electric vehicles

Abstract

This enables the detection of abnormal opening of the changeover switch. [Solution] The electric vehicle comprises a power storage device, a motor for driving with a three-phase open winding, 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 and having a first upper arm and a first lower arm, a second inverter connected to the power line on the opposite side of the power storage device from the first inverter and connected to the other end of the three-phase open winding and having a second upper arm and a second lower arm, a changeover switch provided between the first and second inverters in the power line, and a control device that controls the first and second inverters and the changeover switch. The control device determines an open-circuit abnormality of the changeover switch when the changeover switch is in the ON state and the first and second inverters are being switched on, and it confirms that the absolute value of the zero-sequence current, which is the sum of the phase currents of each phase, is greater than or equal to a threshold.

Description

Technical Field

[0001] The present disclosure relates to an electric vehicle.

Background Art

[0002] Conventionally, an electric vehicle has been proposed that includes a power storage device, a motor for running having a three-phase open winding, a first inverter that is connected to a power line to which the power storage device is connected, is connected to one end side of the three-phase open winding, and has a first upper arm and a first lower arm, a second inverter that is connected to the power line on the opposite side of the power storage device with respect to the first inverter, is connected to the other end side of the three-phase open winding, and has a second upper arm and a second lower arm, and a switching switch provided between the first and second inverters in the power line (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described electric vehicle, when the switching switch is in the on state and the motor is driven by the switching drive of the first and second inverters, if an opening abnormality of the switching switch occurs, the energy on the second inverter side cannot be refluxed to the power storage device side, and there is a concern that the voltage on the second inverter side becomes relatively high. Therefore, there is a need to devise a method for detecting such an opening abnormality of the switching switch.

[0005] The main object of the electric vehicle of the present disclosure is to be able to detect an opening abnormality of the switching switch.

Means for Solving the Problems

[0006] The electric vehicle of this disclosure employs the following means to achieve the main objective described above.

[0007] The electric vehicle disclosed herein is Energy storage device, A motor for traction having a 3-phase open winding, The first inverter is connected to the power line to which the energy storage device is connected and is also connected to one end of the three-phase open winding and has a first upper arm and a first lower arm. A second inverter is connected to the power line opposite to the first inverter and to the other end of the three-phase open winding, and has a second upper arm and a second lower arm. A changeover switch is provided between the first and second inverters in the aforementioned power line, A control device that controls the first and second inverters and the changeover switch, An electric vehicle equipped with, When the control device is in the ON state and the first and second inverters are being switched on, if it confirms that the absolute value of the zero-sequence current, which is the sum of the phase currents of each phase, is greater than or equal to a threshold, it determines that there is an opening abnormality in the changeover switch. This is the gist of it.

[0008] In the electric vehicle of this disclosure, the control device determines an open-circuit abnormality of the changeover switch when the changeover switch is in the ON state and the first and second inverters are being switched-driven, and it confirms that the absolute value of the zero-sequence current, which is the sum of the phase currents of each phase, is greater than or equal to a threshold. When an open-circuit abnormality occurs in the changeover switch, current stops flowing through that part, so the absolute value of the zero-sequence current may become relatively large. The inventors have confirmed this through experiments and analyses. Therefore, an open-circuit abnormality of the changeover switch can be detected by this method.

[0009] In the electric vehicle of this disclosure, if the control device determines that the changeover switch is not open, it may turn on one of the second upper arm and the second lower arm and turn off the other, and switch drive the first inverter.

[0010] In the electric vehicle of this disclosure, the changeover switch has a positive-side switch provided between the first and second inverters on the positive-side line of the power line, and a negative-side switch provided between the first and second inverters on the negative-side line of the power line, and when the control device determines that the changeover switch is not open, it may determine which of the positive-side switch and the negative-side switch is not open based on the sign of the zero-sequence current. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of an electric vehicle according to an embodiment of the disclosure. [Figure 2] This flowchart shows an example of a processing routine executed by the ECU. [Figure 3] This is an explanatory diagram illustrating an example of what happens when an abnormal opening occurs in the positive terminal switch. [Figure 4] A flowchart shows an example of a processing routine for a modified case. [Modes for carrying out the invention]

[0012] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of an electric vehicle 10 according to an embodiment of this disclosure. As shown in the figure, 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, first and second capacitors 30 and 32, a positive-side switch 34p and a negative-side switch 34n as changeover switches, and an electronic control unit (hereinafter referred to as "ECU") 50 as a control device.

[0013] The battery 12 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery and is connected to the power line 28 (positive electrode line 28p and negative electrode line 28n). The motor 20 is configured as a three-phase AC motor and comprises a rotor with permanent magnets embedded in the rotor core and a stator with three-phase (U-phase, V-phase, W-phase) coils (three-phase open windings) wound around the stator core. The rotor is connected to a drive shaft which is linked to the drive wheels via a differential gear.

[0014] The first and second inverters 22 each comprise six transistors T11-T16 and T21-T26 as multiple switching elements, and six diodes D11-D16 and D21-D26 connected in parallel to each of the six transistors T11-T16 and T21-T26. Examples of transistors T11-T16 and T21-T26 include MOSFETs and IGBTs. The transistors T11-T16 and T21-T26 are arranged in pairs, with two transistors acting as the source and two as the sink relative to the positive line 28p and the negative line 28n. Each connection point of a pair of transistors T11-T16 is connected to one end of the three-phase coil of the motor 20. Each connection point of a pair of transistors T21-T26 is connected to the other end of the three-phase coil of the motor 20. In the following, transistors T11-T13 may be referred to as the "first upper arm," transistors T14-T16 as the "first lower arm," transistors T21-T23 as the "second upper arm," and transistors T24-T26 as the "second lower arm."

[0015] The first and second capacitors 30 and 32 are connected to the power line 28 near the first and second inverters 22 and 24, respectively. In this embodiment, the power line 28 is connected in the following order from left to right in Figure 1: battery 12, first capacitor 30, first inverter 22, second inverter 24, and second capacitor 32. The positive-side switch 34p and the negative-side switch 34n are provided between the first and second inverters 22 and 24 on the positive-side line 28p and the negative-side line 28n, respectively. For example, semiconductor switches or isolated switches can be used as the positive-side switch 34p and the negative-side switch 34n.

[0016] The ECU50 is a microcomputer equipped with 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 the ECU50. For example, the ECU50 receives the voltage Vb of battery 12 from voltage sensor 12v, the current Ib of battery 12 from current sensor 12i, and the temperature Tb of battery 12 from temperature sensor 12t. The ECU50 also receives 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. The ECU50 also receives the voltage VH of the first capacitor 30 from voltage sensor 30v and the voltage VL of the second capacitor 32 from voltage sensor 32v. The ECU 50 also receives the following inputs: an on / off signal from the power switch 60, the shift position SP which is the operating position of the shift lever 61 from the shift position sensor 62, the accelerator opening Acc which is the amount the accelerator pedal 63 is pressed from the accelerator pedal position sensor 64, the brake pedal position BP which is the amount the brake pedal 65 is pressed from the brake pedal position sensor 66, and the vehicle speed V from the vehicle speed sensor 67.

[0017] Various control signals are output from the ECU 50. For example, control signals are output from the ECU 50 to the transistors T11 to T16 of the first inverter 22, the transistors T21 to T26 of the second inverter 24, the positive electrode side switch 34p, and the negative electrode side switch 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 the rotational speed Nm of the motor 20 based on the rotational position θm of the rotor of the motor 20.

[0018] In the electric vehicle 10 of the embodiment, the ECU 50 sets the required torque Td* required for running based on the accelerator opening Acc and the vehicle speed V, sets the torque command Tm* of the motor 20 so as to run with the set required torque Td*, and based on the set torque command Tm*, controls the first and second inverters 22 and 24, the positive electrode side switch 34p, and the negative electrode side switch 34n in the Y drive mode or the H drive mode. In the Y drive mode, the positive electrode side switch 34p and the negative electrode side switch 34n are turned off, and one of the second upper arm (transistors T21 to T23) and the second lower arm (transistors T24 to T26) of the second inverter 24 is turned on and the other is turned off, and the first inverter 22 (transistors T11 to T16) is driven by switching. In this case, the neutral point of the motor 20 is formed by the second inverter 24. In the H drive mode, the positive electrode side switch 34p and the negative electrode side switch 34n are turned on, and the first and second inverters 22 and 24 (transistors T11 to T16, T21 to T26) are driven by switching.

[0019] Next, the operation of the electric vehicle 10 of the embodiment will be described. In particular, the operation when an open-circuit abnormality occurs in the positive electrode side switch 34p or the negative electrode side switch 34n will be described. FIG. 2 is a flowchart showing an example of a processing routine executed by the ECU 50. This routine is repeatedly executed when an open-circuit abnormality of the positive electrode side switch 34p or the negative electrode side switch 34n is not detected.

[0020] When this routine is executed, the ECU 50 first determines whether it is in the H drive mode or the Y drive mode (step S100). If it is determined that it is in the Y drive mode, this routine ends. This is because in the Y drive mode, the positive-side switch 34p and the negative-side switch 34n are turned off in the first place.

[0021] When the ECU 50 determines in step S100 that it is in the H drive mode, it calculates the zero-phase current I0, which is the sum of the phase currents Iu, Iv, and Iw of each phase of the motor 20 from the current sensors 20u, 20v, and 20w (step S110), and calculates the zero-phase current average value I0ave, which is the average value of the zero-phase current I0 over a predetermined time T1 (step S120). The predetermined time T1 is determined in advance by experiments, analysis, etc.

[0022] When the ECU 50 calculates the zero-phase current average value I0ave, it determines whether the absolute value of the zero-phase current average value I0ave is greater than or equal to the threshold value I0ref (step S130). When the absolute value of the zero-phase current average value I0ave is greater than or equal to the threshold value I0ref, it determines whether the duration is greater than or equal to a predetermined time T2 (step S140). Here, the threshold value I0ref is a threshold value used to determine whether an open-circuit abnormality has occurred in the positive-side switch 34p or the negative-side switch 34n. The predetermined time T2 is the time required to confirm that an open-circuit abnormality has occurred in the positive-side switch 34p or the negative-side switch 34n. The threshold value I0ref and the predetermined time T2 are determined in advance by experiments, analysis, etc. When both the positive-side switch 34p and the negative-side switch 34n are in the normal on state in the H drive mode, current can flow through the positive-side line 34p and the negative-side line 34n, so it is considered that the possibility of the absolute value of the zero-phase current I0 becoming large is low. On the other hand, when an open-circuit abnormality occurs in the positive-side switch 34p or the negative-side switch 34n in the H drive mode, current cannot flow through the positive-side line 28p or the negative-side line 34n, so the absolute value of the zero-phase current I0 may become relatively large. The inventors confirmed this by experiments, analysis, etc. The processes of steps S130 and S140 are processes based on this fact.

[0023] When the ECU50 determines in step S130 that the absolute value of the zero-sequence current average value I0ave is less than the threshold I0ref, it determines that both the positive-side switch 34p and the negative-side switch 34n are in the normally ON state (no open-circuit abnormality has occurred in either), and terminates this routine.

[0024] If the ECU 50 determines in step S130 that the absolute value of the zero-sequence current average value I0ave is greater than or equal to the threshold I0ref, and also determines in step S140 that its duration is less than the predetermined time T2, it terminates this routine without detecting (confirming) an open circuit abnormality of the positive-side switch 34p or the negative-side switch 34n.

[0025] In step S130, the ECU 50 determines that the absolute value of the zero-sequence current average value I0ave is greater than or equal to the threshold I0ref, and in step S140, it determines that the duration is greater than or equal to a predetermined time T2, at which point it detects (confirms) an open circuit abnormality in the positive-side switch 34p or the negative-side switch 34n (step S150). In this case, the drive mode is switched from H drive mode to Y drive mode (step S160), and this routine is terminated. In this way, an open circuit abnormality in the positive-side switch 34p or the negative-side switch 34n can be detected. Furthermore, in Y drive mode, since the positive-side switch 34p and the negative-side switch 34n are turned off from the start, the vehicle can still perform a retreat drive even when an open circuit abnormality occurs in the positive-side switch 34p or the negative-side switch 34n.

[0026] Figure 3 is an explanatory diagram illustrating an example of what happens when an opening abnormality occurs in the positive-side switch 34p. As shown in the figure, after an opening abnormality occurs in the positive-side switch 34p at time t1, if the absolute value of the zero-sequence current average value I0ave reaches a threshold I0ref or higher at time t2, and the duration of this condition reaches a predetermined time T2 or longer at time t3, an opening abnormality in either the positive-side switch 34p or the negative-side switch 34n is detected. Then, the drive mode is switched from H drive mode to Y drive mode. In this way, an opening abnormality in either the positive-side switch 34p or the negative-side switch 34n can be detected, and then the vehicle can perform a retraction run.

[0027] In the electric vehicle 10 of the embodiment described above, in H drive mode, when the absolute value of the zero-sequence current average value I0ave reaches a threshold I0ref or greater and the duration thereafter reaches a predetermined time T2 or greater, an open-circuit abnormality of the positive-side switch 34p or the negative-side switch 34n is detected. In this way, an open-circuit abnormality of the positive-side switch 34p or the negative-side switch 34n can be detected. When an open-circuit abnormality of the positive-side switch 34p or the negative-side switch 34n is detected, the vehicle switches from H drive mode to Y drive mode. In this way, emergency driving can be performed.

[0028] In the embodiment described above, an open circuit abnormality of the positive-side switch 34p or the negative-side switch 34n is detected when the absolute value of the zero-sequence current average value I0ave reaches a threshold I0ref or greater and the duration therefor reaches a predetermined time T2 or greater. However, the embodiment is not limited to this. For example, an open circuit abnormality of the positive-side switch 34p or the negative-side switch 34n may be detected when the absolute value of the zero-sequence current I0 reaches a threshold I0ref or greater and the duration therefor reaches a predetermined time T2 or greater.

[0029] In the embodiment described above, the ECU 50 executes the processing routine shown in Figure 2, but it may instead execute the processing routine shown in Figure 4. The processing routine in Figure 4 differs from the processing routine in Figure 2 in that steps S152 to S156 are added. Therefore, the same step numbers are used for the processing in the processing routine in Figure 4 that are the same as those in the processing routine in Figure 2, and their detailed explanations are omitted.

[0030] In the processing routine shown in Figure 4, when the ECU 50 detects an open circuit abnormality in either the positive-side switch 34p or the negative-side switch 34n in step S150, it checks the sign of the zero-sequence current average value I0ave (step S152). This is because the sign of the zero-sequence current average value I0ave differs depending on whether the open circuit abnormality is in the positive-side switch 34p or the negative-side switch 34n. If the sign of the zero-sequence current average value I0ave is determined to be negative, it is determined that the open circuit abnormality is in the positive-side switch 34p (step S154), and the process proceeds to step S160. On the other hand, if the sign of the zero-sequence current average value I0ave is determined to be positive, it is determined that the open circuit abnormality is in the negative-side switch 34n (step S156), and the process proceeds to step S160. Through this process, it is possible to determine whether the open circuit abnormality is in the positive-side switch 34p or the negative-side switch 34n.

[0031] In the embodiment described above, the electric vehicle 10 is provided with a positive-side switch 34p and a negative-side switch 34n, but is not limited to this. For example, it may be provided with only either the positive-side switch 34p or the negative-side switch 34n.

[0032] In the embodiments described above, the electric vehicle 10 was provided with a battery 12, a motor 20, and first and second inverters 22 and 24, but it is not limited to this. For example, it may be a hybrid vehicle that further includes an engine in addition to the same hardware configuration as the electric vehicle 10, or a fuel cell vehicle that further includes a fuel cell in addition to the same hardware configuration as the electric vehicle 10.

[0033] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on the main elements of the embodiment and the means for solving the problem will be explained. In the embodiment, the battery 12 corresponds to the "energy storage device", the motor 20 corresponds to the "motor", the first inverter 22 corresponds to the "first inverter", the second inverter 24 corresponds to the "second inverter", the positive side switch 34p and the negative side switch 34n correspond to the "changeover switch", and the ECU 50 corresponds to the "control device". Furthermore, the positive side switch 34p corresponds to the "positive side switch", and the negative side switch 34n corresponds to the "negative side switch".

[0034] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0035] The above describes the forms for implementing this disclosure using embodiments, but this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0036] This disclosure can be used in industries such as electric vehicle manufacturing. [Explanation of Symbols]

[0037] 10 Electric vehicle, 12 Battery, 12i, 20u, 20v, 20w Current sensor, 12t Temperature sensor, 12v, 30v, 32v Voltage sensor, 20 Motor, 20a Rotation position sensor, 22 First inverter, 24 Second inverter, 28 Power line, 28n Negative side line, 28p Positive side line, 30 First capacitor, 32 Second capacitor, 34n Negative side switch, 34p Positive side switch, 50 ECU, 60 Power switch, 61 Shift lever, 62 Shift position sensor, 63 Accelerator pedal, 64 Accelerator pedal position sensor, 65 Brake pedal, 66 Brake pedal position sensor, 67 Vehicle speed sensor, D11~D16 Diode, T11~T16 Transistor.

Claims

1. Energy storage device, A motor for traction having a three-phase open winding, The first inverter is connected to the power line to which the energy storage device is connected and is also connected to one end of the three-phase open winding and has a first upper arm and a first lower arm. A second inverter is connected to the power line on the opposite side of the first inverter from the energy storage device and to the other end of the three-phase open winding, and has a second upper arm and a second lower arm. A changeover switch is provided between the first and second inverters in the aforementioned power line, A control device that controls the first and second inverters and the changeover switch, An electric vehicle equipped with, When the control device is in the ON state and the first and second inverters are being switched on, if it confirms that the absolute value of the zero-sequence current, which is the sum of the phase currents of each phase, is greater than or equal to a threshold, it determines that there is an opening abnormality in the changeover switch. Electric car.

2. The electric vehicle according to claim 1, When the control device detects an abnormal opening of the changeover switch, it turns on one of the second upper arm and the second lower arm and turns off the other, and switches the first inverter. Electric car.

3. An electric vehicle according to claim 1 or 2, The aforementioned changeover switch includes a positive-side switch provided between the first and second inverters on the positive-side line of the power line, and a negative-side switch provided between the first and second inverters on the negative-side line of the power line. When the control device detects an opening abnormality in the changeover switch, it determines which of the positive-side switch and the negative-side switch is experiencing the opening abnormality based on the sign of the zero-sequence current. Electric car.

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