阅读说明：本技术 估计装置、估计方法以及计算机程序 (Estimation device, estimation method, and computer program ) 是由 尾地克弥 于 2020-05-21 设计创作，主要内容包括：估计装置(4)具备：第一取得部(41),取得蓄电元件(3)的充电或者放电或者浮充中的开始时以及结束时的SOC；存储部(42),与多个SOC的范围相应地存储多个劣化系数；确定部(41),基于第一取得部(41)所取得的开始时以及结束时的SOC,从所述存储部(42)中存储的多个劣化系数确定所对应的劣化系数；以及估计部(41),基于确定部(41)所确定的劣化系数,估计蓄电元件(3)的劣化。(The estimation device (4) is provided with: a first acquisition unit (41) that acquires the SOC at the start and end of charging, discharging, or floating of the power storage element (3); a storage unit (42) that stores a plurality of degradation coefficients in accordance with a plurality of SOC ranges; a determination unit (41) that determines a corresponding degradation coefficient from the plurality of degradation coefficients stored in the storage unit (42) on the basis of the SOC at the start and at the end acquired by the first acquisition unit (41); and an estimation unit (41) that estimates the deterioration of the power storage element (3) on the basis of the deterioration coefficient determined by the determination unit (41).)

1. An estimation device is provided with:

a first acquisition unit that acquires the SOC at the start and end of charging, discharging, or floating of the power storage element;

a storage unit that stores a plurality of degradation coefficients in accordance with a plurality of SOC ranges;

a determination unit configured to determine a corresponding degradation coefficient from the plurality of degradation coefficients stored in the storage unit, based on the SOC at the start and at the end acquired by the first acquisition unit; and

an estimation portion that estimates deterioration of the power storage element based on the deterioration coefficient determined by the determination portion.

2. The estimation device as set forth in claim 1,

the storage section stores a plurality of degradation coefficients corresponding to a plurality of SOC ranges in which the SOCs 0 to 100% are divided at different intervals,

the determination unit determines a degradation coefficient of an SOC range having the smallest range width, which includes the SOC at the start and at the end acquired by the first acquisition unit, among the plurality of SOC ranges.

3. The estimation device according to claim 1 or 2, comprising:

a second acquisition unit for acquiring the amount of change in current, voltage, power, or SOC per unit time,

the first acquisition unit acquires the SOC based on the amount of change in the current, voltage, power, or SOC acquired by the second acquisition unit and the amount of change in the current, voltage, power, or SOC acquired last time by the second acquisition unit.

4. The estimation device according to claim 3, comprising:

a first determination unit that determines whether or not to switch from the standing state to the charge/discharge state or to switch between the charge/discharge states based on the amount of change in the current, voltage, power, or SOC obtained by the second obtaining unit and the amount of change in the current, voltage, power, or SOC obtained by the second obtaining unit last time,

when the first determination unit determines that the switching is performed, the first acquisition unit acquires the SOC.

5. The estimation device according to claim 4, comprising:

a second determination unit that determines which of a charge/discharge state, a left state, and a floating state is based on the current, voltage, power, or the amount of change in SOC obtained by the second obtaining unit,

the estimation portion estimates the deterioration based on the state decided by the second decision portion.

6. A method of estimating a power level of a power amplifier,

obtaining the SOC at the beginning and end of the charging or discharging or floating of the storage element,

based on the acquired starting and ending SOCs, a deterioration coefficient predetermined in accordance with a range of a plurality of SOCs is used,

deterioration of the electric storage element is estimated.

7. A computer program for causing a computer to execute a process,

obtaining the SOC at the beginning and end of the charging or discharging or floating of the storage element,

based on the acquired starting and ending SOCs, a deterioration coefficient predetermined in accordance with a range of a plurality of SOCs is used,

deterioration of the electric storage element is estimated.

Technical Field

The present invention relates to an estimation device, an estimation method, and a computer program for estimating deterioration of a power storage element.

Background

An electric storage device capable of storing electric energy and supplying energy as a power source when necessary is being used. The power storage element is applied to portable equipment, power supply devices, transportation equipment including automobiles and railways, industrial equipment including aviation, space and construction, and the like. In order to be able to use the required amount of energy accumulated in advance when necessary, it is important to always grasp the storage capacity of the storage element. It is known that the electric storage element is mainly chemically deteriorated depending on time and frequency of use. Therefore, the energy that can be used decreases with time and frequency of use. In order to utilize a required amount of energy when necessary, it is important to grasp the state of degradation of the power storage element. Up to now, techniques for estimating the deterioration of the power storage element have been developed.

For example, when the power storage element is used in a wind power generation facility, the amount of power generation is frequently switched by wind power, and the mode of power generation is complicated, so the charge/discharge mode of the power storage element is also complicated. For example, in the case of solar power generation, since power is generated in the daytime, the power generation mode is substantially constant, and the charge/discharge mode of the power storage element is also substantially constant. Therefore, the charge/discharge pattern for a predetermined period can be obtained, and the deterioration of the power storage element can be estimated. In the in-vehicle power storage device, a charge/discharge pattern for a predetermined period is also acquired, and deterioration of the power storage device is estimated.

Patent document 1 discloses an invention of a battery system in which a current from a power generation device is distributed to a plurality of battery blocks and distributed at a constant current to at least one of the battery blocks, and an SOC is estimated from the current, voltage, and temperature of the battery block to which the constant current is distributed.

Documents of the prior art

Patent document

Patent document 1 International publication No. 2013/099401

Disclosure of Invention

Problems to be solved by the invention

In the conventional method, particularly in the case of a complicated charge/discharge mode in which charge/discharge is frequently switched, the accuracy of estimating the deterioration of the power storage element may be insufficient. In the battery system of patent document 1, although the SOC can be measured by flowing a constant current for a measurement time, the amount of degradation accumulated in the battery cannot be estimated.

Degradation needs to be well estimated also for complex charge and discharge patterns.

An object of the present invention is to provide an estimation device, an estimation method, and a computer program that can estimate the deterioration of a power storage element with high accuracy.

Means for solving the problems

An estimation device according to an aspect of the present invention includes: a first acquisition unit that acquires the SOC at the start and end of charging, discharging, or floating of the power storage element; a storage unit that stores a plurality of degradation coefficients in accordance with a plurality of SOC ranges; a determination unit configured to determine a corresponding degradation coefficient from the plurality of degradation coefficients stored in the storage unit, based on the SOC at the start and at the end acquired by the first acquisition unit; and an estimation unit that estimates deterioration of the power storage element based on the deterioration coefficient determined by the determination unit.

An estimation method according to an aspect of the present invention acquires the SOC at the start and end of charging, discharging, or floating of an electric storage element, and estimates the deterioration of the electric storage element based on the acquired SOC at the start and end using a deterioration coefficient predetermined in accordance with a range of a plurality of SOCs.

A computer program according to an aspect of the present invention causes a computer to execute: the method includes acquiring the SOC at the start and end of charging, discharging, or floating of the power storage element, and estimating the deterioration of the power storage element based on the acquired SOC at the start and end by using a deterioration coefficient predetermined in accordance with a range of a plurality of SOCs.

Effects of the invention

In the present invention, the deterioration of the power storage element can be estimated with high accuracy.

Drawings

Fig. 1 is a graph showing an example of the charge/discharge mode of wind power generation.

Fig. 2 is a partially enlarged view of fig. 1.

Fig. 3 is a graph showing the relationship between the lowest SOC and Δ SOC and the degradation coefficient in the case where the rate is 1/3C and the temperature is 45 ℃.

Fig. 4 is an explanatory diagram illustrating a method of determining a degradation coefficient.

Fig. 5 is a block diagram showing the configuration of the charging and discharging system and the server according to embodiment 1.

Fig. 6 is an oblique view of the battery module.

Fig. 7 is a block diagram showing the configuration of the BMU.

Fig. 8 is a flowchart showing a processing procedure of the estimation device for the degradation of the power storage element.

Fig. 9 is a flowchart showing another processing procedure of the estimation device for the degradation of the power storage element.

Fig. 10 is a graph showing the results of obtaining the degradation amount by the processing of the flowchart of fig. 8 while changing the ranges of the SOC at the start and end.

Fig. 11 is a graph showing the results of obtaining the relationship between the number of test days and the capacity degradation rate when the wind turbine generator power storage element was simulated to be charged and discharged at a temperature of 15 ℃ and a rate of 1/3C.

Fig. 12 is a graph showing the results of obtaining the relationship between the number of test days and the capacity degradation rate when the wind turbine generator storage element was simulated to be charged and discharged at a temperature of 20 ℃ and a rate of 1/3C.

Fig. 13 is a graph showing the results of obtaining the relationship between the number of test days and the capacity degradation rate when the wind turbine generator storage element was simulated to be charged and discharged at a temperature of 25 ℃ and a rate of 1/3C.

Fig. 14 is a graph showing the results of obtaining the relationship between the number of test days and the capacity degradation rate when the wind turbine generator storage element was simulated to be charged and discharged at a temperature of 35 ℃ and a rate of 1/3C.

Fig. 15 is a graph showing the results of obtaining the relationship between the number of test days and the capacity degradation rate when the wind turbine generator storage element was simulated to be charged and discharged at a temperature of 45 ℃ and a rate of 1/3C.

Fig. 16 is a graph showing the results of obtaining the relationship between the number of test days and the capacity degradation rate when the wind turbine generator storage element was simulated to be charged and discharged at a temperature of 65 ℃ and a rate of 1/3C.

Detailed Description

(outline of embodiment)

An estimation device according to an embodiment includes: a first acquisition unit that acquires the SOC at the start and end of charging, discharging, or floating of the power storage element; a storage unit that stores a plurality of degradation coefficients in accordance with a plurality of SOC ranges; a determination unit configured to determine a corresponding degradation coefficient from the plurality of degradation coefficients stored in the storage unit, based on the SOC at the start and at the end (or a difference between the SOCs at the start and at the end) acquired by the first acquisition unit; and an estimation unit that estimates deterioration of the power storage element based on the deterioration coefficient determined by the determination unit.

In one continuous charge, discharge, or float charge, a plurality of degradation coefficients are stored in the storage unit in advance in accordance with a plurality of SOC ranges. Based on the starting and ending SOCs (or the difference between the starting and ending SOCs), the corresponding degradation coefficients are determined from the degradation coefficients stored in the storage unit, and the degradation of the power storage element is estimated. In the case where the variation of SOC around a predetermined SOC is large, the amount of degradation is large, and even if the variation of SOC is the same, the degradation value varies depending on the central SOC, and the degradation is estimated by batch processing using a degradation coefficient corresponding to the range of Δ SOC and SOC every time charging and discharging is performed, taking into consideration the knowledge and knowledge of japanese patent No. 6428957 by the present applicant. Even when charge and discharge are frequently switched and a complicated charge and discharge pattern (pattern) is provided, deterioration of the power storage element can be estimated with high accuracy. Further, by performing batch processing, the following equivalent effects are obtained: the computational load of the processor can be reduced, and the processing of the processor can be speeded up, or an inexpensive processor can be used without an expensive processor that can perform speedy processing.

In the above-described estimation device, the storage unit may store a plurality of degradation coefficients in accordance with a plurality of SOC ranges obtained by dividing the SOC0 to 100% at different intervals, and the determination unit may determine the degradation coefficient in an SOC range having the smallest range width, which includes the SOC at the start time and at the end time acquired by the first acquisition unit, among the plurality of SOC ranges.

According to the above configuration, the degradation coefficient can be determined favorably.

The estimation device described above may further include: and a second acquisition unit that acquires a change amount of current, voltage, power, or SOC per unit time, wherein the first acquisition unit acquires the SOC based on the change amount of current, voltage, power, or SOC acquired by the second acquisition unit and the change amount of current, voltage, power, or SOC acquired by the second acquisition unit last time.

According to the above configuration, the state transition can be detected based on the amount of change in current, voltage, power, or SOC per unit time.

The estimation device described above may further include: a first determination unit that determines whether or not there is a switch from the standing state to the charge/discharge state or a switch between the charge/discharge states based on the amount of change in the current, the voltage, the power, or the SOC acquired by the second acquisition unit and the amount of change in the current, the voltage, the power, or the SOC acquired by the second acquisition unit last time, and that acquires the SOC when the first determination unit determines that there is the switch.

According to the above configuration, it is possible to confirm the switching of charge and discharge, acquire the SOC at the start and end of charge or discharge, and estimate the deterioration favorably for each charge and discharge.

The estimation device described above may further include: and a second determination unit configured to determine which of a charge/discharge state, a left state, and a floating state is based on the current, voltage, power, or change amount of SOC per unit time acquired by the second acquisition unit, wherein the estimation unit estimates the degradation based on the state determined by the second determination unit.

According to the above configuration, the deterioration can be estimated favorably according to the state of the power storage element.

The estimation method according to the present invention acquires the SOC at the start and end of charging, discharging, or floating of the power storage element, and estimates the degradation of the power storage element based on the acquired SOC at the start and end (or the difference between the SOCs at the start and end) using a degradation coefficient predetermined in advance according to the range of the plurality of SOCs.

According to the above configuration, the deterioration of the power storage element is estimated based on the SOC at the start and the SOC at the end (or the difference between the SOCs at the start and the SOC at the end) using the deterioration coefficient predetermined in advance according to the range of the plurality of SOCs. At each time of charge and discharge, the degradation is estimated by batch processing using a degradation coefficient corresponding to Δ SOC and a range of SOC. Even when charge and discharge are frequently switched and have a complicated charge and discharge pattern, deterioration of the power storage element can be estimated with high accuracy.

A computer program according to an aspect of the present invention causes a computer to execute: the method includes acquiring the SOC at the start and end of charging, discharging, or floating of the power storage element, and estimating the degradation of the power storage element based on the acquired SOC at the start and end (or the difference between the SOCs at the start and end) using a degradation coefficient predetermined in advance according to a range of a plurality of SOCs.

In the description so far, the description has been given of the content related to the estimation of the deterioration of the power storage element using the SOC, but the deterioration can be estimated similarly also from the capacity of the power storage element, that is, the capacity of the power storage element at the start and the end of the charging or discharging or floating of the power storage element (or the change in the capacity of the power storage element from the start to the end). The following description will be made, as an example, of estimating deterioration of the power storage element using the SOC.

The following describes a method of estimating degradation in detail.

Fig. 1 is a graph showing an example of the charge/discharge mode of wind power generation. In fig. 1, the horizontal axis represents time (day) and the vertical axis represents power (W). As shown in fig. 1, since the amount of power generation of wind power generation varies finely due to wind power, charging and discharging are switched in a short period of time, and a complicated pattern is provided.

Fig. 2 is a partially enlarged view of fig. 1. In fig. 2, the horizontal axis represents time (day), the right vertical axis represents SOC (%), and the left vertical axis represents power (W). The left vertical axis also corresponds to the current (a). As shown in fig. 2, the transition is made in a state where the SOC and the power are constant, a state of discharge where the SOC decreases and the power shows a negative value, and a state of charge where the SOC increases and the power shows a positive value. Although not shown in fig. 2, after full charge, there is a floating state in which a small current flows through the bypass circuit so as not to apply a load to the electric storage element.

The following features are present in a wind power plant: the output variation of wind power generation is large if the number of sites is limited to 1, but if a plurality of sites are overlapped, the output variation is gentle due to the smoothing effect.

Further, there is a demand for accurately estimating deterioration and accurately determining the number of power storage elements to be replaced or added after several years, for example, by using millions of power storage elements in one wind turbine generator.

It is necessary to estimate the deterioration with high accuracy in response to frequent charge and discharge variations while also considering the smoothing effect.

The present applicant has found that even if the SOC is the same in the middle (center) of charge and discharge, the deterioration amount differs depending on the variation amount of the SOC, as shown in japanese patent No. 6428957. It is found that the deterioration amount becomes larger as the variation of the SOC becomes larger.

Further, it was found that even if the fluctuation amount of the SOC is the same, the deterioration amount is largely different from the center SOC accordingly.

The present applicant has developed various degradation estimation methods in consideration of degradation of the negative electrode active material.

The present applicant examined the following possibilities in the aforementioned japanese patent No. 6428957: as the magnitude of the SOC fluctuation increases, the expansion (during charging) and contraction (during discharging) of the negative electrode become more significant, and the SEI film formed on the surface of the negative electrode is partially broken, resulting in an increase in the amount of degradation caused by the energization of the power storage element.

In order to increase the current amount in the power storage element for the wind power generation equipment, Li is often used as the positive electrode active material_x(Ni_aCo_cMn_b)O₂(a + b + c is 1, a is not less than 0.5, b is not less than 0, c is not less than 0, and x is not less than 0 and not more than 1.1) and an NCM (Ni + Co + Mn-based mixed positive electrode active material, hereinafter referred to as NCM) in which the amount of Ni is increased. When the SOC variation is large, cracks are likely to occur in the active material layer of the positive electrode due to the lattice change of the NCM caused by insertion/desorption of Li ions. Isolation of the active material due to the crack increases the cut portion of the conductive path, and increases the contact resistance. Accordingly, as the number of charge and discharge cycles (cycle number) increases, the function as the storage element decreases. That is, it is necessary to consider not only the deterioration of the negative electrode active material described above but also the deterioration of the positive electrode active material.

In the present embodiment, the rate and the temperature are stored in advance in accordance with a range of the SOC from the start to the end of one continuous charge or discharge and Δ SOC which is a difference (range) between the SOC at the start and the SOC at the end. The corresponding degradation coefficient is determined from the stored degradation coefficients based on the range of the SOC from the start to the end of the acquired one-time continuous charge or discharge and the Δ SOC. The inventors of the present invention have found that when deterioration is estimated using the deterioration coefficient determined as described above, it is possible to estimate with high accuracy in response to frequent charge and discharge variations, taking into account the above-described deterioration due to the active materials of the positive electrode and the negative electrode and the smoothing effect.

In the present embodiment, it is determined which state is a charge/discharge state, a left state, or a floating state based on the amount of change in current, power, or SOC.

The degradation amount D is calculated by the following equation according to the determined state.

In the case of the charged state or the discharged state, the deterioration amount is calculated by the following formula (1).

D＝Dcal+Dcyc……(1)

Here, Dcal: amount of deterioration with time

Dcyc: amount of deterioration due to charging and discharging

Dcal is calculated by the following formula (2).

Dcal＝kc×√t……(2)

Here, t: elapsed time of state

kc: coefficient of deterioration with time

The degradation model rule may also be a root rule, a straight line rule, or a degradation model rule external thereto.

Dcyc is calculated by the following formula (3).

Dcyc＝kr×ΔSOC……(3)

Here, kr: coefficient of deterioration during charge and discharge

kr is determined as described below.

The degradation model rule may also be a root rule, a straight line rule, or a degradation model rule external thereto.

In the left state, the deterioration amount is calculated by the following equation (4).

D＝Dcal……(4)

In the floating state, when Δ SOC > 0, the amount of degradation is calculated by the following equation (5).

D＝Dcal+Dcyc+Dflt……(5)

Dflt is the deterioration amount in the floating state, and is calculated by the following formula (6).

Dflt＝kf×√t……(6)

Here, kf: coefficient of deterioration at floating

When Δ SOC is 0 in the floating state, the deterioration amount is calculated by the following equation (7).

D＝Dcal+Dflt……(7)

Dcal and Dflt are obtained by a root rule, and Dcyc is obtained by a straight rule, but for example, Dcal and Dflt may be obtained by a straight rule, and Dcyc may be obtained by a root rule.

In the present embodiment, the root rule is used in the floating state, but the degradation model rule may be a straight line rule or a degradation model rule other than the straight line rule.

The degradation coefficient kr is determined as follows.

The rate and temperature are varied, and the relationship between Δ SOC and SOH (State of Health) is obtained by changing the start time and end time of charging or discharging, and the degradation coefficient kr is obtained for each of the start time of charging (the lowest SOC of charging and discharging, corresponding to the range of SOC from the start time to the end time) and Δ SOC. Fig. 3 is a graph showing the relationship between the lowest SOC and Δ SOC and the degradation coefficient kr in the case where the rate is 1/3C and the temperature is 45 ℃. In fig. 3, the abscissa indicates Δ SOC (%), the ordinate indicates the lowest SOC (%) during charge and discharge, and the size of the circle at each point indicates the size of the value of the degradation coefficient kr.

Fig. 4 is an explanatory diagram illustrating a method of determining a degradation coefficient. The left-right direction of fig. 4 is SOC (%). Based on the results of fig. 3, a degradation coefficient kr is given for each Δ SOC. In the case of Δ SOC25, a, b, c, and d are given as degradation coefficients kr according to the start time and the end time of charging (or discharging), in the case of Δ SOC50, e and f are given as degradation coefficients kr, and in the case of Δ SOC100, g is given as degradation coefficients kr.

As shown in the example of FIG. 4, when the SOC range is 10 to 30%, the deterioration coefficient kr is selected which includes the entire SOC range 10 to 30% and has the smallest Δ SOC (SOC range width). In this case, the degradation coefficient e of Δ SOC50 is selected.

The Δ SOC to be stored is not limited to 25%, 50%, and 100%. The degradation coefficient may be obtained by interpolation calculation.

Note that the arrows in fig. 4 may be provided by dividing the range of SOC 100% in each Δ SOC at equal intervals, or may not be at equal intervals (the arrows do not overlap). The interval may also be changed in accordance with the SOC.

(embodiment mode 1)

Hereinafter, a charge/discharge system for a wind turbine generator will be described as an example of embodiment 1.

Hereinafter, a case where the storage element is a lithium ion secondary battery will be described, but the storage element is not limited to the lithium ion secondary battery.

Fig. 5 is a block diagram showing the configuration of the charge/discharge system 1 and the server 13 according to embodiment 1.

The charge/discharge system 1 includes a Battery module 3, a BMU (Battery Management Unit) 4, a control device 6, a voltage sensor 8, a current sensor 9, and a temperature sensor 10. The charge/discharge system 1 supplies power to the load 5.

In the battery module 3, lithium ion secondary batteries (hereinafter, referred to as batteries) 2 as a plurality of power storage elements are connected in series. The control device 6 controls the entire charge/discharge system 1.

The server 13 includes a communication unit 14 and a control unit 15.

The control device 6 includes a control unit 61, a display unit 62, and a communication unit 63.

The control device 6 is connected to the control unit 15 via the communication unit 63, the network 12, and the communication unit 14. The control device 6 transmits and receives data to and from the control unit 15 via the network 12.

In the present embodiment, one of the BMU4, the control device 6, and the control unit 15 functions as an estimation device of the present invention. In addition, when the control unit 15 does not function as the estimation device, the charge/discharge system 1 may not be connected to the server 13.

Fig. 5 shows a case where a single set of battery modules 3 is provided. The number of battery modules is not limited to this case.

BMU4 may also be a battery ECU.

The voltage sensor 8 is connected in parallel to the battery module 3, and outputs a detection result corresponding to the voltage of the entire battery module 3. The voltage sensor 8 is connected to a positive terminal 23 and a negative terminal 26 of each battery 2, which will be described later, and is used to measure a voltage V between the terminals 23 and 26 of each battery 2₁Measurement is performed to detect V of each battery 2₁The total value of (a) is a voltage V between a negative electrode lead 33 and a positive electrode lead 36 of the battery module 3, which will be described later.

The current sensor 9 is connected in series to the battery module 3, and detects a current I flowing through the battery module 3.

The temperature sensor 10 detects the temperature near the battery module 3.

Fig. 6 is an oblique view of the battery module 3.

The battery module 3 includes a rectangular parallelepiped case (case)31 and a plurality of the batteries 2 accommodated in the case 31.

The battery 2 includes a rectangular parallelepiped case body 21, a cover plate 22, and a terminal 23, a terminal 26, a burst valve 24, and an electrode body 25 provided on the cover plate 22. The electrode body 25 is formed by laminating a positive electrode plate, a separator, and a negative electrode plate, and is accommodated in the case body 21.

The electrode body 25 may be obtained by winding a positive electrode plate and a negative electrode plate in a flat shape with a separator interposed therebetween.

The positive electrode plate has an active material layer formed on a positive electrode base material foil, which is a plate-like (sheet-like) or strip-like metal foil made of, for example, aluminum or an aluminum alloy. The negative electrode plate has an active material layer formed on a negative electrode base foil, which is a plate-like (sheet-like) or strip-like metal foil made of copper, copper alloy, or the like, for example. The separator is, for example, a microporous sheet made of a synthetic resin.

The positive electrode active material used in the active material layer of the positive electrode is made of, for example, Li_x(Ni_aMn_bCo_cM_d)O₂(M is a metal element other than Li, Ni, Mn, Co, 0. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.1, 0. ltoreq. c.ltoreq.1, a + b + c + d. ltoreq.1, 0. ltoreq. x.ltoreq.1.1, and a and c are not 0 at the same time). The positive electrode active material has a layered rock salt crystal structure. The a preferably satisfies 0.5. ltoreq. a.ltoreq.1. In this case, Ni is contained in a large amount in the transition metal site.

The positive electrode active material preferably contains Li (d ═ 0)_x(Ni_aCo_cMn_b)O₂The NCM (a + b + c is 1, a is more than or equal to 0.5, b is more than or equal to 0, c is more than or equal to 0, and x is more than 0 and less than or equal to 1.1). a is more preferably 0.6 or more, and still more preferably 0.8 or more.

The positive electrode active material may be formed of Li, with M being Al, b being 0_x(Ni_aCo_cAl_d)O₂The NCA (a + c + d is 1, a is more than or equal to 0.5, c is more than or equal to 0, d is more than or equal to 0, and x is more than 0 and less than or equal to 1.1). a is more preferably 0.6 or more, and still more preferably 0.8 or more。

The NCM or NCA is not limited to the case where the metals other than Li and Ni are each composed of 2 kinds of metals, and may be composed of 3 or more kinds of metals. For example, small amounts of Ti, Nb, B, W, Zr, Ti, Mg, etc. may be included.

The positive electrode active material may be, for example, LiMeO₂-Li₂MnO₃Solid solution, Li₂O-LiMeO₂Solid solution, Li₃NbO₄-LiMeO₂Solid solution, Li₄WO₅-LiMeO₂Solid solution, Li₄TeO₅-LiMeO₂Solid solution, Li₃SbO₄-LiFeO₂Solid solution, Li₂RuO₃-LiMeO₂Solid solution, Li₂RuO₃-Li₂MeO₃Li-excess active materials such as solid solutions.

Below, for the use of Ni: co: mn is 5: 2: the case where the NCM of 3 is a positive electrode active material will be described.

Examples of the negative electrode active material used in the negative electrode active material layer include metals or alloys such as hard carbon, Si, Sn, Cd, Zn, Al, Bi, Pb, Ge, and Ag, and chalcogenides containing these metals or alloys. An example of the chalcogenide is SiO.

The adjacent terminals 23, 26 of the adjacent cells 2 of the battery module 3 are different in polarity, and the terminals 23, 26 are electrically connected to each other by the bus bar 32, thereby connecting the plurality of cells 2 in series.

The terminals 23 and 26 of the batteries 2 at both ends of the battery module 3, which have different polarities from each other, are provided with leads 34 and 33 for extracting electric power.

Fig. 7 is a block diagram showing the structure of BMU 4. The BMU4 includes a control unit 41, a storage unit 42, an input unit 46, and an interface unit 47. The units are connected to each other via a bus so as to be able to communicate with each other. In the present embodiment, the control unit 41 functions as a first acquisition unit, a second acquisition unit, a determination unit, a first determination unit, and a second determination unit.

The input unit 46 receives input of detection results from the voltage sensor 8, the current sensor 9, and the temperature sensor 10. The interface unit 47 is configured by, for example, a LAN interface, a USB interface, or the like, and communicates with another device such as the control device 6 by wire or wirelessly.

The storage unit 42 is configured by, for example, a Hard Disk Drive (HDD) or the like, and stores various programs and data. The storage unit 42 stores, for example, an estimation program 43 for executing a degradation estimation process described later. The estimation program 43 is supplied in a state of being stored in a computer-readable recording medium 50 such as a CD-ROM, a DVD-ROM, or a USB memory, and is installed in the BMU4 and stored in the storage unit 42. The estimation program 43 may be acquired from an external computer not shown connected to the communication network and stored in the storage unit 42.

The storage unit 42 also stores history data 44 of charge and discharge. The history of charge and discharge is an operation history of the battery module 3, and is information including information indicating a period (use period) during which the battery module 3 is charged or discharged, information on the charge or discharge of the battery module 3 during the use period, and the like. The information indicating the usage period of the battery module 3 includes information indicating the start and end times of charging or discharging, an accumulated usage period during which the battery module 3 is used, and the like. The information on the charge or discharge of the battery module 3 is information indicating the voltage, rate, and the like at the time of charge or discharge of the battery module 3.

The storage unit 42 further stores a deterioration coefficient table 45, and the deterioration coefficient table 45 stores a deterioration coefficient kr which is obtained in advance through experiments for each of a plurality of Δ SOC and SOC ranges, in terms of rate and temperature. The deterioration coefficient table 45 may be updated by a predetermined method as appropriate. The deterioration coefficient table 45 is not limited to the case of storing the minute rate and the temperature. Instead of the SOC range, the degradation coefficient kr may be stored by associating the SOC at the start time, the end time, or the center time of charge/discharge with Δ SOC.

The storage unit 42 also stores the above-described temporal degradation coefficient kc and the above-described degradation coefficient kf during fluctuation in terms of rate and temperature. The temporal degradation coefficient kc and the floating degradation coefficient kf may be constant values.

The control Unit 41 is configured by, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the operation of the BMU4 by executing a computer program such as the estimation program 43 Read from the storage Unit 42. The control unit 41 reads and executes the estimation program 43, thereby functioning as a processing unit that executes the degradation estimation process.

Fig. 8 is a flowchart showing a procedure of processing for estimating deterioration of the power storage element by the BMU4 as the estimation device.

First, the control unit 41 obtains the current I and the voltage V (S1).

Control unit 41 calculates SOC (S2). The control unit 41 calculates SOC based on the acquired V and SOC-OCV curves, for example.

The control unit 41 determines whether or not the SOC of the previous state is stored (S3).

If it is determined that the SOC of the previous state is stored (yes in S3), control unit 41 calculates Δ SOC (ds) of the current state (S4). The control unit 41 calculates Δ soc (ds) from the current I and the elapsed time, for example. When the SOC of the previous state is stored, the difference between the SOC of the current state and the SOC of the previous state is calculated.

The control unit 41 determines whether or not 0 < dS/dt < I_f(S5). dS/dt corresponds to I. I is_fIs a threshold value of the current for determining whether or not the current is in a floating state. When the control unit 41 determines that 0 < dS/dt < I_fIf (S5: YES), the process proceeds to S15.

The control unit 41 determines that the value is not 0 < dS/dt < I_fWhen (S5: NO), that is, when it is determined that the current state is being represented by I_fWhen the current I is in a charged state, a discharging state (dS/dt < 0), or a left state (dS/dt is 0), Dcal is calculated (S6). The controller 41 calculates Dcal from the above expression (2) using the temporal degradation coefficient kc stored in the storage 42.

The control unit 41 determines whether or not Δ SOC (dS) of the previous state is stored₀) (S7). Control ofThe part 41 determines that dS is not stored₀If (S7: NO), the process proceeds to S18.

The control unit 41 determines that dS is stored₀In the case of (S7: YES), dS × dS is judged₀Whether or not it is 0 or less (S8). The control unit 41 determines dS × dS₀If not more than 0 (S8: YES), dS is judged₀Whether or not it is not 0 (S9). When the control unit 41 determines that dS is present₀If not 0 (yes in S9), that is, if it is determined that the state is switched from charging to discharging, from discharging to charging, or from charging to discharging to leaving, the SOC at the start of charging or discharging and at the end of charging or discharging is obtained (S10). The SOC at the end corresponds to the SOC calculated in S2.

At the time of this sampling t₂The last sampling time t₁Last sampling time t₀Is set as SOC₂、SOC₁、SOC₀In the case of (1), dS is Δ SOC₂＝SOC₂-SOC₁，dS₀＝ΔSOC₁＝SOC₁-SOC₀. Since Δ SOC is a positive value in the case of charging and a negative value in the case of discharging, it is dS × dS₀If negative, it can be determined that the charge is switched to the discharge or the discharge is switched to the charge. When dS is 0, it can be determined that charge/discharge is switched to leaving.

When the control unit 41 determines that dS is present₀If the result is 0 (no in S9), that is, if it is determined that the standing state is maintained or the charging/discharging operation is switched from the standing state to the charging/discharging operation, the process proceeds to S14.

Control unit 41 calculates Δ SOC of the difference between the start time and the end time of charging or discharging (S11).

The control unit 41 reads the degradation coefficient table 45, and determines the degradation coefficient kr as described above based on the range of the SOC from the start time to the end time and the minimum Δ SOC (S12).

Using the determined degradation coefficient kr and the time t of charge/discharge, the control unit 41 calculates Dcyc from Dcyc — kr × Δ SOC in equation (3) (S13).

The control part 41 is judgingIs defined as dS × dS₀If it is not 0 or less (no in S8), that is, if it is determined that charge and discharge are continuous, the process proceeds to S18.

The control unit 41 calculates the degradation amount D (S14). When the current state is a charged or discharged state, the degradation amount D is calculated from D ═ Dcal + Dcyc in the above formula (1). When the current state is the standing state, the degradation amount D is calculated from D ═ Dcal in the above formula (4).

When the control unit 41 determines that 0 < dS/dt < I_fIn the case of (S5: YES), Dflt is calculated (S15).

The control unit 41 determines whether or not dS is present₀/dt≥I_fOr dS₀/dt＜0(S16)。

When the control unit 41 determines that dS is present₀/dt≥I_fOr dS₀If/dt < 0 (yes in S16), that is, if it is determined that the charge/discharge is switched to the floating state, the process proceeds to S10, and in S14, the degradation amount D is calculated from D ═ Dcal + Dcyc + Dflt in equation (5).

When the control unit 41 determines that the data is not dS₀/dt≥I_fOr dS₀If/dt < 0 (no in S16), that is, if it is determined that the float is continuing or the float is switched from the standing to the floating, the process proceeds to S14, and the degradation amount D is calculated from D ═ Dcal + Dflt in equation (7).

Control unit 41 updates the start SOC (S17).

Control unit 41 updates the SOC of the previous state with the SOC of the current state (S18), and ends the process.

Fig. 9 is a flowchart showing another processing procedure of the degradation estimation of the power storage element by the BMU 4.

First, the control unit 41 obtains the current I and the voltage V (S21).

Control unit 41 calculates SOC (S22).

The control section 41 determines whether or not 0 < I_f(S23)。I_fIs a threshold value of the current for determining whether or not the current is in a floating state. The control unit 41 determines that 0 < I_fIf (S23: YES), the process proceeds to S33.

The control unit 41 is determiningIs not 0 < I_fWhen (S23: NO), that is, when it is determined that the current state is being represented by I_fWhen the current I is in a charged state, a discharging state (I < 0), or a left state (I ═ 0), Dcal is calculated (S24). The controller 41 calculates Dcal from the above expression (2) using the temporal degradation coefficient kc stored in the storage 42.

The control section 41 determines whether or not the previous state I is stored₀(S25). The control unit 41 determines that I is not stored₀If (S25: NO), the process proceeds to S35.

The control unit 41 determines that I is stored₀In the case of (S25: YES), I × I is judged₀Whether or not it is 0 or less (S26). The control unit 41 determines that I × I₀When the value is 0 or less (S26: YES), the judgment is made that I is₀Whether or not it is not 0 (S27). Determined as I by the control unit 41₀If not 0 (yes in S27), it is determined that the SOC at the start of charging or discharging and at the end of charging or discharging is acquired when switching from charging to discharging, from discharging to charging, or from charging to discharging to leaving (S28).

The current is positive in the case of charging and negative in the case of discharging, and therefore is at I × I₀If negative, it can be determined that the charge is switched to the discharge or the discharge is switched to the charge. When I is 0, it can be determined that charge/discharge is switched to leaving.

Determined as I by the control unit 41₀If 0 is detected (no in S27), that is, if it is determined that the standing state is continued or the charging/discharging operation is switched from the standing state to the charging/discharging operation, the process proceeds to S32.

Control unit 41 calculates Δ SOC of the difference between the start time and the end time of charging or discharging (S29).

The control unit 41 reads the degradation coefficient table 45, and determines the degradation coefficient kr as described above based on the range of the SOC from the start time to the end time and the minimum Δ SOC (S30).

The control unit 41 calculates Dcyc by equation (3) using the determined degradation coefficient kr and the time t of charge and discharge (S31).

The control unit 41 determines that I × I₀If it is not 0 or less (no in S26), that is, if it is determined that charge and discharge are continuous, the process proceeds to S36.

The control unit 41 calculates the degradation amount D (S32). When the current state is a charged or discharged state, the degradation amount D is calculated from D ═ Dcal + Dcyc in the above formula (1). When the current state is the standing state, the degradation amount D is calculated from D ═ Dcal in the above formula (4).

The control unit 41 determines that 0 < I_fIn the case of (S23: YES), Dflt is calculated (S33).

The control unit 41 determines whether or not the value is I₀≥I_fOr I₀＜0(S34)。

The control unit 41 determines that I₀≥I_fOr I₀If < 0 (yes in S34), that is, if it is determined that the previous state is the charged state or the discharged state, the process proceeds to S28, and in S32, the degradation amount D is calculated from D ═ Dcal + Dcyc + Dflt in equation (5).

When the control unit 41 determines that the value is not I₀≥I_fOr I₀If < 0 (NO in S34), that is, if 0 < I is judged₀＜I_fIn the case of (3), the process proceeds to S32, and the degradation amount D is calculated from D ═ Dcal + Dflt in equation (7).

Control unit 41 updates the start SOC (S35).

The control unit 41 updates I with the current I₀(S36), the process is ended.

In the flowchart of fig. 9, the power can be used instead of the current, and the degradation amount can be calculated in the same manner as in the case of the current.

In the present embodiment, based on the range of SOC from the start to the end of one continuous charge and discharge and the Δ SOC at the start and the end, the corresponding degradation coefficient kr is determined from the degradation coefficients kr stored in the storage unit 42, and the degradation of the battery module 3 is estimated. At each time of charge and discharge, the degradation is estimated by batch processing using the degradation coefficient kr corresponding to the Δ SOC and the range of the SOC. Even when charge and discharge are frequently switched and have a complicated charge and discharge pattern, it is possible to estimate the deterioration of the battery module 3 with high accuracy.

Fig. 10 is a graph showing the results of obtaining the degradation amount by the processing of the flowchart of fig. 8 while changing the ranges of the SOC at the start and end. The vertical axis represents the capacity deterioration rate (%) as the deterioration amount.

Fig. 11 is a graph showing the results of obtaining the relationship between the number of days of the test and the capacity degradation rate when the wind turbine generator power storage element was simulated to have been charged and discharged to/from the battery module 3 at a temperature of 15 ℃ and a rate of 1/3C. The horizontal axis represents the number of days of the test (day), and the vertical axis represents the capacity deterioration rate (%). Fig. 11 shows a graph of actual measurement values, a graph of a comparative example in which the degradation amount is calculated by a conventional estimation method, and a graph of an example in which the degradation amount is calculated by an estimation method according to an embodiment.

Fig. 12, 13, 14, 15, and 16 are graphs showing the results of obtaining the relationship between the number of test days and the capacity deterioration rate in the same manner as in fig. 11, with the temperature being replaced with 20 ℃, 25 ℃, 35 ℃, 45 ℃, and 65 ℃, respectively, at the rate 1/3C.

As can be seen from fig. 11 to 16, in the case of the example, the estimation accuracy was improved as compared with the comparative example.

As described above, it was confirmed that when a plurality of charge/discharge modes are provided like a power storage device used in a wind turbine generator, the deterioration amount is calculated every time charging and discharging is performed in the example, and deterioration can be estimated favorably. The deterioration can be estimated with high accuracy in response to frequent charge/discharge changes, taking into account the deterioration due to the active materials of the positive electrode and the negative electrode and the smoothing effect, and the number of power storage elements to be replaced after a predetermined period can be determined with high accuracy. And resources can be saved, and the cost can be reduced.

The described embodiments are not limiting. The scope of the present invention is intended to include the meaning of the claims and their equivalents as well as all modifications within the scope.

For example, the estimation device according to the present invention is not limited to a charging/discharging system for wind power generation, and can be applied to other charging/discharging systems such as a vehicle-mounted, railroad regenerative power storage device, and a solar power generation system.

The storage element is not limited to the lithium ion secondary battery. The electric storage element may be another secondary battery, a primary battery, or an electrochemical cell such as a capacitor.

Description of the reference symbols

1 charging and discharging system

2 Battery (storage battery element)

3 Battery module (storage battery element)

4 BMU

41 control part

42 storage unit

43 estimation procedure

44 historical data

6 control device

61 control part

62 display part

63 communication part

12 network

13 server

15 a control unit.