10), but is not limited thereto. In some embodiments, the control unit (30) can be included in the inverter (10). In some embodiments, the control unit (30) can control the overall operation of the electric vehicle and, as a part of its function, can include controlling the inverter (10).

[0042] The control unit (30) can control the inverter (10) based on the noise detected by the noise detection unit (20).

[0043] Specifically, the pulse width modulation method used by the inverter (10) is a method of controlling the voltage by varying the duty of the pulse. The control unit (30) can convert and use the applied voltage by changing the duty value. For example, when a voltage of 12 V is applied, if a duty value of 50% is used, a power of 6 V is provided, and if a duty value of 10% is used, a power of 1.2 V is provided. The noise of the motor (40) can be affected by the cycle of the pulse width modulation. The control unit (30) can control the cycle of the pulse width modulation to reduce the noise of the motor (40).

[0044] In addition, the control unit (30) can update the duty value of the pulse width modulation at a preset update cycle. The update cycle can be set based on the cycle of the pulse width modulation. The update cycle can be a multiple of the cycle of the pulse width modulation. For example, the duty value of the pulse width modulation can be updated for every pulse width modulation. In another example, in cases where the operation time of the control unit (30) is insufficient, the duty value of the pulse width modulation can be updated for every two or more pulse width modulations.

[0045] It has not been known that the update cycle of the duty value of conventional pulse width modulation affects the noise of the motor (40). However, the noise of the motor (40) may be affected by the update cycle. Accordingly, the control unit (30) can control the update cycle of the duty value of pulse width modulation to reduce the noise of the motor (40). As a result, the noise of the motor (40) can be reduced or the frequency of the noise can be changed to a specific frequency band to prevent the noise of the motor (40) from becoming audible.

[0046] The detailed operation of the control unit (30) will be described with reference to FIGS. 2 to 6 below.

[0047] Figure 2 is a flowchart of an inverter control method for an electric vehicle according to one embodiment.

[0048] The inverter control method for an electric vehicle described below (hereinafter referred to as the “inverter control method”) can be performed by an inverter control device.

[0049] Referring to FIG. 2, an inverter control method according to one embodiment includes a step (S10) of determining whether noise has occurred, and a step (S20) of changing an update cycle of a duty value of the pulse width modulation based on the noise if it is determined that noise has occurred.

[0050] In step S10, the control unit (30) can determine whether noise is generated by the motor (40) based on the noise detected by the noise detection unit (20). The control unit (30) can determine that noise has been generated if the level of noise received by the noise detection unit (20) is higher than a preset value. The control unit (30) can determine that noise has been generated if a user input is input to the noise detection unit (20).

[0051] The inverter control method may further include a step (S11) of calculating a frequency band of detected noise and a step (S12) of determining whether the calculated frequency band of noise is within a preset frequency band range corresponding to an update cycle of a duty value of pulse width modulation.

[0052] In step S11, if the control unit (30) determines that noise has been generated, it can analyze the sound signal received from the noise detection unit (20) to calculate the frequency band of the detected noise.

[0053] In step S12, the control unit (30) can determine whether the frequency band of the generated noise is similar to the update cycle. The preset frequency band range may be a range preset to include the frequency of the update cycle. The preset frequency band range may vary depending on changes in the update cycle.

[0054] In step S20, if it is determined that noise has occurred, the control unit (30) can change the update cycle to a second cycle that is different from the previously set first cycle.

[0055] In step S20, the control unit (30) may change the update cycle only when it is determined that the frequency band of the noise is within a preset frequency band range. However, this is not limited thereto, and steps S11 and S12, which compare the frequency band of the noise with the preset frequency band range, may be omitted. Step S20 may further include a step of changing the duty value of the pulse width modulation.

[0056] The inverter control method may further include a step (S30) of checking whether the waveform of the phase current driving the motor (40) has changed according to the change in the update cycle after changing the update cycle, and a step (S31) of determining whether noise continues to occur in the frequency band of the noise.

[0057] In step S30, the control unit (30) can first change the update cycle and then use FFT (Fast Fourier Transform) analysis of the waveform of the phase current to determine whether the FFT waveform of the phase current has changed according to the change in the update cycle. In some embodiments, step S30 may be omitted.

[0058] In step S31, the control unit (30) can determine whether noise continues to occur in the frequency band of the noise detected in step S11. If the control unit (30) determines that noise continues to occur, the control unit (30) can return to step S20 and change the update cycle. If the control unit (30) determines that noise is no longer occurring in step S31, the control unit (30) can maintain the update cycle (S32). In some embodiments, the control unit (30) can determine whether noise continues to occur based on the noise detected by the noise detection unit (20). In some embodiments, the control unit (30) can determine whether noise continues to occur based on FFT waveform analysis of the phase current.

[0059] FIG. 3 is a diagram illustrating the relationship between the period of pulse width modulation and the update period of the pulse width modulation duty value according to one embodiment. FIG. 4 is a diagram illustrating FFT waveform graphs of the motor driving phase current before and after changing the update period according to one embodiment. FIG. 5 is a graph illustrating the noise level measured before changing the update period according to one embodiment. FIG. 6 is a graph illustrating the noise level measured after changing the update period according to one embodiment.

[0060] Referring to FIGS. 3 to 6, the update cycle of the duty value of pulse width modulation is changed by the inverter control method, and accordingly, the FFT waveform of the phase current is changed, and accordingly, the noise of the motor (40) can be changed.

[0061] Referring to FIG. 3, as described above, in step S20, the control unit (30) can change the update cycle of the duty value of the pulse width modulation from the first cycle to the second cycle based on the noise of the motor (40).

[0062] For example, as shown in the upper part of Fig. 3, before changing the update cycle, the duty value of the pulse width modulation may be updated every four pulse width modulations. In this case, the frequency of the update cycle may be, for example, 5 kHz. Thereafter, as shown in the lower part of Fig. 3, when changing the update cycle, the duty value of the pulse width modulation may be updated every two pulse width modulations. In this case, the frequency of the update cycle may be, for example, 10 kHz.

[0063] Referring further to Fig. 4, the noise generated from the motor (40) is related to the shape of the FFT waveform of the phase current. This is because the power that rotates the motor (40) is the phase current, and force is applied to the motor (40) according to the shape of this phase current. If there is a distortion of a specific frequency in this phase current, noise of a specific frequency may be generated from the motor (40).

[0064] The FFT waveform of the phase current can be changed by changing the update cycle. For example, referring to the upper part of Fig. 4, before changing the update cycle, the frequency of the update cycle is 5 kHz, and noise can be detected in the 5 kHz band in the phase current FFT waveform. However, as shown in the lower part of Fig. 4, for example, after changing the update cycle, the frequency of the update cycle is 10 kHz, and noise can be detected in the 10 kHz band in the phase current FFT waveform. In other words, the FFT waveform of the phase current can be changed in response to the change in the update cycle.

[0065] Using these characteristics, after primarily changing the update cycle, the control unit (30) can analyze the phase current waveform using FFT in step S30 and check whether the change in the update cycle is reflected in the phase current waveform.

[0066] Referring to FIGS. 5 and 6, for example, as shown in FIG. 5, when the frequency of the update cycle is 5 kHz, it can be confirmed that noise is detected in the 5 kHz band. However, as shown in FIG. 6, for example, when the frequency of the update cycle is changed to 10 kHz, it can be confirmed that noise is detected in the 10 kHz band. That is, it can be confirmed that the FFT waveform of the phase current changes according to the change in the update cycle, and also, the noise frequency band changes.

[0067] As described above, the inverter control method according to one embodiment can reduce noise by controlling the update cycle of the duty value of pulse width modulation. Furthermore, the inverter control method according to one embodiment can selectively reduce noise in a specific frequency band by shifting the frequency band of the noise to another frequency band.

[0068] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. In an inverter control device that converts direct current power received from a battery into alternating current power using a pulse width modulation method and controls an inverter that transmits the converted alternating current power to a motor, A noise detection unit that detects noise generated from the above motor; and An inverter control device, comprising a control unit that controls the update cycle of the duty value of the pulse width modulation based on the noise detected by the noise detection unit.

2. In paragraph 1, An inverter control device, wherein when noise is detected by the noise detection unit, the control unit changes the update cycle to a second cycle different from the preset first cycle.

3. In paragraph 1, An inverter control device wherein the above update cycle is a multiple of the cycle of the pulse width modulation.

4. In paragraph 1, An inverter control device, wherein the control unit calculates a frequency band of the noise and changes the update cycle when the frequency band is within a preset frequency band range corresponding to the update cycle.

5. In paragraph 1, The above control unit is an inverter control device that checks whether the waveform of the phase current driving the motor has changed according to the change in the update cycle after changing the update cycle, and determines whether noise continues to occur in the frequency band of the noise.

6. In paragraph 1, The above control unit is an inverter control device that changes the update cycle when the size of the noise detected by the noise detection unit is greater than a preset value.

7. In paragraph 1, The above control unit is an inverter control device that changes the update cycle when the noise detected by the noise detection unit is within a specific frequency band.

8. A control method for controlling an inverter for an electric vehicle that converts direct current power received from a battery into alternating current power using a pulse width modulation method and transmits the converted alternating current power to a motor. Step for determining whether noise is generated; and In case it is determined that noise has occurred, a step of controlling the update cycle of the duty value of the pulse width modulation based on the noise is included. Inverter control method.

9. In paragraph 8, An inverter control method, wherein, before changing the update cycle, the step of changing the update cycle includes, if it is determined that noise is occurring, a step of changing the update cycle to a second cycle different from a preset first cycle.

10. In paragraph 8, An inverter control method wherein the above update cycle is a multiple of the cycle of the pulse width modulation.

11. In paragraph 8, An inverter control method further comprising: a step of calculating a frequency band of the noise when it is determined that noise is generated; and a step of determining whether the calculated frequency band is within a preset frequency band range corresponding to an update cycle of a duty value of pulse width modulation.

12. In paragraph 8, An inverter control method further comprising: a step of checking whether the waveform of the phase current driving the motor has changed according to the change in the update cycle after changing the update cycle; and a step of determining whether noise continues to occur in the frequency band of the noise.

13. In paragraph 8, An inverter control method further comprising a step of determining whether the size of the above noise is greater than a preset value.

14. In paragraph 8, An inverter control method further comprising a step of determining whether the above noise is within a specific frequency band.

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