Power conversion device, electric motor drive device, and refrigeration cycle application device

Abstract

A power conversion device (300) comprises: a converter (3) that rectifies power supply voltage applied from an AC power supply (1); a capacitor (5) that is connected to an output end of the converter (3); an inverter (30) that is connected to both ends of the capacitor (5); and a control device (10) that controls an operation of the inverter (30) to perform a vibration suppression control for suppressing a load vibration. The control device (10) calculates a d-axis current command (id *) used in flux weakening control, on the basis of a voltage saturation amount (ΔV) calculated from a voltage limit value determined by a DC voltage value applied to the inverter (30) and a voltage command applied to the inverter (30). The voltage saturation amount (ΔV) is divided into a DC component and an AC component, and the d-axis current command (id *) is generated on the basis of an excitation current command (id *_FB1) calculated on the basis of the DC component and another excitation current command (id *_FB2) calculated on the basis of the AC component.

Description

Power conversion devices, electric motor drive devices, and refrigeration cycle application devices

[0001] The present disclosure relates to a power conversion device that performs power conversion, and an electric motor drive device and a refrigeration cycle application device that are provided with the power conversion device.

[0002] Many power conversion devices are connected to machinery that experiences periodic fluctuations in load torque, i.e., periodic load torque pulsation. Power conversion devices have traditionally used control to suppress this type of load torque pulsation. Load torque pulsation can cause vibrations and noise in machinery connected to the power conversion device and in the electric motors that power the machinery. For this reason, control that compensates for load torque pulsation is also called "vibration suppression control."

[0003] Furthermore, in power conversion devices, a control called "overmodulation control" is performed to increase the voltage utilization rate of the inverter. The overmodulation region in which overmodulation control is performed is a region in which the relationship between a voltage command and the inverter output voltage, which is the output voltage of the inverter, is nonlinear and not proportional. Patent Document 1 listed below discloses a technology for performing vibration suppression control in the overmodulation region while suppressing a decrease in efficiency.

[0004] Furthermore, power conversion devices also perform a control called "flux-weakening control," which controls the d-axis current to reduce the apparent magnetic flux even during overmodulation, thereby enabling the motor to rotate even when the rotation speed or torque is high.

[0005] International Publication No. 2020 / 234971

[0006] Flux-weakening control is also effective in suppressing transient voltage saturation that can occur when vibration suppression control is performed. However, because the controller for flux-weakening control is configured as an outer loop of current control, considering control stability, it can only be designed to have a response speed that is about 1 / 10 of the response speed of current control. In other words, conventional flux-weakening control required a response speed that was about 10 times slower than the current control response. Therefore, simply combining conventional vibration suppression control and conventional flux-weakening control posed the problem of a slow control response of flux-weakening control, making it impossible to perform sufficient flux-weakening control in the overmodulation region.

[0007] The present disclosure has been made in consideration of the above, and aims to provide a power conversion device that can perform sufficient flux-weakening control in the overmodulation region even when vibration suppression control and flux-weakening control are combined.

[0008] To solve the above-mentioned problems and achieve the object, a power conversion apparatus according to the present disclosure is a power conversion apparatus that supplies AC power to an electric motor that drives a load. The power conversion apparatus includes a converter that rectifies a power supply voltage applied from an AC power supply, a capacitor connected to an output terminal of the converter, an inverter connected across the capacitor, and a control device that performs vibration suppression control that controls the operation of the inverter to suppress vibration of the load. The control device calculates an excitation current command used in flux-weakening control based on a voltage saturation amount calculated from a voltage limit value determined by a DC voltage value applied to the inverter and a voltage command to be applied to the inverter. The voltage saturation amount is divided into a DC component and an AC component, and the excitation current command is generated based on a first excitation current command calculated based on the DC component and a second excitation current command calculated based on the AC component.

[0009] According to the power conversion device according to the present disclosure, even when vibration suppression control and flux-weakening control are combined, it is possible to achieve sufficient flux-weakening control in the overmodulation region.

[0010] FIG. 10 is a block diagram showing an example of the configuration of a control device provided in the power conversion device according to embodiment 1; FIG. 11 is a diagram showing the relationship between a command modulation factor and an actual modulation factor in a general inverter; FIG. 12 is a diagram used to explain a modulation factor correction method, which is a method for obtaining the characteristics shown in FIG. 4; FIG. 13 is a block diagram showing an example of the configuration of a voltage command calculation unit provided in the control device according to embodiment 1; 9 is a flowchart illustrating a procedure for setting a limiter value set in the control unit; FIG. 10 is a diagram illustrating changes in various torques, command values ​​and operation values ​​of various currents, command values ​​and operation values ​​of various voltages, and command modulation factor and actual modulation factor when the excitation current command control unit shown in FIG. 9 is provided with only an FB flux-weakening control unit without a FB auxiliary type flux-weakening control unit; FIG. 11 is a diagram illustrating changes in various torques, command values ​​and operation values ​​of various currents, command values ​​and operation values ​​of various voltages, and command modulation factor and actual modulation factor when the excitation current command control unit shown in FIG. 9 is provided with both an FB auxiliary type flux-weakening control unit and an FB flux-weakening control unit; FIG. 12 is a diagram illustrating an example of a hardware configuration for realizing a control device provided in a power conversion device according to embodiment 1;

[0011] Hereinafter, a power conversion device, an electric motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0012] First Embodiment. Fig. 1 is a diagram illustrating a configuration example of a power conversion device 300 according to a first embodiment. Fig. 2 is a diagram illustrating a configuration example of an inverter 30 included in the power conversion device 300 according to the first embodiment. The power conversion device 300 is connected to an AC power source 1 and a compressor 50. The compressor 50 is an example of a load having a characteristic in which the load torque fluctuates periodically when driven. The compressor 50 includes an electric motor 7. An example of the electric motor 7 is a three-phase permanent magnet synchronous motor. The power conversion device 300 converts a power supply voltage applied from the AC power source 1 into an AC voltage having a desired amplitude and phase and applies the AC voltage to the electric motor 7. The power conversion device 300 includes a reactor 2, a converter 3, a capacitor 5, a voltage detection unit 8, a control device 10, an inverter 30, and a current detection unit 40. The power conversion device 300 and the electric motor 7 included in the compressor 50 form an electric motor drive device 400.

[0013] Converter 3 includes four diodes D1, D2, D3, and D4. The four diodes D1 to D4 are bridge-connected to form a rectifier circuit. Converter 3 rectifies the power supply voltage applied from AC power supply 1 using the rectifier circuit formed by the four diodes D1 to D4. One end of the input side of converter 3 is connected to AC power supply 1 via reactor 2, and the other end of the input side is also connected to AC power supply 1. In addition, converter 3 has an output side connected to capacitor 5.

[0014] The converter 3 may have a boost function for boosting the rectified voltage in addition to the rectification function. A converter with a boost function may be configured with one or more transistor elements, or one or more switching elements in which a transistor element and a diode are connected in anti-parallel, in addition to or instead of a diode. The arrangement and connection of the transistor elements or switching elements in a converter with a boost function are well known, and therefore will not be described here.

[0015] The capacitor 5 is connected to the output terminal of the converter 3 via DC buses 9a and 9b. The DC bus 9a is a positive DC bus, and the DC bus 9b is a negative DC bus. The capacitor 5 smoothes the rectified voltage applied from the converter 3. Examples of the capacitor 5 include an electrolytic capacitor and a film capacitor.

[0016] The inverter 30 is connected to both ends of the capacitor 5 via the DC buses 9a and 9b. The inverter 30 converts the DC voltage smoothed by the capacitor 5 into an AC voltage for the compressor 50 and applies it to the motor 7 of the compressor 50. The voltage applied to the motor 7 is a three-phase AC voltage whose frequency and voltage value are variable.

[0017] 2, the inverter 30 includes an inverter main circuit 310 and a drive circuit 350. The inverter main circuit 310 includes switching elements 311 to 316. Freewheeling rectifying elements 321 to 326 are connected in anti-parallel to the switching elements 311 to 316, respectively.

[0018] In the inverter main circuit 310, the switching elements 311 to 316 are assumed to be IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), etc., but any elements capable of switching may be used. Note that if the switching elements 311 to 316 are MOSFETs, the same effect can be obtained without connecting the freewheeling rectifier elements 321 to 326 in anti-parallel because MOSFETs have parasitic diodes due to their structure.

[0019] Furthermore, the material forming the switching elements 311 to 316 is not limited to silicon (Si), and wide bandgap semiconductors such as silicon carbide (SiC), gallium nitride (GaN), diamond, etc. Forming the switching elements 311 to 316 using wide bandgap semiconductors can further reduce loss.

[0020] The drive circuit 350 generates drive signals Sr1 to Sr6 based on PWM (Pulse Width Modulation) signals Sm1 to Sm6 output from the control device 10. The drive circuit 350 controls the on / off of the switching elements 311 to 316 using the drive signals Sr1 to Sr6. This enables the inverter 30 to apply a variable frequency and variable voltage three-phase AC voltage to the electric motor 7 via the output lines 331 to 333.

[0021] The PWM signals Sm1 to Sm6 are signals having a signal level of a logic circuit, for example, a magnitude of 0 V to 5 V. The PWM signals Sm1 to Sm6 are signals with the ground potential of the control device 10 as a reference potential. On the other hand, the drive signals Sr1 to Sr6 are signals having a voltage level required to control the switching elements 311 to 316, for example, a magnitude of −15 V to +15 V. The drive signals Sr1 to Sr6 are signals with the potential of the negative terminal, i.e., the emitter terminal, of the corresponding switching element as a reference potential.

[0022] The voltage detection unit 8 detects the bus voltage Vdc by detecting the voltage across the capacitor 5. The bus voltage Vdc is the voltage between the DC buses 9a and 9b. The voltage detection unit 8 includes, for example, a voltage divider circuit that divides the voltage using resistors connected in series. The voltage detection unit 8 converts the detected bus voltage Vdc using the voltage divider circuit to a voltage suitable for processing in the control device 10, for example, a voltage of 5 V or less, and outputs the voltage detection signal, which is an analog signal, to the control device 10. The voltage detection signal output from the voltage detection unit 8 to the control device 10 is converted from an analog signal to a digital signal by an AD (Analog to Digital) converter (not shown) within the control device 10 and is used for internal processing in the control device 10.

[0023] The current detection unit 40 includes a shunt resistor inserted in the DC bus 9b. The current detection unit 40 detects the capacitor output current i.d.c. using the shunt resistor. The capacitor output current i.d.c. is the input current to the inverter 30, i.e., the current output from the capacitor 5 to the inverter 30. The current detection unit 40 outputs the detected capacitor output current i.d.c. to the control device 10 as a current detection signal, which is an analog signal. The current detection signal output from the current detection unit 40 to the control device 10 is converted from an analog signal to a digital signal by an AD conversion unit (not shown) within the control device 10 and is used for internal processing in the control device 10.

[0024] The control device 10 generates the above-mentioned PWM signals Sm1 to Sm6 to control the operation of the inverter 30. Specifically, the control device 10 changes the angular frequency ωe and voltage value of the inverter output voltage based on the PWM signals Sm1 to Sm6.

[0025] The angular frequency ωe of the inverter output voltage determines the rotational angular velocity of the electric motor 7 in terms of electrical angle. In this paper, this rotational angular velocity will also be represented by the same symbol ωe. The rotational angular velocity ωm of the electric motor 7 in terms of mechanical angle is equal to the rotational angular velocity ωe of the electric motor 7 divided by the number of pole pairs P. Therefore, there is a relationship expressed by the following equation (1) between the rotational angular velocity ωm of the electric motor 7 in terms of mechanical angle and the angular frequency ωe of the inverter output voltage. In this paper, the rotational angular velocity will sometimes be simply referred to as the "rotational speed" and the angular frequency will sometimes be simply referred to as the "frequency."

[0026] ωm=ωe / P…(1)

[0027] Next, a description will be given of the control device 10. Fig. 3 is a block diagram showing an example of the configuration of the control device 10 provided in the power conversion device 300 according to embodiment 1. The control device 10 includes an operation control unit 11 and an inverter control unit 12.

[0028] The operation control unit 11 receives command information Qe from the outside and generates a frequency command ωe* based on this command information Qe. The frequency command ωe* can be calculated by multiplying the rotation speed command ωm*, which is a command for the rotation speed of the electric motor 7, by the number of pole pairs P, as shown in the following equation (2).

[0029] ωe*=ωm*×P…(2)

[0030] When controlling an air conditioner as a refrigeration cycle-applied device, the control device 10 controls the operation of each part of the air conditioner based on command information Qe. The command information Qe is, for example, a temperature detected by a temperature sensor (not shown), information indicating a set temperature instructed from a remote control (not shown), which is an operation unit, information on the selection of an operation mode, and instruction information for starting and stopping operation. The operation mode is, for example, heating, cooling, dehumidification, etc. The operation control unit 11 may be located outside the control device 10. In other words, the control device 10 may be configured to obtain a frequency command ωe* from an external device.

[0031] The inverter control unit 12 includes a voltage command calculation unit 13, an electrical angle phase calculation unit 14, a space vector modulation unit 15, a PWM signal generation unit 16, a current restoration unit 17, a coordinate conversion unit 18, an excitation current command control unit 19, and a vibration suppression control unit 55.

[0032] The current restoration unit 17 restores the phase currents iu, iv, and iw flowing through the motor 7 based on the capacitor output current idc detected by the current detection unit 40, and inputs the restored phase currents to the coordinate conversion unit 18. The current restoration unit 17 can restore the phase currents iu, iv, and iw by sampling the detected value of the capacitor output current idc detected by the current detection unit 40 at timing determined based on the PWM signals Sm1 to Sm6 generated by the PWM signal generation unit 16. Note that current detectors may be provided on the output lines 331 to 333 to directly detect the phase currents iu, iv, and iw and input them to the coordinate conversion unit 18. In this configuration, the current restoration unit 17 is not necessary.

[0033] The coordinate conversion unit 18 converts the phase currents iu, iv, iw restored by the current restoration unit 17 into a d-axis current id, which is an excitation current, and a q-axis current iq, which is a torque current, i.e., into current values ​​on the d- and q-axes, using the electrical angle phase θe generated by the electrical angle phase calculation unit 14, which will be described later.

[0034] The excitation current command control unit 19 generates a d-axis current command id*, which is an excitation current command, based on the q-axis current iq obtained from the coordinate conversion unit 18, the command modulation factor M obtained from the operation control unit 11, and the d-axis voltage command Vd** and q-axis voltage command Vq** calculated by the voltage command calculation unit 13 (described later). The excitation current command control unit 19 calculates a current phase angle at which the output torque of the electric motor 7 is equal to or greater than a set value or at its maximum value, and calculates the d-axis current command id* based on the calculated current phase angle. When calculating the d-axis current command id*, the excitation current command control unit 19 performs flux-weakening control and command modulation factor correction to determine the d-axis current command id*. The specific configuration and operation of the excitation current command control unit 19 will be described later. The excitation current command control unit 19 may calculate the d-axis current command id* using the motor current flowing through the electric motor 7 instead of the output torque of the electric motor 7. In this case, the d-axis current command id* is calculated based on the current phase angle at which the motor current flowing through the motor 7 is equal to or less than the set value or is at the minimum value.

[0035] The vibration suppression control unit 55 generates a q-axis current compensation value iq_trq* for vibration suppression control based on the frequency estimated value ωest acquired from the voltage command calculation unit 13, which will be described later. Specifically, the vibration suppression control unit 55 generates the q-axis current compensation value iq_trq* so that the output torque of the electric motor 7 follows the periodic fluctuations in the load torque of the compressor 50. The q-axis current compensation value iq_trq* is a compensation value for the q-axis current command iq*. The q-axis current command iq* is a torque current command, and is generated by a speed controller 131, which will be described later.

[0036] The voltage command calculation unit 13 generates a d-axis voltage command Vd**, a q-axis voltage command Vq**, a frequency estimate ωest, a command modulation factor M*, and a voltage phase θv based on the frequency command ωe* obtained from the operation control unit 11, the d-axis current id and q-axis current iq obtained from the coordinate conversion unit 18, the d-axis current command id* obtained from the excitation current command control unit 19, and the q-axis current compensation value iq_trq* obtained from the vibration suppression control unit 55. The command modulation factor M* and the voltage phase θv are used in the space vector modulation unit 15, the d-axis voltage command Vd** and the q-axis voltage command Vq** are used in the excitation current command control unit 19, and the frequency estimate ωest is used inside the electrical angle phase calculation unit 14, the vibration suppression control unit 55, and the voltage command calculation unit 13. In this paper, when distinguishing between the command modulation factor M acquired from the operation control unit 11 and the command modulation factor M* calculated by the voltage command calculation unit 13 without signs, the former will be called the "first command modulation factor" and the latter will be called the "second command modulation factor."

[0037] The electrical angle phase calculation unit 14 calculates the electrical angle phase θe by integrating the frequency estimate value ωest obtained from the voltage command calculation unit 13 .

[0038] The space vector modulation unit 15 generates three-phase voltage commands Vu*, Vv*, and Vw*, which are output voltage commands in a three-phase coordinate system, using the command modulation factor M* and voltage phase θv obtained from the voltage command calculation unit 13, and the electrical angle phase θe obtained from the electrical angle phase calculation unit 14.

[0039] The PWM signal generation unit 16 generates PWM signals Sm1 to Sm6 based on the three-phase voltage commands Vu*, Vv*, and Vw* obtained from the space vector modulation unit 15. Space vector modulation is a modulation method that combines six basic space vectors and two zero vectors to generate voltage vectors of any magnitude at any position in a hexagon and in a vector space within the hexagon. For each PWM modulation cycle, the PWM signal generation unit 16 uses the switching pattern of two adjacent space vectors during a specified period and the zero vector during the remaining period to generate PWM signals Sm1 to Sm6 whose switching patterns and pulse on times are controlled, and outputs the PWM signals to the inverter 30.

[0040] As described above, in a power conversion device, overmodulation control is performed to increase the voltage utilization rate of the inverter. FIG. 4 is a diagram showing the relationship between the command modulation rate and the actual modulation rate in a typical inverter. In FIG. 4, the region where the command modulation rate shown on the horizontal axis exceeds 1 is the overmodulation region. The command modulation rate is a value indicating the ratio of the voltage command amplitude in the voltage command given to the inverter 30 to the DC voltage value applied to the inverter 30. The actual modulation rate shown on the vertical axis is a value indicating the ratio of the inverter output voltage to the DC voltage value. As shown in FIG. 4, the relationship between the command modulation rate and the actual modulation rate is a nonlinear characteristic.

[0041] 5 is a diagram illustrating a modulation factor correction method, which is a technique for obtaining the characteristics shown in FIG. 4. The overmodulation region is a nonlinear region in which the voltage command and the inverter output voltage are not proportional. Therefore, in this overmodulation region, as shown in FIG. 5, control is performed to obtain the intended inverter output voltage by multiplying the actual modulation factor by a nonlinear modulation factor correction coefficient according to the value of the actual modulation factor.

[0042] 6 is a block diagram showing an example of the configuration of voltage command calculation unit 13 included in control device 10 according to embodiment 1. Voltage command calculation unit 13 includes adders 130, 132, 133, and 139, a speed controller 131, a d-axis current controller 134, a q-axis current controller 135, a frequency estimator 136, a voltage command amplitude calculator 137, a modulation factor correction coefficient calculator 138, and a command modulation factor and voltage phase calculator 140.

[0043] The frequency estimator 136 estimates the frequency of the voltage applied to the motor 7 based on the d-axis current id, the q-axis current iq, the d-axis voltage command Vd*, and the q-axis voltage command Vq*, and outputs the frequency estimated value ωest. Note that the frequency estimated value ωest output from the frequency estimator 136 to the outside of the voltage command calculator 13 in Fig. 6 is the frequency estimated value ωest output from the voltage command calculator 13 to the electrical angle phase calculator 14 in Fig. 3. The adder / subtractor 130 subtracts the frequency estimated value ωest from the frequency command ωe*, and outputs a frequency deviation del_ω between the frequency command ωe* and the frequency estimated value ωest.

[0044] The speed controller 131 calculates and outputs a q-axis current command iq* based on the frequency deviation del_ω. The q-axis current command iq* is a command value of the q-axis current iq that makes the frequency deviation del_ω zero, that is, a command value of the q-axis current iq that makes the frequency command ωe* coincide with the frequency estimated value ωest. An example of the speed controller 131 is a proportional-integral (PI) controller, but is not limited to this example.

[0045] The adder-subtractor 132 subtracts the d-axis current id from the d-axis current command id* and outputs the deviation (id*-id) between the d-axis current command id* and the d-axis current id. The d-axis current controller 134 performs PI control to converge the deviation (id*-id) between the d-axis current command id* and the d-axis current id to zero. During this PI control, the d-axis current controller 134 may perform reduction control to reduce pulsating components generated by the dead time of the switching elements 311-316 of the inverter 30 and the induced voltage distortion of the motor 7, or may perform decoupling control to suppress mutual interference with the d-axis due to the q-axis current command iq*. The d-axis current controller 134 outputs a d-axis voltage command Vd* using PI control.

[0046] The adder-subtractor 133 adds the q-axis current command iq* and the q-axis current compensation value iq_trq* obtained from the vibration suppression control unit 55, i.e., superimposes the q-axis current compensation value iq_trq* on the q-axis current command iq* to generate the q-axis current command iq**. The adder-subtractor 139 subtracts the q-axis current iq from the q-axis current command iq** and outputs the deviation (iq**-iq) between the q-axis current command iq** and the q-axis current iq. The q-axis current controller 135 performs PI control to converge the deviation (iq**-iq) between the q-axis current command iq** and the q-axis current iq to zero. During this PI control, the q-axis current controller 135 may perform reduction control to reduce pulsating components generated due to the dead time of the switching elements 311 to 316 provided in the inverter 30 and the influence of induced voltage distortion of the motor 7, or may perform non-interference control to suppress mutual interference with the q-axis due to the d-axis current command id*. The q-axis current controller 135 outputs a q-axis voltage command Vq* by PI control.

[0047] The voltage command amplitude calculation unit 137 calculates a voltage command amplitude Vdq*_abs shown in the following equation (3) using the d-axis voltage command Vd* and the q-axis voltage command Vq*.

[0048] Vdq*_abs=√(Vd* ２ +Vq* ２ ) … (3)

[0049] The voltage command amplitude Vdq*_abs calculated by the voltage command amplitude calculation unit 137 is divided by a value obtained by multiplying the bus voltage Vdc by 1 / √2, and the result is input to the modulation factor correction coefficient calculation unit 138 .

[0050] The modulation factor correction coefficient calculation unit 138 calculates a modulation factor correction coefficient K using the voltage command amplitude Vdq*_abs. The modulation factor correction coefficient calculation unit 138 holds a table of characteristics such as those shown in FIG. 5 . The modulation factor correction coefficient calculation unit 138 recognizes an input value as a command modulation factor, and when the input value is 1 or less, sets the value of the modulation factor correction coefficient K by which the command modulation factor is multiplied to "1.0." When the voltage command amplitude Vdq*_abs exceeds 1, the modulation factor correction coefficient calculation unit 138 sets and outputs the corresponding value of the modulation factor correction coefficient K. Note that the means for realizing the modulation factor correction coefficient calculation unit 138 does not have to be a table. For example, the modulation factor correction coefficient calculation unit 138 may be configured to determine the value of the modulation factor correction coefficient K corresponding to the command modulation factor by calculation processing.

[0051] Inside the voltage command calculation unit 13, the d-axis voltage command Vd* is multiplied by the modulation factor correction coefficient K, and the multiplied value is output as the d-axis voltage command Vd**. Similarly, inside the voltage command calculation unit 13, the q-axis voltage command Vq* is multiplied by the modulation factor correction coefficient K, and the multiplied value is output as the q-axis voltage command Vq**. In this paper, when the d-axis voltage command Vd* before being multiplied by the modulation factor correction coefficient K and the d-axis voltage command Vd** after being multiplied by the modulation factor correction coefficient K are distinguished without signs, the former will be referred to as the "first d-axis voltage command" and the latter will be referred to as the "second d-axis voltage command." Similarly, when the q-axis voltage command Vq* before being multiplied by the modulation factor correction coefficient K and the q-axis voltage command Vq** after being multiplied by the modulation factor correction coefficient K are distinguished without signs, the former will be referred to as the "first q-axis voltage command" and the latter will be referred to as the "second q-axis voltage command."

[0052] The d-axis voltage command Vd** and the q-axis voltage command Vq** calculated by the voltage command calculation unit 13 are output to a command modulation factor and voltage phase calculation unit 140 inside the voltage command calculation unit 13. Furthermore, the d-axis voltage command Vd** and the q-axis voltage command Vq** calculated by the voltage command calculation unit 13 are output to an excitation current command control unit 19 shown in FIG.

[0053] 7 is a block diagram showing an example of the configuration of command modulation factor and voltage phase calculation unit 140 included in voltage command calculation unit 13 according to embodiment 1. Command modulation factor and voltage phase calculation unit 140 includes command modulation factor calculation unit 141 and voltage phase calculation unit 144. Furthermore, command modulation factor calculation unit 141 includes voltage command amplitude calculation unit 142.

[0054] A d-axis voltage command Vd**, a q-axis voltage command Vq**, and a bus voltage Vdc are input to the command modulation factor calculation unit 141. A voltage command amplitude calculation unit 142 uses the d-axis voltage command Vd** and the q-axis voltage command Vq** to calculate a voltage command amplitude Vdq**_abs shown in the following equation (4).

[0055] Vdq**_abs=√(Vd** ２ +Vq** ２ ) … (4)

[0056] The voltage command amplitude Vdq**_abs calculated by the voltage command amplitude calculation unit 142 is divided by a value obtained by multiplying the bus voltage Vdc by 1 / √2, and the result is output as a command modulation factor M*.

[0057] Furthermore, the voltage phase calculation unit 144 calculates the voltage phase θv shown in the following equation (5) using the d-axis voltage command Vd** and the q-axis voltage command Vq**.

[0058] θv = tan －１ (Vd** / Vq**)…(5)

[0059] As described above, the command modulation factor M* and voltage phase θv calculated by the command modulation factor and voltage phase calculation unit 140 are used in the space vector modulation unit 15 .

[0060] 8 is a block diagram showing an example of the configuration of vibration suppression control unit 55 included in inverter control unit 12 according to Embodiment 1. Vibration suppression control unit 55 includes a calculation unit 550, a cosine calculation unit 551, a sine calculation unit 552, multiplication units 553, 554, 561, and 562, low-pass filters 555 and 556, adders and subtractors 557, 558, and 563, and frequency control units 559 and 560.

[0061] When the compressor 50 is a single rotary compressor, a scroll compressor, or the like, a load torque pulsation occurs in the compressor 50 once per mechanical angle cycle. Due to this load torque pulsation, the most dominant frequency component among the pulsation components contained in the capacitor output current i.dc is the 1x component of the mechanical frequency, which is the operating frequency of the electric motor 7. Hereinafter, for simplicity's sake, the nx component of the mechanical frequency will be referred to as "mechanical nf." For example, the 1x component of the mechanical frequency would be "mechanical 1f." Note that n is an integer equal to or greater than 1. Furthermore, in the capacitor output current i.dc, a frequency at which pulsation appears, although not as dominant as mechanical 1f, is expressed by the following equation (6):

[0062] |Power supply frequency × m - Mechanical frequency × n| ... (6)

[0063] In the above equation (6), the power supply frequency is the frequency of the power supply voltage, and is generally 50 Hz or 60 Hz. m is an integer of 1 or greater that represents an integer multiple of the power supply frequency. Hereinafter, for simplicity, the m-th multiple of the power supply frequency will be referred to as "power supply mf." For example, the 1-times multiple of the power supply frequency is "power supply 1f."

[0064] Generally, the dominant component of the bus voltage Vdc is the double power supply frequency component, i.e., power supply 2f. Therefore, excluding machine 1f, the large components in the capacitor output current idc are |machine 2f| when m=0 and n=2, |power supply 2f-machine 1f| when m=2 and n=1, and |power supply 2f-machine 2f| when m=2 and n=2.

[0065] The calculation unit 550 calculates the mechanical angle phase θmn, which indicates the rotational position of the electric motor 7, by integrating the frequency estimate value ωest and dividing by the number of pole pairs P. The cosine calculation unit 551 calculates a cosine value cos θmn based on the mechanical angle phase θmn. The sine calculation unit 552 calculates a sine value sin θmn based on the mechanical angle phase θmn.

[0066] The multiplier 553 multiplies the frequency estimate ω by the cosine value cos θ to calculate the cosine component ω·cos θ of the frequency estimate ω. The multiplier 554 multiplies the frequency estimate ω by the sine value sin θ to calculate the sine component ω·sin θ of the frequency estimate ω. The cosine component ω·cos θ and the sine component ω·sin θ calculated by the multipliers 553 and 554 contain not only the pulsating component with a frequency ω but also pulsating components with frequencies higher than ω, i.e., harmonic components.

[0067] The low-pass filters 555 and 556 are first-order lag filters whose transfer function is expressed as 2 / (1+s·Tf). Here, s is a Laplace operator. Tf is a time constant determined to remove pulsating components at frequencies higher than the frequency ωmn. Note that "removal" includes the case where a portion of the pulsating components is attenuated, i.e., reduced. The time constant Tf is set by the operation control unit 11 based on the speed command value, and may be notified to the low-pass filters 555 and 556 by the operation control unit 11, or may be stored by the low-pass filters 555 and 556. The first-order lag filters for the low-pass filters 555 and 556 are merely an example, and moving average filters or the like may also be used. The type of filter is not limited as long as it can remove high-frequency pulsating components.

[0068] The low-pass filter 555 performs low-pass filtering on the cosine component ω·cos θ to remove pulsating components of frequencies higher than ω, and outputs a low-frequency component ω_c, which is a direct current quantity representing the cosine component of the pulsating components of the frequency estimate ω, the cosine component having the frequency ω.

[0069] The low-pass filter 556 performs low-pass filtering on the sine component ω·sinθ to remove pulsating components of frequencies higher than the frequency ω, and outputs a low-frequency component ω_s, which is a direct current quantity representing the sine component having the frequency ω among the pulsating components of the frequency estimate ω.

[0070] An adder-subtractor 557 calculates the difference (ωest_c−0) between zero and the low frequency component ωest_c output from the low pass filter 555. An adder-subtractor 558 calculates the difference (ωest_s−0) between zero and the low frequency component ωest_s output from the low pass filter 556.

[0071] The frequency control unit 559 performs an integral operation on the difference (ωest_c-0) calculated by the adder / subtractor 557 to calculate a cosine component iq_trq_c of a current command that brings the difference (ωest_c-0) closer to zero. By generating the cosine component iq_trq_c in this manner, the frequency control unit 559 performs control to make the low frequency component ωest_c coincide with zero. Note that the integral operation here is an example, and a proportional integral operation may be performed instead of the integral operation.

[0072] The frequency control unit 560 performs an integral operation on the difference (ωest_s-0) calculated by the adder / subtractor 558 to calculate a sine component iq_trq_s of a current command that brings the difference (ωest_s-0) closer to zero. By generating the sine component iq_trq_s in this manner, the frequency control unit 560 performs control to make the low frequency component ωest_s coincide with zero. Note that the integral operation here is an example, and a proportional integral operation may be performed instead of the integral operation.

[0073] The multiplication unit 561 generates iq_trq_c·cos θmn by multiplying the cosine component iq_trq_c output from the frequency control unit 559 by the cosine value cos θmn. iq_trq_c·cos θmn is an AC component having a frequency n·ωest.

[0074] The multiplication unit 562 generates iq_trq_s·sin θmn by multiplying the sine component iq_trq_s output from the frequency control unit 560 by a sine value sin θmn. iq_trq_s·sin θmn is an AC component having a frequency n·ωest.

[0075] The adder / subtractor 563 obtains the sum of iq_trq_c·cos θmn output from the multiplier 561 and iq_trq_s·sin θmn output from the multiplier 562. The vibration suppression control unit 55 outputs the value obtained by the adder / subtractor 563 as the q-axis current compensation value iq_trq*.

[0076] The vibration suppression control unit 55 having the configuration shown in Fig. 8 is configured to suppress the pulsation of one frequency component having a frequency of ωmn. To suppress the pulsation of multiple frequency components, multiple control systems having the configuration shown in Fig. 8 may be provided, one for each frequency component, and these multiple control systems may be connected in parallel.

[0077] 9 is a block diagram showing an example of the configuration of the excitation current command control unit 19 included in the inverter control unit 12 according to embodiment 1. The excitation current command control unit 19 includes a voltage command amplitude calculation unit 191, adders and subtractors 192 and 199, a maximum torque per amp (MTPA) control unit 193, a feedback (FB) flux-weakening control unit 194, an id* comparison unit 195, a band elimination filter 196, a signal correction unit 197, and an feedback auxiliary flux-weakening control unit 198. The band elimination filter 196 and the feedback flux-weakening control unit 194 constitute a first controller 201, and the signal correction unit 197 and the feedback auxiliary flux-weakening control unit 198 constitute a second controller 202.

[0078] A d-axis voltage command Vd** and a q-axis voltage command Vq** are input to the voltage command amplitude calculation unit 191. The d-axis voltage command Vd** and the q-axis voltage command Vq** are voltage commands after modulation factor correction. The voltage command amplitude calculation unit 191 uses the d-axis voltage command Vd** and the q-axis voltage command Vq** to calculate the voltage command amplitude Vdq**_abs shown in the above equation (4).

[0079] The MTPA control unit 193 performs MTPA control on the q-axis current iq acquired from the coordinate conversion unit 18, and calculates a d-axis current command id*_MTPA, which is one of the d-axis current commands to be input to the id* comparison unit 195. The MTPA control is a control that adjusts the current phase of the current flowing through the electric motor 7 so as to maximize the torque generated by the electric motor 7. The MTPA control is well known, and since general MTPA control is used in this paper, a detailed description thereof will be omitted here.

[0080] Inside the excitation current command control unit 19, the command modulation factor M is divided by 1 / √2 times the bus voltage Vdc, and the divided value is input as a voltage limit value Vom*, which is a limit value of the d-axis and q-axis voltages, to an adder-subtractor 192. In addition, the adder-subtractor 192 also receives as input the voltage command amplitude Vdq**_abs calculated by the voltage command amplitude calculation unit 191.

[0081] The adder-subtractor 192 calculates the deviation between the voltage limit value Vom* and the voltage command amplitude Vdq**_abs, and generates the calculated deviation as a voltage saturation amount ΔV. The voltage saturation amount ΔV is input to both the first controller 201 and the second controller 202.

[0082] Since the voltage saturation amount ΔV is generated using the d-axis voltage command Vd** and the q-axis voltage command Vq**, which are voltage commands after modulation factor correction, a signal correction unit 197 is provided in the preceding stage of the feedback auxiliary flux-weakening control unit 198. The signal correction unit 197 multiplies the voltage saturation amount ΔV by "1 / K", which is the reciprocal of the modulation factor correction coefficient K, and outputs the multiplied value to the feedback auxiliary flux-weakening control unit 198 as a correction value ΔV_a for the voltage saturation amount ΔV.

[0083] FIG. 10 is a diagram for explaining the reason why a signal correction unit 197 is required in the preceding stage of the FB auxiliary type flux-weakening control unit 198 provided in the excitation current command control unit 19 according to the first embodiment.

[0084] The horizontal axis of Figure 10 is time, the solid line represents the command modulation factor calculated using the voltage command before modulation factor correction, and the dashed line represents the command modulation factor calculated using the voltage command after modulation factor correction. The number "1" indicates the boundary value of the command modulation factor at which flux-weakening control is performed. The region where the command modulation factor exceeds 1 is the overmodulation region, and the region where the command modulation factor is 1 or less is the non-overmodulation region.

[0085] The waveform shown by the dashed line in FIG. 10 has a large value only in the overmodulation region due to the modulation factor correction of the first embodiment. Therefore, if the waveform shown by the dashed line is used, the value of the voltage saturation amount ΔV in the overmodulation region will be inappropriate. On the other hand, the waveform shown by the solid line is calculated using the voltage command before modulation factor correction, so the value of the voltage saturation amount ΔV is appropriate in both the overmodulation region and the non-overmodulation region. Therefore, in order to use an appropriate value of the voltage saturation amount ΔV, a signal correction unit 197 is provided before the feedback auxiliary flux-weakening control unit 198. By multiplying the voltage saturation amount ΔV by the reciprocal of the modulation factor correction coefficient K, the output of the feedback auxiliary flux-weakening control unit 198 becomes the intended control amount. The modulation factor correction coefficient K used in the signal correction unit 197 can be the value of the modulation factor correction coefficient K calculated by the modulation factor correction coefficient calculation unit 138 shown in FIG. 6.

[0086] As described in the section [Problems to be Solved by the Invention], the response speed of the feedback flux-weakening controller 194 included in the first controller 201 is set to about 1 / 10 of the response speed of the current control. On the other hand, the response speed of the feedback auxiliary flux-weakening controller 198 included in the second controller 202 is set to be faster than the response speed of the feedback flux-weakening controller 194 and to be desirably 1 / 3 or less, more desirably 1 / 5 or less, of the response speed of the vibration suppression control. With these settings, the feedback flux-weakening controller 194 can be operated as a controller that compensates for steady-state voltage saturation, and the feedback auxiliary flux-weakening controller 198 can be operated as a controller that reduces frequency components synchronized with pulsation of the q-axis current. Looking at the configuration of the excitation current command control unit 19 from this perspective, the first controller 201 is configured as a controller that controls the DC component of the voltage saturation amount ΔV, and the second controller 202 is configured as a controller that controls the AC component of the voltage saturation amount ΔV.

[0087] The band-elimination filter 196 is not an essential component, but is provided to effectively reduce the frequency components compensated for by the FB auxiliary flux-weakening control unit 198, i.e., the frequency components synchronized with the pulsation of the q-axis current.

[0088] The band elimination filter 196 reduces the frequency components synchronized with the pulsation of the q-axis current, allowing the FB flux-weakening controller 194 to output a suitable control amount for compensating for the DC component, which is the steady voltage saturation component in the voltage saturation amount ΔV. Similarly, the band elimination filter 196 reduces the frequency components synchronized with the pulsation of the q-axis current, allowing the FB auxiliary flux-weakening controller 198 to output a suitable control amount for compensating for the AC component synchronized with the pulsation of the q-axis current in the voltage saturation amount ΔV.

[0089] The FB flux-weakening control unit 194 integrates the output of the band elimination filter 196 to calculate a d-axis current command id*_FB1, which is another d-axis current command to be input to the id* comparison unit 195. The integral gain Kfw of the FB flux-weakening control unit 194 is set by the following equation (7).

[0090] Kfw=ωfw / (KωeLd)…(7)

[0091] In the above formula (7), ωfw is the cutoff angular frequency when the FB flux-weakening controller 194 is viewed as a low-pass filter, Ld is the d-axis inductance, and ωe is the angular frequency of the inverter output voltage, as described above.

[0092] Generally, the gain of integral control in flux-weakening control is ωfw / (ωeLd), but in the excitation current command control unit 19 in the first embodiment, the flux-weakening control is performed using a voltage command after modulation factor correction, and therefore, as in the above equation (7), the denominator of the integral gain Kfw needs to include the modulation factor correction coefficient K. By using the integral gain Kfw shown in the above equation (7), it is possible to stabilize operation in the overmodulation region even when the modulation factor correction method and flux-weakening control are combined.

[0093] The feedback auxiliary type flux-weakening controller 198 integrates the output of the band elimination filter 196 to calculate a d-axis current command id*_FB2, which is another d-axis current command to be input to the id* comparison unit 195. The feedback auxiliary type flux-weakening controller 198 will be further described with reference to FIG.

[0094] 11 is a block diagram showing an example of the configuration of the feedback auxiliary flux-weakening control unit 198 included in the excitation current command control unit 19 according to embodiment 1. The feedback auxiliary flux-weakening control unit 198 includes multiplication units 601, 602, 610, and 611, low-pass filters 603 and 604, adder-subtractors 605, 606, and 612, integral controllers 607 and 608, and a limit processing unit 609.

[0095] A multiplication unit 601 multiplies a correction value ΔV_a of the voltage saturation amount ΔV by a cosine value cosωmn, and a multiplication unit 602 multiplies the correction value ΔV_a of the voltage saturation amount ΔV by a sine value sinωmn. The outputs of the multiplication units 601 and 602 contain a pulsation component of angular frequency ωmn as well as a pulsation component of angular frequency higher than the angular frequency ωmn.

[0096] The low-pass filters 603 and 604 are first-order lag filters whose transfer function is expressed as 2 / (1+s·Ta). Here, s is a Laplace operator. Ta is a time constant determined to remove pulsating components at frequencies higher than the angular frequency ωmn. Note that "removal" includes the case where a portion of the pulsating components is attenuated, i.e., reduced. The time constant Ta is set by the operation control unit 11 based on the speed command value, and may be notified to the low-pass filters 603 and 604 by the operation control unit 11, or may be stored by the low-pass filters 603 and 604. The first-order lag filters for the low-pass filters 603 and 604 are merely an example, and moving average filters or the like may also be used. The type of filter is not limited as long as it can remove high-frequency pulsating components.

[0097] The low-pass filter 603 performs low-pass filtering on the output of the multiplication unit 601 to remove pulsating components of frequencies higher than the angular frequency ωmn, and outputs a low-frequency component ΔV_a_c. The low-frequency component ΔV_a_c is a DC amount representing a cosine component with an angular frequency ωmn among the pulsating components of the correction value ΔV_a of the voltage saturation amount ΔV.

[0098] The low-pass filter 604 performs low-pass filtering on the output of the multiplication unit 602 to remove pulsating components of frequencies higher than the angular frequency ωmn, and outputs a low-frequency component ΔV_a_s. The low-frequency component ΔV_a_s is a DC amount representing a sine component with an angular frequency ωmn among the pulsating components of the correction value ΔV_a of the voltage saturation amount ΔV.

[0099] An adder-subtractor 605 calculates the difference (ΔV_a_c−0) between zero and the low frequency component ΔV_a_c output from the low pass filter 603. An adder-subtractor 606 calculates the difference (ΔV_a_s−0) between zero and the low frequency component ΔV_a_s output from the low pass filter 604.

[0100] The integral controller 607 performs an integral operation on the difference (ΔV_a_c-0) calculated by the adder / subtractor 605 to calculate a cosine component id_FB_c of the d-axis current command that brings the difference (ΔV_a_c-0) closer to zero. By generating the cosine component id_FB_c in this manner, the integral controller 607 performs control to make the low frequency component ΔV_a_c coincide with zero. Note that the integral operation here is an example, and a proportional integral operation may be performed instead of the integral operation.

[0101] The integral controller 608 performs an integral operation on the difference (ΔV_a_s-0) calculated by the adder / subtractor 606 to calculate a sine component id_FB_s of the d-axis current command that brings the difference (ΔV_a_s-0) closer to zero. By generating the sine component id_FB_s in this manner, the integral controller 608 performs control to make the low frequency component ΔV_a_s equal to zero. Note that the integral operation here is an example, and a proportional integral operation may be performed instead of the integral operation.

[0102] The integral gain Kfw_a of the integral controllers 607, 608 in the feedback auxiliary flux-weakening control unit 198 is set by the following equation (8).

[0103] Kfw_a=ωfw_a / (ωeLd)…(8)

[0104] In the above equation (8), ωfw_a is the cutoff angular frequency when the integral controllers 607, 608 are viewed as low-pass filters. Furthermore, Ld and ωe are the angular frequencies of the d-axis inductance and the inverter output voltage, respectively. As described above, the response speed of the feedback auxiliary flux-weakening control unit 198 is set to be ⅓ or less or ⅕ or less of the response speed of the vibration suppression control, and therefore the integral gain Kfw_a of the integral controllers 607, 608 is set to satisfy these criteria.

[0105] The limiting unit 609 limits the magnitudes of the cosine component id_FB_c and the sine component id_FB_s based on the limiter value id_FB_lim of the d-axis current command id*. The limiting unit 609 outputs a limit cosine component id_FB_c_lim and a limit sine component id_FB_s_lim. The limiter value id_FB_lim is set with an upper limit equal to the total limiter value of the d-axis current command minus the d-axis current command id*_FB1 set by the FB flux-weakening control unit 194. Therefore, in the excitation current command control unit 19, control by the FB auxiliary flux-weakening control unit 198 takes precedence. As a result, in the excitation current command control unit 19, the d-axis current command that controls the DC component of the voltage saturation amount ΔV is set with priority over the d-axis current command that controls the AC component of the voltage saturation amount ΔV.

[0106] A multiplier 610 multiplies the limited cosine component id_FB_c_lim output from the limit processor 609 by a cosine value cosωmn and outputs the result, and a multiplier 611 multiplies the limited sine component id_FB_s_lim output from the limit processor 609 by a sine value sinωmn and outputs the result. An adder / subtractor 612 adds the output of the multiplier 610 and the output of the multiplier 611 and outputs the sum as a d-axis current command id*_FB2.

[0107] 9 , the adder-subtractor 199 receives the d-axis current command id*_FB1 generated by the FB flux-weakening control unit 194 and the d-axis current command id*_FB2 generated by the FB auxiliary flux-weakening control unit 198. The adder-subtractor 199 adds the d-axis current command id*_FB1 and the d-axis current command id*_FB2 together, and outputs the sum to the id* comparison unit 195 as the d-axis current command id*_FB.

[0108] The id* comparison unit 195 selects the larger negative value from the d-axis current command id*_MTPA output from the MTPA control unit 193 and the d-axis current command id*_FB output from the adder / subtractor 199, and outputs the selected value as the d-axis current command id* to the voltage command calculation unit 13. In this document, when the d-axis current command id*_FB1 output from the FB flux-weakening control unit 194 and the d-axis current command id*_FB2 output from the FB auxiliary flux-weakening control unit 198 are distinguished without signs, the former will be called a "first d-axis current command" or a "first excitation current command," and the latter will be called a "second d-axis current command" or a "second excitation current command."

[0109] Fig. 12 is a diagram illustrating a setting method of the limiter value id_FB_lim set in the feedback auxiliary flux-weakening control unit 198 shown in Fig. 11. Fig. 13 is a flowchart illustrating a setting procedure of the limiter value id_FB_lim set in the feedback auxiliary flux-weakening control unit 198 shown in Fig. 11.

[0110] In FIG. 12 , a voltage limit circle 22 having a radius equal to the voltage limit value Vom* is shown by a dashed line on the dq plane. Here, the average value of the voltage command amplitude Vdq*_abs is called the "average voltage command" and is represented by Vave*. FIG. 12 shows a state in which the magnitude of the average voltage command Vave* is the voltage limit value Vom* and the tip of the average voltage command Vave*, which is a vector, is located on the voltage limit circle 22. Here, the calculation of the average voltage command Vave* uses, for example, the voltage command amplitude Vdq*_abs calculated by the voltage command amplitude calculation unit 137, rather than the voltage command amplitude Vdq**_abs calculated by the voltage command amplitude calculation unit 142. In other words, the calculation of the average voltage command Vave* uses the voltage command before modulation factor correction, rather than the voltage command after modulation factor correction. All other vector components shown in FIG. 12 are also converted to values ​​before modulation factor correction.

[0111] When the average voltage command Vave* is in the state shown in FIG. 12, if load torque pulsation suppression control, which suppresses the pulsation component of the load torque, and power supply pulsation suppression control, which suppresses the pulsation component that is an integer multiple of the power supply frequency, are performed, the change components of the d-axis voltage are added to the average voltage command Vave*, and the magnitude of the dq-axis voltage command Vconv* exceeds the voltage limit value Vom* as shown in the figure.

[0112] To position the tip of the dq-axis voltage command Vconv* on the voltage limit circle 22 while performing both the load torque pulsation suppression control and the power supply pulsation suppression control, ΔVq shown in the figure can be applied to the dq-axis voltage command Vconv*. This ΔVq means a transient shortage of the q-axis voltage, and will be referred to as the "q-axis voltage shortage" hereinafter. When the arrow of the q-axis voltage shortage ΔVq is pointed downward, the value of the q-axis voltage shortage ΔVq is negative, meaning that the q-axis voltage is insufficient. Conversely, when the arrow of the q-axis voltage shortage ΔVq is pointed upward, the value of the q-axis voltage shortage ΔVq is positive, meaning that the q-axis voltage is sufficient.

[0113] In the feedback auxiliary flux-weakening controller 198 according to the first embodiment, the q-axis voltage deficiency amount ΔVq is calculated using the procedure shown in Fig. 13 , and the limiter value id_FB_lim is set based on the q-axis voltage deficiency amount ΔVq. Hereinafter, the procedure for setting the limiter value id_FB_lim will be described with reference to Fig. 13 .

[0114] The control device 10 performs low-pass filtering on the q-axis voltage command Vq* (step S11). By performing low-pass filtering on the q-axis voltage command Vq*, the q-axis voltage change component that appears in the q-axis direction due to the pulsation component Δid of the d-axis current is reduced in the filtered output. The control device 10 uses the filtered output to calculate the q-axis component Vqconv* of the dq-axis voltage command Vconv* shown in the following equation (9).

[0115] Vqconv*=|Vave*|cos(θave)_lpf…(9)

[0116] In the above equation (9), the subscript "_lpf" means that the output is after filtering.

[0117] The control device 10 performs low-pass filtering on the d-axis voltage command Vd* (step S12). By performing low-pass filtering on the d-axis voltage command Vd*, the d-axis voltage change component that appears in the d-axis direction due to the pulsation component Δiq of the q-axis current is reduced in the filtered output.

[0118] The control device 10 adds the d-axis voltage change amount due to the load torque pulsation suppression control to the filtered value of the d-axis voltage command Vd* (step S13). This process calculates the d-axis component Vdconv* of the dq-axis voltage command Vconv* shown in the following equation (10).

[0119] Vdconv*=-|Vave*|sin(θave)_lpf -ωeLqΔiq_1...(10)

[0120] In the above equation (10), "ωe" is the angular frequency of the inverter output voltage, and "Lq" is the q-axis inductance of the motor 7. Furthermore, "ωeLqΔiq_1" on the right-hand side is the amount of change in the d-axis voltage due to the load torque pulsation suppression control. The "-" sign indicates that it appears in the negative direction of the d-axis. Furthermore, when power supply pulsation suppression control is taken into consideration, this can be expressed by the following equation (11).

[0121] Vdconv*=-|Vave*|sin(θave)_lpf -ωeLqΔiq_1-ωeLqΔiq_2...(11)

[0122] In the above equation (11), "ωeLqΔiq_2" on the right side is the amount of change in the d-axis voltage due to the power supply pulsation suppression control.

[0123] The control device 10 calculates a required q-axis voltage command vqlim that is required to realize the d-axis voltage command Vdconv* during load torque pulsation suppression control within the range of the voltage limit circle 22 (step S14). The required q-axis voltage command vqlim can be obtained by the following equation (12) using Pythagorean theorem.

[0124] Vqlim=√{(Vom*) ２ -(Vdconv*)２} ...(12)

[0125] The control device 10 calculates the q-axis voltage shortage ΔVq that needs to be reduced in order to make the q-axis voltage Vqconv*, which takes into account only the d-axis current id, the DC component, equal to the required q-axis voltage command Vqlim (step S15). The q-axis voltage shortage ΔVq can be calculated using the following equation (13).

[0126] ΔVq=Vqlim−Vqconv*…(13)

[0127] The control device 10 converts the q-axis voltage undershoot ΔVq into an amplitude value id_lim_buf of the d-axis current id (step S16). The amplitude value id_lim_buf of the d-axis current id can be calculated using the following equation (14).

[0128] id_lim_buf=ΔVq / (ωeLd)...(14)

[0129] In the above formula (14), “Ld” is the d-axis inductance of the electric motor 7 .

[0130] The control device 10 calculates the limiter value id_FB_lim in consideration of the current margin, giving priority to the d-axis current command id_FB1 based on the FB flux-weakening control (step S17). The processing of step S17 will be described using the following equation (15).

[0131] if (id_lim_buf<0) { id_lim=|id_lim_buf|; id_FB_lim=LIM(0, id_lim-id_FB1);}else{ id_FB_lim=0;}...(15)

[0132] The control device 10 determines whether the amplitude value id_lim_buf of the d-axis current id is positive or negative. If the amplitude value id_lim_buf is equal to or greater than zero, the control device 10 sets the limiter value id_FB_lim to zero.

[0133] When the amplitude value id_lim_buf is equal to or greater than zero, voltage saturation does not occur, and there is no need to perform flux-weakening control. Since performing flux-weakening control reduces efficiency, the control in this paper sets the limiter value id_FB_lim to zero. This setting stops the flux-weakening control, making it possible to prevent the efficiency of the power conversion device 300 from deteriorating.

[0134] Furthermore, if the amplitude value id_lim_buf is negative, the control device 10 sets the absolute value of the amplitude value id_lim_buf to the temporary limiter value id_lim. The control device 10 then sets the minimum value of the limiter value id_FB_lim to zero and sets the maximum value of the limiter value id_FB_lim to "id_lim - id_FB1." The reason for subtracting the d-axis current command id_FB1 based on the feedback flux-weakening control from the temporary limiter value id_lim is to prioritize control based on the d-axis current command id_FB1, i.e., to prioritize flux-weakening control of the DC component. Therefore, the flux-weakening control of the AC component by the feedback auxiliary flux-weakening control unit 198 utilizes the remaining current margin obtained by subtracting the control amount by the feedback flux-weakening control unit 194 from the total current margin, thereby enabling efficient and stable control.

[0135] Next, the effect of using the feedback auxiliary flux-weakening control unit 198 will be described with reference to Fig. 14 and Fig. 15. Fig. 14 is a diagram showing how various torques, command values ​​and operating values ​​of various currents, command values ​​and operating values ​​of various voltages, command modulation rates, and actual modulation rates change when the excitation current command control unit 19 shown in Fig. 9 is equipped with only the feedback flux-weakening control unit 194 without the feedback auxiliary flux-weakening control unit 198. Fig. 15 is a diagram showing how various torques, command values ​​and operating values ​​of various currents, command values ​​and operating values ​​of various voltages, command modulation rates, and actual modulation rates change when the excitation current command control unit 19 shown in Fig. 9 is equipped with both the feedback auxiliary flux-weakening control unit 198 and the feedback flux-weakening control unit 194.

[0136] 14 and 15 show, from top to bottom, waveforms of speed (estimated speed, command value, actual speed), torque (load torque, motor torque), current (three-phase current: Iu, Iv, Iw), current (d-axis current command, d-axis current, limiter value), current (q-axis current command, q-axis current), voltage (d-axis voltage command, d-axis voltage), voltage (q-axis voltage command, q-axis voltage), command modulation rate, and actual modulation rate. The horizontal axis in FIGS. 14 and 15 represents time.

[0137] 14 and 15 show operational waveforms when the command modulation factor (command modulation factor M) is set to 1.1. That is, in both Fig. 14 and Fig. 15, the motor is set to operate with the command modulation factor M set to 1.1. The distinctive features of these operational waveforms are as follows:

[0138] 14 and 15, the q-axis current follows the q-axis current command without a large delay, but current distortion is reduced in Fig. 15 compared to Fig. 14. ・The d-axis current command fluctuates more in Fig. 15 compared to Fig. 14, which shows that the control by the FB auxiliary flux-weakening control unit 198 is working sufficiently. ・The pp (peak to peak) value of the command modulation factor (command modulation factor M*) is significantly reduced in Fig. 15 compared to Fig. 14.

[0139] As can be understood from the above, by using the feedback auxiliary type flux-weakening control unit 198 proposed in this paper, it is possible to make the flux-weakening control function sufficiently in the overmodulation region.

[0140] Further, consider the waveforms in Fig. 14 and Fig. 15. In the waveform diagram of the actual modulation factor shown at the bottom of Fig. 14, the level indicating a command modulation factor of 2.0 is indicated by a dashed line. In the operating waveforms of Fig. 14, the line indicating a command modulation factor of 2.0 and the peak value of the actual modulation factor approximately coincide with each other, and it can be seen that inside the excitation current command control unit 19, operation is performed with the command modulation factor M* at a maximum value of approximately 2.0.

[0141] In addition, in the waveform diagram of the actual modulation factor shown at the bottom of Fig. 15, the level indicating a command modulation factor of 1.3 is indicated by a dashed line, and the level indicating the average value of the actual modulation factor (=1.046) is indicated by a dashed line. In the operating waveforms of Fig. 15, the line indicating a command modulation factor of 1.3 and the peak value of the actual modulation factor approximately coincide with each other, and it can be seen that inside the excitation current command control unit 19, operation is performed with the command modulation factor M* at a maximum value of approximately 1.3.

[0142] Furthermore, the ratio of the peak value of the actual modulation rate to the average value of the actual modulation rate can be calculated as (1.065 - 1.046) × 100 / 1.046 = 1.8164...≈2%. Therefore, when the feedback auxiliary flux-weakening controller 198 proposed in this paper is used, it is expected that the peak value of the actual modulation rate will be controlled to fall within a range of +2% of the average value of the actual modulation rate. In other words, if the peak value of the actual modulation rate can be controlled to fall within a range of +2% of the average value of the actual modulation rate, it is expected that current distortion of the q-axis current can be reduced while performing vibration suppression control, even in the overmodulation region.

[0143] As described above, the power conversion device according to the first embodiment includes a converter that rectifies a power supply voltage applied from an AC power supply, a capacitor connected to the output terminal of the converter, an inverter connected across the capacitor, and a control device that controls the operation of the inverter to perform vibration suppression control to suppress load vibration. The control device calculates an excitation current command used in flux-weakening control based on a voltage saturation amount calculated from a voltage limit value determined by a DC voltage value applied to the inverter and a voltage command to be applied to the inverter. The voltage saturation amount is divided into a DC component and an AC component, and the excitation current command is generated based on a first excitation current command calculated based on the DC component and a second excitation current command calculated based on the AC component. By using a power conversion device configured in this manner, sufficient flux-weakening control can be performed in the overmodulation region even when vibration suppression control and flux-weakening control are combined.

[0144] In the flux-weakening control performed by the power conversion device according to the first embodiment, the DC component is controlled to compensate for steady-state voltage saturation, and the AC component is controlled to reduce frequency components synchronized with pulsation in the torque current. The response speed of the control response for controlling the AC component is set to be preferably ⅓ or less, and more preferably ⅕ or less, of the response speed of the vibration suppression control. This configuration makes it possible to suitably design the controller for controlling the AC component in relation to the controller for performing vibration suppression control.

[0145] According to the power conversion device of the first embodiment, the voltage saturation amount is controlled so that the peak value of the actual modulation factor falls within a range of +2% with respect to the average value of the actual modulation factor, which is a value indicating the ratio of the inverter output voltage to the DC voltage. If the peak value of the actual modulation factor can be controlled in this manner, it becomes possible to reduce current distortion of the torque current while performing vibration suppression control, even in the overmodulation region.

[0146] In the first embodiment, the control device performs modulation factor correction in a region where the command modulation factor, which indicates the ratio of the voltage command amplitude in the voltage command given to the inverter to the DC voltage value applied to the inverter, exceeds 1. When the control device is configured to determine the excitation current command for flux-weakening control from the voltage command after modulation factor correction, the controller that controls the DC component is configured to input the voltage saturation amount after modulation factor correction, and the controller that controls the AC component is configured to input the voltage saturation amount converted to the value before modulation factor correction. With this configuration, it is possible to input appropriate voltage saturation amount values ​​to both controllers.

[0147] In the first embodiment, the gain of the flux-weakening control in the FB flux-weakening control unit is an important parameter for stabilizing the operation of the control device. When the control device is configured to determine the excitation current command for the flux-weakening control from the voltage command after modulation factor correction, as in the first embodiment, it is desirable to set the gain of the flux-weakening control including the modulation factor correction coefficient. Configuring the control device in this way can contribute to stabilizing the operation of the control device.

[0148] Next, a description will be given of the hardware configuration of the control device 10 included in the power conversion device 300. Fig. 16 is a diagram showing an example of a hardware configuration that realizes the control device 10 included in the power conversion device 300 according to embodiment 1. The control device 10 is realized by a processor 501 and a memory 502.

[0149] The processor 501 is a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, a DSP (Digital Signal Processor), or a system LSI (Large Scale Integration). The memory 502 can be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read-Only Memory). The memory 502 is not limited to these, and may also be a magnetic disk, an optical disk, a compact disk, a minidisc, or a DVD (Digital Versatile Disc).

[0150] Embodiment 2. In the first embodiment, a control device configured using a technique for performing flux-weakening control using a voltage command after modulation factor correction has been described. In the second embodiment, a control device configured using a technique for performing flux-weakening control using a voltage command before modulation factor correction will be described.

[0151] FIG. 17 is a block diagram showing a configuration example of a control device 10A included in a power conversion device 300 according to the second embodiment. The control device 10A includes an operation control unit 11 and an inverter control unit 12A. The inverter control unit 12A includes a voltage command calculation unit 13A, an electrical angle phase calculation unit 14, a space vector modulation unit 15, a PWM signal generation unit 16, a current restoration unit 17, a coordinate conversion unit 18, an excitation current command control unit 19A, and a vibration suppression control unit 55. In FIG. 17, components having different functions from those of the control device 10 of the first embodiment shown in FIG. 3 are indicated by the subscript A. The same applies to FIGS. 18, 19, and 20. Hereinafter, the second embodiment will be described focusing on the functions of the components that differ from those of the first embodiment.

[0152] The excitation current command control unit 19A generates a d-axis current command id*, which is an excitation current command, based on the q-axis current iq obtained from the coordinate conversion unit 18, the command modulation factor M obtained from the operation control unit 11, and the d-axis voltage command Vd* and q-axis voltage command Vq* calculated by the voltage command calculation unit 13A. The excitation current command control unit 19A calculates a current phase angle at which the output torque of the electric motor 7 is equal to or greater than a set value or at its maximum value, and calculates the d-axis current command id* based on the calculated current phase angle. When calculating the d-axis current command id*, the excitation current command control unit 19A performs flux-weakening control and command modulation factor correction to determine the d-axis current command id*. The specific configuration and operation of the excitation current command control unit 19A will be described later. The excitation current command control unit 19A may calculate the d-axis current command id* using the motor current flowing through the electric motor 7 instead of the output torque of the electric motor 7. In this case, the d-axis current command id* is calculated based on the current phase angle at which the motor current flowing through the motor 7 is equal to or less than the set value or is at the minimum value.

[0153] The voltage command calculation unit 13A generates a d-axis voltage command Vd*, a q-axis voltage command Vq*, a frequency estimate value ωest, a command modulation factor M**, and a voltage phase θv based on the frequency command ωe* obtained from the operation control unit 11, the d-axis current id and q-axis current iq obtained from the coordinate conversion unit 18, the d-axis current command id* obtained from the excitation current command control unit 19A, and the q-axis current compensation value iq_trq* obtained from the vibration suppression control unit 55. The command modulation factor M** and the voltage phase θv are used in the space vector modulation unit 15, the d-axis voltage command Vd* and the q-axis voltage command Vq* are used in the excitation current command control unit 19A, and the frequency estimate value ωest is used inside the electrical angle phase calculation unit 14 and the voltage command calculation unit 13A.

[0154] 18 is a block diagram showing an example configuration of a voltage command calculation unit 13A included in a control device 10A according to embodiment 2. The voltage command calculation unit 13A includes adder-subtractors 130, 132, 133, and 139, a speed controller 131, a d-axis current controller 134, a q-axis current controller 135, a frequency estimation unit 136, and a command modulation factor and voltage phase calculation unit 140A.

[0155] Comparing voltage command calculation unit 13A shown in Fig. 18 with voltage command calculation unit 13 shown in Fig. 6, in Fig. 18, components such as voltage command amplitude calculation unit 137 and modulation factor correction coefficient calculation unit 138 are deleted from the configuration in Fig. 6. As described above, embodiment 2 employs a technique for performing flux-weakening control using a voltage command before modulation factor correction, and therefore components such as voltage command amplitude calculation unit 137 and modulation factor correction coefficient calculation unit 138 are not necessary.

[0156] The d-axis voltage command Vd* and the q-axis voltage command Vq* calculated by the voltage command calculation unit 13A are output to a command modulation factor and voltage phase calculation unit 140A inside the voltage command calculation unit 13A. Moreover, the d-axis voltage command Vd* and the q-axis voltage command Vq* calculated by the voltage command calculation unit 13A are output to an excitation current command control unit 19A shown in FIG. 17 outside the voltage command calculation unit 13A.

[0157] 19 is a block diagram showing an example of the configuration of a command modulation factor and voltage phase calculation unit 140A included in a voltage command calculation unit 13A according to Embodiment 2. The command modulation factor and voltage phase calculation unit 140A includes a command modulation factor calculation unit 141A and a voltage phase calculation unit 144A. Furthermore, the command modulation factor calculation unit 141A includes a voltage command amplitude calculation unit 142A and a command modulation factor correction unit 146A.

[0158] The d-axis voltage command Vd*, the q-axis voltage command Vq*, and the bus voltage Vdc are input to the command modulation factor calculation unit 141A. The voltage command amplitude calculation unit 142A uses the d-axis voltage command Vd* and the q-axis voltage command Vq* to calculate a voltage command amplitude Vdq*_abs shown in the following equation (16).

[0159] Vdq*_abs=√(Vd* ２ +Vq* ２ ) … (16)

[0160] The voltage command amplitude Vdq*_abs calculated by the voltage command amplitude calculation unit 142A is divided by a value obtained by multiplying the bus voltage Vdc by 1 / √2, and the result is input to the command modulation factor correction unit 146A as a command modulation factor M*.

[0161] The command modulation factor M* input to the command modulation factor correcting section 146A is calculated using the voltage command before modulation factor correction. Furthermore, the command modulation factor correcting section 146A has a table equivalent to that of the modulation factor correction coefficient calculating section 138. When the value of the input command modulation factor M* is 1 or less, the command modulation factor correcting section 146A outputs the value of the command modulation factor M* as is, and when the value of the command modulation factor M* exceeds 1, the command modulation factor correcting section 146A multiplies the command modulation factor M* by the corresponding modulation factor correction coefficient K and outputs the multiplied value as the command modulation factor M**.

[0162] Furthermore, the voltage phase calculation unit 144A uses the d-axis voltage command Vd* and the q-axis voltage command Vq* to calculate the voltage phase θv shown in the following equation (17).

[0163] θv = tan －１ (Vd* / Vq*)…(17)

[0164] The command modulation factor M** and voltage phase θv calculated by the command modulation factor and voltage phase calculation unit 140A are used in the space vector modulation unit 15.

[0165] 20 is a block diagram showing an example of the configuration of an excitation current command control unit 19A included in an inverter control unit 12A according to embodiment 2. The excitation current command control unit 19A includes a command modulation factor corrector 190A, a voltage command amplitude calculator 191A, adders and subtractors 192 and 199, an MTPA control unit 193, an FB flux-weakening control unit 194A, an id* comparator 195, a band elimination filter 196, and an FB auxiliary flux-weakening control unit 198A. The band elimination filter 196 and the FB flux-weakening control unit 194A constitute a first controller 201A, and the FB auxiliary flux-weakening control unit 198A constitutes a second controller 202A.

[0166] The d-axis voltage command Vd* and the q-axis voltage command Vq* are input to the voltage command amplitude calculation unit 191A, which uses the d-axis voltage command Vd* and the q-axis voltage command Vq* to calculate the voltage command amplitude Vdq*_abs shown in the above equation (16).

[0167] The MTPA control unit 193 performs MTPA control on the q-axis current iq acquired from the coordinate conversion unit 18 and calculates one d-axis current command id*_MTPA of the d-axis current commands to be input to the id* comparison unit 195 .

[0168] The command modulation factor correcting section 190A has a table equivalent to that of the command modulation factor correcting section 146A. When the value of the input command modulation factor M is 1 or less, the command modulation factor correcting section 190A outputs the value of the command modulation factor M as is. When the value of the command modulation factor M exceeds 1, the command modulation factor correcting section 190A multiplies the command modulation factor M by the reciprocal 1 / k of the corresponding modulation factor correction coefficient K and outputs the multiplied value. The command modulation factor M is multiplied by the reciprocal 1 / k in order to align the comparison level with the voltage command amplitude Vdq*_abs output from the voltage command amplitude calculating section 191A. In other words, because the voltage command amplitude Vdq*_abs is generated using a voltage command before modulation factor correction, the command modulation factor M is multiplied by the reciprocal 1 / k in relation to this processing.

[0169] Inside the excitation current command control unit 19A, the output of the command modulation factor corrector 190A is divided by 1 / √2 times the bus voltage Vdc, and the divided value is input as a voltage limit value Vom*, which is a limit value for the d-axis and q-axis voltages, to an adder-subtractor 192. In addition, the adder-subtractor 192 also receives as input a voltage command amplitude Vdq*_abs calculated by a voltage command amplitude calculation unit 191A.

[0170] The adder-subtractor 192 calculates the deviation between the voltage limit value Vom* and the voltage command amplitude Vdq*_abs, and generates the calculated deviation as a voltage saturation amount ΔV'. The voltage saturation amount ΔV' is input to both the first controller 201A and the second controller 202A. Note that the voltage saturation amount ΔV' is generated using the d-axis voltage command Vd* and the q-axis voltage command Vq*, which are voltage commands before modulation factor correction. Therefore, unlike the first embodiment, the signal correction unit 197 provided in the stage preceding the feedback auxiliary flux-weakening control unit 198 is not required.

[0171] The FB flux-weakening control unit 194A integrates the output of the band elimination filter 196 to calculate a d-axis current command id*_FB1, which is another d-axis current command to be input to the id* comparison unit 195. The integral gain Kfw of the FB flux-weakening control unit 194A is set by the following equation (18).

[0172] Kfw=ωfw / (ωeLd)…(18)

[0173] In the above equation (18), ωfw is the cutoff angular frequency when the FB flux-weakening controller 194A is viewed as a low-pass filter, Ld is the d-axis inductance, and ωe is the angular frequency of the inverter output voltage, as described above.

[0174] In the excitation current command control unit 19 in the first embodiment, flux-weakening control is performed using a voltage command after modulation factor correction, and therefore, as in the above equation (7), the modulation factor correction coefficient K is required in the denominator of the integral gain Kfw. In contrast, in the excitation current command control unit 19A in the second embodiment, flux-weakening control is performed using a voltage command before modulation factor correction, and therefore, as in the above equation (18), the modulation factor correction coefficient K is not required. In the excitation current command control unit 19 in the first embodiment, if an integral gain using the modulation factor correction coefficient K is used as in the excitation current command control unit 19 in the first embodiment, operation will become unstable. Therefore, by using the integral gain Kfw shown in the above equation (18), it is possible to stabilize operation in the overmodulation region even when the modulation factor correction method and flux-weakening control are combined.

[0175] The FB auxiliary flux-weakening control unit 198A calculates a d-axis current command id*_FB2, which is another one of the d-axis current commands to be input to the id* comparison unit 195, by integrating the voltage saturation amount ΔV′.

[0176] The adder-subtractor 199 receives the d-axis current command id*_FB1 generated by the FB flux-weakening control unit 194A and the d-axis current command id*_FB2 generated by the FB auxiliary flux-weakening control unit 198A. The adder-subtractor 199 adds the d-axis current command id*_FB1 and the d-axis current command id*_FB2 together, and outputs the sum to the id* comparison unit 195 as the d-axis current command id*_FB.

[0177] The id* comparison unit 195 selects the larger negative value from the d-axis current command id*_MTPA output from the MTPA control unit 193 and the d-axis current command id*_FB output from the adder / subtractor 199, and outputs the selected value as the d-axis current command id* to the voltage command calculation unit 13A.

[0178] As described above, the power conversion device according to the second embodiment includes a converter that rectifies a power supply voltage applied from an AC power supply, a capacitor connected to the output terminal of the converter, an inverter connected across the capacitor, and a control device that performs vibration suppression control that controls the operation of the inverter to suppress load vibration. The control device calculates an excitation current command used in flux-weakening control based on a voltage saturation amount calculated from a voltage limit value determined by a DC voltage value applied to the inverter and a voltage command applied to the inverter. The voltage saturation amount is divided into a DC component and an AC component, and the excitation current command is generated based on a first excitation current command calculated based on the DC component and a second excitation current command calculated based on the AC component. The control device according to the second embodiment performs flux-weakening control using a voltage command before modulation factor correction. Even when the power conversion device according to the second embodiment is used, the effects of the first embodiment can be achieved. That is, when the power conversion device according to the second embodiment is used, sufficient flux-weakening control can be performed in the overmodulation region even when vibration suppression control and flux-weakening control are combined.

[0179] In the second embodiment, the gain of the flux-weakening control in the FB flux-weakening control unit is an important parameter for stabilizing the operation of the control device. When the control device is configured to determine the excitation current command for the flux-weakening control from the voltage command before the modulation factor correction, as in the second embodiment, it is desirable to set the gain of the flux-weakening control without including the modulation factor correction coefficient. Configuring the control device in this way can contribute to stabilizing the operation of the control device.

[0180] Third Embodiment Fig. 21 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to a third embodiment. The refrigeration cycle-applied device 900 according to the third embodiment includes the power conversion device 300 described in the first or second embodiment. The refrigeration cycle-applied device 900 according to the third embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 21, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0181] The refrigeration cycle application equipment 900 includes a compressor 50 incorporating the electric motor 7 in embodiment 1 or embodiment 2, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are attached via refrigerant piping 912.

[0182] The compressor 50 includes a compression mechanism 52 that compresses the refrigerant and an electric motor 7 that operates the compression mechanism 52 .

[0183] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 52 is driven by an electric motor 7 that is variable speed controlled.

[0184] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 52 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902 and returns to the compression mechanism 52.

[0185] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 52 and sent out, and returns to the compression mechanism 52 through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0186] 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 reduces the pressure of the refrigerant to expand it.

[0187] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0188] 1 AC power supply, 2 Reactor, 3 Converter, 5 Capacitor, 7 Motor, 8 Voltage detection unit, 9a, 9b DC bus, 10, 10A Control device, 11 Operation control unit, 12, 12A Inverter control unit, 13, 13A Voltage command calculation unit, 14 Electric angle phase calculation unit, 15 Space vector modulation unit, 16 PWM signal generation unit, 17 Current restoration unit, 18 Coordinate conversion unit, 19, 19A Excitation current command control unit, 22 Voltage limit circle, 30 Inverter, 40 Current detection unit, 50 Compressor, 52 Compression mechanism, 55 Vibration suppression control unit, 130, 132, 133, 139, 192, 199, 557, 558, 563, 605, 606, 612 Adder / subtractor, 131 Speed ​​controller, 134 d-axis current controller, 135 q-axis current controller, 136 frequency estimation unit, 137, 142, 142A, 191, 191A voltage command amplitude calculation unit, 138 modulation factor correction coefficient calculation unit, 140, 140A command modulation factor and voltage phase calculation unit, 141, 141A command modulation factor calculation unit, 144, 144A voltage phase calculation unit, 146A, 190A command modulation factor correction unit, 193 MTPA control unit, 194, 194A FB flux weakening control unit, 195 id* comparison unit, 196 band elimination filter, 197 signal correction unit, 198 FB auxiliary flux weakening control unit, 201, 201A first controller, 202, 202A second controller, 300 power conversion device, 310 inverter main circuit, 311 to 316 switching elements, 321 to 326 Rectifying element, 331 to 333 output lines, 350 drive circuit, 400 motor drive device, 501 processor, 502 memory, 550 calculation unit, 551 cosine calculation unit, 552 sine calculation unit, 553, 554, 561, 562, 601, 602, 610, 611 multiplication unit, 555, 556, 603, 604 low pass filter, 559, 560 frequency control unit, 607, 608 integral controller, 609 limit processing unit, 900 refrigeration cycle applied equipment, 902 four-way valve, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping, D1 to D4 diodes.

Claims

1. A power conversion device that supplies AC power to an electric motor that drives a load, comprising: a converter that rectifies a power supply voltage applied from an AC power supply; a capacitor connected to an output end of the converter; an inverter connected to both ends of the capacitor; and a control device that performs vibration suppression control that controls the operation of the inverter to suppress vibration of the load, wherein the control device calculates an excitation current command used in flux-weakening control based on a voltage saturation amount calculated from a voltage limit value determined by a DC voltage value applied to the inverter and a voltage command to be given to the inverter, the voltage saturation amount is divided into a DC component and an AC component, and the excitation current command is generated based on a first excitation current command calculated based on the DC component and a second excitation current command calculated based on the AC component.

2. The power conversion device according to claim 1, wherein in the flux-weakening control, the DC component is controlled so as to compensate for a steady-state voltage saturation component, and the AC component is controlled so as to reduce a frequency component synchronized with a pulsation of a torque current.

3. The power conversion device according to claim 1 or 2, wherein the response speed of the control response for controlling the AC component is set to 1 / 3 or less of the response speed of the vibration suppression control.

4. The power conversion device according to claim 1, wherein the DC component is generated by passing the voltage saturation amount through a band elimination filter.

5. The power conversion device according to any one of claims 1 to 4, wherein the control device performs modulation factor correction in a region where a command modulation factor indicating a ratio of a voltage command amplitude in a voltage command given to the inverter to a DC voltage value applied to the inverter exceeds 1, and when the control device is configured to determine an excitation current command for flux-weakening control from a voltage command after modulation factor correction, a corrected voltage saturation amount after modulation factor correction is input to a first controller that controls the DC component, and a voltage saturation amount converted to a value before modulation factor correction is input to a second controller that controls the AC component.

6. The power conversion device according to claim 5, wherein when the control device is configured to determine an excitation current command for flux-weakening control from a voltage command after modulation factor correction, a gain for the flux-weakening control that controls the DC component is set including a modulation factor correction coefficient.

7. A power conversion device as claimed in any one of claims 1 to 4, wherein the control device performs modulation factor correction in a region where a command modulation factor indicating a ratio of a voltage command amplitude in a voltage command given to the inverter to a DC voltage value applied to the inverter exceeds 1, and when the control device is configured to determine an excitation current command for flux-weakening control from a voltage command before modulation factor correction, a voltage saturation amount before correction without modulation factor correction is input to both a first controller that controls the DC component and a second controller that controls the AC component.

8. The power conversion device according to claim 7, wherein when the control device is configured to determine an excitation current command for flux-weakening control from a voltage command before modulation factor correction, a gain for the flux-weakening control that controls the DC component is set without including a modulation factor correction coefficient.

9. The power conversion device according to any one of claims 5 to 8, wherein the limiter value of the excitation current set in the second controller is calculated based on an average value of the pulsating component of the torque current, the voltage limit value, and the voltage command amplitude.

10. The power conversion device according to claim 9, wherein the pulsating component of the torque current, the voltage limit value and the average value of the voltage command amplitude are all converted into values ​​before modulation factor correction.

11. A power conversion device according to any one of claims 5 to 10, wherein the limiter value of the excitation current set in the second controller is set to an upper limit value obtained by subtracting the excitation current command set in the first controller from the overall limiter value of the excitation current command.

12. A power conversion device as claimed in any one of claims 1 to 11, wherein the control device controls the voltage saturation amount so that the peak value of the actual modulation factor falls within a range of +2% with respect to an average value of the actual modulation factor, the average value being a value indicating the ratio of the output voltage of the inverter to the DC voltage value.

13. An electric motor drive device comprising a power conversion device according to any one of claims 1 to 12.

14. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 12.

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