AC motor control device and control method

Abstract

To provide a control apparatus and a control method for an AC electric motor capable of suppressing reduction in control response speed.SOLUTION: In a motor system 10a of an embodiment, a controller 20a includes a voltage information generation unit 21, a coordinate conversion unit 22, a voltage command value output unit 23 and a phase number conversion unit 24. The voltage information generation unit 21 generates a dq-axis voltage command value v*d,q for an AC motor 50 from v*d,q=g-1(τdot*) on the basis of a torque differential command value τdot* input from the outside such as from a host system or the like. Also, the coordinate conversion unit 22 converts the dq-axis voltage command value v*d,q into an αβ-axis voltage command value v*α,β on the basis of an electric angle θre of an output shaft of the AC motor 50. Further, the voltage command value output unit 23 outputs the αβ-axis voltage command value v*α,β as an αβ-axis voltage command value v**α,β to an inverter 30 via the phase number conversion unit 24 when a voltage vector (v*α, v*β) expressed by the αβ-axis voltage command value v*α,β falls within a range of an output limit range 23a of the inverter 30.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device and a control method for an AC motor. [Background technology]

[0002] Examples of control devices and control methods for AC motors include the "Motor Control Device and Motor Control Method" and "AC Motor Control Device" disclosed in Patent Documents 1 and 2 listed below. In these types of devices, for example, current vector control is performed on the AC motor. In current vector control, the current output to each phase of the AC motor is vector-decomposed into a q-axis current component that generates torque in the AC motor and a d-axis current component that generates magnetic flux in the rotor of the AC motor, and each component is controlled independently. Therefore, information on the current flowing through each phase or any phase of the AC motor is converted into a d-axis current and a q-axis current, and then fed back and used for control (Patent Document 1: Figures 1 and 7, Patent Document 2: Figures 5 and 6). Note that in this specification, the AC motor may be simply referred to as a "motor." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-180441 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-113026 [Non-patent literature]

[0004] [Non-Patent Document 1] Yosuke Nakayama and Shinji Michiki, "Design of a Band-Rejection Filter for PMSM Vector Control in the Inverter Overmodulation Region," IEEJ Transactions on Power Systems, Vol. 138, No. 11, pp. 884-893, 2018 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, AC motors that undergo such control are typically used as power sources for mobile objects, a representative example of which is an electric vehicle. Therefore, to supply AC power to an AC motor, an inverter is used that converts DC power output from a DC voltage source, such as a battery or a voltage converter, into AC power. The inverter is controlled by a control device, but it cannot output a voltage that exceeds the output voltage of the DC voltage source. Due to the limit value of the voltage that the inverter can output (output limit voltage), the following problems can occur in current vector control performed by the control device. Note that it is assumed here that the AC motor is a three-phase AC motor.

[0006] (1) As shown in FIG. 2 of Patent Document 1, in a voltage vector diagram showing the relationship between a stationary coordinate system representing the voltage axes of each phase (U, V, and W phases) of a three-phase AC motor and a rotating coordinate system representing the voltage supplied to the motor in a vector space with two orthogonal axes (d and q axes), the range of voltage V_max that can be supplied to the motor is expressed as a hexagon. In other words, this hexagon represents the inverter's output voltage limit. Therefore, while it is desirable for a control device to control the inverter so that its output voltage reaches the boundaries corresponding to each side of the hexagon, this requires an algorithm that enables complex limiter control that is tailored to each side. Therefore, the time required for such calculation processing can lead to a decrease in the response speed to control commands.

[0007] (2) For this reason, in the control device of Patent Document 1, in the overmodulation region within the hexagon beyond the inscribed circle C_2 of the hexagon, a process is performed to calculate the d-axis voltage deficiency Vdn beyond the inscribed circle C_2 and correct the q-axis current command value. The d-axis priority control and cross-current control performed in such an overmodulation region tend to require complex calculations. Furthermore, in current vector control, as shown in Figures 1 and 7 of Patent Document 1, both the d-axis current and the q-axis current are generated by PI control (d-axis current controller, q-axis current controller), and this process often involves integral calculations using an integrator or the like. Therefore, these calculation processes can ultimately lead to a decrease in the control response speed.

[0008] (3) Furthermore, as shown in Non-Patent Document 1, it is known that in inverter control in the overmodulation region, various harmonics are contained in the current fed back by the control device (see, for example, Figs. 1 and 6 in Non-Patent Document 1). If these harmonics are superimposed on the feedback current as disturbances, motor control may become unstable or control performance may deteriorate. Therefore, a configuration is often adopted in which the harmonics are removed using a filter. However, such filtering generally involves an integral operation using an integrator or the like, and the delay time associated with this integral operation can reduce the response speed of the control.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a control device and a control method for an AC motor that can suppress a decrease in the response speed of control. [Means for solving the problem]

[0010] When the AC motor is an Interior Permanent Magnet Synchronous Motor (IPMSM), the voltage equation of the IPMSM in the dq rotating coordinate system (d-axis voltage v d ,q-axis voltage v q ) is known to be expressed by the following equation (1):

[0011]

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[0012] Based on the above equation (1), the d-axis current i d and q-axis current i q By differentiating these with respect to time, the following equations (2) and (3) are obtained, and the torque (output torque) τ of the output shaft of the AC motor is expressed by equation (4), where P is the number of pole pairs of the AC motor.

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[0013] In this way, the mathematical model of an IPMSM can be expressed by the above three equations (2) to (4), and its output torque τ is expressed by the above equation (4). Therefore, current vector control of an AC motor is performed based on the above equations (1) and (2). That is, in current vector control, a sensor detects information about the AC current (motor current) flowing through the AC motor, and this information is fed back to perform PI (proportional-integral) control so that the motor current matches the command current value, thereby obtaining the target output torque. Therefore, an IPMSM AC motor can be expressed as a motor model such as the one shown in Figure 1(A).

[0014] In FIG. 1(A), R is the winding resistance of the coils of each phase that make up the AC motor 50 (AC electric motor), and L is the inductance of those coils. s is the Laplace operator. Also, v is the AC voltage applied to the coils, and i is the motor current that flows through those coils. τ is the output torque of the AC motor 50. f(i) is a predetermined transfer function that converts the AC current i that flows through each phase of the coil into the output torque τ. In the case of a dq rotating coordinate system, v is v d,q and i is i d,q In addition, in this specification and drawings, v d,q ya i u,v,wIn subscripts, two or three characters separated by a comma (,) are sometimes written, but this means that these subscripts should be added one by one to the character to which the subscript is attached, but this notation has been omitted (for example, v d,q is v d and v q means).

[0015] More specifically, as shown in FIG. 24, when current vector control is performed on the AC motor 130 in the motor system 100, the motor current i detected by the current sensor 140 is u,v,w After converting the coordinates and phase numbers for d ,i q The control device 110 receives an externally input torque command value τ * Based on this, the d-axis and q-axis current command values i * d ,i * q is generated by the current command generating unit 111 and the current information i d ,i q is the d,q axis current command value i * d ,i * q The d-axis and q-axis voltage command values v are PI controlled to approach * d ,v * q is generated by the d-axis current PI control unit 112 and the q-axis current PI control unit 113. The generated voltage command value v * d ,v * q is converted into a voltage command value v by the coordinate and phase number conversion unit 115. * u,v,w The voltage command value v * u,v,w According to the switching control inverter 120 to AC voltage V u,v,w is output and supplied to the AC motor 130.

[0016] However, current vector control, which can be said to be a typical control method for such AC motors, requires integral calculations, which cause delays in the control process, due to the need for PI control. In the configuration example shown in Figure 24, integral calculations are always performed in the d-axis current PI control unit 112 and the q-axis current PI control unit 113, and the delay time associated with these integral calculations reduces the response speed to a torque command. In other words, current vector control of AC motors has limitations in preventing a decrease in the control response speed as long as it includes integral calculations using an integrator or the like.

[0017] Therefore, according to the results of a computer simulation in the case where current vector control is performed as in the motor system 100 of the comparative example shown in FIG. 24, as shown in FIG. 25(A), the input torque command value τ * It can be seen that the torque (output torque) τ output from the output shaft of the AC motor 130 may overshoot due to a decrease in response speed (in the dashed ellipse in the figure). Also, as shown in FIG. 25(B), the d-axis and q-axis current i d ,i q It can be seen that overshoot due to response delay can occur even in . In the figure, the hat (^) symbol above τ indicates that τ is an estimated value obtained by calculation.

[0018] Therefore, the inventors of the present application focused on the torque differential value τdot with respect to the output torque τ and considered the AC motor as a motor model as shown in FIG. 1(B). In the figure, v (v in the dq rotating coordinate system) d,q ) is the AC voltage applied to the coil of each phase that constitutes the AC motor 50 (AC electric motor), and g(v) is a transfer function that converts the AC voltage v applied to the coil of each phase into a torque differential value τdot. In the figure, the dot symbol "·" above τ denotes time differentiation, and is synonymous with the "dot" in τdot in the specification (the same applies hereinafter).

[0019] g(v) of the motor model shown in Figure 1(B) can be calculated as follows. In other words, by time-differentiating the above equation (4), the following equation (5) is obtained. Substituting the above equations (2) and (3) into this, equation (6) is obtained. Furthermore, equation (6) is used to calculate the d-axis voltage v d and the q-axis voltage v q By rearranging these, we obtain equation (7) for g(v). Note that g(v) expressed by equation (7) can correspond to the "predetermined function" described in the claims.

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[0020] Since the above equations (6) and (7) are linear functions with time-varying coefficients for voltage, it becomes possible to manage the torque differential value simply by manipulating the voltage. In other words, it is possible to control the output torque τ of the AC motor 50 (AC electric motor) without current control or an integral element such as an integrator. It also becomes possible to perform feedforward control of the torque differential value. Hereinafter, this type of torque response management type voltage vector control will be referred to as "this voltage vector control."

[0022] Based on these technical grounds In order to achieve the above object, the following claims are included: 7According to this means, the invention of a control method for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor, and the voltage command value is a time differential value of an output torque required of the AC motor, and is input as a command value and is generated based on the torque differential value expressed by the above equations (7) and (8), i.e., the torque differential command value.

[0023] As a result, in the invention of the control device for an AC motor or the control method for an AC motor, as described above, it is possible to control the output torque of the AC motor (perform constant value control of the output torque) based on the torque differential command value without performing current control, and therefore, for example, there is no need for integral calculation in the PI control processing (reference numerals 112 and 113 shown in FIG. 24) as is performed in general current vector control.

[0024] Also, claims described in the claims 1According to this means, the invention of a control device for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value being a time derivative of an output torque required of the AC motor and being input as a command value and generated based on a torque differential value expressed by the above equations (7) and (8). The control device also has a voltage information generation unit, a coordinate conversion unit, and a voltage command value output unit, and generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value, and converts the rotating coordinate system voltage information from the rotating coordinate system to stationary coordinate system voltage information corresponding to the two orthogonal axes of a stationary coordinate system based on the rotation angle of the output shaft of the AC motor. If a voltage vector represented by the stationary coordinate system voltage information is within the inverter's output limit voltage range, the stationary coordinate system voltage information is output to the inverter as a voltage command value. If the voltage vector is outside the output limit voltage range, the stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size within the output limit voltage range, is output to the inverter as a voltage command value. In some cases, the voltage command value is output via a phase number conversion unit that adapts the number of phases of the voltage command value to the number of phases of the AC motor. As a result, as constant value control of the output torque based on the torque differential command value, when the voltage vector represented by the stationary coordinate system voltage information is within the range of the inverter's output limit voltage, the stationary coordinate system voltage information is output to the inverter as a voltage command value, and when the voltage vector is outside the range of the output limit voltage, stationary coordinate system voltage information representing a changed voltage vector whose size is changed to fit within the range of the output limit voltage is output to the inverter as a voltage command value.

[0025] Also, claims described in the claims 2According to this technical means, the invention of a control device for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor. The voltage command value is generated based on a torque differential value, which is a time differential value of output torque required of the AC motor and is input as a command value. The control device also includes a voltage information generation unit, a coordinate conversion unit, and a voltage command value output unit, and generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value, and converts the rotating coordinate system voltage information from the rotating coordinate system to stationary coordinate system voltage information corresponding to the two orthogonal axes of a stationary coordinate system based on the rotation angle of the output shaft of the AC motor. If a voltage vector represented by the stationary coordinate system voltage information is within the inverter's output limit voltage range, the stationary coordinate system voltage information is output to the inverter as a voltage command value. If the voltage vector is outside the output limit voltage range, the stationary coordinate system voltage information representing a changed voltage vector, which is changed to a size within the output limit voltage range, is output to the inverter as a voltage command value. Note that the voltage command value may be output via a phase number conversion unit that matches the number of phases of the AC motor. When the two axes of the rotating coordinate system are a d-axis parallel to the magnetic pole direction of the rotor constituting the AC motor and a q-axis perpendicular to the d-axis, that is, in a dq rotating coordinate system, the voltage information generator generates, as rotating coordinate system voltage information, coordinate information of a voltage vector having a magnitude up to the point of intersection that intersects with a line expressed by a predetermined function including "torque differential value, d-axis current, q-axis current, and angular velocity of the output shaft" This obtains a voltage vector with the minimum voltage amplitude, making it possible to output a voltage command value of the minimum voltage (minimum voltage amplitude) corresponding to the torque differential command value to the inverter.

[0026] Also, claims described in the claims 3According to this technical means, the invention of a control device for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor. The voltage command value is generated based on a torque differential value, which is a time differential value of output torque required of the AC motor and is input as a command value. The control device also includes a voltage information generation unit, a coordinate conversion unit, and a voltage command value output unit, and generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value, and converts the rotating coordinate system voltage information from the rotating coordinate system to stationary coordinate system voltage information corresponding to the two orthogonal axes of a stationary coordinate system based on the rotation angle of the output shaft of the AC motor. If a voltage vector represented by the stationary coordinate system voltage information is within the inverter's output limit voltage range, the stationary coordinate system voltage information is output to the inverter as a voltage command value. If the voltage vector is outside the output limit voltage range, the stationary coordinate system voltage information representing a changed voltage vector, which is changed to a size within the output limit voltage range, is output to the inverter as a voltage command value. Note that the voltage command value may be output via a phase number conversion unit that matches the number of phases of the AC motor. When the two axes of the rotating coordinate system are the d-axis parallel to the magnetic pole direction of the rotor that constitutes the AC motor and the q-axis perpendicular to the d-axis, that is, in a dq rotating coordinate system, the voltage information generator generates rotating coordinate system voltage information based on the torque differential value, d-axis current, q-axis current, angular velocity of the output shaft, and a time differential command value of the d-axis current in MTPA (Maximum Torque Per Ampere) control. This makes it possible to obtain a voltage vector that maximizes the output torque of the AC motor relative to the inverter's output current, making it possible to output to the inverter a voltage command value that provides the most efficient output torque corresponding to the torque differential command value.

[0027] Also, claims described in the claims 4According to this technical means, the invention of a control device for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor. The voltage command value is generated based on a torque differential value, which is a time differential value of output torque required of the AC motor and is input as a command value. The control device also includes a voltage information generation unit, a coordinate conversion unit, and a voltage command value output unit, and generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value, and converts the rotating coordinate system voltage information from the rotating coordinate system to stationary coordinate system voltage information corresponding to the two orthogonal axes of a stationary coordinate system based on the rotation angle of the output shaft of the AC motor. If a voltage vector represented by the stationary coordinate system voltage information is within the inverter's output limit voltage range, the stationary coordinate system voltage information is output to the inverter as a voltage command value. If the voltage vector is outside the output limit voltage range, the stationary coordinate system voltage information representing a changed voltage vector, which is changed to a size within the output limit voltage range, is output to the inverter as a voltage command value. Note that the voltage command value may be output via a phase number conversion unit that matches the number of phases of the AC motor. If the voltage vector is outside the range of the output limit voltage, the voltage command value output unit reduces the torque differential value until the changed voltage vector falls within the range of the output limit voltage. As a result, if the voltage vector is outside the range of the output limit voltage, that is, if an unrealizable voltage command value is requested, the torque differential value is reduced until it falls within the range of the output limit voltage, so that the voltage command value output unit can output a realizable voltage command value to the inverter without performing an integral operation.

[0028] Also, claims described in the claims 5According to this technical means, the invention of a control device for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor. The voltage command value is generated based on a torque differential value, which is a time differential value of output torque required of the AC motor and is input as a command value. The control device also includes a voltage information generation unit, a coordinate conversion unit, and a voltage command value output unit, and generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value, and converts the rotating coordinate system voltage information from the rotating coordinate system to stationary coordinate system voltage information corresponding to the two orthogonal axes of a stationary coordinate system based on the rotation angle of the output shaft of the AC motor. If a voltage vector represented by the stationary coordinate system voltage information is within the inverter's output limit voltage range, the stationary coordinate system voltage information is output to the inverter as a voltage command value. If the voltage vector is outside the output limit voltage range, the stationary coordinate system voltage information representing a changed voltage vector, which is changed to a size within the output limit voltage range, is output to the inverter as a voltage command value. Note that the voltage command value may be output via a phase number conversion unit that matches the number of phases of the AC motor. When the two axes of the rotating coordinate system are a d-axis parallel to the magnetic pole direction of the rotor of the AC motor and a q-axis perpendicular to the d-axis, i.e., in a dq rotating coordinate system, if the voltage vector is outside the output limit voltage range, i.e., if an unrealizable voltage command value is requested, the voltage command value output unit performs the following control: In the rotating coordinate system, when the most parallel side of six sides constituting a hexagon representing the output limit voltage range intersects with a line expressed by a predetermined function including "torque differential value, d-axis current, q-axis current, and angular velocity of the output shaft," the voltage vector extending to the intersection point is designated as a modified voltage vector, and stationary coordinate system voltage information representing the modified voltage vector is output to the inverter as a voltage command value. As a result, the modified voltage vector reaches one of the six sides of the hexagon representing the output limit voltage range, allowing the voltage command value output unit to output the maximum possible voltage command value to the inverter without, for example, using limiter control requiring complex calculations or performing integral calculations.

[0029] Also, claims described in the claims 6According to this technical means, the invention of a control device for an AC motor outputs a voltage command value of an AC voltage to be output to an inverter capable of supplying three-phase AC power to the AC motor. The voltage command value is generated based on a torque differential value, which is a time differential value of output torque required of the AC motor and is input as a command value. The control device also includes a voltage information generation unit, a coordinate conversion unit, and a voltage command value output unit, and generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value, and converts the rotating coordinate system voltage information from the rotating coordinate system to stationary coordinate system voltage information corresponding to the two orthogonal axes of a stationary coordinate system based on the rotation angle of the output shaft of the AC motor. If a voltage vector represented by the stationary coordinate system voltage information is within the inverter's output limit voltage range, the stationary coordinate system voltage information is output to the inverter as a voltage command value. If the voltage vector is outside the output limit voltage range, the stationary coordinate system voltage information representing a changed voltage vector, which is changed to a size within the output limit voltage range, is output to the inverter as a voltage command value. Note that the voltage command value may be output via a phase number conversion unit that matches the number of phases of the AC motor. When the two axes of the rotating coordinate system are the d-axis parallel to the magnetic pole direction of the rotor constituting the AC motor and the q-axis perpendicular to the d-axis, that is, when the voltage vector is outside the output limit voltage range in the dq rotating coordinate system, that is, when an unrealizable voltage command value is requested, the voltage command value output unit performs the following control: In the rotating coordinate system, when the most parallel of the six sides constituting the hexagon representing the range of the output limit voltage does not intersect with a line expressed by a predetermined function including "torque differential value, d-axis current, q-axis current, and angular velocity of the output shaft," the voltage vector with the larger torque differential value of the two voltage vectors representing the endpoints of the most parallel side is set as the modified voltage vector, and stationary coordinate system voltage information representing this modified voltage vector is output to the inverter as a voltage command value.As a result, the changed voltage vector reaches one of the six vertices of the hexagon representing the range of the output limit voltage, so the voltage command value output unit can output the maximum value as a achievable voltage command value to the inverter without using, for example, limiter control that requires complex calculations, or without performing integral calculations. [Effects of the Invention]

[0030] request request 7 In this invention, since it is possible to perform constant value control of the output torque based on the torque differential command value without performing current control, for example, there is no need for integral calculation in the PI control process (reference numerals 112 and 113 shown in FIG. 24) that is performed in general current vector control. Therefore, since there is no delay time associated with integral calculation, it is possible to suppress a decrease in the response speed to a control command.

[0031] Claim 1 In the invention, as constant value control of the output torque based on the torque differential command value, when a voltage vector represented by stationary coordinate system voltage information is within the range of the inverter's output limit voltage, stationary coordinate system voltage information is output to the inverter as a voltage command value, and when the voltage vector is outside the range of the output limit voltage, stationary coordinate system voltage information representing a changed voltage vector changed to a size that falls within the range of the output limit voltage is output to the inverter as a voltage command value. Therefore, not only when the voltage vector represented by the stationary coordinate system voltage information is within the range of the output limit voltage, but also when it is outside the range of the output limit voltage, the stationary coordinate system voltage information can be output to the inverter as a voltage command value within the range of the output limit voltage.

[0032] Claim 2 In the present invention, since the minimum value is obtained as the voltage vector, it is possible to output to the inverter a voltage command value of the minimum voltage (minimum voltage amplitude) corresponding to the torque differential command value. Therefore, for example, if there is a need to minimize the output voltage of the inverter or the input voltage of the AC motor, this can be met.

[0033] Claim 3 In the invention, a voltage vector that maximizes the output torque of the AC motor relative to the inverter output current can be obtained, making it possible to output to the inverter a voltage command value that provides the most efficient output torque corresponding to the torque differential command value. This allows for a smooth transition to MTPA control, which can satisfy needs such as minimizing the inverter output current relative to the required torque.

[0034] Claim 4 In the present invention, when the voltage vector is outside the output limit voltage range, i.e., when an unrealizable voltage command value is requested, the torque differential value is reduced until it falls within the output limit voltage range, so that the voltage command value output unit can output a realizable voltage command value to the inverter without performing an integral calculation. Therefore, since there is no delay time associated with the integral calculation, it is possible to suppress a decrease in the response speed to the control command.

[0035] Claim 5 In the invention, since the changed voltage vector reaches one side of the hexagon representing the range of the output limit voltage, the voltage command value output unit can output the maximum value as a achievable voltage command value to the inverter without using, for example, limiter control requiring complex calculations or performing integral calculations. Therefore, since there is no delay time associated with complex calculations or integral calculations, it is possible to suppress a decrease in the response speed to control commands.

[0036] Claim 6 In the invention, since the changed voltage vector reaches one vertex of the hexagon representing the range of the output limit voltage, the voltage command value output unit can output the maximum value as a achievable voltage command value to the inverter without using, for example, limiter control requiring complex calculations or performing integral calculations. Therefore, since there is no delay time associated with complex calculations or integral calculations, it is possible to suppress a decrease in the response speed to control commands. [Brief explanation of the drawings]

[0037] [Figure 1] These are conceptual diagrams of motor models that mathematically represent AC motors. Figure 1(A) is a model used in current vector control, and Figure 1(B) is a model that focuses on the torque differential value with respect to the output torque. [Figure 2] Fig. 2(A) is a block diagram showing an example of the hardware configuration of a motor system to which the control device and control method for an AC motor of the present invention are applied, and Fig. 2(B) is a circuit diagram showing an example of the configuration of an inverter included in the motor system of this embodiment. [Figure 3] 1 is a block diagram showing a first configuration example of control system elements that make up the motor system of the present embodiment. [Figure 4] 4A and 4B are conceptual diagrams of the voltage vector control performed by the controller shown in FIG. 3, where FIG. 4A shows a conceptual example of a generation algorithm for a voltage command value performed in a voltage information generation unit, and FIG. 4B shows a conceptual example of a control algorithm performed in a voltage command value output unit. [Figure 5] 5A and 5B are explanatory diagrams showing the results of a computer simulation of this voltage vector control using the controller shown in FIG. 3, where FIG. 5A shows the torque command value, output torque value, etc., and FIG. 5B shows the trajectory of the inverter output voltage. [Figure 6] FIG. 4 is a block diagram showing a second configuration example of control system elements that make up the motor system of the present embodiment. [Figure 7] 7 is a flowchart showing the flow of a voltage command value output process performed by a controller shown in FIG. 6. [Figure 8] 8A and 8B are explanatory diagrams showing the results of a computer simulation of this voltage vector control using the controller shown in FIG. 6, where FIG. 8A shows the output torque value relative to the torque command value, FIG. 8B shows the d-axis and q-axis current values, and FIG. 8C shows the motor current value. [Figure 9]9A and 9B are explanatory diagrams showing the results of a computer simulation of this voltage vector control by the controller shown in FIG. 6, where FIG. 9A shows the trajectory of the inverter output voltage, and FIG. 9B shows the switching waveforms input to the switching elements of each phase that make up the inverter. [Figure 10] 10A and 10B are explanatory diagrams showing the results of measuring the torque command value, torque estimation value, and d-axis and q-axis current values using an actual device when this voltage vector control is performed using the controller shown in FIG. 6. FIG. 10A shows the case of linear region operation that does not include overmodulation operation, and FIG. 10B shows the case of linear region operation that includes temporary overmodulation operation. [Figure 11] FIG. 4 is a block diagram showing a third configuration example of control system elements that make up the motor system of the present embodiment. [Figure 12] 12 is a conceptual diagram of the voltage vector control performed by the controller shown in FIG. 11, showing a conceptual example of a generation algorithm of a voltage command value performed in a voltage information generating unit. [Figure 13] 13A and 13B are explanatory diagrams showing the results of a computer simulation of this voltage vector control using the controller shown in FIG. 11, where FIG. 13A shows the torque command value and output torque value, FIG. 13B shows the d-axis and q-axis current values, and FIG. 13C shows the motor current value. [Figure 14] FIG. 1 is a conceptual diagram of the voltage vector control performed by the controllers of the control system element configuration examples 1 to 3, and shows a conceptual example of a voltage command value correction algorithm performed in a voltage command value output unit. [Figure 15] 15 is a flowchart showing the flow of a voltage command value correction process (I) corresponding to the voltage command value correction algorithm shown in FIG. [Figure 16] FIG. 10 is a conceptual diagram of the voltage vector control performed by the controllers of the control system element configuration examples 1 to 3, and shows a conceptual example of another example of the voltage command value correction algorithm performed in the voltage command value output unit. [Figure 17]17 is a flowchart showing the flow of a voltage command value correction process (II) corresponding to the voltage command value correction algorithm shown in FIG. 16. [Figure 18] 10 is a flowchart showing the flow of integrated control processing in the voltage vector control performed by the controllers of the first to third configuration examples of the control system elements. [Figure 19] 19A and 19B are explanatory diagrams showing the results of a computer simulation of this voltage vector control using the integrated control processing shown in FIG. 18, where FIG. 19A shows the torque command value, output torque value, d-axis and q-axis current values, motor current value, etc., and FIG. 19B shows the three-phase voltage command value output to the inverter. [Figure 20] 20A and 20B are explanatory diagrams showing the results of a computer simulation of this voltage vector control using integrated control processing under conditions different from those of FIG. 19, where FIG. 20A shows the torque command value, output torque value, d-axis and q-axis current values, motor current value, etc., and FIG. 20B shows the three-phase voltage command value output to the inverter. [Figure 21] FIG. 10 is a block diagram showing a fourth configuration example of control system elements that make up the motor system of the present embodiment. [Figure 22] 22A and 22B are explanatory diagrams showing the results of a computer simulation of this voltage vector control using the controller shown in FIG. 21, where FIG. 22A shows the torque command value and output torque value, FIG. 22B shows the d-axis and q-axis current values, and FIG. 22C shows the motor current value. [Figure 23] FIG. 23(A) is an explanatory diagram relating to an arbitrary coordinate system, and FIG. 23(B) is an explanatory diagram relating to a stationary coordinate system. [Figure 24] FIG. 2 is a block diagram showing an example of the configuration of control system elements when current vector control is performed in a motor system. [Figure 25] 25A and 25B are explanatory diagrams showing the results of a computer simulation when current vector control is performed, in which FIG. 25A shows the torque command value and output torque value, and FIG. 25B shows the d-axis current value and q-axis current value. DETAILED DESCRIPTION OF THE INVENTION

[0038] An embodiment of a motor system 10 to which an AC motor control device and control method of the present invention are applied will be described below with reference to the drawings. First, the hardware constituting the motor system of this embodiment will be described with reference to Figs. 1 to 3.

[0039] As shown in FIG. 2(A), the motor system 10 is mainly composed of a controller 20, an inverter 30, a rotation angle sensor 45, an AC motor 50, etc., and is used, for example, in a drive motor system that controls the running motor of an electric vehicle, an electric railcar, etc., or in a servo motor system that controls the drive motor of a robot, etc.

[0040] The controller 20 is an example of a control device for an AC motor, and is typically a so-called microcomputer board (not shown) that includes, for example, a microcomputer (CPU), a semiconductor memory device such as a ROM, a RAM, and an EEPROM, and an input / output interface. The controller 20 is connected to an inverter 30, current sensors 41, 42, and 43, a rotation angle sensor 45, and a host system (not shown). These sensors 41 to 43 and 45 detect the motor current i supplied to the AC motor 50. u,v,w and the rotation angle (mechanical angle) θ of the shaft (output shaft) of the AC motor 50 rm and information (command value) of the output torque τ required of the AC motor 50 is input from a higher-level system.

[0041] Based on this information, the controller 20 calculates the voltage command value v in accordance with the algorithm of this voltage vector control using the control system element configuration examples 1 to 4 described below. * u,v,wand outputs it to the inverter 30. For this reason, the EEPROM or the like of the controller 20 stores in advance a program for implementing in software the functions of the "voltage information generating unit 21, coordinate conversion unit 22, voltage command value output unit 23, phase number conversion unit 24, etc.", which will be described later, as components constituting the algorithm of this voltage vector control. The inventors of the present application have focused on the torque differential value τdot with respect to the output torque τ of the AC motor 50, and have regarded the AC motor as a motor model as shown in FIG. 1(B) ("dot" means that the letter or symbol immediately before it is a time differential value; the same applies hereinafter). For this reason, the command value input from the upper system is, in principle, the output torque (torque command value) τ required of the AC motor 50. * Instead, the torque differential value (torque differential command value) τdot * is.

[0042] The inverter 30 is a power conversion device that converts a DC voltage suitable for driving the AC motor 50 into an AC voltage corresponding to the number of phases of the AC motor 50 and outputs the converted voltage. In this embodiment, since the AC motor 50 is a three-phase AC motor, the DC voltage input from the outside is converted into a voltage command value v input from the controller 20. * u,v,w According to AC voltage (output voltage) V u,v,w and supplies it to the AC motor 50. To this end, the inverter 30 is connected to a DC voltage source Batt that outputs a voltage capable of driving the AC motor 50. The inverter 30 converts the DC voltage into an AC voltage v corresponding to each phase of the AC motor 50. u,v,w and a switching circuit (Fig. 2(B)) that converts this switching circuit into a voltage command value v * u,v,w The DC voltage source Batt may be a battery itself, or may be a voltage converter connected to a battery when voltage step-up or step-down is required.

[0043] As shown in FIG. 2B, the inverter 30 has a switching circuit in which two series-connected switching elements (upper and lower arms) are connected in parallel, the number of which corresponds to the number of phases of the AC voltage output by the inverter 30. A DC voltage source Batt is connected to both ends of each of the upper and lower arms, and each phase coil of the AC motor 50 is connected to the midpoint between the upper and lower arms, i.e., the connection between the switching elements. In this embodiment, since the AC motor 50 is a three-phase AC motor, the switching elements are IGBTs 31 to 36 with FWDs, a total of six, in the upper and lower arms. The positive electrode side of the DC voltage source Batt is connected to IGBTs 31, 33, and 35 of the upper arm, and the negative electrode side is connected to IGBTs 32, 34, and 36 of the lower arm. Terminals of the U-phase coil, V-phase coil, and W-phase coil of the AC motor 50 are connected to the connection between the IGBTs 31 and 32, the connection between the IGBTs 33 and 34, and the connection between the IGBTs 35 and 36, respectively. The switching elements may be transistors such as power MOSFETs.

[0044] The current sensors 41 to 43 are detection devices configured to be able to measure AC current, and measure the current value of AC power supplied from the inverter 30 to the AC motor 50 and output the measured value to the controller 20. For example, current information i of each of the U, V, and W phases is obtained from the current sensors 41 to 43 attached to the electrical wiring of each phase connecting the inverter 30 and the AC motor 50. u,v,w is output and input to the controller 20. The current information i input from the current sensors 41 to 43 is u,v,w In the controller 20, the dq axis current information i d,q It is used after being phase-transformed into

[0045] The rotation angle sensor 45 is a detection device configured to be able to measure the rotation angle of the shaft of the AC motor 50. For example, the rotation angle sensor 45 is attached to the anti-load side of the shaft and outputs angle information (mechanical angle) θ rm In this embodiment, an absolute encoder or resolver capable of detecting the rotation angle in absolute value is used. The absolute encoder outputs angle information θ rm is output as a digital value, and the resolver outputs angle information θrm The angle information θ input from the rotation angle sensor 45 is output as an analog value (sine wave). rm is a mechanical angle, the controller 20 calculates the electrical angle θ re or angular velocity ω re is converted to and used.

[0046] The AC motor 50 is, for example, an interior permanent magnet synchronous motor (IPMSM) that is driven by a supply of three-phase AC power, and the number of poles P is set to 4. The structure of the AC motor 50 is not particularly shown, but it is mainly composed of, for example, a cylindrical stator having a plurality of slots on the inner periphery around which coils of the U, V, and W phases are wound, a shaft (output shaft) that is connected to a load at one end (load side) and to which a rotation angle sensor 45 or the like can be connected at the other end (anti-load side), a cylindrical rotor that passes through the shaft at the center and in which multiple sets of permanent magnets are embedded in the circumferential direction, and a case that houses these components except for both ends (load side and anti-load side) of the shaft.

[0047] If the motor model of the AC motor 50 is expressed in a block diagram, it is expressed by control system elements that are an extension of the motor model shown in FIG. 1(B). That is, as shown in FIG. 3, the AC motor 50 has the functions of a coordinate transformation element 51, a function element 52, and an integral element 53. The coordinate transformation element 51 is a three-phase voltage vector (v u ,v v ,v w ) into the voltage vector (v d ,v q The function element 52 and the integral element 53 are similar to the motor model of the AC motor 50 described with reference to FIG. 1(B).

[0048] The motor system 10 having the hardware configured in this manner can be conceptualized as, for example, configuration example 1 of control system elements represented by a block diagram as shown in Fig. 3. From here, configuration example 1 of the control system elements of the motor system 10 (10a) will be described with reference to Figs. 3 to 15.

[0049] [Control system element configuration example 1] As shown in FIG. 3, in a motor system 10a of configuration example 1 of control system elements (hereinafter referred to as “configuration example 1”), a controller 20a has the functions of a voltage information generation unit 21, a coordinate conversion unit 22, a voltage command value output unit 23, and a phase number conversion unit 24.

[0050] As described above, the controller 20a receives the torque differential command value τdot as a command value from the upper system (not shown). * As explained with reference to FIG. 1B, when the torque differential value τdot of the output torque τ is considered, the AC motor 50 can be expressed by two control system elements: a function element of g(v) and an integral element of 1 / s. The former is expressed by the above-mentioned equation (7), τdot=A(i d ,i q )v d +B(i d ,i q )v q +C(i d ,i q ,ω re ) and the latter is a pure integrator. In other words, g(v) expressed as τdot = A... is the torque differential value τdot on the left side and the voltage vector (v d ,v q ) are in a linear and static relationship. It can also be seen that an integral element is included in the AC motor 50 that is the object of control, while an integral element such as an integrator is not included in the controller 20a (voltage information generating unit 21, etc.) that performs the control.

[0051] Therefore, the voltage vector (v d ,v q ) to directly specify the torque differential value τdot, and vice versa. However, the torque differential value τdot can be calculated by the voltage vector (v d ,v q ) specifies the inverse function of g(v) v=g -1 (τdot) is the voltage vector (v d ,v q) is a function that takes two variables as input, so the selectable d-axis voltage v d and the q-axis voltage v q However, the inverse function v=g -1 Since (τdot) is a linear function, it is unlikely to become a complex algorithm and can be realized with simpler information processing than in the case of a nonlinear function. Also, as explained with reference to Figures 24 and 25, for current vector control which always includes integral calculations (integral elements), the inverse function v=g -1 Since the calculation process of (τdot) does not include an integral calculation (integral element), an overshoot of the output torque τ (within the dashed ellipse in FIG. 25) caused by the delay time associated with the integral calculation that occurs in current vector control does not occur. Therefore, there is no need for anti-windup processing or the like to suppress the occurrence of such an overshoot of the output torque τ.

[0052] For this reason, the voltage information generating unit 21 uses the inverse function v of the equation (7) described in the section [Problem to be Solved by the Invention]. * d,q =g -1 (τdot * ) In other words, the torque differential command value τdot * is input, and current information i is output from the current sensors 41 to 43. u,v,w and angle information θ from the rotation angle sensor 45 rm When the torque differential value τdot is input, the d-axis voltage command value v * d and the q-axis voltage command value v * q (Rotating coordinate system voltage information) is output from the voltage information generating unit 21. Current information i u,v,w and angle information θ rm is the current information i d,q or angular velocity ω re is converted to and used.

[0053] As mentioned above, the voltage vector (v d ,v q ) is a function that takes two variables as input, so the d-axis voltage vd and q-axis voltage v q Therefore, the voltage information generating unit 21 selects a voltage command value according to a generation algorithm (voltage vector calculation process (I)) shown in the conceptual diagram of FIG.

[0054] As shown in FIG. 4(A), in the voltage vector calculation process (I), for example, the voltage vector (v d ,v q ) (voltage vector 71) exists in the dq rotating coordinate system v d -v q In the plane, the torque differential command value τdot * The torque differential line 91 obtained by the above equation is given, and the intersection point where the two lines intersect at the shortest distance is found. The voltage vector 71 having the magnitude up to the intersection point is expressed as the voltage command value v * d,q In other words, the requested torque differential value τdot (torque differential command value τdot * ) is the voltage vector 71 that minimizes the voltage amplitude. * d,q Select as.

[0055] More specifically, the controller 20a calculates the voltage command value v * d,q The voltage command value v selected by the calculation of equation (9) is obtained. * d,q Hereinafter, the operation control of the AC motor 50 performed using the above will be referred to as "voltage amplitude minimum control." Note that A, B, and C are the values of A(i d ,i q ),B(i d ,i q ),C(i d ,i q ,ω re )

number

[0056] The above equation (7) is used to calculate the q-axis voltage vq After solving for the d-axis voltage v d , q-axis voltage v q , and the torque differential value τdot are respectively substituted with the command values, the following equation (10) is obtained: d -v q In a plane, equation (10) is expressed by a torque differential value line 91 with a gradient of -A / B. Therefore, in order for the voltage vector 71 to intersect with this torque differential value line 91 at the shortest distance, the voltage vector 71 must intersect with the line 91 at a right angle (be perpendicular). In other words, the voltage vector 71 only needs to satisfy equation (11). Therefore, from the above-mentioned equation (9) which is obtained by solving the simultaneous equations of these two equations (10) and (11), the d-axis voltage command value v * d and the q-axis voltage command value v * q (dq-axis voltage command value v * d,q ) is obtained.

[0057]

number

number

[0058] The coordinate conversion unit 22 converts the voltage vector (v d ,v q ) into the voltage vector (v α ,v β ) Here, the d-axis voltage command value v output from the voltage information generating unit 21 is converted into * d and the q-axis voltage command value v * q α-axis voltage command value v * α and the β-axis voltage command value v * β (stationary coordinate system voltage information) and output. The conversion from rotating coordinates to stationary coordinates is performed using the conversion formula (v * α=v * d cosθ re -v * q sinθ re ,v * β =v * d sinθ re +v * q cosθ re ) is used in the coordinate conversion unit 22. * d and the q-axis voltage command value v * q In addition to this, angle information θ rm is the electrical angle θ re is converted to and used.

[0059] The voltage command value output unit 23 converts the α-axis voltage command value v * α and the β-axis voltage command value v * β The voltage vector (v * α ,v * β ) is changed to a value that falls within the range of the output limit range 23a, which is the limit value of the voltage that the inverter 30 can output, to obtain the α-axis voltage command value v ** α and the β-axis voltage command value v ** β The inverter 30 has a function (limiter function) of outputting a voltage command value (voltage command value). The inverter 30 cannot output a voltage that exceeds the output voltage of the DC voltage source Batt input to the inverter 30. In other words, the output limit range 23a of the inverter 30 is predetermined based on its specifications and the output voltage of the DC voltage source Batt input to the inverter 30. Therefore, it is possible to determine the output limit range 23a having a regular hexagonal shape as shown in the conceptual diagram of FIG. 4(B).

[0060] The regular hexagon (hereinafter referred to as the "hexagon") representing this output limit range 23a is obtained by extending three axes (U-axis, V-axis, and W-axis) that divide the coordinate plane of the αβ stationary coordinate system into thirds at 120-degree intervals around the intersection of the orthogonal α-axis and β-axis, and then connecting these six lines that extend in an "*" shape, at the intersection point. The range within the hexagon (light gray range) that extends beyond the inscribed circle of this hexagon (the dashed circle in Figure 4(B)) is the so-called overmodulation region. Current vector control configured as shown in Figure 24 enables control of the voltage vector that reaches this overmodulation region by performing complex calculations such as d-axis priority control and sash current control.

[0061] For details on d-axis priority control, see, for example, "A Driving Method for Interior Permanent Magnet Synchronous Motors with Priority on d-Axis Voltage" by Kenji Takahashi, Kiyoshi Oishi, and Toshiyuki Ueno, Transactions on Electrical Engineers of Japan, Vol. 131, No. 9, pp. 1103-1111, 2011. For details on cross-coupling control, see, for example, "Verification and Consideration of Motor Control Response in Voltage Saturation State" by Shingo Makishima, Keiichi Uezono, and Masao Nagai, Transactions on Electrical Engineers of Japan, Vol. 130, No. 5, pp. 663-670, 2010.

[0062] The voltage command value output unit 23 converts the voltage vector (v * α ,v * β ) is outside the output limit range 23a of the inverter 30, and if it is determined that it is not outside the output limit range 23a (is within the range), the input voltage vector (v * α ,v * β ) is used as the α-axis voltage command value v ** α and the β-axis voltage command value v ** βto the phase number conversion unit 24, and when it is determined that the voltage is outside the output limit range 23a (not within the range), the voltage vector (v * α ,v * β ), the α-axis voltage command value v ** α and the β-axis voltage command value v ** β to the phase number conversion unit 24. For convenience of distinguishing between the command value input to the voltage command value output unit 23 and the command value output from the voltage command value output unit 23, the latter command value is labeled " ** " is attached.

[0063] Because the output limit range 23a is predetermined based on the specifications of the inverter 30 and the output voltage of the DC voltage source Batt, each side of the hexagon of the output limit range 23a can be specified as a linear function on the coordinate plane of the αβ stationary coordinate system. By solving the equations representing the sides of the hexagon as simultaneous equations representing the line segments represented by the voltage vector 71, it can be seen that there is one intersection for each solution. If there are two or more solutions, there will also be two or more intersections; if there is no solution, there will be no intersection.

[0064] For this reason, first, a process is performed to calculate the intersections where six linear functions representing each side of the hexagon of output limit range 23a intersect with the line segments represented by voltage vector 71, and then a process is performed to determine whether such intersections have been found (whether an intersection exists). If an intersection exists, it is determined that voltage vector 71 is outside (not within) the hexagon of output limit range 23a, and if no intersection exists, it is determined that voltage vector 71 is within the hexagon of output limit range 23a.

[0065] The "range of the output limit range 23a" does not include the sides and vertices of the hexagon that represents the range of the output limit range 23a. Therefore, if the coordinates that represent the tip position of the voltage vector 71 overlap with the sides or vertices of the hexagon, that is, if there is an intersection, it is determined that it is outside the range of the output limit range 23a. Note that the "reducing the voltage vector (v * α ,v * β The process of "changing the control system element" will be described later in the second example of the configuration of the control system element.

[0066] The phase number conversion unit 24 converts the two-phase voltage vector (v α ,v β ) into the three-phase voltage vector (v u ,v v ,v w ) Here, the α-axis voltage command value v output from the voltage command value output unit 23 is converted into ** α and the β-axis voltage command value v ** β , the U-phase voltage command value v * u and V-phase voltage command value v * v and the W-phase voltage command value v * w and output (voltage command value v * u,v,w ) The voltage command value v of this UVW phase * u,v,w is output from the controller 20a and input to the inverter 30. As a result, the inverter 30, as described above, calculates the voltage command value v * u,v,w By switching IGBT31 to 36 according to u,v,w is generated (converted) and supplied to the AC motor 50.

[0067] As described above, in the motor system 10a of the first exemplary configuration, the controller 20a includes a voltage information generating unit 21, a coordinate conversion unit 22, a voltage command value output unit 23, and a phase number conversion unit 24. The voltage information generating unit 21 converts the torque differential command value τdot * Based on the inverse function v of equation (7), * d,q =g -1 (τdot * ) to obtain the dq-axis voltage command value v of the dq rotating coordinate system of the AC motor 50. * d,q (rotating coordinate system voltage information). The coordinate conversion unit 22 also generates the electrical angle θ of the output shaft of the AC motor 50. re Based on the dq-axis voltage command value v * d,q (Rotating coordinate system voltage information) to αβ axis voltage command value v * α,β (stationary coordinate system voltage information). Then, the voltage command value output unit 23 converts the αβ-axis voltage command value v * α,β The voltage vector (v * α ,v * β ) is within the output limit range 23a of the inverter 30, the αβ-axis voltage command value v * α,β The αβ-axis voltage command value v ** α,β and outputs it to the inverter 30 via the phase number converter 24.

[0068] As a result, in the voltage amplitude minimum control by the controller 20a, the torque differential command value τdot * Therefore, for example, integral calculation in the PI control process (reference numerals 112 and 113 in FIG. 24) performed in general current vector control is not required. Therefore, since there is no delay time associated with integral calculation, it is possible to suppress a decrease in the response speed to a control command.

[0069] Such technical effects can be achieved, for example, by computer simulation of the voltage vector control by the controller 20a, as shown in FIG. 5(A) and the response characteristics of the output torque and the like, as shown in FIG. 5(B), and the output voltage (AC voltage v u,v,w ) is obtained, which will be explained with reference to FIG.

[0070] In the simulation, as shown in the dashed rectangular frame at the bottom of FIG. 3, a subtraction unit 25 and a torque control unit 26 are provided in front of the voltage information generation unit 21, so that the torque differential command value τdot * The subtractor 25 receives the torque command value τ * and the calculated torque estimate τhat are input, and the torque command value τ * The result of subtracting the torque estimate τhat from the torque command value τ * The torque differential command value τdot * is τdot * =K(τ * The torque control unit 26 changes the magnitude of the control gain K to obtain the torque differential command value τdot * It is possible to control the magnitude of the output torque τ and the rise time of the output torque τ.

[0071] In the figure, the hat symbol "^" above τ denotes an estimated value, and is expressed as "hat" in the specification. Note that τhat is the ratio of the rotation speed of the AC motor 50 to the motor current i u,v,w In this simulation, an arbitrary value is input as a setting condition for the gain K of the torque control unit.

[0072] The conditions for this simulation are as follows: AC motor 50 rotation speed: 1800 min -1 (constant) Torque control gain K: 2000rad / sec (time constant 500μsec) Torque command value τ * :Increases from 0N·m to 1N·m

[0073] In this simulation, the torque command value τ * is set to a value (1 N·m) that can be realized within the output limit range 23a of the inverter 30. Therefore, as shown in FIG. 5(A), it was confirmed that the output torque τ rises inside the hexagon (output limit range 23a) within the first calculation processing time (within 500 μsec) of the controller 20a. It was also confirmed that no overshoot occurs in the output torque τ. The rise time of the output torque τ is * This is the time required from the start of control after input until the torque reaches 63.2% of the target value. The time constant in the above condition is the design value of the rise time.

[0074] Also, the output voltage v of the inverter 30 shown in FIG. α ,v β is the output voltage v of the inverter 30 u,v,w The αβ axis voltage v is calculated by converting the α,β The output voltage v of the inverter 30 α ,v β In the locus of * Before the input of the torque command value τ * The output torque τ rises (symbol 71b) when input is applied, and returns to a circle (symbol 71c) when it settles down. Even at the rising peak 71b', the output torque τ is contained within the hexagon (output limit range 23a), which confirms that the theoretical response performance is being obtained. Note that, since the AC motor 50 is a synchronous motor, this output voltage v α ,v β The locus of the rotation speed of the AC motor 50 (three-phase AC voltage v u,v,w It rotates in synchronization with the frequency of the

[0075] As can be seen from both Fig. 5(A) and (B), the output torque τ is * That is, in this voltage vector control, the voltage information generating unit 21 (inverse function v=g -1 Since the calculation processing of (τdot)) and the coordinate transformation unit 22 do not include integral calculations (integral elements), even if the unit is not equipped with anti-windup processing, overshoot that may be caused by delay time associated with the calculation processing does not occur in the output torque τ.

[0076] By the way, the voltage command value output unit 23 calculates the voltage vector (v * α ,v * β ) is outside the output limit range 23a, it must be changed to a size that falls within the output limit range 23a. This is because the inverter 30 cannot output a voltage that exceeds the output limit range 23a to the AC motor 50. Therefore, in such a case, a second configuration example of the control system elements of the motor system 10 (10b) shown in FIG. 6 is used to address this. Next, a second configuration example of the control system elements of the motor system 10 (10b) will be described with reference to FIGS. 6 to 10.

[0077] [Control system element configuration example 2] As shown in Fig. 6, in motor system 10b of configuration example 2 of control system elements (hereinafter referred to as "configuration example 2"), controller 20b has the functions of voltage information generator 21, coordinate converter 22, voltage command value output unit 23, phase number converter 24, subtractor 25, and torque controller 26. In other words, controller 20b differs from controller 20a of motor system 10a of configuration example 1 (Fig. 3) in that the functions of subtractor 25 and torque controller 26 have been added to controller 20b. Therefore, in the description of controller 20b, the same components as those of controller 20a will be denoted by the same reference numerals and description thereof will be omitted.

[0078] The subtraction unit 25 and torque control unit 26 are almost the same as those used in the simulation of the motor system 10a of configuration example 1, but differ in that the control gain K of the torque control unit 26 can be controlled externally, which will be explained below.

[0079] The torque control unit 26 is a torque control unit capable of controlling the control gain K from the outside, and in the controller 20b of the second configuration example, a control input capable of increasing or decreasing the gain K is connected to the voltage command value output unit 23, so that the gain K can be controlled by the voltage command value output unit 23. As a result, the torque control unit 26 receives the torque command value τ * Estimated deviation of output torque τ from (τ * -τhat) is input, and the deviation is multiplied by the gain K to obtain the torque differential command value τdot * to the voltage information generating unit 21 (τdot * =K(τ * Since the magnitude of the gain K is controlled by the voltage command value output unit 23, the voltage command value output unit 23 outputs the torque differential command value τdot * It is possible to decrease or increase the

[0080] In this way, the controller 20b receives the torque command value τ * is input, and the torque command value τ * The torque differential command value τdot is obtained by reducing or increasing the estimated deviation of the output torque τ with the gain K. * Therefore, the voltage command value output unit 23 controls the gain K to obtain the voltage vector (v * α ,v * β ) is outside the output limit range 23a, it can be changed to a size that falls within the output limit range 23a.

[0081] As explained in the first configuration example, the voltage command value output unit 23 converts the voltage vector (v * α ,v * β ) is determined to be within the output limit range 23a of the inverter 30, and if it is determined to be outside the output limit range 23a, the voltage vector (v * α ,v * β ) is changed. Then, the α-axis voltage command value v ** α and the β-axis voltage command value v ** β to the phase number converter 24.

[0082] Specifically, for example, the controller 20b performs a voltage command value output process as shown in Fig. 7. This process is stored in advance in the EEPROM or the like of the controller 20b as a program for implementing the function of the voltage command value output unit 23 in software. Similarly, programs for implementing the functions of the subtraction unit 25 and torque control unit 26 in software are also stored in advance in the EEPROM or the like of the controller 20b.

[0083] 7, in the voltage command value output process, after voltage vector calculation process is performed in step S101, it is determined in step S103 whether or not the voltage vector 71 is outside the output limit range 23a of the inverter 30. These are the contents described in configuration example 1. That is, the voltage vector calculation process in step S101 is a process of calculating an intersection point where six linear functions representing each side of the hexagon of the output limit range 23a intersect with a line segment represented by the voltage vector 71, and the determination process in step S103 is a process of determining whether or not such an intersection point has been found (whether or not an intersection point exists), that is, whether or not the voltage vector 71 is outside the hexagon of the output limit range 23a (is not within the range).

[0084] If it is determined by this determination process that the voltage vector 71 is outside the hexagonal range of the output limit range 23a (S103; Yes), control information for reducing the gain K is output to the torque control unit 26 by the subsequent gain control information output process (S105). Thereafter, the process returns to step S101 again to perform the voltage vector calculation process (S101), and then the determination process (S103) is performed. When the torque control unit 26 reduces the gain K, the voltage vector 71 becomes smaller than the previous calculation. Therefore, by repeating the gain control information output process (S105) → voltage vector calculation process (S101) → determination process (S103), the "voltage vector 71 with the minimum voltage amplitude" calculated by the above-mentioned equation (9) is changed by the voltage command value output unit 23 to a size that falls within the output limit range 23a.

[0085] Then, when it is determined that the voltage vector 71 is within the hexagonal range of the output limit range 23a (S103; No), the αβ-axis voltage command value output process (S107) outputs the changed voltage vector (changed voltage vector) (v * α ,v * β ) represents the α-axis voltage command value v ** α and the β-axis voltage command value v ** β is output to the phase number conversion unit 24. Note that if the voltage vector (v * α ,v * β ) is used as the α-axis voltage command value v ** α and the β-axis voltage command value v ** β is output to the phase converter 24.

[0086] In this way, in the motor system 10b of the second configuration example, when the voltage vector 71 is outside the output limit range 23a, the voltage command value output unit 23 decreases (reduces) the gain K of the torque control unit 26 until the changed voltage vector falls within the output limit range 23a. * As a result, when the voltage vector 71 is outside the output limit range 23a, that is, when the unrealizable αβ-axis voltage command value v * α,β is requested, the torque differential command value τdot * In the process of repeating the gain control information output process (S105) → voltage vector calculation process (S101) → determination process (S103), the process is performed by the subtraction unit 25 and the torque control unit 26, and therefore the only control parameter is the gain K. Therefore, when focusing on the control parameters, the output torque τ is expressed as follows: τ=τ * (1-e (-Kt) ) where t represents time.

[0087] Therefore, the output torque τ is * It can be seen that no overshoot occurs with respect to v and that management is easy. In addition, since no integral element is included, for example, processing based on past history is not performed. Therefore, in the motor system 10b of configuration example 2, the αβ-axis voltage command value v that can be immediately realized is ** α,β can be output to the inverter 30 via the phase number converter 24. Furthermore, since there is no delay time associated with the integral calculation, it is possible to suppress a decrease in the response speed to a control command.

[0088] Such technical effects can be seen, for example, as a result of computer simulation of this voltage vector control by the controller 20b, in response characteristics such as output torque shown in FIG. 8 and output voltage (AC voltage v) for the inverter 30 shown in FIG. u,v,w ) are obtained, which will be explained with reference to FIGS.

[0089] The conditions for this simulation are as follows: AC motor 50 rotation speed: 3600 min -1 (constant) Torque control gain K: 2000rad / sec (time constant 500μsec) Torque command value τ * :Increases from 0N·m to 3N·m

[0090] 8 and 9, the control by the controller 20b of Configuration Example 2 and the control by the controller 20a of Configuration Example 1 are used for different periods. That is, the simulation results shown in FIGS. 8 and 9 were obtained by controlling the first 3 msec period from the start of control by the controller 20b (Configuration Example 2) and controlling the second half of the period thereafter by the controller 20a (Configuration Example 1). Therefore, from these simulation results, it is possible to confirm the response characteristics of the controller 20b of Configuration Example 2 during the first 3 msec period from the start of control, and to confirm that a seamless transition occurs at the boundary between the first and second halves of the control, without generating noise, vibration, or the like, when switching control from Configuration Example 2 to Configuration Example 1. Note that, because the functions of the controllers 20a and 20b can be realized by the same hardware, such control switching can be handled by software.

[0091] In this simulation, the torque command value τ * As a result, a value (3 N·m) that can be realized by temporarily using the overmodulation region (the light gray region shown in Fig. 4(B)) within the output limit range 23a of the inverter 30 is set. Therefore, even when such a condition is set, which would likely cause an overshoot in the output torque τ in normal current vector control, as shown in Fig. 8(A), it was confirmed that no overshoot occurs in the waveforms of the output torque τ and the torque estimate value τhat in this voltage vector control. Furthermore, it was confirmed that no noise occurs in the waveforms of the output torque τ and the torque estimate value τhat even at the timing of switching control from Configuration Example 2 to Configuration Example 1. Note that Fig. 8(B) shows the dq-axis current id,q 8(C) shows the waveform of the motor current |i|. |i| is the motor current i of the U, V, and W phases. u,v,w The dq axis current i is calculated by taking the square root of the sum of squares of the squares of the above. d,q It can be seen that there is no overshoot or noise due to switching in the waveforms of the motor current |i|.

[0092] 9A, the locus of the output voltage of the inverter 30 is the same as that described in the first configuration example. α ,v β is the output voltage v of the inverter 30 u,v,w is converted to the αβ stationary coordinate system. In this simulation, the torque command value τ * is intentionally set to a value (3 N·m) that temporarily uses the overmodulation region within the output limit range 23a of the inverter 30. α ,v β The portion (reference numeral 71d) where the output torque τ reaches the overmodulation region traces a trajectory that follows the edge of the hexagon of the output limit range 23a, but this does not indicate that an overshoot has occurred in the output torque τ.

[0093] Furthermore, as shown in FIG. 9B, when observing the waveforms (switching waveforms) of the switching signals input to the IGBTs 31 to 36 of the inverter 30, it can be seen that there is a period in which no switching signals are input to the IGBTs 31 to 36. During this period, the output voltage v of the inverter 30 α ,v β In the figure, the vertical axis of each phase indicates the ON timing of IGBTs 31, 33, and 35 in the upper arm with "1.0" and the ON timing of IGBTs 32, 34, and 36 in the lower arm with "0.0."

[0094] For the motor system 10b of the second example configuration, an experiment using an actual machine has also been conducted, and the results will be described with reference to FIG. 10. FIG. 10(A) shows the experimental results for linear region operation without overmodulation operation, and FIG. 10(B) shows the experimental results for linear region operation with temporary overmodulation operation. In these experimental results, the torque command value τ * , torque estimate τhat, d-axis current i d , q-axis current i q In this experiment, the responsiveness of the output torque is confirmed from the torque estimation value τhat instead of the output torque τ.

[0095] The conditions for this experiment are as follows: AC motor 50 rotation speed: 1000 min -1 (constant) Control gain K of torque control section: 2000 rad / sec (time constant 500 μsec) in Figure 10(A), 5000 rad / sec (time constant 200 μsec) in Figure 10(B) Torque command value τ * :Increases from 0N·m to 2N·m

[0096] As shown in FIG. 10(A), in the case of linear region operation that does not include overmodulation operation, the output torque is determined based on the torque command value τ * It was confirmed that the torque response was almost without overshoot. Furthermore, the time constant obtained from the waveform of the torque estimation value τhat was 600 μsec, which was also confirmed to be nearly close to the design value for the rise time (time constant 500 μsec). Therefore, it was confirmed that it was possible to manage the torque response in the linear region that does not include overmodulation operation within the output limit range 23a.

[0097] As shown in FIG. 10(B), in the case of linear region operation including temporary overmodulation operation, the output torque is determined based on the torque command value τ *It was confirmed that the output torque increased linearly toward τhat, but responded without overshooting. Therefore, it was confirmed that within the output limit range 23a, even if the system temporarily shifted to overmodulation operation, it responded without overshooting. It can be seen that the waveform of the estimated torque value τhat begins to rise approximately 200 μsec after the start of control. Therefore, in this figure, the settling time of the estimated torque value τhat is 800 μsec, but if this delay of approximately 200 μsec is removed, it can be seen that the output torque rises at a value close to the design value of the rise time, just like the waveform of the estimated torque value τhat shown in Figure 10(A).

[0098] [Control system element configuration example 3] Next, a third configuration example (hereinafter referred to as "Configuration Example 3") of the control system elements of the motor system 10 (10c) will be described with reference to Figs. 11 to 20. In the motor system 10a of Configuration Example 1, the voltage information generating unit 21 calculates the dq-axis voltage command value v according to the voltage vector calculation process (I) (a generation algorithm represented by the conceptual diagram shown in Fig. 4(A)). * d,q As described above, the d-axis voltage command value v obtained by the voltage information generating unit 21 was selected. * d and the q-axis voltage command value v * q The voltage vector (v d ,v q ) is a function that takes two variables as input, so the d-axis voltage v d and q-axis voltage v q This is because the selection of is still arbitrary.

[0099] In a synchronous motor such as the AC motor 50, the motor current i u,v,w When AC motor 50 is driven at a phase angle of , the copper loss of each phase coil is minimized. Therefore, motor current i u,v,wMTPA (Maximum Torque Per Ampere) control, which maximizes the output torque τ relative to the input torque, is widely used in drive motor systems, servo motor systems, etc. For example, when a host system controls the operation of an AC motor 50 using MTPA control, the control information from the host system is a d-axis current command value i * d The controller 20 acquires the dq-axis voltage command value v * d,q Therefore, it is possible to select the dq-axis voltage command value v by the voltage information generating unit 21 in the case of the voltage amplitude minimum control by the controller 20a of the first configuration example. * d,q As another example of the selection, a motor system 10c of a third configuration example that can be applied when the operation of the AC motor 50 is controlled by MTPA control will be described.

[0100] As shown in FIG. 11 , in motor system 10c of Configuration Example 3, controller 20c has the functions of voltage information generator 21, coordinate converter 22, voltage command value output unit 23, phase number converter 24, subtractor 25, torque controller 26, subtractor 27, current controller 28, and voltage information generator 29. That is, controller 20c differs from motor system 10a of Configuration Example 1 ( FIG. 3 ) in that it has the functions of subtractor 25, torque controller 26, subtractor 27, current controller 28, and voltage information generator 29 added to it. Also, motor system 10b of Configuration Example 2 ( FIG. 6 ) differs from controller 20b in that it has the functions of subtractor 27, current controller 28, and voltage information generator 29 added to it. Therefore, in the description of controller 20c, the same components as controllers 20a and 20b will be denoted by the same reference numerals, and description thereof will be omitted.

[0101] The subtraction unit 27 is the same as that used in the simulation of the motor system 10a of the first exemplary configuration, but the information input thereto is different. The subtraction unit 27 receives the d-axis current command value i * d_MTPAand d-axis current i d and are input, and the d-axis current command value i * d_MTPA From d-axis current i d The result of subtracting (d-axis current command value i * d_MTPA d-axis current i d The deviation between the two is input to the current control unit 28.

[0102] The current control unit 28 is a control unit having a control gain G, and calculates the d-axis current i d The deviation of is multiplied by the gain G to obtain the d-axis current differential command value idot * d Output as (idot * d =G(i * d_MTPA -i d The magnitude of the gain G is set in advance. The d-axis current differential command value idot * d is input to the voltage information generating unit 29 and is used to generate the d-axis voltage command value v * d is used to calculate

[0103] The voltage information generating unit 29 calculates the inverse function v * d =h -1 (idot * d ) In other words, the d-axis current command value i * d_MTPA When input, the d-axis current differential command value idot * d The d-axis voltage command value v can be calculated using * d is output from the voltage information generating unit 29. The d-axis voltage command value v * d is input to the voltage information generating unit 21 and the coordinate conversion unit 22. Note that the d-axis current differential command value idot * d is the d-axis current command value i * d_MTPAis the time-differentiated command value of the d-axis current in MTPA control.

[0104] The voltage information generating unit 21 calculates the d-axis voltage command value v * d is input from the voltage information generating unit 29, a voltage command value is selected in accordance with a generation algorithm (voltage vector calculation process (II)) represented by the conceptual diagram shown in FIG.

[0105] As shown in FIG. 12, in the voltage vector calculation process (II), for example, the voltage vector (v d ,v q ) (voltage vector 72) exists in the dq rotating coordinate system v d -v q In the plane, the torque differential command value τdot * In the voltage vector calculation process (I) in the above-described configuration example 1, the intersection point where the two intersect with each other at the shortest distance is found, and the voltage vector 71 having the magnitude up to the intersection point is calculated as the voltage command value v * d,q was selected as.

[0106] However, in this case, the voltage information generating unit 21 receives the d-axis voltage command value v output from the voltage information generating unit 29. * d is input, the d-axis voltage command value v obtained by the voltage information generating unit 21 * d and the q-axis voltage command value v * q The voltage vector (v d ,v q ) one of the two variables, d-axis voltage v d Therefore, the other q-axis voltage v q is also determined, the voltage vector 72 suitable for MTPA control is the voltage command value v * d,q It is selected as.

[0107] More specifically, the controller 20c calculates the voltage command value v *d,q The voltage command value v selected by the calculation of equation (12) is obtained. * d,q Hereinafter, the operation control of the AC motor 50 performed using the above will be referred to as "current amplitude minimum control." Note that A, B, and C are the A(i d ,i q ),B(i d ,i q ),C(i d ,i q ,ω re )

number

[0108] When some of the variables in the above-mentioned equations (7) and (2) are replaced with command values, the following equations (13) and (14) are obtained. Then, the d-axis current differential command value idot * d As explained above, it is expressed by equation (15), so equations (13) and (14) are used to obtain the d-axis voltage command value v * d and the q-axis voltage command value v * q By solving the above equation (12), the above-mentioned equation (12) is obtained. In the following equation (15), the d-axis current command value i * d_MTPA is "i * d Please note that it is written as ".

[0109]

number

number

number

[0110] In this way, in the motor system 10c of the third example configuration, in the dq rotating coordinate system, the voltage information generating unit 21 calculates the torque differential value τdot, the d-axis current i d , q-axis current i q , angular velocity ω re and d-axis current differential command value idot * d Based on this, the d-axis voltage command value v * d and the q-axis voltage command value v * q This generates the output current i of the inverter 30. u,v,w The voltage vector (v d ,v q ) is obtained, the torque differential command value τdot * The voltage command value αβ-axis voltage command value v ** α,β can be output to the inverter 30 via the phase number converter 24. Therefore, in the motor system 10c of the third configuration example, for example, the torque command value τ * (required torque) u,v,w In addition, the voltage vector 72 suitable for MTPA control can be set to the voltage command value v * d,q Therefore, a smooth transition to MTPA control can be achieved.

[0111] Such technical effects can be seen, for example, from the response characteristics of the output torque and the like shown in FIG. 13, which are obtained as a result of computer simulation of this voltage vector control by the controller 20c, and will be described with reference to FIG. 13.

[0112] The conditions for this simulation are as follows: AC motor 50 rotation speed: 1000 min -1 (constant) Torque control gain K: 5000rad / sec (time constant 1msec) Current control gain G: 1000rad / sec (time constant 1msec) Torque command value τ * :Increases from 0N·m to 4N·m

[0113] 13, the control by the controller 20c of the configuration example 3 and the control by the controller 20a of the configuration example 1 are used for different periods. That is, the simulation results shown in FIG. 8 were obtained by controlling the first 1.2 msec period from the start of control by the controller 20a (configuration example 1) and controlling the second half of the period thereafter by the controller 20c (configuration example 3). Therefore, from this simulation result, it is possible to confirm the response characteristics of the controller 20a of the configuration example 1 in the first 1.2 msec period from the start of control, and it is also possible to confirm that there is a seamless transition without the occurrence of fluctuations in the output torque τ, noise, vibration, etc. when switching control from the configuration example 1 to the configuration example 3 at the boundary between the first and second halves and thereafter, and that there is a seamless transition without the occurrence of fluctuations in the output torque τ, noise, vibration, etc., when switching control from the configuration example 1 to the configuration example 3, and that there is a d-axis current command value i by the MTPA control. * d d-axis current i d It is possible to check the response characteristics, etc. Since the functions of the controllers 20a and 20c can be realized by the same hardware, such control switching can be handled by software.

[0114] In this simulation, the torque command value τ * is set to a value (4 N·m) that can be realized by temporarily using the overmodulation region within the output limit range 23a of the inverter 30. Therefore, the response characteristic of the controller 20a of the first configuration example during the period of 1.2 msec from the start of control is that the output torque τ is * It was confirmed that the d-axis current command value i * dIn response to this, the d-axis current i d is the d-axis current command value i * d It was also confirmed that the transition to MTPA control was smooth, as the actual speed was approaching 1000 sq m.

[0115] Here, an algorithm of the voltage command value output unit 23 that can be commonly applied to the motor systems 10a to 10c of the first to third configuration examples will be described with reference to FIGS. [Modification example 1 of configuration examples 1 to 3]

[0116] As described above, the voltage command value output unit 23 converts the α-axis voltage command value v * α and the β-axis voltage command value v * β The voltage vector (v * α ,v * β ) is changed to a value that falls within the range of the output limit range 23a, which is the limit value of the voltage that the inverter 30 can output, to obtain the α-axis voltage command value v ** α and the β-axis voltage command value v ** β Therefore, the voltage vector (v * α ,v * β ) is determined to be outside the output limit range 23a, the controller 20b of the second configuration example uses an algorithm (FIG. 7; voltage command value output process) in which the voltage command value output unit 23 reduces the gain K of the torque control unit 26 until the changed voltage vector falls within the output limit range 23a.

[0117] However, as shown in Fig. 14, even when it is determined that the voltage vectors 71 and 72 obtained by the above-described equations (9) and (12) are outside the output limit range 23a, they may be able to fall within the output limit range 23a by changing them to another operating point on the torque differential value line 93. Therefore, in the voltage command value output process by the voltage command value output unit 23 of configuration example 2, the voltage vectors are simply changed to a size that falls within the output limit range 23a, but this algorithm is not necessarily appropriate. For example, if there is a point where the torque differential value line 93 intersects with the regular hexagon that represents the output limit range 23a, the vector extending to the intersection can be changed from the original voltage vectors 71 and 72 to a new voltage vector 73, thereby falling within the output limit range 23a.

[0118] Therefore, in this modified example 1, even when it is determined that the voltage vectors 71 and 72 obtained by the above-described formula (9) or (12) based on the conceptual example of the voltage command value correction algorithm shown in FIG. 14 are outside the output limit range 23a, a voltage command value correction process (I) is performed to allow the voltage vectors 71 and 72 to fall within the output limit range 23a. Note that in this modified example 1 and the next modified example 2, the "range of the output limit range 23a" includes each side and each vertex of the hexagon representing the range of the output limit range 23a. Therefore, even when the coordinates representing the tip position of the changed voltage vector 73 overlap with the sides or vertices of the hexagon, the voltage vector is determined to be within the range of the output limit range 23a. Note that this point differs from the above-described configuration examples 1 to 3.

[0119] Just to be sure, we will explain the relationship between the αβ stationary coordinate system and the dq rotating coordinate system shown in Figure 14. v in the αβ stationary coordinate system α -v β The plane is fixed, whereas the v in the dq rotating coordinate system d -v q The plane rotates counterclockwise in synchronization with the rotation speed of the AC motor 50. d -v q The plane has an electrical angle of θ re It expresses the moment when the object rotates by 100%. α -v βOnly the hexagon of the output limit range 23a is shown on the plane. The voltage vectors 71, 72, 73 and the torque differential value line 93 outside the hexagon are d -v q It is represented on a plane, and v d -v q It rotates together with the plane in synchronization with the rotation speed of the AC motor 50 .

[0120] The voltage command value correction process (I) shown in Fig. 15 will be described. This process is performed on the assumption that the torque differential value line 93 and the output voltage limit line have one or more intersections. The output voltage limit lines are the six sides that form the hexagon that represents the output limit range 23a. This process is stored in advance in the EEPROM or the like of the controllers 20a to 20c as a program that realizes the function of the voltage command value output unit 23 in this first modified example in software.

[0121] 15, in the voltage command value correction process (I), first, in step S201, a process of calculating the intersection of the torque differential value line 93 and the output voltage limit line is performed. This process is similar to the "process of calculating the intersection of the six linear functions representing the sides of the hexagon of the output limit range 23a and the line segment represented by the voltage vector 71" already described in configuration example 1. Therefore, a description of the process of step S201 will be omitted.

[0122] If two or more solutions to the simultaneous equations are obtained by the intersection calculation process in step S201, this means that there are two or more intersections between the torque differential value line 93 and the output voltage limit line, and in such a case (S203; Yes), the next step S205 is an intersection selection process. On the other hand, if there are no multiple intersections between the two (S203; No), the process proceeds to the voltage command value change process in step S207. In this case, the intersection is selected.

[0123] In the intersection selection process of step S205, for example, of two or more sides having an intersection, the side that is closest to being parallel to the torque differential value line 93 is identified, and an intersection included in that side is selected. For example, in the example shown in FIG. 14, the side having intersection 80a is closer to being parallel to the torque differential value line 93 than the side having intersection 80b. Therefore, in this case, intersection 80a is selected from the sides having intersection 80a. Note that whether or not the sides of the hexagon and the torque differential value line 93 are close to being parallel is determined, for example, by calculating the difference between the slope of the side to be determined and the slope of the torque differential value line 93, and determining that the smaller the difference between the slopes, the closer the sides are to being parallel.

[0124] In the voltage command value change process in step S207, based on the coordinate information of the intersection selected in step S205, etc., vector information is generated with the intersection coordinates as the tip coordinates, and the original voltage vector is replaced with the generated vector information. For example, in the example shown in FIG. 14, based on the coordinate information of the selected intersection 80a, information on a voltage vector 73 with the intersection coordinates as the tip coordinates is generated, and the original voltage vectors 71 and 72 are replaced with this new voltage vector 73. As a result, the α-axis voltage command value v of the new voltage vector 73 is * α and the β-axis voltage command value v * β is output from the voltage command value output unit 23.

[0125] In this way, in the present modified example 1, in the dq rotating coordinate system, the torque differential value τdot and the d-axis current i d , q-axis current i q and angular velocity ω re When the side that is closest to parallel among the six sides constituting the hexagon that represents the output limit range 23a intersects with the torque differential value line 93 that is represented by a predetermined function including * α , β-axis voltage command value v * β The αβ-axis voltage command value v ** α,βand outputs it to the inverter 30 via the phase number converter 24.

[0126] As a result, the voltage vector 73 reaches one of the six sides of the hexagon representing the range of the output limit range 23a, and the voltage command value output unit 23 can output the maximum value as a realizable voltage command value to the inverter 30 via the phase number conversion unit 24 without using, for example, limiter control requiring complex calculations or performing integral calculations. Therefore, since there is no delay time associated with complex calculations or integral calculations, the torque differential command value τdot * and torque command value τ * It is possible to suppress a decrease in response speed to the

[0127] [Modification example 2 of configuration examples 1 to 3] In the above-described first modification, the voltage command value correction process (I) executed as a function of the voltage command value output unit 23 has been described, but this process is based on the premise that the torque differential value line 93 and the output voltage limit line have one or more intersections. Therefore, for example, when there is no intersection between the torque differential value line 94 and the output voltage limit line, that is, when the two do not intersect, as shown in Fig. 16, the voltage command value correction process (I) cannot be applied.

[0128] Next, a voltage command value correction process (II) applicable to the case where the torque differential value line 94 does not intersect with the output voltage limit line will be described. As shown in FIG. 16, the torque differential value line 94 does not intersect with the output voltage limit line when the hexagon representing the output limit range 23a and the torque differential value line 94 are separated from each other, or when the two are close to each other but the sides of the hexagon and the torque differential value line 93 are parallel or nearly parallel to each other. Such cases can be resolved by the voltage command value correction process (II) shown in FIG. 17. This process is stored in advance in the EEPROM or the like of the controllers 20a to 20c as a program that realizes the function of the voltage command value output unit 23 in this second modified example in software.

[0129] As shown in FIG. 17, in the voltage command value correction process (II), first, in step S301, a process is performed to calculate the degree of parallelism between the torque differential value line 94 and the output voltage limit line (six sides of the hexagon). For example, the degree of parallelism of these lines is determined by calculating the difference in slope between the two lines, and determining that the smaller the difference between the slopes, the greater the degree of parallelism (closer to parallelism). Therefore, in step S301, a calculation process is performed to find the slope of the torque differential value line 94 and the slope of each side of the hexagon from a linear function that can identify these lines. As a result, six degrees of parallelism corresponding to each side of the hexagon are obtained.

[0130] In the next step S303, a specific limit line selection process, the side with the maximum parallelism is identified from the six parallelism degrees corresponding to the sides of the hexagon obtained in step S301. If there are two or more sides with the maximum parallelism, the side closest to the torque differential value line 93 is identified from those two sides. For example, the separation distance is calculated from the positional relationship between the coordinates of the midpoints of those two sides and the coordinates of a predetermined position on the torque differential value line 93.

[0131] In the subsequent process of obtaining both end coordinates in step S305, information on the coordinates of both ends of the output voltage limit line (specific side of the hexagon) identified in step S301 is obtained. For example, in the example shown in FIG. 16, coordinate information on end points 81 and 82 is obtained. Then, in the process of calculating both voltage vectors in step S307, information on voltage vectors whose tip coordinates are the coordinates of the end points is generated based on this coordinate information, and both voltage vectors (v d ,v q ) d-axis voltage v d and the q-axis voltage v q Then, these voltage vectors (v d ,v q ) d-axis voltage v d and the q-axis voltage v q By substituting these values into the above-mentioned equation (7) relating to the torque differential line 94, the torque differential value τdot of these voltage vectors is calculated.

[0132] In the end point selection process of step S309, an end point corresponding to the tip position of the voltage vector with the larger torque differential value τdot of the two voltage vectors calculated in step S307 is selected. For example, in the example shown in Fig. 16, of the two voltage vectors 74 and 75, end point 82 of voltage vector 74 with the larger torque differential value τdot is selected.

[0133] Then, in the voltage command value change process in step S311, the vector information of the voltage vector selected in step S309 is replaced with the original voltage vector. For example, in the example shown in FIG. 16, the selected voltage vector 74 is replaced with the original voltage vectors 71 and 72. As a result, the α-axis voltage command value v of the new voltage vector 74 is * α and the β-axis voltage command value v * β is output from the voltage command value output unit 23.

[0134] In this way, in the present modified example 2, in the dq rotating coordinate system, the torque differential value τdot and the d-axis current i d , q-axis current i q and angular velocity ω re When the most parallel side of the six sides constituting the hexagon representing the output limit range 23a does not intersect with the torque differential value line 93 represented by this predetermined function, the voltage vector 74 having the larger torque differential value τdot out of the two voltage vectors 74, 75 representing the end points 81, 82 of the most parallel side is set as the (changed voltage vector), and the α-axis voltage command value v representing that vector is set as the (changed voltage vector). * α , β-axis voltage command value v * β The αβ-axis voltage command value v ** α,β and outputs it to the inverter 30 via the phase number converter 24.

[0135] As a result, voltage vector 74 reaches one of the six vertices of a hexagon that represents the range of output limit range 23a, and therefore voltage command value output unit 23 can output the maximum value as a feasible voltage command value to inverter 30 via phase number conversion unit 24 without using limiter control or the like that requires complex calculations and without performing integral calculations. Therefore, since there is no delay time associated with complex calculations or integral calculations, it is possible to suppress a decrease in the response speed to a control command.

[0136] [Modification example 3 of configuration examples 1 to 3] The above-described first and second modifications have different roles and are complementary to each other. That is, the first modification is a process that assumes that the torque differential value line 93 and the output voltage limit line have one or more intersections, while the second modification is a process that assumes that there is no intersection between these two. Therefore, as preprocessing for the first and second modifications, it is better to provide a process that determines whether the torque differential value line 93 or the like intersects with the output voltage limit line, and to configure an algorithm that allocates control so as to conform to the respective preconditions of the first and second modifications.

[0137] 13 in Configuration Example 3, for example, AC motor 50 may be controlled with the minimum voltage amplitude control of Configuration Example 1 from the start of AC motor 50 until the output torque reaches the required torque, and after the output torque reaches the required torque, AC motor 50 may be controlled to switch to the minimum current amplitude control of Configuration Example 3 so as to smoothly transition to MTPA control. In this way, an algorithm that links the minimum voltage amplitude control of Configuration Example 1 and the minimum current amplitude control of Configuration Example 3 according to the operating conditions of AC motor 50 is also useful.

[0138] Therefore, in this modified example 3, by configuring an integrated control processing algorithm as shown in Figure 18 in the controller 20 (20a to 20c) of the motor system 10 (10a to 10c), it is possible to link voltage amplitude minimum control and current amplitude minimum control according to the operating status of the AC motor 50, and to allocate control that is compatible with the respective prerequisites for the above-mentioned modified examples 1 and 2.

[0139] Since the functions of the controllers 20a to 20c can be realized by the same hardware, such control switching can be handled by software. This integrated control process is stored in advance in the EEPROM or the like of the controller 20 as a program for realizing this process. Furthermore, this integrated control process is repeatedly executed by the CPU or the like of the controller 20 at a predetermined control period from the start to the end of operation control of the AC motor 50.

[0140] As shown in FIG. 18, in the integrated control process, first, a voltage vector calculation process (II) is performed in step S501. This process has been described with reference to FIG. 12 in the configuration example 3. Therefore, here, the controller 20c in the configuration example 3 causes the voltage information generator 21 to perform the following process in preparation for performing the current amplitude minimum control. The voltage information generator 21 receives the d-axis voltage command value v from the voltage information generator 29. * d When is input, the voltage vector (v d ,v q ) The d-axis voltage v d is determined, so the remaining q-axis voltage v q Therefore, the voltage vector 72 suitable for MTPA control is determined automatically as the voltage command value v * d,q and output to the coordinate conversion unit 22. The coordinate conversion unit 22 converts the input voltage command value v * d,q is transformed from the dq rotating coordinate system to the αβ stationary coordinate system to obtain the αβ axis voltage command value v * α,β is output to the voltage command value output unit 23.

[0141] Then, in the next step S503, the voltage command value output unit 23 determines whether or not the voltage vector 72 is within the output limit range 23a of the inverter 30. If it is determined by this determination process that the voltage vector 72 is within the hexagonal range of the output limit range 23a (S503; Yes), there is no need to change the magnitude of the voltage vector 72, and therefore the voltage command value output unit 23 changes the αβ-axis voltage command value v ** α,β to the phase number converter 24. In this case, the current amplitude minimum control of the configuration example 3 is performed.

[0142] In the next step S511, the phase number converter 24 converts the input αβ-axis voltage command value v ** α,β The voltage command value v is obtained by converting the two-phase voltage vector in the αβ stationary coordinate system into a three-phase voltage vector in the UVW stationary coordinate system. * u,v,w The voltage command value v output from the phase number converter 24 is * u,v,w is input to the inverter 30. The inverter 30 outputs a voltage command value v * u,v,w The switching operation according to the generated AC voltage v u,v,w is supplied to the AC motor 50.

[0143] On the other hand, if the determination process in step S503 determines that the voltage vector 72 is not within the hexagonal range of the output limit range 23a (outside the range) (S503; No), the voltage command value output unit 23 discards the voltage vector 72.

[0144] Then, in the integrated control process, the discarding of the voltage vector 72 is used as a trigger to perform the voltage vector calculation process (I) in step S505. This process has been described with reference to FIG. 4(A) in the configuration example 1. Therefore, here, the controller 20a of the configuration example 1 calculates the torque differential command value τdot * The voltage vector 71 that minimizes the voltage amplitude is the voltage command value v * d,qThe voltage command value v of the selected vector 71 is * d,q is converted into the αβ-axis voltage command value v by the coordinate conversion unit 22. * α,β After being converted into the above, it is output to the voltage command value output unit 23.

[0145] Then, in the next step S507, the voltage command value output unit 23 performs a process of determining whether or not the voltage vector 71 is within the output limit range 23a of the inverter 30. If it is determined that the voltage vector 71 is within the hexagonal range of the output limit range 23a (S507; Yes), it is not necessary to change the magnitude of the voltage vector 71, so the voltage command value output unit 23 changes the αβ-axis voltage command value v ** α,β is output to the phase number conversion unit 24. In this case, the voltage amplitude minimum control of the configuration example 1 is performed. In the voltage command value output process of step S511, the same process as described above is performed to obtain the AC voltage v u,v,w is supplied to the AC motor 50.

[0146] On the other hand, if it is determined in step S507 that voltage vector 71 is not within the hexagonal range of output limit range 23a (outside the range) (S507; No), a further determination process is performed in step S509.

[0147] In step S509, a process is performed to determine whether the torque differential value line 91 and the output voltage limit line (the sides of the hexagon representing the output limit range 23a) intersect. This process is the "preprocessing for Modifications 1 and 2" described above. Therefore, if the voltage command value output unit 23 determines that they intersect (S509; Yes), the two have one or more intersection points, and the process proceeds to voltage command value correction process (I) of Modification 1, which is based on the assumption that they intersect (S200). On the other hand, if the voltage command value output unit 23 determines that the torque differential value line 91 and the output voltage limit line do not intersect (S509; No), the two do not intersect, and the process proceeds to voltage command value correction process (II) of Modification 2, which is based on the assumption that they do not intersect (there is no intersection point) (S300).

[0148] The voltage command value correction process (I) (S200) of the first modified example and the voltage command value correction process (II) (S300) of the second modified example have already been described, and therefore will not be described here. By these voltage command value correction processes (I) and (II) (S200, S300), even when the voltage vector 71 or the like does not fit within the hexagon of the output limit range 23a, the voltage vectors are changed to voltage vectors 73, 74, 75 having sizes on the sides or vertices of the hexagon ( FIGS. 14 and 16 ). As a result, in such cases, so-called one-pulse control (single-pulse drive) is performed.

[0149] As a result of computer simulation of this voltage vector control in the integrated control processing by the controllers 20a to 20c, the response characteristics of the output torque and the like shown in FIGS. 19 and 20 and the voltage command values v of the U, V, and W phases output to the inverter 30 are obtained. * u,v,w The simulation conditions are different between Figure 19 and Figure 20.

[0150] Simulation conditions for the results shown in Figure 19 AC motor 50 rotation speed: 1800 min -1 (constant) Torque control gain K: 5000rad / sec Torque command value τ * :Increases from 0N·m to 1N·m

[0151] Simulation conditions for the results shown in Figure 20 AC motor 50 rotation speed: 1000 min -1 (constant) Torque control gain K: 5000rad / sec Torque command value τ * :Increases from 0N·m to 4N·m

[0152] First, in the simulation results shown in FIG. 19, the torque command value τ *The output torque τ for the voltage command value v of the U, V, and W phases rises relatively quickly (Fig. 19(A)). * u,v,w Since the waveform of τ remains stuck at the positive maximum voltage and the negative minimum voltage, it can be seen that one-pulse control was performed by Modification 2 during this period (Fig. 19(B)). * Therefore, it is estimated that one-pulse control was performed by Modification Example 2. Note that no overshoot occurred in the output torque τ (inside the dashed ellipse shown in FIG. 19(A)). It was also confirmed that no noise or the like occurred in the waveforms of the output torque τ and the torque estimation value τhat at the timing of switching control from Modification Example 2 to Configuration Example 1.

[0153] The simulation results for the current vector control of the comparative example are shown in Fig. 25. The simulation conditions for this comparative example are set as follows, similar to the simulation conditions for the results shown in Fig. 19. Therefore, the two can be compared.

[0154] The simulation conditions for the comparative example (FIGS. 24 and 25) are as follows: AC motor 50 rotation speed: 1800 min -1 (constant) ACR (current controller) response frequency: 5000rad / sec Torque command value τ * :Increases from 0N·m to 1N·m

[0155] Therefore, comparing the simulation results of Fig. 19(A) and Fig. 25(A), it is clear that the output torque τ and the torque estimation value τhat are overshooting in the current vector control of the comparative example (within the dashed ellipse in Fig. 25(A)). However, in the voltage vector control of Modification Example 3 and Configuration Example 1, the αβ-axis voltage command value v ** α,βIt can be seen from the broken ellipse in FIG. 19(A) that even if the limit is imposed, no overshoot due to this occurs in the output torque τ, etc.

[0156] Furthermore, as can be seen from the simulation results shown in Fig. 20, even when the simulation conditions are different, the αβ-axis voltage command value v ** α,β It can be seen from the dashed ellipse in Figure 20(A) that even if the limit is imposed, no overshoot occurs in the output torque τ, etc. Furthermore, from the simulation results shown in Figures 19 and 20, it can be seen that when control is switched from Modified Configuration 2 to Configuration Example 1, a seamless transition occurs without generating noise, vibration, etc.

[0157] In this way, in Modification Example 3, by performing integrated control processing in controller 20 (20a to 20c), it becomes possible to link the minimum voltage amplitude control of Configuration Example 1 with the minimum current amplitude control of Configuration Example 3 depending on the operating conditions of AC motor 50, or to allocate control between Modification Examples 1 and 2 in accordance with their respective preconditions, thereby switching between various algorithms (Configuration Examples 1 to 3, Modification Examples 1 and 2) related to this voltage vector control during operation control of AC motor 50. As a result, for example, AC motor 50 can be operated with the minimum voltage amplitude control of Configuration Example 1 from the start of AC motor 50 until the output torque reaches the required torque, and after the output torque reaches the required torque, it can be switched to the minimum current amplitude control of Configuration Example 3, thereby operating AC motor 50 with high power efficiency.

[0158] [Control system element configuration example 4] Next, a fourth configuration example (hereinafter referred to as "fourth configuration example") of the control system elements of the motor system 10 (10d) will be described with reference to FIGS. 21 and 22. The controllers 20 (20a to 20c) constituting the motor systems 10 (10a to 10c) of the first to third configuration examples described so far have not mentioned overcurrent protection of the current (motor current) flowing from the inverter 30 to the AC motor 50. However, overcurrent protection is an essential function in an actual machine. Therefore, the controller 20d of the fourth configuration example employs a configuration having an overcurrent protection function. The overcurrent protection function of the fourth configuration example is used, for example, by adding it to the first to third configuration examples.

[0159] 21, in motor system 10d of configuration example 4, controller 20d has the functions of voltage information generator 21, coordinate converter 22, voltage command value output unit 23, phase number converter 24, subtractor 25', and torque controller 26'. In other words, motor system 10b of configuration example 2 (FIG. 6) has subtractor 25 and torque controller 26 in addition to voltage information generator 21, etc., so motor system 10d of configuration example 4 is configured in almost the same way as motor system 10b of configuration example 2.

[0160] However, in the motor system 10d of the fourth example, the |i lim | 2 and the motor current |i| obtained from the current sensors 41 to 43. 2 and is input to the subtraction unit 25', and the subtraction unit 25' outputs the current limit value |i lim | 2 Motor current |i| 2 Current deviation (|i lim | 2 -|i| 2 ) is calculated and output. Here, the current limit value |i lim | 2 and motor current |i| 2 is expressed in square form simply for the sake of ease of calculation. u,v,wSince it is necessary to calculate the square root of the sum of squares to calculate the motor current |i| from the above, the subtractor 25' performs the calculation in square form to simplify the calculation process by omitting the square root calculation.

[0161] The current deviation (|i lim | 2 -|i| 2 ) is input to a torque control section 26' having a control gain Ki. The torque control section 26' calculates the input current deviation (|i lim | 2 -|i| 2 ) multiplied by the control gain Ki (Ki(|i lim | 2 -|i| 2 )) is the torque differential command value τdot * is input to the voltage information generating unit 21 instead.

[0162] However, the torque control section 26' to τdot * =Ki(|i lim | 2 -|i| 2 ) is input to the voltage information generating unit 21 when the motor current |i| flowing through the AC motor 50 is equal to or exceeds the current limit value i lim If it reaches or exceeds (|i lim | 2 ≦|i| 2 ) Therefore, in other cases, that is, when the motor current |i| is less than the current limit value i lim If the torque differential command value τdot is smaller than the predetermined value, the voltage information generating unit 21 receives the torque differential command value τdot * is entered.

[0163] 21 shows the control system elements when the overcurrent protection function is active. By configuring the controller 20d in this way, for example, the current limit value i limis set to 8 A (amperes), the subtraction unit 25' detects that a current of 8 A or more flows through the AC motor 50, and when this information is input to the torque control unit 26', the torque control unit 26' calculates the torque differential command value τdot * Instead of τdot * =Ki(|i lim | 2 -|i| 2 ) is input to the voltage information generating unit 21. As a result, the voltage information generating unit 21 calculates the motor current as a current limit value i lim Therefore, the current flowing through the AC motor 50 is controlled to be less than the current limit value i lim It drops below.

[0164] As a result of computer simulation of the overcurrent protection function of AC motor 50 by controller 20d, response characteristics such as output torque and motor current |i| of AC motor 50 shown in Fig. 21 were obtained, which will now be described. The simulation conditions were as follows:

[0165] AC motor 50 rotation speed: 3600 min -1 (constant) Torque control gain K: 10rad / sec Torque command value τ * :Increased from 2N·m to 6N·m Current limit value i lim :8A

[0166] In this simulation, it was known from the specifications of AC motor 50 that when the output torque reaches 6 N·m or more, a motor current |i| of 8 A or more would flow. Therefore, the torque command value τ * The torque command value τ *is increased to 6 N m, the motor current |i| temporarily exceeds 8 A in response, but torque control section 26' (current limiter) immediately functions, and it can be seen that the operation control of AC motor 50 switches from torque control mode to current amplitude control mode. In other words, it can be seen that the operation control is changed from torque control according to configuration example 1 to current amplitude control according to configuration example 4 (see FIG. 22(C)). In the current control mode, motor current |i| is controlled and maintained at approximately 8 A, and therefore the output torque τ of AC motor 50 is not controlled, but is maintained at approximately 3 N m.

[0167] Configuration example 4 has two limiters: a limiter related to voltage that controls the voltage vector within the output limit range 23a by the voltage command value output unit 23 that is originally provided in the controller 20, and a limiter related to current that functions by the subtraction unit 25' and torque control unit 26' described above. Note that, from the simulation result shown in Fig. 22, it can be confirmed that when switching control from configuration example 1 to configuration example 4, a seamless transition occurs without generating any major shock such as noise or vibration.

[0168] In this way, in the configuration example 4, the motor current |i| flowing through the AC motor 50 is set to a predetermined current limit value (threshold value) i lim If the current is equal to or greater than the predetermined current limit value i, the torque control of the AC motor 50 by the voltage vector control that has been performed until then is switched to current control of the AC motor 50. In this current control, the motor current |i| is controlled to be equal to or close to a predetermined current limit value i lim If a motor current |i| equal to or exceeding this flows through the AC motor 50, the motor current |i| is reduced to a predetermined current limit value, thereby making it possible to protect the AC motor 50 from breakdowns or failures caused by overcurrent.

[0169] In the above-described embodiment, the rotating coordinate system of the AC motor is described as having two axes "a d-axis parallel to the magnetic pole direction of the rotor constituting the AC motor and a q-axis perpendicular to the d-axis," that is, the rotating coordinate system is a dq rotating coordinate system. However, as long as it is a coordinate system of an AC motor, it may be a maximum torque control coordinate system or any other rotating coordinate system. It may also be a stationary coordinate system (fixed coordinate system). For example, as shown in FIG. 23(A), in the case where an arbitrary rotating coordinate system of γδ axes leads the dq rotating coordinate system (shown in light black in the figure) by a phase difference θ and rotates in synchronization with the rotor of the motor together with the dq rotating coordinate system, v in the rotating coordinate transformation formula expressed by the following formula (16) can be used. d ,v q By substituting this into the above-mentioned equation (7) and rearranging, the following equation (17) is obtained.

[0170]

number

number

[0171] Based on this idea, as a special example of an arbitrary rotating coordinate system, θ=-θ reBy setting θ, it is possible to obtain the equation for the torque differential value τdot for the stationary coordinates (fixed coordinates) of the AC motor in the same way as for the case of an arbitrary rotating coordinate system. re is the electrical angle of the AC motor 50. v of the rotation coordinate transformation formula expressed by the following formula (18) d ,v q By substituting into the above-mentioned equation (7) and rearranging, the following equation (19) is obtained.

[0172]

number

number

[0173] In the above-described embodiment, the control device and control method are described for controlling an IPMSM AC motor 50 as an AC motor, but it is also possible to control a synchronous AC motor, for example, a surface permanent magnet synchronous motor (SPMSM) or a reluctance motor, using the above-described control device and control method. In addition, in the above-described embodiment, it is described as an example of controlling a three-phase AC motor (motor 150) that is driven by a supply of three-phase AC power, but it is also possible to control a polyphase AC motor, for example, a two-phase, five-phase, seven-phase, or other AC motor, using the above-described control device and control method.

[0174] In the case of a two-phase AC motor, there is no need to perform phase number conversion, so the phase number conversion unit 24 is not required, and the α-axis voltage command value v is output from the voltage command value output unit 23 to the inverter 30. ** α and the β-axis voltage command value v ** β In the case of a five-phase AC motor or a seven-phase AC motor, instead of the phase number converter 24, the α-axis voltage command value v ** α and the β-axis voltage command value v ** β A phase number conversion unit is required to convert the output limit range 23a, which is a regular hexagon, into a five-phase or seven-phase voltage command value. In addition, in the case of a three-phase AC motor, the regular hexagonal output limit range 23a becomes a regular polygon with twice the number of vertices as the number of phases, corresponding to the number of phases of the motor, such as a regular square for two phases, a regular decagon for five phases, or a regular tetragon for seven phases.

[0175] Furthermore, in the above-described embodiment, the controller 20 is configured using a microcomputer board as a control device for an AC motor, but the controller 20 may be configured using a logic circuit, gate array, PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array) that realizes the functions of the voltage information generating unit 21, coordinate conversion unit 22, voltage command value output unit 23, phase number conversion unit 24, etc. in hardware.

[0176] In the above-described embodiment, instead of the torque (output torque) value generated on the output shaft of the AC motor, the torque estimation value τhat calculated by the controller 20 is input to the subtraction unit 25 to obtain the torque command value τ * The difference between (τ *Although the above description has been given by way of example of a configuration in which the subtractor 25 outputs (τ -τ hat) as the estimated deviation of the output torque τ, it is also possible to configure the system so that, for example, a torque sensor capable of measuring the output torque is attached to the shaft (output shaft) of the AC motor 50, and information on the output torque τ output from the torque sensor is input to the subtractor 25. Since highly accurate information on the output torque τ can be input to the subtractor 25 in real time, it becomes possible to use real deviation information on the controlled object as the deviation of the output torque τ for control, rather than an estimated value.

[0177] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications or alterations of the above-described specific examples. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives alone is technically useful. Note that the descriptions in parentheses in the [Explanation of Symbols] column may clarify the correspondence between the terms used in the above-described embodiments and the terms described in the claims. [Explanation of symbols]

[0178] 10, 10a, 10b, 10c, 10d...Motor system 20, 20a, 20b, 20c, 20d...Controller (control device for AC motor) 21...Voltage information generation unit 22... Coordinate conversion section 23...Voltage command value output section 23a...Output limit range (output limit voltage range) 24...Phase converter 25, 25', 27...Subtraction section 26, 26a... Torque control section 28...Current control section 29...Voltage information generation unit 30...Inverter 31~36...IGBT 41~43...Current sensors 45...Rotation angle sensor 50...AC motor (AC electric motor) 51...Coordinate transformation element 52...Function element 53...Integral element 71, 71a, 71b, 71c, 72...Voltage vectors 73~75...Voltage vector (changed voltage vector) 80a,80b…intersection 81,82...Endpoint 91 to 94...Torque differential value line (line expressed by a specified function) i d …d-axis current i * d …d-axis current command value i q …q-axis current i * q …q-axis current command value v d …d-axis voltage v * d …d-axis voltage command value (rotating coordinate system voltage information) v q …q-axis voltage v * q …q-axis voltage command value (rotating coordinate system voltage information) v u,v,w …AC voltage v * u,v,w …UVW phase voltage command value (voltage command value of AC voltage to be output to AC motor) v * α …α-axis voltage command value (stationary coordinate system voltage information) v ** α …α-axis voltage command value (voltage command value) v * β …β-axis voltage command value (stationary coordinate system voltage information) v ** β …β-axis voltage command value (voltage command value) τ: Output torque τ *... Torque command value (output torque required for AC motor, control command value) τdot: Torque differential value (time differential value of output torque required for AC motor) τdot * ...Torque differential command value (torque differential value input as a command value, control command value) θ rm …Rotation angle (mechanical angle) ω re …angular velocity

Claims

1. A control device for an AC motor that outputs a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, The voltage command value is a time differential value of an output torque required of the AC motor, and is input as a command value and is generated based on a torque differential value expressed by the following equation: a voltage information generating unit that generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value; a coordinate conversion unit that converts the rotating coordinate system voltage information from the rotating coordinate system into stationary coordinate system voltage information corresponding to two orthogonal axes of a stationary coordinate system based on a rotation angle of an output shaft of the AC motor; a voltage command value output unit that outputs the stationary coordinate system voltage information to the inverter as the voltage command value when a voltage vector represented by the stationary coordinate system voltage information is within a range of an output limit voltage of the inverter, and that outputs stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size that falls within the range of the output limit voltage, to the inverter as the voltage command value when the voltage vector is outside the range of the output limit voltage; A control device for an AC motor, comprising: However, A(i d ,i q ), B(i d ,i q ), C(i d ,i q ,ω re )teeth, and In the AC motor, two orthogonal axes of a rotating coordinate system are a d-axis parallel to the magnetic pole direction of a rotor constituting the AC motor and a q-axis orthogonal to the d-axis, and in the above equation, τ with a dot "·" symbol is the torque differential value, i d is the d-axis current, i q is the q-axis current, ω re is the electrical angular velocity of the output shaft of the AC motor, L d is the inductance of the d-axis equivalent coil, L q is the inductance of the q-axis equivalent coil, k e is the back electromotive force constant, and R is the winding resistance of the coil of each phase that constitutes the AC motor.

2. A control device for an AC motor that outputs a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value is a time differential value of an output torque required of the AC motor, and is generated based on a torque differential value input as a command value; a voltage information generating unit that generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value; a coordinate conversion unit that converts the rotating coordinate system voltage information from the rotating coordinate system into stationary coordinate system voltage information corresponding to two orthogonal axes of a stationary coordinate system based on a rotation angle of an output shaft of the AC motor; a voltage command value output unit that outputs the stationary coordinate system voltage information to the inverter as the voltage command value when a voltage vector represented by the stationary coordinate system voltage information is within a range of an output limit voltage of the inverter, and that outputs stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size that falls within the range of the output limit voltage, to the inverter as the voltage command value when the voltage vector is outside the range of the output limit voltage; It is equipped with When the two axes of the rotating coordinate system are a d-axis parallel to the magnetic pole direction of a rotor constituting the AC motor and a q-axis perpendicular to the d-axis, The voltage information generating unit, in the rotating coordinate system, a control device for an AC motor, characterized in that it generates, as the rotating coordinate system voltage information, coordinate information of a voltage vector having a magnitude up to an intersection point that intersects with a straight line expressed by a predetermined function including "the torque differential value, a d-axis current, a q-axis current, and the angular velocity of the output shaft" at the shortest distance.

3. A control device for an AC motor that outputs a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value is a time differential value of an output torque required of the AC motor, and is generated based on a torque differential value input as a command value; a voltage information generating unit that generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value; a coordinate conversion unit that converts the rotating coordinate system voltage information from the rotating coordinate system into stationary coordinate system voltage information corresponding to two orthogonal axes of a stationary coordinate system based on a rotation angle of an output shaft of the AC motor; a voltage command value output unit that outputs the stationary coordinate system voltage information to the inverter as the voltage command value when a voltage vector represented by the stationary coordinate system voltage information is within a range of an output limit voltage of the inverter, and that outputs stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size that falls within the range of the output limit voltage, to the inverter as the voltage command value when the voltage vector is outside the range of the output limit voltage; It is equipped with When the two axes of the rotating coordinate system are a d-axis parallel to the magnetic pole direction of a rotor constituting the AC motor and a q-axis perpendicular to the d-axis, the voltage information generating unit generates the rotating coordinate system voltage information based on the torque differential value, a d-axis current, a q-axis current, an angular velocity of the output shaft, and a time differential command value of the d-axis current in MTPA (Maximum Torque Per Ampere) control.

4. A control device for an AC motor that outputs a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value is a time differential value of an output torque required of the AC motor, and is generated based on a torque differential value input as a command value; a voltage information generating unit that generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value; a coordinate conversion unit that converts the rotating coordinate system voltage information from the rotating coordinate system into stationary coordinate system voltage information corresponding to two orthogonal axes of a stationary coordinate system based on a rotation angle of an output shaft of the AC motor; a voltage command value output unit that outputs the stationary coordinate system voltage information to the inverter as the voltage command value when a voltage vector represented by the stationary coordinate system voltage information is within a range of an output limit voltage of the inverter, and that outputs stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size that falls within the range of the output limit voltage, to the inverter as the voltage command value when the voltage vector is outside the range of the output limit voltage; It is equipped with When the voltage vector is outside the range of the output limit voltage, the voltage command value output unit a torque differential value being reduced until the changed voltage vector falls within a range of the output limit voltage.

5. A control device for an AC motor that outputs a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value is a time differential value of an output torque required of the AC motor, and is generated based on a torque differential value input as a command value; a voltage information generating unit that generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value; a coordinate conversion unit that converts the rotating coordinate system voltage information from the rotating coordinate system into stationary coordinate system voltage information corresponding to two orthogonal axes of a stationary coordinate system based on a rotation angle of an output shaft of the AC motor; a voltage command value output unit that outputs the stationary coordinate system voltage information to the inverter as the voltage command value when a voltage vector represented by the stationary coordinate system voltage information is within a range of an output limit voltage of the inverter, and that outputs stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size that falls within the range of the output limit voltage, to the inverter as the voltage command value when the voltage vector is outside the range of the output limit voltage; It is equipped with When the two axes of the rotating coordinate system are a d-axis parallel to the magnetic pole direction of a rotor constituting the AC motor and a q-axis perpendicular to the d-axis, When the voltage vector is outside the range of the output limit voltage, the voltage command value output unit calculates, in the rotating coordinate system, a voltage vector extending to a point of intersection of a line expressed by a predetermined function including "the torque differential value, a d-axis current, a q-axis current, and the angular velocity of the output shaft" and a side that is closest to parallel among six sides constituting a hexagon that represents the range of the output limit voltage, is set to the changed voltage vector, and static coordinate system voltage information that represents the changed voltage vector is output to the inverter as the voltage command value.

6. A control device for an AC motor that outputs a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value is a time differential value of an output torque required of the AC motor, and is generated based on a torque differential value input as a command value; a voltage information generating unit that generates rotating coordinate system voltage information corresponding to two orthogonal axes of a rotating coordinate system of the AC motor based on the torque differential value; a coordinate conversion unit that converts the rotating coordinate system voltage information from the rotating coordinate system into stationary coordinate system voltage information corresponding to two orthogonal axes of a stationary coordinate system based on a rotation angle of an output shaft of the AC motor; a voltage command value output unit that outputs the stationary coordinate system voltage information to the inverter as the voltage command value when a voltage vector represented by the stationary coordinate system voltage information is within a range of an output limit voltage of the inverter, and that outputs stationary coordinate system voltage information representing a changed voltage vector, which has been changed to a size that falls within the range of the output limit voltage, to the inverter as the voltage command value when the voltage vector is outside the range of the output limit voltage; It is equipped with When the two axes of the rotating coordinate system are a d-axis parallel to the magnetic pole direction of a rotor constituting the AC motor and a q-axis perpendicular to the d-axis, When the voltage vector is outside the range of the output limit voltage, the voltage command value output unit calculates, in the rotating coordinate system, a control device for an AC motor, wherein, when the most parallel side of six sides constituting a hexagon representing the range of the output limit voltage does not intersect with the line expressed by a predetermined function including "the torque differential value, a d-axis current, a q-axis current, and the angular velocity of the output shaft," the voltage vector representing both end points of the most parallel side, which has a larger torque differential value, is set as the changed voltage vector, and static coordinate system voltage information representing the changed voltage vector is output to the inverter as the voltage command value.

7. 1. A method for controlling an AC motor, comprising: outputting a voltage command value of an AC voltage to be output to an AC motor to an inverter capable of supplying three-phase AC power to the AC motor, the voltage command value is a time differential value of an output torque required of the AC motor, and is input as a command value and is generated based on a torque differential value expressed by the following equation: However, A(i d ,i q ), B(i d ,i q ), C(i d ,i q ,ω re )teeth, and In the AC motor, two orthogonal axes of a rotating coordinate system are a d-axis parallel to the magnetic pole direction of a rotor constituting the AC motor and a q-axis orthogonal to the d-axis, and in the above equation, τ with a dot "·" symbol is the torque differential value, i d is the d-axis current, i q is the q-axis current, ω re is the electrical angular velocity of the output shaft of the AC motor, L d is the inductance of the d-axis equivalent coil, L q is the inductance of the q-axis equivalent coil, k e is the back electromotive force constant, and R is the winding resistance of the coil of each phase that constitutes the AC motor.

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