Electric vehicle

Abstract

The suppression current continuously flows to specific phases of the motor, the first inverter and the second inverter in a concentrated manner. When the motor is in a locked state, the electric vehicle sets a phase voltage command correction value so as to cancel the difference between a zero-phase current, which is the sum of the phase currents of the phases, and a zero-phase current command based on an electric angle and a torque command of the motor. The first and second inverters are controlled by adding the phase voltage command correction value to the phase voltage command base value for each phase based on the torque command to set the phase voltage command for each phase.

Description

Technical Field

[0001] This disclosure pertains to electric vehicles. Background Technology

[0002] Previously, an electric vehicle was proposed, which includes: an energy storage device; a motor having a three-phase open-circuit winding and driving a drive wheel; and first and second inverters connected to a power line connected to the energy storage device and respectively connected to one end and the other end of the three-phase open-circuit winding (for example, see Patent Document 1).

[0003] Existing technical documents

[0004] Patent Document 1: Japanese Patent Application Publication [ <typ-1>] Announcement

[0005] In the aforementioned electric vehicles, when the motor is locked, current is concentrated and continuously flows to a specific phase, potentially causing the motor, the first inverter, and the second inverter to reach relatively high temperatures. The main objective of the electric vehicle disclosed herein is to suppress the concentrated and continuous current flow to the motor, the first inverter, and the second inverter. Summary of the Invention

[0006] To achieve the aforementioned main objectives, the electric vehicle of this disclosure employs the following means. The electric vehicle of this disclosure includes: an energy storage device; a motor having three open-circuit windings and driving drive wheels; a first inverter connected to a power line connected to the energy storage device and connected to one end of the three open-circuit windings; a second inverter connected to the power line and connected to the other end of the three open-circuit windings; and a control device for controlling the first and second inverters. The electric vehicle is characterized in that, when the motor is in a locked state, the control device sets a phase voltage command correction value by eliminating the difference between the sum of the phase currents of each phase (i.e., the zero-phase current) and the zero-phase current command based on the motor's electrical angle and torque command. The phase voltage command correction value is added to the basic value of the phase voltage command for each phase based on the torque command to set the phase voltage command for each phase, thereby controlling the first and second inverters.

[0007] In the electric vehicle disclosed herein, when the motor is in a locked state, a phase voltage command correction value is set by eliminating the difference between the sum of the phase currents of each phase, i.e., the zero-phase current, and the zero-phase current command based on the motor's electrical angle and torque commands. The phase voltage command of each phase is set by adding the phase voltage command correction value to the basic value of the phase voltage command of each phase based on the torque command, thereby controlling the first and second inverters.

[0008] Therefore, it is possible to suppress the maximum absolute value of the phase current of each phase, that is, to suppress the current from continuously flowing to specific phases of the motor, the first and second inverters. Attached Figure Description

[0009] Figure 1 This is a schematic structural diagram of an electric vehicle according to an embodiment of the present disclosure.

[0010] Figure 2 This is a flowchart illustrating an example of a processing routine.

[0011] Figure 3 This is an explanatory diagram illustrating an example of the relationship between the sum of electrical angle and current command phase and the phase current of each phase.

[0012] Explanation of reference numerals in the attached figures

[0013] 10 Electric vehicles, 12 Batteries, 12i, 20u, 20v, 20w Current sensors, 12v, 30v, 32v Voltage sensors, 20 Motors, 20a Rotary position sensors, 22 First inverters, 24 Second inverters, 28 Power lines, 28n Negative lines, 28p Positive lines, 30, 32 Capacitors, 34n, 34p Switches, 50 ECUs, D11~D16, D21~D26 Diodes, T11~T16, T21~T26 Transistors. Detailed Implementation

[0014] The embodiments (implementations) for carrying out this disclosure will be described with reference to the accompanying drawings. Figure 1 This is a schematic structural diagram of an electric vehicle 10 according to an embodiment of the present disclosure. As shown, the electric vehicle 10 of the embodiment includes a battery 12 as an energy storage device, a motor 20, first and second inverters 22 and 24, power lines 28 (positive line 28p and negative line 28n), capacitors 30 and 32, switches 34p and 34n, and an electronic control unit (hereinafter referred to as "ECU") 50 as a control device.

[0015] Battery 12, for example, is configured as 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, having a rotor with permanent magnets embedded in its rotor core and a stator with three-phase (U-phase, V-phase, W-phase) coils (open-circuit windings) wound in its stator core. The rotor is connected to a drive shaft via a differential gear to a drive wheel.

[0016] The first and second inverters 22 and 24 each include six transistors T11-T16 and T21-T26 as switching elements, and six diodes D11-D16 and D21-D26 connected in parallel with the six transistors T11-T16 and T21-T26, respectively. Transistors T11-T16 and T21-T26 may be MOSFETs, IGBTs, or similar devices. Transistors T11-T16 and T21-T26 are arranged in pairs, with the positive line 28p and negative line 28n as the source and drain sides, respectively. The connection points of the pairs of transistors T11-T16 are connected to one end of the three-phase coil of the motor 20. The connection points of the pairs of transistors T21-T26 are connected to the other end of the three-phase coil of the motor 20. Hereinafter, transistors T11 to T13 are sometimes referred to as the "first upper bridge arm", transistors T14 to T16 are referred to as the "first lower bridge arm", transistors T21 to T23 are referred to as the "second upper bridge arm", and transistors T24 to T26 are referred to as the "second lower bridge arm".

[0017] Capacitors 30 and 32 are connected near the first inverters 22 and 24 in power line 28, respectively. In this embodiment, on power line 28, from... Figure 1 Starting from the left side, the following components are connected in sequence: battery 12, capacitor 30, first inverter 22, second inverter 24, and capacitor 32. Switches 34p and 34n are respectively located between the first inverter 22 and the second inverter 22 in the positive line 28p and the negative line 28n.

[0018] ECU50 is equipped with a microcomputer featuring a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and logic ICs. Signals from various sensors are input to ECU50. For example, inputs include the voltage Vb of battery 12 from voltage sensor 12V, the current Ib of battery 12 from current sensor 12i, the rotational position θm of the rotor of motor 20 from rotational position sensor 20a, and the phase currents Iu, Iv, and Iw of each phase of motor 20 from current sensors 20u, 20V, and 20W. Also inputs include the voltage VH of capacitor 30 from voltage sensor 30V and the voltage VL of capacitor 32 from voltage sensor 32V. Other inputs include the on / off signal from the power switch, the gear lever operating position (gear SP) from the gear position sensor, the accelerator pedal depressor position (accelerator opening Acc) from the accelerator pedal position sensor, the brake pedal depressor position (brake pedal position BP) from the brake pedal position sensor, and the vehicle speed V from the vehicle speed sensor. Various control signals are output from ECU 50. For example, control signals are also output to transistors T11-T16 of the first inverter 22, transistors T21-T26 of the second inverter 24, and switches 34p and 34n. ECU 50 calculates the state of charge (SOC) of battery 12 based on the accumulated value of current Ib of battery 12, or calculates the electrical angle θe and rotational speed Nm of motor 20 based on the rotational position θm of the rotor of motor 20.

[0019] In the electric vehicle 10 of this embodiment, the ECU 50 sets the required torque Td* for driving based on the accelerator opening Acc and the vehicle speed V. It then sets the torque command Tm* of the motor 20 to drive the vehicle according to the set torque Td*. In either Y-drive or H-drive mode, the ECU 50 controls the first and second inverters 22 and 24 and switches 34p and 34n to drive the motor 20 using the set torque command Tm*. In Y-drive mode, switches 34p and 34n are set to the off state, and one of the three-phase upper bridge arms (transistors T21-T23) and the three-phase lower bridge arms (transistors T24-T26) of the second inverter 24 is set to the on state while the other is set to the off state. The three phases (transistors T11-T16) of the first inverter 22 are switched on and off. In this case, the U-phase, V-phase, and W-phase of the motor 20 are coupled to the neutral point via the second inverter 24. In H-drive mode, switches 34p and 34n are turned on, and the three phases (transistors T11-T16 and T21-T26) of the first and second inverters 22 and 24 are switched and driven. Y-drive mode or H-drive mode is selected, for example, based on the speed Nm or torque command Tm*.

[0020] Next, the operation of the electric vehicle 10 according to the embodiment will be explained. Figure 2 This is a flowchart illustrating an example of a processing routine repeatedly executed by ECU 50. When this routine is executed, ECU 50 inputs the phase currents Iu, Iv, Iw, electrical angle θe, speed Nm, and torque command Tm* of each phase of motor 20 (step S100), and uses the electrical angle θe to transform the coordinates of the phase currents Iu, Iv, Iw of each phase (3-phase to 2-phase transformation) into the d-axis and q-axis currents Id and Iq (step S110). Next, the d-axis and q-axis current commands Id* and Iq* are set based on the torque command Tm* (step S120), and the d-axis reference current command phase θi* is calculated based on the set d-axis and q-axis current commands Id* and Iq* (step S130). The processing in step S120 can be performed, for example, by applying the torque command Tm* to a predetermined mapping based on experiments or analysis, which is a relationship between the torque command Tm* and the current commands Id* and Iq* on the d-axis and q-axis, respectively, and deriving the corresponding current commands Id* and Iq* on the d-axis and q-axis. This relationship is determined, for example, by minimizing the square root of the sum of the squares of the current commands Id* and Iq*. The current command phase θi* can be calculated as the angle of the current command vector, which has components Id* and Iq*, relative to the d-axis.

[0021] Then, by eliminating the difference between the currents Id and Iq of the d-axis and q-axis and the current commands Id* and Iq*, the voltage commands Vd* and Vq* of the d-axis and q-axis are calculated by feedback control (step S140). The voltage commands Vd* and Vq* of the d-axis and q-axis are transformed (2-phase to 3-phase transformation) into the basic values ​​of the phase voltage commands Vubs, Vvbs, and Vwbs of each phase using the electrical angle θe (step S150).

[0022] Furthermore, it is determined whether the absolute value of the rotational speed Nm is less than the threshold Nmref (step S160), and whether the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase is greater than the threshold Iref (step S170). The thresholds Nmref and Iref are 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 rotational speed Nm is greater than the threshold 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 less than the threshold 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 basic values ​​of the phase voltage command Vubs, Vvbs, and Vwbs of each phase to calculate the phase voltage commands Vu*, Vv*, and Vw* of each phase (step S220), and the routine ends. In this case, for example, the Y-drive mode or the H-drive mode is selected based on the rotational speed Nm, torque command Tm*, etc. Next, switching commands for 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 transistors T11–T16 and T21–T26 are used to control the switching of transistors T11–T16 and T21–T26, and switches 34p and 34n are controlled based on the selected drive mode.

[0023] In step S160, if the absolute value of the rotational speed Nm is determined to be less than the threshold Nmref, and in step S170, if the maximum value of the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase is determined to be greater than the threshold Iref, then the motor 20 is determined to be in a locked state. In this case, the sum of the phase currents Iu, Iv, and Iw of each phase, i.e., the zero-phase current I0, is calculated (step S190), and the zero-phase current command I0* is set based on the electrical angle θe and the current command phase θi* (step S200). Next, the phase voltage command correction value Va is calculated by feedback control in a way that eliminates the difference between the zero-phase current I0 and the zero-phase current command I0* (step S210). The phase voltage command correction value Va is added to the basic phase voltage command values ​​Vubs, Vvbs, and Vwbs of each phase to calculate the phase voltage commands Vu*, Vv*, and Vw* of each phase (step S220), and the routine ends. The processing in step S190 can be performed, for example, by applying the sum of the electrical angle θe and the current command phase θi* to a predetermined mapping based on experiments or analysis, which is 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 predetermined in advance in such a way that the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw of each phase decreases. In addition, when calculating the phase voltage commands Vu*, Vv*, and Vw* of each phase, the H-drive mode is selected, and the switching commands for transistors T11 to T16 and T21 to T26 are generated based on the H-drive mode and the phase voltage commands Vu*, Vv*, and Vw* of each phase. Then, the switching control of transistors T11 to T16 and T21 to T26 is performed using the switching commands for transistors T11 to T16 and T21 to T26, and switches 34p and 34n are turned on based on the H-drive mode. Through this series of processes, the maximum absolute value of the phase currents Iu, Iv, and Iw in each phase can be suppressed, that is, the current concentrated and continuous flow to specific phases of the motor 20 and the first and second inverters 22 and 24 can be suppressed. As a result, the temperature of the motor 20 and the first and second inverters 22 and 24 can be prevented from becoming relatively high.

[0024] Figure 3 This is an explanatory diagram illustrating an example of the relationship between the sum of the electrical angle θe and the current command phase θi* when the motor 20 is in the locked state and the phase currents Iu, Iv, and Iw of each phase. Figure 3 (A) indicates the implementation method. Figure 3 (B) indicates a comparative example. In the comparative example, the basic phase voltage command values ​​Vubs, Vvbs, and Vwbs for each phase are directly set to the phase voltage commands Vu*, Vv*, and Vw* for each phase (the phase voltage command correction value Va is 0). For example... Figure 3 (A) and Figure 3 As shown in (B), it can be seen that in the implementation case, compared with the comparative example, it is possible to suppress the maximum value of the absolute values ​​of phase currents Iu, Iv, and Iw from increasing.

[0025] In the electric vehicle 10 described above, when the motor 20 is in a locked state, a phase voltage command correction value Va is calculated by eliminating 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* 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 basic phase voltage command values ​​Vubs, Vvbs, and Vwbs of each phase to calculate the phase voltage commands Vu*, Vv*, and Vw* of each phase. Based on the calculated phase voltage commands Vu*, Vv*, and Vw* of each phase, the first and second inverters 22 and 24 are controlled. This suppresses the maximum absolute value of the phase currents Iu, Iv, and Iw of each phase, i.e., it suppresses the continuous flow of current concentrated to specific phases of the motor 20 and the first and second inverters 22 and 24.

[0026] In the above implementation, when the absolute value of the rotational speed Nm is less than the threshold Nmref and the maximum value among the absolute values ​​of the phase currents Iu, Iv, and Iw is greater than the threshold Iref, it is determined that the motor 20 is in a locked state. However, it is also possible to determine that the motor 20 is in a locked state regardless of the phase currents Iu, Iv, and Iw when the absolute value of the rotational speed Nm is less than the threshold Nmref.

[0027] In the above implementation, when the motor 20 is not in the locked state, the phase voltage command correction value Va is set to 0. When the motor 20 is in the locked state, the phase voltage command correction value Va is calculated in a way that eliminates the difference between the zero phase current I0 and the zero phase current command I0*. However, when switching between the former and the latter, the phase voltage command correction value Va can be changed slowly by means of slow change processing such as rate processing and smoothing processing.

[0028] In the above embodiment, when the motor 20 is in the 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* can also be set based on the electrical angle θe, the torque command Tm*, and the component temperature Ti. In this case, for example, the maximum value of each temperature of transistors T11 to T16 and T21 to T26 can be set as the component temperature Ti. Alternatively, the zero-phase current command I0* can be calculated by multiplying the basic value of the zero-phase current command I0bs based on the electrical angle θe and the torque command Tm* by a correction factor k, which increases as the component temperature Ti increases.

[0029] In the above-described embodiments, the electric vehicle 10 includes switches 34p and 34n, but may not include at least one of switches 34p and 34n. Additionally, a battery 12 is included as an energy storage device, but a capacitor or the like may be included in addition to or in place of the battery 12.

[0030] In the above embodiments, the structure is set as an electric vehicle 10 having a battery 12, a motor 20, and first and second inverters 22 and 24. However, it may also be a hybrid vehicle having an engine in addition to the same hardware structure as the electric vehicle 10, or a fuel cell vehicle having a fuel cell in addition to the same hardware structure as the electric vehicle 10.

[0031] The above describes the methods for implementing this disclosure using the embodiments, but this disclosure is not limited to such embodiments. Of course, it can be implemented in various ways without departing from the spirit of this disclosure.

[0032] Industrial availability

[0033] This disclosure can be applied to industries such as electric vehicle manufacturing.

Claims

1. An electric vehicle comprising: an energy storage device; a motor having three-phase open-circuit windings and driving a drive wheel; a first inverter connected to a power line connected to the energy storage device and connected to one end of the three-phase open-circuit windings; a second inverter connected to the power line and connected to the other end of the three-phase open-circuit windings; and a control device for controlling the first inverter and the second inverter. in, When the motor is in a locked state, the control device sets a phase voltage command correction value by eliminating the difference between the sum of the phase currents of each phase, i.e., the zero-phase current, and the zero-phase current command based on the motor's electrical angle and torque command. The phase voltage command correction value is added to the basic value of the phase voltage command of each phase based on the torque command to set the phase voltage command of each phase, thereby controlling the first inverter and the second inverter.

Images