Motor drive device

Abstract

A motor drive device converts and outputs direct current supplied from a direct current power supply to a motor, the motor drive device including: a power conversion circuit that converts direct current; a direct current path that connects the direct current power supply and the power conversion circuit; a smoothing capacitor connected to the direct current path; a detection sensor that detects at least one of a voltage and a current of the direct current; and a control device that determines a degree of resonance of a resonance circuit formed by including the smoothing capacitor based on an alternating current component of a direct current component and an alternating current component of the direct current included in a detection value of the detection sensor.

Description

Technical Field

[0001] This invention relates to electric motor drive devices. Background Technology

[0002] For example, Patent Document 1 discloses a control system equipped with a temperature sensor for detecting the temperature of an inverter. The control system disclosed in Patent Document 1, based on the temperature detected by the temperature sensor, suppresses excessive temperature rise of heat-generating components and suppresses overcurrent flowing through capacitors, etc.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 7188265 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] However, if a power conversion device, in which the power conversion circuit and the smoothing capacitor are connected in parallel with the DC power supply, is mounted in a vehicle, a resonant circuit (LC circuit) is formed by the parasitic inductance of the DC power supply, wiring, etc., and the smoothing capacitor. The power supplied from the DC power supply to the power conversion circuit contains both DC and AC components, and the resonant circuit resonates due to the influence of the AC components. When the resonance degree of the resonant circuit is high, the current flowing through the DC path is greatly amplified, increasing the heat generated by the heat-generating components connected to that path. For example, in the case of using Patent Document 1 to suppress the heating of the heat-generating components, a temperature sensor for detecting the temperature is required. Furthermore, in order to detect the temperature of multiple heat-generating components individually, multiple temperature sensors corresponding to each heat-generating component are required.

[0008] The present invention was made in view of the above-mentioned problems, and its object is 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.

[0009] Technical solutions for solving technical problems

[0010] The first aspect of the present invention is a motor drive device that converts power supplied from a DC power source (i.e., DC electricity) and outputs it to a motor, comprising: a power conversion circuit that converts the DC electricity; a DC power path that connects the DC power source to 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 electricity; and a control device that determines the resonance degree of a resonant circuit including the smoothing capacitor based on the AC component of the DC component and AC component of the DC electricity included in the detection value of the detection sensor.

[0011] Invention Effects

[0012] According to the present invention, the resonance degree of a resonant circuit is determined based on the AC component contained in the direct current. If the resonance degree increases, the AC component contained in the direct current is amplified compared to the case of a low resonance degree. Therefore, the resonance degree of the resonant circuit can be determined based on the AC component. According to this invention, the resonance state of a resonant circuit including a smoothing capacitor can be determined without a temperature sensor. Attached Figure Description

[0013] Figure 1 This is a circuit diagram showing the schematic structure of the electric motor drive device according to the first embodiment of the present invention.

[0014] Figure 2 This is a block diagram showing the functional structure of the control device included in the electric motor drive device according to the first embodiment of the present invention.

[0015] Figure 3 This is a flowchart illustrating the operation of the control device included in the electric motor drive device according to the first embodiment of the present invention.

[0016] Figure 4 This is a circuit diagram showing the schematic structure of the electric motor drive device according to the second embodiment of the present invention.

[0017] Figure 5 This is a circuit diagram showing the schematic structure of the electric motor drive device according to the third embodiment of the present invention.

[0018] Figure 6 This is a circuit diagram illustrating a schematic structure of a modified example of the third embodiment of the present invention. Detailed Implementation

[0019] Hereinafter, an embodiment of the electric motor drive device of the present invention will be described with reference to the accompanying drawings.

[0020] (First Implementation)

[0021] Figure 1 This is a circuit diagram showing the schematic structure of the electric motor drive device 1 according to this embodiment. The electric motor drive device 1 of this embodiment is mounted in vehicles such as electric vehicles and is a power conversion device that drives the electric motor M by converting the power supplied from the battery B (DC power source) and supplying it to the electric motor M. For example, the electric motor drive device 1 converts the DC power supplied from the battery B into three-phase AC power and supplies it to the electric motor M. Additionally, the electric motor drive device 1 converts the regenerated power (AC power) from the electric motor M into DC power and supplies it to the battery B.

[0022] Battery B is a secondary battery such as a lithium-ion battery, which is formed by connecting multiple battery modules in series. Figure 1 As shown, battery B has a parasitic inductance BL and a parasitic resistance BR.

[0023] Furthermore, battery B is connected to the motor drive device 1 of this embodiment via wiring harness H. That is, wiring harness H connects battery B to the motor drive device 1 of this embodiment. Figure 1 As shown, the wire harness H has parasitic inductance HL and parasitic resistance HR.

[0024] like Figure 1 As shown, the motor drive device 1 of this embodiment is connected to the battery B via a wiring harness H. This motor drive device 1 of this embodiment includes a positive bus 2 (DC path), a negative bus 3 (DC path), a power conversion circuit 4, a smoothing capacitor 5, a noise reduction capacitor 6, a voltage sensor 7, and a control device 10.

[0025] Positive busbar 2 is a conductive component connected to the positive terminal of battery B via wiring harness H. Negative busbar 3 is a conductive component connected to the negative terminal of battery B via wiring harness H. For example... Figure 1 As shown, a power conversion circuit 4, a smoothing capacitor 5, and a noise removal capacitor 6 are connected in parallel on these positive busbars 2 and negative busbars 3.

[0026] Positive bus 2 and negative bus 3 form the power path connecting power conversion circuit 4 to battery B. The power output from battery B (hereinafter referred to as direct current) is primarily a direct current component, but also contains an alternating current component. This direct current is supplied to power conversion circuit 4, smoothing capacitor 5, and noise reduction capacitor 6 via positive bus 2.

[0027] Power conversion circuit 4 is an inverter circuit used to convert the direct current supplied from battery B into alternating current supplied to motor M. For example... Figure 1 As shown, the power conversion circuit 4 has three bridge arms 4a corresponding to each motor M. Each bridge arm 4a has an upper arm 4b and a lower arm 4c. The upper arm 4b is connected to the positive terminal of the battery B via the positive bus 2. The lower arm 4c is connected to the negative terminal of the battery B via the negative bus 3. These upper arms 4b and lower arms 4c are connected in series. An output terminal connecting the bridge arm 4a to the motor M is connected between the upper arm 4b and the lower arm 4c.

[0028] Each upper arm 4b and lower arm 4c is equipped with a power transistor. The control terminals of these power transistors are connected to the control device 10. The power conversion circuit 4 is driven by controlling these power transistors through the control device 10.

[0029] Such power transistors are formed using single or multiple semiconductor elements. Examples of such semiconductor elements include IGBTs (Insulated Gate Bipolar Transistors). Alternatively, the semiconductor elements can also be those using SiC (silicon carbide) or GaN (gallium nitride).

[0030] like Figure 1 As shown, the smoothing capacitor 5 is a capacitor element with one end connected to the positive bus 2 and the other end connected to the negative bus 3. Alternatively, the smoothing capacitor 5 can be formed by multiple capacitor elements connected in series. One end of such a smoothing capacitor 5 is connected to the positive terminal of the battery B via the positive bus 2. The other end of the smoothing capacitor 5 is connected to the negative terminal of the battery B via the negative bus 3. This smoothing capacitor 5 smooths the pulsation of the direct current output from the battery B.

[0031] The noise removal capacitor 6 is formed by two capacitor elements 6a (heat-generating components) connected in series. Alternatively, the noise removal capacitor 6 can be formed by more capacitor elements 6a. One end of the noise removal capacitor 6 is connected to the positive bus 2, and the other end is connected to the negative bus 3. That is, one end of the noise removal capacitor 6 is connected to the positive terminal of the battery B via the positive bus 2. The other end of the noise removal capacitor 6 is connected to the negative terminal of the battery B via the negative bus 3. Furthermore, the midpoints of the capacitor elements 6a of the noise removal capacitor 6 are grounded.

[0032] This noise removal uses capacitor 6 together with a core (not shown) to form a noise filter. The noise filter suppresses changes in current flowing in the positive bus 2 and the negative bus 3, thus suppressing the generation of electromagnetic noise.

[0033] Voltage sensor 7 is a sensor that detects the voltage of the direct current output from battery B (i.e., the voltage applied to the positive bus 2 and the negative bus 3). In this embodiment, voltage sensor 7 is connected to one end and the other end of smoothing capacitor 5, and the voltage of the direct current supplied to smoothing capacitor 5 is detected by detecting the voltage across the smoothing capacitor 5. Figure 1 As shown, voltage sensor 7 is connected to control device 10. The detected value output from voltage sensor 7 is input to control device 10.

[0034] In the motor drive device 1 of this embodiment, the capacitor elements 6a of the smoothing capacitor 5 and the noise removal capacitor 6 heat up when supplied with direct current. That is, in this embodiment, the capacitor elements 6a of the smoothing capacitor 5 and the noise removal capacitor 6 are heating components. The amount of heat generated by these heating components varies depending on the magnitude of the direct current. As described above, the direct current contains both direct current and alternating current components. The alternating current component is significantly amplified due to the increased resonance degree of the resonant circuit 100 described later. Therefore, when the resonance degree of the resonant circuit 100 increases and the alternating current component is significantly amplified, the amount of heat generated by the heating components increases, and the temperature of the heating components rises.

[0035] When the electric motor drive unit 1 is connected to the vehicle's battery B and wiring harness H, a resonant circuit 100 is formed, including the parasitic inductance BL of battery B, the parasitic inductance HL of wiring harness H, and the smoothing capacitor 5. The resonant circuit 100 resonates due to the influence of the AC component contained in the direct current. The direct current generates AC components containing various frequencies corresponding to the driving of the electric motor M. While the resonant circuit 100 is always in a state of vibration due to the various frequencies contained in the AC components, it resonates significantly when the dominant frequency of the AC components coincides with the resonant frequency of the resonant circuit 100. That is, the degree of resonance of the resonant circuit 100 varies according to the driving conditions of the electric motor M, and the degree of resonance increases under specific driving conditions.

[0036] When the resonance degree of the resonant circuit 100 increases, the AC component contained in the direct current is amplified significantly. As a result, the current value of the direct current increases. Thus, when the amplified AC component of the direct current is supplied to the capacitor element 6a of the smoothing capacitor 5 and the noise removal capacitor 6, as described above, the heat generation of the heat-generating components increases.

[0037] The control device 10 controls the speed of the motor M by controlling the power conversion circuit 4. The control device 10 performs PWM control on the motor M by controlling the power conversion circuit 4. This control device 10 can adjust the output torque of the motor M by controlling the current supplied to the motor M.

[0038] Furthermore, in this embodiment, the control device 10 determines the resonance degree of the resonant circuit 100 based on the detection value (voltage value) of the voltage sensor 7. Additionally, when the resonance degree of the resonant circuit 100 is high, the control device 10 estimates the temperature of the heat-generating components (the capacitor element 6a of the smoothing capacitor 5 and the noise removal capacitor 6). Furthermore, the control device 10 estimates the temperature of the heat-generating components. Additionally, if the estimated temperature of the heat-generating components exceeds a preset heat resistance temperature for each heat-generating component, the control device 10 suppresses the current supplied to the motor M, thereby reducing the output torque of the motor M.

[0039] Additionally, the control device 10 is connected to a higher-level control unit (e.g., ECU: Electronic Control Unit), which is not shown in the figure. In this embodiment, when the resonance degree of the resonant circuit 100 is large, the control device 10 calculates the effective value of the DC current and outputs it to the aforementioned control unit (i.e., the outside of the motor drive device 1).

[0040] Figure 2 This is a block diagram showing the functional structure of the control device 10. As shown in the figure, the control device 10 includes an AD conversion unit 11, a resonant estimated temperature calculation unit 12, a non-resonant estimated temperature calculation unit 13, a switching unit 14, a temperature comparison unit 15, a power conversion circuit control unit 16, and a current RMS value calculation unit 17.

[0041] 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 calculation unit 12 estimates the temperature of the heating element by including the temperature rise caused by the AC component of the DC current. The resonance-time estimated temperature calculation unit 12 calculates the estimated temperature of the heating element used when the resonant circuit 100 resonates. Here, "resonance time" refers to the degree of resonance of the resonant circuit 100 (the AC component of the DC current) exceeding a pre-stored reference value. The resonance-time estimated temperature calculation unit 12 determines the degree of resonance of the resonant circuit 100 based on the DC component of the DC current and the AC component of the AC current contained in the voltage value of the voltage sensor 7.

[0042] To explain in more detail, such as Figure 2 As shown, the above-mentioned resonant 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-resonant AC component acquisition unit 30, and a comparator 31.

[0043] The input-side low-pass filter 20 is a filter that removes the AC component from the voltage value output from the AD converter 11, allowing only the DC component to pass. With this input-side low-pass filter 20, only the DC component is extracted from the voltage value.

[0044] 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. In addition, for example, coefficients for converting DC components into current values ​​are pre-stored in the control device 10, and the DC component current value calculation unit 21 uses these coefficients to calculate the DC component current value.

[0045] The DC component temperature rise calculation unit 22 calculates the DC component temperature rise value (DC component temperature rise value) based on the DC component current value. In addition, for example, in the control device 10, a coefficient for converting the DC component current value into the DC component temperature rise value is stored for each heating element, and the DC component temperature rise value calculation unit 22 calculates the temperature rise value for each heating element.

[0046] The input-side high-pass filter 23 is a filter that removes the DC component from the voltage value output from the AD converter 11, allowing only the AC component to pass. With this input-side high-pass filter 23, only the AC component is extracted from the voltage value.

[0047] 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. In addition, for example, coefficients for converting AC components into current values ​​are pre-stored in the control device 10, and the AC component current value calculation unit 24 uses these coefficients to calculate the AC component current value.

[0048] The AC component temperature rise calculation unit 25 calculates the AC component temperature rise value (AC component temperature rise value) based on the AC component current value. Furthermore, for example, in the control device 10, a coefficient for converting the AC component current value into the AC component temperature rise value is stored for each heating element, and the AC component temperature rise value calculation unit 25 calculates the temperature rise value for each heating element.

[0049] The first adder 26 adds the temperature rise value caused by the DC component (DC component temperature rise value) calculated by the DC component temperature rise value calculation unit 22 to the temperature rise value caused by the AC component (AC component temperature rise value) calculated by the AC component temperature rise value calculation unit 25. Furthermore, in the first adder 26, the DC component temperature rise value and the AC component temperature rise value are added for each heat-generating component.

[0050] The reference temperature calculation unit 27 calculates the temperature (reference temperature) of each heating element when no direct current is supplied. For example, the temperature of the heating element varies depending on the ambient temperature, the temperature of the housing containing the heating element, and the temperature of the cooling device. The reference temperature calculation unit 27 obtains parameters from a sensor (not shown) and a host control device that show the temperature changes of the heating element when no direct current is supplied, and calculates the reference temperature based on these parameters.

[0051] The second adder 28 adds the sum of the first adder 26 to the reference temperature calculated by the reference temperature calculation unit 27. That is, the second adder 28 outputs the sum of the DC component temperature rise, the AC component temperature rise, and the reference temperature. The sum of these DC component temperature rise, AC component temperature rise, and reference temperature becomes the estimated temperature of the heating component when the resonant circuit 100 resonates (when the resonance degree is large).

[0052] The output-side low-pass filter 29 removes noise components from the signal output from the second adder 28. The output of the output-side low-pass filter 29 becomes the output of the estimated resonance temperature calculation unit 12. That is, the estimated resonance temperature calculation unit 12 outputs the estimated resonance temperature of the resonant circuit 100 for each heat-generating component. The estimated temperature of the heat-generating component at resonance of the resonant circuit 100 is then input to the switching unit 14.

[0053] The non-resonant AC component acquisition unit 30 acquires the current value of the AC component contained in the DC current when the resonant circuit 100 is not in resonance. For example, the control device 10 stores a table showing the relationship between the driving state of the motor M and the current value (reference value) of the AC component contained in the DC current when the resonant circuit 100 is not in resonance. Based on this table and a signal (e.g., torque command value) input from an external source indicating the driving state of the motor M, the non-resonant AC component acquisition unit 30 acquires the current value (non-resonant AC component current value) of the DC current contained in the resonant circuit 100 when the resonant circuit 100 is not in resonance. In addition, "non-resonant" here means that the resonance degree (AC component of DC current) of the resonant circuit 100 does not exceed the pre-stored reference value.

[0054] Comparator 31 compares the AC component current value calculated by AC component current value calculation unit 24 with the non-resonant AC component current value obtained by non-resonant AC component acquisition unit 30. Furthermore, if the AC component current value calculated by AC component current value calculation unit 24 exceeds the non-resonant AC component current value (reference value), comparator 31 outputs a determination result indicating a high degree of resonance. On the other hand, if the AC component current value calculated by AC component current value calculation unit 24 does not exceed the non-resonant AC component current value (reference value), comparator 31 outputs a determination result indicating a low degree of resonance.

[0055] Thus, the estimated temperature calculation unit 12 at resonance time extracts the DC component of the DC current and the AC component of the AC current value contained in the voltage value of the voltage sensor 7 through the aforementioned input-side high-pass filter 23 and AC component current value calculation unit 24. Furthermore, the estimated temperature calculation unit 12 at resonance time determines the degree of resonance of the resonant circuit 100 through the non-resonant AC component acquisition unit 30 and the comparator 31.

[0056] The non-resonant estimated temperature calculation unit 13 calculates the estimated temperature (non-resonant estimated temperature) of the heat-generating components based on the premise that the resonant circuit 100 is in a non-resonant state. For example, the non-resonant estimated temperature calculation unit 13 calculates the estimated temperature of each heat-generating component based on a signal (such as a torque command value) indicating the driving state of the motor M.

[0057] The switching unit 14 inputs the estimated resonance temperature from the estimated resonance temperature calculation unit 12 and the estimated non-resonance temperature from the estimated non-resonance temperature calculation unit 13. Based on the determination result input from the comparator 31, the switching unit 14 outputs either the estimated resonance temperature or the estimated non-resonance temperature. For example, if the determination result input from the comparator 31 indicates a high degree of resonance, the comparator 31 outputs the estimated resonance temperature. On the other hand, if the determination result input from the comparator 31 indicates a low degree of resonance, the comparator 31 outputs the estimated non-resonance temperature.

[0058] The temperature comparison unit 15 compares the estimated temperature (estimated temperature at resonance or estimated temperature at non-resonance) output from the switching unit 14 with the heat resistance temperature of each heat-generating component and outputs the result. The comparison result of the temperature comparison unit 15 is input to the power conversion circuit control unit 16. Furthermore, the heat resistance temperature here does not refer to the temperature at which the heat-generating component will immediately fail if the heat resistance temperature is exceeded, but rather to the temperature at which the temperature of the heat-generating component needs to be monitored. That is, the heat resistance temperature here is a temperature set with a certain margin relative to the temperature at which the heat-generating component will fail.

[0059] The power conversion circuit control unit 16 controls the power conversion circuit 4 based on commands (e.g., torque command values) input from external sources such as a higher-level control device. That is, the power conversion circuit control unit 16 adjusts the power supplied to the motor M via the power conversion circuit 4 and adjusts the output torque of the motor M based on commands input from external sources such as a higher-level control device.

[0060] 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 resistance temperature, it suppresses the direct current supplied to the power conversion circuit 4 compared to the case where the estimated temperature does not exceed the heat resistance temperature, thereby reducing the output torque of the motor M. This reduction in direct current suppresses the temperature rise of the heating element.

[0061] The effective current value calculation unit 17 calculates the effective value of the DC current 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. Furthermore, the effective current value calculation unit 17 outputs the calculated effective current value to an external unit such as a higher-level control unit. Therefore, for example, the higher-level control unit can perform control based on the effective current value of the DC current. Specifically, the higher-level control unit can estimate the state of battery B and wiring harness H based on the effective current value of the DC current, and adjust the torque command value, etc., based on the estimation result.

[0062] Next, refer to Figure 3 This section will describe a portion of the operation of the motor drive device 1 according to this embodiment. Furthermore, a portion of the operation based on the resonant state of the resonant circuit 100 will be described here.

[0063] Figure 3 This is a flowchart illustrating a portion of the operation of the electric motor drive device 1 in this embodiment. (For example...) Figure 3 As shown, the control device 10 obtains a voltage value from the voltage sensor 7 (step S1). Next, the control device 10 extracts the DC and AC components from the voltage value obtained in step S1 (step S2). Specifically, the control device 10 extracts the DC component by passing the output signal of the AD converter 11 through the input-side low-pass filter 20. Additionally, the control device 10 extracts the AC component by passing the output signal of the AD converter 11 through the input-side high-pass filter 23.

[0064] Next, the control device 10 determines whether the AC component extracted in step S2 is larger 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 AC component current value during non-resonance obtained by the AC component acquisition unit 30 using comparator 31. If the AC component current value calculated by the AC component current value calculation unit 24 exceeds the AC component current value during non-resonance, the control device 10 determines that the resonance degree 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 AC component current value during non-resonance, the control device 10 determines that the resonance degree is small.

[0065] In step S3, if the resonance level is determined to be low, the control device 10 returns to step S1. That is, if the resonance level is low, steps S1 to S3 are repeated. Furthermore, although not shown in the flowchart, if the resonance level is low, the control device 10 compares the estimated temperature of the heating element calculated by the non-resonant estimated temperature calculation unit 13 with the heat resistance temperature of the heating element, and monitors the state of the heating element.

[0066] If the resonance degree is determined to be high in step S3, the control device 10 estimates the temperature of the heating element based on the DC component and AC component extracted in step S2 (step S4). Specifically, the control device 10 calculates the temperature rise based on the DC component using the DC component temperature rise calculation unit 22, based on the DC component current value. Additionally, the AC component temperature rise calculation unit 25 calculates the temperature rise caused by the AC component based on the AC component current value. Furthermore, the control device 10 adds the DC component temperature rise calculated by the DC component temperature rise calculation unit 22, the AC component temperature rise calculated by the AC component temperature rise calculation unit 25, and the reference temperature calculated by the reference temperature calculation unit 27 using the first adder 26 and the second adder 28 to calculate the estimated temperature of the heating element when the resonant circuit 100 resonates (in the case of a high resonance degree).

[0067] Next, the control device 10 determines whether the temperature of the heating element (the estimated temperature calculated in step S3) exceeds the heat resistance temperature of the heating element during resonance (step S5). Specifically, the control device 10 compares the estimated temperature calculated in step S3 with the heat resistance temperature using the temperature comparison unit 15, and performs the above determination.

[0068] If the temperature of the heating element at resonance in step S5 (the estimated temperature calculated in step S3) does not exceed the heat resistance temperature of the heating element, the control device 10 returns to step S1. On the other hand, if the temperature of the heating element at resonance in step S5 (the estimated temperature calculated in step S3) exceeds the heat resistance temperature of the heating element, 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 DC current supplied to the power conversion circuit 4 via the power conversion circuit control unit 16, thereby reducing the output torque of the motor M. Furthermore, after step S6, the control device 10 returns to step S1.

[0069] This embodiment of the motor drive device 1 converts the direct current (DC) power supplied from the battery B and outputs it to the motor M. Furthermore, this embodiment of the motor drive device 1 includes a power conversion circuit 4, a positive bus 2 and a negative bus 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 2 and the negative bus 3 are connected to the battery B and the power conversion circuit 4. The smoothing capacitor 5 is connected to the positive bus 2 and the negative bus 3. The voltage sensor 7 detects the DC voltage. The control device 10 determines the resonance level of the resonant circuit 100 formed including the smoothing capacitor 5 based on the DC component and the AC component of the AC component contained in the detection value of the voltage sensor 7.

[0070] According to the motor drive device 1 of this embodiment, the resonance degree of the resonant circuit 100 is determined based on the AC component contained in the direct current. If the resonance degree increases, the AC component contained in the direct current is amplified compared to the case of a low resonance degree. Therefore, the resonance degree of the resonant circuit 100 can be determined based on the AC component. According to the motor drive device 1 of this embodiment, the resonance state of the resonant circuit 100 including the smoothing capacitor 5 can be determined without a temperature sensor.

[0071] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 determines that the resonance degree of the resonant circuit 100 is large when the AC component exceeds a predetermined reference value (the current value of the AC component contained in the DC current when it is not resonant).

[0072] 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.

[0073] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 calculates the estimated temperature of the heating element based on both the DC and AC components. According to this embodiment, the motor drive device 1 uses not only the temperature rise caused by the AC component but also the temperature rise caused by the DC component, thereby enabling the estimation of the heating element's temperature. Therefore, the motor drive device 1 of this embodiment can accurately estimate the temperature of the heating element. Moreover, by accurately estimating the temperature of the heating element in this way, excessive suppression of the temperature rise of the heating element can be prevented.

[0074] Furthermore, in the electric motor drive device 1 of this embodiment, the control device 10 suppresses the direct current supplied from the battery B to the power conversion circuit 4 when the estimated temperature exceeds a predetermined heat resistance temperature. According to this embodiment of the electric motor drive device 1, it is possible to prevent the temperature of the heat-generating component from exceeding its heat resistance temperature and thus rising.

[0075] Furthermore, in the motor drive device 1 of this embodiment, the aforementioned detection value is obtained using a voltage sensor 7 that detects the voltage applied to the positive bus 2 and the negative bus 3. For example, if a voltage sensor for measuring the voltage between the terminals of the smoothing capacitor 5 is provided for other purposes, that voltage sensor can be used as the voltage sensor 7 of the motor drive device 1 of this embodiment. Therefore, the resonance state of the resonant circuit 100 can be determined without increasing the number of components.

[0076] Furthermore, in the motor drive device 1 of this embodiment, after the control device 10 converts the AC component contained in the detection value of the voltage sensor into a current value, it determines the resonance degree of the resonant circuit 100, which includes the smoothing capacitor 5, based on the AC component. According to this motor drive device 1 of the present embodiment, the temperature rise value can be calculated based on the current value.

[0077] Furthermore, in the motor drive device 1 of this embodiment, the control device 10 can calculate the effective value of the DC current based on the DC and AC components, and output the effective value of the current to the outside. According to the motor drive device 1 of this embodiment, for example, the upper control unit can estimate the state of the battery B and the wiring harness H based on the effective value of the DC current, and adjust the torque command value based on the estimation result, etc.

[0078] (Second Implementation)

[0079] Next, refer to Figure 4 The second embodiment of the present invention will now be described. Furthermore, in the description of this embodiment, parts that are the same as those in the first embodiment described above will be omitted or simplified.

[0080] Figure 4 This is a circuit diagram showing the schematic structure of the motor drive device 1A according to this embodiment. As shown in the diagram, 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 the direct current output from the battery B (i.e., the current of the direct current flowing through the positive bus 2 and the negative bus 3). In this embodiment, the current sensor 8 is arranged to surround the positive bus 2 to detect the current flowing through the positive bus 2. Figure 4 As shown, the current sensor 8 is connected to the control device 10. The detection value output from the current sensor 8 is input to the control device 10.

[0081] 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 resonance degree of the resonant circuit 100. That is, the control device 10 determines the resonance degree of the resonant circuit 100, which includes the smoothing capacitor 5, based on the DC component of the DC current and the AC component of the AC current included in the detection value of the current sensor 8.

[0082] The specific functional structure of the control device 10 in this embodiment is the same as that of the control device 10 in 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, the description of the specific functional structure of the control device 10 in this embodiment will be omitted here.

[0083] According to the motor drive device 1A of this embodiment, the control device 10 does not need to have a DC component current value calculation unit 21 and an AC component current value calculation unit 24. Therefore, the structure of the control device 10 can be simplified, and the processing burden of the control device 10 can be reduced.

[0084] In addition, such as Figure 4 As shown, the motor drive device 1A of this embodiment includes a voltage sensor 7. However, in the motor drive device 1A of this embodiment, the voltage sensor 7 can also be omitted.

[0085] (Third Implementation)

[0086] Next, refer to Figure 5 The third embodiment of the present invention will be described. Furthermore, in the description of this embodiment, parts that are the same as those in the first embodiment described above are omitted or simplified.

[0087] Figure 5 This is a circuit diagram showing the schematic structure of the electric motor drive device 1B according to this embodiment. As shown in the figure, the electric motor drive device 1B of this embodiment includes two sets consisting of a positive bus 2, a negative bus 3, a power conversion circuit 4, a smoothing capacitor 5, a noise reduction capacitor 6, a voltage sensor 7, and a control device 10. These two sets are connected in parallel with respect to the same battery B.

[0088] In the motor drive device 1B of this embodiment, two smoothing capacitors 5 are provided, thus forming a resonant circuit 100 including one smoothing capacitor 5 and a resonant circuit 100 including the other smoothing capacitor 5. The resonant states of these resonant circuits 100 are sometimes different.

[0089] However, according to the motor drive device 1B of this embodiment, the temperature of the heating element can be accurately estimated based on the DC power supplied to each power conversion circuit 4 by means of the control devices 10 in each group. Therefore, even with such a plurality of groups of motor drive devices 1B, excessive heating of the heating element can be suppressed, and excessive suppression of the output torque of the motor M can be prevented.

[0090] Furthermore, in this embodiment, such as Figure 6 As shown, each group may also include the current sensor 8 described in the second embodiment above. By including such a current sensor 8, each control device 10 can use the detection value of the current sensor 8 to replace the detection value of the voltage sensor 7 in the first embodiment above to determine the resonance degree of the resonant circuit 100. With such a current sensor 8, the voltage sensor 7 can also be omitted.

[0091] Preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. The shapes, combinations, etc. of the constituent components shown in the above embodiments are examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0092] Furthermore, the above-described embodiments can also be described, for example, as in the following notes.

[0093] (Note 1)

[0094] An electric motor drive device for converting direct current (DC) power supplied from a DC power source and outputting it to an electric motor, characterized in that it comprises: a power conversion circuit for converting the DC power; a DC power path connecting the DC power source to the power conversion circuit; a smoothing capacitor connected to the DC power path; a detection sensor for detecting at least one of the voltage and current of the DC power; and a control device for determining the resonance degree of a resonant circuit including the smoothing capacitor based on the AC component of the DC power and the AC component of the DC power contained in the detection value of the detection sensor.

[0095] (Note 2)

[0096] According to the motor drive device described in Appendix 1, the control device determines that the resonance degree of the resonant circuit is large when the AC component exceeds a predetermined reference value.

[0097] (Note 3)

[0098] According to the motor drive device described in Appendix 2, the control device calculates the estimated temperature of the heating element that is heated by the supplied DC power based on the DC component and the AC component.

[0099] (Note 4)

[0100] According to the motor drive device described in Appendix 3, 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.

[0101] (Note 5)

[0102] The motor drive device according to any one of Appendices 1 to 4 is characterized in that the detection sensor is a voltage sensor that detects the voltage applied to the DC power path.

[0103] (Note 6)

[0104] According to the motor drive device described in Appendix 5, the control device, after converting the AC component contained in the detection value of the voltage sensor into a current value, determines the degree of resonance of the resonant circuit formed by including the smoothing capacitor based on the AC component.

[0105] (Note 7)

[0106] The motor drive device according to any one of Appendices 1 to 4 is characterized in that the detection sensor is a current sensor that detects the current of the DC power flowing through the DC power path.

[0107] (Note 8)

[0108] The motor drive device as described in any one of Appendices 1 to 7 is characterized in that the control device is capable of calculating the effective value of the DC current based on the DC component and the AC component, and outputting the effective value of the current to the outside.

[0109] Explanation of reference numerals in the attached figures

[0110] 1: Electric motor drive device

[0111] 1A: Electric motor drive unit

[0112] 1B: Electric motor drive unit

[0113] 2: Positive bus (DC path)

[0114] 3: Negative bus (DC path)

[0115] 4: Power conversion circuit

[0116] 5: Smoothing capacitor (heat-generating component)

[0117] 6: Capacitors for noise removal

[0118] 6a: Capacitor element (heat-generating component)

[0119] 7: Voltage sensor (detection sensor)

[0120] 8: Current sensor (detection sensor)

[0121] 10: Control device

[0122] 11: AD Conversion Section

[0123] 12: Estimated temperature calculation section at resonance

[0124] 13: Estimated Temperature Calculation Section during Non-Resonance

[0125] 14: Switching Unit

[0126] 15: Temperature Comparison Section

[0127] 16: Power Conversion Circuit Control Unit

[0128] 17: Current RMS Value Calculation Section

[0129] 20: Input-side low-pass filter

[0130] 21: DC component current value calculation section

[0131] 22: DC component temperature rise calculation unit

[0132] 23: Input-side high-pass filter

[0133] 24: AC component current value calculation section

[0134] 25: Calculation Department for Temperature Rise of AC Components

[0135] 26: First Adder

[0136] 27: Reference Temperature Calculation Department

[0137] 28: Second Adder

[0138] 29: Output-side low-pass filter

[0139] 30: Acquisition of AC component during non-resonance

[0140] 31: Comparator

[0141] 100: Resonant circuit

[0142] B: Battery (DC power supply)

[0143] H: Wiring harness

[0144] M: Electric motor

Claims

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

2. The electric motor drive device according to claim 1, characterized in that, When the AC component exceeds a predetermined reference value, the control device determines that the resonance degree of the resonant circuit is large.

3. The electric motor drive device according to claim 2, characterized in that, The control device calculates the estimated temperature of the heating element that is heated by the supplied DC power based on the DC component and the AC component.

4. The electric 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 the predetermined heat resistance temperature.

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

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

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

8. The electric motor drive device according to any one of claims 1 to 4, characterized in that, The control device can calculate the effective value of the DC current based on the DC component and the AC component, and output the effective value of the current to the outside.

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