electric vehicles

Abstract

To prevent short-circuit current from flowing in a relay when connecting the relay to a neutral point of a three-phase AC motor.SOLUTION: A bypass relay is turned off and a neutral point relay is turned on to connect a DC charger to a neutral point of a three-phase AC motor and a negative electrode-side line of a power line. When the voltage of external DC power is risen to start charging a battery. the bypass relay is turned off in a state where a system main relay is turned off, and a pre-charge circuit of the system main relay is turned on in a state where the neutral point relay is turned on.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electric vehicle, and more particularly to an electric vehicle including a battery, a three-phase AC motor, and a DC charger that charges the battery using external DC power. [Background technology]

[0002] Conventionally, as this type of electric vehicle, an electric vehicle has been proposed that includes a battery, a three-phase AC motor, an inverter connected to the battery by a power line and using power from the battery to drive the three-phase AC motor, and a charger connected to the neutral point of the three-phase AC motor via a relay and using external power to charge the battery (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-205909 Summary of the Invention [Problem to be solved by the invention]

[0004] In an electric vehicle including a battery, a three-phase AC motor, and an inverter connected to the battery by a power line and using power from the battery to drive the three-phase AC motor, a charger may be provided that is connected to the negative side of the power line and the neutral point of the three-phase AC motor and that charges the battery by boosting DC power from an external power source using the inverter. In this case, it is necessary to turn on a relay for connecting to the neutral point of the three-phase AC motor, but if another component fails, a short-circuit current may flow through the relay, which may cause the relay to weld.

[0005] The electric vehicle of the present disclosure has a primary object to prevent a short-circuit current from flowing through a relay when the relay is connected to the neutral point of a three-phase AC motor. [Means for solving the problem]

[0006] The electric vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The electric vehicle of the present disclosure includes: An electric vehicle including: a battery; a three-phase AC motor; an inverter that drives the three-phase AC motor using power from the battery; a system main relay with a pre-charge function that is provided in a power line that connects the battery and the inverter; a DC charger that charges the battery using external DC power supplied from an external charging connector; and a control device, The DC charger includes a charging power line connected between the external charging connector and the inverter on the power line, a bypass relay attached to a positive side line of the charging power line, a neutral point charging line connecting a neutral point of the three-phase AC motor to the external charging connector on the positive side line of the charging power line and the bypass relay, a neutral point relay attached to the neutral point charging line, and a power line connected from the neutral point relay on the neutral point charging line to the external charging connector. a neutral point side interrupting circuit connected to the external charging connector side of the charging power line, a negative side interrupting circuit attached to the negative side line of the charging power line, a capacitor connected to the power line side of the negative side line of the charging power line from the negative side interrupting circuit and between the neutral point relay and the neutral point side interrupting circuit of the neutral point charging line, and a voltage sensor connected to the external charging connector side of the neutral point side interrupting circuit of the neutral point charging line and to the external charging connector side of the negative side line of the charging power line, the control device turns off the bypass relay with the system main relay turned off, and turns on a precharge circuit of the system main relay with the neutral point relay turned on at the start of neutral point charging, in which charging of the battery using the external DC power is started with the bypass relay turned off and the neutral point relay turned on; It is characterized by:

[0008] In the electric vehicle disclosed herein, when neutral point charging begins, the battery is charged using external DC power with the bypass relay turned off and the neutral point relay turned on. The system main relay is turned off, the bypass relay is turned off, and the neutral point relay is turned on, with the pre-charge circuit of the system main relay turned on. If there is no fault in the inverter or motor elements, no voltage acts on the capacitor, so no short-circuit current flows through the neutral point relay. On the other hand, if there is a fault in the inverter or motor elements, the capacitor voltage rises, but the pre-charge circuit prevents short-circuit current from flowing through the neutral point relay. As a result, it is possible to prevent short-circuit current from flowing through the neutral point relay, regardless of whether there is a fault in the inverter or motor elements.

[0009] In the electric vehicle of the present disclosure, when the voltage detected by the voltage sensor increases when the precharge circuit of the system main relay is turned on at the start of neutral point charging, the control device may determine that a fault has occurred in an element of the inverter or an element of the three-phase AC motor, and may prohibit charging of the battery using the external DC power. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an outline of the configuration of an electric vehicle 20 according to an embodiment of the present disclosure. [Figure 2] 4 is a flowchart showing an example of a boost charging start process executed by an electronic control unit 60. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, a mode (embodiment) for carrying out the present disclosure will be described. Fig. 1 is a configuration diagram showing an outline of the configuration of an electric vehicle 20 according to an embodiment of the present disclosure. The electric vehicle 20 of the embodiment includes a motor 22 for driving, an inverter 24 that drives the motor 22, a battery 26, a charger 40, and an electronic control unit 60.

[0012] The motor 22 is configured as a well-known synchronous generator-motor, for example, including a rotor with a permanent magnet attached to its outer surface and a stator around which a three-phase coil is wound. The inverter 24 is configured with six transistors T1-T6 and six diodes D1-D6 connected in parallel in the opposite directions to the transistors T1-T6. The transistors T1-T6 are arranged in pairs, two on the source side and two on the sink side of the positive and negative buses that the inverter 24 shares as a power line 30. Each of the three-phase coils (U-phase, V-phase, and W-phase) of the motor 22 is connected to each of the junctions between the paired transistors. Therefore, by controlling the proportion of the on-time of the paired transistors T1-T6 when a voltage is applied between the positive and negative buses, a rotating magnetic field can be generated in the three-phase coils, thereby driving the motor 22 to rotate. A smoothing capacitor 34 is connected to the power line 30.

[0013] Battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to power line 30. A system main relay 28 is attached to power line 30. System main relay 28 has a positive relay SMRB provided on the positive line of power line 30, a negative relay SMRG provided on the negative line of power line 30, and a precharge circuit in which a precharge resistor R and a precharge relay SMRP are connected in series to bypass the negative relay SMRG. A filter 32 that removes noise is also attached to power line 30.

[0014] The charger 40 includes an external charging connector 42 that connects to an external power source, a charging power line 43 (positive side line 44 and negative side line 45) that is connected to the external charging connector 42 and is connected between the system main relay 28 and the inverter 24 of the power line 30 (between the filter 32 and the inverter 24 in FIG. 1 ), and a neutral point charging line 50 that is connected to the positive side line 44 of the charging power line 43 and the neutral point of the motor 22.

[0015] A charging relay 48 and a noise filter 49 including a smoothing capacitor are attached to the charging power line 43, in this order from the external charging connector 42 side. The charging relay 48 has a positive relay CHRB provided on a positive line 44 of the charging power line 43 and a negative relay CHRG provided on a negative line 45 of the charging power line 43. A bypass relay 46 is attached to the positive line 44 of the charging power line 43. A negative cutoff circuit 47 is attached to the negative line 45 of the charging power line 43. The negative cutoff circuit 47 is configured to connect in parallel a diode whose forward direction is from the battery 26 to the external charging connector 42, a transistor as a switching element, and a varistor.

[0016] A neutral point relay 51 and a neutral point side shutoff circuit 52 are attached to the neutral point charging line 50, in this order from the motor 22 side. Similar to the negative side shutoff circuit 47, the neutral point side shutoff circuit 52 is configured by connecting in parallel a diode whose forward direction is from the battery 26 to the external charging connector 42, a transistor as a switching element, and a varistor.

[0017] Terminals of a capacitor 53 are connected between the neutral point relay 51 and the neutral point side interrupting circuit 52 of the neutral point charging line 50, and to the battery 26 side of the negative side interrupting circuit 47 of the negative side line 45 of the charging power line 43. A voltage sensor 54 that detects the voltage between the neutral point charging line 50 and the negative side line 45 is connected to the external charging connector 42 side of the neutral point side interrupting circuit 52 of the neutral point charging line 50, and to the external charging connector 42 side of the negative side interrupting circuit 47 of the negative side line 45 of the charging power line 43. A leakage detection circuit 55 that detects leakage current is also attached to the neutral point charging line 50 and the negative side line 45.

[0018] Although not shown, the electronic control unit 60 is configured as a microprocessor centered on a CPU. In addition to the CPU, the electronic control unit 60 includes a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory, input / output ports, and communication ports. Signals from various sensors are input to the electronic control unit 60 via the input ports. Examples of signals input to the electronic control unit 60 include the rotational position θm from a rotational position detection sensor (e.g., a resolver) 23 that detects the rotational position of the rotor of the motor 22, phase currents flowing through the three-phase coils (U-phase, V-phase, and W-phase) of the motor 22, a voltage VL from a voltage sensor 54 provided in the charger 40, and a detection signal from a leakage detection circuit 55. The electronic control unit 60 is also connected to a communication line for communicating with an external DC power supply via the external charging connector 42. The electronic control unit 60 also functions as a control device for the electric vehicle 20, and therefore also receives inputs such as a shift position, accelerator position, and brake position.

[0019] Various control signals are output via output ports from the electronic control unit 60. Examples of signals output from the electronic control unit 60 include a switching control signal to the transistors T1 to T6 of the inverter 24, a drive control signal to the system main relay 28, a drive control signal to the charging relay 48, a drive control signal to the bypass relay 46, a drive control signal to the neutral point relay 51, a drive control signal to the negative pole side shutoff circuit 47, and a drive control signal to the neutral point side shutoff circuit 52.

[0020] When an external DC power supply is connected to the external charging connector 42 of the charger 40, the electronic control unit 60 inputs the voltage Vd of DC power supplied by the external DC power supply (external DC voltage Vd), and when the external DC voltage Vd is higher than the voltage Vb of the battery 26, the electronic control unit 60 charges the battery 26 by normal charging using the charger 40. When the external DC voltage Vd is lower than the voltage Vb of the battery 26, the electronic control unit 60 charges the battery 26 by boost charging using the charger 40. In normal charging, the bypass relay 46 is turned on, the neutral point relay 51 is turned off, and the system main relay 28 is turned on, and the battery 26 is charged using the positive line 44 and negative line 45 of the charging power line 43. In boost charging, the bypass relay 46 is turned off, the neutral point relay 51 is turned on, and the system main relay 28 is turned on, and the battery 26 is charged using the neutral point charging line 50 and the negative line 45 of the charging power line 43. In this boost charging, the combination of the three-phase coils (U phase, V phase, W phase) of the motor 22 and each phase of the inverter 24 functions as a boost circuit by switching the transistors T1 to T6 of the inverter 24, thereby boosting the voltage of the external DC power and charging the battery 26.

[0021] Next, a description will be given of the operation of the electric vehicle 20 configured as described above, in particular the operation when starting boost charging by the charger 40. FIG.

[0022] When the boost charging start process is executed, the electronic control unit 60 first verifies that the voltage Vb of the battery 26 is higher than the voltage (external DC voltage) Vd supplied from the external DC power supply (step S100). If this confirmation cannot be made, it is determined that boost charging is not in progress, and this process ends. On the other hand, if this confirmation is made, the neutral point relay 51 is turned on (step S110), and then the positive side relay SMRB and the precharge relay SMRP of the system main relay 28 are turned on (step S120). Now, consider a case where a continuity fault occurs in an element of the inverter 24 or the motor 22. If the positive side relay SMRB and the negative side relay SMRG of the system main relay 28 are turned on after the neutral point relay 51 is turned on, or if the positive side relay SMRB and the negative side relay SMRG of the system main relay 28 are turned on after the positive side relay SMRB and the negative side relay SMRG of the system main relay 28 are turned on, there is a concern that a short-circuit current will flow through the neutral point relay 51 or the capacitor 53, causing a welding fault in the neutral point relay 51. In order to prevent such a welding failure of the neutral point relay 51, the positive side relay SMRB and pre-charge relay SMRP of the system main relay 28 are turned on after the neutral point relay 51 is turned on. By operating the relays in this manner, even if a continuity failure occurs in the elements of the inverter 24 or motor 22, it is possible to prevent a short-circuit current from flowing through the neutral point relay 51 or capacitor 53 and causing a welding failure of the neutral point relay 51.

[0023] Next, it is determined whether the neutral point voltage Vc has increased based on the voltage Vc (neutral point voltage) detected by the voltage sensor 54 (step S130). When a continuity fault occurs in the elements of the inverter 24 or motor 22, current flows through the neutral point relay 51 or capacitor 53, causing the neutral point voltage Vc to increase. When a continuity fault does not occur in the elements of the inverter 24 or motor 22, no current flows through the neutral point relay 51 or capacitor 53, causing the neutral point voltage Vc to not increase. If it is determined that the neutral point voltage Vc has not increased, it is determined that no continuity fault has occurred in the elements of the inverter 24 or motor 22, and boost charging is initiated (step S140), and this process ends. On the other hand, if it is determined that the neutral point voltage Vc has increased, it is determined that a continuity fault has occurred in the elements of the inverter 24 or motor 22, and boost charging is prohibited (step S150), and this process ends.

[0024] In the electric vehicle 20 according to the embodiment described above, when the charger 40 starts charging the battery 26 by boost charging, the neutral point relay 51 is turned on, and then the positive-side relay SMRB and pre-charge relay SMRP of the system main relay 28 are turned on. This prevents a short-circuit current from flowing through the neutral point relay 51 or the capacitor 53, which could cause a welding failure in the neutral point relay 51, even if a continuity failure occurs in the elements of the inverter 24 or the motor 22. Furthermore, with the positive-side relay SMRB and pre-charge relay SMRP of the system main relay 28 turned on after the neutral point relay 51 is turned on, boost charging is started if the neutral point voltage Vc has not risen, and if the neutral point voltage Vc has risen, a continuity failure is determined to have occurred in the elements of the inverter 24 or the motor 22, and boost charging is prohibited. This allows boost charging by the charger 40 to be performed more appropriately.

[0025] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problems" section will be described below. In the embodiment, the battery 26 corresponds to the "battery," the motor 22 corresponds to the "three-phase AC motor," the inverter 24 corresponds to the "inverter," the system main relay 28 corresponds to the "system main relay," the external charging connector 42 corresponds to the "external charging connector," the charger 40 corresponds to the "DC charger," and the electronic control unit 60 corresponds to the "control device." Furthermore, the power line 30 corresponds to the "power line", the charging power line 43 corresponds to the "charging power line", the bypass relay 46 corresponds to the "bypass relay", the neutral point charging line 50 corresponds to the "neutral point charging line", the neutral point relay 51 corresponds to the "neutral point relay", the neutral point side shut-off circuit 52 corresponds to the "neutral point side shut-off circuit", the negative side shut-off circuit 47 corresponds to the "negative side shut-off circuit", the capacitor 53 corresponds to the "capacitor", and the voltage sensor 54 corresponds to the "voltage sensor".

[0026] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, because the embodiments are examples for specifically explaining the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0027] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be embodied in various forms without departing from the spirit of the present disclosure. [Industrial Applicability]

[0028] The present disclosure is applicable to the electric vehicle manufacturing industry and the like. [Explanation of symbols]

[0029] 20 electric vehicle, 22 motor, 24 inverter, 26 battery, 28 system main relay, 30 power line, 32 filter, 34 capacitor, 40 charger, 42 external charging connector, 43 charging power line, 44 positive side line, 45 negative side line, 46 bypass relay, 47 negative side cutoff circuit, 48 charging relay, 49 filter, 50 neutral point charging line, 51 neutral point relay, 52 neutral point side cutoff circuit, 53 capacitor, 54 voltage sensor, 55 leakage detection circuit, 60 electronic control unit, CHRB positive side relay, CHRG negative side relay, SMRB positive side relay, SMRG negative side relay, SMRP precharge relay, R precharge resistor.

Claims

1. An electric vehicle including: a battery; a three-phase AC motor; an inverter that drives the three-phase AC motor using power from the battery; a system main relay with a pre-charge function that is provided in a power line that connects the battery and the inverter; a DC charger that charges the battery using external DC power supplied from an external charging connector; and a control device, The DC charger includes a charging power line connected between the external charging connector and the inverter on the power line, a bypass relay attached to a positive side line of the charging power line, a neutral point charging line connecting a neutral point of the three-phase AC motor to the external charging connector on the positive side line of the charging power line and the bypass relay, a neutral point relay attached to the neutral point charging line, and a power line connected from the neutral point relay on the neutral point charging line to the external charging connector. a neutral point side interrupting circuit connected to the external charging connector side of the charging power line, a negative side interrupting circuit attached to the negative side line of the charging power line, a capacitor connected to the power line side of the negative side line of the charging power line from the negative side interrupting circuit and between the neutral point relay and the neutral point side interrupting circuit of the neutral point charging line, and a voltage sensor connected to the external charging connector side of the neutral point side interrupting circuit of the neutral point charging line and to the external charging connector side of the negative side line of the charging power line, the control device turns off the bypass relay with the system main relay turned off, and turns on a precharge circuit of the system main relay with the neutral point relay turned on at the start of neutral point charging, in which charging of the battery using the external DC power is started with the bypass relay turned off and the neutral point relay turned on; An electric vehicle characterized by:

2. The electric vehicle according to claim 1, When the voltage detected by the voltage sensor increases when the precharge circuit of the system main relay is turned on at the start of the neutral point charging, the control device determines that a fault has occurred in an element of the inverter or an element of the three-phase AC motor. Electric car.

3. The electric vehicle according to claim 1, the control device prohibits charging of the battery using the external DC power if the voltage detected by the voltage sensor increases when a precharge circuit of the system main relay is turned on at the start of the neutral point charging. Electric car.

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