Electric vehicle and charging control method for electric vehicle

Abstract

The present disclosure relates to an electric vehicle and a charging control method for an electric vehicle. An output voltage acquisition unit (701) receives information from an external charging device (80) and acquires the maximum output voltage (Vc) of the external charging device (80) based on this information. An upper limit voltage calculation unit (402) calculates a battery voltage (VBu) that is the voltage between terminals when charging of the battery (10) ends. A switching unit (704) receives a comparison result from a comparison unit (704). When Vc ≥ VBu in the comparison result, the switching unit (704) switches a charging relay (30) to connect a DC connection port to a power line (La) and a power line (Na). When Vc < VBu, the switching unit (704) switches the charging relay (30) to connect the DC connection port to a bypass power line (Lb) and a bypass power line (Nb).

Description

Technical Field

[0001] The present disclosure relates to an electric vehicle, and more particularly to an electric vehicle including a power storage device that can be charged by an external power supply, and a charging control method for the electric vehicle. Background Art

[0002] In recent years, electric vehicles, such as electric vehicles and plug-in hybrid vehicles, have become increasingly popular. These vehicles are equipped with a power storage device that can be charged using electricity supplied from an external power source. Hereinafter, charging a power storage device using electricity supplied from an external power source will also be referred to as "external charging."

[0003] For example, Japanese Patent Application Laid-Open No. 2019-047677 discloses that a power storage device is charged using a boost device based on the highest voltage output from an external charger (charging station, etc.) as an external power source.

[0004] The electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2019-047677 is equipped with an ultra-high voltage (e.g., 800V) power storage device. The maximum voltage Vmax of the power output from the charging station is compared with a predetermined reference voltage Vref. If the maximum voltage Vmax is below the reference voltage Vref, the external charging mode is set to high-voltage charging mode. If the maximum voltage Vmax is higher than the reference voltage Vref, the external charging mode is set to ultra-high-voltage charging mode.

[0005] When the external charging mode is high-voltage charging mode, the high voltage supplied from the charging station is boosted to an ultra-high voltage (800V) by the booster. The power storage device is charged using the power at the boosted voltage. When the external charging mode is ultra-high-voltage charging mode, the power supplied from the charging station is at an ultra-high voltage (800V) and is not boosted by the booster. The power storage device is charged using the power at the unboosted voltage.

[0006] The inter-terminal voltage of a power storage device mounted on an electric vehicle fluctuates depending on the SOC (State of Charge) of the power storage device. Typically, as the SOC decreases, the inter-terminal voltage decreases. In the electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2019-047677, the reference voltage Vref is a fixed value (e.g., 500V). Therefore, when the inter-terminal voltage is lower than the reference voltage Vref due to the low SOC of the power storage device, but the maximum voltage Vmax at the charging station is lower than the reference voltage Vref, a high-voltage charging mode is set. The power storage device is then charged using the power of the voltage boosted by the boost device. As such, in the electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2019-047677, the boost device is operated even when the power storage device can be charged without the boost device. Furthermore, the power storage device can be charged using the power of the boosted voltage. The boosting operation of the boost device is accompanied by power loss, so if the power storage device is charged while the boost device is operating, the charging efficiency will decrease. Summary of the Invention

[0007] The present disclosure has been made to solve the above-mentioned problem, and an object of the present disclosure is to perform external charging while suppressing a decrease in charging efficiency in an electric vehicle including a power storage device that can be charged by an external power supply.

[0008] The electric vehicle disclosed herein is an electric vehicle provided with a power storage device that can be charged using electric power supplied from an external power source. The electric vehicle includes a boost device, a bypass path, and a control device. The boost device boosts the voltage of the electric power supplied from the external power source, and supplies the electric power of the boosted voltage to the power storage device. The bypass path is configured to bypass the boost device, and is configured to supply the electric power supplied from the external power source to the power storage device instead of the boost device. The control device controls the charging of the power storage device. The control device is configured to charge the power storage device using the boost device when the maximum voltage of the electric power supplied from the external power source is lower than the voltage between the terminals of the power storage device at the end of charging of the power storage device, and to charge the power storage device using the bypass path when the maximum voltage is higher than the voltage between the terminals at the end of charging.

[0009] With this configuration, the maximum voltage of the power supplied from the external power supply is higher than the inter-terminal voltage at the completion of charging of the power storage device. Therefore, when charging of the power storage device is possible without operating the boost device, the power storage device is charged using the bypass path. This allows charging of the power storage device without incurring losses due to the boost device, thus minimizing a decrease in charging efficiency.

[0010] Preferably, the control device is configured to charge the power storage device using the boost device when the power storage device is charged using the bypass path and the maximum voltage drops below the inter-terminal voltage of the power storage device.

[0011] The maximum voltage is higher than the inter-terminal voltage at the end of charging. Therefore, if the maximum voltage falls below the inter-terminal voltage due to fluctuations in the inter-terminal voltage during charging of the power storage device without the booster, charging will not proceed. With this configuration, when charging the power storage device without the booster, if the maximum voltage of the power supplied from the external power source falls below the inter-terminal voltage of the power storage device, making it impossible to avoid charging, the booster operates. Thus, the power storage device is charged using power at the voltage boosted by the booster. As a result, the power storage device can be reliably charged.

[0012] Preferably, the control device is configured to charge the power storage device using the bypass path when the maximum voltage is lower than the inter-terminal voltage at the end of charging and the difference between the maximum voltage and the inter-terminal voltage at the end of charging is smaller than a first predetermined value.

[0013] If the boost device is operating, charging efficiency may decrease due to power loss associated with the boost device's operation, potentially extending charging time. Even if the maximum voltage of the power supplied from the external power supply is lower than the inter-terminal voltage of the power storage device at the end of charging, if the difference between the maximum voltage and the inter-terminal voltage at the end of charging is less than a first predetermined value, charging is performed without using the boost device. This results in a reduction in charging time.

[0014] Preferably, the control device is configured to charge the power storage device using the boost device when the maximum voltage is higher than the inter-terminal voltage at the end of charging and the difference between the maximum voltage and the inter-terminal voltage at the end of charging is smaller than a second predetermined value.

[0015] If the maximum voltage is higher than the inter-terminal voltage at the end of charging and the power storage device is charged without a booster, and the maximum voltage falls below the inter-terminal voltage due to fluctuations in the inter-terminal voltage, charging may become impossible, the initially scheduled charging time after starting charging using the booster may be extended, or charging may become unstable. Even if the maximum voltage is higher than the inter-terminal voltage at the end of charging, if the difference between the maximum voltage and the inter-terminal voltage at the end of charging is less than a second predetermined value, the power storage device is charged using the booster. This reduces the frequency with which the charging voltage falls below the inter-terminal voltage. As a result, stable charging can be facilitated.

[0016] Preferably, the external power source is an external charging device that supplies DC power to the electric vehicle. The electric vehicle charging relay is configured to selectively switch the path of the DC power supplied from the external charging device to a path for supplying DC power to the boost device or a bypass path. The control device includes an output voltage acquisition unit, an upper limit voltage calculation unit, a comparison unit, and a switching unit. The output voltage acquisition unit acquires the maximum voltage of the power supplied from the external power source based on information received from the external charging device. The upper limit voltage calculation unit calculates the voltage between the terminals of the storage device at the end of charging of the storage device based on the SOC of the storage device. The comparison unit compares the magnitude of the maximum voltage with the magnitude of the voltage between the terminals at the end of charging. The switching unit switches the charging relay according to the comparison result of the comparison unit.

[0017] With this configuration, the charging relay is switched based on the result of a comparison between the maximum voltage obtained based on information received from the external charging facility and the inter-terminal voltage at the end of charging, which is determined based on the SOC of the power storage device at the end of charging. This allows the power storage device to be charged without incurring losses in the booster device. Consequently, a decrease in charging efficiency can be minimized.

[0018] The charging control method disclosed herein is a charging control method for an electric vehicle. The electric vehicle includes a power storage device and a boost device. The power storage device is configured to be charged using an external power supply provided outside the electric vehicle. The boost device boosts the voltage of the power supplied from the external power supply and supplies the power of the boosted voltage to the power storage device. The charging control method includes the following steps: comparing the maximum voltage of the power supplied from the external power supply with the terminal voltage of the power storage device at the end of charging of the power storage device; when the maximum voltage is lower than the terminal voltage at the end of charging, operating the boost device to charge the power storage device; and when the maximum voltage is higher than the terminal voltage at the end of charging, not operating the boost device to charge the power storage device.

[0019] According to this charging control method, when the maximum voltage of the power supplied from the external power supply is higher than the inter-terminal voltage at the end of charging of the power storage device, and the power storage device can be charged even without using a booster, the power storage device is charged using the bypass path. This allows the power storage device to be charged without losses caused by the booster. As a result, a decrease in charging efficiency can be suppressed.

[0020] Preferably, the charging control method further includes the step of calculating the inter-terminal voltage at the end of charging based on the SOC of the power storage device at the end of charging.

[0021] The charge level of the power storage device can be freely set based on, for example, the charging time, the amount of charging power, and the SOC at completion of charging. The terminal voltage of the power storage device at the completion of charging is determined by the SOC at the completion of charging. Therefore, by determining the SOC at the completion of charging based on information such as the charging time, the amount of charging power, and the SOC at the completion of charging, the terminal voltage at the completion of charging can be calculated.

[0022] The foregoing and other objects, features, aspects and advantages of the disclosure will become more apparent from the following detailed description of the disclosure when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 1 is a diagram showing the overall structure of an electric vehicle according to this embodiment.

[0024] Figure 2 This is a diagram showing the flow of charging power when the maximum output voltage Vc is lower than the battery voltage VBu.

[0025] Figure 3 This is a diagram showing the flow of charging power when the maximum output voltage Vc is higher than the battery voltage VBu.

[0026] Figure 4 This is a diagram showing functional blocks configured within the ECU 70 .

[0027] Figure 5 This is a flowchart schematically showing the processing executed by the ECU 70 .

[0028] Figure 6 This is a flowchart schematically showing the processing executed by the ECU 70 in the first modification.

[0029] Figure 7 This is a flowchart schematically showing the processing executed by the ECU 70 in the second modification.

[0030] Figure 8 This is a flowchart schematically showing the processing executed by the ECU 70 in the third modification.

[0031] Figure 9 This is a diagram showing another configuration example of a charging relay. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0033] Figure 1This is a diagram showing the overall structure of an electric vehicle according to this embodiment. In this embodiment, electric vehicle 100 is, for example, an electric vehicle. Electric vehicle 100 includes a power control unit (PCU) 1, a motor generator (MG) 2 serving as a rotating electrical machine, a power transmission gear 3, drive wheels 4, a battery 10 serving as an example of a power storage device, a monitoring unit 11, a system main relay (SMR) 40, and an electronic control unit (ECU) 70 serving as an example of a control device.

[0034] MG2 is, for example, an embedded permanent magnet synchronous motor (IPM motor) and functions as both an electric motor and a generator. Output torque of MG2 is transmitted to drive wheels 4 via a power transmission gear 3 including a speed reducer and a differential.

[0035] When electric vehicle 100 brakes, MG2 is driven by drive wheels 4, and MG2 operates as a generator. Consequently, MG2 also functions as a braking device that performs regenerative braking, converting kinetic energy of electric vehicle 100 into electricity. Regenerative power generated by the regenerative braking force of MG2 is stored in battery 10.

[0036] The PCU 1 is a power conversion device that converts electric power bidirectionally between the MG 2 and the battery 10. The PCU 1 includes, for example, an inverter and a converter that operate based on control signals from the ECU 70.

[0037] The converter boosts the voltage supplied from battery 10 during discharge of battery 10 and supplies the boosted voltage to the inverter. The inverter converts the DC power supplied from the converter into AC power and drives MG2 using the converted power.

[0038] On the other hand, when charging battery 10, the inverter converts the AC power generated by MG2 into DC power and supplies the converted power to the converter. The converter steps down the voltage supplied from the inverter to a voltage suitable for charging battery 10 and supplies the stepped-down voltage to battery 10.

[0039] The PCU 1 stops charging and discharging by stopping the operation of the inverter and the converter based on a control signal from the ECU 70. The converter may be omitted from the PCU 1.

[0040] SMR 40 is electrically connected to power lines PL and PN. Power lines PL and PN connect battery 10 and PCU 1. When SMR 40 is closed (ON) (i.e., in the conductive state) in response to a control signal from ECU 70, power can be transmitted and received between battery 10 and PCU 1. On the other hand, when SMR 40 is opened (OFF) (i.e., in the disconnected state) in response to a control signal from ECU 70, the electrical connection between battery 10 and PCU 1 is severed. When externally charging battery 10, SMR 40 is closed (ON) in response to a signal from ECU 70.

[0041] Battery 10 stores electricity for driving MG2. Battery 10 is a rechargeable DC power source (secondary battery). Battery 10 comprises a plurality of stacked cells (battery cells), for example, electrically connected in series. The cells can be lithium-ion batteries or nickel-metal hydride batteries. Battery 10 can also be replaced by a power storage device such as an electric double-layer capacitor.

[0042] Monitoring unit 11 includes a voltage sensor, a current sensor, and a temperature sensor (none of which are shown). The voltage sensor detects voltage VB across the terminals of battery 10. The current sensor detects current IB, which is the input and output current of battery 10. The temperature sensor detects temperature TB of battery 10. Each sensor outputs its detection results to ECU 70.

[0043] Electric vehicle 100 includes a DC inlet 31. Battery 10 can be rapidly charged from an external DC power supply as a charging device. DC inlet 31 is configured to connect to a connector 81 provided at the tip of a charging cable of an external DC power supply (external charging device) 80.

[0044] Charging relay 30 is electrically connected to power lines La and Na. Power lines La and Na are configured to connect DC inlet 31 to boost converter (DC-DC converter) 20, serving as a voltage step-up device. Charging relay 30 includes, for example, C-contact relay 30a and C-contact relay 30b. C-contact relay 30a is configured to be connectable to power line La and bypass power line Lb. Bypass power line Lb bypasses boost converter 20 and connects to power line PL. C-contact relay 30b is configured to be connectable to power line Na and bypass power line Nb. Bypass power line Nb bypasses boost converter 20 and connects to power line PN. Charging relay 30 selectively switches the power path between DC inlet 31 and boost converter 20 in response to a control signal from ECU 70. When charging relay 30 is switched to connect DC inlet 31 to power lines La and Na, power at a voltage boosted by boost converter 20 is supplied to battery 10 via power lines PL and PN. This charges battery 10. When charging relay 30 is switched to connect DC inlet 31 to bypass power line Lb and bypass power line Nb, the power supplied from external charger 80 is not boosted by boost converter 20. In other words, the power supplied from external charger 80 is directly supplied to battery 10. This charges battery 10.

[0045] Boost converter 20 is, for example, a non-insulated boost converter. Boost converter 20 boosts the voltage of the electric power (DC power) supplied to power lines La and Na, and outputs the boosted voltage (DC power) to power lines PL and PN. Boost converter 20 may also be an isolated boost converter.

[0046] External charging equipment 80 converts AC power from a system power source (e.g., a commercial power source) into DC power. External charging equipment 80 is configured to output charging power from a connector 81 via a charging cable to electric vehicle 100. External charging equipment 80 is provided with an operation panel 82, which enables various operations on external charging equipment 80.

[0047] When connector 81 of external charger 80 is connected to DC inlet 31, a signal line (not shown) is connected in addition to the power line. These connections enable communication between external charger 80 and ECU 70 using CAN (Controller Area Network) communication and / or PLC (Power Line Communication) communication.

[0048] The HMI device 90 provides the user with information to assist in driving the electric vehicle 100. The HMI device 90 is typically a display installed indoors and may also include, for example, a speaker. The HMI device 90 also functions as a user-operated touchscreen. By touching the touchpad, the user can input charging request information, such as the charging start time and charge level of the battery 10, into the HMI device 90.

[0049] ECU70 includes a CPU (Central Processing Unit) and a memory. The memory includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). Based on the signals received from the monitoring unit 11, the signals from various sensors (not shown), and information such as mappings and programs stored in the memory, ECU70 controls each device so that the electric vehicle 100 is in the desired state. The signals from the above-mentioned various sensors are, for example, accelerator opening signals or vehicle speed signals. ECU70 calculates the SOC of the battery 10 based on the detected values of the input and output currents and / or voltages of the battery 10 from the monitoring unit 11. The SOC of the battery 10 represents the stored charge, for example, expressed as a percentage of the current stored charge relative to the full charge capacity of the battery 10.

[0050] In this embodiment, the inter-terminal voltage (rated voltage or nominal voltage) of battery 10 is, for example, 600V. The specifications of external charging equipment 80, which serves as charging infrastructure, are determined by international standards, but various specifications exist regarding the maximum output voltage of external charging equipment 80. For example, when charging battery 10 in this embodiment using an external charging equipment with a maximum output voltage of 400V, a boost converter has been used to charge battery 10. Specifically, the boost converter boosts the 400V power supplied from the external charging equipment to 600V, and then charges battery 10 using the boosted voltage. When charging battery 10 in this embodiment using an external charging equipment with a maximum output voltage of 800V, the boost converter 20 has not been operated, and battery 10 has been charged.

[0051] The boost operation of the boost converter 20 is accompanied by losses such as switching loss and conduction loss. When charging is performed by boosting the voltage of 400V, which is the voltage of the power supplied from the external charging device 80, to 600V, the charging efficiency decreases. The inter-terminal voltage of the battery 10 fluctuates depending on the SOC, and as the SOC decreases, the inter-terminal voltage decreases. Therefore, if the SOC at the end of charging is low, the inter-terminal voltage of the battery 10 at the end of charging may be below 400V. Therefore, when external charging is performed using a charging device with a maximum output voltage of 400V, the inter-terminal voltage of the battery 10 at the end of charging can be used to charge the battery 10 without using the boost function of the boost converter 20, depending on the inter-terminal voltage of the battery 10 at the end of charging.

[0052] In this embodiment, battery voltage VBu, which is the voltage across the terminals of battery 10 at the end of charging, is determined based on the SOC of battery 10 at the end of charging. Battery voltage VBu is compared with the maximum output voltage Vc of external charging device 80. If maximum output voltage Vc is lower than battery voltage VBu, boost converter 20 is used to boost the maximum output voltage Vc of external charging device 80 to charge battery 10. If maximum output voltage Vc is higher than battery voltage VBu, boost converter 20 is not operated and battery 10 is charged.

[0053] Figure 2 : is a diagram showing the flow of charging power when the maximum output voltage Vc is lower than the battery voltage VBu. Figure 2 As shown by the arrows, charging relay 30 is switched to connect DC inlet 31 to power line La and power line Na. As a result, the power having the voltage boosted by boost converter 20 is supplied to battery 10. As a result, battery 10 is charged.

[0054] Figure 3 : is a diagram showing the flow of charging power when the maximum output voltage Vc is higher than the battery voltage VBu. Figure 3 As shown by the arrows, charging relay 30 is switched to connect DC inlet 31 to bypass power lines Lb and Nb. This allows battery 10 to be charged using a bypass path (bypass power lines Lb and Nb) that bypasses boost converter 20. Specifically, the bypass path directs the power supplied from external charger 80 to battery 10 rather than boost converter 20. Therefore, the voltage of the power from external charger 80 is not boosted by boost converter 20, and battery 10 is charged.

[0055] Figure 4This diagram shows the functional blocks within ECU 70. Each functional block is implemented by the hardware of ECU 70 and software processing executed by a program. Output voltage acquisition unit 701 receives information from external charger 80 using CAN communication and / or PLC communication. Based on this information, output voltage acquisition unit 701 acquires the maximum output voltage Vc of external charger 80. Maximum output voltage Vc is the maximum voltage that can be stably output from external charger 80 and can be, for example, the rated output voltage. Maximum output voltage Vc corresponds to the "maximum voltage" in this disclosure.

[0056] The upper-limit voltage calculation unit 702 calculates the battery voltage VBu, which is the inter-terminal voltage at the end of charging of the battery 10. The inter-terminal voltage of the battery 10 fluctuates depending on the SOC. As the SOC increases, the inter-terminal voltage increases, and as the SOC decreases, the inter-terminal voltage decreases. In this embodiment, the upper-limit voltage calculation unit 702 calculates the battery voltage VBu based on the SOC at the end of charging of the battery 10. The charge capacity of the battery 10 can be freely set by the user. For example, the user can set the charging time of the battery 10 or the charge capacity (Ah) of the battery 10 by operating the HMI device 90 or the operation panel 82. If the charging time is set, the charge capacity (Ah) is calculated based on the charging current (A) output from the external charging device 80 and the charging time. The SOC at the end of charging is calculated based on the calculated charge capacity (Ah) and the SOC of the battery 10 at the start of charging. If the charge capacity (Ah) is set, the SOC at the end of charging is calculated based on the charge capacity (Ah) and the SOC of the battery 10 at the start of charging.

[0057] The charge capacity of the battery 10 can also be determined by the SOC at the time of charging completion. In this case, the SOC at the time of charging completion is set by operating the HMI device 90 and can be used as the SOC at the time of charging completion of the battery 10. The upper limit voltage calculation unit 702 obtains the SOC at the time of charging completion of the battery 10 based on the charge capacity set using the HMI device 90 or the operation panel 82. The upper limit voltage calculation unit 702 can also determine the battery voltage VBu based on a map representing the relationship between the SOC and the inter-terminal voltage. The map representing the relationship between the SOC and the inter-terminal voltage is determined in advance through experiments and stored in memory.

[0058] Comparator 703 compares the maximum output voltage Vc obtained by output voltage acquirer 701 with battery voltage VBu calculated by upper-limit voltage calculator 702 . Comparator 703 outputs the comparison result to switch 704 and converter controller 705 .

[0059] The switching unit 704 receives the comparison result from the comparison unit 703 and switches the charging relay 30 based on this comparison result. When the maximum output voltage Vc is lower than the battery voltage VBu (Vc < VBu), the switching unit 704 switches the charging relay 30 to connect the DC inlet 31 to the power line La and the power line Na (see Figure 2 ). When the maximum output voltage Vc is equal to or higher than the battery voltage VBu (Vc ≥ VBu), the switching unit 704 switches the charging relay 30 to connect the DC inlet 31 to the bypass power line Lb and the bypass power line Nb (see Figure 3 ).

[0060] The converter control unit 705 receives the comparison result from the comparison unit. When the maximum output voltage Vc is lower than the battery voltage VBu (Vc < VBu) in this comparison result, it operates the boost converter 20 while starting the charging of the battery 10.

[0061] The charging current control unit 706 controls, for example, the start and end of the charging of the battery 10. As an example, when the mutual authentication with the external charging device 80 is established, the charging current control unit 706 sends a request for output of charging power to the external charging device 80 and starts the charging of the battery 10. When the set charging time has elapsed since the start of charging, when the set charging amount (Ah) has been charged, or when the SOC of the battery 10 becomes the SOC at the end of charging, the charging current control unit 706 sends a request to stop the charging power to the external charging device 80 and ends the charging.

[0062] [[ID=;13]] Figure 5 is a schematic flowchart showing the processing executed by the ECU 70. The processing of this flowchart is executed when the connector 81 is connected to the DC inlet 31. When the connector 81 is connected to the DC inlet 31, first, in step (hereinafter, steps will be abbreviated as S) 10, the ECU 70 receives information from the external charging device 80 through CAN communication and / or PLC communication, obtains the maximum output voltage Vc of the external charging device 80 based on this information, and advances the processing to S11.

[0063] In S11, the ECU 70 calculates the battery voltage VBu, which is the inter-terminal voltage at the end of charging of the battery 10, based on the SOC at the end of charging of the battery 10. The ECU 70 calculates the battery voltage VBu according to the map showing the relationship between the SOC and the inter-terminal voltage. As described above, the SOC at the end of charging of the battery 10 is obtained based on, for example, the charging time, the charging amount (Ah), and the SOC at the end of charging set by the user.

[0064] In the subsequent S12, the ECU 70 compares the magnitude of the maximum output voltage Vc with the magnitude of the battery voltage VBu. When the maximum output voltage Vc is above the battery voltage VBu (Vc ≥ VBu), a negative determination is made and the process proceeds to S13. In S13, the ECU 70 switches the charging relay 30 to connect the DC inlet 31 to the bypass power line Lb and the bypass power line Nb (refer to Figure 3 ), and the process proceeds to S14. In S14, the ECU 70 sends an output request for power to the external charging device 80 and starts charging. After that, the process proceeds to S17.

[0065] In S12, when the maximum output voltage Vc is lower than the battery voltage VBu (Vc < VBu), an affirmative determination is made and the process proceeds to S15. In S15, the ECU 70 switches the charging relay 30 to connect the DC inlet 31 to the power line La and the power line Na (refer to Figure 2 ), and the process proceeds to S16. In S16, the ECU 70 sends an output request for power to the external charging device 80 and operates the boost converter 20. Thereby, charging starts, and after that, the process proceeds to S17.

[0066] In S17, the ECU 70 determines whether the charging of the battery 10 has ended. For example, when the SOC at the end of charging is set by the user and the SOC of the battery 10 becomes the SOC at the end of charging, the ECU 70 determines that the charging has ended. When a charging time is set and the set charging time has elapsed since the start of charging, the ECU 70 determines that the charging has ended. When a charging amount (Ah) is set and the charging amount from the start of charging has reached the set charging amount, the ECU 70 determines that the charging has ended. When the charging of the battery 10 has not ended, charging continues until charging ends. When the charging of the battery 10 ends, an affirmative determination is made and the process proceeds to S18.

[0067] In S18, after the ECU 70 executes the charging end operation, it ends the current routine. The charging end operation is, for example, sending a stop request for the charging power to the external charging device 80 to stop the power supply from the external charging device 80. In S13, when the ECU 70 switches the charging relay 30 to connect the DC inlet 31 to the bypass power line Lb and the bypass power line Nb, the ECU 70 switches the charging relay 30 to connect the DC inlet 31 to the power line La and the power line Na. In S16, when the ECU 70 operates the boost converter 20, it stops the operation of the boost converter 20.

[0068] According to this embodiment, when the maximum output voltage Vc is equal to or greater than the battery voltage VBu, the boost converter 20 is not operated and the battery 10 is charged. Therefore, when the battery 10 can be charged without using the boost function of the boost converter 20, charging is performed without using the boost converter 20. As a result, the battery 10 can be charged without incurring losses due to the boost converter 20, and a decrease in charging efficiency can be suppressed.

[0069] In this embodiment, when maximum output voltage Vc is greater than battery voltage VBu (Vc ≥ VBu) in S12, charging relay 30 is switched in S13 to connect DC inlet 31 to bypass power line Lb and bypass power line Nb. However, when maximum output voltage Vc is greater than battery voltage VBu (Vc > VBu), charging relay 30 may be switched to connect DC inlet 31 to bypass power line Lb and bypass power line Nb. Furthermore, when maximum output voltage Vc is less than battery voltage VBu (Vc ≤ VBu), charging relay 30 may be switched to connect DC inlet 31 to power line La and power line Na.

[0070] (Variation 1)

[0071] The inter-terminal voltage VB of battery 10 fluctuates, for example, depending on the temperature of battery 10. For example, when charging battery 10, inter-terminal voltage VB tends to increase as the temperature decreases. Therefore, when the maximum output voltage Vc is higher than battery voltage VBu and battery 10 is charged without using boost converter 20, inter-terminal voltage VB is affected by temperature, for example. As a result, inter-terminal voltage VB may be higher than battery voltage VBu calculated using a map. In this case, there is a possibility that the maximum output voltage Vc is lower than inter-terminal voltage VB and charging may not proceed. Alternatively, the accuracy of calculating battery voltage VBu may decrease due to changes in battery 10's condition, such as aging. Furthermore, when the maximum output voltage Vc is higher than battery voltage VBu and battery 10 is charged without using boost converter 20, the maximum output voltage Vc may be lower than inter-terminal voltage VB. As a result, charging may not proceed. In the first modification, while battery 10 is being charged without using boost converter 20 , battery 10 can be charged even if maximum output voltage Vc is lower than inter-terminal voltage VB.

[0072] Figure 6 This is a flowchart schematically showing the processing executed by the ECU 70 in the first modification. Figure 6 The flowchart is in Figure 5 The flowchart of S20 to S22 is added. Figure 5 Although the description is omitted, Figure 6 S10 to S18 in the flowchart of Figure 5 The steps S10 to S18 in the flowchart are the same.

[0073] Reference Figure 6 In S14, after ECU 70 transmits a power output request to external charging equipment 80 to initiate charging, the process proceeds to S20. In S20, ECU 70 determines whether charging of battery 10 has been completed. The process in S20 is identical to that in S17. If charging of battery 10 has been completed and a positive determination is made in S20, the process proceeds to S18. After executing the charging termination operation in S18, ECU 70 terminates this routine. If charging of battery 10 has not been completed, a negative determination is made and the process proceeds to S21.

[0074] In S21, the ECU 70 determines whether the inter-terminal voltage VB of the battery 10 detected by the voltage sensor of the monitoring unit 11 is greater than the maximum output voltage Vc. If the inter-terminal voltage VB is less than the maximum output voltage Vc (VB ≤ Vc), the process returns to S20 and charging is continued until charging is completed. If the inter-terminal voltage VB is greater than the maximum output voltage Vc (VB > Vc), the process proceeds to S22.

[0075] In S22, the ECU 70 interrupts charging. Specifically, after the ECU 70 sends a request to stop charging power to the external charger 80 and stops the power supply from the external charger 80, the process proceeds to S15. In S15, the ECU 70 switches the charging relay 30 to connect the DC inlet 31 to the power line La and the power line Na (see Figure 2 ), causing the process to enter S16.

[0076] In this first variation, if battery 10 is charged without using boost converter 20 and the maximum output voltage Vc is lower than the inter-terminal voltage VB, a positive determination is made in S21. The process then proceeds to S22, where charging is temporarily suspended. Subsequently, in S15, charging relay 30 is switched to connect DC inlet 31 to power lines La and Na, allowing boost converter 20 to boost the voltage. This resumes charging of battery 10. In S17, charging continues until battery 10 is fully charged. As a result, charging of battery 10 is reliably performed.

[0077] (Variation 2)

[0078] When charging the battery 10 using the boost converter 20, the charging efficiency deteriorates due to the losses caused by the boost converter 20. Therefore, when continuing to charge the battery 10 using the boost converter 20 until the charged amount (Ah) set by the user or the charging completion SOC is reached, the charging time may be extended. In the case where the charging fee is charged depending on the charging time, the extended charging time makes the unit price of the charging fee higher relative to the charged amount. In the second modification, it is possible to suppress the increase in the unit price of the charging fee.

[0079] Figure 7 It is a flowchart outlining the processing performed by the ECU 70 in the second modification. Figure 7 The flowchart of Figure 5 The flowchart of Figure 5 The flowchart of Figure 7 is different in that S30 to S32 are added to the flowchart of Figure 5 Although its description is omitted, [[ID=X]]

[0080] Refer to Figure 7 In S12, when the maximum output voltage Vc is lower than the battery voltage VBu (Vc < VBu), an affirmative determination is made and the process proceeds to S30. In S30, the ECU 70 determines whether the difference between the maximum output voltage Vc and the battery voltage VBu, that is, "VBu - Vc", is smaller than a predetermined value α. The predetermined value α corresponds to the "first predetermined value" of the present disclosure. For example, it can also be set to a value of 5% of the battery voltage VBu. When a negative determination is made for "VBu - Vc ≥ α", the process proceeds to S15. When an affirmative determination is made for "VBu - Vc < α", the process proceeds to S13.

[0081] In this way, in the second modification, even when the maximum output voltage Vc is lower than the battery voltage VBu (an affirmative determination is made in S12), when the difference between the maximum output voltage Vc and the battery voltage VBu is smaller than the predetermined value α (an affirmative determination is made in S30), the process proceeds to S13. Then, the ECU 70 switches the charging relay 30 to connect the DC input port 31 to the bypass power line Lb and the bypass power line Nb. Thereby, using the bypass path that bypasses the boost converter 20, the battery 10 is charged without the voltage of the power supplied from the external charging device 80 being boosted by the boost converter 20.

[0082] In S31, ECU 70 determines whether charging of battery 10 has been completed. The processing in S31 is identical to that in S17. If charging of battery 10 has been completed and a positive determination is made in S31, the process proceeds to S18. In S18, ECU 70 executes the charging completion operation and then terminates this routine. If charging of battery 10 has not been completed, a negative determination is made and the process proceeds to S32.

[0083] In S32, the ECU 70 determines whether the inter-terminal voltage VB of the battery 10, detected by the voltage sensor of the monitoring unit 11, is greater than the maximum output voltage Vc. If the inter-terminal voltage VB is less than the maximum output voltage Vc (VB ≤ Vc), the process returns to S31, and charging continues until it is completed. If the inter-terminal voltage VB is greater than the maximum output voltage Vc (VB > Vc), the process proceeds to S18. After executing the charging completion operation in S18, the ECU 70 terminates this routine.

[0084] In this second variation, even if the maximum output voltage Vc is lower than the battery voltage VBu, and the difference between the two is smaller than a predetermined value α, a bypass path bypassing the boost converter 20 is used, allowing the boost converter 20 to be charged without operating. Then, while charging the battery 10, if the inter-terminal voltage VB of the battery 10 exceeds the maximum output voltage Vc, charging is terminated before reaching the user-set charge capacity (Ah) or the charge completion SOC. Thus, until the user-set charge capacity (Ah) or charge completion SOC is reached, charging of the battery 10 using the boost converter 20 is essentially stopped. This results in a reduction in charging time and a reduction in the unit price of charging. The predetermined value α can also be set appropriately by the user. Thus, the SOC at the end of charging, due to the inter-terminal voltage VB exceeding the maximum output voltage Vc, is within a range acceptable to the user, who considers the SOC and charging cost.

[0085] When "VBu-Vc<α" is established by combining the processes of S12 and S30, the process proceeds to S13. When "VBu-Vc<α" is not established (VBu-Vc≥α), the process may proceed to S15.

[0086] (Variation 3)

[0087] The inter-terminal voltage VB of battery 10 fluctuates, for example, depending on the temperature of battery 10. When the maximum output voltage Vc is higher than the battery voltage VBu and the battery 10 is charged without using the boost converter 20, the fluctuation in inter-terminal voltage VB may cause the maximum output voltage Vc to fall below the inter-terminal voltage VB. As a result, charging may not proceed, or charging may begin with the boost converter 20, causing charging to become unstable. Unstable charging may, for example, extend the initially scheduled charging time. Alternatively, the accuracy of calculating the battery voltage VBu may decrease depending on the temperature of the battery 10, resulting in the calculated battery voltage VBu being lower than the actual inter-terminal voltage at the end of charging. If the maximum output voltage Vc frequently falls below the inter-terminal voltage VB while the battery 10 is being charged without using the boost converter 20, charging may not proceed, or charging may begin with the boost converter 20, causing charging to become unstable. Unstable charging may, for example, extend the initially scheduled charging time. Modification 3 facilitates stable charging.

[0088] Figure 8 This is a flowchart schematically showing the processing executed by the ECU 70 in the third modification. Figure 8 The flowchart is in Figure 5 The flowchart of S40 to S43 is added. Figure 5 Although the description is omitted, Figure 8 S10 to S18 in the flowchart of Figure 5 The steps S10 to S18 in the flowchart are the same.

[0089] Reference Figure 8 In S12, if the maximum output voltage Vc is greater than or equal to the battery voltage VBu (Vc ≥ VBu), a negative determination is made, and the process proceeds to S40. In S40, the ECU 70 determines whether the difference between the maximum output voltage Vc and the battery voltage VBu, namely "Vc - VBu," is less than a predetermined value β. The predetermined value β corresponds to the "second predetermined value" of the present disclosure and may be set, for example, to 5% of the battery voltage VBu. If a positive determination is made that "Vc - VBu < β," the process proceeds to S15. If a negative determination is made that "Vc - VBu ≥ β," the process proceeds to S13.

[0090] As described above, in Modification 3, even if maximum output voltage Vc is higher than battery voltage VBu (a negative determination in S12), if the difference between maximum output voltage Vc and battery voltage VBu is less than predetermined value β (a positive determination in S40), the process proceeds to S15. ECU 70 then switches charging relay 30 to connect DC inlet 31 to power lines La and Na. This allows the voltage of the power supplied from external charging device 80 to be boosted by boost converter 20, and the boosted voltage is used to charge battery 10.

[0091] In S41, ECU 70 determines whether charging of battery 10 has been completed. The processing in S41 is identical to that in S17. If charging of battery 10 has been completed and a positive determination is made in S41, the process proceeds to S18. After executing the charging completion operation in S18, ECU 70 terminates this routine. If charging of battery 10 has not been completed, a negative determination is made and the process proceeds to S42.

[0092] In S42, the ECU 70 determines whether the inter-terminal voltage VB of the battery 10, detected by the voltage sensor of the monitoring unit 11, is greater than the maximum output voltage Vc. If the inter-terminal voltage VB is less than the maximum output voltage Vc (VB ≤ Vc), the process returns to S41, and charging continues until charging is completed. If the inter-terminal voltage VB is greater than the maximum output voltage Vc (VB > Vc), the process proceeds to S43. Charging is then interrupted, and the process proceeds to S15.

[0093] In this third modification, even when maximum output voltage Vc is higher than battery voltage VBu, boost converter 20 is used to charge battery 10 if the difference between maximum output voltage Vc and battery voltage VBu is less than a predetermined value β. While maximum output voltage Vc is higher than battery voltage VBu by the predetermined value β, boost converter 20 operates to charge battery 10. This reduces the frequency with which the charging voltage falls below battery 10's inter-terminal voltage VB. Consequently, stable charging can be facilitated.

[0094] In the present embodiment, charging relay 30 includes c-contact relay 30a and c-contact relay 30b, but the structure of charging relay 30 is not limited thereto. Figure 9 FIG. 1 is a diagram showing another structural example of a charging relay. Figure 9As shown, the charging relay may also be a charging relay 300 comprising four a-contact relays. Charging relay 300 includes four a-contact relays. This configuration reliably electrically disconnects battery 10 from DC inlet 31 when connector 81 is not connected to DC inlet 31 and all a-contact relays are disconnected (OFF). In this embodiment, during the charging termination operation (S18), charging relay 30 is switched to connect DC inlet 31 to power lines La and Na at the end of charging. This allows the battery 10 to be electrically disconnected from DC inlet 31 for insulation purposes, even when boost converter 20 is non-insulated. Even when boost converter 20 is non-insulated, the electrical connection between battery 10 and DC inlet 31 can be effectively disconnected by a diode located on the positive line of the connected power line pair. In this embodiment, the inter-terminal voltage (rated voltage or nominal voltage) of battery 10 is 600V, but it may alternatively be 500V, 700V, or 800V.

[0095] Figure 1 Although electric vehicle 100 is an electric vehicle, the present disclosure is not limited to electric vehicle 100. For example, the present disclosure can also be applied to plug-in hybrid vehicles including an engine and a motor generator, fuel cell vehicles including an externally rechargeable battery, and industrial vehicles such as forklifts.

[0096] While the embodiments of the present disclosure have been described, they should be considered in all respects to be illustrative and not restrictive. The scope of the present disclosure is indicated by the claims, and all modifications within the meaning and scope of the equivalents of the claims are intended to be encompassed.

Claims

1. An electric vehicle comprising a power storage device that can be charged with electric power supplied from an external power supply, wherein: The electric vehicle comprises: a boosting device for boosting the voltage of the electric power supplied from the external power supply and supplying the electric power of the boosted voltage to the power storage device; a bypass path that bypasses the boosting device, the bypass path being configured to supply the electric power supplied from the external power supply to the power storage device instead of the boosting device, and a control device for controlling charging of the power storage device, The control device is configured as follows: When the maximum voltage of the electric power supplied from the external power supply is lower than the inter-terminal voltage of the electric power storage device at the completion of charging of the electric power storage device, the electric power storage device is charged using the boost device when the difference between the maximum voltage and the inter-terminal voltage at the completion of charging is equal to or greater than a first predetermined value, and the electric power storage device is charged using the bypass path when the difference between the maximum voltage and the inter-terminal voltage at the completion of charging is less than the first predetermined value. When the maximum voltage is higher than the inter-terminal voltage at the end of the charging, the power storage device is charged using the bypass path.

2. The electric vehicle according to claim 1, wherein: The control device is configured to charge the power storage device using the boost device when the power storage device is charged using the bypass path and the maximum voltage drops below the inter-terminal voltage of the power storage device.

3. The electric vehicle according to claim 1, wherein: The external power supply is an external charging device that supplies DC power to the electric vehicle. The electric vehicle includes a charging relay configured to selectively switch the path of the DC power supplied from the external charging device to a path for supplying the DC power to the boost device or to the bypass path. The control device comprises: an output voltage acquisition unit that acquires the maximum voltage of the electric power supplied from the external power source based on information received from the external charging device; an upper limit voltage calculation unit that calculates the inter-terminal voltage of the power storage device when the charging of the power storage device is completed based on the SOC of the power storage device; a comparing unit that compares the magnitude of the maximum voltage with the magnitude of the inter-terminal voltage at the end of the charging; and The switching unit switches the charging relay according to the comparison result of the comparing unit.

4. A charging control method for an electric vehicle, wherein: The electric vehicle comprises: a power storage device capable of being charged by an external power supply provided outside the electric vehicle; a boosting device for boosting the voltage of the electric power supplied from the external power supply and supplying the electric power of the boosted voltage to the power storage device; as well as a bypass path that bypasses the boosting device, the bypass path being configured to supply the electric power supplied from the external power supply to the power storage device instead of the boosting device, The charging control method comprises the following steps: comparing a maximum voltage of the electric power supplied from the external power supply with a voltage between terminals of the power storage device when charging of the power storage device is completed; operating the boost device to charge the power storage device when the maximum voltage is lower than the inter-terminal voltage at the end of charging and the difference between the maximum voltage and the inter-terminal voltage at the end of charging is equal to or greater than a first predetermined value; When the maximum voltage is lower than the inter-terminal voltage at the end of charging and the difference between the maximum voltage and the inter-terminal voltage at the end of charging is smaller than the first predetermined value, the power storage device is charged using the bypass path. When the maximum voltage is higher than the inter-terminal voltage at the end of the charging, the power storage device is charged using the bypass path.

5. The method for controlling charging of an electric vehicle according to claim 4, wherein: The following steps are also included: The inter-terminal voltage at the time of completion of the charging is calculated based on the SOC of the power storage device at the time of completion of the charging.

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