Power converter and drive unit

Abstract

To provide a power conversion device that can calculate a correct direct current value even when a power conversion circuit is faulty.SOLUTION: The power conversion device includes a power conversion circuit that converts direct current power to alternating-current power using PWM control and outputs three-phase alternating current to a motor, a three-phase to two-phase conversion unit 805 that converts three-phase alternating current Iu, Iv and Iw to dq-axis current Id and Iq, a direct current voltage sensor that detects a direct-current voltage value Vdc of the direct current power, and a direct-current current calculation unit 807 that calculates dq-axis voltages Vd and Vq on the basis of motor parameters and dq-axis currents Id and Iq of the motor and calculates a direct-current current calculation value Idc1 of the direct current power on the basis of the dq-axis voltages Vd and Vq, the dq-axis currents Id and Iq, and the direct-current voltage value Vdc.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a power conversion device and a drive device.

Background Art

[0002] In vehicles that use a motor for vehicle running, such as hybrid vehicles and electric vehicles, DC power supplied from a DC power source is converted into AC power by an in-vehicle power conversion device to drive a motor or the like. In such a power conversion device, a technique for calculating a DC current supplied from the DC power source to the power conversion device is known in order to monitor the state of the DC power source and diagnose the inside of the power conversion device.

[0003] For example, Patent Document 1 discloses a technique for calculating AC power from dq-axis voltage commands and dq-axis current commands and calculating a DC current based on the AC power. Further, Patent Document 2 discloses a technique for calculating a DC current using an AC current value and a duty value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the power conversion circuit fails and cannot output a voltage as commanded, the command and the actual output voltage deviate. Therefore, there is a problem that a correct DC current value cannot be calculated by a method of calculating a DC current using a value corresponding to a command such as a voltage command value or a duty value as in the techniques described in Patent Documents 1 and 2.

Means for Solving the Problems

[0006] A power conversion device according to an aspect of the present invention comprises: a power conversion circuit that converts DC power into AC power by PWM control and outputs a three-phase AC current to a motor; a three-phase to two-phase conversion unit that converts the three-phase AC current into a dq-axis current; a DC voltage detection unit that detects the DC voltage value of the DC power; and a first calculation unit that calculates the dq-axis voltage based on the motor parameters of the motor and the dq-axis current, and calculates a first DC current value of the DC power based on the dq-axis voltage, the dq-axis current, and the DC voltage value. A drive device according to an aspect of the present invention comprises a motor and a power conversion device that converts DC power into AC power by PWM control and supplies a three-phase AC current to the motor. [Effects of the Invention]

[0007] According to the present invention, the correct DC current value can be calculated even when the power conversion circuit is malfunctioning. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of the vehicle. [Figure 2] Figure 2 shows a schematic configuration of the drive unit. [Figure 3] Figure 3 shows an example of a power conversion circuit configuration. [Figure 4] Figure 4 is a control block diagram showing the details of the control circuit's functions. [Figure 5] Figure 5 illustrates a second embodiment of the present invention. [Figure 6] Figure 6 shows the correspondence between the operating state and the selected DC current calculation value. [Figure 7] Figure 7 shows an example of the operation of the selection unit. [Figure 8] Figure 8 shows an example of a case where the switching operation is performed in multiple stages. [Figure 9] Figure 9 illustrates a third embodiment of the present invention. [Figure 10]Figure 10 is a diagram illustrating the operation of the selection unit in the third embodiment. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the present invention will be described below with reference to the figures. The following description and drawings are illustrative examples for explaining the present invention, and have been omitted and simplified as appropriate for clarity of explanation. In addition, in the following description, the same or similar elements and processes are denoted by the same reference numerals, and redundant explanations may be omitted. It should be noted that the contents described below are merely examples of embodiments of the present invention, and the present invention is not limited to the embodiments described below, and can be carried out in various other forms.

[0010] (First Embodiment) A first embodiment of the present invention will be described with reference to Figures 1 to 4. Figure 1 is a schematic diagram of a vehicle powered by a motor (not shown). The vehicle 1 is equipped with a drive unit 2 to which power is supplied from a DC power supply 5. Although not shown, the drive unit 2 includes a power converter, a motor, and a reduction gear. The driving force of the motor is transmitted via the reduction gear to the axle 4 on which the wheel 3a is attached.

[0011] In the example shown in Figure 1, the drive unit 2 is installed on the axle 4 of the front wheel (wheel 3a), but it may also be installed on the axle of the rear wheel (wheel 3b). Alternatively, the drive unit 2 may be installed on the axles 4 of both the front and rear wheels, or independent drive units 2 may be installed on each of the left and right wheels 3a and 3b instead of the axles. Furthermore, in addition to the drive unit 2 shown in Figure 1, a drive unit using an internal combustion engine may be installed in parallel with the drive unit 2 on the axle 4.

[0012] Figure 2 is a diagram showing the schematic configuration of the drive device 2. Around the drive device 2, a DC power supply 5, a control device 6, and a failure notification device 7 are provided. The control device 6 transmits to the drive device 2 the target torque τs, operation mode information Sm, etc. Further, the control device 6 receives the output torque calculation value τ and the DC current calculation value Idc output from the drive device 2. In this embodiment, only one control device 6 is described, but a plurality of control devices may perform the transmission and reception of information. Further, this control device 6 also has the control function of the drive device using the above-described internal combustion engine.

[0013] The DC power supply 5 is a power supply for driving the motor 9 in the drive device 2, and for example, a battery or the like corresponds. The failure notification device 7 receives the failure detection signal Sf from the drive device 2 and notifies the occupant of the occurrence of a failure. Examples of the failure notification method include lighting a lamp, generating a warning sound, and notifying by voice.

[0014] The drive device 2 includes a power conversion device 8, a motor 9, and a speed reducer (not shown). The speed reducer amplifies the driving force of the motor 9 and has the role of transmitting it to the axle 4 (or the wheels 3a, 3b). The motor 9 is a three-phase motor having three windings inside, and for example, a synchronous motor using permanent magnets or an induction motor not using permanent magnets corresponds.

[0015] The motor 9 includes a motor angle sensor 91 and a motor temperature sensor 92. The motor angle sensor 91 measures the rotation angle of the motor rotor and outputs the measured angle as the motor angle sensor value θm to the power conversion device 8. The motor temperature sensor 92 measures the temperature of the motor 9 and outputs the measured temperature as the motor temperature sensor value Tm to the power conversion device 8.

[0016] Based on the target torque and the like input from the control device 6, the power conversion device 8 converts the DC power supplied from the DC power supply 5 into AC power and supplies it to the motor 9. Further, the power conversion device 8 also has a function of converting the power of the motor 9 into DC power and charging the DC power supply 5.

[0017] The power conversion device 8 includes a control circuit 80, a driver circuit 81, a power conversion circuit 82, a DC voltage sensor 83, and an AC current sensor 84. The control circuit 80 generates a PWM (Pulse Width Modulation) signal pwm for controlling the current of each of the U, V, and W phases output from the power conversion device 8 to a predetermined value based on the target torque τs and the operation mode information Sm from the control device 6. The details of the control circuit 80 will be described later. The driver circuit 81 outputs a drive signal for switching on / off a plurality of power semiconductors provided in the power conversion circuit 30 based on the PWM signal pwm output from the control circuit 80.

[0018] The DC voltage sensor 83 is a sensor that measures the output voltage of the DC power supply 5, and outputs the measured voltage value to the control circuit 80 as the DC voltage sensor value Vdc. The AC current sensor 84 is a sensor that measures the AC current flowing in each phase (U phase, V phase, W phase) of the motor 9. The AC current values of each phase measured by the AC current sensor 84 are input to the control circuit 80 as the AC current sensor values Iu, Iv, and Iw. In the example shown in FIG. 2, the AC current sensor 84 has one sensor for each phase, but it may be provided for only two phases. Since the relationship "U-phase current + V-phase current + W-phase current = 0" holds, in the case of a configuration with sensors provided for only two phases, the control circuit 80 calculates the AC current sensor value for the remaining one phase by calculation.

[0019] The power conversion circuit 82 receives the drive signal from the driver circuit 81, drives the internal power semiconductors, and controls the current flowing through the motor 9. FIG. 3 is a diagram showing an example of the configuration of the power conversion circuit 82. The power conversion circuit 82 has an internal smoothing capacitor 821 and six power semiconductors 822. For each phase (U phase, V phase, W phase), two power semiconductors 822 that constitute the upper arm and the lower arm are provided respectively. The output terminals of the upper and lower arms of each phase are connected to the corresponding phase winding of the motor 9.

[0020] The power semiconductor 822 switches on and off in response to the drive signal input from the driver circuit 81, performing the conversion between DC power and AC power. Examples of power semiconductors 822 include power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). In the example shown in Figure 3, an IGBT is used as the power semiconductor 822.

[0021] The smoothing capacitor 821 is a capacitor that smooths the current generated by the on / off switching of the power semiconductor 822, thereby suppressing ripple in the DC current supplied from the DC power supply 5 to the power conversion circuit 82. For example, an electrolytic capacitor or a film capacitor can be used for the smoothing capacitor 821.

[0022] In this embodiment, the motor neutral point is floating, but it may be connected to ground (not shown). Methods for connecting the motor neutral point to ground include direct grounding, resistance grounding, compensating reactor grounding, and arc-extinguishing reactor grounding.

[0023] Figure 4 is a control block diagram showing the details of the control circuit 80's functions. The control circuit 80 includes a CPU, RAM, ROM, communication circuits, etc., which are not shown internally. The CPU realizes the functions of each part described later by loading the program stored in ROM into RAM and executing it. The ROM may be an electrically rewritable EEPROM (Electrically Erasable Programmable ROM) or flash ROM.

[0024] The control circuit 80 includes a state control unit 801, a target current calculation unit 802, a current control unit 803, a PWM signal generation unit 804, a 3-phase to 2-phase conversion unit 805, a motor speed calculation unit 806, a DC current calculation unit 807, an output torque calculation unit 808, and a diagnostic unit 809.

[0025] The motor speed calculation unit 806 calculates the motor angular velocity ω0 from the change in the motor angle sensor value θm. The calculated motor angular velocity ω0 is input to the target current calculation unit 802, the DC current calculation unit 807, and the output torque calculation unit 808.

[0026] The 3-phase to 2-phase conversion unit 805 performs a dq conversion on the 3-phase AC current sensor values ​​Iu, Iv, and Iw based on the motor angle sensor value θm, as shown in equation (1), to calculate the d-axis current value Id and the q-axis current value Iq. The calculated d-axis current value Id and q-axis current value Iq are output to the current control unit 803 and the DC current calculation unit 807.

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[0027] In equation (1), Iu, Iv, and Iw are the AC current sensor values ​​for the U-phase, V-phase, and W-phase measured by the AC current sensor 84, respectively. θ is the electrical angle of the motor 9. The electrical angle θ can be calculated by multiplying the motor angle sensor value θm, measured by the motor angle sensor 91, by the number of pole pairs of the motor 9. In equation (1), the dq transformation is calculated using the coefficients of the absolute transformation, but it may also be calculated using the coefficients of the relative transformation.

[0028] The state control unit 801 transitions the operating state of the power converter 8 using the operating mode information Sm and the fault detection signal Sf output by the diagnostic unit 809, and outputs the current operating state to the PWM signal generation unit 804. Examples of operating states include, for example, a PWM state, a three-phase short-circuit state, and a three-phase open-circuit state.

[0029] The target current calculation unit 802 uses the target torque τs, the DC voltage sensor value Vdc, and the motor angular velocity ω0 to calculate the target current value required for the motor 9 to output the same torque as the target torque τs. The target current value is output to the current control unit 803. The target current value is expressed, for example, in the form of a d-axis target current value and a q-axis target current value.

[0030] The current control unit 803 uses the target current value, the d-axis current value Id, the q-axis current value Iq, and the DC voltage sensor value Vdc to perform feedback control so that the d-axis current value Id and the q-axis current value Iq follow the target current value, and calculates the duty cycles Du, Dv, and Dw for the three phases in PWM control. The duty cycles Du, Dv, and Dw are input to the PWM signal generation unit 804.

[0031] The PWM signal generation unit 804 switches the signal it outputs to the driver circuit 81 according to the operating state output from the state control unit 801. The PWM signal generation unit 804 has an internal timer (not shown), and when the operating state is the PWM state, it generates a PWM signal pwm using this timer value and the duty cycles Du, Dv, and Dw of each phase output by the current control unit 803. The PWM signal generation unit 804 then outputs the generated PWM signal pwm to the driver circuit 81.

[0032] On the other hand, when the operating state is a three-phase open state, a PWM signal pwm is generated that turns off all six power semiconductors 822 (see Figure 3) in the power conversion circuit 82. Also, when the operating state is a three-phase short state, a PWM signal pwm is generated that turns off all of the power semiconductors 822 in the upper arm and turns on all of the power semiconductors 822 in the lower arm, or a PWM signal pwm that turns on all of the power semiconductors 822 in the upper arm and turns off all of the power semiconductors 822 in the lower arm.

[0033] The DC current calculation unit 807 calculates the d-axis voltage value Vd and the q-axis voltage value Vq based on the d-axis current value Id, the q-axis current value Iq, the motor angular velocity ω0, and the motor parameters R, Ld, Lq, Φ, using the following equation (2).

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[0034] In equation (2), R represents the winding resistance of motor 9, Ld represents the d-axis inductance of motor 9, Lq represents the q-axis inductance of motor 9, ω represents the electrical angular velocity of motor 9, and Φ represents the magnetic flux of motor 9. The electrical angular velocity ω can be calculated by multiplying the motor angular velocity ω0 by the number of motor pole pairs. Note that P is a symbol representing differential calculus.

[0035] The motor parameters R, Ld, Lq, and Φ are set based on the measurement results obtained after pre-measuring the characteristics of the motor 9. Furthermore, since the winding resistance R and magnetic flux Φ also change with the temperature of the motor 9, in this embodiment, the winding resistance R and magnetic flux Φ are corrected using the motor temperature sensor value Tm to improve calculation accuracy. Note that under conditions where the d-axis current value Id and the q-axis current value Iq are approximately constant, the influence of the derivative term on the calculation result becomes small, and therefore, the calculation of the derivative term may be omitted to reduce computational processing.

[0036] Next, the DC current calculation unit 807 calculates the DC current value Idc based on the calculated d-axis voltage value Vd and q-axis voltage value Vq, the d-axis current value Id, the q-axis current value Iq, and the DC voltage sensor value Vdc, using the following equation (3). Equation (3) is derived from the relationship that the DC power input to the power conversion circuit 82 and the AC power output by the power conversion circuit 82 are approximately equal. In equation (3), the numerator on the right side, =VdId+VqIq, represents the AC power output by the power conversion circuit 82. The DC current calculation unit 807 outputs the calculated DC current value Idc to the output torque calculation unit 808 and the external control device 6.

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[0037] In the DC current calculation unit 807, the AC power is calculated using the d-axis current value Id and q-axis current value Iq, which are obtained by converting the actually measured AC current sensor values ​​Iu, Iv, and Iw, and the d-axis voltage value Vd and q-axis voltage value Vq, which are calculated from the d-axis current value Id and q-axis current value Iq and equation (2). Therefore, even if the power conversion circuit 82 malfunctions and the AC voltage and AC current according to the duty cycle Du, Dv, and Dw output by the current control unit 803 cannot be output, the AC power being output and the DC current actually flowing can be calculated correctly.

[0038] The output torque calculation unit 808 calculates the output torque τ output by the motor 9 based on the DC voltage sensor value Vdc, the DC current calculation value Idc, and the motor angular velocity ω0. The calculated output torque τ is output to the diagnostic unit 809 and the external control device 6.

[0039] The diagnostic unit 809 diagnoses faults inside the power converter 8. If the diagnostic unit 809 detects a fault through its diagnosis, it outputs the details of the fault location as a fault detection signal Sf to the state control unit 801 or an external fault notification device 7. For example, by comparing the target torque τs with the output torque τ, the diagnostic unit 809 determines that there is a fault if the output torque τ deviates from the target torque τs by a certain amount or more. Of course, the diagnostics performed by the diagnostic unit 809 are not limited to this; it also diagnoses sensors and the power converter circuit 82 using various sensor values, but a detailed explanation is omitted.

[0040] By the way, if it is desired to continue operating the vehicle 1 even after a failure occurs in the power conversion circuit 82, a function is needed to detect further failures and safely stop the vehicle 1, from the standpoint of ensuring safety. As described above, in this embodiment, even if a failure occurs in the power conversion circuit 82, the correct DC current can be calculated, and the output torque τ of the motor 9 can also be calculated correctly. Therefore, even after a failure, the diagnostic unit 809 can diagnose the discrepancy between the target torque τs and the output torque τ. In this way, if another failure occurs after a failure in the power conversion circuit 82, that failure can be detected by the diagnostic unit 809. As a result, even after a failure in the power conversion circuit 82, the vehicle 1 can continue operating, albeit with some functions reduced, like a limp home.

[0041] Furthermore, in hybrid vehicles and other vehicles where another drive system, such as an engine, is mounted on the vehicle 1, it is necessary to coordinate the control of the output torque of multiple drive systems. In this embodiment, even after a failure occurs in the power conversion circuit 82, the correct output torque τ can be transmitted to the external control device 6. Therefore, even after a failure occurs in the power conversion circuit 82, the control device 6 can continue coordinate control with the other drive system based on the output torque τ.

[0042] (Second embodiment) Figure 5 illustrates a second embodiment of the present invention and, as with Figure 4 described above, is a control block diagram of the control circuit 80. Note that the configurations other than the control circuit 80 are the same as those of the first embodiment. Furthermore, in Figure 5, components common to the first embodiment are denoted by the same reference numerals, and the following description will mainly focus on the differences.

[0043] In the second embodiment, the control circuit 80 further includes a DC current calculation unit 810 and a selection unit 811 in addition to the configuration shown in Figure 4. The DC current calculation unit 807 calculates the DC current value Idc using equations (2) and (3), as in the first embodiment. On the other hand, unlike the DC current calculation unit 807, the DC current calculation unit 810 calculates the DC current value Idc using the AC current sensor values ​​Iu, Iv, and Iw measured by the AC current sensor 84 using the following equation (4).

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[0044] In equation (4), Du, Dv, and Dw are the duty cycles of the U-phase, V-phase, and W-phase generated by the current control unit 803. The DC current calculation unit 810 receives the AC current sensor values ​​Iu, Iv, and Iw, and the duty cycles Du, Dv, and Dw, and calculates the DC current calculation value Idc based on equation (4). Hereinafter, the DC current calculation value calculated by the DC current calculation unit 807 will be denoted by the symbol Idc1, and the DC current calculation value calculated by the DC current calculation unit 810 will be denoted by the symbol Idc2.

[0045] The selection unit 811 receives Idc1 from the DC current calculation unit 807 and Idc2 from the DC current calculation unit 810 as DC current calculation values. The selection unit 811 also receives the operating status of the power converter 8 (e.g., PWM state, 3-phase short circuit state, 3-phase open circuit state, etc.) from the state control unit 801. The selection unit 811 selects either DC current calculation value Idc1 or Idc2 according to the operating status output by the state control unit 801 and outputs it as DC current calculation value Idc to the output torque calculation unit 808 or the external control device 6.

[0046] Figure 6 shows the correspondence between the operating state and the DC current calculation value selected by the selection unit 811. When the power converter 8 is in PWM operation state, the DC current calculation value Idc2 is selected. When the power converter 8 is in a 3-phase open state or a 3-phase short state, the DC current calculation value Idc1 is selected.

[0047] As shown in equation (2), the DC current calculation unit 807 uses motor parameters R, Ld, Lq, and Φ for its calculations. Therefore, it is susceptible to parameter deviations from the actual motor constants of the motor 9, and the calculated DC current value Idc1 may be less accurate than the calculated DC current value Idc2. For this reason, when the power converter 8 is in PWM operation mode, the DC current value Idc2, which has higher calculation accuracy, is used.

[0048] When the power converter 8 is in a three-phase open state, all six power semiconductors 822 (see Figure 3) are in the off state. Therefore, the duty cycles Du, Dv, and Dw in equation (4) are all 0, and the calculated DC current value Idc2 is 0 [A]. Also, when the power semiconductor 822 on the upper arm is turned off in a three-phase short-circuit state, the duty cycles Du, Dv, and Dw are all 0, just as in the three-phase open state, and the calculated DC current value Idc2 is 0 [A]. On the other hand, when the power semiconductor 822 on the upper arm is turned on in a three-phase short-circuit state, the duty cycles Du, Dv, and Dw are all 1, and the DC current value is the sum of the AC current sensor values ​​Iu, Iv, and Iw. However, according to Kirchhoff's laws, the sum of the three-phase AC currents is 0 [A], so in this case as well, the calculated DC current value Idc2 is 0 [A].

[0049] Thus, in the three-phase open and three-phase short-circuit states, the calculated DC current value Idc2 is always 0 [A]. Therefore, if a small amount of DC current is actually flowing, the calculated DC current value Idc1 may be more accurate. For this reason, in the three-phase open and three-phase short-circuit states, the calculated DC current value Idc1, which is the result of the DC current calculation unit 807, is used. In this way, by providing two DC current calculation units 807 and 810 and selecting and using the DC current calculation value with higher accuracy according to the operating state of the power converter 8, the correct DC current value can be used.

[0050] By the way, when the DC current calculation value to be used is switched by the selection unit 811, if the difference between the DC current calculation value before and after the switch is large, the switching operation may affect the output torque calculation. Therefore, if the difference between the DC current calculation value before and after the switch is greater than a predetermined value, the selection unit 811 outputs a value between the DC current calculation value Idc1 and the DC current calculation value Idc2, and then switches to the DC current calculation values ​​Idc1 and Idc2 to reduce the effect of the switching operation.

[0051] Figure 7 shows an example of the switching operation by the selection unit 811. In the example shown in Figure 7, the input operating state is a PWM operating state until timing t1, and the switching operation is shown when the operating state becomes a 3-phase short-circuit state or a 3-phase open-circuit state at timing t2. Until timing t1, the DC current calculation value Idc2 suitable for the PWM operating state is selected.

[0052] At the next timing t2, the operating state changes to either a three-phase short-circuit state or a three-phase open state. However, instead of immediately switching to the calculated DC current value Idc1, the selection unit 811 outputs the average value of the calculated DC current value Idc1 and the calculated DC current value Idc2 (Idc1 + Idc2) / 2 as the calculated DC current value Idc. Then, at the next timing t3, it switches to the calculated DC current value Idc1. In this way, by performing the switching operation in stages so that the difference before and after the switching is small, the impact of the switching operation can be reduced.

[0053] In the example shown in Figure 7, the switching is performed as Idc2 → (Idc1 + Idc2) / 2 → Idc1, but the switching method is not limited to this. For example, it is also possible to have more steps to transition from Idc2 to Idc1. Specifically, as shown in Figure 8, the ratio of Idc1 to Idc2 can be changed in multiple steps, such as t1 (0:10) → t2 (2:8) → t3 (5:5) → t4 (8:2) → t5 (10:0), while switching the DC current value used from the calculated DC current value Idc2 to the calculated DC current value Idc1. As a result, the impact of the switching operation can be made smaller.

[0054] (Third embodiment) Figure 9 illustrates a third embodiment of the present invention and is a control block diagram of the control circuit 80. Note that the configuration other than the control circuit 80 is the same as that of the second embodiment. In the configuration of the control circuit 80 shown in Figure 5 of the second embodiment described above, the operating state of the power converter 8 (e.g., PWM state, 3-phase short-circuit state, 3-phase open-circuit state, etc.) was input to the selection unit 811 from the state control unit 801. On the other hand, in the control circuit 80 shown in Figure 9, information regarding the fault state inside the power converter 8 is input to the selection unit 811 from the diagnostic unit 809. The other configurations are the same as those of the control circuit 80 shown in Figure 5 described above. The following will mainly describe the differences from the second embodiment.

[0055] The selection unit 811 receives the DC current calculation values ​​Idc1 and Idc2 from the DC current calculation units 807 and 810, respectively, as well as the fault condition from the diagnostic unit 809, as described above. The selection unit 811 selects one of the DC current calculation values ​​Idc1, Idc2, or other alternative values ​​according to the input fault condition. The selection unit 811 then outputs the selected value as the DC current calculation value Idc to the output torque calculation unit 808 or the external control device 6. Figure 10 is a diagram illustrating the operation of the selection unit 811. Figure 10 shows whether calculations can be performed in the DC current calculation units 807 and 810, and the value to be selected, depending on the fault location.

[0056] (If the power conversion circuit 82 fails) First, let's explain what happens when the power conversion circuit 82 fails. When the power conversion circuit 82 fails, the DC current calculation unit 810's calculation will not yield the correct DC current calculation value Idc2 because the duty cycles Du, Dv, and Dw in equation (4) will deviate from the actual on / off state of the power semiconductor 822. On the other hand, the DC current calculation value Idc1, which is the result of the DC current calculation unit 807's calculation, will be the correct value because it is based on the measured AC current sensor values ​​Iu, Iv, and Iw. Therefore, when the power conversion circuit 82 fails, the selection unit 811 selects and outputs the DC current calculation value Idc1.

[0057] (In the event of a failure of sensors 91, 92, or 83, or a deviation in motor parameters) Next, we will explain what happens when the motor angle sensor 91, motor temperature sensor 92, and DC voltage sensor 83 fail, or when the motor parameters R, Ld, Lq, and Φ deviate from the actual values. In equation (1) for calculating the d-axis current value Id and the q-axis current value Iq, the electrical angle θ is calculated from the motor angle sensor value θm measured by the motor angle sensor 91. In equation (2) for calculating the d-axis voltage value Vd and the q-axis voltage value Vq, the electrical angular velocity ω based on the motor parameters R, Ld, Lq, Φ, and the motor angle sensor value θm is used. In this case, the winding resistance value R and magnetic flux Φ are corrected using the motor temperature sensor value Tm. In equation (3) for calculating the DC current value Idc, the DC voltage sensor value Vdc is used.

[0058] Thus, the calculation of the DC current calculation value Idc1 uses the measurement results of the motor angle sensor 91, motor temperature sensor 92, and DC voltage sensor 83, as well as the motor parameters R, Ld, Lq, and Φ. Therefore, if the motor angle sensor 91, motor temperature sensor 92, and DC voltage sensor 83 fail, or if the motor parameters R, Ld, Lq, and Φ deviate from the actual motor constants, the DC current calculation unit 807 will not be able to perform the calculation correctly. In such cases, the selection unit 811 selects and outputs the DC current calculation value Idc2 input from the DC current calculation unit 810.

[0059] (If the AC current sensor 84 malfunctions) The AC current sensor values ​​Iu, Iv, and Iw are used by both the DC current calculation unit 807 and the DC current calculation unit 810, as shown in equations (1) and (4). Therefore, if the AC current sensor 84 fails, both the DC current calculation units 807 and 810 will be unable to correctly calculate the DC current value. Accordingly, if the AC current sensor 84 fails, the selection unit 811 selects and outputs a preset alternative value.

[0060] Regarding alternative values, it is pre-arranged that if the calculation results from the DC current calculation units 807 and 810 are unreliable, the selection unit 811 will output alternative values. Alternatively, the process of outputting alternative values ​​may involve outputting the DC current calculation value (Idc1 or Idc2) along with reliability information. For example, the reliability information could be 1 if the DC current calculation value is reliable, and 0 if it is unreliable.

[0061] In this way, by pre-setting alternative values ​​for cases where the DC current value cannot be calculated correctly, the output torque calculation unit 808 and the external control device 6 can determine that the calculation result is unreliable when an alternative value is output. This allows subsequent processing to take measures such as not using the calculated DC current value.

[0062] As described above, in the third embodiment, the selection unit 811 selects and outputs either the calculation results of the DC current calculation units 807 and 810 or alternative information depending on the failure state of the power converter 8. As a result, the DC current calculation values ​​can be used appropriately depending on the failure state. Furthermore, if the DC current calculation values ​​Idc1 and Idc2 cannot be calculated, such as when the AC current sensor 84 fails, the selection unit 811 outputs alternative values, thereby preventing the use of unreliable DC current calculation values.

[0063] In the first to third embodiments described above, some or all of the above configurations, functions, and processing units may be implemented in hardware, for example, by designing them as integrated circuits. Alternatively, the above configurations and functions may be implemented in software by having the processor interpret and execute programs that implement each function. Information such as programs, tables, and files that implement each function can be stored in memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card or DVD.

[0064] According to the first to third embodiments of the present invention described above, the following effects are achieved.

[0065] (C1) As shown in Figures 2, 4, etc., the power converter 8 includes a power conversion circuit 82 that converts DC power into AC power by PWM control and outputs a three-phase AC current to the motor 9, a three-phase to two-phase conversion unit 805 that converts the three-phase AC currents Iu, Iv, Iw into dq-axis currents (d-axis current Id and q-axis current Iq), a DC voltage detection unit (DC voltage sensor 83) that detects the DC voltage value Vdc of the DC power, and a first calculation unit (DC current calculation unit 807) that calculates the dq-axis voltage (d-axis voltage Vd and q-axis voltage Vq) based on the motor parameters of the motor 9 and the dq-axis currents Id, Iq, and calculates a first DC current value (DC current calculation value Idc1) of the DC power based on the dq-axis voltages Vd, Vq, dq-axis currents Id, Iq and DC voltage value Vdc.

[0066] As described above, the DC current value Idc1 is calculated based on the motor parameters and the measured three-phase AC currents Iu, Iv, Iw and DC voltage value Vdc. Therefore, the correct DC current value can be calculated even during normal operation (PWM operation, three-phase open-circuit operation, three-phase short-circuit operation) and in the event of a failure in the power conversion circuit 82. As a result, processing that uses the DC current value can be performed appropriately.

[0067] (C2) In (C1) above, as shown in Figure 4, the DC current calculation unit 807 calculates the DC current calculation value Idc1 when at least one of the switching elements (power semiconductors 822) provided in the power conversion circuit 82 fails. In this way, when the power semiconductor 822 provided in the power conversion circuit 82 fails, the DC current calculation unit 807 calculates the DC current calculation value Idc1, thereby enabling the calculation of the correct DC current value.

[0068] (C3) In (C1) above, as shown in Figures 5, 9, etc., the power converter 8 further comprises an AC current detection unit (AC current sensor 84) that detects the AC current values ​​(AC current sensor values ​​Iu, Iv, Iw) of the three-phase AC current, and a second calculation unit (DC current calculation unit 810) that calculates a second DC current value (DC current calculation value Idc2) of the DC power based on the duty cycles Du, Dv, Dw for the three phases in PWM control and the AC current sensor values ​​Iu, Iv, Iw. Depending on the operating state and / or fault state of the power converter 8, either the DC current calculation value Idc1 or Idc2 is selected and used.

[0069] Therefore, if the DC current calculation value Idc1 cannot be calculated correctly (due to failure of the motor angle sensor 91, motor temperature sensor 92, and DC voltage sensor 83, or deviation from actual motor parameters) or if the calculation accuracy is poor (PWM operation), the DC current calculation value Idc2 is selected and used. On the other hand, if the DC current calculation value Idc2 cannot be calculated correctly (due to open-circuit operation of all three phases, short-circuit operation of all three phases, or failure of the power conversion circuit 82), the DC current calculation value Idc1 is selected and used. In this way, by selecting and using either the DC current calculation value Idc1 or Idc2 depending on the operating state and / or failure state of the power conversion device 8, the DC current value can be calculated correctly under various conditions.

[0070] (C4) In (C3) above, as shown in Figures 5 and 6, for example, if the operating state of the power converter 8 is a three-phase short circuit or a three-phase open circuit, the DC current calculation unit 810 cannot calculate correctly, so the power converter 8 selects and uses the DC current calculated value Idc1 from the DC current calculation unit 807.

[0071] (C5) In (C3) above, as shown in Figures 9 and 10, for example, if the power conversion circuit 82 is faulty, the DC current calculation unit 810 cannot calculate correctly, so the power conversion device 8 selects and uses the DC current calculated value Idc1 from the DC current calculation unit 807.

[0072] (C6) In (C3) above, as shown in Figures 2, 9, 10, etc., the motor 9 has a motor angle sensor 91 that measures the motor rotation angle (motor angle sensor value θm) and a motor temperature sensor 92 that measures the motor temperature (motor temperature sensor value Tm). If any of the DC voltage detection unit (DC voltage sensor 83), motor angle sensor 91, or motor temperature sensor 92 of the power converter 8 is faulty, the DC current calculation unit 807 cannot calculate correctly, so the power converter 8 selects and uses the DC current calculated value Idc2 from the DC current calculation unit 810.

[0073] (C7) In the above (C3), as shown in Figures 9 and 10, if the AC current detection unit (AC current sensor 84) fails, the DC current calculation units 807 and 810 cannot correctly calculate the DC current value. Therefore, instead of using the DC current calculation values ​​Idc1 and Idc2, the power converter 8 uses alternative information that indicates that the DC current calculation values ​​Idc1 and Idc2 are unreliable. For example, instead of the DC current calculation values ​​Idc1 and Idc2, the selection unit 811 outputs an alternative value (a value defined as unreliable).

[0074] (C8) In (C3) above, as shown in Figure 7, etc., when switching the DC current value to be used from the calculated DC current value Idc1 to the calculated DC current value Idc2, or from the calculated DC current value Idc2 to the calculated DC current value Idc1, depending on the operating state and / or failure state of the power converter 8, the DC current value to be used is first transitioned to a third DC current value between the calculated DC current value Idc2 and the calculated DC current value Idc1, and then transitioned to the DC current value after the switch.

[0075] For example, as shown in the example in Figure 7, the third DC current value is set to the average value = (Idc1 + Idc2) / 2. By transitioning the DC current value used in this way during switching, the temporal change in the DC current value during switching can be made gradual, thereby suppressing the effects of the switching operation.

[0076] (C9) Furthermore, in (C8) above, as shown in Figure 8, multiple third DC current values ​​of different magnitudes may be set at the timings t2 to t4 of the switching section, and the DC current value used may be transitioned so that it approaches the calculated DC current value Idc2 after the switching in a stepwise manner from the calculated DC current value Idc1 before the switching. In Figure 8, the ratio of Idc1 to Idc2 at t2, t3, and t4 is set as (2:8), (5:5), and (8:2). In this way, by transitioning the DC current value used from the calculated DC current value Idc2 to the calculated DC current value Idc1 in multiple steps, the change in the DC current value between each timing can be made more gradual. As a result, the impact of the switching operation can be suppressed.

[0077] (C10) As shown in Figures 2 and 3, the drive unit 2 comprises a motor 9 and a power converter 8 as described in (C1) above, which converts DC power into AC power by PWM control and supplies a three-phase AC current to the motor 9. As described in (C1) above, the power converter 8 of the drive unit 2 can calculate the correct DC current value even during normal operation (PWM operation, three-phase open operation, three-phase short-circuit operation) and in the event of a failure of the power converter circuit 82. As a result, the drive unit 2 can perform processing using the DC current value appropriately.

[0078] The embodiments described above are merely examples, and the present invention is not limited to these, as long as the features of the invention are not impaired. Other embodiments conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. For example, the selection unit 811 in Figure 9 may be configured to receive not only the fault state from the diagnostic unit 809 but also the operating state of the state control unit 801 as shown in Figure 5, and to perform selection processing based on both the fault state and the operating state. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of Symbols]

[0079] 1...Vehicle, 2...Drive unit, 5...DC power supply, 6...Control unit, 7...Fault notification device, 8...Power converter, 9...Motor, 80...Control circuit, 81...Driver circuit, 82...Power converter circuit, 83...DC voltage sensor, 84...AC current sensor, 91...Motor angle sensor, 92...Motor temperature sensor, 801...State control unit, 802...Target current calculation unit, 803...Current control unit, 804...PWM signal generation unit, 805...3-phase to 2-phase conversion unit, 806...Motor speed calculation unit, 807, 810...DC current calculation unit, 808...Output torque calculation unit, 809...Diagnostic unit, 811...Selection unit, 822...Power semiconductor

Claims

1. A power conversion circuit that converts DC power into AC power using PWM control and outputs a three-phase AC current to a motor, A three-phase to two-phase conversion unit that converts the aforementioned three-phase alternating current into a dq-axis current, A DC voltage detection unit that detects the DC voltage value of the DC power, A first calculation unit calculates the dq-axis voltage based on the motor parameters of the motor and the dq-axis current, and calculates a first DC current value of the DC power based on the dq-axis voltage, the dq-axis current, and the DC voltage value. A power conversion device equipped with the following features.

2. In the power conversion device according to claim 1, The first calculation unit is a power conversion device that performs the calculation of the first DC current value when at least one of the switching elements provided in the power conversion circuit fails.

3. In the power conversion device according to claim 1, An AC current detection unit for detecting the AC current value of the three-phase AC current, The system further comprises a second calculation unit that calculates a second DC current value of the DC power based on the duty cycles of the three phases in the PWM control and the AC current values, A power converter that selects and uses either the first DC current value or the second DC current value depending on the operating state and / or failure state of the power converter.

4. In the power conversion device according to claim 3, A power converter that, when the operating state is a three-phase short circuit or a three-phase open circuit, selects and uses a first DC current value determined by the first calculation unit.

5. In the power conversion device according to claim 3, A power conversion device that, in the event that the power conversion circuit is malfunctioning, selects and uses the first DC current value calculated by the first calculation unit.

6. In the power conversion device according to claim 3, The motor has a motor angle sensor for measuring the motor rotation angle and a motor temperature sensor for measuring the motor temperature. A power conversion device that, if any of the DC voltage detection unit, the motor angle sensor, or the motor temperature sensor is faulty, selects and uses the second DC current value calculated by the second calculation unit.

7. In the power conversion device according to claim 3, A power converter that, in the event of a failure of the AC current detection unit, uses alternative information indicating that the first and second DC current values ​​are unreliable, instead of the first and second DC current values.

8. In the power conversion device according to claim 3, When switching the DC current value used from the first DC current value to the second DC current value, or from the second DC current value to the first DC current value, depending on the operating state and / or failure state of the power converter, A power converter that transitions the DC current value to be used to a third DC current value between the first DC current value and the second DC current value, and then transitions it to the DC current value after the switch.

9. In the power conversion device according to claim 8, A power conversion device that sets multiple third DC current values ​​of different magnitudes and transitions the DC current value used so that it gradually approaches the DC current value after switching from the DC current value before switching.

10. Motor and, A power conversion device according to claim 1, which converts DC power into AC power by PWM control and supplies a three-phase AC current to the motor, A drive device equipped with the following features.

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