Battery control device and battery system

Abstract

A battery control device for a battery system includes: a first calculation unit for calculating a first state of charge of the battery using a first method based on the current value, voltage value, and internal resistance value of the battery; a second calculation unit for calculating a second state of charge of the battery using a second method different from the first method; and a correction unit for correcting the internal resistance value. When a difference greater than a predetermined value is detected between the first and second states of charge, the correction unit corrects the internal resistance value using a resistance correction amount corresponding to the difference and the current value.

Description

Technical Field

[0001] The present invention relates to a battery control device and a battery system. Background Art

[0002] The electric vehicle system installed in electric vehicles such as electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs) includes a battery as a power supply source and a battery control unit. To maximize the battery's performance, the battery control unit detects the battery's voltage, temperature, and current, and based on these data calculates the battery's state of charge (SOC), state of health (SOH), and the battery's available power input and output.

[0003] As batteries degrade, their internal resistance increases. Therefore, in addition to calculating the battery's internal resistance in real time to appropriately calculate the battery's available power input and output, the ratio of the initial internal resistance to the degraded internal resistance is calculated as the SOH, which serves as a target value for battery replacement.

[0004] Here, methods for calculating the internal resistance of the battery include a method based on the internal resistance calculated from the ratio of the battery voltage change and the current change, and a method based on the internal resistance calculated from an equivalent circuit model of the battery.

[0005] For example, Patent Document 1 discloses the following technology: detecting the SOC difference between the SOC calculated based on the internal resistance obtained by the latter's internal resistance calculation method based on the equivalent circuit model and the SOC based on the current accumulation (hereinafter referred to as SOCi), and correcting the internal resistance used in the SOH calculation as the change in internal resistance accompanies battery deterioration.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5439126 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] In the aforementioned conventional technology, the correction value for the internal resistance, which is determined to require correction due to an SOC difference, is set to a relatively small fixed value, emphasizing computational stability. Therefore, even when the calculated SOH value recognized by the battery control unit differs significantly from the actual SOH of the battery being controlled (also known as the true SOH value), the internal resistance can be corrected using the small fixed value. This leads to a problem in which the calculated SOH value converges slowly to the true SOH value.

[0011] An object of the present invention is to solve the above-mentioned problem and to provide a battery control device and a battery system that can accelerate the convergence speed of the SOH calculation value and estimate the internal resistance value with high accuracy.

[0012] Means used to solve problems

[0013] In order to solve the above-mentioned problems, in the present invention, a battery control device includes: a first calculation unit, which calculates a first charge state of the above-mentioned battery using a first method based on the current value, voltage value and internal resistance value of the battery; a second calculation unit, which calculates a second charge state of the above-mentioned battery using a second method different from the above-mentioned first method; and a correction unit, which corrects the above-mentioned internal resistance value, and when the above-mentioned correction unit detects a difference greater than a specified value between the above-mentioned first charge state and the above-mentioned second charge state, corrects the above-mentioned internal resistance value using a resistance correction amount corresponding to the above-mentioned difference and the above-mentioned current value.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to achieve both convergence and accuracy in the calculated value of the internal resistance of the battery, thereby ensuring the reliability of the battery system and effectively using the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a block diagram showing the configuration of an electric power system of a hybrid vehicle according to the first embodiment of the present invention.

[0017] Figure 2 It means composition Figure 1 A block diagram showing the configuration of a single cell control unit of a battery system.

[0018] Figure 3 It means composition Figure 1 A block diagram showing the configuration of a battery pack control unit of a battery system.

[0019] Figure 4 This is a diagram showing the SOC table, internal resistance table, and polarization resistance table.

[0020] Figure 5 This is a block diagram showing the configuration of an SOC calculation unit constituting the battery pack control unit of the first embodiment.

[0021] Figure 6 This is a characteristic example showing the relationship between the SOC and OCV of a single battery.

[0022] Figure 7 This is a diagram showing an example of an equivalent circuit model of a single cell.

[0023] Figure 8 This diagram illustrates the voltage behavior of a single battery.

[0024] Figure 9 This is a block diagram showing the configuration of an internal resistance calculation execution determination unit according to the first embodiment.

[0025] Figure 10 This is a block diagram showing the configuration of the SOH calculation unit of the first embodiment.

[0026] Figure 11 This is a diagram showing an internal resistance correction amount map according to the first embodiment.

[0027] Figure 12 This is a flowchart showing the SOH calculation process of the first embodiment.

[0028] Figure 13 This is a diagram showing a graph of SOH calculation when a charge / discharge pulse is input according to the conventional technology.

[0029] Figure 14 This is a diagram showing a graph of SOH calculation when a charge / discharge pulse is input in Example 1.

[0030] Figure 15 This is a block diagram showing the structure of the SOH calculation unit of the second embodiment.

[0031] Figure 16 This is a diagram showing an internal resistance correction amount map according to the second embodiment.

[0032] Figure 17 This is a diagram showing a graph of SOH calculation when a charge / discharge pulse is input in a high temperature range in Example 1.

[0033] Figure 18 This is a diagram showing an SOH calculation curve when a charge / discharge pulse is input in a high-temperature region in Example 2.

[0034] Figure 19 This is a diagram showing a resistance correction amount map according to a modified example of the second embodiment. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described based on the accompanying drawings. The figures referred to in the description of the present invention are merely illustrative, and the present invention is not limited to the following embodiments. Forms in which a part or all of the embodiments and modifications are combined without contradiction are also included in the disclosure of the present invention. In the following, only the structures and processes associated with the present invention are described, and the description of other structures and processes may be omitted. In addition, in the following, the same reference numerals are given to the same or similar structures and processes, and repeated descriptions are omitted. In addition, in the later embodiments, repeated descriptions of the same or similar structures and processes as those of the already appeared embodiments may be omitted.

[0036] In the following description, when multiple elements with the same name (e.g., "xxx100a" and "xxx100b") are collectively referred to as having the same number with a branch number appended, the same number is used, such as "xxx100." Similarly, when multiple elements with the same name (e.g., "YYYzzz1" and "YYYzzz2") are collectively referred to as having the same number with a suffix appended, the same number is used, such as "YYY."

[0037] The following embodiments illustrate applications to a power storage device that serves as a power source for a hybrid electric vehicle (HEV). However, the present invention is not limited to this embodiment and can also be applied to a power storage device control circuit that serves as a power source for passenger vehicles such as plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs), or industrial vehicles such as hybrid rail vehicles.

[0038] In the following embodiments, a lithium-ion battery is used as the storage device constituting the storage unit. However, other storage devices such as nickel-metal hydride batteries, lead-acid batteries, electric double-layer capacitors, and hybrid capacitors may also be used.

[0039] Example 1

[0040] based on Figures 1 to 14 Example 1 of the present invention will be described.

[0041] Figure 1 This is a block diagram showing the configuration of an electric system S of a hybrid vehicle according to a first embodiment of the present invention. In the electric system S of this embodiment, a battery system 100 is connected to an inverter 400 and a motor 410 via relays 300 and 310. The vehicle control unit 200 determines the distribution of driving force, etc., based on information such as the SOC of the battery system 100, information from the inverter 400 and motor 410, and information from the engine (not shown).

[0042] The configuration of the battery system 100 will be described. The battery system 100 includes a battery pack 110 composed of a plurality of cells 111, a cell management unit 120 that monitors the status of the cells 111, a current detection unit 130 that detects the current flowing through the battery system 100, a voltage detection unit 140 that detects the total voltage of the battery pack 110, a battery pack control unit 150 that controls the battery pack 110, and a storage unit 180 that stores information related to the battery characteristics of the cells 111, the cell group 112, and the battery pack 110.

[0043] The battery pack control unit 150 receives inputs such as the battery voltage and temperature of the battery cells 111 transmitted from the battery cell management unit 120, the current flowing through the battery system 100 transmitted from the current detection unit 130, and the total voltage of the battery pack 110 transmitted from the voltage detection unit 140. Furthermore, the diagnosis result of whether the battery cells 111 are overcharged or overdischarged, and an abnormality signal output when a communication error occurs in the battery cell management unit 120, and performs battery pack 110 status detection based on this input information. Furthermore, the results of the processing performed by the battery pack control unit 150 are transmitted to the battery cell management unit 120 and the vehicle control unit 200.

[0044] The battery pack 110 is composed of a plurality of cells 111 (lithium-ion batteries) electrically connected in series, each capable of storing and releasing electrical energy (charging and discharging DC power). For example, the output voltage of a cell 111 is 3.0 to 4.2 V (average output voltage: 3.6 V). The relationship between the OCV and SOC of the cell 111 is as follows: Figure 6 The case of the correlation shown is described as an example, but voltage specifications other than this may also be used.

[0045] The cells 111 that make up the battery pack 110 are grouped into a predetermined number of units for state management and control. The grouped cells 111 are electrically connected in series to form a cell group 112. The predetermined number of units can be an equal number of units, such as 1, 4, 6, etc., or a composite number, such as a combination of 4 and 6.

[0046] The cell management unit 120 that monitors the status of the cells 111 constituting the battery pack 110 is composed of a plurality of cell control units 121. One cell control unit 121 is assigned to each of the cell groups 112 grouped as described above. The cell control unit 121 operates by receiving power from the assigned cell group 112 and monitors the battery voltage and temperature of the cells 111 constituting the cell group 112. Figure 1In the embodiment, cell control units 121a and 121b are provided corresponding to cell groups 112a and 112b. In this embodiment, for simplicity of description, the cell group 112 is configured to have four cells 111 electrically connected in series, and a single cell control unit 121 is configured to monitor the four cells 111.

[0047] Figure 2 It means composition Figure 1 This is a block diagram of the configuration of the cell control unit 121 of the battery system 100. The cell control unit 121 includes a voltage detection circuit 122, a control circuit 123, a signal input / output circuit 124, and a temperature detection unit 125. The voltage detection circuit 122 measures the voltage between the terminals of each cell 111. The temperature detection unit 125 measures the temperature of the cell group 112. The control circuit 123 receives the measurement results from the voltage detection circuit 122 and the temperature detection unit 125 and transmits them to the battery pack control unit 150 via the signal input / output circuit 124. The circuit configuration typically incorporated into the cell control unit 121 to equalize voltage and SOC variations among the cells 111 due to self-discharge and current consumption variations is well known and therefore will not be described here.

[0048] Figure 2 The temperature detection unit 125 included in the cell control unit 121 has the function of measuring the temperature of the cell group 112. The temperature detection unit 125 measures a single temperature for the entire cell group 112 and uses this temperature as a representative value for the temperature of the cells 111 constituting the cell group 112. The temperature measured by the temperature detection unit 125 is used in various calculations to detect the status of the cells 111, the cell group 112, or the battery pack 110. Figure 2 Because the temperature representative value is used as a premise, the cell control unit 121 is provided with a single temperature detection unit 125. Alternatively, a temperature detection unit 125 may be provided for each cell 111 to measure the temperature of each cell 111 and perform various calculations based on the temperature of each cell 111. However, in this case, the number of temperature detection units 125 increases, and the configuration of the cell control unit 121 becomes correspondingly more complex.

[0049] exist Figure 2 , the temperature detection unit 125 is simply shown. In practice, a temperature sensor is installed on the target object. This temperature sensor outputs temperature information as a voltage. The measurement result is sent to the signal input / output circuit 124 via the control circuit 123. The signal input / output circuit 124 outputs the measurement result to the outside of the cell control unit 121. The function that implements this series of processes is implemented as the temperature detection unit 125 in the cell control unit 121. However, the voltage detection circuit 122 can also be used to measure the temperature information (voltage).

[0050] Back to Figure 1 Description. The battery pack control unit 150 and the single battery management unit 120 transmit and receive signals via the signal communication unit 160 via an insulating element 170 such as an optical coupler. The insulating element 170 is provided because the operating power sources of the battery pack control unit 150 and the single battery management unit 120 are different. That is, the single battery management unit 120 receives power from the battery pack 110 to operate, while the battery pack control unit 150 uses a battery for vehicle auxiliary equipment (for example, a 12V battery) as a power source. The insulating element 170 can be installed on either the circuit substrate constituting the single battery management unit 120 or the circuit substrate constituting the battery pack control unit 150. In addition, the insulating element 170 can also be omitted depending on the system configuration.

[0051] The signal communication unit 160 between the battery pack control unit 150 and the cell control units 121a and 121b of this embodiment will be described. The cell control units 121a and 121b are connected in series, with the potentials of the cell groups 112a and 112b they monitor arranged in descending order. Signals sent from the battery pack control unit 150 are input to the cell control unit 121a via the insulating element 170 by the signal communication unit 160. Similarly, the output of the cell control unit 121a and the input of the cell control unit 121b are connected via the signal communication unit 160 to transmit signals.

[0052] In this embodiment, the insulating element 170 is not interposed between the cell control units 121a and 121b, but an insulating element 170 may be interposed. Furthermore, the output of the cell control unit 121b is input to the battery pack control unit 150 via the insulating element 170 via the signal communication unit 160. In this manner, the battery pack control unit 150 and the cell control units 121a and 121b are connected in a ring configuration via the signal communication unit 160. This ring configuration is sometimes referred to as a daisy chain connection.

[0053] based on Figure 3 The configuration of the battery pack control unit 150 will be described. Figure 3 It means composition Figure 1 This is a block diagram showing the configuration of the battery pack control unit 150 of the battery system 100. In this embodiment, for simplicity, description is omitted regarding the processing of abnormality signals output based on diagnostic results related to the battery cells 111 or when a communication error occurs in the battery management unit 120. Instead, the configuration for calculating SOC and SOH is described.

[0054] The battery pack control unit 150 includes an SOC calculation unit 151, an internal resistance calculation execution determination unit 152, and an SOH calculation unit 153. The SOC calculation unit 151 receives as input the average voltage of each cell 111 comprising the battery pack 110, the current flowing through the battery pack 110, the temperature of the battery pack 110, and the SOH output by the SOH calculation unit 153, and outputs the SOC and SOCv. The details of the SOC and SOCv calculation processes will be described later.

[0055] The internal resistance calculation execution determination unit 152 uses as input the average voltage of each cell 111 comprising the battery pack 110, the current flowing through the battery pack 110, the temperature of the battery pack 110, and the SOC and SOCv output by the SOC calculation unit 151 to determine whether the SOH calculation can be executed and outputs the determination result. The SOH calculation unit 153 uses as input the SOC and SOCv output by the SOC calculation unit 151, the temperature, the current, and the determination result output by the internal resistance calculation execution determination unit 152 to calculate and output the SOH. The calculated SOC and SOH are transmitted to the vehicle control unit 200.

[0056] The storage unit 180 stores information such as the internal resistance characteristics of the battery pack 110, the cells 111, and the cell group 112, their fully charged capacities, polarity resistance characteristics, degradation characteristics, individual difference information, and the relationship between SOC and OCV. While the storage unit 180 is external to the battery pack control unit 150 or the cell management unit 120 in this embodiment, it may alternatively be provided within the battery pack control unit 150 or the cell management unit 120.

[0057] Figure 4 181 is a diagram showing an SOC table 181 , an internal resistance table 182 , and a polarization resistance table 183 . The SOC table 181 , the internal resistance table 182 , and the polarization resistance table 183 are stored in the storage unit 180 .

[0058] like Figure 4 As shown in (a), the SOC table 181 is a data table describing the correspondence between the SOC and OCV (Open Circuit Voltage) of the battery cell 111 in accordance with the temperature.

[0059] In addition, if Figure 4 As shown in (b), the internal resistance table 182 is a data table that describes the correspondence between the temperature and SOC of the battery 111 and the initial resistance value RoInit of Ro. Figure 7 In this manner, the resistance value Ro of the cell 111 when the battery is new is expressed by the equivalent circuit.

[0060] In addition, if Figure 4As shown in (c), the polarization resistance table 183 is a data table that describes the correspondence between the temperature and SOC of the battery 111 and the initial resistance value RpInit of Rp. Figure 7 In this manner, the resistance value Rp of the battery 111 when it is new is expressed by the equivalent circuit.

[0061] In addition, a data table is used in the description of this embodiment, but the corresponding relationships may be expressed by mathematical formulas or the like, and the format is not limited to the data table shown in the figure.

[0062] based on Figure 5 and Figure 6 The SOC calculation unit 151 constituting the battery pack control unit 150 will be described. Figure 5 This is a block diagram showing the configuration of the SOC calculation unit 151 constituting the battery pack control unit 150 of the first embodiment. Figure 6 This is a characteristic example showing the relationship between the SOC and OCV of the battery cell 111 .

[0063] like Figure 5 As shown, the SOC calculation unit 151 includes an SOCi calculation unit 151 - 1 , an SOCv calculation unit 151 - 2 , and a combined calculation unit 151 - 3 .

[0064] The SOCi calculation unit 151-1 takes the current and the previous value of the SOC calculation result (calculation result one cycle ago) output by the combination calculation unit 151-3 as input, calculates the SOC based on the integrated value of the current (hereinafter referred to as SOCi), and outputs it. The SOCv calculation unit 151-2 calculates OCV based on the battery voltage, current, and temperature. Figure 4 (a) and Figure 6 The SOC (hereinafter referred to as SOCv) is calculated based on the correspondence relationship between OCV and SOC. The combined calculation unit 151 - 3 takes the SOCi and SOCv as inputs, performs a weighted average of the SOCi and SOCv, and outputs the result.

[0065] Next, the SOCi calculation unit 151 - 1 will be described. SOCi is calculated as shown in the following equation (1) by adding the change in SOC due to the flow of current to the previous value (calculation result one cycle ago) of the result output by the combined calculation unit 151 - 3 .

[0066] [Mathematical formula 1]

[0067]

[0068] Here, SOC_old is the previous value of SOC (the calculation result one cycle ago) obtained by equation (4) described later, I is the current, Qmax is the full charge capacity of the battery 111, and ts is the control cycle (sampling cycle of current or voltage, etc.).

[0069] based on Figure 7 and Figure 8 The SOCv calculation unit 151 - 2 will be described. Figure 7 An equivalent circuit diagram of the cell 111 is shown. Figure 8 This shows the voltage behavior when a charging current flows through the cell 111. The cell 111 is a circuit consisting of a DC power supply simulating the battery's open circuit voltage (OCV), Ro representing the resistance of the electrodes and electrolyte, and a parallel circuit of Rp and C, which model the resistance component (polarization component) associated with the battery's electrochemical reaction, connected in series.

[0070] like Figure 8 As shown in FIG. 1 , if the charging current flows, the voltage rise caused by Ro relative to OCV occurs, and then the voltage rise caused by Rp gradually occurs (polarization voltage). If the voltage rise caused by Ro is Vo and the polarization voltage is Vp, then according to Figure 7 In the equivalent circuit shown, OCV is expressed by the following equation (2).

[0071] [Mathematical formula 2]

[0072]

[0073] Ro and Rp included in equation (2) above are obtained by multiplying the initial resistance values ​​RoInit and RpInit of the cell 111 by SOH_old, which represents the rate of increase (%) of internal resistance, as shown in equation (3) below. SOH_old in equation (3) is the previous value (calculated one cycle ago) obtained by equation (6) described below.

[0074] [Mathematical formula 3]

[0075]

[0076] RoInit and RpInit in the above formula (3) are calculated based on the SOC and temperature at the current time point by referring to the internal resistance table 182 and the polarization resistance table 183 stored in the storage unit 180 in advance. The SOCv calculation unit 151-2 calculates OCV based on the first to third formulas of the above formula (2), as shown in the fourth formula. Figure 4 (a) and Figure 6 The SOC corresponding to the OCV is calculated as SOCv.

[0077] The combined calculation unit 151 - 3 is described below. The combined calculation unit 151 - 3 takes the SOCi calculated by the SOCi calculation unit 151 - 1 , the SOCv calculated by the SOCv calculation unit 151 - 2 , the current, and the temperature as inputs, and calculates the SOC based on the following equation (4).

[0078] [Formula 4]

[0079] SOC=w×SOCv+(1-w)×SOCi…(4)

[0080] Here, w represents a weight coefficient, which is calculated, for example, according to the following formula (5).

[0081] [Formula 5]

[0082]

[0083] According to equations (4) and (5), when the current is high, w decreases, thereby increasing the weighting toward SOCi. Conversely, when the current is low, w increases, thereby increasing the weighting toward SOCv. In this embodiment, a weighting coefficient such as that in equation (5) is provided to avoid the influence of SOCv errors associated with resistance errors during current flow, but the present invention is not limited to this.

[0084] Then, based on Figure 9 The internal resistance calculation execution determination unit 152 will be described. Figure 9 1 is a block diagram showing the configuration of the internal resistance calculation execution determination unit 152 according to the first embodiment.

[0085] First, based on Figure 9 The following describes the configuration of the internal resistance calculation execution determination unit 152. The internal resistance calculation execution determination unit 152 includes an internal resistance error detection unit 152-1, which receives the SOC and SOCv inputs from the SOC calculation unit 151 and determines whether the resistance value used for the SOCv calculation has an error greater than a specified value; a calculation execution determination unit 152-2, which determines whether the SOC, current, and voltage are within a specified range; and a correction feasibility determination unit 152-3, which determines whether the internal resistance correction process can be executed based on the determination results of the internal resistance error detection unit 152-1 and the calculation execution determination unit 152-2.

[0086] When the absolute value of the difference between the SOC and SOCv output by the SOC calculation unit 151 (the SOCv error) is greater than a predetermined value, the internal resistance error detection unit 152-1 determines that there is a discrepancy between the internal resistance value used for the SOCv calculation and the internal resistance value of the battery to be controlled, and outputs the determination result.

[0087] Next, calculation execution determination unit 152-2 uses the SOC, current, and temperature as inputs to determine whether to execute the internal resistance correction calculation. Specifically, it checks whether the SOC, current, and temperature calculated by SOC calculation unit 151 are within specified ranges. If all conditions are met, the calculation is deemed enabled and the determination result is output. The specified ranges for SOC, current, and temperature are determined based on battery characteristics, SOC errors, and the effects of current and temperature sensor errors, and are stored in storage unit 180.

[0088] Correction determination unit 152-3 determines whether to execute the internal resistance correction calculation based on the determination results of internal resistance error detection unit 152-1 and calculation execution determination unit 152-2. In this embodiment, the resistance error is detected, and the internal resistance correction calculation is executed when the SOC, temperature, and current are within the specified range. Otherwise, the internal resistance correction calculation is not executed.

[0089] Then, based on Figure 10 The configuration of the SOH calculation unit 153 will be described. Figure 10 This is a block diagram showing the configuration of the SOH calculation unit of Example 1. The SOH calculation unit 153 includes an internal resistance correction amount calculation unit 153 - 1 , an internal resistance correction unit 153 - 2 , and an SOH calculation unit 153 - 3 .

[0090] The internal resistance correction amount calculation unit 153-1 takes the SOC, SOCv and current as inputs and calculates the internal resistance correction amount based on the Figure 11 The internal resistance correction amount is calculated using the resistance correction amount map shown in FIG. The internal resistance correction amount is output to the internal resistance correction unit 153-2. The internal resistance correction unit 153-2 receives the determination result of the internal resistance calculation execution determination unit 152, the SOC, and the temperature as input. If it is determined that the calculation of the internal resistance correction amount can be executed, the internal resistance correction unit 153-2 corrects the initial resistance value RoInit of the internal resistance Ro corresponding to the SOC and temperature in the internal resistance table 182 stored in the storage unit 180 and outputs the corrected internal resistance value Ro to the SOH calculation unit 153-3.

[0091] The SOH calculation unit 153-3 calculates the SOH using the following equation (6) based on the corrected internal resistance value Ro and the initial resistance value RoInit corresponding to the SOC and temperature. In addition to calculating the SOH based on the following equation (6), the corrected internal resistance value Ro can also be used for various battery controls. In the example shown in the following equation (6), the SOH is set as the ratio of Ro to RoInit, but it can also be set as the ratio of the corrected Rp to RpInit, similar to Ro.

[0092] [Formula 6]

[0093]

[0094] If the internal resistance correction unit 153-2 determines that the internal resistance calculation cannot be performed based on the determination results of either the internal resistance error detection unit 152-1 or the calculation execution determination unit 152-2, it does not correct the internal resistance value. In other words, it outputs the internal resistance value calculated in the most recent calculation cycle in which the internal resistance calculation was determined to be executable. For example, when calculation processing is performed in a predetermined calculation cycle, if the internal resistance calculation was determined to be executable in the cycle immediately before the calculation cycle determined to be impossible, the internal resistance value calculated in the calculation cycle immediately before the previous cycle is output.

[0095] Then, based on Figure 11 The processing contents of the internal resistance correction amount calculation unit 153 - 1 will be described. Figure 11 An example of a map showing the resistance correction amount corresponding to the current value and the SOC difference (SOCv - SOC). This embodiment assumes control to detect the SOC difference as an error associated with internal resistance variation and to correct the internal resistance. Therefore, the greater the SOC difference, the greater the internal resistance variation. In other words, the greater the SOC difference, the greater the internal resistance to be corrected, i.e., the larger the resistance correction amount is set.

[0096] Next, consider the current dependence of the correction amount. When the SOC difference is constant, that is, when the SOCv error is constant, the errors in Vo and Vp caused by internal resistance variation are also the same, according to equation (2). Since the errors in Vo and Vp are determined by the product of current and internal resistance, when the errors in Vo and Vp are constant, the internal resistance variation increases with smaller currents, and decreases with larger currents. If the internal resistance correction amount is specified to reflect this characteristic, the smaller the absolute value of the current, the larger the resistance correction amount, and the larger the absolute value of the current, the smaller the resistance correction amount.

[0097] To summarize, the resistance correction amount map can be constructed so that the internal resistance correction amount is set to a larger value as the difference between the SOC calculated using the internal resistance (SOCv) and the SOC calculated using a method other than SOCv increases and the absolute value of the current decreases.

[0098] in addition, Figure 11 The internal resistance correction amount corresponding to the SOC difference and the current may be determined in advance as a map or table and stored in the storage unit 180 , or the relationship may be described as a mathematical expression and implemented as a mathematical expression.

[0099] Next, refer to Figure 12The flowchart of Example 1 illustrates the SOH calculation process. Figure 12 : is a flowchart showing the SOH calculation process of Example 1. The SOH calculation process is repeatedly executed by the battery control unit 150 from the start to the shutdown of the electric system S including the battery system 100 .

[0100] First, in step S11, the battery pack control unit 150 calculates SOCi using the aforementioned equation (1) in the SOCi calculation unit 151-1 of the SOC calculation unit 151. Next, in step S12, the battery pack control unit 150 calculates SOCi using the aforementioned equations (2) and (3) in the SOCv calculation unit 151-2 of the SOC calculation unit 151. Next, in step S13, the battery pack control unit 150 calculates SOC using the aforementioned equations (4) and (5) in the combined calculation unit 151-3 of the SOC calculation unit 151. The battery pack control unit 150 stores the SOC calculated in step S13 in the variable SOC_old.

[0101] Next, in step S14, the battery pack control unit 150 determines whether the SOCv error (the absolute value of the difference between the SOC and SOCv) is greater than a specified value in the internal resistance calculation execution determination unit 152, and determines whether the input SOC, current, and temperature are all within a specified range in the calculation execution determination unit 152-2. If the result of step S14 is "yes," the battery pack control unit 150 determines that the internal resistance correction calculation is to be executed in the correction possibility determination unit 152-3 of the internal resistance calculation execution determination unit 152, and the processing proceeds to step S15. If the result of step S14 is "no," the internal resistance correction calculation is not to be executed, and the processing returns to step S11.

[0102] In step S15, the battery pack control unit 150 takes the SOC, SOCv and current as inputs to the internal resistance correction amount calculation unit 153-1 of the SOH calculation unit 153, and calculates the current according to the internal resistance correction amount calculation unit 153-1. Figure 11 The internal resistance correction amount is calculated using the internal resistance correction amount map shown in FIG. Next, in step S16, the battery pack control unit 150 uses the determination result of the internal resistance calculation execution determination unit 152, the SOC, and the temperature as inputs in the internal resistance correction unit 153-2 of the SOH calculation unit 153. The internal resistance correction unit 153-2 corrects the initial resistance value RoInit corresponding to the SOC and temperature in the internal resistance table 182 based on the first equation of equation (3) and outputs the corrected internal resistance value Ro to the SOH calculation unit 153-3.

[0103] Next, in step S17, the battery control unit 150 calculates the SOH using the above equation (6) based on the corrected internal resistance value Ro and the initial resistance value RoInit corresponding to the SOC and temperature in the SOH calculation unit 153-3. The battery control unit 150 stores the SOH calculated in step S18 in the variable SOH_old.

[0104] Next, in step S18, the battery control unit 150 determines whether the electric system S including the battery system 100 is shut down. If it is shut down (step S18: Yes), the present SOH calculation process is terminated. If it is not shut down (step S18: No), the process returns to step S11.

[0105] Next, refer to Figure 13 and Figure 14 The effects of Example 1 will be described. Figure 13 This is a diagram showing a profile of SOH calculation when a charge / discharge pulse is input according to the conventional technology. Figure 14 This is a diagram showing a graph of SOH calculation when a charge / discharge pulse is input in Example 1.

[0106] Figure 13 and Figure 14 Waveforms of (a) SOC calculation value, (b) current, and (c) SOH (internal resistance increase rate) calculation value when a rectangular wave charge / discharge current that repeatedly performs charge or discharge is input are shown. Figure 13 The results of the conventional method (fixed resistance correction value) before the present invention is applied are shown. Figure 14 The results obtained when the present invention was applied are shown. Figure 13 and Figure 14 In the example, the initial SOH value is assumed to be 100%, and a state with a large deviation from the true value is assumed.

[0107] observe Figure 13 In the SOC waveform shown in (a), in the region just beginning to charge and discharge, the waveform of the SOC (SOCv) based on the internal resistance deviates significantly from the SOC calculated value due to the influence of the SOH calculation error (internal resistance error). Here, the difference between SOCv and SOC is extracted, the internal resistance is corrected with a fixed value, and the SOH calculated value is gradually updated ( Figure 13 (c) If the internal resistance is updated with a fixed value, the SOCv approaches the calculated SOC value, which reduces the SOC difference. At the end of charge and discharge, the calculated SOH value converges to the actual SOH value, and the SOC difference also reduces.

[0108] Next, the waveforms of SOC, current, and SOH when the present invention is applied are shown in FIG. Figure 14 Observation Figure 14 As can be seen from the waveform of SOC shown in (a), in the region where charge and discharge start, Figure 13 As with the conventional technology shown above, the waveform of SOCv deviates greatly from SOC due to the influence of SOH error. Here, the difference between SOCv and SOC is extracted and the internal resistance is corrected. However, by using Figure 11 The resistance correction map shown shows that the larger the SOC difference, the larger the internal resistance correction amount. This indicates that the SOH update speed, as it approaches the true value, is faster than with conventional methods. Since the resistance correction amount decreases as the SOC difference decreases, the update speed slows down. However, it is clear that the calculated value ultimately converges to the true value at approximately half the speed of conventional methods.

[0109] According to this embodiment, the internal resistance is corrected and the SOH is calculated using an internal resistance correction amount determined by the difference between the SOC (SOCv) based on the internal resistance and the SOC calculated by a method different from the SOCv and the current value. As a result, compared with the case where the internal resistance correction amount is set to a fixed value as in the past, the convergence of the SOH calculation is greatly improved, and the accuracy of the SOH calculation (the difference between the final converged value and the true value) can be maintained at the same accuracy as before.

[0110] Specifically, by correcting the internal resistance value based on the SOC difference and current value changes, the resistance correction amount can be set larger when the difference between the SOH recognized by the battery control unit and the actual SOH value of the controlled battery is large, thereby improving the convergence of the calculated SOH value. Furthermore, as the calculated SOH value approaches the updated actual value, the internal resistance correction amount decreases, allowing for highly accurate SOH calculation without compromising stability. As a result, both calculation accuracy and convergence are achieved, enabling accurate understanding of the battery's available input and output power and accurate calculation of battery replacement indicators.

[0111] Example 2

[0112] based on Figure 15 and Figure 16 Example 2 of the present invention will be described.

[0113] In the first embodiment, a method of controlling the correction amount of the internal resistance value based on the difference between the SOC (SOCv) calculated based on the resistance and the SOC obtained by combining the SOC (SOCi) based on the current and SOCv, and the current value, has been described.

[0114] This embodiment describes an example in which the battery temperature is further used in controlling the internal resistance correction amount. The description of this embodiment focuses on the differences from Example 1, and descriptions of components identical to Example 1 are omitted. This embodiment differs from Example 1 in that the battery pack control unit 150 includes an SOH calculation unit 153B in place of the SOH calculation unit 153. SOH calculation unit 153B is described below.

[0115] based on Figure 15 The SOH calculation unit 153B of this embodiment will be described. Figure 15 This is a block diagram showing the configuration of SOH calculation unit 153B in Example 2. Compared to SOH calculation unit 153 in Example 1, SOH calculation unit 153B includes internal resistance correction calculation unit 153-1B in place of internal resistance correction calculation unit 153-1, and adds the battery temperature as an input. Internal resistance correction calculation unit 153-1B calculates the internal resistance correction value using the SOC difference, current, and temperature as inputs, and outputs the result to internal resistance correction unit 153-2.

[0116] based on Figure 16 A method for calculating the internal resistance correction amount by the internal resistance correction amount calculation unit 153 - 1B will be described. Figure 16 1 is a diagram showing an internal resistance correction amount map according to the second embodiment, showing the internal resistance correction amount corresponding to the SOC difference for each temperature T.

[0117] Typically, a battery's internal resistance decreases as temperature rises. Therefore, setting a uniform internal resistance correction value based on temperature T may result in an amount that is too large relative to the internal resistance value itself. When calculating the SOH as the ratio of the current internal resistance value to the internal resistance value when the battery was new, if the internal resistance correction value is too large relative to the internal resistance value, the SOH value will fluctuate significantly, potentially causing oscillation. Conversely, if the internal resistance correction value is too small relative to the internal resistance value, the SOH value will fluctuate less, potentially slowing the convergence of the calculated SOH value to the true value.

[0118] So, if Figure 16 As shown in the resistance correction amount map, Figure 10Compared to the resistance correction amount map shown in FIG. 1 , the internal resistance correction amount is generally set to a smaller value in a high-temperature range where the internal resistance value decreases, and conversely, the internal resistance correction amount is generally set to a larger value in a low-temperature range where the internal resistance value increases. In other words, in this embodiment, the resistance correction amount map is constructed so that the internal resistance correction amount is set to a larger value as the difference between the SOC calculated value (SOCv) based on the internal resistance and the SOC calculated using a method different from SOCv increases, the absolute value of the current decreases, and the battery temperature increases.

[0119] By constructing such a resistance correction amount map, it is possible to execute an SOH calculation while ensuring convergence and stability for an internal resistance value that varies with temperature.

[0120] In addition, about Figure 16 The internal resistance correction amount corresponding to the SOC difference, current, and temperature may be determined in advance as a map or table and stored in the storage unit 180, or the relationship may be described as a mathematical expression and implemented as a mathematical expression.

[0121] Next, refer to Figure 17 and Figure 18 The effects of this embodiment will be described.

[0122] Figure 17 and Figure 18 Waveforms of (a) SOC calculation value, (b) current, and (c) SOH (internal resistance increase rate) calculation value when a rectangular wave charge / discharge current that repeatedly performs charge or discharge is input are shown. Figure 17 For example, an example of calculation results when the SOH calculation is performed in a high temperature range (eg, 50° C.) using the internal resistance correction amount set in a normal temperature range (eg, 25° C.) is shown.

[0123] When calculating SOH in a high temperature region where the internal resistance value is small, as shown in formula (6), although the initial resistance value RoInit of the denominator is smaller than that at room temperature, when calculating the internal resistance value Ro at the current time point of the numerator, the calculated value of SOH fluctuates greatly due to the influence of the large correction amount of the internal resistance. Figure 17 As shown in (c), there is a possibility that the calculated value does not converge and vibrates near the true value of SOH.

[0124] On the other hand, if an appropriate internal resistance correction amount is set for each temperature, that is, the internal resistance correction amount is set to a smaller value in the high temperature range and then calculated, then Figure 18 As shown in (c), it can be confirmed that a calculation can be realized that can suppress the vibration near the true value of SOH and ensure convergence.

[0125] According to this embodiment, the internal resistance is corrected and the SOH is calculated using an internal resistance correction amount determined by the difference between the SOC (SOCv) based on the internal resistance and the SOC calculated by a method different from the SOCv, the current value, and the temperature. This allows the SOH to be calculated with stability and convergence ensured even for internal resistance values ​​that vary depending on the temperature.

[0126] In this embodiment, the example of adjusting the correction amount is described with attention to the fact that the internal resistance value varies with temperature. However, the internal resistance value also varies with, for example, the degree of battery degradation. Therefore, the internal resistance correction amount can also be determined based on the degree of degradation. That is, Figure 19 As shown in the resistance correction amount map of the modification of the second embodiment, Figure 10 Compared to the resistance correction amount map shown in the figure, when the product is new, the degradation degree SOH is small and the internal resistance is small, so the internal resistance correction amount is set to be small overall. If the degradation degree SOH increases and the internal resistance increases as the degradation progresses, the internal resistance correction amount is set to be large overall. Figure 19 The internal resistance correction amount corresponding to the SOC difference, current, and degree of degradation shown above may be determined in advance as a map or table and stored in the storage unit 180 , or the relationship may be described as a mathematical expression and implemented as a mathematical expression.

[0127] Specifically, the resistance correction amount map is constructed so that the greater the difference between the SOC calculated based on the internal resistance (SOCv) and the SOC calculated using a method other than SOCv, the smaller the absolute value of the current, and the greater the degree of battery degradation, the larger the internal resistance correction amount is set. This allows the internal resistance to be corrected using an internal resistance correction amount appropriate for ensuring stability and convergence, depending on the degree of battery degradation. Consequently, both stability and convergence of the SOH calculated value can be achieved.

[0128] The above description is only an example, and the present invention is not limited to the configuration of the above embodiment, and includes various variations. For example, the above embodiment is described in detail in order to easily explain the present invention, and is not limited to having all the configurations described. In addition, a part of the configuration of a certain embodiment can be replaced with the configuration of other embodiments, and the configuration of other embodiments can be added to the configuration of a certain embodiment. In addition, for a part of the configuration of each embodiment, other configurations can be added, deleted, or replaced. In addition, as long as the steps in the processing of each embodiment can obtain the same result, they can also be executed in an appropriately replaced order.

[0129] Label Description

[0130] S…Electric system; 100…Battery system; 110…Battery pack; 111…Single cell; 112…Single cell group; 120…Single cell management unit; 121…Single cell control unit; 122…Voltage detection circuit; 123…Control circuit; 124…Signal input / output circuit; 125…Temperature detection unit; 130…Current detection unit; 140…Voltage detection unit; 150…Battery pack control unit; 151…SOC calculation unit; 151-1…SOCi calculation unit; 151-2…SOCv calculation unit; 151-3…Combination calculation unit; 152…Internal resistance operation Calculation execution determination unit; 152-1…internal resistance error detection unit; 152-2…calculation execution determination unit; 152-3…correction possibility determination unit; 152-4…power-on time measurement unit; 153…SOH calculation unit; 153-1…internal resistance correction amount calculation unit; 153-2…internal resistance correction unit; 153-3…SOH calculation unit; 160…signal communication unit; 170…insulation element; 180…storage unit; 200…vehicle control unit; 300; 310…relay; 400…inverter; 410…motor; 420…motor / inverter control unit.

Claims

1. A battery control device, characterized in that: include: A first calculation unit calculates a first state of charge of the battery using a first method based on the current value, voltage value, and internal resistance value of the battery; a second calculation unit calculates a second state of charge of the battery using a second method different from the first method; an internal resistance calculation execution determination unit determines that internal resistance correction calculation can be executed when the difference between the first and second states of charge is greater than a specified value and the second state of charge, the current value, and the temperature of the battery are within a specified range; an internal resistance correction amount calculation unit calculates a resistance correction amount corresponding to the absolute value of the difference between the first and second states of charge and the absolute value of the current value; and an internal resistance correction unit, when the determination is made that the calculation can be executed, corrects the internal resistance value using the calculated resistance correction amount, wherein even if the absolute value of the difference is the same, the smaller the absolute value of the current value, the larger the resistance correction amount.

2. The battery control device according to claim 1, wherein The system further includes a degradation degree calculation unit that calculates a degradation degree of the battery based on the internal resistance value corrected by the internal resistance correction unit.

3. The battery control device according to claim 1, wherein: The internal resistance correction unit does not correct the internal resistance value when the difference is not detected or the second state of charge is not within the specified range, and outputs the internal resistance value corrected in the most recent calculation cycle in which the difference is detected and it is determined that the second state of charge, the current value, and the temperature of the battery are within the specified range.

4. The battery control device according to claim 1, wherein: The larger the absolute value of the difference and the smaller the absolute value of the current value, the larger the resistance correction amount becomes.

5. The battery control device according to claim 4, wherein: The resistance correction amount is a value also corresponding to the temperature of the battery.

6. The battery control device according to claim 5, wherein: The resistance correction amount becomes a smaller value as the battery temperature increases.

7. The battery control device according to claim 4, wherein: The resistance correction amount is a value corresponding to the degree of degradation of the battery.

8. The battery control device according to claim 7, wherein: The greater the degree of battery degradation, the greater the resistance correction amount.

9. A battery system, characterized in that: The invention comprises: the battery control device according to any one of claims 1 to 8; and a battery pack composed of a plurality of connected batteries, which is controlled by the battery control device.

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