Electric power system of vehicle

Abstract

To enable an auxiliary machine to be supplied with electric power, even when limiting charge / discharge power of an auxiliary machine battery of a lithium-ion battery.SOLUTION: Electric power is supplied from an auxiliary apparatus battery 16 to an auxiliary apparatus 14. Electric power is supplied to and charged into the auxiliary apparatus battery 16 from a battery 12 for driving that supplies electric power to an electric motor for driving a vehicle through a DC-DC converter 30. Charge / discharge power of the auxiliary apparatus battery 16 is limited on the basis of a temperature and power storage amounts of the auxiliary apparatus battery 16. When the charge / discharge power of the auxiliary apparatus battery 16 is limited, power corresponding to shortage of power that is supplied to the auxiliary apparatus is supplied from the battery 12 for driving thereto.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to vehicle power systems, and more particularly to powering on-board accessories. [Background technology]

[0002] Electric vehicles, hybrid vehicles, and other electrically powered vehicles include a drive battery that supplies power to the vehicle drive motor, and an auxiliary battery that supplies power to on-board auxiliaries such as lighting, air conditioning, and a control unit. The auxiliary battery is charged with power from the drive battery. Patent Document 1 listed below describes a battery system in which the auxiliary battery can be charged with power from a solar power generation device in addition to power from the drive battery (see paragraphs 0013, 0020, etc.). Patent Document 1 listed below also describes the use of a lead secondary battery as the auxiliary battery (see paragraph 0020). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-46679 A Summary of the Invention [Problem to be solved by the invention]

[0004] When using a lithium-ion battery as an auxiliary battery, it is important to manage the amount of stored power and the charge / discharge current. In order to accurately grasp the amount of stored power in a lithium-ion battery, it is necessary to measure the voltage with the charge / discharge current set to zero. In addition, in order to suppress battery deterioration, the charge / discharge current of a lithium-ion battery may be limited depending on the battery condition. However, while the vehicle is running, it is necessary to supply power to the auxiliary equipment, and it may be difficult to set the charge / discharge power of the auxiliary battery to zero or to limit it. [Means for solving the problem]

[0005] The vehicle energy system of the present invention comprises a first power source including a lithium ion battery that supplies power to auxiliary equipment provided in the vehicle, a second power source that supplies power to be charged to the first power source, and a power control unit that controls the charging and discharging power of the first power source and the second power source, and when there is a request to limit the charging and discharging power of the first power source, the power control unit controls the second power source to supply the shortfall in power supplied to the auxiliary equipment.

[0006] The second power source may be a drive battery that supplies power to an electric motor that drives the vehicle, or the second power source may include a drive battery that supplies power to an electric motor that drives the vehicle, and a solar power generation device. Effect of the Invention

[0007] Even if the first power source is limited in its charge / discharge power, it is possible to supply the necessary power to the auxiliary equipment. Therefore, the charge / discharge current of the lithium-ion battery of the first power source can be appropriately limited, and deterioration of the battery can be suppressed. Furthermore, when the charge / discharge current of the lithium-ion battery of the first power source is limited to zero, the amount of stored power can be accurately grasped. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a schematic configuration of a power system according to an embodiment of the present invention; [Diagram 2] 5 is a flowchart showing a control performed when a charge / discharge current of an auxiliary battery is limited. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a power system 10 of a vehicle according to this embodiment. The power system 10 has, as power sources, a drive battery 12 that supplies power to an electric motor (not shown) that drives the vehicle, an auxiliary battery 16 that supplies power to an auxiliary device 14 provided in the vehicle, and a solar power generation device 18. The auxiliary device 14 is, for example, a lighting device 20 such as a headlight, a direction indicator, or a control unit 22 that controls devices such as an engine, a drive motor, and a transmission, or an audio device 24, or an air conditioner 26, and is supplied with a voltage lower than that of the drive motor, for example, a voltage of 12 volts. The auxiliary battery 16 is formed of a lithium ion battery. Charging and discharging of the auxiliary battery 16 are controlled by an auxiliary battery control unit 28. The solar power generation device 18 includes a solar cell installed on the roof of the vehicle and a control unit that controls charging and discharging of the solar cell.

[0010] The driving battery 12 is charged with electric power generated by a generator driven by the on-board engine. It is also charged with electric power generated by regenerative braking when the vehicle decelerates. It may also be charged with electric power from an external power source. In a vehicle that runs only on an electric motor, the driving battery 12 is charged with electric power from an external power source and regenerative electric power.

[0011] The auxiliary battery 16 is charged with power from the drive battery 12. The high voltage of the drive battery 12 is stepped down by a DC-DC converter 30, and power is supplied to and charged by the auxiliary battery 16. The auxiliary battery 16 may also be charged with power from a solar power generation device 18.

[0012] The auxiliary battery control unit 28 monitors the auxiliary battery 16. Specifically, the auxiliary battery control unit 28 integrates the charge and discharge power based on the output of the current sensor 32A to obtain the amount of charge stored in the auxiliary battery 16 at that time. The auxiliary battery control unit 28 determines the upper limit of the charge and discharge current according to the obtained amount of charge stored, based on a predetermined relationship between the amount of charge stored and the upper limit of the charge and discharge current. The charge and discharge current is controlled to be equal to or lower than this upper limit. When the lithium ion battery is charged or discharged when the amount of charge stored is low or high, deterioration progresses. For this reason, the auxiliary battery control unit 28 sets a lower upper limit when the amount of charge stored is low or high, compared to when the amount of charge stored is medium. The charge and discharge current is controlled to be equal to or lower than this upper limit. Specifically, the upper limit may be decreased stepwise or continuously as the amount of charge stored approaches 0% and 100%.

[0013] Lithium ion batteries deteriorate when they are charged and discharged at low and high temperatures. For this reason, the auxiliary battery control unit 28 determines the upper limit of the charge and discharge current according to the temperature at that time based on the temperature of the auxiliary battery 16 and on a relationship between a predetermined temperature and the upper limit of the charge and discharge current. The charge and discharge current is controlled to be equal to or lower than this upper limit. The auxiliary battery control unit 28 acquires the temperature of the auxiliary battery 16 by the temperature sensor 34, and determines the upper limit of the charge and discharge current lower when the temperature is low and high than when the temperature is medium. The upper limit of the charge and discharge power may be set to zero when the temperature is equal to or lower than a predetermined lower limit temperature and when the temperature is equal to or higher than a predetermined upper limit temperature. The upper limit may be decreased stepwise or continuously as the temperature approaches the lower limit temperature. Similarly, the upper limit may be decreased stepwise or continuously as the temperature approaches the upper limit temperature.

[0014] Under conditions where both an upper limit value of the charge / discharge current based on the amount of stored power and an upper limit value of the charge / discharge current based on the temperature are set, the lower of the two upper limits is set.

[0015] The power system 10 has a power control unit 36 ​​that controls the power supplied from the drive battery 12 to an auxiliary system consisting of the auxiliary equipment 14 and the auxiliary battery 16. The power control unit 36 ​​obtains the power supplied from the drive battery 12 to the auxiliary system based on the current detected by a current sensor 32B. The power control unit 36 ​​also obtains the power supplied from the solar power generation device 18 to the auxiliary system based on the current detected by a current sensor 32C. The power control unit 36 ​​also obtains the power supplied to the auxiliary equipment 14 based on the current detected by a current sensor 32D. The power control unit 36 ​​also obtains the amount of charge and the temperature of the auxiliary battery 16 from the auxiliary battery control unit 28.

[0016] The power control unit 36 ​​controls charging and discharging of the auxiliary battery 16. When the amount of stored power acquired by the auxiliary battery control unit 28 falls below a predetermined value, the power control unit 36 ​​controls the DC-DC converter 30 to charge the auxiliary battery 16 with power from the driving battery 12. At this time, the charging and discharging current is controlled to be equal to or below an upper limit value determined based on the amount of stored power and the temperature of the auxiliary battery 16.

[0017] As described above, the auxiliary battery control unit 28 estimates the amount of stored power based on the integrated value of the charge and discharge current. The error in the amount of stored power based on the integrated value increases over time. Therefore, the auxiliary battery control unit 28 periodically sets the charge and discharge current of the auxiliary battery 16 to zero and obtains the amount of stored power based on the terminal voltage at that time. The terminal voltage when the charge and discharge current is zero has a high correlation with the amount of stored power, and an accurate amount of stored power can be obtained. By periodically obtaining an accurate amount of stored power, the error in the amount of stored power calculated by integrating the charge and discharge power is prevented from becoming large.

[0018] As described above, in the auxiliary battery 16 using a lithium-ion battery, it is necessary to limit or zero the charge / discharge power. Meanwhile, the auxiliary 14 to which power is supplied from the auxiliary battery 16 always consumes power while the vehicle is running. In order to control the engine, the electric motor, etc., the control unit 22 always needs to be supplied with power. The brake lights belonging to the lighting device 20 need to be turned on during braking, and in recent years, some vehicles turn on some of the lights even during the day. Therefore, if the charge / discharge power is limited based on a request from the auxiliary battery 16, it may not be possible to supply the necessary power to the auxiliary 14. In the following, "limiting the charge / discharge power" also includes setting the charge / discharge power to zero.

[0019] When the power supply to the auxiliary device 14 is insufficient due to limitations on the charge / discharge power of the auxiliary battery 16, the power control unit 36 ​​controls the supply of the shortfall to the auxiliary device 14 from at least one of the drive battery 12 and the solar power generation device 18.

[0020] 2 is a flowchart showing the control performed when there is a restriction on the charging and discharging power of the auxiliary battery 16. The following control is realized by the power control unit 36 ​​operating in accordance with a predetermined program.

[0021] The power control unit 36 ​​judges whether or not there is a request to limit the charge / discharge current from the auxiliary battery control unit 28 (S100). When there is no limit request, the power control unit 36 ​​repeatedly judges whether or not there is a limit request at a predetermined interval. As described above, the auxiliary battery control unit 28 determines the upper limit value of the charge / discharge current based on the amount of charge and the temperature of the auxiliary battery 16. When this upper limit value is lower than the normal value, for example, when the amount of charge is close to 100% or close to 0%, and when the temperature is low or high, the auxiliary battery control unit 28 requests the power control unit 36 ​​to limit the charge / discharge current. When there is a request to limit the charge / discharge current, the power control unit 36 ​​acquires the upper limit value C of the discharge power of the auxiliary battery 16 based on the upper limit value of the charge / discharge current (S102). Next, it is judged whether the solar power generation device 18 is generating power (S104), and if not, it acquires the current power usage amount B of the auxiliary device 14 (S106). Then, the system calculates the shortage power supply amount A to make up for the limited power from the auxiliary battery 16 (S108). Specifically, the power supply amount A from the drive battery 12 to the auxiliary system is determined as the amount of power usage B of the auxiliary 14 minus the upper limit C of the discharge power of the auxiliary battery 16 (A=BC). Then, power A is supplied from the drive battery 12 to the auxiliary system (S110).

[0022] When solar power generation is being performed, the amount of power generated by solar power generation D is obtained (S112). Next, the amount of power usage B of the auxiliary equipment 14 at that time is obtained (S114). Then, the amount of power supply A to compensate for the shortage is calculated to make up for the limited power from the auxiliary battery 16 (S116). Specifically, the amount of power supply A from the drive battery 12 to the auxiliary system is determined as the amount of power usage B of the auxiliary equipment 14 minus the sum of the amount of power generated by solar power generation D and the upper limit C of the discharge power of the auxiliary battery 16 (A=B(C+D)). Then, power A is supplied from the drive battery 12 to the auxiliary system (S110).

[0023] The electric power supplied from the drive battery 12 to the auxiliary system may be greater than the calculated electric power supply amount A. If the auxiliary battery 16 is in a state where it can be charged, the surplus electric power exceeding the supply amount A is charged to the auxiliary battery 16. This surplus electric power is controlled to a value that satisfies the conditions of the current limit of the auxiliary battery 16.

[0024] If it is determined in step S104 that solar power generation is being performed, the solar power generation may be stopped and the processes of steps S106, S109, and S110 may be executed.

[0025] The power system 10 is a system equipped with a solar power generation device 18, but in a power system of a vehicle that does not have a solar power generation device, when power from the auxiliary battery is restricted, the shortfall is supplied to the auxiliary from the drive battery. [Explanation of symbols]

[0026] 10 power system, 12 drive battery (second power source), 14 auxiliary equipment, 16 auxiliary battery (first power source), 18 solar power generation device (second power source), 20 lighting device, 22 control unit, 24 acoustic device, 26 air conditioning unit, 28 auxiliary battery control unit, 30 DC-DC converter, 32A-D current sensor, 34 temperature sensor, 36 power control unit.

Claims

[Claim 1] A first power source including a lithium ion battery and configured to supply power to an auxiliary device of the vehicle; A second power source that supplies power to be charged to the first power source; a power control unit that controls charging and discharging power of the first power source and the second power source; Equipped with When there is a request to limit the charging / discharging power of the first power source, the power control unit controls the second power source to supply a shortage of power supplied to the auxiliary device. Vehicle power system.

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