Motor control device

Abstract

Provided is a motor control device. The control parameters of the motor are determined without rotating the motor and without passing an overcurrent. The control device (2) is provided with: a parameter identification unit (5) that identifies a parameter of the motor (1); and a current control unit (6) that determines a control parameter of the motor (1) on the basis of the parameter identified by the parameter identification unit (5), and controls the current of the motor. The parameter identification unit (5) includes a resistance identification unit (5a) that identifies a resistance value when a predetermined DC voltage is applied to the motor (1), a time constant identification unit (5b) that identifies an electrical time constant when the predetermined DC voltage is applied to the motor (1), and a magnetic pole position identification unit (5c) that identifies a magnetic pole position of the motor when the predetermined DC voltage is applied to the motor (1). And an inductance identification unit (5d) that identifies the inductance of the dq axis by using the identified magnetic pole position when a predetermined AC voltage is applied to the motor (1).

Description

Technical Field

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

[0002] Patent Document 1 discloses a control device having a function of automatically measuring the electrical constants of a permanent magnet type synchronous motor. The control device includes a DC test unit for obtaining winding resistance, an AC test unit for obtaining the inductance in the direction of the permanent magnet and the inductance in the direction perpendicular to the permanent magnet, a rotation test unit for obtaining the magnetic flux of the permanent magnet, and a setting storage unit for storing the electrical constants obtained by each unit in a memory.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-312498 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the control device described in Patent Document 1, the DC test unit for determining the winding resistance may pass an overcurrent to the motor or a power converter for applying voltage to the motor. In addition, the inductance identification unit cannot determine the inductance if the rotor is not in a rotatable state.

[0008] The present disclosure is to solve the above-mentioned problem. An object of the present disclosure is to provide a control device for a motor that can determine a control parameter of a motor without rotating the motor and without passing an overcurrent.

[0009] Means used to solve problems

[0010] The control device of the motor disclosed in the present invention comprises: a parameter identification unit that outputs a voltage instruction to a power conversion device, the voltage instruction being used to apply a voltage for identifying the parameters of the motor to the motor; and a current control unit that determines the control parameters of the motor and controls the current of the motor. The parameter identification unit comprises: a resistance identification unit that identifies the resistance value of the motor when a predetermined DC voltage is applied from the power conversion device to the motor; a time constant identification unit that identifies the electrical time constant of the motor when the predetermined DC voltage is applied from the power conversion device to the motor; a magnetic pole position identification unit that identifies the magnetic pole position of the motor when the predetermined DC voltage is applied from the power conversion device to the motor; and an inductance identification unit that identifies the inductance of the dq axis of the motor using the magnetic pole position when a predetermined AC voltage is applied from the power conversion device to the motor. The current control unit determines the control parameters of the motor based on the parameters identified by the parameter identification unit during the stop of the motor.

[0011] Effects of the Invention

[0012] According to the electric motor control device of the present disclosure, it is possible to determine the control parameters of the electric motor without rotating the electric motor and without passing an overcurrent. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a block diagram showing the configuration of the motor drive system according to the first embodiment.

[0014] Figure 2 This is a flowchart showing an example of a process of identifying a resistance value by the resistance identification unit in the first embodiment.

[0015] Figure 3 This is a diagram showing an example of the time history of voltage and current when the resistance identification unit in the first embodiment identifies the resistance value.

[0016] Figure 4 This is a flowchart showing a processing example of dead time correction performed by the resistance identification unit in the first embodiment.

[0017] Figure 5 1 is a flowchart showing an example of a process of time constant identification performed by the time constant identification unit in the first embodiment.

[0018] Figure 6 This is a diagram showing an example of the time history of voltage and current when the time constant identification unit in the first embodiment performs the time constant identification.

[0019] Figure 7This is a flowchart showing an example of processing of magnetic pole position identification performed by the magnetic pole position identification unit in the first embodiment.

[0020] Figure 8 This is a diagram showing an example of the time history of voltage and current when the magnetic pole position identification unit in the first embodiment performs magnetic pole position identification.

[0021] Fig. 9 1 is a flowchart showing an example of inductance identification processing performed by the inductance identification unit in the first embodiment.

[0022] Fig.10 This is a diagram showing an example of the time history of voltage and current when the inductance identification unit in the first embodiment performs inductance identification.

[0023] Fig.11 This is a flowchart showing a processing example of the magnetic pole position identification unit and the inductance identification unit in the modification example of the first embodiment.

[0024] Description of Reference Numerals

[0025] 1 electric motor, 2 control device, 3 power conversion device, 4 current sensor, 5 parameter identification unit, 5a resistance identification unit, 5b time constant identification unit, 5c magnetic pole position identification unit, 5d inductance identification unit, 6 current control unit, 7 brake. DETAILED DESCRIPTION

[0026] Hereinafter, the embodiments are described with reference to the accompanying drawings. In each of the drawings, the same reference numerals are given to the same or corresponding parts. In the present disclosure, repeated descriptions are appropriately simplified or omitted. In the following description, for convenience, the positional relationship of each structure is sometimes expressed with reference to the illustrated state. In addition, the present disclosure is not limited to the embodiments and their variations shown below. Any structural elements described in the following embodiments and their variations can be freely combined, deformed or omitted without departing from the scope of the main purpose of the present disclosure.

[0027] Implementation method 1.

[0028] Figure 1 1 is a block diagram showing the structure of the motor drive system according to Embodiment 1. Figure 1 As shown, the motor drive system of the present embodiment includes a motor 1 , a control device 2 for controlling the motor 1 , a power conversion device 3 for driving the motor 1 , a current sensor 4 , and a brake 7 .

[0029] The motor 1 is a permanent magnet synchronous motor. For the motor 1, either a surface magnet type or an embedded magnet type can be applied. The control device 2 outputs a voltage command for applying a voltage to the motor 1 to the power conversion device 3. The power conversion device 3 applies a voltage to the 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 the current flowing to the motor 1. The current sensor 4 can detect the current of the three phases of the motor 1, and can also detect the current of the two phases.

[0030] The control device 2 of the motor 1 includes a parameter identification unit 5 and a current control unit 6. The parameter identification unit 5 identifies the parameters of the motor 1. The parameter identification unit 5 outputs a voltage command to the power conversion device 3, and the voltage command applies a voltage for identifying the parameters of the motor 1 to the motor 1. The current control unit 6 determines the control parameters of the motor 1 and controls the current of the motor 1.

[0031] The parameter identification unit 5 includes 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 voltage commands corresponding to the resistance identification unit 5a, the time constant identification unit 5b, the magnetic pole position identification unit 5c, and the inductance identification unit 5d, respectively. As an example, the parameter identification unit 5 uses the information of the output voltage command and the information of the current detected by the current sensor 4 as input data to identify the parameters of the motor 1. The current control unit 6 uses the parameters identified by the parameter identification unit 5 to determine the control parameters.

[0032] The resistance identification unit 5a identifies the resistance value of the motor 1 when a predetermined DC voltage is applied from the power conversion device 3 to the motor 1. The time constant identification unit 5b identifies the time constant of the motor 1 when a predetermined DC voltage is applied from the power conversion device 3 to the motor 1. The magnetic pole position identification unit 5c identifies the magnetic pole position of the motor 1 when a predetermined DC voltage is applied from the power conversion device 3 to the motor 1. The inductance identification unit 5d identifies the dq axis inductance of the motor 1 using the above-mentioned magnetic pole position when a predetermined AC voltage is applied from the power conversion device 3 to the motor 1. 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 when the motor 1 is stopped. According to such a structure, the control parameters of the motor 1 can be determined without rotating the motor 1 and without passing an overcurrent.

[0033] 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 voltage to the motor 1 according to the voltage command. At this time, the shaft of the motor 1 may rotate according to the voltage command or the specifications of the motor 1. When the shaft of the motor 1 rotates, the identification accuracy of the magnetic pole position deteriorates. In addition, by generating an induced voltage, the identification accuracy of the resistance value, the time constant and the inductance will also deteriorate. Therefore, it is more preferable to implement the identification of the parameters of the motor 1 when the motor 1 is braked by the brake 7 so that the shaft does not rotate.

[0034] A specific example of parameter identification performed by the resistance identification unit 5 a , the time constant identification unit 5 b , the magnetic pole position identification unit 5 c , and the inductance identification unit 5 d constituting the parameter identification unit 5 will be described in more detail below.

[0035] Figure 2 This is a flowchart showing an example of a process of resistance value identification by the resistance identification unit 5a in Embodiment 1. When the resistance value identification is started by the parameter identification unit 5, the resistance identification unit 5a outputs a voltage command so that the voltage applied to the motor 1 increases stepwise (step S201).

[0036] As an example, the resistance identification unit 5a outputs a voltage command so that a three-phase voltage is applied to the motor 1. In addition, the resistance identification unit 5a may output a voltage command so that a one-phase voltage is applied to the motor 1, or may output a voltage command so that a two-phase voltage is applied to the motor 1. When a one-phase voltage is applied to the motor 1, the resistance value of the phase to which the voltage is applied can be identified. When a two-phase voltage is applied to the motor 1, the resistance value of the two phases to which the voltage is applied can be identified. When a three-phase voltage is applied to the motor 1, the resistance value of all phases can be identified.

[0037] After the process of step S201, the resistance identification unit 5a determines whether the current value detected by the current sensor 4 reaches the specified current value when acquiring the 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 the voltage and current data as the data for resistance value identification (step S203).

[0038] It is desirable to obtain the voltage and current data for resistance value identification at more than 2 points. That is, it is desirable to set more than 2 specified current values ​​for obtaining the data for resistance value identification. Thus, the resistance value can be identified using the variation of voltage and current. If such a method for identifying the resistance value is used, the influence of the error between the voltage command and the voltage actually applied by the power conversion device 3 can be eliminated, and the identification accuracy can be improved. The method for identifying the resistance value using the variation of voltage and current will be described in detail later.

[0039] After the process of step S203 , the resistance identification unit 5 a identifies 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 to, for example, the rated current of the motor 1 or the allowable current of the power converter 3 .

[0040] When the voltage applied to the motor 1 is increased step by step by the process of step S201, the current value of the motor 1 is also increased step by step. At this time, if an excessive current flows, the motor 1 may be demagnetized or burned. In addition, if an excessive current flows, the power conversion device 3 may be damaged. 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. In this way, damage to each hardware can be prevented.

[0041] In step S204, when the current is less than the reference current value, the process returns to step S201. In step S204, when the current is greater than the reference current value, the process of stopping the application of voltage to the motor 1 is executed (step S205). After stopping the application of voltage, the resistance value is identified using the data obtained in step S203 (step S206).

[0042] Here, the principle of resistance value identification performed by the resistance identification unit 5a is described. The current values ​​of the two points obtained as data for resistance value identification are assumed to be I1 and I2. The voltage values ​​in the voltage command at this time are assumed to be V1 and V2. In addition, the voltage value actually applied to the motor 1 by the power conversion device 3 is assumed to be V1. * and V2 * .

[0043] The relationship between the voltage value in the voltage command and the actually applied voltage value is expressed by the following equations (1) and (2). In addition, the resistance value R can be calculated by the following equation (3) using Ohm's law. In addition, ΔV refers to the error between the voltage command and the actually applied voltage.

[0044]

[0045]

[0046]

[0047] The voltage information obtained by the resistance identification unit 5a of the parameter identification unit 5 is the voltage command information. The resistance identification unit 5a uses the voltage command information to obtain the resistance identification value R * The resistance identification value R can be expressed by the following formula (4) using the voltage values ​​V1 and V2 in the voltage command: * .

[0048]

[0049] In this way, the resistance identification value R is calculated by using the voltage difference and the current difference. ＊ , which can offset the error between the voltage command and the actual voltage, thereby identifying the resistance value with high accuracy.

[0050] Figure 3 This is a diagram showing an example of the time history of voltage and current when the resistance identification unit 5 a in the first embodiment identifies the resistance value. Figure 3 The voltage in represents the phase voltage of motor 1. Figure 3 The current in represents the phase current of motor 1. Figure 3 1 shows the time history of one phase. As described above, the voltage applied for resistance value identification may be three-phase or two-phase.

[0051] exist Figure 3 , an example using a ramp function as a stepwise voltage command is shown. Any voltage command may be used as long as it increases the voltage in steps, and other functions may be used instead of the ramp function.

[0052] When the voltage is increased step by step, the current value also increases. The voltage is increased until the current reaches the reference current value. During this period, the voltage command and current value data are obtained at more than two points. Figure 3 In the example of , voltage values ​​V1 and V2 and current values ​​I1 and I2 of the voltage command are obtained.

[0053] Here, the voltage value of the voltage command when the current reaches the reference current value may be stored as the reference voltage value. The reference voltage value is the voltage value required to pass the reference current value to the motor 1. The reference voltage value can be used when each part other than the resistance identification part 5a of the parameter identification part 5 identifies a parameter.

[0054] In the case where the power conversion device 3 is a PWM inverter, there is a voltage drop caused by the dead time. Therefore, it is preferable to perform dead time correction (Td correction). The 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. In addition, near the current becoming zero, the Td correction value sometimes jitters, and accurate correction may not be performed. Therefore, near the current becoming zero, a process such that the Td correction value is smoothed can also be implemented.

[0055] In the resistance identification unit 5a of the present embodiment, since the resistance value is identified by the DC voltage that increases in stages, the sign of the voltage to be applied is known. In addition, the sign of the current is also the same as the sign of the voltage and is known. Therefore, by performing dead time correction according to the sign of the voltage to be applied, the voltage drop caused by the dead time of the power conversion device 3 can be compensated with a simple structure in terms of feedforward.

[0056] Figure 4 4 is a flowchart showing an example of a process in which the resistance identification unit 5a in the first embodiment performs dead time correction. First, the resistance identification unit 5a determines whether the voltage command is positive (step S401). When the voltage command is positive, a positive current is passed, and therefore, a positive Td correction value is added to the voltage command (step S402). When the voltage command is negative, a negative current is passed, and therefore, a negative Td correction value is added to the voltage command (step S403).

[0057] As described above, the resistance identification unit 5a of the parameter identification unit 5 can prevent damage to the hardware and can accurately identify the resistance value of the motor 1. In this embodiment, by monitoring the current value of the motor 1 and increasing the voltage command in stages, 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. In addition, by using the difference between the voltage and the current to identify the resistance value, the resistance value can be identified with high accuracy. In addition, by performing dead time correction based on the sign of the voltage, the voltage drop caused by the dead time can be compensated with a simple structure.

[0058] Next, a specific example of identification of the time constant by the time constant identification unit 5b of the parameter identification unit 5 is described. The “time constant” identified by the time constant identification unit 5b is an electrical time constant T=L / R determined by the resistance value R and the inductance L of the motor 1.

[0059] 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 the resistance value R and the inductance L are connected in series. At this time, when the voltage is applied in a step-like manner, the current becomes a response of a first-order lag system. Here, by measuring the time when the convergence value of the current is at a predetermined ratio, for example, 63%, the time constant can be identified.

[0060] Figure 5 1 is a flowchart showing an example of a process of time constant identification performed by the time constant identification unit 5b in the first embodiment. The time constant identification unit 5b outputs a voltage command so that the reference voltage value obtained by the resistance identification unit 5a is applied in a step-like manner (step S501). As described above, the reference voltage value is a voltage value when a current of a reference current value is passed. By using this reference voltage value, it is possible to prevent an overcurrent from flowing to the motor 1 or the power conversion device 3. In addition, by using the reference voltage value, since the current value of the motor 1 is known in advance, it is easy to identify the time constant.

[0061] After the processing of step S501, the time constant identification unit 5b starts measuring the time from the application of voltage (step S502). In the present embodiment, the time constant is identified based on the time until the current of the motor 1 reaches 63% of the prescribed ratio as the reference current value. After the processing of step S502, it is determined whether the current of the motor 1 reaches 63% of the reference current value (step S503). If it does not reach 63% of the reference current value, the application of voltage and the measurement of time are continued. If it reaches 63% of the reference current value, the measurement of time is stopped (step S504). Then, the time constant is identified based on the measured time (step S505).

[0062] In addition, although an example of applying a voltage of a reference voltage value is shown, the time constant can also be identified by applying a voltage of an arbitrary voltage value. In this case, for example, after measuring the current flowing to an arbitrary voltage command, the time until the current reaches a predetermined proportion of the current measured by applying the same voltage command can be measured.

[0063] When the resistance value has been identified by the resistance identification unit 5a, the inductance L of the motor 1 can be solved as L=T×R* using the time constant identification value T and the resistance identification value R*. However, in the internal magnet type motor 1, the inductance L is different in the d and q axes, so it is difficult to identify the accurate inductance L at this point in time. Therefore, the inductance identification unit 5d can be used for identification as described later.

[0064] Figure 6: is a diagram showing an example of the time history of voltage and current when the time constant identification unit 5b in the first embodiment performs time constant identification. As described above, the time constant identification unit 5b outputs a voltage command so that a voltage of a reference voltage value is applied in a step-like manner. The applied voltage is the same as that in the resistance value identification, and can be 1 phase, 2 phases, or all 3 phases. The time is measured from the start of the application of the voltage, and the time T when the current value reaches a prescribed proportion of 63% of the reference current value is identified as the time constant identification value T. In addition, here, the reference of the current for identifying the time constant is set to 63% of the reference current value as a normal theoretical value, but it can be set to any value as long as the time constant can be measured. In addition, the time constant identification unit 5b can perform dead time correction in the same way as the resistance identification unit 5a, and the value obtained by adding the Td correction value is used as the voltage command value.

[0065] As described above, the time constant identification unit 5 b of the parameter identification unit 5 can identify the time constant of the motor 1 while preventing damage to the hardware by using the reference voltage value obtained by the resistance identification unit 5 a .

[0066] Next, a specific example of the identification of the magnetic pole position by the magnetic pole position identification unit 5c of the parameter identification unit 5 will be described. In the present embodiment, a pulse voltage is applied to the motor 1, and the magnetic pole position is identified based on the current at that time.

[0067] When a pulse voltage is applied, when the phase of the magnetic pole of the rotor of the motor 1 is in the same direction as the phase of the applied voltage, the magnetic flux caused by the current generated by the applied voltage is in the same direction as the magnetic flux of the rotor magnet. Therefore, the total value of the magnetic flux increases, and the core of the motor 1 is magnetically saturated. When magnetically saturated, the winding inductance of the motor 1 decreases, and the current amplitude of the motor 1 increases. On the other hand, when the phase of the magnetic pole of the rotor is in the opposite direction to the phase of the applied voltage, the magnetic flux caused by the current generated by the applied voltage is in the opposite direction to the magnetic flux of the rotor magnet. Therefore, the total value of the magnetic flux decreases, and the core of the motor 1 does not produce magnetic saturation. When magnetic saturation does not occur, the winding inductance of the motor 1 increases, and the current amplitude of the motor 1 decreases.

[0068] Thus, depending on the relationship between the phase of the magnetic pole of the rotor and the phase of the voltage application, the degree of magnetic saturation of the core of the motor 1 varies, and the current amplitude of the motor 1 changes. This property is used to identify the magnetic pole position.

[0069] Figure 7 2 is a flowchart showing an example of the processing of magnetic pole position identification by the magnetic pole position identification unit 5c. First, the pulse width of the pulse voltage is determined using the time constant identified by the time constant identification unit 5b (step S701).

[0070] As described above, it is necessary to flow current through the motor 1 to produce magnetic saturation. It is necessary to apply a pulse voltage so that the current that produces magnetic saturation is passed through the motor 1. As the simplest method for this, a voltage with the maximum amplitude that can be applied can be applied. However, when the voltage with the maximum amplitude is applied for a long time, an excessive current may flow through the motor 1 or the power conversion device 3, which may cause damage. Therefore, the pulse width of the pulse voltage can be determined using the identified time constant. Since it is possible to know in advance what degree of current will flow in response to the applied pulse voltage, it is possible to prevent overcurrent and the passage of current that produces magnetic saturation.

[0071] After the pulse width of the pulse voltage is determined in the process of step S701, the pulse voltage is actually applied to the motor 1 (step S702). Then, the current when the pulse voltage is applied is measured (step S703). The pulse voltage is intermittently applied multiple times in different angular directions of the electrical angle of the motor 1 while changing the phase. Each time the pulse voltage is applied multiple times, the current is measured. After the processing of steps S702 and S703, the measured current is used to identify the magnetic pole position (step S704).

[0072] Figure 8 : is a diagram showing an example of the time history of voltage and current when the magnetic pole position identification unit 5c in the first embodiment performs magnetic pole position identification. Figure 8 In FIG. 1 , an example is shown in which a voltage is applied while changing the phase between the α-axis and the β-axis of the motor 1. In addition, the voltage application is not limited to the αβ-axis, and the voltage may be applied in a three-phase manner from the beginning. Figure 8 In FIG. 1 , an example in which the pulse voltage is applied six times is shown, but the pulse voltage may be applied any number of times as long as the magnetic pole position can be identified.

[0073] When identifying the magnetic pole position, the current is measured each time a pulse voltage is applied. Figure 8 In the example, Iα1 to Iα6 and Iβ1 to Iβ6 are measured. The amplitudes of these currents increase and decrease according to magnetic saturation, thereby enabling the magnetic pole position to be identified. The calculation formula for magnetic pole position identification is the following formula (5). Here, θ refers to the magnetic pole position.

[0074]

[0075] As described above, the magnetic pole position identification unit 5 c of the parameter identification unit 5 makes the width of the pulse voltage appropriate using the time constant obtained by the time constant identification unit 5 b , thereby being able to identify the magnetic pole position of the motor 1 while preventing hardware damage.

[0076] Next, a specific example of the identification of the inductance L performed by the inductance identification unit 5d of the parameter identification unit 5 is described. By using the magnetic pole position of the motor 1 identified by the magnetic pole position identification unit 5c, the dq axis of the motor 1 can be determined. By applying an AC voltage to the determined dq axis and measuring the current as a response, the inductance L of the dq axis can be identified.

[0077] 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 a resistance value R is connected in series with an inductance L. At this time, it is considered that when a high-frequency AC voltage with a sufficiently high frequency is applied, the response of the current to the voltage can be considered to depend only on the inductance L, and the inductance L can be identified from the ratio of the voltage to the current. Therefore, even if the motor 1 is an embedded magnet type, the inductance L can be identified.

[0078] At this time, if the amplitude of the applied AC voltage is too large, an excessive current may flow into the motor 1 or the power conversion device 3. Therefore, as with the resistance identification unit 5a, a voltage command may be output so that the voltage amplitude increases in stages, thereby preventing overcurrent and performing inductance identification. In addition, the frequency of the AC voltage is arbitrary, but it needs to be a frequency that treats the motor 1 as only an inductance component, which is usually a frequency of several hundred Hz or more.

[0079] Fig. 9 1 is a flowchart showing an example of the process of inductance identification performed by the inductance identification unit 5d in Embodiment 1. The inductance identification unit 5d outputs a voltage command so that an AC voltage for inductance identification is applied to the motor 1 in a manner in which the amplitude is increased in stages (step S901). Following the process of step S901, it is determined whether the current of the motor 1 is greater than a reference current value (step S902). When the current is less than the reference value, the process returns to step S901 and the amplitude of the AC voltage is increased in stages.

[0080] If the current of the motor 1 is above the reference current value, the amplitude of the AC voltage is fixed (step S903). After the amplitude is fixed, the data for inductance identification is obtained (step S904). The data for inductance identification is information on the amplitude of the voltage and the current. In addition, the information on the amplitude of the voltage can be the information on the amplitude of the voltage in the voltage command. As a method for obtaining the amplitude of the current, Fourier transform can be used, the maximum and minimum values ​​of the current can be measured, and the amplitude of the current can be measured by any other method.

[0081] The inductance is identified using the data acquired in the process of step S904 (step S905). The identification formula of the inductance L is expressed by the following formula (6): Here, ω is the frequency of the AC voltage, Va is the voltage amplitude, and Iaa is the current amplitude.

[0082] L=1 / ω×Va / Ia (6)

[0083] Fig.10 : is a diagram showing an example of the time history of voltage and current when the inductance identification unit 5d in the first embodiment performs inductance identification. As described above, the voltage amplitude is increased until the current of the motor 1 reaches the reference current value, and the voltage amplitude is fixed when the current reaches the reference current value, and the information of the voltage and current amplitudes as data for inductance identification is obtained. Then, the inductance L is identified by equation (6) using the obtained data. When the inductance L of each of the dq axes is identified, for example, the inductance identification of the q axis is performed after the inductance of the d axis is identified, and the inductance identification in each axis is performed independently.

[0084] The inductance identification unit 5d of the parameter identification unit 5 increases the applied voltage stepwise while monitoring the current value, thereby applying the voltage within the range that does not exceed the allowable current of the motor 1 or the power conversion device 3. This allows the inductance L of the motor 1 to be identified while preventing damage to the hardware.

[0085] The information of each parameter identified by the parameter identification unit 5 is sent to the current control unit 6. The current control unit 6 can use the identified resistance value R and inductance L to determine the control gain, and use the identified magnetic pole position to perform control in the dq axis. In addition, using the identified magnetic pole position, the current of the motor 1 detected by the current sensor 4 is converted into a dq axis current. Through this series of controls, current control can be implemented even for the motor 1 whose parameters are unknown. Moreover, as described above, the parameters can be identified and the control parameters can be determined without rotating the motor 1 and without passing an overcurrent.

[0086] also, Fig.11 This is a flowchart showing a processing example of the magnetic pole position identification unit 5c and the inductance identification unit 5d in a modification of Embodiment 1. In this modification, the identification accuracy of each parameter is improved by repeatedly performing magnetic pole position identification by the magnetic pole position identification unit 5c and inductance identification by the inductance identification unit 5d.

[0087] First, the magnetic pole position identification unit 5c performs magnetic pole position identification (step S1101). In the first step S1101, as in the above-mentioned embodiment, a pulse voltage with a pulse width determined by the time constant identified by the time constant identification unit 5b is applied to identify the magnetic pole position. Following the processing of step S1101, the inductance identification unit 5d performs inductance identification (step S1102).

[0088] Next, the inductance identified in step S1102 is used to re-identify the time constant, and the pulse width of the pulse voltage used for magnetic pole position identification is determined again (step S1103). After the processing of step S1103, it is determined whether the parameter identification has been implemented a specified number of times (step S1104). If the identification has not been implemented a specified number of times, return to step S1101, and use the pulse voltage with the pulse width determined in step S1103 to identify the magnetic pole position again. Then, using the magnetic pole position identified again, the dq axis is established, and the inductance is identified again. Furthermore, using the inductance identified again, the pulse width of the pulse voltage used for magnetic pole position identification is determined again. Then, it is determined whether the parameter identification has been implemented a specified number of times.

[0089] By repeatedly identifying the pulse width and inductance of the pulse voltage for magnetic pole position identification in this way, the identification accuracy is improved, and a parameter with high reliability can be obtained. In step S1104, when it is determined that the identification has been completed for a predetermined number of times, the magnetic pole position and inductance identified last are determined as the final identification values ​​and saved (step S1105). In addition, in this modified example, it is also desirable to implement parameter identification in a state where the motor 1 is not rotating due to the brake 7.

[0090] Hereinafter, various aspects of the present disclosure are collectively described as supplementary notes.

[0091] (Note 1)

[0092] A control device for an electric motor, characterized by comprising:

[0093] a parameter identification unit that outputs a voltage command to the power conversion device, the voltage command being used to apply a voltage to the motor for identifying a parameter of the motor; and

[0094] a current control unit, which determines the control parameters of the motor and controls the current of the motor,

[0095] The parameter identification unit has:

[0096] a resistance identification unit that identifies a resistance value of the motor when a predetermined DC voltage is applied from the power conversion device to the motor;

[0097] a time constant identification unit that identifies an electrical time constant of the motor when the predetermined DC voltage is applied from the power conversion device to the motor;

[0098] a magnetic pole position identification unit that identifies a magnetic pole position of the electric motor when the predetermined DC voltage is applied from the power conversion device to the electric motor; and

[0099] an inductance identification unit that identifies the inductance of the dq axis of the motor using the magnetic pole position when a predetermined AC voltage is applied from the power conversion device to the motor;

[0100] The current control unit determines the control parameter of the motor based on the parameter identified by the parameter identification unit while the motor is stopped.

[0101] (Note 2)

[0102] A control device for a motor according to Supplement 1, wherein:

[0103] The parameter identification unit identifies the parameters of the motor in a state where the motor is braked by a brake.

[0104] (Note 3)

[0105] The control device for the electric motor according to Supplement 1 or Supplement 2, wherein:

[0106] The resistance identification unit increases the predetermined DC voltage in stages until the current of the motor reaches a reference current value, and identifies the resistance value based on a change amount of the DC voltage and a change amount of the current of the motor.

[0107] (Note 4)

[0108] The control device for the electric motor according to any one of Supplement 1 to Supplement 3, wherein:

[0109] 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 voltage of the reference voltage value as the specified DC voltage to the motor in a step-by-step manner, and measures the time it takes for the current of the motor to reach a specified proportion of the reference current value, thereby identifying the electrical time constant.

[0110] (Note 5)

[0111] The control device for the electric motor according to any one of Supplement 1 to Supplement 4, wherein:

[0112] At least one of the resistance identification unit and the time constant identification unit performs dead time correction of the power conversion device according to the sign of the predetermined DC voltage.

[0113] (Note 6)

[0114] A control device for a motor according to any one of Appendix 1 to Appendix 5, wherein:

[0115] The magnetic pole position identification unit outputs a voltage instruction so that a pulse voltage with a pulse width determined by the electrical time constant is applied to the motor. The magnetic pole position identification unit identifies the magnetic pole position based on the current of the motor when the pulse voltage is intermittently applied multiple times in different angular directions of the electrical angle of the motor.

[0116] (Note 7)

[0117] A control device for a motor according to any one of Supplementary Notes 1 to 6, wherein:

[0118] The inductance identification unit uses the magnetic pole position to apply a high-frequency voltage to the d-axis or q-axis of the motor, so that the amplitude of the high-frequency voltage increases in stages until the current of the motor reaches a reference current value. The inductance identification unit identifies the inductance of the d-axis or q-axis based on the high-frequency voltage and the current of the motor.

[0119] (Note 8)

[0120] A control device for a motor according to Supplementary Note 6, wherein:

[0121] After the inductance identification unit completes the inductance identification, the magnetic pole position identification unit determines the pulse width again using the inductance identified by the inductance identification unit, and identifies the magnetic pole position again.

[0122] The inductance identification unit performs inductance identification again using the re-identified magnetic pole position.

Claims

1. A control device for an electric motor, characterized in that: have: a parameter identification unit that outputs a voltage command to the power conversion device, the voltage command being used to apply a voltage to the motor for identifying a parameter of the motor; and a current control unit, which determines the control parameters of the motor and controls the current of the motor, The parameter identification unit has: a resistance identification unit that identifies a resistance value of the motor when a predetermined DC voltage is applied from the power conversion device to the motor; a time constant identification unit that identifies an electrical time constant of the motor when the predetermined DC voltage is applied from the power conversion device to the motor; a magnetic pole position identification unit that identifies a magnetic pole position of the electric motor when the predetermined DC voltage is applied from the power conversion device to the electric motor; as well as an inductance identification unit that identifies the inductance of the dq axis of the motor using the magnetic pole position when a predetermined AC voltage is applied from the power conversion device to the motor; The current control unit determines the control parameter of the motor based on the parameter identified by the parameter identification unit while the motor is stopped.

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

3. The control device for the electric motor according to claim 1 or 2, wherein: The resistance identification unit increases the predetermined DC voltage in stages until the current of the motor reaches a reference current value, and identifies the resistance value based on a change amount of the DC voltage and a change amount of the current of the motor.

4. The control device for an electric motor according to any one of claims 1 to 3, 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 voltage of the reference voltage value as the specified DC voltage to the motor in a step-by-step manner, and measures the time it takes for the current of the motor to reach a specified proportion of the reference current value, thereby identifying the electrical time constant.

5. The control device for an electric motor according to any one of claims 1 to 4, wherein: At least one of the resistance identification unit and the time constant identification unit performs dead time correction of the power conversion device according to the sign of the predetermined DC voltage.

6. The control device for an electric motor according to any one of claims 1 to 5, wherein: The magnetic pole position identification unit outputs a voltage instruction so that a pulse voltage with a pulse width determined by the electrical time constant is applied to the motor. The magnetic pole position identification unit identifies the magnetic pole position based on the current of the motor when the pulse voltage is intermittently applied multiple times in different angular directions of the electrical angle of the motor.

7. The control device for an electric motor according to any one of claims 1 to 6, wherein: The inductance identification unit uses the magnetic pole position to apply a high-frequency voltage to the d-axis or q-axis of the motor, so that the amplitude of the high-frequency voltage increases in stages until the current of the motor reaches a reference current value. The inductance identification unit identifies the inductance of the d-axis or q-axis based on the high-frequency voltage and the current of the motor.

8. The control device for the electric motor according to claim 6, wherein: After the inductance identification unit completes the inductance identification, the magnetic pole position identification unit determines the pulse width again using the inductance identified by the inductance identification unit, and identifies the magnetic pole position again. The inductance identification unit performs inductance identification again using the re-identified magnetic pole position.

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