Charging control system

Abstract

In a charging control system comprising a charger, a high-voltage battery, and a low-voltage battery, the low-voltage battery can be charged directly from the charger while the high-voltage battery is in standby mode, while keeping cost increases to a minimum. [Solution] The system includes a DC-DC converter 6 connected to a high-voltage battery 3 that steps down the first power Pbat of the high-voltage battery 3 and supplies it to a low-voltage battery 7; a charger 4 connected to the converter 6 and the high-voltage battery 3 that supplies a second power Pchg obtained from an external power source to at least one of the converter 6 and the high-voltage battery 3; a current sensor 3a that acquires the current value Ibat of the first power Pbat flowing from the high-voltage battery 3 to the converter 6; and a BMS 5 that receives the signal from the current sensor 3a and outputs a command value PI of the second power Pchg output from the charger 4 to the charger 4, wherein the BMS 5 outputs a command value PI of the second power Pchg based on the current value Ibat.

Description

Technical Field

[0001] The present invention relates to a charging control system.

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, research and development on secondary batteries that contribute to energy efficiency have been carried out. For example, Patent Document 1 discloses a technique aimed at continuing power supply to a low-voltage battery even when the temperature of a power converter in a power supply device of an electric vehicle rises excessively. That is, when supplying power from an external charger to a low-voltage battery, it has a mode of supplying via a high-voltage battery (first supply mode) and a mode of supplying without passing through the high-voltage battery (second supply mode), and it is disclosed that the supply mode is switched based on various temperatures.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the technology related to secondary batteries, a lithium-ion battery used for a high-voltage battery may promote battery deterioration when charged and discharged in a low-temperature environment such as a cold region. Therefore, when the temperature of the high-voltage battery is low, in order to suppress the deterioration of the high-voltage battery, it is desired to not output from the high-voltage battery as much as possible and to be able to charge the low-voltage battery directly from the charger. However, in the circuit described in Patent Document 1, if the second supply mode is selected when the temperature of the high-voltage battery is low, the low-voltage battery can be charged from the charger as described above. However, this requires the provision of a converter corresponding to each mode, which increases costs.

[0005] Therefore, the present invention aims to provide a charging control system comprising a charger, a high-voltage battery, and a low-voltage battery, which allows the low-voltage battery to be charged directly from the charger while the high-voltage battery is in standby mode, while suppressing cost increases. This, in turn, contributes to energy efficiency. [Means for solving the problem]

[0006] As a means of solving the above problems, a first aspect of the present invention is a charging control system (1) comprising: a voltage converter (6) connected to a high-voltage battery (3) that steps down the first power (Pbat) of the high-voltage battery (3) and supplies the stepped-down power to a low-voltage battery (7); a charger (4) connected to the voltage converter (6) and the high-voltage battery (3) that supplies second power (Pchg) obtained from an external power source to at least one of the voltage converter (6) and the high-voltage battery (3); a current detection unit (3a) that acquires the current value (Ibat) of the first power (Pbat) flowing from the high-voltage battery (3) to the voltage converter (6); and a control unit (5) that receives the signal from the current detection unit (3a) and outputs a command value (PI) of the second power (Pchg) output from the charger (4) to the charger (4), wherein the control unit (5) outputs the command value (PI) of the second power (Pchg) based on the current value (Ibat). In this configuration, a control unit that controls the charger's output power outputs a power command value to the charger based on the current value of the output power flowing from the high-voltage battery to the voltage converter. By balancing the charger's output power with the auxiliary equipment's power consumption, the output power of the high-voltage battery is suppressed. Therefore, compared to a configuration with converters between the charger and the low-voltage battery, and between the high-voltage battery and the low-voltage battery, this configuration allows for charging the low-voltage battery without going through the high-voltage battery using the charger's output power, while keeping the number of converters to a minimum.

[0007] A second aspect of the present invention is characterized in that, in the first aspect described above, the control unit (5) outputs a command value (PI) for the second power (Pchg) of the charger (4) such that the current value (Ibat) of the first power (Pbat) flowing from the high-voltage battery (3) to the voltage converter (6) becomes zero. In this configuration, the control unit that controls the output power of the charger outputs a power command value to the charger so that the current flowing from the high-voltage battery to the voltage converter becomes zero. This suppresses the output power of the high-voltage battery to zero, allowing the low-voltage battery to be charged from the charger without going through the high-voltage battery.

[0008] A third aspect of the present invention is characterized in that, in the first or second aspect described above, a temperature acquisition unit (3b) is provided to acquire the temperature of the high-voltage battery (3), and the control unit (5) outputs the command value (PI) of the second power (Pchg) based on the current value (Ibat) when the temperature of the high-voltage battery (3) acquired by the temperature acquisition unit (3b) falls below a threshold value. In this configuration, the control unit that controls the charger's output power outputs a power command value to the charger based on the high-voltage battery temperature. For example, if the high-voltage battery temperature drops (when the battery is cold), the output power of the high-voltage battery is reduced, and the low-voltage battery can be charged with the charger's output power. Therefore, power supply to the low-voltage battery can be continued by the charger while suppressing the degradation of the high-voltage battery.

[0009] A fourth aspect of the present invention is characterized in that, in the third aspect described above, the control unit (5) outputs the command value (PI) of the second power (Pchg) such that the second power (Pchg) output from the charger (4) is equal to the power consumed by the voltage converter (6). With this configuration, the output power of the high-voltage battery can be reduced to zero, allowing the low-voltage battery to be charged from the charger without going through the high-voltage battery.

[0010] A fifth aspect of the present invention is characterized in that, in the third aspect described above, the control unit (5) increases the current value output from the charger (4) to make the current value (Ibat) of the first power (Pbat) zero. With this configuration, the output power of the high-voltage battery can be reduced to zero simply by adjusting the current value output from the charger. [Effects of the Invention]

[0011] According to the present invention, in a charging control system comprising a charger, a high-voltage battery, and a low-voltage battery, it is possible to directly charge the low-voltage battery from the charger while the high-voltage battery is in standby mode, while suppressing an increase in costs. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram showing the configuration of a charging control system in an embodiment of the present invention. [Figure 2] This block diagram illustrates the calculation of the charging current command value in the above-described charging control system. [Figure 3] This graph shows the changes in the parameters of the above charging control system. [Figure 4] This is an explanatory diagram showing the power flow when charging a lead-acid battery in a low-temperature environment in the charging control system of the embodiment. [Figure 5] This flowchart shows the processing performed by the control unit when performing charging control in the above charging control system. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. In the embodiments, a charging control system 1 for an electric vehicle capable of charging a high-voltage battery 3 from an external power source will be described as an example. Hereinafter, the electric vehicle may be simply referred to as "vehicle".

[0014] <Charging control system 1> Figure 1 is a diagram showing the configuration of the charging control system 1 according to the embodiment. Figure 2 is a block diagram illustrating the calculation of the charging current command value PI in the charging control system 1. As shown in Figure 1, the charging control system 1 enables charging of the high-voltage battery 3 mounted on the vehicle by connecting a charging gun (not shown) extending from an external power source to an inlet on the vehicle side (an example of a connection point for the external power source, not shown). The vehicle may be, for example, a pure electric vehicle equipped only with a motor generator as its drive system, or a hybrid electric vehicle equipped with both a motor generator and an engine (internal combustion engine) as its drive system.

[0015] The high-voltage battery 3 stores power supplied to the motor generator, which is the drive source of the vehicle. "High voltage" means that it is a higher voltage than the 12V used for the vehicle's auxiliary equipment. The high-voltage battery 3 is connected to the motor generator for driving via an inverter. The inverter is controlled by a driving control device (not shown). The inverter converts the DC power from the high-voltage battery 3 into AC power, which can then be supplied to the motor generator. This power supply allows the motor generator to accelerate the vehicle. The inverter also enables the motor generator to function as a generator. This regeneration allows the vehicle to decelerate, and the generated AC current can be converted into DC current and stored in the high-voltage battery 3.

[0016] The high-voltage battery 3 is connected to an external charging system 2 that is supplied with power from an external power source. In the figure, line 2a indicates the positive electrode conduction line, and line 2b indicates the negative electrode conduction line. For example, a current sensor 3a for obtaining the value of the current input to or output from the high-voltage battery 3 is provided on the positive electrode conduction line 2a. Note that the DC-DC converter (voltage converter) 6 may be simply referred to as the converter 6. The external charging system 2 includes a charger 4 connected to the high-voltage battery 3 via the respective conduction lines 2a and 2b. The charger 4 is connected to an external power source when a charging gun is fitted and connected to an inlet (not shown). The charger 4 includes an AC-DC converter and can convert the AC power of the external power source into DC power and supply it to the high-voltage battery 3 or the like. Note that the charger 4 is provided with a diode (not shown) or the like for preventing power from flowing from the power output destination (vehicle side) to the charger 4 side. Reference numeral 3b in the figure indicates a temperature sensor that detects the temperature of the lithium-ion battery (battery body) in the high-voltage battery 3.

[0017] The high-voltage battery 3 is connected to a low-voltage system 8 including a low-voltage battery 7 such as a 12V lead battery and vehicle accessories (not shown). The low-voltage system 8 is connected to the high-voltage battery 3 and the external charging system 2 via a DC-DC converter 6. The DC-DC converter 6 can step down the power of the high-voltage battery 3 and the external charging system 2 and supply it to loads such as the low-voltage battery 7 and vehicle accessories. The charge control system 1 includes a BMS (Battery Management System) 5 provided integrally or separately from the high-voltage battery 3 for controlling the charge and discharge of the high-voltage battery 3.

[0018] When the charging gun is fitted and connected to the inlet, the charge control system 1 is activated, and charging of the high-voltage battery 3 and the like is started. At this time, at least one of the output power of the charger 4 and the stored power of the high-voltage battery 3 is supplied to the low-voltage system 8 via the DC-DC converter 6. The low-voltage battery 7 is charged by the power of at least one of the charger 4 and the high-voltage battery 3, avoiding overcharging of the low-voltage battery 7, and power is supplied to vehicle accessories (not shown).

[0019] Here, when the high-voltage battery 3 is a lithium-ion battery, charging or discharging at a low temperature (for example, 0°C) may be prohibited. This is because charging or discharging a lithium-ion battery at a low temperature may accelerate battery degradation. Therefore, in a low-temperature environment (a situation where the temperature of the high-voltage battery 3 is low), for example, a charging circuit (not shown) provided in the high-voltage battery 3 may be interrupted, and charging or discharging of the high-voltage battery 3 may be prohibited. For this reason, the charge control system 1 may maintain a charge / discharge standby state of the high-voltage battery 3 until the prohibition of charging or discharging of the high-voltage battery 3 is released (for example, until the outside air temperature rises and the temperature of the high-voltage battery 3 increases) (charge / discharge standby control). On the other hand, generally, the power of the low-voltage battery 7 is used as a power source for system startup. When the voltage of the low-voltage battery 7 does not have a sufficient voltage to start the system due to the vehicle being left unattended for a long time or the like, the system cannot be started. To avoid this situation, it is desired to supply power from the high-voltage battery 3 to the low-voltage battery 7 to increase the voltage of the low-voltage battery 7. However, in the charge / discharge standby state of the high-voltage battery 3, since the output of the high-voltage battery 3 is limited, power cannot be supplied from the high-voltage battery 3 to the low-voltage battery 7. Therefore, in a low-temperature environment, there is a risk that the low-voltage battery 7 may experience a battery boost.

[0020] Therefore, in the charge control system 1 of the embodiment, by maintaining the charge / discharge standby state of the high-voltage battery 3 while charging the low-voltage battery 7, a battery boost of the low-voltage battery 7 is avoided. At this time, since charging of the high-voltage battery 3 at a low temperature is prohibited, the BMS 5 estimates the power consumption (power supplied to the low-voltage system 8) in the on state of the converter 6, and controls the output of the charger 4 so that the charger 4 outputs this amount of power. That is, the BMS 5 controls the output of the charger 4 so that the power consumption of vehicle accessories (including the low-voltage battery 7) connected to the converter 6 is supplied from the charger 4 to the converter 6.

[0021] Referring to Figure 2, the BMS5 calculates a charging current command value PI such that the output current of the high-voltage battery 3 becomes zero, thereby creating a state where the output of the charger 4 and the power consumption of the auxiliary equipment are balanced, and suppressing the output power of the high-voltage battery 3 to zero. The BMS5 calculates the output power of the charger 4 so that the detected value of the current sensor 3a becomes zero, and outputs the charging current command value PI to the charger 4 (feedback control, charging output control). The BMS5 outputs a control signal for the charger 4 based on the current value of the high-voltage battery 3.

[0022] If we denote the output power of the high-voltage battery 3 during the zero-charge control described later as "Pbat", the output power of the charger 4 as "Pchg", and the auxiliary power consumption as "Paux", then the following equation 1 holds true. Paux=Pchg+Pbat...Formula 1

[0023] The BMS5 calculates a charging current command value PI such that the current detection value (current value) Ibat of the high-voltage battery 3 becomes zero, and transmits it to the charger 4. When Ibat=0, Pbat=0. In this case, equation 1 above becomes Paux=Pchg. Therefore, all of the power consumed by the vehicle's auxiliary equipment (including the low-voltage battery 7) is supplied by the charger 4, and as a result, the output power Pbat of the high-voltage battery 3 becomes zero.

[0024] Figure 3 is a time chart showing the time evolution of Pchg, Pbat, and Paux in the charging control system 1. As shown in Figure 3, for example, suppose that at time t0 the ambient temperature is low and the temperature of the high-voltage battery 3 is below a specified threshold (e.g., 0°C), an external power supply is connected to the charger 4 in a low-temperature environment (a situation where the temperature of the high-voltage battery 3 is low). In this case, for example, until the specified time t1, control is performed such that the output power Pbat of the high-voltage battery 3 is set to value A, the output power Pchg of the charger 4 is set to value B, and the auxiliary power consumption Paux is set to the sum of values ​​A and B, C. After that, at the specified time t1, zero-charge control is turned on, which sets the charging current from the high-voltage battery 3 to the low-voltage battery 7 to zero.

[0025] When the zero-charge control is turned on, the output power Pchg of the charger 4 gradually increases due to the change in the charging current command value PI from the BMS 5 (increasing from value B to value C). On the other hand, the output power Pbat of the high-voltage battery 3 gradually decreases by the amount of the increase in the output power Pchg of the charger 4, and eventually the output power Pbat of the high-voltage battery 3 decreases from value A to zero. The auxiliary power consumption Paux is maintained at value C regardless of the temperature of the high-voltage battery 3. In this way, when the zero-charge control is started, the output power Pchg of the charger 4 and the auxiliary power consumption Paux become balanced, and the output power Pbat of the high-voltage battery 3 becomes zero.

[0026] Figure 4 is an explanatory diagram showing the power flow when charging a low-voltage battery 7 in a low-temperature environment in the charging control system 1 of the embodiment. As shown in Figure 4, the charge control system 1 of this embodiment is configured such that the charger 4 outputs power (output power Pchg) equal to the auxiliary power consumption Paux. The output power Pchg of the charger 4 is supplied directly to the converter 6 as the auxiliary power consumption Paux. This eliminates the risk of deterioration of the high-voltage battery 3 and battery failure of the low-voltage battery 7 due to discharge in low-temperature environments.

[0027] In the charging control system 1 of this embodiment, when the charger 4 is connected in a low-temperature environment, the charger 4 outputs power equal to the auxiliary power consumption Paux, and the output power Pchg of the charger 4 and the auxiliary power consumption Paux are balanced. As a result, compared to a configuration in which a converter 6 is provided for both the low-voltage system 8 and the high-voltage system (external charging system 2), the low-voltage battery 7 can be charged by the output power Pchg of the charger 4 with a simpler configuration that suppresses the increase in the number of converters.

[0028] Figure 5 is a flowchart showing the processing in the BMS5 when performing charge control in the charge control system 1 of the embodiment. As shown in Figure 5, when the charging gun is connected to the vehicle's inlet, the BMS 5 starts charging control for the high-voltage battery 3, etc. (Step S1). At this time, the BMS 5 measures the temperature of the high-voltage battery 3 and determines whether the high-voltage battery 3 is low temperature or not (whether it is above a threshold or not) (Step S2). If the high-voltage battery 3 is not cold (NO in step S2), normal charging control is performed (step S3). In normal charging control, the charger 4 supplies power Pchg to the high-voltage battery 3 and the power converter 6. At this time, no power is output from the high-voltage battery 3, and the power converter 6 steps down the power output from the charger 4 and supplies it to the low-voltage battery 7.

[0029] If the high-voltage battery 3 is at a low temperature (YES in step S2), the output power Pbat of the high-voltage battery 3 is reduced from value A to d, the output power Pchg of the charger 4 is increased from value B to a relatively large value C, and the auxiliary power consumption Paux remains at value C (step S4). As a result, the output power Pchg of the charger 4 and the auxiliary power consumption Paux are balanced, and the output power Pbat of the high-voltage battery 3 is suppressed.

[0030] As described above, the charging control system 1 in the above embodiment includes: a voltage converter (DC-DC converter) 6 connected to a high-voltage battery 3 that steps down the first power (output power) Pbat of the high-voltage battery 3 and supplies the stepped-down power to a low-voltage battery 7; a charger 4 connected to the converter 6 and the high-voltage battery 3 that supplies a second power (output power) Pchg obtained from an external power source to at least one of the converter 6 and the high-voltage battery 3; a current detection unit (current sensor 3a) that acquires the current value Ibat of the first power Pbat flowing from the high-voltage battery 3 to the converter 6; and a control unit (BMS) 5 that receives the signal from the current sensor 3a and outputs a command value PI of the second power Pchg output from the charger 4 to the charger 4. In this charging control system 1, the BMS 5 outputs the command value PI of the second power Pchg based on the current value Ibat.

[0031] In this configuration, the control unit (BMS5) that controls the output power Pchg of the charger 4 outputs a power command value PI to the charger 4 based on the current value Ibat of the output power Pbat flowing from the high-voltage battery 3 to the converter 6. By balancing the output power Pchg of the charger 4 with the auxiliary power consumption Paux, the output power Pbat of the high-voltage battery 3 is suppressed. Therefore, compared to a configuration that has converters between the charger 4 and the low-voltage battery 7, and between the high-voltage battery 3 and the low-voltage battery 7, the number of converters can be kept to a minimum, and the low-voltage battery 7 can be charged with the output power Pchg of the charger 4 without going through the high-voltage battery 3.

[0032] Furthermore, in the charging control system 1 described above, the BMS 5 outputs a command value PI for the second power Pchg of the charger 4 so that the current value Ibat of the first power Pbat flowing from the high-voltage battery 3 to the converter 6 becomes zero. In this configuration, the BMS 5, which controls the output power Pchg of the charger 4, outputs a power command value PI to the charger 4 so that the current value Ibat flowing from the high-voltage battery 3 to the converter 6 becomes zero. This suppresses the output power Pbat of the high-voltage battery 3 to zero, and allows the low-voltage battery 7 to be charged from the charger 4 without going through the high-voltage battery 3.

[0033] Furthermore, the charging control system 1 is equipped with a temperature acquisition unit (temperature sensor) 3b that acquires the temperature of the high-voltage battery 3, and the BMS 5 outputs the command value PI of the second power Pchg based on the current value Ibat when the temperature of the high-voltage battery 3 acquired by the temperature sensor 3b falls below a threshold. In this configuration, the BMS 5, which controls the output power Pchg of the charger 4, outputs a power command value PI to the charger 4 based on the temperature of the high-voltage battery 3. For example, when the temperature of the high-voltage battery 3 decreases (when the battery is cold), the output power Pbat of the high-voltage battery 3 is reduced, and the low-voltage battery 7 can be charged with the output power Pchg of the charger 4. Therefore, power supply to the low-voltage battery 7 can be continued by the charger 4 while suppressing the degradation of the high-voltage battery 3.

[0034] Furthermore, in the charging control system 1 described above, the BMS 5 outputs the command value PI for the second power Pchg such that the second power Pchg output from the charger 4 is equal to the power (Paux) consumed by the converter 6. With this configuration, the output power Pbat of the high-voltage battery 3 can be set to zero, allowing the low-voltage battery 7 to be charged from the charger 4 without going through the high-voltage battery 3.

[0035] Furthermore, in the charging control system 1 described above, the BMS 5 increases the current value output from the charger 4, thereby setting the current value Ibat of the first power Pbat to zero. With this configuration, the output power Pbat of the high-voltage battery 3 can be reduced to zero simply by adjusting the current value Ibat output from the charger 4.

[0036] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention, such as replacing the components of the embodiments with well-known components. For example, although the charging control system of this embodiment is exemplified as being applicable to an electric vehicle, it may also be applied to saddle-type vehicles such as two-wheeled or three-wheeled vehicles in which the driver straddles the vehicle. The present invention is not limited to vehicles, but may also be applied to various transportation equipment such as aircraft and ships, as well as various vehicles and mobile objects such as construction machinery and industrial machinery. Furthermore, the present invention is broadly applicable to equipment other than vehicles, such as push lawnmowers and cleaning machines. [Explanation of Symbols]

[0037] 1. Charging control system 3 High-voltage battery 3a Current sensor (current detection unit) 3b Temperature sensor (temperature acquisition part) 4 charger 5. BMS (Control Unit) 6. DC-DC converter (voltage converter) 7 Low-voltage battery Ibat current value Paux Auxiliary Power Consumption Pbat High-Voltage Battery Output Power (First Power) PCHG charger output power (secondary power) PI Charging current command value (command value)

Claims

1. A voltage converter (6) is connected to a high-voltage battery (3), which steps down the first power (Pbat) of the high-voltage battery (3) and supplies the stepped-down power to a low-voltage battery (7), A charger (4) connected to the voltage converter (6) and the high-voltage battery (3) supplies a second power (Pchg) obtained from an external power source to at least one of the voltage converter (6) and the high-voltage battery (3), A current detection unit (3a) that acquires the current value (Ibat) of the first power (Pbat) flowing from the high-voltage battery (3) to the voltage converter (6), A control unit (5) receives the signal from the current detection unit (3a) and outputs the command value (PI) of the second power (Pchg) output from the charger (4) to the charger (4), A charging control system (1) having a temperature acquisition unit (3b) that acquires the temperature of the high-voltage battery (3), The charge control system is characterized in that the control unit (5) outputs a command value (PI) for the second power (Pchg) based on the current value (Ibat) when the temperature of the high-voltage battery (3) acquired by the temperature acquisition unit (3b) falls below a threshold.

2. The charging control system according to claim 1, wherein the temperature below the threshold includes a temperature range of 0° or less.

3. The charging control system according to claim 1, characterized in that the control unit (5) outputs a command value (PI) for the second power (Pchg) of the charger (4) such that the current value (Ibat) of the first power (Pbat) flowing from the high-voltage battery (3) to the voltage converter (6) becomes zero.

4. The charging control system according to claim 1, characterized in that the control unit (5) outputs the command value (PI) of the second power (Pchg) output from the charger (4) and the power consumed by the voltage converter (6) are equal.

5. The charging control system according to claim 1, characterized in that the control unit (5) increases the current value output from the charger (4) to make the current value (Ibat) of the first power (Pbat) zero.

6. A voltage converter (6) connected to a high-voltage battery (3), which steps down the first power (Pbat) of the high-voltage battery (3) and supplies the stepped-down power to a low-voltage battery (7), A charger (4) connected to the voltage converter (6) and the high-voltage battery (3) supplies a second power (Pchg) obtained from an external power source to at least one of the voltage converter (6) and the high-voltage battery (3), A current detection unit (3a) that acquires the current value (Ibat) of the first power (Pbat) flowing from the high-voltage battery (3) to the voltage converter (6), A control unit (5) receives the signal from the current detection unit (3a) and outputs the command value (PI) of the second power (Pchg) output from the charger (4) to the charger (4), A charging control system (1) having a temperature acquisition unit (3b) that acquires the temperature of the high-voltage battery (3), When the temperature of the high-voltage battery (3) obtained by the temperature acquisition unit (3b) falls below a threshold, the control unit (5) outputs a command value (PI) for the second power (Pchg) based on the current value (Ibat), A charging control system characterized in that the control unit (5) outputs the command value (PI) of the second power (Pchg) such that the second power (Pchg) output from the charger (4) is equal to the power consumed by the voltage converter (6).

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