Charging device and charging method

Abstract

To appropriately control an operation of two chargers in a configuration in which a charger connected to a system power supply and a charger connected to another power supply simultaneously charge a battery.SOLUTION: A charging device includes a first power converter connected to a system power supply, a first power converter connected to a second power supply, and a control unit. The control unit performs a first charging control for controlling the first and second power converters to charge a battery with a constant current until a voltage of the battery reaches a predetermined target voltage, and performs second charging control for controlling the first and second power converters to charge the battery with a constant voltage or power after the voltage of the battery reaches a target voltage. In the second charging control, the controller preferentially reduces the second charging current supplied from the second power converter to the battery over the first charging current supplied from the first power converter to the battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charging device and a charging method for charging a battery. [Background technology]

[0002] In many cases, batteries installed in electric vehicles are charged using power supplied from a grid power supply. The grid power supply is, for example, an AC power supply provided by an electric power company. However, rapid charging methods are not widely used, and battery charging times can be long. For example, charging can take several hours when the electric vehicle is not in use.

[0003] On the other hand, in electric industrial vehicles such as battery forklifts, depending on the frequency of use, the battery power may be used up within the working hours. In such cases, rapid charging is preferable, but charging devices capable of rapid charging are expensive.

[0004] For this reason, a method has been proposed for charging an on-board battery by simultaneously using a grid power supply and an external battery. Specifically, a method has been proposed in which a stationary charger is provided separately from the on-board charger installed on the electric vehicle to perform rapid charging (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-223310 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a charger connected to a grid power supply and a charger connected to an external battery are simultaneously performing charging, it is not yet clear how each charger should be controlled.

[0007] An object of one aspect of the present invention is to provide a method for appropriately controlling the operation of two chargers in a configuration in which a charger connected to a grid power source and a charger connected to another power source simultaneously charge a battery. [Means for solving the problem]

[0008] A charging device according to one aspect of the present invention includes a first power converter for charging a battery using power supplied from a grid power source and a second power source, a second power converter for charging the battery using power supplied from the second power source, and a control unit for controlling the first power converter and the second power converter. The control unit performs first charging control to control the first power converter and the second power converter to charge the battery with a constant current until the battery voltage reaches a predetermined target voltage, and performs second charging control to control the first power converter and the second power converter to charge the battery with a constant voltage or power after the battery voltage reaches the target voltage. In the second charging control, the control unit preferentially reduces the second charging current supplied from the second power converter to the battery over the first charging current supplied from the first power converter to the battery. This configuration simplifies the control unit's control and reduces the processing load. Additionally, for example, when the second power source is an external battery, the risk of the external battery becoming empty is reduced, and the time required to charge the external battery after the charging operation by the charging device is completed can be shortened.

[0009] When the state of the first power converter satisfies a predetermined condition, in the second charging control, the control unit may preferentially reduce the first charging current supplied from the first power converter to the battery over the second charging current supplied from the second power converter to the battery. With this configuration, for example, when the temperature of the first power converter rises, the first charging current generated by the first power converter is preferentially reduced, thereby making it possible to suppress the temperature rise of the first power converter. [Effects of the Invention]

[0010] According to the above-described aspect, in a configuration in which a charger connected to a system power supply and a charger connected to another power supply simultaneously charge a battery, the operations of these two chargers can be appropriately controlled. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of a charging device according to an embodiment of the present invention. [Figure 2] An example of a charging method using the charging device will be described. [Figure 3] FIG. 10 is a diagram illustrating an example of CV charging. [Figure 4] 1A to 1C are diagrams illustrating a first example of a charging method according to an embodiment of the present invention. [Figure 5] 4 is a flowchart showing the process of a charging method according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing a second example of a charging method according to an embodiment of the present invention. [Figure 7] 10 is a flowchart showing the process of a charging method according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1 shows an example of a charging device according to an embodiment of the present invention. The charging device 1 according to the embodiment of the present invention can charge an in-vehicle battery device 200 using a system power supply 100. The charging device 1 can also charge the in-vehicle battery device 200 using the system power supply 100 and a second power supply simultaneously. In this example, the second power supply is an external battery device 150 used as a power storage device.

[0013] The system power supply 100 is an AC power supply provided by an electric power company. The system power supply 100 is, for example, a 200V three-phase AC power supply, although it is not particularly limited thereto. The external battery device 150 includes a battery B1 and a control unit 151. The battery B1 is, for example, a rechargeable secondary battery, such as, but not particularly limited to, a lead battery, a nickel-metal hydride battery, or a lithium-ion battery. The control unit 151 monitors and controls the state of the battery B1. For example, the control unit 151 monitors the state of charge (SOC) of the battery B1.

[0014] In this embodiment, the in-vehicle battery device 200 is mounted on a vehicle. The vehicle on which the in-vehicle battery device 200 is mounted may be an electric vehicle driven by a motor, or an industrial vehicle such as a forklift. The in-vehicle battery device 200 also includes a battery B2 and a control unit 201. Like battery B1, battery B2 is a rechargeable secondary battery such as a lead battery, a nickel-metal hydride battery, or a lithium-ion battery. The control unit 201 monitors the charge amount of battery B2. When battery B2 is charged by the charging device 1, the control unit 201 can also notify the charging device 1 of a current command value representing a target current and a voltage command value representing a target voltage.

[0015] The charging device 1 includes chargers 10 and 20. When the charging device 1 charges the in-vehicle battery device 200, the charger 10 is connected to the system power supply 100, and the charger 20 is connected to the external battery device 150.

[0016] Charger 10 includes a power converter 11, a voltage sensor V1, a current sensor A1, and a control unit 12. To operate as an AC / DC converter, power converter 11 includes a rectifier circuit 11a, a switch circuit SW1, a transformer T1, and a smoothing capacitor C1. Note that power converter 11 may include other circuits or elements not shown in FIG. 1.

[0017] The rectifier circuit 11a rectifies the three-phase AC current supplied from the system power supply 100. The switch circuit SW1 generates a pulse current from the output current of the rectifier circuit 11a in accordance with control by the control unit 12. The transformer T1 transmits the pulse current generated by the switch circuit SW1 on the primary side to the secondary side. The smoothing capacitor C1 smoothes the current flowing on the secondary side of the transformer T1, thereby generating a DC voltage. The voltage sensor V1 monitors the output voltage of the power converter 11. The current sensor A1 monitors the charging current Ic supplied from the power converter 11 to the in-vehicle battery device 200.

[0018] The control unit 12 controls the power converter 11 in cooperation with the control unit 201 of the in-vehicle battery device 200. For example, when the in-vehicle battery device 200 notifies the control unit 12 of a target current, the control unit 12 controls the switch circuit SW1 so that the current detected by the current sensor A1 (i.e., the charging current Ic) approaches a predetermined current value corresponding to the target current. Also, when the in-vehicle battery device 200 notifies the control unit 12 of a target voltage, the control unit 12 controls the switch circuit SW1 so that the voltage detected by the voltage sensor V1 approaches the target voltage. At this time, the control unit 12 controls the switch circuit SW1 by, for example, pulse width modulation (PWM). In this case, the control unit 12 can set the output current or output voltage of the power converter 11 to a desired value by adjusting the pulse width of a drive signal that drives the switch circuit SW1.

[0019] Charger 20 includes a power converter 21, a voltage sensor V2, a current sensor A2, and a control unit 22. The configuration of power converter 21 is substantially the same as that of power converter 11 of charger 10 described above. However, because charger 20 operates as a DC / DC converter, it includes a switch circuit SW2, a transformer T2, and a smoothing capacitor C2, but does not need to include a rectifier circuit. Power converter 21 may also include other circuits or elements not shown in FIG. 1.

[0020] In the charger 20, the switch circuit SW2 generates a pulse current from the current supplied from the external battery device 150 under the control of the control unit 22. The transformer T2 transmits the pulse current generated by the switch circuit SW2 on the primary side to the secondary side. The smoothing capacitor C2 smoothes the current flowing on the secondary side of the transformer T2, thereby generating a DC voltage. The voltage sensor V2 monitors the output voltage of the power converter 21. The current sensor A2 monitors the charging current Iadd supplied from the power converter 21 to the in-vehicle battery device 200.

[0021] The control unit 22 controls the power converter 21 in accordance with instructions received from the control unit 12 implemented in the charger 10. For example, the control unit 22 controls the switch circuit SW2 so that the current detected by the current sensor A2 (i.e., the charging current Iadd) approaches a value instructed by the control unit 12. The control unit 22 also controls the switch circuit SW2 so that the voltage detected by the voltage sensor V2 approaches a value instructed by the control unit 12. At this time, the control unit 22 controls the switch circuit SW2 by, for example, pulse width modulation (PWM). In this case, the control unit 22 can set the output current or output voltage of the power converter 21 to a desired value by adjusting the pulse width of a drive signal that drives the switch circuit SW2.

[0022] In the above configuration, the control unit 12 and the control unit 22 are realized, for example, by processors that are physically independent from each other. In this case, the control unit 12 and the control unit 22 are connected to each other so that they can communicate with each other. However, the control unit 12 and the control unit 22 may also be realized by a single processor. That is, a single processor that realizes the functions of the control unit 12 and the control unit 22 may control the power converter 11 and the power converter 21. In either case, the control unit 12 and the control unit 22 are an example of a control unit that controls the power converter 11 and the power converter 21. In the following description, one or more processors that provide the functions of the control unit 12 and the control unit 22 may be referred to as a "control unit 30."

[0023] 2 shows an example of a charging method by the charging device 1. In this embodiment, the charging device 1 charges the battery B2 of the in-vehicle battery device 200 by a CCCV (Constant-Current Constant-Voltage) method.

[0024] In CCCV charging, the charging device 1 charges battery B2 at a predetermined constant target current until the voltage of battery B2 reaches a predetermined target voltage. In the following description, the operation of charging battery B2 at a constant current may be referred to as "CC charging." The target current is notified to the control device 30 of the charging device 1, for example, from the control device 201 of the in-vehicle battery device 200. The control device 30 then controls the power converters 11 and 21 so that the charging current I supplied from the charging device 1 to battery B2 approaches the target current. In this example, the control device 30 increases the charging current I in stages from zero to the target current.

[0025] After the voltage of battery B2 reaches the target voltage, the control unit 30 controls the power converters 11 and 21 so that the output voltage of the charging device 1 maintains the target voltage. That is, battery B2 is charged at a predetermined constant voltage. In the following description, the operation of charging battery B2 at a constant voltage may be referred to as "CV charging." If charging of battery B2 continues while maintaining the output voltage of the charging device 1 or the voltage of battery B2 at a constant value, the charging current I inevitably decreases. When the charging current I decreases to a predetermined charging termination current, the control unit 30 terminates the charging operation.

[0026] Figure 3 shows an example of CV charging. In this example, the voltage of battery B2 increases due to CC charging as described with reference to Figure 2, and at time T0, the voltage of battery B2 reaches the target voltage. That is, at time T0, charging switches from CC charging to CV charging. Therefore, after time T0, the control unit 30 controls the charging current I supplied from the charging device 1 to battery B2 so that the voltage of battery B2 is maintained at the target voltage.

[0027] At time T0, the control unit 30 reduces the charging current I by ΔI. This causes the voltage of battery B2 to temporarily drop. After this, the charging operation continues at the "target current -ΔI". Therefore, the voltage of battery B2 rises and reaches the target voltage again at time T1. Next, at time T1, the control unit 30 further reduces the charging current I by ΔI. This causes the voltage of battery B2 to temporarily drop. After this, the charging operation continues at the "target current -2ΔI". Then, the voltage of battery B2 reaches the target voltage again at time T2.

[0028] In this way, the voltage of battery B2 is substantially maintained at the target voltage by gradually reducing the charging current I. Then, when the charging current I decreases to the charging termination current shown in Figure 2, the control unit 30 terminates the charging operation.

[0029] In an embodiment of the present invention, charging device 1 can charge battery B2 by simultaneously using two power sources (i.e., system power supply 100 and external battery device 150). Meanwhile, charging current I supplied from charging device 1 to battery B2 is controlled as shown in FIG. 2 or FIG. 3. Here, charging current I is the sum of charging current Ic generated by power converter 11 and charging current Iadd generated by power converter 21. Therefore, control unit 30 controls power converter 11 and power converter 21 so that the sum of charging current Ic and charging current Iadd becomes the charging current I shown in FIG. 2 or FIG. 3.

[0030] <First Example> FIG. 4 shows a first example of a charging method according to an embodiment of the present invention. In this example, the voltage of battery B2 increases through CC charging, as described with reference to FIG. 2, although not specifically shown. At this time, control unit 30 controls power converters 11 and 21 so that the sum of charging current Ic and charging current Iadd becomes the target current shown in FIG. 2. However, in this example, power converters 11 and 21 have different capacities (e.g., maximum currents). Therefore, control unit 30 controls power converters 11 and 21 during CC charging so that the sum of charging current Ic and charging current Iadd satisfies the current command value (i.e., target current) requested by in-vehicle battery device 200, while keeping charging current Ic and charging current Iadd below the maximum currents of power converters 11 and 21, respectively. In the example shown in FIG. 4, charging current Iadd is smaller than charging current Ic. However, depending on the capacities of power converters 11 and 21, charging current Ic and charging current Iadd may be the same, or charging current Iadd may be greater than charging current Ic. Then, when the voltage of battery B2 reaches the target voltage at time T0, the charging device 1 switches the charging mode from CC charging to CV charging.

[0031] In CV charging, as described above, the control unit 30 gradually reduces the charging current I until it reaches the charging termination current. In the first embodiment, the control unit 30 simultaneously reduces the charging current Ic and the charging current Iadd. In the case shown in FIG. 4, at time T0, the control unit 30 reduces the charging current Ic by ΔIc and the charging current Iadd by ΔIadd. Thereafter, at times T1, T2, and T3, the control unit 30 reduces the charging current Ic by ΔIc and the charging current Iadd by ΔIadd, respectively. At this time, it is preferable to reduce the charging current Ic and the charging current Iadd equally. Then, at time T3, when the sum of the charging current Ic and the charging current Iadd decreases to the charging termination current shown in FIG. 2, the control unit 30 terminates the charging operation.

[0032] In this way, when reducing the charging current I during CV charging, the control unit 30 simultaneously reduces the charging current Ic and the charging current Iadd. Therefore, in the first embodiment, the control of the control unit 30 is simple and the amount of processing is small.

[0033] Fig. 5 is a flowchart showing the processing of the charging method according to the first embodiment. Note that in Fig. 5, the steps related to CC charging are omitted.

[0034] In S1, the control unit 30 monitors the voltage of the battery B2. When the voltage of the battery B2 reaches the target voltage, the control unit 30 switches the operation mode of the charging device 1 from CC charging to CV charging.

[0035] In S2, the control unit 30 reduces the charging current Ic by ΔIc and also reduces the charging current Iadd by ΔIadd. This causes the voltage of battery B2 to temporarily drop slightly, as described with reference to FIG. 3. The charging current Ic is controlled, for example, by adjusting the pulse width of the drive signal provided to switch circuit SW1. Similarly, the charging current Iadd is controlled, for example, by adjusting the pulse width of the drive signal provided to switch circuit SW2.

[0036] In S3, the control unit 30 determines whether the sum of the charging current Ic and the charging current Iadd has decreased to the charging termination current. If the sum of the charging current Ic and the charging current Iadd is greater than the charging termination current, the control unit 30 monitors the voltage of battery B2 in S4. When the voltage of battery B2 reaches the target voltage, the control unit 30 returns to S2. That is, the processes of S2 to S4 are repeatedly executed until the sum of the charging current Ic and the charging current Iadd reaches the charging termination current. As a result, when the sum of the charging current Ic and the charging current Iadd has decreased to the charging termination current, the control unit 30 ends the charging operation.

[0037] <Second Example> The charging current Ic is generated by a charger 10 connected to the system power supply 100. In contrast, the charging current Iadd is generated by a charger 20 connected to the external battery device 150. Therefore, the charging current Iadd can only be generated within the capacity of the external battery device 150. Furthermore, after charging of the in-vehicle battery device 200 is completed, the external battery device 150 needs to be charged. However, the more the remaining charge of the external battery device 150 is, the longer the time required to charge the external battery device 150. Furthermore, if charging of the in-vehicle battery device 200 is started when the remaining charge of the external battery device 150 is low, there is a risk that the external battery device 150 will become empty during the charging operation. In this case, the in-vehicle battery device 200 will be charged using only the system power supply 100, which may result in a longer charging time. Therefore, in the second embodiment, during CV charging after the voltage of battery B2 reaches the target voltage, the charging current Iadd generated using the external battery device 150 is preferentially reduced over the charging current Ic generated using the system power supply 100.

[0038] Fig. 6 shows a second example of the charging method according to the embodiment of the present invention. Note that the operation of CC charging is substantially the same as that of the first example shown in Fig. 4, and therefore a description thereof will be omitted.

[0039] When the voltage of battery B2 reaches the target voltage at time T0, control unit 30 reduces charging current Iadd generated by charger 20 by ΔIadd. At this time, charging current Ic generated by charger 10 is maintained at Ic_0. Ic_0 corresponds to the charging current generated by charger 10 in CC charging. After this, control unit 30 gradually reduces charging current Iadd while maintaining charging current Ic. As a result, when the sum of charging current Ic and charging current Iadd decreases to the charging termination current, control unit 30 terminates the charging operation.

[0040] However, in this example, even if the charging current Iadd is reduced to zero, the sum of the charging current Ic and the charging current Iadd does not decrease to the charging termination current. In this case, the control unit 30 gradually reduces the charging current Ic until the sum of the charging current Ic and the charging current Iadd reaches the charging termination current. At this time, the charging current Iadd remains at zero. Then, in the example shown in FIG. 6, the sum of the charging current Ic and the charging current Iadd decreases to the charging termination current at time T4. That is, the charging operation ends at time T4.

[0041] Fig. 7 is a flowchart showing the processing of the charging method according to the second embodiment. Note that, also in Fig. 7, the steps relating to CC charging are omitted.

[0042] In S11, the control unit 30 monitors the voltage of the battery B2. When the voltage of the battery B2 reaches the target voltage, the control unit 30 switches the operation mode of the charging device 1 from CC charging to CV charging.

[0043] In S12, the control unit 30 reduces the charging current Iadd by ΔIadd. In S13, the control unit 30 determines whether the sum of the charging current Ic and the charging current Iadd has decreased to the charging termination current. If the sum of the charging current Ic and the charging current Iadd is greater than the charging termination current, the control unit 30 monitors the voltage of battery B2 in S14. When the voltage of battery B2 reaches the target voltage, the control unit 30 determines whether the charging current Iadd is zero. If the charging current Iadd is not zero, the control unit 30 returns to S12. That is, the processes of S12 to S15 are repeatedly executed until the sum of the charging current Ic and the charging current Iadd reaches the charging termination current. As a result, when the sum of the charging current Ic and the charging current Iadd reaches the charging termination current, the control unit 30 ends the charging operation.

[0044] If the sum of the charging current Ic and the charging current Iadd is still greater than the charging termination current even after the charging current Iadd has decreased to zero, the control unit 30 repeats the steps S16 to S18 until the sum of the charging current Ic and the charging current Iadd reaches the charging termination current. That is, the control unit 30 reduces the charging current Ic in stages. Then, when the sum of the charging current Ic and the charging current Iadd decreases to the charging termination current, the control unit 30 ends the charging operation.

[0045] Thus, in the second embodiment, during CV charging after the voltage of battery B2 has reached the target voltage, the charging current Iadd generated using the external battery device 150 is reduced preferentially over the charging current Ic generated using the system power supply 100. This reduces the risk of the external battery device 150 becoming empty, and also shortens the time required to charge the external battery device 150 after the in-vehicle battery device 200 has been charged.

[0046] The second embodiment is not limited to the procedure shown in Fig. 7. For example, the control unit 30 may monitor the charge level of the battery B1 in cooperation with the control unit 151 implemented in the external battery device 150. In this case, the control unit 30 may reduce the charging current Iadd with priority over the charging current Ic when the charge level of the battery B1 is lower than a predetermined threshold.

[0047] <Third Example> When the charger 10 connected to the system power supply 100 satisfies a predetermined output limiting condition, the control unit 30, during CV charging after the voltage of battery B2 reaches the target voltage, prioritizes reducing the charging current Ic generated using the system power supply 100 over the charging current Iadd generated using the external battery device 150. For example, when the charging current Ic generated by the charger 10 connected to the system power supply 100 is large, the temperature of the charger 10 is likely to rise. Then, when the temperature of the charger 10 exceeds a predetermined threshold, the control unit 30 prioritizes reducing the charging current Ic over the charging current Iadd during CV charging. This makes it possible to suppress a rise in temperature of the charger 10.

[0048] The procedure of the third embodiment is almost the same as that of the second embodiment, except for the following points: (1) Before S11, determine whether the temperature of the charger 10 exceeds a threshold value. (2) In S12, the charging current Ic is decreased by ΔIc. (3) In S15, it is determined whether the charging current Ic is zero. (4) In S16, the charging current Iadd is decreased by ΔIadd. When the temperature of the charger 10 does not exceed the threshold value, the control unit 30 may control the charging operation according to the procedure shown in FIG. 5 or FIG.

[0049] <Other embodiments> The charging device 1 may perform CCCP charging instead of CCCV charging. That is, after the voltage of the battery B2 reaches the target voltage, the control unit 30 may charge the battery B2 with a constant power.

[0050] 1 charges the in-vehicle battery device 200 using the system power supply 100 and the external battery device 150, the present invention is not limited to this configuration. For example, the charging device 1 may use another system power supply instead of the external battery device 150. As an example, the charging device 1 may use 200V three-phase AC and 100V single-phase AC simultaneously. In this case, not only the power converter 11 implemented in the charger 10 but also the power converter 21 implemented in the charger 20 must include a rectifier circuit. [Explanation of symbols]

[0051] 1 Charging device 10, 20 charger 11, 21 Power converter 12, 22 Control section 100 grid power 150 External Battery Device 151 Control Unit 200 Vehicle Battery Device 201 Control Unit

Claims

1. A charging device that charges a battery using a system power supply and a second power supply, a first power converter that charges the battery using power supplied from the system power supply; a second power converter that charges the battery using power supplied from the second power source; a control unit that controls the first power converter and the second power converter, The control unit performing a first charging control for controlling the first power converter and the second power converter so as to charge the battery with a constant current until the voltage of the battery reaches a predetermined target voltage; After the voltage of the battery reaches the target voltage, a second charging control is performed to control the first power converter and the second power converter so as to charge the battery at a constant voltage or power; In the second charging control, the control unit reduces the second charging current supplied from the second power converter to the battery with priority over the first charging current supplied from the first power converter to the battery. A charging device characterized by:

2. A charging device that charges a battery using a system power supply and a second power supply, a first power converter that charges the battery using power supplied from the system power supply; a second power converter that charges the battery using power supplied from the second power source; a control unit that controls the first power converter and the second power converter, The control unit performing a first charging control for controlling the first power converter and the second power converter so as to charge the battery with a constant current until the voltage of the battery reaches a predetermined target voltage; After the voltage of the battery reaches the target voltage, a second charging control is performed to control the first power converter and the second power converter so as to charge the battery at a constant voltage or power; When the state of the first power converter satisfies a predetermined condition, in the second charging control, the control unit reduces a first charging current supplied from the first power converter to the battery with priority over a second charging current supplied from the second power converter to the battery. A charging device characterized by:

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