Power conversion equipment, control system, drive system and power conversion method

Abstract

This disclosure relates to power conversion equipment, control systems, drive systems, and power conversion methods. The power conversion equipment may include: a power conversion circuit configured to perform power conversion for outputting drive power to an induction motor; and a control circuit. The control circuit may be configured to: receive a main command phase from a main power conversion device; generate a voltage command with a command phase in a rotating coordinate system based on a torque target value, wherein a rotating magnetic field for driving the rotor of the induction motor is generated to rotate with the rotating coordinate system; calculate the rotation phase of the rotating coordinate system based on the command phase difference between the main command phase and the command phase to reduce the command phase difference; and, based on the rotation phase and the voltage command, synchronously with the main power conversion device, control the power conversion circuit to output drive power to the induction motor.

Description

Technical Field

[0001] This disclosure relates to power conversion equipment, control systems, drive systems, and power conversion methods. Background Technology

[0002] Japanese Patent Application Publication No. 2017-79580 discloses a system including a motor having a first winding and a second winding, a first inverter corresponding to the first winding, and a second inverter corresponding to the second winding. Summary of the Invention

[0003] This disclosure provides a power conversion device that is effective for synchronizing rotating magnetic fields generated in an induction motor by multiple power conversion devices.

[0004] This document discloses an example power conversion device. The power conversion device may include: a power conversion circuit configured to perform power conversion for outputting drive power to an induction motor; and a control circuit. The control circuit may be configured to: receive a main command phase from a main power conversion device; generate a voltage command with a command phase in a rotating coordinate system based on a torque target value, wherein a rotating magnetic field for driving the rotor of the induction motor is generated to rotate with the rotating coordinate system; calculate the rotation phase of the rotating coordinate system based on the command phase difference between the main command phase and the command phase to reduce the command phase difference; and, based on the rotation phase and the voltage command, control the power conversion circuit to output drive power to the induction motor synchronously with the main power conversion device.

[0005] Furthermore, this paper discloses an example power conversion method. This power conversion method may include: generating a first voltage command having a first command phase in a first rotating coordinate system based on a first torque target value; calculating a first rotation phase of the first rotating coordinate system based on the first torque target value and the rotor speed of an induction motor; outputting a first drive power to the induction motor based on the first rotation phase and the first voltage command; generating a second voltage command having a command phase in a second rotating coordinate system based on a second torque target value, wherein a rotating magnetic field for driving the rotor of the induction motor is generated to rotate with the second rotating coordinate system; calculating a second rotation phase of the second rotating coordinate system based on the command phase difference between the first command phase and the command phase to reduce the command phase difference; and outputting a second drive power to the induction motor synchronously with the first drive power based on the second rotation phase and the second voltage command.

[0006] Furthermore, an example non-transitory memory device stores instructions that, in response to a processed device, cause the processed device to perform an operation. The operation may include: receiving a master command phase from a master power conversion device; generating a voltage command with a command phase in a rotating coordinate system based on a torque target value, wherein a rotating magnetic field for driving the rotor of an induction motor is generated to rotate with the rotating coordinate system; calculating a rotational phase of the rotating coordinate system based on the command phase difference between the master command phase and the command phase to reduce the command phase difference; and, based on the rotational phase and the voltage command, controlling a power conversion circuit, synchronously with the master power conversion device, to output drive power to the induction motor.

[0007] According to this disclosure, a power conversion device can be provided that is effective for synchronously generating rotating magnetic fields in an induction motor by multiple power conversion devices respectively. Attached Figure Description

[0008] Figure 1 This is a diagram illustrating an example overall configuration of the drive system.

[0009] Figure 2 This is a diagram illustrating an example configuration of a power conversion circuit.

[0010] Figure 3 This is a diagram showing an example configuration of a bidirectional switch.

[0011] Figure 4 This is a block diagram illustrating an example configuration of the main control circuit.

[0012] Figure 5 This is a block diagram illustrating an example configuration of a slave control circuit.

[0013] Figure 6 This is a diagram illustrating a modified example of a slave control circuit.

[0014] Figure 7 This is a diagram illustrating a modified example of the master control circuit and slave control circuit.

[0015] Figure 8A and Figure 8B This is a graph illustrating an example relationship between the rotational speed of an induction motor and the correction gain.

[0016] Figure 9 This is a diagram illustrating an example hardware configuration of the master control circuit and the slave control circuit.

[0017] Figure 10 This is a flowchart illustrating an example control process of the power conversion circuit performed by the main control circuit.

[0018] Figure 11 This is a flowchart illustrating an example calculation process for voltage phase.

[0019] Figure 12 This is a flowchart illustrating an example control process of a slave control circuit on a power conversion circuit.

[0020] Figure 13 This is a flowchart illustrating an example torque correction process.

[0021] Figure 14 This is a flowchart illustrating an example calculation process for voltage phase. Detailed Implementation

[0022] The embodiments will now be described in detail with reference to the accompanying drawings. In this specification, the same elements or elements having the same function are represented by the same reference numerals, and redundant descriptions will be omitted.

[0023] drive system

[0024] Figure 1 The drive system 1 shown is a system that uses an induction motor to cause a driven object to perform a desired motion. The drive system 1 includes an electric motor 3 and a control system 2.

[0025] The electric motor 3 is an induction motor and includes: a first set of primary coils 51, 52, and 53 that generate a first rotating magnetic field in response to the supply of AC power; a second set of primary coils 61, 62, and 63 that generate a second rotating magnetic field in response to the supply of AC power; and a rotor 70. The first set of primary coils 51, 52, and 53 and the second set of primary coils 61, 62, and 63 are isolated from each other. Both the first and second rotating magnetic fields generate torque in the rotor 70.

[0026] The control system 2 includes two power conversion devices 4 and 5, which supply AC power to the first set of primary coils 51, 52, 53 and the second set of primary coils 61, 62, 63, respectively.

[0027] The power conversion device 4 includes a power conversion circuit 10A (main power conversion circuit) and a main control circuit 100 (main control circuit). The power conversion circuit 10A converts the primary-side power supplied from the power source 9 into secondary-side power, and supplies the secondary-side power to the primary coils 51, 52, and 53. The primary-side power can be alternating current (AC) or direct current (DC). The secondary-side power is AC. Figure 1 The diagram illustrates a scenario where both the primary and secondary power supplies are three-phase AC power.

[0028] The main control circuit 100 is configured to: calculate the phase (main rotation phase) corresponding to the rotation angle of the rotating coordinate system (main rotating coordinate system) based on the torque target value (main torque target value) and the rotational speed of the motor 3 (rotor speed) (rotor speed of rotor 70); generate a voltage command (main voltage command) in the main rotating coordinate system based on the main torque target value; and control the secondary side voltage of the power conversion circuit 10A to correspond to the main voltage command based on the phase and voltage command of the main rotating coordinate system. Thus, main drive power is output to the motor 3, and a first rotating magnetic field based on the main torque target value is generated. The main voltage command has a main command phase in the main rotating coordinate system.

[0029] The power conversion device 5 includes a power conversion circuit 10B (power conversion circuit) and a slave control circuit 200 (control circuit). The power conversion circuit 10B converts the primary-side power supplied from the power source 9 into secondary-side power and supplies the secondary-side power to the primary coils 61, 62, and 63. If the slave control circuit 200 controls the power conversion circuit 10B in the same manner as the main control circuit 100 controls the power conversion circuit 10A, a second rotating magnetic field is generated based on the torque target value (slave torque target value).

[0030] Therefore, since the first rotating magnetic field generated by the primary coils 51, 52, 53 and the second rotating magnetic field generated by the primary coils 61, 62, 63 act on the rotor 70 respectively, it is possible to prevent the magnitude of each of the power conversion devices 4 and 5 from increasing relative to the amplitude of the torque to be generated from the motor 3.

[0031] Here, since the primary coils 51, 52, 53 and 61, 62, 63 are arranged in the same motor 3, the first rotating magnetic field and the second rotating magnetic field may interfere with each other, which may have an adverse effect on the operation of the rotor 70.

[0032] On the other hand, the power conversion device 5 is configured to: calculate the phase (rotation phase) corresponding to the rotation angle of the rotating coordinate system (subordinate rotating coordinate system) based on the subordinate torque target value and the rotational speed of the motor 3; correct the phase of the subordinate rotating coordinate system to follow the phase of the master rotating coordinate system; generate a voltage command (subordinate voltage command) in the subordinate rotating coordinate system based on the subordinate torque target value; and control the secondary side voltage of the power conversion circuit 10B to correspond to the subordinate voltage command based on the corrected phase of the subordinate rotating coordinate system and the subordinate voltage command. Thus, subordinate drive power is output to the motor 3. The subordinate voltage command has a subordinate command phase in the subordinate rotating coordinate system.

[0033] Therefore, the second rotating magnetic field can be synchronized with the first rotating magnetic field. However, as the rotational speed of the motor 3 increases, the rate of change of the phase of the main rotating coordinate system also increases, making it difficult to receive the phase information of the main rotating coordinate system with high accuracy.

[0034] On the other hand, the slave control circuit 200 is configured to correct the phase of the rotating coordinate system based on the phase of the master voltage command in the master rotating coordinate system (master command phase) (hereinafter referred to as "master voltage phase"). The master voltage phase does not indicate the phase of the master rotating coordinate system itself, but it allows us to understand the deviation of the slave rotating coordinate system's phase relative to the master rotating coordinate system's phase. Therefore, by correcting the phase of the slave rotating coordinate system based on the voltage phase in the master rotating coordinate system, the slave rotating coordinate system can easily follow the master rotating coordinate system. Even if the rotational speed of the induction motor increases, the change in the master voltage phase will not increase. Therefore, by correcting the phase of the slave rotating coordinate system based on the master voltage phase, the second rotating magnetic field can be synchronized with the first rotating magnetic field with high reliability.

[0035] The configurations of power conversion equipment 4 (master equipment) and power conversion equipment 5 (slave equipment) will be described in detail below. In the description of the master equipment, the master torque target value is simply referred to as "torque target value," the master rotating coordinate system is simply referred to as "rotating coordinate system," and the master voltage command is simply referred to as "voltage command." In the description of the slave equipment, the slave torque target value is simply referred to as "torque target value," the slave rotating coordinate system is simply referred to as "rotating coordinate system," and the slave voltage command is simply referred to as "voltage command."

[0036] main equipment

[0037] The power conversion circuit 10A can be any circuit, as long as it converts primary-side power to secondary-side power as described above. For example, if the primary-side power is DC power, then the power conversion circuit 10A can be an inverter circuit. An inverter circuit converts DC power to AC power by switching multiple switching elements on and off.

[0038] If the primary-side power is AC, the power conversion circuit 10A can be a circuit in which a rectifier circuit or a PWM converter circuit is combined with an inverter circuit. The rectifier circuit converts AC power to DC power via a diode bridge. The PWM converter circuit converts AC power to DC power by switching multiple switching elements on and off.

[0039] The power conversion circuit 10A can be a matrix converter circuit that performs power conversion from primary side power to secondary side power and from secondary side power to primary side power. Figure 2This diagram illustrates the configuration when the power conversion circuit 10A is a matrix converter circuit.

[0040] Figure 2 The power conversion circuit 10A shown includes primary side power lines 11R, 11S, 11T, secondary side power lines 12U, 12V, 12W, and nine sets of bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, 20TW.

[0041] Power line 11R is the primary side R-phase power transmission line. Power line 11S is the primary side S-phase power transmission line. Power line 11T is the primary side T-phase power transmission line. Power line 12U is the secondary side U-phase power transmission line. Power line 12V is the secondary side V-phase power transmission line. Power line 12W is the secondary side W-phase power transmission line.

[0042] Each of the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW switches between three states: current flowing from the primary side to the secondary side, current flowing from the secondary side to the primary side, and no current flowing. Bidirectional switch 20RU is inserted between power lines 11R and 12U and switches between a first ON state (current flowing from power line 11R to power line 12U), a second ON state (current flowing from power line 12U to power line 11R), and a bidirectional OFF state (no current flowing). Bidirectional switch 20SU is inserted between power lines 11S and 12U and switches between a first ON state (current flowing from power line 11S to power line 12U), a second ON state (current flowing from power line 12U to power line 11S), and a bidirectional OFF state (no current flowing). A bidirectional switch 20TU is inserted between power line 11T and power line 12U, and switches between a first on state where current flows from power line 11T to power line 12U, a second on state where current flows from power line 12U to power line 11T, and a bidirectional off state where no current flows.

[0043] A bidirectional switch 20RV is inserted between power line 11R and power line 12V, and switches between a first ON state where current flows from power line 11R to power line 12V, a second ON state where current flows from power line 12V to power line 11R, and a bidirectional OFF state where no current flows. A bidirectional switch 20SV is inserted between power line 11S and power line 12V, and switches between a first ON state where current flows from power line 11S to power line 12V, a second ON state where current flows from power line 12V to power line 11S, and a bidirectional OFF state where no current flows. A bidirectional switch 20TV is inserted between power line 11T and power line 12V, and switches between a first ON state where current flows from power line 11T to power line 12V, a second ON state where current flows from power line 12V to power line 11T, and a bidirectional OFF state where no current flows.

[0044] A bidirectional switch 20RW is inserted between power lines 11R and 12W, and switches between a first ON state where current flows from power line 11R to power line 12W, a second ON state where current flows from power line 12W to power line 11R, and a bidirectional OFF state where no current flows. A bidirectional switch 20SW is inserted between power lines 11S and 12W, and switches between a first ON state where current flows from power line 11S to power line 12W, a second ON state where current flows from power line 12W to power line 11S, and a bidirectional OFF state where no current flows. A bidirectional switch 20TW is inserted between power lines 11T and 12W, and switches between a first ON state where current flows from power line 11T to power line 12W, a second ON state where current flows from power line 12W to power line 11T, and a bidirectional OFF state where no current flows.

[0045] like Figure 3 As shown, the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW include two switches 21 and 22. In the ON state, switch 21 transfers current from the primary side to the secondary side, but not from the secondary side to the primary side. In the ON state, switch 22 transfers current from the secondary side to the primary side, but not from the primary side to the secondary side. Furthermore, switches 21 and 22 are reverse-blocking switches, capable of maintaining an ON state relative to a voltage in the direction opposite to the flow direction in the ON state.

[0046] By putting switch 21 into the ON state and switch 22 into the OFF state, the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW enter the first ON state. By putting switch 21 into the OFF state and switch 22 into the ON state, these bidirectional switches enter the second ON state. By putting switches 21 and 22 into the OFF state, these bidirectional switches enter the bidirectional OFF state.

[0047] exist Figure 3 In this configuration, the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW may include diodes connected in series with each of switches 21 and 22, which do not have reverse blocking capability. In this case, the connection point between switch 21 and the diode and the connection point between switch 22 and the diode can be connected.

[0048] Return to Figure 2 The filter 30 reduces the harmonic content of the voltage or current at the primary side power line. For example, the filter 30 includes inductors 31R, 31S, 31T and capacitors 34R, 34S, 34T. Inductors 31R, 31S, 31R are located in the power lines 11R, 11S, 11T, respectively.

[0049] Capacitor 34R is located between power line 11R and the neutral point 35 on the secondary side of inductor 31R (between inductor 31R and bidirectional switches 20RU, 20RV, and 20RW). Capacitor 34S is located between power line 11S and the neutral point 35 on the secondary side of inductor 31S (between inductor 31S and bidirectional switches 20SU, 20SV, and 20SW). Capacitor 34T is located between power line 11T and the neutral point 35 on the secondary side of inductor 31T (between inductor 31T and bidirectional switches 20TU, 20TV, and 20TW).

[0050] The current sensor 40 detects the instantaneous value of the current in the secondary power supply (the current flowing between the matrix converter circuit 10 and the motor 3). For example, the current sensor 40 detects the instantaneous value of the current in the power lines 12U, 12V, and 12W. Hereinafter, the current in the secondary power supply is referred to as the "secondary current". The voltage in the secondary power supply is referred to as the "secondary voltage".

[0051] The current sensor 40 can be configured to detect the secondary current values ​​of all phases of the power lines 12U, 12V, and 12W, or it can be configured to detect the secondary current values ​​of any two phases of the power lines 12U, 12V, and 12W. Since the sum of the current values ​​of phases U, V, and W is zero as long as no zero-phase current is generated, information about the secondary current values ​​of all phases is obtained even when the secondary current values ​​of two phases are detected.

[0052] The main control circuit 100 repeatedly executes the above-described control of the power conversion circuit 10A according to a predetermined control cycle. For example... Figure 4 As shown, the main control circuit 100 includes a torque target value calculation unit 111, a phase calculation unit 112, a current information acquisition unit 113, a voltage command generation unit 114, a PWM control unit 115, and a main information output unit 116 as functional configurations.

[0053] The torque target value calculation unit 111 is configured to calculate the torque target value based on the speed command value ωt and the speed feedback value ωm. For example, the torque target value calculation unit 111 calculates the deviation (speed deviation) between the speed command value ωt and the speed feedback value ωm, as shown in point P01, and calculates the torque target value Tt by performing proportional, proportional-integral, or proportional-integral-derivative operations on the speed deviation, as shown in transfer block B01. The speed feedback value ωm can be a value detected by a sensor, or it can be an estimated value calculated without a sensor. The main control circuit 100 can obtain the torque target value from outside the power conversion device 4.

[0054] Phase calculation unit 112 (main phase calculation unit) is configured to calculate the phase of the rotating coordinate system (coordinate phase θdq_ab) based on the torque target value Tt and the rotational speed of the motor 3 (the speed feedback value ωm mentioned above). The rotating coordinate system is a coordinate system that rotates synchronously with the first rotating magnetic field. For example, the rotating coordinate system is a dq coordinate system, having d-axis and q-axis intersecting the central axis of rotation of the rotor 70. The d-axis and q-axis are mutually perpendicular coordinate axes. Phase calculation unit 112 can calculate the angular frequency command value ω based on the torque target value Tt and the speed feedback value ωm, and can integrate the angular frequency command value ω to calculate the coordinate phase θdq_ab. The coordinate phase θdq_ab is the phase of the dq coordinate system relative to the ab coordinate system, which is a fixed coordinate system. The ab coordinate system has aa-axis and b-axis intersecting the central axis of rotation of the rotor 70. The a-axis and b-axis are mutually perpendicular coordinate axes.

[0055] For example, the phase calculation unit 112 calculates the slip angular velocity of the rotating coordinate system relative to the rotor 70 based on the torque target value Tt, as shown in transfer block B11, and calculates the angular frequency command value ω by adding the speed feedback value ωm to the slip angular velocity, as shown in point P11. Additionally, the phase calculation unit 112 integrates the angular frequency command value ω to calculate the coordinate phase θdq_ab, as shown in transfer block B12.

[0056] Phase calculation unit 112 can calculate the voltage phase θv_ab in the fixed coordinate system based on the voltage phase θv_dq (main voltage phase) in the rotating coordinate system and the coordinate phase θdq_ab. This voltage phase is the phase of the voltage command vector, which represents the voltage command using a single vector. For example, phase calculation unit 112 calculates the voltage phase θv_dq based on the voltage command value Vdt and the voltage command value Vqt calculated in a previous control cycle, as shown in transfer block B13. The voltage command value Vdt is the d-axis component of the voltage command vector, and the voltage command value Vqt is the q-axis component of the voltage command vector. Phase calculation unit 112 calculates the voltage phase θv_ab by adding the voltage phase θv_dq to the coordinate phase θdq_ab, as shown by point P12.

[0057] The current information acquisition unit 113 is configured to calculate current feedback values ​​Id and Iq based on the current feedback values ​​Iu, Iv, and Iw detected by the current sensor 40 of the power conversion circuit 10A. The current feedback value Iu is the current detection value of the power line 12U. The current feedback value Iv is the current detection value of the power line 12V. The current feedback value Iw is the current detection value of the power line 12W. The current feedback value Id is the d-axis component of the current vector representing the current feedback values ​​Iu, Iv, and Iw using a single vector, and the current feedback value Iq is the q-axis component of that current vector.

[0058] For example, the current information acquisition unit 113 calculates the current feedback values ​​Ia and Ib by performing a three-phase to two-phase transformation on the current feedback values ​​Iu, Iv, and Iw, as shown in transfer block B21. The current feedback value Ia is the a-axis component of the current vector, and the current feedback value Ib is the b-axis component of the current vector. The current information acquisition unit 113 calculates the current feedback values ​​Id and Iq by subjecting the current feedback values ​​Ia and Ib to a rotational transformation in the coordinate phase θdq_ab, as shown in transfer block B22.

[0059] The voltage command generation unit 114 (main voltage command generation unit) is configured to generate a voltage command in a rotating coordinate system based on the torque target value Tt. For example, the voltage command generation unit 114 multiplies a predetermined magnetic flux target value Φt by a gain K1 to calculate a current target value Idt, as shown in transfer block B31, and multiplies the torque target value Tt by a gain K2 to calculate a current target value Iqt, as shown in transfer block B32. The current target value Idt is the d-axis component of the current command vector, which represents the current command using a single vector, and the current target value Iqt is the q-axis component of the current command vector.

[0060] The voltage command generation unit 114 is configured to generate voltage commands such that the current feedback value Id follows the current target value Idt, and the current feedback value Iq follows the current target value Iqt. For example, the voltage command generation unit 114 calculates the d-axis current deviation, which is the deviation between the current target value Idt and the current feedback value Id, as shown at point P31, and calculates the voltage command value Vdt, for example, by performing a proportional operation, a proportional-integral operation, or a proportional-integral-differential operation on the d-axis current deviation, as shown in transfer block B33. The voltage command generation unit 114 calculates the q-axis current deviation, which is the deviation between the current target value Iqt and the current feedback value Iq, as shown at point P32, and calculates the voltage command value Vqt, for example, by performing a proportional operation, a proportional-integral operation, or a proportional-integral-differential operation on the q-axis current deviation, as shown in transfer block B34.

[0061] The voltage command generation unit 114 can perform decoupling of voltage commands between the d-axis and q-axis based on the current target values ​​Idt and Iqt and the angular frequency command value ω, as shown in transfer block B35. For example, the voltage command generation unit 114 can correct the voltage command value Vdt based on the current target value Iqt, the equivalent leakage inductance l (l = (L1*L2-M2) / L2), and the angular frequency command value ω, and correct the voltage command value Vqt based on the V / f mode and the angular frequency command value ω, thereby performing decoupling between the d-axis and q-axis. Inductor L1 is the primary inductance of motor 3. Inductor L2 is the secondary inductance of motor 3. Inductor M is the mutual inductance of motor 3. The correction of the voltage command value Vqt can be performed using the current target value Idt, inductor L1, and angular frequency command value ω. Furthermore, the voltage command generation unit 114 can use the current feedback values ​​Id and Iq instead of the current target values ​​Idt and Iqt when performing decoupling.

[0062] The PWM control unit 115 (main control unit) is configured to control the secondary-side voltage of the power conversion circuit 10A to correspond to the voltage command based on the coordinate phase θdq_ab of the rotating coordinate system and the voltage command in the rotating coordinate system. For example, the PWM control unit 115 calculates the voltage command for each phase (U phase, V phase, and W phase) on the secondary side based on the coordinate phase θdq_ab and the voltage command values ​​Vdt and Vqt, and turns on and off the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW of the power conversion circuit 10A, so that the voltage of each phase on the secondary side corresponds to the voltage command.

[0063] The master information output unit 116 (phase information output unit) is configured to output phase information about the rotating coordinate system to the slave control circuit 200 of the power conversion device 5 (slave device). For example, the master information output unit 116 outputs a signal indicating the voltage phase θv_dq in the rotating coordinate system to the slave control circuit 200. As an example, the master information output unit 116 outputs an analog signal indicating the voltage phase θv_dq from the output channel CH13 to the slave control circuit 200.

[0064] As described above, the voltage command values ​​Vdt and Vqt are calculated based on the target torque value Tt, the target flux value Φt, and the current feedback values ​​Id and Iq. Furthermore, the current feedback values ​​Id and Iq are calculated by performing a rotational transformation on the current feedback values ​​Ia and Ib using the coordinate phase θdq_ab. Therefore, it can be said that the voltage command values ​​Vdt and Vqt are calculated based on the coordinate phase θdq_ab. Consequently, the voltage phase θv_dq, i.e., the phase of the voltage command values ​​Vdt and Vqt in the rotating coordinate system, varies according to the coordinate phase θdq_ab. Therefore, the voltage phase θv_dq is an example of a value related to the coordinate phase θdq_ab.

[0065] The master information output unit 116 can also output a signal indicating the coordinate phase θdq_ab itself to the slave control circuit 200. As the signal indicating the coordinate phase θdq_ab itself, the master information output unit 116 can output the sine and cosine values ​​of the coordinate phase θdq_ab to the slave control circuit 200. For example, the master information output unit 116 calculates the sine value of the coordinate phase θdq_ab, as shown in transfer block B51, and outputs an analog signal indicating the calculation result to the slave control circuit 200 from output channel CH11. The master information output unit 116 calculates the cosine value of the coordinate phase θdq_ab, as shown in transfer block B52, and outputs an analog signal indicating the calculation result to the slave control circuit 200 from output channel CH12.

[0066] The master information output unit 116 can also output a torque target value Tt to the slave control circuit 200. For example, the master information output unit 116 outputs an analog signal indicating the torque target value Tt from the output channel CH14 to the slave control circuit 200.

[0067] In the example above, the master information output unit 116 outputs analog signals to the slave control circuit 200, indicating the sine value of the coordinate phase θv_dq, the cosine value of the coordinate phase θdq_ab, and the torque target value Tt. However, the master information output unit 116 can transmit this information to the slave control circuit 200 through digital communication.

[0068] Subordinate equipment

[0069] The power conversion circuit 10B can be any circuit, as long as it converts primary-side power to secondary-side power as described above. For example, if the primary-side power is DC power, then the power conversion circuit 10B can be an inverter circuit. If the primary-side power is DC power, then the power conversion circuit 10B can be a circuit in which a rectifier circuit or a PWM converter circuit is combined with an inverter circuit. The power conversion circuit 10B can also be a matrix converter circuit. Since the specific configuration of the power conversion circuit 10B is the same as that of the power conversion circuit 10A, a more detailed description of it will be omitted.

[0070] The slave control circuit 200 repeatedly executes the above-described control of the power conversion circuit 10B according to a predetermined control cycle. For example... Figure 5 As shown, the slave control circuit 200 includes a master information acquisition unit 211, a torque target value calculation unit 212, a phase calculation unit 213, a phase correction unit 214, a current information acquisition unit 215, a voltage command generation unit 216, and a PWM control unit 217 as functional configurations.

[0071] The main information acquisition unit 211 is configured to acquire phase information about the main rotating coordinate system from the main control circuit 100 of the power conversion device 4 (main device). For example, the main information acquisition unit 211 acquires the voltage phase θv_dq in the main rotating coordinate system from the main control circuit 100. Hereinafter, the voltage phase θv_dq acquired from the main control circuit 100 is referred to as the "main control voltage phase θmv_dq" to distinguish it from the voltage phase θv_dq calculated by the slave control circuit 200. As an example, the main information acquisition unit 211 acquires an analog signal indicating the main voltage phase θmv_dq from the input channel CH23 connected to the output channel CH13.

[0072] The main information acquisition unit 211 can obtain a signal indicating the main coordinate phase θmdq_ab itself from the main control circuit 100. This phase is the phase of the main rotating coordinate system. As the signal indicating the main coordinate phase θmdq_ab itself, the main information acquisition unit 211 can obtain the sine and cosine values ​​of the main coordinate phase θmdq_ab from the power conversion device 4. As an example, the main information acquisition unit 211 obtains an analog signal indicating the sine value of the main coordinate phase θmdq_ab from the input channel CH21 connected to the output channel CH11, and an analog signal indicating the cosine value of the main coordinate phase θmdq_ab from the input channel CH22 connected to the output channel CH12. The main information acquisition unit 211 calculates the main coordinate phase θmdq_ab based on the sine and cosine values ​​of the main coordinate phase θmdq_ab, as shown in the transfer block B101.

[0073] From the output of information by the main information output unit 116 to the acquisition of information by the main information acquisition unit 211, a delay may occur due to communication latency or similar issues. In this case, the main information acquisition unit 211 can perform delay compensation on the main coordinate phase θmdq_ab based on the angular frequency command and the delay time.

[0074] The main information acquisition unit 211 can also obtain the main torque target value Tmt from the main control circuit 100. For example, the main information acquisition unit 211 obtains an analog signal indicating the main torque target value Tmt from the input channel CH24 connected to the output channel CH14.

[0075] The torque target value calculation unit 212 is configured to calculate a torque target value Tt corresponding to the torque target value in the main control circuit 100. For example, the torque target value calculation unit 212 sets the main torque target value Tmt obtained by the main information acquisition unit 211 as the torque target value Tt in the subordinate control circuit 200. The torque target value calculation unit 212 can correct the torque target value Tt based on the speed command value ωt and the speed feedback value ωm. For example, the torque target value calculation unit 212 can calculate the deviation (speed deviation) between the speed command value ωt and the speed feedback value ωm, as shown at point P111, calculate the correction value by performing a proportional calculation on the speed deviation, as shown at transfer block B111, and correct the torque target value by adding the correction value, as shown at point P112. Furthermore, the torque target value calculation unit 212 can calculate the torque limit value Tlim based on the deviation between the speed limit target value ωlim obtained by adding the bias value ωb to the speed command value ωt and the speed feedback value ωm, and set the smaller of the torque target value Tt and the torque limit value Tlim as the torque target value Tt.

[0076] Phase calculation unit 213 (subordinate phase calculation unit) is configured to calculate the phase of the rotating coordinate system (coordinate phase θdq_ab) based on the target torque value Tt and the rotational speed of the motor 3 (the speed feedback value ωm mentioned above). The rotating coordinate system is a coordinate system that rotates synchronously with the second rotating magnetic field. For example, the rotating coordinate system is a dq coordinate system with d-axis and q-axis intersecting the central axis of rotation of the rotor 70. The d-axis and q-axis are mutually perpendicular coordinate axes.

[0077] Phase calculation unit 213 can calculate the angular frequency command value ω of the rotating coordinate system based on the torque target value Tt and the speed feedback value ωm, and can calculate the coordinate phase θdq_ab by integrating the angular frequency command value ω. For example, phase calculation unit 213 calculates the slip angular velocity of rotor 70 relative to the rotating coordinate system based on the torque target value Tt, as shown in transfer block B121, and calculates the angular frequency command value ω by adding the speed feedback value ωm to the slip angular velocity, as shown in point P121. In addition, phase calculation unit 213 integrates the angular frequency command value ω to calculate the coordinate phase θdq_ab, as shown in transfer block B122.

[0078] Phase calculation unit 213 can calculate the voltage phase θv_ab in the fixed coordinate system based on the voltage phase θv_dq and the coordinate phase θdq_ab in the rotating coordinate system. For example, phase calculation unit 213 calculates the voltage phase θv_dq based on the voltage command value Vdt and the voltage command value Vqt calculated in a previous control cycle, as shown in transfer block B123. The voltage command value Vdt is the d-axis component of the voltage command vector, and the voltage command value Vqt is the q-axis component of the voltage command vector. Phase calculation unit 213 calculates the voltage phase θv_ab by adding the voltage phase θv_dq to the coordinate phase θdq_ab, as shown in point P122.

[0079] Phase correction unit 214 is configured to correct the coordinate phase θdq_ab of the rotating coordinate system to follow the phase of the master rotating coordinate system. Phase correction unit 214 corrects the phase of the rotating coordinate system based on the master voltage phase θmv_dq, which is the phase of the master voltage command in the master rotating coordinate system. For example, phase correction unit 214 corrects the phase of the rotating coordinate system based on the difference between the master voltage phase θmv_dq and the voltage phase θv_dq, which is the phase of the calculated voltage command in the rotating coordinate system.

[0080] Phase correction unit 214 can correct the angular frequency command value ω based on the main voltage phase θmv_dq. In this case, phase correction unit 214 can calculate the corrected coordinate phase θdq_ab by integrating the corrected angular frequency command value ω.

[0081] The phase correction unit 214 can correct the coordinate phase θdq_ab based on the principal coordinate phase θmdq_ab of the principal rotating coordinate system when the rotation speed (angular frequency command value ω) of the rotating coordinate system is within a first range band (or below a first threshold). Furthermore, when the rotation speed (coordinate rotation speed) of the rotating coordinate system is within a second range band (or above a second threshold, which is higher than the first threshold) of the first range band, it can correct the coordinate phase θdq_ab based on the principal voltage phase θmv_dq, which is the phase of the principal voltage command in the principal rotating coordinate system. For example, when the rotation speed of the rotating coordinate system is within a first range band, the phase correction unit 214 corrects the coordinate phase θdq_ab based on a first deviation (rotation phase difference), which is the difference between the master coordinate phase θmdq_ab (master rotation phase) and the coordinate phase θdq_ab (slave rotation phase). When the rotation speed of the rotating coordinate system is within a second range band, the phase correction unit 214 corrects the coordinate phase θdq_ab based on a second deviation (command phase deviation), which is the difference between the master voltage phase θmv_dq (master command phase) and the voltage phase θv_dq (slave command phase).

[0082] The phase correction unit 214 can correct the coordinate phase θdq_ab based on the weighted average of the first deviation and the second deviation when the rotation speed of the rotating coordinate system is within the intermediate range between the first range and the second range. Furthermore, as the rotation speed of the rotating coordinate system approaches the upper limit of the intermediate range from the lower limit, the weight of the first deviation can be gradually reduced and the weight of the second deviation can be gradually increased.

[0083] The phase correction unit 214 can correct the angular frequency command value ω based on a first deviation when the rotational speed of the rotating coordinate system is within a first range band, and correct the angular frequency command value ω based on a second deviation when the rotational speed of the rotating coordinate system is within a second range band. In these cases, the phase correction unit 214 can calculate the corrected coordinate phase θdq_ab by integrating the corrected angular frequency command value ω.

[0084] When the rotational speed of the rotating coordinate system is within the first range band, the phase correction unit 214 can correct the coordinate phase θdq_ab based on the sine and cosine values ​​of the principal coordinate phase θmdq_ab. For example, the phase correction unit 214 can correct the coordinate phase θdq_ab based on the principal coordinate phase θmdq_ab calculated by the principal information acquisition unit 211.

[0085] As an example, phase correction unit 214 calculates the first deviation by subtracting the coordinate phase θmdq_ab from the principal coordinate phase θdq_ab, as shown at point P131, and calculates the correction value AV1 by multiplying the first deviation by the gain AK1, as shown at transfer block B131. Phase correction unit 214 calculates the second deviation by subtracting the voltage phase θv_dq from the principal voltage phase θmv_dq, as shown at point P132, and calculates the correction value AV2 by multiplying the second deviation by the gain AK2, as shown at transfer block B132. In addition, phase correction unit 214 adds the correction values ​​AV1 and AV2, as shown at point P133, and performs, for example, a proportional operation, a proportional-integral operation, or a proportional-integral-differential operation on the sum of the correction values ​​AV1 and AV2, as shown at transfer block B133, to calculate the correction value AV. The phase correction unit 214 can calculate the correction value AV by performing proportional operation, proportional-integral operation, proportional-integral-differential operation, etc. on each of the correction values ​​AV1 and AV2 and then adding the results.

[0086] Before being input to the transfer block B121 of the phase calculation unit 213, the phase correction unit 214 adds a correction value AV to the torque target value Tt, as shown by point P134. By adding the correction value AV to the torque target value Tt, the angular frequency command value ω calculated via the transfer block B121 is corrected.

[0087] The gain AK1 is determined based on a first gain curve and the rotational speed of the rotating coordinate system. The first gain curve is predefined to represent the relationship between the rotational speed of the rotating coordinate system and the magnitude of the gain AK1. The first gain curve can be a function or a discrete point sequence of data. For example, the phase correction unit 214 extracts the gain AK1 from the first gain curve corresponding to the rotational speed of the rotating coordinate system.

[0088] Similarly, the gain AK2 is determined based on a second gain curve and the rotational speed of the rotating coordinate system, the second gain curve being predefined to represent the relationship between the rotational speed of the rotating coordinate system and the magnitude of the gain AK2. The second gain curve can be a function or discrete point sequence data. For example, the phase correction unit 214 extracts the gain AK2 from the second gain curve corresponding to the rotational speed of the rotating coordinate system.

[0089] Figure 8A The graph shows the first gain curve, where the horizontal axis indicates the rotation speed of the rotating coordinate system and the vertical axis indicates the magnitude of the gain AK1. Figure 8B The graph shows the second gain curve, where the horizontal axis indicates the rotation speed of the rotating coordinate system and the vertical axis indicates the magnitude of the gain AK2.

[0090] exist Figure 8A In the process, when the rotational speed of the rotating coordinate system is within a first range band of a first threshold ω1 or smaller, the gain AK1 is set to 1; when the rotational speed of the rotating coordinate system is within a second range band of a second threshold ω2 or larger, the gain AK1 is set to 0, where the second threshold ω2 is greater than the first threshold ω1. In the intermediate range band between the first threshold ω1 and the second threshold ω2, the gain AK1 gradually changes from 1 to 0 as it approaches the second threshold ω2.

[0091] On the other hand, Figure 8B In the first range, when the rotation speed of the rotating coordinate system is within the first range, the gain AK2 is set to 0, and when the rotation speed is within the second range, the gain AK2 is set to 1. In the middle range, as the system approaches the second threshold ω2 from the first threshold ω1, the gain AK2 gradually changes from 0 to 1.

[0092] With the above configuration, when the rotational speed of the rotating coordinate system is within the first range, the correction value AV is calculated based on the first deviation; when the rotational speed is within the second range, the correction value AV is calculated based on the second deviation. When the rotational speed is within the intermediate range, the correction value AV is calculated based on the weighted average of the first and second deviations. Furthermore, as the rotational speed approaches the upper limit of the intermediate range from the lower limit, the weight of the first deviation gradually decreases, while the weight of the second deviation gradually increases.

[0093] Return to Figure 5 The current information acquisition unit 215 is configured to calculate current feedback values ​​Id and Iq based on the current feedback values ​​Iu, Iv, and Iw detected by the current sensor 40 of the power conversion circuit 10B. For example, the current information acquisition unit 215 calculates current feedback values ​​Ia and Ib by performing a three-phase to two-phase transformation on the current feedback values ​​Iu, Iv, and Iw, as shown in transfer block B141. As shown in transfer block B142, the current feedback values ​​Ia and Ib undergo a rotation transformation according to the corrected coordinate phase θdq_ab to calculate the current feedback values ​​Id and Iq.

[0094] The slave voltage command generation unit 216 (voltage command generation unit) is configured to generate a voltage command in a rotating coordinate system based on the torque target value Tt. For example, the voltage command generation unit 216 multiplies a predetermined magnetic flux target value Φt by a gain K1 to calculate a current target value Idt, as shown in transfer block B151, and multiplies the torque target value Tt by a gain K2 to calculate a current target value Iqt, as shown in transfer block B152.

[0095] The voltage command generation unit 216 generates a voltage command such that the current feedback value Id follows the current target value Idt, and the current feedback value Iq follows the current target value Iqt. For example, the voltage command generation unit 216 calculates the d-axis current deviation, which is the deviation between the current target value Idt and the current feedback value Id, as shown in point P151, and calculates the voltage command value Vdt, for example, by performing a proportional operation, a proportional-integral operation, or a proportional-integral-differential operation on the d-axis current deviation, as shown in transfer block B153.

[0096] The voltage command generation unit 216 calculates the q-axis current deviation, which is the deviation between the current target value Iqt and the current feedback value Iq, as shown in point P152. The voltage command value Vqt is calculated by performing, for example, proportional operation, proportional-integral operation or proportional-integral-differential operation on the q-axis current deviation, as shown in transfer block B154.

[0097] The voltage command generation unit 216 can perform decoupling of voltage commands between the d-axis and q-axis based on the current target values ​​Idt and Iqt and the angular frequency command value ω, as shown in transfer block B155. For example, the voltage command generation unit 216 can correct the voltage command value Vdt based on the current target value Iqt, the equivalent leakage inductance l (l = (L1*L2-M2) / L2), and the angular frequency command value ω, and correct the voltage command value Vqt based on the V / f mode and the angular frequency command value ω, thereby performing decoupling between the d-axis and q-axis. Furthermore, the voltage command generation unit 216 can use the current feedback values ​​Id and Iq instead of the current target values ​​Idt and Iqt when performing decoupling.

[0098] Similarly, in the power conversion device 5, the voltage command values ​​Vdt and Vqt are also calculated based on the torque target value Tt, the magnetic flux target value Φt, and the current feedback values ​​Id and Iq. Furthermore, the current feedback values ​​Id and Iq are calculated by performing a rotational transformation on the current feedback values ​​Ia and Ib using the coordinate phase θdq_ab. Therefore, it can be said that the voltage command values ​​Vdt and Vqt are calculated based on the coordinate phase θdq_ab.

[0099] The PWM control unit 217 is configured to control the secondary-side voltage of the power conversion circuit 10B to correspond to a voltage command based on the corrected coordinate phase θdq_ab and a voltage command in a rotating coordinate system having the corrected phase θdq_ab. For example, the PWM control unit 217 calculates the voltage command for each phase (U phase, V phase, and W phase) on the secondary side based on the corrected coordinate phase θdq_ab and the voltage command values ​​Vdt and Vqt, and turns on and off the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW of the power conversion circuit 10B such that the voltage of each phase on the secondary side corresponds to the voltage command.

[0100] The slave control circuit 200 can be configured to detect communication anomalies with the master control circuit 100. For example, such as Figure 6 As shown, the slave control circuit 200 includes an anomaly monitoring unit 220.

[0101] The anomaly monitoring unit 220 can detect anomalies in the communication path (e.g., between output channels CH11 and CH12 and input channels CH21 and CH22) used to acquire the sine and cosine values ​​of the principal coordinate phase θmdq_ab based on the degree to which the sum of the square of the sine and the square of the cosine of the principal coordinate phase θmdq_ab deviates from 1. When the principal voltage phase θmv_dq is less than a predetermined level, the anomaly monitoring unit 220 can detect anomalies in the communication path (e.g., between transmit channel CH13 and receive channel CH23) used to acquire the principal voltage phase θmv_dq.

[0102] For example, the anomaly monitoring unit 220 includes a sum-of-squares calculation unit 221 and a disconnection detection unit 222. The sum-of-squares calculation unit 221 is configured to calculate the sum of the squares of the sine and cosine values ​​of the principal coordinate phase θmdq_ab. The disconnection detection unit 222 is configured to detect a disconnection between output channels CH11 and CH12 and input channels CH21 and CH22 when the deviation of the calculation result from one by the sum-of-squares calculation unit 221 exceeds a predetermined threshold. The disconnection detection unit 222 is also configured to detect a disconnection between output channel CH13 and input channel CH23 when the principal voltage phase θmv_dq is less than a predetermined level.

[0103] The anomaly monitoring unit 220 can be configured to also detect anomalies in the communication path used to acquire the target value of the main torque Tmt (e.g., between output channel CH14 and input channel CH24). For example, when the rotational speed of the rotating coordinate system is within a first range, the anomaly monitoring unit 220 detects anomalies in the communication path used to acquire the target value of the main torque Tmt based on a first deviation, and when the rotational speed of the rotating coordinate system is within a second range, it detects anomalies in the communication path used to acquire the target value of the main torque Tmt based on a second deviation. When the rotational speed of the rotating coordinate system is within an intermediate range, the anomaly monitoring unit 220 can detect anomalies in the communication path used to acquire the target value of the main torque Tmt based on a weighted average of the first and second deviations.

[0104] For example, when the rotational speed of the rotating coordinate system is within a first range and the first deviation exceeds a predetermined level, the disconnection detection unit 222 detects a disconnection between the output channel CH14 and the input channel CH24. When the rotational speed of the rotating coordinate system is within a second range and the second deviation exceeds a predetermined level, the disconnection detection unit 222 detects a disconnection between the output channel CH14 and the input channel CH24.

[0105] When the rotational speed of the rotating coordinate system is within the intermediate range and the weighted average of the first and second deviations exceeds a predetermined level, the disconnection detection unit 222 detects a disconnection between the output channel CH14 and the input channel CH24. For example, when the correction value AV exceeds a predetermined level, the disconnection detection unit 222 detects a disconnection between the output channel CH14 and the input channel CH24.

[0106] Although the configurations of power conversion devices 4 and 5 have been described separately above, each of power conversion devices 4 and 5 can be configured to function as a master or slave device depending on user settings. In this case, although the configurations of power conversion devices 4 and 5 are identical, for convenience, an example configuration of power conversion device 5, which can also be used as a master device, will be described.

[0107] like Figure 7 As shown, the power conversion device 5, which can also be used as a master device, further includes a master information output unit 116 and a mode selection unit 311. The mode selection unit 311 is configured to select a master mode or a slave mode based on a mode selection input (e.g., user input to an input device). When the master mode is selected, the power conversion device 5 functions as a master device. When the slave mode is selected, the power conversion device 5 functions as a slave device.

[0108] For example, when the master mode is selected, the mode selection unit 311 disables the functions of the master information acquisition unit 211 and the phase correction unit 214. By disabling the function of the phase correction unit 214, the PWM control unit 217 controls the secondary voltage of the power conversion circuit 10B to correspond to the voltage command based on the uncorrected coordinate phase θdq_ab and the voltage command. Furthermore, the mode selection unit 311 causes the torque target value calculation unit 212 to calculate the torque target value in the same way as the torque target value calculation unit 111 calculates the torque target value Tt, instead of based on the master torque target value Tmt. Additionally, the mode selection unit 311 enables the function of the master information output unit 116. The master information output unit 116 outputs information about the coordinate phase θdq_ab and the torque target value Tt to the slave device.

[0109] When the slave mode is selected, the mode selection unit 311 enables the functions of the torque target value calculation unit 111 and the phase correction unit 214, and controls the torque target value calculation unit 212 to calculate the torque target value Tt based on the main torque target value Tmt according to the above calculation method. When the function of the phase correction unit 214 is enabled, the PWM control unit 217 controls the secondary side voltage of the power conversion circuit 10B to correspond to the voltage command based on the corrected coordinate phase θdq_ab and the voltage command.

[0110] Hardware configuration of control system 2

[0111] Figure 9 This is a schematic diagram illustrating the hardware configuration of control system 2. For example... Figure 9 As shown, the main control circuit 100 includes one or more processors 191, a memory 192, a storage unit 193, an input / output port 194, a switching control circuit 195, and a communication port 196. The storage unit 193 includes a computer-readable storage medium, such as a non-volatile semiconductor memory. The storage unit 193 stores a program for causing the main control circuit 100 to perform the following steps: calculating the phase of the rotating coordinate system (main rotating coordinate system) based on the target torque value and the rotational speed of the motor 3; generating a voltage command (main voltage command) in the main rotating coordinate system based on the main torque target value; and controlling the secondary side voltage of the power conversion circuit 10A to correspond to the main voltage command based on the phase of the main rotating coordinate system and the voltage command. For example, the storage unit 193 stores a program for configuring the aforementioned functional units in the main control circuit 100.

[0112] Memory 192 temporarily stores programs loaded from the storage medium of storage unit 193 and calculation results from processor(s) 191. Processors(s) 191 configure the functional units of the main control circuit 100 by cooperating with memory 192 to execute programs. Input / output port 194 inputs and outputs electrical signals to and from current sensor 40 according to instructions from processor(s) 191. Switching control circuit 195 outputs secondary-side power to motor 3 by turning on and off switching elements in power conversion circuit 10A according to instructions from processor(s) 191. Communication port 196 performs information communication with slave control circuit 200 according to instructions from processor(s) 191.

[0113] The slave control circuit 200 includes one or more processors 291, a memory 292, a storage unit 293, an input / output port 294, a switching control circuit 295, and a communication port 296. The storage unit 293 includes a computer-readable storage medium, such as a non-volatile semiconductor memory. The storage unit 293 stores a program for causing the slave control circuit 200 to repeatedly execute control of the power conversion circuit 10B according to a predetermined control cycle. For example, the storage unit 293 stores a program for configuring the aforementioned functional units in the slave control circuit 200.

[0114] Memory 292 temporarily stores programs loaded from the storage medium of storage unit 293 and calculation results from processor(s) 291. Processors(s) 291 configure the functional units of slave control circuit 200 by cooperating with memory 292 to execute programs. Input / output port 294 inputs and outputs electrical signals to and from current sensor 40 according to instructions from processor(s) 291. Switching control circuit 295 outputs secondary-side power to motor 3 by turning multiple switching elements in power conversion circuit 10B on and off according to instructions from processor(s) 291. Communication port 296 performs information communication with main control circuit 100 according to instructions from processor(s) 291.

[0115] It should be noted that the main control circuit 100 is not necessarily limited to a circuit that configures each function through a program. For example, the main control circuit 100 can be configured with at least some functions through dedicated logic circuits or application-specific integrated circuits (ASICs) that integrate dedicated logic circuits.

[0116] Control process

[0117] Next, as an example of the control method, the main control process executed by the main control circuit 100 and the subordinate control process executed by the subordinate control circuit 200 will be described.

[0118] Main control process

[0119] The process includes: calculating the phase of the rotating coordinate system based on the target torque value and the rotational speed of the motor 3; generating a voltage command in the rotating coordinate system based on the target torque value; controlling the secondary voltage of the power conversion circuit to correspond to the voltage command based on the phase of the rotating coordinate system and the voltage command; and at least outputting the phase of the voltage command in the rotating coordinate system as information about the phase of the rotating coordinate system to the slave control circuit 200.

[0120] For example, such as Figure 10 As shown, the main control circuit 100 executes steps S01, S02, S03, S04, S05, and S06 in sequence. In step S01, the torque target value calculation unit 111 calculates the torque target value Tt based on the speed command value ωt and the speed feedback value ωm.

[0121] In step S02, the phase calculation unit 112 calculates the coordinate phase θdq_ab based on the target torque value Tt and the rotational speed of the motor 3. The phase calculation unit 112 can also calculate the voltage phase θv_ab in the fixed coordinate system based on the voltage phase θv_dq and the coordinate phase θdq_ab in the rotating coordinate system. In this case, the phase calculation unit 112 uses the voltage phase θv_dq of the voltage command values ​​Vdt and Vqt calculated in the previous control cycle. The specific process of step S02 will be described later.

[0122] In step S03, the current information acquisition unit 113 calculates the current feedback values ​​Id and Iq based on the current feedback values ​​Iu, Iv, and Iw detected by the current sensor 40 of the power conversion circuit 10A. For example, the current information acquisition unit 113 calculates the current feedback values ​​Ia and Ib by performing a three-phase to two-phase transformation on the current feedback values ​​Iu, Iv, and Iw, and calculates the current feedback values ​​Id and Iq by performing a rotation transformation on the current feedback values ​​Ia and Ib according to the coordinate phase θdq_ab. In step S04, the voltage command generation unit 114 calculates the voltage command based on the torque target value Tt, the magnetic flux target value Φt, and the current feedback values ​​Id and Iq.

[0123] In step S05, the main information output unit 116 outputs the sine value of the voltage phase θv_dq, the cosine value of the coordinate phase θdq_ab, and the torque target value Tt to the slave control circuit 200.

[0124] In step S06, the PWM control unit 115 turns on and off the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW of the power conversion circuit 10A, so that the secondary side voltage of the power conversion circuit 10A corresponds to the voltage command newly generated in step S04. Afterward, the main control circuit 100 returns the processing to step S01. The main control circuit 100 repeats the above process according to a predetermined control cycle.

[0125] Figure 11 This is a flowchart illustrating the phase calculation process in step S02. For example... Figure 11 As shown, the main control circuit 100 executes steps S11, S12, S13, S14, and S15 sequentially. In step S11, the phase calculation unit 112 calculates the slip angular velocity of the rotating coordinate system relative to the rotor 70 based on the torque target value Tt. In step S12, the phase calculation unit 112 adds the speed feedback value ωm to the slip angular velocity to calculate the angular frequency command value ω. In step S13, the phase calculation unit 112 integrates the angular frequency command value ω to calculate the coordinate phase θdq_ab.

[0126] In step S14, the phase calculation unit 112 calculates the voltage phase θv_dq in the rotating coordinate system based on the voltage command values ​​Vdt and Vqt calculated in the previous control cycle. In step S15, the phase calculation unit 112 calculates the voltage phase θv_ab in the fixed coordinate system by adding the voltage phase θv_dq to the coordinate phase θdq_ab. Thus, the phase calculation process is completed.

[0127] Subordinate control process

[0128] The process includes: calculating the phase of the rotating coordinate system based on the target torque value and the rotational speed of the motor 3; correcting the phase of the rotating coordinate system to follow the phase of the main rotating coordinate system; generating a voltage command in the rotating coordinate system based on the target torque value; and controlling the secondary side voltage of the power conversion circuit to correspond to the voltage command, wherein the phase of the rotating coordinate system is corrected based on the phase of the main voltage command generated by the main device in the rotating coordinate system.

[0129] For example, such as Figure 12 As shown, the slave control circuit 200 first executes steps S21 and S22. In step S21, the master information acquisition unit 211 acquires at least the master voltage phase θmv_dq in the master rotating coordinate system from the master control circuit 100 as information related to the coordinate phase θdq_ab. The master information acquisition unit 211 can also acquire the sine value and cosine value of the master coordinate phase θmdq_ab from the master control circuit 100, and can also acquire the torque target value Tt from the master control circuit 100.

[0130] In step S22, the anomaly monitoring unit 220 checks for any disconnections in the communication path with the main control circuit 100. For example, the anomaly monitoring unit 220 checks for a disconnection between output channel CH13 and input channel CH23 based on whether the main voltage phase θmv_dq is less than a predetermined level. The anomaly monitoring unit 220 checks for a disconnection between output channels CH11 and CH12 and input channels CH21 and CH22 based on the degree to which the sum of the square of the sine value and the square of the cosine value of the main coordinate phase θmdq_ab deviates from 1. The anomaly monitoring unit 220 checks for a disconnection between output channel CH14 and input channel CH24 based on the amplitude of the correction value AV.

[0131] If step S22 determines that the communication path is not broken, then the slave control circuit 200 executes steps S23, S24, S25, S26, S27, and S28. In step S23, the torque target value calculation unit 212 calculates the torque target value Tt based on the main torque target value Tmt. In step S24, the phase correction unit 214 corrects the torque target value Tt based on the main voltage phase θmv_dq and the main coordinate phase θmdq_ab before it is input to the phase calculation unit 213. The specific process of step S24 will be described later.

[0132] In step S25, the phase calculation unit 213 calculates the coordinate phase θdq_ab based on the corrected torque target value Tt and the rotational speed of the motor 3. The phase calculation unit 213 can calculate the voltage phase θv_ab in the fixed coordinate system based on the voltage phase θv_dq and the coordinate phase θdq_ab in the rotating coordinate system. In this case, the phase calculation unit 112 uses the voltage phase θv_dq of the voltage command values ​​Vdt and Vqt calculated in the previous control cycle. The specific process of step S25 will be described later.

[0133] In step S26, the current information acquisition unit 215 calculates the current feedback values ​​Id and Iq based on the current feedback values ​​Iu, Iv, and Iw detected by the current sensor 40 of the power conversion circuit 10B. For example, the current information acquisition unit 215 calculates the current feedback values ​​Ia and Ib by performing a three-phase to two-phase transformation on the current feedback values ​​Iu, Iv, and Iw, and calculates the current feedback values ​​Id and Iq by performing a rotation transformation on the current feedback values ​​Ia and Ib according to the coordinate phase θdq_ab.

[0134] In step S27, the voltage command generation unit 216 calculates the voltage command based on the target torque value Tt, the target magnetic flux value Φt, and the current feedback values ​​Id and Iq. In step S28, the PWM control unit 217 turns on and off the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW of the power conversion circuit 10B, so that the secondary side voltage of the power conversion circuit 10B corresponds to the newly generated voltage command in step S27. Thereafter, the slave control circuit 200 returns the processing to step S21. The slave control circuit 200 repeats the above process according to a predetermined control cycle unless an open circuit is detected in step S22.

[0135] If step S22 determines that the communication path is broken, the slave control circuit 200 executes step S29. In step S29, the PWM control unit 217 stops supplying secondary-side current to the motor 3. For example, the PWM control unit 217 sets each of the bidirectional switches 20RU, 20SU, 20TU, 20RV, 20SV, 20TV, 20RW, 20SW, and 20TW to the bidirectional off state and terminates control of the power conversion circuit 10B.

[0136] Figure 13 This is a flowchart illustrating the correction process for the torque target value Tt in step S24. For example... Figure 13 As shown, the slave control circuit 200 sequentially executes steps S31, S32, S33, S34, and S35. In step S31, the phase correction unit 214 subtracts the coordinate phase θdq_ab from the principal coordinate phase θmdq_ab to calculate the first deviation. At this time, the phase correction unit 214 uses the coordinate phase θdq_ab calculated in the previous control cycle. In step S32, the phase correction unit 214 calculates the gain AK1 based on the aforementioned first gain curve and the rotation speed of the rotating coordinate system.

[0137] In step S33, the phase correction unit 214 subtracts the voltage phase θv_dq from the main voltage phase θmv_dq to calculate the second deviation. In step S34, the phase correction unit 214 calculates the gain AK2 based on the aforementioned second gain curve and the rotation speed of the rotating coordinate system.

[0138] In step S35, the phase correction unit 214 calculates the weighted average of the first deviation and the second deviation according to gains AK1 and AK2, and performs proportional, proportional-integral, proportional-integral-differential, etc., operations on this weighted average to calculate the correction value AV. As described above, when the rotational speed of the rotating coordinate system is within the first range band, gain AK1 is 1 and gain AK2 is 0. Furthermore, when the rotational speed of the rotating coordinate system is within the second range band, gain AK1 is 0 and gain AK2 is 1. Therefore, when the rotational speed of the rotating coordinate system is within the first range band, the correction value AV is calculated primarily based on the first deviation; when the rotational speed of the rotating coordinate system is within the second range band, the correction value AV is calculated primarily based on the second deviation; and when the rotational speed of the rotating coordinate system is within the intermediate range band, the correction value AV is calculated based on the weighted average of the first deviation and the second deviation. In step S36, the phase correction unit 214 adds the correction value AV to the torque target value Tt before it is input to the phase calculation unit 213. Thus, the correction process for the target torque value Tt was completed.

[0139] Figure 14 This is a flowchart illustrating the phase calculation process in step S25. For example... Figure 14 As shown, the slave control circuit 200 sequentially executes steps S41, S42, S43, S44, and S45. In step S41, the phase calculation unit 213 calculates the slip angular velocity of the rotating coordinate system relative to the rotor 70 based on the torque target value Tt with added correction value AV. In step S42, the phase calculation unit 213 adds the speed feedback value ωm to the slip angular velocity to calculate the angular frequency command value ω. In step S43, the phase calculation unit 213 integrates the angular frequency command value ω to calculate the coordinate phase θdq_ab.

[0140] In step S44, the phase calculation unit 213 calculates the voltage phase θv_dq in the rotating coordinate system based on the voltage command values ​​Vdt and Vqt calculated in the previous control cycle. In step S45, the phase calculation unit 213 calculates the voltage phase θv_ab in the fixed coordinate system by adding the voltage phase θv_dq to the coordinate phase θdq_ab. Thus, the phase calculation process is completed.

[0141] Effects of the current embodiment

[0142] As described above, the power conversion device 5 includes: a power conversion circuit 10B that converts primary-side power into secondary-side power and supplies the secondary-side power to an induction motor; a phase calculation unit 213 that calculates the phase of a rotating coordinate system based on a target torque value and the rotational speed of the motor 3 (electric motor); a phase correction unit 214 that corrects the phase of the rotating coordinate system to follow the phase of a main rotating coordinate system, which is the rotating coordinate system in the power conversion device 4 (main device); a voltage command generation unit 216 that generates a voltage command in the rotating coordinate system based on the corrected phase and voltage command of the rotating coordinate system; and a PWM control unit 217 (control unit) that controls the secondary voltage of the power conversion circuit 10B to correspond to the voltage command based on the corrected phase and voltage command of the rotating coordinate system. The phase correction unit 214 corrects the phase of the rotating coordinate system based on the phase of the main rotating coordinate system of the main voltage command generated by the power conversion device 4 (main device).

[0143] By controlling the phase of the rotating coordinate system in the power conversion device 5 to follow the phase of the main rotating coordinate system, the rotating magnetic field (second rotating magnetic field) generated by the power conversion device 5 in the motor 3 (induction motor) can be synchronized with the rotating magnetic field (first rotating magnetic field) generated by the power conversion device 4 (main device) in the motor 3. However, as the rotational speed of the motor 3 increases, the rate of change of the phase of the main rotating coordinate system also increases, making it difficult to receive the phase information of the main rotating coordinate system with high accuracy.

[0144] In response, the phase of the rotating coordinate system (hereinafter referred to as the "subordinate rotating coordinate system") is corrected by the power conversion device 5 based on the phase of the main voltage command generated by the power conversion device 4 in the main rotating coordinate system.

[0145] Although the voltage phase in the principal rotating coordinate system does not indicate the phase of the principal rotating coordinate system itself, the phase deviation of the subordinate rotating coordinate system relative to the principal rotating coordinate system can be determined based on the voltage phase in the principal rotating coordinate system. Therefore, by correcting the calculated phase of the subordinate rotating coordinate system based on the voltage phase in the principal rotating coordinate system, the subordinate rotating coordinate system can easily follow the principal rotating coordinate system.

[0146] Even if the rotational speed of motor 3 increases, the change in the main voltage phase will not increase. Therefore, by correcting the phase of the subordinate rotating coordinate system based on the voltage phase in the main rotating coordinate system, the second rotating magnetic field can be synchronized with the first rotating magnetic field with high reliability. Therefore, the power conversion device 5 is effective for synchronizing the rotating magnetic fields generated by multiple power conversion devices in the induction motor.

[0147] The phase correction unit 214 can correct the phase of the rotating coordinate system based on the phase of the main rotating coordinate system when the rotation speed of the rotating coordinate system is within a first range band, and correct the phase of the rotating coordinate system based on the phase of the main voltage command in the main rotating coordinate system when the rotation speed of the rotating coordinate system is within a second range band higher than the first range band.

[0148] When the rotational speed of the rotating coordinate system is low, the instantaneous change in the phase of the master voltage increases, and it may be difficult to make the subordinate rotating coordinate system follow the master rotating coordinate system based on the phase of the master voltage. In contrast, when the rotational speed of the rotating coordinate system is within the first range band below the second range band, the phase of the rotating coordinate system is corrected based on the phase of the master rotating coordinate system, thereby potentially suppressing the influence of changes in the phase of the master voltage.

[0149] When the rotation speed of the rotating coordinate system is low, it is easier to receive the phase information of the primary rotating coordinate system with high accuracy. Therefore, by making the phase of the subordinate rotating coordinate system follow the phase of the primary rotating coordinate system based on the phase of the primary rotating coordinate system, the second rotating coordinate system can be synchronized with the first rotating coordinate system more reliably. Therefore, the power conversion device 5 is more effective in synchronizing the rotating magnetic field generated in the motor 3 by multiple power conversion devices.

[0150] The phase correction unit 214 can correct the phase of the rotating coordinate system based on a first deviation, which is the difference between the phase of the main rotating coordinate system and the phase of the rotating coordinate system, when the rotation speed of the rotating coordinate system is within a first range band. Furthermore, when the rotation speed of the rotating coordinate system is within a second range band, it can correct the phase of the rotating coordinate system based on a second deviation, which is the difference between the phase of the main rotating coordinate system (as a main voltage command) and the phase of the rotating coordinate system (as a voltage command). In this case, the correction method based on the phase of the main rotating coordinate system (hereinafter referred to as the "first correction method") and the correction method based on the phase of the main rotating coordinate system (hereinafter referred to as the "second correction method") are common in terms of correcting the phase of the rotating coordinate system based on the deviation, thereby allowing for smooth switching between the two methods.

[0151] The phase correction unit 214 can correct the phase of the rotating coordinate system based on a weighted average of the first and second deviations when the rotation speed of the rotating coordinate system is within the intermediate range between the first and second ranges. Furthermore, it can gradually decrease the weight of the first deviation and gradually increase the weight of the second deviation as the rotation speed of the rotating coordinate system approaches the upper limit of the intermediate range from the lower limit. In this case, the switching between the first and second correction methods can be performed more smoothly.

[0152] Phase calculation unit 213 can calculate the angular frequency command value of the rotating coordinate system based on the target torque value and the rotational speed of the motor 3. Phase correction unit 214 can correct the angular frequency command value based on a first deviation when the rotational speed of the rotating coordinate system is within a first range band, and correct the angular frequency command value based on a second deviation when the rotational speed of the rotating coordinate system is within a second range band. Phase calculation unit 213 can calculate the phase of the rotating coordinate system by integrating the corrected angular frequency command value. In this case, in both the first and second correction methods, the phase of the subordinate rotating coordinate system can more reliably follow the phase of the master rotating coordinate system.

[0153] The power conversion device 5 may also include a main information acquisition unit 211, which is configured to obtain the sine value of the phase of the main rotating coordinate system and the cosine value of the phase of the main rotating coordinate system from the power conversion device 4, and when the rotation speed of the rotating coordinate system is within a first range band, the phase correction unit 214 may correct the phase of the rotating coordinate system based on the sine value and the cosine value.

[0154] Because the phase of the principal rotating coordinate system repeats a gradual increase from 0° to 360° and a rapid decrease from 360° to 0°, it is difficult to receive phase information of the principal rotating coordinate system with high accuracy near 360°. On the other hand, the sine and cosine values ​​do not change abruptly as the rapid decrease from 360° to 0° described above. For this reason, the phase of the principal rotating coordinate system is acquired separately from its sine and cosine values ​​from the power conversion device 4, and the phase of the principal rotating coordinate system is calculated based on the sine and cosine values, thereby obtaining the phase information of the principal rotating coordinate system more reliably.

[0155] The power conversion device 5 may also include an anomaly monitoring unit 220, which detects anomalies in the communication path used to acquire the sine and cosine values ​​based on the degree to which the sum of the squares of the sine and cosine values ​​deviates from 1. In this case, anomalies in the communication path used to acquire the sine and cosine values ​​can be easily detected by using the relationship between the sine and cosine values.

[0156] The main information acquisition unit 211 can also acquire the phase of the main voltage command in the main rotating coordinate system from the power conversion device 4, and when the phase of the main voltage command in the main rotating coordinate system is less than a predetermined level, the anomaly monitoring unit 220 can detect an anomaly in the communication path used to acquire the phase of the main voltage command in the main rotating coordinate system.

[0157] As long as torque is generated in motor 3, the phase of the main voltage command in the main rotating coordinate system will not become zero. Therefore, based on whether the phase of the main voltage command in the main rotating coordinate system is less than a predetermined level, anomalies in the communication path used to obtain the phase of the main voltage command in the main rotating coordinate system can be easily detected.

[0158] The power conversion device 5 may further include a torque target value calculation unit 212, which calculates the torque target value based on the main torque target value, which is the torque target value in the main device, and a phase calculation unit 213, which can calculate the phase of the rotating coordinate system based on the torque target value calculated by the torque target value calculation unit 212 and the rotational speed of the motor 3. In this case, by controlling the torque target value to be close to the main torque target value, the second rotating magnetic field can be more reliably synchronized with the first rotating magnetic field.

[0159] The power conversion device 5 may further include a main information acquisition unit 211 for acquiring the main torque target value and an anomaly monitoring unit 220 for detecting anomalies in the communication path used to acquire the main torque target value. The anomaly monitoring unit 220 can detect communication path anomalies based on a first deviation between the phase of the main rotating coordinate system and the phase of the rotating coordinate system when the rotation speed of the rotating coordinate system is within a first range. Furthermore, when the rotation speed of the rotating coordinate system is within a second range, it can detect communication path anomalies based on a second deviation between the phase of the main rotating coordinate system (as the main voltage command) and the phase of the rotating coordinate system (as the voltage command).

[0160] The magnitude of the difference between the phase of the master voltage command in the master rotating coordinate system and the phase of the voltage command in the rotating coordinate system depends on whether the torque target value changes significantly based on the master torque target value. Therefore, by detecting anomalies in the communication path used to obtain the master torque target value based on the difference between the phase of the master voltage command in the master rotating coordinate system and the phase of the voltage command in the rotating coordinate system, anomalies in the communication path used to obtain the master torque target value can be easily detected.

[0161] The primary and secondary power supplies can be AC ​​power, and the power conversion circuit 10B can be a matrix converter circuit that performs power conversion from the primary side to the secondary side and from the secondary side to the primary side. In the matrix converter circuit, as the rotational speed of the rotating coordinate system decreases, the instantaneous change in the phase of the main voltage tends to increase. Therefore, when the rotational speed of the rotating coordinate system is a first rotational speed lower than the second rotational speed, it is more effective to correct the phase of the rotating coordinate system based on the phase of the main rotating coordinate system.

[0162] Although embodiments have been described above, this disclosure is not necessarily limited to the embodiments described above, but various modifications can be made without departing from the scope of this disclosure.

Claims

1. A power conversion apparatus comprising: a power conversion circuit configured to perform power conversion for outputting drive power to an induction motor; and a control circuit configured to: receive a master command phase from a master power conversion apparatus; generate a voltage command having a command phase in a rotating coordinate system based on a torque target value, wherein a rotating magnetic field for driving a rotor of the induction motor is generated to rotate with the rotating coordinate system; calculate a rotating phase of the rotating coordinate system based on a command phase difference between the master command phase and the command phase to reduce the command phase difference; and control the power conversion circuit to output the drive power to the induction motor in synchronization with the master power conversion apparatus based on the rotating phase and the voltage command. the control circuit is further configured to:

2. The power conversion device of claim 1, wherein, receive a master rotating phase from the master power conversion apparatus; if a coordinate rotation speed of the rotating coordinate system is less than a first threshold value, calculate the rotating phase based on a rotating phase difference between the master rotating phase and the rotating phase to reduce the rotating phase difference; and if the coordinate rotation speed is greater than a second threshold value, calculate the rotating phase based on the command phase difference, the second threshold value being equal to or higher than the first threshold value. the control circuit is further configured to:

3. The power conversion device of claim 2, wherein, if the coordinate rotation speed is between the first threshold value and the second threshold value, calculate the rotating phase based on a weighted average of the command phase difference and the rotating phase difference; and gradually decrease a weight of the rotating phase difference and gradually increase a weight of the command phase difference as the coordinate rotation speed approaches the second threshold value from the first threshold value. the control circuit is further configured to:

4. The power conversion device of claim 2, wherein, if the coordinate rotation speed is less than the first threshold value, calculate the rotating phase based on a torque target value, a rotor speed of the induction motor, and the rotating phase difference; and if the coordinate rotation speed is greater than the second threshold value, calculate the rotating phase based on the torque target value, the rotor speed, and the command phase difference. the control circuit is further configured to:

5. The power conversion device of claim 4, wherein, calculate an angular frequency command value of the rotating coordinate system based on the torque target value and the rotor speed; if the coordinate rotation speed is less than the first threshold value, correct the angular frequency command value based on the rotating phase difference; if the coordinate rotation speed is greater than the second threshold value, correct the angular frequency command value based on the command phase difference; and calculate the rotating phase by integrating the corrected angular frequency command value. the control circuit is further configured to:

6. The power conversion device according to any one of claims 2 to 5, wherein, obtain a sine value of the master rotating phase and a cosine value of the master rotating phase from the master power conversion apparatus; and if the coordinate rotation speed is less than the first threshold value, calculate the rotating phase based on the sine value and the cosine value. the control circuit is further configured to detect an abnormality of communication for receiving the sine value and the cosine value based on a sum of squares of the sine value and the cosine value.

7. The power conversion device of claim 6, wherein, ​ 8. The power conversion device of claim 7, wherein, The control circuit is further configured to detect an anomaly in a communication for receiving the master torque target value based on the command phase difference if the coordinate rotation speed is greater than the second threshold value.

9. The power conversion device according to any one of claims 2 to 5, wherein, The control circuit is further configured to: receive a master torque target value from the master power conversion device; calculate the torque target value based on the master torque target value; and generate the voltage command based on the calculated torque target value.

10. The power conversion device of claim 9, wherein, The control circuit is further configured to: detect an anomaly in a communication for receiving the master torque target value based on the rotational phase difference if the coordinate rotation speed is less than the first threshold value; and detect an anomaly in the communication based on the command phase difference if the coordinate rotation speed is greater than the second threshold value.

11. The power conversion device according to any one of claims 1 to 5, wherein, The power conversion circuit is a matrix converter circuit configured to perform bidirectional AC-AC power conversion.

12. The power conversion device of claim 1, wherein, The control circuit is further configured to calculate the rotational phase based on the torque target value, a rotor speed of the induction machine, and the command phase difference.

13. The power conversion device of claim 12, wherein, The control circuit is further configured to: calculate an angular frequency command value of the rotational coordinate system based on the torque target value and a rotor speed of the induction machine; correct the angular frequency command value based on the command phase difference to reduce the command phase difference; and calculate the rotational phase by integrating the corrected angular frequency command value.

14. The power conversion device according to any one of claims 1 to 5, wherein, The power conversion device is configured to operate as the master power conversion device in a first mode or as a second power conversion device in a second mode based on a mode selection input, wherein the control circuit is configured to, in the first mode: generate a master voltage command having the master command phase in a master rotational coordinate system that rotates with the rotor; control the power conversion circuit to output a master drive power to the induction machine based on the master voltage command; wherein the control circuit is further configured to, in the second mode: receive the master command phase from the master power conversion device; generate the voltage command based on the torque target value; calculate the rotational phase based on the command phase difference to reduce the command phase difference; and control the power conversion circuit to output the drive power to the induction machine based on the rotational phase and the voltage command.

15. A control system, comprising: a power conversion device according to any one of claims 1 to 5; and the master power conversion device, wherein the master power conversion device includes: a master power conversion circuit configured to perform master power conversion for outputting a master drive power to the induction machine; and a master control circuit configured to: generate a master voltage command having the master command phase in a master rotational coordinate system that rotates with the rotor; and control the master power conversion circuit to output the master drive power to the induction machine in synchronization with a drive power output by the control circuit of the power conversion device based on the master voltage command.

16. A drive system, comprising: a control system according to claim 15; and the induction machine, wherein the induction machine includes a first set of primary coils and a second set of primary coils, wherein the main power conversion circuit is configured to output the main drive power to the first set of primary coils, and wherein the power conversion circuit is configured to output the drive power to the second set of primary coils.

17. A power conversion method, comprising: generating a first voltage command having a first command phase in a first rotating coordinate system based on a first torque target value; calculating a first rotation phase of the first rotating coordinate system based on the first torque target value and a rotor speed of an induction motor; outputting a first drive power to the induction motor based on the first rotation phase and the first voltage command; generating a second voltage command having a command phase in a second rotating coordinate system based on a second torque target value, wherein a rotating magnetic field for driving a rotor of the induction motor is generated to rotate with the second rotating coordinate system; calculating a second rotation phase of the second rotating coordinate system based on a command phase difference between the first command phase and the command phase to reduce the command phase difference; and outputting a second drive power to the induction motor in synchronization with the first drive power based on the second rotation phase and the second voltage command.

18. The power conversion method according to claim 17, further comprising if a coordinate rotation speed of the second rotating coordinate system is less than a first threshold value, calculating the second rotation phase based on a rotation phase difference between the first rotation phase and the second rotation phase to reduce the rotation phase difference, if the coordinate rotation speed is greater than a second threshold value, calculating the second rotation phase based on the command phase difference, the second threshold value being equal to or greater than the first threshold value. wherein, 19. A non-transitory memory device having instructions stored thereon that, in response to being executed by a processing device, cause the processing device to perform operations comprising: receiving a main command phase from a main power conversion device; generating a voltage command having a command phase in a rotating coordinate system based on a torque target value, wherein a rotating magnetic field for driving a rotor of an induction motor is generated to rotate with the rotating coordinate system; calculating a rotation phase of the rotating coordinate system based on a command phase difference between the main command phase and the command phase to reduce the command phase difference; and controlling a power conversion circuit to output a drive power to the induction motor in synchronization with the main power conversion device based on the rotation phase and the voltage command. The operations further comprise: receiving a main rotation phase from the main power conversion device; and 20. The non-transitory memory device of claim 19, wherein, if a coordinate rotation speed of the rotating coordinate system is less than a first threshold value, calculating the rotation phase based on a rotation phase difference between the main rotation phase and the rotation phase to reduce the rotation phase difference, and wherein if the coordinate rotation speed is greater than a second threshold value, calculating the rotation phase based on the command phase difference, the second threshold value being equal to or greater than the first threshold value. ​ ​

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