JP2021040357A - Power conversion device and power conversion method - Google Patents

Abstract

To provide a power conversion device that is effective for achieving both improving detection accuracy of electric motor resistance and suppressing a driving force ripple during operation.SOLUTION: A power conversion device 1 comprises a power conversion circuit 10 for performing power conversion; a current command generation part 120 for generating a control command including at least a fundamental wave of AC; a power conversion control part 112 for controlling the power conversion circuit 10 in such a manner power on an electric motor 3 side follows the control command; and a resistance calculation part 115 for calculating resistance of an electric motor 3, on the basis of a DC component of a voltage and a DC component of a current that are generated on the electric motor 3 side by the power conversion circuit 10. The current command generation part 120 comprising an adjustment wave generation part 123 for generating an adjustment wave of AC generates the control command including the fundamental wave, the DC component and the adjustment wave, on the basis of a DC component generation part 122 for generating the DC component, a frequency of the fundamental wave and a magnitude of the DC component in such a manner that when an operation velocity of the electric motor 3 is a second velocity smaller than a first velocity is made to be larger than when the operation velocity is the first velocity.SELECTED DRAWING: Figure 1

Description

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

In Non-Patent Document 1, the DC component and the adjustment wave are added to the fundamental wave of the current command in the control of the induction motor, and the resistance of the induction motor is calculated based on the DC component of the output voltage and the DC component of the output current. The method is disclosed. The tuning wave has a frequency equal to twice the frequency of the fundamental wave and an amplitude equal to the magnitude of the DC component.

Lijun He et al. , "An Improved DC-signal-injection Method with Active Torque-ripple Mitigation for Thermal Monitoring of Field-oriented-control

The present disclosure provides a power conversion device that is more effective in both improving the detection accuracy of the resistance of the electric motor during operation and suppressing the driving force ripple of the electric motor.

The power conversion device according to one aspect of the present disclosure includes a power conversion unit that converts power between a power source and an electric motor, a command generation unit that generates a control command including at least an alternating current fundamental wave, and electric power on the electric motor side. Resistance calculation that calculates the resistance of the motor based on the power conversion control unit that controls the power conversion unit so as to follow the control command, and the DC component of the voltage and the DC component of the current generated by the power conversion unit on the motor side. A direct current unit is provided with a direct current unit, and the command generator generates a direct current component so that the operating speed of the electric motor is larger when the second speed is smaller than the first speed than when the operating speed is the first speed. It has a component generation unit, an adjustment wave generation unit that generates an AC adjustment wave based on the frequency of the fundamental wave and the magnitude of the DC component, and includes the fundamental wave, the DC component, and the adjustment wave. Generate a control command.

In the power conversion method according to another aspect of the present disclosure, the power on the motor side controls the power conversion unit that generates a control command including at least an alternating current fundamental wave and performs power conversion between the power supply and the motor. A control command is generated, including controlling to follow the command and calculating the resistance of the motor based on the DC component of the voltage and the DC component of the current generated by the power converter on the motor side. What is done is to generate a DC component so that the operating speed of the motor is larger when the second speed is smaller than the first speed than when the operating speed is the first speed, and the frequency of the fundamental wave. Includes the generation of an alternating current adjustment wave based on the magnitude of the DC component, and the generation of a control command including the fundamental wave, the DC component, and the adjustment wave.

According to the present disclosure, it is possible to provide a power conversion device that is more effective in both improving the detection accuracy of the resistance of the electric motor during operation and suppressing the driving force ripple of the electric motor.

It is a schematic diagram which illustrates the structure of the power conversion apparatus. It is a block diagram which illustrates the structure of the current command generation part. It is a figure which illustrates the fixed coordinate system and the rotating coordinate system. It is a graph which shows an example of a DC component profile, a boost profile and a carrier profile. It is a graph which shows the modification of the DC component profile, the boost profile and the carrier profile. It is a block diagram which illustrates the hardware composition of a control circuit. It is a flowchart which illustrates the power conversion 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 designated by the same reference numerals, and duplicate description will be omitted.

[Power converter]
The power conversion device 1 shown in FIG. 1 is a device that performs power conversion between the power supply 2 and the electric motor 3. The power supply 2 is, for example, a three-phase AC power supply. Specific examples of the power supply 2 include a three-phase AC power system, a three-phase AC uninterruptible power supply, and the like.

The electric motor 3 is an induction motor that operates by supplying alternating current (for example, three-phase alternating current). The electric motor 3 may be a synchronous motor that operates by supplying alternating current. The electric motor 3 may be a rotary type or a linear type. In the following, since the case where the electric motor 3 is a rotary type will be described, the operating amount of the electric motor 3 is referred to as a "rotational angle", the operating speed of the electric motor 3 is referred to as a "rotational speed", and the driving force generated by the electric motor 3 is described. Is called "torque". When the electric motor 3 is a linear type, the driving force generated by the electric motor 3 is, for example, a thrust.

The power conversion device 1 includes a power conversion circuit 10 and a control circuit 100. The power conversion circuit 10 (power conversion unit) performs power conversion between the power supply 2 and the electric motor 3. For example, the power conversion circuit 10 converts AC power from the power source 2 (hereinafter, referred to as “primary power”) into driving AC power (hereinafter, referred to as “secondary power”) and supplies the power to the electric power 3. To do. As an example, the power conversion circuit 10 includes a rectifier circuit 11, a smoothing capacitor 12, an inverter circuit 13, and a current sensor 14.

The rectifier circuit 11 is, for example, a diode bridge circuit or a PWM converter circuit, and converts the primary side power into DC power. The smoothing capacitor 12 smoothes the DC power. The inverter circuit 13 performs power conversion between the DC power and the secondary power.

For example, the inverter circuit 13 converts DC power into secondary side power and supplies it to the electric motor 3 in the power running state, and converts the secondary side power returned from the electric motor 3 into DC power in the regenerated state. The power running state is a state in which the electric motor 3 is operated by the electric power supplied from the inverter circuit 13, and the regenerative state is a state in which the electric motor 3 returns the electric power corresponding to the operation to the inverter circuit 13.

For example, the inverter circuit 13 has a plurality of switching elements 15 and performs the power conversion by switching on / off of the plurality of switching elements 15. The switching element 15 is, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), and switches on / off according to a gate drive signal.

The current sensor 14 detects the current flowing between the inverter circuit 13 and the electric motor 3. For example, the current sensor 14 may be configured to detect the current of all three-phase alternating current (a-phase, b-phase, and c-phase), or detect the current of any two-phase of three-phase alternating current. It may be configured as follows. As long as no leakage current occurs, the total of the a-phase, b-phase, and c-phase currents is zero, so information on the currents of all phases can be obtained even when two-phase currents are detected.

The control circuit 100 generates a control command including at least an AC fundamental wave, controls the power conversion circuit 10 so that the secondary side power follows the control command, and the power conversion circuit 10 is on the motor 3 side. Based on the DC component of the voltage (that is, the voltage of the secondary side power) generated in the motor 3 and the DC component of the current (that is, the current of the secondary side power) generated by the power conversion circuit 10 on the motor 3 side. It is configured to calculate resistance and perform.

Generating the control command means generating a DC component so that the rotation speed of the electric motor 3 becomes larger when the rotation speed is the second speed, which is smaller than the first speed, than when the rotation speed is the first speed. Includes generating an AC tuning wave based on the frequency of the fundamental wave and the magnitude of the DC component, and generating a control command that includes the fundamental wave, the DC component, and the tuning wave.

The control command may be a current command or a voltage command. When the control command is a current command, making the secondary side power follow the control command means making the current of the secondary side power (hereinafter, referred to as "actual current") follow the current command. When the control command is a voltage command, making the secondary side power follow the control command means making the voltage of the secondary side power (hereinafter, referred to as "actual voltage") follow the voltage command. Hereinafter, the configuration when the control command is a current command will be illustrated.

For example, the control circuit 100 includes a current control unit 111, a power conversion control unit 112, a coordinate conversion unit 113, and a three-phase / two-phase conversion unit 114 as functional configurations (hereinafter referred to as “functional blocks”). It has a resistance calculation unit 115, a magnetic flux estimation unit 116, a filter processing unit 117, and a current command generation unit 120.

The current control unit 111 performs an operation for bringing the actual current closer to the current command. For example, the current control unit 111 calculates the voltage command so as to reduce the deviation between the current command and the actual current. The voltage command here is not the voltage command as the control command described above. In order to distinguish it from the voltage command as the control command, the voltage command calculated by the current control unit 111 is referred to as "voltage command for current control" in the following.

For example, the current control unit 111 calculates a voltage command for current control by performing proportional calculation, proportional / integral calculation, or proportional / integral / differential calculation on the deviation between the current command and the actual current. As an example, the current control unit 111 reduces the deviation between the d-axis current command id_ref and the q-axis current command iq_ref and the d-axis current id and the q-axis current iq in the dq coordinate system. And the q-axis voltage command Vq_ref is calculated.

The dq coordinate system is a coordinate system that rotates (moves) with the mover of the electric motor 3, and includes a d-axis and a q-axis as coordinate axes (see FIG. 3). The d-axis is along the magnetic flux direction of the mover of the electric motor 3. The q-axis is perpendicular to the magnetic flux direction. The d-axis current command id_ref is the d-axis direction component of the current command, the q-axis current command iq_ref is the q-axis direction component of the current command, the d-axis current id is the d-axis direction component of the actual current, and the q-axis current. iq is the q-axis direction component of the actual current, the d-axis voltage command Vd_ref is the d-axis direction component of the voltage command for current control, and the q-axis voltage command Vq_ref is the q-axis direction component of the voltage command for current control. is there.

The power conversion control unit 112 controls the power conversion circuit 10 so that the secondary power follows the control command. For example, the power conversion control unit 112 controls the power conversion circuit 10 so that the actual current follows the current command. As an example, the power conversion control unit 112 controls the power conversion circuit 10 so that the actual voltage becomes a magnitude in accordance with the voltage command for current control. More specifically, the power conversion control unit 112 switches the plurality of switching elements 15 on and off in a predetermined carrier cycle so that the actual voltage becomes a magnitude in accordance with the voltage command for current control.

For example, the power conversion control unit 112 sets the switching element 15 so that the actual voltage of each of the three phases (a-phase, b-phase, and c-phase) of the secondary power becomes the magnitude according to the voltage command for current control. Toggle on / off. As an example, in the power conversion control unit 112, the a-phase voltage Va substantially matches the a-phase voltage command Va_ref, the b-phase voltage Vb substantially matches the b-phase voltage command Vb_ref, and the c-phase voltage Vc c. The plurality of switching elements 15 are switched on and off so as to substantially match the phase voltage command Vc_ref. The a-phase voltage Va is the actual voltage of the a-phase, and the a-phase voltage command Va_ref is the a-phase component of the voltage command for current control. The b-phase voltage Vb is the actual voltage of the b-phase, and the b-phase voltage command Vb_ref is the b-phase component of the voltage command for current control. The c-phase voltage Vc is the actual voltage of the c-phase, and the c-phase voltage command Vc_ref is the c-phase component of the voltage command for current control.

The coordinate conversion unit 113 is a calculation unit that performs coordinate conversion between the dq coordinate system and the αβ coordinate system. The αβ coordinate system is a coordinate system fixed to the stator of the electric motor 3, and includes an α axis and a β axis as coordinate axes (see FIG. 3). The α-axis is, for example, along the direction of the a-phase of the secondary power. The β axis is perpendicular to the direction of the a phase. The three-phase / two-phase conversion unit 114 is a calculation unit that performs conversion between a component in the α-axis direction and a component in the β-axis direction and a component in the a phase, a component in the b phase, and a component in the c phase.

For example, the coordinate conversion unit 113 converts the d-axis voltage command Vd_ref and the q-axis voltage command Vq_ref into the α-axis voltage command Vα_ref and the β-axis voltage command Vβ_ref and outputs them to the three-phase / two-phase conversion unit 114. The α-axis voltage command Vα_ref is an α-axis direction component of the voltage command for current control, and the β-axis voltage command Vβ_ref is a β-axis direction component of the voltage command for current control. The three-phase / two-phase conversion unit 114 converts the α-axis voltage command Vα_ref and the β-axis voltage command Vβ_ref into the above-mentioned a-phase voltage command Va_ref, b-phase voltage command Vb_ref, and c-phase voltage command Vc_ref, and power conversion control unit 112. Output to.

Further, the three-phase / two-phase conversion unit 114 converts the a-phase current ia, b-phase current ib, and c-phase current ic into α-axis current iα and β-axis current iβ, and outputs them to the coordinate conversion unit 113. The a-phase current ia is the a-phase real current, the b-phase current ib is the b-phase real current, and the c-phase current ic is the c-phase real current. The α-axis current iα is an α-axis direction component of the actual current, and the β-axis current iβ is a β-axis direction component of the actual current. The coordinate conversion unit 113 converts the α-axis current iα and the β-axis current iβ into the d-axis current id and the q-axis current iq, and feeds them back to the current control unit 111.

The resistance calculation unit 115 calculates the resistance of the electric motor 3 based on the DC component of the voltage generated by the power conversion circuit 10 on the electric motor 3 side and the DC component of the current. For example, the resistance calculation unit 115 calculates the resistance of the electric motor 3 by dividing the DC component of the actual voltage by the DC component of the actual current. When calculating the resistance, the resistance calculation unit 115 may use the detected value of the DC component of the actual current (for example, the DC component of the value detected by the current sensor 14) as the DC component of the actual current. The direct current component of the current command may be used. For example, the resistance calculation unit 115 uses the DC component of the value detected by the current sensor 14 as the DC component of the actual current when calculating the resistance.

When calculating the resistance, the resistance calculation unit 115 may use the detected value of the DC component of the actual voltage as the DC component of the actual voltage, or the voltage command based on the control command (for example, for the current control). The DC component of the voltage command) may be used. For example, the resistance calculation unit 115 uses the DC component of the voltage command for current control when calculating the resistance.

Ｒ：電動機３の抵抗
θ１：αβ座標系に対するｄｑ座標系の回転角度（図３参照） For example, the resistance calculation unit 115 sets the DC component of the actual voltage and the DC component of the actual current as the integrated value of the actual voltage during a predetermined integration period (hereinafter referred to as “voltage integrated value”) and the actual current during the integration period. The resistance is calculated based on the integrated value (hereinafter referred to as "current integrated value"). For example, the resistance calculation unit 115 calculates the resistance of the electric motor 3 by dividing the voltage integral value in one cycle of the fundamental wave by the current integral value in the one cycle. The integration period may be a period obtained by multiplying one period of the fundamental wave by an integer of 2 or more. As an example, the resistance calculation unit 115 calculates the resistance of the electric motor 3 by the following equation.

R: Resistance of electric motor 3 θ1: Rotation angle of dq coordinate system with respect to αβ coordinate system (see FIG. 3)

The magnetic flux estimation unit 116 estimates the magnetic flux λ generated by the mover conductor of the electric motor 3 based on the resistance R calculated by the resistance calculation unit 115, the actual current, and the actual voltage. When estimating the magnetic flux, the magnetic flux estimation unit 116 may use the detected value of the actual current as the actual current, or may use the current command. For example, the magnetic flux estimation unit 116 uses the detected values of the actual current (for example, α-axis current iα and β-axis current iβ) as the actual current when estimating the magnetic flux.

Further, the magnetic flux estimation unit 116 may use the detected value of the actual voltage as the actual voltage when estimating the magnetic flux, or issues a voltage command based on the control command (for example, the voltage command for current control). You may use it. For example, the magnetic flux estimation unit 116 uses the voltage commands for current control (for example, α-axis voltage command Vα_ref and β-axis voltage command Vβ_ref) as the actual voltage when estimating the magnetic flux.

The current command generation unit 120 (command generation unit) generates a control command including at least the fundamental wave. For example, the current command generation unit 120 generates a control command including the fundamental wave, a DC component, and an adjustment wave based on the frequency of the fundamental wave and the magnitude of the DC component, and outputs the control command to the current control unit 111.

The current command generation unit 120 generates the DC component so that the rotation speed of the electric motor 3 becomes larger when the rotation speed is the second speed, which is smaller than the first speed, than when the rotation speed is the first speed. Included in the above control command. Further, the current command generation unit 120 generates an adjustment wave based on the frequency of the fundamental wave and the magnitude of the DC component, and includes this in the control command. As shown in FIG. 2, for example, the current command generation unit 120 has a fundamental wave generation unit 121, a DC component generation unit 122, and an adjustment wave generation unit 123 as more subdivided functional blocks.

The fundamental wave generation unit 121 calculates the fundamental wave based on the resistance R calculated by the resistance calculation unit 115 and the target value (torque target value T_ref) of the torque generated in the electric motor 3. For example, the fundamental wave generation unit 121 generates q for generating torque corresponding to the torque target value T_ref based on the d-axis fundamental wave Ids, the estimated value of the magnetic flux λ by the magnetic flux estimation unit 116, and the torque target value T_ref. The axis fundamental wave Iqs is calculated.

The d-axis fundamental wave Ids is set, for example, by the numerical input of the operator. The d-axis fundamental wave Ids corresponds to the magnetic flux generating component of the secondary side current. The magnetic flux generating component is a component that generates a magnetic flux λ in the mover conductor of the electric motor 3. The q-axis fundamental wave Iqs corresponds to a driving force generating component of the secondary side current.

The DC component generation unit 122 generates a DC component so that the operating speed of the electric motor 3 becomes higher when the operating speed is the second speed, which is smaller than the first speed, than when the operating speed is the first speed. For example, the DC component generation unit 122 operates the electric motor 3 according to the relationship between the DC component and the operating speed set so that the DC component increases as the operating speed decreases (hereinafter, referred to as “DC component profile”). Calculate the DC component corresponding to the speed. The relationship between the operating speed and the DC component is set so that the DC component increases as the operating speed decreases. The operating speed and the DC component decrease as the operating speed increases. It is synonymous with setting the relationship with. The DC component profile may be set as a function, or may be set as a table that discretely shows the correspondence between the operating speed and the DC component.

Examples of DC component profiles are shown in FIGS. 4 and 5. 4 and 5 are graphs showing the relationship between the rotation speed and the DC component, with the horizontal axis indicating the operating speed and the vertical axis indicating the magnitude of the DC component. In both FIGS. 4 and 5, the plot shown by the solid line is the DC component profile.

In the DC component profile of FIG. 4, the DC component gradually decreases as the rotation speed increases, and when the rotation speed reaches a predetermined threshold value ω21 or more, the DC component becomes a constant value. In other words, when the rotation speed is lower than the threshold value ω21, the DC component becomes larger than the above constant value, and as the rotation speed becomes smaller, the DC component gradually increases. According to such a DC component profile, the rotation speed ω12 (of the second speed) smaller than the threshold ω21 is compared with the DC component corresponding to the rotation speed ω11 (example of the first speed) larger than the threshold ω21. The DC component corresponding to (example) becomes large.

In the DC component profile of FIG. 5, the DC component in the speed range smaller than the threshold ω21 is stepwise larger than that in the speed range larger than the threshold ω21, and the DC component in each speed range is constant. .. Even with such a DC component profile, the rotation speed ω12 (example of the second speed) smaller than the threshold ω21 is compared with the DC component corresponding to the rotation speed ω11 (example of the first speed) larger than the threshold ω21. ) Corresponds to the larger DC component.

The adjustment wave generation unit 123 generates an AC adjustment wave based on the frequency of the fundamental wave generated by the fundamental wave generation unit 121 and the magnitude of the DC component generated by the DC component generation unit 122. For example, the adjustment wave generation unit 123 has an amplitude substantially equal to twice the frequency of the fundamental wave generated by the fundamental wave generation unit 121 and an amplitude substantially equal to the magnitude of the DC component generated by the DC component generation unit 122. Generates a tuning wave with and. The term "substantially equal" here includes the case where there is a difference in error level (for example, ± 10%).

As shown by the addition point 125, the current command generation unit 120 includes the fundamental wave generated by the fundamental wave generation unit 121, the DC component generated by the DC component generation unit 122, and the adjustment wave generation unit 123. A control command is generated by adding the wave components. As an example, the current command generation unit 120 generates a current command in the dq coordinate system by the following equation.

θ２：ｄｑ座標系における基本波の位相角（図３参照） By converting the above equation (2) into the αβ coordinate system, the following equation is obtained.

θ2: Phase angle of the fundamental wave in the dq coordinate system (see FIG. 3)

In the formula (3), the α-axis current command iα_ref is the α-axis component of the current command, and the β-axis current command iβ_ref is the β-axis component of the current command. Is · cos (θ1 + θ2) is the α-axis component of the fundamental wave, and Is · sin (θ1 + θ2) is the β-axis component of the fundamental wave. Iinj is a DC component. Further, Iinj · cos (2 · θ1) is an α-axis component of the adjusting wave, and Iinj · sin (2 · θ1) is a β-axis component of the adjusting wave. That is, the equation (3) shows an example of generating a current command by adding the fundamental wave, the DC component, and the adjusting wave. In this example, the DC component is added only to the α-axis component. Therefore, calculating the current command in the dq coordinate system by the equation (2) corresponds to generating the current command by adding the fundamental wave, the DC component, and the adjusting wave.

When the current command generation unit 120 calculates the current command by the equation (2), the calculation of the fundamental wave by the fundamental wave generation unit 121 corresponds to the calculation of Ids and Iqs in the equation (2). The calculation of the DC component by the DC component generation unit 122 corresponds to the calculation of Iinj in the equation (2). The calculation of the adjustment wave by the adjustment wave generation unit 123 is included in the calculation of 2.Iinj.cos (θ1) in the equation (2). That is, according to the equation (2), the calculation of the adjustment wave by the adjustment wave generation unit 123 and the addition of the fundamental wave, the DC component and the adjustment wave are performed at the same time.

In the control circuit 100, the magnetic flux generation component of the current on the electric motor 3 side becomes larger when the rotation speed of the electric motor 3 is the second speed than when the rotation speed is the first speed, and the driving force of the current is generated. It may be configured to change the fundamental wave so that the component becomes smaller. For example, the current command generation unit 120 further includes a fundamental wave changing unit 124.

In the fundamental wave changing unit 124, the d-axis fundamental wave Ids is larger and the q-axis fundamental wave Iqs is smaller when the rotation speed of the electric motor is the second speed than when the rotation speed is the first speed. Change the fundamental wave to. For example, the fundamental wave changing unit 124 has a relationship between an operating speed set so that the magnification of the d-axis fundamental wave Ids increases as the operating speed decreases (hereinafter, referred to as “boost profile”). Therefore, the enlargement ratio corresponding to the operating speed of the electric motor 3 is calculated.

Examples of boost profiles are shown in FIGS. 4 and 5. In FIGS. 4 and 5, the vertical axis with respect to the boost profile indicates the magnitude of the enlargement ratio. In both FIGS. 4 and 5, the plot indicated by the alternate long and short dash line is the boost profile.

In the boost profile of FIG. 4, the enlargement ratio is 1 when the rotation speed is larger than the threshold value ω21. When the rotation speed is lower than the threshold value ω21, the enlargement ratio becomes larger than 1, and as the rotation speed becomes smaller, the enlargement ratio gradually increases. According to such a boost profile, the rotation speed ω12 (example of the second speed) smaller than the threshold ω21 as compared with the enlargement ratio corresponding to the rotation speed ω11 (example of the first speed) larger than the threshold ω21. ) Corresponds to the enlargement rate.

In the boost profile of FIG. 5, the enlargement ratio in the speed range smaller than the threshold value ω21 is stepwise larger than that in the speed range larger than the threshold value ω21. For example, the magnification in the speed range larger than the threshold ω21 is 1, and the magnification in the speed range smaller than the threshold ω21 is a constant larger than 1. Even with such a boost profile, the rotation speed ω12 smaller than the threshold ω21 (example of the second speed) is smaller than the enlargement ratio corresponding to the rotation speed ω11 (example of the first speed) larger than the threshold ω21. The expansion rate corresponding to is increased.

When the calculation result of the enlargement ratio is larger than 1, the fundamental wave changing unit 124 expands the d-axis fundamental wave Ids at the enlargement ratio, and the d-axis fundamental wave Ids after the expansion expands the d-axis fundamental wave Ids to the fundamental wave generation unit 121. Change the waves. In the fundamental wave generation unit 121, the q-axis fundamental wave Iqs is reduced in accordance with the expansion of the d-axis fundamental wave Ids in order to match the torque with the torque target value T_ref. Therefore, the fundamental wave is changed so that the d-axis fundamental wave Ids becomes larger at the above magnification and the q-axis fundamental wave Iqs becomes smaller accordingly.

The control circuit 100 may be configured to further perform low-pass type filtering on the control command before the power conversion control unit 112 causes the power conversion unit to perform power conversion according to the control command. For example, the control circuit 100 further includes a filter processing unit 117.

The filter processing unit 117 performs low-pass type digital filtering on the estimation result of the magnetic flux λ by the magnetic flux estimation unit 116, and outputs the filtered magnetic flux λ to the fundamental wave generation unit 121. Specific examples of digital filtering include finite impulse response filtering. As described above, the fundamental wave generation unit 121 generates the fundamental wave of the current command based on the magnetic flux λ. Therefore, by applying the low-pass type filtering to the magnetic flux λ, the fundamental wave is also subjected to the low-pass type filtering. It means that.

According to the configuration described above, a DC component can be added to the fundamental wave while suppressing torque ripple. Specifically, by adding a DC component to the fundamental wave together with the adjusting wave, torque ripple caused by the addition of the DC component can be suppressed. If only the DC component is added to the fundamental wave, ripples (vibration components) are generated in both the d-axis current command id_ref and the q-axis current command iq_ref in the dq coordinate system, and torque ripples are generated due to these ripples. .. On the other hand, when the DC component is added to the fundamental wave together with the adjustment wave, the ripple of the q-axis current command iq_ref is reduced. For example, as shown in equation (2), the ripple of the q-axis current command iq_ref disappears.

Although ripple remains in the d-axis current command id_ref, this vibration component is significantly attenuated in the process of generating the magnetic flux λ by the d-axis current id. Therefore, the torque ripple generated when the DC component is applied to the fundamental wave together with the adjusting wave is significantly suppressed as compared with the torque ripple when only the DC component is applied to the fundamental wave. By adding a DC component to the fundamental wave while suppressing torque ripple in this way, the accuracy of calculating the resistance based on the DC component is improved.

However, the resistance calculation accuracy tends to decrease as the operating speed of the electric motor 3 decreases. In line with this tendency, the DC component is generated so that the operating speed of the motor 3 is higher when the motor 3 is at the second speed than when it is at the first speed, so that the calculation accuracy of the resistance at the second speed is further improved. Can be improved. On the other hand, by making the DC component at the first speed smaller than the DC component at the second speed, the driving force ripple at the first speed can be further suppressed.

Voltage error (difference between information indicating voltage and actual voltage) affects the accuracy of resistance calculation. Specific examples of the voltage error include the difference between the voltage command for current control (d-axis voltage command Vd_ref and q-axis voltage command Vq_ref) and the actual voltage. The voltage error is caused by, for example, switching in the power conversion circuit 10 (switching on / off of a plurality of switching elements 15) or the like.

The effect of the voltage error on the accuracy of resistance calculation tends to increase as the rotation speed of the motor 3 decreases. Therefore, the control circuit 100 switches the switching cycle (switching on / off of the plurality of switching elements 15) in the power conversion circuit 10 when the operating speed of the electric motor 3 is the second speed rather than when the operating speed is the first speed. It may be configured to lengthen the cycle). Thereby, the expansion of the above influence can be suppressed. For example, the power conversion control unit 112 lengthens the carrier cycle in the power conversion circuit 10 when the operating speed of the electric motor 3 is the first speed, as compared with the case where the operating speed is the first speed. As an example, the power conversion control unit 112 uses the electric motor 3 according to the relationship between the carrier cycle and the operating speed set so that the carrier cycle becomes longer as the operating speed decreases (hereinafter, referred to as “carrier profile”). Calculate the carrier cycle corresponding to the operating speed of.

Examples of carrier profiles are shown in FIGS. 4 and 5. In FIGS. 4 and 5, the vertical axis with respect to the carrier profile indicates the length of the carrier cycle. In both FIGS. 4 and 5, the plot shown by the broken line is the carrier profile.

In the carrier profile of FIG. 4, when the rotation speed is larger than the threshold value ω22, the carrier cycle is set to a constant value (hereinafter, referred to as “normal cycle”). The threshold value ω22 is smaller than the threshold value ω21 described above. The threshold value ω22 may be equal to or higher than the threshold value ω21.
When the rotation speed is lower than the threshold value ω22, the carrier cycle becomes longer than the normal cycle, and as the rotation speed becomes smaller, the carrier cycle gradually becomes longer. According to such a carrier profile, the rotation speed ω12 (example of the second speed) smaller than the threshold ω22 as compared with the carrier cycle corresponding to the rotation speed ω11 (example of the first speed) larger than the threshold ω22. ) Corresponds to a longer carrier cycle.

In the carrier profile of FIG. 5, the carrier cycle in the speed range smaller than the threshold value ω22 is stepwise longer than that in the speed range larger than the threshold value ω22. For example, the carrier period in the speed range larger than the threshold value ω22 is the above-mentioned normal period. Even with such a carrier profile, the rotation speed ω12 smaller than the threshold ω22 (example of the second speed) is smaller than the carrier cycle corresponding to the rotation speed ω11 (example of the first speed) larger than the threshold ω22. The carrier cycle corresponding to is longer.

The power conversion control unit 112 may change the switching cycle by changing the number of cycles at which the switching element 15 is switched on / off instead of changing the carrier cycle.

As described above, the resistance calculated by the resistance calculation unit 115 is used for calculating the q-axis fundamental wave Iqs for generating the torque corresponding to the torque target value T_ref. Note that "used for calculating the q-axis fundamental wave Iqs" here means that it is indirectly used for calculating the q-axis fundamental wave Iqs (for example, a resistor is used for calculating the magnetic flux, and the calculation result of the magnetic flux). Is used to calculate the q-axis fundamental wave Iqs). When a resistor is used to calculate the q-axis fundamental wave Iqs for generating torque that matches the torque target value T_ref, the calculation accuracy of the resistor affects the accuracy of torque control, but the effect is the operating speed of the motor 3. Decreases as becomes larger. Therefore, even if the control circuit 100 is configured to stop the calculation of the resistance of the electric motor 3 when the operating speed of the electric motor 3 is the first speed, and to generate a fundamental wave with the resistance of the electric motor 3 as a constant value. Good. For example, the resistance calculation unit 115 may calculate the resistance of the electric motor 3 in the speed range smaller than the threshold value ω21 and stop the calculation of the resistance of the electric motor 3 in the speed range larger than the threshold value ω21. Further, the resistance calculation unit 115 may stop the calculation of the resistance of the electric motor 3 when the operating speed is zero or extremely close to zero. In line with this, as illustrated in FIGS. 4 and 5, the DC component generation unit 122 has an operating speed of zero even when it follows a DC component profile in which the DC component increases as the operating speed decreases. Alternatively, the DC component may be set to zero when it is extremely close to zero.

During the period when the resistance calculation unit 115 is stopped from calculating the resistance, the fundamental wave generation unit 121 generates the fundamental wave with the resistance of the electric motor 3 as a constant value. For example, the fundamental wave generation unit 121 may use the resistance calculated by the resistance calculation unit 115 immediately before stopping the calculation of the resistance as the constant value, or may use the resistance measured in advance while the motor 3 is stopped. It may be used as a constant value. The DC component generation unit 122 sets the DC component in a speed range larger than the threshold value ω21 to zero. As a result, it is possible to further reduce the torque ripple due to the addition of the DC component while suppressing the decrease in the accuracy of the torque control. In addition, the energy loss associated with the addition of DC components can be reduced.

As described above, even if the DC component is added to the fundamental wave together with the adjustment wave, a minute ripple is generated in the magnetic flux λ due to the ripple of the d-axis current command id_ref. Since the fundamental wave generation unit 121 calculates the q-axis fundamental wave Iqs so that the torque matches the torque target value T_ref, when the ripple of the magnetic flux λ occurs, the q-axis fundamental wave Iqs itself also cancels the ripple. A minute ripple will be generated.

Ｉｑｓ＿ａｖｅ：ｑ軸基本波Ｉｑｓの平均値
ω１：αβ座標系に対するｄｑ座標系の回転角速度
τ：フィルタ処理部１１７によるフィルタリングの時定数 When ripples occur in the q-axis fundamental wave Iqs, the period during which the inverter circuit 13 is in the power running state (hereinafter referred to as “power running period”) and the period during which the inverter circuit 13 is in the regenerative state (hereinafter referred to as “regeneration period”). There is a difference in the resistance calculation accuracy by the resistance calculation unit 115. Specifically, the calculation accuracy of the resistance in the regeneration period is lower than the calculation accuracy of the resistance in the power running period. As an example, the q-axis fundamental wave Iqs in which minute ripples are generated is expressed by the following equation.

Iqs_ave: Mean value of q-axis fundamental wave Iqs ω1: Rotation angular velocity of dq coordinate system with respect to αβ coordinate system τ: Time constant of filtering by filtering unit 117

ｉα＿ｄｃ：α軸電流指令ｉα＿ｒｅｆの直流成分 Considering the ripple of the q-axis fundamental wave Iqs represented by the equation (4), the DC component added to the fundamental wave in the αβ coordinate system is expressed by the following equation.

iα_dc: DC component of α-axis current command iα_ref

In the power running period, Iqs_ave in the formula (5) has a positive value, and in the regeneration period, Iqs_ave in the formula (5) has a negative value. Therefore, in the regeneration period, the DC component added to the fundamental wave becomes smaller than that in the power running period. Therefore, the calculation accuracy of the resistance in the regeneration period is lower than the calculation accuracy of the resistance in the power running period.

In order to suppress a decrease in resistance calculation accuracy during the regeneration period, the control circuit 100 is configured to make the filtering time constant during the regeneration period larger than the filtering time constant during the power running period. May be good. For example, the filter processing unit 117 may make the time constant of filtering applied to the magnetic flux λ during the regeneration period (time constant τ in the equation (5)) larger than the time constant of filtering applied to the magnetic flux λ during the power running period. .. As the time constant τ increases, the absolute value of the second term on the right side of equation (5) decreases. Therefore, the reduction range of the DC component according to the second term on the right side becomes small. Therefore, a decrease in resistance calculation accuracy during the regeneration period is suppressed.

The control circuit 100 may be configured so that the resistance calculated in the immediately preceding power running period is used as the resistance in the regeneration period without calculating the resistance in the regeneration period. For example, the resistance calculation unit 115 may calculate the resistance in the power running period as described above, and in the regeneration period, the resistance calculated in the immediately preceding power running period may be used as the resistance in the regeneration period. In this case, the resistance calculation unit 115 determines whether the inverter circuit 13 is in the power running state or the regenerative state based on, for example, whether the q-axis fundamental wave Iqs has a positive value or a negative value. May be good.

FIG. 6 is a block diagram illustrating a hardware configuration of the control circuit 100. As shown in FIG. 6, the control circuit 100 includes at least one processor 191, a memory 192, a storage 193, and a switching control circuit 194. The storage 193 has a computer-readable storage medium, such as a hard disk. The storage medium may be a removable medium such as a non-volatile semiconductor memory, a magnetic disk, or an optical disk. The storage 193 generates a control command as described above, controls the power conversion circuit 10 so that the secondary side power follows the control command, and the voltage generated by the power conversion circuit 10 on the motor 3 side. The resistance of the motor 3 is calculated based on the DC component of (that is, the voltage of the secondary side power) and the DC component of the current (that is, the current of the secondary side power) generated by the power conversion circuit 10 on the motor 3 side. It stores a program for causing the control circuit 100 to execute the current.

The memory 192 temporarily stores the program loaded from the storage 193 and the calculation result by the processor 191. The processor 191 constitutes each of the above-mentioned functional blocks by executing the above program in cooperation with the memory 192. The switching control circuit 194 generates the gate drive signal in response to a command from the processor 191.

The control circuit 100 is not necessarily limited to the one that configures each function by a program. For example, the control circuit 100 may have at least a part of its functions configured by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) that integrates the logic circuit.

[Power conversion procedure]
Subsequently, as an example of the power conversion method, the power conversion procedure executed by the power conversion device 1 will be illustrated. In this procedure, a control command including at least an alternating current fundamental wave is generated, the power conversion circuit 10 is controlled so that the power on the motor 3 side follows the control command, and the power conversion circuit 10 is on the motor 3 side. The resistance of the motor 3 is calculated based on the DC component of the voltage and the DC component of the current generated in the above, and the control command is generated when the operating speed of the motor 3 is the first speed. The AC adjustment wave is generated based on the generation of the DC component so that it becomes smaller at the second speed, which is larger than the first speed, and the frequency of the fundamental wave and the magnitude of the DC component. It includes generating and generating a control command including a fundamental wave, a DC component, and a tuning wave. In this procedure, the control circuit 100 repeats the detection of the current and the control of the power conversion circuit 10 at a predetermined control cycle.

FIG. 7 is a flowchart illustrating a control procedure executed by the control circuit 100 in one control cycle. As shown in FIG. 7, the control circuit 100 executes steps S01, S02, S03, S04, S05, S06, S07, and S08 in this order. In step S01, the fundamental wave generation unit 121 generates the fundamental wave, the DC component generation unit 122 generates the DC component, the adjustment wave generation unit 123 generates the adjustment wave, and the current command generation unit 120 generates the current command generation unit 120. A current command is generated by adding the fundamental wave, the DC component, and the adjustment wave. When generating the fundamental wave, the fundamental wave generation unit 121 uses the resistor R and the magnetic flux λ calculated in the previous control cycle.

In step S02, the current control unit 111 acquires the detected value of the actual current by the current sensor 14 via the three-phase / two-phase conversion unit 114 and the coordinate conversion unit 113. In step S03, the current control unit 111 calculates the voltage command for current control so as to reduce the deviation between the current command and the actual current.

In step S04, the power conversion control unit 112 acquires information on the rotation speed ω1 of the electric motor 3 and calculates θ1. When the electric motor 3 is provided with a position sensor or a speed sensor, the power conversion control unit 112 may acquire information on the rotation speed using the sensor. When the electric motor 3 is not provided with the sensor, the power conversion control unit 112 may acquire an estimated value of the rotation speed based on the detected value of the actual current or the like.

In step S05, the power conversion control unit 112 sets the switching cycle based on the rotation speed of the electric motor 3. For example, the power conversion control unit 112 sets a carrier period corresponding to the rotation speed of the electric motor 3 based on the carrier profile. In step S06, the power conversion control unit 112 starts on / off switching of the plurality of switching elements 15 so that the actual voltage becomes a magnitude according to the voltage command for current control.

In step S07, the resistance calculation unit 115 calculates the resistance of the electric motor 3 based on the DC component of the voltage generated by the power conversion circuit 10 on the electric motor 3 side and the DC component of the current. In step S08, the magnetic flux estimation unit 116 estimates the magnetic flux λ generated by the mover conductor of the electric motor 3 based on the resistance R calculated by the resistance calculation unit 115, the actual current, and the actual voltage. This completes the control procedure of the control circuit 100 in one control cycle.

[Effect of this embodiment]
As described above, the power conversion device 1 includes a power conversion circuit 10 that performs power conversion between the power supply 2 and the electric motor 3, and a current command generation unit 120 that generates a control command including at least an AC fundamental wave. The power conversion control unit 112 that controls the power conversion circuit 10 so that the power on the electric motor 3 side follows the control command, and the DC component of the voltage and the DC component of the current generated by the power conversion circuit 10 on the electric motor 3 side. Based on this, the resistance calculation unit 115 that calculates the resistance of the electric motor 3 is provided, and the current command generation unit 120 has a second speed that is smaller than the first speed than when the operating speed of the electric motor 3 is the first speed. The DC component generation unit 122 that generates a DC component so that the value is larger, and the adjustment wave generation unit 123 that generates an AC adjustment wave based on the frequency of the fundamental wave and the magnitude of the DC component. , And generates a control command including a fundamental wave, a DC component, and a tuning wave.

According to the power conversion device 1, a DC component and an adjustment wave are added to the fundamental wave. If only the DC component is added to the fundamental wave, ripple occurs in the driving force generating component of the current of the motor 3, and this causes ripple of the driving force of the motor 3 (hereinafter, referred to as "driving force ripple"). .. On the other hand, by adding both the DC component and the adjustment wave to the fundamental wave, the ripple of the driving force generating component can be suppressed. Ripple is generated in the magnetic flux generating component of the current of the electric motor 3, but the driving force ripple caused by the ripple of the magnetic flux generating component is very small. Therefore, the resistance of the electric motor 3 can be calculated with high accuracy by adding a DC component to the fundamental wave while suppressing the driving force ripple.

However, the resistance calculation accuracy tends to decrease as the operating speed of the electric motor 3 decreases. In line with this tendency, the second speed is generated by generating a DC component so that the operating speed of the electric motor 3 is larger when the second speed is smaller than the first speed than when the operating speed is the first speed. The calculation accuracy of the resistance in the above can be further improved. On the other hand, by making the DC component at the first speed smaller than the DC component at the second speed, the driving force ripple at the first speed can be further suppressed. Therefore, it is more effective to improve the resistance detection accuracy of the electric motor 3 during operation and to suppress the driving force ripple of the electric motor 3.

For example, the tuning wave generation unit 123 may generate a tuning wave having a frequency substantially equal to twice the frequency of the fundamental wave and an amplitude substantially equal to the magnitude of the DC component.

In the current command generation unit 120, the magnetic flux generating component of the current on the motor 3 side becomes larger when the operating speed of the motor 3 is the second speed than when the operating speed is the first speed, and the driving force of the current is generated. It may further have a fundamental wave changing unit 124 that changes the fundamental wave so that the component becomes smaller. Even when the DC component and the adjustment wave are added to the fundamental wave, ripple occurs in the magnetic flux generating component. Therefore, when the electric motor 3 is an induction motor, a driving force ripple is generated according to the magnitude of the ripple of the magnetic flux generating component and the magnitude of the driving force generating component. As the DC component increases, the ripple of the magnetic flux generating component expands, so that the driving force ripple also expands. On the other hand, by changing the fundamental wave so that the magnetic flux generating component becomes larger and the driving force generating component becomes smaller when the operating speed of the electric motor 3 is the second speed than when the operating speed is the first speed. The driving force ripple at the second speed can be reduced without changing the magnitude of the torque between the first speed and the second speed.

The resistance calculation unit 115 may calculate the resistance as the DC component of the voltage and the DC component of the current based on the integrated value of the voltage in the predetermined integration period and the integrated value of the current in the integration period. In this case, since the DC component is easily and accurately extracted by integration, the resistance can be calculated easily and accurately.

The power conversion control unit 112 lengthens the switching cycle in the power conversion circuit 10 when the operating speed of the electric motor 3 is the second speed, and the resistance calculation unit 115 calculates the resistance. At this time, as the DC component of the voltage, the detected value of the DC component of the voltage applied to the electric motor 3 or the DC component of the voltage command based on the control command may be used. As the operating speed of the electric motor 3 decreases, the voltage error (difference between the information indicating the voltage and the actual voltage) due to switching has a greater influence on the resistance calculation accuracy. On the other hand, by making the switching cycle at the second speed longer than the switching cycle at the first speed, it is possible to suppress the expansion of the above influence. Therefore, the resistance detection accuracy can be further improved.

When calculating the resistance, the resistance calculation unit 115 may use the DC component of the voltage command as the DC component of the voltage. In this case, when the voltage command is used as the voltage value for calculating the resistance, the above error due to switching becomes larger than when the voltage detection value is used. Therefore, it is more effective to lengthen the carrier cycle as the speed of the electric motor 3 decreases.

The power conversion device 1 further includes a filter processing unit 117 that performs low-pass type filtering on the control command before the power conversion control unit 112 causes the power conversion circuit 10 to execute power conversion according to the control command. , The time constant of filtering in the regeneration period in which the power is returned from the electric motor 3 to the power conversion circuit 10 may be larger than the time constant of filtering in the power running period in which the power is output from the power conversion circuit 10 to the electric motor 3. .. In this case, it is possible to suppress the difference in resistance detection accuracy between the power running period and the regeneration period.

The resistance calculation unit 115 calculates the resistance based on the DC component of the voltage and the DC component of the current during the power running period when the electric power is output to the motor 3, and immediately before the regeneration period when the electric power returns from the electric motor 3. The resistance calculated in the force running period may be used as the resistance in the regeneration period. In this case, it is possible to suppress the difference in resistance detection accuracy between the power running period and the regeneration period.

The current command generation unit 120 may further include a fundamental wave generation unit 121 that calculates a fundamental wave based on the resistance calculated by the resistance calculation unit 115 and the target value of the driving force generated in the electric motor 3. In this case, the resistance calculation result can be utilized for more accurate force control.

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

1 ... Power conversion device, 2 ... Power supply, 3 ... Electric motor, 10 ... Power conversion circuit (power conversion unit), 112 ... Power conversion control unit, 115 ... Resistance calculation unit, 117 ... Filter processing unit, 120 ... Current command generation unit (Command generation unit), 121 ... fundamental wave generation unit, 122 ... DC component generation unit, 123 ... adjustment wave generation unit, 124 ... fundamental wave change unit.

Claims (10)

A power converter that converts power between the power supply and the electric motor,
A command generator that generates control commands that include at least the AC fundamental wave,
A power conversion control unit that controls the power conversion unit so that the electric power on the electric motor side follows the control command.
A resistance calculation unit that calculates the resistance of the electric motor based on the DC component of the voltage and the DC component of the current generated by the power conversion unit on the electric motor side is provided.
The command generator
A DC component generator that generates a DC component so that the operating speed of the electric motor is higher when the second speed is smaller than the first speed than when the operating speed is the first speed.
An adjustment wave generator that generates an AC adjustment wave based on the frequency of the fundamental wave and the magnitude of the DC component.
Have,
A power conversion device that generates the control command including the fundamental wave, the DC component, and the adjustment wave. The power according to claim 1, wherein the tuning wave generator generates a tuning wave having a frequency substantially equal to twice the frequency of the fundamental wave and an amplitude substantially equal to the magnitude of the DC component. Conversion device. In the command generation unit, the magnetic flux generating component of the current on the electric motor side becomes larger when the operating speed of the electric motor is the second speed than when the operating speed of the electric motor is the first speed, and the driving force of the current. The power conversion device according to claim 1 or 2, further comprising a fundamental wave changing unit that changes the fundamental wave so that the generated component becomes smaller. The resistance calculation unit calculates the resistance as a DC component of the voltage and a DC component of the current based on the integrated value of the voltage in a predetermined integration period and the integrated value of the current in the integration period. The power conversion device according to any one of claims 1 to 3. The power conversion control unit makes the switching cycle in the power conversion unit longer when the operating speed of the electric motor is the second speed than when the operating speed is the first speed.
When calculating the resistance, the resistance calculation unit uses the detected value of the DC component of the voltage applied to the electric motor or the DC component of the voltage command based on the control command as the DC component of the voltage. The power conversion device according to any one of claims 1 to 4. The power conversion device according to claim 5, wherein the resistance calculation unit uses the DC component of the voltage command as the DC component of the voltage when calculating the resistance. A filter processing unit that performs low-pass type filtering on the control command before the power conversion control unit causes the power conversion unit to execute power conversion in accordance with the control command is further provided.
The filter processing unit performs the filtering in the regeneration period in which the electric power returns from the electric motor to the power conversion unit as compared with the time constant of the filtering in the power running period in which the electric power is output from the power conversion unit to the electric motor. The power conversion device according to any one of claims 1 to 6, which increases the constant. The resistance calculation unit
In the power running period in which electric power is output to the electric motor, the resistance is calculated based on the DC component of the voltage and the DC component of the current.
The power conversion device according to any one of claims 1 to 7, wherein in the regeneration period in which electric power returns from the electric motor, the resistance calculated in the immediately preceding power running period is used as the resistance in the regeneration period. Claims 1 to 7 further include a fundamental wave generating unit that calculates the fundamental wave based on the resistance calculated by the resistance calculating unit and a target value of a driving force generated in the electric motor. The power conversion device according to any one of the above. To generate a control command that includes at least the AC fundamental wave,
Controlling the power conversion unit that converts electric power between the power source and the electric motor so that the electric power on the electric motor side follows the control command.
Includes calculating the resistance of the motor based on the DC component of the voltage and the DC component of the current generated by the power converter on the motor side.
Generating the control command
The direct current component is generated so that the operating speed of the electric motor becomes larger when the operating speed is the second speed, which is smaller than the first speed, than when the operating speed is the first speed.
To generate an AC adjustment wave based on the frequency of the fundamental wave and the magnitude of the DC component,
A power conversion method comprising generating the control command including the fundamental wave, the DC component, and the adjustment wave.

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