Patent Description:
An energy storage device capable of storing electric energy and supplying energy as a power source when necessary is used. The energy storage device is applied to a portable instrument, a power supply device, a transportation instrument including automobiles and railways, an industrial instrument including aerospace and construction, and the like. It is important to constantly grasp a storage capacity of the energy storage device such that the energy stored as much as necessary can be used when necessary. It is known that the energy storage device is mainly chemically degraded with time and a use frequency. Thus, the energy that can be utilized decreases with time and use frequency. It is important to grasp a degradation state of the energy storage device in order to use the energy as much as necessary when necessary. A technique for estimating the degradation of the energy storage device has been developed so far.

For example, when the energy storage device is used in a wind power generation facility, the amount of power generation is frequently switched by wind power, and the pattern of the power generation is complicated, so that a charge-discharge pattern of the energy storage device is also complicated. In the case of solar power generation, for instance, because power is generated in the daytime, a substantially constant power generation pattern is provided, and the charge-discharge pattern of the energy storage device is also substantially constant. Thus, the degradation of the energy storage device can be estimated by acquiring the charge-discharge pattern for a predetermined period. Also in an on-vehicle energy storage device, the degradation of the energy storage device is estimated by acquiring the charge-discharge pattern for the predetermined period.

Patent Document <NUM> discloses a storage battery system that distributes a current from a power generation device to a plurality of storage battery blocks and distributes a constant current to at least one storage battery block, and estimates a state of charge (SOC) from a current, a voltage, and a temperature of the storage battery block to which the constant current is distributed. In addition, <CIT> discloses an energy storage device state estimation device for estimating a state of an energy storage device at a predetermined point of time. The state of the energy storage device is estimated at the predetermined point of time by using a time dependent deterioration value and a working electricity dependent deterioration value, which are estimated by using information about time dependent deterioration and information about working electricity dependent deterioration corresponding to an acquired charge-discharge history. <CIT> discloses a method for gathering information from battery sensors-for instance, information regarding the state-of-charge, temperature and/or other characteristics of battery cells in a vehicle battery pack-and using that information to estimate or predict battery degradation or state-of-health. According to an exemplary embodiment, the method uses both a time-based algorithm and an event-based algorithm to predict or estimate battery degradation. The event-based algorithm may select certain data from the battery conditions, instead of using the entire set of battery condition data, and may use this information in its prediction or estimate. <CIT> discloses a degradation estimation method, which includes estimating the degradation of a battery in a stop interval based on acquired degradation information, wherein the acquired degradation information corresponds to a state of charge calculated from the battery and a detection temperature or an ambient temperature of the battery and is based based on a first degradation information database showing degradation of the battery in accordance with a set state of charge and a set temperature. <CIT> discloses a method for managing an electrochemical accumulator or a storage battery, which includes determining an estimated value of a state of deterioration of the accumulator from the accumulator's history of voltage values, intensity of current flow, and temperature. The estimated value is a barycentric value of the state of deterioration calculated as a barycenter of at least two values.

In the conventional method, particularly in the case of a complicated charge-discharge pattern in which the charge-discharge is frequently switched, estimation accuracy of the degradation of the energy storage device may not be sufficient. In the storage battery system of Patent Document <NUM>, the SOC can be measured by applying a constant current during a measurement time, but a degradation amount accumulated in the storage battery cannot be estimated.

There is a demand for better estimation of the degradation even for the complicated charge-discharge pattern.

An object of the present invention is to provide an estimation device, an estimation method, and a computer program capable of accurately estimating the degradation of the energy storage device.

This object is achieved by the present invention as claimed in the independent claims. Advantageous and preferred embodiments of the present invention are defined by the dependent claims. Examples, aspects and embodiments presented in the following and not necessarily falling under the scope of the claims are provided in the application to better understand the invention.

In the present invention, the degradation of the energy storage device can be accurately estimated.

According to an aspect of the present invention, an estimation device includes: a first acquisition unit that acquires SOCs at a start and an end in charge, discharge, or floating charge of an energy storage device; a storage that stores a plurality of degradation coefficients corresponding to a plurality of SOC ranges; an identification unit that identifies a corresponding degradation coefficient from the plurality of degradation coefficients stored in the storage based on the SOCs at the start and the end acquired by the first acquisition unit (or a difference in the SOC from the start to the end); and an estimation unit that estimates degradation of the energy storage device based on the degradation coefficient identified by the identification unit.

For a series of the charge, the discharge, or the floating charge, the plurality of degradation coefficients are stored in the storage corresponding to the plurality of SOC ranges. The corresponding degradation coefficient is identified from the plurality of degradation coefficients stored in the storage based on the SOCs at the start and the end (or, the difference in the SOC from the start to the end), and the degradation of the energy storage device is estimated. Furthermore, considering the knowledge of <CIT> of the present applicant (i.e., the degradation amount is large when the fluctuation amount of the SOC around the predetermined SOC is large, and the degradation value changes depending on the center SOC even when the fluctuation amount of the SOC is the same), the degradation is estimated by batch processing. The degradation coefficient corresponding to ΔSOC and the SOC range is used for each time of the charge and the discharge. The degradation of the energy storage device can be accurately estimated even in the case of the complicated charge-discharge pattern in which the charge-discharge is frequently switched. In addition, effects that a calculation load of a processor is reduced, the processing of the processor can be sped up, or an inexpensive processor can be used instead of an expensive processor capable of performing high-speed processing can be obtained by performing the batch processing.

In the estimation device described, the storage stores the plurality of degradation coefficients corresponding to the plurality of SOC ranges obtained by dividing SOC of <NUM> to <NUM>% at different intervals, and the identification unit identifies the degradation coefficient in the SOC range including the SOCs at the start and the end acquired by the first acquisition unit and having a smallest range width in the plurality of SOC ranges.

According to the above configuration, the degradation coefficient can be well identified.

The estimation device further includes a second acquisition unit that acquires a change amount of current, voltage, power, or an SOC in a unit time. The first acquisition unit may acquire the SOC based on the change amount of the current, the voltage, the power, or the SOC acquired by the second acquisition unit and the change amount of the current, the voltage, the power, or the SOC previously acquired by the second acquisition unit.

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

The estimation device further includes a first determination unit that determines presence or absence of switching from leaving to charge-discharge or switching between charge-discharge based on the change amount of the current, the voltage, the power, or the SOC acquired by the second acquisition unit and the change amount of the current, the voltage, the power, or the SOC previously acquired by the second acquisition unit. The first acquisition unit may acquire the SOC when the first determination unit determines that the switching is performed.

According to the above configuration, the switching of the charge-discharge can be checked, the SOCs at the start and the end of the charge or the discharge can be acquired, and the degradation can be well estimated for each of the charge and the discharge.

The estimation device further includes a second determination unit that determines whether a state is a charge-discharge state, a leaving state, or a floating state based on a change amount of current, voltage, power, or an SOC for a unit time acquired by the second acquisition unit. The estimation unit may estimate the degradation based on the state determined by the second determination unit.

According to the above configuration, the degradation can be well estimated depending on the state of the energy storage device.

According to another aspect of the present invention, an estimation method includes: acquiring SOCs at a start and an end in charge, discharge, or floating charge of an energy storage device (or a difference in the SOC from the start to the end); and estimating degradation of the energy storage device using a degradation coefficient previously determined from a plurality of SOC ranges based on the acquired SOCs at the start and the end.

According to the above configuration, the degradation of the energy storage device is estimated using the degradation coefficient previously determined from the plurality of SOC ranges based on the SOCs at the start and the end (or, the difference in the SOC from the start to the end). The degradation is estimated by the batch processing using the degradation coefficient corresponding to the ΔSOC and the SOC range each time of the charge and the discharge. The degradation of the energy storage device can be accurately estimated even in the case of the complicated charge-discharge pattern in which the charge-discharge is frequently switched.

According to still another aspect of the present invention, a computer program causing a computer to execute: acquiring SOCs at a start and an end in charge, discharge, or floating charge of an energy storage device (or a difference in the SOC from the start to the end); and estimating degradation of the energy storage device using a degradation coefficient previously determined from a plurality of SOC ranges based on the acquired SOCs at the start and the end.

In the above, the estimation of the degradation of the energy storage device using the SOC has been described. However, the degradation can be similarly estimated from capacity of the energy storage device, namely, the capacity of the energy storage device at the start and the end of the charge, the discharge, or the floating charge of the energy storage device. Hereinafter, the estimation of the degradation of the energy storage device using the SOC will be described as an example.

A degradation estimation method will be specifically described below.

<FIG> is a graph illustrating an example of the charge-discharge pattern of wind power generation. In <FIG>, a horizontal axis represents time (day), and a vertical axis represents power (W). As illustrated in <FIG>, because an amount of power generation of the wind power generation is finely changed by wind power, the charge and the discharge are switched in a short period, and a complicated pattern is generated.

<FIG> is a partially enlarged view of <FIG>. In <FIG>, 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 current (A). As illustrated in <FIG>, the SOC and the power transition to the leaving state in which the SOC and the power are constant, a discharge state in which the SOC decreases and the power indicates a negative value, and a charge state in which the SOC increases and the power indicates a positive value. Although not illustrated in <FIG>, there is also the floating state in which a minute current flows through a bypass circuit after full charge so as not to apply a load to the energy storage device.

In the wind power generation facility, output fluctuation of the wind power generation is large when limited to one point, but the output fluctuation is moderated by an averaging effect when a plurality of points are overlapped.

For example, millions of energy storage devices are used in one wind power generation facility, and there is also a demand for accurately estimating the degradation and accurately determining the number of energy storage devices replaced or added after several years.

The degradation needs to be accurately estimated in response to a frequent change in the charge-discharge in consideration of the averaging effect.

As disclosed in <CIT>, the present applicant found that the degradation amount is different when the fluctuation amount of the SOC is different even if the center SOC of the charge-discharge is the same. The present applicant found that the degradation amount increases depending on the fluctuation magnitude of the SOC.

The present applicant also found that the degradation amount greatly varies depending on the center SOC even when the fluctuation amount of the SOC is the same.

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

In <CIT>, the present applicant considered a possibility that as the fluctuation magnitude of the SOC increases, expansion (during the charge) and contraction (during the discharge) of the negative electrode become significant, so that the SEI film formed on the surface of the negative electrode is partially destroyed, and the degradation amount of the energy storage device due to energization increases as a result.

In order to increase the amount of current in an energy storage device for a wind power generation facility, NCM (Ni + Co + Mn-based mixed positive active material, hereinafter referred to as NCM) having a large amount of Ni, represented by Lix(NiaCocMnb)O<NUM> (a + b + c = <NUM>, a ≥ <NUM>, b ≥ <NUM>, c ≥ <NUM>, <NUM> < x ≤ <NUM>), is often used as a positive active material. When the fluctuation amount of the SOC is large, an active material layer of the positive electrode is likely to crack due to a change in a crystal lattice of the NCM caused by insertion/extraction of a Li ion. Isolation of the active material due to the crack increases a cut portion of the conductive path and increases a contact resistance. Accordingly, the function as the energy storage device is degraded as the number of times of the charge-discharge (the number of cycles) increases. That is, not only the above-described degradation of the negative active material but also the degradation of the positive active material need to be considered.

In the embodiment, for each rate and temperature, a plurality of degradation coefficients are stored corresponding to the SOC range from the start to the end of one series of the charge or the discharge and the ΔSOC that is the difference (range) between the SOC at the start and the SOC at the end. The corresponding degradation coefficient is identified from the stored degradation coefficients based on the acquired SOC range (start to end) of the continuous charge or discharge and the ΔSOC. The present inventor found that when the degradation is estimated using the degradation coefficient identified as described above, the degradation can be accurately estimated in response to the frequent change in the charge-discharge in consideration of the degradation derived from the active materials of the positive electrode and the negative electrode and the averaging effect, and completed the present invention.

In the embodiment, it is determined whether the state is the charge-discharge state, the leaving state, or the floating state based on the change amount of the current, the power, or the SOC.

A degradation amount D is calculated by the following equation depending on the determined state.

In the case of the charged state or the discharged state, the degradation amount is calculated by the following equation (<NUM>).

Here, Dcal represents a time dependent degradation amount.

Dcyc represents degradation amount due to charge-discharge.

Deal is calculated by the following equation (<NUM>).

Here, t represents elapsed time of the state.

kc represents time degradation coefficient.

The degradation model rule may be a root rule, a linear rule, or other degradation model rules.

Dcyc is calculated by the following equation (<NUM>).

Here, kr represents a degradation coefficient during charge-discharge.

In the case of the leaving state, the degradation amount is calculated by the following equation (<NUM>).

When ΔSOC > <NUM> in the floating state, the degradation amount is calculated by the following equation (<NUM>).

Dflt is the degradation amount in the floating state, and is calculated by the following equation (<NUM>).

Here, kf represents a degradation coefficient at the float timet.

When ΔSOC = <NUM> in the floating state, the degradation amount is calculated by the following equation (<NUM>).

Deal and Dflt are obtained by the root rule, and Dcyc is obtained by the linear rule. However, this is an example, Dcal and Dflt may be obtained by the linear rule, and Dcyc may be obtained by the root rule.

In the embodiment, the root rule is used in the floating state, but the degradation model law may be a linear rule or another degradation model rule.

A degradation coefficient kr is identified as follows.

A relationship between the ΔSOC and a state of health (SOH) is obtained by changing a start point and an end point of the charge or the discharge for each rate and temperature, and the degradation coefficient kr is obtained for each start point of the charge (corresponding to the minimum SOC of the charge-discharge and the SOC range from the start to the end) and the ΔSOC. <FIG> is a graph illustrating a relationship between the lowest SOC and ΔSOC and the degradation coefficient kr when a rate is <NUM>/3C and a temperature is <NUM>. In <FIG>, the horizontal axis represents the ΔSOC (%), the vertical axis represents the lowest SOC (%) of the charge-discharge, and a size of a circle at each point represents the value of the degradation coefficient kr.

<FIG> is an explanatory view illustrating a method for identifying the degradation coefficient. A horizontal direction in <FIG> is SOC (%). Based on the result in <FIG>, the degradation coefficient kr is given for each ΔSOC. In the case of the ΔSOC <NUM>, a, b, c, d are given as the degradation coefficients kr corresponding to the start point and the end point of the charge (or) the discharge. In the case of the ΔSOC <NUM>, e, f are given as the degradation coefficients kr. In the case of the ΔSOC <NUM>, g is given as the degradation coefficient kr.

As illustrated in the example of <FIG>, when the acquired SOC range is <NUM>% to <NUM>%, the degradation coefficient kr including the entire SOC range of <NUM>% to <NUM>% and having the smallest ΔSOC (SOC range width) is selected. In this case, the degradation coefficient e of the ΔSOC50 is selected.

The stored ΔSOC is not limited to <NUM>%, <NUM>%, and <NUM>%. The degradation coefficient may be obtained by interpolation calculation.

In addition, the arrows in <FIG> may be provided by dividing the SOC range of <NUM>% at equal intervals or not at equal intervals (the arrows may overlap) in each ΔSOC. The interval may be changed depending on the SOC.

Hereinafter, an example of a charge-discharge system used in a wind power generation facility will be described as first embodiment.

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

<FIG> is a block diagram illustrating a configuration of a charge-discharge system <NUM> and a server <NUM> of first embodiment.

The charge-discharge system <NUM> includes a battery module <NUM>, a battery management unit (BMU) <NUM>, a control device <NUM>, a voltage sensor <NUM>, a current sensor <NUM>, and a temperature sensor <NUM>. The charge-discharge system <NUM> supplies power to a load <NUM>.

In the battery module <NUM>, lithium-ion secondary batteries (hereinafter, referred to as a battery) <NUM>, a plurality of energy storage devices, are connected in series. The control device <NUM> controls the entire charge-discharge system <NUM>.

The server <NUM> includes a communication unit <NUM> and a controller <NUM>.

The control device <NUM> includes a controller <NUM>, a display <NUM>, and a communication unit <NUM>.

The control device <NUM> is connected to the controller <NUM> through a communication unit <NUM>, a network <NUM>, and the communication unit <NUM>. The control device <NUM> transmits and receives data to and from the controller <NUM> through the network <NUM>.

In the embodiment, any one of the BMU <NUM>, the control device <NUM>, and the controller <NUM> functions as the estimation device of the present invention. When the controller <NUM> does not function as the estimation device, the charge-discharge system <NUM> may not be connected to the server <NUM>.

<FIG> illustrates the case where one set of battery modules <NUM> is provided. The number of battery modules is not limited to this case.

The voltage sensor <NUM> is connected in parallel to the battery module <NUM>, and outputs a detection result corresponding to the entire voltage of the battery module <NUM>. The voltage sensor <NUM> is connected to a terminal <NUM> of the positive electrode and a terminal <NUM> of the negative electrode described later, measures voltage V<NUM> between the terminals <NUM>, <NUM> of each battery <NUM>, and detects voltage V between a lead <NUM> of the negative electrode and a lead <NUM> of the positive electrode described later, the voltage V at the battery module <NUM> being a total value of V<NUM> of the batteries <NUM>.

The current sensor <NUM> is connected in series to the battery module <NUM>, and detects current I flowing through the battery module <NUM>.

The temperature sensor <NUM> detects a temperature near the battery module <NUM>.

<FIG> is a perspective view illustrating the battery module <NUM>.

The battery module <NUM> includes a rectangular parallelepiped case <NUM> and a plurality of the batteries <NUM> accommodated in the case <NUM>.

The battery <NUM> includes a rectangular parallelepiped case body <NUM>, a lid plate <NUM>, terminals <NUM>, <NUM> provided on the lid plate <NUM>, a rupture valve <NUM>, and an electrode body <NUM>. The electrode body <NUM> is formed by stacking a positive electrode plate, a separator and a negative electrode plate, and is accommodated in the case body <NUM>.

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

For example, the positive electrode plate is formed by forming the active material layer on a positive electrode substrate foil that is a plate-like (sheet-like) or elongated strip-like metal foil made of aluminum, an aluminum alloy or the like. The negative electrode plate is, for instance, formed by forming the active material layer on a negative electrode substrate foil that is a plate-like (sheet-like) or elongated strip-like metal foil made of copper, a copper alloy or the like. For example, the separator is a microporous sheet made of a synthetic resin.

The positive active material used for the active material layer of the positive electrode is, for example, a layered oxide represented by Lix(NiaMnbCocMd)O<NUM> (M is a metal element other than Li, Ni, Mn, Co, <NUM> a <NUM>, <NUM> b < <NUM>, <NUM> c < <NUM>, a + b + c + d = <NUM>, <NUM> < x <NUM>, and a, c are not <NUM> at the same time). The positive active material has a layer rock salt-type crystal structure. It is preferable that a satisfies <NUM> a <NUM>. In this case, the transition metal site contains a large amount of Ni.

The positive active material is preferably NCM represented by Lix(NiaCocMnb)O<NUM> with d = <NUM> (a + b + c = <NUM>, a ≥ <NUM>, b > <NUM>, c ≥ <NUM>, <NUM> < x ≤ <NUM>). More preferably a is greater than or equal to <NUM>, and still more preferably a is greater than or equal to <NUM>.

The positive active material may be NCA represented by Lix(NiaCocAld)O<NUM> in which M is Al and b = <NUM> (a + c + d = <NUM>, a ≥ <NUM>, c > <NUM>, d > <NUM>, <NUM> < x ≤ <NUM>). More preferably a is greater than or equal to <NUM>, and still more preferably a is greater than or equal to <NUM>.

In NCM or NCA, the metal other than Li and Ni is not limited to two kinds of metals, but may be made of at least three kinds of metals. For example, a small amount of Ti, Nb, B, W, Zr, Ti, or Mg may be contained.

Examples of the positive active material include Li-excess active materials such as a LiMeO<NUM>-Li<NUM>MnO<NUM> solid solution, a Li<NUM>OLiMeO<NUM> solid solution, a Li<NUM>NbO<NUM>-LiMeO<NUM> solid solution, a Li<NUM>WO<NUM>-LiMeO<NUM> solid solution, a Li<NUM>TeO<NUM>-LiMeO<NUM> solid solution, a Li<NUM>SbO<NUM>-LiFeO<NUM> solid solution, a Li<NUM>RuO<NUM>-LiMeO<NUM> solid solution, and a Li<NUM>RuO<NUM>-Li<NUM>MeO<NUM> solid solution.

The case of using NCM in which Ni:Co:Mn is <NUM>:<NUM>:<NUM> as the positive active material will be described below.

Examples of the negative active material used for the negative active material layer include hard carbon, metals such as Si, Sn, Cd, Zn, Al, Bi, Pb, Ge, Ag or alloys thereof, or chalcogenides containing these. SiO can be cited as an example of the chalcogenide.

The adjacent terminals <NUM>, <NUM> of adjacent batteries <NUM> of battery module <NUM> have different polarities, and the terminals <NUM>, <NUM> are electrically connected to each other by a bus bar <NUM>, so that the plurality of batteries <NUM> are connected in series.

Leads <NUM>, <NUM> that extract the power are provided at the terminals <NUM>, <NUM> of the batteries <NUM> at both ends of the battery module <NUM> having different polarities.

<FIG> is a block diagram illustrating a configuration of the BMU <NUM>. The BMU <NUM> includes a controller <NUM>, a storage <NUM>, an input unit <NUM>, and an interface unit <NUM>. These units are communicably connected to each other through a bus. In the embodiment, the controller <NUM> functions as a first acquisition unit, a second acquisition unit, an identification unit, a first determination unit, and a second determination unit.

The input unit <NUM> receives inputs of detection results from the voltage sensor <NUM>, the current sensor <NUM>, and the temperature sensor <NUM>. The interface unit <NUM> includes, for example, a LAN interface and a USB interface, and communicates with other devices such as the control device <NUM> in a wired or wireless manner.

The storage <NUM> includes, for example, a hard disk drive (HDD), and stores various programs and data. For example, the storage <NUM> stores an estimation program <NUM> executing a degradation estimation processing described later. The estimation program <NUM> is provided while stored in a computer-readable recording medium <NUM> such as a CD-ROM, DVD-ROM, and USB memory, and is stored in the storage <NUM> by installing the estimation program <NUM> in the BMU <NUM>. Alternatively, the estimation program <NUM> may be acquired from an external computer (not illustrated) connected to a communication network, and stored in the storage <NUM>.

The storage <NUM> also stores charge-discharge history data <NUM>. The history of the charge-discharge is an operation history of the battery module <NUM>, and is information including information indicating a period (use period) during which the battery module <NUM> performs the charge or the discharge, information about the charge or the discharge performed by the battery module <NUM> during the use period, and the like. The information indicating the use period of the battery module <NUM> is information including the start and end points of the charge or the discharge, an accumulated service period in which the battery module <NUM> is used, and the like. The information about the charge or the discharge performed by the battery module <NUM> is information indicating the voltage, the rate, and the like during the charge or the discharge performed by the battery module <NUM>.

The storage <NUM> also stores a degradation coefficient table <NUM> that stores the degradation coefficients kr obtained by previous experiments for each of a plurality of ΔSOC and SOC ranges in each rate and temperature. The degradation coefficient table <NUM> may be updated by a conventional method as appropriate. The degradation coefficient table <NUM> is not limited to the case where the degradation coefficient table is stored for each rate and temperature. Instead of the SOC range, the degradation coefficient kr may be stored by associating the SOC at the start time point, the end time point, or the center time point of the charge-discharge with the ΔSOC.

The storage <NUM> also stores the above-described time dependent degradation coefficient kc and the degradation coefficient kf during the floating for each rate and temperature. The time dependent degradation coefficient kc and the degradation coefficient kf during the floating may be constant values.

The controller <NUM> includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like, and controls the operation of the BMU <NUM> by executing a computer program such as the estimation program <NUM> read from the storage <NUM>. The controller <NUM> functions as a processing unit that executes degradation estimation processing by reading and executing the estimation program <NUM>.

<FIG> is a flowchart illustrating a processing procedure of the BMU <NUM>, the estimating device, estimating the degradation of the energy storage device.

The controller <NUM> acquires the current I and the voltage V (S1).

The controller <NUM> calculates the SOC (S2). For example, the controller <NUM> calculates the SOC based on the acquired V and the SOC-OCV curve.

The controller <NUM> determines whether the SOC in the previous state is stored (S3).

When determining that the SOC of the previous state is stored (YES in S3), the controller <NUM> calculates the ΔSOC (dS) of the current state (S4). For example, the controller <NUM> calculates ΔSOC (dS) from the current I and the elapsed time. When the SOC in the previous state is stored, a difference between the SOC in the current state and the SOC in the previous state is calculated.

The controller <NUM> determines whether <NUM> < dS/dt < Iε is satisfied (S5). dS/dt corresponds to I. Iε is a current threshold determining whether the floating state is established. When the controller <NUM> determines that <NUM> < dS/dt < If is satisfied (YES in S5), the processing proceeds to S15.

When determining that <NUM> < dS/dt < Iε is not satisfied (NO in S5), namely, when determining that the current state is the state in which the charge is performed with the current I greater than or equal to Iε, the state in which the discharge is performed (dS/dt < <NUM>), or the state of the leaving (dS/dt = <NUM>), the controller <NUM> calculates Dcal (S6). The controller <NUM> calculates Dcal by the equation (<NUM>) using the time dependent degradation coefficient kc stored in the storage <NUM>.

The controller <NUM> determines whether the ΔSOC (dS<NUM>) in the previous state is stored (S7). When determining that dS<NUM> is not stored (NO in S7), the controller <NUM> advances the processing to S18.

When determining that dS<NUM> is stored (YES in S7), the controller <NUM> determines whether dS × dS<NUM> is less than or equal to <NUM> (S8). When determining that dS × dS<NUM> is less than or equal to <NUM> (YES in S8:), the controller <NUM> determines whether dS<NUM> is not <NUM> (S9). When determining that dS<NUM> is not <NUM> (YES in S9), namely, when determining that switching from the charge to the discharge, from the discharge to the charge, or from the charge-discharge to the leaving is performed, the controller <NUM> acquires the SOC at the start of the charge or the discharge and at the end of the charge or the discharge(S10). The SOC at the end corresponds to the SOC calculated in S2.

When the SOCs at current sampling time t<NUM>, previous sampling time t<NUM>, and sampling time t<NUM> before the previous sampling time are set to SOC<NUM>, SOC<NUM>, and SOC<NUM>, dS = ΔSOC<NUM> = SOC<NUM> -SOC<NUM>, and dS<NUM> = ΔSOC<NUM> = SOC<NUM> - SOC<NUM>. In the case of the charge, the ΔSOC is a positive value, and in the case of the discharge, the ΔSOC is a negative value. Thus, when dS × dS<NUM> is negative, it can be determined that the switching from the charge to the discharge or from the discharge to the charge is performed. In the case of dS = <NUM>, it can be determined that the charge-discharge is switched to the leaving.

When the controller <NUM> determines that dS<NUM> is <NUM> (NO in S9), namely, when the controller <NUM> determines that the leaving is continued or the leaving is switched to the charge-discharge, the processing proceeds to S14.

The controller <NUM> calculates the ΔSOC of the difference between the start and the end in the charge or the discharge (S11).

The controller <NUM> reads a degradation coefficient table <NUM>, and identifies the degradation coefficient kr as described above based on the SOC range from the start to the end and the minimum ΔSOC (S12).

Using the identified degradation coefficient kr and the charge-discharge time t, the controller <NUM> calculates Dcyc from Dcyc = kr × ΔSOC in the equation (<NUM>) (S13).

When the controller <NUM> determines that dS × dS<NUM> is not less than or equal to <NUM> (NO in S8), namely, when the controller <NUM> determines that the charge-discharge is continuous, the processing proceeds to S18.

The controller <NUM> calculates the degradation amount D (S14). When the current state is the charge or discharge state, the degradation amount D is calculated from D = Deal + Dcyc of the equation (<NUM>). When the current state is the leaving state, the degradation amount D is calculated by D = Deal of the equation (<NUM>).

When determining that <NUM> < dS/dt < Iε is satisfied (YES in S5), the controller <NUM> calculates Dflt (S15).

The controller <NUM> determines whether dS<NUM>/dt ≥ If or dS<NUM>/dt < <NUM> is satisfied (S16).

When the controller <NUM> determines that dS<NUM>/dt ≥ If or dS<NUM>/dt < <NUM> is satisfied (YES in S16), namely, when the controller <NUM> determines that the charge-discharge is switched to the floating, the processing proceeds to S10, and the degradation amount D is calculated by D = Deal + Dcyc + Dflt in the equation (<NUM>) in S14.

When the controller <NUM> determines that dS<NUM>/dt ≥ If or dS<NUM>/dt < <NUM> is not satisfied (NO in S16), namely, when the controller <NUM> determines that the floating is continues or the leaving is switched to the floating, the processing proceeds to S14, and the degradation amount D is calculated from D = Dcal + Dflt of the equation (<NUM>).

The controller <NUM> updates the start SOC (S17).

The controller <NUM> updates the SOC in the current state to the SOC in the previous state (S18), and ends the processing.

<FIG> is a flowchart illustrating another processing procedure of the BMU <NUM> estimating the degradation of the energy storage device.

The controller <NUM> acquires the current I and the voltage V (S21).

The controller <NUM> calculates the SOC (S22).

The controller <NUM> determines whether <NUM> < I < If (S23). If is a current threshold determining whether the floating state is established. When the controller <NUM> determines that <NUM> < I < If (YES in S23), the processing proceeds to S33.

When determining that <NUM> < I < Iε is not satisfied (NO in S23), namely, when determining that the current state is the state in which the charge is performed with the current I greater than or equal to Iε, the state in which the discharge is performed (I < <NUM>), or the state in which the battery is left (I = <NUM>), the controller <NUM> calculates Dcal (S24). The controller <NUM> calculates Dcal by the equation (<NUM>) using the time dependent degradation coefficient kc stored in the storage <NUM>.

The controller <NUM> determines whether I<NUM> of the previous state is stored (S25). When the controller <NUM> determines that I<NUM> is not stored (NO in S25), the processing proceeds to S35.

When determining that I<NUM> is stored (YES in S25), the controller <NUM> determines whether I × I<NUM> is less than or equal to <NUM> (S26). When determining that I × I<NUM> is less than or equal to <NUM> (YES in S26), the controller <NUM> determines whether I<NUM> is not <NUM> (S27). When determining that I<NUM> is not <NUM> (YES in S27), and when determining that the switching is performed from the charge to the discharge, the discharge to the charge, or the charge-discharge to the leaving, the controller <NUM> acquires the SOC at the start of the charge or the discharge and at the end of the charge or the discharge (S28).

In the case of the charge, the current is a positive value, and in the case of the discharge, the current is a negative value. Thus, when I × I<NUM> is negative, it can be determined that the switching is performed from the charge to the discharge or from the discharge to the charge. In the case of I = <NUM>, it can be determined that the charge-discharge is switched to the leaving.

When the controller <NUM> determines that I<NUM> is <NUM> (NO in S27), namely, when the controller <NUM> determines that the leaving is continued or the leaving is switched to the charge-discharge, the processing proceeds to S32.

The controller <NUM> calculates ΔSOC of a difference between a start time and an end time in the charge or the discharge (S29).

The controller <NUM> reads the degradation coefficient table <NUM>, and identifies the degradation coefficient kr as described above based on the SOC range from the start to the end and the minimum ΔSOC (S30).

The controller <NUM> calculates Dcyc by the equation (<NUM>) using the identified degradation coefficient kr and the charge-discharge time t (S31).

When the controller <NUM> determines that I × I<NUM> is not less than or equal to zero (NO in S26), namely, when the controller <NUM> determines that the charge-discharge is continuous, the processing proceeds to S36.

The controller <NUM> calculates the degradation amount D (S32). When the current state is the charge or discharge state, the degradation amount D is calculated from D = Deal + Dcyc of the equation (<NUM>). When the current state is the leaving state, the degradation amount D is calculated by D = Deal of the equation (<NUM>).

When determining that <NUM> < I < If (YES in S23), the controller <NUM> calculates Dflt (S33).

The controller <NUM> determines whether I<NUM> ≥ Iε or I<NUM> < <NUM> is satisfied (S34).

When determining that I<NUM> ≥ Iε or I<NUM> < <NUM> (YES in S34), namely, when determining that the previous state is the charge state or the discharge state, the controller <NUM> advances the processing to S28, and the degradation amount D is calculated by D = Deal + Dcyc + Dflt of the equation (<NUM>) in S32.

When determining that I<NUM> ≥ Iε or I<NUM> < <NUM> is not satisfied (NO in S34), namely, when determining that <NUM> < I<NUM> < Iε is satisfied, the controller <NUM> advances the processing to S32, and calculates the degradation amount D by D = Dcal + Dflt of the equation (<NUM>).

The controller <NUM> updates the start SOC (S35).

The controller <NUM> updates the current I to I<NUM> (S36), and ends the processing.

In the flowchart of <FIG>, the power is used instead of the current, and the degradation amount can be calculated in the same manner as the case of the current.

In the embodiment, the degradation coefficient kr corresponding to the degradation coefficient kr stored in the storage <NUM> is identified based on the SOC range from the start to the end of the continuous charge-discharge and the ΔSOC at the start and the end, and the degradation of the battery module <NUM> is estimated. The degradation is estimated by batch processing using the degradation coefficient kr corresponding to the ΔSOC and the SOC range each time of the charge and the discharge. Even for a complicated charge-discharge pattern in which the charge-discharge is frequently switched, the degradation of the battery module <NUM> can be accurately estimated.

<FIG> is a graph illustrating a result of obtaining the degradation amount by the processing of the flowchart in <FIG> while the SOC ranges (start to end) are changed. The vertical axis represents a capacity degradation rate (%) as the degradation amount.

<FIG> is a graph illustrating the result of obtaining the relationship between the number of test days and the capacity degradation rate when the energy storage device for the wind power generation facility is simulated at the temperature of <NUM> and the rate of <NUM>/3C to perform the charge-discharge of the battery module <NUM>. The horizontal axis represents the number of test days (day), and the vertical axis represents the capacity degradation rate (%). A graph of an actual measurement value, a graph of a comparative example in which the degradation amount is calculated by the conventional estimation method, and a graph of an example in which the degradation amount is calculated by the estimation method of the embodiment are illustrated in <FIG>.

<FIG> are graphs illustrating the results of obtaining the relationship between the number of test days and the capacity degradation rate at the rate of <NUM>/3C in the same manner as in <FIG> except that the temperature is changed to <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

From <FIG>, it can be seen that the accuracy of the estimation is improved in the example as compared with the comparative example.

From the above, it is checked that for the example even in the case of having a plurality of charge-discharge patterns as in the energy storage device used in the wind power generation equipment, the degradation amount can be calculated every time of the charge and the discharge, and the degradation can be well estimated. In consideration of the degradation derived from the active materials of the positive electrode and the negative electrode and the averaging effect, it is possible to accurately estimate the degradation corresponding to the frequent change in charge-discharge, and it is possible to accurately determine the number of energy storage devices replaced after a predetermined period. Resource saving and cost reduction can also be achieved.

The above embodiment is not restrictive. The scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the claims.

For example, the estimation device of the present invention is not limited to the charge-discharge system for wind power generation, but can also be applied to other charge-discharge systems such as an in-vehicle regenerative power storage device, a railway regenerative power storage device, and a solar power generation system.

Claim 1:
An estimation device (<NUM>, <NUM>, <NUM>) comprising:
a first acquisition unit that is configured to acquire SOCs at a start and an end in charge, discharge, or floating charge of an energy storage device (<NUM>, <NUM>);
a storage (<NUM>) that is configured to store a plurality of degradation coefficients corresponding to a plurality of SOC ranges;
an identification unit that is configured to identify a corresponding degradation coefficient from the plurality of degradation coefficients stored in the storage based on the SOCs at the start and the end acquired by the first acquisition unit; and
an estimation unit that is configured to estimate degradation of the energy storage device (<NUM>, <NUM>) based on the degradation coefficient identified by the identification unit;
characterized in that
the storage (<NUM>) is configured to store the plurality of degradation coefficients corresponding to the plurality of SOC ranges obtained by dividing SOCs of <NUM> to <NUM>% at different intervals, and
the identification unit is configured to identify the degradation coefficient of an SOC range including the SOCs at the start and end acquired by the first acquisition unit and having a smallest range width in the plurality of SOC ranges.