Motor drive device

Abstract

This motor drive device converts DC power supplied from a DC power supply and outputs the converted DC power to a motor. The motor drive device comprises: a power conversion circuit that converts the DC power; a DC power path that connects the DC power supply and the power conversion circuit; a smoothing capacitor connected to the DC power path; a detection sensor that detects at least one of the voltage and current of the DC power; and a control device that determines the degree of resonance of a resonance circuit formed including the smoothing capacitor on the basis of the AC component among the DC component and the AC component of the DC power which are included in a detection value of the detection sensor.

Description

Motor drive unit

[0001] The present invention relates to a motor drive device.

[0002] For example, Patent Document 1 discloses a control system equipped with a temperature sensor that detects the temperature of an inverter. The control system disclosed in Patent Document 1 attempts to suppress excessive temperature rises in heat-generating components and to suppress overcurrent flow in capacitors and the like based on the temperature detected by the temperature sensor.

[0003] Patent No. 7188265

[0004] When a power conversion device in which a power conversion circuit and a smoothing capacitor are connected in parallel to a DC power source is installed in a vehicle, a resonant circuit (LC circuit) is formed by the smoothing capacitor and parasitic inductance of the DC power source and wiring, etc. The power supplied from the DC power source to the power conversion circuit contains an AC component in addition to a DC component, and the resonant circuit resonates due to the influence of the AC component. If the degree of resonance of the resonant circuit is high, the current in the path through which the DC power flows is significantly amplified, increasing the amount of heat generated by heat-generating components connected to this path. For example, when Patent Document 1 is applied to suppress heat generation in heat-generating components, a temperature sensor for detecting the temperature is required. Furthermore, to detect the temperature of each of multiple heat-generating components, multiple temperature sensors corresponding to each heat-generating component are required.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a motor drive device that can determine the resonant state of a resonant circuit including a smoothing capacitor without the need for a temperature sensor.

[0006] A first aspect of the present invention is a motor drive device that converts DC power, which is power supplied from a DC power source, and outputs the converted power to a motor, and includes a power conversion circuit that converts the DC power, a DC power path that connects the DC power source and the power conversion circuit, a smoothing capacitor connected to the DC power path, a detection sensor that detects at least one of the voltage and current of the DC power, and a control device that determines the degree of resonance of a resonant circuit formed including the smoothing capacitor, based on the AC component of the DC component and AC component of the DC power contained in the detection value of the detection sensor.

[0007] According to the present invention, the degree of resonance of a resonant circuit is determined based on the AC component contained in the DC power. When the degree of resonance increases, the AC component contained in the DC power is amplified compared to when the degree of resonance is low. Therefore, the degree of resonance of the resonant circuit can be determined based on the AC component. According to the present invention, it is possible to determine the resonant state of a resonant circuit including a smoothing capacitor without requiring a temperature sensor.

[0008] Fig. 1 is a circuit diagram showing a schematic configuration of a motor drive device according to a first embodiment of the present invention. Fig. 2 is a block diagram showing the functional configuration of a control device provided in the motor drive device according to the first embodiment of the present invention. Fig. 3 is a flowchart for explaining the operation of the control device provided in the motor drive device according to the first embodiment of the present invention. Fig. 4 is a circuit diagram showing a schematic configuration of a motor drive device according to a second embodiment of the present invention. Fig. 5 is a circuit diagram showing a schematic configuration of a motor drive device according to a third embodiment of the present invention. Fig. 6 is a circuit diagram showing a schematic configuration of a modified example of the third embodiment of the present invention.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A motor drive device according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0010] (First embodiment) Fig. 1 is a circuit diagram showing a schematic configuration of a motor drive device 1 of this embodiment. The motor drive device 1 of this embodiment is a power conversion device that is mounted on a vehicle such as an electric automobile, and converts power supplied from a battery B (a DC power source) and supplies the converted power to a motor M to drive the motor M. For example, the motor drive device 1 converts DC power supplied from the battery B into three-phase AC power and supplies the power to the motor M. The motor drive device 1 also converts regenerative power (AC power) from the motor M into DC and supplies the power to the battery B.

[0011] The battery B is a secondary battery such as a lithium ion battery, and is formed by, for example, connecting a plurality of battery modules in series. As shown in Fig. 1, the battery B has a parasitic inductance BL and a parasitic resistance BR.

[0012] Furthermore, the battery B is connected to the motor drive device 1 of this embodiment via a harness H. That is, the harness H connects the battery B to the motor drive device 1 of this embodiment. As shown in Fig. 1 , the harness H has a parasitic inductance HL and a parasitic resistance HR.

[0013] 1 , the motor drive device 1 of this embodiment is connected to a battery B via a harness H. The motor drive device 1 of this embodiment includes a positive bus bar 2 (DC power path), a negative bus bar 3 (DC power path), a power conversion circuit 4, a smoothing capacitor 5, a noise removal capacitor 6, a voltage sensor 7, and a control device 10.

[0014] The positive bus bar 2 is a conductive member connected to the positive electrode of the battery B via a harness H. The negative bus bar 3 is a conductive member connected to the negative electrode of the battery B via a harness H. As shown in FIG. 1 , a power conversion circuit 4, a smoothing capacitor 5, and a noise removal capacitor 6 are connected in parallel to the positive bus bar 2 and the negative bus bar 3.

[0015] The positive bus bar 2 and the negative bus bar 3 form a power path connecting the power conversion circuit 4 and the battery B. The power output from the battery B (hereinafter referred to as DC power) is a current that is mainly a DC component and also contains an AC component. This DC power is supplied to the power conversion circuit 4, the smoothing capacitor 5, and the noise elimination capacitor 6 via the positive bus bar 2.

[0016] The power conversion circuit 4 is an inverter circuit for converting DC power supplied from the battery B into AC power to be supplied to the motor M. As shown in FIG. 1 , the power conversion circuit 4 has three legs 4a corresponding to the respective phases of the motor M. Each leg 4a has an upper arm 4b and a lower arm 4c. The upper arm 4b is connected to the positive side of the battery B via the positive bus bar 2. The lower arm 4c is connected to the negative side of the battery B via the negative bus bar 3. The upper arm 4b and the lower arm 4c are connected in series. An output terminal that connects the leg 4a and the motor M is connected between the upper arm 4b and the lower arm 4c.

[0017] Each of the upper arm 4b and the lower arm 4c includes a power transistor. The control terminals of these power transistors are connected to the control device 10. These power transistors are controlled by the control device 10, thereby driving the power conversion circuit 4.

[0018] Each of these power transistors is formed using one or more semiconductor elements, such as an IGBT (Insulated Gate Bipolar Transistor). Alternatively, the semiconductor elements may be made of silicon carbide (SiC) or gallium nitride (GaN).

[0019] As shown in FIG. 1 , the smoothing capacitor 5 is a capacitor element having one end connected to the positive bus bar 2 and the other end connected to the negative bus bar 3. The smoothing capacitor 5 may be formed of a plurality of capacitor elements connected in series. One end of the smoothing capacitor 5 is connected to the positive electrode of battery B via the positive bus bar 2. The other end of the smoothing capacitor 5 is connected to the negative electrode of battery B via the negative bus bar 3. The smoothing capacitor 5 smoothes ripples in the DC power output from battery B.

[0020] The noise elimination capacitor 6 is formed of two capacitor elements 6a (heat-generating components) connected in series. The noise elimination capacitor 6 may be formed of a larger number of capacitor elements 6a. One end of the noise elimination capacitor 6 is connected to the positive bus bar 2, and the other end is connected to the negative bus bar 3. That is, one end of the noise elimination capacitor 6 is connected to the positive electrode of battery B via the positive bus bar 2. The other end of the noise elimination capacitor 6 is connected to the negative electrode of battery B via the negative bus bar 3. Furthermore, the midpoint between the capacitor elements 6a of the noise elimination capacitor 6 is connected to ground.

[0021] The noise removal capacitor 6 and a core (not shown) form a noise filter. The noise filter suppresses changes in the current flowing through the positive bus bar 2 and the negative bus bar 3, thereby suppressing the generation of electromagnetic noise.

[0022] The voltage sensor 7 is a sensor that detects the voltage of the DC power output from the battery B (i.e., the voltage applied to the positive bus bar 2 and the negative bus bar 3). In this embodiment, the voltage sensor 7 is connected to one end and the other end of the smoothing capacitor 5, and detects the voltage across the smoothing capacitor 5 to detect the voltage of the DC power supplied to the smoothing capacitor 5. The voltage sensor 7 is connected to the control device 10 as shown in FIG. 1 . The detected value output from the voltage sensor 7 is input to the control device 10.

[0023] In the motor drive device 1 of this embodiment, when DC power is supplied, the capacitor elements 6a of the smoothing capacitor 5 and the noise removal capacitor 6 generate heat. That is, in this embodiment, the smoothing capacitor 5 and the capacitor elements 6a of the noise removal capacitor 6 are heat-generating components. The amount of heat generated by these heat-generating components varies depending on the magnitude of the DC power current. As described above, DC power contains a DC component and an AC component. Of these, the AC component is significantly amplified as the degree of resonance of the resonant circuit 100, which will be described later, increases. Therefore, when the degree of resonance of the resonant circuit 100 increases and the AC component is significantly amplified, the amount of heat generated by the heat-generating components increases, causing the temperature of the heat-generating components to rise.

[0024] When the motor drive device 1 is connected to the vehicle's battery B and harness H, a resonant circuit 100 is formed that includes a parasitic inductance BL of the battery B, a parasitic inductance HL of the harness H, and a smoothing capacitor 5. The resonant circuit 100 resonates due to the influence of an AC component contained in the DC power. The DC power generates an AC component that includes various frequencies according to the drive of the motor M. The AC component includes various frequencies, and the resonant circuit 100 is always in an oscillating state. However, when the main frequency of the AC component matches the resonant frequency of the resonant circuit 100, the resonant circuit 100 resonates strongly. In other words, the degree of resonance of the resonant circuit 100 changes depending on the drive conditions of the motor M, and the degree of resonance becomes greater under certain drive conditions.

[0025] When the degree of resonance of the resonant circuit 100 increases, the AC component contained in the DC power is significantly amplified. As a result, the current value of the DC power increases. When DC power with such a significantly amplified AC component is supplied to the smoothing capacitor 5 or the capacitor element 6a of the noise removal capacitor 6, the amount of heat generated by the heat-generating components increases as described above.

[0026] The control device 10 controls the power conversion circuit 4 to control the rotation speed of the motor M. The control device 10 controls the power conversion circuit 4 to PWM control the motor M. The control device 10 controls the current supplied to the motor M to adjust the output torque of the motor M.

[0027] In this embodiment, the control device 10 determines the degree of resonance of the resonant circuit 100 based on the detection value (voltage value) of the voltage sensor 7. When the degree of resonance of the resonant circuit 100 is high, the control device 10 estimates the temperature of the heat-generating components (the smoothing capacitor 5 and the capacitor element 6a of the noise removal capacitor 6). When the estimated temperature of the heat-generating components exceeds the heat-resistant temperature preset for each heat-generating component, the control device 10 suppresses the current supplied to the motor M to reduce the output torque of the motor M.

[0028] The control device 10 is also connected to a higher-level control unit (e.g., an ECU: Electronic Control Unit) (not shown). In this embodiment, when the degree of resonance of the resonant circuit 100 is high, the control device 10 calculates the effective current value of the DC power and outputs it to the control unit (i.e., outside the motor drive device 1).

[0029] 2 is a block diagram showing the functional configuration of the control device 10. As shown in this figure, the control device 10 includes an AD conversion unit 11, a resonance-time estimated temperature calculation unit 12, a non-resonance-time estimated temperature calculation unit 13, a switching unit 14, a temperature comparison unit 15, a power conversion circuit control unit 16, and a current effective value calculation unit 17.

[0030] The AD converter 11 is connected to the voltage sensor 7 and converts the voltage value input from the voltage sensor 7 into a digital signal. The resonance-time estimated temperature calculator 12 estimates the temperature of the heat-generating component, including the temperature rise due to the AC component of the DC power. The resonance-time estimated temperature calculator 12 calculates the estimated temperature of the heat-generating component used when the resonant circuit 100 resonates. Note that "when resonating" here means that the degree of resonance of the resonant circuit 100 (the AC component of the DC power) exceeds a pre-stored reference value. The resonance-time estimated temperature calculator 12 determines the degree of resonance of the resonant circuit 100 based on the AC component of the DC component and the AC component of the DC power included in the voltage value of the voltage sensor 7.

[0031] More specifically, as shown in FIG. 2 , the resonance-time estimated temperature calculation unit 12 includes an input-side low-pass filter 20, a DC component current value calculation unit 21, a DC component temperature rise value calculation unit 22, an input-side high-pass filter 23, an AC component current value calculation unit 24, an AC component temperature rise value calculation unit 25, a first adder 26, a reference temperature calculation unit 27, a second adder 28, an output-side low-pass filter 29, a non-resonance-time AC component acquisition unit 30, and a comparator 31.

[0032] The input-side low-pass filter 20 is a filter that passes only the DC component by removing the AC component from the voltage value output from the AD conversion unit 11. By using this input-side low-pass filter 20, only the DC component is extracted from the voltage value.

[0033] The DC component current value calculation unit 21 calculates the value of the DC component (DC component current value) by converting the DC component extracted by the input-side low-pass filter 20 into a current value. Note that, for example, a coefficient for converting the DC component into a current value is stored in advance in the control device 10, and the DC component current value calculation unit 21 calculates the DC component current value using this coefficient.

[0034] The DC component temperature rise value calculation unit 22 calculates a temperature rise value due to the DC component (DC component temperature rise value) from the DC component current value. Note that, for example, the control device 10 stores a coefficient for converting the DC component current value into a DC component temperature rise value for each heat-generating component, and the DC component temperature rise value calculation unit 22 calculates the temperature rise value for each heat-generating component.

[0035] The input-side high-pass filter 23 is a filter that passes only the AC component by removing the DC component from the voltage value output from the AD conversion unit 11. By using this input-side high-pass filter 23, only the AC component is extracted from the voltage value.

[0036] The AC component current value calculation unit 24 calculates the value of the AC component (AC component current value) by converting the AC component extracted by the input-side high-pass filter 23 into a current value. Note that, for example, a coefficient for converting the AC component into a current value is stored in advance in the control device 10, and the AC component current value calculation unit 24 calculates the AC component current value using this coefficient.

[0037] The AC component temperature rise value calculation unit 25 calculates a temperature rise value due to the AC component (AC component temperature rise value) from the AC component current value. Note that, for example, the control device 10 stores a coefficient for converting the AC component current value into an AC component temperature rise value for each heat-generating component, and the AC component temperature rise value calculation unit 25 calculates the temperature rise value for each heat-generating component.

[0038] The first adder 26 adds together the temperature rise value due to the DC component (DC component temperature rise value) calculated by the DC component temperature rise value calculation unit 22 and the temperature rise value due to the AC component (AC component temperature rise value) calculated by the AC component temperature rise value calculation unit 25. The first adder 26 adds together the DC component temperature rise value and the AC component temperature rise value for each heat-generating component.

[0039] The reference temperature calculation unit 27 calculates the temperature (reference temperature) of each heat-generating component when no DC power is supplied. For example, the temperature of the heat-generating component changes depending on the outside air temperature, the temperature of the housing that houses the heat-generating component, and the temperature of the cooling device. The reference temperature calculation unit 27 acquires parameters that change the temperature of the heat-generating component when no DC power is supplied from sensors or a higher-level control device (not shown), and calculates the reference temperature based on these parameters.

[0040] The second adder 28 adds the sum of the first adder 26 and the reference temperature calculated by the reference temperature calculation unit 27. That is, the second adder 28 outputs a value obtained by adding the DC component temperature rise value, the AC component temperature rise value, and the reference temperature. The value obtained by adding the DC component temperature rise value, the AC component temperature rise value, and the reference temperature is the estimated temperature of the heat-generating component when the resonant circuit 100 is resonating (when the degree of resonance is large).

[0041] The output low-pass filter 29 removes noise components contained in the signal output from the second adder 28. The output of the output low-pass filter 29 is output from the resonance-time estimated temperature calculation unit 12. That is, the resonance-time estimated temperature calculation unit 12 outputs an estimated temperature (resonance-time estimated temperature) for each heat-generating component when the resonant circuit 100 resonates. Such estimated temperatures of the heat-generating components when the resonant circuit 100 resonates are input to the switching unit 14.

[0042] The non-resonant AC component acquisition unit 30 acquires the current value of the AC component included in the DC power when the resonant circuit 100 is not resonating. For example, the control device 10 stores a table showing the relationship between the drive state of the motor M and the current value (reference value) of the AC component included in the DC power when the resonant circuit 100 is not resonating. The non-resonant AC component acquisition unit 30 acquires the current value of the AC component included in the DC power when the resonant circuit 100 is not resonating (non-resonant AC component current value) based on this table and a signal (e.g., a torque command value) indicating the drive state of the motor M input from the outside. Note that "when not resonating" here means that the degree of resonance of the resonant circuit 100 (the AC component of the DC power) does not exceed a pre-stored reference value.

[0043] The comparator 31 compares the AC component current value calculated by the AC component current value calculation unit 24 with the non-resonance AC component current value acquired by the non-resonance AC component acquisition unit 30. Furthermore, if the AC component current value calculated by the AC component current value calculation unit 24 exceeds the non-resonance AC component current value (reference value), the comparator 31 outputs a determination result indicating that the degree of resonance is large. On the other hand, if the AC component current value calculated by the AC component current value calculation unit 24 does not exceed the non-resonance AC component current value (reference value), the comparator 31 outputs a determination result indicating that the degree of resonance is small.

[0044] In this way, the resonance-time estimated temperature calculation unit 12 extracts the AC component from the DC component and AC component of the DC power contained in the voltage value of the voltage sensor 7 using the input-side high-pass filter 23 and the AC component current value calculation unit 24. Furthermore, the resonance-time estimated temperature calculation unit 12 determines the degree of resonance of the resonant circuit 100 using the non-resonance-time AC component acquisition unit 30 and the comparator 31.

[0045] The non-resonance estimated temperature calculation unit 13 calculates the estimated temperatures of the heat-generating components (non-resonance estimated temperatures) on the assumption that the resonant circuit 100 is in a non-resonance state. For example, the non-resonance estimated temperature calculation unit 13 calculates the estimated temperatures of the heat-generating components based on a signal indicating the driving state of the motor M (e.g., a torque command value, etc.).

[0046] The switching unit 14 receives the resonance-time estimated temperature from the resonance-time estimated temperature calculation unit 12 and the non-resonance-time estimated temperature from the non-resonance-time estimated temperature calculation unit 13. The switching unit 14 outputs either the resonance-time estimated temperature or the non-resonance-time estimated temperature based on the determination result received from the comparator 31. For example, when the determination result received from the comparator 31 indicates that the degree of resonance is high, the switching unit 14 outputs the resonance-time estimated temperature. On the other hand, when the determination result received from the comparator 31 indicates that the degree of resonance is low, the switching unit 14 outputs the non-resonance-time estimated temperature.

[0047] The temperature comparison unit 15 compares the estimated temperature (resonance estimated temperature or non-resonance estimated temperature) output from the switching unit 14 with the heat-resistant temperature of each heat-generating component, and outputs the result. The comparison result from the temperature comparison unit 15 is input to the power conversion circuit control unit 16. Note that the heat-resistant temperature here does not mean a temperature at which the heat-generating component will immediately fail if exceeded, but rather a temperature at which caution is required regarding the temperature of the heat-generating component. In other words, the heat-resistant temperature here is a temperature set with a certain margin of error relative to the temperature at which the heat-generating component will fail.

[0048] The power conversion circuit control unit 16 controls the power conversion circuit 4 based on a command (e.g., a torque command value) input from an external device such as a higher-level control device. In other words, the power conversion circuit control unit 16 adjusts the power supplied to the motor M via the power conversion circuit 4 based on a command input from an external device such as a higher-level control device, thereby adjusting the output torque of the motor M.

[0049] Furthermore, in this embodiment, when the power conversion circuit control unit 16 receives a comparison result from the temperature comparison unit 15 indicating that the estimated temperature exceeds the heat-resistant temperature, the power conversion circuit control unit 16 reduces the DC power supplied to the power conversion circuit 4 compared to when the estimated temperature does not exceed the heat-resistant temperature, thereby reducing the output torque of the motor M. This reduces the DC power and suppresses the temperature rise of the heat-generating components.

[0050] The RMS current calculation unit 17 calculates the RMS current value of the DC power based on the DC component current value output from the DC component current value calculation unit 21 and the AC component current value input from the AC component current value calculation unit 24. The RMS current calculation unit 17 also outputs the calculated RMS current value to an external device such as a higher-level control unit. This allows the higher-level control unit to perform control based on the RMS current value of the DC power, for example. Specifically, the higher-level control unit can estimate the states of the battery B and the harness H based on the RMS current value of the DC power and adjust the torque command value, etc., based on the estimation result.

[0051] Next, a part of the operation of the motor drive device 1 of this embodiment will be described with reference to Fig. 3. Note that, here, a part of the operation based on the resonant state of the resonant circuit 100 will be described.

[0052] 3 is a flowchart illustrating a portion of the operation of the motor drive device 1 of this embodiment. As shown in FIG. 3, the control device 10 acquires a voltage value from the voltage sensor 7 (step S1). Next, the control device 10 extracts a DC component and an AC component from the voltage value acquired in step S1 (step S2). Specifically, the control device 10 extracts the DC component by passing the output signal of the AD conversion unit 11 through the input-side low-pass filter 20. The control device 10 also extracts the AC component by passing the output signal of the AD conversion unit 11 through the input-side high-pass filter 23.

[0053] Next, the control device 10 determines whether the AC component extracted in step S2 is greater than the AC component during non-resonance (step S3). Specifically, the control device 10 compares the AC component output from the input-side high-pass filter 23 with the non-resonance AC component current value acquired by the non-resonance AC component acquisition unit 30 using the comparator 31. The control device 10 determines that the degree of resonance is high if the AC component current value calculated by the AC component current value calculation unit 24 exceeds the non-resonance AC component current value. On the other hand, the control device 10 determines that the degree of resonance is low if the AC component current value calculated by the AC component current value calculation unit 24 does not exceed the non-resonance AC component current value.

[0054] If it is determined in step S3 that the degree of resonance is small, the control device 10 returns to step S1. In other words, if the degree of resonance is small, steps S1 to S3 are repeated. Although not shown in the flowchart, if the degree of resonance is small, the control device 10 compares the estimated temperature of the heat-generating component calculated by the non-resonance estimated temperature calculation unit 13 with the heat-resistant temperature of the heat-generating component to monitor the state of the heat-generating component.

[0055] If it is determined in step S3 that the degree of resonance is high, the control device 10 estimates the temperature of the heat-generating component from the DC component and AC component extracted in step S2 (step S4). Specifically, the control device 10 calculates the temperature rise due to the DC component from the DC component current value using the DC component temperature rise value calculation unit 22. The control device 10 also calculates the temperature rise due to the AC component from the AC component current value using the AC component temperature rise value calculation unit 25. The control device 10 then calculates the estimated temperature of the heat-generating component when the resonant circuit 100 is resonating (when the degree of resonance is high) using the first adder 26 and the second adder 28.

[0056] Next, the control device 10 determines whether the temperature of the heat-generating component during resonance (the estimated temperature calculated in step S3) exceeds the heat-resistant temperature of the heat-generating component (step S5). Specifically, the control device 10 uses the temperature comparison unit 15 to compare the estimated temperature calculated in step S3 with the heat-resistant temperature and makes the above determination.

[0057] If, in step S5, the temperature of the heat-generating component during resonance (the estimated temperature calculated in step S3) does not exceed the heat-resistant temperature of the heat-generating component, the control device 10 returns to step S1. On the other hand, if, in step S5, the temperature of the heat-generating component during resonance (the estimated temperature calculated in step S3) exceeds the heat-resistant temperature of the heat-generating component, the control device 10 adjusts the current supplied to the motor M to reduce the output torque (step S6). Specifically, the control device 10 reduces the output torque of the motor M by causing the power conversion circuit control unit 16 to reduce the DC power supplied to the power conversion circuit 4. After step S6, the control device 10 returns to step S1.

[0058] The motor drive device 1 of this embodiment converts DC power, which is power supplied from battery B, and outputs it to motor M. The motor drive device 1 of this embodiment also includes a power conversion circuit 4, a positive bus bar 2, a negative bus bar 3, a smoothing capacitor 5, a voltage sensor 7, and a control device 10. The power conversion circuit 4 converts DC power. The positive bus bar 2 and the negative bus bar 3 connect battery B to the power conversion circuit 4. The smoothing capacitor 5 is connected to the positive bus bar 2 and the negative bus bar 3. The voltage sensor 7 detects the voltage of the DC power. The control device 10 determines the degree of resonance of resonant circuit 100 formed including smoothing capacitor 5, based on the AC component of the DC component and AC component of the DC power contained in the detection value of voltage sensor 7.

[0059] According to the motor drive device 1 of this embodiment, the degree of resonance of the resonant circuit 100 is determined based on the AC component contained in the DC power. When the degree of resonance increases, the AC component contained in the DC power is amplified compared to when the degree of resonance is low. Therefore, the degree of resonance of the resonant circuit 100 can be determined based on the AC component. According to the motor drive device 1 of this embodiment, it is possible to determine the resonant state of the resonant circuit 100 including the smoothing capacitor 5 without requiring a temperature sensor.

[0060] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 determines that the degree of resonance of the resonant circuit 100 is high when the AC component exceeds a predetermined reference value (the current value of the AC component contained in the DC power when there is no resonance).

[0061] According to the motor drive device 1 of this embodiment, the degree of resonance of the resonant circuit 100 can be easily determined simply by comparing the AC component contained in the DC power with a reference value.

[0062] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 calculates an estimated temperature of the heat-generating component based on the DC component and the AC component. With the motor drive device 1 of this embodiment, it is possible to estimate the temperature of the heat-generating component by using not only the temperature rise value due to the AC component but also the temperature rise value due to the DC component. Therefore, with the motor drive device 1 of this embodiment, it is possible to accurately estimate the temperature of the heat-generating component. Furthermore, by being able to accurately estimate the temperature of the heat-generating component in this way, it is possible to prevent excessive suppression of the temperature rise of the heat-generating component.

[0063] Furthermore, in the motor drive device 1 of this embodiment, when the estimated temperature exceeds a predetermined heat resistance temperature, the control device 10 reduces the DC power supplied from the battery B to the power conversion circuit 4. The motor drive device 1 of this embodiment can prevent the temperature of the heat-generating components from rising above their heat resistance temperature.

[0064] Furthermore, in the motor drive device 1 of this embodiment, the detected values ​​are obtained using a voltage sensor 7 that detects the voltage applied to the positive bus bar 2 and the negative bus bar 3. For example, if a voltage sensor for measuring the terminal voltage of the smoothing capacitor 5 is installed for another purpose, this voltage sensor can be used as the voltage sensor 7 in the motor drive device 1 of this embodiment. Therefore, it is possible to determine the resonant state of the resonant circuit 100 without increasing the number of new parts.

[0065] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 converts the AC component contained in the detection value of the voltage sensor into a current value, and then determines, based on the AC component, the degree of resonance of the resonant circuit 100 formed including the smoothing capacitor 5. With the motor drive device 1 of this embodiment, it is possible to calculate the temperature rise value based on the current value.

[0066] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 is capable of calculating the effective current value of the DC power based on the DC component and the AC component and outputting the effective current value to the outside. With the motor drive device 1 of this embodiment, for example, the upper control unit can estimate the state of the battery B or the harness H based on the effective current value of the DC power and adjust the torque command value, etc., based on the estimation result.

[0067] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Fig. 4. In the description of this embodiment, the description of the same parts as those in the first embodiment will be omitted or simplified.

[0068] FIG. 4 is a circuit diagram showing a schematic configuration of a motor drive device 1A of this embodiment. As shown in this figure, the motor drive device 1A of this embodiment includes a current sensor 8. The current sensor 8 is a sensor that detects the current of DC power output from battery B (i.e., the current of DC power flowing through the positive bus bar 2 and the negative bus bar 3). In this embodiment, the current sensor 8 is provided so as to surround the positive bus bar 2, and detects the current flowing through the positive bus bar 2. The current sensor 8 is connected to a control device 10 as shown in FIG. 4. The detected value output from the current sensor 8 is input to the control device 10.

[0069] In this embodiment, the control device 10 uses the detection value of the current sensor 8 instead of the detection value of the voltage sensor 7 in the first embodiment to determine the degree of resonance of the resonant circuit 100. In other words, the control device 10 determines the degree of resonance of the resonant circuit 100 formed including the smoothing capacitor 5 based on the AC component of the DC component and AC component of the DC power contained in the detection value of the current sensor 8.

[0070] The specific functional configuration of the control device 10 of this embodiment is the same as that of the control device 10 of the first embodiment, except that the DC component current value calculation unit 21 and the AC component current value calculation unit 24 are omitted. Therefore, a description of the specific functional configuration of the control device 10 of this embodiment will be omitted here.

[0071] According to the motor drive device 1A of this embodiment, the control device 10 does not need to have the DC component current value calculation unit 21 and the AC component current value calculation unit 24. This simplifies the configuration of the control device 10, and reduces the processing load on the control device 10.

[0072] 4, the motor drive device 1A of this embodiment includes a voltage sensor 7. However, the voltage sensor 7 may be omitted from the motor drive device 1A of this embodiment.

[0073] Third Embodiment Next, a third embodiment of the present invention will be described with reference to Fig. 5. In the description of this embodiment, the description of the same parts as those in the first embodiment will be omitted or simplified.

[0074] 5 is a circuit diagram showing a schematic configuration of a motor drive device 1B of this embodiment. As shown in this figure, the motor drive device 1B of this embodiment includes two sets of components, each set consisting of a positive bus bar 2, a negative bus bar 3, a power conversion circuit 4, a smoothing capacitor 5, a noise removal capacitor 6, a voltage sensor 7, and a control device 10. These two sets are connected in parallel to the same battery B.

[0075] In the motor drive device 1B of this embodiment, two smoothing capacitors 5 are provided, and therefore a resonant circuit 100 including one smoothing capacitor 5 and a resonant circuit 100 including the other smoothing capacitor 5 are formed. The resonant states of these resonant circuits 100 may differ.

[0076] However, according to motor drive device 1B of this embodiment, each set of control devices 10 can accurately estimate the temperature of the heat-generating components according to the DC power supplied to each power conversion circuit 4. Therefore, even with motor drive device 1B having multiple sets like this, it is possible to suppress excessive heat generation in the heat-generating components and prevent excessive suppression of the output torque of motor M.

[0077] In this embodiment, as shown in Fig. 6, each set may be provided with the current sensor 8 described in the second embodiment. By providing such a current sensor 8, each control device 10 can determine the degree of resonance of the resonant circuit 100 using the detection value of the current sensor 8 instead of the detection value of the voltage sensor 7 in the first embodiment. When such a current sensor 8 is provided, the voltage sensor 7 can be omitted.

[0078] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above-described embodiments. The shapes and combinations of the components shown in the above-described embodiments are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0079] The above embodiment can also be described as follows, for example:

[0080] (Supplementary Note 1) A motor drive device that converts DC power, which is power supplied from a DC power source, and outputs the converted DC power to a motor, comprising: a power conversion circuit that converts the DC power; a DC power path that connects the DC power source and the power conversion circuit; a smoothing capacitor connected to the DC power path; a detection sensor that detects at least one of a voltage and a current of the DC power; and a control device that determines a degree of resonance of a resonant circuit formed including the smoothing capacitor, based on the AC component of a DC component and an AC component of the DC power included in a detection value of the detection sensor.

[0081] (Supplementary Note 2) The motor drive device according to Supplementary Note 1, wherein the control device determines that the degree of resonance of the resonant circuit is high when the AC component exceeds a predetermined reference value.

[0082] (Supplementary Note 3) The motor drive device according to Supplementary Note 2, wherein the control device calculates an estimated temperature of a heat-generating component that generates heat when supplied with the DC power, based on the DC component and the AC component.

[0083] (Supplementary Note 4) The motor drive device according to Supplementary Note 3, wherein the control device suppresses the DC power supplied from the DC power supply to the power conversion circuit when the estimated temperature exceeds a predetermined heat resistance temperature.

[0084] (Supplementary Note 5) The motor drive device according to any one of Supplementary Notes 1 to 4, wherein the detection sensor is a voltage sensor that detects a voltage applied to the DC power path.

[0085] (Appendix 6) The motor drive device according to appendix 5, wherein the control device converts the AC component contained in the detection value of the voltage sensor into a current value, and then determines the degree of resonance of a resonant circuit formed including the smoothing capacitor based on the AC component.

[0086] (Supplementary Note 7) The motor drive device according to any one of Supplementary Notes 1 to 4, wherein the detection sensor is a current sensor that detects the current of the DC power flowing through the DC power path.

[0087] (Appendix 8) The motor drive device according to any one of Appendices 1 to 7, wherein the control device is capable of calculating an effective current value of the DC power based on the DC component and the AC component, and outputting the effective current value to the outside.

[0088] REFERENCE SIGNS LIST 1 Motor drive device 1A Motor drive device 1B Motor drive device 2 Positive bus bar (DC power path) 3 Negative bus bar (DC power path) 4 Power conversion circuit 5 Smoothing capacitor (heat-generating component) 6 Noise removal capacitor 6a Capacitor element (heat-generating component) 7 Voltage sensor (detection sensor) 8 Current sensor (detection sensor) 10 Control device 11 AD conversion unit 12 Resonance estimated temperature calculation unit 13 Non-resonance estimated temperature calculation unit 14 Switching unit 15 Temperature comparison unit 16 Power conversion circuit control unit 17 Current effective value calculation unit 20 Input side low-pass filter 21 DC component current value calculation unit 22 DC component temperature rise value calculation unit 23 Input side high-pass filter 24 AC component current value calculation unit 25 AC component temperature rise value calculation unit 26 First adder 27 Reference temperature calculation unit 28 Second adder 29 Output side low pass filter 30 Non-resonant AC component acquisition unit 31 Comparator 100 Resonant circuit B Battery (DC power supply) H Harness M Motor

Claims

1. A motor drive device that converts DC power supplied from a DC power source and outputs the converted power to a motor, comprising: a power conversion circuit that converts the DC power; a DC power path that connects the DC power source and the power conversion circuit; a smoothing capacitor connected to the DC power path; a detection sensor that detects at least one of the voltage and current of the DC power; and a control device that determines the degree of resonance of a resonant circuit formed including the smoothing capacitor, based on the AC component of the DC and AC components of the DC power contained in the detection value of the detection sensor.

2. The motor drive device according to claim 1, wherein said control device determines that the degree of resonance of said resonant circuit is high when said AC component exceeds a predetermined reference value.

3. The motor drive device according to claim 2, characterized in that the control device calculates an estimated temperature of a heat-generating component that generates heat when supplied with DC power based on the DC component and the AC component.

4. The motor drive device according to claim 3, characterized in that the control device suppresses the DC power supplied from the DC power source to the power conversion circuit when the estimated temperature exceeds a predetermined heat resistance temperature.

5. The motor drive device according to any one of claims 1 to 4, wherein the detection sensor is a voltage sensor that detects the voltage applied to the DC power path.

6. The motor drive device according to claim 5, characterized in that the control device converts the AC component contained in the detection value of the voltage sensor into a current value, and then determines the degree of resonance of the resonant circuit formed including the smoothing capacitor based on the AC component.

7. The motor drive device according to any one of claims 1 to 4, wherein the detection sensor is a current sensor that detects the current of the DC power flowing through the DC power path.

8. A motor drive device according to any one of claims 1 to 4, characterized in that the control device is capable of calculating the effective current value of the DC power based on the DC component and the AC component, and outputting the effective current value to the outside.

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