JP2023170852A - Power conversion device and power conversion method - Google Patents

Abstract

To provide a power conversion device effective in both of quickly suppressing output voltage saturation and achieving stability in output current to a motor.SOLUTION: A power conversion device 2 includes: a power conversion circuit 10; a first current calculation unit 121 for calculating a first current command corresponding to a direction perpendicular to a magnetic direction of a motor 3; a feed-forward calculation unit 122 for calculating a feed-forward current command for canceling an induced voltage of the motor 3 based on characteristic parameters of the motor 3 and the first current command; a filter 130 for suppressing changes in the feed-forward current command in response to changes in the first current command; a second current calculation unit 123 for calculating a second current command corresponding to the magnetic direction of the motor 3 based on the feed-forward current command through the filter 130; and a control unit 115 for controlling the power conversion circuit 10 so that the currents based on the first current command and the second current command are supplied to the motor 3.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a power conversion device and a power conversion method.

Patent Document 1 discloses that the direct axis current command value is calculated so as to maximize the torque/current, and when the speed of the motor is high, the terminal voltage of the motor is calculated to be equal to the maximum output voltage of the power converter. A power conversion method for calculating a direct axis current command value is disclosed.

Japanese Patent Application Publication No. 10-243700

The present disclosure provides a power conversion device that is effective in quickly suppressing output voltage saturation and achieving stability in output current to a motor.

A power conversion device according to one aspect of the present disclosure includes a power conversion circuit that performs power conversion between a power source and an electric motor, and a power conversion circuit that converts power between a power source and an electric motor, and a power conversion circuit that converts power between a power source and an electric motor, and a power conversion circuit that converts electric power between a power source and an electric motor, and a power conversion circuit that converts electric power between a power source and an electric motor. a first current calculation unit that calculates a first current command corresponding to the vertical direction; and a feedforward current command for canceling the induced voltage of the motor based on the characteristic parameters of the motor and the first current command. a feedforward calculation unit, a filter that suppresses a change in the feedforward current command according to a change in the first current command, and a second current command that corresponds to the magnetic pole direction of the motor based on the feedforward current command that has passed through the filter. It includes a second current calculation unit that calculates the current, and a control unit that controls the power conversion circuit to supply the electric motor with a current based on the first current command and the second current command.

A power conversion method according to another aspect of the present disclosure includes calculating a first current command corresponding to a direction perpendicular to the magnetic pole direction of the electric motor so as to cause the electric motor to generate a driving force corresponding to the driving force command; Calculating a feedforward current command for canceling the induced voltage of the motor based on the characteristic parameters of the motor and the first current command, and suppressing changes in the feedforward current command in response to changes in the first current command. applying filtering to the feedforward current command, calculating a second current command corresponding to the magnetic pole direction of the motor based on the filtered feedforward current command, and calculating the first current command and the second current command. and controlling the power conversion circuit to supply the electric motor with a current based on the command.

According to the present disclosure, it is possible to provide a power conversion device that is effective in quickly suppressing output voltage saturation and achieving stability in output current to a motor.

FIG. 2 is a schematic diagram illustrating the configuration of a drive system. FIG. 3 is a diagram illustrating a fixed coordinate system and a rotating coordinate system. FIG. 2 is a block diagram illustrating the configuration of a current command generation section. It is a graph illustrating the relationship between a force-dependent current command and a feedforward current command. FIG. 2 is a block diagram illustrating a hardware configuration of a control circuit. 3 is a flowchart illustrating a power conversion procedure. 3 is a flowchart illustrating a current command generation procedure.

Hereinafter, embodiments will be described in detail with reference to the drawings. In the description, the same elements or elements having the same function are given the same reference numerals, and redundant description will be omitted.

[Drive system]
A drive system 1 shown in FIG. 1 is a system that drives an object to be driven using the power of an electric motor 3. The drive system 1 shown in FIG. The drive system 1 includes an electric motor 3, a magnetic pole position sensor 4, and a power conversion device 2. The electric motor 3 is, for example, a synchronous motor. A specific example of a synchronous motor is an SPM (Surface Permanent Magnet) motor. The electric motor 3 may be a synchronous electric motor having saliency. Having saliency means that the inductance is different between the coordinate axes of the rotating coordinate system. The rotating coordinate system is a coordinate system that rotates in synchronization with the magnetic pole position of the electric motor 3. A specific example of a synchronous motor having saliency includes an IPM (Interior Permanent Magnet) motor and the like. The magnetic pole position of the IPM motor is, for example, the position of the magnetic pole of a field formed by a permanent magnet embedded in an iron core.

The magnetic pole position sensor 4 is a sensor that detects the magnetic pole position of the electric motor 3. The magnetic pole position is expressed, for example, in electrical angle. An example of the magnetic pole position sensor 4 is a Hall sensor.

Power conversion device 2 supplies electric motor 3 with electric power for generating driving force. For example, the power conversion device 2 includes a power conversion circuit 10 and a control circuit 100.

The power conversion circuit 10 performs power conversion between a power source 9 (for example, a power system) and an electric motor 3. For example, the power conversion circuit 10 converts primary power supplied from the power source 9 into secondary power and supplies the secondary power to the electric motor 3. The primary power may be DC power or AC power. The secondary power is AC power. Hereinafter, a configuration of the power conversion circuit 10 in a case where the primary side power and the secondary side power are three-phase AC power will be illustrated.

Power conversion circuit 10 includes a rectifier circuit 11 , a smoothing capacitor 14 , an inverter circuit 15 , and a current sensor 16 . The rectifier circuit 11 is, for example, a diode bridge circuit including a plurality of diodes 12, and converts primary side power into DC power and outputs it to DC buses 13P and 13N. Smoothing capacitor 14 smoothes the DC voltage on DC buses 13P and 13N.

The inverter circuit 15 performs power conversion between the DC power and the secondary power. For example, the inverter circuit 15 converts DC power into secondary power and supplies it to the motor 3 in the power running state, and converts the secondary power generated by the motor 3 into DC power in the regeneration state. For example, the inverter circuit 15 has a plurality of switching elements 17, and performs the power conversion by switching the plurality of switching elements 17 on and off.

The switching element 17 is, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), and is turned on and off according to a gate drive signal. Switch.

Current sensor 16 detects a current flowing between inverter circuit 15 and electric motor 3 (hereinafter referred to as "secondary current"). For example, the current sensor 16 may be configured to detect the current of all phases (U phase, V phase, and W phase) of the secondary power, or may be configured to detect the current of any two phases of the secondary power. It may be configured to detect. Unless a zero-phase current occurs, the sum of the U-phase, V-phase, and W-phase currents is zero, so even when detecting two-phase currents, information on all-phase currents can be obtained.

The configuration of the power conversion circuit 10 shown above is just an example. The configuration of the power conversion circuit 10 can be modified in any way as long as it can convert primary side power into secondary side power and supply it to the electric motor 3. For example, the rectifier circuit 11 may be a PWM converter circuit that converts AC power to DC power. The power conversion circuit 10 may be a matrix converter circuit that performs bidirectional power conversion between primary power and secondary power without converting to direct current. When the power source power is DC power, the power conversion circuit 10 does not need to have the rectifier circuit 11.

The control circuit 100 generates a control command for causing the electric motor 3 to generate a driving force (for example, torque) corresponding to a driving force command (for example, a torque command), and generates secondary power that follows the control command. Controls the power conversion circuit 10. The control command includes at least a voltage command. The control circuit 100 controls the power conversion circuit 10 to apply a secondary voltage corresponding to the voltage command to the electric motor 3.

There is a limit to the driving force that the power conversion circuit 10 can generate in the electric motor 3 due to saturation of the output voltage. Hereinafter, the maximum driving force that the power conversion circuit 10 can generate in the electric motor 3 will be referred to as "maximum driving force." Saturation of the output voltage occurs due to an increase in the induced voltage in the motor 3. Since the induced voltage increases as the operating speed of the electric motor 3 (for example, the rotational speed of the rotor) increases, the maximum driving force decreases as the operating speed of the electric motor 3 increases. Saturation of the output voltage can be suppressed by outputting a field weakening current to the motor 3 to cancel the induced voltage. Therefore, by supplying the field weakening current, the range of driving force (the magnitude of the maximum driving force) can be expanded. Furthermore, the range of operating speeds that the electric motor 3 can follow can also be expanded.

In order to supply the field weakening current, the control circuit 100 calculates a first current command corresponding to a direction perpendicular to the magnetic pole direction of the electric motor 3 so that the electric motor 3 generates a driving force corresponding to the driving force command. and calculating a feedforward current command for canceling the induced voltage of the motor 3 based on the characteristic parameters of the motor 3 and the first current command, and calculating a feedforward current command according to a change in the first current command. applying filtering to the feedforward current command to suppress changes in the current command; calculating a second current command corresponding to the magnetic pole direction of the motor 3 based on the filtered feedforward current command; It is configured to control the power conversion circuit 10 so as to supply the electric motor 3 with a current based on the first current command and the second current command.

According to the configuration in which the second current command is calculated based on the feedforward current command, it is possible to quickly calculate the second current command for expanding the range of driving force and the range of operating speed. However, since a mutual influence loop is formed between the first current command and the second current command, the stability of the secondary current may decrease. In contrast, the control circuit 100 performs filtering to suppress changes in the feedforward current command in response to changes in the first current command. Thereby, the influence of the first current command on the second current command can be suppressed, and a decrease in the stability of the output current can be suppressed. Therefore, this is effective in quickly suppressing saturation of the output voltage and stabilizing the output current to the motor 3.

As shown in FIG. 1, the control circuit 100 includes a current command generation section 120, a coordinate conversion section 111, an angular velocity calculation section 112, and a voltage calculation section as functional components (hereinafter referred to as "functional blocks"). 113, a coordinate transformation unit 114, and a control unit 115, and processes by these functional blocks are repeated at a predetermined control cycle. The current command generation unit 120 calculates the above-described first current command and second current command in each control cycle. For example, the current command generation unit 120 calculates a first current command and a second current command in a rotating coordinate system.

The magnetic pole position of the electric motor 3 is expressed in electrical angle with respect to the stator of the electric motor 3. For example, the fixed coordinate system FC shown in FIG. 2 is a coordinate system fixed to the stator of the electric motor 3, and has an α axis and a β axis as two orthogonal coordinate axes. When the electric motor 3 is a rotary type, the origin of the fixed coordinate system FC (the intersection of the α axis and the β axis) coincides with the rotation center of the rotor of the electric motor 3. The α axis is directed toward the coil of any one phase (for example, U phase) of the electric motor 3. For example, the magnetic pole position PP is expressed as an electrical angle with respect to the α axis. Hereinafter, the electrical angle representing the magnetic pole position PP will be referred to as the magnetic pole direction θ.

The rotating coordinate system RC shown in FIG. 2 is a coordinate system that rotates in synchronization with the rotation of the magnetic pole position, and has a d-axis and a q-axis as two orthogonal coordinate axes. The origin of the rotating coordinate system RC (the intersection of the d-axis and the q-axis) coincides with the origin of the fixed coordinate system FC. The d-axis points toward the magnetic pole position PP.

The current command generation unit 120 calculates a q-axis current command Iq*, which is a current command in the q-axis direction, as a first current command, and calculates a d-axis current command Id, which is a current command in the d-axis direction, as a second current command. *Calculate. The current in the q-axis direction is a current that generates magnetic flux in the q-axis direction, and the current in the d-axis direction is a current that generates magnetic flux in the d-axis direction. The configuration of the current command generation section 120 will be described later. Hereinafter, the current in the d-axis direction will be referred to as "d-axis current", and the current in the q-axis direction will be referred to as "q-axis current".

Returning to FIG. 1, the coordinate transformation unit 111 performs coordinate transformation on the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 16 in each control cycle, and converts the d-axis current Id and q Calculate the shaft current Iq. For example, the coordinate transformation unit 111 performs three-phase/two-phase transformation on the U-phase current Iu, V-phase current Iv, and W-phase current Iw to calculate the α-axis current Iα and the β-axis current Iβ, and calculates the α-axis current Iα and Coordinate transformation is performed on the β-axis current Iβ using the magnetic pole direction θ to calculate the d-axis current Id and the q-axis current Iq.

The angular velocity calculation unit 112 calculates the angular frequency ω of the magnetic pole position PP (angular frequency ω of the rotating coordinate system RC with respect to the fixed coordinate system FC) in each control period. For example, the angular velocity calculation unit 112 calculates the angular frequency ω based on the magnetic pole direction θ detected by the magnetic pole position sensor 4. For example, the angular velocity calculation unit 112 calculates the angular frequency by dividing the difference between the magnetic pole direction θ detected by the magnetic pole position sensor 4 and the magnetic pole direction θ detected by the magnetic pole position sensor 4 in the previous control cycle by the control cycle. Calculate ω.

The voltage calculation unit 113 calculates a voltage command based on the d-axis current command Id* and the q-axis current command Iq* in each control cycle. For example, the voltage calculation unit 113 performs deinterference based on the q-axis current Iq and the angular frequency ω with respect to the command value for reducing the deviation between the d-axis current command Id* and the d-axis current Id. Calculate the shaft voltage command Vd*. Further, the voltage calculation unit 113 calculates an error based on the d-axis current Id, the magnet magnetic flux Φm, and the angular frequency ω with respect to the command value for reducing the deviation between the q-axis current command Iq* and the q-axis current Iq. Interference is performed to calculate the q-axis voltage command Vq*. As an example, the voltage calculation unit 113 calculates the d-axis voltage command Vd* and the q-axis voltage command Vq* based on the following equations.
Vd*=Kd(Id*-Id)-ω・Lq・Iq*...(1)
Vq*=Kq(Iq*-Iq)+ω・Ld・Id*+ω・Φm...(2)
Kd: d-axis current gain Lq: q-axis inductance Kq: q-axis current gain Ld: d-axis inductance Φm: Magnet magnetic flux

Note that although Equation (1) shows an example in which a proportional calculation is performed to reduce the deviation between the d-axis current command Id* and the d-axis current Id, the voltage calculation unit 113 In order to reduce the deviation between * and the d-axis current Id, proportional/integral calculations may be performed, or proportional/integral/differential calculations may be performed. Similarly, although equation (2) shows an example in which a proportional calculation is performed to reduce the deviation between the q-axis current command Iq* and the q-axis current Iq, the voltage calculation unit 113 In order to reduce the deviation between Iq* and q-axis current Iq, proportional/integral calculations may be performed, or proportional/integral/differential calculations may be performed. The d-axis voltage command Vd* and the q-axis voltage command Vq* may be a modulation rate (ratio to the magnitude of the voltage between the DC buses 13P and 13N).

In each control cycle, the coordinate transformation unit 114 performs coordinate transformation on the d-axis voltage command Vd* and the q-axis voltage command Vq* detected by the voltage calculation unit 113, and converts them into U-phase voltage command Vu* and V-phase voltage command. Vv* and W-phase voltage command Vw* are calculated. For example, the coordinate transformation unit 114 calculates Vα* and Vβ* by performing coordinate transformation on the d-axis voltage command Vd* and the q-axis voltage command Vq* according to the magnetic pole direction θ, and calculates Vα* and Vβ* with 2-phase/3-phase The conversion is performed to calculate a U-phase voltage command Vu*, a V-phase voltage command Vv*, and a W-phase voltage command Vw*.

The control unit 115 controls the power conversion circuit 10 to supply the electric motor 3 with a current based on the first current command and the second current command in each control cycle. For example, the control unit 115 controls the power conversion circuit 10 to apply a voltage to the electric motor 3 based on the voltage command calculated by the voltage calculation unit 113. For example, the control unit 115 applies voltages corresponding to the U-phase voltage command Vu*, the V-phase voltage command Vv*, and the W-phase voltage command Vw* to the U-phase, V-phase, and W-phase of the electric motor 3, respectively. Then, the plurality of switching elements 17 are turned on and off.

FIG. 3 is a block diagram illustrating the configuration of the current command generation section 120. The current command generation unit 120 includes a feedforward calculation unit 122, a filter 130, a second current calculation unit 123, and a first current calculation unit 121 as functional blocks. The feedforward calculation unit 122 calculates a feedforward current command for canceling the induced voltage of the motor 3 based on the characteristic parameters of the motor 3 and the first current command.

Examples of characteristic parameters of the electric motor 3 include armature resistance R, d-axis inductance Ld, and q-axis inductance Lq. For example, the feedforward calculation unit 122 calculates the feedforward current command Idff using the following equation.
Idff=[-Φm+{(Vlim/ω) ^2- (Lq・Iq*) ² } ^1/2 ]/Ld...(3)
Vlim: Voltage upper limit value

Note that the voltage upper limit is the upper limit of the voltage that the power conversion circuit 10 can apply to the motor 3, and is determined depending on the voltage between the DC buses 13P and 13N. Since the calculation of the q-axis current command Iq* is not completed at the time of generation of the feedforward current command Idff, the feedforward calculation unit 122 feeds the q-axis current command Iq* calculated in the previous control cycle. It is used to calculate the forward current command Idff.

The filter 130 performs filter processing on the feedforward current command Idff to suppress changes in the feedforward current command Idff in response to changes in the q-axis current command Iq*. For example, the filter 130 may include an extraction filter 131 that extracts components in a predetermined frequency band from the first current command, and may correct the feedforward current command based on the components extracted by the extraction filter 131. Examples of the extraction filter 131 include a high-pass filter or a band-pass filter.

By selectively removing components that tend to get into the loop between the first current command and the second current command from the feedforward current command, the speed of saturation suppression of the output voltage is suppressed from being reduced by the filter 130. be able to.

The filter 130 further includes a second extraction filter 132 that extracts components in a predetermined frequency band from the feedforward current command Idff, and extracts the feedforward current command Idff that has passed through the second extraction filter 132 from the components extracted by the extraction filter 131. Correction may be made based on the component. Examples of the second extraction filter 132 include a low-pass filter, a notch filter, and the like. By using the second extraction filter 132 and the extraction filter 131 in combination, it is possible to more appropriately adjust the balance between the promptness of suppressing saturation of the output voltage and the stability of the output current.

For example, the filter 130 further includes a correction section 133. When the extraction filter 131 is a high-pass filter or a band-pass filter, the correction unit 133 removes at least a part of the component extracted by the extraction filter 131 from the feedforward current command.

As an example, the extraction filter 131 is a high-pass filter, and the correction unit 133 applies a value obtained by multiplying the component extracted by the extraction filter 131 by a predetermined correction gain K from the feedforward current command Idff that has passed through the second extraction filter 132. Subtract. When the extraction filter 131 is a high-pass filter, the cutoff frequency of the second extraction filter 132 may be higher than the cutoff frequency of the extraction filter 131. The balance between the promptness of output voltage saturation suppression and the stability of output current can be adjusted more appropriately.

The second current calculation unit 123 calculates the d-axis current command Id* based on the feedforward current command Idff that has passed through the filter 130. The first current calculation unit 121 calculates a q-axis current command Iq* so that the electric motor 3 generates a driving force corresponding to a driving force command (for example, a torque command T*).

The first current calculation unit 121 may calculate the q-axis current command Iq* based on the torque command T* and the d-axis current command Id* calculated by the second current calculation unit 123. For example, the first current calculation unit 121 calculates the q-axis current command Iq* using the following equation.
Iq*=T*/[Pn{Φm+(Ld-Lq)Id*}] ...(4)
Pn: Number of pole pairs of electric motor 3

Based on the d-axis current command Id*, a more appropriate q-axis current command Iq* can be calculated. Since the d-axis current command Id* is based on the feedforward current that has passed through the filter 130, destabilization of the q-axis current command Iq* due to being based on the d-axis current command Id* is suppressed.

The control circuit 100 may further include a force-dependent calculation section 140 and a mode selection section 150. The force-dependent calculation unit 140 calculates a force-dependent current command Idt based on a driving force command (eg, torque command T*). For example, the force-dependent calculation unit 140 calculates the force-dependent current command Idt based on the torque command T* so as to perform MTPA (Maximum Torque Per Ampere) control. MTPA control is control that maximizes the ratio of driving force to current flowing through the electric motor 3.

The force-dependent calculation unit 140 calculates the force-dependent current command Idt based on the torque command T* and a current profile 141 that is predetermined to represent the relationship between the change in the force-dependent current command Idt and the change in the torque command T*. may be calculated. The force-dependent current command Idt can be easily calculated. When the force-dependent calculation unit 140 calculates the force-dependent current command Idt to perform the MTPA control, the current profile 141 represents the relationship between the change in the force-dependent current command Idt and the change in the driving force command in the MTPA control. It is predetermined as follows. The current profile 141 can be generated in advance by actual machine testing, simulation, or the like. The current profile 141 may be held as an approximate function or may be held as a discrete table.

The force-dependent calculation unit 140 may calculate the force-dependent current command Idt so as to perform control different from MTPA. For example, the force-dependent calculation unit 140 may calculate the force-dependent current command Idt so as to perform efficiency maximization control that maximizes the ratio of driving force to power consumption. The force-dependent calculation unit 140 may calculate the force-dependent current command Idt so as to perform power factor maximization control that maximizes the power factor of the secondary power. In either control, the current profile 141 can be generated in advance by actual machine testing, simulation, or the like.

The mode selection unit 150 selects one of a first mode in which the d-axis current command Id* is calculated based on the force-dependent current command Idt and a second mode in which the d-axis current command Id* is calculated based on the feedforward current command Idff. is selected based on a comparison between the force-dependent current command Idt and the feedforward current command Idff. When the mode selection unit 150 selects either the first mode or the second mode, the second current calculation unit 123 calculates the d-axis current command Id* in the mode selected by the mode selection unit 150. By appropriately switching between the first mode and the second mode, it is possible to achieve both suppression of saturation of the output voltage by the second current command and optimization of the output current with respect to the driving force command.

The mode selection unit 150 selects the first mode when the absolute value of the force-dependent current command Idt is larger than the absolute value of the feedforward current command Idff, and the mode selection unit 150 selects the first mode when the absolute value of the force-dependent current command Idt is larger than the absolute value of the feedforward current command Idff. The second mode may be selected when the absolute value is greater than the absolute value. The first mode and the second mode can be easily and appropriately switched.

The mode selection unit 150 may switch between the first mode and the second mode based on the difference between the absolute value of the force-dependent current command Idt and the absolute value of the feedforward current command Idff. For example, the mode selection unit 150 switches the second mode to the first mode in response to the difference between the absolute value of the force-dependent current command Idt and the absolute value of the feedforward current command Idff, and switches the second mode to the first mode, The first mode may be switched to the second mode in response to the difference between the absolute value of the command Idt and the absolute value of the feedforward current command Idff falling below a second threshold. The first threshold value and the second threshold value may be the same value (for example, zero) or may be different values. For example, the first threshold may be greater than the second threshold. The first threshold may be a positive value and the second threshold may be a negative value.

FIG. 4 is a graph illustrating the relationship between the force-dependent current command and the feedforward current command, where the horizontal axis represents the d-axis current command Id*, and the vertical axis represents the q-axis current command Iq*. Each of the constant torque curves L11, L12, L13, and L14 represents the relationship between the d-axis current command Id* and the q-axis current command Iq* corresponding to a constant driving force command. Constant torque curve L11 represents the case where the driving force command is the first value. Constant torque curve L12 represents a case where the driving force command is a second value larger than the first value. Constant torque curve L13 represents a case where the driving force command is a third value larger than the second value. Constant torque curve L14 represents a case where the driving force command is a fourth value larger than the third value.

MTPA curve L21 represents the relationship between d-axis current Id and q-axis current Iq in MTPA control. When the force-dependent calculation unit 140 calculates the force-dependent current command Idt to perform MTPA control, the force-dependent current command Idt is calculated so that the d-axis current Id and the q-axis current Iq are located on the MTPA curve L21. be done. For example, when the driving force command is the first value, the d-axis current Id at the intersection JP11 between the constant torque curve L11 and the MTPA curve L21 is calculated as the force-dependent current command Idt. When the driving force command is the second value, the d-axis current Id at the intersection JP12 between the constant torque curve L12 and the MTPA curve L21 is calculated as the force-dependent current command Idt. When the driving force command is the third value, the d-axis current Id at the intersection JP13 between the constant torque curve L13 and the MTPA curve L21 is calculated as the force-dependent current command Idt. When the driving force command is the fourth value, the d-axis current Id at the intersection JP14 between the constant torque curve L14 and the MTPA curve L21 is calculated as the force-dependent current command Idt.

Voltage limit ellipse L31 represents the relationship between d-axis current Id and q-axis current Iq in a state where the output voltage and the voltage upper limit value are equal. The feedforward current command Idff is calculated such that the d-axis current Id and the q-axis current Iq are located on the voltage restriction ellipse L31. For example, when the driving force command is the first value, the d-axis current Id at the intersection JP21 of the constant torque curve L11 and the voltage limit ellipse L31 is calculated as the feedforward current command Idff. When the driving force command is the second value, the d-axis current Id at the intersection JP22 of the constant torque curve L12 and the voltage limit ellipse L31 is calculated as the feedforward current command Idff. When the driving force command is the third value, the d-axis current Id at the intersection JP23 of the constant torque curve L13 and the voltage limit ellipse L31 is calculated as the feedforward current command Idff. When the driving force command is the fourth value, the d-axis current Id at the intersection JP24 of the constant torque curve L14 and the voltage limit ellipse L31 is calculated as the feedforward current command Idff.

Inside the voltage limiting ellipse L31, the absolute value of the force-dependent current command Idt is larger than the absolute value of the feedforward current command Idff. For example, the absolute value of the d-axis current Id at the intersection JP11 is greater than the absolute value of the d-axis current Id at the intersection JP21, and the absolute value of the d-axis current Id at the intersection JP12 is greater than the absolute value of the d-axis current Id at the intersection JP22. It's also big. In such a case, the mode selection unit 150 selects the first mode, and the second current calculation unit 123 calculates the d-axis current command Id* based on the force-dependent current command Idt.

Outside the voltage limiting ellipse L31, the absolute value of the force-dependent current command Idt is smaller than the absolute value of the feedforward current command Idff. For example, the absolute value of the d-axis current Id at the intersection JP14 is larger than the absolute value of the d-axis current Id at the intersection JP24. In such a case, the mode selection unit 150 selects the second mode, and the second current calculation unit 123 calculates the d-axis current command Id* based on the feedforward current command Idff.

Returning to FIG. 3, the control circuit 100 may further include a feedback calculation section 124. The feedback calculation unit 124 calculates the feedback current command Idfb so as to reduce the deviation between the voltage command and the voltage applied by the power conversion circuit 10 to the motor 3 based on the voltage command (hereinafter referred to as "voltage deviation"). do. When the control circuit 100 includes the feedback calculation unit 124, the second current calculation unit 123 may calculate the d-axis current command Id* based on the feedforward current command Idff and the feedback current command Idfb. The combination of feedback and feedforward allows saturation of the output voltage to be suppressed quickly and appropriately.

As described above, when the mode selection unit 150 selects either the first mode or the second mode, the second current calculation unit 123 selects the feedforward current command Idff and the feedback current command in the second mode. The d-axis current command Id* may be calculated based on Idfb.

For example, the control circuit 100 further includes a field weakening calculation section 127. Field weakening calculation unit 127 calculates field weakening current command Idfw based on feedforward current command Idff and feedback current command Idfb. As an example, the field weakening calculation unit 127 calculates the field weakening current command Idfw by adding up the feedback current command Idfb from the feedforward current command Idff. The second current calculation unit 123 calculates the d-axis current command Id* based on the field weakening current command Idfw calculated by the field weakening calculation unit 127.

“The voltage applied to the electric motor 3 by the power conversion circuit 10 based on the voltage command” may be a voltage actually detected by a voltage sensor or the like, or may be a voltage calculated backward from the ON periods of the plurality of switching elements 17. There may be. The feedback calculation unit 124 calculates the feedback current command Idfb by performing proportional calculation, proportional/integral calculation, proportional/integral/differential calculation, etc. on the voltage deviation.

The feedback calculation unit 124 calculates the deviation between the maximum voltage that the power conversion circuit 10 can apply to the motor 3 (the voltage upper limit value Vlim) and the voltage command V* as a voltage deviation, and performs a proportional calculation on the calculated deviation. The feedback current command Idfb may be calculated by performing proportional/integral calculations or proportional/integral/differential calculations.

Since the power conversion circuit 10 never outputs a voltage that substantially exceeds the voltage command V*, the above voltage deviation will not be a positive value, but the deviation between the voltage command V* and the voltage upper limit value Vlim is Can be a positive value. Corresponding to this, the control circuit 100 may further include a limiter 125. The limiter 125 limits the field weakening current command Idfw calculated by the field weakening calculation unit 127 to zero or less. For example, the limiter 125 changes the field weakening current command Idfw to zero when the field weakening current command Idfw is a positive value. When the field weakening current command Idfw is less than or equal to zero, the limiter 125 does not change the value of the field weakening current command Idfw. The second current calculation unit 123 calculates the d-axis current command Id* based on the field weakening current command Idfw passed through the limiter 125.

By limiting the field weakening current command Idfw calculated by adding up the feedback current commands Idfb to zero or less, the field weakening current command Idfw is prevented from taking a positive value due to the positive feedback current command Idfb. Since the limiter 125 is applied to the field-weakening current command Idfw instead of the feedback current command Idfb, when calculating the field-weakening current command Idfw, the error in the feedforward current command Idff due to errors in characteristic parameters, etc. is calculated using the feedback current command Idfb. By subtracting , it is possible to correct in the positive direction as well.

For example, even though the voltage command V* is smaller than the voltage upper limit value Vlim and the output voltage is not saturated, an excessive feedforward current command Idff in the negative direction is calculated and the second mode is selected. In this case, by adding up the positive feedback current commands Idfb, it is possible to prevent the field weakening current command Idfw from becoming excessively large in the negative direction. Therefore, saturation of the output voltage can be suppressed more appropriately.

The control circuit 100 may further include a feedforward limiter 126 that limits the feedforward current command Idff to zero or less. For example, the feedforward limiter 126 changes the feedforward current command Idff to zero when the feedforward current command Idff is a positive value. When the feedforward current command Idff is less than or equal to zero, the feedforward limiter 126 does not change the value of the feedforward current command Idff. The mode selection unit 150 may switch between the first mode and the second mode based on the feedforward current command Idff passed through the feedforward limiter 126 and the feedback current command Idfb. The field weakening calculation unit 127 may calculate the field weakening current command Idfw based on the feedforward current command Idff passed through the feedforward limiter 126 and the feedback current command Idfb. By removing obvious error components from the feedforward current command Idff, the complementary action between the feedforward current command Idff and the feedback current command Idfb can be utilized more effectively.

The mode selection unit 150 may include a first switch 151 and a second switch 152. The first switch 151 sets the force-dependent current command Idt to zero when the absolute value of the force-dependent current command Idt is smaller than the absolute value of the feedforward current command Idff. For example, the first switch 151 sets the value of the force-dependent current command Idt as the calculation result of the force-dependent calculation unit 140 based on the difference between the absolute value of the force-dependent current command Idt and the absolute value of the feedforward current command Idff. 1 state and a second state in which the force-dependent current command Idt is set to zero. For example, the first switch 151 switches the second state to the first state in response to the difference between the absolute value of the force-dependent current command Idt and the absolute value of the feedforward current command Idff exceeding the first threshold value, and switches the second state to the first state, The first state is switched to the second state in response to the difference between the absolute value of the current command Idt and the absolute value of the feedforward current command Idff being less than the second threshold.

The second switch 152 sets the feedforward current command Idff to zero when the absolute value of the force-dependent current command Idt is larger than the absolute value of the feedforward current command Idff. For example, the second switch 152 can switch between a first state in which the value of the feedforward current command Idff is zero and a feedforward current state based on the difference between the absolute value of the force-dependent current command Idt and the absolute value of the feedforward current command Idff. A second state in which the command Idff is the calculation result by the feedforward calculation unit 122 is switched. For example, the first switch 151 switches the second state to the first state in response to the difference between the absolute value of the force-dependent current command Idt and the absolute value of the feedforward current command Idff exceeding the first threshold value, and switches the second state to the first state, The first state is switched to the second state in response to the difference between the absolute value of the current command Idt and the absolute value of the feedforward current command Idff being less than the second threshold.

The field-weakening calculation unit 127 calculates the field-weakening current command Idfw based on the feedforward current command Idff passed through the second switch 152 and the feedback current command Idfb, and the second current calculation unit 123 The current command Idfw and the force-dependent current command Idt passed through the first switch 151 are added together to calculate the d-axis current command Id*. According to the first switch 151 and the second switch 152, the first mode and the second mode can be easily and appropriately switched. The first switch 151 and the second switch 152 may be software switches.

In the above, the case where the electric motor 3 is provided with the magnetic pole position sensor 4 has been illustrated, but the electric motor 3 does not need to be provided with the magnetic pole position sensor 4. In this case, the control circuit 100 may be configured to estimate the magnetic pole direction θ without a sensor and perform the above-described processing based on the estimation result of the magnetic pole direction θ.

FIG. 5 is a block diagram illustrating the hardware configuration of the control circuit 100. As shown in FIG. 5, for example, the control circuit 100 includes one or more processors 191, a memory 192, a storage 193, an input/output port 194, and a switching control circuit 195.

Storage 193 includes a nonvolatile storage medium such as a flash memory or a hard disk. The storage 193 calculates a first current command corresponding to a direction perpendicular to the magnetic pole direction of the electric motor 3 so that the electric motor 3 generates a driving force corresponding to the driving force command, and a characteristic parameter of the electric motor 3. Based on the first current command, calculate a feedforward current command for canceling the induced voltage of the motor 3, and perform feedforward filtering to suppress changes in the feedforward current command according to changes in the first current command. calculating a second current command corresponding to the magnetic pole direction of the motor 3 based on the filtered feedforward current command; and calculating a second current command corresponding to the magnetic pole direction of the motor 3 based on the first current command and the second current command. A program for causing the control circuit 100 to control the power conversion circuit 10 to supply current to the electric motor 3 is stored. For example, the storage 193 stores programs for causing the control circuit 100 to configure each of the functional blocks described above.

The memory 192 temporarily stores a program loaded from the storage 193 and data generated during the execution process of the program. One or more processors 191 cause the control circuit 100 to function as each functional block by executing programs stored in the memory 192. The input/output port 194 inputs and outputs electrical signals between the magnetic pole position sensor 4 and the current sensor 16 in response to commands from one or more processors 191 . The switching control circuit 195 turns on and off the plurality of switching elements 17 in response to commands from one or more processors 191. The above hardware configuration is just an example and can be changed as appropriate. For example, at least one of each functional block may be configured with a dedicated circuit element such as an ASIC (Application Specific Integrated Circuit).

[Power conversion procedure]
Next, as an example of a power conversion method, a power conversion procedure executed by the control circuit 100 will be illustrated. This procedure includes calculating a first current command corresponding to a direction perpendicular to the magnetic pole direction of the electric motor 3 so that the electric motor 3 generates a driving force corresponding to the driving force command, and calculating the characteristic parameters of the electric motor 3. Based on the first current command, calculate a feedforward current command for canceling the induced voltage of the motor 3, and perform feedforward filtering to suppress changes in the feedforward current command according to changes in the first current command. calculating a second current command corresponding to the magnetic pole direction of the motor 3 based on the filtered feedforward current command; and calculating a second current command corresponding to the magnetic pole direction of the motor 3 based on the first current command and the second current command. and controlling the power conversion circuit 10 to supply current to the electric motor 3.

As shown in FIG. 6, the control circuit 100 executes steps S01 and S02. In step S01, the coordinate transformation unit 111 performs the coordinate transformation described above on the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 16, and converts the d-axis current Id and the q-axis current Iq. Calculate. In step S02, the angular velocity calculation unit 112 calculates the angular frequency ω based on the magnetic pole direction θ detected by the magnetic pole position sensor 4.

Next, the control circuit 100 executes steps S03, S04, and S05. In step S03, the current command generation unit 120 calculates a d-axis current command Id* and a q-axis current command Iq*. The specific contents of step S03 will be described later. In step S04, voltage calculation unit 113 calculates d-axis voltage command Vd* and q-axis voltage command Vq* based on d-axis current command Id* and q-axis current command Iq*. Coordinate transformation unit 114 performs coordinate transformation on d-axis voltage command Vd* and q-axis voltage command Vq* to calculate U-phase voltage command Vu*, V-phase voltage command Vv*, and W-phase voltage command Vw*. In step S05, voltages corresponding to the U-phase voltage command Vu*, the V-phase voltage command Vv*, and the W-phase voltage command Vw* are applied to the U-phase, V-phase, and W-phase of the electric motor 3, respectively. The control unit 115 starts turning on and off the plurality of switching elements 17 .

Next, the control circuit 100 executes step S06. In step S06, the coordinate conversion unit 111 waits for the control period to elapse. After that, the control circuit 100 returns the process to step S01. The control circuit 100 repeatedly executes the above processing.

FIG. 7 is a flowchart illustrating the procedure for calculating the d-axis current command Id* and the q-axis current command Iq* in step S03. As shown in FIG. 7, the control circuit 100 executes steps S11, S12, S13, and S14. In step S11, the force-dependent calculation unit 140 calculates a force-dependent current command Idt based on the torque command T*. In step S12, the feedforward calculation unit 122 calculates the feedforward current command Idff based on the characteristic parameters of the electric motor 3 and the q-axis current command Iq*. For example, the feedforward calculation unit 122 calculates the feedforward current command Idff based on the q-axis current command Iq* calculated in the previous control cycle. In step S13, the filter 130 performs the above-described filtering process on the feedforward current command Idff to suppress changes in the feedforward current command Idff in response to changes in the q-axis current command Iq*. In step S14, the feedforward limiter 126 limits the feedforward current command Idff to zero or less.

Next, the control circuit 100 executes step S15. In step S15, the mode selection unit 150 checks whether the absolute value of the force-dependent current command Idt is greater than or equal to the absolute value of the feedforward current command Idff. If it is determined in step S15 that the absolute value of the force-dependent current command Idt is greater than or equal to the absolute value of the feedforward current command Idff, the control circuit 100 executes step S16. In step S16, the second switch 152 changes the feedforward current command Idff to zero. If it is determined in step S15 that the absolute value of the force-dependent current command Idt is less than the absolute value of the feedforward current command Idff, the control circuit 100 executes step S17. In step S17, the first switch 151 changes the force-dependent current command Idt to zero.

After step S16 or step S17, the control circuit 100 executes steps S21, S22, S23, and S24. In step S21, the field weakening calculation unit 127 calculates the field weakening current command Idfw based on the feedforward current command Idff and the feedback current command Idfb. In step S22, the limiter 125 limits the field weakening current command Idfw to zero or less. In step S23, the second current calculation unit 123 calculates the d-axis current command Id* based on the force-dependent current command Idt and the field-weakening current command Idfw. In step S24, the first current calculation unit 121 calculates the q-axis current command Iq* based on the torque command T* and the d-axis current command Id* calculated by the second current calculation unit 123. The procedure for calculating the d-axis current command Id* and the q-axis current command Iq* is thus completed.

〔summary〕
As explained above, the power conversion device 2 includes a power conversion circuit 10 that performs power conversion between the power source 9 and the electric motor 3, and a power conversion circuit 10 that converts power between the power source 9 and the electric motor 3, and a A first current calculation unit 121 calculates a first current command corresponding to a direction perpendicular to the magnetic pole direction of the electric motor 3, cancels the induced voltage of the electric motor 3 based on the characteristic parameters of the electric motor 3, and the first current command. A feedforward calculation unit 122 that calculates a feedforward current command for the first current command, a filter 130 that suppresses a change in the feedforward current command according to a change in the first current command, and a feedforward current command that has passed through the filter 130. A second current calculation unit 123 that calculates a second current command corresponding to the magnetic pole direction of the electric motor 3, and a power conversion circuit 10 that is controlled to supply a current to the electric motor 3 based on the first current command and the second current command. A control unit 115 is provided.

According to the configuration in which the second current command is calculated based on the forward current command, the second current command for expanding the range of driving force can be quickly calculated. However, since a mutual influence loop is formed between the first current command and the second current command, the stability of the secondary current may decrease. In contrast, this power conversion device 2 further includes a filter 130 that suppresses changes in the feedforward current command in response to changes in the first current command. Thereby, the influence of the first current command on the second current command can be suppressed, and a decrease in the stability of the output current can be suppressed. Therefore, this is effective in quickly suppressing saturation of the output voltage and stabilizing the output current to the motor 3.

The first current calculation unit 121 may calculate the first current command based on the driving force command and the second current command. Based on the second current command, a more appropriate first current command can be calculated. Since the second current command is based on the feedforward current that has passed through the filter 130, instability of the first current command due to being based on the second current command is suppressed.

The filter 130 includes an extraction filter 131 that extracts a component in a predetermined frequency band from the first current command, and may correct the feedforward current command based on the component extracted by the extraction filter 131. By selectively removing components that are likely to get into the loop from the feedforward current command, it is possible to prevent the filter 130 from reducing the speed of saturation suppression of the output voltage.

The filter 130 may further include a second extraction filter 132 for the feedforward current command, and may correct the feedforward current command that has passed through the second extraction filter 132 based on the extracted component. By using the second extraction filter 132 and the extraction filter 131 in combination, it is possible to more appropriately adjust the balance between the promptness of suppressing saturation of the output voltage and the stability of the output current.

The extraction filter 131 is a high-pass filter for the first current command, and the second extraction filter 132 is a low-pass filter, and the cutoff frequency of the second extraction filter 132 may be higher than the cutoff frequency of the extraction filter 131. By setting the cutoff frequencies of the second extraction filter 132 and the extraction filter 131, it is possible to more appropriately adjust the balance between the speed of saturation suppression of the output voltage and the stability of the output current.

A force-dependent calculation unit 140 that calculates a force-dependent current command based on a driving force command, a first mode that calculates a second current command based on the force-dependent current command, and a second mode that calculates a second current command based on the feedforward current command. The second current calculation unit 123 further includes a mode selection unit 150 that selects one of the second modes based on a comparison between the force-dependent current command and the feedforward current command. The second current command may be calculated in the selected mode. By appropriately switching between the first mode and the second mode, it is possible to achieve both suppression of saturation of the output voltage by the second current command and optimization of the output current with respect to the driving force command.

The force-dependent calculation unit 140 calculates a force-dependent current command based on the driving force command and a current profile 141 that is predetermined to represent the relationship between the change in the force-dependent current command and the change in the driving force command. Good too. Force-dependent current commands can be easily calculated.

The mode selection unit 150 selects the first mode when the absolute value of the force-dependent current command is larger than the absolute value of the feedforward current command, and the absolute value of the force-dependent current command is larger than the absolute value of the feedforward current command. If the difference is large, the second mode may be selected. The first mode and the second mode can be easily and appropriately switched.

The control unit 115 further includes a voltage calculation unit 113 that calculates a voltage command based on the first current command and the second current command, and the control unit 115 controls the power conversion circuit 10 to apply a voltage based on the voltage command to the motor 3. May be controlled. Power conversion circuit 10 can be easily controlled.

The second current calculation unit 123 further includes a feedback calculation unit that calculates a feedback current command so as to reduce the deviation between the voltage command and the voltage applied to the electric motor 3 by the power conversion circuit 10 based on the voltage command, and the second current calculation unit 123 The second current command may be calculated based on the feedforward current command and the feedback current command. The combination of feedback and feedforward allows saturation of the output voltage to be suppressed quickly and appropriately.

The feedback calculation unit 124 calculates the deviation between the voltage command and the maximum voltage that the power conversion circuit 10 can apply to the electric motor 3 as a deviation, and the power conversion device 2 calculates the deviation between the voltage command and the maximum voltage that the power conversion circuit 10 can apply to the electric motor 3. The second current calculation unit 123 may further include a limiter 125 that limits the field weakening current command based on the limiter 125 to zero or less, and the second current calculation unit 123 may calculate the second current command based on the field weakening current command passed through the limiter 125. The deviation between the voltage command and the maximum voltage that the power conversion circuit 10 can apply to the electric motor 3 can be a negative value when the power conversion circuit 10 can apply a voltage corresponding to the voltage command to the electric motor 3. Therefore, it is possible to correct an error in the feedforward current command due to an error in the characteristic parameter or the like in the positive direction by subtracting the feedback current command. According to the deviation calculated based on the voltage command and the maximum voltage that the power conversion circuit 10 can apply to the motor 3, it is possible that the field weakening current command becomes positive due to the feedback current command. However, this phenomenon is prevented by the limiter 125. Therefore, saturation of the output voltage can be suppressed more appropriately.

a force-dependent calculation unit 140 that calculates a force-dependent current command based on the driving force command; and a first unit that makes the force-dependent current command zero when the absolute value of the force-dependent current command is smaller than the absolute value of the feedforward current command. The second current calculation unit 123 further includes a switch 151 and a second switch 152 that sets the feedforward current command to zero when the absolute value of the force-dependent current command is larger than the absolute value of the feedforward current command. The second current command may be calculated based on the feedforward current command, a field weakening current command based on the feedback current command, and the force-dependent current command. It is possible to easily and appropriately switch between the first mode in which the second current command is calculated based on the force-dependent current command and the second mode in which the second current command is calculated based on the feedforward current command.

Although the embodiments have been described above, the present disclosure is not necessarily limited to the embodiments described above, and various changes can be made without departing from the gist thereof.

2... Power converter, 10... Power converter circuit, 9... Power source, 3... Electric motor, 113... Voltage calculation section, 115... Control section, 121... First current calculation section, 122... Feedforward calculation section, 130... Filter, 131... Extraction filter, 132... Second extraction filter, 123... Second current calculation section, 140... Force dependent calculation section, 141... Current profile, 150... Mode selection section, 124... Feedback calculation section, 125... Limiter, 151... First switch, 152...Second switch, 126...Feed forward limiter.

Claims (13)

a power conversion circuit that performs power conversion between a power source and an electric motor;
a first current calculation unit that calculates a first current command corresponding to a direction perpendicular to a magnetic pole direction of the electric motor so as to cause the electric motor to generate a driving force corresponding to the driving force command;
a feedforward calculation unit that calculates a feedforward current command for canceling the induced voltage of the motor based on a characteristic parameter of the motor and the first current command;
a filter that suppresses a change in the feedforward current command in response to a change in the first current command;
a second current calculation unit that calculates a second current command corresponding to the magnetic pole direction of the motor based on the feedforward current command that has passed through the filter;
a control unit that controls the power conversion circuit to supply the electric motor with a current based on the first current command and the second current command;
A power conversion device comprising: The first current calculation unit calculates the first current command based on the driving force command and the second current command.
The power conversion device according to claim 1. The filter includes an extraction filter that extracts a component in a predetermined frequency band from the first current command, and corrects the feedforward current command based on the component extracted by the extraction filter.
The power conversion device according to claim 1. The filter further includes a second extraction filter that extracts a component in a predetermined frequency band from the feedforward current command, and the feedforward current command that has passed through the second extraction filter is extracted from the first extraction filter that has passed through the extraction filter. Correct based on current command,
The power conversion device according to claim 3. The extraction filter is a high pass filter for the first current command,
The second extraction filter is a low-pass filter for the feedforward current command,
the cutoff frequency of the second extraction filter is higher than the cutoff frequency of the extraction filter;
The power conversion device according to claim 4. a force-dependent calculation unit that calculates a force-dependent current command based on the driving force command;
Either a first mode in which the second current command is calculated based on the force-dependent current command or a second mode in which the second current command is calculated based on the feedforward current command is used as the force-dependent current command. a mode selection unit that selects a mode based on comparison with the feedforward current command;
further comprising;
The second current calculation unit calculates the second current command in the mode selected by the mode selection unit.
The power conversion device according to any one of claims 1 to 5. The force-dependent calculation unit calculates a force-dependent current command based on the driving force command and a current profile that is predetermined to represent a relationship between a change in the force-dependent current command and a change in the driving force command. do,
The power conversion device according to claim 6. The mode selection unit selects the first mode when the absolute value of the force-dependent current command is larger than the absolute value of the feedforward current command, and the mode selection unit selects the first mode when the absolute value of the force-dependent current command is larger than the absolute value of the feedforward current command. selecting the second mode when the absolute value of
The power conversion device according to claim 6. further comprising a voltage calculation unit that calculates a voltage command based on the first current command and the second current command,
The control unit controls the power conversion circuit to apply a voltage based on the voltage command to the electric motor.
The power conversion device according to any one of claims 1 to 5. further comprising a feedback calculation unit that calculates a feedback current command so as to reduce a deviation between the voltage command and the voltage applied by the power conversion circuit to the motor based on the voltage command,
The second current calculation unit calculates the second current command based on the feedforward current command and the feedback current command.
The power conversion device according to claim 9. The feedback calculation unit calculates, as the deviation, a deviation between a maximum voltage that the power conversion circuit can apply to the motor and the voltage command,
The power conversion device includes:
further comprising a limiter that limits a field weakening current command based on the feedforward current command and the feedback current command to zero or less,
The second current calculation unit calculates the second current command based on the field weakening current command that has passed through the limiter.
The power conversion device according to claim 10. a force-dependent calculation unit that calculates a force-dependent current command based on the driving force command;
a first switch that sets the force-dependent current command to zero when the absolute value of the force-dependent current command is smaller than the absolute value of the feedforward current command;
a second switch that sets the feedforward current command to zero when the absolute value of the force-dependent current command is greater than the absolute value of the feedforward current command;
further comprising;
The second current calculation unit calculates the second current command based on the feedforward current command, a field weakening current command based on the feedback current command, and the force-dependent current command.
The power conversion device according to claim 10. calculating a first current command corresponding to a direction perpendicular to a magnetic pole direction of the electric motor so as to cause the electric motor to generate a driving force corresponding to the driving force command;
Calculating a feedforward current command for canceling the induced voltage of the motor based on a characteristic parameter of the motor and the first current command;
applying filtering to the feedforward current command to suppress a change in the feedforward current command according to a change in the first current command;
Calculating a second current command corresponding to the magnetic pole direction of the motor based on the filtered feedforward current command;
controlling a power conversion circuit to supply the electric motor with a current based on the first current command and the second current command;
power conversion methods including;

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