electric vehicles

Abstract

This prevents current from concentrating and continuing to flow in specific phases of the motor or first and second inverters. [Solution] When the motor of an electric vehicle is in a locked state, a phase voltage command correction value is set so that the difference between the zero-phase current, which is the sum of the phase currents of each phase, and the zero-phase current command based on the motor's electrical angle and torque command is canceled out, and the phase voltage command correction value is added to the phase voltage command base value of each phase, which is based on the torque command, to set the phase voltage command of each phase, and control the first and second inverters.

Description

[Technical Field]

[0001] The present disclosure relates to electric vehicles. [Background technology]

[0002] Conventionally, an electric vehicle has been proposed that includes a power storage device, a motor having a three-phase open winding and driving a drive wheel, and first and second inverters connected to a power line to which the power storage device is connected and connected to one end and the other end of the three-phase open winding, respectively (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication Summary of the Invention [Problem to be solved by the invention]

[0004] In the electric vehicle described above, when the motor is locked, current may continue to flow in a particular phase, causing the temperature of the motor and the first and second inverters to become relatively high.The electric vehicle disclosed herein has a primary objective of suppressing current from continuing to flow in a particular phase of the motor and the first and second inverters. [Means for solving the problem]

[0005] The electric vehicle of the present disclosure employs the following means to achieve the above-mentioned primary object: The electric vehicle of the present disclosure includes a power storage device, a motor having a three-phase open winding and driving drive wheels, a first inverter connected to a power line to which the power storage device is connected and connected to one end of the three-phase open winding, a second inverter connected to the power line and connected to the other end of the three-phase open winding, and a control device that controls the first and second inverters, wherein when the motor is in a locked state, the control device sets a phase voltage command correction value so as to cancel out a difference between a zero-phase current that is the sum of the phase currents of the phases and a zero-phase current command that is based on the motor's electrical angle and a torque command, and controls the first and second inverters by adding the phase voltage command correction value to a phase voltage command base value of the phase that is based on the torque command to set a phase voltage command of the phase.

[0006] In the electric vehicle disclosed herein, when the motor is locked, a phase voltage command correction value is set so that the difference between the zero-phase current, which is the sum of the phase currents of each phase, and the zero-phase current command based on the motor's electrical angle and torque command is canceled out, and the phase voltage command correction value is added to the phase voltage command base value of each phase, which is based on the torque command, to set a phase voltage command for each phase, thereby controlling the first and second inverters. This makes it possible to suppress the maximum value of the absolute values ​​of the phase currents of each phase, i.e., to suppress current from concentrating and continuing to flow in a specific phase of the motor or the first and second inverters. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic configuration diagram of an electric vehicle according to an embodiment of the present disclosure. [Figure 2] 10 is a flowchart illustrating an example of a processing routine. [Figure 3] FIG. 2 is an explanatory diagram showing an example of the relationship between the sum of the electrical angle and the current command phase and the phase current of each phase. DETAILED DESCRIPTION OF THE INVENTION

[0008] A mode (embodiment) for carrying out the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic configuration diagram of an electric vehicle 10 according to an embodiment of the present disclosure. As shown in the figure, the electric vehicle 10 according to the embodiment includes a battery 12 as an electricity storage device, a motor 20, first and second inverters 22, 24, power lines 28 (positive line 28p and negative line 28n), capacitors 30, 32, switches 34p, 34n, and an electronic control unit (hereinafter referred to as "ECU") 50 as a control device.

[0009] Battery 12 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to power line 28. Motor 20 is configured as a three-phase AC motor, and includes a rotor with a permanent magnet embedded in a rotor core, and a stator with three-phase (U-phase, V-phase, W-phase) coils (open windings) wound around a stator core. The rotor is connected to a drive shaft that is connected to drive wheels via a differential gear.

[0010] The first and second inverters 22 and 24 each include six transistors T11 to T16 and T21 to T26 as switching elements, and six diodes D11 to D16 and D21 to D26 connected in parallel to the six transistors T11 to T16 and T21 to T26, respectively. The transistors T11 to T16 and T21 to T26 may be implemented, for example, as MOSFETs or IGBTs. The transistors T11 to T16 and T21 to T26 are arranged in pairs, two at a time, on the source side and two at the sink side of the positive line 28p and the negative line 28n. The junctions of the paired transistors T11 to T16 are connected to one end of the three-phase coils of the motor 20. The junctions of the paired transistors T21 to T26 are connected to the other end of the three-phase coils of the motor 20. Hereinafter, each of the transistors T11 to T13 may be referred to as a "first upper arm," each of the transistors T14 to T16 as a "first lower arm," each of the transistors T21 to T23 as a "second upper arm," and each of the transistors T24 to T26 as a "second lower arm."

[0011] The capacitors 30 and 32 are connected to the power line 28 near the first inverters 22 and 24, respectively. In this embodiment, the battery 12, the capacitor 30, the first inverter 22, the second inverter 24, and the capacitor 32 are connected to the power line 28 in this order from the left side of FIG. 1. The switches 34p and 34n are provided between the first inverter 22 and the second inverter 22 on the positive line 28p and the negative line 28n, respectively.

[0012] The ECU 50 includes a microcomputer with a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and logic ICs. The ECU 50 receives signals from various sensors, including the voltage Vb of the battery 12 from a voltage sensor 12v, the current Ib of the battery 12 from a current sensor 12i, the rotational position θm of the rotor of the motor 20 from a rotational position sensor 20a, and the phase currents Iu, Iv, and Iw of the motor 20 from current sensors 20u, 20v, and 20w. The ECU 50 also receives the voltage VH of the capacitor 30 from a voltage sensor 30v and the voltage VL of the capacitor 32 from a voltage sensor 32v. The ECU 50 also receives an on / off signal from a power switch, the operating position of the shift lever (shift position SP) from a shift position sensor, the accelerator pedal depression amount (accelerator opening Acc) from an accelerator pedal position sensor, the brake pedal depression amount (brake pedal position BP) from a brake pedal position sensor, and the vehicle speed V from a vehicle speed sensor. Various control signals are output from the ECU 50. For example, control signals are output to the transistors T11 to T16 of the first inverter 22 and the transistors T21 to T26 of the second inverter 24, and control signals are output to the switches 34p and 34n. The ECU 50 calculates the state of charge (SOC) of the battery 12 based on the integrated value of the current Ib of the battery 12, and calculates the electrical angle θe and rotation speed Nm of the motor 20 based on the rotational position θm of the rotor of the motor 20.

[0013] In the electric vehicle 10 of this embodiment, the ECU 50 sets a required torque Td* required for traveling based on the accelerator pedal position Acc and the vehicle speed V, sets a torque command Tm* for the motor 20 so that the vehicle travels at the set required torque Td*, and controls the first and second inverters 22, 24 and switches 34p, 34n in Y drive mode or H drive mode so that the motor 20 is driven at the set torque command Tm*. In Y drive mode, the switches 34p, 34n are turned off, one of the three-phase second upper arms (transistors T21 to T23) and the three-phase second lower arms (transistors T24 to T26) of the second inverter 24 is turned on and the other is turned off, and the three phases (transistors T11 to T16) of the first inverter 22 are switched-drive. In this case, the U-phase, V-phase, and W-phase of the motor 20 are neutral-connected by the second inverter 24. In the H drive mode, the switches 34p and 34n are turned on, and the three phases (transistors T11 to T16, T21 to T26) of the first and second inverters 22 and 24 are switched. The Y drive mode or the H drive mode is selected based on, for example, the rotation speed Nm and the torque command Tm*.

[0014] Next, the operation of the electric vehicle 10 according to this embodiment will be described. Fig. 2 is a flowchart showing an example of a processing routine repeatedly executed by the ECU 50. When this routine is executed, the ECU 50 inputs the phase currents Iu, Iv, and Iw of each phase of the motor 20, the electrical angle θe, the rotation speed Nm, and the torque command Tm* (step S100), and performs coordinate transformation (three-phase to two-phase transformation) of the phase currents Iu, Iv, and Iw of each phase into d-axis and q-axis currents Id and Iq using the electrical angle θe (step S110). Next, the ECU 50 sets the d-axis and q-axis current commands Id* and Iq* based on the torque command Tm* (step S120), and calculates a d-axis-referenced current command phase θi* based on the set d-axis and q-axis current commands Id* and Iq* (step S130). The process of step S120 can be performed, for example, by applying the torque command Tm* to a map that has been determined in advance as the relationship between the torque command Tm* and the d-axis and q-axis current commands Id*, Iq* through experiments, analysis, or the like, and deriving the corresponding d-axis and q-axis current commands Id*, Iq*. This relationship is determined, for example, so that the square root of the sum of the square of the current command Id* and the square of the current command Iq* is minimized. The current command phase θi* can be calculated as the angle of a current command vector, whose components are the current commands Id* and Iq*, relative to the d-axis. Then, the d-axis and q-axis voltage commands Vd* and Vq* are calculated by feedback control so that the differences between the d-axis and q-axis currents Id and Iq and the current commands Id* and Iq* are cancelled out (step S140), and the d-axis and q-axis voltage commands Vd* and Vq* are coordinate-converted (2-phase to 3-phase conversion) to the phase voltage command basic values ​​Vubs, Vvbs, and Vwbs of each phase using the electrical angle θe (step S150).

[0015] Furthermore, it is determined whether the absolute value of the rotation speed Nm is less than a threshold value Nmref (step S160), and it is also determined whether the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase is greater than a threshold value Iref (step S170). The threshold values ​​Nmref and Iref are threshold values ​​used to determine whether the motor 20 is in a locked state. If it is determined in step S160 that the absolute value of the rotation speed Nm is equal to or greater than the threshold value Nmref, or if it is determined in step S170 that the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase is equal to or less than the threshold value Iref, it is determined that the motor 20 is not in a locked state. In this case, the phase voltage command correction value Va is set to 0 (step S180), and the phase voltage command correction value Va is added to the phase voltage command basic values ​​Vubs, Vvbs, and Vwbs of each phase to calculate the phase voltage commands Vu*, Vv*, and Vw* of each phase (step S220), and this routine ends. In this case, for example, the Y drive mode or the H drive mode is selected based on the rotation speed Nm, torque command Tm*, etc. Next, switching commands for the transistors T11-T16 and T21-T26 are generated based on the selected drive mode and the phase voltage commands Vu*, Vv*, and Vw* for each phase. Then, the switching commands for the transistors T11-T16 and T21-T26 are used to control the switching of the transistors T11-T16 and T21-T26, and the switches 34p and 34n are controlled based on the selected drive mode.

[0016] If it is determined in step S160 that the absolute value of the rotation speed Nm is less than the threshold value Nmref and if it is determined in step S170 that the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of the respective phases is greater than the threshold value Iref, it is determined that the motor 20 is in a locked state. In this case, a zero-phase current Io, which is the sum of the phase currents Iu, Iv, and Iw of the respective phases, is calculated (step S190), and a zero-phase current command Io* is set based on the electrical angle θe and the current command phase θi* (step S200). Next, a phase voltage command correction value Va is calculated by feedback control so that the difference between the zero-phase current Io and the zero-phase current command Io* is canceled (step S210). The phase voltage command correction value Va is then added to the phase voltage command basic values ​​Vubs, Vvbs, and Vwbs of the respective phases to calculate the phase voltage commands Vu*, Vv*, and Vw* of the respective phases (step S220), and this routine ends. The process of step S190 can be performed, for example, by applying the sum of the electrical angle θe and the current command phase θi* to a map previously determined through experimentation, analysis, or the like as the relationship between the sum of the electrical angle θe and the current command phase θi* and the zero-phase current command I0*, and deriving the corresponding zero-phase current command I0*. This relationship is previously determined so that the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase is small. After calculating the phase voltage commands Vu*, Vv*, and Vw* for each phase, the H drive mode is selected, and switching commands for the transistors T11-T16 and T21-T26 are generated based on the H drive mode and the phase voltage commands Vu*, Vv*, and Vw* for each phase. The switching commands for the transistors T11-T16 and T21-T26 are used to control the switching of the transistors T11-T16 and T21-T26, and the switches 34p and 34n are turned on based on the H drive mode. This series of processes suppresses the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of the respective phases, i.e., it is possible to prevent current from concentrating and continuing to flow in a specific phase of the motor 20 or the first and second inverters 22, 24. As a result, it is possible to prevent the temperatures of the motor 20 and the first and second inverters 22, 24 from becoming relatively high.

[0017] 3A and 3B are explanatory diagrams showing an example of the relationship between the sum of the electrical angle θe and the current command phase θi* and the phase currents Iu, Iv, and Iw of each phase when the motor 20 is in a locked state. FIG. 3A shows an embodiment, and FIG. 3B shows a comparative example. In the comparative example, the phase voltage command basic values ​​Vubs, Vvbs, and Vwbs of each phase are set directly to the phase voltage commands Vu*, Vv*, and Vw* of each phase (the phase voltage command correction value Va is set to 0). As shown in FIGS. 3A and 3B, in the case of the embodiment, it is possible to suppress an increase in the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw compared to the comparative example.

[0018] In the electric vehicle 10 according to the embodiment described above, when the motor 20 is locked, a phase voltage command correction value Va is calculated to cancel the difference between the zero-phase current I0, which is the sum of the phase currents Iu, Iv, and Iw of each phase, and the zero-phase current command I0*, which is based on the electrical angle θe and the torque command Tm* (current command phase θi*). Next, the phase voltage command correction value Va is added to the phase voltage command basic values ​​Vubs, Vvbs, and Vwbs of each phase to calculate the phase voltage commands Vu*, Vv*, and Vw* of each phase, and the first and second inverters 22 and 24 are controlled based on the calculated phase voltage commands Vu*, Vv*, and Vw* of each phase. This suppresses the maximum value of the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase, i.e., it is possible to prevent current from concentrating and continuing to flow in a specific phase of the motor 20 or the first and second inverters 22 and 24.

[0019] In the above-described embodiment, it is determined that the motor 20 is in a locked state when the absolute value of the rotation speed Nm is less than the threshold value Nmref and the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw is greater than the threshold value Iref. However, it may also be determined that the motor 20 is in a locked state when the absolute value of the rotation speed Nm is less than the threshold value Nmref, regardless of the phase currents Iu, Iv, and Iw.

[0020] In the above-described embodiment, when the motor 20 is not in a locked state, the phase voltage command correction value Va is set to 0, and when the motor 20 is in a locked state, the phase voltage command correction value Va is calculated so that the difference between the zero-phase current I0 and the zero-phase current command I0* is canceled out. However, when switching the phase voltage command correction value Va between the former and latter, the phase voltage command correction value Va may be changed gradually by a slow-change process such as a rate process or an averaging process.

[0021] In the above-described embodiment, when the motor 20 is in a locked state, the zero-phase current command I0* is set based on the electrical angle θe and the torque command Tm* (current command phase θi*). However, for example, the zero-phase current command I0* may be set based on the electrical angle θe, the torque command Tm*, and the element temperature Ti. In this case, for example, the maximum value of the temperatures of the transistors T11 to T16 and T21 to T26 may be set as the element temperature Ti. Furthermore, the zero-phase current command I0* may be calculated by multiplying the zero-phase current command basic value I0bs, which is based on the electrical angle θe and the torque command Tm*, by a correction coefficient k, which increases as the element temperature Ti increases.

[0022] In the above-described embodiment, the electric vehicle 10 includes the switches 34p and 34n, but at least one of the switches 34p and 34n may be omitted. Also, while the electric vehicle 10 includes the battery 12 as the power storage device, a capacitor or the like may be included in addition to or instead of the battery 12.

[0023] In the above-described embodiment, the electric vehicle 10 is configured to include a battery 12, a motor 20, and first and second inverters 22, 24. However, for example, the electric vehicle 10 may be configured as a hybrid vehicle that further includes an engine in addition to the same hardware configuration as the electric vehicle 10, or as a fuel cell vehicle that further includes a fuel cell in addition to the same hardware configuration as the electric vehicle 10.

[0024] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0025] The present disclosure is applicable to the electric vehicle manufacturing industry and the like. [Explanation of symbols]

[0026] 10 electric vehicle, 12 battery, 12i, 20u, 20v, 20w current sensors, 12v, 30v, 32v voltage sensors, 20 motor, 20a rotational position sensor, 22 first inverter, 24 second inverter, 28 power line, 28n negative line, 28p positive line, 30, 32 capacitors, 34n, 34p switches, 50 ECU, D11 to D16, D21 to D26 diodes, T11 to T16, T21 to T26 transistors.

Claims

[Claim 1] an electric vehicle including: a power storage device; a motor having a three-phase open winding and driving drive wheels; a first inverter connected to a power line to which the power storage device is connected and connected to one end of the three-phase open winding; a second inverter connected to the power line and connected to the other end of the three-phase open winding; and a control device that controls the first and second inverters, the control device, when the motor is in a locked state, sets a phase voltage command correction value so that a difference between a zero-phase current, which is the sum of the phase currents of the respective phases, and a zero-phase current command based on the electrical angle and torque command of the motor is canceled out, and adds the phase voltage command correction value to a phase voltage command basic value of each phase based on the torque command to set a phase voltage command of each phase, thereby controlling the first and second inverters. Electric car.

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