Battery system

Abstract

This invention provides a battery system that can suppress deviations in the frequency of ripple current from the target value. [Solution] The battery system 100 includes an ECU 10 capable of adjusting the frequency of the pull current and a current sensor 30. The current sensor 30 detects the amplitude of the ripple current corresponding to each of a plurality of frequencies within a predetermined frequency range that includes a target value for the frequency of the ripple current. Based on the amplitude corresponding to each of the plurality of frequencies, the ECU 10 calculates the rate of change of the amplitude with respect to the frequency within the frequency range and determines whether the rate of change is abnormal or not based on the attenuation curve. If the ECU 10 determines that the rate of change is not abnormal, it sets the frequency to the target value, and if it determines that the rate of change is abnormal, it stops the generation of the ripple current.

Description

Technical Field

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[0001] The present disclosure relates to a battery system.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2010-259217 (Patent Document 1) discloses a drive device that warms up a battery by flowing a ripple current through the battery. In the drive device, the warming of the battery is promoted by increasing the ripple current. The ripple current is an alternating current having a predetermined frequency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above Patent Document 1, as described above, the ripple current is an alternating current having a predetermined frequency. Here, the actual frequency of the ripple current may be different from the frequency (target value) set in the control device. Further, the attenuation rate (the attenuation rate from the actual amplitude of the ripple current flowing through the current detection device to the detected amplitude) in the current detection device for detecting the ripple current varies depending on the frequency. Therefore, in the processing in the battery system, it is conceivable that an attenuation rate corresponding to a frequency different from the actual frequency is used.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a battery system capable of suppressing the deviation of the frequency of the ripple current from the target value.

Means for Solving the Problems

[0006] A battery system according to one aspect of this disclosure comprises a ripple generation device connected to an energy storage device and configured to generate a ripple current in the energy storage device; a current detection device for detecting the ripple current generated by the ripple generation device; and a control device for controlling the ripple generation device. If the relationship between the attenuation rate from a first amplitude (the actual amplitude of the ripple current flowing through the current detection device) to a second amplitude (the amplitude of the value detected by the current detection device) and the frequency of the ripple current is defined as the attenuation curve, the control device is configured to adjust the frequency of the ripple current. The current detection device detects a second amplitude corresponding to each of a plurality of frequencies within a predetermined frequency range, including a target frequency. Based on the second amplitude corresponding to each of the plurality of frequencies, the control device calculates the rate of change of the second amplitude with respect to the frequency within the frequency range, determines whether the rate of change is abnormal based on the attenuation curve, sets the frequency to the target value if it determines the rate of change is not abnormal, and stops the generation of the ripple current if it determines the rate of change is abnormal. [Effects of the Invention]

[0007] According to this disclosure, it is possible to suppress deviations in the frequency of the ripple current from the target value. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a vehicle equipped with the battery system according to this embodiment. [Figure 2] This is a schematic diagram showing the battery configuration according to this embodiment. [Figure 3] This figure shows the decay curve of a current sensor. [Figure 4] This is a flowchart illustrating the control of the battery system according to this embodiment. [Figure 5] Figure 4 is a flowchart showing the details of step S20. [Figure 6] Figure 4 is a flowchart showing the details of step S30. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0010] Figure 1 shows a vehicle 200 equipped with a battery system 100 according to an embodiment of this disclosure.

[0011] Vehicle 200 is electrically connected to power stand 300 via cable 310, enabling power exchange (charging and discharging) between the vehicle and power stand 300. This power exchange takes place with a plug 311 at the end of cable 310 connected to the inlet 210 of vehicle 200. Alternating current flows between power stand 300 and vehicle 200. Power stand 300 exchanges power with the power grid PG.

[0012] Vehicle 200 is equipped with a battery system 100, a motor generator (MG) 220, and a charger / discharger 230.

[0013] The battery system 100 comprises an ECU (Electronic Control Unit) 10, a PCU (Power Control Unit) 20, a current sensor 30, a battery 40, an SMR (System Main Relay) 50, and a relay 60. The ECU 10 and battery 40 are examples of the "control device" and "energy storage device" as disclosed herein, respectively. The PCU 20 and current sensor 30 are examples of the "ripple generation device" and "current detection device" as disclosed herein, respectively.

[0014] The ECU 10 includes a processor 11, RAM (Random Access Memory) 12, and a storage device 13. The storage device 13 is configured to store stored information. In addition to the program, the storage device 13 stores information used by the program (e.g., maps, mathematical formulas, and various parameters). In this embodiment, the processor 11 executes the program stored in the storage device 13, thereby performing various processes by the ECU 10 (e.g., control of ripple current, as described later). However, these processes may be performed solely by hardware (electronic circuits) without the use of software.

[0015] Vehicle 200 is configured to run using electricity stored in battery 40. Vehicle 200 is, for example, an electric vehicle (BEV) without an engine (internal combustion engine). However, it is not limited to this, and vehicle 200 may be a PHEV (plug-in hybrid vehicle) equipped with an internal combustion engine, or another electric vehicle (xEV).

[0016] The charger / discharger 230 and relay 60 are located between the inlet 210 and the battery 40. Each of the charger / discharger 230 and relay 60 is controlled by the ECU 10. In this embodiment, the charge / discharge line, including the inlet 210, charger / discharger 230, and relay 60, is connected between the SMR 50 and the PCU 20. However, it is not limited to this, and the charge / discharge line may be connected between the battery 40 and the SMR 50.

[0017] The charger / discharger 230 charges the battery 40 using power input to the inlet 210 from outside the vehicle. The charger / discharger 230 includes a power conversion circuit (e.g., a converter including an inverter and reactor) and is configured to adjust the charging current. The relay 60 switches the connection / disconnection of the circuit from the inlet 210 to the battery 40.

[0018] In the vehicle 200 in the plugin state, external charging (i.e., charging the battery 40 with electric power from outside the vehicle) and external discharging (i.e., discharging the electric power of the battery 40 to the outside of the vehicle) are possible. Note that the vehicle 200 may be capable of performing only external charging. When external charging and external discharging are performed, the relay 60 is closed (connected state), and when external charging and external discharging are not performed, the relay 60 is open (cut-off state).

[0019] MG220 is, for example, a three-phase AC motor generator. MG220 functions as a driving motor for the vehicle 200. MG220 is driven by the PCU20 to rotate the drive wheels of the vehicle 200. Also, MG220 performs regenerative power generation and outputs the generated electric power to the battery 40. Note that the number of driving motors provided in the vehicle 200 is arbitrary.

[0020] The PCU20 includes a circuit (for example, an inverter and a converter) that drives the MG220 using the electric power supplied from the battery 40. The SMR50 switches the connection / cut-off of the electric path from the battery 40 to the PCU20. Each of the SMR50 and the PCU20 is controlled by the ECU10. The SMR50 is closed (connected state) when the vehicle 200 is running. Also, when power is exchanged between the battery 40 and the inlet 210 (and thus outside the vehicle), the SMR50 is closed.

[0021] The battery 40 includes a plurality of power storage cells (not shown). The power storage cell is a secondary battery, typically a lithium-ion secondary battery. The lithium-ion secondary battery is a battery that uses lithium as a charge carrier, and may include, in addition to the lithium-ion secondary battery with a liquid electrolyte, an all-solid-state battery using a solid electrolyte.

[0022] The ripple current may be generated by the control of the PCU20 by the ECU10. Specifically, the ripple current is generated when a switching element provided in the PCU20 is switched by the ECU10. The ECU10 may be able to adjust the frequency of the ripple current by adjusting the on / off period of the switching element. Note that the method of generating the ripple current is not limited to this example.

[0023] Figure 2 is a schematic diagram showing the configuration of the current sensor 30. The current sensor 30 detects the current flowing between the battery 40 and the SMR 50.

[0024] The current sensor 30 includes a magnetic field detection element 31 and a busbar 32. The current (ripple current) flows through the busbar 32 in the direction of the dashed arrow in Figure 2. In this case, the current flowing through the busbar 32 forms a magnetic field (dashed arrow). As shown in Figure 2, the busbar 32 has a rectangular cross-section 32a that intersects (orthogonal to) the direction in which the current flows. For example, the length of the longer side of the cross-section 32a may be five times or more the length of the shorter side of the cross-section 32a.

[0025] Here, the current near the center of the cross-section 32a decreases as the frequency of the ripple current increases due to the skin effect. Consequently, the higher the frequency of the ripple current, the greater the bias in the magnetic field generated by the ripple current. As a result, the magnetic field input to the magnetic field detection element 31 decreases, and consequently, the current value detected by the current sensor 30 is attenuated.

[0026] Furthermore, the current value detected by the current sensor 30 is also attenuated by low-pass filters (not shown) provided in both the current sensor 30 and the battery ECU 10. The amount of attenuation by the low-pass filter increases as the frequency of the ripple current increases.

[0027] Figure 3 is an attenuation curve showing the relationship between the frequency of the ripple current (horizontal axis) and the attenuation rate in the current sensor 30 (vertical axis). The attenuation rate refers to the rate attenuation from the actual amplitude of the ripple current flowing through the current sensor 30 (busbar 32) to the amplitude of the value detected by the current sensor 30. The data of this attenuation curve may be stored in the storage device 13 of the ECU 10. As shown in Figure 3, the attenuation rate of the current sensor 30 increases as the frequency of the ripple current increases.

[0028] Here, the actual frequency of the ripple current may differ from the set frequency (target value). Furthermore, the attenuation rate in the current sensor that detects the ripple current (the attenuation rate from the actual amplitude of the ripple current flowing through the current sensor 30 to the detected amplitude) changes depending on the frequency of the ripple current. Therefore, in the processing of the battery system, it is conceivable that an attenuation rate corresponding to a frequency different from the actual frequency may be used.

[0029] Therefore, in this embodiment, the ECU 10 calculates the rate of change of amplitude with respect to frequency in a predetermined frequency range, based on the amplitude corresponding to each of a plurality of frequencies in the frequency range including the target frequency, and determines whether the rate of change is abnormal or not based on the attenuation curve. Details will be explained later with reference to Figure 5.

[0030] (Control flow) Figure 4 is a flowchart showing the control performed by the ECU 10. The control flow shown in Figure 4 is executed when raising the temperature of the battery 40 using ripple current.

[0031] In step S10, the ECU10 generates a ripple current by controlling the PCU20, SMR50, and relay 60, etc. At this time, the ECU10 sets the frequency of the ripple current to a predetermined target value (for example, 1000Hz). Next, the process proceeds to step S20.

[0032] In step S20, the ECU10 determines whether there is an abnormality in the frequency of the ripple current. Next, the process proceeds to step S30.

[0033] In step S30, the ECU10 adjusts the amplitude of the ripple current. After that, the process ends.

[0034] Figure 5 is a flowchart showing the details of step S20. Step S20 includes steps S21 to S26.

[0035] In step S21, the ECU 10 changes the frequency of the ripple current within a predetermined frequency range centered on the target value, and acquires information on the amplitude of the ripple current at each frequency from the current sensor 30. For example, with the ripple current amplitude set to a predetermined value (e.g., 500A), the ECU 10 acquires information on the amplitude at frequencies of 900Hz, 1000Hz (target value), and 1100Hz from the current sensor 30.

[0036] In step S22, the ECU 10 calculates the rate of change of amplitude with respect to frequency based on the information obtained from the current sensor 30. Specifically, the ECU 10 calculates the rate of change from the amount of change in amplitude (detected value) in the frequency band from 900 Hz to 1100 Hz. The ECU 10 may calculate the rate of change using, for example, the least squares method.

[0037] In step S23, the ECU10 calculates the rate of change (expected value) of the amplitude in the above frequency range based on the attenuation curve. For example, if the attenuation curve shows that the attenuation rate at 900Hz is 30%, the attenuation rate at 1000Hz is 35%, and the attenuation rate at 1100Hz is 40%, then the rate of change when the amplitude setting is 500A is (500 × 0.7 - 500 × 0.6) / (900 - 1100) = -0.25.

[0038] In step S24, the ECU 10 determines whether the magnitude (absolute value) of the difference between the rate of change (expected value) calculated in step S23 and the rate of change calculated in step S22 is less than or equal to the threshold Th1. If the difference is less than or equal to the threshold Th1 (Yes in S23), the process proceeds to step S25. If the difference is greater than the threshold Th1 (No in S23), the process proceeds to step S26.

[0039] The threshold Th1 may vary based on the amplitude set value and frequency. For example, the threshold Th1 may increase as each of the amplitude set value and frequency increases. The threshold Th1 may be calculated by the ECU10, or it may be determined by the ECU10 based on a map showing the relationship between the amplitude set value and frequency and the threshold Th1.

[0040] In step S25, the ECU 10 sets the frequency of the ripple current to a target value (1000 Hz in this embodiment). Next, the process proceeds to step S30.

[0041] In step S26, the ECU 10 stops generating ripple current. Specifically, the ECU 10 may stop generating ripple current by stopping the switching of the switching element provided in the PCU 20. After that, the process ends.

[0042] Figure 6 is a flowchart showing the details of step S30. Step S30 includes steps S31 to S33.

[0043] In step S31, the ECU 10 restores the amplitude of the ripple current based on the attenuation curve. As described above, if the attenuation rate corresponding to 1000 Hz is 35% based on the attenuation curve, the ECU 10 may restore the amplitude by multiplying the amplitude detected by the current sensor 30 by 100 / 65.

[0044] In step S32, the ECU 10 determines whether the amplitude restored in step S31 is less than or equal to the lithium deposition protection amplitude Th2. The protection amplitude Th2 is the upper limit of the amplitude at which lithium deposition can be suppressed in the battery 40. If the restored amplitude is less than or equal to the protection amplitude Th2 (Yes in S32), the process ends. In this case, the ECU 10 maintains the ripple current amplitude at its current value without changing it. If the restored amplitude is greater than the protection amplitude Th2 (No in S32), the process proceeds to step S33. Note that in step S31, different protection amplitude Th2 values ​​may be used depending on the frequency. A map showing the relationship between the protection amplitude Th2 used in step S31 and the frequency may be stored in the storage device 13 (Figure 1).

[0045] In step S33, the ECU 10 reduces the amplitude setting so that the restored amplitude is the protection amplitude Th2 or substantially equivalent to the protection amplitude Th2. For example, the ECU 10 may gradually reduce the amplitude of the ripple current until the restored amplitude is the protection amplitude Th2 or substantially equivalent to the protection amplitude Th2. After that, the process ends. Substantially equivalent to the protection amplitude Th2 may mean, for example, a range of at least a predetermined percentage of the protection amplitude Th2 (e.g., 95%) and less than the protection amplitude Th2. Furthermore, the reduction of the ripple current amplitude may be achieved by known methods.

[0046] As described above, in this embodiment, the ECU 10 calculates the rate of change of amplitude with respect to frequency in a predetermined frequency range based on the amplitude of the ripple current corresponding to each of the multiple frequencies, and determines whether the rate of change is abnormal or not based on the attenuation curve. If the ECU 10 determines that the rate of change is not abnormal, it sets the frequency to the target value, and if it determines that the rate of change is abnormal, it stops the generation of ripple current. As a result, if the calculated rate of change is not abnormal based on the attenuation curve, the frequency of the ripple current is set accurately, so it is possible to suppress the generation of ripple current with a frequency that deviates from the target value. Also, if the calculated rate of change is abnormal based on the attenuation curve, the generation of ripple current is stopped, so it is possible to suppress the generation of ripple current with a frequency that deviates from the target value.

[0047] (modified version) In the above embodiment, an example was shown in which, when the restored amplitude is greater than the upper amplitude limit, the amplitude of the ripple current is reduced so that the restored amplitude is equal to or substantially equal to the upper amplitude limit. However, the disclosure is not limited thereto. In the above case, for example, the amplitude of the ripple current may be reduced so that the restored amplitude is smaller than the upper amplitude limit by a predetermined amount.

[0048] In the above embodiment, an example was shown in which the amplitude of the ripple current is not changed when the restored amplitude is less than or equal to the upper amplitude limit, but the disclosure is not limited thereto. In the above case, the amplitude of the ripple current may be increased so that the restored amplitude is equal to or substantially equivalent to the upper amplitude limit.

[0049] In the above embodiment, an example was shown in which the cross-section 32a of the busbar 32 of the current sensor 30 has a rectangular shape, but the disclosure is not limited thereto. The cross-section of the busbar may have a shape other than a rectangle (for example, circular or square).

[0050] In the above embodiment, an example was shown in which an abnormality in the rate of change of the amplitude of the ripple current is determined based on the detected value of the current sensor 30 corresponding to each of multiple frequencies, but the disclosure is not limited thereto. The above determination may also be made based on the detected value of the current sensor 30 corresponding to only one frequency (target value).

[0051] In the above embodiment, an example was shown in which a ripple current is generated by controlling the switching elements of the PCU 20, but the disclosure is not limited thereto. For example, a ripple current may be generated by controlling the switching elements of the charger / discharger 230.

[0052] In the above embodiment, an example is shown in which a current sensor 30 is provided that detects the current value based on the magnitude of the magnetic field, but the disclosure is not limited thereto. A current sensor that detects the current value based on the magnitude of the voltage drop due to the shunt resistor may also be provided.

[0053] The configurations of each of the above embodiments and each of the modified examples may be combined with each other.

[0054] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0055] 10 ECU (control unit), 20 PCU (ripple generator), 30 current sensor (current detection device), 31 magnetic field detection element, 32 busbar, 32a cross section, 40 battery (energy storage device), 100 battery system.

Claims

[Claim 1] A ripple generation device connected to a power storage device and configured to generate a ripple current in the power storage device, A current detection device for detecting the ripple current generated by the ripple generation device, The system comprises a control device for controlling the ripple generation device, If the curve showing the relationship between the attenuation rate from the first amplitude, which is the actual amplitude of the ripple current flowing through the current detection device, to the second amplitude, which is the amplitude of the value detected by the current detection device, and the frequency of the ripple current is defined as the attenuation curve, The control device is configured to be able to adjust the frequency of the ripple current, The current detection device detects the second amplitude corresponding to each of a plurality of frequencies within a predetermined frequency range including the target value of the frequency, The control device is Based on the second amplitude corresponding to each of the plurality of frequencies, the rate of change of the second amplitude with respect to the frequency in the frequency range is calculated. Based on the aforementioned damping curve, it is determined whether the rate of change is abnormal or not. If it is determined that the rate of change is not abnormal, the frequency is set to the target value. A battery system that stops the generation of the ripple current when it is determined that the rate of change is abnormal.

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