Motor control device and motor control method

Abstract

The purpose of the present invention is to improve response speed to load fluctuation. An inverter control unit comprises: a motor position estimation unit that estimates the position of a motor; and a current command generation unit (20) that generates a current command for rotating the motor at a target speed. The current command generation unit (20) is equipped with: a speed control unit (22) that calculates a torque command for rotating the motor at a target speed; a compensating torque calculation unit (23) that calculates a compensating torque by the product of a compensation coefficient that varies according to the position of the motor and a smoothed torque command obtained by smoothing the torque command; a correction unit (24) that corrects the torque command by using the compensating torque; and a current conversion unit (25) that generates a current command by using the corrected torque command.

Description

Motor control device and motor control method

[0001] The present disclosure relates to a motor control device and a motor control method.

[0002] For example, in a compressor, steady load torque fluctuations occur due to changes in refrigerant gas pressure during each of the suction, compression, and discharge strokes during one rotation. Meanwhile, the drive motor connected to the compressor is operated to generate a constant drive torque during one rotation, so the imbalance between this drive torque and the load torque causes fluctuations in rotation speed, resulting in noise.

[0003] A known method for reducing rotational speed fluctuations resulting from such an imbalance between the drive torque and the load torque is disclosed in, for example, Patent Document 1. Patent Document 1 discloses a method for suppressing speed fluctuations by multiplying a torque command, which is the output of a speed control unit, by a predetermined torque pattern to calculate a compensation torque that matches the estimated position of the motor, and adding this compensation torque to the torque command.

[0004] Japanese Patent Application Laid-Open No. 2008-245506

[0005] In Patent Document 1, the torque pattern is normalized so that the torque compensation amount during one rotation of the motor is zero, so the response frequency of the speed control unit needs to be slower than the steady-state fluctuation frequency of the load torque. For this reason, for example, as described in detail below, when speed fluctuations occur in the load, it is difficult to quickly control the motor output in response to the speed fluctuations.

[0006] For example, consider a case where the speed is low in region A of the torque pattern where the compensation value is large, and high in region B where the compensation value is small, as shown in Figure 8. In this case, in region A, the rotor position does not advance, so the time during which the compensation torque is large becomes longer, and conversely, in region B, the rotor position advances, so the time during which the compensation torque is small becomes shorter. As a result, the average compensation value during one rotation of the motor becomes a value greater than zero.

[0007] In contrast to this, consider a case where the speed is low in region C of the torque pattern where the compensation value is small, and high in region D where the compensation value is large, as shown in Figure 9. In this case, the rotor position does not advance in region C, so the time during which the compensation torque is small becomes longer, and conversely, the rotor position advances in region D, so the time during which the compensation torque is large becomes shorter. As a result, the average compensation value during one rotation of the motor becomes a value smaller than zero.

[0008] Thus, in the invention of Patent Document 1, although the torque pattern is designed so that the average value of the compensation torque during one rotation of the motor is zero, if a speed change occurs during one rotation of the motor, the intended compensation torque cannot be set, resulting in a problem of reduced control accuracy.

[0009] Furthermore, since the response frequency of the speed control section needs to be slower than the steady-state fluctuation frequency of the load torque, it is difficult to improve the responsiveness of the speed control, and there is a problem that it is not possible to respond quickly when an unexpected speed fluctuation of the load occurs.

[0010] In particular, in the low-speed region where the motor speed is slow, fluctuations in the torque compensation amount are more pronounced than in the high-speed region where the motor speed is fast, so there is a risk that the accuracy of motor control will decrease in the low-speed region.

[0011] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a motor control device and a motor control method that can improve the response speed to load fluctuations.

[0012] A motor control device according to one aspect of the present disclosure is a motor control device that includes an inverter that converts a DC voltage into a three-phase AC voltage and outputs the voltage to a motor, and an inverter control unit that controls the inverter, and that controls a motor connected to a load that generates periodic torque fluctuations, wherein the inverter control unit includes a motor position estimator that estimates the position of the motor, and a current command generator that generates a current command for rotating the motor at a target speed, and the current command generator includes a speed control unit that calculates a torque command for rotating the motor at the target speed, a compensation torque calculation unit that calculates a compensation torque by multiplying a compensation coefficient that varies depending on the position of the motor by a smoothing torque command that smooths the torque command, a correction unit that corrects the torque command using the compensation torque, and a current conversion unit that generates a current command using the corrected torque command.

[0013] A motor control method according to one aspect of the present disclosure is a motor control method for controlling a motor connected to a load that generates periodic torque fluctuations, in which a computer executes a motor position estimation process that estimates the position of the motor, and a current command generation process that generates a current command for rotating the motor at a target speed, and the current command generation process includes a speed control process that calculates a torque command for rotating the motor at the target speed, a compensation torque calculation process that calculates a compensation torque by multiplying a compensation coefficient that varies depending on the motor position by a smoothed torque command that smooths the torque command, a correction process that corrects the torque command using the compensation torque, and a current conversion process that generates a current command using the corrected torque command.

[0014] The response speed to load fluctuations can be improved.

[0015] FIG. 1 is a diagram schematically illustrating a configuration of a motor control device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a hardware configuration of an inverter control unit according to an embodiment of the present disclosure. FIG. 3 is a functional configuration diagram of a current command generation unit according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of compensation information according to an embodiment of the present disclosure. FIG. 5 is a functional configuration diagram of a current command generation unit according to a first modified example of the present disclosure. FIG. 6 is a diagram illustrating an example of a configuration of an air conditioner to which a motor control device according to an embodiment of the present disclosure is applied. FIG. 7 is a diagram for explaining problems in the related art. FIG. 8 is a diagram for explaining problems in the related art.

[0016] An embodiment of a motor control device, a motor control method, and a program according to the present disclosure will be described below with reference to the drawings. Fig. 1 is a diagram schematically illustrating the configuration of a motor control device 1 according to an embodiment of the present disclosure. As shown in Fig. 1, the motor control device 1 includes, for example, a converter 2 that converts AC power from an AC power source into DC power, an inverter 3 that converts the DC power output from the converter 2 into three-phase AC power and outputs the AC power to a motor 4, and an inverter control unit 10 that controls the inverter 3.

[0017] The inverter 3 includes, for example, upper arm switching elements and lower arm switching elements provided corresponding to each phase, and these switching elements are on / off controlled by a gate drive signal S provided from the inverter control unit 10, thereby controlling the motor voltages of the U phase, V phase, and W phase supplied to the motor 4. The motor 4 is, for example, a permanent magnet synchronous motor used as a drive source for a compressor of an air conditioner.

[0018] The motor control device 1 is equipped with a current sensor 5 that measures the motor current (currents of U-phase, V-phase, and W-phase) flowing through the motor 4, and a voltage sensor 6 that measures the input DC voltage Vdc of the inverter 3. The motor current may be detected for two phases, and the remaining phase may be calculated from the detected two phases. Instead of this measurement method, a three-phase motor current may be measured by providing a shunt resistor on a DC bus (not shown). In this way, there is no particular limitation on the method for obtaining the three-phase motor current.

[0019] The three-phase motor current detected by the current sensor 5 is converted into a digital signal by an A / D converter (not shown), and the input DC voltage detected by the voltage sensor 6 is converted into a digital signal by an A / D converter (not shown), and output to the inverter control unit 10.

[0020] The inverter control unit 10 generates gate drive signals S for each phase so that the rotation speed of the motor 4 matches the motor rotation speed command given by a higher-level control device (not shown), and controls the inverter 3 by giving these signals to the switching elements corresponding to each phase of the inverter 3, thereby supplying the desired three-phase AC voltage to the motor 4.

[0021] FIG. 2 is a diagram showing an example of a hardware configuration of the inverter control unit 10. As shown in FIG. 2, the inverter control unit 10 is, for example, a computer and includes a processing circuit 60. The processing circuit 60 includes, for example, a processor 61, a main memory 62, a secondary storage 63, and the like. The inverter control unit 10 may also include a communication interface 64 for transmitting and receiving information to and from other devices. These units are connected directly or indirectly via a bus 65.

[0022] Examples of the processor 61 include a CPU (Central Processing Unit), a microprocessor, a microcomputer, and a DSP (Digital Signal Processor).

[0023] The main memory device 62 is composed of writable memory such as cache memory or RAM (Random Access Memory), and is used as a working area for reading the execution program of the processor 61 and writing the processing data by the execution program.

[0024] The secondary storage device 63 is a non-transitory computer-readable storage medium. Examples of the secondary storage device 63 include a flash memory and an SSD (Solid State Drive). Other examples of the secondary storage device 63 include a magnetic disk, a magneto-optical disk, a CD-ROM, and a DVD-ROM. A plurality of secondary storage devices may be provided, and programs and data for realizing the functions described below may be divided and stored in each secondary storage device.

[0025] A series of processes for realizing the various functions described below is stored in the secondary storage device 63 in the form of a program, for example, and the processor 61 reads this program into the main storage device 62 and executes information processing and arithmetic processing to realize the various functions. The program may be pre-installed in the secondary storage device 63, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0026] 1 illustrates an example of functions provided in the inverter control unit 10. Specifically, the inverter control unit 10 includes a motor position estimator 12 and a current command generator 20.

[0027] Furthermore, the inverter control unit 10 includes a three-phase / two-phase conversion unit 11 , a voltage command generation unit 30 , a two-phase / three-phase conversion unit 16 , and a gate drive signal generation unit 17 .

[0028] The three-phase / two-phase converter 11 converts the three-phase motor currents output from the A / D converter (not shown) into two-phase currents, i.e., q-axis current and d-axis current, and outputs them to the motor position estimator 12. The motor position estimator 12 uses the q-axis current and d-axis current from the three-phase / two-phase converter 11 and the two-phase voltage command calculated by the voltage command generator 30 in the previous clock cycle, i.e., the q-axis voltage command vq ＊ and d-axis voltage command vd ＊ The estimated position θes of the motor and the estimated rotation speed ωes of the motor are calculated using the above equations. The estimated position θes of the motor and the estimated rotation speed ωes of the motor are output to the current command generator 20.

[0029] The current command generating unit 20 generates a current command corresponding to the torque component of the load, and generates a rotation speed command ω given from a higher-level control device, for example, a higher-level control device that controls an air conditioner. ＊ and the estimated rotation speed ωes from the motor position estimator 12, the deviation Δω between ＊ , d-axis current command id ＊ The current command generating unit 20 will be described in detail later.

[0030] The voltage command generator 30 generates the q-axis current command iq ＊ and d-axis current command id ＊ Using the q-axis voltage command vq ＊ , d-axis voltage command vd ＊ Generate.

[0031] The voltage command generating unit 30 includes, for example, a deviation calculating unit 31 and a current PI control unit 32. The deviation calculating unit 31 calculates the q-axis current command iq generated by the current command generating unit 20. ＊ and the deviation between the q-axis current iq output from the three-phase / two-phase conversion unit 11 and the d-axis current command id generated by the current command generation unit 20. ＊ and the d-axis current id output from the three-phase / two-phase conversion unit 11.

[0032] The current PI control unit 32 calculates the q-axis voltage command vq such that the deviation calculated by the deviation calculation unit 31 approaches zero. ＊ and d-axis voltage command vd＊ Specifically, by performing proportional-integral control (PI control) on each deviation, the q-axis voltage command vq ＊ and d-axis voltage command vd ＊ Calculate.

[0033] The two-phase / three-phase converter 16 converts the estimated position θes of the motor and the q-axis voltage command vq generated by the voltage command generator 30. ＊ and d-axis voltage command vd ＊ The three-phase voltage command vu ＊ , vv ＊ , vw ＊ Convert to.

[0034] The gate drive signal generator 17 receives the three-phase voltage command vu output from the two-phase / three-phase converter 16. ＊ , vv ＊ , vw ＊ and an input DC voltage Vdc from an A / D converter (not shown). The gate drive signal generator 17 generates a triangular wave with a predetermined carrier frequency, and combines this triangular wave with a three-phase voltage command vu ＊ , vv ＊ , vw ＊ and the duty width of the PWM pulse is corrected using the input DC voltage Vdc, thereby generating a gate drive signal S corresponding to each phase and outputting it to the inverter 3.

[0035] Next, the current command generating unit 20 according to this embodiment will be described with reference to the drawings. Fig. 3 is a functional configuration diagram of the current command generating unit 20. As shown in Fig. 3, the current command generating unit 20 includes a speed control unit 22, a compensation torque calculation unit 23, and a correction unit 24. Furthermore, the current command generating unit 20 includes a deviation calculation unit 21 and a current conversion unit 25.

[0036] The deviation calculation unit 21 calculates the rotation speed command ω ＊ The speed control unit 22 calculates a torque command for rotating the motor 4 at a target speed. For example, the speed control unit 22 includes a proportional control unit 26 and an integral control unit 27. The speed control unit 22 calculates a deviation between the rotation speed command ω calculated by the deviation calculation unit 21 and the estimated rotation speed ωes. ＊A torque command is generated by performing proportional-integral control (PI control) on the deviation between the estimated rotation speed ωes and the estimated rotation speed ωes.

[0037] The compensation torque calculation unit 23 calculates the compensation torque by multiplying a compensation coefficient that varies depending on the motor position θes by a smoothing torque command that smoothes the torque command. In this embodiment, the output of the integral control unit 27 is used as the smoothing torque command.

[0038] For example, the compensation torque calculation unit 23 obtains a compensation coefficient corresponding to the estimated position θes of the motor 4 from compensation information in which the compensation coefficient is set based on the periodic torque fluctuation of the load, and calculates the compensation torque by multiplying the obtained compensation coefficient by the smoothing torque command, i.e., the output of the integral control unit 27.

[0039] FIG. 4 is a diagram showing an example of compensation information. As shown in FIG. 4, the compensation information associates an estimated motor position with a compensation coefficient, with the horizontal axis representing the motor position (in other words, the rotor rotation angle) and the vertical axis representing the compensation coefficient. This compensation information is set based on periodic torque fluctuations of a load to which the motor is connected. In other words, the compensation information is set so as to be linked to fluctuations in load torque of a load (e.g., an electric compressor) to which the motor 4 is connected, with a large compensation coefficient set at a position where the load torque is large and a small compensation coefficient set at a position where the load torque is small. The compensation coefficients are set as normalized data so that the sum of the compensation coefficients during one rotation of the motor is zero.

[0040] The compensation information may be stored as a table in which the motor position and the compensation coefficient are associated, or may be stored in a predetermined storage area as an arithmetic formula that calculates the compensation coefficient using the motor position as a variable.

[0041] The compensation torque calculation unit 23 obtains a compensation coefficient corresponding to the estimated motor position θes output from the compensation information by the motor position estimator 12, and calculates the compensation torque by multiplying the obtained compensation coefficient by the smoothing torque command, i.e., the output from the integral control unit 27. For example, multiple pieces of compensation information may be provided according to the value of the motor current, and the compensation information may be switched according to the motor current detected by the current sensor 5. In this case, the compensation information is set, for example, so that the amplitude of the compensation coefficient (deviation between the maximum and minimum values) increases as the motor current increases. However, the sum of the correction coefficients during one motor rotation is still set to zero.

[0042] The correcting unit 24 corrects the torque command using the compensation torque. Specifically, the correcting unit 24 calculates the corrected torque command by adding the torque command and the compensation torque.

[0043] The current conversion unit 25 generates a current command for the motor using the corrected torque command. For example, the current conversion unit 25 converts the corrected torque command into a q-axis current command iq corresponding to the q-axis torque component. ＊ , d-axis current command id corresponding to the d-axis torque component ＊ Here, the q-axis current command iq ＊ , d-axis current command id ＊ is adjusted so as not to exceed a preset upper limit value.

[0044] The q-axis current command iq thus generated ＊ , d-axis current command id ＊ is output to the voltage command generating unit 30, and the above-mentioned processing is continued.

[0045] Next, the operation of the inverter control unit 10 according to this embodiment will be described. First, the three-phase current detection values ​​detected by the current sensor 5 and converted into digital signals by the A / D converter are converted into two-phase q-axis current and d-axis current by the three-phase / two-phase converter 11. The motor position estimator estimates the q-axis current iq and the d-axis current id, and the q-axis voltage command vq calculated by the voltage command generator 30 in the previous clock cycle. ＊ and d-axis voltage command vd＊ The estimated position θes of the motor and the estimated rotation speed ωes of the motor are calculated using the above.

[0046] In the current command generating unit 20, the speed control unit 22 generates a rotation speed command ω ＊ The torque command is generated by performing proportional-plus-integral control on the deviation between the estimated rotational speed ωes and the estimated rotational speed ωes. Furthermore, in the current command generating unit 20, the output of the integral control unit 27 is output to the compensation torque calculating unit 23 as a smoothing torque command.

[0047] The compensation torque calculation unit 23 obtains a compensation coefficient corresponding to the estimated position θes of the motor from the compensation information, and multiplies the obtained compensation coefficient by the smoothing torque command to calculate the compensation torque.

[0048] In the correction unit 24, the torque command is corrected by adding the compensation torque to the torque command, and in the current conversion unit 25, the q-axis current command iq is calculated using the corrected torque command. ＊ and d-axis current command id ＊ is generated.

[0049] q-axis current command iq ＊ and d-axis current command id ＊ are output to the voltage command generating unit 30, and the q-axis voltage command vq ＊ , d-axis voltage command vd ＊ is generated.

[0050] In the two-phase / three-phase conversion unit 16, the q-axis voltage command vq is calculated using the motor position θes. ＊ and d-axis voltage command vd ＊ is the three-phase voltage command vu ＊ , vv ＊ , vw ＊ This three-phase voltage command vu ＊ , vv ＊ , vw ＊ and the input DC voltage Vdc, a gate drive signal S corresponding to each phase is generated. Then, the inverter 3 is driven based on this gate drive signal S, and an output voltage according to the motor load is supplied to the motor 4.

[0051] As described above, according to this embodiment, the motor control device 1 controls the motor 4 connected to a load that generates periodic torque fluctuations, and includes an inverter 3 that converts a DC voltage into a three-phase AC voltage and outputs the voltage to the motor 4, and an inverter control unit 10 that controls the inverter 3. The inverter control unit 10 includes a motor position estimator 12 that estimates the position of the motor 4, and a current command generator 20 that generates a current command for rotating the motor 4 at a target speed. The current command generator 20 includes a speed control unit 22 that calculates a torque command for rotating the motor 4 at the target speed, a compensation torque calculator 23 that calculates a compensation torque by multiplying a compensation coefficient that varies depending on the position of the motor 4 by a smoothing torque command that smooths the torque command, a corrector 24 that corrects the torque command using the compensation torque, and a current converter 25 that generates a current command using the corrected torque command.

[0052] As described above, the motor control device 1 according to this embodiment calculates the compensation torque by multiplying a smoothed torque command obtained by smoothing the torque command by a compensation coefficient that varies depending on the position of the motor 4. Using a smoothed torque command obtained by smoothing the torque command in this manner makes it possible to obtain a stable compensation torque. By using a smoothed torque command obtained by smoothing the torque command rather than the torque command itself to generate the compensation torque, the process of generating the compensation torque can be separated from the torque command. This eliminates the need to make the response frequency of the speed control unit slower than the steady-state fluctuating frequency of the load torque, as in Patent Document 1. Instead, the speed control unit 22 can be designed to improve its response frequency by, for example, increasing the proportional gain. This improves the response speed to load fluctuations.

[0053] Although the present disclosure has been described above using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments without departing from the gist of the present disclosure, and such modifications or improvements are also included in the technical scope of the present disclosure.

[0054] [Variation 1] For example, in the current command generating unit 20 illustrated in Fig. 3, the output of the integral control unit 27 is used as the smoothing torque command, but this is not limiting. For example, as shown in Fig. 5, the current command generating unit 20a may include a smoothing processing unit 28 that smooths the torque command to calculate the smoothing torque command. For example, the smoothing processing unit 28 may include a low-pass filter and smooth the torque command using the low-pass filter. Instead of using a low-pass filter, the smoothing processing unit 28 may stabilize the value by zero-order hold synchronized with the load fluctuation period.

[0055] [Modification 2] Furthermore, by combining this embodiment with the above-described modification 1, as shown in Fig. 6, the current command generating unit 20b may input the integral torque command output from the integral control unit 27 to the smoothing processing unit 28. In this way, the integral torque command smoothed by the integral operation is further smoothed using a low-pass filter, thereby making it possible to further improve the stability of the compensation torque.

[0056] [Application Example] Fig. 7 is a diagram showing an example configuration of an air conditioner 50 to which the motor control device 1 according to this embodiment is applied. In Fig. 7, the air conditioner 50 includes a refrigerant circuit 51. The refrigerant circuit 51 mainly includes, for example, a compressor 52 that compresses and sends out a refrigerant, a condenser 54, an expansion valve 55, and an evaporator 56. The refrigerant circuit 51 is also provided with a switching valve 53 that switches the circulation direction of the refrigerant. The compressor 52 is controlled by a compressor motor 5a that is driven by the motor control device 1 according to this embodiment.

[0057] (Additional Notes) The motor control device, motor control method, and program described in the above-described embodiment can be understood, for example, as follows.

[0058] A motor control device (1) according to a first aspect of the present disclosure is a motor control device comprising an inverter (3) that converts a DC voltage into a three-phase AC voltage and outputs the voltage to a motor (4), and an inverter control unit (10) that controls the inverter, and that controls a motor connected to a load that generates periodic torque fluctuations, wherein the inverter control unit comprises a motor position estimator (12) that estimates the position of the motor, and a current command generator (20, 20a, 20b) that generates a current command for rotating the motor at a target speed, and the current command generator comprises a speed control unit (22) that calculates a torque command for rotating the motor at the target speed, a compensation torque calculator (23) that calculates a compensation torque by multiplying a compensation coefficient that varies depending on the position of the motor by a smoothing torque command that smooths the torque command, a correction unit (24) that corrects the torque command using the compensation torque, and a current conversion unit (25) that generates a current command using the corrected torque command.

[0059] According to the above aspect, the compensation torque is calculated by multiplying a smoothed torque command obtained by smoothing the torque command by a compensation coefficient that varies depending on the position of the motor. In this way, a stable compensation torque can be obtained by using a smoothed torque command obtained by smoothing the torque command. By using a smoothed torque command obtained by smoothing the torque command, the process of generating the compensation torque can be separated from the torque command. This eliminates the need to make the response frequency of the speed control unit slower than the steady-state fluctuation frequency of the load torque, as in Patent Document 1, and enables a design that improves the response frequency of the speed control unit. This makes it possible to improve the response speed to load fluctuations.

[0060] In the motor control device (1) according to the second aspect of the present disclosure, in the first aspect, the compensation torque calculation unit (23) obtains a compensation coefficient corresponding to the position of the motor from compensation information in which the compensation coefficient is set based on periodic torque fluctuations of the load, and calculates the compensation torque by multiplying the obtained compensation coefficient by the smoothing torque command.

[0061] According to the above aspect, the compensation coefficient corresponding to the position of the motor is obtained from compensation information in which the compensation coefficient is set based on the periodic torque fluctuation of the load, so that the compensation torque can be easily calculated.

[0062] In the motor control device (1) according to a third aspect of the present disclosure, in the first or second aspect, the compensation torque calculation unit (23) calculates the compensation torque using an integral torque command calculated by performing integral control on the difference between the motor rotation speed command and the motor rotation speed as the smoothing torque command.

[0063] According to the above aspect, by calculating the compensation torque using the integral torque command as the smoothing torque command, it is possible to calculate the compensation torque with a simple configuration and processing. Here, the rotation speed of the motor may be detected by a sensor, or may be estimated from the motor current or the like.

[0064] A motor control device (1) according to a fourth aspect of the present disclosure is, in the first or second aspect described above, provided with a smoothing processing unit that smooths the torque command to calculate the smoothed torque command, and the smoothing processing unit includes a low-pass filter.

[0065] According to the above aspect, it is possible to obtain a smoothing torque command with a simple configuration.

[0066] In the motor control device (1) according to the fifth aspect of the present disclosure, in the fourth aspect described above, an integral torque command calculated by performing integral control on the difference between the motor rotation speed command and the motor rotation speed is input to the smoothing processing unit.

[0067] According to the above aspect, it is possible to obtain a more stable smoothing torque command with a simple configuration. Here, the rotation speed of the motor may be detected by a sensor, or may be estimated from the motor current or the like.

[0068] A compressor (52) according to a sixth aspect of the present disclosure includes the motor control device according to any one of the first to fifth aspects, and a motor controlled by the motor control device.

[0069] According to the above aspect, by setting the compensation information so as to follow the load torque of the compressor, it is possible to reduce fluctuations in the rotation speed of the compressor.

[0070] An air conditioner (50) according to a seventh aspect of the present disclosure includes a compressor (5) including the motor control device described in any one of the first to fifth aspects and a motor controlled by the motor control device.

[0071] A motor control method according to an eighth aspect of the present disclosure is a motor control method for controlling a motor connected to a load that generates periodic torque fluctuations, wherein a computer executes a motor position estimation process that estimates the position of the motor, and a current command generation process that generates a current command for rotating the motor at a target speed, and the current command generation process includes a speed control process that calculates a torque command for rotating the motor at the target speed, a compensation torque calculation process that calculates a compensation torque by multiplying a compensation coefficient that varies depending on the motor position by a smoothed torque command that smooths the torque command, a correction process that corrects the torque command using the compensation torque, and a current conversion process that generates a current command using the corrected torque command.

[0072] A program according to a ninth aspect of the present disclosure is a program for causing a computer to execute the motor control method according to the eighth aspect.

[0073] DESCRIPTION OF SYMBOLS 1: Motor control device 2: Converter 3: Inverter 4: Motor 5: Current sensor 5a: Compressor motor 6: Voltage sensor 10: Inverter control unit 12: Motor position estimation unit 17: Gate drive signal generation unit 20: Current command generation unit 20a: Current command generation unit 20b: Current command generation unit 21: Deviation calculation unit 22: Speed ​​control unit 23: Compensation torque calculation unit 24: Correction unit 25: Current conversion unit 26: Proportional control unit 27: Integral control unit 28: Smoothing processing unit 30: Voltage command generation unit 31: Deviation calculation unit 32: Current PI control unit 50: Air conditioner 51: Refrigerant circuit 52: Compressor 53: Switching valve 54: Condenser 55: Expansion valve 56: Evaporator 60: Processing circuit 61: Processor 62: Main storage device 63: Secondary storage device 64: Communication interface 65: Bus

Claims

1. A motor control device comprising an inverter that converts DC voltage into three-phase AC voltage and outputs it to a motor, and an inverter control unit that controls the inverter, and that controls a motor connected to a load that generates periodic torque fluctuations, wherein the inverter control unit comprises: a motor position estimator that estimates the position of the motor; and a current command generator that generates a current command for rotating the motor at a target speed, and the current command generator comprises: a speed control unit that calculates a torque command for rotating the motor at the target speed; a compensation torque calculator that calculates a compensation torque by multiplying a compensation coefficient that varies depending on the motor position by a smoothed torque command that smooths the torque command; a correction unit that corrects the torque command using the compensation torque; and a current conversion unit that generates a current command using the corrected torque command.

2. The motor control device according to claim 1, wherein the compensation torque calculation unit obtains a compensation coefficient corresponding to the position of the motor from compensation information in which the compensation coefficient is set based on the periodic torque fluctuation of the load, and calculates the compensation torque by multiplying the obtained compensation coefficient by the smoothing torque command.

3. A motor control device as described in claim 1, wherein the compensation torque calculation unit calculates the compensation torque using an integral torque command calculated by performing integral control on the difference between the motor rotation speed command and the motor rotation speed as the smoothing torque command.

4. The motor control device according to claim 1, further comprising a smoothing processing unit that smooths the torque command to calculate the smoothed torque command, wherein the smoothing processing unit comprises a low-pass filter.

5. The motor control device according to claim 4, wherein the smoothing processing unit receives an integral torque command calculated by performing integral control on the difference between the motor rotation speed command and the motor rotation speed.

6. A compressor comprising: a motor control device according to any one of claims 1 to 5; and a motor controlled by the motor control device.

7. An air conditioner comprising a compressor equipped with a motor control device according to any one of claims 1 to 5 and a motor controlled by said motor control device.

8. A motor control method for controlling a motor connected to a load that generates periodic torque fluctuations, wherein a computer executes a motor position estimation process for estimating the position of the motor, and a current command generation process for generating a current command for rotating the motor at a target speed, the current command generation process including: a speed control process for calculating a torque command for rotating the motor at the target speed; a compensation torque calculation process for calculating a compensation torque by multiplying a compensation coefficient that varies depending on the motor position by a smoothed torque command that smooths the torque command; a correction process for correcting the torque command using the compensation torque; and a current conversion process for generating a current command using the corrected torque command.

9. A program for causing a computer to execute the motor control method according to claim 8.

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