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 first 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 first 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 bidirectional converter is controlled so that the capacitor is pre-charged by boosting the voltage using power from the second energy storage device via the bidirectional converter 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 a power storage device using 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 this voltage is applied 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: a first energy storage device; a driving motor having a three-phase open winding; a first inverter connected to a power line to which the first 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 on the power line; and a capacitor connected to the power line on the second inverter side of the changeover switch, wherein the electric vehicle further comprises: a charging connector connected to the power line on the second inverter side of the changeover switch; a second energy storage device having a lower rated voltage than the first energy storage device; and the second inverter and second capacitor on the second power line. The system comprises a bidirectional converter connected between the charging connector and the charging relay and also connected to the second energy storage device, and a control device that controls the first and second inverters so that when the changeover switch is off, power from the external DC power supply is supplied to the first energy storage device via the second inverter, the motor, and the first inverter when the charging connector and the external DC power supply are connected and the changeover switch is off. The gist of the control device is that, when the charging connector and the external DC power supply are connected and the voltage of the first energy storage device is below the allowable lower limit voltage of the external DC power supply, the bidirectional converter is controlled so that, before the start of power supply from the external DC power supply, the capacitor is pre-charged with voltage boosting by the bidirectional converter using power from the second energy storage device with the changeover switch off. With this configuration, external charging can be performed without providing a dedicated step-down circuit for external charging, which is charging of the first energy storage device using power from the external DC power supply. In addition, it is possible to suppress the flow of overcurrent in the path of the charging connector, capacitor, and charging connector when power supply from the external DC power supply is started. [Brief explanation of the drawing]

[0006] [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]

[0007] 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 (first 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, a relay 44, an auxiliary battery 50 (second energy storage device), power lines 52, 54, and 56, a bidirectional DC / DC converter 58 (bidirectional converter), relays 60 and 62, an AC charger 64, and a vehicle ECU 50 (control device).

[0008] The main battery 12 is configured as, for example, a lithium-ion secondary battery or 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 MOSFETs or IGBTs, for example. 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.

[0009] 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. The relay 44 is located between the second inverter 24 and the second capacitor 32 on the power line 28 and the charging relay 42.

[0010] The auxiliary battery 50 is configured as, for example, a lithium-ion secondary battery or lead-acid battery with a rated voltage of about 12V, and is connected to power line 52. Power line 54 is connected to the main battery 12 side of the system main relay SMR of power line 28. Power line 56 is connected between the charging relay 42 and relay 44 of power line 28. The bidirectional DC / DC converter 58 is connected to power lines 52, 54, and 56, and is configured to exchange power with voltage conversion between power line 52 and one of the selected power lines 54 or 56. Relays 60 and 62 are provided on power lines 54 and 56, respectively. The AC charger 64 is connected to the bidirectional DC / DC converter 58 side of relay 60 on power line 54 and to the bidirectional DC / DC converter 58 side of relay 62 on power line 56. This AC charger 64 is configured to convert the AC power in the power line 56 into DC power and convert the voltage, and supply it to the power line 54, when the charging connector 42 is connected to an external AC power source and the charging relay 42 and relays 60 and 62 are ON.

[0011] The vehicle ECU 70 is equipped with a microcomputer, various drive circuits, and various logic ICs. Signals from various sensors are input to the vehicle ECU 70. For example, the vehicle ECU 70 receives the voltage Vb1 of the main battery 12 from the voltage sensor 12V, the current Ib of the main 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, the voltages VH, VL of the first and second capacitors 30, 32 from the voltage sensors 30V, 32V, and the voltage Vb2 of the auxiliary battery 50 from the voltage sensor 50a. Various control signals are output from the vehicle ECU 70. For example, the vehicle ECU 70 outputs control signals to the transistors T11-T16, 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), the charging relay 42, relays 44, 60, and 62, the bidirectional DC / DC converter 58, and the AC charger 64. The vehicle ECU 70 calculates the charge level (SOC) of the main battery 12 based on the integrated value of the current Ib of the main 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 70 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 70, 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 70.

[0013] In the electric vehicle 10 of this embodiment, when the vehicle ECU 50 receives an instruction to start external charging, which is charging the main 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 off), the changeover switch 34, the positive side relay SMRB, the negative side relay SMRG, the pre-charge relay SMRP, the charging relay 42, and relays 44 and 62 are all off, and the AC charger 64 is stopped. Basically, relay 60 is off and the bidirectional DC / DC converter 58 is stopped, but relay 60 is turned on as needed, and the bidirectional DC / DC converter 58 exchanges power between power lines 52 and 54 with voltage conversion.

[0014] When this routine is executed, the vehicle ECU 50 first compares the voltage Vb of the battery 12 with the allowable lower limit voltage Vsmin of the charging station 80 (step S100). If the voltage Vb is greater than or equal to the allowable lower limit voltage Vsmin, the first pre-charge control is executed (step S110). 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 first and second capacitors 30 and 32 are pre-charged in parallel using power from the main battery 12 while suppressing the inrush current to the first and second capacitors 30 and 32. 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 reaches the threshold). When the first pre-charge control is terminated, the changeover switch 34 is turned off, the negative side relay SMRG is turned on, and the pre-charge relay SMRP is turned off. Next, external charging control is performed (step S130), and this routine is terminated. In the external charging control, the charging relays 42 and 44 are turned on, and the requested power is sequentially transmitted to the stand 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 state of charge (SOC) of the battery 12. In this way, external charging can be performed without providing a dedicated step-down circuit for external charging. The external charging control is terminated, for example, when the state of charge (SOC) of the battery 12 reaches a threshold Sref or above, or when a predetermined time has elapsed since the instruction to start external charging. When the external charging control is terminated, the first and second inverters 22 and 24, the changeover switch 34, etc. are returned to the state they were in when this routine started.

[0015] If the voltage Vb in step S100 is less than the allowable lower limit voltage Vsmin, the second precharge control is executed (step S120), followed by the execution of external charge control (step S130), and then the routine is terminated. Figure 3 is an explanatory diagram showing the second precharge control. As shown in the figure, the second precharge control turns on the positive side relay SMRB, the precharge relay SMRP, and relays 44 and 62, and controls the bidirectional DC / DC converter 58 so that power is supplied from power line 52 to power line 56 with voltage conversion. As a result, the first capacitor 30 is precharged using power from the main battery 12, and the second capacitor 32 is precharged using power from the auxiliary battery 50 with voltage boosting by the bidirectional DC / DC converter 58. The second precharge control is terminated, for example, when the voltage Vb of battery 12 and the voltage VH of the first capacitor 30 become approximately equal and the voltage VL of the second capacitor 32 reaches or exceeds the allowable lower limit voltage Vsmin. When the second pre-charge control is completed, the negative electrode relay SMRG is turned ON, and the pre-charge relay SMRP and relay 62 are turned OFF. 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 main 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 a 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, thereby suppressing the flow of overcurrent through the charging connector 40, the second capacitor 32, and the charging connector 40.

[0016] In the embodiment described above, the electric vehicle 10 is configured to include a battery 12, a driving motor 20, first and second inverters 22 and 24, first and second capacitors 30 and 32, a changeover switch 34, a system main relay SMR, a charging connector 40, and a charging relay 42, but is not limited to this. For example, a hybrid vehicle configuration may be provided, which further includes an engine in addition to the same hardware configuration as the electric vehicle 10, or a fuel cell vehicle configuration may be provided, which further includes a fuel cell in addition to the same hardware configuration as the electric vehicle 10.

[0017] 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]

[0018] This disclosure can be used in industries such as electric vehicle manufacturing. [Explanation of Symbols]

[0019] 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 Auxiliary battery, 58 Bidirectional DC / DC converter, 70 Vehicle ECU.

Claims

[Claim 1] An electric vehicle comprising: a first energy storage device; a motor for driving having a three-phase open winding; a first inverter connected to a power line to which the first energy 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 side of the changeover switch that is closer to the second inverter, The system comprises a charging connector connected to the second inverter side of the power line beyond the changeover switch, a second energy storage device having a lower rated voltage than the first energy storage device, a bidirectional converter connected between the second inverter and the second capacitor of the second power line and the charging relay, and also connected to the second energy storage device, and a control device that controls the first and second inverters so that when the charging connector is connected to an external DC power supply and the changeover switch is off, power from the external DC power supply is supplied to the first energy storage device via the second inverter, the motor, and the first inverter. The control device, when the charging connector and the external DC power supply are connected and the voltage of the first energy storage device is below the allowable lower limit voltage of the external DC power supply, controls the bidirectional converter so that, before the start of power supply from the external DC power supply, the capacitor is precharged using power from the second energy storage device with voltage boosting by the bidirectional converter while the changeover switch is in the off state. Electric car.

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