Power system and method for controlling the power system

Abstract

Even during cold starts, the power system is quickly activated to begin vehicle operation. [Solution] The power system comprises a first battery unit and a second battery unit having a smaller charging capacity than the first battery unit. Based on the temperature of the second battery unit and ambient temperature forecast information for predicting the trend of ambient temperature, the system predicts the temperature trend of the second battery unit. If the predicted temperature of the second battery unit falls below a predetermined temperature threshold, a preheating process is performed to charge and discharge the second battery unit so that its temperature becomes equal to or above the predetermined temperature threshold at least at a predetermined time.

Description

Technical Field

[0001] The present disclosure relates to a power system and a control method for a power system.

Background Art

[0002] An electric vehicle that rotates a driving motor by the power charged in a battery and travels by the driving torque output from the driving motor has been put into practical use. As a secondary battery mounted on an electric vehicle, the use of an all-solid-state battery has been studied. The all-solid-state battery has a wider operating temperature range than a battery using an electrolytic solution such as a lithium-ion battery and can operate at high temperatures. However, the performance of the all-solid-state battery deteriorates at temperatures lower than the operating range, such as in cold regions.

[0003] On the other hand, when the temperature of the battery is low at the start of vehicle operation, there is a technique for warming up the battery to raise its temperature. For example, in Patent Document 1, when it is detected that a driver performs a start preparation operation before starting a hybrid system, a DC / DC converter is adjusted to charge and discharge between a high-voltage battery electrically connected to a motor generator and a low-voltage battery electrically connected to the high-voltage battery via the DC / DC converter, thereby raising the internal temperature of the high-voltage battery.

[0004] Furthermore, Patent Document 2 discloses a power supply system comprising a capacity-type first battery, an output-type second battery with a smaller thermal capacity than the first battery, a voltage converter for converting voltage between the first and second power circuits, a power converter for converting power between the first power circuit and a drive motor, and power control means for operating the voltage converter and power converter to control the charging and discharging of the first and second batteries. The power control means, after startup, performs power path control to exchange power between the first and second batteries until the combined upper limit of the first and second batteries exceeds a driving threshold, and then performs second priority control to discharge the second battery more than the first battery until the first upper limit of the first battery exceeds a margin driving threshold, thereby rapidly raising the temperature of the second battery with a smaller thermal capacity and ensuring power output performance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-114311 [Patent Document 2] Japanese Patent Publication No. 2022-144934 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the technologies disclosed in Patent Documents 1 and 2 both involve raising the battery temperature when the vehicle starts up, which may prevent the vehicle from starting up or limit the vehicle's driving torque until the warm-up is complete.

[0007] This disclosure has been made in view of the above-mentioned issues, and the purpose of this disclosure is to provide a power system and a method for controlling the power system that can quickly start the power system and start the operation of a vehicle even when the vehicle is cold. [Means for solving the problem]

[0008] To solve the above problems, according to one aspect of this disclosure, a first battery unit having a plurality of battery cells, a second battery unit having a plurality of battery cells made of solid-state batteries, having a smaller charging capacity than the first battery unit and a larger heat capacity than the first battery unit, a power converter that converts power between the first battery unit and the second battery unit and a drive motor, a first transformer circuit that converts voltage between the first battery unit and the second battery unit, a second transformer circuit that converts voltage between the second battery unit and the power converter, and the first battery unit and the second A power system is provided comprising: a control device for controlling the charging and discharging of a battery unit, the control device having a temperature change prediction unit that predicts the temperature change of the second battery unit when the operation of the vehicle and the charging and discharging of the second battery unit are stopped and left unattended, based on outside temperature prediction information for predicting the temperature change of the outside temperature during vehicle operation; and a charge / discharge control unit that, if the predicted temperature of the second battery unit falls below a predetermined temperature threshold, performs a preheating process to charge and discharge the second battery unit so that the temperature of the second battery unit becomes equal to or above the predetermined temperature threshold at least at a predetermined time.

[0009] Furthermore, in order to solve the above problems, according to another aspect of this disclosure, a first battery unit having a plurality of battery cells, a second battery unit having a plurality of battery cells and having a smaller charging capacity than the first battery unit, a power converter that converts power between the first battery unit and the second battery unit and a drive motor, a first transformer circuit that converts voltage between the first battery unit and the second battery unit, a second transformer circuit that converts voltage between the second battery unit and the power converter, and the first battery unit and the second A power system is provided comprising: a control device for controlling the charging and discharging of a second battery unit, the control device including: a temperature change prediction unit that predicts the temperature change of the second battery unit when the vehicle is stopped or after it has stopped, based on ambient temperature prediction information for predicting the temperature change of the ambient temperature; and a charge / discharge control unit that, if the predicted temperature of the second battery unit falls below a predetermined temperature threshold, performs a preheating process to charge and discharge the second battery unit so that the temperature of the second battery unit becomes equal to or above the predetermined temperature threshold at least at a predetermined time.

[0010] Furthermore, in order to solve the above problems, according to yet another aspect of this disclosure, a first battery unit having a plurality of battery cells, a second battery unit having a plurality of battery cells and having a smaller charging capacity than the first battery unit, a power converter that converts power between the first battery unit and the second battery unit and a drive motor, a first transformer circuit that converts voltage between the first battery unit and the second battery unit, a second transformer circuit that converts voltage between the second battery unit and the drive motor, and the first A control method for a power system comprising a battery unit and a control device for controlling the charging and discharging of the second battery unit is provided, wherein the control method predicts the temperature trend of the second battery unit based on the temperature of the second battery unit and ambient temperature forecast information for predicting the trend of ambient temperature, and if the predicted temperature of the second battery unit falls below a predetermined temperature threshold, the control method for a power system is provided which performs a preheating process to charge and discharge the second battery unit so that the temperature of the second battery unit becomes equal to or above the predetermined temperature threshold at least at a predetermined time. [Effects of the Invention]

[0011] As explained above, according to this disclosure, the power system can be quickly started up and the vehicle can be started even during a cold start. [Brief explanation of the drawing]

[0012] [Figure 1] This is an explanatory diagram showing an example configuration of an electric vehicle equipped with a power system according to an embodiment of the present disclosure. [Figure 2] This is a block diagram showing an example configuration of a power system according to the same embodiment. [Figure 3] This is a flowchart showing the processing performed by the power system according to the same embodiment while an electric vehicle is in operation. [Figure 4] This flowchart shows the normal charging and discharging control of an electric vehicle during operation using the power system according to the same embodiment. [Figure 5] It is a flowchart showing normal charge / discharge control during the operation of an electric vehicle by the power system according to the same embodiment. [Figure 6] It is a flowchart showing warming charge / discharge control during the operation of an electric vehicle by the power system according to the same embodiment. [Figure 7] It is a flowchart showing warming charge / discharge control during the operation of an electric vehicle by the power system according to the same embodiment. [Figure 8] It is a flowchart showing warming charge / discharge control during the operation of an electric vehicle by the power system according to the same embodiment. [Figure 9] It is an explanatory diagram showing the state of the power system during warming charge / discharge control during the operation of an electric vehicle according to the same embodiment. [Figure 10] It is an explanatory diagram showing the state of the power system during warming charge / discharge control during the operation of an electric vehicle according to the same embodiment. [Figure 11] It is a flowchart showing the processes during and after the stop of an electric vehicle by the power system according to the same embodiment. [Figure 12] It is a flowchart showing warming charge / discharge control during and after the stop of an electric vehicle by the power system according to the same embodiment. [Figure 13] It is an explanatory diagram showing the state of the power system during warming charge / discharge control during and after the stop of an electric vehicle according to the same embodiment. [Figure 14] It is an explanatory diagram showing the state of the power system at the cold start of an electric vehicle according to the same embodiment.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in the following embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0014] <1. Overall Configuration of Electric Vehicle> First, a configuration example of an electric vehicle equipped with a power system according to an embodiment of the present disclosure will be described.

[0015] FIG. 1 is an explanatory diagram showing a configuration example of an electric vehicle 1. The power system 10 of the electric vehicle 1 is constructed as a system for controlling the drive system of the electric vehicle 1. The electric vehicle 1 is an electric vehicle having a driving motor 11 driven by electric power stored in a first battery unit 15 and a second battery unit 19 as a driving power source. The power system 10 includes a driving motor 11, a power converter 13, a first battery unit 15, a voltage conversion circuit 17, a second battery unit 19, and a control device 50.

[0016] The electric vehicle 1 may be provided with a power generation device such as a fuel cell, a turbine power generation device, or an engine power generation device. Further, the electric vehicle 1 may be an electric vehicle having a configuration in which the second battery unit 19 and the first battery unit 15 are charged by receiving power supply from an external charging device.

[0017] The electric vehicle 1 shown in FIG. 1 is a front-wheel drive vehicle, and the driving motor 11 outputs a driving torque distributed to the left and right front wheels by a differential mechanism 5. The driving motor 11 may be, for example, a three-phase AC radial motor, but may also be a motor having another configuration such as an axial gap motor. The driving motor 11 is driven by an alternating current supplied through the power converter 13 during acceleration of the electric vehicle 1 to output a driving torque. On the other hand, the driving motor 11 generates electricity by being regenerated by the power converter 13 during deceleration of the electric vehicle 1.

[0018] Note that the electric vehicle 1 may be a rear-wheel drive vehicle or a four-wheel drive vehicle. Further, the electric vehicle 1 may be provided with a front-wheel driving motor and a rear-wheel driving motor, or may be provided with a driving motor corresponding to each of the four wheels.

[0019] The power converter 13 is configured with an inverter circuit. When the electric vehicle 1 is accelerating, the power converter 13 converts the DC current supplied from the first battery unit 15 or the second battery unit 19 into AC current and supplies it to the drive motor 11, thereby driving the drive motor 11 in power. Furthermore, when the electric vehicle 1 is decelerating, the power converter 13 regenerates power from the drive motor 11, converts the generated AC current into DC current and supplies it to the first battery unit 15 and the second battery unit 19.

[0020] The first battery unit 15 and the second battery unit 19 are high-voltage power sources that supply power to the drive motor 11. The rated voltage of the drive motor 11 is exemplified as 200V or 400V, but is not particularly limited. The first battery unit 15 and the second battery unit 19 are each composed of multiple battery modules housed in a casing. Each battery module has multiple battery cells connected in series, and the multiple battery modules are connected in series and in parallel. In this embodiment, the battery cells are all-solid-state batteries. However, at least the battery cells of the second battery unit 19 may be all-solid-state batteries.

[0021] The first battery unit 15 and the second battery unit 19 are electrically connected via a transformer circuit 17 and are both used as power sources for the drive motor 11. The first battery unit 15 is used as the main battery, and the second battery unit 19 is used as a sub-battery. The maximum charging capacity of the second battery unit 19 is smaller than the maximum charging capacity of the first battery unit 15, and when the electric vehicle 1 is in operation, the power from the first battery unit 15 is mainly used.

[0022] Furthermore, the number of battery modules in series in the first battery unit 15 and the second battery unit 19 are different. For example, the number of battery modules in series in the first battery unit 15 is greater than the number of battery modules in series in the second battery unit 19. The maximum output voltage of the first battery unit 15 is equivalent to the rated voltage of the drive motor 11, while the maximum output voltage of the second battery unit 19 is lower than the rated voltage of the drive motor 11. For this reason, for example, if the number of battery modules in parallel in the first battery unit 15 and the second battery unit 19 were the same, the current flowing through the second battery unit 19 would be greater than the current flowing through the first battery unit 15 when charging and discharging a predetermined current with the drive motor 11. Consequently, the second battery unit 19 has higher heat generation characteristics than the first battery unit 15.

[0023] The heat capacity of the second battery unit 19 is greater than that of the first battery unit 15. For example, the housing of the second battery unit 19 is constructed using an insulating material. The second battery unit 19 may also be housed in a container made of an insulating material. For this reason, the second battery unit 19 has higher heat retention than the first battery unit 15.

[0024] The first battery unit 15 and the second battery unit 19 are each equipped with a first battery controller 31 and a second battery controller 33, respectively, for managing their states. The first battery controller 31 and the second battery controller 33 each include one or more processors and electronic circuits including various peripheral components. The first battery controller 31 and the second battery controller 33 each have the function of outputting information on the voltage, current, remaining capacity, and temperature of the first battery unit 15 and the second battery unit 19 to the control device 50.

[0025] The transformer circuit 17 is configured to include converter circuits for boosting and lowering voltage. The transformer circuit 17 includes a first transformer circuit that converts voltage between the first battery unit 15 and the second battery unit 19, and a second transformer circuit that converts voltage between the second battery unit 19 and the power converter 13. The first transformer circuit and the second transformer circuit may be provided as separate units.

[0026] A first switch 21 and a second switch 23 are provided on the power line connecting the first battery unit 15 and the power converter 13. The first switch 21 and the second switch 23 are driven by the control device 50 to switch the electrical connection and disconnection between the first battery unit 15 and the power converter 13. A third switch 25 and a fourth switch 27 are provided on the power line connecting the transformer circuit 17 and the power converter 13. The third switch 25 and the fourth switch 27 are driven by the control device 50 to switch the electrical connection and disconnection between the transformer circuit 17 and the power converter 13.

[0027] The control device 50 includes one or more processors that control the charging and discharging of the first battery unit 15 and the second battery unit 19. The control device 50 is configured to acquire information such as voltage, current, remaining capacity, and temperature of the first battery unit 15 and the second battery unit 19 from the first battery controller 31 and the second battery controller 33. The control device 50 may be divided into multiple control devices, each for the function of controlling the operation of the power converter 13 and the transformer circuit 17 to power and regenerate the drive motor 11, and the function of controlling the charging of the first battery unit 15 and the second battery unit 19. In this case, the multiple control devices are connected to a communication bus such as CAN (Controller Area Network) and are configured to send and receive messages to each other.

[0028] Furthermore, the electric vehicle 1 is equipped with a GNSS (Global Navigation Satellite System) antenna 41, an outside temperature sensor 43, an accelerator pedal position sensor 45, a brake sensor 47, and a wheel speed sensor 49. The GNSS antenna 41 receives signals transmitted from positioning satellites such as GPS (Global Positioning System) satellites and obtains the position information of the electric vehicle 1 on map data. The position information may be latitude and longitude information. The GNSS antenna 41 may also be configured to receive satellite signals from satellite systems other than GPS satellites.

[0029] The outside temperature sensor 43 detects the temperature outside the vehicle. The accelerator pedal position sensor 45 detects the accelerator pedal position. The brake sensor 47 detects the amount of brake operation. The wheel speed sensor 49 detects the rotational speed of one or more wheels. The GNSS antenna 41, outside temperature sensor 43, accelerator pedal position sensor 45, brake sensor 47, and wheel speed sensor 49 each output signals representing the acquired information to the control device 50.

[0030] Furthermore, the electric vehicle 1 is equipped with a notification device 39. The notification device 39 provides predetermined notifications to the occupants of the electric vehicle 1. The notification device 39 is configured to include, for example, at least one of a display device and a speaker. However, the type of notification device 39 is not particularly limited.

[0031] <2. Power Systems> Figure 2 is a block diagram showing an example configuration of the power system 10 of the electric vehicle 1. The control device 50 comprises a processing unit 51, a storage unit 53, a map data storage unit 55, and a communication unit 57. The processing unit 51 is composed of one or more processors such as CPUs (Central Processing Units) and various peripheral components. Part or all of the processing unit 51 may be composed of updatable components such as firmware, or it may be a program module that is executed by commands from the CPU, etc.

[0032] The control device 50 functions as a device that realizes the functions described below by having one or more processors execute a computer program. The computer program is a computer program that causes the processor to execute the operations that the processing unit 51 is to perform, as described later. The computer program executed by the processor may be recorded on a recording medium that functions as a memory unit 53 provided in the control device 50, or it may be recorded on a recording medium built into the processing unit 51 or on any external recording medium that can be attached to the control device 50.

[0033] Recording media for storing computer programs may include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs, DVDs (Digital Versatile Discs), and Blu-ray®; magneto-optical media such as floppy disks; memory elements such as RAM (Random Access Memory) and ROM (Read Only Memory); flash memory such as USB (Universal Serial Bus) memory and SSDs (Solid State Drives); and other media capable of storing programs.

[0034] The control device 50 acquires information detected by the GNSS antenna 41, ambient temperature sensor 43, accelerator pedal position sensor 45, brake sensor 47, and wheel speed sensor 49. The control device 50 is also connected to the first battery controller 31 and the second battery controller 33 via a dedicated line or a communication bus such as CAN. The control device 50 also controls the operation of the first switch 21, the second switch 23, the third switch 25, the fourth switch 27, the power converter 13, the transformer circuit 17, and the notification device 39.

[0035] The memory unit 53 is composed of one or more memory elements such as RAM or ROM that are connected to the processing unit 51 in a communicative manner. However, the type and number of memory units 53 are not particularly limited. The memory unit 53 stores computer programs executed by the processing unit 51, various parameters used in arithmetic processing, detection data, calculation results, and other information. A portion of the memory unit 53 is used as the work area of ​​the processing unit 51.

[0036] The map data storage unit 55 is composed of a memory element such as RAM or ROM, or a storage medium such as an HDD, CD, DVD, SSD, USB flash drive, or storage device, which is connected to the processing unit 51 in a communicative manner. The map data stored in the map data storage unit 55 is associated with latitude and longitude information, and the processing unit 51 can identify the position of the electric vehicle 1 on the map data based on the latitude and longitude information transmitted from the GNSS antenna 41.

[0037] The communication unit 57 is an interface for the processing unit 51 to communicate with the telematics service 70 outside the vehicle. The communication unit 57 may be an interface for communicating with the telematics service 70, for example, via mobile communication, but the method of communication with the telematics service 70 is not particularly limited.

[0038] The processing unit 51 executes processes to control the power system 10. The processing unit 51 includes a temperature transition prediction unit 61, a power converter control unit 64, a transformer circuit control unit 65, and a switch drive unit 67. The power converter control unit 64 and the transformer circuit control unit 65 function as a charge / discharge control unit 63. Each of these units is a function realized by the execution of a computer program by one or more processors. However, some or all of the temperature transition prediction unit 61, the power converter control unit 64, the transformer circuit control unit 65, and the switch drive unit 67 may be configured using analog circuits.

[0039] (Temperature change prediction section) The temperature change prediction unit 61 predicts the temperature change of the second battery unit 19 based on the temperature of the second battery unit 19 and ambient temperature prediction information for predicting the ambient temperature change. For example, the temperature change prediction unit 61 predicts the temperature change of the second battery unit 19 based on the ambient temperature detected by the ambient temperature sensor 43, hourly ambient temperature data for the area in which the electric vehicle 1 is driving, and the temperature of the second battery unit 19 output from the second battery controller 33.

[0040] For example, the temperature transition prediction unit 61 predicts the temperature transition of the second battery unit 19 when the operation of the electric vehicle 1 and the charging and discharging of the second battery unit 19 are stopped and left idle, based on the temperature of the second battery unit 19 and the outside temperature forecast information while the vehicle is in operation. In addition, the temperature transition prediction unit 61 predicts the temperature transition of the second battery unit 19 when the vehicle is stopped or after it has stopped, based on the temperature of the second battery unit 19 and the outside temperature forecast information.

[0041] (Charge / Discharge Control Unit) The charge / discharge control unit 63, which is composed of a power converter control unit 64 and a transformer circuit control unit 65, controls the traction and regeneration of the drive motor 11, as well as the charging and discharging of the first battery unit 15 and the second battery unit 19.

[0042] The power converter control unit 64 controls the drive of the power converter 13 and controls the powering and regenerative braking of the drive motor 11. For example, the power converter control unit 64 calculates the required drive torque based on the accelerator opening detected by the accelerator opening sensor 45 and the vehicle speed calculated from the wheel speed detected by the wheel speed sensor 49, and drives the drive motor 11 in power mode. In addition, the power converter control unit 64 calculates the required braking torque based on the brake operation amount detected by the brake sensor 47, and drives the drive motor 11 in regenerative braking mode.

[0043] When the electric vehicle 1 is driving in automatic driving mode, the power converter control unit 64 acquires information on the required drive torque and required braking torque from a control device (not shown) that controls automatic driving, and controls the traction or regeneration of the drive motor 11.

[0044] The transformer circuit control unit 65 controls the drive of the transformer circuit 17. When the transformer circuit control unit 65 drives the drive motor 11 with power from the second battery unit 19, it boosts the output voltage of the second battery unit 19 and supplies it to the power converter 13. When the transformer circuit control unit 65 charges the second battery unit 19 with regenerative power from the drive motor 11, it lowers the voltage of the regenerative power and supplies it to the second battery unit 19. Also, when the transformer circuit control unit 65 supplies power from the second battery unit 19 to the first battery unit 15, it boosts the output voltage of the second battery unit 19 and supplies it to the first battery unit 15. When the transformer circuit control unit 65 supplies power from the first battery unit 15 to the second battery unit 19, it lowers the output voltage of the first battery unit 15 and supplies it to the second battery unit 19.

[0045] In this embodiment, if the predicted temperature of the second battery unit 19 falls below a predetermined temperature threshold, the charge / discharge control unit 63 performs a preheating process to charge and discharge the second battery unit 19 so that its temperature is at or above the predetermined temperature threshold at least at a preset time. For example, the preset time may be a time set by the user, or it may be a time when the ambient temperature is predicted to reach its lowest temperature. If the temperature of the second battery unit 19 at the time when the ambient temperature is predicted to reach its lowest temperature is at or above the predetermined temperature threshold, the temperature of the second battery unit 19 can be maintained at or above the predetermined temperature threshold at the times before and after that time.

[0046] For example, if the temperature of the second battery unit 19 predicted to occur during operation of the electric vehicle 1 falls below a predetermined temperature threshold, the charge / discharge control unit 63 performs a preheating process to charge and discharge the second battery unit 19 so that its temperature is at least above the predetermined temperature threshold at the time when the ambient temperature is predicted to reach its lowest temperature. Also, if the temperature of the second battery unit 19 predicted to occur when the electric vehicle 1 is stopped or after it has stopped falls below a predetermined temperature threshold, the charge / discharge control unit 63 performs a preheating process to charge and discharge the second battery unit so that its temperature is at least above the predetermined temperature threshold at the time when the ambient temperature is predicted to reach its lowest temperature.

[0047] (Switch drive unit) The switch drive unit 67 drives the first switch 21, the second switch 23, the third switch 25, and the fourth switch 27. The switch drive unit 67 switches the first switch 21, the second switch 23, the third switch 25, and the fourth switch 27 on or off depending on whether the drive motor 11 is being driven or regenerated, and whether the first battery unit 15 or the second battery unit 19 is being charged or discharged.

[0048] <3. Operation of the Power System> Up to this point, the configuration of the power system 10 according to this embodiment has been described. Next, the operation of the power system 10 will be described separately for operation while the electric vehicle 1 is running and operation when the electric vehicle 1 is stopped or after it has stopped. In this embodiment, an example will be described in which the control device 50 performs a preheating treatment so that the temperature of the second battery unit 19 is above the operating lower limit temperature at the time when the outside temperature becomes the lowest temperature, and performs a process to maintain the temperature of the second battery unit 19 at or above the operating lower limit temperature when the power system 10 is started.

[0049] (Operations while driving an electric vehicle) Figure 3 shows a flowchart illustrating the operation of the power system 10 while the electric vehicle 1 is in operation. While the power system 10 is running, the temperature trend prediction unit 61 of the control device 50 acquires outside temperature prediction information to predict the trend of the outside temperature (step S11). For example, the temperature trend prediction unit 61 acquires hourly temperature data for the current location from a telematics service based on the location information of the electric vehicle 1 acquired from the GNSS antenna 41. The temperature trend prediction unit 61 also refers to map data and acquires altitude information for the current location based on the location information. The temperature trend prediction unit 61 also acquires the current outside temperature Te_act information from the outside temperature sensor 43.

[0050] Next, the temperature change prediction unit 61 predicts the time TI_te_min when the outside temperature Te becomes the lowest temperature Te_min and the lowest temperature Te_min based on the acquired outside temperature prediction information (step S13). For example, the temperature change prediction unit 61 uses hourly temperature data of the current location as a basis, modifies the trend of the outside temperature Te according to the altitude of the current location and the current outside temperature Te_act, and predicts the time TI_te_min when the lowest temperature Te_min becomes Te_min and the lowest temperature Te_min.

[0051] The time TI_te_min may be, for example, the time when the most recent lowest temperature Te_min occurs. This allows for preheating in preparation for the start of operation of the electric vehicle 1 the following day. Alternatively, it may be the time when the lowest temperature Te_min occurs between the current scheduled end of use of the electric vehicle 1, which is predicted based on the destination and arrival time information of the electric vehicle 1 obtainable from the navigation system. This prevents wasting time on preheating while the electric vehicle 1 is on its way to its destination.

[0052] Next, the temperature transition prediction unit 61 predicts the temperature Tb of the second battery unit 19 based on the current temperature Tb_act of the second battery unit 19 and the ambient temperature prediction information, assuming that the operation of the electric vehicle 1 and the charging and discharging of the second battery unit 19 are stopped and left idle (step S15). For example, the temperature transition prediction unit 61 obtains the current temperature Tb_act information from the second battery controller 33 and predicts the temperature Tb of the second battery unit 19 based on the previously stored information on the heat dissipation characteristics of the second battery unit 19 and the transition prediction information of the current temperature Tb_act and ambient temperature Te.

[0053] Next, the temperature transition prediction unit 61 determines whether the temperature Tb of the second battery unit 19 at time TI_te_min, when the ambient temperature Te becomes the lowest temperature Te_min, is below a predetermined temperature threshold Tb_0 (step S17). The predetermined temperature threshold Tb_0 is set to a temperature that is any margin higher than the operating lower limit temperature Tb_min of the second battery unit 19, which consists of an all-solid-state battery. For example, if the operating lower limit temperature Tb_min of the all-solid-state battery is -30℃, the predetermined temperature threshold Tb_0 may be set to -25℃.

[0054] If the temperature transition prediction unit 61 does not determine that the temperature Tb of the second battery unit 19 at time TI_te_min is below a predetermined temperature threshold Tb_0 (S17 / No), it proceeds to step S29 because there is no need to warm up the electric vehicle 1 for the next start.

[0055] On the other hand, if the temperature transition prediction unit 61 determines that the temperature Tb of the second battery unit 19 at time TI_te_min is below a predetermined temperature threshold Tb_0 (S17 / Yes), it calculates a target temperature Tb_tgt to make the temperature Tb of the second battery unit 19 at time TI_te_min the predetermined temperature threshold Tb_0 (step S19). For example, similar to step S15, the temperature transition prediction unit 61 calculates the target temperature Tb_tgt of the second battery unit 19 based on information on the heat dissipation characteristics of the second battery unit 19 and the transition prediction information of the current temperature Tb_act and ambient temperature Te.

[0056] Next, the temperature transition prediction unit 61 determines whether the current temperature Tb_act of the second battery unit 19 is less than the target temperature Tb_tgt (step S21). If the temperature transition prediction unit 61 does not determine that the current temperature Tb_act of the second battery unit 19 is less than the target temperature Tb_tgt (S21 / No), the temperature transition prediction unit 61 does not need to raise the current temperature Tb_act of the second battery unit 19, and proceeds to step S29.

[0057] On the other hand, if the temperature transition prediction unit 61 determines that the current temperature Tb_act of the second battery unit 19 is less than the target temperature Tb_tgt (S21 / Yes), the charge / discharge control unit 63 calculates the total energy amount Pw_total, which is the sum of the energy amount Pw_1 charged in the first battery unit 15 and the energy amount Pw_2 charged in the second battery unit 19 (step S23). For example, the charge / discharge control unit 63 calculates the total energy amount Pw_total based on the remaining capacity SOC_1 of the first battery unit 15 and the remaining capacity SOC_2 of the second battery unit 19.

[0058] Next, the charge / discharge control unit 63 determines whether there is a margin in the calculated total energy amount Pw_total (step S25). Steps S23 to S25 determine whether there is surplus power to be used to raise the temperature of the second battery unit 19. For example, the charge / discharge control unit 63 determines whether the total energy amount Pw_total exceeds the amount of energy corresponding to the maximum charging capacity of the second battery unit 19. This determination indicates that even if the second battery unit 19 is fully charged, there will be power to be used to drive the electric vehicle 1. However, the method for determining whether there is a margin in the total energy amount Pw_total is not particularly limited.

[0059] If the charge / discharge control unit 63 does not determine that there is sufficient margin in the total power amount Pw_total (S25 / No), it cannot perform the process of raising the temperature of the second battery unit 19. Therefore, it activates the notification device 39 to notify that it cannot maintain the temperature of the second battery unit 19 above the operating lower limit temperature until the next start of the electric vehicle 1 (step S27).

[0060] Next, the charge / discharge control unit 63 sets the control mode of the power system 10 to the normal charge / discharge control mode (step S29).

[0061] Figures 4 and 5 show flowcharts of the charge / discharge control process in the normal charge / discharge control mode. In the normal charge / discharge control mode, since there is no need to preheat the second battery unit 19, the operation of the electric vehicle 1 is controlled by primarily charging and discharging the first battery unit 15, which has a larger charging capacity, as long as there is no power surplus or deficit.

[0062] The charge / discharge control unit 63 determines whether the required acceleration Acc of the electric vehicle 1 is greater than zero (step S41). For example, the charge / discharge control unit 63 determines whether the required acceleration Acc is greater than zero based on the sensor signal of the accelerator opening sensor 45. If the electric vehicle 1 is in automatic driving control mode, the charge / discharge control unit 63 obtains information on the required acceleration Acc from the control device that controls automatic driving and determines whether the required acceleration Acc is greater than zero.

[0063] If the charge / discharge control unit 63 determines that the required acceleration Acc is greater than zero (S41 / Yes), that is, when controlling the drive motor 11 in power mode, it calculates the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 based on the required acceleration Acc (step S43). For example, the charge / discharge control unit 63 calculates the amount of energy Pw_drv that can output the required drive torque based on the required drive torque Tq_drv and rotational speed of the drive motor 11.

[0064] Next, the charge / discharge control unit 63 calculates the amount of energy Pw_1_out that can be output from the first battery unit 15 (step S45). For example, the charge / discharge control unit 63 calculates the amount of energy Pw_1_out that can be output from the first battery unit 15 based on the voltage of the first battery unit 15 obtained from the first battery controller 31.

[0065] Next, the charge / discharge control unit 63 determines whether the amount of energy Pw_1_out that can be output from the first battery unit 15 exceeds the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 (step S47). If the charge / discharge control unit 63 determines that the amount of energy Pw_1_out that can be output from the first battery unit 15 exceeds the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 (S47 / Yes), it drives the drive motor 11 in power mode using the power supplied from the first battery unit 15 (step S49).

[0066] On the other hand, if the charge / discharge control unit 63 does not determine that the amount of power Pw_1_out that can be output from the first battery unit 15 exceeds the amount of power Pw_drv that can be output to provide the required drive torque for the drive motor 11 (S47 / No), it primarily uses the power supplied from the first battery unit 15 and drives the drive motor 11 in power mode, supplementing any shortfall with power supplied from the second battery unit 19 (step S51).

[0067] On the other hand, in step S41 above, if the charge / discharge control unit 63 does not determine that the required acceleration Acc is greater than zero (S41 / No), that is, if the drive motor 11 is regenerating power, it calculates the regenerative power amount Pw_reg of the drive motor 11 (step S53). For example, the charge / discharge control unit 63 determines the required deceleration torque from the brake operation amount indicated by the sensor signal of the brake sensor 47, and calculates the regenerative power amount Pw_reg based on the required deceleration torque and the rotational speed of the drive motor 11. When the electric vehicle 1 is in automatic driving control mode, the charge / discharge control unit 63 obtains information on the required deceleration from the control device that controls automatic driving and determines the required deceleration torque.

[0068] Next, the charge / discharge control unit 63 calculates the amount of energy Pw_1_in that can be charged into the first battery unit 15 (step S55). For example, the charge / discharge control unit 63 calculates the amount of energy Pw_1_in that can be charged into the first battery unit 15 based on the voltage of the first battery unit 15 obtained from the first battery controller 31.

[0069] Next, the charge / discharge control unit 63 determines whether the amount of energy Pw_1_in that can be charged to the first battery unit 15 exceeds the amount of regenerative energy Pw_reg from the drive motor 11 (step S57). If the charge / discharge control unit 63 determines that the amount of energy Pw_1_in that can be charged to the first battery unit 15 exceeds the amount of regenerative energy Pw_reg from the drive motor 11 (S57 / Yes), it regenerates power from the drive motor 11 and charges the first battery unit 15 with the regenerated power (step S59).

[0070] On the other hand, if the charge / discharge control unit 63 does not determine that the amount of energy Pw_1_in that can be charged to the first battery unit 15 exceeds the amount of regenerative energy Pw_reg from the drive motor 11 (S57 / No), it regenerates power from the drive motor 11, mainly charges the first battery unit 15 with the regenerated power, and charges the surplus to the second battery unit 19 (step S61).

[0071] The charge / discharge control unit 63 repeatedly executes the processes described in steps S41 to S61 while the control mode of the power system 10 is set to the normal charge / discharge control mode.

[0072] Returning to Figure 3, if the charge / discharge control unit 63 determines that there is sufficient margin in the total power amount Pw_total (S25 / Yes), it sets the control mode of the power system 10 to the temperature-raising charge / discharge control mode in order to perform the process of raising the temperature of the second battery unit 19 (step S31).

[0073] Figures 6 to 8 show flowcharts of the charge / discharge control process in the temperature rise charge / discharge control mode. In the temperature rise charge / discharge control mode, the operation of the electric vehicle 1 is controlled mainly by charging and discharging the second battery unit 19 in order to preheat the second battery unit 19, as long as there is no power surplus or deficit.

[0074] The charge / discharge control unit 63 determines whether the remaining capacity SOC_2 of the second battery unit 19 exceeds a predetermined threshold SOC_thr (step S71). Step S71 corresponds to the process of determining whether it is necessary to charge the second battery unit 19 by power supply from the first battery unit 15. The predetermined threshold SOC_thr is set to a lower threshold SOC_thr_L or an upper threshold SOC_thr_H in steps S73 and S97.

[0075] If the charge / discharge control unit 63 determines that the remaining capacity SOC_2 of the second battery unit 19 exceeds a predetermined threshold SOC_thr (S71 / Yes), it sets the predetermined threshold SOC_thr to a lower threshold SOC_thr_L (step S73). The lower threshold SOC_thr_L may be set to, for example, 30%, but is not limited to this value. As a result, unless the determination in step S71 determines that the remaining capacity SOC_2 of the second battery unit 19 does not exceed the predetermined threshold SOC_thr (becomes less than or equal to the lower threshold SOC_thr_L), the second battery unit 19 will not be charged by power supplied from the first battery unit 15.

[0076] Next, the charge / discharge control unit 63 determines whether the required acceleration Acc of the electric vehicle 1 is greater than zero, similar to step S41 (step S75). If the charge / discharge control unit 63 determines that the required acceleration Acc is greater than zero (S75 / Yes), that is, when controlling the drive motor 11 in power mode, it calculates the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 based on the required acceleration Acc, similar to step S43 (step S77).

[0077] Next, the charge / discharge control unit 63 calculates the amount of energy Pw_2_out that can be output from the second battery unit 19 (step S79). For example, the charge / discharge control unit 63 calculates the amount of energy Pw_2_out that can be output from the second battery unit 19 based on the voltage of the second battery unit 19 obtained from the second battery controller 33.

[0078] Next, the charge / discharge control unit 63 determines whether the amount of energy Pw_2_out that can be output from the second battery unit 19 exceeds the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 (step S81). If the charge / discharge control unit 63 determines that the amount of energy Pw_2_out that can be output from the second battery unit 19 exceeds the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 (S81 / Yes), it drives the drive motor 11 in power using the power supplied from the second battery unit 19 (step S83).

[0079] On the other hand, if the charge / discharge control unit 63 does not determine that the amount of power Pw_2_out that can be output from the second battery unit 19 exceeds the amount of power Pw_drv that can be output to provide the required drive torque for the drive motor 11 (S81 / No), it primarily uses the power supplied from the second battery unit 19 and drives the drive motor 11 in power mode, supplementing any shortfall with the power supplied from the first battery unit 15 (step S85).

[0080] On the other hand, in step S75 above, if the charge / discharge control unit 63 does not determine that the required acceleration Acc is greater than zero (S75 / No), that is, if the drive motor 11 is regenerating power, it calculates the regenerative power amount Pw_reg of the drive motor 11 in the same manner as in step S53 (step S87).

[0081] Next, the charge / discharge control unit 63 calculates the amount of energy Pw_2_in that can be charged into the second battery unit 19 (step S89). For example, the charge / discharge control unit 63 calculates the amount of energy Pw_2_in that can be charged into the second battery unit 19 based on the voltage of the second battery unit 19 obtained from the second battery controller 33.

[0082] Next, the charge / discharge control unit 63 determines whether the amount of energy Pw_2_in that can be charged to the second battery unit 19 exceeds the amount of regenerative energy Pw_reg from the drive motor 11 (step S91). If the charge / discharge control unit 63 determines that the amount of energy Pw_2_in that can be charged to the second battery unit 19 exceeds the amount of regenerative energy Pw_reg from the drive motor 11 (S91 / Yes), it regenerates power from the drive motor 11 and charges the second battery unit 19 with the regenerated power (step S93).

[0083] Figure 9 shows the state of the power system 10 in which only the second battery unit 19 is charged and discharged in steps S83 and S93. In this state, the first switch 21 and the second switch 23 are turned off, while the third switch 25 and the fourth switch 27 are connected. Power is supplied from the second battery unit 19 to the drive motor 11 via the transformer circuit 17 and the power converter 13, and regenerative power from the drive motor 11 is used to charge the second battery unit 19.

[0084] On the other hand, if the charge / discharge control unit 63 does not determine that the amount of energy Pw_2_in that can be charged to the second battery unit 19 exceeds the amount of regenerative energy Pw_reg from the drive motor 11 (S91 / No), it regenerates power from the drive motor 11, mainly charges the second battery unit 19 with the regenerated power, and charges the first battery unit 15 with the surplus (step S95).

[0085] Furthermore, in step S71 described above, if the charge / discharge control unit 63 does not determine that the remaining capacity SOC_2 of the second battery unit 19 exceeds a predetermined threshold SOC_thr (S71 / No), it sets the predetermined threshold SOC_thr to an upper threshold SOC_thr_H (step S98). The upper threshold SOC_thr_H may be set to, for example, 80%, but is not limited to this value. As a result, unless the determination in step S71 determines that the remaining capacity SOC_2 of the second battery unit 19 exceeds the predetermined threshold SOC_thr (upper threshold SOC_thr_H), the second battery unit 19 is charged by power supplied from the first battery unit 15.

[0086] Next, the charge / discharge control unit 63 determines whether the required acceleration Acc of the electric vehicle 1 is greater than zero, similar to step S41 (step S99). If the charge / discharge control unit 63 determines that the required acceleration Acc is greater than zero (S99 / Yes), that is, when controlling the drive motor 11 in power mode, it calculates the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 based on the required acceleration Acc, similar to step S43 (step S101).

[0087] Next, the charge / discharge control unit 63 calculates the amount of energy Pw_1_out that can be output from the first battery unit 15, similar to step S45 (step S103). Next, the charge / discharge control unit 63 calculates the amount of energy Pw_2_in that can be charged into the second battery unit 19, similar to step S89 (step S105). Next, the charge / discharge control unit 63 determines whether the amount of energy Pw_1_out that can be output from the first battery unit 15 exceeds the sum of the amount of energy Pw_drv that can output the required drive torque of the drive motor 11 and the amount of energy Pw_2_in that can be charged into the second battery unit 19 (step S107).

[0088] If the charge / discharge control unit 63 determines that step S107 is correct (S107 / Yes), it drives the drive motor 11 in power mode using the power supplied from the first battery unit 15 and charges the second battery unit 19 (step S109). On the other hand, if the charge / discharge control unit 63 determines that step S107 is incorrect (S107 / No), it drives the drive motor 11 in power mode using the power supplied from the first battery unit 15 and charges the second battery unit 19 if there is any surplus power (step S111).

[0089] Figure 10 shows the state of the power system 10 in steps S109 and S111, where the first battery unit 15 is charged and discharged, and any surplus power is used to charge the second battery unit 19. In this state, the first switch 21 and the second switch 23 are connected, while the third switch 25 and the fourth switch 27 are disconnected. Power is supplied from the first battery unit 15 to the drive motor 11 via the power converter 13, and power is also supplied from the first battery unit 15 to the second battery unit 19 via the transformer circuit 17, thereby charging the second battery unit 19.

[0090] In step S111, if the amount of energy Pw_1_out that can be output from the first battery unit 15 is less than the amount of energy Pw_drv that can output the required drive torque of the drive motor 11, the charge / discharge control unit 63 limits the output of the drive motor 11 and notifies the occupants of this fact via the notification device 39.

[0091] On the other hand, in step S99 above, if the charge / discharge control unit 63 does not determine that the required acceleration Acc is greater than zero (S99 / No), that is, if the drive motor 11 is to be regenerated, the process proceeds to step S87 and the charge / discharge control is executed according to the procedure shown in Figure 7.

[0092] The charge / discharge control unit 63 repeatedly executes the processes described in steps S71 to S111 while the control mode of the power system 10 is set to the temperature rise charge / discharge control mode.

[0093] (Operation of electric vehicles when stopped and after stopping) Figure 11 shows a flowchart of the operation of the power system 10 when the electric vehicle 1 is stopped and after it has stopped. The processes shown in Figure 11 may be executed when the electric vehicle 1 is stopped and the power system 10 is turned off, or they may be executed after the power system 10 has been turned off. When the control device 50 executes the processes after the power system 10 has been turned off, it may start the power system 10 after a predetermined time has elapsed since the power system 10 was turned off and execute the processes, or it may start the power system 10 at regular or irregular time intervals after the power system 10 has been turned off and execute the processes.

[0094] The temperature transition prediction unit 61 acquires outside temperature prediction information for predicting the trend of the outside temperature, similar to steps S11 to S13, and predicts the time TI_te_min when the outside temperature Te becomes the lowest temperature Te_min, and that lowest temperature Te_min (steps S121 to S123). The time TI_te_min may be, for example, the time when the most recent lowest temperature Te_min occurs. This enables preheating in preparation for the start of operation of the electric vehicle 1 the following day. Alternatively, the usage pattern of the electric vehicle 1 may be determined based on the driving record, and the time when the lowest temperature Te_min immediately preceding the predicted next use of the electric vehicle 1 may occur.

[0095] Next, the temperature transition prediction unit 61 predicts the temperature Tb of the second battery unit 19 based on the current temperature Tb_act of the second battery unit 19 and the ambient temperature forecast information (step S125). For example, the temperature transition prediction unit 61 obtains the current temperature Tb_act information from the second battery controller 33 and predicts the temperature Tb of the second battery unit 19 based on the previously stored information on the heat dissipation characteristics of the second battery unit 19, the current temperature Tb_act, and the ambient temperature Te transition forecast information.

[0096] Next, the temperature transition prediction unit 61, similar to step S17, determines whether the temperature Tb of the second battery unit 19 at time TI_te_min, when the ambient temperature Te becomes the lowest temperature Te_min, is below a predetermined temperature threshold Tb_0 (step S127).

[0097] If the temperature transition prediction unit 61 does not determine that the temperature Tb of the second battery unit 19 at time TI_te_min is below a predetermined temperature threshold Tb_0 (S127 / No), it does not need to warm up the electric vehicle 1 for the next start-up, and therefore puts the power system 10 into standby mode (step S143).

[0098] On the other hand, if the temperature transition prediction unit 61 determines that the temperature Tb of the second battery unit 19 at time TI_te_min is below a predetermined temperature threshold Tb_0 (S127 / Yes), it calculates a target temperature Tb_tgt to make the temperature Tb of the second battery unit 19 at time TI_te_min the predetermined temperature threshold Tb_0, similar to step S19 (step S129).

[0099] Next, the charge / discharge control unit 63 calculates the amount of energy Pw(Tb_act→Tb_tgt) and the time required to raise the temperature Tb of the second battery unit 19 from the current temperature Tb_act to the target temperature Tb_tgt (step S131). For example, the charge / discharge control unit 63 calculates the amount of energy Pw(Tb_act→Tb_tgt) and the time required to raise the temperature Tb of the second battery unit 19 from the current temperature Tb_act to the target temperature Tb_tgt based on the previously stored information on the heat dissipation characteristics of the second battery unit 19 and the amount of heat generated when the second battery unit 19 is charged and discharged.

[0100] Next, the charge / discharge control unit 63 calculates the total energy amount Pw_total, which is the sum of the energy amount Pw_1 charged in the first battery unit 15 and the energy amount Pw_2 charged in the second battery unit 19, in the same manner as in step S23 (step S133).

[0101] Next, the charge / discharge control unit 63 determines whether the calculated total energy amount Pw_total exceeds the energy amount Pw(Tb_act→Tb_tgt) required to raise the temperature Tb of the second battery unit 19 from the current temperature Tb_act to the target temperature Tb_tgt (step S135). Steps S133 to S135 determine whether there is surplus power available to raise the temperature of the second battery unit 19.

[0102] If the charge / discharge control unit 63 does not determine that the total energy amount Pw_total exceeds the required energy amount Pw(Tb_act→Tb_tgt) (S135 / No), it cannot perform the process of raising the temperature of the second battery unit 19. Therefore, it activates the notification device 39 to notify that it cannot maintain the temperature of the second battery unit 19 above the operating lower limit temperature until the next start of the electric vehicle 1 (step S137). This notification may also be performed when the power system 10 is started up next. After that, the charge / discharge control unit 63 puts the power system 10 into standby mode (sleep state) (step S143).

[0103] On the other hand, if the charge / discharge control unit 63 determines that the total energy amount Pw_total exceeds the required energy amount Pw(Tb_act→Tb_tgt) (S135 / Yes), it determines whether the required time is longer than the time ΔTI from the current time to the time TI_te_min when the minimum temperature Te_min is reached (step S139). Step S139 corresponds to determining whether there is enough time to raise the temperature of the second battery unit 19 before the minimum temperature Te_min is reached.

[0104] If the charge / discharge control unit 63 does not determine that the required time is longer than the time ΔTI from the current time to the time TI_te_min when the minimum temperature Te_min is reached (S139 / No), it activates the notification device 39 to notify that the temperature of the second battery unit 19 cannot be kept above the operating lower limit temperature until the next start of the electric vehicle 1 (step S137). This notification may also be given when the power system 10 is started up next time. After that, the charge / discharge control unit 63 puts the power system 10 into standby mode (sleep state) (step S143).

[0105] On the other hand, if the charge / discharge control unit 63 determines that the required time is longer than the time ΔTI from the current time to the time TI_te_min when the lowest temperature Te_min is reached (S139 / Yes), it sets the control mode of the power system 10 to the temperature-raising charge / discharge control mode in order to perform the process of raising the temperature of the second battery unit 19 (step S141).

[0106] Figure 12 shows a flowchart of the charge / discharge control process in the temperature rise charge / discharge control mode while the electric vehicle 1 is stopped. In the temperature rise charge / discharge control mode while the electric vehicle 1 is stopped, the first battery unit 15 and the second battery unit 19 are repeatedly charged and discharged in order to preheat the second battery unit 19.

[0107] The charge / discharge control unit 63 determines whether the time ΔTI from the current time to the time TI_te_min when the minimum temperature Te_min is reached is equal to the required time plus a predetermined buffer time TI_α (step S151). The buffer time TI_α is the time required to ensure that the heating of the second battery unit 19 is completed by the time TI_te_min when the minimum temperature Te_min is reached, and may be set to any value.

[0108] If the charge / discharge control unit 63 does not determine that time ΔTI has reached the required time plus a predetermined buffer time TI_α (S151 / No), it repeats the determination in step S151. On the other hand, if the charge / discharge control unit 63 determines that time ΔTI has reached the required time plus a predetermined buffer time TI_α (S151 / Yes), it starts the timer count (step S153).

[0109] Next, it is determined whether the ratio of the remaining capacity SOC_2 of the second battery unit 19 to the remaining capacity SOC_1 of the first battery unit 15 exceeds a predetermined threshold R_thr (step S155). Step S155 corresponds to the process of determining whether the second battery unit 19 is in a state suitable for discharging or a state suitable for charging. The predetermined threshold R_thr is set to the first threshold R_thr_1 or the second threshold R_thr_2 in steps S157 and S163.

[0110] If the charge / discharge control unit 63 determines that the ratio of the remaining capacity SOC_2 of the second battery unit 19 to the remaining capacity SOC_1 of the first battery unit 15 exceeds a predetermined threshold R_thr (S155 / Yes), it sets the predetermined threshold R_thr to the first threshold R_thr_1 (step S157). The first threshold R_thr_1 is set to a value smaller than the second threshold R_thr_2, and is an appropriate value that allows it to determine that the remaining capacity SOC_2 of the second battery unit 19 has a relatively large margin relative to the remaining capacity SOC_1 of the first battery unit 15. As a result, unless the determination in step S155 determines that the ratio of the remaining capacity SOC_2 of the second battery unit 19 to the remaining capacity SOC_1 of the first battery unit 15 does not exceed the predetermined threshold R_thr, the first battery unit 15 is charged by power supplied from the second battery unit 19.

[0111] Next, the charge / discharge control unit 63 determines the optimal current pattern for charging the first battery unit 15 with power supplied from the second battery unit 19 (step S159). For example, the charge / discharge control unit 63 considers that the amount of heat generated by the second battery unit 19 will reach its maximum in the shortest time, and determines the maximum allowable current from the charge / discharge characteristics of the first battery unit 15 and the second battery unit 19 at that time as the charge / discharge current.

[0112] Next, the charge / discharge control unit 63 charges the first battery unit 15 with the output power from the second battery unit 19 according to the determined current (step S161).

[0113] On the other hand, in step S155, if the charge / discharge control unit 63 does not determine that the ratio of the remaining capacity SOC_2 of the second battery unit 19 to the remaining capacity SOC_1 of the first battery unit 15 exceeds a predetermined threshold R_thr (S155 / No), it sets the predetermined threshold R_thr to a second threshold R_thr_2 (step S163). The second threshold R_thr_2 is a value greater than the first threshold R_thr_1 and is set to an appropriate value that allows it to determine that there is insufficient remaining capacity SOC_2 of the second battery unit 19 relative to the remaining capacity SOC_1 of the first battery unit 15. As a result, unless the determination in step S155 determines that the ratio of the remaining capacity SOC_2 of the second battery unit 19 to the remaining capacity SOC_1 of the first battery unit 15 exceeds a predetermined threshold R_thr, the second battery unit 19 is charged by power supplied from the first battery unit 15.

[0114] Next, the charge / discharge control unit 63 determines the optimal current for charging the second battery unit 19 using power supplied from the first battery unit 15 (step S165). For example, the charge / discharge control unit 63 considers that the amount of heat generated by the second battery unit 19 will reach its maximum in the shortest time, and determines the maximum allowable current based on the charge / discharge characteristics of the first battery unit 15 and the second battery unit 19 at that time as the charge / discharge current.

[0115] Next, the charge / discharge control unit 63 charges the second battery unit 19 with the output power from the first battery unit 15 according to the determined current pattern (step S167).

[0116] Figure 13 shows the state of the power system 10 in steps S161 and S167, where the first battery unit 15 and the second battery unit 19 supply and charge each other. In this state, the first switch 21, the second switch 23, the third switch 25, and the fourth switch 27 are all turned off. Power is then exchanged between the first battery unit 15 and the second battery unit 19 via the transformer circuit 17.

[0117] Next, the charge / discharge control unit 63 determines whether the elapsed time since the timer count started in step S153 has reached the time obtained by adding a predetermined buffer time TI_α to the required time for the temperature Tb of the second battery unit to be equal to or greater than the target temperature Tb_tgt (step S169). If the charge / discharge control unit 63 does not determine that the elapsed time has reached the time obtained by adding a predetermined buffer time TI_α to the required time (S169 / No), it returns to step S155 and continues the charge / discharge control. On the other hand, if the charge / discharge control unit 63 determines that the elapsed time has reached the time obtained by adding a predetermined buffer time TI_α to the required time (S169 / Yes), it terminates the charge / discharge control.

[0118] (Operation when starting an electric vehicle) In the power system 10 according to this embodiment, the control device 50 starts the power system 10 while maintaining the temperature of the second battery unit 19 above the operating lower limit temperature. Therefore, during the cold start of the electric vehicle 1, the control device 50 drives the drive motor 11 with the power output from the second battery unit 19 until the temperature of the first battery unit 15 reaches or exceeds the operating lower limit temperature.

[0119] Figure 14 shows the state of the power system 10 during a cold start of the electric vehicle 1. In this state, the first switch 21, the second switch 23, the third switch 25, and the fourth switch 27 are all connected. The output power of the second battery unit 19 is supplied to the drive motor 11 via the transformer circuit 17 and the power converter 13, and the drive motor 11 is driven in power mode. When the drive motor 11 is regenerating power, the second battery unit 19 is mainly charged with regenerated power. If there is surplus regenerated power, the first battery unit 15 is charged with regenerated power. Furthermore, if the remaining capacity SOC_1 of the second battery unit 19 decreases, power may be supplied from the first battery unit 15 to the second battery unit 19 under low load conditions to charge the second battery unit 19.

[0120] <4. Effects> As described above, the power system 10 according to this embodiment includes a first battery unit 15 having a plurality of battery cells, a second battery unit 19 having a plurality of battery cells and having a smaller charging capacity than the first battery unit 15, a power converter 13 that converts power between the first battery unit 15 and the second battery unit 19 and the drive motor 11, a voltage transformer circuit 17 that converts voltage between the first battery unit 15 and the second battery unit 19, a voltage transformer circuit 17 that converts voltage between the second battery unit 19 and the power converter 13, and a control device 50 that controls the charging and discharging of the first battery unit 15 and the second battery unit 19.

[0121] The control device 50 includes a temperature transition prediction unit 61 that predicts the temperature transition of the second battery unit 19 when the operation of the electric vehicle 1 and the charging and discharging of the second battery unit 19 are stopped and left unattended, based on ambient temperature prediction information for predicting the temperature transition of the second battery unit 19 and the ambient temperature Te while the electric vehicle 1 is in operation, and a charge / discharge control unit 63 that, if the predicted temperature Tb of the second battery unit 19 falls below a predetermined temperature threshold Tb_0, performs a preheating process to charge and discharge the second battery unit 19 so that the temperature Tb of the second battery unit 19 becomes equal to or greater than the predetermined temperature threshold Tb_0 at time TI_te_min, which is predicted to be the minimum ambient temperature Te_min.

[0122] Therefore, when the electric vehicle 1 is running, and after the electric vehicle 1 stops and the power system 10 stops, the power system 10 can be started when the electric vehicle 1 is restarted, with the temperature Tb of the second battery unit 19 at or above the operating lower limit temperature Tb_min. Consequently, even when the electric vehicle 1 is cold-started, the delay in starting operation due to the warming up of the power system 10 is suppressed, and operation can be started quickly.

[0123] Furthermore, in the power system 10 according to this embodiment, when the electric vehicle 1 is in operation, the charge / discharge control unit 63 calculates a target temperature Tb_tgt for the second battery unit 19 that will maintain the temperature of the second battery unit 19 at or above the predetermined temperature threshold Tb_0 if the predicted temperature Tb of the second battery unit 19 falls below a predetermined temperature threshold Tb_0. When the electric vehicle 1 is in operation, the control unit 63 performs a preheating process when the temperature Tb of the second battery unit 19 falls below the target temperature Tb_tgt. Therefore, when the electric vehicle 1 is in operation, if there is a possibility that the temperature Tb of the second battery unit 19 will fall below the operating lower limit temperature Tb_min when the electric vehicle 1 is stopped, the preheating process is automatically started. Consequently, when the electric vehicle 1 is restarted, it can be started quickly.

[0124] Furthermore, in the power system 10 according to this embodiment, the charge / discharge control unit 63 increases the charge / discharge power of the first battery unit 15 to that of the second battery unit 19 when preheating is not performed while the electric vehicle 1 is in operation, and increases the charge / discharge power of the second battery unit 19 to that of the first battery unit 15 when preheating is performed. As a result, when preheating of the second battery unit 19 is not required, stable charge / discharge control can be performed using the first battery unit 15, which has a larger charging capacity. Also, when preheating of the second battery unit 19 is required, the charge / discharge amount and the number of charge / discharge cycles of the second battery unit 19 increase, so that the temperature of the second battery unit 19 can be reliably raised.

[0125] Furthermore, in the power system 10 according to this embodiment, if the temperature Tb of the second battery unit 19 predicted to be at or after the electric vehicle 1 is stopped falls below a predetermined temperature threshold Tb_0, the charge / discharge control unit 63 performs a preheating process to charge and discharge the second battery unit 19 so that the temperature Tb of the second battery unit 19 becomes equal to or greater than the predetermined temperature threshold Tb_0 at least the time when the ambient temperature Te is predicted to become the minimum temperature Te_min.

[0126] Therefore, when the electric vehicle 1 is parked, the power system 10 can be started when the temperature Tb of the second battery unit 19 is above the operating lower limit temperature Tb_min, which is the next time the electric vehicle 1 is restarted. Consequently, even when the electric vehicle 1 is cold-started, the delay in starting operation due to the warming up of the power system 10 is suppressed, and operation can be started quickly.

[0127] Furthermore, in the power system 10 according to this embodiment, when the electric vehicle 1 is stopped or after it is stopped, the charge / discharge control unit 63 calculates a target temperature Tb_tgt for the second battery unit 19 so as to maintain the temperature Tb of the second battery unit 19 at time TI_te_min, when the ambient temperature Te is predicted to become the lowest temperature Te_min, at or above a predetermined temperature threshold Tb_0, and performs a preheating process until the temperature Tb of the second battery unit 19 becomes equal to or above the target temperature Tb_tgt. As a result, even when the power system 10 is stopped after the preheating process, the temperature Tb of the second battery unit 19 at time TI_te_min, when the ambient temperature Te becomes the lowest temperature Te_min, can be maintained at or above the operating lower limit temperature Tb_min.

[0128] Furthermore, in the power system 10 according to this embodiment, the temperature transition prediction unit 61 predicts the temperature transition of the second battery unit 19 when the electric vehicle 1 stops, and the charge / discharge control unit 63 performs a preheating process if the predicted temperature Tb of the second battery unit 19 falls below a predetermined temperature threshold Tb_0. As a result, after the electric vehicle 1 stops and the power system 10 is stopped after the preheating process is performed, the temperature Tb of the second battery unit 19 can be maintained at or above the operating lower limit temperature Tb_min.

[0129] Furthermore, in the power system 10 according to this embodiment, the temperature transition prediction unit 61 predicts the temperature transition of the second battery unit 19 at regular or irregular time intervals after the electric vehicle 1 is stopped, and the charge / discharge control unit 63 performs a preheating process if the predicted temperature Tb of the second battery unit 19 falls below a predetermined temperature threshold Tb_0. As a result, even if there is a risk that the temperature Tb of the second battery unit 19 will fall below the operating lower limit temperature Tb_min after the power system 10 is stopped, the temperature of the second battery unit 19 can be raised to maintain the temperature Tb of the second battery unit 19 at or above the operating lower limit temperature Tb_min.

[0130] Furthermore, in the power system 10 according to this embodiment, when the electric vehicle 1 is stopped or after it has stopped, if the predicted temperature Tb of the second battery unit 19 falls below a predetermined temperature threshold Tb_0, the charge / discharge control unit 63 calculates the required time for preheating to maintain the temperature Tb of the second battery unit 19 at the predicted time TI_te_min, when the ambient temperature Te is expected to reach the lowest temperature Te_min, at a time earlier than the required time TI_te_min, when the ambient temperature Te is expected to reach the lowest temperature Te_min. This eliminates the need to repeatedly perform preheating until the electric vehicle 1 is restarted, thereby reducing power consumption.

[0131] While preferred embodiments of the present disclosure have been described in detail above with reference to the attached drawings, the technology of the present disclosure is not limited to such examples. It is clear to any person with ordinary skill in the art to which the present disclosure belongs that various modifications or alterations may be conceived within the scope of the technical idea set forth in the claims, and these will naturally also be understood to fall within the technical scope of the present disclosure.

[0132] Furthermore, the technology of this disclosure can also be realized as a vehicle equipped with the power system described in the above-described embodiment, a method for controlling the power system executed by the control device, a computer program that causes a computer to function as the control device described above, and a non-temporary tangible recording medium on which the computer program is recorded.

[0133] For example, in the above embodiment, a configuration example was described in which the first battery unit and the second battery unit are equipped with multiple battery cells made of all-solid-state batteries. However, the first battery unit, or the first battery unit and the second battery unit, do not necessarily have to be equipped with multiple battery cells made of all-solid-state batteries.

[0134] For example, in the above embodiment, an example of performing operations while an electric vehicle is in operation includes a configuration in which the control device raises the temperature of the second battery unit before the electric vehicle stops, and maintains the temperature of the second battery unit above a predetermined temperature threshold even after the electric vehicle stops. Therefore, it is desirable that the second battery unit is configured to have multiple battery cells made of solid-state batteries that can operate at higher temperatures, while the first battery unit does not necessarily have to be configured to have multiple battery cells made of solid-state batteries.

[0135] Furthermore, the example of performing operations when the electric vehicle is stopped or after it has stopped in the above embodiment includes a configuration in which the control device raises the temperature of the second battery unit in accordance with a preset time. Therefore, when the configuration is set to perform operations only when the electric vehicle is stopped or after it has stopped, temperature control is performed according to the temperature rise characteristics of the second battery unit, so it is not necessary for both the first and second battery units to be equipped with multiple battery cells made of solid-state batteries.

[0136] Furthermore, although the above embodiment describes a configuration in which the thermal capacity of the second battery unit is greater than that of the first battery unit, the thermal capacities of the first and second battery units are not particularly limited when the configuration is designed to perform only operations when the electric vehicle is stopped or after it has stopped. The example of performing operations when the electric vehicle is stopped or after it has stopped includes a configuration in which the control device raises the temperature of the second battery unit in accordance with a preset time. Therefore, even if the configuration is not such that the thermal capacity of the second battery unit is greater than that of the first battery unit, the above effects can still be obtained.

[0137] Furthermore, in the above embodiment, an example was described in which the temperature of the second battery unit 19 is set to a predetermined temperature threshold at the time when the outside temperature is expected to reach its lowest temperature. However, the preset time may be a time arbitrarily specified by the user. For example, the user may be able to register their next planned departure time. This makes it unnecessary to warm up the second battery unit when starting the electric vehicle 1 next time, and even in the case of a cold start, delays in starting the operation due to warming up the power system 10 are suppressed, allowing the vehicle to start operating quickly. [Explanation of Symbols]

[0138] 1: Electric vehicle 10: Power Systems 11: Drive motor 13: Power Converter 15: First battery unit 17: Transformer Circuit 19: Second battery unit 50: Control device 61: Temperature change prediction section 63: Charge / Discharge Control Unit 64: Power converter control unit 65: Transformer Circuit Control Unit 67: Switch drive unit

Claims

1. A first battery unit having multiple battery cells, A second battery unit comprising multiple battery cells made of all-solid-state batteries, having a charging capacity smaller than that of the first battery unit and a thermal capacity larger than that of the first battery unit, A power converter that converts power between the first battery unit, the second battery unit, and the drive motor, A first voltage transformer circuit that converts voltage between the first battery unit and the second battery unit, A second transformer circuit that converts voltage between the second battery unit and the power converter, The system comprises a control device for controlling the charging and discharging of the first battery unit and the second battery unit, The control device is A temperature change prediction unit predicts the temperature change of the second battery unit when the vehicle is in operation and the charging and discharging of the second battery unit is stopped and left unattended, based on ambient temperature prediction information for predicting the temperature change of the second battery unit and ambient temperature during vehicle operation. A charge / discharge control unit that, when the predicted temperature of the second battery unit falls below a predetermined temperature threshold, performs a preheating process to charge and discharge the second battery unit so that the temperature of the second battery unit becomes equal to or greater than the predetermined temperature threshold at least at a predetermined time, A power system equipped with the necessary components.

2. The power system according to claim 1, wherein the charge / discharge control unit performs the preheating process with the preset time set as the time when the ambient temperature is predicted to reach its lowest temperature.

3. The power system according to claim 1, wherein the charge / discharge control unit calculates a target temperature for the second battery unit to maintain the temperature of the second battery unit at or above the predetermined temperature threshold when the predicted temperature of the second battery unit falls below the predetermined temperature threshold, and performs the preheating treatment when the temperature of the second battery unit falls below the target temperature during the operation of the vehicle.

4. The power system according to claim 1, wherein the charge / discharge control unit makes the charge / discharge power of the first battery unit greater than the charge / discharge power of the second battery unit when the preheating treatment is not performed, and makes the charge / discharge power of the second battery unit greater than the charge / discharge power of the first battery unit when the preheating treatment is performed.

5. A first battery unit having multiple battery cells, A second battery unit comprising multiple battery cells and having a charging capacity smaller than that of the first battery unit, A power converter that converts power between the first battery unit, the second battery unit, and the drive motor, A first voltage transformer circuit that converts voltage between the first battery unit and the second battery unit, A second transformer circuit that converts voltage between the second battery unit and the power converter, The system comprises a control device for controlling the charging and discharging of the first battery unit and the second battery unit, The control device is A temperature change prediction unit predicts the temperature change of the second battery unit when the vehicle is stopped or after it has stopped, based on ambient temperature prediction information for predicting the temperature change of the ambient temperature, A charge / discharge control unit that, when the predicted temperature of the second battery unit falls below a predetermined temperature threshold, performs a preheating process to charge and discharge the second battery unit so that the temperature of the second battery unit becomes equal to or greater than the predetermined temperature threshold at least at a predetermined time, A power system equipped with the necessary components.

6. The power system according to claim 5, wherein the charge / discharge control unit performs the preheating process with the preset time set as the time when the ambient temperature is predicted to reach its lowest temperature.

7. The power system according to claim 5, wherein the charge / discharge control unit calculates a target temperature for the second battery unit that maintains the temperature of the second battery unit at a predetermined time above a predetermined temperature threshold, and performs the preheating process until the temperature of the second battery unit reaches or exceeds the target temperature.

8. The heat capacity of the second battery unit is greater than the heat capacity of the first battery unit. The temperature change prediction unit predicts the temperature change of the second battery unit when the vehicle is stopped. The power system according to claim 5, wherein the charge / discharge control unit performs the preheating treatment when the predicted temperature of the second battery unit falls below the predetermined temperature threshold.

9. The temperature change prediction unit predicts the temperature change of the second battery unit at regular or irregular time intervals after the vehicle has stopped. The power system according to claim 5, wherein the charge / discharge control unit performs the preheating treatment when the predicted temperature of the second battery unit falls below the predetermined temperature threshold.

10. The power system according to claim 8 or 9, wherein the charge / discharge control unit calculates the required time for the preheating process to maintain the temperature of the second battery unit at a predetermined temperature threshold if the predicted temperature of the second battery unit falls below a predetermined temperature threshold, and starts the preheating process at a time before the required time that is set in advance.

11. A first battery unit having multiple battery cells, A second battery unit comprising multiple battery cells and having a charging capacity smaller than that of the first battery unit, A power converter that converts power between the first battery unit, the second battery unit, and the drive motor, A first voltage transformer circuit that converts voltage between the first battery unit and the second battery unit, A second voltage transformer circuit that converts voltage between the second battery unit and the drive motor, A control method for a power system comprising a control device for controlling the charging and discharging of the first battery unit and the second battery unit, Based on the temperature of the second battery unit and the ambient temperature forecast information for predicting the trend of ambient temperature, the temperature trend of the second battery unit is predicted. A power system control method comprising: if the predicted temperature of the second battery unit falls below a predetermined temperature threshold, performing a preheating process to charge and discharge the second battery unit so that the temperature of the second battery unit becomes equal to or greater than the predetermined temperature threshold at least at a predetermined time.

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