Electric vehicle

Abstract

To perform more proper equalization processing even during actuation of an electric load.SOLUTION: An electric vehicle comprises a battery in which a plurality of lithium ion secondary battery cells are connected in series, an equalization circuit, an electric load, a power generation device, and a control device. When performing equalization of the plurality of lithium ion secondary battery cells by means of the equalization circuit during actuation of the electric load, the control device controls the equalization circuit so as to equalize the plurality of lithium ion secondary battery cells as a state where the power generation device is controlled in such a manner that differentials between generation power supplied by the power generation device and consumption power consumed by the electric load are approximately coincident within a predetermined range.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electric vehicle, and more particularly to an electric vehicle equipped with a battery in which a plurality of lithium-ion secondary battery cells are connected in series. [Background technology]

[0002] Conventionally, for this type of electric vehicle, a system has been proposed in which a determination is made as to whether or not to perform equalization processing based on ignition state information, and if it is determined that equalization processing should be performed, the equalization processing is performed simultaneously with the start of A / D conversion processing of values ​​other than cell voltage values ​​(see, for example, Patent Document 1). In this electric vehicle, accurate equalization processing is performed even for large-capacity battery packs, thereby preventing a decrease in the battery capacity of the battery packs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-065123 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the electric vehicles described above, the difference in the open-circuit voltage (OCV) of each lithium-ion secondary battery cell is generally obtained to determine the difference in the state of charge (SOC) of the multiple lithium-ion secondary battery cells that make up the battery. However, when an electrical load is operating, such as while the vehicle is running, the accuracy of the state of charge is reduced due to the influence of the internal resistance of the battery cells, making it difficult to perform appropriate equalization processing.

[0005] The electric vehicle of the present disclosure has a primary objective of performing more appropriate equalization processing even while the electric load is in operation. [Means for solving the problem]

[0006] The electric vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The electric vehicle of the present disclosure includes: a battery in which a plurality of lithium-ion secondary battery cells are connected in series; an equalization circuit that equalizes the voltages of the plurality of lithium ion secondary battery cells; an electric load that operates by receiving power from a power line connected to the battery; a power generation device capable of supplying generated power to the power line; a control device that controls the equalization circuit, the electrical load, and the power generation device; An electric vehicle comprising: When equalizing the plurality of lithium-ion secondary battery cells using the equalization circuit while the electric load is in operation, the control device controls the equalization circuit to equalize the plurality of lithium-ion secondary battery cells while controlling the power generation device so that a difference between the power generated by the power generation device and the power consumed by the electric load is approximately equal to each other within a predetermined range. It is characterized by:

[0008] The electric vehicle disclosed herein includes a battery having multiple lithium-ion secondary battery cells connected in series, an equalization circuit that equalizes the voltages of the multiple lithium-ion secondary battery cells, an electric load that operates by receiving power from a power line connected to the battery, a power generation device that can supply generated power to the power line, and a control device that controls the equalization circuit, the electric load, and the power generation device. When the control device equalizes the multiple lithium-ion secondary battery cells using the equalization circuit while the electric load is operating, the control device controls the power generation device so that the difference between the generated power supplied by the power generation device and the power consumed by the electric load approximately matches within a predetermined range, thereby equalizing the multiple lithium-ion secondary battery cells. When the generated power and the power consumption approximately match, the voltage of each lithium-ion secondary battery cell approximates its open-circuit voltage, allowing for more accurate detection of the state of charge (SOC) of each lithium-ion secondary battery cell. As a result, the multiple lithium-ion secondary battery cells can be more accurately equalized even while the electric load is operating.

[0009] The equalization of the lithium-ion secondary battery cells during the operation of the electrical load may be performed when the maximum power that can be generated by the power generation device is greater than the power consumed by the electrical load, thereby enabling more appropriate equalization of the lithium-ion secondary battery cells. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an outline of the configuration of an electric vehicle 20 according to an embodiment of the present disclosure. [Figure 2] 10 is a flowchart showing an example of an equalization execution process executed by an electronic control unit 60. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, a mode (embodiment) for carrying out the present disclosure will be described. Fig. 1 is a configuration diagram showing an outline of the configuration of an electric vehicle 20 as one embodiment of the present disclosure. As shown in the figure, the electric vehicle 20 of the embodiment includes a battery 30, an equalization circuit 32, a power conversion device 40, a motor 42, an electric load 44, a power generation device 50, and an electronic control unit 60.

[0012] The battery 30 is configured by connecting a plurality of lithium ion secondary battery cells BC1 to BC4 in series, and a power line connected to the output terminal thereof is connected to the power conversion device 40 via system main relays SMR1 and SMR2.

[0013] The equalization circuit 32 is configured as a circuit for equalizing the state of charge (SOC) of the multiple lithium ion secondary battery cells BC1 to BC4 of the battery 30. The equalization circuit 32 is configured so that, for each of the lithium ion secondary battery cells BC1 to BC4, a first loop circuit is formed from the positive terminal to a resistor R1, a switch SW, the resistor R1, and the negative terminal, and a second loop circuit is formed from the positive terminal to a resistor R2, a capacitor C, the resistor R1, and the negative terminal, and each capacitor C is equipped with a voltage sensor V that detects a voltage Vc between its terminals. The switch SW is configured from a field effect transistor (FET) or the like, and its on / off is controlled by the electronic control unit 60. The equalization of the power storage ratios SOC of the plurality of lithium ion secondary battery cells BC1 to BC4 (hereinafter referred to as equalization processing) is basically performed by detecting the open-circuit voltages of the lithium ion secondary battery cells BC1 to BC4 when the battery 30 is not being charged or discharged, calculating the power storage ratio SOC of each lithium ion secondary battery cell BC1 to BC4 from the open-circuit voltage, and turning on the switch SW of the first loop circuit for the lithium ion secondary battery cell with the largest power storage ratio SOC to discharge the cell and bring it closer to the power storage ratio SOC of the other battery cells, performing this operation multiple times.

[0014] The power conversion device 40 is composed of a boost converter that boosts the power from the battery 30, an inverter for applying three-phase AC power to the motor 42, an inverter for supplying power to the electrical load 44, and the like.

[0015] The motor 42 may be, for example, a synchronous generator motor, and drives the drive wheels of the electric vehicle 20. The electrical load 44 may be, for example, an air conditioner for air conditioning the passenger compartment, a compressor, or the like.

[0016] Examples of the power generation device 50 include an on-board fuel cell system, a solar power generation device, a generator that generates electricity using power from an internal combustion engine, etc. The power generation device 50 is connected to the power line between the battery 30 and the power conversion device 40 via relays GR1 and GR2.

[0017] The electronic control unit 60 is composed of a microcomputer centered around a CPU (not shown). The electronic control unit 60 receives inputs such as the battery cell voltage Vbc from each voltage sensor V in the equalization circuit 32, phase currents from current sensors (not shown) that detect the three-phase current applied to the motor 42 installed in the power conversion device 40, and the power generation output voltage Vg and power generation output current Ig from voltage and current sensors that detect the output power of the power generation device 50. The electronic control unit 60 also controls the running of the electric vehicle 20, and therefore also receives inputs such as the shift position SP, accelerator pedal position Acc, brake position BP, vehicle speed, and acceleration α. ​​The electronic control unit 60 outputs drive control signals to each switch SW in the equalization circuit 32, a drive control signal to the power conversion device 40, a drive control signal to the power generation device 50, and drive control signals to the system main relays SMR1 and SMR2 ​​and relays GR1 and GR2.

[0018] Next, we will explain the operation of the electric vehicle 20 of this embodiment configured as described above, particularly the operation when performing the equalization process while the motor 42 and the electric load 44 are operating. Figure 2 is a flowchart showing an example of the equalization execution process executed by the electronic control unit 60 when performing the equalization process while the motor 42 and the electric load 44 are operating.

[0019] When the equalization execution process is executed, the electronic control unit 60 first calculates the load power Ph, which is the sum of the drive power for driving the motor 42 and the power consumption of the electrical load 44 (step S100), and also calculates the maximum power generation Pgmax that can be generated by the power generation device 50 (step S110). The maximum power generation Pgmax that can be generated by the power generation device 50 is the maximum power generation in the state of the fuel cell system at that time if the power generation device 50 is a fuel cell system, or is the maximum power generation that can be generated by the solar power generation device depending on the weather at that time if the power generation device 50 is a solar power generation device.

[0020] Next, it is determined whether the maximum power generation Pgmax is equal to or greater than the load power Ph (step S120). If it is determined that the maximum power generation Pgmax is less than the load power Ph, it is determined that it is not appropriate to perform the equalization process, and this process is terminated.

[0021] If it is determined in step S120 that the maximum power generation Pgmax is equal to or greater than the load power Ph, the power generation device 50 is controlled so that the power generation Pg of the power generation device 50 is equal to the load power Ph (step S130). The process waits until the absolute value of the output power Pb of the battery 30 becomes less than the threshold value Pref (step S140), executes the equalization process (step S150), and terminates this process. The threshold value Pref is a threshold value used to determine whether the output power Pb of the battery 30 is approximately zero, and a value close to zero can be used. When the absolute value of the output power Pb of the battery 30 is less than the threshold value Pref, the voltage Vb of the battery 30 can be regarded as an open-circuit voltage, and therefore the equalization process can be performed satisfactorily. Note that the absolute value of the output power Pb of the battery 30 is the difference between the power generation power Pg of the power generation device 50 and the load power Ph. Therefore, it is equivalent to execute the equalization process after waiting until the difference between the power generation power Pg of the power generation device 50 and the load power Ph becomes less than the threshold value Pref.

[0022] In the electric vehicle 20 of the embodiment described above, when equalization processing is performed while the motor 42 or the electrical load 44 is operating, the power generation device 50 is controlled so that the power generation power Pg of the power generation device 50 is equal to the load power Ph, and the equalization processing is performed after the absolute value of the output power Pb of the battery 30 becomes less than the threshold value Pref. This makes it possible to perform the equalization processing more appropriately even while the motor 42 or the electrical load 44 is operating. Moreover, the equalization processing is performed when it is determined that the maximum power generation power Pgmax that can be generated by the power generation device 50 is equal to or greater than the load power Ph, so that the equalization processing can be performed more appropriately.

[0023] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problems" section will be described below. In the embodiment, the plurality of lithium ion secondary battery cells BC1 to BC4 correspond to the "plurality of lithium ion secondary battery cells," the battery 30 corresponds to the "battery," the equalization circuit 32 corresponds to the "equalization circuit," the motor 42 and the electric load 44 correspond to the "electric load," the power generation device 50 corresponds to the "power generation device," and the electronic control unit 60 corresponds to the "control device."

[0024] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0025] The present disclosure has been described above using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be embodied in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0026] The present disclosure is applicable to the electric vehicle manufacturing industry and the like. [Explanation of symbols]

[0027] 20 electric vehicle, 30 battery, 32 equalization circuit, 40 power conversion device, 42 motor, 44 electric load, 50 power generation device, 60 electronic control unit, BC1 to BC4 lithium-ion secondary battery cells, C capacitor, GR1, GR2 relay, R1, R2 resistor, SMR1, SMR2 ​​system main relay, SW switch, V voltage sensor.

Claims

[Claim 1] a battery in which a plurality of lithium-ion secondary battery cells are connected in series; an equalization circuit that equalizes the voltages of the plurality of lithium ion secondary battery cells; an electric load that operates by receiving power from a power line connected to the battery; a power generation device capable of supplying generated power to the power line; a control device that controls the equalization circuit, the electrical load, and the power generation device; An electric vehicle comprising: When equalizing the plurality of lithium-ion secondary battery cells using the equalization circuit while the electric load is in operation, the control device controls the equalization circuit to equalize the plurality of lithium-ion secondary battery cells while controlling the power generation device so that a difference between the power generated by the power generation device and the power consumed by the electric load is approximately equal to each other within a predetermined range. An electric vehicle characterized by:

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