WO2022180771A1

WO2022180771A1 - Power storage management device, power storage device, and method for managing power storage unit

Info

Publication number: WO2022180771A1
Application number: PCT/JP2021/007280
Authority: WO
Inventors: 健志 ▲濱▼田
Original assignee: 武蔵精密工業株式会社
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2022-09-01
Also published as: JPWO2022180771A1

Abstract

The present invention suppresses the occurrence of an overcurrent state of a secondary battery while suppressing a decline in high-output characteristics caused by a capacitor. This power storage management device manages a power storage unit comprising parallel blocks, in each of which a secondary battery and a capacitor are connected in parallel to each other. The power storage management device comprises: a current measurement part for measuring currents flowing in the parallel blocks; a voltage measurement part for measuring terminal voltages of the parallel blocks; an abnormality determination part for carrying out abnormal-time processing, under the necessary condition that a current flowing in any one of the parallel blocks as measured by the current measurement part has exceeded an overcurrent threshold value; an OCV estimation part for estimating OCVs of the capacitors; and a threshold value change part for changing the overcurrent threshold value in accordance with OCV differences, that is, differences between the OCVs of the capacitors estimated by the OCV estimation part and a reference OCV.

Description

Power storage management device, power storage device, and method for managing power storage unit

The present invention relates to a power storage management device, a power storage device, and a method for managing a power storage unit.

Conventionally, a power storage unit is known that includes a parallel block in which a lithium ion secondary battery and a lithium ion capacitor are connected in parallel. According to such a power storage unit, the lithium ion secondary battery exhibits high capacity characteristics, and the lithium ion capacitor exhibits high output characteristics (see Patent Document 1 below).

JP 2011-216685 A

In the above conventional power storage unit, for example, a large current may periodically or sporadically flow through the power storage unit depending on the operating state of the load. In the initial stage when a large current starts to flow in the power storage unit, the current flowing in the power storage unit mainly flows through the lithium ion capacitor with a low internal resistance. However, during discharge, the voltage of the lithium ion capacitor decreases as the discharge duration from the point at which a large current begins to flow becomes longer. When the voltage of the lithium-ion capacitor drops and the voltage difference with the lithium-ion secondary battery increases, the current flowing to the power storage unit mainly flows to the lithium-ion secondary battery, and as a result, the lithium-ion secondary battery may enter an overcurrent condition. It should be noted that during charging, contrary to discharging, the longer the charging duration from the time when a large current started to flow, the greater the voltage of the lithium ion capacitor and the larger the voltage difference with the lithium ion battery. As a result, the lithium ion secondary battery may enter an overcurrent state.

Therefore, in order to suppress the occurrence of an overcurrent state in the lithium-ion secondary battery, when the current flowing in the storage unit exceeds a certain overcurrent threshold, abnormal processing such as cutting off the current path to the storage unit can be considered. However, in such an abnormality processing based on a constant overcurrent threshold, the abnormality processing based on the overcurrent threshold functions even in the initial stage when the current flowing in the power storage unit mainly flows through the lithium-ion capacitor, which has a low internal resistance. . As a result, there arises a problem that the high output characteristics of the lithium ion capacitor are not sufficiently exhibited.

Such problems are not limited to the combination of a lithium-ion secondary battery and a lithium-ion capacitor, but are common to power storage units in which a non-lithium-ion secondary battery and a capacitor are connected in parallel. be.

An object of the present invention is to provide a power storage management device, a power storage device, and a method for managing a power storage unit that can solve the above-described problems.

(1) The power storage management device disclosed in this specification is a power storage unit that includes one parallel block in which a secondary battery and a capacitor are connected in parallel, or a plurality of parallel blocks that are connected in series to each other. and a current measuring unit for measuring the current flowing through the parallel block, a voltage measuring unit for measuring the terminal voltage of the parallel block, and the parallel current measured by the current measuring unit. An abnormality determination unit that performs abnormality processing on the condition that the current flowing through the block exceeds the overcurrent threshold as a necessary condition, the current flowing through the parallel block measured by the current measurement unit, and the voltage measurement unit the capacitor based on at least one of the terminal voltage of the parallel block, the internal resistance of the secondary battery, the internal resistance of the capacitor, the current duration of the storage unit, and the capacitance of the capacitor and an OCV estimating unit that estimates the OCV of the capacitor, and a threshold changing unit that changes the overcurrent threshold according to the OCV difference, which is the difference between the OCV of the capacitor estimated by the OCV estimating unit and the reference OCV. .

The current flowing through the parallel block measured by the current measuring unit is the sum of the current flowing through the secondary battery and the current flowing through the capacitor. Here, the current flowing through the capacitor correlates with the OCV of the capacitor, and the OCV (voltage) of the capacitor changes linearly during charging and discharging compared to the secondary battery. Therefore, the inventor of the present invention has made extensive studies to grasp the changes in the current flowing in the capacitor and the current flowing in the secondary battery, which are not directly measured, based on the change in the OCV of the capacitor. We have newly found that the threshold can be appropriately changed. In this power storage management device, the overcurrent threshold is changed according to the difference between the OCV of the capacitor estimated by the OCV estimation unit and the reference OCV. As a result, according to the power storage management device, it is possible to suppress the occurrence of an overcurrent state in the secondary battery while suppressing deterioration of high output characteristics due to the capacitor.

(2) In the power storage management device, the reference OCV is a value corresponding to the OCV of the secondary battery, and the threshold changing unit reduces the absolute value of the overcurrent threshold as the OCV difference increases. It is good also as a structure which carries out. According to this power storage management device, for example, compared to the case where the reference OCV is a predetermined fixed value, it is possible to grasp the current flowing in the capacitor more accurately, so while suppressing the deterioration of the high output characteristics due to the capacitor It is possible to more effectively suppress the occurrence of an overcurrent state in the secondary battery.

(3) In the power storage management device, the overcurrent threshold during charging may be decreased as the OCV of the capacitor is higher than the reference OCV and as the OCV difference is larger. According to this power storage management device, during charging, it is possible to suppress the occurrence of an overcurrent state in the secondary battery while suppressing deterioration of high output characteristics due to the capacitor.

(4) In the power storage management device, the overcurrent threshold during discharging may be decreased as the OCV of the capacitor is lower than the reference OCV and as the OCV difference is larger. According to this power storage management device, during discharging, it is possible to suppress the occurrence of an overcurrent state in the secondary battery while suppressing deterioration of high output characteristics due to the capacitor.

(5) The power storage management device may further include a threshold correction unit that corrects the overcurrent threshold according to the SOC of the secondary battery or the parallel block. According to this power storage management device, for example, compared to a configuration that does not consider the SOC of the secondary battery or the parallel block, excessive The current threshold can be set to an appropriate value.

(6) The power storage management device further includes a temperature measuring unit that measures the temperature of the parallel block, and an SOC estimating unit that estimates the SOC of the secondary battery or the parallel block, wherein the OCV estimating unit , from the temperature measured by the temperature measuring unit and the SOC estimated by the SOC estimating unit, reference is made to pre-stored related information that associates the temperature, SOC, and current duration of the parallel block. , the internal resistance of the secondary battery and the internal resistance of the capacitor may be estimated. According to this power storage management device, for example, compared to a configuration that does not consider changes in the internal resistance of the secondary battery or capacitor, the OCV of the capacitor can be accurately estimated, and the occurrence of the overcurrent state of the secondary battery can be more effectively prevented. can be suppressed to

(7) In the power storage management device, if the average value of the current flowing through the parallel block measured by the current measuring unit in a predetermined period exceeds a reference average value, regardless of the OCV difference, the overcurrent The configuration may include a forced change unit that reduces the absolute value of the threshold. According to this power storage management device, it is possible to prevent the occurrence of an overcurrent state in the secondary battery in the event of an abnormality in which, for example, a large amount of current continuously flows through the parallel block.

(8) In the power storage management device, further, when the OCV of the capacitor exceeds a predetermined overvoltage threshold, the capacitor is determined to be in an overvoltage state and a predetermined overvoltage process is executed, and the OCV of the capacitor exceeds the predetermined overvoltage threshold. The configuration may include an execution unit that determines that the capacitor is in a low voltage state and executes predetermined low voltage processing when the voltage falls below the low voltage threshold. According to this power storage management device, it is possible to suppress the occurrence of an overvoltage state and a low voltage state of the capacitor.

(9) In the power storage device, the power storage unit includes one parallel block in which a secondary battery and a capacitor are connected in parallel, or a plurality of the parallel blocks connected in series, and the power storage management device. , may be provided. According to this power storage device, it is possible to suppress the occurrence of an overcurrent state in the secondary battery while suppressing deterioration in high output characteristics due to the capacitor.

(10) The power storage unit management method disclosed in this specification includes one parallel block in which a secondary battery and a capacitor are connected in parallel, or a plurality of the parallel blocks in which a secondary battery and a capacitor are connected in series. A method for managing a power storage unit comprising: a power storage unit; a current measurement unit that measures current flowing through the parallel block; and a voltage measurement unit that measures terminal voltage of the parallel block, wherein the current measured by the current measurement unit is: a step of performing abnormality processing on the condition that the current flowing through the parallel block exceeds an overcurrent threshold as a necessary condition; and the current flowing through the parallel block measured by the current measurement unit and the voltage measurement unit measuring based on at least one of the terminal voltage of the parallel block, the internal resistance of the secondary battery, the internal resistance of the capacitor, the current duration of the power storage unit, and the capacitance of the capacitor, the estimating an OCV of a capacitor; and modifying the overcurrent threshold in response to an OCV difference, which is the difference between the estimated OCV of the capacitor and a reference OCV. According to this power storage unit management method, it is possible to suppress the occurrence of an overcurrent state in the secondary battery while suppressing deterioration of high output characteristics due to the capacitor.

The technology disclosed in this specification can be implemented in various forms, for example, in the form of a power storage management device, a power storage device, a management method thereof, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows roughly the structure of the electrical storage apparatus 100 in embodiment Explanatory diagram showing an example of an internal resistance estimation table Flowchart showing overcurrent suppression processing executed in power storage device 100 Equivalent circuit of parallel block 11 during discharge A first time chart showing changes in each element in the process in which power storage unit 10 transitions from a discharged state to a stopped state. A second time chart showing changes in each element in the process in which power storage unit 10 transitions from the discharged state to the stopped state.

A. Embodiment:
A-1. Configuration of power storage device 100:
FIG. 1 is an explanatory diagram schematically showing the configuration of a power storage device 100 according to this embodiment. The power storage device 100 includes a power storage unit 10 and a power storage management device 20 .

The power storage unit 10 has a configuration in which one or more parallel blocks 11 are connected in series. As shown in FIG. 1 , in this embodiment, the power storage unit 10 is composed of a plurality of parallel blocks 11 . Each parallel block 11 includes a lithium ion battery (hereinafter referred to as "LIB") 12b and a lithium ion capacitor (hereinafter referred to as "LIC") 12c which are connected in parallel, and thus has a large energy capacity and high output. It can be charged and discharged. The parallel block 11 further includes a LIB resistor Rb serially connected to the LIB 12b and a LIC resistor Rc serially connected to the LIC 12c. The LIB 12b is an example of a secondary battery in the claims, and the LIC 12c is an example of a capacitor in the claims. Power storage unit 10 is connected to a load (not shown) and an external power source via positive terminal 42 and negative terminal 44 .

The power storage management device 20 is a device for managing the power storage device 100 including the power storage unit 10 . The power storage management device 20 includes a voltmeter 22, an ammeter 24, a thermometer 26, a monitoring unit 28, a line switch 40, a control unit 60, a recording unit 72, a history unit 74, and an interface (I/ F) portion 76;

One voltmeter 22 is provided for each parallel block 11 . Each voltmeter 22 is connected in parallel to each parallel block 11 , measures the voltage of each parallel block 11 , and outputs a signal indicating the voltage measurement value to the monitoring section 28 . Ammeter 24 is connected in series with power storage unit 10 . Ammeter 24 measures the current flowing through power storage unit 10 (parallel block 11 ) and outputs a signal indicating the current measurement value to monitoring unit 28 . Thermometer 26 is arranged near power storage unit 10 . Thermometer 26 measures the temperature of power storage unit 10 (parallel block 11 ) and outputs a signal indicating the temperature measurement value to monitoring unit 28 . Based on the signals received from voltmeter 22, ammeter 24, and thermometer 26, monitoring unit 28 sends signals indicating the voltage of each parallel block 11, the current flowing through power storage unit 10, and the temperature of power storage unit 10 to control unit 60. output to. The voltmeter 22 and the monitoring unit 28 are examples of the voltage measuring unit, the ammeter 24 and the monitoring unit 28 are examples of the current measuring unit, and the thermometer 26 and the monitoring unit 28 are examples of the battery temperature measuring unit. be.

The line switch 40 is installed between the power storage section 10 and the negative terminal 44 . Line switch 40 is ON/OFF-controlled by control unit 60 to open and close connections between power storage unit 10 and a load and an external power source.

The control unit 60 is configured using, for example, a multi-core CPU and programmable devices (Field Programmable Gate Array (FPGA), Programmable Logic Device (PLD), etc.), and controls the operation of the power storage management device 20. The control unit 60 includes an OCV (open circuit voltage) estimating unit 62, an internal resistance estimating unit 64, a threshold changing unit 66, an SOC (state of charge, charging rate) estimating unit 68, and an abnormality determining unit. 70 and a forced change unit 78 . The functions of these units will be described together with the description of the overcurrent suppression process described later.

The recording unit 72 is composed of, for example, a ROM, a RAM, a hard disk drive (HDD), etc., and stores various programs and data, and is used as a work area and a data storage area when executing various processes. . For example, the recording unit 72 stores a computer program for executing overcurrent suppression processing, which will be described later. The computer program is provided in a state stored in a computer-readable recording medium (not shown) such as a CD-ROM, DVD-ROM, or USB memory, and installed in the power storage device 100 to the recording unit 72. Stored.

In addition, the recording unit 72 stores an internal resistance estimation table (T=0, T=1, T=3...). Each internal resistance estimation table is a table used for estimating the internal resistance of each of the LIB 12b and LIC 12c provided in each parallel block 11. FIG. FIG. 2 is an explanatory diagram showing an example of an internal resistance estimation table. Each internal resistance estimation table is a table that associates the SOC of parallel block 11 , the temperature, and the internal resistances of LIB 12 b and LIC 12 c for each duration T of the current state of power storage unit 10 . The current state of power storage unit 10 includes a charged state in which power storage unit 10 is charged, a discharged state in which power storage unit 10 is discharged, and a stopped state in which power storage unit 10 is neither charged nor discharged. be. The relationships defined in the internal resistance estimation table are determined experimentally in advance. By referring to the internal resistance estimation table corresponding to each duration T of the current state, the internal resistance of each of LIB 12b and LIC 12c can be estimated based on the SOC and temperature of power storage unit 10. FIG. In FIG. 2, the internal resistances of the LIB 12b and the LIC 12c are shown as Z1, Z2, .

The history unit 74 is composed of, for example, a ROM, a RAM, a hard disk drive (HDD), etc., and records various histories related to the power storage device 100 . Such a history includes, for example, current continuation time (discharge continuation time, charge continuation time, stop continuation time) of power storage unit 10, which will be described later. The interface unit 76 performs wired or wireless communication with other devices. For example, the history recorded in the history section 74 is updated by communication with another device via the interface section 76 .

A-2. Overcurrent suppression processing:
Next, the overcurrent suppression process executed by the power storage management device 20 in the power storage device 100 will be described. FIG. 3 is a flowchart showing overcurrent suppression processing executed in power storage device 100 . The overcurrent suppression process is a process for determining whether or not power storage unit 10 or each parallel block 11 is in an overcurrent state, and executing abnormality processing according to the determination result. The overcurrent state refers to a state in which the value of current Ibat (charging current) flowing through power storage unit 10 exceeds an overcurrent threshold Ioc during charging when power storage unit 10 is being charged, and when power storage unit 10 is discharging. Then, it refers to a state in which the current value of the current Ibat (discharge current) flowing through the power storage unit 10 exceeds the overcurrent threshold value Iod during discharge. The overcurrent suppression process may be performed by determining whether or not the power storage unit 10 as a whole is in an overcurrent state, and executing an abnormality processing according to the determination result. It may be determined whether or not each of the blocks 11 is in an overcurrent state, and when it is determined that at least one parallel block 11 is in an overcurrent state, the abnormality processing may be executed. The overcurrent suppression process is started, for example, automatically when power storage device 100 is started, or in response to an instruction from an administrator. In the following description, the current value of charging current flowing into power storage unit 10 is defined as "positive", and the current value of discharging current flowing out of power storage unit 10 is defined as "negative". Also, one parallel block 11 included in the power storage unit 10 will be described as an example.

When the overcurrent suppression process (FIG. 3) is started, the controller 60 of the power storage management device 20 first performs various initial settings (S110). For example, the control unit 60 sets the OCV (Vob) of the LIB 12b and the OCV (Voc) of the LIC 12c to the same value (eg, the initial OCV, which is the voltage of the parallel block 11 measured when the power storage device 100 is started). . Also, the overcurrent threshold Ioc during charging is set to the initial value Ioc,int. This initial value Ioc,int is a value (a value with a large absolute value) that is slightly higher than the current value of the maximum current (rush current) that flows into the parallel block 11 at the start of charging, for example. Also, the overcurrent threshold value Iod during discharge is set to the initial value Iod,int. This initial value Iod, int is a value slightly lower (larger in absolute value) than the current value of the maximum current (inrush current) that flows out from the parallel block 11 at the start of discharge, for example.

Next, the abnormality determination unit 70 (FIG. 1) of the power storage management device 20 determines whether or not the parallel block 11 is in an overcurrent state (including an overcurrent state of the LIC 12c alone and an overcurrent state of the LIB 12b alone). Processing is performed (S120). During charging of the power storage unit 10, the abnormality determination unit 70 determines that the measured current value of the current Ibat (charging current) flowing through the parallel block 11 (power storage unit 10) exceeds the overcurrent threshold value Ioc during charging. It determines that the parallel block 11 is in an overcurrent state. During discharging of the power storage unit 10, the abnormality determination unit 70 determines whether the parallel block 11 is overcharged on the condition that the current measurement value of the current Ibat (discharge current) flowing through the parallel block 11 is below the overcurrent threshold value Iod during discharging. It is judged to be in a current state.

When it is determined that the parallel block 11 is in the overcurrent state (S120: YES), the abnormality determination unit 70 executes abnormality processing corresponding to the overcurrent abnormality in the parallel block 11 (power storage unit 10) (S130). , the overcurrent threshold adjustment process ends. The abnormal process includes, for example, a process of notifying an overcurrent abnormality of power storage unit 10 to the outside via interface unit 76, a process of closing negative terminal 44 and prohibiting charging/discharging of power storage unit 10, and the like. is.

On the other hand, if it is determined that the parallel block 11 is in a normal state rather than an overcurrent state (S120: NO), the control unit 60 determines whether the OCV (Voc) of the LIC 12c is within a predetermined range. (S140). Here, the predetermined range is, for example, the allowable voltage range in specifications defined in the LIC 12c, which is equal to or less than a predetermined overvoltage threshold and equal to or more than a predetermined low voltage threshold. Here, the OCV estimation processing of the LIC 12c will be described later (see S220, S320, S430).

When it is determined that the OCV of the LIC 12c is not within the predetermined range (S140: NO), the control unit 60 executes abnormality processing corresponding to the voltage abnormality of the OCV of the LIC 12c (S130), and performs the overcurrent threshold adjustment processing. finish. Specifically, when the OCV of the LIC 12c exceeds a predetermined overvoltage threshold, the control unit 60 determines that the LIC 12c is in an overvoltage state and executes predetermined overvoltage processing. Further, when the OCV of the LIC 12c is below a predetermined low voltage threshold, the control unit 60 determines that the LIC 12c is in a low voltage state and executes predetermined low voltage processing. In the present embodiment, the overvoltage process includes, for example, a process of notifying an overvoltage abnormality of the LIC 12c to the outside via the interface unit 76, or a process of closing the negative terminal 44 to prohibit charging of the power storage unit 10. processing to The low-voltage process includes, for example, a process of notifying the outside of the LIC 12c of a low-voltage abnormality via the interface unit 76, a process of closing the negative terminal 44 and prohibiting the discharge of the power storage unit 10, and the like. . At this time, the control unit 60 functions as an execution unit in the claims.

On the other hand, if it is determined that the OCV of the LIC 12c is within the predetermined range (S140: YES), the voltage abnormality of the LIC 12c has not occurred. , stop state) is determined (S150). For example, the signal output from the ammeter 24 is a signal corresponding to the presence or absence of the current Ibat flowing through the power storage unit 10 and the direction of flow (depending on the level of the voltage across a detection resistor (not shown) provided in the ammeter 24). The control unit 60 determines the current state (charged state, discharged state, stopped state) of the power storage unit 10 based on the level of the signal output from the ammeter 24 and the level inversion of the signal. do.

A-2-1. When discharging:
When it is determined that power storage unit 10 is in a discharging state (S150: discharging), the current Ib flowing through LIB 12b and the current Ic flowing through LIC 12c during discharging are calculated, and the OCV during discharging of LIC 12c is estimated.

First, the internal resistance estimation unit 64 (FIG. 1) of the power storage management device 20 estimates the internal resistance Zb of the LIB 12b and the internal resistance Zc of the LIC 12c (S300). The internal resistance estimation unit 64 selects an internal resistance estimation table corresponding to the discharge duration Td from the recording unit 72, and refers to the selected internal resistance estimation table, based on the SOC and temperature of the parallel block 11, Estimate internal resistances Zb and Zc of LIB 12b and LIC 12c, respectively. Note that the initial SOC of the parallel block 11 can be estimated by various known estimation methods. For example, the initial SOC is calculated based on the initial OCV and the curve representing the SOC-OCV characteristic, and the SOC of the parallel block 11 can be estimated based on the initial SOC and the current integrated value of the current Ibat of the power storage unit 10. .

Next, the OCV estimator 62 (FIG. 1) of the power storage management device 20 calculates the current Ib flowing through the LIB 12b and the current Ic flowing through the LIC 12c (S310). Specifically, it is as follows. FIG. 4 is an equivalent circuit of the parallel block 11 during discharging. "Ibatd" in FIG. 4 means the discharge current, "Vbat" means the terminal voltage of the parallel block 11, and "C" means the capacitance of the LIC 12c. As is clear from FIG. 4, the current Ic (discharge current Icd) flowing through the LIC 12c can be obtained by the following equation (1).

Further, the current Ib (discharge current Ibd) flowing through the LIB 12b can be obtained by subtracting the discharge current Icd of the LIC 12c from the discharge current Ibatd of the electric storage unit 10 (Ibd=Ibatd−Icd).

Next, the OCV estimation unit 62 executes an OCV estimation process for estimating the OCV (Vocd) during discharging of the LIC 12c (S320). In this discharge OCV estimation process, the OCV estimation unit 62 estimates the OCV during discharge of the LIC 12c using, for example, the following equations 2 to 5 (see FIG. 4).

“Vocd1” in Equation 2 is the value of LIC 12c when changes in internal resistances Zb and Zc of LIB 12b and LIC 12c due to the duration of the discharge state of power storage unit 10 (hereinafter referred to as “discharge duration”) are not considered. A first virtual OCV. The first virtual OCV can be obtained by Equation 3 below.

"Vocd0" in Equation 3 is the initial OCV of the parallel block 11, for example. “C” is the capacitance of power storage unit 10 . “Td” is the discharge duration time of power storage unit 10 . For example, control unit 60 counts time at a predetermined sampling cycle, and records the determination result of current state determination (S150) of power storage unit 10 described above in history unit 74 in association with the count at the time of determination. do. Therefore, the OCV estimating unit 62 can identify the current discharge duration time Td from the history stored in the history unit 74 .

Also, "Ic0" in Equation 3 is the discharge current that flows out from the LIC 12c at the start of discharge (hereinafter referred to as "initial discharge current"), and can be obtained by Equation 4 below.

"Icc" in Equation 4 is a charging current that flows from LIB 12b to LIC 12c when power storage unit 10 is discharged, and has an initial value of zero when power storage device 100 starts to discharge for the first time after activation.

“Vocd2” in Equation 2 is the second virtual OCV of LIC 12c when changes in internal resistances Zb and Zc of LIB 12b and LIC 12c with the discharge duration time of power storage unit 10 are considered. The second virtual OCV can be obtained by Equation 5 below.

Next, the control unit 60 first determines whether or not to perform adjustment processing (S340 to S360) for the overcurrent threshold value Iod during discharge. Specifically, the control unit 60 determines whether or not the currently set discharge overcurrent threshold Iod is equal to or less than the lower current threshold Iod,min (S330). The lower limit current threshold Iod,min is, for example, the lowest value (lowest current value) of the allowable voltage range on specifications defined in the LIB 12b. In this embodiment, this determination is made based on whether or not the absolute value of the overcurrent threshold value Iod during discharge is equal to or greater than the absolute value of the minimum current value.

If it is determined that the overcurrent threshold Iod during discharge exceeds the lower limit current threshold Iod,min (S330: NO), the processing for changing the overcurrent threshold Iod during discharge (S340 to S360) described below is executed. Without doing so, the process returns to S120. This prevents the overcurrent threshold Iod during discharge from being set outside the allowable voltage range of the LIB 12b.

On the other hand, if it is determined that the overcurrent threshold Iod during discharge is equal to or lower than the lower current threshold Iod,min (S330: YES), the threshold change unit 66 determines the OCV of the LIC 12c estimated by the OCV estimation process and the reference OCV. The overcurrent threshold Iod during discharging is changed according to the OCV difference ΔVd, which is the difference between the two (S340). In this embodiment, the reference OCV is a value corresponding to the OCV of the parallel block 11, and may be the OCV of the LIB 12b or the OCV of the parallel block 11, for example. For example, the SOC estimator 68 calculates the initial SOC based on the initial OCV of the parallel block 11 and the curve representing the SOC-OCV characteristic of the LIB 12b, and based on the initial SOC and the current integrated value of the current Ib of the LIB 12b. The SOC of LIB 12b can be estimated, and the OCV of LIB 12b can be estimated based on the SOC and the curve representing the SOC-OCV characteristics of LIB 12b. Also, the OCV of the parallel block 11 can be estimated based on the SOC of the parallel block 11 estimated by the initial SOC estimation process and the curve representing the OC-OCV characteristics of the parallel block 11 . The threshold change unit 66 reduces the absolute value of the overcurrent threshold Iod during discharge according to the increase in the OCV difference ΔVd. In this embodiment, the OCV of the LIC 12c decreases relative to the OCV of the LIB 12b as the discharge duration time elapses, and the OCV difference increases. The overcurrent threshold Iod during discharge is changed to a higher value according to the amount of increase in the OCV difference.

Next, the forced change unit 78 of the power storage management device 20 changes the average value of the current Ibat flowing through the parallel block 11 measured by the ammeter 24 in a predetermined period (hereinafter referred to as the “period average current value”) to the reference average value. The reference average value is, for example, a value whose absolute value is slightly smaller than the upper limit of the allowable current range that can flow through the parallel block 11 (during discharging, the upper limit of the allowable current range If the period average current value falls below the reference average value, it means that there is an abnormal state in which a relatively large discharge current is continuously flowing from the parallel block 11. Therefore, If it is determined that the period average current value is lower than the reference average value (S350: YES), the forced change unit 78 reduces the absolute value of the overcurrent threshold regardless of the OCV difference ΔVd (S360), and returns to S120. In this embodiment, the overcurrent threshold Iod during discharge is forcibly changed to a value (for example, the lower limit current threshold Iod,min) whose absolute value is smaller than the overcurrent threshold Iod during discharge set in S340. As a result, it is possible to prevent an overcurrent state from occurring in the LIB 12b, for example, in the event of an abnormality in which a large amount of current continuously flows to the power storage unit 10. On the other hand, if the period average current value is equal to or greater than the reference average value, If so (S350: NO), an abnormality in which a large amount of current continuously flows into power storage unit 10 does not occur, so the overcurrent threshold value Iod during discharge changed in S340 is maintained, and the process returns to S120.

A-2-2. When charging:
When it is determined that power storage unit 10 is in a charged state (S150: charging), control unit 60 executes the processing during charging (S200 to S260). This adjustment process is the same as the above-described discharge process (S300 to S360). It differs in that Iod is "negative". In S240, the threshold change unit 66 reduces the absolute value of the overcurrent threshold Ioc during charging according to the increase in the OCV difference. In this embodiment, the OCV of the LIC 12c increases relative to the OCV of the LIB 12b as the charging duration elapses, and the OCV difference increases. The overcurrent threshold Iod during charging is changed to a lower value according to the amount of increase in the OCV difference. A detailed description of the processing during charging (S200 to S260) is omitted.

A-2-3. When stopped:
When it is determined that the power storage unit 10 is in the stopped state (S150: stop), the control unit 60 first determines whether the OCV (Voc) of the LIC 12c substantially matches the OCV (Vob) of the LIB 12b. (S400). In this embodiment, the OCV of LIB 12b is the initial OCV. The fact that the OCV of the LIC 12c and the OCV of the LIB 12b do not substantially match is because the current Ibat does not flow through the power storage unit 10, but the state immediately before the power storage unit 10 is stopped, for example, is in the charged state or the discharged state. , means that the difference between the OCV of LIC12c and the OCV of LIB12b remains. At this time, currents flow through the LIB 12b and the LIC 12c that configure the parallel block 11 in directions that reduce the difference from the OCV.

Therefore, the control unit 60 adjusts the overcurrent threshold according to the OCV difference of the LIC 12c when the power storage unit 10 is stopped. Note that the OCV of LIB 12b can be regarded as the initial OCV. As a result, when discharging or charging of power storage unit 10 is resumed while current is still flowing through LIB 12b or LIC 12c in the stopped state of power storage unit 10, the overcurrent threshold is set to LIC 12c immediately before the start of discharging or charging. can be adjusted from an appropriate value considering the difference between the OCV of LIB12b and the OCV of LIB12b.

If it is determined that the OCV of the LIC 12c and the OCV of the LIB 12b do not substantially match (S400: YES), the control unit 60 executes the same internal resistance estimation process as in S300 (S410), is specified (S420). For example, if the state immediately before the power storage unit 10 was in the discharged state, the LIC 12c is charged by the current flowing from the LIB 12b to the LIC 12c when the power storage unit 10 is in the stopped state. A charging current (Icc) flowing from the LIB 12b to the LIC 12c at the beginning of the stop can be obtained by the following equation (6).

"Vbat" in Equation 6 is the terminal voltage of the parallel block 11 when stopped. “Voc” in Equation 6 is the OCV of LIC 12c during charging estimated in S220 when the state immediately before power storage unit 10 was in the charged state, and the state immediately before power storage unit 10 was in the discharged state. In this case, it is the OCV (Vocd) of the LIC 12c during discharge estimated in S320.

Next, the control unit 60 estimates the OCV (Vocs) of the LIC 12c when stopped (S430). In this stop OCV estimation process, the OCV estimating unit 62 estimates the OCV of the LIC 12c when stopped using, for example, Equation 7 below. That is, the OCV (Vocs) during discharging of the LIC 12c can be obtained by the following equation 2.

“Ts” is the stop duration time of power storage unit 10 . The control unit 60 can identify the current stop duration time from the history stored in the history unit 74, for example.

Next, the threshold change unit 66 changes the overcurrent threshold Ios at stop according to the OCV difference ΔVd, which is the difference between the OCV of the LIC 12c estimated by the OCV estimation process and the reference OCV (S440). The threshold changing unit 66 reduces the absolute value of the overcurrent threshold Ios at the time of stop according to the increase in the OCV difference ΔVd. In this embodiment, when the previous state was the discharge state, the OCV of the LIC 12c increases to approach the OCV of the LIB 12b as the stop duration time elapses, and the OCV difference decreases. The overcurrent threshold Ios at stop is changed to a lower value (a value with a larger absolute value) according to the amount of decrease in the OCV difference. If the previous state was the charging state, the OCV of the LIC 12c decreases to approach the OCV of the LIB 12b as the stop duration time elapses, and the OCV difference decreases. According to the amount of decrease in the OCV difference, the overcurrent threshold Ios at stop is changed to a higher value (a value with a larger absolute value).

On the other hand, when it is determined that the OCV of the LIC 12c and the OCV of the LIB 12b substantially match (S400: NO), the control unit 60 executes processing (S410 to S440) for changing the overcurrent threshold Ios at stop. without returning to S120. As a result, wasteful execution of the process for changing the overcurrent threshold is suppressed.

A-3. Effect of this embodiment:
As described above, in the power storage device 100 of the present embodiment, the current Ibat flowing through the parallel block 11 measured by the ammeter 24 is the sum of the current Ib flowing through the LIB 12b and the current Ic flowing through the LIC 12c ( See Figure 4). Here, the current Ic flowing through the LIC 12c correlates with the OCV of the LIC 12c, and the OCV (terminal voltage) of the LIC 12c changes linearly during charge and discharge compared to the LIB 12b. Therefore, the present inventors have made intensive studies, and found that changes in the current Ic flowing through the LIC 12c and the current Ib flowing through the LIB 12b, which are not directly measured, can be grasped based on changes in the OCV of the LIC 12c. It was newly discovered that the threshold values Ioc, Iod, and Ios can be appropriately changed. In this embodiment, the overcurrent threshold is changed according to the difference between the OCV of the LIC 12c estimated by the OCV estimation process (S220, S320, S430) and the reference OCV. As a result, according to the present embodiment, it is possible to suppress the occurrence of an overcurrent state in the LIB 12b while suppressing deterioration of the high-output characteristics of the LIC 12c.

A case where power storage unit 10 transitions from a discharged state to a stopped state will be described below as an example. FIG. 5 is a first time chart showing changes in each element in the process in which power storage unit 10 shifts from the discharged state to the stopped state, and FIG. 4 is a second time chart showing changes in each element; The horizontal axis of each figure is the current duration (discharge duration, stop duration). In addition, the “discharge” in the “current state” means the discharge state of the power storage unit 10. Specifically, the line switch 40 is in the ON state, or the constant current control is performed by the ON/OFF control, and the power storage device This is a state in which a constant current is flowing through a load (for example, a motor) connected to 100 . "Stopped" in "current state" means a stopped state of power storage unit 10. Specifically, line switch 40 is in an open state and power is not supplied to the load. Also, in each figure, the OCV (Vob) of the LIB 12b is assumed to be substantially constant.

As shown in FIG. 5, when the electric storage unit 10 is discharged (see t0), a relatively large discharge current Ibat begins to flow from the parallel block 11 . At the initial stage when the discharge current Ibat starts to flow from the parallel block 11, the discharge current Ibat is mainly the discharge current Ic (Icd) from the LIC 12c having a small internal resistance. At this time, since the overcurrent threshold Iod during discharge is set to a relatively large value (low value), it is erroneously determined that an overcurrent state exists due to the rising current at the start of discharge, and power storage device 100 is shut down. It is possible to suppress the occurrence of problems such as non-operation.

After that, the OCV of the LIC 12c decreases as the discharge duration Td elapses (see t0 to t3), and the OCV difference ΔV, which is the difference between the OCV of the LIC 12c and the OCV of the LIB 12b, increases. Accordingly, the discharge current Ic from the LIC 12c decreases (increases), the discharge current Ib from the LIB 12b increases (decreases), and then the discharge current Ibat from the parallel block 11 is mainly discharged from the LIB 12b. It becomes the current Ib (Ibd). At this time, the overcurrent threshold value Iod during discharging is changed to a smaller value (higher value) step by step according to the OCV difference ΔV. As a result, the LIB 12b can be prevented from entering an overcurrent state, compared to a configuration in which the overcurrent threshold value Iod during discharge is not changed from the initial value at the start of discharge.

When the discharge current Ibat from the parallel block 11 becomes equal to or less than the overcurrent threshold Iod during discharge (see t3), the power storage unit 10 changes from the discharged state to the stopped state. As a result, when a sufficient current flows through the LIC 12c, it is not judged to be an overcurrent abnormality. After that, when there is a risk of a large current flowing through the LIB 12b due to insufficient current flowing through the LIC 12c, it is judged as an overcurrent abnormality. and protect 12b. When the power storage unit 10 is stopped, the discharge current Ib from the LIB 12b flows into the LIC 12c, and the LIC 12c starts to be charged. After that, the OCV difference ΔV decreases as the stop duration time Ts elapses (t3 to t6). At this time, the overcurrent threshold value Iod at the time of stop is changed to a larger value (lower value) step by step according to the OCV difference ΔV while taking over the previous value. As a result, even when the power storage unit 10 changes from a stopped state to a discharging state in a state where the OCV of the LIC 12c and the OCV of the LIB 12b do not substantially match, the LIB 12b can be prevented from entering an overcurrent state with accuracy. .

In the example of FIG. 6, a pulse current with a shorter discharge duration is flowing through the power storage unit 10 than in the example of FIG. Power storage unit 10 changes from a discharged state to a stopped state (see t2), returns to a discharged state shortly thereafter (see t3), and soon thereafter enters a stopped state (see t4). During this period, the discharge continuation time and the stop continuation time are relatively short, and the OCV difference ΔV changes little, so the overcurrent threshold Iod is kept constant (see t2 to t5). As described above, in the present embodiment, when the energized state (discharged state or charged state) and the stopped state are repeated in relatively short periods, the change in the overcurrent threshold is suppressed, and the electric state of the power storage unit 10 is suppressed. is controlled so that it is set to an appropriate value regardless of the transition to any state.

In this embodiment, in the OCV estimation process (S220, S320, S430) of the LIC 12c, the reference OCV is a value corresponding to the OCV of the parallel block 11. According to the present embodiment, the current Ic and the like flowing through the LIC 12c can be grasped more accurately than when the reference OCV is a predetermined fixed value. occurrence of the overcurrent state can be more effectively suppressed.

In this embodiment, the higher the OCV of the LIC 12c than the reference OCV and the larger the OCV difference, the smaller the overcurrent threshold Ioc during charging (S240 in FIG. 3). As a result, during charging, it is possible to suppress the occurrence of an overcurrent state in the LIB 12b while suppressing deterioration in the high-output characteristics of the LIC 12c.

In this embodiment, as the OCV of 12c is lower than the reference OCV and as the OCV difference is larger, the overcurrent threshold Iod during discharging is decreased (S340 in FIG. 3). As a result, during discharging, it is possible to suppress the occurrence of an overcurrent state in the LIB 12b while suppressing deterioration in the high-output characteristics of the LIC 12c.

B. Variant:
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the scope of the invention. For example, the following modifications are possible.

The configuration of the power storage device 100 in the above embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, the LIB 12b is used as an example of the secondary battery, but the secondary battery is not limited to this, and may be a secondary battery other than a lithium-based battery. In addition, although the LIC12c is exemplified as a capacitor, the capacitor is not limited to this, and a capacitor other than a lithium-based capacitor may be used. In addition, the parallel block may have a configuration in which the secondary battery (LIB 12b) and the capacitor (LIC 12c) are accommodated in separate cases and connected in parallel, or the secondary battery and the capacitor are arranged in parallel in the same case. may be connected to the In the latter case, for example, one or more secondary batteries, one or more capacitors, and an electrolytic solution may be accommodated in the same space, or one or more secondary batteries and one or more capacitors may be housed in different spaces (cell chamber, battery case).

The content of the overcurrent suppression process in the above embodiment is merely an example, and various modifications are possible. In the overcurrent suppression process (FIG. 3), the configuration may be such that the process of S140 is not performed. Further, in the OCV estimation processing (S220, S320, S430) of the LIC 12c, the internal resistance of the LIB 12b and the LIC 12c may be set to a fixed value, and the internal resistance estimation processing (S200, S300, S410) may not be executed. Also, in the overcurrent suppression process (FIG. 3), the configuration may be such that the processes of S250 and S350 are not executed.

In changing the overcurrent threshold (S240, S340, S440), the reference OCV is not limited to the OCV of the LIB 12b or the OCV of the parallel block 11. For example, the terminal voltage of the parallel block 11 may be used, and changes in the OCV of the LIB 12b are ignored. It may be a fixed value (eg, zero).

The formulas 1 to 7 in the above embodiment are only examples, and other formulas may be used without being limited to them.

In the above embodiment, the overcurrent threshold may be corrected according to the SOC of the LIB 12b or the parallel block 11. Specifically, in some LIBs, when the SOC falls below a predetermined lower limit (for example, 10%), the OCV change rate and internal resistance of the LIB 12b increase. It is preferable to correct the absolute value of the overcurrent threshold during discharge to a smaller value according to the decrease in the SOC of the parallel block 11 . In some LIBs, when the SOC exceeds a predetermined upper limit (for example, 90%), the OCV change rate and internal resistance of the LIB 12b increase. It is preferable to correct the absolute value of the overcurrent threshold during charging to a smaller value according to the increase in the SOC. In this case, the controller 60 functions as a threshold corrector.

10: Power storage unit 11: Parallel block 12b: LIB 12c: LIC 20: Power storage management device 22: Voltmeter 24: Ammeter 26: Thermometer 28: Monitoring unit 40: Line switch 42: Plus terminal 44: Minus terminal 60: Control Unit 62: OCV estimation unit 64: Internal resistance estimation unit 66: Threshold change unit 68: SOC estimation unit 70: Abnormal judgment unit 72: Recording unit 74: History unit 76: Interface unit 78: Forced change unit 100: Power storage device Rb: LIB resistance　Rc: LIC resistance　Zb, Zc: internal resistance

Claims

A power storage management device for managing a power storage unit comprising one parallel block in which a secondary battery and a capacitor are connected in parallel or a plurality of the parallel blocks connected in series,
a current measuring unit that measures the current flowing through the parallel block;
a voltage measurement unit that measures the terminal voltage of the parallel block;
an abnormality determination unit that performs an abnormality processing on the condition that the current flowing through the parallel block measured by the current measurement unit exceeds an overcurrent threshold as a necessary condition;
the current flowing through the parallel block measured by the current measuring unit; the terminal voltage of the parallel block measured by the voltage measuring unit; the internal resistance of the secondary battery; the internal resistance of the capacitor; an OCV estimation unit that estimates the OCV of the capacitor based on at least one of a current duration of the unit and a capacitance of the capacitor;
a threshold changing unit that changes the overcurrent threshold according to an OCV difference that is a difference between the OCV of the capacitor estimated by the OCV estimating unit and a reference OCV;
A power storage management device.
The power storage management device according to claim 1,
The reference OCV is a value corresponding to the OCV of the secondary battery,
The power storage management device, wherein the threshold changing unit reduces the absolute value of the overcurrent threshold according to an increase in the OCV difference.
The power storage management device according to claim 1 or claim 2,
The power storage management device, wherein the higher the OCV of the capacitor than the reference OCV and the larger the OCV difference, the smaller the overcurrent threshold during charging.
The power storage management device according to any one of claims 1 to 3,
The power storage management device, wherein the OCV of the capacitor is lower than the reference OCV and the larger the OCV difference, the smaller the overcurrent threshold during discharging.
The power storage management device according to any one of claims 1 to 4,
The power storage management device further includes a threshold correction unit that corrects the overcurrent threshold according to the SOC of the secondary battery or the parallel block.
The power storage management device according to any one of claims 1 to 5,
Furthermore, a temperature measuring unit that measures the temperature of the parallel block;
an SOC estimation unit that estimates the SOC of the secondary battery or the parallel block;
The OCV estimating unit associates the pre-stored temperature, SOC, and current duration of the parallel block from the temperature measured by the temperature measuring unit and the SOC estimated by the SOC estimating unit. A power storage management device that estimates the internal resistance of the secondary battery and the internal resistance of the capacitor by referring to related information.
The power storage management device according to any one of claims 1 to 6,
Furthermore, when the average value of the current flowing through the parallel block measured by the current measurement unit in a predetermined period exceeds a reference average value, regardless of the OCV difference, the absolute value of the overcurrent threshold is forced to be changed to a smaller value. A power storage management device comprising a unit.
The power storage management device according to any one of claims 1 to 7,
Further, when the OCV of the capacitor exceeds a predetermined overvoltage threshold, the capacitor is determined to be in an overvoltage state and a predetermined overvoltage process is executed, and when the OCV of the capacitor is less than the predetermined low voltage threshold, the A power storage management device comprising an execution unit that determines that a capacitor is in a low voltage state and executes predetermined low voltage processing.
a power storage unit including one parallel block in which a secondary battery and a capacitor are connected in parallel, or a plurality of the parallel blocks connected in series;
A power storage device comprising the power storage management device according to any one of claims 1 to 8.
a power storage unit including one parallel block in which a secondary battery and a capacitor are connected in parallel, or a plurality of the parallel blocks connected in series;
a current measuring unit that measures the current flowing through the parallel block;
A method for managing a power storage unit, comprising: a voltage measuring unit that measures a terminal voltage of the parallel block;
a step of performing abnormality processing on the condition that the current flowing through the parallel block measured by the current measuring unit exceeds an overcurrent threshold as a necessary condition;
the current flowing through the parallel block measured by the current measuring unit; the terminal voltage of the parallel block measured by the voltage measuring unit; the internal resistance of the secondary battery; the internal resistance of the capacitor; estimating an OCV of the capacitor based on at least one of a current duration of a section and a capacitance of the capacitor;
varying the overcurrent threshold in response to an OCV difference, which is the difference between the estimated OCV of the capacitor and a reference OCV;
A method of managing a power storage unit, including