Charge control device

Abstract

To suppress that charging voltage exceeds target voltage during charging of a power storage device.SOLUTION: An ECU is a device for controlling charging of a battery and includes a CPU and a communication part for communicating with a charger for outputting charging power to the power storage device. The CPU predicts voltage of the battery after rising during a period required to reduce charging power to zero (step S111), and controls the communication part to transmit a command to reduce charging power on condition that predicted voltage reaches prescribed charging target voltage (steps S112 and S113).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a charge control device, and more particularly to a charge control device that controls charging of a power storage device. [Background technology]

[0002] In the past, some vehicles equipped with a power storage device set a limit value for charge / discharge power based on the rate of change of the charge / discharge power and the rate of change of the voltage of the power storage device (see, for example, Patent Document 1). In Patent Document 1, when the voltage of the power storage device falls within a reference region determined based on the rate of change of the charge / discharge power and the rate of change of the voltage of the power storage device, the limit value is reduced according to the rate of change of the charge / discharge power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-239646 A Summary of the Invention [Problem to be solved by the invention]

[0004] Charging of an electric storage device is generally performed by CCCV (constant current, constant voltage) charging or CPCV (constant power, constant voltage) charging. In CCCV charging and CPCV charging, when the charging voltage reaches a predetermined charging target voltage as the battery approaches full charge, charging is controlled to maintain the charging target voltage until the battery is fully charged. In a cell having a steep SOC (State Of Charge)-OCV (Open Circuit Voltage) characteristic near full charge, such as an LFP (Li,Fe,P: lithium iron phosphate) battery, the cell voltage rises sharply just before the battery is fully charged. When CV (constant voltage) charging is performed, the charging power needs to be rapidly reduced in order to keep the rapidly rising cell voltage constant. However, if the response speed of the charger is slow, the charging power is slow to follow up. As a result, the cell voltage may exceed the target voltage.

[0005] This disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a charging control device that can prevent the charging voltage from exceeding a target voltage during charging of a storage device. [Means for solving the problem]

[0006] The charge control device according to the present disclosure is a charge control device that controls charging of a power storage device, and includes a processor and a communication unit for communicating with a charger that outputs charging power to the power storage device. The processor predicts the voltage of the power storage device after it has increased during the period required to reduce the charging power to 0, and controls the communication unit to transmit a command to reduce the charging power on condition that the predicted voltage reaches a predetermined charging target voltage.

[0007] According to this configuration, it is possible to prevent the charging voltage of the power storage device from exceeding a predetermined charging target voltage before the charging power is reduced to 0. As a result, it is possible to provide a charging control device that can prevent the charging voltage from exceeding the target voltage during charging of the power storage device. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an overall configuration of a charging system according to an embodiment of the present invention; [Diagram 2] 4 is a flowchart showing a flow of a charging control process in this embodiment. [Diagram 3] FIG. 4 is a diagram showing changes in parameters during external charging in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0010] FIG. 1 is a diagram that shows a schematic overall configuration of a charging system 9 according to this embodiment. With reference to FIG. 1, the charging system 9 includes a vehicle 1, a charger 3, and a charging outlet 5. The charger 3 is for quick charging and is installed, for example, at a public charging stand (also called a charging spot or a charging station). The charger 3 converts AC power (for example, a three-phase 200V power supply) supplied from a commercial power supply into DC power, and supplies the DC power to the vehicle 1. The charging outlet 5 is for normal charging and is installed, for example, at a residence. The charging outlet 5 supplies AC power from the AC power supply (for example, a three-phase 200V power supply) supplied from the commercial power supply to the vehicle 1.

[0011] The vehicle 1 is, for example, an electric vehicle equipped with a battery 11. The vehicle 1 is configured to be capable of external charging, in which the battery 11 is charged with DC power supplied from the charger 3, in a state in which the vehicle 1 and a charger 3 are electrically connected by a charging cable 4 extending from the charger 3. The vehicle 1 is also configured to be capable of external charging, in which the battery 11 is charged with AC power supplied from the charging outlet 5, in a state in which the vehicle 1 and a charging outlet 5 are electrically connected by a charging cable 6. Note that the vehicle 1 may be a plug-in hybrid vehicle or a fuel cell vehicle as long as it is configured to be capable of external charging.

[0012] The vehicle 1 includes a battery 11, a monitoring unit 111, a system main relay (SMR) 121, a power control unit (PCU) 122, a motor generator (MG) 123, a power transmission gear 124, drive wheels 125, and an ECU (Electronic Control Unit) 10.

[0013] The battery 11 is a rechargeable power storage device, and is configured to include cells of an LPF battery using lithium iron phosphate as a positive electrode active material. However, without being limited thereto, the battery 11 may be configured to include cells of a secondary battery such as a lithium ion secondary battery, a nickel metal hydride battery, or an all-solid-state battery. The battery 11 supplies power to the PCU 122 for generating a driving force for the vehicle 1. The battery 11 is charged by power generated by regenerative braking of the motor generator 123, or by power supplied from the charger 3. Instead of the battery 11, a capacitor such as an electric double layer capacitor may be used.

[0014] The monitoring unit 111 monitors the state of the battery 11. Although none of these are shown, the monitoring unit 111 includes a voltage sensor, a current sensor, and a temperature sensor. The voltage sensor detects the voltage Vb of the battery 11. The current sensor detects the current Ib input to and output from the battery 11. The temperature sensor detects the temperature of the battery 11. Each sensor outputs the detection result to the ECU 10. The ECU 10 can calculate the SOC (State Of Charge) of the battery 11 based on the detection results of each sensor.

[0015] The SMR 121 is electrically connected between the battery 11 and the PCU 122. The closing / opening of the SMR 121 is controlled in response to a command from the ECU 10.

[0016] The PCU 122 is a power conversion device that performs power conversion between the battery 11 and the motor generator 123 in accordance with a command from the ECU 10. The PCU 122 includes an inverter that receives power from the battery 11 and drives the motor generator 123, and a converter that adjusts the level of the DC voltage supplied to the inverter.

[0017] The motor generator 123 is an AC motor. The motor generator 123 is driven by an inverter included in the PCU 122 to rotate a drive shaft. Torque output by the motor generator 123 is transmitted to drive wheels 125 via a power transmission gear 124, thereby causing the vehicle 1 to run. Furthermore, when braking the vehicle, the motor generator 123 receives the rotational force of the drive wheels 125 to generate electricity. The electric power generated by the motor generator 123 is charged into the battery 11 via the PCU 122.

[0018] The vehicle 1 further includes a charging relay 131 as a configuration for external charging, power lines PL, GL and an inlet 135 as a configuration for rapid charging, and power lines UL, VL, WL, an inlet 136 and an on-board charger 13 as a configuration for normal charging.

[0019] The charger 3 includes a control device 30 and a power supply unit 31. The charging cable 4 for quick charging includes a power line 42, a communication line 43, and a connector 41. The charging cable 6 for normal charging includes a power line 62 and a connector 61.

[0020] During rapid charging of the battery 11, the connector 41 of the charging cable 4 is connected to the inlet 135. DC power from the charger 3 is supplied to the vehicle 1 through the power line 42 in the charging cable 4, and is transmitted to the charging relay 131 through the power lines PL and GL.

[0021] During normal charging of the battery 11, the connector 61 of the charging cable 6 is connected to the inlet 136. AC power from the charging outlet 5 is supplied to the vehicle 1 through a power line 62 in the charging cable 6 and transmitted to the on-board charger 13 through power lines UL, VL, and WL. The on-board charger 13 converts the AC power from the charging outlet 5 into DC power. The DC power from the on-board charger 13 is transmitted to the charging relay 131 through power lines PL and GL.

[0022] The charging relay 131 and the SMR 121 are electrically connected between the battery 11 and the inlet 135. When the charging relay 131 is closed and the SMR 121 is closed, power transmission between the inlet 135 or the in-vehicle charger 13 and the battery 11 becomes possible.

[0023] The ECU 10 includes a CPU (Central Processing Unit) 101, a memory 102, a communication unit 103, an input / output port for inputting and outputting various signals, etc. The ECU 10 controls each device (such as the SMR 121, the PCU 122, and the charging relay 131) in the vehicle 1 so that the vehicle 1 is in a desired state.

[0024] When the vehicle 1 and the charger 3 are connected by the charging cable 4, the ECU 10 is configured to be able to perform bidirectional communication with the control device 30 of the charger 3 via the communication unit 103, the communication line 43 in the charging cable 4, and the in-vehicle network 16. The ECU 10 is configured to be able to communicate with the in-vehicle charger 13 via the communication unit 103 and the in-vehicle network 16.

[0025] If the battery 11 is charged with high power or voltage, the battery 11 may break down or its lifespan may be shortened. For this reason, a limit value Win of the charging power is determined in advance for each battery 11 according to the SOC, temperature, voltage, and current of the battery 11.

[0026] Charging of an energy storage device is generally performed by CCCV charging or CPCV charging. In CCCV charging and CPCV charging, when the charging voltage approaches a predetermined charging target voltage as the battery approaches full charge, charging is controlled to maintain the charging target voltage until the battery reaches full charge. In a cell having a steep SOC-OCV characteristic near full charge, such as an LFP battery, the cell voltage rises sharply just before the battery reaches full charge. When performing CV charging, in order to keep the rapidly rising cell voltage constant, it is necessary to rapidly reduce the charging power. However, if the response speed of the charger is slow, the follow-up of the reduced charging power is delayed. As a result, the cell voltage may exceed the target voltage.

[0027] Therefore, it is conceivable that the CPU 101 of the ECU 10 predicts the voltage of the battery 11 after it has risen during the period required to reduce the charging power to 0, and controls the communication unit 103 to transmit a command to the charger 3 or the in-vehicle charger 13 to reduce the charging power on condition that the predicted voltage reaches a predetermined charging target voltage. This makes it possible to prevent the charging voltage of the battery 11 from exceeding the predetermined charging target voltage before the charging power is reduced to 0. As a result, it is possible to prevent the charging voltage from exceeding the target voltage during charging by the charging device.

[0028] Fig. 2 is a flowchart showing the flow of the charging control process in this embodiment. Referring to Fig. 2, a program for this charging control process is stored in memory 102, and is called from a higher-level process and executed by CPU 101 at predetermined intervals. The history of the output power of charger 3 or in-vehicle charger 13 and the voltage of battery 11 during external charging is stored in memory 102. CPU 101 calculates a predicted ultimate voltage from the history of the output power and the voltage of battery 11 stored in memory 102 (step S111).

[0029] Fig. 3 is a diagram showing parameter changes during external charging in this embodiment. Referring to Fig. 3(A), a maximum power fluctuation ΔW that can be tracked is determined for each charger according to the performance of the charger. For example, if ΔW=b(W / 100ms), CPU 101 calculates the period T required to throttle down the charging power when the charging power is a(W) as T=a / ΔW=100a / b(ms).

[0030] Referring to FIG. 3(B), in the case where the history of an increase in the voltage of battery 11 by e(V) in the most recent 1(s) is stored in memory 102, if the current closed circuit voltage (CCV) is c(V), CPU 101 calculates the predicted reached voltage d(V)=c(V)+e(V / s)×T(ms) / 1000=c+e×a / 10b.

[0031] Returning to FIG. 2, when the ultimate voltage calculated in step S111 reaches the charging target voltage, CPU 101 calculates the amount of power reduction required to keep the charging voltage of battery 11 constant (step S112).

[0032] 3(C), first, CPU 101 calculates the OCV rise amount f due to charging for a period of 100 ms = maximum cell voltage rise in the past 100 ms. Next, CPU 101 calculates the current reduction amount g that generates a drop voltage that offsets the rise amount f = f × internal resistance of the cell of battery 11. Then, CPU 101 calculates the commanded power reduction amount h = g × current maximum cell voltage × number of cells in series × margin. The margin is a value that takes into account the delay in calculation.

[0033] 2, CPU 101 calculates a charging power limit value Win based on the power reduction amount h calculated in step S112, and commands the calculated Win to charger 3 or in-vehicle charger 13 (step S113). For example, CPU 101 calculates a new Win by subtracting the power reduction amount h (or a value obtained by multiplying the power reduction amount h by a safety factor (such as 1.05)) from Win before the calculation. Then, CPU 101 returns the process to be executed to the caller of this charging control process.

[0034] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0035] 1 vehicle, 3 charger, 4,6 charging cable, 5 charging outlet, 9 charging system, 10 ECU, 11 battery, 13 on-board charger, 16 on-board network, 30 control device, 31 power supply unit, 41,61 connector, 42,62,GL,PL,UL,VL,WL power line, 43 communication line, 101 CPU, 102 memory, 103 communication unit, 111 monitoring unit, 121 SMR, 122 PCU, 123 motor generator, 124 power transmission gear, 125 drive wheel, 131 charging relay, 135,136 inlet.

Claims

[Claim 1] A charge control device that controls charging of a power storage device, A processor; a communication unit for communicating with a charger that outputs charging power to the power storage device; The processor, predicting a voltage of the power storage device after it has risen during a period required to reduce the charging power to zero; The charge control device controls the communication unit to transmit a command to reduce the charging power on condition that the predicted voltage has reached a predetermined charging target voltage.

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