Power converter, and method for estimating DC current in a power converter.

Abstract

This power conversion device comprises: an upper arm switching element and a lower arm switching element that are connected in series between a DC positive side terminal and a DC negative side terminal; an AC current detection unit that detects the AC current derived from the connection point between the upper arm switching element and the lower arm switching element; a switching element inter-terminal voltage detection unit that detects the inter-terminal voltage of either the upper arm switching element or the lower arm switching element and / or a mirror current detection unit that detects the mirror current flowing through a mirror element connected in parallel with each of the switching elements; and a DC current estimation unit that estimates the DC 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 AC current.

Description

Technical Field

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[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 on / off of a switching element to convert a direct current supplied from a direct current power supply into an alternating current to drive a motor. The power conversion device includes a direct current sensor for detecting the direct current input to the power conversion device.

[0003] Patent Document 1 discloses a current detection device connected between an electrical load and a power supply, including a power MOSFET for controlling the current flowing through the electrical load, a mirror MOSFET connected in parallel with the power MOSFET through which a part of the current flowing through the power MOSFET flows, a current detection resistor connected between the source electrode of the power MOSFET and the source electrode of the mirror MOSFET, and conversion means for converting the positive and negative voltages generated at both ends of this current detection resistor into positive or negative voltages.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The device described in Patent Document 1 does not consider the detection of direct current, and a direct current sensor is required.

Means for Solving the Problems

[0006] A power conversion device according to a first aspect of the present invention comprises an upper arm switching element and a lower arm switching element connected in series between a positive terminal and a negative terminal of a DC power supply; an AC current detection unit for detecting an AC current derived from the connection point between the upper arm switching element and the lower arm switching element; a switch element terminal voltage detection unit for detecting the terminal voltage of either the upper arm or lower arm switching element; and a DC current estimation unit for estimating the DC current flowing between the positive terminal and the negative terminal based on the terminal voltage and the AC current, wherein the switch element terminal voltage detection unit detects the collector-emitter voltage, which is the voltage between the collector and emitter of the switching element. A power conversion device according to a second aspect of the present invention comprises an upper arm switching element and a lower arm switching element connected in series between a positive terminal and a negative terminal of a DC power supply; an AC current detection unit for detecting an AC current derived from the connection point between the upper arm switching element and the lower arm switching element; a mirror current detection unit for detecting a mirror current flowing through a mirror element connected in parallel to each of the switching elements; and a DC current estimation unit for estimating a DC current flowing between the positive terminal and the negative terminal based on the mirror current and the AC current. The DC current estimation unit measures the ON time of the switching element based on the mirror current, and if the AC current is greater than a predetermined value, it estimates the DC current based on the measured ON time, the mirror current, and the AC current. A power conversion device according to a third aspect of the present invention comprises an upper arm switching element and a lower arm switching element connected in series between the positive and negative terminals of a DC power supply; an AC current detection unit for detecting an AC current derived from the connection point between the upper arm switching element and the lower arm switching element; a switch element terminal voltage detection unit for detecting the terminal voltage of either the upper arm or lower arm switching element; a mirror current detection unit for detecting a mirror current flowing through a mirror element connected in parallel to each of the switching elements; and a power conversion device based on the terminal voltage, the mirror current, and the AC current. The device includes a DC current estimation unit that estimates the DC current flowing between the positive terminal and the negative terminal, the switch element terminal voltage detection unit detects the collector-emitter voltage, which is the voltage between the collector and emitter of the switching element, and / or the gate-emitter voltage, which is the voltage between the gate and emitter of the switching element, and the DC current estimation unit has a priority order for determining which of the estimations based on the collector-emitter voltage, the estimation based on the gate-emitter voltage, and the estimation based on the Miller current is to be prioritized, and estimates the DC current flowing between the positive terminal and the negative terminal according to the priority order. A method for estimating a DC current in a power conversion device according to a fourth aspect of the present invention comprises an upper arm switching element and a lower arm switching element connected in series between the positive and negative terminals of a DC power converter; an AC current detection unit for detecting an AC current derived from the connection point between the upper arm switching element and the lower arm switching element; and a switch element terminal voltage detection unit for detecting a collector-emitter voltage, which is the voltage between the collector and emitter of the switching element. In this method for estimating a DC current in a power conversion device, the DC current flowing between the positive and negative terminals is estimated based on the ON time of the switching element based on the collector-emitter voltage and the AC current. A method for estimating DC current in a power conversion device according to a fifth aspect of the present invention comprises an upper arm switching element and a lower arm switching element connected in series between the positive and negative terminals of a DC power supply, an AC current detection unit for detecting an AC current derived from the connection point between the upper arm switching element and the lower arm switching element, and a Miller current detection unit for detecting a Miller current flowing through a Miller element connected in parallel to each of the switching elements, wherein the method for estimating DC current in a power conversion device comprises: When the AC current is greater than a predetermined value, The ON time of the switching element based on the Miller current, The Miller current and, Based on the aforementioned alternating current, the direct current flowing between the positive terminal and the negative terminal is estimated. A method for estimating a DC current in a power conversion device according to a sixth aspect of the present invention comprises: an upper arm switching element and a lower arm switching element connected in series between the positive and negative terminals of a DC power converter; an AC current detection unit that detects an AC current derived from the connection point between the upper arm switching element and the lower arm switching element; a switch element terminal voltage detection unit that detects a collector-emitter voltage, which is the voltage between the collector and emitter of the switching element, and / or a gate-emitter voltage, which is the voltage between the gate and emitter of the switching element; and a Miller current detection unit that detects a Miller current flowing through a Miller element connected in parallel to each of the switching elements. In this method for estimating a DC current in a power conversion device, the priority order of which to prioritize—estimation based on the collector-emitter voltage, estimation based on the gate-emitter voltage, and estimation based on the Miller current—is stored in advance, and the DC current flowing between the positive terminal and the negative terminal is estimated according to the priority order. [Effects of the Invention]

[0007] According to the present invention, a DC current sensor is unnecessary, and it becomes possible to estimate the DC current with high accuracy. [Brief explanation of the drawing]

[0008] [Figure 1]This is a circuit diagram of a power conversion device according to an embodiment of the present invention. [Figure 2] (A)(B) These are waveform diagrams showing the Vce voltage and ON time of the power module on the upper arm. [Figure 3] (A)(B) These are waveform diagrams showing the Vge voltage and ON time of the power module on the upper arm. [Figure 4] (A)(B)(C)(D) These are waveform diagrams showing Miller current and ON time. [Figure 5] This is a detailed diagram of the DC current estimation unit. [Figure 6] This table shows the relationship between the operating mode and the estimated DC current. [Figure 7] This table shows the order of precedence for the operation terms in each phase. [Figure 8] This flowchart shows the operation of the DC current estimation process in the DC current determination circuit. [Figure 9] a~h This table shows the priority order for the U, V, and W phases, including Miller current calculation terms that cannot be used. [Figure 10] (A)(B)(C) These figures show the waveforms of the AC currents in the U, V, and W phases. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are illustrative for illustrating the present invention, and have been omitted and simplified as appropriate for clarity of explanation. The present invention can also be carried out in various other forms. Unless otherwise specified, each component may be singular or plural.

[0010] The positions, sizes, shapes, and ranges of the components shown in the drawings may not represent their actual positions, sizes, shapes, and ranges in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings.

[0011] [Embodiment] FIG. 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 direct current supplied from a direct current power source 200 into an alternating current, and supplies the alternating current to a motor winding (not shown) to drive the motor. The direct current power source 200 is, for example, a rechargeable battery.

[0012] Between the positive terminal 201 and the negative terminal 202 of the direct current power source 200, an upper-arm power module 10 and a lower-arm power module 11 are connected in series to constitute a conversion unit for one phase. Although not shown, the power conversion device 100 is constituted by a three-phase bridge circuit in which conversion units for one phase are connected in parallel to form three phases. An alternating current Ix is derived from a connection point 203 between the upper-arm power module 10 and the lower-arm power module 11 of each phase to the motor winding. The alternating current Ix is a generic term for the U-phase alternating current Iu, the V-phase alternating current Iv, and the W-phase alternating current Iw. Although a direct current Idc is supplied from the direct current power source 200 to the power conversion device 100, in this embodiment, the value of the direct current Idc is estimated without using a direct current sensor. The estimated direct current is referred to as Idc_cal.

[0013] The upper-arm power module 10 includes a switching element 10I and a diode 10D connected in antiparallel, and a current mirror circuit 10C. The current mirror circuit 10C includes a mirror element, and 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 via a mirror current detector 24. The switching element 10I is, for example, an IGBT. The current mirror circuit 10C is used for detecting a short circuit 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 with respect to the collector current. The lower-arm power module 11 has a similar configuration, and includes a switching element 11I and a diode 11D connected in antiparallel, and a current mirror circuit 11C.

[0014] A PWM signal is input to the gates of the switching element 10I and the switching element 11I from the gate drive circuits 14 and 15, respectively, and the switching element 10I and the switching element 11I are controlled to be ON / OFF by the PWM signal. Although the control device that generates the PWM signal is not shown, the control device is composed of a microcomputer or the like, and in accordance with a torque command from a higher-level control device, referring to the rotational speed of the motor, the alternating current Ix, the direct current Idc_cal, etc., generates a PWM signal in the normal PWM mode. The control device designates the operation modes of the switching elements 10I and 11I of the upper arm and the lower arm. Although the details will be described later, the operation modes include a PWM mode, a one-sided three-phase short-circuit mode, a three-phase open mode, etc. In addition to the operation mode, the control device outputs a failure state and a priority order to be described later. These are referred to as information S such as the operation 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, and the Vce voltage is detected. The detected Vce voltage is input to a Vce measurement circuit 17. Appropriate threshold values are set in the Vce measurement circuit 17 at the rising and falling edges of the Vce voltage, and it is detected whether the Vce voltage changes beyond the threshold value, that is, the edge of the Vce voltage. Then, the interval between the rising edge and the falling edge of the detected Vce voltage, that is, the ON time based on the rectangular wave of the Vce voltage indicating the ON / OFF of the switching element 10I is measured, and this is output to the direct 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 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 has appropriate thresholds set for the rising and falling edges of the Vce voltage, and detects whether the Vce voltage has changed beyond the threshold, i.e., the edge of the Vce voltage. The circuit then measures the interval between the rising and falling edges of the detected Vce voltage, i.e., the ON time based on the square wave of the Vce voltage indicating the ON / OFF state of the switching element 11I, and outputs this as the ON time of the lower arm based on the Vce voltage to the DC current estimation unit 40.

[0017] A Vge (gate-emitter voltage) detector 20 is provided between the gate and emitter of the switching element 10I in the upper arm, and the Vge voltage is detected. The detected Vge voltage is input to the Vge measurement circuit 21. The Vge measurement circuit 21 has appropriate thresholds set for the rising and falling edges of the Vge voltage, and detects whether the Vge voltage has changed beyond the threshold, i.e., the edge of the Vge voltage. The circuit then measures the interval between the rising and falling edges of the detected Vge voltage, i.e., the ON time based on the square wave of the Vge voltage indicating the ON / OFF state of the switching element 10I, and outputs this as the ON time of the upper arm based on the Vge voltage to the DC current estimation unit 40.

[0018] A Vge (gate-emitter voltage) detector 22 is provided between the gate and emitter of the switching element 11I in the lower arm, and the Vge voltage is detected. The detected Vge voltage is input to the Vge measurement circuit 23. The Vge measurement circuit 23 has appropriate thresholds set for the rising and falling edges of the Vge voltage, and detects whether the Vge voltage has changed beyond the threshold, i.e., the edge of the Vge voltage. The circuit then measures the interval between the rising and falling edges of the detected Vge voltage, i.e., the ON time based on the square wave of the Vge voltage indicating the ON / OFF state of the switching element 11I, and outputs this as the ON time of the lower arm based on the Vge voltage to the DC current estimation unit 40.

[0019] The upper arm's mirror current detector 24 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 has appropriate thresholds set for the rising and falling edges of the mirror current, and detects whether the mirror current has changed beyond the threshold, i.e., it detects the edge of the mirror current. Then, it measures the interval between the detected rising and falling edges of the mirror current, i.e., the ON time based on the rectangular wave of the mirror current indicating the ON / OFF state of the switching element 10I, and outputs this as the ON time of the upper arm based on the mirror current to the DC current estimation unit 40.

[0020] The lower arm's mirror current detector 26 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 has appropriate thresholds set for the rising and falling edges of the mirror current, and detects whether the mirror current has changed beyond the threshold, i.e., it detects the edge of the mirror current. Then, it measures the interval between the detected rising and falling edges of the mirror current, i.e., the ON time based on the rectangular wave of the mirror current indicating the ON / OFF state of the switching element 11I, and outputs this as the ON time of the lower arm based on the mirror current to the DC current estimation unit 40.

[0021] As already mentioned, Figure 1 illustrates a single-phase conversion unit in which the upper arm power module 10 and the lower arm power module 11 are connected in series. Vce detectors 16, 18, Vce measurement circuits 17, 19, Vge detectors 20, 22, Vge measurement circuits 21, 23, Miller current detectors 24, 26, and Miller current measurement circuits 25, 27 are provided for this single-phase conversion unit. These circuits are similarly provided for the other two phases, which are not shown. The ON times obtained from each Vce measurement circuit 17, 19, Vge measurement circuits 21, 23, and Miller current measurement circuits 25, 27 are output to the DC current estimation unit 40. In addition, AC current sensors 30 are provided on the wiring of each phase that is led from the connection point 203 between the upper arm power module 10 and the lower arm power module 11 to the motor windings. The AC current Ix of each phase detected by the AC current sensors 30 is output to the DC current estimation unit 40.

[0022] The DC current estimation unit 40 estimates the DC current based on information S such as the ON time of each phase, the AC current Ix of each phase, and the operating mode, which are input from each measurement circuit 17, 19, 21, 23, 25, and 27, and outputs the estimated DC current Idc_cal.

[0023] Figures 2(A) and 2(B) are waveform diagrams showing the Vce voltage and ON time of the upper arm power module 10. Figure 2(A) shows the Vce voltage of the upper arm power module 10, and Figure 2(B) shows the ON time of the upper arm power module 10. The AC current is considered positive when it flows into the motor and negative when it flows in the opposite direction. 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 one phase. Figure 2(A) is the waveform detected by the Vce detector 16, and Figure 2(B) is the ON time output from the Vce measurement circuit 17.

[0024] As shown in Figure 2(A), the switching element 10I of the upper arm is switched ON / OFF by a 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 edges of the Vce voltage that exceed the threshold values ​​Va and Vb during the rising and falling of the Vce voltage, and detects the ON state of the switching element 10I. Since detection is performed at the edges of the Vce voltage, it is not necessary to consider the gain accuracy of the physical quantity of the element compared to when analog values ​​are used. When the AC current is positive, as shown in Figure 2(B), the time when the switching element 10I is in the ON state, i.e., 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 switching element 10I is in the ON state, i.e., 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. In Figure 2(B), the ON time of the upper arm when the AC current is positive is represented as "IGBT ON time," and the ON time of the upper arm when the AC current is negative is represented as "Diode ON time."

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

[0026] Figures 3(A) and 3(B) are waveform diagrams showing the Vge voltage and ON time of the upper arm power module 10. Figure 3(A) shows the Vge voltage of the upper arm power module 10, and Figure 3(B) shows the ON time of the upper arm power module 10. In each figure, the left side shows the case when the AC current is positive, and the right side shows the case when the AC current is negative. These waveform diagrams show one phase. Figure 3(A) is the waveform detected by the Vge detector 20, and Figure 3(B) is the ON time output from the Vge measurement circuit 21.

[0027] As shown in Figure 3(A), the upper arm switching element 10I is switched ON / OFF by the PWM signal regardless of the positive or negative polarity of the AC current. The Vge voltage is the drive voltage applied between the gate and emitter of the switching element 10I by the PWM signal. The Vge measurement circuit 21 detects the edges of the Vge voltage that change beyond the thresholds Vc and Vd during the rising and falling of the Vge voltage, and detects the ON state of the switching element 10I. Since detection is performed at the edges of the Vge voltage, it is not necessary to consider the gain accuracy of the physical quantity of the element compared to when analog values ​​are used. Then, as shown in Figure 3(B), the time during which the switching element 10I is in the ON state, i.e., the time during which the Vge voltage is applied, is output as the ON time of the upper arm based on the Vge voltage. In Figure 3(B), the ON time of the upper arm when the AC current is positive is represented as "IGBT ON time", and the ON time of the upper arm when the AC current is negative is represented as "Diode ON time".

[0028] Figures 4(A), 4(B), 4(C), and 4(D) are waveform diagrams showing Miller current and ON time. Figure 4(A) shows the Miller current of the upper arm switching element 10I, Figure 4(B) shows the ON time of the upper arm switching element 10I, Figure 4(C) shows the Miller current of the lower arm switching element 11I, and Figure 4(D) shows the ON time of the lower arm switching element 11I. 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 one phase. Figure 4(A) is the detection waveform by the Miller current detector 24, and Figure 4(B) is the ON time output from the Miller current measurement circuit 25. Figure 4(C) is the detection waveform by the Miller current detector 26, and Figure 4(D) is the ON time output from the Miller current measurement circuit 27. Note that the Miller current detectors 24 and 26 detect the Miller current of the switching elements 10I and 11I, but do not detect the current of the diodes 10D and 11D. However, when the AC current is negative, as shown in Figure 4(B), it is possible to estimate the ON time of the diode 10D in the upper arm from the ON time of the switching element 11I in the lower arm.

[0029] As shown in Figure 4(A), when the AC current is positive, the Miller current of the upper arm changes accordingly when the switching element 10I of the upper arm is turned ON / OFF by the PWM signal. On the other hand, as shown in Figure 4(C), the Miller current of the lower arm does not change even when the switching element 11I of the lower arm is turned ON / OFF. Also, when the AC current is negative, the Miller current of the lower arm changes accordingly when the switching element 11I of the lower arm is turned ON / OFF by the PWM signal. On the other hand, as shown in Figure 4(A), the Miller current of the upper arm does not change even when the switching element 10I of the upper arm is turned ON / OFF. The Miller current measurement circuits 25 and 27 detect the edges of the Miller current that change beyond the thresholds Ia and Ib on the rising and falling edges of the Miller current, and detect the ON state of the switching element 10I. Since detection is performed at the edges of the Miller current, it is not necessary to consider the gain accuracy of the physical quantity of the element compared to when analog values ​​are used.

[0030] As shown in Figures 4(B) and 4(D), the time during which the switching elements 10I and 11I are in the ON state, i.e., when Miller current is flowing, is output as the ON time of the upper arm and lower arm, respectively, based on the Miller current. When calculating the ON time of the upper arm, if the AC current is positive, the ON time of the upper arm switching element 10I is measured using the Miller current of the upper arm, and the ON time of the upper arm is calculated from the measured ON time of the upper arm switching element 10I. If the AC current is negative, the ON time of the lower arm switching element 11I is measured using the Miller current of the lower arm, and the ON time of the upper arm is estimated from the measured ON time of the lower arm switching element 11I. In Figure 4(B), the ON time of the upper arm when the AC current is positive is shown as "IGBT ON time," and the ON time of the upper arm when the AC current is negative is shown as "Diode ON time." When calculating the ON time of the lower arm, if the AC current is positive, the ON time of the upper arm's switching element 10I is measured using the Miller current of the upper arm, and the ON time of the lower arm is estimated from the measured ON time of the upper arm's switching element 10I. If the AC current is negative, the ON time of the lower arm's switching element 11I is measured using the Miller current of the lower arm, and the ON time of the lower arm is calculated from the measured ON time of the lower arm's switching element 11I. Although not shown in Figure 4, the ON time of the lower arm when the AC current is positive is called the "Diode ON time," and the ON time of the lower arm when the AC current is negative is called the "IGBT ON time."

[0031] Furthermore, when the AC current is small, it is difficult for the DC current estimation unit 40 to set the thresholds Ia and Ib. The DC current estimation unit 40 has a pre-set range in which the Miller current cannot be used, corresponding to the magnitude of the AC current, according to the characteristics of the switching elements 10I and 11I. If the AC current is within this range in which the Miller current cannot be used, the measurement result of the ON time based on the Miller current is not used.

[0032] Furthermore, since the Miller current is a mirror of the collector currents of the switching elements 10I and 11I, the current value fluctuates like an AC current. For example, it is desirable to set the threshold values ​​Ia and Ib within the ranges given by equations (1) and (2) below. Threshold Ia, Ib + α < | Upper limit of Miller current unusable range | * Scale ratio ... (1) Threshold Ia, Ib + α > | Lower limit of Miller current unusable range | * Scale ratio ... (2) Here, α is the margin, the scale ratio is AC current / Miller current, and the lower limit of the Miller current unusable range is a small value.

[0033] Figure 5 is a detailed view of the DC current estimation 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 each inputted with the ON time of each phase, and further inputted with the AC current Ix of each phase.

[0034] Here, the estimated DC current Idc_cal can be obtained by the following equation (3). Idc_cal=Du*Iu+Dv*Iv+Dw*Iw···(3) Du, Dv, and Dw are the duty cycles of the U, V, and W phases, respectively, and are calculated in the Vce current estimation circuit 41, M current estimation circuit 42, and Vge current estimation circuit 43 based on the ON time and PWM period of each phase. Iu, Iv, and Iw are the AC currents of each phase. For the estimation of the DC current Idc_cal, estimation can be performed using either the current flowing into or out of each phase, so either the ON time of the upper arm or the ON time of the lower arm is used. Figure 1 shows a configuration in which both the ON time of the upper arm and the ON time of the lower arm are measured, but a configuration in which only one of them is measured is also acceptable.

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

[0036] The M current estimation circuit 42 calculates the duty cycles Du_m, Dv_m, and Dv_m for each phase based on the ON time of each phase from the Miller current measurement circuits 25 and 27. The duty cycles of each phase are collectively referred to as Dx_m. The duty cycle Dx_m for each phase is calculated as follows: When the AC current Ix > 0A (0 amperes), Dx_m = (ON time of the upper arm) / PWM period. When the AC current Ix < 0A (0 amperes), Dx_m = (PWM period - (ON time of the lower arm)) / PWM period. Then, the calculation terms for each phase shown in equation (3) are calculated. The calculation terms for each phase are calculated by the following equations: Du_m*Iu, Dv_m*Iv, and Dv_m*Iw. The calculation terms for each phase are collectively referred to as Dx_m*Ix. The M current estimation circuit 42 outputs the calculation terms Dx_m*Ix for each phase calculated as described above.

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

[0038] The DC current determination circuit 44 receives the calculation terms Dx_c*Ix, Dx_m*Ix, and Dx_g*Ix from the Vce current estimation circuit 41, M current estimation circuit 42, and Vge current estimation circuit 43, respectively. The DC current determination circuit 44 also receives information S, such as the operating mode, from a control device (not shown in the diagram). The DC current determination circuit 44 selects the calculation terms Dx_c*Ix, Dx_m*Ix, and Dx_g*Ix according to the information S, specifically the operating mode, fault condition, and priority described later, and uses the selected calculation terms to calculate the DC current Idc_cal based on equation (3). This calculation result is then output to the control device as the estimated DC current.

[0039] Note that for DC and AC currents, the direction in which they flow into the motor is considered positive. When calculating the DC current using the ON time of the lower arm, the direction in which the AC current returns to the DC power supply 200 is considered positive. Therefore, since the direction in which the DC current flows into the motor is considered positive, a negative multiplier is applied to the calculation.

[0040] When estimating the DC current using the ON time of the upper arm, if the AC current is positive, the duty cycle Dx is calculated using the IGBT ON times shown in Figures 2(B), 3(B), and 4(B), respectively, as follows: duty cycle Dx = (IGBT ON time) / PWM period, for example, by equation (4). If the AC current is negative, the duty cycle Dx is calculated using the diode ON times shown in Figures 2(B), 3(B), and 4(B), respectively, as follows: duty cycle Dx = (Diode ON 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, if the AC current is positive, the duty cycle Dx is calculated as (Diode ON time) / PWM period, for example, using equation (5). If the AC current is negative, the duty cycle Dx is calculated as (IGBT ON time) / PWM period. Idc_cal=Du*(-Iu)+Dv*(-Iv)+Dw*(-Iw)...(5)

[0042] Figure 6 is a table showing the relationship between the operating mode and the estimated DC current. In the table shown in Figure 6, column 300 shows the operating mode, column 301 shows the fault condition, column 302 shows the DC current estimation based on the Vce voltage, column 303 shows the DC current estimation based on the Vge voltage, and column 304 shows the DC current estimation based on the Miller current. In this table, a circle (○) indicates that the DC current estimation is appropriate, and a cross (×) indicates that it is not appropriate.

[0043] The operating modes include PWM mode, one-sided 3-phase short-circuit mode, 3-phase open-circuit mode for low motor speeds, and 3-phase open-circuit mode for high motor speeds.

[0044] The PWM mode is a mode in which the motor is driven by controlling the ON / OFF state of the switching elements 10I and 11I of the upper and lower arms based on a PWM signal. The one-sided three-phase short-circuit mode is a mode in which all three phase switching elements 10I and 11I of the upper or lower arm are short-circuited. The three-phase open-circuit mode is a mode in which all three phase switching elements 10I and 11I of the upper and lower arms are open. For example, the one-sided three-phase short-circuit mode or the three-phase open-circuit mode is specified in vehicle standby mode, vehicle safety mode in the event of a vehicle failure, vehicle towing, etc.

[0045] The PWM mode is a mode in which the motor is driven or regenerated by controlling the ON / OFF state of the switching elements 10I and 11I of the upper and lower arms using a PWM signal generated in response to a torque command. A dead time is provided between the ON and ON periods of the switching elements 10I and 11I of the upper and lower arms to prevent short circuits.

[0046] The one-sided three-phase short-circuit mode turns on all three switching elements 10I on the upper arm, or on all three switching elements 11I on the lower arm. For example, in the one-sided three-phase short-circuit mode, it is desirable to reduce the output torque when the vehicle is in a safe state, but the output torque is high at low rotational speeds. In such cases, it is also necessary to estimate the DC current.

[0047] In the 3-phase open mode, all three phases of the switching elements 10I and 11I on the upper and lower arms are turned OFF. In the 3-phase open mode, the goal is to reduce output torque in a safe vehicle state, but the output torque becomes high at high rotational speeds. For example, at low motor speeds, the DC current is about 0A, but at high motor speeds, if the induced voltage becomes greater than the battery voltage of the DC power supply 200, current will flow to the battery side through diodes 10D and 11D, potentially damaging the system. In such cases, it is necessary to estimate the DC current.

[0048] Fault conditions are divided into normal and single-phase open fault for each operating mode. A single-phase open fault occurs when fault diagnosis detects that one of the three switching elements 10I and 11I of the upper and lower arms remains fixed in the OFF state. Normal operation occurs when no fault is detected during fault diagnosis.

[0049] The estimation of DC current using the Vce voltage shown in column 302 of the table in Figure 6 is applicable to all operating modes and fault conditions. The estimation of DC current using the Vge voltage shown in column 303 is applicable to all operating modes in normal conditions without faults. The reason why the estimation of DC current using the Vge voltage excludes single-phase open faults is that it is based on the voltage as a command value input to the gates of switching elements 10I and 11I, and therefore will not show the true value if switching elements 10I and 11I are faulty. The estimation of DC current using Miller current shown in column 304 is applicable to PWM mode and one-sided three-phase short-circuit mode, regardless of whether there is a fault or not. However, the estimation of DC current using Miller current is applicable when the AC current is greater than a predetermined value.

[0050] Figure 7 is a table showing the order of precedence of the operation terms in each phase. The Vce current estimation circuit 41 outputs the Vce calculation term Dx_c*Ix, i.e., the calculation terms Du_c*Iu, Dv_c*Iv, and Dv_c*Iw for each phase, and this is given the highest priority. The M current estimation circuit 42 outputs the Miller current calculation term Dx_m*Ix, i.e., the calculation terms Du_m*Iu, Dv_m*Iv, and Dv_m*Iw for each phase, and this is given the next highest priority. The Vge current estimation circuit 43 outputs the Vge calculation term Dx_g*Ix, i.e., the calculation terms Du_g*Iu, Dv_g*Iv, and Dv_g*Iw for each phase, and this is given the lowest priority. In the following explanation, the priority order shown in Figure 7 will be used as an example, but other priorities may be determined depending on the characteristics of the switching elements 10I, 11I and diodes 10D, 11D, etc.

[0051] The DC current determination circuit 44 stores the information shown in the table in Figure 7 in a memory unit (not shown). It then selects a calculation term based on this priority order and the input information S, applies the selected calculation term to equation (3), and finally estimates the DC current Idc_cal to be output.

[0052] Figure 8 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 operating mode based on the input information S. If it is the 3-phase open mode, it proceeds to step S102. If it is a mode other than the 3-phase open mode, i.e., the PWM mode or the one-sided 3-phase short mode, it proceeds to step S103.

[0053] In step S102, the Miller current calculation term Dx_m*Ix for all phases is disabled. This is because in the 3-phase open mode, there are only current paths through diodes 10D and 11D, and the M current estimation circuit 42 cannot measure the current flowing through diodes 10D and 11D. After processing in step S102, the process proceeds to step S103.

[0054] In step S103, the magnitude of the alternating current Ix for each phase, i.e., the alternating current Iu for the U phase, the alternating current Iv for the V phase, and the alternating current Iw for the W phase, is determined. If the alternating current Ix in any phase is within the range where Miller current is unusable, the process proceeds to step S104. If the alternating current Ix in all phases is not within the range where Miller current is unusable, the process proceeds to step S105.

[0055] In step S104, the Miller current calculation term Dx_m*Ix for phases that are within the Miller current unusable range is disabled. After processing in step S104, the process proceeds to step S105.

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

[0057] In step S106, the Vge calculation term Dx_g*Ix for the phase with the one-phase open fault is disabled. Specifically, the calculation term Du_g*Iu, Dv_g*Iv, or Dv_g*Iw for the phase with the one-phase open fault is disabled. This is because the estimation of the DC current using Vge does not show the true value in the case of a one-phase open fault. After processing in step S106, the process proceeds to step S110.

[0058] In step S107, the Vce operation term Dx_c*Ix and the Vge operation term Dx_g*Ix are calculated for each phase, 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 calculation term Dx_c*Ix and the value of the Vge calculation term Dx_g*Ix, an abnormality in the Vce calculation term is detected. If an abnormality is found, the process proceeds to step S109. If there is no abnormality, the process proceeds to step S110. This is for the following reason: For example, if the determination in step S105 is that there is no single-phase open fault, then the switching elements 10I and 11I are normal, and the Vge calculation term is basically correct. However, this is to prevent the Vce calculation term from being incorrectly selected if there is a fault in the circuit within the Vce current estimation circuit 41.

[0060] In step S109, the DC current estimation is deemed impossible, an error value is output to the control device, and the DC current estimation process is terminated.

[0061] In step S110, for each phase, the valid calculation term is determined from among the three calculation terms: the Vce calculation term Dx_c*Ix, the Miller current calculation term Dx_m*Ix, and the Vge calculation term Dx_g*Ix. If all three calculation terms are valid, proceed to step S111. If only two calculation terms are valid, proceed to step S114.

[0062] In step S111, the differences between the three calculation terms are compared. For example, if the Vce calculation term, Miller current calculation term, and Vge calculation term for each phase are 101A (amperes), 99A (amperes), and 150A (amperes), respectively, then the following relationships (6), (7), and (8) hold. |Vce calculation term - Miller current calculation term| = 2A < threshold ... (6) |Miller current calculation term - Vge calculation term| = 51A ≥ threshold ... (7) |Vge operation term - Vce operation term| = 49A ≥ threshold ... (8) Here, the threshold is the threshold for determining the difference comparison. From this, it can be seen that there is an anomaly in the Vge calculation term. In this case, the Vge calculation term is disabled in the later step S113.

[0063] After processing in step S111, proceed to step S112. In step S112, if the difference of the arithmetic terms is greater than or equal to a specified value, proceed to step S113 and invalidate the arithmetic term of the corresponding phase. After processing in step S113, proceed to step S116. In step S112, if the difference of the arithmetic terms is less than a specified value, proceed to step S116.

[0064] In step S114, the remaining two terms are compared. Then, in the next step S115, the difference between the two operation terms is compared. If the difference is greater than or equal to a specified value, proceed to step S109. If the difference is less than a specified value, proceed to step S116.

[0065] In step S116, it is determined whether there are any valid operation terms remaining for each phase. If there are no valid operation terms remaining, proceed to step S109. If there are valid operation terms remaining, proceed to step S117.

[0066] In step S117, the DC current determination circuit 44 selects the highest priority calculation term from the remaining valid calculation terms for each phase, applies the selected calculation terms to equation (3) to calculate the DC current, and outputs this to the control device to complete the DC current estimation process.

[0067] Furthermore, the DC current estimation process by the DC current determination circuit 44 is designed to minimize the impact of delays in acquiring the ON time, such as by setting the calculation period of the estimation process within the PWM period.

[0068] The above DC current estimation process is organized by condition and explained below. Condition 1: Steps S101~S102 In the 3-phase open mode, the Miller current calculation term for all phases is not used. Condition 2: Steps S103~S104 When the alternating current is small in each phase, the Miller current calculation term is not used.

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

[0070] Use a valid operation term that does not fall under conditions 1 to 3 above. Condition 4: Steps S110~S113 The Vce calculation term, Miller current calculation term, and Vge calculation term for each phase are compared, and any calculation term whose difference exceeds a specified value is not used. The three-way comparison is performed when all three methods are valid. Condition 5: Step S117

[0071] From the valid calculation terms that do not fall under conditions 1 to 4 above, select the calculation term with the highest priority to estimate the final DC current. Condition 6: Steps S109, S116 If no operation term is selected based on conditions 1 through 4 above, an error value will be output.

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

[0073] Based on the above conditions 1 to 7, the highest priority calculation term is selected for each phase from the remaining calculation terms to estimate the final output DC current Idc_cal. For example, if the Miller current calculation term Du_m*Iu has the highest priority in the U phase, the Vce calculation term Dv_c*Iv has the highest priority in the V phase, and the Vce calculation term Dw_c*Iw has the highest priority in the W phase, then these calculation terms are applied to equation (3) and the DC current Idc_cal is calculated using the following equation (9). Idc_cal=Du_m*Iu+Dv_c*Iv+Dw_c*Iw...(9)

[0074] Next, we will explain the case of condition 2 (when the alternating current is small in each phase of steps S103 to S104, the Miller current calculation term is not used) using Figures 9 and 10 as an example.

[0075] Figures 9a to 9h are tables showing the priority order of Miller current calculation terms, including those that cannot be used, for the U, V, and W phases. In the figures, the Miller current calculation terms that cannot be used are shown in gray.

[0076] Figure 9a is a table showing the priority order for calculations where the AC current is not small and no unusable Miller current calculation terms are included. In this case, it is possible to use the Miller current calculation terms for the U, V, and W phases, and the three-way comparison of calculation terms explained in step S111 of Figure 8 is possible.

[0077] Figure 9b shows that the AC current in the W phase is small, making the Miller current calculation term for the W phase unusable. Figure 9c shows that the AC current in the V phase is small, making the Miller current calculation term for the V phase unusable.

[0078] Figure 9d shows that the AC currents in the V and W phases are small, making the Miller current calculation terms for the V and W phases unusable. Figure 9e shows that the AC current in the U phase is small, making the Miller current calculation term for the U phase unusable.

[0079] Figure 9f shows that the AC currents in the U and W phases are small, and the Miller current calculation terms for the U and W phases cannot be used. Figure 9g shows that the AC currents in the U and V phases are small, and the Miller current calculation terms for the U and V phases cannot be used. Figure 9h shows that the AC currents in the U, V, and W phases are small, and the Miller current calculation terms for the U, V, and W phases cannot be used. In the conditions shown in Figures 9b to 9f, the tripartite comparison of calculation terms explained in step S111 of Figure 8 is not performed.

[0080] Figures 10(A), 10(B), and 10(C) show the waveforms of the alternating currents of the U, V, and W phases. Figure 10(A) shows an example where the alternating current is large, Figure 10(B) shows an example where the alternating current is moderate, and Figure 10(C) shows an example where the alternating current is small. In each figure, the Miller current unusable range MI and the alternating current are shown. Solid lines are shown to delineate the intervals where the alternating current waveform of each phase falls within the Miller current unusable range MI.

[0081] In Figure 10(A), if the AC currents of all phases (U, V, and W) do not fall within the Miller current unusable range (MI), the DC current estimation process is performed based on the table shown in Figure 9a. This interval is indicated by 'a' in the figure.

[0082] In Figure 10(A), if the AC current of the W phase falls within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9b. This section is indicated by b in Figure 10(A). In this section, the Miller current calculation term for the W phase is disabled.

[0083] In Figure 10(A), if the AC current of the V phase falls within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9c. This interval is indicated by c in the figure. In this interval, the Miller current calculation term for the V phase is disabled.

[0084] In Figure 10(A), if the AC current of the U phase falls within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9e. This interval is indicated by e in the figure. In this interval, the Miller current calculation term for the U phase is disabled.

[0085] In Figure 10(B), if the AC currents of the U-phase and W-phase fall within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9f. This interval is indicated by f in the figure. In this interval, the Miller current calculation terms for the U-phase and W-phase are disabled.

[0086] In Figure 10(B), if the AC currents of the V-phase and W-phase fall within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9d. This interval is indicated by 'd' in the figure. In this interval, the Miller current calculation terms for the V-phase and W-phase are disabled.

[0087] In Figure 10(B), if the AC currents of the U-phase and V-phase fall within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9g. This interval is indicated by g in the figure. In this interval, the Miller current calculation terms for the U-phase and V-phase are disabled.

[0088] In Figure 10(C), if all AC currents in the U, V, and W phases fall within the Miller current disabling range MI, the DC current estimation process is performed based on the table shown in Figure 9h. This applies to the entire range, indicated by h in the figure. In this case, the Miller current calculation terms for the U, V, and W phases are disabled.

[0089] According to the first embodiment of the present invention, a DC current sensor is not required, and it becomes possible to estimate the DC current with high accuracy. In estimating the DC current, the accuracy is improved by measuring the ON time based on Vce voltage, the ON time based on Miller current, and the ON time based on Vge voltage at the edges of each waveform. Furthermore, by appropriately combining the estimation of DC current using Vce voltage, estimation of DC current using Miller current, and estimation of DC current using Vge voltage, availability and reliability can be improved.

[0090] [Configuration Example 1] In the embodiment described above, a combination of three methods was used: estimating the DC current using the Vce voltage, estimating the DC current using the Miller current, and estimating the DC current using the Vge voltage. However, it is also possible to use at least one of the methods: estimating the DC current using the Vce voltage and estimating the DC current using the Vge voltage.

[0091] In this case, the configuration includes a switch element terminal voltage detection unit that detects the 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 terminal voltage detected by the switch element terminal voltage detection unit and the AC current detected by the AC current detection unit (AC current sensor 30). The switch element terminal voltage detection unit detects the Vce voltage or Vge voltage of the switching element.

[0092] Specifically, the power converter 100 has a circuit configuration that is the same as the configuration shown in Figure 1, but with the components related to estimating DC current by Miller current, such as Miller current detectors 24 and 26 and Miller current measurement circuits 25 and 27, removed. It is a circuit configuration that includes at least one of the following: estimation of DC current by Vce voltage and estimation of DC current by Vge voltage. In this case, the Vce detectors 16 and 18, Vce measurement circuits 17 and 19, Vge detectors 20 and 22, and Vge measurement circuits 21 and 23 may be provided corresponding to the switching elements of either the upper arm or the lower arm, and may be configured to measure either the ON time of the upper arm or the ON time of the lower arm.

[0093] Estimating DC current using Vce voltage is applicable to all operating modes and fault conditions. Similarly, estimating DC current using Vge voltage is applicable to all operating modes under normal, fault-free conditions. Therefore, estimating DC current using either of these methods, or a combination thereof, eliminates the need for a DC current sensor and allows for accurate DC current estimation. Accuracy in DC current estimation is improved by measuring the ON time based on Vce voltage and ON time based on Vge voltage at the edges of their respective waveforms. Furthermore, combining DC current estimation using Vce voltage and DC current estimation using Vge voltage as appropriate can improve availability and reliability.

[0094] [Configuration Example 2] In the embodiment described above, a combination of three methods was used: estimating the DC current using the Vce voltage, estimating the DC current using the Miller current, and estimating the DC current using the Vge voltage. However, it is also possible to use only the estimation of the DC current using the Miller current.

[0095] In this case, the configuration includes a mirror current detection unit that detects the mirror current flowing through mirror elements connected in parallel to each switching element of the upper and lower arms, and a DC current estimation unit that estimates the DC current flowing between the positive and negative terminals 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 converter 100 has a circuit configuration that excludes components related to the estimation of DC current based on Vce voltage and Vge voltage, such as Vce detectors 16, 18, Vce measurement circuits 17, 19, Vge detectors 20, 22, and Vge measurement circuits 21, 23, from the configuration shown in Figure 1. Since Miller current cannot measure the current flowing through diodes 10D and 11D, Miller current detectors 24, Miller current measurement circuit 25, and Miller current detectors 26 and Miller current measurement circuit 27 are provided on both the upper and lower arms.

[0097] Estimating DC current using Miller current is applicable to PWM mode and one-sided three-phase short-circuit mode, regardless of fault status, when the AC current is greater than a predetermined value. Therefore, this DC current estimation method eliminates the need for a DC current sensor and allows for accurate estimation of DC current. In DC current estimation, the accuracy is improved by measuring the ON time based on Miller current at the edges of its waveform.

[0098] Furthermore, a configuration combining Configuration Example 1 and Configuration Example 2 may be used. Specifically, the configuration necessary for estimating DC current using Miller current may be added to the configuration necessary for estimating DC current using Vce voltage. Alternatively, the configuration necessary for estimating DC current using Miller current may be added to the configuration necessary for estimating DC current using Vge voltage. By combining these and using them for DC current estimation, availability and reliability can be improved.

[0099] In the embodiment described above, the operation of the DC current estimation process in the DC current determination circuit 44 was explained with reference to the flowchart in Figure 8. The operation of this estimation process in the DC current determination circuit 44 may be performed by a control device such as a microcontroller, which is not shown. The flowchart shown in Figure 8 explains the process performed by executing a program, but since the program is executed by a processor (e.g., CPU, GPU) and performs defined processes using memory resources (e.g., memory) and / or interface devices (e.g., communication ports) as appropriate, the processor may be the main entity performing the processing. Similarly, the main entity performing the processing by executing a program may be a controller, device, system, computer, or node having a processor. The main entity performing the processing by executing a program may be an arithmetic unit, and may include a dedicated circuit (e.g., FPGA or ASIC) that performs a specific process.

[0100] A program may be installed from its program source into a device such as a computer. The program source may be, for example, a program distribution server or a computer-readable storage medium. If the program source is a program distribution server, the program distribution server includes a processor and storage resources for storing the program to be distributed, and the processor of the program distribution server may distribute the program to other computers. Furthermore, in the following description, two or more programs may be implemented as a single program, or one program may be implemented as two or more programs.

[0101] According to the embodiments described above, the following effects and advantages can be obtained. (1) The power converter 100 includes an upper arm switching element 10I and a lower arm switching element 11I connected in series between the DC positive terminal 201 and the DC negative terminal 202, an AC current detection unit (AC current sensor 30) that detects the AC current Ix derived from the connection point 203 between the upper arm switching element 10I and the lower arm switching element 11I, and a switch element terminal voltage detection unit (Vce detection) that detects the terminal voltage of either the upper arm or lower arm switching element 10I or 11I. The system includes components 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 detectors 24, 26, mirror current measurement circuits 25, 27) that detects the mirror current flowing through the mirror elements connected in parallel to each switching element 10I, 11I, and a DC current estimation unit 40 that estimates the DC current Idc_cal flowing between the positive terminal 201 and the negative terminal 202 based on the terminal voltages (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) The method for estimating the DC current in the power converter 100 includes an upper arm switching element 10I and a lower arm switching element 11I connected in series between the DC positive terminal 201 and the DC negative terminal 202, an AC current detection unit (AC current sensor 30) that detects the AC current Ix derived from the connection point 203 between the upper arm switching element 10I and the lower arm switching element 11I, and a collector-emitter voltage detection unit (Vce detectors 16, 18, Vce measurement circuits 17, 19) between the collector and emitter of the switching elements 10I and 11I, and / or the gate of the switching elements 10I and 11I. In a power converter 100 that includes at least one of a gate-emitter voltage detection unit (Vge detectors 20, 22, Vge measurement circuits 21, 23) between the emitter and the power converter, and / or a mirror current detection unit (mirror current detectors 24, 26, mirror current measurement circuits 25, 27) for detecting the mirror current flowing through mirror elements connected in parallel to each switching element 10I, 11I, the DC current Idc_cal flowing between the positive terminal 201 and the negative terminal 202 is estimated based on the collector-emitter voltage, the gate-emitter voltage, the ON time of at least one of the mirror currents, 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.

[0103] The present invention is not limited to the embodiments described above, and other forms conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention, as long as they do not impair the features of the present invention. Furthermore, the above embodiments may be combined with configuration examples 1 and 2. [Explanation of symbols]

[0104] 10...Upper arm power module, 11...Lower arm power module, 10I, 11I...Switching elements, 10D, 11D...Diodes, 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... Miller 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 converter, 200... DC power supply, 201... Positive terminal, 202... Negative terminal, 203... Intermediate connection point.

Claims

1. An upper arm switching element and a lower arm switching element are connected in series between the positive and negative terminals of the DC circuit. An AC current detection unit that detects the AC current derived from the connection point between the switching element of the upper arm and the switching element of the lower arm, A switch element terminal voltage detection unit detects the terminal voltage of either the upper arm or the lower arm switching element, The system includes a DC current estimation unit that estimates the DC current flowing between the positive terminal and the negative terminal based on the terminal voltage and the AC current, The aforementioned switching element terminal voltage detection unit is a power conversion device that detects the collector-emitter voltage, which is the voltage between the collector and emitter of the switching element.

2. In the power conversion device according to claim 1, The DC current estimation unit is a power conversion device that 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.

3. An upper arm switching element and a lower arm switching element are connected in series between the positive and negative terminals of the DC circuit. An AC current detection unit that detects the AC current derived from the connection point between the switching element of the upper arm and the switching element of the lower arm, A mirror current detection unit detects the mirror current flowing through a mirror element connected in parallel to each of the aforementioned switching elements, The system includes a DC current estimation unit that estimates the DC current flowing between the positive terminal and the negative terminal based on the Miller current and the AC current, The DC current estimation unit measures the ON time of the switching element based on the Miller current, and when the AC current is greater than a predetermined value, it estimates the DC current based on the measured ON time, the Miller current, and the AC current.

4. In the power conversion device according to claim 2 or claim 3, A three-phase converter is formed by connecting the switching elements of the upper arm and the switching elements of the lower arm in series, and then connecting these one-phase converters in parallel. The DC current estimation unit is a power conversion device that estimates the DC current according to the operating modes of the switching elements of the upper arm and the lower arm.

5. In the power conversion device according to claim 4, The power converter has three operating modes: a PWM mode in which the motor is driven by controlling the ON / OFF switching elements of the upper arm and the lower arm; a one-sided three-phase short-circuit mode in which all three phase switching elements of the upper arm or the lower arm are short-circuited; and a three-phase open-circuit mode in which all three phase switching elements of the upper arm and the lower arm are open.

6. An upper arm switching element and a lower arm switching element are connected in series between the positive and negative terminals of the DC circuit. An AC current detection unit that detects the AC current derived from the connection point between the switching element of the upper arm and the switching element of the lower arm, A switch element terminal voltage detection unit detects the terminal voltage of either the upper arm or the lower arm switching element, A mirror current detection unit detects the mirror current flowing through a mirror element connected in parallel to each of the aforementioned switching elements, The system includes a DC current estimation unit that estimates the DC current flowing between the positive terminal and the negative terminal based on the terminal voltage, the Miller current, and the AC current. The switch element terminal voltage detection unit detects the collector-emitter voltage, which is the voltage between the collector and emitter of the switching element, and / or the gate-emitter voltage, which is the voltage between the gate and emitter of the switching element. The DC current estimation unit includes a priority order for determining which of the estimations based on the collector-emitter voltage, the gate-emitter voltage, and the Miller current is prioritized, and the power converter estimates the DC current flowing between the positive terminal and the negative terminal according to the priority order.

7. In the power conversion device according to claim 6, A three-phase converter is formed by connecting the switching elements of the upper arm and the switching elements of the lower arm in series, and then connecting these one-phase converters in parallel. The aforementioned priority order is set for each phase of the three-phase power converter.

8. In the power conversion device according to claim 6 or claim 7, The priority order is, in descending order of priority, estimation based on the collector-emitter voltage, estimation based on the gate-emitter voltage, and estimation based on the Miller current in the power conversion device.

9. An upper arm switching element and a lower arm switching element are connected in series between the positive and negative terminals of the DC circuit. An AC current detection unit that detects the AC current derived from the connection point between the switching element of the upper arm and the switching element of the lower arm, A method for estimating DC current in a power conversion device, which includes a switch element terminal voltage detection unit that detects the collector-emitter voltage, which is the voltage between the collector and emitter of the switching element, A method for estimating a DC current in a power converter, which estimates the DC current flowing between the positive terminal and the negative terminal based on the ON time of the switching element based on the collector-emitter voltage and the AC current.

10. An upper arm switching element and a lower arm switching element are connected in series between the positive and negative terminals of the DC circuit. An AC current detection unit that detects the AC current derived from the connection point between the switching element of the upper arm and the switching element of the lower arm, A method for estimating DC current in a power conversion device, which includes a mirror current detection unit that detects the mirror current flowing through a mirror element connected in parallel to each of the aforementioned switching elements, A method for estimating a DC current in a power converter, which estimates the DC current flowing between the positive terminal and the negative terminal based on the ON time of the switching element based on the Miller current, the Miller current, and the AC current, when the AC current is greater than a predetermined value.

11. An upper arm switching element and a lower arm switching element are connected in series between the positive and negative terminals of the DC circuit. An AC current detection unit that detects the AC current derived from the connection point between the switching element of the upper arm and the switching element of the lower arm, A switch element terminal voltage detection unit that detects the collector-emitter voltage, which is the voltage between the collector and emitter of the switching element, and / or the gate-emitter voltage, which is the voltage between the gate and emitter of the switching element, A method for estimating DC current in a power conversion device, which includes a mirror current detection unit that detects the mirror current flowing through a mirror element connected in parallel to each of the aforementioned switching elements, A method for estimating DC current in a power converter, which involves pre-storing a priority order for which to prioritize estimation based on the collector-emitter voltage, estimation based on the gate-emitter voltage, and estimation based on the Miller current, and estimating the DC current flowing between the positive terminal and the negative terminal according to the priority order.

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