JP2022119590A - Control device for inverter - Google Patents

Abstract

To provide a control device for an inverter capable of suppressing the generation of noise due to the overlapping of plurality types of frequencies while suppressing the reduction in efficiency and suppressing deterioration of functionality.SOLUTION: It is determined whether a motor has entered a rotation speed range in which the motor rotation speed is to be set by adding or subtracting a predetermined value to or from a rotation speed N at which two or more of a carrier frequency fc generated from the motor, a carrier sideband frequency fs, a motor's natural frequency fr, and a torque ripple occurrence frequency fo overlap. Then, when a predetermined time elapses while the motor speed remains in the speed range including the rotation speed N, the carrier frequency fc about the motor is raised to the predetermined frequency.SELECTED DRAWING: Figure 2

Description

The present invention relates to an inverter control device.

For example, a series-type hybrid vehicle is equipped with a motor that generates power from the power of the engine and a motor that generates power for running.

Pulse width modulation (PWM) control is widely used for controlling inverters that drive these motors. When the harmonic component (frequency fs of the carrier sideband) around the carrier frequency fc, which determines the pulse width modulation period, matches the natural frequency fr of the motor, noise from the motor increases.

To solve this problem, for example, it has been proposed to increase the carrier frequency fc so that the frequency fs of the carrier sideband does not match the natural frequency fr of the motor over the entire rotation range of the motor. However, the efficiency decreases due to the increased switching times over the entire rotation range of the motor. Moreover, in the high rotation range of the motor, the frequency fo of the order in which the torque ripple of the motor is generated coincides with the frequency fs of the carrier sideband, and noise is generated from the motor.

It has also been proposed to switch the carrier frequency according to the rotation speed of the motor so that the frequency fs of the carrier sideband and the natural frequency fr of the motor do not match in the high rotation range of the motor. Decrease in efficiency in the operating range and generation of noise from the motor are unavoidable.

It has also been proposed to finely switch the carrier frequency fc so that the carrier sideband frequency fs and the order frequency fo at which the torque ripple of the motor is generated are different. However, as the number of times the carrier frequency is switched increases, the user's sensitivity to the switching sound of the carrier frequency deteriorates.

JP 2009-284719 A JP 2019-161704 A

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inverter control device capable of suppressing the generation of noise due to overlapping of multiple types of frequencies while suppressing a decrease in efficiency and deterioration of sensory perception.

In order to achieve the above object, an inverter control device according to the present invention is a control device for controlling an inverter for driving a motor by pulse width modulation, wherein the number of revolutions of the motor is controlled by a plurality of types of motors generated when the motor is energized. It is determined that the rotation speed region where the frequencies overlap is entered, and the carrier frequency of the pulse width modulation is raised in response to the determination that the rotation speed of the motor has entered the rotation speed region continues for a predetermined time.

According to this configuration, the pulse width modulation is performed only when the rotation speed of the motor enters a rotation speed range in which a plurality of types of frequencies generated when the motor is energized overlaps, and the state in the rotation speed range continues for a predetermined time. carrier frequency is increased. As a result, it is possible to suppress the generation (increase) of noise due to the overlap of multiple types of frequencies, while suppressing the period in which the carrier frequency is increased to a short period, suppressing the decrease in efficiency, and increasing the carrier frequency. It is possible to suppress the deterioration of the user's sensuality to the switching sound of the carrier frequency by suppressing the number of times of switching.

Preferably, the plurality of frequencies are at least two of the carrier frequency, the frequency of the carrier sideband, the natural frequency of the motor, and the frequency of the order at which the torque ripple of the motor occurs.

Generation (increase) of noise due to overlapping of these frequencies can be suppressed.

ADVANTAGE OF THE INVENTION According to this invention, generation|occurrence|production of the noise by which multiple types of frequency overlap can be suppressed, suppressing the fall of efficiency and deterioration of sensory perception.

1 is a block diagram showing the configuration of a control system to which a control device according to an embodiment of the invention is applied; FIG. FIG. 10 is a diagram showing the relationship between the motor rotation speed and various frequencies, showing changes in carrier frequency due to carrier frequency change processing.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Control system>
FIG. 1 is a block diagram showing the configuration of a control system 1 to which a control device according to one embodiment of the invention is applied.

The control system 1 can be suitably used for a series hybrid system. The control system 1 includes two motors (MG1, MG2) 11, 12, a battery (BAT) 13 and a PCU (Power Control Unit) 14. FIG.

A series-type hybrid system constitutes a hybrid vehicle by being mounted on a vehicle together with an engine. Motors 11 and 12 are, for example, permanent magnet synchronous motors. The motor (MG1) 11 is a generator motor that generates power using the power of the engine, and its rotating shaft is mechanically connected to the crankshaft of the engine 11 via gears or the like. The motor (MG2) 12 serves as a drive motor that generates driving force for running the hybrid vehicle, and has a rotating shaft coupled to the drive system of the hybrid vehicle. The drive system includes, for example, a differential gear, and the power of the motor 12 is transmitted to the differential gear and distributed from the differential gear to the left and right drive wheels.

The battery 13 is an assembled battery in which a plurality of secondary batteries (for example, lithium ion batteries) are combined. Battery 13 outputs DC power of about 200 to 350 V (volt), for example.

The PCU 14 is a unit for controlling the driving of the motors 11 and 12, and includes inverters (INV1 and INV2) 21 and 22, a converter 23 and an MGECU 24.

An inverter (INV1) 21 is a three-phase voltage source inverter for driving the motor 11, and a series circuit of two IGBTs (Insulated Gate Bipolar Transistors) is connected to U-phase, V-phase and W-phase. , and the series circuits are connected in parallel between the plus wiring and the minus wiring. The inverter 21 converts DC power into AC power and supplies the AC power to the motor 11 when the motor 11 is powered. Further, the inverter 21 converts AC power generated by the motor 11 into DC power when the motor 11 is in regenerative operation (power generation).

The inverter (INV2) 22 is a three-phase voltage source inverter for driving the motor 12. Similar to the inverter 21, the inverter (INV2) 22 is provided with a series circuit of two IGBTs corresponding to each of the U-phase, V-phase and W-phase. , are connected in parallel between the positive wiring and the negative wiring. The inverter 22 converts DC power into AC power and supplies the AC power to the motor 12 when the motor 12 is powered. Further, the inverter 22 converts AC power generated by the motor 12 into DC power during regenerative operation (power generation) of the motor 12 .

Converter 23 boosts the DC power output from battery 14 and supplies it to inverters 21 and 22 when motors 11 and 12 are powered. Also, during regenerative operation of the motors 11 and 12 , the DC power output from the inverters 21 and 22 is stepped down and supplied to the battery 13 .

The MGECU 24 includes a microcomputer (microcontroller unit), and the microcomputer incorporates, for example, a CPU, nonvolatile memory such as flash memory, and volatile memory such as DRAM (Dynamic Random Access Memory). A hybrid vehicle is equipped with a plurality of ECUs each having a microcomputer, and the MGECU 24 is connected to these ECUs so as to be capable of two-way communication using a CAN (Controller Area Network) communication protocol.

The MGECU 24 sets the d-axis current command value and the q-axis current command value in the dq coordinate system for each of the motors 11 and 12 based on torque command values received from other ECUs. The dq coordinate system is a rotational orthogonal coordinate system composed of d-axes and q-axes that rotate in synchronization with the rotors of the motors 11 and 12 . The d-axis is the axis along the direction of the magnetic flux formed by the rotor, and the q-axis is the axis along the direction of the torque generated by the motor generator 2 . The MGECU 24 obtains a d-axis voltage command value and a q-axis voltage command value based on the d-axis current command value and the q-axis current command value, and calculates the d-axis voltage command value and the q-axis voltage command value as dq/three-phase The inverters 21 and 22 are pulse width modulated (PWM) controlled based on the U-phase voltage command value, the V-phase voltage command value and the W-phase voltage command value obtained by AC coordinate conversion. As a result, the motors 11 and 12 output torque corresponding to the respective torque command values.

<Carrier frequency change processing>
FIG. 2 is a diagram showing the relationship between the motor rotation speed and various frequencies, showing changes in the carrier frequency due to the carrier frequency changing process.

When the motors 11 and 12 are energized, for each of the motors 11 and 12, the carrier frequency fc, which is the frequency that determines the pulse width modulation period of the PWM control, and the harmonic components appearing on the high frequency side and the low frequency side around the carrier frequency fc. A carrier sideband frequency fs, a natural frequency fr of the motors 11 and 12, and a frequency fo of the order at which torque ripples of the motors 11 and 12 are generated.

The MGECU 24 determines that the rotation speeds of the motors 11 and 12 are such that any two or more of the carrier frequency fc generated from each of the motors 11 and 12, the carrier sideband frequency fs, the motor natural frequency fr, and the torque ripple generation frequency fo overlap. A determination is made as to whether or not the number of revolutions has entered a range set by adding or subtracting a predetermined value to the number N. The predetermined value is a positive number equal to or greater than 0.

When the MGECU 24 determines that the rotation speeds of the motors 11 and 12 have entered the rotation speed region including the rotation speed N, a predetermined time has passed since the determination that the rotation speeds of the motors 11 and 12 have entered the rotation speed region. or not. Then, after a predetermined period of time has elapsed while the rotation speeds of the motors 11 and 12 are in the rotation speed range including the rotation speed N, the MGECU 24 raises the carrier frequency fc of the motors 11 and 12 to a predetermined frequency.

Thereafter, when the rotation speeds of the motors 11 and 12 deviate from the rotation speed range including the rotation speed N, the MGECU 24 restores the carrier frequency fc to the original frequency.

<Effect>
As described above, the number of rotations of the motors 11 and 12 is determined by the plurality of frequencies generated when the motors 11 and 12 are energized, that is, the carrier frequency fc, the carrier sideband frequency fs, the motor natural frequency fr, and the torque ripple generation frequency fo. The carrier frequency fc of the pulse width modulation is increased only when two or more of them enter an overlapping rotation speed range and the state of entering the rotation speed range continues for a predetermined period of time. As a result, it is possible to suppress the generation (increase) of noise due to the overlap of multiple types of frequencies, while suppressing the period in which the carrier frequency fc is increased to a short period, suppressing the decrease in efficiency, and increasing the carrier frequency. It is possible to reduce the number of switching times of fc and suppress deterioration of the user's sensuality to the switching sound of the carrier frequency fc.

<Modification>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other forms.

For example, in the above-described embodiment, the carrier frequency fc is increased after a predetermined period of time has elapsed since it was determined that the rotation speeds of the motors 11 and 12 entered the rotation speed range including the rotation speed N. The predetermined time may be a predetermined fixed time, or may be variably set depending on the volume relationship between motor noise and other noise. When the volume of the motor noise is large, the predetermined time may be set longer than when the volume of the motor noise is equal to or higher than the volume of the other noises.

Noises other than motor noise include engine noise that varies depending on the number of rotations and output of the hybrid vehicle engine, road noise and wind noise caused by the hybrid vehicle running, audio and air-conditioner noise in the cabin of the hybrid vehicle, and hybrid vehicle noise. The sound of opening and closing a window can be exemplified. The volume of road noise can be predicted from vehicle speed, tire and/or rotational fluctuations of the motors 11 and 12 . The volume of wind noise can be predicted from the vehicle speed. Each volume of the audio sound, the air conditioner sound, and the window opening/closing sound can be obtained by sensing the volume in the vehicle interior. Further, the volumes of the audio sound, air conditioner sound, and window opening/closing sound may be obtained from information received by communication from an ECU that controls these operations. That is, the volume of the audio sound can be obtained from the information of the amplifier output, the volume of the air conditioner sound can be predicted from the information of the set air volume, and the volume of the opening and closing sound of the window can be determined whether the window is being opened or closed. From this information, it is possible to obtain a constant value depending on whether the opening/closing operation is being performed or not.

The predetermined time depends on whether or not the motor noise is likely to enter the vehicle interior. If the predetermined time is set to a relatively long time and even one window is open, the predetermined time may be set to a relatively short time. Alternatively, the predetermined time may be set shorter as the number of open windows increases.

Further, when the rotation speeds of the motors 11 and 12 deviate from the rotation speed range including the rotation speed N, the carrier frequency fc is returned to the original frequency. The carrier frequency fc may be returned to the original frequency in response to leaving a rotation speed range that is wider than the number range. Further, the carrier frequency fc may be returned to the original frequency when the motor noise falls below the other noise by a certain amount.

The present invention is not limited to a configuration including two motors 11 and 12, and can be applied to a configuration including only one motor and a configuration including three or more motors.

In addition, various design changes can be made to the above configuration within the scope of the matters described in the claims.

11, 12: Motor 21, 22: Inverter 24: MGECU (control device)

Claims (2)

A control device for controlling an inverter that drives a motor by pulse width modulation,
determining that the rotation speed of the motor has entered a rotation speed range in which a plurality of types of frequencies generated when the motor is energized overlap;
A control device that raises a carrier frequency of pulse width modulation in response to determination that the number of revolutions of the motor has entered the range of number of revolutions for a predetermined period of time. 2. The plurality of types of frequencies according to claim 1, wherein the plurality of types of frequencies are at least two types of the carrier frequency, the frequency of carrier sidebands, the natural frequency of the motor, and the frequency of the order at which torque ripple of the motor is generated. Control device.

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