Electric drive system control device

Abstract

Provided is an electric drive system control device that calculates an input command value that commands a power converter in order to drive an electric motor at a desired operating point. The electric drive system control device predicts and calculates a current waveform component of power input to the electric motor in accordance with the input command value, predicts and calculates a loss generated in a plurality of components of the electric motor from the current waveform component, predicts and calculates the temperatures of the plurality of components of the electric motor on the basis of the loss, and, when the predicted temperature of at least one component of the electric motor exceeds each management temperature, corrects the input command value so that the predicted temperature of the component becomes equal to or less than the management temperature and outputs the corrected input command value to the power converter.

Description

Electric drive system control device

[0001] The present invention relates to a control device for an electric drive system of an automobile or the like.

[0002] With growing global awareness of protecting the global environment, the automotive industry is shifting from traditional internal combustion engines to electric motors, which do not emit greenhouse gases during operation. Electric drive systems, essential for the electrification of automobiles, comprise a power converter, an electric motor, and a control device to generate driving force from battery power. Electrically driven vehicles offer similar vehicle performance characteristics, such as acceleration / deceleration, top speed, and continuous driving characteristics, to those of internal combustion engines. Unlike internal combustion engines, electric motors do not require combustion temperature management. However, losses occur in each component during the process of converting electrical energy into rotational power using electromagnetic circuits. These losses can cause components to heat up and, depending on the component, can lead to irreversible performance degradation. Particularly during continuous driving, components continue to heat up and generate losses, which limits the motor's performance in order to prevent component temperature rise. Thermal protection of electric motor components is typically achieved by attaching temperature sensors to the coil ends and analyzing the sensor values ​​to determine the conditions under which each component's temperature does not exceed a specified control temperature. Then, when the temperature sensor value reaches a preset threshold value so that the temperature of each component does not exceed the control temperature, the input to the motor is limited to prevent an increase in loss of the motor while it is running, thereby suppressing heat generation from the components.

[0003] As an example of this type, Patent Document 1 discloses a method of calculating losses occurring in an electric motor from the difference between the input and output of the electric motor, and if the estimated temperature of the electric motor calculated by accumulating these losses exceeds a threshold value, limiting the input power to the electric motor to prevent the electric motor from overheating.

[0004] Furthermore, Patent Document 2 discloses a method for minimizing loss by comparing the loss of one-pulse control with that of other control methods and selecting the method that results in the smallest loss.

[0005] International Publication No. WO 17 / 126093 International Publication No. WO 08 / 107992

[0006] However, in the method disclosed in Patent Document 1, the input power to the motor is limited to thermally protect the components, making it difficult to continuously drive the motor at a desired operating point. Also, in the method disclosed in Patent Document 2, although motor loss can be suppressed, in situations where loss that cannot be thermally protected from the motor at the desired operating point is unavoidable, the operating point of the motor must be lowered and the input power of the motor must be limited, as in the method of Patent Document 1, making it difficult to drive the motor at a desired operating point according to operation.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control device for an electric drive system that can search for conditions under which the components of the electric motor are thermally protected and suppress restrictions on the input power to the electric motor in order to maintain the desired output of the electric motor.

[0008] In order to achieve the above object, the present invention provides a control device for an electric drive system that calculates an input command value to be given to a power converter, the power converter converting power from a power source and outputting input power to the motor, in order to drive the motor at a desired operating point, the control device comprising: a current waveform component calculation unit that predicts and calculates a current waveform component of the power input from the power converter to the motor when the calculated input command value is output; a motor component loss calculation unit that predicts and calculates, from the current waveform component calculated by the current waveform component calculation unit, losses that will occur in a plurality of components of the motor when the input command value is output, and a motor component temperature calculation unit that predicts and calculates, based on the losses calculated by the motor component loss calculation unit, temperatures of the plurality of components of the motor when the input command value is output; and when the temperature of at least one component of the motor exceeds a respective preset control temperature, the control device corrects the input command value and outputs the corrected input command value to the power converter so that the temperature of the at least one component of the motor becomes equal to or lower than the control temperature.

[0009] According to the present invention, it is possible to search for a condition where the components of the motor are thermally protected, and to suppress the restriction of the input power to the motor in order to maintain the desired output of the motor.

[0010] FIG. 1 is a functional block diagram showing the main parts of a control device for an electric drive system according to a first embodiment of the present invention; FIG. 2 is an explanatory diagram of a specific example of input command value correction processing by the control device for the electric drive system according to the first embodiment of the present invention, showing predicted losses of electric motor components for the input command value before correction; FIG. 3 is an explanatory diagram of a specific example of input command value correction processing by the control device for the electric drive system according to the first embodiment of the present invention, showing predicted temperatures of electric motor components for the input command value before correction; FIG. 4 is an explanatory diagram of a specific example of input command value correction processing by the control device for the electric drive system according to the first embodiment of the present invention, showing predicted temperatures of electric motor components for the input command value after correction; FIG. 5 is an explanatory diagram of a specific example of input command value correction processing by the control device for the electric drive system according to the first embodiment of the present invention, showing a comparison of predicted temperatures of electric motor components before and after correction of the input command value; FIG. 6 is a functional block diagram showing the main parts of a control device for an electric drive system according to a second embodiment of the present invention;

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] First Embodiment - Electric Drive System - FIG. 1 is a functional block diagram showing the main parts of a control device for an electric drive system according to a first embodiment of the present invention.

[0013] The electric drive system of this embodiment is mounted on an electric vehicle or a hybrid vehicle, and includes a control device 101 , a power converter 102 , and an electric motor 103 .

[0014] The control device 101 is a computer, and includes an arithmetic device such as a CPU, and memories such as RAM and ROM. Values ​​related to the operating point (rotation speed and torque of the electric motor 103) of the electric motor 103, which are calculated separately in response to the operation of an operating device (accelerator, brake, shift lever, etc.), are input to the control device 101. The control device 101 calculates an input command value to be issued to the power converter 102 in accordance with a program stored in the memory, and outputs the input command value to the power converter 102 so that the electric motor 103 is driven at the input operating point.

[0015] The power converter 102 is, for example, an inverter, and converts the power of a power source (not shown), such as a battery or generator, mounted on the electric vehicle based on an input command value from the control device 101 so that the power can be supplied to the electric motor 103, and inputs the converted power to the electric motor 103. Of the power input to the electric motor 103, the current is proportional to the torque of the electric motor 103, and the voltage is proportional to the rotation speed. The type of the power converter 102 is not particularly limited.

[0016] The electric motor is, for example, an AC electric motor, and is driven by power input from the power converter 102 to run the electric vehicle. Although not shown in Fig. 1, the output of the electric motor 103 is transmitted to the axle via a reduction gear in an electric vehicle, or via a transmission or a power split mechanism in a hybrid vehicle. The type of the electric motor 103 is not particularly limited.

[0017] -Control Device- The control device 101 includes a control unit 111, a current waveform component calculation unit 112, a motor component loss calculation unit 113, a motor component temperature calculation unit 114, and a loss / temperature comparison unit 115. The control unit 111, the current waveform component calculation unit 112, the motor component loss calculation unit 113, the motor component temperature calculation unit 114, and the loss / temperature comparison unit 115 are hardware elements such as circuits that execute the respective processes, or software elements such as programs.

[0018] Control Unit The control unit 111 calculates an input command value to the power converter 102 for driving the electric motor 103 at a desired operating point.

[0019] Current Waveform Component Calculation Unit The current waveform component calculation unit 112 predicts and calculates components (e.g., fundamental wave components, n-th order current In, d-axis component Idn of the n-th order current, q-axis component Iqn of the n-th order current, and order n of the n-th order current) contained in the current waveform of power input from the power converter 102 to the electric motor 103 when the input command value calculated by the control unit 111 is output without correction. The method of calculating the current waveform components in the current waveform component calculation unit 112 is not particularly limited. For example, a map of d- and q-axis inductances for each operating point can be stored in memory, and the d-axis current and q-axis current at the input operating point can be calculated. The current waveform component calculation unit 112 also has a function of correcting the input command value (e.g., the current phase or carrier frequency of the input command value) according to the calculation results of the downstream electric motor component loss calculation unit 113, electric motor component temperature calculation unit 114, and loss / temperature comparison unit 115, and outputting the corrected input command value to the control unit 111.

[0020] Motor Component Loss Calculation Unit: The motor component loss calculation unit 113 uses the current waveform components calculated by the current waveform component calculation unit 112 to predict and calculate losses that will occur in multiple temperature-controlled components (e.g., coils and permanent magnets) of the motor 103 when the input command value calculated by the control unit 111 is output without correction. The method by which the motor component loss calculation unit 113 calculates the component losses of the motor 103 is not particularly limited. One example of the method is to prepare a loss map in memory that calculates the losses of each temperature-controlled component through electromagnetic field analysis for each operating point of the motor 103, store the loss map in memory, and then perform two-dimensional interpolation to calculate the losses of each temperature-controlled component at the input operating point. Other examples of calculation methods include an approximation formula based on the results of electromagnetic field analysis of the motor 103, or a method that uses an empirical formula obtained based on data actually measured by a measuring instrument for the motor 103. The loss calculation formula is constructed using, for example, the rotational frequency of the motor 103, current harmonic components and their orders and coefficients, etc.

[0021] Motor component temperature calculation unit The motor component temperature calculation unit 114 predicts and calculates the temperatures of the temperature-controlled components of the motor 103 when the input command value calculated by the control unit 111 is output without correction, based on the losses of the temperature-controlled components of the motor 103 calculated by the motor component loss calculation unit 113. The method for calculating the component temperatures of the motor 103 in the motor component temperature calculation unit 114 is not particularly limited, and the component temperatures can be calculated using a thermal calculation tool based on a thermal circuit network, for example. The component temperatures can also be calculated using a thermal fluid analysis tool.

[0022] Loss / Temperature Comparison Unit The loss / temperature comparison unit 115 compares the losses of each temperature-controlled component of the electric motor 103 calculated by the motor component loss calculation unit 113 and the temperatures of each temperature-controlled component of the electric motor 103 calculated by the motor component temperature calculation unit 114 with characteristic curves (characteristic curves of loss and temperature against current conditions) pre-stored in memory for each temperature-controlled component and with control temperatures pre-set and stored in memory for each temperature-controlled component. The control temperatures vary depending on the temperature-controlled component. For example, some components, such as the conductors that make up the coil, have a control temperature set according to a predetermined heat resistance grade, while other components, such as permanent magnets, have a control temperature set to a temperature that does not cause irreversible thermal demagnetization. For example, if a material that is prone to performance degradation under high heat, such as recycled magnets, is used, the control temperature is set taking this into consideration.

[0023] If, as a result of the comparison by loss / temperature comparison unit 115, the temperature of at least one of the multiple temperature-controlled components of electric motor 103 for which loss and temperature have been predicted and calculated exceeds the corresponding control temperature, current waveform component calculation unit 112 corrects the input command value and outputs it to control unit 111 so that the temperature of the at least one temperature-controlled component that exceeds the control temperature becomes equal to or lower than the corresponding control temperature, and the corrected input command value is output to power converter 102 via control unit 111.

[0024] At this time, the corrected input command value may be processed by current waveform component calculation unit 112, motor component loss calculation unit 113, motor component temperature calculation unit 114, and loss / temperature comparison unit 115, and after confirming that there are no temperature-controlled components in motor 103 that exceed the control temperature, the corrected input command value may be output to control unit 111. Note that, with regard to the input command value calculated by control unit 111, if there are no temperature-controlled components in motor 103 that exceed the control temperature, the input command value calculated by control unit 111 is output from current waveform component calculation unit 112 to control unit 111 without being corrected.

[0025] - Example of Correction - Figures 2 to 5 are explanatory diagrams of specific examples of input command value correction processing by the control device 101. Figure 2 is a diagram showing losses in temperature-controlled components (here, coil jump permanent magnets are shown as examples) of the electric motor 103 predicted for an input command value before correction at a certain operating point calculated in response to an operation. Figure 3 is a diagram showing temperatures of the temperature-controlled components of the electric motor 103 predicted for an input command value before correction under the conditions of Figure 2. Figure 4 is a diagram showing temperatures of the temperature-controlled components of the electric motor 103 predicted for an input command value after correction under the conditions of Figure 2. Figure 5 is a diagram showing a comparison of predicted temperatures of the temperature-controlled components of the electric motor 103 before and after correction of the input command value.

[0026] In this embodiment, for example, if it is expected that a temperature-controlled component of the electric motor 103 will exceed its control temperature if the input command value calculated by the control unit 111 according to the operating point is output without correction, the current input condition (for example, current phase) of the input command value is changed, and a condition under which loss in the temperature-controlled component that exceeds the control temperature will be minimized is calculated, for example, based on a characteristic line that defines the relationship between the current input condition and component loss.

[0027] As shown in Fig. 2, the control unit 111 determines an input command value based on a characteristic line at an operating point of the electric motor 103 according to the operation under conditions where loss in a predetermined temperature control component (a coil in the example of Fig. 2) with strict temperature constraints is minimized. Therefore, for other temperature control components (permanent magnets in the example of Fig. 2), the input command value calculated by the control unit 111 may not minimize loss. This component loss calculation is performed by the electric motor component loss calculation unit 113.

[0028] When the component temperatures are calculated using the characteristic curves between the current conditions and the component temperatures for the example shown in Fig. 2, if the input command value calculated by the control unit 111 is output without correction, the coil temperature is expected to fall below the management temperature, but the permanent magnet temperature is expected to exceed the management temperature, as shown in Fig. 3. Such calculation of component temperatures and comparison with the management temperatures are performed by the motor component temperature calculation unit 114 and the loss / temperature comparison unit 115, as described above.

[0029] However, like the loss shown in Fig. 2, the temperature of the permanent magnet does not become a local minimum under the conditions of the input command value calculated by the control unit 111, and there is a margin for decrease at the same operating point. The temperature of the permanent magnet becomes a local minimum when the current input condition of the input command value is shifted to the left (the current phase is delayed) on the characteristic line of the operating point in Fig. 3. Therefore, in this embodiment, the correction function of the current waveform component calculation unit 112 corrects the current input condition (current phase) of the input command value so that the temperature of the permanent magnet becomes a local minimum at the operating point in Fig. 3.

[0030] When the temperatures of the temperature-controlled components are calculated again under these corrected conditions, it is expected that the temperature of the permanent magnet will be lower than the control temperature and that the temperature of the coil will also be maintained lower than the control temperature, as shown in Figure 4. As shown in Figure 5, under the corrected input command value conditions, compared to the conditions under the input command value before correction, the temperature of one of the multiple temperature-controlled components of motor 103 (the permanent magnet in this example) that exceeded the control temperature under the conditions before correction will fall by ΔT1 to below the control temperature, while the temperature of another temperature-controlled component (the coil in this example) that was originally below the control temperature will rise by ΔT2, but a condition can be found under which the temperatures of all temperature-controlled components will be below the control temperature.

[0031] If a current input condition is found under which the temperature of any temperature-controlled component does not exceed the controlled temperature, the motor 103 can be continuously driven without changing the operating point (under the operating point characteristics of Figures 2 to 5).

[0032] If correcting the input conditions causes another temperature control component to exceed the control temperature, the correction is repeated and the temperature of each temperature control component is recalculated, for example, by correcting to a condition that minimizes loss in the temperature control component that now exceeds the control temperature. If there are no current input conditions that cause all temperature control components to be at or below the control temperature (for example, if the conditions are not satisfied even after repeating correction a set number of times, or if the conditions are not satisfied even after attempting correction under conditions that minimize loss for all temperature control components), in that case the operating point is lowered by a specified amount and the above process, such as calculating the component temperatures, is repeated.

[0033] In addition, although the current phase is corrected as a current input condition of the input command value in this example, the current input condition to be corrected is not limited to the current phase. For example, the carrier frequency of the input command value can also be corrected. The modulation method in the control unit 111 is also not particularly limited, and for example, a three-phase modulation method or a two-phase modulation method can be applied.

[0034] Effect (1) According to this embodiment, component losses and component temperatures of the electric motor 103 are predicted and calculated for an input command value calculated according to a desired operating point. If there are temperature-controlled components that exceed their respective management temperatures, the current conditions of the input command value to the power converter are corrected so that the temperatures of the individual temperature-controlled components are kept below their respective management temperatures without changing the operating point. As a result, at an operating point where any of the temperature-controlled components of the electric motor 103 exceed their management temperatures and the electric motor 103 cannot be driven, the input command value to the power converter 102 is corrected. This allows the electric motor 103 to be driven at a desired operating point while suppressing the component temperatures of the electric motor 103 below their management temperatures without limiting the input power to the electric motor 103. The corrected input command value deviates from the minimum loss value for all temperature-controlled components other than those whose losses are suppressed. Therefore, the temperature rises compared to when the input command value is not corrected, and the overall loss of each temperature-controlled component is not necessarily reduced compared to before the correction. In some cases, the correction may even increase the overall loss. However, by searching for conditions under which all temperature-controlled components are kept below the controlled temperature and avoiding restrictions on the input power to the electric motor 103, it is possible to maintain the desired operating point and ensure the target torque of the electric motor 103.

[0035] As described above, according to this embodiment, it is possible to search for conditions under which the temperature control components of the electric motor 103 are thermally protected, and to suppress the restriction of the input power to the electric motor 103 in order to maintain the desired output of the electric motor 103.

[0036] (2) In the control device 101, for example, the current phase of the input command value is corrected as a correction target. By advancing or lagging the phase of the input current to the electric motor 103, the balance of the d- and q-axis components of the current changes. This results in differences in the sensitivity of copper loss in the coils and magnetic loss in the permanent magnets, causing the loss balance to increase or decrease for each temperature-controlled component of the electric motor 103. Under certain conditions, the temperature of temperature-controlled components that are within the controlled temperature range increases, while the temperature of temperature-controlled components that exceed the controlled temperature decreases. This makes it possible to ensure the desired torque output of the electric motor 103 while thermally protecting the temperature-controlled components of the electric motor 103.

[0037] (3) As another example of a correction target, the carrier frequency of the input command value is corrected in the control device 101. Increasing the carrier frequency when calculating the input current to the electric motor 103 reduces the harmonic components of the input current to the electric motor 103, thereby reducing the overall loss of the electric motor 103. Since the reduction in loss also reduces the temperature of the components of the electric motor 103, similarly to the above, it is possible to ensure the desired torque output of the electric motor 103 while thermally protecting the temperature-controlled components of the electric motor 103.

[0038] Second Embodiment Fig. 6 is a functional block diagram showing the main parts of a control device for an electric drive system according to a second embodiment of the present invention. Fig. 6 corresponds to Fig. 1. In Fig. 6, elements that are the same as or correspond to those in the first embodiment are given the same reference numerals as those in the previously mentioned drawings, and descriptions thereof will be omitted where appropriate.

[0039] The difference between this embodiment and the first embodiment is that when the temperatures of all of the temperature-controlled components of the electric motor 103 are below the controlled temperature, the torque of the operating point of the electric motor 103 is corrected to increase according to the difference between the controlled temperature and the predicted temperature.

[0040] This embodiment is the same as the first embodiment in that the input command value is corrected so that temperature-controlled components exceeding their control temperatures are set to or below their control temperatures at operating points where the respective temperature-controlled components can be thermally protected. The difference is that when a margin is created in the output torque of the electric motor 103 due to the correction of the input command value, the torque condition of the operating point that is the basis for the calculation of the input command value is raised by that amount, and the input command value is recalculated by the control unit 111 for the operating point where the torque is improved. As in the first embodiment, the current waveform component calculation unit 112, the electric motor component loss calculation unit 113, the electric motor component temperature calculation unit 114, and the loss / temperature comparison unit 115 execute the processing for the calculated input command value, and the newly calculated input command value is corrected as necessary, so that the electric motor 103 can be driven at a new operating point where the torque is higher than the desired operating point.

[0041] The basic configuration of the control device for the drive system is the same as that of the first embodiment, but in the first embodiment, the configuration was such that thermal protection was provided by lowering the temperature of temperature control parts that exceeded the control temperature.

[0042] In other respects, this embodiment is similar to Embodiment 1. As shown in Fig. 7, according to this embodiment, the electric motor 103 can be driven under a torque condition higher by the margin created by the correction of the input command value.

[0043] The concept of operating point correction according to this embodiment can be combined with the following third and subsequent embodiments and modifications.

[0044] (Third embodiment) Fig. 8 is a functional block diagram showing the main parts of a control device for an electric drive system according to a third embodiment of the present invention. Fig. 8 corresponds to Fig. 1 of the first embodiment. In Fig. 8, elements that are the same as or correspond to those in the previously described embodiments are given the same reference numerals as in the previously described drawings, and descriptions thereof will be omitted where appropriate.

[0045] This embodiment differs from the first embodiment in that it further includes a converter component loss calculator 116. Converter component loss calculator 116 executes the same processing as that of motor component loss calculator 113 for the power converter 102, and, like current waveform component calculator 112, is hardware such as a circuit or software such as a program. Specifically, converter component loss calculator 116 predicts and calculates losses that will occur in each temperature-controlled component of power converter 102 when an input command value is output, from the current waveform components calculated by current waveform component calculator 112.

[0046] In this embodiment, the losses of each temperature-controlled component of the electric motor 103 calculated by the motor component loss calculation unit 113, as well as the losses of each temperature-controlled component of the power converter 102 calculated by the converter component loss calculation unit 116, are input to the loss / temperature comparison unit 115. The loss / temperature comparison unit 115 reads, for example, characteristic lines stored in memory for each operating point of each temperature-controlled component of the electric motor 103 and the power converter 102, i.e., the relationship between current conditions and losses. The current waveform component calculation unit 112 then corrects the input command value so that the sum of the losses of each temperature-controlled component of the electric motor 103 and each temperature-controlled component of the power converter 102 is minimized under the condition that the temperature of each temperature-controlled component of the electric motor 103 is below its respective control temperature. For example, the current waveform component calculation unit 112 compares the magnitude of the total losses of each temperature-controlled component of the electric motor 103 and the power converter 102 under multiple conditions under which the temperature of each temperature-controlled component of the electric motor 103 is below its respective control temperature, and selects the condition that minimizes the total loss.

[0047] In other respects, this embodiment is similar to the first embodiment.

[0048] In this embodiment, in addition to obtaining the same effects as in the first embodiment, it is possible to reduce losses in the entire electric drive system as much as possible.

[0049] The concept of minimizing overall loss according to this embodiment can also be combined with the following fourth embodiment and modified examples.

[0050] (Fourth embodiment) Fig. 9 is a functional block diagram showing the main parts of a control device for an electric drive system according to a fourth embodiment of the present invention. Fig. 9 corresponds to Fig. 1 of the first embodiment. In Fig. 9, elements that are the same as or correspond to those in the previously described embodiments are given the same reference numerals as in the previously described drawings, and descriptions thereof will be omitted where appropriate.

[0051] This embodiment differs from the first embodiment in that it further includes a converter component loss calculation unit 116 and a converter component temperature calculation unit 117. The converter component loss calculation unit 116 is the same as in the third embodiment. The converter component temperature calculation unit 117 executes the same processing as the motor component temperature calculation unit 114 for the power converter 102, and, like the current waveform component calculation unit 112 and the like, is hardware such as a circuit or software such as a program. Specifically, the converter component temperature calculation unit 117 calculates the temperature of each temperature-controlled component of the power converter 102 when the input command value calculated by the control unit 111 is output, based on the loss of each temperature control component of the power converter 102 calculated by the converter component loss calculation unit 116.

[0052] In this embodiment, the temperatures of each temperature-controlled component of the electric motor 103 calculated by the electric motor component temperature calculation unit 114, as well as the temperatures of each temperature-controlled component of the power converter 102 calculated by the converter component temperature calculation unit 117, are input to the loss / temperature comparison unit 115. The loss / temperature comparison unit 115 compares the temperatures of each temperature-controlled component of the power converter 102 calculated by the converter component temperature calculation unit 117 and the temperatures of each temperature-controlled component of the electric motor 103 calculated by the electric motor component temperature calculation unit 114 with the corresponding control temperatures. If the predicted temperature of at least one of the temperature-controlled components of the power converter 102 and the electric motor 103 exceeds the corresponding control temperature, the correction function of the current waveform component calculation unit 112 corrects the input command value so that the predicted temperature of the at least one temperature-controlled component becomes equal to or lower than the corresponding control temperature. Thereafter, as in the first embodiment, the temperatures of the temperature-controlled components of the power converter 102 and the electric motor 103 are predicted and calculated under conditions after the input command value has been corrected as necessary, and when it is confirmed that the predicted temperatures of all the temperature-controlled components are below the control temperature, the corrected input command value is output to the power converter 102 via the control unit 111.

[0053] In other respects, this embodiment is similar to the first embodiment.

[0054] In this embodiment, in addition to obtaining the same effects as in the first embodiment, it is possible to thermally protect not only the electric motor 103 but also the entire electric drive system including the power converter 102 .

[0055] (Modifications) The present invention is not limited to the above-described embodiments and may include various modifications. For example, each embodiment does not necessarily include all of the components described above. For example, some of the components of one embodiment may be replaced with the components of another embodiment. Furthermore, some components may be omitted or added in each embodiment. For example, the control temperature of each temperature-controlled component of the electric motor 103 may be variable rather than being a fixed value set uniformly for each component. For example, in each embodiment, by setting the temperature lowered by correcting the current input conditions as the control temperature for each temperature-controlled component, the material of the temperature-controlled component can be replaced with one with lower heat resistance. Heat resistance varies depending on the material, even for the same type of temperature-controlled component. For example, in the case of a permanent magnet, heat resistance decreases when a heavy rare earth-free permanent magnet with reduced or no heavy rare earth added is used, so the control temperature can be set lower as described above. In addition, the heat resistance of coils also decreases when enameled copper wire manufactured by recycling used coils is used instead of new coils. By setting the temperature of each component lowered by correcting the input command value as the control temperature as described above, temperature-controlled components with relatively lower heat resistance can be used.

[0056] 101...control device, 102...power converter, 103...motor, 111...control unit, 112...current waveform component calculation unit, 113...motor component loss calculation unit, 114...motor component temperature calculation unit, 115...loss / temperature comparison unit, 116...converter component loss calculation unit, 117...converter component temperature calculation unit

Claims

1. A control device for an electric drive system that calculates an input command value to be issued to a power converter, which converts power from a power source and outputs input power to an electric motor, in order to drive the motor at a desired operating point, comprising: a current waveform component calculation unit that predicts and calculates a current waveform component of the power input from the power converter to the electric motor when the calculated input command value is output; a motor component loss calculation unit that predicts and calculates losses that will occur in multiple components of the motor when the input command value is output, from the current waveform component calculated by the current waveform component calculation unit; and a motor component temperature calculation unit that predicts and calculates temperatures of the multiple components of the motor when the input command value is output, based on the losses calculated by the motor component loss calculation unit; and when the temperature of at least one component of the motor exceeds a respective preset management temperature, the input command value is corrected and output to the power converter so that the temperature of the at least one component of the motor becomes equal to or lower than the management temperature.

2. A control device for an electric drive system as claimed in claim 1, characterized in that, compared to the input command value before correction, under the input command value after correction, the temperature of at least one of the multiple components of the electric motor decreases and the temperature of at least one of the other components increases.

3. The control device for an electric drive system according to claim 1, wherein the current phase of the input command value is corrected.

4. The control device for an electric drive system according to claim 1, further comprising: a carrier frequency of the input command value being corrected.

5. A control device for an electric drive system according to claim 1, characterized in that, when the temperatures of any of a plurality of components of said electric motor fall below said control temperature, the torque of the operating point of said electric motor is corrected in the increasing direction in accordance with the difference between said control temperature and said temperature.

6. A control device for an electric drive system according to claim 1, further comprising a converter component loss calculation unit which predicts and calculates losses which will occur in a plurality of components of said power converter when said input command value is output, from said current waveform components calculated by said current waveform component calculation unit, and corrects said input command value so that the sum of the losses in said motor components and the losses in said power converter components is minimized under the condition that said temperature of said at least one component of said electric motor is equal to or lower than said control temperature.

7. A control device for an electric drive system as claimed in claim 1, comprising: a converter component loss calculation unit which predicts and calculates losses which will occur in a plurality of components of said power converter when said input command value is output, from the current waveform components calculated by said current waveform component calculation unit; and a converter component temperature calculation unit which calculates the temperatures of the components of said power converter when said input command value is output, based on the losses calculated by said converter component loss calculation unit; and when the temperature of at least one component of said power converter exceeds a respective preset management temperature, said input command value is corrected and output to said power converter so that the temperature of at least one component of said power converter becomes equal to or lower than said management temperature.

Images