Battery management device, battery management method, and power storage system

Abstract

A battery management device, a battery management method, and a power storage system that manage a battery that can be charged and discharged are provided. The battery management device includes a battery state calculation section that calculates a degree of deterioration of the battery, a deterioration speed calculation section that calculates a deterioration speed of the battery based on the degree of deterioration, and an upper limit temperature setting section that sets an upper limit temperature of the battery based on the deterioration speed, the upper limit temperature setting section causing the upper limit temperature to rise as the deterioration speed decreases.

Description

[0001] This application is a divisional application of patent application filed on March 12, 2019, with application number 201980050972.2 and entitled "Battery Management Device, Battery Management Method and Power Storage System". Technical Field

[0002] This invention relates to a battery management device, a battery management method, and an energy storage system. Background Technology

[0003] In recent years, from the perspective of global warming, the use of power transmission systems that generate electricity from renewable energy sources such as solar or wind power and achieve output stabilization through the use of Battery Energy Storage Systems (BESS) is expanding. Furthermore, such battery energy storage systems are also widely used in mobile transportation systems such as automobiles to limit emissions.

[0004] Existing conventional power storage systems consist of a battery composed of multiple battery cells, a cooling system for regulating the temperature of the battery, and a battery management device for controlling the charging and discharging of the battery to maintain the system in a safe state. In such conventional power storage systems, a cooling system is used to forcibly cool the battery so that the battery temperature is below a preset upper limit temperature.

[0005] On the other hand, due to the intended use of energy storage systems, sometimes reducing size or weight is crucial. Therefore, energy storage systems utilizing batteries that employ natural cooling without a dedicated cooling system are also being developed. In such naturally cooled energy storage systems, battery charge / discharge control needs to consider operating conditions and the surrounding environment to ensure the battery temperature does not exceed its upper limit. Here, the upper limit temperature is typically set to a constant value throughout the battery's lifespan. However, as repeated charge / discharge cycles exacerbate battery degradation, the battery's internal resistance increases, leading to increased heat generation per unit charge / discharge current. Consequently, the longer the battery's lifespan, the lower the charge / discharge current that can flow through it, resulting in decreased energy storage system performance. Therefore, when using naturally cooled energy storage systems, the upper limit temperature of the battery needs to be appropriately adjusted throughout the entire operating period to balance system performance and utilization.

[0006] Regarding charge and discharge control corresponding to the battery's degradation state, the technology described in Patent Document 1 is known. Patent Document 1 discloses a battery control device comprising: a battery information acquisition unit that acquires information about the battery; a degradation progress rate calculation unit that calculates the degradation progress rate of the battery based on the information acquired by the battery information acquisition unit; a limit value setting unit that sets a limit value for controlling the charge and discharge of the battery based on the degradation progress rate calculated by the degradation progress rate calculation unit; a timing determination unit that determines the timing at which the limit value should be output based on the information acquired by the battery information acquisition unit; and a limit value output unit that outputs the limit value based on the timing determined by the timing determination unit.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent document 1: International Publication No. 2017 / 043239. Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In the battery control device of Patent Document 1, the charging and discharging current or SOC limit value of the battery can be changed according to the battery's deterioration state, but it is difficult to properly adjust the upper limit temperature of the battery.

[0012] Technical solutions for solving the problem

[0013] The battery management device of the present invention is a device for managing a rechargeable battery, comprising: a battery state calculation unit for calculating the degree of degradation of the battery; a degradation rate calculation unit for calculating the degradation rate of the battery based on the degree of degradation; and an upper limit temperature setting unit for setting an upper limit temperature of the battery based on the degradation rate, wherein the battery state calculation unit calculates the increase in the internal resistance of the battery as the degree of degradation, the degradation rate calculation unit calculates the time derivative of the increase in the internal resistance of the battery as the degradation rate decreases, and the upper limit temperature setting unit causes the upper limit temperature to increase as the degradation rate decreases.

[0014] The battery management method of the present invention is a method for managing a rechargeable battery. Using a computer, the increase in the internal resistance of the battery is calculated as the degree of degradation of the battery. Then, based on the calculated degree of degradation, the time derivative of the increase in the internal resistance of the battery is calculated as the rate of degradation of the battery. Based on the calculated rate of degradation, an upper limit temperature of the battery is set so that the upper limit temperature increases as the rate of degradation decreases.

[0015] The power storage system of the present invention includes a battery management device, a rechargeable battery, and a charging and discharging device, which charges and discharges the battery based on an allowable value of the charging and discharging current of the battery set by the battery management device according to the upper limit temperature of the battery after the rise.

[0016] Invention Effects

[0017] According to the present invention, the upper limit temperature of the battery can be appropriately adjusted according to the battery's degradation state. Attached Figure Description

[0018] Figure 1 This is a schematic structural diagram of an electric power storage system according to one embodiment of the present invention.

[0019] Figure 2 This is a diagram showing the functional blocks of the battery management device according to the first embodiment of the present invention, which handles the upper limit temperature setting process and the allowable current calculation process.

[0020] Figure 3 This is a diagram representing the function blocks of the battery state calculation unit.

[0021] Figure 4 This is a diagram illustrating an example of the equivalent circuit of a battery cell in a battery model.

[0022] Figure 5 This is a diagram representing the function block of the degradation rate calculation unit.

[0023] Figure 6 This is a diagram representing the functional blocks of the timing determination section.

[0024] Figure 7 This is a graph showing the changes in the increase in internal resistance, the rate of degradation, and the upper limit temperature achieved by the battery management device according to the first embodiment of the present invention.

[0025] Figure 8 This is a diagram illustrating the effect of the battery management device according to the first embodiment of the present invention.

[0026] Figure 9 This is a diagram showing the functional blocks of the battery management device according to the second embodiment of the present invention, which handles the upper limit temperature setting process and the allowable current calculation process.

[0027] Figure 10 This is a graph showing the changes in the increase in internal resistance, the rate of degradation, and the upper limit temperature achieved by the battery management device according to the second embodiment of the present invention.

[0028] Figure 11 This figure illustrates the effect of the battery management device according to the second embodiment of the present invention.

[0029] Figure 12 This is a diagram showing the function block of the degradation rate calculation unit in the modified example. Detailed Implementation

[0030] The embodiments of the present invention will now be described.

[0031] (First Implementation)

[0032] Figure 1 This is a schematic structural diagram of an energy storage system according to one embodiment of the present invention. Figure 1 The illustrated Battery Energy Storage System (BESS) 1 includes a battery pack 101, a battery management device 102, a current sensor 103, a unit controller 104, a voltage sensor 105, a temperature sensor 106, and a relay 107. The BESS 1 is connected to a load 3, such as an AC motor, via an inverter 2. The BESS 1 and the inverter 2 are connected to a higher-level controller 4 via a communication line (not shown).

[0033] The battery pack 101 is constructed by connecting multiple rechargeable and discharging battery cells in series and parallel. When the load 3 is in operation, the DC power discharged from the battery pack 101 is converted into AC power by the inverter 2 and supplied to the load 3. Conversely, when the load 3 is in regenerative operation, the AC power output from the load 3 is converted into DC power by the inverter 2 and charged to the battery pack 101. The operation of the inverter 2 thus charges and discharges the battery pack 101. The operation of the inverter 2 is controlled by the upper-level controller 4.

[0034] Current sensor 103 detects the current flowing through battery pack 101 and outputs the detection result to battery management device 102. Unit controller 104 detects the voltage of each battery cell in battery pack 101 and outputs the detection result to battery management device 102. Voltage sensor 105 detects the voltage (total voltage) of battery pack 101 and outputs the detection result to battery management device 102. Temperature sensor 106 detects the temperature of battery pack 101 and outputs the detection result to battery management device 102. Relay 107 switches the connection state between power storage system 1 and inverter 2 according to the control of the upper-level controller 4.

[0035] The battery management device 102 performs charge and discharge control of the battery pack 101 based on the detection results from the current sensor 103, the cell controller 104, the voltage sensor 105, and the temperature sensor 106. The charge and discharge control of the battery pack 101 performed by the battery management device 102 includes, for example, determining the upper limit temperature T of the battery pack 101 during charge and discharge. limit Upper limit temperature setting processing, according to the upper limit temperature T limit To determine the allowable value I of the charging and discharging current of battery pack 101. limitThe battery management device 102 performs allowable current calculations and balance control to adjust the charging state of each battery cell. It also communicates with the upper-level controller 4 to control the charging and discharging of the battery pack 101.

[0036] Furthermore, the power storage system 1 is a system that relies on natural cooling without cooling devices such as cooling fans or water-cooled radiators. During the charging and discharging of the battery pack 101, the temperature of the battery pack 101 changes due to electrochemical reactions or phase transitions in each battery cell, Joule heating, and the surrounding environment. The amount of temperature change at this time is highly dependent on the charging and discharging current. Therefore, in the power storage system 1, the upper limit temperature T during charging and discharging is determined through the upper limit temperature setting process and the allowable current calculation process of the battery management device 102. limit The allowable value of charging and discharging current I limit Based on these values, the charging and discharging current is limited. This suppresses the rapid temperature rise of the battery pack 101 during charging and discharging, maintaining the temperature of the battery pack 101 at the upper limit temperature T. limit the following.

[0037] In existing control methods for secondary battery systems that rely on natural cooling, the upper limit temperature of the battery is typically maintained at a constant value throughout the system's operation. However, secondary batteries typically deteriorate due to repeated charge-discharge cycles, resulting in reduced charging capacity and increased internal resistance. This increased internal resistance leads to increased heat generation during charge and discharge, so even with a constant upper limit temperature, the permissible charge and discharge current decreases as the secondary battery deteriorates. Consequently, as the system's operating period lengthens, the usable current or power during charge and discharge decreases, leading to reduced system utilization.

[0038] Therefore, in this embodiment, the upper limit temperature T is appropriately adjusted according to the degradation state of the battery pack 101. limit This method aims to solve the problems of existing control methods described above and improve the overall system utilization during operation. The specific method is explained below.

[0039] Figure 2 This diagram illustrates the functional blocks of the battery management device 102 according to the first embodiment of the present invention, specifically regarding the upper limit temperature setting process and the allowable current calculation process. The battery management device 102 of this embodiment includes functional blocks for a battery state calculation unit 501, a current limit value calculation unit 502, a degradation rate calculation unit 503, a timing determination unit 504, and an upper limit temperature setting unit 505. These functional blocks are implemented, for example, by a computer executing a predetermined program.

[0040] The battery state calculation unit 501 obtains the current I, closed-circuit voltage CCV, and battery temperature T detected when the battery pack 101 is charging or discharging from the current sensor 103, voltage sensor 105, and temperature sensor 106, respectively. cell Then, based on this information, the open-circuit voltage OCV, state of charge SOC, polarization voltage Vp, charge capacity reduction SOHQ, and internal resistance increase SOHR representing the current state of the battery pack 101 are calculated. Furthermore, detailed calculation methods for these state values ​​calculated by the battery state calculation unit 501 will be provided later. Figure 3 Please provide an explanation.

[0041] The current limit value calculation unit 502 acquires the state values ​​of the battery pack 101 calculated by the battery state calculation unit 501, and acquires the battery temperature T from the temperature sensor 106. cell In addition, the upper limit temperature T set by the upper limit temperature setting unit 505 is also acquired. limit Then, based on the information obtained, the allowable value I of the charging and discharging current of the battery pack 101 is calculated. limit Furthermore, regarding the allowable value I of the charging and discharging current calculated by the current limit value calculation unit 502... limit The calculation method can use various well-known calculation methods, but in this embodiment, its specific description is omitted.

[0042] The degradation rate calculation unit 503 acquires a state value representing the degree of degradation of the battery pack 101 from the various state values ​​of the battery pack 101 calculated by the battery state calculation unit 501. Then, based on the acquired degree of degradation, it calculates the degradation rate of the battery pack 101. In this embodiment, an example will be described whereby the degradation rate calculation unit 503 acquires the increase in internal resistance SOHR from the battery state calculation unit 501 as a state value representing the degree of degradation of the battery pack 101, and calculates the time derivative value dSOHR / dt of the increase in internal resistance SOHR as the degradation rate of the battery pack 101. Furthermore, as will be described later, if the upper limit temperature T limit If the value is constant, the longer the battery pack 101 is used, the smaller the time derivative of the increase in internal resistance SOHR, dSOHR / dt. For a detailed calculation method of the degradation rate of the battery pack 101, i.e., the time derivative of the increase in internal resistance SOHR, dSOHR / dt, calculated by the degradation rate calculation unit 503, please refer to [link / reference] later. Figure 5 Please provide an explanation.

[0043] The timing determination unit 504 acquires the degradation rate dSOHR / dt of the battery pack 101 calculated by the degradation rate calculation unit 503. Then, based on the acquired degradation rate dSOHR / dt, it determines the upper limit temperature T of the battery pack 101 to be maintained. limitThe timing of the rise is determined, and a flag value indicating the result is output. In this embodiment, the timing determination unit 504 obtains the currently set upper limit temperature T from the upper limit temperature setting unit 505. limit The value of dSOHR / dt is used to determine whether the degradation rate dSOHR / dt meets the upper limit temperature T for the current condition. limit Pre-set conditions. As a result, when it is determined that the conditions are not met, the upper limit temperature setting unit 505 determines that it will set the upper limit temperature T by changing the flag value output to the upper limit temperature setting unit 505. limit The timing of the rise. Furthermore, regarding the upper limit temperature T determined by the timing determination unit 504. limit For a detailed method on determining the timing of an upward move, please refer to the following. Figure 6 Please provide an explanation.

[0044] The upper limit temperature setting unit 505 sets the upper limit temperature T according to the degradation state of the battery pack 101. limit The value is output to the current limit value calculation unit 502. In this embodiment, the upper limit temperature setting unit 505 sets the upper limit temperature T according to the timing determined by the timing determination unit 504. limit The value increases in stages. That is, when the flag value input from the timing determination unit 504 changes, the upper limit temperature setting unit 505 sets a new upper limit temperature T corresponding to the changed flag value. limit The value will replace the previous upper limit temperature T. limit The value of T makes the upper limit temperature T limit The temperature increases in stages. Furthermore, the upper limit temperature T for each flag value... limit The value is preset in the upper limit temperature setting unit 505.

[0045] The battery management device 102 determines the upper limit temperature T based on the upper limit temperature. limit The permissible value I of the calculated charging and discharging current limit The battery management device 102 sends data to the upper-level controller 4 for control of the inverter 2, etc. Thus, in the power storage system 1, the charging and discharging of the battery pack 101 is controlled to maintain the battery temperature T. cell Not exceeding the upper limit temperature T limit At this time, inverter 2 operates according to the allowable value I of the charging and discharging current. limit The battery pack 101 is charged and discharged.

[0046] Figure 3 This is a diagram showing the functional blocks of the battery state calculation unit 501. The battery state calculation unit 501 includes a battery model unit 601 and a degradation state detection unit 602.

[0047] The battery model unit 601 stores a battery model modeled from the battery pack 101. Using this battery model, the open-circuit voltage OCV, state of charge (SOC), and polarization voltage Vp are calculated. The battery model of the battery model unit 601 is set based on, for example, the number of series and parallel connections of the battery cells in the actual battery pack 101, and the equivalent circuit of each battery cell. The battery model unit 601 calculates the open-circuit voltage (CCV) and battery temperature (T) by obtaining the current I, closed-circuit voltage (CCV), and battery temperature T from the current sensor 103, voltage sensor 105, and temperature sensor 106, respectively. cell Applied to this battery model, the open-circuit voltage OCV, state of charge SOC, and polarization voltage Vp corresponding to the state of battery pack 101 can be calculated.

[0048] Figure 4 This is a diagram showing an example of the equivalent circuit of the battery cell of the battery model set in the battery model section 601. Figure 4 The equivalent circuit of the battery cell shown is constructed by connecting in series an open-circuit voltage source 603 with voltage value Voc, an internal resistor 604 with resistance value R, a polarized capacitor 605 with capacity value Cp, and a polarized resistor 606 with resistance value Rp. In this equivalent circuit, the voltage across the open-circuit voltage source 603, i.e., the voltage value Voc, is equivalent to the open-circuit voltage OCV, and the voltage across the parallel circuit of the polarized capacitor 605 and the polarized resistor 606 is equivalent to the polarized voltage Vp. Furthermore, the value obtained by adding the applied voltage I×R of the internal resistor 604 when the current I flows through this equivalent circuit, the polarized voltage Vp, and the open-circuit voltage OCV is equivalent to the closed-circuit voltage CCV. Furthermore, Figure 4 The values ​​of the circuit constants of the equivalent circuit are based on the battery temperature T. cell Therefore, in the battery model section 601, based on these relationships, the current I, closed-circuit voltage CCV, and battery temperature T are determined. cell The open-circuit voltage OCV and polarization voltage Vp of the battery pack 101 are calculated. Then, based on the calculation result of the open-circuit voltage OCV, the state of charge (SOC) can be calculated.

[0049] Return to Figure 3 The degradation state detection unit 602 detects the degradation state of the battery pack 101 and calculates the decrease in charging capacity (SOHQ) and the increase in internal resistance (SOHR) corresponding to the degradation state. Each battery cell in the battery pack 101 degrades due to repeated charging and discharging, resulting in a decrease in charging capacity and an increase in internal resistance depending on its degradation state. The degradation state detection unit 602 pre-stores information, for example, representing the relationship between the current, voltage, and temperature of the battery pack 101 and its degradation state. Using this information, based on the current I, closed-circuit voltage CCV, and battery temperature T obtained from the current sensor 103, voltage sensor 105, and temperature sensor 106 respectively... cellThe degradation state of battery pack 101 is detected. Then, based on the pre-stored relationship between the degradation state and the decrease in charging capacity SOHQ and the increase in internal resistance SOHR, the decrease in charging capacity SOHQ and the increase in internal resistance SOHR corresponding to the detection results of the degradation state of battery pack 101 can be calculated.

[0050] Figure 5 This is a diagram showing the functional blocks of the degradation rate calculation unit 503. The degradation rate calculation unit 503 includes a storage unit 607, a smoothing filter 608, and a differential operation unit 609.

[0051] The storage unit 607 records the value of the internal resistance increase SOHR obtained from the current limit value calculation unit 502 in a time sequence. The smoothing filter 608 smooths the data by calculating, for example, a moving average of the internal resistance increase SOHR recorded in the storage unit 607 to remove short-term fluctuations contained in the historical data of the internal resistance increase SOHR. Through the operation of this smoothing filter 608, the long-term trend of the degradation state of the battery pack 101 can be grasped. The differential calculation unit 609 calculates the degradation rate of the battery pack 101 by calculating the time differential value dSOHR / dt of the internal resistance increase SOHR smoothed by the smoothing filter 608.

[0052] Furthermore, the calculation frequency of the degradation rate calculated by the degradation rate calculation unit 503 is determined based on the usage frequency and charging / discharging tendency of the battery pack 101, and this calculation frequency varies depending on the application of the power storage system 1. For example, in the case of the power storage system 1 used in a hybrid electric vehicle, the degradation rate calculation unit 503 calculates the degradation rate on a weekly basis.

[0053] Figure 6 This is a diagram representing the functional blocks of the timing determination unit 504. The timing determination unit 504, for example, has a condition table 610. Using this condition table 610, the upper limit temperature T is determined based on the degradation rate dSOHR / dt. limit The opportune moment for an upward trend.

[0054] exist Figure 6 In the example shown, as condition table 610, for T limit1 ~T limitN The upper limit temperature values ​​indicate N preset degradation rates dSOHR / dt and corresponding flag values ​​1 to N for each condition. N is an integer greater than or equal to 2. Furthermore, in the first row of condition table 610, the initial value of the flag indicating the start of operation (BOL: Beginning Of Life) of battery pack 101 is shown as 1. Timing determination unit 504, by referring to condition table 610, selects and outputs the current upper limit temperature T set by upper limit temperature setting unit 505. limitThe value corresponds to the flag value. Additionally, obtain the value related to the current upper limit temperature T. limit The condition for the degradation rate dSOHR / dt corresponding to the value is defined. When the value of the degradation rate dSOHR / dt input from the degradation rate calculation unit 503 does not meet this condition, a flag value corresponding to the following condition is output. Thus, the flag value changes according to the degradation rate dSOHR / dt.

[0055] For example, when the flag value is 1, the upper limit temperature setting unit 505 sets the upper limit temperature T. limit The value is set to T limit1 At this point, the timing determination unit 504 refers to the second row of the condition table 610 and compares the degradation rate dSOHR / dt with a predetermined threshold A1. Then, while the degradation rate dSOHR / dt is greater than the threshold A1, the flag value remains unchanged at 1; when it falls below the threshold A1, the flag value changes from 1 to 2. As this flag value changes, the upper limit temperature T set by the upper limit temperature setting unit 505 is adjusted. limit The value from T limit1 Become a T limit2 (T) limit1 <T limit2 By performing such processing on each of the N conditions, the upper limit temperature T set by the upper limit temperature setting unit 505 is determined. limit The value from the initial value T limit1 It changes in N stages to the final value T. limitN .

[0056] Figure 7 This represents the increase in internal resistance SOHR, the degradation rate dSOHR / dt, and the upper limit temperature T achieved by the battery management device 102 of the first embodiment of the present invention. limit A diagram showing the changes. In Figure 7 In the case where, for example, the battery management device 102 of this embodiment is applied as N=3 (hereinafter referred to as "when the present invention is applied"), the graphs (a), (b), and (c) respectively represent the increase in internal resistance SOHR, the degradation rate dSOHR / dt, and the upper limit temperature T corresponding to the usage time of the power storage system 1. limit The changing circumstances. Furthermore, in Figure 7 In the curves (a) to (c) above, as a comparative example, the use of the upper limit temperature T is also shown. limit The case of the previous control method that keeps the value constant (hereinafter referred to as "previous control").

[0057] exist Figure 7In the graphs (a) to (b), the horizontal axis represents the system usage time of battery pack 101, from the start of use (BOL) to the end of use (EOL), in years. On the other hand, Figure 7 The vertical axis of (a) in the figure represents the increase in internal resistance SOHR (%) when the initial value of the internal resistance R of the battery pack 101 is set to 100%. Figure 7 In (b), the vertical axis represents the magnitude of the degradation rate dSOHR / dt. Figure 7 The vertical axis of (c) in the diagram represents the upper limit temperature T. limit The value (°C). In Figure 7 In (a) of the diagram, the dashed line 611 and the solid line 612 represent the increase in internal resistance SOHR during conventional control and when the present invention is applied, respectively. Figure 7 In (b) of the diagram, the dashed line 613 and the solid line 614 represent the degradation rates dSOHR / dt under conventional control and when the present invention is applied, respectively. Figure 7 In section (c), the dashed line 615 and the solid line 616 represent the upper limit temperature T under conventional control and when the present invention is applied, respectively. limit .

[0058] like Figure 7 As shown by the dashed line 611 in (a) of the diagram, under conventional control, the increase in internal resistance SOHR gradually increases with the usage time of the battery pack 101. The shorter the usage time, the steeper the slope of the dashed line 611, and the steeper it becomes as the usage time increases. Therefore, as... Figure 7 As shown by the dashed line 613 in (b) of the diagram, the degradation rate dSOHR / dt under previous control conditions decreases with usage time. Furthermore, as... Figure 7 As shown by the dashed line 615 in (c), the upper limit temperature T during previous control is... limit Not from the initial value T limit1 Change begins.

[0059] On the other hand, when applying the present invention, when Figure 7 The solid line 614 in (b) shows the degradation rate dSOHR / dt at time t. 1_2 When the value falls below the predetermined threshold A1, the flag value output from the timing determination unit 504 changes from 1 to 2. Therefore, as Figure 7 As shown by the solid line 616 in (c), through the processing of the upper limit temperature setting unit 505, at time t 1_2 At that time, the upper limit temperature T limit From T limit1 Become a higher T limit2 The result is as follows: Figure 7As shown by the solid lines 612 and 614 in (a) and (b), the tendency of the increase in internal resistance SOHR and the degradation rate dSOHR / dt at time t 1_2 Previously and time t 1_2 The situation changes thereafter. Subsequently, while the degradation rate dSOHR / dt exceeds the specified threshold A2, the flag value output from the timing determination unit 504 remains at 2.

[0060] when Figure 7 The solid line 614 in (b) shows the degradation rate dSOHR / dt at time t. 2_3 When the value is below the threshold A2, the flag value output from the timing determination unit 504 changes from 2 to 3. Therefore, as Figure 7 As shown by the solid line 616 in (c), through the processing of the upper limit temperature setting unit 505, at time t 2_3 At that time, the upper limit temperature T limit From T limit2 Become a higher T limit3 At this time, it is also related to time t. 1_2 Similarly, the tendency of the increase in internal resistance SOHR and the degradation rate dSOHR / dt at time t 2_3 Previously and time t 2_3 This will change later. Subsequently, until the end of service (EOL) of battery pack 101, the upper limit temperature T... limit All maintained at T limit3 .

[0061] According to the battery management device 102 of this embodiment, the above-described processing enables the upper limit temperature T to be controlled. limit It increases in stages as the degradation rate dSOHR / dt decreases.

[0062] Figure 8 This is a diagram illustrating the effect of the battery management device 102 according to the first embodiment of the present invention. Figure 8 In this context, (a) represents the maximum value I of the charging and discharging current available when applying the present invention and in conventional control, respectively. available max The changing situation. Figure 8 In (a) of the middle, with Figure 7 Similarly, in the various graphs, the horizontal axis represents the system usage time of battery pack 101, from the start of operation (BOL) to the end of operation (EOL), in years. On the other hand, Figure 8 In (a), the vertical axis represents the maximum value I of the charging and discharging current. available max The absolute value. In Figure 8 In (a), the dashed line 617 and the solid line 618 represent the maximum value I of the charging and discharging current under conventional control and when the present invention is applied, respectively. available maxThe absolute value of the charge / discharge current. Furthermore, the maximum value of the charge / discharge current I. available max The current limit value calculation unit 502 calculates the upper limit temperature T. limit The calculated allowable value I of the charging and discharging current limit Corresponding. Additionally. Figure 8 (b) in the text represents the upper limit temperature T. limit The changes, which are related to Figure 7 The situation shown in (c) is the same.

[0063] In terms of past control methods, such as Figure 8 As shown by the dashed line 615 in (b), the upper limit temperature T limit T with initial value limit1 The resistance remains unchanged. Therefore, the internal resistance R of the battery pack 101 continuously increases over time, and consequently, the heat generated by the battery pack 101 during charging and discharging also continuously increases. Therefore, as... Figure 8 As shown by the dashed line 617 in (a) above, the maximum value I of the charging and discharging current increases as the battery pack 101 is used for a longer period of time. available max The absolute value decreases.

[0064] On the other hand, in relation to the application of this invention, such as Figure 8 As shown by the solid line 616 in (b), the upper limit temperature T limit At time t 1_2 and time t 2_3 It rises in stages. Therefore, as... Figure 8 As shown by the solid line 618 in (a) at time t 1_2 From now on, compared with previous control methods, the maximum value of the charging and discharging current I will be... available max The absolute value increases. Furthermore, at time t... 2_3 Subsequently, the difference between the control time and the previous control time further increased.

[0065] According to the battery management device 102 of this embodiment, as described above, by setting the upper limit temperature T... limit The degradation rate increases in stages as dSOHR / dt decreases, and compared to previous control methods, the maximum value of the charge / discharge current I can be increased. available max The absolute value of . Therefore, the utilization rate of the power storage system 1 can be increased. As a result, for example, in the case of hybrid vehicles, fuel consumption can be significantly reduced.

[0066] According to the first embodiment of the present invention described above, the following effects can be achieved.

[0067] (1) The battery management device 102 is a device for managing a rechargeable battery pack 101, comprising: a battery state calculation unit 501 that calculates the increase in internal resistance SOHR, which represents the degree of degradation of the battery pack 101; a degradation rate calculation unit 503 that calculates the degradation rate dSOHR / dt of the battery pack 101 based on the increase in internal resistance SOHR; and an upper limit temperature setting unit 505 that sets the upper limit temperature T of the battery pack 101 based on the degradation rate dSOHR / dt. limit The upper limit temperature setting unit 505 sets the upper limit temperature T. limit It increases as the degradation rate dSOHR / dt decreases. Therefore, the upper limit temperature T of the battery pack 101 can be appropriately adjusted according to the degradation state of the battery pack 101. limit .

[0068] (2) The battery management device 102 includes a timing determination unit 504, which determines the upper limit temperature T based on the degradation rate dSOHR / dt. limit The timing of the increase. The upper limit temperature setting unit 505 sets the upper limit temperature T according to the timing determined by the timing determination unit 504. limit The temperature increases in stages. This allows the upper limit temperature T to be reached. limit As the rate of degradation dSOHR / dt increases at the appropriate time.

[0069] (3) Timing determination unit 504 is based on the degradation rate dSOHR / dt and the current upper limit temperature T. limit Determine the upper limit temperature T limit The timing of the rise. Therefore, it is possible to appropriately determine the upper limit temperature T. limit The timing of a phased rise.

[0070] (4) Timing determination unit 504 uses, for example Figure 6 The conditions shown in Table 610 correlate the degradation rate dSOHR / dt with the upper limit temperature T for each temperature range. limit The value is compared with a pre-set degradation rate condition, and the upper limit temperature T is determined based on the result of this comparison. limit The timing of the rise. Therefore, it is easy to determine the upper limit temperature T. limit The opportune moment for an upward trend.

[0071] (Second Implementation)

[0072] Next, a second embodiment of the present invention will be described. In this embodiment, another method of setting the upper limit temperature for the battery management device 102 will be described. Furthermore, the structure of the power storage system in this embodiment is different from that described in the first embodiment. Figure 1 The same applies to the energy storage system (BESS)1, so the description is omitted.

[0073] Figure 9 This diagram illustrates the functional blocks of the battery management device 102 according to the second embodiment of the present invention, specifically regarding the upper limit temperature setting process and the allowable current calculation process. The battery management device 102 of this embodiment includes functional blocks for a battery state calculation unit 501, a current limit value calculation unit 502, a degradation rate calculation unit 503, an upper limit temperature calculation unit 506, and an upper limit temperature setting unit 505. These functional blocks are implemented, for example, by a computer executing a predetermined program.

[0074] Figure 9 The battery state calculation unit 501, current limit value calculation unit 502, and degradation rate calculation unit 503 are respectively the same as those described in the first embodiment. Figure 2 The same applies to the battery management device 102. Therefore, the following mainly focuses on the replacement. Figure 2 The timing determination part 504 is set up Figure 9 The operation of the upper limit temperature calculation unit 506 and the corresponding upper limit temperature setting unit 505 will be described, omitting... Figure 9 Description of other functional blocks.

[0075] The upper limit temperature calculation unit 506 acquires the degradation rate dSOHR / dt of the battery pack 101 calculated by the degradation rate calculation unit 503. Then, based on the acquired degradation rate dSOHR / dt, it calculates the upper limit temperature T representing the battery pack 101. limit The upper limit temperature value T of the set value limit_value The output is sent to the upper limit temperature setting unit 505. The upper limit temperature setting unit 505 sets the upper limit temperature based on the upper limit temperature value T. limit_value Make the upper limit temperature T limit The value changes continuously.

[0076] The upper limit temperature calculation unit 506 uses, for example, the function shown in equation (1) below to directly calculate the upper limit temperature value T at time t based on the degradation rate dSOHR / dt. limit_value (t).

[0077] T limit_value (t)=f(x1(t),……,x p (t))・・・(1)

[0078] In the function of equation (1), the independent variables are x1(t), ..., x p(t) represents the degradation rate information of battery pack 101. In this embodiment, an example is given where the independent variable is set to one, and the time derivative dSOHR / dt of the internal resistance increase SOHR calculated as the degradation rate of battery pack 101 is equivalent to this independent variable. Furthermore, the number of independent variables in equation (1) is not limited to one and can be arbitrarily set. In addition, the function represented by equation (1) has the following characteristic: the smaller the value of the independent variable, the more the degradation rate decreases due to the degradation of battery pack 101, and the upper limit temperature value T limit_value The larger the value of (t), the better. This function, for example, is a pre-defined function based on various experimental data obtained under various temperature conditions and is stored in the upper limit temperature calculation unit 506.

[0079] Figure 10 This represents the increase in internal resistance SOHR, the degradation rate dSOHR / dt, and the upper limit temperature T achieved by the battery management device 102 of the second embodiment of the present invention. limit A diagram showing the changes. In Figure 10 In the case where the battery management device 102 of this embodiment is applied (hereinafter referred to as "when the present invention is applied"), the graphs (a), (b), and (c) respectively represent the increase in internal resistance SOHR, the degradation rate dSOHR / dt, and the upper limit temperature T corresponding to the usage time of the power storage system 1. limit The changing circumstances. Furthermore, in Figure 10 In the curves (a) to (c) above, the curves are similar to those described in the first embodiment. Figure 7 Similarly, as a comparative example, the curves (a) to (c) also show the upper limit temperature T. limit The situation under previous control methods that maintained a constant value.

[0080] Figure 10 The horizontal and vertical axes of the curves in (a) to (c) are respectively compared with those described in the first embodiment. Figure 7 The same applies to curves (a) through (c) in the graph. Figure 10 In (a) of the diagram, the dashed line 611 and the solid line 619 represent the increase in internal resistance (SOHR) under conventional control and when the present invention is applied, respectively. Figure 10 In (b) of the diagram, the dashed line 613 and the solid line 620 represent the degradation rates dSOHR / dt under conventional control and when the present invention is applied, respectively. Figure 10 In section (c), the dashed line 615 and the solid line 621 represent the upper limit temperature T under conventional control and when the present invention is applied, respectively. limit .

[0081] In relation to the application of this invention, Figure 10The degradation rate dSOHR / dt, shown by the solid line 620 in (b) of the diagram, decreases with the passage of time, and subsequently, as... Figure 10 As shown by the solid line 621 in (c) of the upper limit temperature T, limit It increases continuously. That is, the upper limit temperature T limit The upper limit temperature value T is calculated using a function of equation (1) with the aforementioned characteristics. limit_value Continuous variation to make the upper limit temperature T limit It increases as the degradation rate dSOHR / dt decreases. The result is as follows: Figure 10 As shown by the solid lines 619 and 620 in (a) and (b), the longer the usage time, the greater the difference between the increase in internal resistance SOHR and the degradation rate dSOHR / dt and the previous control time.

[0082] According to the battery management device 102 of this embodiment, the processing described above enables the upper limit temperature T to be controlled. limit It increases continuously as the degradation rate dSOHR / dt decreases.

[0083] Figure 11 This figure illustrates the effect of the battery management device 102 according to the second embodiment of the present invention. Figure 11 In this context, (a) represents the maximum value I of the charging and discharging current available when applying the present invention and in conventional control, respectively. available max The changing situation. Figure 11 The horizontal and vertical axes of the curves in (a) and (b) are respectively compared with those described in the first embodiment. Figure 8 The curves in (a) and (b) are the same. Figure 11 In (a), the dashed line 617 and the solid line 622 represent the maximum values ​​of the charging and discharging current I under conventional control and when the present invention is applied, respectively. available max The absolute value. Additionally, Figure 11 (b) in the text represents the upper limit temperature T. limit The changes, which are related to Figure 10 The situation shown in (c) is the same.

[0084] In relation to the application of this invention, such as Figure 11 As shown by the solid line 621 in (b) of the diagram, the upper limit temperature T is... limit It increases continuously over time. Therefore, as... Figure 11 As shown by the solid line 622 in (a) above, the maximum value of the charging and discharging current I compared to previous control methods is... available max The absolute value gradually increases.

[0085] According to the battery management device 102 of this embodiment, as described above, by setting the upper limit temperature T... limitThe degradation rate dSOHR / dt increases continuously, and compared with previous control methods, the maximum value of the charge / discharge current I can be increased. available max The absolute value increases. Therefore, the utilization rate of the power storage system 1 can be increased. As a result, in applications such as hybrid vehicles, fuel consumption can be significantly reduced.

[0086] According to the second embodiment of the present invention described above, in addition to the effects of (1) already described in the first embodiment, the following effects can also be achieved.

[0087] (5) The battery management device 102 includes an upper limit temperature calculation unit 506, which calculates and represents the upper limit temperature T based on the degradation rate dSOHR / dt. limit The upper limit of the temperature value T limit_value The upper limit temperature setting unit 505 is based on the upper limit temperature value T calculated by the upper limit temperature calculation unit 506. limit_value Make the upper limit temperature T limit The temperature increases. Therefore, the upper limit temperature T can be increased. limit The degradation rate dSOHR / dt increases continuously.

[0088] (6) The upper limit temperature calculation unit 506 calculates the upper limit temperature value T using the pre-set function of the above formula (1). limit_value Therefore, the appropriate upper limit temperature value T can be easily calculated. limit_value .

[0089] (Variation example)

[0090] Furthermore, in the first and second embodiments described above, an example was given in which only the time derivative value dSOHR / dt of the increase in internal resistance SOHR was calculated as the degradation rate of the battery pack 101 in the degradation rate calculation unit 503. However, other degradation rate information can also be calculated as the degradation rate of the battery pack 101. For example, in addition to calculating the time derivative value dSOHR / dt of the increase in internal resistance SOHR, the time derivative value dSOHQ / dt of the decrease in charging capacity SOHQ can also be calculated as the degradation rate of the battery pack 101.

[0091] Figure 12 This is a diagram showing the functional blocks of the degradation rate calculation unit 503 in a modified example. The degradation rate calculation unit 503 includes a storage unit 607a, a smoothing filter 608a, and a differential operation unit 609a corresponding to the increase in internal resistance SOHR, and a storage unit 607b, a smoothing filter 608b, and a differential operation unit 609b corresponding to the decrease in charging capacity SOHQ.

[0092] exist Figure 12In this process, the storage unit 607a, the smoothing filter 608a, and the differential calculation unit 609a respectively compare the internal resistance increase SOHR obtained from the current limit value calculation unit 502 with the data obtained from the current limit value calculation unit 502. Figure 5 The same processing described above applies. Therefore, as one of the deterioration rate information of the battery pack 101, the time derivative value dSOHR / dt of the internal resistance increase SOHR is calculated. Furthermore, the storage unit 607b, the smoothing filter 608b, and the differential calculation unit 609b perform the same processing on the charging capacity reduction SOHQ obtained from the current limit value calculation unit 502 as the storage unit 607a, the smoothing filter 608a, and the differential calculation unit 609a. Therefore, as one of the deterioration rate information of the battery pack 101, the time derivative value dSOHQ / dt of the charging capacity reduction SOHQ is calculated.

[0093] In the case where the above-described modified example is applied in the first embodiment, the timing determination unit 504 determines the upper limit temperature T based on the degradation rates dSOHR / dt and dSOHQ / dt calculated by the degradation rate calculation unit 503. limit The timing of the rise. In this situation, in Figure 6 In the condition table 610 shown, in addition to the aforementioned degradation rate dSOHR / dt condition, a degradation rate dSOHQ / dt condition is also set. Then, it is determined whether the degradation rates dSOHR / dt and dSOHQ / dt satisfy each condition. Based on the result of this determination, a flag value is changed, thereby enabling the upper limit temperature T set by the upper limit temperature setting unit 505 to be adjusted. limit The value changes in stages.

[0094] Furthermore, in the second embodiment where the above-described modified example is applied, the upper limit temperature calculation unit 506 calculates the upper limit temperature value T based on the degradation rates dSOHR / dt and dSOHQ / dt calculated by the degradation rate calculation unit 503. limit_value In this case, by using the degradation rates dSOHR / dt and dSOHQ / dt as independent variables of the function expressed by the above equation (1), the upper limit temperature value T at time t can be directly calculated based on the degradation rates dSOHR / dt and dSOHQ / dt. limit_value (t), so that the upper limit temperature T set by the upper limit temperature setting unit 505 is... limit The value changes continuously.

[0095] Furthermore, in the aforementioned variation, an example was described where the degradation rate information for the battery pack 101 was provided using the time derivative dSOHR / dt of the internal resistance increase SOHR and the time derivative dSOHQ / dt of the charge capacity decrease SOHQ. However, other degradation rate information can also be used. Alternatively, a degradation rate information combining multiple degradation rate information can be calculated by setting weighting coefficients for each of these multiple degradation rate information and performing a weighted addition operation. Using this degradation rate information, the upper limit temperature T can be adjusted. limit The value changes.

[0096] According to the above-described variations of the present invention, in addition to the effects of (1) to (6) already described in the first and second embodiments, the following effects can also be achieved.

[0097] (7) The battery state calculation unit 501 calculates various degrees of degradation of the battery pack 101 (reduction in charging capacity SOHQ and increase in internal resistance SOHR). The degradation rate calculation unit 503 calculates the degradation rate (time derivative of increase in internal resistance SOHR dSOHR / dt and time derivative of reduction in charging capacity SOHQ dSOHQ / dt) for each of the various degrees of degradation calculated by the battery state calculation unit 501. The upper limit temperature setting unit 505 uses the various degradation rates dSOHR / dt and dSOHQ / dt calculated by the degradation rate calculation unit 503 to set the upper limit temperature T. limit Therefore, it is possible to reflect the degradation state of battery pack 101 in more detail and thus increase the upper limit temperature T. limit Things have changed.

[0098] (8) The aforementioned multiple degrees of degradation may include at least the increase in internal resistance SOHR of battery pack 101 and the decrease in charging capacity SOHQ of battery pack 101. Thus, a degree of degradation that appropriately represents the degradation state of battery pack 101 can be defined.

[0099] Furthermore, while the above embodiments describe an application example of a power storage system using natural cooling, the present invention can also be applied to power storage systems using forced cooling methods, such as cooling fans or water-cooled radiators, to cool the battery pack 101.

[0100] The embodiments or variations described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. For example, the phased upper limit temperature T described in the first embodiment can also be incorporated. limit The changes and the continuous upper limit temperature T as described in the second embodiment limit The change in temperature corresponds to the upper limit temperature T that is proportional to the degradation rate of the battery pack 101. limitThe adjustment. Alternatively, in the second embodiment, the upper limit temperature T can also be... limit The temperature is maintained at a constant value until the specified rate of degradation is reached, after which the upper limit temperature T is calculated using a function such as equation (1). limit_value The upper limit temperature T corresponding to the degradation rate of battery pack 101 is set. limit The adjustment.

[0101] Furthermore, information indirectly representing the degradation rate of battery pack 101 can be used instead of values ​​that directly represent the degradation rate of battery pack 101, such as the time derivative of internal resistance increase SOHR dSOHR / dt or the time derivative of charge capacity decrease SOHQ dSOHQ / dt, as degradation rate information for determining the upper limit temperature T. limit Adjustment. For example, the total previous output power of battery pack 101, the total driving distance and total parking time of the vehicle (in the case of an electric storage system installed in the vehicle), and the total provision time of auxiliary services (in the case of an electric storage system connected to the power grid) can be used as information on the degradation rate of battery pack 101. Furthermore, in that case, appropriate conditions or functions are required depending on the type of degradation rate information.

[0102] The present invention is not limited to the above-described embodiments or variations, and various modifications can be made without departing from the spirit of the present invention.

[0103] The disclosure of the following priority-based application is cited herein.

[0104] Japanese Patent Application 2018-142467 (filed on July 30, 2018)

[0105] Symbol Explanation

[0106] 1. Battery Energy Storage System (BESS)

[0107] 2 Inverter

[0108] 3. Load

[0109] 4. Upper-level controller

[0110] 101 Battery Pack

[0111] 102 Battery Management Device

[0112] 103 Current Sensor

[0113] 104-unit controller

[0114] 105 Voltage Sensor

[0115] 106 Temperature Sensor

[0116] 107 Relay

[0117] 501 Battery Status Calculation Unit

[0118] 502 Current Limit Value Calculation Section

[0119] 503 Deterioration Rate Calculation Department

[0120] 504 Timing Determination Department

[0121] 505 Upper Limit Temperature Setting Section

[0122] 506 Upper Limit Temperature Calculation Department

[0123] 601 Battery Model Department

[0124] 602 Deterioration Condition Detection Department

[0125] 603 Open Circuit Voltage Source

[0126] 604 internal resistance

[0127] 605 polarization capacity

[0128] 606 polarization resistor

[0129] 607 Storage Unit

[0130] 608 smoothing filter

[0131] 609 Differential Operations Unit

[0132] 610 Condition Table.

Claims

1. A battery management device for managing rechargeable batteries, characterized in that, include: A battery state calculation unit that calculates the degree of degradation of the battery; A degradation rate calculation unit that calculates the degradation rate of the battery based on the degradation degree; An upper limit temperature setting unit that sets the upper limit temperature of the battery based on the degradation rate; and A timing determination unit that determines when to raise the upper limit temperature; The battery state calculation unit calculates various degrees of degradation of the battery, including the increase in the battery's internal resistance and the decrease in the battery's charging capacity. The degradation rate calculation unit calculates the time derivative of the increase in internal resistance and the time derivative of the decrease in charging capacity, respectively, as the degradation rate. The timing determination unit has a condition table, which sets conditions for the time derivative of the increase in internal resistance and the time derivative of the decrease in charging capacity. The timing determination unit determines whether the time derivative of the increase in internal resistance and the time derivative of the decrease in charging capacity satisfy each condition, and determines the timing for raising the upper limit temperature based on the determination result. The upper limit temperature setting unit causes the upper limit temperature to increase in stages as the degradation rate decreases, according to the timing determined by the timing determination unit.

2. The battery management device according to claim 1, characterized in that: The degradation rate calculation unit includes a storage unit, a smoothing filter, and a differential operation unit. The storage unit records the value of the increase in internal resistance and the value of the decrease in charging capacity in a timely manner. The smoothing filter removes short-term fluctuations from historical records by calculating a moving average recorded in the storage unit, thereby smoothing the data. The differential calculation unit calculates the time differential value of the increase in internal resistance and the time differential value of the decrease in charging capacity by calculating the smoothed time differential value.

3. The battery management device according to claim 2, characterized in that: In the condition table, for each of the multiple upper limit temperature values, there are pre-set conditions for the time derivative of the increase in internal resistance and the time derivative of the decrease in charging capacity.

4. A battery management method using a computer to manage a rechargeable battery, characterized in that, Include: The steps for calculating the increase in internal resistance and the decrease in charging capacity of the battery as a measure of its degradation. The step of calculating the time derivative of the increase in internal resistance and the time derivative of the decrease in charging capacity based on the increase in internal resistance and the decrease in charging capacity as the degradation rate of the battery. Using a condition table that sets corresponding time derivative conditions for the increase in internal resistance and the decrease in charging capacity for multiple upper temperature values, the step is to determine whether the current time derivative value of the increase in internal resistance and the time derivative value of the decrease in charging capacity satisfy each condition respectively. The steps to determine when to raise the upper limit temperature based on the judgment results; and The step of causing the upper limit temperature to increase in stages as the rate of degradation decreases, according to a determined timing.

5. An electricity storage system, characterized in that, include: The battery management device according to any one of claims 1 to 3; Rechargeable batteries; and A charging and discharging device that charges and discharges the battery based on the allowable value of the charging and discharging current of the battery, which is set by the battery management device according to the upper limit temperature of the battery after the rise.

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