Power transmission system

Abstract

The ECU of the power transmission system of the present application performs the following processing, which includes a step of starting the temperature increase if the battery temperature is lower than a target temperature, a step of stopping the temperature increase if the SOC reaches a stop SOC, a step of resuming the temperature increase if the SOC reaches a resume SOC, and a step of stopping the temperature increase when the battery temperature reaches the target temperature.

Description

Technical Field

[0001] This disclosure relates to power transmission systems. Background Technology

[0002] It is known that there are technologies for power transmission systems that connect vehicle-mounted energy storage devices to power transmission stations connected to power grids or the like for power transmission. For example, Japanese Patent Application Publication No. 2022-116971 discloses a technology that reports an inquiry message asking whether the power transmission system should be stopped when the amount of electricity transferred between the energy storage device and the equipment is less than a threshold, when the power generation of the solar power generation device is less than a threshold during a period of time, or when the electricity price is cheaper than at other times of the day and the energy storage device is fully charged.

[0003] In power transmission systems like those described above, for example, when the temperature of an onboard energy storage device is low before charging, control is sometimes implemented to raise the temperature of the energy storage device using a heating device. However, if the power output from the power transmission station by the user is limited to a lower amount than the power used to activate the heating device, the energy storage device's power may be depleted, reducing its remaining capacity and making it impossible to transmit power to the power grid using the energy storage device. Summary of the Invention

[0004] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a power transmission system that suppresses the reduction of the remaining capacity of an on-board energy storage device to the remaining capacity where power transmission is limited.

[0005] One aspect of this disclosure relates to a power transmission system comprising a vehicle equipped with an energy storage device and a power transmission station capable of transmitting power between the vehicle and the vehicle. The vehicle includes: a first acquisition device for acquiring the temperature of the energy storage device; a second acquisition device for acquiring the remaining capacity of the energy storage device; a heating device for consuming electricity to heat the energy storage device; and a control device for controlling the heating device. The control device sets a first threshold value for the remaining capacity used to stop the operation of the heating device to a value higher than the remaining capacity of the energy storage device to which power transmission is restricted.

[0006] In this way, even if the remaining capacity of the energy storage device decreases during power transmission and the operation of the heating device, the operation of the heating device can be stopped when the first threshold is reached. Therefore, it is possible to prevent the remaining capacity of the energy storage device from becoming the remaining capacity that limits power transmission.

[0007] In one embodiment, if the remaining capacity becomes greater than a second threshold than a first threshold after the operation of the heating device is stopped, the control device restarts the operation of the heating device.

[0008] In this way, if the remaining capacity exceeds the second threshold, the heating device can be restarted, thus enabling the energy storage device to be heated to a temperature suitable for power transmission.

[0009] In another embodiment, the power transmission station notifies the vehicle of the upper limit of the power it can output and supplies the vehicle with power set by the user. If the power supplied from the power transmission station is lower than the power required for the heating device to operate, the control device sets a first threshold.

[0010] Thus, if the power supplied from the power transmission station is lower than the power when the heating device is operating, there is a situation where the remaining capacity of the energy storage device decreases during power transmission. Therefore, by setting a first threshold, it is possible to prevent the remaining capacity of the energy storage device from becoming the remaining capacity that limits power transmission.

[0011] According to this disclosure, a power transmission system is available that can suppress the reduction of the remaining capacity of an on-board energy storage device to the remaining capacity where power transmission is limited. Attached Figure Description

[0012] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, wherein,

[0013] Figure 1 This is a diagram illustrating an example of the structure of a power transmission system.

[0014] Figure 2 This is a diagram illustrating an example of information exchanged between a power transmission station and a vehicle.

[0015] Figure 3 This is a graph used to illustrate an example of the change in the SOC of a battery under conditions of continued heating.

[0016] Figure 4 This is a flowchart illustrating an example of a process performed by an ECU.

[0017] Figure 5 This is a graph illustrating an example of how battery temperature and state of charge (SOC) change during power transmission. Detailed Implementation

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, identical or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will not be repeated.

[0019] Hereinafter, an example of the configuration of the power transmission system 1 in this embodiment will be described. Figure 1This is a diagram illustrating an example of the configuration of power transmission system 1. (See diagram for example.) Figure 1 As shown, the power transmission system 1 includes a vehicle 200 and a power transmission station 10 located outside the vehicle 200. The vehicle 200 can be any vehicle capable of transmitting power to external facilities, such as a battery electric vehicle, a plug-in hybrid electric vehicle, or other electric vehicles.

[0020] The vehicle 200 includes an ECU (Electronic Control Unit) 100 as a control device, a display device 110, a heating device 150, a battery 214, an inverter 216, an MG (Motor Generator) 218, and a socket 220.

[0021] The storage battery 214 can be any rechargeable storage device, such as a nickel-metal hydride battery, a lithium-ion battery with liquid or solid electrolyte, or a large-capacity capacitor.

[0022] The inverter 216 is configured to bidirectionally convert the DC power from the battery 214 and the AC power from the MG218 according to the control signal from the ECU 100.

[0023] MG218 is the drive source for the drive wheels 222 of the vehicle 200, and is composed of a three-phase AC rotary motor, etc. MG218 functions as an electric motor (motor) that uses the power of the storage battery 214 to drive the vehicle 200, and as a generator that generates power (e.g., regenerative power) for charging the storage battery 214.

[0024] The socket 220 has the shape of a connector 17 that can be installed in the power transmission station 10. The socket 220 is electrically connected to the battery 214.

[0025] The ECU 100 is connected to a voltage sensor 102, a current sensor 104, and a temperature sensor 106 for obtaining the voltage, current, and temperature of the battery 214. The ECU 100 includes a CPU (Central Processing Unit) and a memory (neither shown). Based on signals received from the various sensors and information such as mappings and programs stored in the memory, the ECU 100 controls the various devices in a manner that allows the vehicle 200 to reach a desired state.

[0026] The ECU 100 has the function of sequentially calculating the SOC (State of Charge) representing the remaining capacity of the battery 214 based on the detection values ​​of the voltage sensor 102, the current sensor 104, and the temperature sensor. Various known methods can be used to calculate the SOC, such as methods based on current accumulation (coulomb counting) or estimation methods based on open circuit voltage (OCV). The ECU 100 is configured to communicate with the communication unit 13 of the power transmission station 10, which will be described later.

[0027] The display device 110 may be, for example, a display section of a touch panel display located around the driver's seat. The display section may be, for example, an LCD (Liquid Crystal Display) or an organic EL (Electro-Luminescence) display.

[0028] The heating device 150 is configured to raise the temperature of the battery 214 according to a control signal from the ECU 100. The heating device 150 includes an electric heater or the like that uses electricity from the battery 214 for heating. In addition to the electric heater, the heating device 150 may also include, for example, a radiator capable of exchanging heat with the battery 214, a heat exchanger capable of exchanging heat with a heat source (e.g., an engine, heater, other electrical equipment), a medium (e.g., coolant, gas), a pump for pressurizing the medium, and a medium passage for facilitating the flow of the medium.

[0029] When the battery 214 is heated, the ECU 100 activates the heating device 150. For example, if the temperature of the battery 214 is lower than the lower limit of a predetermined temperature range, including the target temperature, the ECU 100 activates the heating device 150.

[0030] When the temperature of the battery 214 is within a predetermined temperature range, the ECU 100 shuts down the heating device 150. The heating device 150 is configured, for example, to operate using at least one of the power supplied from the vehicle 200 to the connector 220 (power from an external power source) and the power supplied from the battery 214.

[0031] The power transmission station 10 includes a communication unit 13, a control unit 14, a transmission unit 15, a cable 16, and a connector 17. For example, the power transmission station 10 transmits power from the system power supply 400 to the vehicle 200's battery 214 to charge the battery 214, and transmits power from the battery 214 to the system power supply 400 to discharge the battery 214.

[0032] When the connector 17 is connected to the socket 220 of the vehicle 200, the communication unit 13 communicates with the ECU 100 of the vehicle 200 via cable 16 through wired communication such as power line communication, CAN (Control Area Network) communication, or LAN communication. In addition, communication can also be carried out through various standard wireless communications (such as Wi-Fi).

[0033] The control unit 14 controls the operation of the transmission unit 15 (e.g., transmitting voltage, transmitting current) based on control signals received from the ECU 100. The control unit 14 includes a CPU and a memory (neither shown). The control unit 14 controls the transmission unit 15 based on information received from the vehicle 200 using the communication unit 13, and information such as mappings and programs stored in the memory.

[0034] The transmission unit 15 converts AC power from the system power supply 400 constituting the power grid into DC power, or converts DC power from the storage battery 214 into AC power, based on control signals from the control unit 14. One end of the cable 16 is connected to the transmission unit 15. A connector 17 is connected to the other end of the cable 16.

[0035] The connector 17 has a shape that allows it to be installed in the socket 220. When the connector 17 is installed in the socket 220, it can be in either a first state where it can supply DC power from the transmission unit 15 to the battery 214 based on a control signal received from the ECU 100 in the control unit 14, or a second state where it can supply AC power from the transmission unit 15 to the system power supply 400. For example, when requesting external charging, the ECU 100 sends a control signal to the control unit 14 in the first state when the connector 17 is installed in the socket 220. For example, when requesting discharging to the power transmission station 10, the ECU 100 sends a control signal to the control unit 14 in the second state when the connector 17 is installed in the socket 220.

[0036] For example, if the SOC of the battery 214 is below a threshold, the ECU 100 requests fast charging. Additionally, for example, when performing power transfer between the vehicle 200 and a facility (e.g., one's own home) equipped with the power transfer station 10 (hereinafter referred to as V2H: Vehicle to Home), the ECU 100 requests discharge when using the battery 214 as a power source for the facility, and requests charging when storing remaining power in the battery 214.

[0037] In power transmission using battery 214, ECU 100 uses the detection values ​​of voltage sensor 102, current sensor 104 and temperature sensor 106 to obtain the SOC of battery 214 and the temperature of battery 214 (hereinafter referred to as battery temperature).

[0038] In the power transmission system 1 described above, when the temperature of the battery 214 is low before charging, control is performed to raise the temperature of the battery 214 using the heating device 150. However, when the power output from the power transmission station 10 by the user is limited to a lower power than that used to activate the heating device 150, the power stored in the battery 214 is sometimes consumed, the state of charge (SOC) of the battery 214 decreases, and V2H using the battery 214 becomes unusable.

[0039] Figure 2 This diagram illustrates an example of information exchanged between power transmission station 10 and vehicle 200. If connector 17 is installed in socket 220, then... Figure 2 As shown, power line communication is used to communicate between the power transmission station 10 and the vehicle 200 (specifically, the ECU 100). At this time, the power transmission station 10 notifies the ECU 100 of information regarding the possible charging output (maximum output). Figure 2 In this context, the charging output that can be output, for example, informs the ECU100 that the main information is 5kW.

[0040] On the other hand, at the power transmission station 10, sometimes the user limits the output of the power transmission station to a lower power than the upper limit. For example, when limited to 1kW, 1kW of power is output from the power transmission station 10 to the vehicle 200. In the ECU 100 of the vehicle 200, for example, when the battery temperature is lower than the target temperature, information from the power transmission station 10 regarding the upper limit output is used to determine whether to operate the heating device 150 with 5kW of power.

[0041] In this case, such as Figure 2 As shown in section (A), a notification of a 5kW charging output is sent, while the actual charging output is 1kW. The power consumed by the heating device 150 is 5kW, resulting in a power difference of 4kW being consumed by the battery 214. Consequently, the SOC of the battery 214 continues to decrease during the heating process using the heating device 150.

[0042] Figure 3 This is a diagram used to illustrate an example of the change in the SOC of battery 214 under conditions of continued heating. Figure 3 The vertical axis of section (A) represents the battery temperature. Figure 3 The vertical axis of part (B) represents SOC. Figure 3 Part (A) and Figure 3 The horizontal axis of each part (B) represents time. Figure 3Part (A) LN1 (dashed line) represents an example of the time-varying temperature of the battery. Figure 3 Part (B) LN2 (solid line) represents an example of the time variation of SOC.

[0043] For example, if connector 17 is installed in socket 220 and the battery temperature is below a predetermined temperature range, ECU 100 activates heating device 150. Figure 3 As shown in LN1 of part (A), the battery temperature rises over time due to the operation of the heating device 150.

[0044] On the other hand, through the operation of the heating device 150, the power of the storage battery 214 is consumed, therefore, as Figure 3 As shown in LN2 of section (B), the SOC of battery 214 gradually decreases over time. As a result, sometimes at time T(0), the SOC of battery 214 exceeds the lower limit SOC. The lower limit SOC represents the lower limit of the range of SOC of battery 214 when power transmission is not restricted (i.e., the upper limit of the range of the lower SOC of battery 214 when power transmission is restricted). Therefore, there are situations where the SOC of battery 214 decreases to exceed the lower limit SOC, making it impossible to supply power from battery 214 to the power grid and thus preventing V2H.

[0045] Therefore, in this embodiment, the ECU100 sets a first threshold of SOC (i.e., stop SOC) for stopping the operation of the heating device 150 to a value higher than the SOC of the battery 214 whose power transmission is restricted (i.e., a value higher than the lower limit SOC).

[0046] In this way, even if the SOC of the battery 214 decreases during power transmission, the operation of the heating device 150 can be stopped when the first threshold is reached. Therefore, it is possible to suppress the SOC from decreasing to a level that limits power transmission (i.e., a value lower than the lower limit SOC).

[0047] The following is for reference Figure 4 Here is an example of a process performed by ECU100. Figure 4 This is a flowchart illustrating an example of a process performed by ECU100.

[0048] In step (hereinafter referred to as S) 100, ECU 100 determines whether the battery temperature is lower than a target temperature. The target temperature may be a predetermined value within a temperature range that does not promote degradation even when power is being transmitted using the battery 214, or it may be a value set by obtaining the outside air temperature and using a mapping representing the relationship between the outside air temperature and the target temperature. ECU 100 obtains the battery temperature via temperature sensor 106. If it is determined that the battery temperature is lower than the target temperature (yes in S100), the process proceeds to S102.

[0049] In S102, ECU100 begins to heat up. That is, ECU100 activates the heating device 150. After that, the process moves to S104.

[0050] In S104, ECU100 determines whether the SOC of battery 214 has reached the stop SOC. The stop SOC is a predetermined value that is higher than the lower limit of the range of SOCs within which battery 214 can be used for V2H (hereinafter referred to as the lower limit SOC). The lower limit SOC is, for example, a value larger than the lower limit of the range of usable SOCs of battery 214, representing the lower limit of the range of SOCs that can be adaptively adjusted through experiments or other means without promoting degradation even when used for V2H. ECU100 may also obtain the outside air temperature, for example, and set the stop SOC using a mapping that represents the relationship between the outside air temperature and the stop SOC. If it is determined that the SOC of battery 214 has reached the stop SOC (yes in S104), ECU100 moves the process to S106.

[0051] In S106, ECU100 stops heating. That is, ECU100 stops the operation of heating device 150. Then, the process moves to S108.

[0052] In S108, ECU100 determines whether the SOC of battery 214 has reached the restart SOC. The restart SOC is a value that is at least higher than the stop SOC, and is a predetermined value. The restart SOC can also be set to a value that is greater than the stop SOC by a predetermined value. If it is determined that the SOC of battery 214 has reached the restart SOC (yes in S108), the process moves to S110.

[0053] In S110, ECU100 starts heating up again. That is, ECU100 activates the heating device 150 again. Then, the process moves to S112. Furthermore, if the SOC of the battery 214 has not reached the stop SOC (which was not the case in S104), the process moves to S112.

[0054] In S112, ECU100 determines whether the battery temperature has reached the target temperature. If it is determined that the battery temperature has reached the target temperature (yes in S112), the process moves to S114.

[0055] In S114, ECU100 stops heating. That is, ECU100 stops the operation of heating device 150. After that, the process ends. Furthermore, if it is determined that the battery temperature is above the target temperature (not in S100), the process ends. Moreover, if it is determined that the SOC has not been reached and the SOC restart is not performed (not in S108), the process returns to S108. Moreover, if it is determined that the battery temperature has not reached the target temperature (not in S112), the process returns to S104.

[0056] Side reference Figure 5 The operation of the power transmission system 1 according to this embodiment based on the above-described structure and flowchart will be explained. Figure 5 This is a graph illustrating an example of how battery temperature changes with state of charge (SOC) during power transmission. Figure 5 The vertical axis of section (A) represents the battery temperature. Figure 5 The vertical axis of part (B) represents SOC. Figure 5 Part (A) and Figure 5 The horizontal axis of section (B) represents time. Figure 5 The LN3 (dashed line) represents the change in battery temperature over time. Figure 5 LN4 (solid line) represents the time-dependent change in the SOC of battery 214.

[0057] For example, suppose connector 17 is connected to port 220 of vehicle 200 and a charge request is made from ECU 100 to power transmission station 10.

[0058] At time T(1), in power transmission station 10, the charging power is limited to 1kW, and, as Figure 5 As shown in LN3 of section (A), the battery temperature is set to be lower than the target temperature. At this time, the power transmission station 10 notifies the vehicle 200 of the information that the upper limit of the charging output is 5kW, and the charging power supplied to the vehicle 200 will be limited to 1kW.

[0059] Since the battery temperature is lower than the target temperature (yes in S100), the ECU100 activates the heating device 150 to begin heating (S102). If heating begins, the power supplied from the power transmission station 10 is consumed in the heating device 150.

[0060] Therefore, during the period from time T(1) to time T(2), such as Figure 5As shown in part (A) of LN3, the battery temperature gradually increases, and as... Figure 5 As shown in part (B) of LN4, the SOC of battery 214 gradually decreases.

[0061] When the SOC of the battery 214 reaches the stop SOC at time T(2) (yes in S104), the operation of the heating device 150 is stopped (S106). If the operation of the heating device 150 is stopped, power supplied from the power transmission station 10 is supplied to the battery 214, thus charging the battery 214.

[0062] Therefore, during the period from time T(2) to time T(3), such as Figure 5 As shown in part (A) of LN3, the battery temperature gradually decreases, and as... Figure 5 As shown in part (B) of LN4, the SOC of battery 214 gradually increases.

[0063] If the SOC of the battery 214 reaches the restart SOC at time T(3) (yes in S108), the heating device 150 is activated again and heating begins again (S110). If heating begins again, the power supplied from the power transmission station 10 is consumed again in the heating device 150.

[0064] Therefore, during the period from time T(3) to time T(4), such as Figure 5 As shown in part (A) of LN3, the battery temperature gradually increases, and as... Figure 5 As shown in part (B) of LN4, SOC gradually decreases.

[0065] If the battery temperature reaches the target temperature at time T(4) (yes in S112), the heating is stopped (S114). If the heating is stopped, the power supplied from the power transmission station 10 is supplied to the battery 214, and thus the battery 214 is charged.

[0066] Therefore, after time T(4), as Figure 5 As shown in part (A) of LN3, the battery temperature gradually decreases, and as... Figure 5 As shown in LN4 of part (B), SOC gradually increases.

[0067] In this way, the operation of the heating device 150 is limited until the SOC reaches the stop SOC, thus preventing the SOC of the battery 214 from dropping to the lower limit SOC.

[0068] As described above, according to the power transmission system 1 of this embodiment, even when the SOC of the battery 214 decreases during power transmission, the operation of the heating device 150 can be stopped when the stop SOC is reached. Therefore, it is possible to suppress the SOC from falling below the lower limit and reaching the SOC where V2H is limited. Thus, a power transmission system that can suppress the remaining capacity of the vehicle's energy storage device from decreasing to the remaining capacity where power transmission is limited can be provided.

[0069] Furthermore, when the SOC reaches a higher restart SOC than the stop SOC after the operation of the heating device 150 stops, the operation of the heating device 150 is restarted, thereby enabling the battery 214 to be heated to the target temperature.

[0070] The following is an explanation of the variations.

[0071] In the above embodiment, the operation of the heating device 150 is stopped when the SOC reaches a preset stop SOC during operation. However, the ECU 100 may also set the stop SOC when the power supplied from the power transmission station 10 is lower than the power consumed when the heating device 150 is operating.

[0072] In this way, when the power supply is set to be higher than the power supplied from the power transmission station 10, the power supply when the heating device 150 is operated can be prevented from dropping to a level exceeding the lower limit of SOC.

[0073] Furthermore, in the above embodiment, the operation of the heating device 150 is described in the case where the stop SOC is reached and then restarted. However, it is not particularly limited to such an operation. For example, the heating device 150 may also be controlled in a way that the SOC is maintained at the stop SOC when the stop SOC is reached.

[0074] Furthermore, in the above embodiment, the case where a predetermined value is added to the stop SOC to set the restart SOC has been described. However, for example, the restart SOC can also be calculated by adding ΔSOC, which corresponds to the electrical force required to balance the difference ΔT between the current battery temperature and the target temperature, to the stop SOC. This prevents the SOC of the battery 214 from dropping back to the stop SOC before the battery temperature reaches the target temperature. Repeated increases and decreases in battery temperature can be suppressed.

[0075] In addition, the above-mentioned variations can also be implemented by combining all or part of them appropriately.

[0076] All points in the embodiments disclosed herein should be considered illustrative and not intended to limit the invention. The scope of the invention is not limited by the above description of the embodiments, but is defined by the technical solutions and is intended to include equivalents and all modifications within that scope.

Claims

1. A power transmission system, characterized in that, The power transmission system includes: Vehicles equipped with energy storage devices; and The power transmission station is capable of transmitting power to the vehicle. The vehicles include: A first acquisition device acquires the temperature of the energy storage device; The second acquisition device acquires the remaining capacity of the energy storage device; A heating device that consumes electricity to heat the energy storage device; and Control device, controls the heating device. The control device sets a first threshold for the remaining capacity used to stop the operation of the heating device to a value higher than the remaining capacity of the energy storage device where power transmission is restricted.

2. The power transmission system according to claim 1, characterized in that, If the remaining capacity becomes greater than a second threshold (which is larger than the first threshold) after the operation of the heating device is stopped, the control device restarts the operation of the heating device.

3. The power transmission system according to claim 1, characterized in that, The power transmission station notifies the vehicle of the upper limit of the power it can output, and supplies the vehicle with the power set by the user. If the power supplied from the power transmission station is lower than the power required for the heating device to operate, the control device sets the first threshold.

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