Motor control method and motor control device

Abstract

To achieve both reduction of noise and suppression of efficiency decrease generated accompanied by operation of a motor.SOLUTION: Provided is a motor control method of generating a PWM control signal using a reference wave determined from a reference current and a carrier wave, and operating a power converter 200 by use of the PWM control signal to drive a motor 300. In the motor control method, a frequency of noise accompanied by operation of the motor is estimated based on an operating state of the motor. When the estimated frequency is determined to be included in a prescribed frequency range, a carrier frequency changing process for changing a carrier frequency and a harmonic current superposition process for superposing a harmonic current for suppressing an electromagnetic excitation force of the motor onto the reference current are executed.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an electric motor control method and an electric motor control device. [Background technology]

[0002] Patent Document 1 discloses a control method for controlling the operation of an electric motor that functions as a driving source for an electric vehicle by operating an inverter through PWM (Pulse Width Modulation) control. In particular, the control method of Patent Document 1 suppresses noise generated inside the vehicle by changing the carrier frequency from a basic value determined for driving in situations such as when the noise level around the vehicle is low. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 148521 Summary of the Invention [Problem to be solved by the invention]

[0004] In the control method described in Patent Document 1, the carrier frequency is changed by detecting a situation in which noise is easily noticeable by occupants, such as when the noise level around the vehicle (background noise level) is low as described above. Therefore, the carrier frequency is changed even when the noise level generated inside the vehicle itself is low to begin with, which leads to an increase in switching loss and a decrease in efficiency.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a motor control method and a motor control device that can simultaneously reduce noise generated by the operation of the motor and suppress a decrease in efficiency. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a motor control method for generating a PWM control signal using a reference wave and a carrier wave determined from a fundamental current, and for operating a power converter by the PWM control signal to drive a motor.

[0007] In this motor control method, a noise frequency is estimated as a frequency of noise caused by the operation of the motor based on the operating state of the motor, and when it is determined that the noise frequency is within a specified frequency range, a carrier frequency changing process is executed to change the carrier frequency, and a harmonic current superposition process is executed to superpose a harmonic current on a fundamental current to suppress the electromagnetic excitation force of the motor. Effect of the Invention

[0008] According to the present invention, it is possible to simultaneously reduce noise generated in association with the operation of an electric motor and suppress a decrease in efficiency. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of a motor system common to each embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining a manner in which the carrier frequency is switched. [Diagram 3] FIG. 3 is a flowchart showing details of the noise suppression process execution determination according to the first embodiment. [Figure 4] FIG. 4 is a graph showing the relationship between the resonant frequency of the electromagnetic excitation force and the resonant frequency of the structural system. [Diagram 5] FIG. 5 is a flowchart showing details of the noise suppression process execution determination according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] [First embodiment] 1 is a control block diagram showing the configuration of a motor system 1 that realizes an electric motor control method according to the present embodiment. The motor system 1 of the present embodiment is mounted on a hybrid vehicle or an electric vehicle (EV) that uses an electric motor as a driving source.

[0012] In particular, the motor system 1 is mainly composed of a motor control unit 100, an inverter 200 that functions as a power converter, and a motor 300 that functions as an electric motor.

[0013] The motor control unit 100 is configured by a computer (on-vehicle control unit) having a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), an input / output interface (I / O interface), etc. The motor control unit 100 is configured by one or more computer hardware units.

[0014] The motor control unit 100 determines a power command value (a three-phase AC voltage command value v , which will be described later) based on input parameters (particularly, a command torque) that indicate a required output for the motor 300. u ** , v v ** , v w ** ) and outputs it to the inverter 200. The detailed configuration of the motor control unit 100 will be described later.

[0015] The inverter 200 mainly controls the three-phase AC voltage command value v u ** , v v ** , v w ** and a semiconductor switching element (e.g., a SiC switching element) that operates in a switching pattern according to the PWM control signal. The switching operation of the semiconductor switching element based on the PWM control signal converts the output power of a DC power source (particularly, an on-board battery) (not shown) into three-phase AC power and supplies it to the motor 300.

[0016] Furthermore, in this embodiment, the inverter 200 refers to the control execution flag from the motor control unit 100 and adjusts the carrier frequency f c , the basic carrier frequency f c1 and the corrected carrier frequency f c2 Switch between.

[0017] Figure 2 shows the carrier frequency f c As shown in the figure, when the control execution flag is off, the inverter 200 switches the carrier frequency f c The basic carrier frequency f c1 When the control execution flag is on, the carrier frequency f c Correct the carrier frequency f c2 Set to.

[0018] Here, the fundamental carrier frequency f c1 is set to an appropriate value from the viewpoint of reducing switching losses and optimizing the operation efficiency of the inverter 200. More specifically, the fundamental carrier frequency f c1 can be set within the range of several kHz to 10 kHz, for example.

[0019] On the other hand, the corrected carrier frequency f c2 From the viewpoint of performing the superposition of high-frequency currents described later, the basic carrier frequency f c1 In particular, the corrected carrier frequency f c2 is the fundamental carrier frequency f c1 More specifically, the corrected carrier frequency f c2 can be set within the range of 15 kHz to 20 kHz, for example.

[0020] Returning to FIG. 2, the motor 300 is, for example, a three-phase AC synchronous motor such as a permanent magnet synchronous motor (IPM motor), and functions as a drive source for driving the vehicle.

[0021] Next, a detailed description will be given of the motor control unit 100. As shown in Fig. 1, the motor control unit 100 includes a current control circuit 10, a first superposition control circuit 30, and a second superposition control circuit 50.

[0022] The current control circuit 10 includes a base current controller 11 , a subtractor 12 , a superposition control unit 13 , an adder 14 , a dq / three-phase converter 15 , and a three-phase / dq converter 16 .

[0023] The fundamental current controller 11 calculates the fundamental current deviation (i d * -i d ), (i q * -i q ) is calculated by PI calculation (proportional-integral calculation) to obtain the basic dq-axis voltage command value v d * , v q * Calculate.

[0024] The subtractor 12 subtracts the dq-axis current i d , i q and the basic dq-axis current command value i d * , i q * The difference between and is the fundamental wave current deviation (i d * -i d ), (i q * -i q ) is used.

[0025] The superimposition control unit 13 controls the motor rotation speed N mBased on this, the superimposition control unit 13 judges whether or not to superimpose the high frequency current on the fundamental current. In particular, when the superimposition control unit 13 judges to superimpose the high frequency current, it outputs a first superimposed voltage and a second superimposed voltage, which will be described later, to the adder 14, and also turns on a control execution flag and outputs them to the inverter 200. On the other hand, the superimposition control unit 13 outputs each superimposition voltage command value as 0 to the adder 14, and also turns off the control execution flag and outputs them to the inverter 200. The details of the high frequency current superimposition execution judgment (hereinafter referred to as "noise suppression processing execution judgment") will be described later.

[0026] The adder 14 calculates the basic dq-axis voltage command value v d * , v q * The first superimposed voltage and the second superimposed voltage are added to obtain the corrected dq-axis voltage command value v d ** , v q ** and outputs it to the inverter 200.

[0027] The dq / three-phase converter 15 outputs the corrected dq-axis voltage command value v d ** , v q ** The three-phase AC voltage command value v is calculated by converting the dq-axis coordinate system into the three-phase AC coordinate system using the electrical angle θ of the motor 300. u ** , v v ** , v w ** and outputs it to the inverter 200. The electrical angle θ can be determined from a detection value of a rotational position sensor (not shown), such as a resolver.

[0028] The three-phase / dq converter 16 converts the actual measured value of the motor current (three-phase current i u , i v , i w ), the dq-axis current i is calculated by converting the three-phase AC coordinate system to the dq-axis coordinate system using the electrical angle θ. d , i q The three-phase current i u , iv , i w can be determined from the detection value of a current sensor (not shown).

[0029] The first superposition control circuit 30 is a circuit that controls the harmonic components contained in the motor current in an orthogonal coordinate system that rotates at a frequency equivalent to the harmonic components of a predetermined order that are generated when the motor current is controlled only by the fundamental current controller 11, i.e., in a harmonic coordinate system (dh1qh1-axis coordinate system) that rotates at a frequency that is an integer multiple (order m1) of the frequency of the fundamental current.

[0030] In particular, the first superposition control circuit 30 calculates the basic dq-axis voltage command value v d * , v q * When a PWM signal is generated based on the above, the first superimposition control circuit 30 calculates a first superimposition voltage so as to suppress an electromagnetic excitation force of 6nth order (n is any integer) generated in the motor 300, and outputs the first superimposition voltage to the superimposition control unit 13. Note that the first superimposition control circuit 30 preferably determines a first superimposition voltage capable of generating a high-frequency current including order components higher and lower than the order of the assumed electromagnetic excitation force. For example, when a sixth order (n=1) electromagnetic excitation force is assumed to be suppressed, the first superimposition voltage is determined so that a high-frequency current in which fifth order (m1=5) and seventh order (m1=7) components are combined can be superimposed on the basic current.

[0031] In particular, the first superposition control circuit 30 includes a superposition current controller 31, a subtractor 32, a dh1qh1 / dq converter 35, and a dq / dh1qh1 converter .

[0032] The superimposed current controller 31 calculates a first superimposed current deviation (i dh1 * -i dh1 ), (i qh1 * -i qh1 ) is subjected to PI (proportional-integral) calculation to obtain the first superimposed voltage command value v dh1 * , v qh1 * Calculate.

[0033] The subtractor 32 calculates a first superimposed current i dh1 , i qh1 and a predetermined first superimposed current command value i dh1 * , i qh1 * The difference between and is the first superimposed current deviation (i dh1 * -i dh1 ), (i qh1 * -i qh1 ) is used.

[0034] The dh1qh1 / dq converter 35 converts the electrical angle θ and the first superimposed voltage command value v dh1 * , v qh1 * The dh1qh1 / dq converter 35 calculates the first superimposed voltage using the electrical angle θ and outputs the first superimposed voltage to the superimposition control unit 13. More specifically, the dh1qh1 / dq converter 35 calculates a value θ obtained by multiplying the electrical angle θ by the order k1. h1 The sum of and is phase (θ+θ h1 ) The dh1qh1 / dq converter 35 calculates the first superimposed voltage command value v dh1 * , v qh1 * For phase (θ+θ h1 ) to convert the dh1qh1-axis coordinate system into the dq-axis coordinate system to calculate the first superimposition voltage and output it to the superimposition control unit 13.

[0035] The dq / dh1qh1 converter 36 converts the electrical angle θ and the dq-axis current i d , i q The first superimposed current i dh1 , i qh1 More specifically, the dq / dh1qh1 converter 36 calculates the phase (θ+θ) from the electrical angle θ, similarly to the dh1qh1 / dq converter 35. h1 ) is calculated. Then, the dq / dh1qh1 converter 36 calculates the dq axis current i d , i q For phase (θ+θ h1) to convert the dq-axis coordinate system to the dh1qh1-axis coordinate system, the first superimposed current i dh1 , i qh1 Calculate.

[0036] The second superposition control circuit 50 is a circuit that controls the harmonic components contained in the motor current in an orthogonal coordinate system that rotates at a frequency equivalent to the harmonic components of a different order from that of the first superposition control circuit 30, that is, in a harmonic coordinate system (dh2qh2 axis coordinate system) that rotates at a frequency that is an integer multiple (order m2 times) of the frequency of the fundamental current. In particular, the second superposition control circuit 50 controls the fundamental dq axis voltage command value v d * , v q * When a PWM signal is generated based on this, a second superimposed voltage is calculated so as to suppress the 6kth (k is any integer different from n) electromagnetic vibration force generated in the motor 300, and the second superimposed voltage is output to the superimposition control unit 13.

[0037] The second superposition control circuit 50 generates a high-frequency superposition current for reducing an electromagnetic excitation force of a different order from that of the first superposition control circuit 30. In the second superposition control circuit 50, it is preferable to determine a second superposition voltage capable of generating a high-frequency current including order components higher and lower than the order of the assumed electromagnetic excitation force. For example, when a 12th-order electromagnetic excitation force is assumed to be suppressed, the second superposition voltage is determined so that a high-frequency current in which 11th-order (m2=11) and 13th-order (m2=13) components are combined can be superimposed on the fundamental current.

[0038] In particular, the second superposition control circuit 50 includes a superposition current controller 51, a subtractor 52, a dh2qh2 / dq converter 55, and a dq / dh2qh2 converter 56.

[0039] Each element in the second superposition control circuit 50 calculates a second superposition voltage by performing calculations using the same logic as each element in the first superposition control circuit 30 , and outputs the second superposition voltage to the superposition control unit 13 .

[0040] As described above, the superimposition control unit 13 determines whether or not to execute the first superimposition voltage and the second superimposition voltage depending on the result of the noise suppression process execution determination, and outputs a corresponding control execution flag to the inverter 200. Furthermore, in the inverter 200, when the control execution flag is off, the carrier frequency f c The basic carrier frequency f c1 On the other hand, if the control execution flag is on, the carrier frequency f c Correct the carrier frequency f c2 Set to.

[0041] Therefore, in this embodiment, the carrier frequency f c Correct the carrier frequency f c2 (hereinafter referred to as "carrier frequency changing process") and a process of superimposing a harmonic current on a fundamental current (hereinafter referred to as "harmonic current superimposition process") are executed at the same timing. In this manner, in this embodiment, the carrier frequency changing process and the harmonic current superimposition process are executed at the same timing, so that it is possible to suppress noise generated by the operation of the motor 300 while suppressing switching loss and improving efficiency.

[0042] The technical significance of executing the carrier frequency changing process and the harmonic current superimposition process at the same timing will be described below.

[0043] In the above-mentioned Patent Document 1, the carrier frequency f c However, the noise generated by the operation of the motor 300 is reduced by changing the carrier frequency f c It cannot be reduced by changing

[0044] Here, the noise (signal) generated by the operation of the motor 300 is due to the effect of electromagnetic excitation force generated by changes in magnetic flux that occur when the rotor rotates. Methods for reducing such electromagnetic excitation force include adopting structural measures such as rotor skew or short-pitch winding in the motor 300, or implementing the above-mentioned harmonic current superposition process.

[0045] However, when a structure such as rotor skew or short pitch winding is adopted, the maximum torque and efficiency of the motor 300 generally tend to decrease. On the other hand, in the harmonic current superposition process, although the decrease in the maximum torque and efficiency can be avoided, the frequency of the harmonic current that can be generated is increased by the carrier frequency f c In other words, the control region in which harmonic current superposition processing can be performed is limited by the carrier frequency f c In particular, in the high rotation speed range (high vehicle speed range) of the motor 300, the carrier frequency f is larger than that in the low rotation speed range (low vehicle speed range) in order to perform the harmonic current superposition process. c Therefore, it is necessary to increase the carrier frequency f in order to expand the control range of the harmonic current superposition process. c One possible method would be to always set a high value, but this would increase switching loss and reduce efficiency.

[0046] In contrast to this, in this embodiment, the timing for executing the harmonic current superimposition process is accurately detected by the above-mentioned noise suppression process execution determination, and the carrier frequency change process and the harmonic current superimposition process are simultaneously executed only at that timing, thereby making it possible to avoid a decrease in efficiency while reducing noise accompanying the operation of the motor 300. Details of the noise suppression process execution determination will be described below.

[0047] 3 is a flowchart showing details of the noise suppression process execution decision. Each process shown in FIG. 3 is repeatedly executed by the superimposition control unit 13 at a predetermined calculation cycle.

[0048] As shown in the figure, in this routine, first, the motor rotation speed N m The motor rotation speed N m can be calculated appropriately from the detection value of the rotational position sensor.

[0049] Next, the motor rotation speed N m Based on this, the frequency of the noise generated by the operation of the motor 300 (hereinafter, the noise frequency f mo More specifically, the motor rotation speed N m From the prepared motor rotation speed N m and noise frequency f mo By referring to the relationship between the noise frequency f mo Estimate.

[0050] Furthermore, the estimated noise frequency f mo is included in the vibration increase frequency range R (S300). Here, the vibration increase frequency range R means a frequency range where the resonant frequency of the electromagnetic excitation force of the motor 300 and the resonant frequency of the structural system overlap.

[0051] Fig. 4 is a graph showing the relationship between the resonant frequency of the electromagnetic excitation force and the resonant frequency of the structural system. In Fig. 4, the resonant frequency of the 6n-th order electromagnetic excitation force is given the symbol "C1", and the resonant frequency of the 6k-th order electromagnetic excitation force is given the symbol "C2". Also, the resonant frequency band of the structural system that is a relatively low frequency band (hereinafter referred to as the "low frequency resonance band") is given the symbol "A re_L " and the relatively high frequency band (hereinafter referred to as "high frequency resonance band") is marked with the symbol "A re_H " is added.

[0052] The vibration increase frequency range R is made up of the resonance frequencies C1 and C2 and the low frequency resonance band A. re_L or high frequency resonance band A re_HIn particular, in the example of FIG. 4, two increased vibration frequency ranges R1 and R2 are defined on the high frequency side, and one increased vibration frequency range R3 is defined on the low frequency side. In this embodiment, the data of the increased vibration frequency range R that is prepared in advance in a predetermined storage area is referenced, and the noise frequency f mo The comparison result is referred to determine whether or not noise suppression processing can be performed.

[0053] More specifically, the noise frequency f mo If the noise frequency f is within the vibration increase frequency range R (Yes in S300), the control execution flag is turned on (S400). mo If the frequency of the vibration increase is not included in the vibration increase frequency range R (No in S300), the control execution flag is turned off (S500).

[0054] In addition, in Figure 4, low frequency resonance band A re_L The common area between the resonance frequency C1 and the resonance frequency C2 of the 6k-th order electromagnetic excitation force is defined as the vibration increase frequency range R3. On the other hand, the vibration increase frequency range R3 is included in a lower rotation speed region compared to the vibration increase frequency ranges R1 and R2, so the carrier frequency f c Even if the basic carrier frequency f c1 Therefore, even if the noise frequency f mo It is preferable to adopt a logic that turns on the control execution flag when the frequency is within the high-frequency vibration increase frequency ranges R1 and R2, and turns off the control execution flag when the frequency is within the low-frequency vibration increase frequency range R3. In particular, the control execution flag should be switched on in the high-frequency vibration increase frequency range R, and the control execution flag should be switched off in the high-frequency vibration increase frequency range R4. m It is possible to employ logic for making a determination by referring to the above.

[0055] Furthermore, as shown in FIG. 4, each of the vibration increase frequency ranges R1, R2, and R3 corresponds to the motor rotation speed N m N m1 ~N m2 The range of values ​​for N m3 ~N m4The range of values ​​of and N m5 ~N m6 The motor rotation speed N is a parameter that indicates the frequency of the noise generated by the operation of the motor 300. m Alternatively, the logic for making the determination in S300 may be adopted by using the above as is.

[0056] The configuration, operation and effects of the motor control method according to the present embodiment described above will now be described.

[0057] In this embodiment, the fundamental current (i d * ,i q * ) based on the reference wave (v d ** ,v q ** The present invention provides a motor control method that generates a PWM control signal using a carrier wave and a power converter (inverter 200) to drive a motor (motor 300).

[0058] In this motor control method, a noise frequency f as the frequency of noise generated by the operation of the motor 300 is calculated based on the operating state of the motor 300. mo Estimate the noise frequency f mo is determined to be within the specified frequency range (vibration increase frequency range R), the carrier frequency f c and a harmonic current superposition process for superimposing a harmonic current on the fundamental current in order to suppress an electromagnetic excitation force generated by driving the motor 300.

[0059] This makes it possible to appropriately detect scenes requiring noise suppression, and simultaneously change the carrier frequency fc and superimpose the harmonic current only in those scenes, thereby reducing noise generated by the motor 300 as an excitation source. This makes it possible to simultaneously reduce noise generated by the operation of the motor 300 and suppress a decrease in efficiency.

[0060] In particular, by executing the control according to this embodiment, it is possible to suppress the electromagnetic excitation force without providing the motor 300 with a structure such as rotor skew or short-pitch winding. In other words, it is possible to obtain the required noise suppression effect while avoiding the decrease in efficiency that would otherwise accompany the adoption of this efficiency.

[0061] In addition, in the carrier frequency change process of this embodiment, the carrier frequency f c Given the fundamental carrier frequency f c1 A corrected carrier frequency f c2 Set to.

[0062] This makes it possible to more reliably suppress the carrier frequency f c This can relax the constraints imposed by

[0063] Furthermore, in this embodiment, the vibration increase frequency range R is set to the motor rotation speed (motor rotation speed N m ) and the resonance frequency band of the structural system (especially the high frequency resonance band A re_H ) is defined as the frequency range where and overlap.

[0064] This makes it possible to more accurately detect scenes in which the resonance of the structural system and the resonance of the electromagnetic excitation force overlap, causing particularly increased vibrations associated with the operation of the motor 300, and to perform carrier frequency change processing and harmonic current superposition processing.

[0065] In this embodiment, the vibration increase frequency range R is determined based on the respective resonance frequencies C1 and C2 in the electromagnetic excitation forces of multiple orders (6n order and 6k order).

[0066] This makes it possible to reduce not only single-order electromagnetic excitation forces but also multiple orders of electromagnetic excitation forces, thereby improving the noise suppression effect. In particular, compared to methods of reducing electromagnetic excitation forces using structural innovations such as rotor skew and short-pitch winding, it is possible to obtain a reduction effect on electromagnetic excitation forces of a greater variety of orders.

[0067] It is also possible to adopt a configuration in which the vibration increase frequency range R is adjusted based on the detection value of an acceleration sensor provided in the vehicle. More specifically, it is preferable to adopt a control logic in which the vibration increase frequency range R is made wider as the detection value of the acceleration sensor (the actual output torque of the motor 300) increases, and the vibration increase frequency range R is made narrower as the detection value decreases.

[0068] In other words, the resonant frequencies C1 and C2 of the electromagnetic excitation force of motor 300 have the characteristic of changing according to the actual output torque of motor 300, and by adopting the above control logic, it is possible to detect scenes requiring noise suppression with greater accuracy while taking into account such characteristics.

[0069] Furthermore, in this embodiment, there is provided a motor control unit 100 that functions as an electric motor control device suitable for carrying out the above-described electric motor control method.

[0070] In particular, the motor control unit 100 determines a noise frequency f as the frequency of noise generated by the operation of the motor 300 based on the operating state of the motor 300. mo and an estimation unit (superimposition control unit 13) that estimates the estimated noise frequency f mo is determined to be within the specified frequency range (vibration increase frequency range R), the carrier frequency f c and a noise suppression processing unit (inverter 200, superposition control unit 13, adder 14) that executes a carrier frequency changing process that changes the carrier frequency, and a harmonic current superposition process that superposes a harmonic current on a fundamental current in order to suppress an electromagnetic excitation force generated by driving the motor 300.

[0071] [Second embodiment] The second embodiment will be described below. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. In this embodiment, in particular, an example in which a logic for determining whether or not to execute noise suppression processing is different from that in the first embodiment will be described.

[0072] 5 is a flowchart showing details of the noise suppression process execution determination in this embodiment. As shown in the figure, the noise suppression process execution determination in this embodiment further includes determining (S350) whether the volume of background noise in the cabin of the vehicle equipped with the motor system 1 is equal to or less than a predetermined reference value.

[0073] Here, background noise in the vehicle cabin refers to noise other than noise generated by the operation of the motor 300 or the inverter 200, such as road noise and wind noise during driving. Therefore, in the determination at S350, the magnitude of the background noise is estimated from any parameter correlated with the above noise. In particular, in this embodiment, the magnitude of the background noise can be estimated from the detection value of a wheel speed sensor (not shown) or the like.

[0074] In this embodiment, the noise frequency f mo is included in the vibration increase frequency range R (if S300 is Yes), and if the magnitude of the estimated background noise is equal to or less than the reference value (if S350 is Yes), the control execution flag is turned on. mo Even if the frequency of the background noise is within the vibration increase frequency range R, if the magnitude of the background noise exceeds the reference value (if No in S350), the control execution flag is turned off.

[0075] As described above, in this embodiment, a motor control method is provided that is executed for the motor 300 mounted on a vehicle. In this motor control method, a noise frequency f mo If it is determined that the frequency of the vehicle is within the vibration increase frequency range R, it is determined whether the volume of the background noise in the vehicle cabin is equal to or lower than a reference value.

[0076] If the background noise is equal to or less than the reference value, the carrier frequency change process and the harmonic current superimposition process are executed, whereas if the background noise exceeds the reference value, neither the carrier frequency change process nor the harmonic current superimposition process is executed.

[0077] This allows the noise reduction process to be executed only in a scene where the background noise is small and the noise caused by the operation of the motor 300 is easily recognized by the occupant. In other words, in a scene where the background noise is small and the noise caused by the operation of the motor 300 is not easily recognized by the occupant, the noise reduction process is not executed and the carrier frequency f c The basic carrier frequency f c1 Since the switching loss can be maintained at 0.1 V, the effect of suppressing the decrease in efficiency due to the increase in switching loss can be further improved.

[0078] Although each embodiment of the present invention has been described above, the above-mentioned embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments.

[0079] For example, in the control of each of the above embodiments, the explanation has been given assuming an example in which the electromagnetic excitation force to be suppressed has two orders, nth order and kth order, but it is also possible to adopt a control logic capable of superimposing a high-frequency current on a basic current assuming suppression of electromagnetic excitation forces of three or more orders. This control logic can be realized, for example, by providing a third superimposition control circuit for reducing an mth order (m ≠ n, k) in addition to a first superimposition control circuit 30 for reducing an nth order electromagnetic excitation force and a second superimposition control circuit 50 for reducing a kth order electromagnetic excitation force shown in FIG.

[0080] In the above embodiments, in the carrier frequency change process, the carrier frequency f c The basic carrier frequency f c1 From the fundamental carrier frequency f c1 A fixed compensation carrier frequency f c2 On the other hand, instead of this, the carrier frequency f c A configuration in which the carrier frequency f c The basic carrier frequency f c1 Alternatively, a configuration may be adopted in which the frequency is periodically changed in a frequency band higher than the frequency band.

[0081] Furthermore, in each of the above embodiments, the inverter 200 includes a SiC switching element (S i In the above embodiment, the inverter 200 is used as a S-type inverter. However, the present invention is not limited to this. i Even if the inverter is a type different from the C inverter (such as a Si inverter), the operation can be performed in the same manner. On the other hand, in order to broaden the control range for executing the harmonic current superposition process, the carrier frequency f c S, which can be made relatively high i It is more preferable to use a C inverter. [Explanation of symbols]

[0082] 1 Motor System 100 Motor control unit 200 Inverter 300 Motor

Claims

1. A motor control method for generating a PWM control signal using a reference wave and a carrier wave determined from a fundamental current, and operating a power converter by the PWM control signal to drive a motor, comprising: estimating a frequency of noise caused by operation of the electric motor based on an operating state of the electric motor; When it is determined that the estimated frequency is within a specified frequency range, A carrier frequency changing process is executed to change a carrier frequency, and a harmonic current superimposing process is executed to superimpose a harmonic current on the fundamental current in order to suppress an electromagnetic excitation force of the electric motor. Electric motor control method.

2. 2. A method for controlling an electric motor according to claim 1, comprising: In the carrier frequency change process, Setting the carrier frequency to a correction carrier frequency higher than a predetermined base carrier frequency. Electric motor control method.

3. 3. The motor control method according to claim 2, The specified frequency range is defined as a frequency range in which a resonance frequency of the electromagnetic excitation force corresponding to the motor rotation speed and a resonance frequency band of a structural system overlap. Electric motor control method.

4. 4. The motor control method according to claim 3, The specified frequency range is determined based on each of the resonant frequencies of the electromagnetic excitation forces of a plurality of orders. Electric motor control method.

5. 2. A method for controlling an electric motor according to claim 1, comprising: The electric motor is mounted on a vehicle, The specified frequency range is adjusted based on a detection value of an acceleration sensor provided in the vehicle. Electric motor control method.

6. 3. The motor control method according to claim 2, The electric motor is mounted on a vehicle, If it is determined that the frequency is within the specified frequency range, it is determined whether the volume of background noise in the vehicle cabin is equal to or less than a reference value; If the magnitude of the background noise is equal to or less than the reference value, the carrier frequency changing process and the harmonic current superposition process are executed. If the magnitude of the background noise exceeds the reference value, neither the carrier frequency changing process nor the harmonic current superposition process is executed. Electric motor control method.

7. A motor control device that generates a PWM control signal using a reference wave and a carrier wave determined from a fundamental current, and drives a motor by operating a power converter using the PWM control signal, an estimation unit that estimates a noise frequency as a frequency of noise associated with operation of the electric motor based on an operating state of the electric motor; and a noise suppression processing unit that executes a carrier frequency changing process for changing a carrier frequency when it is determined that the estimated frequency is within a specified frequency range, and a harmonic current superimposing process for superimposing a harmonic current on the fundamental current to suppress an electromagnetic excitation force of the motor. Motor control device.

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