Control device for electric motor

Abstract

To determine a control parameter of an electric motor without rotating the electric motor or conducting an overcurrent.SOLUTION: A control device 2 comprises: a parameter identification unit 5 which identifies parameters of an electric motor 1; and a current control unit 6 which determines a control parameter of the electric motor 1 on the basis of the parameters identified by the parameter identification unit 5 and controls the current of the electric motor. The parameter identification unit 5 includes: a resistance identification part 5a which identifies a resistance value when a specified DC voltage is applied to the electric motor 1; a time constant identification part 5b which identifies an electrical time constant when the specified DC voltage is applied to the electric motor 1; a magnetic pole position identification part 5c which identifies a magnetic pole position of the electric motor when the specified DC voltage is applied to the electric motor 1; and an inductance identification part 5d which identifies inductances of d-axis and q-axis, respectively, by using the identified magnetic pole position when a specified AC voltage is applied to the electric motor 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a control device for an electric motor. [Background technology]

[0002] Patent Document 1 discloses a control device having a function for automatically measuring the electrical constants of a permanent magnet type synchronous motor. This control device is equipped with a DC test means for determining the winding resistance, an AC test means for determining the inductance in the direction of the permanent magnet and inductance in the direction perpendicular to the permanent magnet, a rotation test means for determining the magnetic flux of the permanent magnet, and a setting storage means for storing the electrical constants determined by each means in a memory. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-312498 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the control device described in Patent Document 1, the DC test means for determining the winding resistance may pass an overcurrent to the motor or to the power conversion device that applies a voltage to the motor. Also, the inductance identification means cannot determine the inductance unless the rotor is in a state where it can rotate.

[0005] The present disclosure is made to solve the above-mentioned problems, and an object of the present disclosure is to provide a control device for an electric motor that can determine control parameters of the electric motor without rotating the electric motor and without passing an overcurrent. [Means for solving the problem]

[0006] The motor control device according to the present disclosure includes a parameter identification unit that outputs a voltage command to a power conversion device to apply a voltage to the motor for identifying parameters of the motor, and a current control unit that determines control parameters of the motor and controls a current of the motor. The parameter identification unit includes a resistance identification unit that identifies a resistance value of the motor when a specified DC voltage is applied to the motor from the power conversion device, a time constant identification unit that identifies an electrical time constant of the motor when the specified DC voltage is applied to the motor from the power conversion device, a magnetic pole position identification unit that identifies a magnetic pole position of the motor when the specified DC voltage is applied to the motor from the power conversion device, and an inductance identification unit that identifies a dq-axis inductance of the motor using the magnetic pole position when a specified AC voltage is applied to the motor from the power conversion device. The current control unit determines the control parameters of the motor based on the parameters identified by the parameter identification unit while the motor is stopped. Effect of the Invention

[0007] According to the motor control device according to the present disclosure, it is possible to determine the control parameters of the motor without rotating the motor and without passing an overcurrent. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a configuration of an electric motor drive system according to a first embodiment. [Diagram 2] 5 is a flowchart showing an example of a resistance value identification process performed by a resistance identifying unit in the first embodiment. [Diagram 3] 5 is a diagram showing an example of a time history of voltage and current when a resistance value is identified by a resistance identifying unit in the first embodiment. FIG. [Figure 4] 5 is a flowchart showing an example of a process of dead time correction by a resistance identifying unit in the first embodiment. [Diagram 5] 5 is a flowchart showing an example of a process of identifying a time constant by a time constant identifying unit in the first embodiment. [Figure 6] 4 is a diagram showing an example of a time history of voltage and current when a time constant is identified by a time constant identifying unit in the first embodiment. FIG. [Figure 7] 5 is a flowchart showing an example of a process for identifying a magnetic pole position by a magnetic pole position identifying unit according to the first embodiment. [Figure 8] 5 is a diagram showing an example of a time history of voltage and current when a magnetic pole position is identified by a magnetic pole position identifying unit in the first embodiment. FIG. [Figure 9] 5 is a flowchart showing an example of an inductance identification process performed by an inductance identifying unit according to the first embodiment. [Figure 10] 4 is a diagram showing an example of a time history of voltage and current when an inductance is identified by an inductance identifying unit in the first embodiment. FIG. [Figure 11] 13 is a flowchart showing an example of processing by a magnetic pole position identifying unit and an inductance identifying unit in a modification of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are given the same reference numerals. In this disclosure, duplicated descriptions will be appropriately simplified or omitted. In the following description, for convenience, the positional relationship of each structure may be expressed based on the illustrated state. Note that this disclosure is not limited to the following embodiments and their modified examples. Any components described in the following embodiments and their modified examples can be freely combined, modified, or omitted within the scope of the present disclosure.

[0010] Embodiment 1 Fig. 1 is a block diagram showing the configuration of an electric motor drive system according to embodiment 1. As shown in Fig. 1, the electric motor drive system according to the present embodiment includes an electric motor 1, a control device 2 for controlling the electric motor 1, a power conversion device 3 for driving the electric motor 1, a current sensor 4, and a brake 7.

[0011] The electric motor 1 is a permanent magnet type synchronous motor. Either a surface magnet type or an embedded magnet type can be used for the electric motor 1. The control device 2 outputs a voltage command to the power conversion device 3 for applying a voltage to the electric motor 1. The power conversion device 3 applies a voltage to the electric motor 1 according to the voltage command output from the control device 2. The power conversion device 3 is, for example, a PWM inverter. The current sensor 4 detects a current flowing through the electric motor 1. The current sensor 4 may detect three-phase currents of the electric motor 1, or may detect two-phase currents.

[0012] The control device 2 for the electric motor 1 includes a parameter identification unit 5 and a current control unit 6. The parameter identification unit 5 identifies the parameters of the electric motor 1. The parameter identification unit 5 outputs a voltage command to the power conversion device 3 for applying to the electric motor 1 a voltage for identifying the parameters of the electric motor 1. The current control unit 6 determines the control parameters of the electric motor 1 and controls the current of the electric motor 1.

[0013] The parameter identification unit 5 has a resistance identification unit 5a, a time constant identification unit 5b, a magnetic pole position identification unit 5c, and an inductance identification unit 5d. The parameter identification unit 5 outputs a voltage command corresponding to each of the resistance identification unit 5a, the time constant identification unit 5b, the magnetic pole position identification unit 5c, and the inductance identification unit 5d. As an example, the parameter identification unit 5 identifies parameters of the electric motor 1 using information on the output voltage command and information on the current detected by the current sensor 4 as input data. The current control unit 6 uses the parameters identified by the parameter identification unit 5 to determine control parameters.

[0014] The resistance identification unit 5a identifies the resistance value of the motor 1 when a specified DC voltage is applied to the motor 1 from the power conversion device 3. The time constant identification unit 5b identifies the time constant of the motor 1 when a specified DC voltage is applied to the motor 1 from the power conversion device 3. The magnetic pole position identification unit 5c identifies the magnetic pole position of the motor 1 when a specified DC voltage is applied to the motor 1 from the power conversion device 3. The inductance identification unit 5d identifies the dq-axis inductance of the motor 1 using the magnetic pole position when a specified AC voltage is applied to the motor 1 from the power conversion device 3. Then, the current control unit 6 determines the control parameters of the motor 1 based on the resistance value, time constant, magnetic pole position, and dq-axis inductance identified by each unit of the parameter identification unit 5 while the motor 1 is stopped. With this configuration, the control parameters of the motor 1 can be determined without rotating the motor 1 and without passing an overcurrent.

[0015] The brake 7 brakes the motor 1. The brake 7 is used to lock the shaft of the motor 1. When identifying the parameters of the motor 1, the parameter identification unit 5 outputs a voltage command for identifying the parameters to the power conversion device 3. The power conversion device 3 applies a voltage to the motor 1 according to the voltage command. At this time, depending on the voltage command or the specifications of the motor 1, the shaft of the motor 1 may rotate. When the shaft of the motor 1 rotates, the identification accuracy of the magnetic pole position deteriorates. In addition, the occurrence of an induced voltage also deteriorates the identification accuracy of the resistance value, the time constant, and the inductance. For this reason, it is more preferable to perform the identification of the parameters of the motor 1 in a state in which the motor 1 is braked by the brake 7 so that the shaft does not rotate.

[0016] In the following, specific examples of parameter identification by the resistance identification unit 5a, the time constant identification unit 5b, the magnetic pole position identification unit 5c, and the inductance identification unit 5d that constitute the parameter identification unit 5 will be described in more detail.

[0017] 2 is a flowchart showing an example of a process of resistance value identification by the resistance identifying unit 5a in the embodiment 1. When the identification of the resistance value is started by the parameter identifying unit 5, the resistance identifying unit 5a outputs a voltage command so that the voltage applied to the electric motor 1 is increased stepwise (step S201).

[0018] As an example, the resistance identification unit 5a outputs a voltage command to apply a voltage for three phases to the motor 1. The resistance identification unit 5a may output a voltage command to apply a voltage for one phase to the motor 1, or may output a voltage command to apply a voltage for two phases to the motor 1. When a voltage for one phase is applied to the motor 1, the resistance value in the phase to which the voltage is applied can be identified. When a voltage for two phases is applied to the motor 1, the resistance values ​​in the two phases to which the voltage is applied can be identified. When a voltage for three phases is applied to the motor 1, the resistance values ​​in all phases can be identified.

[0019] After the process of step S201, the resistance identification unit 5a judges whether or not the current value detected by the current sensor 4 reaches a specified current value for acquiring data for resistance value identification (step S202). If the current does not reach the specified current value, the process returns to step S201. If the current reaches the specified current value, the resistance identification unit 5a acquires and stores data on the voltage and current as data for resistance value identification (step S203).

[0020] It is desirable to obtain two or more points of voltage and current data for resistance value identification. In other words, it is desirable to set two or more specified current values ​​when obtaining data for resistance value identification. This makes it possible to identify the resistance value using the amount of change in voltage and current. With such a method for identifying the resistance value, it is possible to eliminate the influence of an error that exists between the voltage command and the voltage actually applied by the power conversion device 3, and to improve the identification accuracy. The method for identifying the resistance value using the amount of change in voltage and current will be described in detail later.

[0021] After the process of step S203, the resistance identification unit 5a determines whether the current value detected by the current sensor 4 is equal to or greater than a reference current value (step S204). The reference current value is set as, for example, a rated current of the electric motor 1 or an allowable current of the power conversion device 3.

[0022] When the voltage applied to the motor 1 is increased stepwise by the process of step S201, the current value of the motor 1 also increases stepwise. If an excessive current flows at this time, it may cause demagnetization and burning of the motor 1. In addition, if an excessive current flows, it may cause damage to the power conversion device 3. Therefore, the rated current of the motor 1 or the reference current of the power conversion device 3 is set as the reference current value to control the applied voltage. This can prevent damage to each piece of hardware.

[0023] If the current is less than the reference current value in step S204, the process returns to step S201. If the current is equal to or greater than the reference current value in step S204, the process stops the application of voltage to the motor 1 (step S205). When the application of voltage is stopped, the resistance value is identified using the data acquired in step S203 (step S206).

[0024] Here, the principle of resistance value identification by the resistance identifying unit 5a will be described. Two current values ​​acquired as data for resistance value identification are I1 and I2. Voltage values ​​in the voltage command at those times are V1 and V2. The voltage value actually applied to the motor 1 by the power conversion device 3 is V1. * and V2 * Let us assume that.

[0025] The relationship between the voltage value in the voltage command and the voltage value actually applied is expressed by the following equations (1) and (2). Furthermore, according to Ohm's law, the resistance value R can be calculated by the following equation (3). Note that ΔV means the error that exists between the voltage command and the voltage actually applied.

[0026] TIFF2024176069000002.tif1863

[0027] The voltage information obtained by the resistance identification unit 5a of the parameter identification unit 5 is voltage command information. The resistance identification unit 5a uses the voltage command information to obtain a resistance identification value R * The resistance identification value R* can be expressed by the following formula (4) using the voltage value V1 and the voltage value V2 in the voltage command.

[0028] TIFF2024176069000003.tif6160

[0029] In this way, the resistance identification value R is calculated using the voltage difference and the current difference. * By calculating the above, the error between the voltage command and the actual voltage can be offset, and the resistance value can be identified with high accuracy.

[0030] Fig. 3 is a diagram showing an example of a time history of voltage and current when resistance value identification is performed by resistance identification unit 5a in embodiment 1. The voltage in Fig. 3 indicates the phase voltage of motor 1. The current in Fig. 3 indicates the phase current of motor 1. Note that Fig. 3 shows a time history for one phase, but the voltage applied for resistance value identification may be for three phases or two phases, as described above.

[0031] An example in which a ramp function is used as a stepwise voltage command is shown in Fig. 3. However, other functions may be used instead of the ramp function as long as the voltage command increases stepwise.

[0032] When the voltage is increased stepwise, the current value also increases accordingly. The voltage is increased until the current reaches the reference current value. During this time, data on the voltage command and current value is acquired at two or more points. In the example of Figure 3, the voltage command voltage values ​​V1 and V2 and the current values ​​I1 and I2 are acquired.

[0033] Here, the voltage value of the voltage command when the current reaches the reference current value may be stored as the reference voltage value. This reference voltage value is a voltage value required to supply the reference current value to the motor 1. The reference voltage value can be used by each unit other than the resistance identification unit 5a of the parameter identification unit 5 when identifying parameters.

[0034] When the power conversion device 3 is a PWM inverter, a voltage drop occurs due to dead time. Therefore, it is preferable to perform dead time correction (Td correction). Dead time correction is performed according to the sign of the current. If the current is positive, a positive Td correction value is added to the voltage command, and if the current is negative, a negative Td correction value is added to the voltage command. Note that the Td correction value may chatter near where the current becomes zero, which may prevent accurate correction. Therefore, processing may be performed to smooth the Td correction value near where the current becomes zero.

[0035] In the resistance identification unit 5a in this embodiment, the resistance value is identified by a stepwise increasing DC voltage, so the sign of the applied voltage is known. In addition, the sign of the current is also known and is the same as the sign of the voltage. Therefore, by performing dead time correction according to the sign of the applied voltage, it is possible to compensate for the voltage drop due to the dead time of the power conversion device 3 with a simple feedforward configuration.

[0036] 4 is a flowchart showing an example of the process of dead time correction by the resistance identifying unit 5a in the first embodiment. First, the resistance identifying unit 5a judges whether or not the voltage command is positive (step S401). If the voltage command is positive, a positive current flows, and therefore a positive Td correction value is added to the voltage command (step S402). If the voltage command is negative, a negative current flows, and therefore a negative Td correction value is added to the voltage command (step S403).

[0037] As described above, the resistance identification unit 5a of the parameter identification unit 5 can accurately identify the resistance value of the motor 1 while preventing damage to the hardware. In this embodiment, by gradually increasing the voltage command while monitoring the current value of the motor 1, it is possible to apply a voltage within a range that does not exceed the allowable current of the motor 1 or the power conversion device 3. Furthermore, by identifying the resistance value using the difference between the voltage and the current, it is possible to accurately identify the resistance value. Moreover, by performing dead time correction according to the sign of the voltage, it is possible to compensate for the voltage drop due to the dead time with a simple configuration.

[0038] Next, a specific example of identification of a time constant by the time constant identification unit 5b of the parameter identification unit 5 will be described. The "time constant" identified by the time constant identification unit 5b means an electrical time constant T=L / R determined by the resistance value R and inductance L of the electric motor 1.

[0039] When the motor 1 is stopped, the transfer characteristics from the voltage to the current of the motor 1 can be expressed by an equivalent circuit in which a resistance value R and an inductance value L are connected in series. When a voltage is applied in a stepped manner, the current responds as a first-order lag system. Here, the time constant can be identified by measuring the time at which the current reaches a specified percentage of the convergence value, for example, 63%.

[0040] 5 is a flowchart showing an example of a process of time constant identification by the time constant identifying unit 5b in the first embodiment. The time constant identifying unit 5b outputs a voltage command to apply the reference voltage value acquired by the resistance identifying unit 5a in a stepped manner (step S501). As described above, the reference voltage value is a voltage value when a current of the reference current value is applied. By using this reference voltage value, it is possible to prevent an overcurrent from flowing in the electric motor 1 or the power conversion device 3. Furthermore, by using the reference voltage value, the current value of the electric motor 1 is known in advance, making it easier to identify the time constant.

[0041] After the process of step S501, the time constant identification unit 5b starts measuring the time from the application of the voltage (step S502). In this embodiment, the time constant is identified from the time it takes for the current of the motor 1 to reach 63%, which is a specified percentage of the reference current value. After the process of step S502, it is determined whether the current of the motor 1 has reached 63% of the reference current value (step S503). If the current has not reached 63% of the reference current value, the application of the voltage and the measurement of the time are continued. If the current has reached 63% of the reference current value, the measurement of the time is stopped (step S504). Then, the time constant is identified from the measured time (step S505).

[0042] Although an example of applying a voltage of a reference voltage value has been shown, the time constant may be identified by applying a voltage of an arbitrary voltage value. In this case, for example, after measuring how much current flows for an arbitrary voltage command, the same voltage command is applied and the time until the measured current reaches a specified ratio may be measured.

[0043] If the resistance value has already been identified by the resistance identifying unit 5a, it is possible to obtain the inductance L of the motor 1 as L=T×R* using the time constant identified value T and the resistance identified value R*. However, since the inductance L differs for each of the d-axis and q-axis in the interior permanent magnet type motor 1, it is difficult to accurately identify the inductance L at this point. Therefore, it is recommended to perform identification by the inductance identifying unit 5d as described below.

[0044] FIG. 6 is a diagram showing an example of the time history of the voltage and current when the time constant is identified by the time constant identifying unit 5b in the first embodiment. As described above, the time constant identifying unit 5b outputs a voltage command so that the voltage of the reference voltage value is applied in a stepwise manner. The voltage to be applied may be for one phase, two phases, or all three phases, as in the case of resistance value identification. The time is measured from the start of voltage application, and the time T at which the current value reaches 63%, which is a specified ratio of the reference current value, is identified as the time constant identification value T. Note that here, the reference of the current for identifying the time constant is set to 63% of the reference current value, which is a general theoretical value, but any value may be set as long as the time constant can be measured. In addition, the time constant identifying unit 5b may perform dead time correction in the same manner as the resistance identifying unit 5a, and may set a value obtained by adding a Td correction value as the voltage command value.

[0045] As described above, the time constant identifying section 5b of the parameter identifying section 5 can identify the time constant of the electric motor 1 while preventing damage to the hardware by using the reference voltage value determined by the resistance identifying section 5a.

[0046] Next, a specific example will be described of identification of the magnetic pole position by the magnetic pole position identifying unit 5c of the parameter identifying unit 5. In this embodiment, a pulse voltage is applied to the electric motor 1, and the magnetic pole position is identified from the current at that time.

[0047] When a pulse voltage is applied, if the phase of the magnetic poles of the rotor of the motor 1 and the phase of the applied voltage are in the same direction, the magnetic flux due to the current generated by the applied voltage and the magnetic flux of the rotor magnet will be in the same direction. As a result, the total magnetic flux value becomes large, and magnetic saturation occurs in the iron core of the motor 1. When magnetic saturation occurs, the winding inductance of the motor 1 becomes small, and the current amplitude of the motor 1 becomes large. On the other hand, when the phase of the magnetic poles of the rotor and the phase of the applied voltage are in opposite directions, the magnetic flux due to the current generated by the applied voltage and the magnetic flux of the rotor magnet will be in opposite directions. As a result, the total magnetic flux value becomes small, and magnetic saturation does not occur in the iron core of the motor 1. When magnetic saturation does not occur, the winding inductance of the motor 1 becomes large, and the current amplitude of the motor 1 becomes small.

[0048] In this way, the degree of magnetic saturation of the iron core of the motor 1 differs depending on the relationship between the phase of the rotor's magnetic poles and the phase of the applied voltage, and the current amplitude of the motor 1 changes. This property is used to identify the magnetic pole position.

[0049] 7 is a flowchart showing an example of a process for identifying a magnetic pole position by the magnetic pole position identifying unit 5c.First, the pulse width of a pulse voltage is determined using the time constant identified by the time constant identifying unit 5b (step S701).

[0050] As described above, it is necessary to pass a current so that magnetic saturation occurs in the motor 1. It is necessary to apply a pulse voltage so that a current that causes magnetic saturation flows through the motor 1. The simplest method for this is to apply a voltage of the maximum amplitude that can be applied. However, if a voltage of the maximum amplitude is applied for a long period of time, an excessive current that may cause damage may flow through the motor 1 or the power conversion device 3. Therefore, it is advisable to determine the pulse width of the pulse voltage using the identified time constant. Since it is possible to know in advance how much current will flow for the applied pulse voltage, it is possible to pass a current that causes magnetic saturation while preventing overcurrent.

[0051] After the pulse width of the pulse voltage is determined in the process of step S701, the pulse voltage is actually applied to the electric motor 1 (step S702). Then, the current when the pulse voltage is applied is measured (step S703). The pulse voltage is applied intermittently multiple times in different angular directions of the electrical angle of the electric motor 1 while changing the phase. Each time the pulse voltage is applied multiple times, the current is measured. After the processes of steps S702 and S703, the magnetic pole position is identified using the measured current (step S704).

[0052] Fig. 8 is a diagram showing an example of a time history of voltage and current when the magnetic pole position is identified by the magnetic pole position identifying unit 5c in the first embodiment. Fig. 8 shows an example in which voltage is applied while changing the phase on the α-axis and β-axis of the electric motor 1. Note that the voltage application is not limited to the αβ-axis, and may be applied in three phases from the beginning. Also, Fig. 8 shows an example in which the pulse voltage is applied six times, but the number of times the pulse voltage is applied may be any number of times as long as the magnetic pole position can be identified.

[0053] In magnetic pole position identification, current is measured every time a pulse voltage is applied. In the example of FIG. 8, Iα1 to Iα6 and Iβ1 to Iβ6 are measured. The magnetic pole position can be identified by the amplitude of these currents increasing or decreasing due to magnetic saturation. The calculation formula for magnetic pole position identification is the following formula (5). Here, θ represents the magnetic pole position.

[0054] TIFF2024176069000004.tif873

[0055] As described above, the magnetic pole position identification unit 5c of the parameter identification unit 5 can identify the magnetic pole position of the motor 1 while preventing damage to the hardware by adjusting the width of the pulse voltage using the time constant determined by the time constant identification unit 5b.

[0056] Next, a specific example of identification of the inductance L by the inductance identification unit 5d of the parameter identification unit 5 will be described. The dq axes of the motor 1 can be determined by using the magnetic pole position of the motor 1 identified by the magnetic pole position identification unit 5c. The inductance L of the dq axes can be identified by applying an AC voltage to the determined dq axes and measuring the current, which is the response.

[0057] When the motor 1 is stopped, the transfer characteristics from voltage to current of the motor 1 can be expressed by an equivalent circuit in which resistance R and inductance L are connected in series. In this case, if a high-frequency AC voltage is applied, the response of the current to the voltage can be considered to depend only on inductance L, and it is possible to identify inductance L from the ratio of voltage to current. This makes it possible to identify inductance L even if the motor 1 is an interior permanent magnet type.

[0058] At this time, if the amplitude of the applied AC voltage is too large, there is a possibility that an excessive current will flow to the motor 1 or the power conversion device 3. Therefore, similar to the resistance identification unit 5a, it is advisable to output a voltage command to increase the voltage amplitude stepwise, and perform inductance identification while preventing an overcurrent. Note that the frequency of the AC voltage is arbitrary, but it is necessary that the frequency be such that the motor 1 can be regarded as having only an inductance component, generally a frequency of several hundred Hz or more.

[0059] 9 is a flowchart showing an example of the process of inductance identification by the inductance identifying unit 5d in the first embodiment. The inductance identifying unit 5d outputs a voltage command so that an AC voltage for inductance identification is applied to the electric motor 1 while increasing the amplitude stepwise (step S901). After the process of step S901, it is determined whether the current of the electric motor 1 is equal to or greater than a reference current value (step S902). If the current is smaller than the reference value, the process returns to step S901 and the amplitude of the AC voltage is increased stepwise.

[0060] If the current of the electric motor 1 is equal to or greater than the reference current value, the amplitude of the AC voltage is fixed (step S903). After the amplitude is fixed, data for inductance identification is acquired (step S904). The data for inductance identification is information on the amplitude of the voltage and current. Note that the information on the amplitude of the voltage may be information on the amplitude of the voltage in the voltage command. As a method for acquiring the amplitude of the current, a Fourier transform may be used, or the maximum and minimum values ​​of the current may be measured, or the amplitude of the current may be measured by any other method.

[0061] Inductance identification is performed using the data acquired in the process of step S904 (step S905). The identification equation for inductance L is expressed by the following equation (6): where ω is the frequency of the AC voltage, Va is the voltage amplitude, and Iaa is the current amplitude.

[0062] TIFF2024176069000005.tif749

[0063] 10 is a diagram showing an example of a time history of voltage and current when inductance is identified by the inductance identifying unit 5d in the first embodiment. As described above, the voltage amplitude is increased until the current of the motor 1 reaches the reference current value, and when the current reaches the reference current value, the voltage amplitude is fixed and information on the amplitude of the voltage and current, which is data for inductance identification, is acquired. Then, using the acquired data, the inductance L is identified by equation (6). When identifying the inductance L of each of the d-axis and q-axis, for example, the inductance identification for each axis is performed independently, for example, the inductance identification for the q-axis is performed after the inductance identification for the d-axis.

[0064] The inductance identification unit 5d of the parameter identification unit 5 gradually increases the applied voltage while monitoring the current value, thereby enabling voltage application within a range that does not exceed the allowable current of the motor 1 or the power conversion device 3. This makes it possible to identify the inductance L of the motor 1 while preventing damage to the hardware.

[0065] Information on each parameter identified by the parameter identification unit 5 is sent to the current control unit 6. The current control unit 6 determines a control gain using the identified resistance value R and inductance L, etc., and can perform control on the dq axis using the identified magnetic pole position. In addition, the current of the electric motor 1 detected by the current sensor 4 is converted to a dq axis current using the identified magnetic pole position. This series of controls makes it possible to perform current control even for an electric motor 1 whose parameters are unknown. And, as described above, the parameters can be identified and the control parameters can be determined without rotating the electric motor 1 and without passing an overcurrent.

[0066] 11 is a flowchart showing an example of processing by the magnetic pole position identifying unit 5c and the inductance identifying unit 5d in the modification of embodiment 1. In this modification, the magnetic pole position identifying unit 5c and the inductance identifying unit 5d are repeatedly performed multiple times to improve the identification accuracy of each parameter.

[0067] First, the magnetic pole position is identified by the magnetic pole position identifying unit 5c (step S1101). In the first step S1101, as in the above embodiment, a pulse voltage having a pulse width determined using the time constant identified by the time constant identifying unit 5b is applied to identify the magnetic pole position. After the process of step S1101, the inductance identifying unit 5d identifies the inductance (step S1102).

[0068] Next, the time constant is re-identified using the inductance identified in step S1102, and the pulse width of the pulse voltage for identifying the magnetic pole position is determined again (step S1103). After the processing of step S1103, it is determined whether or not parameter identification has been performed a specified number of times (step S1104). If identification has not been performed the specified number of times, the process returns to step S1101, and the magnetic pole position is identified again by the pulse voltage with the pulse width determined in step S1103. Then, the dq axes are established using the re-identified magnetic pole position, and the inductance is identified again. Furthermore, the pulse width of the pulse voltage for identifying the magnetic pole position is determined again using the re-identified inductance. Then, it is determined whether or not parameter identification has been performed a specified number of times.

[0069] In this manner, by repeatedly identifying the pulse width and inductance of the pulse voltage for identifying the magnetic pole position, the identification accuracy is improved, and highly reliable parameters can be obtained. If it is determined in step S1104 that the identification has been completed the specified number of times, the last identified magnetic pole position and inductance are determined and stored as the final identified values ​​(step S1105). Note that, in this modified example as well, it is desirable to perform parameter identification while the motor 1 is braked by the brake 7 so as not to rotate.

[0070] Various aspects of the present disclosure are summarized below as appendices.

[0071] (Appendix 1) a parameter identification unit that outputs a voltage command to a power conversion device for applying a voltage to the electric motor for identifying parameters of the electric motor; a current control unit that determines a control parameter of the electric motor and controls a current of the electric motor; Equipped with The parameter identification unit a resistance identification unit that identifies a resistance value of the motor when a specified DC voltage is applied to the motor from the power conversion device; a time constant identification unit that identifies an electrical time constant of the electric motor when the specified DC voltage is applied to the electric motor from the power conversion device; a magnetic pole position identifying unit that identifies a magnetic pole position of the electric motor when the specified DC voltage is applied from the power conversion device to the electric motor; an inductance identification unit that identifies a dq-axis inductance of the motor using the magnetic pole position when a specified AC voltage is applied to the motor from the power conversion device; having The motor control device according to claim 1, wherein the current control unit determines the control parameters of the motor based on the parameters identified by the parameter identification unit while the motor is stopped. (Appendix 2) 2. The motor control device according to claim 1, wherein the parameter identification unit identifies the parameters of the motor in a state in which the motor is braked by a brake. (Appendix 3) 3. The motor control device according to claim 1, wherein the resistance identification unit increases the specified DC voltage in a stepwise manner until a current of the motor reaches a reference current value, and identifies the resistance value from an amount of change in the DC voltage and an amount of change in the current of the motor. (Appendix 4) 4. The motor control device of claim 1, wherein the time constant identification unit stores as a reference voltage value a voltage value of the specified DC voltage when a current of the motor becomes a reference current value, applies the reference voltage value to the motor in steps as the specified DC voltage, and identifies the electrical time constant by measuring the time it takes for the current of the motor to reach a specified proportion of the reference current value. (Appendix 5) 5. The motor control device according to claim 1, wherein at least one of the resistance identification unit and the time constant identification unit performs dead time correction of the power conversion device in accordance with the sign of the specified DC voltage. (Appendix 6) 6. The motor control device according to claim 1, wherein the magnetic pole position identification unit outputs a voltage command to apply to the motor a pulsed voltage having a pulse width determined from the electrical time constant, and identifies the magnetic pole position from a current of the motor when the pulsed voltage is intermittently applied a plurality of times in different angular directions of an electrical angle of the motor. (Appendix 7) 7. The motor control device of claim 1, wherein the inductance identification unit applies a high-frequency voltage to a d-axis or q-axis of the motor using the magnetic pole position, increases an amplitude of the high-frequency voltage in stages until a current of the motor reaches a reference current value, and identifies an inductance of the d-axis or q-axis from the high-frequency voltage and the current of the motor. (Appendix 8) the magnetic pole position identifying unit, after the inductance identifying unit has completed identifying the inductance, determines again the pulse width using the inductance identified by the inductance identifying unit, and identifies the magnetic pole position again; 7. The motor control device according to claim 6, wherein the inductance identification unit performs inductance identification again by using the re-identified magnetic pole position. [Explanation of symbols]

[0072] REFERENCE SIGNS LIST 1 electric motor, 2 control device, 3 power conversion device, 4 current sensor, 5 parameter identification section, 5a resistance identification section, 5b time constant identification section, 5c magnetic pole position identification section, 5d inductance identification section, 6 current control section, 7 brake

Claims

1. a parameter identification unit that outputs a voltage command to a power conversion device for applying a voltage to the electric motor for identifying parameters of the electric motor; a current control unit that determines a control parameter of the electric motor and controls a current of the electric motor; Equipped with The parameter identification unit a resistance identification unit that identifies a resistance value of the electric motor when a specified DC voltage is applied to the electric motor from the power conversion device; a time constant identification unit that identifies an electrical time constant of the electric motor when the specified DC voltage is applied to the electric motor from the power conversion device; a magnetic pole position identifying unit that identifies a magnetic pole position of the electric motor when the specified DC voltage is applied from the power conversion device to the electric motor; an inductance identification unit that identifies dq-axis inductances of the motor using the magnetic pole position when a specified AC voltage is applied to the motor from the power conversion device; having The motor control device according to claim 1, wherein the current control unit determines the control parameters of the motor based on the parameters identified by the parameter identification unit while the motor is stopped.

2. The motor control device according to claim 1 , wherein the parameter identification unit identifies the parameters of the motor in a state in which the motor is braked by a brake.

3. 3. The motor control device according to claim 1, wherein the resistance identification unit increases the specified DC voltage in stages until the current of the motor reaches a reference current value, and identifies the resistance value from an amount of change in the DC voltage and an amount of change in the current of the motor.

4. 3. The motor control device according to claim 1, wherein the time constant identification unit stores the voltage value of the specified DC voltage when the current of the motor becomes a reference current value as a reference voltage value, applies the reference voltage value to the motor in steps as the specified DC voltage, and identifies the electrical time constant by measuring the time it takes for the current of the motor to reach a specified proportion of the reference current value.

5. 3. The motor control device according to claim 1, wherein at least one of the resistance identifying section and the time constant identifying section performs dead time correction of the power conversion device in accordance with the sign of the specified DC voltage.

6. 3. The motor control device according to claim 1, wherein the magnetic pole position identification unit outputs a voltage command to apply to the motor a pulsed voltage having a pulse width determined from the electrical time constant, and identifies the magnetic pole position from a current of the motor when the pulsed voltage is intermittently applied a plurality of times in different angular directions of an electrical angle of the motor.

7. 3. The motor control device according to claim 1, wherein the inductance identification unit applies a high-frequency voltage to the d-axis or q-axis of the motor using the magnetic pole position, gradually increases the amplitude of the high-frequency voltage until the current of the motor reaches a reference current value, and identifies the inductance of the d-axis or q-axis from the high-frequency voltage and the current of the motor.

8. the magnetic pole position identifying unit, after the inductance identifying unit has completed identifying the inductance, determines again the pulse width using the inductance identified by the inductance identifying unit, and identifies the magnetic pole position again; The motor control device according to claim 6 , wherein the inductance identification unit performs inductance identification again by using the re-identified magnetic pole position.

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