Control device for AC motor and control method for AC motor

Abstract

The present invention provides an AC motor control device equipped with a winding switching function that enables optimal and highly accurate winding selection for multiple fluctuating parameters related to the operating state, while suppressing the number of data points in the table map for winding selection. [Solution] The invention comprises an AC motor having multiple windings, a power converter for controlling the AC motor, a controller for controlling the power converter, and a winding switching device for switching the connection state of the AC motor windings in response to a command from the controller, wherein the controller has a winding switching control unit that calculates a winding switching command for switching the connection state of the AC motor windings, and the winding switching control unit calculates a winding switching command for switching the connection state of the AC motor windings based on a torque limiter command for each connection state of the AC motor windings.

Description

Technical Field

[0001] The present invention relates to a configuration and a control method of a control device for an alternating current motor that controls a power converter for driving the alternating current motor, and particularly relates to a technique effective when applied to a control device for an alternating current motor having a winding switching function.

Background Art

[0002] In order to meet the requirements of miniaturization and weight reduction, the rotational speed of the rotor of an alternating current motor used in an electric vehicle or the like is increasing. However, a permanent magnet synchronous motor (hereinafter referred to as "PM motor") widely applied as an alternating current motor becomes difficult to output torque in a high-speed rotation range because the induced electromotive force increases due to the permanent magnet embedded in the rotor when designed for high-speed rotation for high efficiency and high output density.

[0003] Therefore, it is inevitable to reduce the number of turns of the coil to obtain large current and low voltage characteristics, which increases the output current of the inverter and the inverter loss. From this, while the high-speed rotation of the alternating current motor enables improvement of the motor output density and miniaturization and weight reduction, there are problems that lead to deterioration of system efficiency and electricity cost.

[0004] Therefore, in response to such problems, conventionally, a control technique for a winding switching motor that switches the connection of the stator winding (hereinafter simply referred to as "winding") between a low-speed rotation range and a high-speed rotation range to enable high-efficiency operation in a wide rotation range from the low-speed rotation range to the high-speed rotation range is known. In a winding switching motor, by appropriately switching the connection state of the winding according to the operating point, the inductance is reduced in the high-speed rotation range to ensure the motor output, while the inductance is increased in the low-speed rotation range to reduce the current and reduce the inverter loss or increase the output torque.

[0005] As a winding switching control technology for winding-switching motors, for example, the technology disclosed in Patent Document 1 is described. Patent Document 1 describes a multidimensional table map reference method for determining the optimal winding based on an energy efficiency map of an AC motor for each operating condition such as rotational speed, torque, power supply voltage, and temperature. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-150655 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The technology described in Patent Document 1 above determines the optimal winding using a multidimensional table map with variable parameters such as rotational speed, torque, power supply voltage, and temperature as input variables. However, in order to accurately switch to the optimal winding according to the operating conditions, the number of data points (memory) in the table map increases, which presents a challenge. On the other hand, if the number of data points in the table map is reduced even if the number of variable parameters increases, the table resolution decreases, and the accuracy of selecting the optimal winding deteriorates.

[0008] Therefore, the object of the present invention is to provide an AC motor control device and an AC motor control method that enable optimal and highly accurate winding selection for multiple fluctuating parameters related to the operating state, while suppressing the number of data points in the table map for winding selection, in an AC motor control device equipped with a winding switching function. [Means for solving the problem]

[0009] To solve the above problems, the AC motor control device of the present invention comprises an AC motor having a plurality of windings, a power converter for controlling the AC motor, a controller for controlling the power converter, and a winding switching device for switching the connection state of the windings of the AC motor in response to a command from the controller, wherein the controller has a winding switching control unit that calculates a winding switching command for switching the connection state of the windings of the AC motor, and the winding switching control unit calculates a winding switching command for switching the connection state of the windings of the AC motor based on a torque limiter command for each connection state of the windings of the AC motor.

[0010] Furthermore, the present invention relates to a control method for an AC motor that is executed by a control device for an AC motor equipped with a winding switching function, and is characterized by comprising: (a) a step of calculating a torque limiter command for each connection state of the windings of the AC motor; and (b) a step of calculating a winding switching command for switching the connection state of the windings of the AC motor based on the torque limiter command obtained in step (a). [Effects of the Invention]

[0011] According to the present invention, in an AC motor control device equipped with a winding switching function, it is possible to realize an AC motor control device and an AC motor control method that can perform optimal and highly accurate winding selection for multiple fluctuating parameters related to the operating state while suppressing the number of data points in the table map for winding selection.

[0012] This can contribute to improving the performance and miniaturizing the size and weight of AC motors.

[0013] Other issues, configurations, and effects not mentioned above will be clarified by the following description of embodiments for carrying out the invention. [Brief explanation of the drawing]

[0014] [Figure 1] This is a block diagram showing the schematic configuration of a control device for an AC motor according to Embodiment 1 of the present invention. [Figure 2]It is a block diagram showing a configuration example of the torque limiter command calculation unit 112 in FIG. 1. [Figure 3A] It is a characteristic diagram showing an example of the relationship between the motor rotation speed, DC voltage, and torque limiter value in the first positive torque limiter command calculation unit 201 in FIG. 2. [Figure 3B] It is a characteristic diagram showing an example of the relationship between the motor rotation speed, DC voltage, and torque limiter value in the second positive torque limiter command calculation unit 202 in FIG. 2. [Figure 4] It is a block diagram showing a modified example of FIG. 2. [Figure 5A] It is a characteristic diagram showing an example of the relationship between the flux limiter value and torque limiter value in the first positive torque limiter command calculation unit 201b in FIG. 4. [Figure 5B] It is a characteristic diagram showing an example of the relationship between the flux limiter value and torque limiter value in the second positive torque limiter command calculation unit 202b in FIG. 4. [Figure 6] It is a block diagram showing a configuration example of the winding changeover command calculation unit 113 in FIG. 1. [Figure 7] It is a diagram schematically showing the function of the conventional winding changeover command calculation means. [Figure 8A] It is a map image diagram of the winding changeover command in Example 1 (when the torque command is positive). [Figure 8B] It is a map image diagram of the winding changeover command in Example 1 (when the torque command is negative). [Figure 9] It is a block diagram showing the schematic configuration of the AC motor control device according to Example 2 of the present invention. [Figure 10] It is a block diagram showing a configuration example of the winding changeover command calculation unit 113c in FIG. 9. [Figure 11A] It is a map image diagram of the winding changeover command in Example 2 (when the torque command is positive). [Figure 11B] It is a map image diagram of the winding changeover command in Example 2 (when the torque command is negative). [Figure 12] It is a block diagram showing the schematic configuration of the AC motor control device according to Example 3 of the present invention. [Figure 13] It is a block diagram showing a configuration example of the torque limiter command calculation unit 112d in FIG. 12. [Figure 14] It is a block diagram showing a schematic configuration of a control device for an alternating current motor according to Embodiment 4 of the present invention. [Figure 15] It is a block diagram showing a configuration example of the torque limiter command calculation unit 112e in FIG. 14.

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and detailed descriptions of overlapping parts are omitted.

Embodiment

[0016] Referring to FIGS. 1 to 8B, a control device for an alternating current motor and a control method for an alternating current motor according to Embodiment 1 of the present invention will be described. FIGS. 4 to 5B are diagrams showing modified examples of this embodiment corresponding to FIGS. 2 to 3B. FIG. 7 is a diagram schematically showing the function of a conventional winding switching command calculation means for the purpose of making the present invention easier to understand.

[0017] FIG. 1 is a block diagram showing a schematic configuration of a control device 100 for an alternating current motor of this embodiment. This device mainly includes a power converter 102 that drives an alternating current motor (PM motor) 103, a controller 101 that controls the power converter 102, a winding switching device 104 that switches the windings of the alternating current motor 103, a phase current detection unit 121 that detects the current flowing through the alternating current motor 103, and a rotor position detection unit 124 that detects the rotor position of the alternating current motor 103. In some cases, it may be referred to as a "control device for an alternating current motor" including the alternating current motor 103 as the control object.

[0018] The AC motor 103 is an electric motor controlled by AC power output from the power converter 102. In each embodiment of the present invention, the AC motor 103 has, for example, the start and end ends of some windings drawn out and connected to a winding switching device 104 so that the connection state of the windings can be switched between series and parallel connections. The winding switching device 104 switches the connection state of at least some of the windings of the AC motor 103 to either series or parallel connections.

[0019] Furthermore, the present invention is applicable to AC motors having connection states other than series and parallel connections, and also to AC motors having two or more winding states. In addition, although the present invention is explained using a PM motor as an example of an AC motor 103 in each embodiment of the present invention, the present invention is applicable to all other AC motors. Moreover, although the present invention is explained using an AC motor as an example in each embodiment of the present invention, the effects of the present invention can also be obtained when an AC generator is the controlled object.

[0020] The power converter 102 includes input terminals 123a and 123b that supply power to the power converter 102, a main circuit section 132 composed of six switching elements Sup to Swn, a gate driver 133 that directly drives the main circuit section 132, a DC resistor 134 installed for overcurrent protection of the power converter 102, and a smoothing capacitor 131. Based on the gate command signal generated by the controller 101, the power converter 102 converts the DC power supplied from the input terminals 123a and 123b into AC power and supplies the AC power to the PM motor 103.

[0021] The winding switching device 104 has a circuit configuration that can switch the connection state of the windings of the PM motor 103, and switches the connection state of the windings based on the winding switching command signal Swc* from the winding switching command calculation unit 113. The present invention is applicable to both mechanical winding switching devices and semiconductor winding switching devices.

[0022] The phase current detection unit 121 detects the alternating currents iu and iw flowing from the power converter 102 to the PM motor 103. The phase current detection unit 121 is implemented by a current sensor, for example, using a Hall element. Although the phase current detection unit 121 in Figure 1 is configured for two-phase detection of alternating current, it may also be configured for three-phase detection. Alternatively, instead of using a phase current sensor, the alternating current value may be estimated from the current value flowing through the DC resistor 134 installed for overcurrent protection of the power converter 102.

[0023] The rotor position detection unit 124 outputs an angle signal φ corresponding to the rotor position (rotation angle) of the PM motor 103. The rotor position detection unit 124 can be implemented using, for example, a resolver, encoder, or magnetic sensor. When controlling an AC motor that requires detection of the rotor position, such as a PM motor, the rotational speed may be detected using an encoder or the like instead of the rotor position detection unit 124, and the rotor position of the AC motor may be calculated based on that rotational speed information. Furthermore, a configuration without a rotational position sensor or a position sensor may be implemented by estimating the electrical angular frequency ω1 and rotor position θd of the PM motor 103 based on voltage command values ​​or current detection values, without using rotational position sensors or speed sensors.

[0024] The controller 101 comprises an inverter control unit 111, a torque limiter command calculation unit 112, and a winding switching command calculation unit 113. The torque limiter command calculation unit 112 and the winding switching command calculation unit 113 together are sometimes referred to as the "winding switching control unit." The controller 101 generates gate command signals for driving the switching elements Sup~Swn of the power converter 102 from the calculation results of the current control system and phase control system based on the angle signal φ corresponding to the rotor position (rotation angle) of the PM motor 103 from the rotor position detection unit 124, the AC current detection values ​​Iu,Iw which are the detected AC currents iu,iw flowing through the PM motor 103 from the phase current detection unit 121, and the DC voltage detection value Ecf from the smoothing capacitor 131, and supplies these to the gate driver 133 of the power converter 102. Furthermore, the controller 101 supplies the winding switching command signal Swc* from the winding switching command calculation unit 113 to the winding switching device 104.

[0025] The configuration of the controller 101 shown in Figure 1 will be explained in detail below.

[0026] The inverter control unit 111 calculates a voltage command to control the torque generated by the PM motor 103 based on the angle signal φ corresponding to the rotor position (rotation angle) of the PM motor 103 from the rotor position detection unit 124, the AC currents iu and iw flowing through the PM motor 103 from the phase current detection unit 121, and the DC voltage detection value Ecf from the smoothing capacitor 131. Based on this voltage command, it outputs a gate command signal generated by the calculation result of pulse width modulation.

[0027] Furthermore, the inverter control unit 111 calculates the electrical angular frequency ω1 of the rotational speed of the PM motor 103 based on the angle signal φ from the rotor position detection unit 124 and supplies it to the torque limiter command calculation unit 112. In addition, it calculates the torque command Tm* that has been limited based on the torque limiter command for each winding connection state from the torque limiter command calculation unit 112 and supplies it to the winding switching command calculation unit 113.

[0028] In each embodiment of the present invention, the inverter control unit 111 is configured to control the torque generated by the PM motor 103 based on the torque command Tm*, but it may also be configured to control the rotational speed or rotor position of the PM motor 103, for example. Furthermore, the inverter control unit 111 switches control constants such as winding resistance, inductance, and induced voltage coefficient of the PM motor 103 in the voltage command calculation based on the winding switching command signal Swc*. In addition, in order to suppress the occurrence of torque shock due to winding switching, the inverter control unit 111 may, for example, control the current to zero before the winding connection state is switched by the winding switching device 104 based on the winding switching command signal Swc*, change the magnitude of the weakening flux current, or perform a current restart process after the winding switching is completed.

[0029] The torque limiter command calculation unit 112 calculates a torque limiter command for each winding connection state of the PM motor 103 based on the electrical angular frequency ω1 of the rotational speed of the PM motor 103 output by the inverter control unit 111 and the DC voltage detection value Ecf from the smoothing capacitor 131, and outputs it to the inverter control unit 111 and the winding switching command calculation unit 113. In this embodiment, the winding connection state of the PM motor 103 is switched between series connection and parallel connection. The positive torque limiter value when the PM motor 103 is connected in series is the first positive torque limiter command Tlim-1p*, and the negative torque limiter value is the first negative torque limiter command Tlim-1m*. The positive torque limiter value when connected in parallel is the second positive torque limiter command Tlim-2p*, and the negative torque limiter value is the second negative torque limiter command Tlim-2m*.

[0030] The winding switching command calculation unit 113 calculates a winding switching command signal Swc* according to the operating state based on the torque command Tm* output by the inverter control unit 111 and the torque limiter commands Tlim-1p*, Tlim-1m*, Tlim-2p*, Tlim-2m* for each winding connection state output by the torque limiter command calculation unit 112, and outputs it to the inverter control unit 111 and the winding switching device 104.

[0031] Next, the torque limiter command calculation unit 112 and the winding switching command calculation unit 113, which are characteristic parts of this embodiment, will be described in detail.

[0032] Figure 2 is a block diagram showing an example configuration of the torque limiter command calculation unit 112 shown in Figure 1. As shown in Figure 2, the torque limiter command calculation unit 112 comprises a first positive torque limiter command calculation unit 201, a second positive torque limiter command calculation unit 202, a first negative torque limiter command calculation unit 203, and a second negative torque limiter command calculation unit 204.

[0033] The torque limiter command calculation unit 112 takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103 from the inverter control unit 111 and the DC voltage detection value Ecf from the smoothing capacitor 131 as inputs, calculates and outputs the first positive torque limiter command Tlim-1p*, which is the positive torque limiter value when the PM motor 103 is connected in series, the first negative torque limiter command Tlim-1m*, which is the negative torque limiter value when the motor is connected in series, the second positive torque limiter command Tlim-2p*, which is the positive torque limiter value when the motor is connected in parallel, and the second negative torque limiter command Tlim-2m*, which is the negative torque limiter value when the motor is connected in parallel.

[0034] In the torque limiter command calculation unit 112, the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* can be configured, for example, using a reference table that takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103 and the DC voltage detection value Ecf as input variables.

[0035] The table data referenced by the first positive torque limiter command calculation unit 201, the second positive torque limiter command calculation unit 202, the first negative torque limiter command calculation unit 203, and the second negative torque limiter command calculation unit 204 is table data representing the correspondence between the electrical angular frequency ω1 and the detected DC voltage value Ecf of the rotational speed of the PM motor 103 and the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m*, respectively. For example, data obtained in advance from tests or analyses may be used. Alternatively, instead of the reference table, a function formula, approximation formula, design formula, etc., may be used.

[0036] Figures 3A and 3B are characteristic diagrams showing an example of the relationship between motor rotation speed, DC voltage, and torque limiter value in the torque limiter command calculation unit 112 of Figure 2. Figure 3A shows the relationship between motor rotation speed, DC voltage, and torque limiter value (Tlim-1p*) in the first positive torque limiter command calculation unit 201, and Figure 3B shows the relationship between motor rotation speed, DC voltage, and torque limiter value (Tlim-2p*) in the second positive torque limiter command calculation unit 202.

[0037] As shown in Figures 3A and 3B, the torque limiter values ​​Tlim-1p* and Tlim-2p* change depending on the magnitude of the DC voltage and motor rotation speed, because the output torque of the PM motor 103 is limited by the magnitude of the voltage that the power converter 102 can output. Furthermore, when the windings of the PM motor 103 are connected in series, it is possible to output greater torque in the low-speed rotation range compared to when they are connected in parallel, and when they are connected in parallel, it is possible to output torque up to a higher rotation range compared to when they are connected in series.

[0038] Furthermore, the torque limiter values ​​of the first negative torque limiter command calculation unit 203 and the second negative torque limiter command calculation unit 204 also exhibit similar dependence on motor rotation speed and DC voltage, as well as the characteristics of output torque with series and parallel winding connections, although there are slight differences due to the difference in the positive and negative of the output torque.

[0039] A modified version of Figures 2 to 3B will be explained using Figures 4 to 5B. This embodiment can also be realized by using the torque limiter command calculation unit 112b in Figure 4 instead of the torque limiter command calculation unit 112 in Figure 2.

[0040] Figure 4 is a modified example of Figure 2 and is a block diagram showing an example configuration of the torque limiter command calculation unit 112b. As shown in Figure 4, the torque limiter command calculation unit 112b comprises a first positive torque limiter command calculation unit 201b, a second positive torque limiter command calculation unit 202b, a first negative torque limiter command calculation unit 203b, a second negative torque limiter command calculation unit 204b, and a magnetic flux limiter command calculation unit 205b.

[0041] The torque limiter command calculation unit 112b takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103 from the inverter control unit 111 and the DC voltage detection value Ecf from the smoothing capacitor 131 as inputs, calculates and outputs the first positive torque limiter command Tlim-1p*, which is the positive torque limiter value when the PM motor 103 is connected in series, the first negative torque limiter command Tlim-1m*, which is the negative torque limiter value when the motor is connected in series, the second positive torque limiter command Tlim-2p*, which is the positive torque limiter value when the motor is connected in parallel, and the second negative torque limiter command Tlim-2m*, which is the negative torque limiter value when the motor is connected in parallel.

[0042] The magnetic flux limiter command calculation unit 205b calculates a magnetic flux limiter value λlim* equivalent to the output voltage limit of the power converter 102, based on the electrical angular frequency ω1 of the rotational speed of the PM motor 103 from the inverter control unit 111 and the DC voltage detection value Ecf from the smoothing capacitor 131, and outputs it to the first positive torque limiter command calculation unit 201b, the second positive torque limiter command calculation unit 202b, the first negative torque limiter command calculation unit 203b, and the second negative torque limiter command calculation unit 204b. The magnetic flux limiter value λlim* is a function that is proportional to the DC voltage detection value Ecf and inversely proportional to the electrical angular frequency ω1 of the rotational speed of the PM motor 103. For example, it is calculated using the following equation (1).

[0043]

number

[0044] Furthermore, the modulation rate command limit value Ylim* is set to a value of 4 / π or less when a relative transformation is used in the coordinate transformation of current and voltage from the stator coordinate system representing the phase of the stator windings of the PM motor 103 to the rotor coordinate system representing the magnetic pole position of the rotor of the PM motor 103. When PWM control is performed in the power converter 102 with a synchronous 1 pulse that yields the maximum output voltage, the modulation rate command limit value Ylim* becomes 4 / π. In addition, the modulation rate command limit value Ylim* may be used as the target modulation rate for field weakening control when field weakening control is performed in the inverter control unit 111, or as a modulation rate equivalent to the output voltage limit value determined from the operating conditions of the PWM control.

[0045] In the torque limiter command calculation unit 112b, the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* can be configured, for example, using a reference table with the magnetic flux limiter value λlim* as an input variable.

[0046] The table data referenced by the first positive torque limiter command calculation unit 201b, the second positive torque limiter command calculation unit 202b, the first negative torque limiter command calculation unit 203b, and the second negative torque limiter command calculation unit 204b is table data representing the correspondence between the magnetic flux limiter value λlim* and the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m*. For example, data obtained in advance from tests or analyses may be used. Alternatively, instead of the reference table, a function formula, approximation formula, design formula, etc., may be used.

[0047] Figures 5A and 5B are characteristic diagrams showing an example of the relationship between the magnetic flux limiter value λlim* and the torque limiter value in the torque limiter command calculation unit 112b of Figure 4. Figure 5A shows the relationship between the magnetic flux limiter value λlim* and the torque limiter value (Tlim-1p*) in the first positive torque limiter command calculation unit 201b, and Figure 5B shows the relationship between the magnetic flux limiter value λlim* and the torque limiter value (Tlim-2p*) in the second positive torque limiter command calculation unit 202b. In Figures 5A and 5B, the horizontal axis of each graph is the reciprocal of the magnetic flux limiter value λlim*.

[0048] As shown in Figures 5A and 5B, the torque limiter values ​​Tlim-1p* and Tlim-2p* change depending on the magnitude of the DC voltage and motor rotation speed, because the output torque of the PM motor 103 is limited by the magnitude of the voltage that the power converter 102 can output. However, when using the magnetic flux limiter value λlim*, the torque limiter values ​​Tlim-1p* and Tlim-2p* can be combined into a single torque curve with respect to the magnetic flux limiter value λlim*. Furthermore, when the windings of the PM motor 103 are connected in series, it is possible to output greater torque in the low-speed rotation range compared to when they are connected in parallel, and when they are connected in parallel, it is possible to output torque up to a higher rotation range compared to when they are connected in series.

[0049] Furthermore, the torque limiter values ​​of the first negative torque limiter command calculation unit 203b and the second negative torque limiter command calculation unit 204b also exhibit similar dependence on the magnetic flux limiter value λlim* and the characteristics of output torque between series and parallel winding connections, although there are slight differences depending on the polarity of the output torque.

[0050] Figure 6 is a block diagram showing an example configuration of the winding switching command calculation unit 113 in Figure 1. As shown in Figure 6, the winding switching command calculation unit 113 comprises a magnitude comparison calculation unit 301, a magnitude comparison calculation unit 302, and a winding status signal calculation unit 401. The winding switching command calculation unit 113 receives the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* from the torque limiter command calculation unit 112 or torque limiter command calculation unit 112b, and the torque command Tm* from the inverter control unit 111 as inputs, calculates a winding switching command signal Swc* for selecting the optimal winding according to the operating state, and outputs it to the inverter control unit 111 and the winding switching device 104.

[0051] The magnitude comparison calculation unit 301 compares the magnitude of the first positive torque limiter command Tlim-1p*, which is the positive torque limiter value when the PM motor 103 is connected in series, with the second positive torque limiter command Tlim-2p*, which is the positive torque limiter value when the PM motor 103 is connected in parallel. The unit selects a winding capable of outputting a larger positive torque in the operating state of the PM motor 103 and outputs a winding switching command signal Swc-p* for positive torque commands. For example, the winding switching command signal Swc-p* for positive torque commands outputs 1 if the first positive torque limiter command Tlim-1p* is greater than the second positive torque limiter command Tlim-2p*, and outputs 2 if the second positive torque limiter command Tlim-2p* is greater than the first positive torque limiter command Tlim-1p*.

[0052] The magnitude comparison calculation unit 302 compares the magnitude of the first negative torque limiter command Tlim-1m*, which is the negative torque limiter value when the PM motor 103 is connected in series, with the second negative torque limiter command Tlim-2m*, which is the negative torque limiter value when the PM motor 103 is connected in parallel, and selects a winding capable of outputting a larger negative torque in the operating state of the PM motor 103, and outputs a winding switching command signal Swc-m* for negative torque commands. For example, the winding switching command signal Swc-m* for negative torque commands outputs 1 if the first negative torque limiter command Tlim-1m* is negatively greater than the second negative torque limiter command Tlim-2m*, and outputs 2 if the second negative torque limiter command Tlim-2m* is negatively greater than the first negative torque limiter command Tlim-1m*.

[0053] The winding status signal calculation unit 401 calculates a winding switching command signal Swc* for selecting the optimal winding according to the operating state, based on the winding switching command signal Swc-p* for positive torque commands from the magnitude comparison calculation unit 301, the winding switching command signal Swc-m* for negative torque commands from the magnitude comparison calculation unit 302, and the torque command Tm* from the inverter control unit 111, and outputs it to the inverter control unit 111 and the winding switching device 104.

[0054] In the winding status signal calculation unit 401, the positive or negative sign of the torque command Tm* from the inverter control unit 111 is determined. If the torque command Tm* is positive, the winding switching command signal Swc* outputs the calculation result of the winding switching command signal Swc-p*. If the torque command Tm* is negative, the winding switching command signal Swc* outputs the calculation result of the winding switching command signal Swc-m*.

[0055] The above describes the configuration example of Embodiment 1 of the present invention. Next, we will explain how Embodiment 1 improves the accuracy of optimal winding selection for multiple variable parameters.

[0056] Figure 7 is a schematic diagram illustrating the function of a conventional winding switching command calculation means. Figure 7 shows an example of the relationship between the fluctuating parameters of motor rotation speed, DC voltage, and torque, and the optimal winding status according to the operating state, as a map image diagram of the winding switching command. As shown in Figure 7, in the conventional technology, the optimal winding of the PM motor 103 is determined by a multidimensional table map reference method that uses motor rotation speed, DC voltage, and torque as input variables. However, in order to switch to the optimal winding with high accuracy according to the operating state, the number of data points (memory) in the table map increases. Furthermore, if the number of data points in the table map is reduced, the table resolution with respect to the fluctuating parameters decreases, and the accuracy of optimal winding selection deteriorates, especially when controlling a PM motor with strong nonlinearity due to magnetic saturation.

[0057] Therefore, in this embodiment, instead of using a multidimensional table map reference method that outputs a winding switching command signal using motor rotation speed, DC voltage, and torque as input variables, the winding switching command signal is calculated based on the torque limiter command when the windings of the PM motor 103 are connected in series and in parallel.

[0058] Figures 8A and 8B are map diagrams of the winding switching command in this embodiment. Figure 8A shows the case where the torque command is positive, and Figure 8B shows the case where the torque command is negative. Figures 8A and 8B show an example of the relationship between the motor rotation speed, DC voltage, and torque fluctuation parameters and the optimal winding status according to the operating state, as a map diagram of the winding switching command. Note that Figures 8A and 8B are map diagrams of the winding switching command when the torque limiter command calculation unit 112b is used instead of the torque limiter command calculation unit 112, and the horizontal axis of each graph is the reciprocal of the magnetic flux limiter value λlim*.

[0059] As shown in Figure 6, in this embodiment, the torque limiter command for the series connection of the PM motor 103 and the torque limiter command for the parallel connection are compared, and the optimal winding connection state that can output a larger torque for each operating state is selected. Therefore, the switching operating conditions for the first winding connection representing the series connection and the second winding connection representing the parallel connection are a1, a2, b1, and b2, which are the reciprocals of the magnetic flux limiter value λlim*. Although the map image of the winding switching command is simplified, the number of table data required for winding switching command calculation can be greatly reduced.

[0060] In this embodiment, the winding switching command signal is calculated based on the calculation results of the torque limiter command calculation unit 112 and the winding switching command calculation unit 113. However, it is also possible to implement this by creating a table that only contains the winding switching conditions a1, a2, b1, and b2 based on the magnetic flux limiter value λlim* shown in Figures 8A and 8B.

[0061] Furthermore, in this embodiment, the winding switching command is calculated using the torque limiter command for each winding from the torque limiter command calculation unit 112. However, in the control of a PM motor, limiter processing is applied to the torque command that becomes the input to the feedback control system in order to prevent the feedback control system from diverging or becoming unstable. Therefore, the torque limiter command that is originally provided can also be used to calculate the winding switching command, and if it is shared as table data for calculating the torque limiter command for controlling the PM motor, then in effect, table data specifically required for calculating the winding switching command will not be necessary.

[0062] As explained above, according to this embodiment, instead of directly obtaining the winding switching command signal using a table map reference method, a method is used to select the winding connection state that can output a larger torque according to the operating state as the optimal winding. This makes it possible to reduce the number of table data while improving the accuracy of optimal winding selection for multiple fluctuating parameters. [Examples]

[0063] Referring to Figures 9 to 11B, a control device for an AC motor and a control method for an AC motor according to Embodiment 2 of the present invention will be described.

[0064] In Embodiment 2, in calculating the winding switching command signal Swc* to the winding switching device 104 by the winding switching command calculation unit 113, the determination results of comparing the magnitudes of the first positive torque limiter command Tlim-1p* and the second positive torque limiter command Tlim-2p* from the torque limiter command calculation unit 112, and the determination results of comparing the magnitudes of the first negative torque limiter command Tlim-1m* and the second negative torque limiter command Tlim-2m* are used, in addition to the determination results of comparing the magnitudes of the torque command Tm* from the inverter control unit 111 and each of the torque limiter commands Tlim-1p*, Tlim-1m*, Tlim-2p*, and Tlim-2m*.

[0065] This enables the selection of the optimal winding for more complex operating conditions and the setting of hysteresis during winding switching. This allows for the construction of a more optimal winding switching logic for torque control according to operating conditions such as forward and reverse, acceleration, and braking in electric vehicles, and also suppresses the occurrence of unnecessary winding switching. As a result, a control device for AC motors that enables more efficient operation than in Example 1 can be realized.

[0066] Figure 9 is a block diagram showing the schematic configuration of the control device 100a for the AC motor in this embodiment. Only the differences in configuration compared to Embodiment 1 (Figure 1) will be explained.

[0067] In Figure 9, the control device 100a for the AC motor in this embodiment can be realized by using a winding switching command calculation unit 113c instead of the winding switching command calculation unit 113 in Embodiment 1 (Figure 1). The other configurations are the same as in Embodiment 1 (Figure 1).

[0068] Figure 10 is a block diagram showing an example configuration of the winding switching command calculation unit 113c shown in Figure 9. As shown in Figure 10, the winding switching command calculation unit 113c comprises a magnitude comparison calculation unit 301, a magnitude comparison calculation unit 302, a magnitude comparison calculation unit 303c, a magnitude comparison calculation unit 304c, a magnitude comparison calculation unit 305c, a magnitude comparison calculation unit 306c, and a winding status signal calculation unit 401c. The winding switching command calculation unit 113c receives the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* from the torque limiter command calculation unit 112 or the torque limiter command calculation unit 112b, and the torque command Tm* from the inverter control unit 111 as inputs, calculates a winding switching command signal Swc* to select the optimal winding according to the operating state, and outputs it to the inverter control unit 111 and the winding switching device 104.

[0069] The magnitude comparison calculation unit 303c compares the magnitude of the first positive torque limiter command Tlim-1p*, which is the positive torque limiter value when the windings of the PM motor 103 are connected in series, with the torque command Tm* from the inverter control unit 111, and determines whether the windings of the PM motor 103 can output the torque required by the torque command Tm* when connected in series, and outputs the winding switching command signal Swc-1p*. The winding switching command signal Swc-1p* outputs, for example, 1 if the torque command Tm* is smaller than the first positive torque limiter command Tlim-1p*, and outputs 0 if the torque command Tm* is larger than the first positive torque limiter command Tlim-1p*.

[0070] The magnitude comparison calculation unit 304c compares the magnitude of the second positive torque limiter command Tlim-2p*, which is the positive torque limiter value when the windings of the PM motor 103 are connected in parallel, with the torque command Tm* from the inverter control unit 111. It determines whether the windings of the PM motor 103 can output the torque required by the torque command Tm* when connected in parallel, and outputs the winding switching command signal Swc-2p*. The winding switching command signal Swc-2p* outputs, for example, 1 if the torque command Tm* is smaller than the second positive torque limiter command Tlim-2p*, and outputs 0 if the torque command Tm* is larger than the second positive torque limiter command Tlim-2p*.

[0071] The magnitude comparison calculation unit 305c compares the magnitude of the first negative torque limiter command Tlim-1m*, which is the negative torque limiter value when the windings of the PM motor 103 are connected in series, with the torque command Tm* from the inverter control unit 111. It determines whether the windings of the PM motor 103 can output the negative torque required by the torque command Tm* when connected in series, and outputs the winding switching command signal Swc-1m*. The winding switching command signal Swc-1m* outputs, for example, 1 if the torque command Tm* is negatively smaller than the first negative torque limiter command Tlim-1m*, and outputs 0 if the torque command Tm* is negatively larger than the first negative torque limiter command Tlim-1m*.

[0072] The magnitude comparison calculation unit 306c compares the magnitude of the second negative torque limiter command Tlim-2m*, which is the negative torque limiter value when the windings of the PM motor 103 are connected in parallel, with the torque command Tm* from the inverter control unit 111. It determines whether the windings of the PM motor 103 can output the negative torque required by the torque command Tm* when connected in parallel, and outputs the winding switching command signal Swc-2m*. The winding switching command signal Swc-2m* outputs, for example, 1 if the torque command Tm* is negatively smaller than the second negative torque limiter command Tlim-2m*, and outputs 0 if the torque command Tm* is negatively larger than the second negative torque limiter command Tlim-2m*.

[0073] The winding status signal calculation unit 401c calculates a winding switching command signal Swc* for selecting the optimal winding according to the operating state, based on the winding switching command signal Swc-p* for positive torque commands from the magnitude comparison calculation unit 301, the winding switching command signal Swc-m* for negative torque commands from the magnitude comparison calculation unit 302, the winding switching command signal Swc-1p* from the magnitude comparison calculation unit 303c, the winding switching command signal Swc-2p* from the magnitude comparison calculation unit 304c, the winding switching command signal Swc-1m* from the magnitude comparison calculation unit 305c, the winding switching command signal Swc-2m* from the magnitude comparison calculation unit 306c, and the torque command Tm* from the inverter control unit 111, and outputs it to the inverter control unit 111 and the winding switching device 104.

[0074] Note that the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* are inputs for setting the hysteresis region during winding switching, but constants may be used instead.

[0075] The above describes the configuration example of Embodiment 2 of the present invention. Next, we will explain how Embodiment 2 improves the output of torque control and increases the efficiency of operation.

[0076] Figures 11A and 11B are map diagrams of the winding switching command in this embodiment. Figure 11A shows an example of the relationship between the motor rotation speed, DC voltage, and torque fluctuation parameters and the optimal winding status according to the operating state when the torque command is positive, and Figure 11B shows an example of the relationship between the motor rotation speed, DC voltage, and torque fluctuation parameters and the optimal winding status according to the operating state when the torque command is negative. Note that Figures 11A and 11B are map diagrams of the winding switching command when the torque limiter command calculation unit 112b is used instead of the torque limiter command calculation unit 112, and the horizontal axis of each graph is the reciprocal of the magnetic flux limiter value λlim*.

[0077] As shown in Figure 10, in Embodiment 2, the results of comparing the magnitude of each torque command Tm* and each torque limiter command Tlim-1p*, Tlim-1m*, Tlim-2p*, and Tlim-2m* are used. This makes it possible to determine whether the desired torque command Tm* is within the range where the PM motor 103 windings can output torque in both series and parallel connections, or only in series connection, or only in parallel connection, given the motor rotation speed and DC voltage operating conditions. This allows for the selection of the optimal winding according to the operating conditions of forward / reverse and positive / negative torque commands.

[0078] In Figure 11A, for example, when moving forward (motor rotation speed is positive) and the torque command Tm* is positive, instead of switching between the series-connected first winding state and the parallel-connected second winding state at point a1 where the relative magnitudes of the first positive torque limiter command Tlim-1p* and the second positive torque limiter command Tlim-2p* are reversed, the condition for switching windings is set to be when the magnetic flux limiter value λlim* is greater than point a3 where the first positive torque limiter command Tlim-1p* is less than 1.8 times the second positive torque limiter command Tlim-2p*, and the torque command Tm* is less than the first positive torque limiter command Tlim-1p*. This allows setting a previous value retention command to introduce a hysteresis region during winding switching. By setting a previous value retention command, the range of use in series connection can be expanded depending on the operating state, enabling more efficient operation.

[0079] Furthermore, in Figure 11B, for example, when moving forward (motor rotation speed is positive) and the torque command Tm* is negative, it is possible to suppress the occurrence of unnecessary winding changes by setting a command to retain the previous value, using the condition that the magnetic flux limiter value λlim* is smaller than point b1 where the relative magnitudes of the first negative torque limiter command Tlim-1m* and the second positive torque limiter command Tlim-2m* are reversed during forward movement.

[0080] Note that b3 in Figure 11B can be determined, similar to a1, by setting the condition that the first negative torque limiter command Tlim-1m* becomes negatively smaller than 1.8 times the value of the second negative torque limiter command Tlim-2m* during reverse movement. Furthermore, the coefficient 1.8 multiplied by the second positive torque limiter command Tlim-2p* and the second negative torque limiter command Tlim-2m* to set the hysteresis region is not limited to this value. For example, if the coefficient is set to 0, the selection region for the previous value retention command to set the hysteresis region for winding switching during forward movement with a positive torque command and during reverse movement with a negative torque command will be eliminated, and a winding switching command that selects parallel connection will be output in both cases.

[0081] As explained above, according to this embodiment, by calculating the winding switching command signal based on the results of the comparison between the torque command Tm* and each torque limiter command Tlim-1p*, Tlim-1m*, Tlim-2p*, and Tlim-2m*, it is possible to select the optimal winding for more complex operating conditions and suppress the occurrence of unnecessary winding switching by setting hysteresis in winding switching, thereby improving the efficiency of the AC motor control device. [Examples]

[0082] Referring to Figures 12 and 13, a control device for an AC motor and a control method for an AC motor according to Embodiment 3 of the present invention will be described.

[0083] In Embodiment 3, when the torque limiter command calculation unit 112 calculates the torque limiter command according to the connection state of the windings of the PM motor 103, in addition to the motor rotation speed and DC voltage, the influence of the magnet temperature fluctuation of the PM motor 103 is considered as a variable parameter for the winding switching condition. As a result, a more optimal winding can be selected in torque control according to the operating state, thereby realizing a control device for an AC motor that enables highly efficient operation.

[0084] Figure 12 is a block diagram showing the schematic configuration of the AC motor control device 100b in this embodiment. Only the differences in configuration compared to Embodiment 1 (Figure 1) will be explained.

[0085] In Figure 12, the control device 100b for the AC motor in this embodiment can be realized by adding a motor magnet temperature estimation unit 114d to the controller 101 of Embodiment 1 (Figure 1), and using a torque limiter command calculation unit 112d instead of a torque limiter command calculation unit 112. The other configurations are the same as in Embodiment 1 (Figure 1).

[0086] Figure 13 is a block diagram showing an example configuration of the torque limiter command calculation unit 112d shown in Figure 12. As shown in Figure 13, the torque limiter command calculation unit 112d comprises a first positive torque limiter command calculation unit 201d, a second positive torque limiter command calculation unit 202d, a first negative torque limiter command calculation unit 203d, and a second negative torque limiter command calculation unit 204d.

[0087] The torque limiter command calculation unit 112d takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103 from the inverter control unit 111, the DC voltage detection value Ecf from the smoothing capacitor 131, and the magnet temperature estimation value Tmag from the motor magnet temperature estimation unit 114d as inputs, calculates and outputs the first positive torque limiter command Tlim-1p*, which is the positive torque limiter value when the PM motor 103 is connected in series, the first negative torque limiter command Tlim-1m*, which is the negative torque limiter value when the motor is connected in series, the second positive torque limiter command Tlim-2p*, which is the positive torque limiter value when the motor is connected in parallel, and the second negative torque limiter command Tlim-2m*, which is the negative torque limiter value when the motor is connected in parallel.

[0088] In the torque limiter command calculation unit 112d, the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* can be constructed using a reference table that takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103, the DC voltage detection value Ecf, and the magnet temperature estimation value Tmag as input variables.

[0089] The table data referenced by the first positive torque limiter command calculation unit 201d, the second positive torque limiter command calculation unit 202d, the first negative torque limiter command calculation unit 203d, and the second negative torque limiter command calculation unit 204d is table data representing the correspondence between the electrical angular frequency ω1 of the rotational speed of the PM motor 103, the detected DC voltage value Ecf, and the estimated magnet temperature value Tmag, and the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m*, respectively. For example, data obtained in advance from tests or analyses may be used. Alternatively, instead of the reference table, a function formula, approximation formula, design formula, etc., may be used.

[0090] Furthermore, in the torque limiter command calculation unit 112d, the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* can also be configured using a reference table that takes the magnetic flux limiter value λlim* as an input variable, for example.

[0091] The table data referenced by the first positive torque limiter command calculation unit 201d, the second positive torque limiter command calculation unit 202d, the first negative torque limiter command calculation unit 203d, and the second negative torque limiter command calculation unit 204d is table data representing the correspondence between the magnetic flux limiter value λlim* and the estimated magnet temperature value Tmag, and the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m*, respectively. For example, data obtained in advance from tests or analyses may be used. Alternatively, instead of the reference table, a function formula, approximation formula, design formula, etc., may be used.

[0092] The motor magnet temperature estimation unit 114d estimates the magnet temperature of the PM motor 103. Alternatively, the motor magnet temperature estimation unit 114d may use a value estimated from the frame (housing) temperature and stator coil temperature of the PM motor 103, rather than the magnet temperature of the PM motor 103 itself. It may also detect or estimate the magnitude of the induced voltage corresponding to the rotational speed of the PM motor 103 and estimate the magnet temperature Tmag from that value. Furthermore, instead of the estimated magnet temperature, a magnet temperature detection value obtained by directly measuring the magnet temperature using a temperature sensor may be used.

[0093] As explained above, according to this embodiment, by calculating a torque limiter command according to the winding connection state using the motor rotation speed, DC voltage, and PM motor magnet temperature as variable parameters, it is possible to take into account the fluctuations in the output torque due to fluctuations in the PM motor magnet temperature. Therefore, it is possible to select a more optimal winding according to the operating state and improve the operating efficiency of the AC motor control device. [Examples]

[0094] Referring to Figures 14 and 15, a control device for an AC motor and a control method for an AC motor according to Embodiment 4 of the present invention will be described.

[0095] In Embodiment 4, when the torque limiter command calculation unit 112 calculates the torque limiter command according to the connection state of the windings of the PM motor 103, in addition to the motor rotation speed and DC voltage, the current limit value flowing to the PM motor 103 or power converter 102 is considered as a variable parameter for the winding switching condition. This enables torque control according to the state of the AC motor control system, and by selecting the optimal winding in accordance with the winding switching control, highly efficient operation becomes possible.

[0096] Figure 14 is a block diagram showing the schematic configuration of the control device 100c for the AC motor in this embodiment. Only the differences in configuration compared to Embodiment 1 (Figure 1) will be explained.

[0097] In Figure 14, the control device 100c for the AC motor in this embodiment can be realized by using a torque limiter command calculation unit 112e instead of a torque limiter command calculation unit 112e, and an inverter control unit 111e instead of an inverter control unit 111e, in the controller 101 of Embodiment 1 (Figure 1). The other configurations are the same as in Embodiment 1 (Figure 1).

[0098] Figure 15 is a block diagram showing an example configuration of the torque limiter command calculation unit 112e shown in Figure 14. As shown in Figure 15, the torque limiter command calculation unit 112e comprises a first positive torque limiter command calculation unit 201e, a second positive torque limiter command calculation unit 202e, a first negative torque limiter command calculation unit 203e, and a second negative torque limiter command calculation unit 204e.

[0099] The torque limiter command calculation unit 112e takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103 from the inverter control unit 111e, the DC voltage detection value Ecf from the smoothing capacitor 131, and the motor current limit value I1* from the inverter control unit 111e as inputs, calculates and outputs the first positive torque limiter command Tlim-1p*, which is the positive torque limiter value when the PM motor 103 is connected in series, the first negative torque limiter command Tlim-1m*, which is the negative torque limiter value when the PM motor 103 is connected in series, the second positive torque limiter command Tlim-2p*, which is the positive torque limiter value when the PM motor 103 is connected in parallel, and the second negative torque limiter command Tlim-2m*, which is the negative torque limiter value when the PM motor 103 is connected in parallel.

[0100] In the torque limiter command calculation unit 112e, the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* can be configured using a reference table that takes the electrical angular frequency ω1 of the rotational speed of the PM motor 103, the DC voltage detection value Ecf, and the motor current limit value I1* as input variables.

[0101] The table data referenced by the first positive torque limiter command calculation unit 201e, the second positive torque limiter command calculation unit 202e, the first negative torque limiter command calculation unit 203e, and the second negative torque limiter command calculation unit 204e is table data representing the correspondence between the electrical angular frequency ω1 of the rotational speed of the PM motor 103, the detected DC voltage value Ecf, and the motor current limit value I1*, and the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m*. For example, data obtained in advance from tests or analyses may be used. Alternatively, instead of the reference table, a function formula, approximation formula, design formula, etc., may be used.

[0102] Furthermore, in the torque limiter command calculation unit 112e, the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m* can also be configured using, for example, a reference table that takes the magnetic flux limiter value λlim* and the motor current limit value I1* as input variables.

[0103] The table data referenced by the first positive torque limiter command calculation unit 201e, the second positive torque limiter command calculation unit 202e, the first negative torque limiter command calculation unit 203e, and the second negative torque limiter command calculation unit 204e is table data representing the correspondence between the magnetic flux limiter value λlim* and the motor current limit value I1* and the first positive torque limiter command Tlim-1p*, the first negative torque limiter command Tlim-1m*, the second positive torque limiter command Tlim-2p*, and the second negative torque limiter command Tlim-2m*. For example, data obtained in advance from tests or analyses may be used. Alternatively, instead of the reference table, a function formula, approximation formula, design formula, etc., may be used.

[0104] The torque limiter command calculation unit 112e may use the inverter current limit value Iinv* instead of the motor current limit value I1*.

[0105] Furthermore, when heat generation becomes a problem, such as the magnet temperature and frame temperature of the PM motor 103, the coil temperature of the stator, the temperature of the switching elements Sup~Swn of the power converter 102, or the temperature of the housing, the torque limiter command corresponding to the winding connection state is calculated by using at least one of these temperature information values ​​as a variable parameter to adjust the motor current limit value I1* or inverter current limit value Iinv* according to the degree of heat generation, thereby preventing equipment failure due to heat generation in the control device of the AC motor.

[0106] The inverter control unit 111e calculates a voltage command to control the torque generated by the PM motor 103 based on the angle signal φ corresponding to the rotor position (rotation angle) of the PM motor 103 from the rotor position detection unit 124, the AC currents iu and iw flowing through the PM motor 103 from the phase current detection unit 121, and the DC voltage detection value Ecf from the smoothing capacitor 131. Based on this voltage command, it outputs a gate command signal generated by the calculation result of pulse width modulation.

[0107] Furthermore, the inverter control unit 111e calculates the electrical angular frequency ω1 of the rotational speed of the PM motor 103 based on the angle signal φ from the rotor position detection unit 124 and supplies it to the torque limiter command calculation unit 112e. In addition, it supplies the motor current limit value I1* to the torque limiter command calculation unit 112e. The motor current limit value I1* may be a constant, or it may be calculated using a reference table, a function formula, an approximation formula, a design formula, etc. Then, it calculates the torque command Tm* that has been limited based on the torque limiter command for each winding connection state from the torque limiter command calculation unit 112e and supplies it to the winding switching command calculation unit 113.

[0108] As described above, according to this embodiment, by calculating a torque limiter command according to the winding connection state using the motor rotation speed and DC voltage, as well as the motor current limit value I1* or inverter current limit value Iinv* as variable parameters, it is possible to select a more optimal winding according to the current limit value in the AC motor control device and suppress the temperature rise of the AC motor control device, thereby improving the operating efficiency of the AC motor control device.

[0109] The embodiments of the present invention have been described above. The same method can be applied to any AC motor other than permanent magnet synchronous motors (PM motors). For example, wound-wound synchronous motors and synchronous motors using reluctance torque are also applicable. Furthermore, the method can be similarly applied to the control of generators.

[0110] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0111] Furthermore, the configurations and processes exemplified in the above-described embodiments and modifications may be integrated, separated, or their processing order rearranged as appropriate depending on the implementation form and processing efficiency. Also, for example, some or all of the above-described embodiments and modifications may be combined to the extent that they do not contradict each other. [Explanation of Symbols]

[0112] 100, 100a, 100b, 100c... Control devices for AC motors 101, 101c, 101d, 101e… controllers 102... Power converter 103... AC motor (PM motor) 104...Winding switching device 111,111e… Inverter control unit 112, 112b, 112d, 112e... Torque limiter command calculation unit 113,113c...Winding switching command calculation unit 114d...Motor magnet temperature estimation unit 121... Phase current detection unit 123a, 123b… Input terminals 124... Rotor position detection unit 131...Smoothing capacitor 132…Main circuit section 133... Gate Driver 134…DC resistor 201, 201b, 201d, 201e... First positive torque limiter command calculation unit 202, 202b, 202d, 202e... Second positive torque limiter command calculation unit 203, 203b, 203d, 203e... First negative torque limiter command calculation unit 204, 204b, 204d, 204e... Second negative torque limiter command calculation unit 205b... Magnetic flux limiter command calculation unit 301,302,303c,304c,305c,306c...Size comparison calculation section 401, 401c... Winding status signal calculation unit Sup, Sun, Svp, Svn, Swp, Swn... switching elements.

Claims

1. An AC motor having multiple windings, The power converter that controls the aforementioned AC motor, A controller for controlling the power converter, The system includes a winding switching device that switches the connection state of the windings of the AC motor in response to a command from the controller, The controller includes a winding switching control unit that calculates a winding switching command for switching the connection state of the windings of the AC motor. The winding switching control unit is characterized by calculating a winding switching command to switch the connection state of the windings of the AC motor based on a torque limiter command for each connection state of the windings of the AC motor.

2. A control device for an AC motor according to claim 1, The winding switching control unit is a control device for an AC motor, characterized in that it calculates a torque limiter command for each connection state of the windings of the AC motor based on the rotational speed of the AC motor and the DC voltage of the power converter.

3. A control device for an AC motor according to claim 2, The control device for an AC motor is characterized in that the winding switching control unit calculates a magnetic flux limiter command that is proportional to the DC voltage of the power converter and inversely proportional to the rotational speed of the AC motor, and calculates a torque limiter command for each connection state of the windings of the AC motor based on the magnetic flux limiter command.

4. A control device for an AC motor according to claim 1, The winding switching control unit is characterized by calculating a winding switching command to switch the connection state of the windings of the AC motor based on the torque limiter command for each connection state of the windings of the AC motor and the torque command of the AC motor.

5. A control device for an AC motor according to claim 1, The aforementioned AC motor is a permanent magnet synchronous motor, The winding switching control unit is characterized by calculating a torque limiter command for each connection state of the windings of the permanent magnet synchronous motor based on the magnet temperature of the permanent magnet synchronous motor.

6. A control device for an AC motor according to claim 1, The control device for an AC motor is characterized in that the winding switching control unit calculates a torque limiter command for each connection state of the windings of the AC motor based on at least one of the current limit value of the AC motor and the current limit value of the power converter.

7. A control device for an AC motor according to claim 1, The control device for an AC motor is characterized in that the winding switching control unit calculates a torque limiter command for each connection state of the windings of the AC motor based on at least one of the housing temperature of the AC motor, the coil temperature of the AC motor, the housing temperature of the power converter, and the element temperature of the power converter.

8. A control device for an AC motor according to claim 1, The winding switching device is a control device for an AC motor, characterized in that it switches the connection state of at least some of the plurality of windings to either a series connection or a parallel connection.

9. A method for controlling an AC motor, which is performed by a control device for an AC motor equipped with a winding switching function, (a) A step of calculating the torque limiter command for each connection state of the windings of the AC motor, (b) A step of calculating a winding switching command to switch the connection state of the windings of the AC motor based on the torque limiter command obtained in step (a), A control method for an AC motor, characterized by having [a specific feature].

10. A control method for an AC motor according to claim 9, A method for controlling an AC motor, characterized in that the control device for the AC motor has a function to switch the connection state of at least some of the windings of the AC motor to either a series connection or a parallel connection.

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