electric vehicles

Abstract

This design enables external charging without requiring a dedicated step-down circuit for external charging, while also suppressing overcurrent flow when power supply from an external DC power source is initiated. [Solution] When the electric vehicle is connected to the charging connector and an external DC power supply, the changeover switch is in the off position and the first and second inverters are controlled so that power from the external DC power supply is supplied to the energy storage device via the second inverter, motor, and first inverter. Furthermore, when the charging connector and an external DC power supply are connected and the voltage of the energy storage device is below the allowable lower limit voltage of the external DC power supply, the changeover switch is in the off position and the first and second inverters are controlled so that the capacitor is pre-charged using power from the energy storage device, accompanied by voltage boosting by the motor and the second inverter, before the start of power supply from the external DC power supply.

Description

Technical Field

[0001] This disclosure relates to electric vehicles.

Background Art

[0002] Conventionally, an electric vehicle has been proposed that includes a power storage device, auxiliary component parts that operate at the system voltage of the power storage device, a DC inlet to which a voltage higher than the system voltage is applied from an external DC power source, and a step-down circuit that is connected to the power storage device and the DC inlet and steps down the power from the DC inlet to supply it to the power storage device (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 an electric vehicle, it is required to enable external charging without providing a dedicated step-down circuit for external charging, that is, a dedicated step-down circuit for charging the power storage device using the power from an external DC power source. Also, when the power supply from the external DC power source starts, if the voltage difference between the allowable lower limit voltage of the external DC power source and the voltage of the capacitor to which the voltage acts is large, there is a possibility that an overcurrent will flow through the path of the DC inlet (charging connector), capacitor, and charging connector. The main object of the electric vehicle of this disclosure is to enable external charging without providing a dedicated step-down circuit for external charging and to suppress the flow of overcurrent when the power supply from the external DC power source starts.

Means for Solving the Problems

[0005] The electric vehicle of this disclosure employs the following means to achieve the main objective described above. The electric vehicle of this disclosure comprises: an energy storage device; a driving motor having a three-phase open winding; a first inverter connected to a power line to which the energy storage device is connected and to one end of the three-phase open winding; a second inverter connected to the power line on the opposite side of the power line from the first inverter and to the other end of the three-phase open winding; a changeover switch provided between the first and second inverters of the power line; and a capacitor connected to the power line on the second inverter side of the changeover switch, wherein the electric vehicle comprises: a charging connector connected to the power line on the second inverter side of the changeover switch; and the charging connector The system includes a control device that controls the first and second inverters so that when an external DC power supply is connected, power from the external DC power supply is supplied to the energy storage device via the second inverter, the motor, and the first inverter while the changeover switch is in the off state. The control device controls the first and second inverters so that, when the charging connector is connected to the external DC power supply and the voltage of the energy storage device is below the allowable lower limit voltage of the external DC power supply, the capacitor is precharged using power from the energy storage device with voltage boosting by the motor and the second inverter, while the changeover switch is in the off state, before the start of power supply from the external DC power supply.

[0006] In the electric vehicle of this disclosure, when the charging connector and the external DC power supply are connected, the first and second inverters are controlled so that power from the external DC power supply is supplied to the energy storage device via the second inverter, motor, and first inverter with the changeover switch in the off position. This makes it possible to perform external charging without providing a dedicated step-down circuit for external charging, which is charging of the energy storage device using power from the external DC power supply. Furthermore, in the electric vehicle of this disclosure, when the charging connector and the external DC power supply are connected and the voltage of the energy storage device is below the allowable lower limit voltage of the external DC power supply, the first and second inverters are controlled so that, before the start of power supply from the external DC power supply, the capacitor is pre-charged using power from the energy storage device with voltage boosting by the motor and the second inverter, with the changeover switch in the off position. This makes it possible to suppress the flow of overcurrent in the charging connector, capacitor, and charging connector path when power supply from the external DC power supply is started. Furthermore, before starting power supply from an external DC power source, the changeover switch may be turned ON to precharge the capacitor using power from the energy storage device. If the voltage of the energy storage device is below the allowable lower limit voltage of the external DC power source, the changeover switch may be turned OFF to control the first and second inverters so that the capacitor is further precharged using power from the energy storage device, accompanied by voltage boosting by the motor and the second inverter. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of an electric vehicle and a charging station according to an embodiment of the present disclosure. [Figure 2] This is a flowchart showing an example of a processing routine. [Figure 3] This is an explanatory diagram showing the second pre-charge control process. [Modes for carrying out the invention]

[0008] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of an electric vehicle 10 and a charging station 80 according to an embodiment of this disclosure. As shown in the figure, the electric vehicle 10 of the embodiment includes a battery 12 (energy storage device), a motor 20, first and second inverters 22 and 24, power lines 28 (positive side line 28p and negative side line 28n), a first capacitor 30, a second capacitor 32 (capacitor), a changeover switch 34, a system main relay SMR, a charging connector 40, a charging relay 42, and a vehicle ECU 50 (control device).

[0009] The battery 12 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery with a rated voltage of several hundred volts and is connected to the power line 28. 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 wheel via a differential gear. 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. Transistors T11-T16 and T21-T26 can be, for example, MOSFETs or IGBTs. 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, and 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. Hereinafter, transistors T11-T13 and T21-T23 may be referred to as the "upper arm," and transistors T14-T16 and T24-T26 as the "lower arm." The first and second capacitors 30 and 32 are connected to the vicinity of the first and second inverters 22 and 24 of the power line 28, 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 changeover switch 34 is located between the first and second inverters 22 and 24 on the positive side line 28p. The changeover switch 34 can be, for example, a semiconductor switch or an isolated switch (relay).

[0010] The system main relay SMR is located between the battery 12 and the first capacitor 30 on the power line 28. Specifically, the system main relay SMR comprises a positive-side relay SMRB located on the positive-side line 28p, a negative-side relay SMRG located on the negative-side line 28n, and a pre-charge circuit in which a pre-charge relay SMRP and a resistor R are connected in series to bypass the negative-side relay SMRG. The charging connector 40 is connected to the second capacitor 32 side of the second inverter 24 on the power line 28 and is configured to be connectable to the stand connector 82 of the charging stand 80. The charging relay 42 is located between the second inverter 24 and the second capacitor 32 on the power line 28 and the charging connector 40.

[0011] The vehicle ECU 50 is equipped with a microcomputer, various drive circuits, and various logic ICs. Signals from various sensors are input to the vehicle ECU 50. For example, the vehicle ECU 50 receives the voltage Vb of the battery 12 from the voltage sensor 12V, the current Ib of the battery 12 from the current sensor 12i, the rotational position θm of the motor 20 rotor from the rotational position sensor 20a, the phase currents Iu, Iv, Iw of each phase of the motor 20 from the current sensors 20u, 20V, 20W, and the voltages VH, VL of the first and second capacitors 30, 32 from the voltage sensors 30V, 32V. Various control signals are output from the vehicle ECU 50. For example, the vehicle ECU 50 outputs control signals to the transistors T11-T16 and T21-T26 of the first and second inverters 22 and 24, the changeover switch 34, the system main relay SMR (positive side relay SMRB, negative side relay SMRG, pre-charge relay SMRP), and the charging relay 42. The vehicle ECU 50 calculates the charge level (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 rotational speed Nm of the motor 20 based on the rotational position θm of the rotor of the motor 20. The vehicle ECU 50 can communicate with the stand ECU 86 of the charging station 80.

[0012] The charging station 80 comprises a stand connector 82, a power supply device 84, and a stand ECU 86. The stand connector 82 is configured to be connectable to the charging connector 40 of the electric vehicle 10. The power supply device 84 is configured to convert AC power from the power grid or the like into DC power and to supply it to the stand connector 82 after adjusting the voltage and current. The stand ECU 86, like the vehicle ECU 50, is equipped with a microcomputer, various drive circuits, and various logic ICs. Signals from various sensors are input to the stand ECU 86. Control signals are output from the stand ECU 86 to the power supply device 84. As described above, the stand ECU 86 can communicate with the vehicle ECU 50.

[0013] In the electric vehicle 10 of this embodiment, when the vehicle ECU 50 receives an instruction to start external charging, which is charging of the battery 12 using power from the charging station 80, while the charging connector 40 and the stand connector 82 are connected, it executes the processing routine shown in Figure 2. At the start of this routine, the first and second inverters 22 and 24 are in a shut-down state (all transistors T11-T16 and T21-T26 are in the off state), and the changeover switch 34, positive side relay SMRB, negative side relay SMRG, pre-charge relay SMRP, and charging relay 42 are all in the off state.

[0014] When this routine is executed, the vehicle ECU 50 first performs the first pre-charge control (step S100). In the first pre-charge control, the changeover switch 34 is turned ON, and then the positive side relay SMRB and the pre-charge relay SMRP are turned ON. As a result, the inrush current to the first and second capacitors 30 and 32 is suppressed in the path from the battery 12, the positive side line 28p (including the positive side relay SMRB), the first and second capacitors 30 and 32, the negative side line 28n (including the pre-charge circuit), and the battery 12, while the first and second capacitors 30 and 32 are pre-charged in parallel. The first pre-charge control is terminated, for example, when the voltage Vb of the battery 12 and the voltages VH and VL of the first and second capacitors 30 and 32 become approximately equal (the difference becomes less than or equal to a threshold).

[0015] Next, voltage-current adjustment control is performed (step S110). In voltage-current adjustment control, the changeover switch 34 is turned off, the negative-side relay SMRG is turned on, and the pre-charge relay SMRP is turned off. The first and second inverters 22 and 24 are controlled so that the voltages VH and VL of the first and second capacitors become approximately equal and the phase currents Iu, Iv, and Iw of each phase of the motor 20 become approximately 0. Voltage-current adjustment control is terminated, for example, when the voltages VH and VL of the first and second capacitors become approximately equal (the deviation becomes below the threshold) and the phase currents Iu, Iv, and Iw of each phase of the motor 20 become approximately 0 (the absolute value becomes below the threshold). At this time, the changeover switch 34 is in the off state and the positive-side relay SMRB and the negative-side relay SMRG are in the on state.

[0016] Then, the voltage Vb of the battery 12 (voltage VL of the capacitor 32) is compared with the allowable lower limit voltage Vsmin of the charging station 80 (step S120). If the voltage Vb is greater than or equal to the allowable lower limit voltage Vsmin, external charging control is executed (step S140), and this routine is terminated. In the external charging control, the charging relay 42 is turned on, and the requested power is sequentially transmitted to the station ECU 86 to supply the requested power from the power supply device 84 to the vehicle. At the same time, the first and second inverters 22 and 24 are controlled so that the power from the power supply device 84 is supplied to the battery 12 via the second inverter 24, the motor 20, and the first inverter 22. The requested power is set, for example, based on the charge level SOC of the battery 12. In this way, external charging can be performed without providing a dedicated step-down circuit for external charging. External charging control is terminated, for example, when the charge level SOC of the battery 12 reaches a threshold Sref or when a predetermined time has elapsed since the instruction to start external charging. When external charging control is terminated, the first and second inverters 22 and 24, the changeover switch 34, the positive side relay SMRB, the negative side relay SMRG, the pre-charge relay SMRP, and the charging relay 42 are returned to their state at the start of this routine.

[0017] If the voltage Vb in step S120 is less than the allowable lower limit voltage Vsmin, the second precharge control is executed (step S130), followed by external charging control (step S140), and then this routine is terminated. Figure 3 is an explanatory diagram showing the second precharge control. In Figure 3, only the V-phase current is shown for the motor 20 and the first and second inverters 22 and 24, but the U-phase and W-phase are similar. As shown in the figure, in the second precharge control, the upper arm (transistors T11 to T13) of the first inverter 22 is turned ON and the lower arm (transistors T14 to T16) is turned OFF, and the second inverter 24 is switched on. As a result, the second capacitor 32 is precharged using power from the battery 12, accompanied by voltage boosting by the motor 20 and the second inverter 24. The second precharge control is terminated, for example, when the voltage VL of the capacitor 32 reaches or exceeds the allowable lower limit voltage Vsmin.

[0018] In the first pre-charge control described above, the voltage VL of the second capacitor 32 cannot be made higher than the voltage Vb1 of the battery 12. For this reason, if the voltage Vb (voltage VL) is less than the allowable lower limit voltage Vsmin, for example, when the voltage Vb is about 400V and the allowable lower limit voltage Vsmin is about 800V, if the second pre-charge control is not performed before the start of external charging control (before the start of power supply from the charging station 80), the voltage difference between the voltage VL at the start of power supply from the charging station 80 and the allowable lower limit voltage Vsmin is relatively large, and there is a possibility that an overcurrent will flow through the charging connector 40, the second capacitor 32, and the charging connector 40. In contrast, in this embodiment, by performing the second pre-charge control before the start of external charging control, the voltage difference between the voltage VL at the start of power supply from the charging station 80 and the allowable lower limit voltage Vsmin can be reduced, and the flow of an overcurrent through the charging connector 40, the second capacitor 32, and the charging connector 40 can be suppressed.

[0019] In the above-described embodiment, the electric vehicle 10 is configured to include the battery 12, the driving motor 20, the first and second inverters 22 and 24, the first and second capacitors 30 and 32, the changeover switch 34, the system main relay SMR, the charging connector 40, and the charging relay 42. However, the present disclosure is not limited thereto. For example, a configuration of a hybrid vehicle further including an engine in addition to the hardware configuration similar to that of the electric vehicle 10 may be adopted, or a configuration of a fuel cell vehicle further including a fuel cell in addition to the hardware configuration similar to that of the electric vehicle 10 may be adopted.

[0020] As described above, the embodiments for implementing the present disclosure have been described using the embodiments. However, the present disclosure is not limited to such embodiments, and it is needless to say that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure.

Industrial Applicability

[0021] The present disclosure can be used in the manufacturing industry of electric vehicles and the like.

Explanation of Reference Numerals

[0022] 10 Electric vehicle, 20 Motor, 22 First inverter, 24 Second inverter, 30 First capacitor, 32 Second capacitor, 34 Changeover switch, 40 Charging connector, 42 Charging relay, 50 Vehicle ECU.

Claims

[Claim 1] An electric vehicle comprising: a power storage device; a motor for driving having a three-phase open winding; a first inverter connected to a power line to which the power storage device is connected and also connected to one end of the three-phase open winding; a second inverter connected to the power line on the opposite side of the power line from the first inverter and also connected to the other end of the three-phase open winding; a changeover switch provided between the first and second inverters on the power line; and a capacitor connected to the power line on the second inverter side of the changeover switch, A charging connector connected to the second inverter side of the power line's changeover switch, A control device that controls the first and second inverters so that when the charging connector and the external DC power supply are connected, and the changeover switch is in the off state, power from the external DC power supply is supplied to the energy storage device via the second inverter, the motor, and the first inverter, Equipped with, The control device, when the charging connector and the external DC power supply are connected and the voltage of the energy storage device is below the allowable lower limit voltage of the external DC power supply, controls the first and second inverters so that, before the start of power supply from the external DC power supply, the capacitor is precharged using the power from the energy storage device with the motor and the second inverter boosting voltage, while the changeover switch is in the off state. Electric car.

Images