Control device for electric motor, method for controlling electric motor

Abstract

This invention provides a highly reliable electric motor control device that not only predicts the coil temperature but also predicts the temperature of each component, enabling control with the optimal torque limiting ratio for each component. [Solution] A control device for an electric motor that controls an electric motor using a power converter, comprising: a current command value generation unit that generates a current command value based on a torque command value; a plurality of temperature prediction units that predict the temperature of each component of the power converter and the electric motor; and a torque limiting unit that outputs a limiting torque to limit the output torque of the electric motor when the temperature of each component exceeds its respective limiting temperature, wherein the torque limiting unit generates a limiting torque and a limiting time corresponding to the component that has exceeded the limiting temperature, and outputs the corresponding limiting torque prioritizing the component with the shortest limiting time.

Description

Technical Field

[0001] The present invention relates to a configuration and method of a control device for driving and controlling an electric motor, and particularly relates to a technology effective when applied to a control device for an in-vehicle electric motor that requires high stability.

Background Art

[0002] With the progress of the electrification and high performance of automobiles, the number of electric motors (motors) mounted on automobiles has been continuously increasing, and various motor systems are used according to applications, such as motors for electric power steering, motors for electric brakes, and main drive motors in the power trains of electric vehicles.

[0003] When using a motor in an automobile or the like, it is necessary to change the rotational speed and direction as required, and an optimal control method is adopted based on the type of motor and the required accuracy, such as PID control, PWM control, vector control, microcomputer control, etc. One of these motor control methods is "torque control" that detects the generated torque from an engine or a motor and keeps it within a torque setting range and at a certain level. Torque control is generally "current control" that performs torque control by controlling the current of the motor.

[0004] On the other hand, when the generated torque from an engine or a motor exceeds the set torque, there is "torque limit" that controls so as not to exceed the set value and completely disconnects the driving shaft and the driven shaft. Torque limit, like torque control, has "current limit" that suppresses the generated torque by limiting the current flowing through the motor, and has the merit that the system is simpler and can be installed at a lower cost compared to torque control.

[0005] As the background art in this technical field, for example, there is a technology such as Patent Document 1. Patent Document 1 discloses a "control device capable of operating a motor at its limit and improving the output".

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] International Publication No. 2020 / 136765 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the aforementioned "torque limiting" method, conventionally, the torque limiting coefficient was determined based solely on the temperature of the coils constituting the motor, using temperature information acquired from sensors. This problem arose because it was difficult to acquire actual temperature data used for temperature estimation and heating / cooling characteristics used in the temperature prediction section for each component of the motor.

[0008] Patent Document 1, mentioned above, describes calculating the saturation temperature using a thermal circuit model, identifying the part that deviates the most from the limit temperature, and continuing to apply current until that part reaches the limit temperature.

[0009] In the technique described in Patent Document 1, which determines the energizing time using only information on the component with the highest saturation temperature, there is a risk of overlooking components that reach the limit temperature quickly, which could lead to a sudden drop in torque when the limit temperature is reached.

[0010] Therefore, the object of the present invention is to provide a highly reliable electric motor control device and an electric motor control method using the same, which can predict not only the coil temperature but also the temperature of each component and control it with an optimal torque limiting ratio according to each component. [Means for solving the problem]

[0011] To solve the above problems, the present invention provides a motor control device for controlling an electric motor using a power converter, comprising: a current command value generation unit that generates a current command value based on a torque command value; a plurality of temperature prediction units that predict the temperature of each component of the power converter and the electric motor; and a torque limiting unit that outputs a limiting torque to limit the output torque of the electric motor when the temperature of each component exceeds its respective limiting temperature, wherein the torque limiting unit generates a limiting torque and a limiting time corresponding to the component that has exceeded the limiting temperature, and outputs the corresponding limiting torque prioritizing the component with the shortest limiting time among the components.

[0012] Furthermore, the present invention relates to a method for controlling an electric motor using a power converter, comprising: (a) generating a current command value based on a torque command value; (b) predicting the temperature of each component of the power converter and the electric motor; (c) outputting a limiting torque to limit the output torque of the electric motor when the temperature of each component exceeds its respective limiting temperature; and (d) generating a limiting torque and a limiting time corresponding to the component that has exceeded its limiting temperature, characterized in that the limiting torque is output in priority to the component with the shortest limiting time among the components. [Effects of the Invention]

[0013] According to the present invention, it is possible to realize a highly reliable electric motor control device and an electric motor control method using the same, which can predict not only the coil temperature but also the temperature of each component and control it with the optimal torque limiting ratio according to each component.

[0014] This allows for stable vehicle control without causing a sudden power drop due to temperature protection, by, for example, setting a high torque limit rate and short duration for components that experience rapid temperature changes, and setting a low torque limit rate and long duration for components that experience slow temperature changes.

[0015] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0016] [Figure 1] This is a diagram showing the schematic configuration of a control device for an electric motor according to Embodiment 1 of the present invention. [Figure 2] This is a diagram showing the basic configuration of each temperature prediction unit in FIG. 1. [Figure 3] This is a flowchart showing the control method of the electric motor according to Embodiment 1 of the present invention. [Figure 4] This is a flowchart showing a modified example of FIG. 3. [Figure 5] This is a diagram showing the configuration of a temperature prediction unit according to Embodiment 2 of the present invention. [Figure 6] This is a diagram showing the configuration of a temperature prediction unit according to Embodiment 3 of the present invention. [Figure 7] This is a diagram showing the configuration of a torque limiting unit according to Embodiment 4 of the present invention.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same configurations, and detailed descriptions of overlapping portions are omitted.

Embodiment

[0018] Referring to FIGS. 1 to 4, a control device for an electric motor and a control method for an electric motor according to Embodiment 1 of the present invention will be described. FIG. 1 is a diagram showing the schematic configuration of the control device 1 for an electric motor of this embodiment. FIG. 2 is a diagram showing the basic configurations of the temperature prediction units 2, 3, and 4 in FIG. 1. FIG. 3 is a flowchart showing the control method of the electric motor of this embodiment. FIG. 4 is a modified example of FIG. 3.

[0019] As shown in FIG. 1, the control device 1 for an electric motor of this embodiment receives a torque demand value (torque command value) 207 from an upper control device (not shown), and drives and controls an electric motor (motor) 7 using a power conversion device (inverter) 6.

[0020] The motor control device 1 comprises, as its main components, temperature prediction units 2, 3, and 4 that predict the temperature of each component of the power converter 6 and the motor 7; a limit temperature exceedance determination unit 5 that determines whether the temperature of each component exceeds its respective limit temperature; a current command value generation unit 10 that generates a current command value based on the torque request value 207; and a torque limiting unit 30 that outputs a limit torque to limit the output torque of the motor 7 based on the determination result of the limit temperature exceedance determination unit 5. In the example shown in Figure 1, the temperature prediction units include an inverter temperature prediction unit 2 that predicts the temperature of the power converter 6, a coil temperature prediction unit 3 that predicts the temperature of the coils of the motor 7, and a magnet temperature prediction unit 4 that predicts the temperature of the magnets of the motor 7. However, the components subject to temperature prediction are not limited to these.

[0021] Each temperature prediction unit 2, 3, and 4 predicts the temperature of each component of the power converter 6 and the motor 7 based on motor operating state information 203, which is information about the operating state of the motor 7 obtained from the power converter 6 and the motor 7, and external temperature sensor information 204, which is information from temperature sensors that measure the temperature of each component of the power converter 6 and the motor 7, respectively. The temperatures of each component predicted by each temperature prediction unit 2, 3, and 4 are input to the limit temperature exceedance determination unit 5.

[0022] The temperature limit exceeding determination unit 5 determines whether the predicted temperature of each input component exceeds a predetermined limit temperature. The determination result from the temperature limit exceeding determination unit 5 is input to the torque limiting unit 30.

[0023] If the temperature limit exceedance determination unit 5 determines that the predicted temperature for all components does not exceed the limit temperature, the torque limiting unit 30 will not perform torque limiting. Instead, the current command value generated by the current command value generation unit 10 will be output directly to the power converter 6 to control the electric motor 7.

[0024] On the other hand, if it is determined that the predicted temperature of any one of the components exceeds the limit temperature, the torque limiting unit 30 outputs a limit torque (limited torque command 304) to the power converter 6 to limit the output torque of the electric motor 7, and controls the electric motor 7 based on the limited torque command. At this time, the torque limiting unit 30 generates a limit torque and a limit time corresponding to the component that has exceeded the limit temperature, and outputs the corresponding limit torque starting with the component with the shortest limit time.

[0025] The basic configuration of each temperature prediction unit 2, 3, and 4 will be explained using Figure 2. In Figure 2, the temperature prediction units 2, 3, and 4 are shown as a temperature prediction unit 20a. The temperature prediction unit 20a consists of a loss calculation unit 201 and a temperature calculation unit 202. The loss calculation unit 201 calculates the loss based on the motor operating state information 203. The loss calculation may be performed using a predetermined calculation formula or by referencing a map using a pre-set map. The temperature calculation unit 202 calculates the predicted temperature 205 based on the loss calculated by the loss calculation unit 201 and the external temperature sensor information 204.

[0026] Alternatively, the predicted temperature 205 calculated by the temperature calculation unit 202 may be fed back to the loss calculation unit 201 and used in the loss calculation by the loss calculation unit 201. This is expected to improve the accuracy of the loss calculation by the loss calculation unit 201.

[0027] Using Figure 3, the method of controlling the electric motor using the electric motor control device 1 shown in Figure 1 will be explained.

[0028] When processing begins in the motor control device 1, first, in step S1, it receives a torque request value (torque command value) 207 from a higher-level control device.

[0029] Next, in step S2, the current command value generation unit 10 generates a current command value based on the torque request value (torque command value) 207.

[0030] Next, in step S3, each temperature prediction unit 2, 3, and 4 calculates a predicted temperature Te for each component (each part) of the power converter 6 and the motor 7, respectively, based on the motor operating status information 203 and the external temperature sensor information 204.

[0031] Next, in step S4, the limit temperature exceedance determination unit 5 determines whether there are any components (parts) whose predicted temperature value Te calculated by each temperature prediction unit 2, 3, and 4 exceeds a predetermined limit temperature (Tlim). If it is determined that there are no components (parts) that exceed the limit temperature (Tlim) (N), the process proceeds to step S12, and the torque limiting unit 30 does not perform torque limiting, but instead energizes the power converter 6 according to the current command value generated by the current command value generation unit 10, thereby controlling the motor 7. On the other hand, if it is determined that the predicted temperature value Te of any one component exceeds the limit temperature (Tlim) (Y), the process proceeds to step S5.

[0032] Next, in step S5, the torque limiting unit 30 generates and outputs a limiting torque (Tqdr1, Tqdr2, ..., Tqdrn) and a limiting time (t1, t2, ..., tn) corresponding to the part that has exceeded the limiting temperature (Tlim).

[0033] Next, in step S6, which is a torque limiting step, the motor control device 1 performs torque limiting on the motor 7. In step S6, first, in step S7, the torque limiting step is started.

[0034] Next, in step S8, current is supplied with the limiting current Ii calculated using the limiting torque (Tqdri).

[0035] Next, in step S9, it is determined whether or not the time limit (ti) has elapsed. If it is determined that the time limit (ti) has not elapsed (N), the determination process in step S9 is repeated until it is determined that the time limit (ti) has elapsed. On the other hand, if it is determined that the time limit (ti) has elapsed (Y), the process proceeds to step S10.

[0036] In this process, the limit time (ti) is set shorter for each smaller limit torque (Tqdri), i.e., for each larger torque limiting ratio. The torque limiting unit 30 then outputs the corresponding limit torque (Tqdri) prioritizing those with shorter limit times (ti). Torque requests are constantly received even during torque limiting, and the limit torque (Tqdri) is updated if a smaller limit torque (Tqdri) is calculated.

[0037] Next, in step S10, it is determined whether or not a limiting torque (Tqdri) exists. If it is determined that a limiting torque (Tqdri) exists (Y), the process returns to step S8 and the subsequent steps are repeated. On the other hand, if the limiting torque (Tqdri) is not updated and the time limit (ti) has elapsed, and it is determined that there is no next limiting torque (Tqdri) (N), the process proceeds to step S11 and the torque limiting is terminated.

[0038] As shown in Figure 4, temperature prediction calculations may be performed continuously even during torque limiting, and the limiting torque (Tqdri) and limiting time (ti) may be updated sequentially.

[0039] According to the present invention described in this embodiment, it becomes possible to predict the temperature of each component by modeling the loss, which is the input for temperature calculation and heat generation, based on a calculation formula. In this invention, future temperatures are predicted using a thermal circuit model, and all parts that will exceed the limit temperature are taken into consideration, and torque is sequentially limited according to the limit rate of each part.

[0040] Conventional techniques, such as those described in Patent Document 1, which determine the energizing time using only information on the component with the highest saturation temperature, carry the risk of overlooking components that reach the limit temperature quickly, resulting in a rapid torque drop when the limit temperature is reached. In the present invention, in order to properly protect the components, it is possible to slow down the torque change and increase the rate at which the required torque is met, based on the predicted temperature of each component.

[0041] Furthermore, as described in Patent Document 1, not only is the coil temperature predicted, but the temperature of each component is also predicted, allowing for control with the optimal torque limit rate for each component. For example, by setting a high torque limit rate and short duration for components that change temperature quickly, and a low torque limit rate and long duration for components that change temperature slowly, it becomes possible to control the vehicle without causing a sudden drop in output due to temperature protection. [Examples]

[0042] Referring to Figure 5, a motor control device and motor control method according to Embodiment 2 of the present invention will be described. Figure 5 is a diagram showing the configuration of the temperature prediction unit 20b in this embodiment.

[0043] In Example 1 (Figure 2), the temperature calculation unit 202 calculates the predicted temperature 205 based on the loss calculated by the loss calculation unit 201 and the external temperature sensor information 204. In contrast, as shown in Figure 5, the temperature calculation unit 202 in this embodiment differs from Example 1 (Figure 2) in that it also uses information regarding the refrigerant of a cooler installed around the motor 7 to cool the heat generated by the motor 7 in order to calculate the predicted temperature 205. The other configurations are the same as in Example 1 (Figures 1 and 2).

[0044] As shown in this embodiment (Figure 5), refrigerant state information 206, which indicates the state of the refrigerant, may be used in the temperature calculation by the temperature calculation unit 202. In the case of a combined water-cooling and oil-cooling system, either information about the cooling water or the cooling oil may be used for the refrigerant state information 206, or both may be used. By using the refrigerant state information 206 in the calculation of the predicted temperature 205 by the temperature calculation unit 202, more accurate temperature prediction becomes possible. [Examples]

[0045] Referring to Figure 6, the control device and control method for an electric motor according to Embodiment 3 of the present invention will be described. Figure 6 is a diagram showing the configuration of the temperature prediction unit 21 in this embodiment.

[0046] As shown in Figure 6, for each component constituting the power converter 6 or the electric motor 7, if there are parts with different temperature characteristics within the same component, such as when the cooling characteristics differ between the upstream side 211 and the downstream side 212 of the refrigerant in the cooler that cools the component, the temperature prediction logic may be divided for each part. In the example in Figure 6, the cooling upstream side 211 is configured with a loss calculation unit 201a and a temperature calculation unit 202a, and the cooling downstream side 212 is configured with a loss calculation unit 201b and a temperature calculation unit 202b.

[0047] When predicting the temperature of different parts of the same component, as shown in Figure 6, a temperature calculation result consolidation unit 213 may be provided to ensure that the final output predicted temperature 205 is one predicted temperature 205 for each component, or all predicted temperatures 205 for each part may be output individually. [Examples]

[0048] Referring to Figure 7, the control device and control method for an electric motor according to Embodiment 4 of the present invention will be described. Figure 7 is a diagram showing an example of the configuration of the torque limiting unit 30 in Figure 1.

[0049] As shown in Figure 7, the torque limiting unit 30 consists of a component-specific torque limiting rate / limiting time calculation unit 301 that calculates the torque limiting rate set for each component, and a limiting torque calculation unit 302 that generates a post-limiting torque command 304. The torque limiting rate and limiting time for each component are calculated based on limiting temperature exceeding part information 303, which is information about the part where the predicted temperature 205 exceeds the limiting temperature.

[0050] The limited torque command 304 is calculated by the limited torque calculation unit 302 based on the maximum torque limit rate among the torque limit rates calculated by the component-specific torque limit rate / limit time calculation unit 301 and the higher torque requirement value 207. Information on parts where the predicted temperature 205 exceeds the limit temperature is updated sequentially, the torque limit rates for each part at that moment are compared, and the maximum value is output as the torque limit rate.

[0051] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0052] 1…Control device for electric motors 2…Inverter temperature prediction unit 3…Coil temperature prediction unit 4…Magnetic temperature prediction unit 5... Temperature limit exceeded determination unit 6…Power converter (inverter) 7…Electric motor 10...Current command value generation unit 20, 20a, 20b, 21… Temperature prediction section 30... Torque limiting section 201,201a,201b...Loss calculation section 202,202a,202b…Temperature calculation section 203... Motor operating status information 204…External temperature sensor information 205... Predicted temperature 206... Refrigerant status information 207... Torque requirement value (torque command value) 211... Cooling upstream side 212…Cooling downstream side 213…Temperature calculation result organization section 301... Torque limit rate and time limit calculation unit for each component 302... Torque Limit Calculation Unit 303... Information on body parts exceeding the temperature limit 304... Torque limit directive.

Claims

1. A motor control device that controls an electric motor using a power converter, A current command value generation unit that generates a current command value based on a torque command value, A plurality of temperature prediction units that predict the temperature of each component of the power converter and the electric motor, The system includes a torque limiting unit that outputs a limiting torque to limit the output torque of the electric motor when the temperature of each of the aforementioned components exceeds its respective limiting temperature. The torque limiting unit generates a limiting torque and a limiting time corresponding to the component that has exceeded the limiting temperature. A control device for an electric motor that prioritizes outputting the corresponding limiting torque for the component with the shortest time limit among the aforementioned components.

2. A control device for an electric motor according to claim 1, Each of the aforementioned temperature prediction units includes a loss calculation unit that calculates losses based on motor operating state information, which is information relating to the operating state of the motor, A temperature calculation unit calculates the temperature based on the loss calculated by the loss calculation unit and the external temperature sensor information, which is information from the temperature sensor. A control device for an electric motor.

3. A control device for an electric motor according to claim 2, The temperature calculation unit further calculates the temperature based on information regarding the refrigerant of a cooler that cools the heat generated from the electric motor.

4. A control device for an electric motor according to claim 2, The loss calculation unit comprises a first loss calculation unit and a second loss calculation unit. The temperature calculation unit comprises a first temperature calculation unit and a second temperature calculation unit. The control device for an electric motor is configured such that the second loss calculation unit and the second temperature calculation unit calculate the temperature of different parts within the same component as the first loss calculation unit and the first temperature calculation unit.

5. A control device for an electric motor according to claim 1, The torque limiting unit includes a component-specific torque limiting rate / limiting time calculation unit that calculates the torque limiting rate set for each component, A control device for an electric motor, comprising a torque limiting calculation unit that calculates a torque limiting command after limiting based on the maximum torque limiting rate among the torque limiting rates calculated by the component-specific torque limiting rate / time limiting calculation unit and the torque command value.

6. A method for controlling an electric motor using a power converter, (a) A step of generating a current command value based on a torque command value, (b) A step of predicting the temperature of each component of the power converter and the electric motor, (c) A step of outputting a limiting torque to limit the output torque of the electric motor when the temperature of each component exceeds its respective limiting temperature, (d) The step of generating a limiting torque and a limiting time corresponding to the part that has exceeded the limiting temperature, A control method for an electric motor characterized by prioritizing the output of the corresponding limiting torque for the component with the shortest time limit among the aforementioned components.

7. A method for controlling an electric motor according to claim 6, In step (b) above, (b1) A step of calculating losses based on motor operating state information, which is information relating to the operating state of the motor, (b2) A step of calculating the temperature based on the loss calculated in step (b1) and the external temperature sensor information, which is information from the temperature sensor. A method for controlling an electric motor, characterized by having the following features.

8. A method for controlling an electric motor according to claim 7, A method for controlling an electric motor, characterized in that, in step (b2) above, the temperature is calculated based on information regarding the refrigerant of a cooler that cools the heat generated from the electric motor.

9. A method for controlling an electric motor according to claim 6, A method for controlling an electric motor, characterized in that, in step (b), the temperature of different parts within the same component is calculated.

10. A method for controlling an electric motor according to claim 6, In step (c) above, (c1) A step of calculating the torque limit rate set for each part, (c2) A step of calculating a limited torque command based on the maximum torque limiting ratio among the torque limiting ratios calculated in step (c1) and the torque command value, A method for controlling an electric motor, characterized by having the following features.

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