Control device for electric motor

Abstract

The present invention provides a control device for an electric motor, capable of reliably determining an abnormality in a DC current estimation unit without using a special sensor such as a DC current sensor.　The present invention includes a first DC current estimation unit 20A for generating a first DC current estimation value by a first calculation technique, a second DC current estimation unit 20B for generating a second DC current estimation value that is different from the first DC current estimation value by a second calculation technique that is different from the first calculation technique, a third DC current estimation unit 20C for generating a third DC current estimation value that is different from the first DC current estimation value and the second DC current estimation value by a third calculation technique that is different from the first calculation technique and the second calculation technique, and a validity diagnosis unit 21 for determining validity of the first DC current estimation value on the basis of the first DC current estimation value, the second DC current estimation value, and the third DC current estimation value.

Description

Electric motor control device

[0001] The present invention relates to a control device for an electric motor used in an automobile or the like, and more particularly to a control device for an electric motor that performs inverter control.

[0002] Hybrid vehicles and electric vehicles are equipped with power conversion devices to drive motors. The power conversion device converts direct current (DC) supplied from a battery into alternating current (AC) by switching the switching elements of the power converter, thereby driving a three-phase electric motor.

[0003] This power conversion device is equipped with a three-phase AC current sensor that measures the current flowing through the motor, as well as a DC current sensor that measures the DC current supplied from the battery to the power converter. Hereinafter, the AC current sensor may be referred to as an AC current sensor, and the DC current sensor may be referred to as a DC current sensor. Furthermore, alternating current may be referred to as AC, and direct current may be referred to as DC.

[0004] In recent years, the publication of functional safety standards for automobiles has increased the need to detect abnormalities and failures in power conversion devices, which has led to the need to implement diagnostic processing that can detect abnormalities and failures in DC current sensors as well.

[0005] For example, Japanese Patent Application Laid-Open Publication No. 2017-208893 (Patent Document 1) discloses that in order to detect abnormalities or failures in a DC current sensor, a DC current estimate value of the DC current supplied to a power converter is calculated, and this current estimate value is compared with the DC current detection value of the DC current sensor to detect abnormalities or failures in the DC current sensor.

[0006] The concept of Patent Document 1 is shown in Figure 5. In Figure 5, the motor control device is provided with a validity diagnosis unit 30, which receives a detected DC current value used for controlling the motor from a DC current sensor 31. Similarly, a DC current estimated value used for diagnosis is input to validity diagnosis unit 30 from a DC current estimator 32. This DC current estimated value is obtained by multiplying the AC current detected by an AC current sensor by the pulse duty value that drives the switching elements of the power converter.

[0007] The validity diagnosing unit 30 functions so that if the detected DC current value and the estimated DC current value have a predetermined relationship, the DC current sensor 31 is deemed to be operating normally, and if the detected DC current value and the estimated DC current value deviate from the predetermined relationship, the validity diagnosing unit 30 is deemed to be operating abnormally, meaning that the DC current sensor 31 is not operating correctly. Thus, when the validity diagnosing unit 30 determines that the DC current sensor 31 is in an abnormal state, it activates the abnormality countermeasure unit 33 to perform backup control, etc.

[0008] JP 2017-208893 A

[0009] In this type of motor control device, it has been proposed to eliminate the DC current sensor in order to reduce the number of parts and manufacturing costs, etc. In this case, the DC current value estimated by the DC current estimator described above is used to control the motor.

[0010] However, when a DC current estimation unit is used, it is necessary to detect abnormalities in the DC current estimation unit (e.g., a decrease in detection accuracy) from the perspective of functional safety standards. Therefore, there is a demand for a motor control device that can reliably determine abnormalities in the DC current estimation unit without using a special sensor such as a DC current sensor.

[0011] An object of the present invention is to provide a motor control device that can reliably determine whether a DC current estimation unit has an abnormality without using a special sensor such as a DC current sensor.

[0012] The present invention provides an electric motor control device including a power converter unit that converts DC current into AC current to drive the electric motor, and a control unit that controls the power converter unit, wherein the control unit includes at least a first DC current estimation unit that generates a first DC current estimate using a first calculation method, a second DC current estimation unit that generates a second DC current estimate that is different from the first DC current estimate using a second calculation method that is different from the first calculation method, a third DC current estimation unit that generates the first DC current estimate and a third DC current estimate that is different from the second DC current estimate using a third calculation method that is different from the first and second calculation methods, and a validity diagnosis unit that evaluates the relationships between the first, second, and third DC current estimates to determine the validity of the first DC current estimate.

[0013] According to the present invention, it is possible to reliably determine whether or not there is an abnormality in a DC current estimation unit used to control an electric motor, without using a special sensor such as a DC current sensor.

[0014] Fig. 1 is a configuration diagram showing the configuration of an electric motor control device according to an embodiment of the present invention; Fig. 2 is a configuration diagram showing the configuration of a validity diagnosis unit for explaining the concept of the present invention; Fig. 3 is an explanatory diagram for explaining the concept of the present invention; Fig. 4 is a control flowchart diagram for explaining the operation of the electric motor control device of the present invention; Fig. 5 is a configuration diagram showing the configuration of a validity diagnosis unit in Patent Document 1;

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and application examples within the technical concept of the present invention are also included within its scope.

[0016] First, the configuration of an electric motor control device according to an embodiment of the present invention will be briefly described with reference to Fig. 1. The electric motor control device INV is composed of a power converter unit 10 and a control unit 11. The control device INV operates to drive and control a three-phase electric motor MTR. The three-phase electric motor MTR is a three-phase brushless electric motor having a stator 12 with U-phase, V-phase, and W-phase coils, and a rotor 13 with a magnet rotatably supported relative to the stator 12.

[0017] As described above, the control device IVT includes the power converter unit 10 and the control unit 11. The power converter unit 10 includes a U-phase arm in which the upper arm switching element 14u and the lower arm switching element 15u are connected in series, a V-phase arm in which the upper arm switching element 14v and the lower arm switching element 15v are connected in series, and a W-phase arm in which the upper arm switching element 14w and the lower arm switching element 15w are connected in series.

[0018] The arms of the power converter unit 10 are connected in parallel between a positive electrode line Lp and a negative electrode line Ln of an on-board DC power supply 16, forming a three-phase bridge circuit. A capacitor 17 is connected in parallel with each arm between the positive electrode line Lp and the negative electrode line Ln. Each of the switching elements 14u to 15w includes an anti-parallel diode, and is configured by a power semiconductor element such as a field effect transistor (FET) or an insulated gate bipolar transistor (IGBT).

[0019] The power converter unit 10 also includes an AC current sensor 18 for detecting an AC current value. The detected AC current value Ia from the AC current sensor 18 is input to the control unit 11. The detected AC current value from the AC current sensor 18 is multiplied by the pulse duty value of the power converter unit 10 to obtain an estimated DC current value.

[0020] This calculation method is the first calculation method, by which the first DC current estimated value Ai is obtained, and further this first DC current estimated value Ai is used to control the electric motor.

[0021] The control unit 11 includes at least a power converter control unit 19, a DC current estimating unit 20, and a validity diagnosing unit 21. The power converter control unit 19 has a function of generating a command signal PWMist for a gate driver 22 that generates gate pulses for the upper-arm and lower-arm switching elements 14u to 15w. The gate driver 22 also has a function of transmitting a readback signal PWMleb to the power converter control unit 19. The pulse duty value (here, the on-duty value) of the power converter unit 10 can be obtained from the readback signal PWMleb.

[0022] The DC current estimator 20 has a function of generating at least three types of DC current estimates: (1) a first DC current estimator that generates a first DC current estimate Ai using a first calculation method, (2) a second DC current estimator that generates a second DC current estimate Bi that is different from the first DC current estimate Ai using a second calculation method that is different from the first calculation method, and (3) a third DC current estimator that generates the first DC current estimate Ai and a third DC current estimate Ci that is different from the second DC current estimate Bi using a third calculation method that is different from the first and second calculation methods.

[0023] Here, the first DC current estimate Ai is a current value for controlling the motor, and the 22nd DC current estimate Bi and the third DC current estimate Ci are current values ​​for diagnosing the first DC current estimate Ai.

[0024] These three types of DC current estimated values ​​are sent to a validity diagnosis unit 21, which diagnoses the validity of the first DC current estimated value Ai. That is, it is determined whether the DC current estimated value currently being used to control the electric motor MTR (here, the first DC current estimated value Ai) is valid, that is, whether it is in a normal state.

[0025] This determination is made by evaluating the relationship between the current value differences of the DC current estimates for different combinations of the first DC current estimate Ai, the second DC current estimate Bi, and the third DC current estimate Ci, and diagnosing the validity of the first DC current estimate Ai. Details of this validity diagnosing unit 21 will be described later.

[0026] Here, the control unit 11 is configured to communicate with an external control device via a CAN (Controller Area Network) or the like, and its main components are a microcomputer having an A / D converter, a processor such as a CPU (Central Processing Unit), a writable memory such as a RAM (Random Access Memory), and a read-only memory such as a ROM (Read Only Memory).

[0027] Next, the concept of the present invention will be explained with reference to FIGS. 2 and 3. FIG. 2 shows the DC current estimation unit 20 and the validity diagnosis unit 21 of FIG. 1. As described above, the DC current estimation unit 20 has the function of calculating a DC current estimate using three different calculation methods. Furthermore, the validity diagnosis unit 21 determines the validity of the first DC current estimate Ai based on the current value differences between the DC current estimates of different combinations of the first DC current estimate Ai, the second DC current estimate Bi, and the third DC current estimate Ci. This diagnosis method is shown in FIG. 3.

[0028] For example, three types of calculation methods for obtaining the DC current estimated value in the DC current estimating unit 20 are as shown in FIG.

[0029] (1) The first DC current estimation unit 20A generates a first DC current estimation value Ai by a first calculation method (method A). This first DC current estimation value Ai is a DC current estimation value for control used in actual control of the electric motor.

[0030] The first calculation method (method A) is a calculation method in which the AC current value (Ia) flowing through the power converter unit 10 is multiplied by the on-duty value (Don) of the pulse that drives and controls the upper arm of the power converter unit 10 ("Ia x Don") to generate a first DC current estimate value Ai.

[0031] (2) The second DC current estimator 20B generates a second DC current estimate Bi by a second calculation method (method B). The second DC current estimate Bi is a diagnostic DC current estimate used to diagnose the first DC current estimate Ai.

[0032] The second calculation method (method B) is a calculation method in which a second DC current estimation value Bi is generated by subtracting a loss (Loss) in the motor control system (here, at least the power converter) from a sum obtained by multiplying a q-axis voltage command value (Vq*) and a q-axis current value (Iq) of the electric motor MTR ("Vq* × Iq") and a d-axis voltage command value (Vd*) and a d-axis current value (Id) ("Vd* × Id"), and dividing the result by the power supply voltage (Vbt). In other words, the second DC current estimation value Bi is obtained by calculating "(Vq* × Iq ​​+ Vd* × Id - Loss) / Vbt."

[0033] (3) The third DC current estimator 20C generates a third DC current estimate Ci by a third calculation method (method C). This third DC current estimate Ci is also a diagnostic DC current estimate used to diagnose the first DC current estimate Ai.

[0034] The third calculation method (method C) is a method of generating a third DC current estimate Ci by multiplying the AC current value (Ia) flowing through the power converter unit 10 by the power factor (θa) and modulation factor (Ma) of the AC current supplied to the motor. In other words, the third DC current estimate Ci is found by calculating "3 / 2 × √2 × Ia × θa × Ma."

[0035] Here, the second calculation method (method B) and the third calculation method (method C) do not use the on-duty value (Don) of the pulse that drives and controls the upper arm in the calculation formula, and therefore are not affected by switching delays of the switching elements, which has the effect of obtaining accurate DC current estimates. Note that the calculation methods for the first DC current estimate Ai, the second DC current estimate Bi, and the third DC current estimate Ci described above are shown as examples, and other calculation methods may also be used.

[0036] The first DC current estimate Ai, the second DC current estimate Bi, and the third DC current estimate Ci thus obtained are sent to a validity determination unit 21, which determines whether the first DC current estimate Ai is normal. A specific example will be described with reference to FIG. 3.

[0037] If the first DC current estimate Ai is normal, the first DC current estimate Ai is selected and output, whereas if the first DC current estimate Ai is abnormal, the second DC current estimate Bi or the third DC current estimate Ci is selected and output, or the abnormality countermeasure unit 23 performs a backup or other process.

[0038] Next, the concept of the diagnostic method of the validity diagnostic unit 21 will be explained with reference to Fig. 3. This diagnostic method is based on diagnosing whether the first DC current estimate Ai, which is used as a DC current estimate for control, is normal or not.

[0039] 3, the first DC current estimated value Ai and the second DC current estimated value Bi are compared, and if the two DC current estimated values ​​have a predetermined relationship, the first DC current estimated value Ai is determined to be normal.Furthermore, the first DC current estimated value Ai and the third DC current estimated value Ci are compared, and if the two DC current estimated values ​​have a predetermined relationship, the first DC current estimated value Ai is determined to be normal.

[0040] On the other hand, if the first DC current estimated value Ai and the second DC current estimated value Bi, and the first DC current estimated value Ai and the third DC current estimated value Ci do not have a predetermined relationship, and the second DC current estimated value Bi and the third DC current estimated value Ci are compared to find that the two DC current estimated values ​​have a predetermined relationship, it is ultimately determined that the first DC current estimated value Ai is not normal.

[0041] In this embodiment, the predetermined relationship is whether the absolute value of the difference ΔI between different combinations of the DC current estimated values ​​Ai to Ci is less than a predetermined difference threshold Ishd. Here, if the absolute value of the difference ΔI is less than the difference threshold Ishd, it is determined to be normal.

[0042] For this reason, as described above, if the first DC current estimate Ai is not normal, the second DC current estimate Bi or the third DC current estimate Ci is selected and output, or a fixed DC current estimate is output while a process such as backing up is executed by the abnormality countermeasure unit 23. Note that if the second DC current estimate Bi and the third DC current estimate Ci do not have a predetermined relationship, it is deemed impossible to make a determination and the process is terminated.

[0043] Based on the above-described concept, the specific control operation will now be described with reference to the control flow shown in Fig. 4. The control flow below mainly describes the control operations in the DC current estimation unit 20 and the validity diagnosis unit 21 shown in Fig. 1.

[0044] <Step S10> In step S10, the first DC current estimation unit 20A, the second DC current estimation unit 20B, and the third DC current estimation unit 20C shown in Fig. 2 calculate and determine the first DC current estimation value Ai, the second DC current estimation value Bi, and the third DC current estimation value Ci. Once the respective DC current estimation values ​​have been determined, the process proceeds to step S11.

[0045] <Step S11> In step S11, differences between the different combinations of the obtained DC current estimates are calculated. The differences are calculated as absolute values ​​using the following methods: (1) Difference ΔIab between the first DC current estimate Ai and the second DC current estimate Bi; ΔIab = |Ai - Bi| (2) Difference ΔIac between the first DC current estimate Ai and the third DC current estimate Ci; ΔIac = |Ai - Ci| (3) Difference ΔIbc between the second DC current estimate Bi and the third DC current estimate Ci; ΔIbc = |Bi - Ci| Once the differences between the different combinations of DC current estimates have been calculated, the process proceeds to step S12.

[0046] In step S12, it is determined whether the difference ΔIab between the first DC current estimate Ai and the second DC current estimate Bi is equal to or greater than a first difference threshold Ishd1. If it is determined that the difference ΔIab is less than the first difference threshold Ishd1 (NO determination), the process proceeds to step S20.

[0047] On the other hand, if it is determined that the difference ΔIab is equal to or greater than the first difference threshold Ishd1 (YES determination), the process proceeds to step S13. This determination means that either the first DC current estimated value Ai or the second DC current estimated value Bi is not a normal current value. In this state, it is not yet determined whether the first DC current estimator 20A is normal.

[0048] In step S13, it is determined whether the difference ΔIac between the first DC current estimate Ai and the third DC current estimate Ci is equal to or greater than the first difference threshold Ishd1. If it is determined that the difference ΔIac is less than the first difference threshold Ishd1 (NO determination), the process proceeds to step S20.

[0049] On the other hand, if it is determined that the difference ΔIac is equal to or greater than the first difference threshold Ishd1 (YES determination), the process proceeds to step S14. This determination means that either the first DC current estimation value Ai or the third DC current estimation value Ci is not a normal current value. In this state, it is not yet determined whether the first DC current estimation unit 20A is normal.

[0050] Step S14: In step S14, it is determined whether the difference ΔIbc between the second DC current estimate Bi and the third DC current estimate Ci is equal to or greater than the first difference threshold Ishd1. If it is determined that the difference ΔIbc is equal to or greater than the first difference threshold Ishd1 (YES determination), the process proceeds to step S15. This determination is made based on the assumption that either the second DC current estimate Bi or the third DC current estimate Ci is not a normal current value.

[0051] On the other hand, if it is determined that the difference ΔIbc is less than the first difference threshold Ishd1 (NO determination), the process proceeds to step S16. This determination means that the second DC current estimation value Bi and the third DC current estimation value Ci are normal current values. In this state, the second DC current estimation unit 20B and the third DC current estimation unit 20C can be considered normal.

[0052] <Step S15> In steps S12, S13, and S14, it is determined that the differences ΔIab, ΔIac, and ΔIbc are equal to or greater than the first difference threshold Ishd1. Therefore, in step S15, it is determined that there is a high possibility that the first DC current estimation unit 20A, the second DC current estimation unit 20B, and the third DC current estimation unit 20C are abnormal, and that diagnosis of the first DC current estimation unit 20A is not possible.

[0053] The diagnosis result can be displayed on a display means (not shown). It can also be stored as an error code (abnormality information). Furthermore, step S15e can be added to set a fixed DC current estimated value. After steps S15 and S15e are executed, the process goes to END to end the process and prepare for the next startup timing.

[0054] <Step S16> Because the second DC current estimation unit 20B and the third DC current estimation unit 20C are deemed to be normal in step S15, it is determined in step S16 from the determinations in steps S12 to S14 that the first DC current estimation unit 20A is not normal, that is, that an abnormality has occurred. This determination result can be displayed on a display means (not shown) and can also be stored as an error code (abnormality information). If it is determined that an abnormality has occurred, the process proceeds to step S17.

[0055] In step S17, it is determined whether the difference ΔIbc between the second DC current estimate value Bi and the third DC current estimate value Ci is equal to or less than a second difference threshold Ishd2, where the second difference threshold Ishd2 is set to be smaller than the first difference threshold Ishd1.

[0056] If the difference ΔIbc is equal to or smaller than the second difference threshold Ishd2 (YES determination), the process proceeds to step S18, and if the difference ΔIbc exceeds the second difference threshold Ishd2 (NO determination), the process proceeds to step S19.

[0057] When the difference ΔIbc is equal to or less than the second difference threshold Ishd2, it is assumed that both the second DC current estimation unit 20B and the third DC current estimation unit 20C are calculating accurate DC current values, and conversely, when the difference ΔIbc exceeds the second difference threshold Ishd2, it is assumed that both the second DC current estimation unit 20B and the third DC current estimation unit 20C are not calculating sufficiently accurate DC current values.

[0058] <Step S18> Because it is assumed in step S17 that both the second DC current estimation unit 20B and the third DC current estimation unit 20C are calculating accurate DC current values, in step S18, switching is performed to the second DC current estimation unit 20B or the third DC current estimation unit 20C. The switched DC current estimation value is used to control the motor in place of the first DC current estimation value Ai.

[0059] It is also possible to use a predetermined DC current estimation value (fixed current value) instead of the first DC current estimation value Ai for controlling the motor without switching to the second DC current estimation unit 20B or the third DC current estimation unit 20C. After the control of step S18 is executed, the process goes to END to end the process and prepare for the next start timing.

[0060] <Step S19> Because it is determined in step S17 that the second DC current estimation unit 20B and the third DC current estimation unit 20C do not calculate sufficiently accurate DC current values, in step S19, switching to the second DC current estimation unit 20B or the third DC current estimation unit 20C is not performed. In this case, the process proceeds to control for limiting the torque of the motor without using the first DC current estimated value Ai. After the control of step S19 is executed, the process exits to END and ends, and preparations are made for the next start-up timing.

[0061] <Step S20> Returning to steps S12 and S13, it is determined that the difference ΔIab between the first DC current estimate Ai and the second DC current estimate Bi, and the difference ΔIac between the first DC current estimate Ai and the third DC current estimate Ci are less than the first difference threshold Ishd1 (NO determination). This indicates that the first DC current estimator 20A is in a normal state.

[0062] Therefore, in step S20, it is determined whether the difference ΔIab is equal to or less than the third difference threshold Ishd3. If it is determined that the difference ΔIab is equal to or less than the third difference threshold Ishd3 (YES determination), the process proceeds to step S21. Here, the relationship is set such that the third difference threshold Ishd3 is smaller than the first difference threshold Ishd1. Alternatively, the relationship may be set such that the second difference threshold Ishd2 is equal to the third difference threshold Ishd3.

[0063] On the other hand, if it is determined that the difference ΔIab exceeds the third difference threshold Ishd1 (NO determination), the process proceeds to step S24. This determination is made on the assumption that the first DC current estimate Ai is not a sufficiently normal current value.

[0064] <Step S21> In step S21, it is determined whether the difference ΔIac is equal to or less than the third difference threshold Ishd3. If it is determined that the difference ΔIac is equal to or less than the third difference threshold Ishd3 (YES determination), the process proceeds to step S22.

[0065] On the other hand, if it is determined that the difference ΔIac exceeds the third difference threshold Ishd3 (NO determination), the process proceeds to step S24. This determination is made on the assumption that the first DC current estimate Ai is not a sufficiently normal current value.

[0066] Step S22: In step S22, it is determined whether the difference ΔIbc is equal to or less than the third difference threshold Ishd3. If it is determined that the difference ΔIbc is equal to or less than the third difference threshold Ishd3 (YES determination), the process proceeds to step S23. This determination is made on the assumption that the second DC current estimated value Bi or the third DC current threshold Ci is a normal current value.

[0067] On the other hand, if it is determined that the difference ΔIbc exceeds the third difference threshold Ishd3 (NO determination), the process proceeds to step S24. This determination is made on the assumption that the second DC current estimated value Bi or the third DC current threshold Ci is not a sufficiently normal current value.

[0068] <Step S23> Steps S20, S21, and S22 determine that the first DC current estimation unit 20A, the second DC current estimation unit 20B, and the third DC current estimation unit 20C are likely to be normal. Therefore, the first DC current estimation value Ai by the first DC current estimation unit 20A is used to control the motor. After the control of step S23 is executed, the process skips to END and ends, and preparations are made for the next start timing.

[0069] Here, if there is abnormality information (such as information displayed on a display means or a stored error code) indicating that the first DC current estimation value Ai was previously abnormal, the abnormality information can be deleted if it is determined in steps S20, S21, and S22 that the first DC current estimation unit 20A is likely to be normal. Also, if it is determined in steps S20, S21, and S22 that the first DC current estimation unit 20A is likely to be normal, the abnormality information can be deleted for each drive cycle.

[0070] That is, if there is abnormality information indicating that the first DC current estimated value Ai was previously determined to be abnormal, the abnormality information is deleted when the first DC current estimating unit 20A returns to a normal state.

[0071] <Step S24> In steps S20, S21, and S22, the first DC current estimate Ai, the second DC current estimate Bi, and the third DC current estimate Ci are deemed not to be sufficiently normal current values. Therefore, in step S24, the current first DC current estimate Ai is not used, and the first DC current estimate Ai used at the previous startup timing is used to control the motor. After the control of step S24 is executed, the process exits to END and preparations for the next startup timing are made.

[0072] As described above, the present invention provides an electric motor control device including a power converter unit that converts DC current into AC current to drive the electric motor, and a control unit that controls the power converter unit, wherein the control unit includes at least a first DC current estimation unit that generates a first DC current estimate using a first calculation method, a second DC current estimation unit that generates a second DC current estimate that is different from the first DC current estimate using a second calculation method that is different from the first calculation method, a third DC current estimation unit that generates the first DC current estimate and a third DC current estimate that is different from the second DC current estimate using a third calculation method that is different from the first and second calculation methods, and a validity diagnosis unit that evaluates the relationships between the first, second, and third DC current estimates to determine the validity of the first DC current estimate.

[0073] This makes it possible to reliably determine whether the DC current estimation unit is abnormal without using a special sensor such as a DC current sensor.

[0074] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0075] 10...power converter unit, 11...control unit, 12...stator, 13...rotor, 14u, 14v, 14w...switching elements (upper arm), 15u, 15v, 15w...switching elements (lower arm), 16...battery, 17...capacitor, 18...AC current sensor, 19...power converter control unit, 20...DC current estimation unit, 20A...first DC current estimation unit, 20B...second DC current estimation unit, 20C...third DC current estimation unit, 21...validity diagnosis unit.

Claims

1. An electric motor control device comprising a power converter unit that converts DC current to AC current to drive an electric motor, and a control unit that controls the power converter unit, wherein the control unit comprises at least: a first DC current estimation unit that generates a first DC current estimate using a first calculation method; a second DC current estimation unit that generates a second DC current estimate that is different from the first DC current estimate using a second calculation method that is different from the first calculation method; a third DC current estimation unit that generates the first DC current estimate and a third DC current estimate that is different from the second DC current estimate using a third calculation method that is different from the first and second calculation methods; and a validity diagnosis unit that evaluates the relationship between the first DC current estimate, the second DC current estimate, and the third DC current estimate to determine the validity of the first DC current estimate.

2. An electric motor control device according to claim 1, wherein the validity diagnosis unit evaluates the current value differences of the DC current estimated values ​​for different combinations of the first DC current estimated value, the second DC current estimated value, and the third DC current estimated value, to determine the validity of the first DC current estimated value.

3. An electric motor control device according to claim 2, wherein the first DC current estimated value is a control DC current estimated value used to control the electric motor, and the second DC current estimated value and the third DC current estimated value are diagnostic DC current estimated values ​​used to diagnose the first DC current estimated value.

4. A motor control device according to claim 3, wherein the validity diagnosis unit determines that the first DC current estimation value is abnormal when the current value difference between the first DC current estimation value and the second DC current estimation value, and the current value difference between the first DC current estimation value and the third DC current estimation value are both greater than a predetermined threshold value, and the current value difference between the second DC current estimation value and the third DC current estimation value is smaller than the predetermined threshold value.

5. A motor control device as set forth in claim 4, wherein the validity diagnosis unit, when determining that the first DC current estimation value is not normal, uses the second DC current estimation value or the third DC current estimation value as the control DC current estimation value used to control the motor.

6. An electric motor control device according to claim 4, wherein the validity diagnosis unit, when determining that the first DC current estimation value is not normal, uses a predetermined value of the DC current estimation value as the DC current estimation value for control.

7. An electric motor control device according to claim 4, wherein the validity diagnosis unit limits the torque of the electric motor when it determines that the first DC current estimated value is not normal.

8. An electric motor control device according to claim 4, wherein the validity diagnosis unit, if there is abnormality information indicating that the first DC current estimated value was previously determined to be abnormal, deletes the abnormality information when the first DC current estimated value returns to normal.

9. An electric motor control device according to claim 2, wherein the first DC current estimation unit generates the first DC current estimation value based on the AC current value flowing through the power converter unit and the pulse duty value that drives and controls the upper arm of the power converter unit.

10. An electric motor control device according to claim 9, wherein the second DC current estimation unit generates the second DC current estimation value based on a d-axis voltage command value and a d-axis current value to the electric motor, a q-axis voltage command value and a q-axis current value, a loss value in at least the power converter unit, and a power supply voltage value of the power converter unit.

11. An electric motor control device according to claim 10, wherein the third DC current estimation unit generates the third DC current estimation value based on the AC current value and the modulation rate and power factor of the AC current to the electric motor.

12. An electric motor control device according to claim 4, wherein the validity diagnosis unit, when determining that the first DC current estimation unit is not normal, notifies an external notification means that the first DC current estimation unit is not normal.

13. A control method for an electric motor control device comprising a power converter unit that converts DC current to AC current to drive an electric motor, and a control unit that controls the power converter unit, wherein the control unit executes at least: a first step of generating a first DC current estimate using a first calculation method; a second step of generating a second DC current estimate different from the first DC current estimate using a second calculation method different from the first calculation method; a third step of generating the first DC current estimate and a third DC current estimate different from the second DC current estimate using a third calculation method different from the first and second calculation methods; and a fourth step of evaluating the respective relationships between the first DC current estimate, the second DC current estimate, and the third DC current estimate to determine the validity of the first DC current estimate.

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