Motor drive device and refrigeration cycle application device

Abstract

A motor drive device (5) comprises: an inverter (20) that converts direct current into multi-phase alternating current; and a control unit (4) that generates a switching signal for controlling the inverter (20). The control unit (4) comprises: a speed control unit (42) that controls the rotational speed of a motor (31); a flux-weakening control unit (41) that controls the magnetic flux of the motor (31); and a current control unit (43) that generates, on the basis of current commands output from the speed control unit (42) and the flux-weakening control unit (41), a voltage command that is the command value of a voltage to be applied to the motor (31). The flux-weakening control unit (41) is provided with a controller for suppressing power pulsation superimposed on the power of the motor (31).

Description

Motor drive systems and refrigeration cycle application equipment

[0001] This disclosure relates to a motor drive device for driving a motor and equipment for use in a refrigeration cycle.

[0002] As an example of a motor, a permanent magnet synchronous motor has the characteristic that the induced voltage increases as the rotational speed increases. In a permanent magnet synchronous motor, when the induced voltage induced in the stator winding reaches the voltage applied to the permanent magnet synchronous motor, it becomes impossible to increase the rotational speed. To solve this problem, a technique called "flux weakening control" is widely used, which suppresses the induced voltage by passing a negative d-axis current. By using flux weakening control, it is possible to expand the high-speed operation range. This flux weakening control includes a method called "modulation rate feedback type flux weakening control," which controls the d-axis current so that the modulation rate of the inverter remains constant, and the specific details of this method are disclosed in Patent Document 1 below.

[0003] Japanese Patent Publication No. 2006-141095

[0004] Modulation rate feedback type flux weakening control has a problem in that, depending on the operating conditions and motor parameters, the disturbance suppression performance due to flux weakening control decreases, causing pulsations in the power supplied to the motor. The power pulsations that occur at this time are low-frequency pulsations caused by flux weakening control. This type of power pulsation can cause overcurrent and overvoltage, leading to increased noise and losses.

[0005] This disclosure has been made in view of the above, and aims to provide a motor drive device that can reduce noise and loss by suppressing low-frequency pulsations caused by flux weakening control.

[0006] To solve the above-mentioned problems and achieve the objectives, the motor drive device according to this disclosure is a motor drive device for driving a motor, comprising an inverter that converts DC to multiphase AC, and a control unit that generates switching signals for controlling the inverter. The control unit comprises a speed control unit that controls the rotational speed of the motor, a flux weakening control unit that controls the magnetic flux of the motor, and a current control unit that generates a voltage command, which is a command value of the voltage to be applied to the motor based on the current command output from the speed control unit and the flux weakening control unit. The flux weakening control unit comprises a controller that suppresses power pulsations superimposed on the motor's power.

[0007] The motor drive device described herein has the effect of suppressing low-frequency pulsations caused by flux weakening control, thereby reducing the increase in noise and losses.

[0008] A block diagram showing an example configuration of a motor drive device according to Embodiment 1. A circuit diagram showing an example configuration of a DC-AC converter according to Embodiment 1. A block diagram showing an example configuration of a control unit according to Embodiment 1. A block diagram showing an example configuration of a flux weakening control unit according to Embodiment 1. A diagram used to explain the disturbance suppression performance in the flux weakening control unit according to Embodiment 1. A diagram showing an example of an operating waveform when a conventional modulation rate feedback type flux weakening control is applied. A diagram showing an example of an operating waveform when a modulation rate feedback type flux weakening control according to Embodiment 1 is applied. A block diagram showing an example configuration of a flux weakening control unit according to Embodiment 4. A block diagram showing an example configuration of a flux weakening control unit according to Embodiment 5. A diagram showing an example configuration of a refrigeration cycle application device according to Embodiment 6.

[0009] The motor drive device and refrigeration cycle application equipment according to the embodiments of this disclosure will be described in detail below with reference to the attached drawings.

[0010] Embodiment 1. Figure 1 is a block diagram showing an example configuration of a motor drive device 5 according to Embodiment 1. The motor drive device 5 comprises a power supply unit 1, a DC-AC converter 2, and a control unit 4. The motor drive device 5 is connected to a load 3 equipped with a motor 31. A typical example of the motor 31 is a synchronous motor, and a typical example of a synchronous motor is a permanent magnet synchronous motor. When the motor drive device 5 is used in an air conditioner, the load 3 is a compressor or a fan, and the motor 31 is a compressor motor or a fan motor. The load 3 is equipped with a position detection unit 32 that detects the rotation angle of the motor 31 as its phase.

[0011] Figure 2 is a circuit diagram showing an example configuration of a DC-AC converter 2 according to Embodiment 1. Figure 2 also shows a load 3 and a control unit 4 along with the DC-AC converter 2. As shown in Figure 2, the DC-AC converter 2 comprises an inverter 20, a DC bus voltage detection unit 22, and a current detection unit 23.

[0012] The inverter 20 is a voltage-type inverter equipped with switching elements 21a to 21f connected in a three-phase bridge configuration. The inverter 20 converts DC to multiphase AC by the ON and OFF operations of the switching elements 21a to 21f. The DC bus voltage detection unit 22 detects the DC bus voltage, which is the voltage between DC bus 24a and DC bus 24b. The current detection unit 23 detects the motor current supplied from the DC-AC converter 2 to the motor 31.

[0013] Although the motor 31 is a three-phase motor, the current detection unit 23 does not need to detect all of the phase currents of the three phases flowing through the motor 31. It may detect only two of the three phases and calculate or determine the current of the remaining phase from the currents of the two phases. Alternatively, the currents flowing through the switching elements 21a, 21c, and 21e, or the currents flowing through the switching elements 21b, 21d, and 21f, may be used as the three-phase currents. Or, the three-phase currents may be reconstructed or estimated from the currents flowing through the DC buses 24a and 24b.

[0014] The control unit 4 generates a switching signal 51 for controlling the inverter 20 based on the detected value of the position detection unit 32, the DC bus voltage, and the detected motor current. The switching signal 51 controls the switching elements 21a to 21f to be switched on and off, and this on / off control generates a drive voltage for the motor 31. The drive voltage for the motor 31 is applied to the motor 31, causing the motor 31 to rotate. Alternatively, the control unit 4 may use position sensorless control, which does not use the detected value of the position detection unit 32. In this case, the control unit 4 drives the motor 31 without using the detected value of the position detection unit 32.

[0015] An example of the switching elements 21a to 21f is the IGBT (Insulated Gate Bipolar Transistor) shown in the figure, but it is not limited to IGBTs. Any element can be used as the switching elements 21a to 21f as long as it is capable of switching operation. Another example of the switching elements 21a to 21f is the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

[0016] Figure 3 is a block diagram showing an example configuration of the control unit 4 according to Embodiment 1. The control unit 4 comprises a flux weakening control unit 41, a speed control unit 42, a current control unit 43, coordinate transformation units 44a and 44b, and a switching signal generation unit 45. The flux weakening control unit 41 generates a current command for controlling the magnetic flux of the motor 31. The speed control unit 42 generates a current command for controlling the rotational speed of the motor 31. The current control unit 43 generates a voltage command, which is the command value of the voltage to be applied to the motor 31, based on the current commands output from the flux weakening control unit 41 and the speed control unit 42.

[0017] Although each control unit of the control unit 4 shown in Figure 3 is shown as a control unit in a dq-axis rotating coordinate system, it may also be configured as a control unit in a γδ-axis rotating coordinate system. In this paper, we will explain using the dq axis, assuming it coincides with the γδ axis. In this paper, the γ axis and d axis are sometimes collectively referred to as the "excitation axis," and the δ axis and q axis are sometimes collectively referred to as the "torque axis."

[0018] The flux weakening control unit 41 generates a d-axis current command 46 using the DC bus voltage 52 and the dq-axis voltage command 48. The dq-axis voltage command 48 is a general term encompassing both the d-axis voltage command and the q-axis voltage command. The flux weakening control unit 41 may also generate the d-axis current command 46 using an estimated value of the DC bus voltage 52 instead of using the DC bus voltage 52.

[0019] The speed control unit 42 generates a q-axis current command 47 using the speed command 50 and the rotational speed 53. Alternatively, the speed control unit 42 may generate the q-axis current command 47 using an estimated value of the rotational speed instead of the rotational speed 53.

[0020] The coordinate transformation unit 44b generates the dq-axis current 56 using the three-phase current 54 and the electrical angular phase 55. Alternatively, the coordinate transformation unit 44b may generate the dq-axis current 56 using estimated values ​​of the three-phase current 54 and the electrical angular phase 55 without using them.

[0021] The current control unit 43 generates a dq-axis voltage command 48 using the d-axis current command 46, the q-axis current command 47, the dq-axis current 56, and the rotational speed 53. Alternatively, the current control unit 43 may generate the dq-axis voltage command 48 using an estimated value of the rotational speed 53 instead of using the rotational speed 53.

[0022] The coordinate transformation unit 44a generates a three-phase voltage command 49 using the dq-axis voltage command 48 and the electrical angular phase 55. Alternatively, the coordinate transformation unit 44a may generate the three-phase voltage command 49 using an estimated value of the electrical angular phase 55 instead of using the electrical angular phase 55 itself.

[0023] The switching signal generation unit 45 generates a switching signal 51 using a three-phase voltage command 49 and a DC bus voltage 52. Alternatively, the switching signal generation unit 45 may generate the switching signal 51 using a dq-axis voltage command 48, an electrical angular phase command 55, and a DC bus voltage 52 instead of the three-phase voltage command 49. Furthermore, the switching signal generation unit 45 may generate the switching signal 51 using estimated values ​​for at least one of the electrical angular phase command 55 and the DC bus voltage 52.

[0024] FIG. 4 is a block diagram showing a configuration example of a flux-weakening control unit 41 according to Embodiment 1. The flux-weakening control unit 41 includes a dq-axis voltage norm command generation unit 420, a first flux-weakening controller 410, a second flux-weakening controller 411, a dq-axis voltage norm calculation unit 412, and subtractors 413a and 413b. As shown in FIG. 4, input signals to the flux-weakening control unit 41 are a DC bus voltage 52 and a dq-axis voltage command 48, and an output signal of the flux-weakening control unit 41 is a d-axis current command 46.

[0025] The dq-axis voltage norm command generation unit 420 generates a dq-axis voltage norm command 415 using the DC bus voltage 52 or an estimated value of the DC bus voltage 52. The dq-axis voltage norm command 415 corresponds to a modulation factor, and the modulation factor of the inverter 20 can be controlled by adjusting the dq-axis voltage norm command 415.

[0026] The dq-axis voltage norm calculation unit 412 generates a dq-axis voltage norm 416 using the dq-axis voltage command 48. Here, let the d-axis voltage command be v ｄ and the q-axis voltage command be v ｑ , then "V" representing the dq-axis voltage norm 416 Ａｍｐ can be expressed by the following formula (1).

[0027]

[0028] The subtractor 413a generates a dq-axis voltage norm deviation 417 which is a difference between the dq-axis voltage norm command 415 output from the dq-axis voltage norm command generation unit 420 and the dq-axis voltage norm 416 output from the dq-axis voltage norm calculation unit 412, and outputs the dq-axis voltage norm deviation 417 to the first flux-weakening controller 410.

[0029] The first flux-weakening controller 410 generates a first signal serving as a basis of the d-axis current command 46 using the dq-axis voltage norm deviation 417. Hereinafter, the output of the first flux-weakening controller 410 is referred to as "first flux-weakening controller output 418".

[0030] An example of the first flux-weakening controller 410 is a PID (Proportional Integral Differential) controller. When configuring the first flux-weakening controller 410, it is sufficient to set the control gain for PID control, and the first flux-weakening controller 410 can be configured by arbitrarily combining one or more of a P (Proportional) controller, an I (Integral) controller, and a D (Differential) controller. Note that the configuration of the first flux-weakening controller 410 is not limited to PID control.

[0031] Further, the second flux-weakening controller 411 generates a second signal that is a basis for the d-axis current command 46 using the dq-axis voltage norm 416. Note that the second flux-weakening controller 411 does not use the dq-axis voltage norm 416, and instead uses the d-axis voltage command v ｄ and the q-axis voltage command v ｑ any one or at least one of the foregoing, or any one or at least one of the d-axis voltage and the q-axis voltage, to generate the second signal. Hereinafter, the output of the second flux-weakening controller 411 is referred to as "second flux-weakening controller output 419".

[0032] The subtracter 413b generates a signal representing a difference between the first flux-weakening controller output 418 that is the first signal and the second flux-weakening controller output 419 that is the second signal, and outputs the generated signal as the d-axis current command 46.

[0033] An example of the second flux-weakening controller 411 is a band-pass filter (Band Pass Filter). When the second flux-weakening controller 411 is configured as a band-pass filter, the transfer function G ＢＰＦ（ｓ） can be expressed by the following formula (2).

[0034]

[0035] In the above formula (2), K ＢＰＦ is the band-pass filter gain, ω ｒｉｐ is the angular frequency of power pulsation superimposed on the motor 31, and Q is the quality factor of the band-pass filter. Further, the angular frequency ω of the power pulsation ｒｉｐThis can be expressed by the following equation (3).

[0036]

[0037] In equation (3) above, ω ｃ L is the angular frequency of the control response in the current control unit 43. ｄ L is the d-axis inductance of motor 31. ｑ ω is the q-axis inductance of motor 31, R is the phase resistance of motor 31, and ω ｅ ω is the electrical angular velocity corresponding to the rotational speed of motor 31. Note that the angular frequency ω of the power pulsation is also shown. ｒｉｐ This can also be determined without using equation (3) above, by using at least one of the following: power, voltage, current, speed, acceleration, torque, phase, DC bus voltage 52 in the motor 31, and the pulsating voltage or current superimposed on the power supply unit 1.

[0038] Furthermore, as can be understood from equation (3) above, the pulsation component fluctuates depending on the physical quantities and control parameters of the motor 31. For this reason, the quality factor Q should be determined according to the range of fluctuation of the pulsation component.

[0039] Figure 5 is a diagram illustrating the disturbance suppression performance of the flux weakening control unit 41 according to Embodiment 1. Figure 5 shows an example of the gain characteristics of modulation rate feedback type flux weakening control, where the dashed line represents the gain characteristics of the conventional method and the solid line represents the gain characteristics of the present invention.

[0040] In the conventional method, it can be seen that the gain exceeds 0 [dB] around 100 [rad / s]. Furthermore, when the present invention method is applied, it can be seen that a reduction of 36.5 [dB] is achieved compared to the conventional method.Therefore, when the present invention method is applied as a modulation rate feedback type flux weakening control, it is possible to obtain extremely high disturbance suppression performance compared to the conventional method.

[0041] Figure 6 shows an example of an operating waveform when a conventional modulation rate feedback type flux weakening control is applied. Figure 7 also shows an example of an operating waveform when a modulation rate feedback type flux weakening control according to Embodiment 1 is applied. Figures 6 and 7 show the waveforms of rotational speed, dq-axis voltage norm, d-axis current, q-axis current, and torque, in order from the top. The horizontal axis in Figures 6 and 7 represents time.

[0042] In the case of the conventional technology, as shown in Figure 6, low-frequency pulsations occur in the rotational speed, dq-axis voltage norm, dq-axis current, and torque. As mentioned above, this type of pulsation causes overcurrent and overvoltage, leading to increased noise and losses, and therefore countermeasures are necessary. On the other hand, in the case of Embodiment 1, as shown in Figure 7, the pulsation is reduced. The reduction in pulsation is due to the extremely high disturbance suppression performance of the flux weakening control unit 41 according to Embodiment 1, as shown in Figure 5. Therefore, by applying the method of Embodiment 1, it is possible to suppress low-frequency pulsations caused by flux weakening control and reduce the increase in noise and losses.

[0043] As described above, the motor drive device according to Embodiment 1 includes an inverter that converts DC to multiphase AC and a control unit that generates switching signals for controlling the inverter. The control unit includes a speed control unit that controls the rotational speed of the motor, a flux weakening control unit that controls the magnetic flux of the motor, and a current control unit that generates a voltage command, which is a command value of the voltage applied to the motor based on the current command output from the speed control unit and the flux weakening control unit. The flux weakening control unit includes a controller that suppresses power pulsations superimposed on the motor's power. With a motor drive device configured in this way, it is possible to suppress low-frequency pulsations caused by flux weakening control and reduce the increase in noise and loss.

[0044] In the motor drive device according to Embodiment 1, the flux weakening control unit is configured to include a first flux weakening controller that generates an excitation shaft current command that matches the average value of the norm of the rotation coordinate voltage to the norm command value of the rotation coordinate voltage, and a second flux weakening controller for suppressing power pulsations superimposed on the motor power. The second flux weakening controller includes a bandpass filter, and at least one of the norm of the rotation coordinate voltage, the excitation shaft voltage, and the torque shaft voltage is input to the bandpass filter, and the output of the bandpass filter is subtracted from the output of the first flux weakening controller. With the motor drive device configured in this way, the disturbance suppression performance of the flux weakening control unit is enhanced by the second flux weakening controller, making it possible to significantly reduce power pulsations superimposed on the motor power.

[0045] Embodiment 2. Embodiment 2 describes a different configuration example of the flux weakening control unit 41 provided in the control unit 4 of the motor drive device 5 described in Embodiment 1. Components that have the same or equivalent functions as those of the motor drive device 5 and load 3 described in Embodiment 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0046] In Embodiment 2, a high-pass filter is used in the second flux weakening controller 411 provided in the flux weakening control unit 41. Even with the use of a high-pass filter, the same effects as in Embodiment 1 can be obtained. Transfer function G when the second flux weakening controller 411 is configured with a high-pass filter. ＨＰＦ（ｓ） This can be expressed by equation (4) below.

[0047]

[0048] In equation (4) above, K ＨＰＦ ω is the high-pass filter gain. ＨＰＦ is the cutoff angular frequency of the high-pass filter. High-pass filter gain K ＨＰＦ And the cutoff angular frequency ω ＨＰＦBy adjusting these, the disturbance suppression performance of the flux weakening control unit 41 can be improved. Although equation (4) above shows the transfer function of a first-order high-pass filter, the second flux weakening controller 411 may be constructed using a second-order or higher high-pass filter. Furthermore, the second flux weakening controller 411 does not use the dq-axis voltage norm 416, but uses the d-axis voltage command v ｄ and q-axis voltage command v ｑ The second flux weakening controller output 419 may be generated using any one or at least one of the following, or using either the d-axis voltage or the q-axis voltage, or at least one of them.

[0049] As described above, in the motor drive device according to Embodiment 2, the second flux weakening controller in the flux weakening control unit is equipped with a high-pass filter, and at least one of the norm of the rotation coordinate voltage, the excitation shaft voltage, and the torque shaft voltage is input to the high-pass filter, and the output of the high-pass filter is subtracted from the output of the first flux weakening controller. With the motor drive device configured in this way, it is possible to suppress low-frequency pulsations caused by flux weakening control and reduce the increase in noise and loss, and the disturbance suppression performance of the flux weakening control unit is enhanced by the second flux weakening controller, so that power pulsations superimposed on the motor power can be greatly reduced.

[0050] Embodiment 3. Embodiment 3 describes a different configuration example of the flux weakening control unit 41 provided in the control unit 4 of the motor drive device 5 described in Embodiment 1. Components that have the same or equivalent functions as those of the motor drive device 5 and load 3 described in Embodiment 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0051] In Embodiment 3, the second flux weakening controller 411 provided in the flux weakening control unit 41 is configured as a proportional controller capable of setting a proportional gain. Even with this configuration of the second flux weakening controller 411, the same effects as in Embodiment 1 can be obtained. Also, similar to Embodiment 1, the second flux weakening controller 411 does not use the dq-axis voltage norm 416, but uses the d-axis voltage command v ｄ and q-axis voltage command v ｑThe second flux weakening controller output 419 may be generated using any one or at least one of the following, or using either the d-axis voltage or the q-axis voltage, or at least one of them.

[0052] As described above, in the motor drive device according to Embodiment 3, the second flux weakening controller in the flux weakening control unit is configured to include a proportional controller capable of setting a proportional gain. At least one of the norm of the rotation coordinate voltage, the excitation shaft voltage, and the torque shaft voltage is input to the proportional controller, and the output of the proportional controller is subtracted from the output of the first flux weakening controller. With a motor drive device configured in this way, it is possible to suppress low-frequency pulsations caused by flux weakening control and reduce the increase in noise and loss. Furthermore, since the disturbance suppression performance of the flux weakening control unit is enhanced by the second flux weakening controller, it is possible to significantly reduce power pulsations superimposed on the motor power.

[0053] Embodiment 4. Embodiment 4 describes a different configuration example of the flux weakening control unit 41 provided in the control unit 4 of the motor drive device 5 described in Embodiment 1. Components having the same or equivalent functions as those of the motor drive device 5 and load 3 described in Embodiment 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0054] Figure 8 is a block diagram showing an example configuration of the flux weakening control unit 41 according to Embodiment 4. In the flux weakening control unit 41 according to Embodiment 1 shown in Figure 4, an example configuration is shown where the input to the second flux weakening controller 411 is the dq-axis voltage norm 416. However, as shown in Figure 8, the dq-axis voltage norm deviation 417 may be configured as the input to the second flux weakening controller 411. The adder 414 adds the output 418 of the first flux weakening controller and the output 419 of the second flux weakening controller. The signal added in the adder 414 is output as a d-axis current command 46.

[0055] Furthermore, in Embodiment 4, a sinusoidal tracking controller is used for the second flux weakening controller 411. An example of a sinusoidal tracking controller is an R (Resonant) controller. The R controller is a controller that improves disturbance suppression performance while improving tracking performance for a specified angular frequency. Transfer function G of the R controller Ｒ（ｓ） This can be expressed by equation (5) below.

[0056]

[0057] In equation (5) above, K Ｒ ω is the controller gain and ζ is the damping coefficient. Here, in equation (5) above, the angular frequency of the power pulsation ω is the angular frequency of the controller. ｒｉｐ By specifying this, the disturbance suppression performance is improved.

[0058] Furthermore, in Embodiment 4, the second flux weakening controller 411 may be an S (Sinusoidal) controller, which is another example of a sinusoidal tracking controller. Transfer function G of the S controller Ｓ（ｓ） This can be expressed by equation (6) or equation (7) below.

[0059]

[0060] In equations (6) and (7) above, K Ｓ This is the S control gain. Equation (6) is the transfer function obtained by Laplace transforming the cosine function, and equation (7) is the transfer function obtained by Laplace transforming the sine function. The S controller, like the R controller, is a controller that can improve disturbance suppression performance while improving tracking performance for a specified angular frequency. For this reason, even if an S controller is used instead of an R controller, it is possible to improve the disturbance suppression performance in the flux weakening control unit 41.

[0061] As described above, in the motor drive device according to Embodiment 4, the second flux weakening controller in the flux weakening control unit is configured to include a sinusoidal tracking controller. The sinusoidal tracking controller is configured to receive input for the deviation between the norm command value of the rotation coordinate voltage and the average value of the norm of the rotation coordinate voltage, so that the output of the sinusoidal tracking controller is added to the output of the first flux weakening controller. With a motor drive device configured in this way, it is possible to suppress low-frequency pulsations caused by flux weakening control and reduce the increase in noise and loss. Furthermore, since the disturbance suppression performance of the flux weakening control unit is enhanced by the second flux weakening controller, it is possible to significantly reduce power pulsations superimposed on the motor power.

[0062] Embodiment 5. Embodiment 5 describes a different configuration example of the flux weakening control unit 41 provided in the control unit 4 of the motor drive device 5 described in Embodiments 1 to 4. Components that have the same or equivalent functions as those of the motor drive device 5 and load 3 described in Embodiment 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0063] Figure 9 is a block diagram showing an example configuration of the flux weakening control unit 41 according to Embodiment 5. Comparing the configuration shown in Figure 9 with that of Figure 4, Figure 9 adds a second flux weakening controller activation determination unit 421 that takes the pulsation amount 57 as input. The second flux weakening controller activation determination unit 421 generates an activation determination signal 422 using the pulsation amount 57. The second flux weakening controller 411 determines whether or not to output the second flux weakening controller output 419 based on the activation determination signal 422.

[0064] The pulsation amount 57 is a physical quantity that represents the pulsation component that may be included in the power supplied to the motor 31, and can be determined using at least one of the following: power, voltage, current, speed, acceleration, torque, phase, DC bus voltage 52, and the pulsating voltage or current superimposed on the power supply unit 1.

[0065] The second flux weakening controller activation determination unit 421 determines the level of the activation determination signal 422 so that the output 419 of the second flux weakening controller is output from the second flux weakening controller 411 if the pulsation amount 57 exceeds a specified value. Also, the second flux weakening controller activation determination unit 421 determines the level of the activation determination signal 422 so that the output 419 of the second flux weakening controller is not output from the second flux weakening controller 411, that is, so that flux weakening control is performed only by the first flux weakening controller 410, if the pulsation amount 57 is less than or equal to the specified value.

[0066] The second flux weakening controller output 419 is a damping signal to enhance the disturbance suppression performance of the flux weakening control unit 41. When the damping signal is output, the losses in the motor drive unit 5 increase somewhat compared to when the damping signal is not output. In the motor drive unit 5 according to Embodiment 5, the second flux weakening controller output 419 is output to the subtractor 413b only when truly necessary. This makes it possible to reduce losses in the motor drive unit 5 while enhancing the disturbance suppression performance of the flux weakening control unit 41.

[0067] Figure 9 is an example of the case where the input to the second flux weakening controller 411 is the dq-axis voltage norm 416, and as explained in Embodiment 1, the input to the second flux weakening controller 411 is the d-axis voltage command v ｄ and q-axis voltage command v ｑ It may be any one of these, or at least one, or either the d-axis voltage and the q-axis voltage, or at least one. Also, as described in Embodiment 4, the input to the second flux weakening controller 411 may be the dq-axis voltage norm deviation 417.

[0068] As described above, the motor drive device according to Embodiment 5 is configured such that, in the motor drive devices according to Embodiments 1 to 4, when the amount of power pulsation in the motor is below a specified value, flux weakening control is performed only by the first flux weakening controller. With a motor drive device configured in this way, a damping signal is output from the second flux weakening controller only when truly necessary, making it possible to reduce losses in the motor drive device while improving the disturbance suppression performance of the flux weakening control unit.

[0069] Embodiment 6. Figure 10 shows an example of the configuration of a refrigeration cycle application device 900 according to Embodiment 6. The refrigeration cycle application device 900 according to Embodiment 6 includes a motor drive device 5 as described in Embodiments 1 to 5. The refrigeration cycle application device 900 according to Embodiment 6 can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters.

[0070] The refrigeration cycle equipment 900 includes a compressor 33 with a built-in motor 31 as in Embodiments 1 to 5, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, all connected via refrigerant piping 912. Inside the compressor 33 are a compression mechanism 904 for compressing the refrigerant and a motor 31 for operating the compression mechanism 904. The refrigeration cycle equipment 900 can operate in heating or cooling mode by switching the four-way valve 902.

[0071] The compression mechanism 904 is driven by a motor 31 with variable speed control. During heating operation, as shown by the solid arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, returning to the compression mechanism 904 through the four-way valve 902, indoor heat exchanger 906, expansion valve 908, outdoor heat exchanger 910, and four-way valve 902. During cooling operation, as shown by the dashed arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, returning to the compression mechanism 904 through the four-way valve 902, outdoor heat exchanger 910, expansion valve 908, indoor heat exchanger 906, and four-way valve 902. During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 depressurizes the refrigerant and causes it to expand.

[0072] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. For example, the control method described above can also be applied to DC-AC converters.

[0073] 1 Power supply unit, 2 DC-AC converter, 3 Load, 4 Control unit, 5 Motor drive unit, 20 Inverter, 21a, 21b, 21c, 21d, 21e, 21f Switching elements, 22 DC bus voltage detection unit, 23 Current detection unit, 24a, 24b DC bus, 31 Motor, 32 Position detection unit, 33 Compressor, 41 Magnetic flux weakening control unit, 42 Speed ​​control unit, 43 Current control unit, 44a, 44b Coordinate transformation unit, 45 Switching signal generation unit, 46 d-axis current command, 47 q-axis current command, 48 dq-axis voltage command, 49 3-phase voltage command, 50 Speed ​​command, 51 Switching signal, 52 DC bus voltage, 53 Rotational speed, 54 3-phase current, 55 Electrical angle phase, 56 dq-axis current, 57 Pulsation amount, 410 411 First flux weakening controller, 412 Second flux weakening controller, 413a, 413b DQ-axis voltage norm calculation unit, 413a, 413b Subtractor, 414 Adder, 415 DQ-axis voltage norm command, 416 DQ-axis voltage norm, 417 DQ-axis voltage norm deviation, 418 Output of first flux weakening controller, 419 Output of second flux weakening controller, 420 DQ-axis voltage norm command generation unit, 421 Second flux weakening controller activation determination unit, 422 Activation determination signal, 900 Refrigeration cycle application equipment, 902 Four-way valve, 904 Compression mechanism, 906 Indoor heat exchanger, 908 Expansion valve, 910 Outdoor heat exchanger, 912 Refrigerant piping.

Claims

1. A motor drive device for driving a motor, comprising: an inverter that converts direct current to multiphase alternating current; and a control unit that generates switching signals for controlling the inverter, wherein the control unit comprises: a speed control unit that controls the rotational speed of the motor; a flux weakening control unit that controls the magnetic flux of the motor; and a current control unit that generates a voltage command which is a command value of the voltage to be applied to the motor based on the current command output from the speed control unit and the flux weakening control unit, wherein the flux weakening control unit comprises a controller that suppresses power pulsations superimposed on the power of the motor.

2. The motor drive device according to claim 1, wherein the flux weakening control unit comprises a first flux weakening controller that generates an excitation shaft current command that matches the average value of the norm of the rotation coordinate voltage to the norm command value of the rotation coordinate voltage, and a second flux weakening controller for suppressing power pulsation, wherein the second flux weakening controller comprises a bandpass filter, and at least one of the norm of the rotation coordinate voltage, the excitation shaft voltage, and the torque shaft voltage is input to the bandpass filter, and the output of the bandpass filter is subtracted from the output of the first flux weakening controller.

3. The motor drive device according to claim 1 or 2, characterized in that the angular frequency of the power pulsation is determined by the inductance, phase resistance, and rotational speed of the motor, and the angular frequency of the control response in the current control unit.

4. The motor drive device according to claim 1, wherein the flux weakening control unit comprises a first flux weakening controller that generates an excitation shaft current command that matches the average value of the norm of the rotation coordinate voltage to the norm command value of the rotation coordinate voltage, and a second flux weakening controller for suppressing power pulsation, wherein the second flux weakening controller comprises a high-pass filter, at least one of the norm of the rotation coordinate voltage, the excitation shaft voltage, and the torque shaft voltage is input to the high-pass filter, and the output of the high-pass filter is subtracted from the output of the first flux weakening controller.

5. The motor drive device according to claim 1, wherein the flux weakening control unit comprises a first flux weakening controller that generates an excitation shaft current command that matches the average value of the norm of the rotation coordinate voltage to the norm command value of the rotation coordinate voltage, and a second flux weakening controller for suppressing power pulsation, wherein the second flux weakening controller is configured to include a proportional controller capable of setting a proportional gain, and at least one of the norm of the rotation coordinate voltage, the excitation shaft voltage, and the torque shaft voltage is input to the proportional controller, and the output of the proportional controller is subtracted from the output of the first flux weakening controller.

6. The motor drive device according to claim 1, wherein the flux weakening control unit comprises a first flux weakening controller that generates an excitation shaft current command that matches the average value of the norm of the rotation coordinate voltage to the norm command value of the rotation coordinate voltage, and a second flux weakening controller for suppressing power pulsation, wherein the second flux weakening controller is configured to include a sine wave tracking controller, and the sine wave tracking controller receives input for the deviation between the norm command value of the rotation coordinate voltage and the average value of the norm of the rotation coordinate voltage, and the output of the sine wave tracking controller is added to the output of the first flux weakening controller.

7. A motor drive device according to any one of claims 1 to 6, characterized in that when the amount of power pulsation in the motor is less than or equal to a specified value, flux weakening control is performed using only the first flux weakening controller.

8. The motor drive device according to any one of claims 1 to 7, characterized in that the motor is a synchronous motor.

9. The motor drive device according to claim 8, characterized in that the synchronous motor is a permanent magnet synchronous motor.

10. A refrigeration cycle application device comprising a motor drive device according to any one of claims 1 to 9.

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