Power conversion device and method for estimating DC current in power conversion device

Abstract

A power conversion device according to the present invention comprises: a switching element of an upper arm and a switching element of a lower arm connected in series between a DC positive-side terminal and a DC negative-side terminal; an AC current detection unit that detects an AC current led out from a connection point between the switching element of the upper arm and the switching element of the lower arm; a switching element inter-terminal voltage detection unit and / or a mirror current detection unit that detects an inter-terminal voltage of any one of the switching elements of the upper arm and the lower arm, and that detects a mirror current flowing through a mirror element connected in parallel to each of the switching elements; and a direct current estimation unit that estimates a direct current flowing between the positive-side terminal and the negative-side terminal on the basis of the inter-terminal voltage and / or the mirror current and the alternating current.

Description

Technical Field

[0001] The present invention relates to a power conversion device and a method for estimating a direct current in the power conversion device. Background Art

[0002] The power conversion device controls the switching element to be turned on and off, converts the DC current provided by the DC power supply into AC current to drive the motor, and includes a DC current sensor to detect the DC current input to the power conversion device.

[0003] Patent document 1 discloses a current detection device, including: a power MOSFET, which is connected between an electric load and a power supply to control the current flowing through the electric load; a mirror MOSFET, which is connected in parallel with the power MOSFET to allow a portion of the current flowing through the power MOSFET to flow; a current detection resistor, which is connected between a source electrode of the power MOSFET and a source electrode of the mirror MOSFET; and a conversion unit, which converts the positive and negative direction voltages generated at both ends of the current detection resistor into a positive voltage or a negative voltage. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2004-201427 Summary of the invention Technical problem to be solved by the invention

[0005] The device described in Patent Document 1 does not take into account detection of direct current, and requires a direct current sensor. Technical means for solving technical problems

[0006] The power conversion device of the present invention includes: a switching element of an upper arm and a switching element of a lower arm connected in series between a positive terminal and a negative terminal of a direct current; an alternating current detection unit, which detects an alternating current derived from a connection point between the switching element of the upper arm and the switching element of the lower arm; a switching element terminal voltage detection unit and / or a mirror current detection unit, which detects a terminal voltage of any one of the switching elements of the upper arm and the lower arm, and detects a mirror current flowing through a mirror element connected in parallel with each of the switching elements; and a direct current estimation unit, which estimates a direct current flowing between the positive terminal and the negative terminal based on the terminal voltage and / or the mirror current and the alternating current. In the method for estimating a DC current in a power conversion device of the present invention, the power conversion device includes: a switching element of an upper arm and a switching element of a lower arm connected in series between a positive terminal and a negative terminal of a DC current; an AC current detection unit, which detects an AC current derived from a connection point between the switching element of the upper arm and the switching element of the lower arm; and at least one of a collector-emitter voltage detection unit between a collector and an emitter of the switching element, and / or a gate-emitter voltage detection unit between a gate and an emitter of the switching element, and / or a mirror current detection unit that detects a mirror current flowing through a mirror element connected in parallel to each of the switching elements, the DC current estimation method estimates the DC current flowing between the positive terminal and the negative terminal based on the conduction time of at least one of the collector-emitter voltage, the gate-emitter voltage, and the mirror current, and the AC current. Effects of the Invention

[0007] According to the present invention, a DC current sensor is not required, and the DC current can be estimated with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a circuit configuration diagram of a power conversion device according to an embodiment of the present invention. Figure 2 (A) (B) is a waveform diagram showing the Vce voltage and on-time of the power module of the upper arm. Figure 3 The waveform diagrams show the Vge voltage and on-time of the power module of the upper arm (A) and (B). Figure 4 It is a waveform diagram showing (A)(B)(C)(D) mirror current and conduction time. Figure 5 This is a detailed diagram of the DC current estimation unit. Figure 6 This is a table showing the relationship between the operation mode and the estimation of the DC current. Figure 7 This is a table showing the priority of operation terms of each phase. Figure 8 : is a flowchart showing the operation of the DC current estimation process in the DC current determination circuit. Fig. 9 This is a table showing the priority of mirror current calculation terms that cannot be used in a to h U phases, V phases, and W phases. Fig.10 (A) (B) (C) are diagrams showing waveforms of the U-phase, V-phase, and W-phase AC currents. DETAILED DESCRIPTION

[0009] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. The following description and drawings are examples for illustrating the present invention, and are appropriately omitted and simplified for clarity of the description. The present invention may also be implemented in various other ways. Unless otherwise specified, each structural element may be singular or plural.

[0010] In order to facilitate understanding of the present invention, the positions, sizes, shapes, ranges, etc. of the various structural elements shown in the drawings may not represent actual positions, sizes, shapes, ranges, etc. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, ranges, etc. disclosed in the drawings.

[0011] [Implementation Method] Figure 1 1 is a circuit configuration diagram of a power conversion device 100 according to an embodiment of the present invention. The power conversion device 100 converts a DC current supplied from a DC power source 200 into an AC current, and supplies the AC current to a winding of a motor (not shown) to drive the motor. The DC power source 200 is, for example, a chargeable and dischargeable battery.

[0012] Between the positive terminal 201 and the negative terminal 202 of the DC connected to the DC power supply 200, the power module 10 of the upper arm and the power module 11 of the lower arm are connected in series to form a conversion unit of one phase. Although the illustration is omitted, the conversion unit of the one phase is connected in parallel to form a three-phase three-phase bridge circuit, thereby forming a power conversion device 100. The AC current Ix is derived from the connection point 203 in the middle of the power module 10 of the upper arm and the power module 11 of the lower arm of each phase to the winding of the motor. The AC current Ix is a general term for the AC current Iu of the U phase, the AC current Iv of the V phase, and the AC current Iw of the W phase. A DC current Idc is provided from the DC power supply 200 to the power conversion device 100, but in this embodiment, the value of the DC current Idc is estimated without using a DC current sensor. The estimated DC current is called Idc_cal.

[0013] The power module 10 of the upper arm connects the switching element 10I and the diode 10D in reverse parallel, and includes a current mirror circuit 10C. The current mirror circuit 10C includes a mirror element, the collector of the mirror element is connected to the collector of the switching element 10I, the base of the mirror element is connected to the base of the switching element 10I, and the emitter of the mirror element is connected to the emitter of the switching element 10I through a mirror current detector 24. The switching element 10I is, for example, an IGBT. The current mirror circuit 10C is used for short-circuit detection of the switching element 10I. The mirror current is a mirror of the current flowing through the switching element 10I, and has a value of about 1 / 1000 to 1 / 10000 relative to the collector current. The power module 11 of the lower arm also has the same structure, connecting the switching element 11I and the diode 11D in reverse parallel, and includes a current mirror circuit 11C.

[0014] PWM signals are input from gate drive circuits 14 and 15 to the gates of switch elements 10I and 11I, respectively, and the switch elements 10I and 11I are controlled to be turned on / off by the PWM signals. The control device that generates the PWM signal is omitted in the figure, but the control device is composed of a microcomputer, etc., and generates a PWM signal in a normal PWM mode according to the torque instruction from the upper control device, referring to the speed of the motor, the AC current Ix, the DC current Idc_cal, etc. The control device specifies the action mode of each switch element 10I and 11I of the upper arm and the lower arm. Although the action mode will be described in detail later, there are PWM mode, single-sided three-phase short-circuit mode, three-phase open-circuit mode, etc. In addition, in addition to outputting the action mode, the control device also outputs the fault state and priority order described later. They are referred to as information S such as action mode.

[0015] A Vce (collector-emitter voltage) detector 16 is provided between the collector and the emitter of the switching element 10I of the upper arm to detect the Vce voltage. The detected Vce voltage is input to the Vce measurement circuit 17. The Vce measurement circuit 17 sets an appropriate threshold value in the rise and fall of the Vce voltage, and detects whether the Vce voltage changes by exceeding the threshold value, that is, the edge of the Vce voltage. Then, the interval between the rising and falling edges of the detected Vce voltage, that is, the on-time of the rectangular wave of the Vce voltage indicating the on / off of the switching element 10I is measured, and it is output to the DC current estimation unit 40 as the on-time of the upper arm based on the Vce voltage.

[0016] A Vce (collector-emitter voltage) detector 18 is provided between the collector and the emitter of the switching element 11I of the lower arm, and the Vce voltage is detected. The detected Vce voltage is input to the Vce measurement circuit 19. The Vce measurement circuit 19 sets an appropriate threshold value in the rise and fall of the Vce voltage, and detects whether the Vce voltage changes by exceeding the threshold value, that is, the edge of the Vce voltage. Then, the interval between the rising and falling edges of the detected Vce voltage, that is, the on-time of the rectangular wave of the Vce voltage indicating the on / off of the switching element 11I is measured, and it is output to the DC current estimation unit 40 as the on-time of the lower arm based on the Vce voltage.

[0017] A Vge (gate-emitter voltage) detector 20 is provided between the gate and the emitter of the switching element 10I of the upper arm to detect the Vge voltage. The detected Vge voltage is input to the Vge measurement circuit 21. The Vge measurement circuit 21 sets an appropriate threshold value in the rise and fall of the Vge voltage, and detects whether the Vge voltage changes by exceeding the threshold value, that is, the edge of the Vge voltage. Then, the on-time of the rectangular wave of the Vge voltage indicating the on / off of the switching element 10I based on the interval between the rising and falling edges of the detected Vge voltage is measured, and it is output to the DC current estimation unit 40 as the on-time of the upper arm based on the Vge voltage.

[0018] A Vge (gate-emitter voltage) detector 22 is provided between the gate and the emitter of the switching element 11I of the lower arm to detect the Vge voltage. The detected Vge voltage is input to the Vge measurement circuit 23. The Vge measurement circuit 23 sets an appropriate threshold value in the rise and fall of the Vge voltage, and detects whether the Vge voltage changes by exceeding the threshold value, that is, the edge of the Vge voltage. Then, the interval between the rising and falling edges of the detected Vge voltage, that is, the on-time of the rectangular wave of the Vge voltage indicating the on / off of the switching element 11I is measured, and it is output to the DC current estimation unit 40 as the on-time of the lower arm based on the Vge voltage.

[0019] The mirror current detector 24 of the upper arm is connected between the current mirror circuit 10C and the emitter of the switching element 10I, and detects the mirror current flowing through the mirror element. The detected mirror current is input to the mirror current measurement circuit 25. The mirror current measurement circuit 25 sets an appropriate threshold value in the rise and fall of the mirror current, and detects whether the mirror current changes by exceeding the threshold value, that is, the edge of the mirror current. Then, the interval between the rising edge and the falling edge of the detected mirror current, that is, the conduction time of the rectangular wave of the mirror current indicating the conduction / cutoff of the switching element 10I is measured, and it is output to the DC current estimation unit 40 as the conduction time of the upper arm based on the mirror current.

[0020] The mirror current detector 26 of the lower arm is connected between the current mirror circuit 11C and the emitter of the switching element 11I, and detects the mirror current flowing through the mirror element. The detected mirror current is input to the mirror current measurement circuit 27. The mirror current measurement circuit 27 sets an appropriate threshold value in the rise and fall of the mirror current, and detects whether the mirror current changes by exceeding the threshold value, that is, the edge of the mirror current. Then, the interval between the rising edge and the falling edge of the detected mirror current, that is, the conduction time of the rectangular wave of the mirror current indicating the conduction / cutoff of the switching element 11I is measured, and it is output to the DC current estimation unit 40 as the conduction time of the lower arm based on the mirror current.

[0021] As mentioned above, in Figure 1 , a conversion unit of one phase is shown in which the power module 10 of the upper arm and the power module 11 of the lower arm are connected in series. The conversion unit of one phase is provided with Vce detectors 16, 18, Vce measurement circuits 17, 19, Vge detectors 20, 22, Vge measurement circuits 21, 23, mirror current detectors 24, 26, and mirror current measurement circuits 25, 27. These circuits are provided similarly for the other two phases which are omitted from the illustration. Then, the conduction time obtained by each Vce measurement circuit 17, 19, Vge measurement circuit 21, 23, and mirror current measurement circuit 25, 27 is output to the DC current estimation unit 40. In addition, an AC current sensor 30 is provided in the wiring of each phase which is led from the connection point 203 between the power module 10 of the upper arm and the power module 11 of the lower arm of each phase to the winding of the motor. The AC current Ix of each phase detected by the AC current sensor 30 is output to the DC current estimation unit 40.

[0022] The DC current estimation unit 40 estimates the DC current based on the conduction time of each phase, the AC current Ix of each phase, the operation mode information S and the like input from the measurement circuits 17 , 19 , 21 , 23 , 25 , 27 , and outputs the estimated DC current Idc_cal.

[0023] Figure 2 (A) Figure 2 (B) is a waveform diagram showing the Vce voltage and the on-time of the power module 10 of the upper arm. Figure 2 (A) represents the Vce voltage of the power module 10 of the upper arm, Figure 2 (B) shows the conduction time of the power module 10 of the upper arm. Regarding the AC current, the direction of the AC current flowing into the motor is positive, and the reverse direction is negative. In each figure, the left side shows the case where the AC current is positive, and the right side shows the case where the AC current is negative. These waveform diagrams show the waveform of one phase. Figure 2 (A) is the detection waveform of the Vce detector 16, Figure 2 (B) is the on-time output from the Vce measurement circuit 17 .

[0024] like Figure 2 As shown in (A), the switch element 10I of the upper arm is turned on / off by the PWM signal. When the AC current is negative, the voltage Vf of the diode 10D is measured as the Vce voltage of the power module 10. The Vce measurement circuit 17 detects the edge of the Vce voltage that changes when it exceeds the thresholds Va and Vb during the rise and fall of the Vce voltage, and detects the on state of the switch element 10I. Since the detection is performed at the edge of the Vce voltage, it is not necessary to consider the gain accuracy of the physical quantity of the element compared to the case of using analog values. Then, when the AC current is positive, as shown in FIG. Figure 2 As shown in (B), the time when the switch element 10I is in the on state, that is, the time when the Vce voltage is 0V, is output as the on time of the upper arm based on the Vce voltage. When the AC current is negative, the time when the switch element 10I is in the on state, that is, the time when the voltage Vf of the diode 10D is 0V, is output as the on time of the upper arm based on the Vce voltage. Figure 2 In (B), the on-time of the upper arm when the AC current is positive is represented by “IGBT on-time”, and the on-time of the upper arm when the AC current is negative is represented by “diode on-time”.

[0025] Since the Vce detector 16 measures the voltage across the switching element 10I and the diode 10D connected in antiparallel, the Vce measurement circuit 17 can measure the on-time of the power module 10 of the upper arm independently of the direction of the AC current.

[0026] Figure 3 (A) Figure 3 (B) is a waveform diagram showing the Vge voltage and the on-time of the power module 10 of the upper arm. Figure 3 (A) represents the Vge voltage of the power module 10 of the upper arm, Figure 3 (B) shows the on-time of the power module 10 of the upper arm. In each figure, the left side shows the case where the AC current is positive, and the right side shows the case where the AC current is negative. These waveform diagrams show the waveform of one phase. Figure 3 (A) is the detection waveform of the Vce detector 20, Figure 3 (B) is the on-time output from the Vce measurement circuit 21 .

[0027] like Figure 3As shown in (A), regardless of the positive or negative of the AC current, the switch element 10I of the upper arm is turned on / off by the PWM signal. The Vge voltage is a driving voltage applied to the gate-emitter of the switch element 10I by the PWM signal. The Vge measurement circuit 21 detects the edge of the Vge voltage that changes when it exceeds the thresholds Vc and Vd during the rise and fall of the Vge voltage, and detects the on state of the switch element 10I. Since the detection is performed at the edge of the Vge voltage, there is no need to consider the gain accuracy of the physical quantity of the element compared to the case of using analog values. Then, as shown in Figure 3 As shown in (B), the time when the switching element 10I is in the on state, that is, the time when the Vge voltage is applied, is output as the on time of the upper arm based on the Vge voltage. Figure 3 In (B), the on-time of the upper arm when the AC current is positive is represented by “IGBT on-time”, and the on-time of the upper arm when the AC current is negative is represented by “diode on-time”.

[0028] Figure 4 (A) Figure 4 (B) Figure 4 (C) Figure 4 (D) is a waveform diagram showing the mirror current and the conduction time. Figure 4 (A) represents the mirror current of the switching element 10I of the upper arm, Figure 4 (B) represents the on-time of the switching element 10I of the upper arm, Figure 4 (C) represents the mirror current of the switching element 11I of the lower arm, Figure 4 (D) shows the on-time of the switching element 11I of the lower arm. In each figure, the left side shows the case where the AC current is positive, and the right side shows the case where the AC current is negative. These waveform diagrams show the waveform of one phase. Figure 4 (A) is the detection waveform of the mirror current detector 24, Figure 4 (B) is the on-time output from the mirror current measurement circuit 25 . Figure 4 (C) is the detection waveform of the mirror current detector 26, Figure 4 (D) is the conduction time output from the mirror current measurement circuit 27. The mirror current detectors 24 and 26 detect the mirror current of the switching elements 10I and 11I, and do not detect the current of the diodes 10D and 11D. However, when the AC current is negative, as shown in FIG. Figure 4 As shown in (B), the conduction time of the diode 10D of the upper arm can be estimated from the conduction time of the switching element 11I of the lower arm.

[0029] like Figure 4 As shown in (A), when the AC current is positive, when the switch element 10I of the upper arm is turned on / off by the PWM signal, the mirror current of the upper arm changes accordingly. Figure 4 As shown in (C), even if the switch element 11I of the lower arm is turned on / off, the mirror current of the lower arm does not change. In addition, when the AC current is negative, when the switch element 11I of the lower arm is turned on / off by the PWM signal, the mirror current of the lower arm changes accordingly. Figure 4 As shown in (A), even if the switch element 10I of the upper arm is turned on / off, the mirror current of the upper arm does not change. The mirror current measurement circuits 25 and 27 detect the edge of the mirror current that changes when it exceeds the thresholds Ia and Ib during the rise and fall of the mirror current, and detect the conduction state of the switch element 10I. Since the edge of the mirror current is detected, it is not necessary to consider the gain accuracy of the physical quantity of the element compared to the case of using analog values.

[0030] like Figure 4 (B) Figure 4 As shown in (D), the time when the switch elements 10I and 11I are in the on state, that is, the time when the mirror current flows, is output as the on time of the upper arm and the lower arm based on the mirror current. When calculating the on time of the upper arm, when the AC current is positive, the mirror current of the upper arm is used to measure the on time of the switch element 10I of the upper arm, and the on time of the upper arm is calculated based on the measured on time of the switch element 10I of the upper arm. When the AC current is negative, the mirror current of the lower arm is used to measure the on time of the switch element 11I of the lower arm, and the on time of the upper arm is estimated based on the measured on time of the switch element 11I of the lower arm. Figure 4 In (B), the on-time of the upper arm when the AC current is positive is represented by "IGBT on-time", and the on-time of the upper arm when the AC current is negative is represented by "diode on-time". When calculating the on-time of the lower arm, when the AC current is positive, the on-time of the switching element 10I of the upper arm is measured using the mirror current of the upper arm, and the on-time of the lower arm is estimated based on the measured on-time of the switching element 10I of the upper arm. When the AC current is negative, the on-time of the switching element 11I of the lower arm is measured using the mirror current of the lower arm, and the on-time of the lower arm is calculated based on the measured on-time of the switching element 11I of the lower arm. Although Figure 4 Although not described in, the conduction time of the lower arm when the AC current is positive is referred to as the "diode conduction time", and the conduction time of the lower arm when the AC current is negative is referred to as the "IGBT conduction time".

[0031] When the AC current is small, it is difficult for the DC current estimation unit 40 to set the threshold values ​​Ia and Ib. In the DC current estimation unit 40, a mirror current unusable range corresponding to the magnitude of the AC current is pre-set based on the characteristics of the switching elements 10I and 11I, and if the AC current is within the mirror current unusable range, the measurement result of the conduction time based on the mirror current is not used.

[0032] Since the mirror current is a mirror image of the collector current of the switching elements 10I and 11I, the current value fluctuates like an alternating current. For example, the threshold values ​​Ia and Ib are preferably set within the range of the following equations (1) and (2). Threshold Ia, Ib + α < | Upper limit of the range where mirror current cannot be used | * scale ratio... (1) Threshold Ia, Ib+α>|Lower limit of the range where mirror current cannot be used|*Scale ratio···(2) Here, α is a margin, the scale ratio is AC current / mirror current, and |the lower limit of the mirror current unusable range| is a smaller value.

[0033] Figure 5 It is a detailed diagram of the DC current estimating unit 40 . The DC current estimation unit 40 includes a Vce current estimation circuit 41, an M current estimation circuit 42, a Vge current estimation circuit 43, and a DC current determination circuit 44. The Vce current estimation circuit 41, the M current estimation circuit 42, and the Vge current estimation circuit 43 are respectively input with the on time of each phase and the AC current Ix of each phase.

[0034] Here, the estimated DC current Idc_cal is obtained by the following equation (3). Idc_cal=Du*Iu+Dv*Iv+Dw*Iw· · · (3) Du, Dv, and Dw are the duty ratios of the U phase, V phase, and W phase, and are calculated in the Vce current estimation circuit 41, the M current estimation circuit 42, and the Vge current estimation circuit 43 based on the on-time of each phase and the PWM period. Iu, Iv, and Iw are the AC currents of each phase. In estimating the DC current Idc_cal, it is sufficient to use either the current flowing into each phase or the current flowing out, so either the on-time of the upper arm or the on-time of the lower arm is used. Figure 1 Although the configuration for measuring both the on-time of the upper arm and the on-time of the lower arm is shown in FIG. 1 , a configuration for measuring either one of them may be used.

[0035] The Vce current estimation circuit 41 calculates the duty ratio Du_c, Dv_c, and Dv_c of each phase based on the conduction time of each phase from the Vce measurement circuits 17 and 19. The duty ratio of each phase is collectively referred to as Dx_c. The duty ratio Dx_c of each phase is calculated by Dx_c=conduction time / PWM period. Then, the operation terms of each phase shown in formula (3) are calculated. Specifically, the operation terms of each phase are calculated by various formulas of Du_c*Iu, Dv_c*Iv, and Dv_c*Iw. The operation terms of each phase are collectively referred to as Dx_c*Ix. The Vce current estimation circuit 41 outputs the operation terms Dx_c*Ix of each phase calculated as above.

[0036] The M current estimation circuit 42 calculates the duty ratio Du_m, Dv_m, and Dv_m of each phase based on the conduction time of each phase from the mirror current measurement circuits 25 and 27. The duty ratio of each phase is collectively referred to as Dx_m. When the AC current Ix>0A (0 ampere), the duty ratio Dx_m of each phase is calculated by Dx_m=(conduction time of the upper arm) / PWM period. When the AC current Ix<0A (0 ampere), it is calculated by Dx_m=(PWM period-(conduction time of the lower arm) / PWM period. Then, the operation terms of each phase shown in formula (3) are calculated. The operation terms of each phase are calculated by various formulas of Du_m*Iu, Dv_m*Iv, and Dv_m*Iw. The operation terms of each phase are collectively referred to as Dx_m*Ix. The M current estimation circuit 42 outputs the operation terms Dx_m*Ix of each phase calculated as above.

[0037] The Vge current estimation circuit 43 calculates the duty ratio Du_g, Dv_g, and Dv_g of each phase based on the conduction time of each phase from the Vce measurement circuits 17 and 19. The duty ratio of each phase is collectively referred to as Dx_g. The duty ratio Dx_g of each phase is calculated by Dx_g=conduction time / PWM period. Then, the operation terms of each phase shown in formula (3) are calculated. The operation terms of each phase are calculated by various formulas of Du_g*Iu, Dv_g*Iv, and Dv_g*Iw. The operation terms of each phase are collectively referred to as Dx_g*Ix. The Vge current estimation circuit 43 outputs the operation terms Dx_g*Ix of each phase calculated as above.

[0038] The operation terms Dx_c*Ix, Dx_m*Ix, and Dx_g*Ix are inputted from the Vce current estimation circuit 41, the M current estimation circuit 42, and the Vge current estimation circuit 43 to the DC current determination circuit 44, respectively. The DC current determination circuit 44 also inputs information S such as the operation mode from the control device (not shown). The DC current determination circuit 44 selects the operation terms Dx_c*Ix, Dx_m*Ix, and Dx_g*Ix based on the information S such as the operation mode, specifically, based on the operation mode, fault state, and priority described later, and calculates the DC current Idc_cal using the selected operation terms according to equation (3), and outputs the calculation result as the estimated DC current to the control device.

[0039] When calculating the DC current using the on-time of the lower arm, the direction of the AC current returning to the DC power supply 200 is positive, and the direction of the DC current flowing into the motor is positive, so it is multiplied by a negative sign for calculation.

[0040] When the DC current is estimated using the conduction time of the upper arm, when the AC current is positive, use Figure 2 (B) Figure 3 (B) Figure 4 The IGBT on-time represented in (B) is set to duty ratio Dx = (IGBT on-time) / PWM period, for example, calculated by equation (4). When the AC current is negative, use Figure 2 (B) Figure 3 (B) Figure 4 The diode conduction time shown in (B) is defined as duty ratio Dx=(diode conduction time) / PWM period. Idc_cal=Du*Iu+Dv*Iv+Dw*Iw··· (4)

[0041] When estimating the DC current using the on-time of the lower arm, when the AC current is positive, the duty ratio Dx=(diode on-time) / PWM period is calculated, for example, by equation (5). When the AC current is negative, the duty ratio Dx=(IGBT on-time) / PWM period is calculated. Idc_cal=Du*(-Iu)+Dv*(-Iv)+Dw*(-Iw)···(5)

[0042] Figure 6 This is a table showing the relationship between the operation mode and the estimation of the DC current. Figure 6Column 300 of the table shown indicates the operation mode, column 301 indicates the fault state, column 302 indicates the estimation of the DC current based on the Vce voltage, column 303 indicates the estimation of the DC current based on the Vge voltage, and column 304 indicates the estimation of the DC current based on the mirror current. In the table, a ○ mark is indicated when the estimation of the DC current is appropriate, and an × mark is indicated when it is inappropriate.

[0043] The operation modes include PWM mode, one-side three-phase short-circuit mode, three-phase open-circuit mode when the motor rotates at low speed, and three-phase open-circuit mode when the motor rotates at high speed.

[0044] The PWM mode is a mode in which the switching elements 10I and 11I of the upper arm and the lower arm are turned on / off according to the PWM signal to drive the motor. The single-side three-phase short-circuit mode is a mode in which all the three-phase switching elements 10I and 11I of the upper arm or the lower arm are short-circuited. The three-phase open-circuit mode is a mode in which all the three-phase switching elements 10I and 11I of the upper arm and the lower arm are open-circuited. For example, the single-side three-phase short-circuit mode or the three-phase open-circuit mode is specified in the vehicle standby state, the vehicle safety state when the vehicle fails, the vehicle towing, etc.

[0045] The PWM mode is a mode in which the switching elements 10I and 11I of the upper arm and the lower arm are turned on / off controlled according to the PWM signal generated by the torque command, so that the motor performs power operation or regeneration. In order to prevent the switching elements 10I and 11I of the upper arm and the lower arm from being short-circuited, a dead time is provided between the on time and the off time.

[0046] The single-side three-phase short-circuit mode turns on the switch elements 10I of all three phases of the upper arm. Alternatively, the switch elements 11I of all three phases of the lower arm are turned on. For example, the single-side three-phase short-circuit mode is intended to reduce the output torque in the vehicle safety state, but at low rotation, the output torque becomes high. Even in such a case, it is necessary to estimate the DC current.

[0047] The three-phase open circuit mode is a mode in which all the three-phase switching elements 10I and 11I of the upper arm and the lower arm are set to off. The three-phase open circuit mode is intended to reduce the output torque in the vehicle safety state, but the output torque becomes higher at high rotation. For example, when the motor is at low rotation, the DC current is about 0A, but when the motor is at high rotation, if the induced voltage is greater than the battery voltage of the DC power supply 200, the current flows to the battery side through the diodes 10D and 11D, which may damage the system. Even in such a case, it is necessary to estimate the DC current.

[0048] The fault state is divided into normal and 1-phase open circuit fault according to each operation mode. 1-phase open circuit fault is a situation where one phase of the three-phase switching elements 10I and 11I of the upper arm and the lower arm is fixed to the off state through fault diagnosis. Normal is a situation where no fault is detected through fault diagnosis.

[0049] Figure 6 The estimation of the DC current based on the Vce voltage shown in column 302 of the table shown is applicable to all operation modes and fault conditions. The estimation of the DC current based on the Vge voltage shown in column 303 is applicable to all operation modes under normal conditions without faults. The reason why the single-phase open circuit fault is excluded from the estimation of the DC current based on the Vge voltage is that it is based on the voltage as the command value input to the gate of the switching elements 10I and 11I, and therefore does not represent the true value when the switching elements 10I and 11I fail. The estimation of the DC current based on the mirror current shown in column 304 can be applied in the PWM mode and the single-sided three-phase short-circuit mode regardless of the presence or absence of a fault. Among them, the estimation of the DC current based on the mirror current is applicable to the case where the AC current is greater than the specified value.

[0050] Figure 7 This is a table showing the priority of operation terms of each phase. The Vce operation term Dx_c*Ix, i.e., the operation terms Du_c*Iu, Dv_c*Iv, and Dv_c*Iw of each phase, is output from the Vce current estimation circuit 41, and is given the highest priority. The mirror current operation term Dx_m*Ix, i.e., the operation terms Du_m*Iu, Dv_m*Iv, and Dv_m*Iw of each phase, is output from the M current estimation circuit 42, and is given the next priority. The Vge operation term Dx_g*Ix, i.e., the operation terms Du_g*Iu, Dv_g*Iv, and Dv_g*Iw of each phase, is output from the Vge current estimation circuit 43, and is given the lowest priority. In the following description, Figure 7 The case of the priority shown is described as an example, but the priority may be determined by other priorities according to the characteristics of the switching elements 10I, 11I, the diodes 10D, 11D, etc.

[0051] The DC current determining circuit 44 will Figure 7 The information shown in the table is stored in a storage unit (not shown). Then, the operation term is selected with reference to the priority or the input information S, and the selected operation term is applied to the equation (3) to calculate and estimate the DC current Idc_cal to be output finally.

[0052] Figure 8 2 is a flowchart showing the operation of the DC current estimation process in the DC current determination circuit 44 . In step S101, the DC current determination circuit 44 determines the operation mode based on the input information S. If it is the three-phase open mode, the process proceeds to step S102. If it is a mode other than the three-phase open mode, that is, the PWM mode or the one-side three-phase short-circuit mode, the process proceeds to step S103.

[0053] In step S102, the mirror current calculation term Dx_m*Ix of all phases is invalidated. This is because in the three-phase open circuit mode, there are only current paths of diodes 10D and 11D, and the M current estimation circuit 42 cannot measure the current flowing through diodes 10D and 11D. After the processing of step S102, the process proceeds to step S103.

[0054] In step S103, the magnitude of the AC current Ix is determined for each phase, that is, the AC current Iu of the U phase, the AC current Iv of the V phase, and the AC current Iw of the W phase. If the AC current Ix is within the range where the mirror current cannot be used in any phase, the process proceeds to step S104. If the AC current Ix is not within the range where the mirror current cannot be used in all phases, the process proceeds to step S105.

[0055] In step S104, the mirror current calculation term Dx_m*Ix of the phase in the mirror current unusable range is invalidated. After the processing of step S104, the process proceeds to step S105.

[0056] In step S105, the DC current determination circuit 44 determines the fault state of each phase based on the input information S. The fault state of the switching elements 10I and 11I is diagnosed by a fault diagnosis circuit (not shown) and input as the information S. When it is determined that there is a one-phase open-circuit fault in any phase of the switching elements 10I and 11I, the process proceeds to step S106. When it is determined that there is no one-phase open-circuit fault, the process proceeds to step S107.

[0057] In step S106, the Vge operation item Dx_g*Ix of the phase with a 1-phase open circuit fault is invalidated. Specifically, the operation items Du_g*Iu, Dv_g*Iv, or Dv_g*Iw of the corresponding phase with a 1-phase open circuit fault are invalidated. This is because in a 1-phase open circuit fault, the estimation of the DC current based on Vge does not represent the true value. After the processing of step S106, the process proceeds to step S110.

[0058] In step S107 , a Vce operation term Dx_c*Ix and a Vge operation term Dx_g*Ix are calculated for each phase, and their values ​​are compared, and the process proceeds to step S108 .

[0059] In step S108, if there is a large difference between the value of the Vce operation item Dx_c*Ix and the value of the Vge operation item Dx_g*Ix, it is detected as an abnormality of the Vce operation item. If there is an abnormality, proceed to step S109. If there is no abnormality, proceed to step S110. The reason is as follows. For example, in the case where it is determined in step S105 that there is no 1-phase open circuit fault, the switching elements 10I and 11I are normal, so the Vge operation item is basically correct. However, this is to prevent the Vce operation item from being erroneously selected when a circuit in the Vce current estimation circuit 41 fails.

[0060] In step S109 , the DC current estimation cannot be performed, an error value is output to the control device, and the DC current estimation process is terminated.

[0061] In step S110, for each phase, determine which of the three operation terms, namely, the Vce operation term Dx_c*Ix, the mirror current operation term Dx_m*Ix, and the Vge operation term Dx_g*Ix, is valid. If the three operation terms are valid, proceed to step S111. If the two operation terms are valid, proceed to step S114.

[0062] In step S111, the differences of the three operation terms are compared. For example, when the Vce operation term, mirror current operation term, and Vge operation term of each phase are 101A (ampere), 99A (ampere), and 150A (ampere), respectively, the following relationships of equations (6), (7), and (8) hold. |Vce operation term - mirror current operation term| = 2A < threshold value · · · (6) |Mirror current operation term - Vge operation term| = 51A ≥ threshold value · · · (7) |Vge operation term - Vce operation term| = 49A ≥ threshold value · · · (8) Here, the threshold is a threshold used for determination of the difference comparison. It can be seen from this that there is an abnormality in the Vge operation term. In this case, the Vge operation term is invalidated in the subsequent step S113.

[0063] After the processing of step S111, the process proceeds to step S112. In step S112, if the difference of the operation terms is greater than the specified value, the process proceeds to step S113 to invalidate the operation terms of the phase. After the processing of step S113, the process proceeds to step S116. In step S112, even if the difference of the operation terms is less than the specified value, the process proceeds to step S116.

[0064] In step S114, the remaining two are compared. Then, in the next step S115, the difference between the two operands is compared. If the difference is greater than a predetermined value, the process proceeds to step S109. If the difference is less than a predetermined value, the process proceeds to step S116.

[0065] In step S116, it is determined whether a valid operation term remains for each phase. If no valid operation term remains, the process proceeds to step S109. If a valid operation term remains, the process proceeds to step S117.

[0066] In step S117, the DC current determination circuit 44 selects a higher priority operation item from the remaining valid operation items for each phase, substitutes the selected operation item into equation (3) for calculation, and outputs it to the control device, thereby completing the DC current estimation process.

[0067] The DC current estimation process performed by the DC current determination circuit 44 is designed so that the calculation cycle of the estimation process is set within the PWM cycle, etc., to reduce the influence of the acquisition delay of the on-time.

[0068] The above-described DC current estimation process is divided into conditions and organized into conditions, and described below. Condition 1: Steps S101 to S102 In the three-phase open-circuit mode, the mirror current operation items of all phases are not used. Condition 2: Steps S103 to S104 When the AC current in each phase is small, the mirror current operation term is not used.

[0069] Condition 3: Steps S105 to S106 In each phase, when the switching elements 10I, 11I are in a fault state, the Vge operation term is not used.

[0070] Use a valid operation term that does not meet conditions 1 to 3 above. Condition 4: Steps S110 to S113 The Vce operation item, mirror current operation item, and Vge operation item of each phase are compared, and the operation item whose difference is greater than the specified value is not used. The three-way comparison is performed when the three are valid. Condition 5: Step S117

[0071] Among the valid operation items that do not meet the above conditions 1 to 4, the operation item with a higher priority is selected to estimate the final DC current. Condition 6: Steps S109 and S116 In the above conditions 1 to 4, when there is no selected operation item, an error value is output.

[0072] Condition 7: Steps S108 and S109 When the switching elements 10I and 11I are not in a faulty state, the Vce operation term is monitored, and in the case of an abnormality, the Vce operation term is not used.

[0073] In the above conditions 1 to 7, among the remaining operation items, the operation items with higher priority are selected for each phase to estimate the final output DC current Idc_cal. For example, in the U phase, the mirror current operation item Du_m*Iu has the highest priority, in the V phase, the Vce operation item Dv_c*Iv has the highest priority, and in the W phase, the Vce operation item Dw_c*Iw has the highest priority. These operation items are applied to formula (3) to calculate the DC current Idc_cal by the following formula (9). Idc_cal=Du_m*Iu+Dv_c*Iv+Dw_c*Iw···(9)

[0074] Next, taking the case of condition 2 (in each phase of steps S103 to S104, when the AC current is small, the mirror current operation term is not used) as an example, refer to Fig. 9 , Fig.10 Provide explanation.

[0075] Fig. 9 a~ Fig. 9 h is a table showing the priority of mirror current calculation terms that cannot be used in the U phase, the V phase, and the W phase. In the figure, the mirror current calculation terms that cannot be used are colored gray for illustration.

[0076] Fig. 9 a is a table showing the priority of the mirror current operation items that are not small and do not include unusable mirror current operation items. In this case, the mirror current operation items of the U phase, V phase, and W phase can be used, and the Figure 8 The three comparisons of the operation items described in step S111 are performed.

[0077] Fig. 9 b means that the AC current of phase W is small and the mirror current operation term of phase W cannot be used. Fig. 9 c means that the AC current of phase V is small, and the mirror current operation term of phase V cannot be used.

[0078] Fig. 9 d indicates that the AC current of phase V and phase W is small, and the mirror current operation items of phase V and phase W cannot be used. Fig. 9 e indicates that the AC current of phase U is small, and the mirror current operation term of phase U cannot be used.

[0079] Fig. 9f means that the AC current of phase U and phase W is small, and the mirror current operation items of phase U and phase W cannot be used. Fig. 9 g means that the AC current of phase U and phase V is small, and the mirror current operation items of phase U and phase V cannot be used. Fig. 9 h means that the AC current of phase U, phase V, and phase W is small, and the mirror current operation items of phase U, phase V, and phase W cannot be used. Fig. 9 b~ Fig. 9 In the state shown in f, no Figure 8 The three comparisons of the operation items described in step S111 are performed.

[0080] Fig.10 (A) Fig.10 (B) Fig.10 (C) is a diagram showing waveforms of the alternating currents of the U phase, the V phase, and the W phase. Fig.10 (A) shows an example of a case where the AC current is large. Fig.10 (B) shows an example of a medium AC current. Fig.10 (C) shows an example of a case where the AC current is small. In each figure, the mirror current unusable range MI and the AC current are shown. In addition, a solid line is shown dividing the range according to the waveform of the AC current of each phase with respect to the mirror current unusable range MI.

[0081] exist Fig.10 In (A), when the AC currents of all phases U, V, and W do not enter the mirror current unusable range MI, the Fig. 9 The DC current estimation process of the table shown in a. This section is indicated by a in the figure.

[0082] exist Fig.10 In (A), when the W-phase AC current enters the mirror current unusable range MI, the Fig. 9 b shows the DC current estimation process. Fig.10 (A) b indicates that in this interval, the mirror current operation term of the W phase is invalid.

[0083] exist Fig.10 In (A), when the V-phase AC current enters the mirror current unusable range MI, the Fig. 9 c. This section is indicated by c in the figure. In this section, the mirror current operation term of the V phase is invalid.

[0084] exist Fig.10 In (A), when the U-phase AC current enters the mirror current unusable range MI, the Fig. 9The DC current estimation process of the table shown in FIG. e. This section is indicated by e in the figure. In this section, the mirror current calculation term of the U phase is invalid.

[0085] exist Fig.10 In (B), when the AC current of the U phase and the W phase enters the mirror current unusable range MI, the Fig. 9 The DC current estimation process of the table shown in f is performed. This section is indicated by f in the figure. In this section, the mirror current calculation terms of the U phase and the W phase are invalid.

[0086] exist Fig.10 In (B), when the AC current of the V phase and the W phase enters the mirror current unusable range MI, the Fig. 9 d. This interval is indicated by d in the figure. In this interval, the mirror current calculation terms of the V phase and the W phase are invalid.

[0087] exist Fig.10 In (B), when the AC current of the U phase and the V phase enters the mirror current unusable range MI, the Fig. 9 g. This section is indicated by g in the figure. In this section, the mirror current calculation terms of the U phase and the V phase are invalid.

[0088] exist Fig.10 In (C), when the AC current of all phases of the U phase, V phase, and W phase enters the mirror current unusable range MI, the Fig. 9 h. In this case, the entire interval is indicated by h in the figure. In this case, the mirror current operation terms of the U phase, V phase, and W phase are invalid.

[0089] According to the first embodiment of the present invention, a DC current sensor is not required, and the DC current can be estimated with high accuracy. In the estimation of the DC current, the accuracy is improved by measuring the on-time based on the Vce voltage, the on-time based on the mirror current, and the on-time based on the Vge voltage at the edge of each waveform. Furthermore, by appropriately combining the estimation of the DC current based on the Vce voltage, the estimation of the DC current based on the mirror current, and the estimation of the DC current based on the Vge voltage, the usability and reliability can be improved.

[0090] [Structural Example 1] In the above-mentioned embodiment, three estimations of DC current based on Vce voltage, DC current based on mirror current, and DC current based on Vge voltage are used in combination, but at least one of the estimation of DC current based on Vce voltage and the estimation of DC current based on Vge voltage may also be used.

[0091] In this case, the configuration includes a switching element inter-terminal voltage detection unit that detects the inter-terminal voltage of each switching element of the upper arm and the lower arm, and a DC current estimation unit that estimates the DC current flowing between the positive terminal and the negative terminal based on the inter-terminal voltage detected by the switching element inter-terminal voltage detection unit and the AC current detected by the AC current detection unit (AC current sensor 30). The switching element inter-terminal voltage detection unit detects the Vce voltage or the Vge voltage of the switching element.

[0092] Specifically, the power conversion device 100 is Figure 1 The structure shown in the figure is a circuit structure in which the structures related to the estimation of the DC current based on the mirror current, such as the mirror current detectors 24 and 26 and the mirror current measurement circuits 25 and 27, are removed. Therefore, the circuit structure is a circuit structure including at least one of the estimation of the DC current based on the Vce voltage and the estimation of the DC current based on the Vge voltage. In this case, the following structure may be adopted: the Vce detectors 16 and 18, the Vce measurement circuits 17 and 19, the Vge detectors 20 and 22, and the Vge measurement circuits 21 and 23 may also be provided corresponding to the switching elements of either the upper arm or the lower arm, and either the conduction time of the upper arm or the conduction time of the lower arm may be measured.

[0093] The estimation of the DC current based on the Vce voltage can be applied in all operation modes and fault conditions. In addition, the estimation of the DC current based on the Vge voltage can be applied in all operation modes under normal conditions without faults. Therefore, according to the estimation of the DC current based on any of the above, and according to the estimation of the DC current based on the above combination, a DC current sensor is not required, and the DC current can be estimated with high accuracy. In the estimation of the DC current, the accuracy is improved by measuring the on-time based on the Vce voltage and the on-time based on the Vge voltage at the edges of each waveform. Furthermore, by appropriately combining the estimation of the DC current based on the Vce voltage and the estimation of the DC current based on the Vge voltage, the availability and reliability can be improved.

[0094] [Structural Example 2] In the above embodiment, three estimations of DC current based on Vce voltage, DC current based on mirror current, and DC current based on Vge voltage are used in combination. However, only DC current estimation based on mirror current may be used.

[0095] In this case, the structure includes: a mirror current detection unit, which detects a mirror current flowing through a mirror element connected in parallel with each switching element of the upper arm and the lower arm; and a DC current estimation unit, which estimates the DC current flowing between the positive side terminal and the negative side terminal based on the mirror current detected by the mirror current detection unit and the AC current detected by the AC current detection unit.

[0096] Specifically, the power conversion device 100 is Figure 1 The illustrated structure does not include the circuit structure related to the estimation of the DC current based on the Vce voltage or the Vge voltage, such as the Vce detectors 16 and 18, the Vce measurement circuits 17 and 19, the Vge detectors 20 and 22, and the Vge measurement circuits 21 and 23. Since the mirror current cannot measure the current flowing through the diodes 10D and 11D, the mirror current detector 24 and the mirror current measurement circuit 25 as well as the mirror current detector 26 and the mirror current measurement circuit 27 are provided in both the upper arm and the lower arm.

[0097] When the AC current is greater than the specified value, the DC current estimation based on the mirror current can be applied in the PWM mode and the single-side three-phase short-circuit mode regardless of whether there is a fault. Therefore, according to the DC current estimation, the DC current sensor is not required, and the DC current can be estimated with high accuracy. In the estimation of the DC current, the accuracy is improved by measuring the conduction time based on the mirror current at the edge of its waveform.

[0098] It is also possible to add the structure of Structural Example 2 to Structural Example 1. Specifically, it is also possible to add the structure required for estimating the DC current based on the mirror current to the structure required for estimating the DC current based on the Vce voltage. Alternatively, it is also possible to add the structure required for estimating the DC current based on the mirror current to the structure required for estimating the DC current based on the Vge voltage. By combining them for estimating the DC current, it is possible to improve availability and reliability.

[0099] In the above embodiment, referring to Figure 8 The flowchart of FIG. 4 illustrates the operation of the DC current estimation process in the DC current determination circuit 44. The operation of the DC current estimation process in the DC current determination circuit 44 may also be executed by a control device such as a microcomputer not shown in the figure. Then, Figure 8The flowchart shown illustrates the processing performed by the execution program, but since the program is executed by a processor (e.g., CPU, GPU), the specified processing is performed while appropriately using storage resources (e.g., memory) and / or interface devices (e.g., communication ports), and the subject of the processing can be the processor. Similarly, the subject of the execution program for processing can also be a controller, device, system, computer, or node with a processor. The subject of the processing performed by the execution program can be any computing unit, and can also include a dedicated circuit (e.g., FPGA, ASIC) that performs specific processing.

[0100] The program can be installed from a program source to a device such as a computer. The program source can be, for example, a program distribution server or a computer-readable storage medium. When the program source is a program distribution server, the program distribution server includes a storage resource for storing a processor and a distribution object program, and the processor of the program distribution server can also distribute the distribution object program to other computers. In addition, in the following description, two or more programs can be implemented as one program, and one program can also be implemented as two or more programs.

[0101] According to the above-described embodiment, the following effects can be obtained. (1) The power conversion device 100 includes: a switching element 10I of an upper arm and a switching element 11I of a lower arm connected in series between a positive terminal 201 and a negative terminal 202 of a DC current; an AC current detection unit (AC current sensor 30) that detects an AC current Ix derived from a connection point 203 between the switching element 10I of the upper arm and the switching element 11I of the lower arm; a switching element terminal voltage detection unit (Vce detectors 16, 18, Vce measurement circuits 17, 19, Vge detectors 20, 22, Vge measurement circuits 21, 23) and / or a mirror current detection unit (mirror current sensor 31). Current detectors 24, 26, mirror current measurement circuits 25, 27), the switching element terminal voltage detection unit detects the terminal voltage of any one of the switching elements 10I, 11I of the upper arm and the lower arm, the mirror current detection unit detects the mirror current flowing through the mirror element connected in parallel with each switching element 10I, 11I; and a DC current estimating unit 40, the DC current estimating unit 40 estimates the DC current Idc_cal flowing between the positive side terminal 201 and the negative side terminal 202 based on the terminal voltage (Vce voltage, Vge voltage) and / or the mirror current, and the AC current Ix. This eliminates the need for a DC current sensor and makes it possible to estimate the DC current with high accuracy.

[0102] (2) A method for estimating a DC current in a power conversion device 100 is to estimate a DC current Idc_cal flowing between a positive terminal 201 and a negative terminal 202 in the power conversion device 100 based on an on-time of at least one of a collector-emitter voltage, a gate-emitter voltage, and a mirror current and an AC current Ix, wherein the power conversion device 100 includes: a switching element 10I of an upper arm and a switching element 11I of a lower arm connected in series between the DC positive terminal 201 and the negative terminal 202; and an AC current detection unit (AC current sensor 30) for detecting a DC current flowing from the switching element 10I of the upper arm to the switching element 11I of the lower arm. The invention relates to an AC current Ix derived from the connection point 203 of the switching element 11I; and at least one of the collector-emitter voltage detection unit (Vce detectors 16, 18, Vce measurement circuits 17, 19) between the collector and emitter of the switching elements 10I, 11I, and / or the gate-emitter voltage detection unit (Vge detectors 20, 22, Vge measurement circuits 21, 23) between the gate and emitter of the switching elements 10I, 11I, and / or the mirror current detection unit (mirror current detectors 24, 26, mirror current measurement circuits 25, 27) for detecting the mirror current flowing in the mirror element connected in parallel to each switching element 10I, 11I. Thus, a DC current sensor is not required, and the DC current can be estimated with high accuracy.

[0103] The present invention is not limited to the above-mentioned embodiment, and other modes that can be considered within the technical concept of the present invention are also included in the scope of the present invention as long as the characteristics of the present invention are not impaired. In addition, a structure combining the above-mentioned embodiment and structure examples 1 and 2 is also possible. Description of symbols

[0104] 10…power module of the upper arm, 11…power module of the lower arm, 10I, 11I…switching element, 10D, 11D…diode, 10C, 11C…current mirror circuit, 16, 18…Vce detector, 17, 19…Vce measurement circuit, 20, 22…Vge detector, 21, 23…Vge measurement circuit, 24, 26…mirror current detector, 25, 27…mirror current measurement circuit, 30…AC current sensor, 40…DC current estimation unit, 41…Vce current estimation circuit, 42…M current estimation circuit, 43…Vge estimation circuit, 44…DC current determination circuit, 100…power conversion device, 200…DC power supply, 201…positive side terminal, 202…negative side terminal, 203…intermediate connection point.

Claims

1. A power conversion device, characterized in that: include: A switching element of an upper arm and a switching element of a lower arm, wherein the switching element of the upper arm and the switching element of the lower arm are connected in series between a positive terminal and a negative terminal of a direct current; an alternating current detection unit that detects an alternating current derived from a connection point between the switching element of the upper arm and the switching element of the lower arm; a switching element terminal voltage detection unit and / or a mirror current detection unit, wherein the switching element terminal voltage detection unit detects a terminal voltage of any one of the switching element of the upper arm and the switching element of the lower arm, and the mirror current detection unit detects a mirror current flowing through a mirror element connected in parallel with each of the switching elements; as well as A DC current estimating unit estimates a DC current flowing between the positive terminal and the negative terminal based on the inter-terminal voltage and / or the mirror current and the AC current.

2. The power conversion device according to claim 1, characterized in that: The switching element inter-terminal voltage detection unit detects a collector-emitter voltage between a collector and an emitter of the switching element.

3. The power conversion device according to claim 2, characterized in that: The DC current estimation unit measures the on-time of the switching element based on the collector-emitter voltage, and estimates the DC current based on the measured on-time and the AC current.

4. The power conversion device according to claim 1, characterized in that: The switching element inter-terminal voltage detection unit detects a gate-emitter voltage between a gate and an emitter of the switching element.

5. The power conversion device according to claim 4, characterized in that: The DC current estimating unit measures the on-time of the switching element based on the gate-emitter voltage, and estimates the DC current based on the measured on-time and the AC current when the switching element is not faulty.

6. The power conversion device according to claim 1, characterized in that: The DC current estimating unit measures the on-time of the switching element based on the mirror current, and estimates the DC current based on the measured on-time, the mirror current, and the AC current when the AC current is greater than a predetermined value.

7. The power conversion device according to claim 3 or claim 5 or claim 6, characterized in that: A three-phase converter is formed by connecting the switching element of the upper arm and the switching element of the lower arm in series in parallel. The DC current estimation unit estimates the DC current based on operation modes of the switching elements of the upper arm and the lower arm.

8. The power conversion device according to claim 7, characterized in that: The operation mode is a PWM mode for driving the motor by controlling the on / off of each switching element of the upper arm and the lower arm, a one-sided three-phase short-circuit mode for short-circuiting all the three-phase switching elements of the upper arm or the lower arm, and a three-phase open-circuit mode for opening all the three-phase switching elements of the upper arm and the lower arm.

9. The power conversion device according to claim 1, characterized in that: The switching element inter-terminal voltage detection unit detects a collector-emitter voltage between a collector and an emitter of the switching element and a gate-emitter voltage between a gate and an emitter of the switching element. The DC current estimation unit estimates a DC current flowing between the positive terminal and the negative terminal based on the AC current and at least one of the collector-emitter voltage, the gate-emitter voltage, and the mirror current.

10. The power conversion device according to claim 9, characterized in that: A three-phase converter is formed by connecting the switching element of the upper arm and the switching element of the lower arm in series in parallel. The DC current estimating unit does not perform estimation based on the mirror current in a three-phase open mode in which all three-phase switching elements of the upper arm and the lower arm are opened.

11. The power conversion device according to claim 9, characterized in that: The DC current estimation unit includes a priority order for giving priority to one of the estimation based on the collector-emitter voltage, the estimation based on the gate-emitter voltage, and the estimation based on the mirror current, and estimates the DC current according to the priority order.

12. The power conversion device according to claim 11, characterized in that: A three-phase converter is formed by connecting the switching element of the upper arm and the switching element of the lower arm in series in parallel. The priority order is set for each of the three phases.

13. The power conversion device according to claim 11 or 12, characterized in that: The estimation based on the collector-emitter voltage, the estimation based on the gate-emitter voltage, and the estimation based on the mirror current are performed in descending order of priority.

14. A method for estimating a direct current in a power conversion device, wherein the power conversion device comprises: A switching element of an upper arm and a switching element of a lower arm, wherein the switching element of the upper arm and the switching element of the lower arm are connected in series between a positive terminal and a negative terminal of a direct current; an alternating current detection unit that detects an alternating current derived from a connection point between the switching element of the upper arm and the switching element of the lower arm; and The DC current estimation method is characterized in that at least one of a collector-emitter voltage detection unit between the collector and emitter of the switching element, and / or a gate-emitter voltage detection unit between the gate and emitter of the switching element, and / or a mirror current detection unit that detects a mirror current flowing in a mirror element connected in parallel to each of the switching elements, A direct current flowing between the positive terminal and the negative terminal is estimated based on the on-time of at least one of the collector-emitter voltage, the gate-emitter voltage, and the mirror current, and the alternating current.

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