Power conversion device and driving device

Abstract

The power conversion device for converting direct current into three-phase alternating current and outputting the three-phase alternating current comprises an alternating current sensor for detecting the current value of two phases in the three-phase alternating current based on the three-phase alternating current; a target current calculation unit that calculates a target current on the basis of the target torque; a voltage command calculation unit that calculates a voltage command value on the basis of the target current and a detection value from the AC current sensor; and an AC current sensor diagnosis unit that determines an abnormality of the AC current sensor on the basis of a detection value of the AC current sensor. The AC current sensor diagnosis unit is provided with: a first diagnosis unit that determines the abnormality on the basis of a two-phase voltage command value obtained by converting the voltage command value into a value of a two-phase orthogonal coordinate system with respect to any one of the output phases; and a second diagnosis unit that determines the abnormality on the basis of a two-phase current detection value obtained by converting a detection value of the AC current sensor into a value of the two-phase orthogonal coordinate system, the AC current sensor diagnosis unit determining the abnormality on the basis of an operation condition of the power conversion device. And a switching unit that switches between the determination of the abnormality by the first diagnosis unit and the determination of the abnormality by the second diagnosis unit.

Description

Technical Field

[0001] The invention relates to a power conversion device and a driving device. Background Art

[0002] In the past, in a power conversion device (inverter) that converts direct current into alternating current and supplies it to an AC motor to drive the AC motor, an AC current sensor for detecting the AC current output from the power conversion device to the AC motor was provided inside. If the AC current sensor fails, the output current of the power conversion device cannot be correctly controlled, which may cause the motor output torque to be excessive. Therefore, it is necessary to diagnose the failure of the AC current sensor.

[0003] Regarding the fault diagnosis of the AC current sensor, for example, the technologies of Patent Documents 1 and 2 are known. Patent Document 1 describes the invention of a motor control device that uses the sum of three-phase AC current values ​​to diagnose the fault of the AC current sensor. Patent Document 2 describes the invention of a motor control device that uses the deviation between the command value and the predicted value of the d-axis voltage and the deviation between the command value and the predicted value of the q-axis voltage to detect the faults of various sensors and detection circuits. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2009-131043 Patent Document 2: Japanese Patent Application Publication No. 2017-127121 Summary of the invention Technical problem to be solved by the invention

[0005] In a power conversion device that provides three-phase AC power to a motor, it is sufficient to detect the AC current of at least two phases using an AC current sensor, and the AC current of the remaining one phase can be calculated based on the fact that the sum of the three-phase AC currents is zero. Therefore, in order to control the power conversion device, it is sufficient to set AC current sensors only for two phases. However, in order to use the diagnostic method of Patent Document 1, it is necessary to set AC current sensors for all three phases, so there is a technical problem that the manufacturing cost of the power conversion device becomes higher than when AC current sensors are set for only two phases.

[0006] On the other hand, the diagnostic method of Patent Document 2 can also be applied to a structure in which AC current sensors are provided for only two phases. However, under motor operating conditions where deviations between the voltage command value and the predicted value are not easily generated, there is a technical problem that a fault of the AC current sensor cannot be detected with high accuracy.

[0007] In view of the above problems, the main object of the present invention is to realize a power conversion device and a drive device capable of detecting a fault of an AC current sensor with high accuracy under any motor operating condition without providing AC current sensors for all three phases. Technical solutions to technical problems

[0008] The power conversion device of the present invention is a device that converts direct current into three-phase alternating current and outputs it, including: an alternating current sensor that detects the current value of two phases in the three-phase alternating current based on the three-phase alternating current; a target current calculation unit that calculates the target current based on the target torque; a voltage command calculation unit that calculates the voltage command value based on the target current and the detection value of the alternating current sensor; and an alternating current sensor diagnosis unit that determines the abnormality of the alternating current sensor based on the detection value of the alternating current sensor, the alternating current sensor diagnosis unit having: a first diagnosis unit that determines the abnormality based on a two-phase voltage command value obtained by converting the voltage command value into a value of an orthogonal coordinate system of two phases based on any output phase; and a second diagnosis unit that determines the abnormality based on a two-phase current detection value obtained by converting the detection value of the alternating current sensor into a value of an orthogonal coordinate system of the two phases, the alternating current sensor diagnosis unit switches the determination of the abnormality based on the first diagnosis unit and the determination of the abnormality based on the second diagnosis unit according to the operating conditions of the power conversion device. The driving device of the present invention includes a power conversion device and an AC motor driven by a three-phase AC current output from the power conversion device, and a vehicle is driven by the driving force of the AC motor. Effects of the Invention

[0009] According to the present invention, it is possible to realize a power conversion device and a drive device that can detect a failure of an AC current sensor with high accuracy under any motor operating condition without providing AC current sensors for all three phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing a vehicle equipped with a drive device according to an embodiment of the present invention. Figure 2 It is a diagram showing a configuration example of a power conversion device and a drive device according to an embodiment of the present invention. Figure 3 It is a diagram showing a configuration example of a power conversion circuit and a motor. Figure 4 This is a flowchart showing an example of determination switching processing by the first diagnosis unit and the second diagnosis unit in the first embodiment of the present invention. Figure 5This is a flowchart showing an example of abnormality diagnosis processing of the first diagnosis unit in the first embodiment of the present invention. Figure 6 This is a flowchart showing an example of abnormality diagnosis processing of the second diagnosis unit in the first embodiment of the present invention. Figure 7 This is a diagram showing an example of two-phase voltage command values ​​and two-phase current detection values ​​when an AC current sensor fails in one embodiment of the present invention. Figure 8 This is a flowchart showing an example of abnormality diagnosis processing of the first diagnosis unit in the second embodiment of the present invention. Fig. 9 This is a flowchart showing an example of abnormality diagnosis processing by the second diagnosis unit in the second embodiment of the present invention. Fig.10 This is a flowchart showing an example of determination switching processing by the first diagnosis unit and the second diagnosis unit in the third embodiment of the present invention. Fig.11 This is a flowchart showing an example of determination switching processing by the first diagnosis unit and the second diagnosis unit in the fourth embodiment of the present invention. DETAILED DESCRIPTION

[0011] The following describes an embodiment of the present invention. In each of the following embodiments, an example is described in which, in a power conversion device that converts direct current into three-phase alternating current and outputs it to a motor, an alternating current sensor is provided for only two phases of the three-phase alternating current flowing through the motor, and when any of the alternating current sensors fails, the failure can be detected with high accuracy.

[0012] (First embodiment) Figure 1 1 is a diagram showing a vehicle equipped with a drive device according to an embodiment of the present invention. The drive device 1 mounted on the vehicle 200 is connected to the axle 201 of the vehicle 200, and has a power conversion device, an electric motor, and a speed reducer inside. Then, according to the operation of the accelerator pedal by the driver, the power conversion device and the electric motor are controlled to generate driving force, and the driving force is transmitted to the axle 201 via the speed reducer, so that the driving wheels 202 provided at both ends of the axle 201 rotate, and the vehicle 200 travels. The speed reducer has the function of amplifying the driving force of the electric motor and transmitting it to the axle 201.

[0013] In addition, Figure 1 In the embodiment, the front wheels of the vehicle 200 are used as the driving wheels 202, and the driving device 1 is connected to the axle 201 of the front wheels, but the rear wheels may be used as the driving wheels, and the driving device 1 may be connected to the axle of the rear wheels. In addition, the driving device 1 may be connected to the axles of the front and rear wheels respectively, and the independent driving devices 1 may be connected to the left and right wheels instead of the axles.

[0014] Figure 2 1 is a diagram showing a configuration example of a power conversion device and a drive device according to an embodiment of the present invention. Figure 1 The vehicle 200 is connected to a DC power supply 2, an electronic control device 3 and a fault notification device 4, and has a power conversion device 10 and an electric motor 20.

[0015] The DC power supply 2 supplies DC power to the power conversion device 10 in the drive device 1. The DC power supplied by the DC power supply 2 is converted into three-phase AC power by the power conversion device 10, and is output from the power conversion device 10 to the motor 20, thereby driving the motor 20. As described above, the driving force of the motor 20 is transmitted to the axle 201 of the vehicle 200 through the speed reducer (not shown), so that the vehicle 200 travels. The DC power supply 2 is configured using a rechargeable battery such as a lithium ion battery, for example.

[0016] The electronic control device 3 transmits information such as target torque to the drive device 1 based on the driver's driving operation, etc. The target torque information transmitted from the electronic control device 3 is input to the control circuit 100 in the power conversion device 10 in the drive device 1 .

[0017] Fault notification device 4 receives a fault notification signal from drive device 1 and notifies passengers of vehicle 200 of the occurrence of a fault. Examples of methods for notifying a fault include lighting a lamp, sounding a warning sound, and notifying by voice.

[0018] The motor 20 is a three-phase AC motor having windings corresponding to three phases inside, and is equivalent to, for example, a synchronous motor using permanent magnets, an induction motor not using permanent magnets, etc. The motor 20 is equipped with an angle sensor (not shown) for measuring the rotation angle of the rotor in the motor 20, that is, the electrical angle of the motor 20. The angle sensor outputs the measured electrical angle as an angle sensor value to the power conversion device 10. The angle sensor of the motor 20 is configured using, for example, a rotary transformer.

[0019] The power conversion device 10 converts the DC power obtained from the DC power supply 2 into three-phase AC power and outputs it to the motor 20 to drive the motor 20. In addition, the power conversion device 10 also has a function of converting the AC power generated by the motor 20 into DC power and charging the DC power supply 2. The power conversion device 10 has a control circuit 100, a drive circuit 120, a power conversion circuit 130, a voltage sensor 140, and an AC current sensor 150. In addition, the power conversion device 10 may have a circuit breaker (not shown) for cutting off the DC power provided by the DC power supply 2 and a circuit breaker drive circuit (not shown) for driving the circuit breaker.

[0020] The power conversion circuit 130 receives the drive signal from the drive circuit 120, drives the internal power semiconductor, and controls the current flowing through the motor 20. Figure 3 The internal structure of the power conversion circuit 130 will be described.

[0021] Figure 3 1 is a diagram showing a configuration example of a power conversion circuit 130 and a motor 20. The power conversion circuit 130 includes six power semiconductors 131 and a smoothing capacitor 132 therein.

[0022] Each power semiconductor 131 switches on / off according to a drive signal input from the drive circuit 120. Each power semiconductor 131 is connected to the DC power supply 2 and the motor 20, respectively, and performs conversion between DC power supply 2 and AC power between the DC power supply 2 and the motor 20 by switching on / off corresponding to the drive signal. The power semiconductor 131 uses, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). In the following embodiment, an example of using an IGBT as the power semiconductor 131 is described, but the same is true when other semiconductor elements such as a power MOSFET are used.

[0023] In the power conversion circuit 130 , six power semiconductors 131 are arranged in two upper and lower parts for each phase. Outputs from the pairs of power semiconductors 131 for each phase are connected to the windings of each phase of the motor 20 .

[0024] In addition, in this embodiment, Figure 3 The three power semiconductors 131 on the upper side are collectively referred to as upper arms, and the three power semiconductors 131 on the lower side are collectively referred to as lower arms. That is, the power conversion circuit 130 is provided with three sets of series circuits of upper arms and lower arms, and these series circuits are connected to the windings of each phase of the motor 20 as branches 130U corresponding to U, branches 130V corresponding to V, and branches 130W corresponding to W, respectively.

[0025] The smoothing capacitor 132 is a capacitor for smoothing current fluctuations caused by turning on and off each power semiconductor 131 and suppressing ripples in the DC current supplied from the DC power supply 2 to the power conversion device 130. For example, an electrolytic capacitor or a film capacitor is used as the smoothing capacitor 132.

[0026] In addition, in the present embodiment, the motor neutral point 21 connected to the windings of each phase of the motor 20 is in a floating state, but it may be connected to the ground (not shown) of the power conversion device 10. In addition, there are direct grounding, resistance grounding, compensating reactor grounding, arc extinguishing reactor grounding, etc., and any method may be used when connecting the motor neutral point 21 to the ground.

[0027] return Figure 2 The voltage sensor 140 is a sensor for measuring the output voltage of the DC power supply 2, and is connected between the DC power supply 2 and the power conversion circuit 130. The voltage sensor 140 outputs the measured voltage value to the control circuit 100 as a voltage sensor value.

[0028] The AC current sensor 150 is a sensor for measuring two-phase AC currents among the three-phase AC currents output from the power conversion circuit 130 to the motor 20, and is connected between the power conversion circuit 130 and the motor 20. The AC current sensor 150 outputs the measured two-phase current values ​​to the control circuit 100 as AC current sensor values.

[0029] In addition, Figure 2 In the example of FIG. 1 , the AC current sensor 150 is provided for the U phase and the V phase, but the phases for which the AC current sensor 150 is provided are not necessarily limited to the two phases. In addition, in the present embodiment, the current flowing from the power conversion circuit 130 to the motor 20 is treated as a positive current, and the current flowing from the motor 20 to the power conversion circuit 130 is treated as a negative current.

[0030] The drive circuit 120 receives a PWM (Pulse Width Modulation) signal outputted from the control circuit 100 , generates a drive signal for switching on / off of each power semiconductor 131 of the power conversion circuit 130 , and outputs the drive signal to the power conversion circuit 130 .

[0031] The control circuit 100 communicates with the electronic control device 3 and receives the target torque of the motor 20 from the electronic control device 3. Based on the target torque, the control circuit 100 controls the PWM signal so as to control the current of each phase output from the power conversion device 10 to the motor 20 to a predetermined value, and outputs it to the drive circuit 120. The control circuit 100 drives the power conversion circuit 130 via the drive circuit 120 by driving the drive signal output by the drive circuit 120 according to the PWM signal.

[0032] In addition, the control circuit 100 diagnoses whether a fault has occurred inside the power conversion device 10, and when it is determined that a fault has occurred, outputs a fault notification signal to the fault notification device 4. Thus, the fault notification device 4 performs the above-mentioned fault notification to the passengers of the vehicle 200, and the passengers can be notified of the occurrence of the fault.

[0033] The control circuit 100 includes a motor speed calculation unit 101, a 1-phase current calculation unit 102, a target current calculation unit 103, a voltage command calculation unit 104, a PWM signal generation unit 105, a voltage command 2-phase conversion unit 106, a current 2-phase conversion unit 107, and an AC current sensor diagnosis unit 108. The control circuit 100 includes a CPU, a RAM, a ROM, a communication circuit, etc. (none of which are shown in the figure) inside, and the functions represented by the above-mentioned functional blocks can be realized by executing a predetermined program stored in the ROM in the CPU. In addition, the ROM of the control circuit 100 may be an electrically rewritable ROM such as an EEPROM (Electrically Erasable Programmable ROM) or a flash ROM, for example.

[0034] The motor speed calculation unit 101 obtains an angle sensor value outputted from an angle sensor in the motor 20 and calculates the rotation speed of the motor 20 based on the temporal change of the angle sensor value. The calculated rotation speed of the motor 20 is then outputted to the target current calculation unit 103 as a motor speed value.

[0035] The 1-phase current calculation unit 102 obtains the 2-phase AC current sensor values ​​output from the AC current sensor 150, and calculates the remaining 1-phase AC current value that has not been measured, based on the relationship that U-phase current + V-phase current + W-phase current = 0. Then, the calculated 1-phase AC current value is output to the voltage command calculation unit 104 and the current 2-phase conversion unit 107.

[0036] The target current calculation unit 103 calculates the current value that should flow through the motor 20 in order for the motor 20 to output the same torque as the target torque, using the target torque sent from the electronic control device 3, the voltage sensor value output from the voltage sensor 140, and the motor speed value output from the motor speed calculation unit 101. Then, the calculated current value is output as the target current to the voltage command calculation unit 104. The target current is expressed by a value of a two-phase orthogonal coordinate system such as a d-axis target current value and a q-axis target current value.

[0037] The voltage command calculation unit 104 calculates the voltage command values ​​of the three phases to be output to the motor 20 based on the target current output from the target current calculation unit 103 and the AC current sensor values ​​of the two phases output from the AC current sensor 150. At this time, the voltage command calculation unit 104 uses the angle sensor value output from the angle sensor in the motor 20 to perform feedback control so that the AC current sensor values ​​of the two phases and the AC current value of the remaining one phase output from the one-phase current calculation unit 102 follow the target current, thereby calculating the voltage command values ​​of the three phases. In addition, based on the calculated voltage command values ​​of the three phases, the duty ratio value of each phase is calculated. Then, the calculated duty ratio value is output to the PWM signal generation unit 105, and the voltage command values ​​of the three phases are output to the voltage command two-phase conversion unit 106.

[0038] The PWM signal generation unit 105 uses the duty cycle value of each phase output from the voltage command calculation unit 104 to generate a PWM signal for each power semiconductor 131 of the power conversion circuit 130, and outputs it to the drive circuit 120. The PWM signal generation unit 105 has a timer (not shown) inside, and generates a timer value that changes continuously at regular intervals through the timer. Then, the PWM signal can be generated based on the generated timer value and the duty cycle value of each phase.

[0039] In addition, the PWM signal generation unit 105 switches the signal output to the drive circuit 120 according to the fault notification information output from the AC current sensor diagnosis unit 108. Specifically, when the fault notification information indicating that the AC current sensor 150 is abnormal is not output from the AC current sensor diagnosis unit 108, the PWM signal generation unit 105 generates a PWM signal based on the duty value of each phase as described above, and outputs it to the drive circuit 120. On the other hand, when the fault notification information indicating that the AC current sensor 150 is abnormal is output from the AC current sensor diagnosis unit 108, the PWM signal generation unit 105 generates a PWM signal that makes the motor 20 a non-driving state regardless of the duty value of each phase, and outputs it to the drive circuit 120. The so-called non-driving state of the motor 20 includes, for example, a state in which all six power semiconductors 131 of the power conversion circuit 130 are turned off, a state in which all upper arms of the six power semiconductors 131 are turned on and all lower arms are turned off, a state in which all upper arms of the six power semiconductors 131 are turned off and all lower arms are turned on, and the like.

[0040] The voltage command 2-phase conversion unit 106 performs 2-phase conversion on the 3-phase voltage command values ​​output from the voltage command calculation unit 104 to calculate 2-phase voltage command values ​​obtained by representing the 3-phase voltage command values ​​with values ​​of a 2-phase orthogonal coordinate system based on any one phase. As a method of 2-phase conversion performed at this time, for example, αβ conversion or dq conversion can be cited. Then, the calculated 2-phase voltage command values ​​are output to the AC current sensor diagnosis unit 108.

[0041] In addition, in the voltage command calculation unit 104, the three-phase AC current values ​​can also be converted into d-axis current values ​​and q-axis current values, and the two-phase voltage indication values ​​are obtained by respectively calculating the differences between the two-phase current command values ​​and the d-axis target current value and the q-axis target current value and converted into three-phase voltage command values, thereby calculating the voltage command values. In this case, the voltage command 2-phase conversion unit 106 is omitted by outputting the two-phase voltage command values ​​from the voltage command calculation unit 104 to the AC current sensor diagnosis unit 108.

[0042] The current two-phase conversion unit 107 performs two-phase conversion on the two-phase AC current sensor values ​​output from the AC current sensor 150 and the remaining one-phase AC current value output from the one-phase current calculation unit 102, thereby calculating a two-phase current detection value obtained by representing the three-phase AC current values ​​with values ​​of a two-phase orthogonal coordinate system based on an arbitrary phase. As a method of two-phase conversion performed at this time, similar to the voltage command two-phase conversion unit 106, for example, αβ conversion or dq conversion can be cited. Then, the calculated two-phase current command value is output to the AC current sensor diagnosis unit 108.

[0043] In addition, in the voltage command calculation unit 104, as described above, the three-phase AC current values ​​can be converted into d-axis current values ​​and q-axis current values, and the two-phase voltage indication values ​​can be obtained based on the two-phase current command values ​​obtained by respectively calculating the differences between the two-phase current command values ​​and the d-axis target current value and the q-axis target current value and converted into three-phase voltage command values, thereby calculating the voltage command values. In this case, the current two-phase conversion unit 107 is omitted by outputting the d-axis current value and the q-axis current value from the voltage command calculation unit 104 to the AC current sensor diagnosis unit 108.

[0044] The AC current sensor diagnosis unit 108 determines an abnormality of the AC current sensor 150 based on the AC current sensor value output from the AC current sensor 150. In this abnormality determination, the AC current sensor diagnosis unit 108 uses the two-phase voltage command value output from the voltage command two-phase conversion unit 106 and the two-phase current detection value output from the current two-phase conversion unit 107 based on the AC current sensor value to perform a fault determination of the AC current sensor 150, and outputs fault notification information corresponding to the determination result. The fault notification information output from the AC current sensor diagnosis unit 108 includes, for example, information of "no fault" when the AC current sensor 150 is normal, and information of "AC current sensor fault" when a fault in the AC current sensor 150 is detected.

[0045] The AC current sensor diagnostic unit 108 includes a first diagnostic unit 1081 that performs abnormality determination based on the two-phase voltage command values ​​output from the voltage command two-phase conversion unit 106, and a second diagnostic unit 1082 that performs abnormality determination based on the two-phase current detection values ​​output from the current two-phase conversion unit 107. In addition, the AC current sensor diagnostic unit 108 switches between the abnormality determination performed by the first diagnostic unit 1081 and the abnormality determination performed by the second diagnostic unit 1082 according to the operating conditions of the power conversion device 10. This point will be described in detail below.

[0046] Figure 4 1081 and 1082 in the first embodiment of the present invention. Figure 4 The determination switching process shown in the flowchart is performed, thereby switching the abnormality determination of the first diagnosis unit 1081 and the abnormality determination of the second diagnosis unit 1082 according to the operating conditions of the power conversion device 10.

[0047] In step S10, the AC current sensor diagnostic unit 108 determines whether the fundamental frequency of the three-phase AC current flowing through the motor 20 is greater than or equal to a predetermined value. Here, for example, the fundamental frequency of the three-phase AC current is calculated based on the motor speed value output from the motor speed calculation unit 101, and the calculation result is compared with the predetermined value, thereby making the determination in step S10 possible.

[0048] If it is determined in step S10 that the fundamental frequency of the three-phase AC current is greater than or equal to the predetermined value, the process proceeds to step S20, where the second diagnostic unit 1082 performs an abnormality determination. Figure 6 The process shown in the flowchart is used to determine whether the AC current sensor 150 is abnormal. After the abnormality determination of the second diagnosis unit 1082 is performed in step S20, the process ends. Figure 4The process is shown in the flowchart.

[0049] On the other hand, if it is determined in step S10 that the fundamental frequency of the three-phase AC current is less than the specified value, the process proceeds to step S30, and the first diagnostic unit 1081 performs an abnormality determination. Figure 5 The process shown in the flowchart is used to determine whether the AC current sensor 150 is abnormal. After the abnormality determination of the first diagnosis unit 1081 is performed in step S30, the process ends. Figure 4 The process is shown in the flowchart.

[0050] Figure 5 This is a flowchart showing an example of abnormality diagnosis processing by the first diagnosis unit 1081 in the first embodiment of the present invention.

[0051] In step S110, the first diagnostic unit 1081 detects the variation of the magnitude of the two-phase voltage command value output from the voltage command 2-phase conversion unit 106, and determines whether the variation is above a predetermined threshold value. Here, for example, the d-axis voltage command value and the q-axis voltage command value are obtained from the voltage command 2-phase conversion unit 106 as the two-phase voltage command values, and the time variation of the magnitude of the vector when these values ​​are represented by a vector on the dq plane is observed, and the variation of the two-phase voltage command value is obtained based on the maximum value and the minimum value. By comparing the variation of the two-phase voltage command value obtained in this way with the predetermined threshold value, the determination of step S110 can be performed.

[0052] According to the determination of step S110, if it is determined that the change in the magnitude of the two-phase voltage command value is greater than the threshold, the process proceeds to step S120, where it is determined that the AC current sensor 150 is faulty. On the other hand, if it is determined that the change in the magnitude of the two-phase voltage command value is less than the threshold, the process proceeds to step S130, where it is determined that the AC current sensor 150 is normal. After the processing of step S120 or S130 is performed, the first diagnostic unit 1081 outputs fault notification information corresponding to the determination result, and the process ends. Figure 5 The process is shown in the flowchart.

[0053] Figure 6 This is a flowchart showing an example of abnormality diagnosis processing by the second diagnosis unit 1082 in the first embodiment of the present invention.

[0054] In step S210, the second diagnostic unit 1082 detects the change in the magnitude of the two-phase current detection value output from the current two-phase conversion unit 107, and determines whether the change is above a predetermined threshold value. Here, for example, the d-axis current value and the q-axis current value are obtained from the current two-phase conversion unit 107 as the two-phase current detection value, and the time change of the magnitude of the vector when these values ​​are represented by a vector on the dq plane is observed, and the change in the two-phase current detection value is obtained based on the maximum and minimum values. By comparing the change in the two-phase current detection value obtained in this way with the predetermined threshold value, the determination in step S210 can be performed.

[0055] In the case where the variation of the magnitude of the two-phase current detection values ​​is determined to be greater than the threshold value through the determination of step S210, the process proceeds to step S220, where it is determined that the AC current sensor 150 is faulty. On the other hand, in the case where the variation of the magnitude of the two-phase current detection values ​​is determined to be less than the threshold value, the process proceeds to step S230, where it is determined that the AC current sensor 150 is normal. After the processing of step S220 or S230 is performed, the second diagnostic unit 1082 outputs the fault notification information corresponding to the determination result, and the process ends. Figure 6 The process is shown in the flowchart.

[0056] Next, refer to Figure 7 In the specific example shown, the following describes changes in the two-phase voltage indication values ​​and the two-phase current detection values ​​when a failure occurs in the AC current sensor 150. Figure 7 This is a diagram showing an example of two-phase voltage command values ​​and two-phase current detection values ​​when an AC current sensor fails in one embodiment of the present invention.

[0057] upper section Figure 7 (a) shows an example of two-phase voltage command values ​​and two-phase current detection values ​​when the fundamental frequency of the three-phase AC current is lower than the specified value. Figure 7 In (a), the left side of the figure shows the time change of the two-phase voltage command value, and the right side of the figure shows the time change of the two-phase current detection value. In this case, when a fault occurs in the AC current sensor 150, the two-phase voltage instruction value and the two-phase current detection value change significantly. Therefore, it can be seen that the first diagnostic unit 1081 can determine whether the AC current sensor 150 has a fault based on the change in the size of the two-phase voltage command value.

[0058] Lower Figure 7 (b) shows an example of two-phase voltage command values ​​and two-phase current detection values ​​when the fundamental frequency of the three-phase AC current is higher than a specified value. Figure 7In (b), the left side graph shows the time variation of the two-phase voltage command value, and the right side graph shows the time variation of the two-phase current detection value. In this case, when a fault occurs in the AC current sensor 150, the two-phase current detection value changes greatly, while the two-phase voltage command value hardly changes. Therefore, it can be seen that the first diagnostic unit 1081 cannot determine whether the AC current sensor 150 has a fault, but the second diagnostic unit 1082 can be used to determine whether the AC current sensor 150 has a fault based on the change in the magnitude of the two-phase current detection value.

[0059] The above-described difference in fluctuation between the two-phase voltage command value and the two-phase current detection value caused by the fundamental frequency of the three-phase AC current is caused by the influence of the current feedback control performed by the voltage command calculation unit 104. This point will be described in detail below.

[0060] The voltage command calculation unit 104 generally uses PI control as current feedback control to calculate the voltage command value. In this case, the difference between the target current and the actual current becomes the P control term, and the value obtained by accumulating the difference between the target current and the actual current over time becomes the I control term. Therefore, when the current changes slowly, that is, when the basic frequency of the AC current is low, when the AC current sensor 150 fails, the I control term has a strong effect in a state where the difference between the target current and the actual current is easily accumulated, and the voltage command calculation unit 104 needs to more strongly correct the deviation between the target current and the actual current obtained by adding the error amount caused by the failure of the AC current sensor 150. As a result, the magnitude of the two-phase voltage command value changes greatly, while the magnitude of the two-phase current detection value changes relatively small. On the contrary, when the current changes quickly, that is, when the basic frequency of the AC current is high, the correction based on the I control term does not have a strong effect. Therefore, the magnitude of the two-phase voltage command value hardly changes, while the two-phase current detection value changes greatly.

[0061] As described above, when the fundamental frequency of the alternating current is low, since the two-phase voltage command values ​​vary greatly, the abnormality determination of the two-phase voltage command values ​​based on the first diagnostic unit 1081 can obtain a correct determination result compared to the abnormality determination of the two-phase current detection values ​​based on the second diagnostic unit 1082. Conversely, when the fundamental frequency of the alternating current is high, the abnormality determination of the two-phase current detection values ​​based on the second diagnostic unit 1082 can obtain a correct determination result compared to the abnormality determination of the two-phase voltage command values ​​based on the first diagnostic unit 1081.

[0062] According to the first embodiment of the present invention described above, the following effects are achieved.

[0063] (1) The power conversion device 10 converts direct current into three-phase alternating current and outputs the three-phase alternating current. The power conversion device 10 includes an alternating current sensor 150 that detects current values ​​of two phases of three-phase alternating current based on the three-phase alternating current; a target current calculation unit 103 that calculates a target current based on a target torque; a voltage command calculation unit 104 that calculates a voltage command value based on the target current and the detection value of the alternating current sensor 150; and an alternating current sensor diagnosis unit 108 that determines an abnormality of the alternating current sensor 150 based on the detection value of the alternating current sensor 150. The alternating current sensor diagnosis unit 108 includes a first diagnosis unit 1081 that determines an abnormality of the alternating current sensor 150 based on a two-phase voltage command value obtained by converting the voltage command value into a value of a two-phase orthogonal coordinate system with any output phase as a reference; and a second diagnosis unit 1082 that determines an abnormality of the alternating current sensor 150 based on a two-phase current detection value obtained by converting the detection value of the alternating current sensor 150 into a value of a two-phase orthogonal coordinate system. The AC current sensor diagnosis unit 108 switches between abnormality determination by the first diagnosis unit 1081 and abnormality determination by the second diagnosis unit 1082 according to the operating conditions of the power conversion device 10. Thus, it is possible to realize a power conversion device 10 that can detect a fault of the AC current sensor 150 with high accuracy under any motor operating conditions without providing AC current sensors 150 for all three phases.

[0064] (2) When the fundamental frequency of the three-phase AC current is less than a predetermined value (step S10: No), the AC current sensor diagnostic unit 108 determines the abnormality of the AC current sensor 150 by the first diagnostic unit 1081 (step S30), and when the fundamental frequency of the three-phase AC current is greater than the predetermined value (step S10: Yes), the second diagnostic unit 1082 determines the abnormality of the AC current sensor 150 (step S20). Thus, when the voltage command value is calculated using PI control, the abnormality of the AC current sensor 150 can be correctly detected regardless of the fundamental frequency of the AC current.

[0065] (3) When the variation in the magnitude of the two-phase voltage command value is greater than or equal to a predetermined threshold value (step S110: Yes), the first diagnostic unit 1081 determines that there is an abnormality in the AC current sensor 150 (step S120). Thus, when a failure occurs in the AC current sensor 150, the first diagnostic unit 1081 can reliably detect the failure.

[0066] (4) When the variation in the magnitude of the two-phase current detection value is greater than a predetermined threshold value (step S210: Yes), the second diagnostic unit 1082 determines that there is an abnormality in the AC current sensor 150 (step S220). Thus, when a failure occurs in the AC current sensor 150, the second diagnostic unit 1082 can reliably detect the failure.

[0067] (5) The drive device 1 includes a power conversion device 10 and an AC motor 20 driven by a three-phase AC current output from the power conversion device 10, and the vehicle 200 is driven to travel using the driving force of the AC motor 20. Thus, it is possible to realize a drive device 1 in which a failure of the AC current sensor 150 can be detected with high accuracy under any motor operating condition without providing the AC current sensor 150 for all three phases in the power conversion device 10.

[0068] (Second embodiment) Next, a second embodiment of the present invention will be described. In this embodiment, an example of a power conversion device capable of determining a failure of the AC current sensor 150 in a shorter time will be described. Note that description of parts common to the first embodiment will be omitted unless particularly necessary.

[0069] In the present embodiment, the diagnostic methods of the first diagnostic unit 1081 and the second diagnostic unit 1082 in the AC current sensor diagnostic unit 108 are different from those in the first embodiment. In the present embodiment, the first diagnostic unit 1081 has a function of calculating the target value of the two-phase voltage command value and performing abnormality determination of the AC current sensor 150 based on the target value. In addition, the second diagnostic unit 1082 has a function of calculating the target value of the two-phase current detection value and performing abnormality determination of the AC current sensor 150 based on the target value.

[0070] Figure 8 This is a flowchart showing an example of abnormality diagnosis processing by the first diagnosis unit 1081 in the second embodiment of the present invention.

[0071] In step S110A, the first diagnostic unit 1081 obtains a target value for the two-phase voltage command value output from the voltage command two-phase conversion unit 106, obtains a difference between the target value and the current two-phase voltage command value actually output from the voltage command two-phase conversion unit 106, and determines whether the difference value is above a predetermined threshold value. Here, for example, by obtaining the target current output from the target current calculation unit 103, the target value for the two-phase voltage command value is calculated based on the value of the target current, so that a target value equivalent to the two-phase voltage command value when the AC current sensor 150 is normal can be obtained, and the determination of step S110A is performed.

[0072] In the case where the difference between the target value and the actual value of the two-phase voltage command value is determined to be greater than the threshold value through the determination of step S110A, the process proceeds to step S120, where it is determined that the AC current sensor 150 is faulty. On the other hand, in the case where the difference between the target value and the actual value of the two-phase voltage command value is determined to be less than the threshold value, the process proceeds to step S130, where it is determined that the AC current sensor 150 is normal. After the processing of step S120 or S130 is performed, the first diagnostic unit 1081 outputs fault notification information corresponding to the determination result, and the process ends. Figure 8 The process is shown in the flowchart.

[0073] Fig. 9 This is a flowchart showing an example of abnormality diagnosis processing by the second diagnosis unit 1082 in the second embodiment of the present invention.

[0074] In step S210A, the second diagnostic unit 1082 obtains a target value for the two-phase current detection value output from the current two-phase conversion unit 107, obtains a difference between the target value and the current two-phase current detection value actually output from the current two-phase conversion unit 107, and determines whether the difference value is above a predetermined threshold value. Here, for example, by obtaining the target current output from the target current calculation unit 103, the value of the target current is set as the target value for the two-phase current detection value, so that a target value equivalent to the two-phase current detection value when the AC current sensor 150 is normal can be obtained, and the determination of step S210A is performed.

[0075] In the case where the difference between the target value and the actual value of the two-phase current detection value is determined to be greater than the threshold value through the determination of step S210A, the process proceeds to step S220, where it is determined that the AC current sensor 150 is faulty. On the other hand, in the case where the difference between the target value and the actual value of the two-phase current command value is determined to be less than the threshold value, the process proceeds to step S230, where it is determined that the AC current sensor 150 is normal. After the processing of step S220 or S230 is performed, the second diagnostic unit 1082 outputs fault notification information corresponding to the determination result, and the process ends. Fig. 9 The process is shown in the flowchart.

[0076] In the above-mentioned first embodiment, the first diagnostic unit 1081 uses the change in the size of the two-phase voltage command value output from the voltage command 2-phase conversion unit 106 to determine whether the AC current sensor 150 has a fault. In addition, the second diagnostic unit 1082 uses the change in the size of the two-phase current detection value output from the current 2-phase conversion unit 107 to determine whether the AC current sensor 150 has a fault. In these determination methods, since it takes time to confirm whether there is a change in each piece of information, there is a problem that it takes a long time to determine the fault. On the other hand, in the present embodiment, the target values ​​and actual values ​​of the two-phase voltage command value and the two-phase current detection value are compared, and when a deviation occurs in these values ​​due to a fault of the AC current sensor 150, the deviation can be immediately determined. Therefore, compared with the first embodiment, the fault determination can be performed in a short time.

[0077] According to the second embodiment of the present invention described above, the first diagnostic unit 1081 obtains the target value for the two-phase voltage instruction (step S110A), and when the difference between the target value and the actual two-phase voltage instruction value is greater than a predetermined threshold value (step S110A: Yes), it is determined that the AC current sensor 150 is abnormal (step S120). In addition, the second diagnostic unit 1082 obtains the target value for the two-phase current detection value (step S210A), and when the difference between the target value and the actual two-phase current detection value is greater than a predetermined threshold value (step S210A: Yes), it is determined that the AC current sensor 150 is abnormal (step S220). As a result, the fault determination of the AC current sensor 150 can be performed in a shorter time in the first diagnostic unit 1081 and the second diagnostic unit 1082, respectively.

[0078] (Third embodiment) Next, a third embodiment of the present invention will be described. In this embodiment, an example of a power conversion device that performs a determination switching process of the first diagnostic unit 1081 and the second diagnostic unit 1082 according to an operating condition different from that of the first embodiment will be described. In addition, the description of the parts common to the first embodiment will be omitted unless they are particularly necessary.

[0079] Fig.10 This is a flowchart showing an example of the determination switching process of the first diagnosis unit 1081 and the second diagnosis unit 1082 in the third embodiment of the present invention.

[0080] In step S10A, AC current sensor diagnostic unit 108 determines whether the magnitude of the target current for motor 20 is greater than or equal to a predetermined value. Here, for example, the target current output from target current calculation unit 103 may be obtained and the determination in step S10A may be performed using the target current value.

[0081] According to the determination of step S10A, if it is determined that the target current is greater than the specified value, the process proceeds to step S20, and the second diagnostic unit 1082 makes an abnormality determination. On the other hand, if it is determined that the target current is less than the specified value, the process proceeds to step S30, and the first diagnostic unit 1081 makes an abnormality determination. If an abnormality determination is made by the first diagnostic unit 1081 or the second diagnostic unit 1082 in either step S20 or S30, the process ends. Fig.10 The process is shown in the flowchart.

[0082] As described in the first embodiment, the first diagnosis unit 1081 is in a state where the fault determination of the AC current sensor 150 is easier to perform if the current correction force based on the current feedback control is strong, and conversely, the second diagnosis unit 1082 is in a state where the fault determination of the AC current sensor 150 is easier to perform if the current correction force based on the current feedback control is weak. For the P control item and the I control item of the current feedback control in the voltage command calculation unit 104, the larger the difference between the target current and the actual current, the stronger the correction based on these controls. Here, when the actual current deviates from the target current by a certain amount due to the fault of the AC current sensor 150, if the target current is small, the difference between the actual current and the target current becomes large, and the correction of the control of the voltage command calculation unit 104 becomes strong, so the influence of the fault of the AC current sensor 150 becomes relatively large. On the contrary, if the target current is large, the difference between the actual current and the target current becomes small, and the correction of the control of the voltage command calculation unit 104 becomes weak, so the influence of the fault becomes relatively small.

[0083] As described above, if the target current is small, the correction of the control of the voltage command calculation unit 104 is strong, so it is easier to obtain a correct judgment result based on the abnormality judgment of the two-phase voltage command value performed by the first diagnostic unit 1081. On the contrary, if the target current is large, the correction of the control of the voltage command calculation unit 104 is weak, so it is easier to obtain a correct judgment result based on the abnormality judgment of the two-phase current detection value performed by the second diagnostic unit 1082. Therefore, as in the present embodiment, even if the fault judgment method is switched by replacing the basic frequency of the AC current with the target current, the fault of the AC current sensor 150 can be judged with high accuracy.

[0084] According to the third embodiment of the present invention described above, when the target current is less than the specified value (step S10A: No), the AC current sensor diagnostic unit 108 performs abnormality determination (step S30) of the AC current sensor 150 by the first diagnostic unit 1081, and when the target current is greater than the specified value (step S10A: Yes), the AC current sensor 150 is abnormally determined by the second diagnostic unit 1082 (step S20). Thus, similarly to the first embodiment, when the voltage command value is calculated using PI control, the abnormality of the AC current sensor 150 can be correctly detected regardless of the basic frequency of the AC current.

[0085] (Fourth embodiment) Next, a fourth embodiment of the present invention will be described. In this embodiment, an example of a power conversion device that performs a determination switching process of the first diagnostic unit 1081 and the second diagnostic unit 1082 according to an operating condition different from that of the first and third embodiments will be described. In addition, the description of the parts common to the first embodiment will be omitted unless they are particularly necessary.

[0086] Fig.11 This is a flowchart showing an example of the determination switching process of the first diagnosis unit 1081 and the second diagnosis unit 1082 in the fourth embodiment of the present invention.

[0087] In step S10B, the AC current sensor diagnostic unit 108 determines whether the target torque for the motor 20 is greater than or equal to a predetermined value. Here, for example, information on the target torque transmitted from the electronic control unit 3 is acquired and the determination in step S10B can be performed using the target torque information.

[0088] According to the determination of step S10B, if it is determined that the target torque is greater than the specified value, the process proceeds to step S20, where the second diagnostic unit 1082 makes an abnormality determination. On the other hand, if it is determined that the target torque is less than the specified value, the process proceeds to step S30, where the first diagnostic unit 1081 makes an abnormality determination. If an abnormality determination is made by the first diagnostic unit 1081 or the second diagnostic unit 1082 in either step S20 or S30, the process ends. Fig.11 The process is shown in the flowchart.

[0089] As described in the third embodiment, when the actual current deviates from the target current by a certain amount due to a fault in the AC current sensor 150, when the target current is small, the abnormality determination based on the two-phase voltage command value by the first diagnostic unit 1081 is more likely to obtain a correct determination result, and conversely, when the target current is large, the abnormality determination based on the two-phase current detection value by the second diagnostic unit 1082 is more likely to obtain a correct determination result. Here, if the target torque is large, the target current also tends to become larger, so even if the fault determination method is switched using the target torque instead of the target current as in this embodiment, the fault of the AC current sensor 150 can be determined with high accuracy.

[0090] According to the fourth embodiment of the present invention described above, when the target torque is less than the specified value (step S10B: No), the AC current sensor diagnostic unit 108 performs abnormality determination (step S30) of the AC current sensor 150 by the first diagnostic unit 1081, and when the target torque is greater than the specified value (step S10B: Yes), the AC current sensor 150 is abnormally determined by the second diagnostic unit 1082 (step S20). Thus, similarly to the first embodiment, when the voltage command value is calculated using the PI control, the abnormality of the AC current sensor 150 can be correctly detected regardless of the basic frequency of the AC current.

[0091] In addition, in the first to fourth embodiments described above, only one prescribed value of the basic frequency of the alternating current, the target current, and the target torque for switching the fault determination method of the alternating current sensor 150 is used respectively, but a plurality of such prescribed values ​​may be used. For example, in the case of using the first prescribed value and the second prescribed value (the first prescribed value < the second prescribed value), the ranges of the first diagnostic unit 1081 and the second diagnostic unit 1082 may be set and used together, so that if the values ​​of the basic frequency, the target current, and the target torque of the alternating current are less than the first prescribed value, only the abnormality determination of the first diagnostic unit 1081 is performed, and if the values ​​of the basic frequency, the target current, and the target torque of the alternating current are greater than the first prescribed value and less than the second prescribed value, the abnormality determination of the first diagnostic unit 1081 and the second diagnostic unit 1082 is performed together, and if the values ​​of the basic frequency, the target current, and the target torque of the alternating current are greater than the second prescribed value, only the abnormality determination of the second diagnostic unit 1082 is performed.

[0092] In the above-described embodiments, the AC current sensor 150 is provided for only two phases. However, the diagnosis method of the AC current sensor 150 of the present invention can also be applied to a configuration in which the AC current sensor 150 is provided for three phases.

[0093] In addition, the present invention is not limited to the above-mentioned embodiments, but also includes various modified examples. For example, the above-mentioned embodiments are detailed descriptions for the purpose of explaining the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to including all the structures described. In addition, a part of the structure of a certain embodiment can be replaced with the structure of other embodiments, and the structure of other embodiments can also be added to the structure of a certain embodiment. In addition, with respect to a part of the structure of each embodiment example, other structures can also be added, deleted, or replaced. In addition, the above-mentioned structures, functions, processing units, processing units, etc. can also be implemented in hardware by designing a part or all of them, such as by integrated circuits. In addition, the above-mentioned structures, functions, etc. can also be implemented in software by interpreting and executing programs that implement their respective functions through a processor. Information such as programs, tables, files, etc. that implement each function can be placed in a recording device such as a memory, a hard disk, an SSD (Solid State Drive: Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

[0094] In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made within a scope not departing from the gist of the present invention. Description of symbols

[0095] 1: drive device, 2: DC power supply, 3: electronic control device, 4: fault notification device, 10: power conversion device, 20: motor, 100: control circuit, 101: motor speed calculation unit, 102: 1-phase current calculation unit, 103: target current calculation unit, 104: voltage command calculation unit, 105: PWM signal generation unit, 106: voltage command 2-phase conversion unit, 107: current 2-phase conversion unit, 108: AC current sensor diagnosis unit, 120: drive circuit, 130: power conversion circuit, 140: voltage sensor, 150: AC current sensor, 1081: 1st diagnosis unit, 1082: 2nd diagnosis unit.

Claims

1. A power conversion device, which converts direct current into three-phase alternating current and outputs it, characterized in that: include: an AC current sensor that detects current values ​​of two phases among three-phase AC currents based on the three-phase AC power; a target current calculation unit that calculates a target current based on a target torque; a voltage command calculation unit that calculates a voltage command value based on the target current and a detection value of the AC current sensor; and an AC current sensor diagnostic unit for determining an abnormality of the AC current sensor based on a detection value of the AC current sensor, The AC current sensor diagnostic unit includes: a first diagnostic unit that determines the abnormality based on a two-phase voltage command value obtained by converting the voltage command value into a value of a two-phase orthogonal coordinate system based on any one output phase; and a second diagnostic unit that determines the abnormality based on two-phase current detection values ​​obtained by converting the detection values ​​of the AC current sensor into values ​​of the two-phase orthogonal coordinate system, The AC current sensor diagnosis unit switches between determination of the abnormality by the first diagnosis unit and determination of the abnormality by the second diagnosis unit according to an operating condition of the power conversion device.

2. The power conversion device according to claim 1, characterized in that: The AC current sensor diagnosis unit determines the abnormality by the first diagnosis unit when the fundamental frequency of the three-phase AC current is less than a predetermined value, and determines the abnormality by the second diagnosis unit when the fundamental frequency of the three-phase AC current is greater than or equal to the predetermined value.

3. The power conversion device according to claim 1, characterized in that: The AC current sensor diagnosis unit determines the abnormality by the first diagnosis unit when the target current is smaller than a predetermined value, and determines the abnormality by the second diagnosis unit when the target current is larger than the predetermined value.

4. The power conversion device according to claim 1, characterized in that: The AC current sensor diagnosis unit determines the abnormality by the first diagnosis unit when the target torque is smaller than a predetermined value, and determines the abnormality by the second diagnosis unit when the target torque is larger than the predetermined value.

5. The power conversion device according to claim 1, characterized in that: The first diagnostic unit determines that the AC current sensor is abnormal when the amount of change in the magnitude of the two-phase voltage command value is equal to or larger than a predetermined threshold value.

6. The power conversion device according to claim 1, characterized in that: The first diagnostic unit acquires a target value for the two-phase voltage command, and determines that the AC current sensor is abnormal when a difference between the target value and an actual two-phase voltage instruction value is equal to or larger than a predetermined threshold.

7. The power conversion device according to claim 1, characterized in that: The second diagnosis unit determines that the AC current sensor is abnormal when the amount of change in the magnitude of the two-phase current detection value is equal to or greater than a predetermined threshold value.

8. The power conversion device according to claim 1, characterized in that: The second diagnosis unit acquires a target value for the two-phase current detection value, and determines that the AC current sensor is abnormal when a difference between the target value and an actual two-phase current detection value is equal to or larger than a predetermined threshold value.

9. A driving device, characterized in that: include: A power conversion device as claimed in any one of claims 1 to 8; as well as an AC motor driven by a three-phase AC current output from the power conversion device, The vehicle is driven to travel using the driving force of the AC motor.

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