JP2016166864A - Power storage element managing device, power storage element management method, power storage element module, power storage element management program, and moving body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely acquire SOC of a power storage element.SOLUTION: A current integration method for determining SOC of a power storage element by integration of current flowing through the power storage element with time, and an OCV method for determining SOC based on a V-SOC correlation relationship between voltage and a charged state of the power storage element can be executed. A predetermined value in a second SOC area is adopted as an SOC estimation value when a first SOC area, namely an SOC area with which SOC determined by the current integration method belongs, and the second SOC area, namely an SOC area with which SOC determined by the OCV method belongs mutually differ when the V-SOC correlation relationship is divided into a plurality of SOC areas. The predetermined value is set between a boundary value at a side close to the first SOC area from among boundary values for dividing the second SOC area and a middle value of the second SOC area.SELECTED DRAWING: Figure 4

Description

  The technology disclosed in this specification relates to a technology for acquiring a state of charge (SOC) of a storage element such as a lithium ion battery.

  2. Description of the Related Art Conventionally, there is a current integration method as an example of a method for estimating SOC at an arbitrary time point in a storage element such as a secondary battery that is used while being repeatedly charged and discharged. In this method, the amount of electric power entering and exiting the battery is measured by constantly measuring the charge / discharge current of the battery, and the SOC is determined by adjusting this from the initial capacity. This method has the advantage that the SOC can be estimated even when the battery is in use. However, on the other hand, since current is always measured and charge / discharge electric energy is integrated, there is a disadvantage that measurement errors of a current sensor and the like accumulate and become gradually inaccurate.

  In view of this, for example, an OCV method that uses an SOC determination method based on an open circuit voltage (OCV) of a battery has been developed. This is based on the fact that there is a relatively accurate correlation between the OCV and the SOC when no current is flowing through the battery, and the battery voltage when the current is not flowing through the battery, that is, the open circuit voltage. The SOC corresponding to the measured OCV is obtained by referring to the correlation between the measured and stored OCV and SOC, and the SOC estimated by the current integration method is corrected. Thereby, since the accumulation of errors can be cut off, the accuracy of SOC estimation by the current integration method can be increased.

  Incidentally, in recent years, lithium ion batteries using lithium iron phosphate as a positive electrode active material have attracted attention. In this type of lithium ion battery, as shown in FIG. 1, for example, there is a flat region (voltage flat region) in which the OCV hardly changes even though the SOC changes in a wide range. Are known. This means that with this type of lithium ion battery, it is difficult to improve the SOC estimation error even by the OCV method.

  That is, for example, in the case of a lithium ion battery having OCV-SOC characteristics as shown in FIG. 1, when the OCV is about 3.33 V indicating that it is a voltage flat region, the SOC is approximately 15% to 95%. It can only be said that there is crab. For this reason, in this type of battery, the SOC correction by the OCV can be performed only in the voltage gradient region where the OCV has a certain inclination in the OCV-SOC characteristics, and the frequency of the SOC correction by the OCV is reduced. As a result, there is a limit to improving the accuracy of SOC estimation.

  Such an SOC estimation error may cause an undesired situation of lack of power, particularly in an electric vehicle using a battery as a drive source.

  On the other hand, for example, in the technology disclosed in Japanese Patent Application Laid-Open No. 2010-266221, when it is detected by charging that the SOC has changed from a position lower than the lower limit value of the voltage flat area to the voltage flat area. , SOC is reset to the lower limit value of the voltage flat region.

JP 2010-266221 A

  However, the technique disclosed in Japanese Patent Application Laid-Open No. 2010-266221 captures the timing when the battery is discharged to a considerable extent and the SOC changes into the voltage flat region from a position lower than the lower limit value of the voltage flat region. Therefore, the frequency is not necessarily high, and there is a limit to improving accuracy.

  In the present specification, a technique capable of accurately obtaining the SOC of a power storage element is disclosed.

  A storage element management method according to a technique disclosed in this specification is a method for determining an estimated SOC value that is a value indicating a charge state of a storage element, and determines the SOC of the storage element by different methods. The first and second SOC determination methods can be executed, and when the V-SOC correlation between the voltage of the power storage element and the charge state is divided into a plurality of SOC regions, the first SOC determination method If the first SOC region, which is the SOC region to which the SOC determined by the above, belongs, and the second SOC region, which is the SOC region to which the SOC determined by the second SOC determination method, are different from each other, the predetermined value is It is adopted as an estimated SOC value, and the predetermined value is a value close to a boundary value closer to the first SOC region among boundary values dividing the second SOC region. It has characterized in that is set to a value between the intermediate value of the second SOC region and the boundary value.

  Further, the storage element management device according to the technology disclosed in the present specification outputs an estimated SOC value that is a value indicating the charge state of the storage element, and determines the SOC of the storage element by different methods. And an information processing unit capable of executing each of the first and second SOC determination methods, wherein the information processing unit divides the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC regions. Sometimes, a first SOC region that is an SOC region to which the SOC determined by the first SOC determination method belongs, and a second SOC region that is an SOC region to which the SOC determined by the second SOC determination method belongs, Are different from each other, a predetermined value is adopted as the SOC estimated value, and the predetermined value is the first SOC area among the boundary values that divide the second SOC area. Characterized in place are set to a value between the intermediate values of close values or the second SOC region and the boundary value near side of the boundary value.

  The first SOC determination method is a method for determining the SOC of the power storage element using data obtained by measuring the current flowing through the power storage element, and the second SOC determination method is a method for determining the voltage of the power storage element. When the measured data is used to determine the SOC of the electricity storage element, the voltage measurement data is obtained while taking advantage of the timeliness of the first SOC determination method using the measured current data. There is an advantage that the accuracy can be improved with reference to the value obtained by the second SOC determination method used.

  In addition, when the first SOC region and the second SOC region are the same, it is preferable that the SOC determined based on the current integration method is adopted as the SOC estimated value. Further, one of the SOC regions is more preferably a region in which the voltage of the power storage element corresponds to a voltage flat region in which a change in voltage with respect to a change in SOC in the V-SOC correlation is smaller than the others. .

  Note that the technology disclosed in this specification can be realized as a power storage element management device, a power storage element management method, and a power storage element module, a moving body, or a program in which these devices or methods are mounted.

  According to the technique of this specification, it is possible to suppress the estimation error of the SOC of the storage element because the SOC obtained by the two methods is referred to.

The graph which shows an example of the OCV-SOC characteristic of a lithium ion battery The graph which shows the example of the OCV-SOC characteristic of the lithium ion battery which concerns on this embodiment The block diagram which shows the structure of the battery module of one Embodiment. The flowchart figure which shows the flow of a SOC determination sequence

(Outline of this embodiment)
First, an outline of the storage element management method and apparatus of the present embodiment will be described. The present technology determines an SOC estimated value that is a value indicating a charging state of a storage element such as a lithium ion battery, for example. The current sensor detects a current flowing through the storage element, and a current flows through the storage element. And a voltage sensor for detecting a voltage when a minute current is flowing. The power storage element is mounted on a moving body such as a vehicle, a train, a ship, and an aircraft.

  On the other hand, some types of power storage elements have a relatively high reproducibility correlation between the voltage (V) and the state of charge (SOC), such as a lithium ion battery. Therefore, the correlation of such a storage element is previously stored as a V-SOC correlation and stored in a memory. For example, an information processing unit including a CPU and a memory that stores a required operation program is provided, and the information processing unit obtains the charge / discharge power amount by time integration of the current detected by the current sensor. The current integration method for determining the SOC and the OCV method for determining the SOC based on the V-SOC correlation from the detection result of the voltage sensor can be executed.

Then, the estimated SOC value is determined depending on the relationship between the SOCs determined by the respective methods. In this case, the V-SOC correlation is divided into a plurality of SOC regions in advance, and it is determined to which SOC region each SOC determined by the current integration method and the OCV method belongs. Depending on whether they are the same or different, the estimated SOC value is determined as follows. (1) That is, the SOC region to which the SOC determined by the current integration method belongs (this is referred to as “first SOC region”) and the SOC region to which the SOC determined by the OCV method belongs (this is referred to as “second SOC region”). ”), The SOC determined based on the current integration method is adopted as the estimated SOC value.
(2) When the first SOC region and the second SOC region are different from each other, a predetermined one of the second SOC regions (regions to which the SOC acquired based on the OCV method belongs) The predetermined value is adopted as the estimated SOC value, and the predetermined value is a boundary value that is close to the first SOC region among boundary values that divide the second SOC region, and an intermediate value between the second SOC region and the second SOC region. And set between.

  For example, as the SOC that can be taken by the power storage element, there is an SOC region 1 in which the change in voltage (V) with respect to the SOC change is larger than a predetermined value from the region where the SOC is small to the large region, and then the voltage (V ) Change in the SOC region 2 (voltage flat region) smaller than the predetermined value, and there is an SOC region 3 in which the voltage (V) change relative to the SOC change is larger than the predetermined value, the current integration method Table 1 shows how the determined SOC (hereinafter referred to as SOC (I)) and the SOC determined by the OCV method (hereinafter referred to as SOC (V)) belong to each region. As shown in Fig. 9, there are nine ways of embodiment 1 to embodiment 9.

上述のＳＯＣ推定値の決定方法によれば、次のような利点が得られる。
態様１，５，９のように、電流積算法により得られるＳＯＣ(I)が属する領域（第一ＳＯＣ領域）とＯＣＶ法により得られるＳＯＣ(V)が属する領域（第二ＳＯＣ領域）とが同一である場合には、ＳＯＣ(I)の値に信頼を置くことができるから、ＳＯＣ(I)をそのままＳＯＣ推定値として採用してＯＣＶによるＳＯＣの修正は行わない。 In each of these aspects, according to the above conditions (1) and (2), the adopted SOC estimated value is as described in the “employed SOC estimated value” column at the right end of Table 1. here,
“SOC (I)” indicates SOC determined based on the current integration method.
“Region 1 upper half value” is a predetermined value between the SOC belonging to SOC region 1 and the upper limit value which is the boundary value on the region 2 side to which SOC (I) belongs from the intermediate SOC (intermediate value) of that region. Means that.
The “region 2 lower half value” is a predetermined value between the SOC (intermediate value) of the SOC belonging to the SOC region 2 and the lower limit value which is the boundary value on the region 1 side to which SOC (I) belongs. It means that.
The “region 2 upper half value” is a predetermined value between the SOC (intermediate value) of the SOC belonging to the SOC region 2 and the lower limit value that is the boundary value on the region 3 side to which the SOC (I) belongs. It means that.
The “region 3 lower half value” is a value between the SOC (intermediate value) of the SOC belonging to the SOC region 3 and the lower limit value that is a boundary value on the region 2 side to which the SOC (I) belongs. It means a predetermined value.

According to the method for determining the estimated SOC value, the following advantages are obtained.
As in Embodiments 1, 5, and 9, there are a region to which SOC (I) obtained by the current integration method belongs (first SOC region) and a region to which SOC (V) obtained by the OCV method belongs (second SOC region). If they are the same, the value of SOC (I) can be relied on, so SOC (I) is directly adopted as the estimated SOC value and the SOC is not corrected by the OCV.

  As in modes 2 and 3, the region to which SOC (V) belongs (second SOC region) is SOC region 1, but the region to which SOC (I) belongs (first SOC region) is different from SOC region 1 In the case of (SOC region 2 or region 3), there is a high possibility that errors are accumulated in the calculation by the current integration method. Therefore, in this case, an upper limit value that is a boundary value on the side of the region 2 or region 3 that is the first SOC region to which the SOC (I) belongs from the intermediate SOC (intermediate value) of the SOC region 1 that is the second SOC region. The SOC is corrected by OCV at a predetermined value (region 1 upper half value) in between to eliminate the accumulated error. The reason for correcting in this way is that the SOCV is present in the SOC region 1 by the OCV method, and that the SOC is larger than that by the current integration method. This is because if the value is the upper half value of the SOC region 1, it is considered to be closest to the true value. The upper half value of the region I is preferably an upper limit value or a value close thereto.

  On the other hand, as in aspect 4, the region to which SOC (V) belongs (second SOC region) is SOC region 2 while the region to which SOC (I) belongs (first SOC region) is SOC region 1. There is a high possibility that errors are accumulated in the calculation by the current integration method. Therefore, in this case, out of the SOCs belonging to the SOC region 2 which is the second SOC region, the lower limit value which is the boundary value on the SOC region 2 side to which the SOC (I) belongs from the intermediate SOC (intermediate value) of that region. The SOC is corrected by the OCV at a predetermined value (region 2 lower half value) between them, and the accumulated error can be eliminated.

  Conversely, as in the aspect 6, the second SOC region (the SOC region to which the SOC (V) belongs) is the SOC region 2, but the first SOC region (the SOC region to which the SOC (I) belongs) is the SOC region 3. Even in some cases, there is a high possibility that errors have accumulated in the calculation by the current integration method. Therefore, in this case, the boundary value from the middle SOC (intermediate value) to the first SOC region (SOC region 3 to which SOC (I) belongs) of the SOCs belonging to the second SOC region (SOC region 2). The SOC is corrected by the OCV with a predetermined value (region 2 upper half value) between the upper limit value and the accumulated error is eliminated.

  And, as in aspects 7 and 8, when the second SOC region to which the SOC (V) belongs is the SOC region 3, the first SOC region to which the SOC (I) belongs is the SOC region 1 or the region 2, There is a high possibility that errors have accumulated in the calculation by the current integration method. Therefore, in this case, of the SOCs belonging to the SOC region 3 that is the second SOC region, the lower limit value that is the boundary value on the side of the SOC region 1 or 2 that is the first SOC region from the intermediate SOC (intermediate value) of that region The SOC is corrected by the OCV at a predetermined value between the two (region 3 lower half value) to eliminate the accumulated error. The reason for correcting in this way is that SOC is present in the SOC region 3 by the OCV method, and that the SOC is smaller than that by the current integration method. This is because if the value is the lower half value of the SOC region 3, it is considered that the value is closest to the true value. The lower half value of region 3 is preferably a lower limit value or a value close thereto.

Thus, while determining the SOC based on the current integration type SOC determination process, the value can be corrected with high frequency by the reset process when the SOC regions to which the SOC (I) and the SOC (V) belong are different. Therefore, there is an advantage that the SOC can be determined even when the power storage element is used, and the accumulation of errors, which is a drawback of the current integration method, is prevented, and the accuracy of the estimated SOC value is increased.
In addition, in order to obtain the SOC of a battery having a plateau region with high accuracy by the current integration method, high-speed current integration processing is performed so that current values are not missed while using current measurement means with high measurement accuracy. Are required, but the cost is high to realize them. Further, in order to improve the accuracy of SOC estimation of a battery having a plateau region, a method of calculating dV / dQ and capturing an inflection point in the OCV-SOC characteristic has been proposed, but when implementing this method, In order to capture the inflection point, high-level arithmetic processing and a large-capacity memory are required. To realize this, it is expected that the cost will be high and the verification work will require a lot of time. On the other hand, the present invention is a method for determining whether or not the SOC including the error of the current measuring means is within the SOC range, so that a highly accurate current measuring means is not required and processing is performed. This is also simpler than the means for calculating dV / dQ.

  Since the storage element management device according to the technology disclosed in this specification is suitable for managing storage elements having a voltage flat region in the V-SOC correlation, an iron phosphate-based positive electrode is used as a management target. A lithium ion battery using an active material is exemplified. In particular, it is most suitable when estimating the state of charge of a lithium ion battery of a type having a plurality of voltage flat regions. The presence of a plurality of voltage flat regions means that there is a voltage gradient region between them, and the reset process is frequently performed using the difference between the results of the current integration method and the OCV method. And the accuracy of the estimated SOC value is increased.

(Details of the embodiment)
Hereinafter, an embodiment in which the technology disclosed in this specification is applied to a battery module for driving an electric vehicle such as EV, HEV, and PHEV will be described in detail with reference to FIGS. 2 to 4.

  As shown in FIG. 3, the battery module of the present embodiment includes a plurality of secondary batteries 30 connected in series, a battery manager (hereinafter referred to as BM) 50 that manages these secondary batteries 30, and a secondary battery. A current sensor 40 that detects a current flowing through the current sensor 30; The BM 50 is an example of a “storage element management device”.

  The secondary battery 30 is an example of a “storage element”, is charged by a charger (not shown), and supplies DC power to an inverter (shown as a load 10) that drives a motor for driving a vehicle. The secondary battery 30 is a lithium ion battery using, for example, a negative electrode active material made of graphite material and an iron phosphate-based positive electrode active material such as LiFePO 4, for example, an open circuit voltage (OCV) and a charged state (SOC). 2) is the correlation shown here (referred to herein as the “V-SOC correlation”). In this V-SOC correlation, the state of charge of the secondary battery 30 is divided into the following five regions.

Area SOC range area I Less than 30% area II 30% to less than 66% area III 66% to less than 68% area IV 68% to less than 95% area V 95% or more Three of these areas I, III, At V, the OCV curve of the battery corresponding to the SOC has a certain upward slope, that is, the change in voltage (OCV) is relatively large with respect to the change in the state of charge (SOC), and is equal to or greater than a predetermined value. . Therefore, these are referred to as “voltage gradient regions” I, III, and V.

  On the other hand, in the regions (regions II and IV) other than the voltage gradient regions I, III, and V described above, the slope of the OCV curve of the battery corresponding to the SOC is extremely small, that is, the state of charge (SOC) changes. On the other hand, the change in voltage (OCV) is not more than the predetermined value. Therefore, these regions are referred to as “voltage flat regions” II and IV.

  The BM 50 includes a control unit 60, a voltage measurement unit 70, and a current measurement unit 80. The control unit 60 includes a central processing unit (hereinafter referred to as CPU) 61 as an information processing unit and a memory 63. Various programs for controlling the operation of the BM 50 are stored in the memory 63, and the CPU 61 performs “current integration type SOC determination processing” and “voltage reference type SOC determination processing, which will be described later, according to the program read from the memory 63. ”,“ First reset process ”,“ second reset process ”,“ third reset process ”and the like are executed. Further, in the memory 63, data necessary for executing the above SOC determination sequence, for example, the V-SOC correlation tabulated for the secondary battery 30, the upper limit value and the lower limit value of the state of charge of each region I to V, The state of charge as the initial value of the secondary battery 30 is stored.

  The voltage measuring unit 70 is connected to both ends of the secondary battery 30 via the voltage detection line, and functions to measure the voltage V [V] of each secondary battery 30 every predetermined period. The current measuring unit 80 has a function of measuring a current flowing through the secondary battery 30 via the current sensor 40.

  Now, an SOC determination sequence for determining the SOC of the secondary battery 30 will be described with reference to FIG. The SOC determination sequence is started, for example, when the BM 50 receives an execution command from an in-vehicle ECU (not shown), and after the start, a series of steps shown in FIG. Is done.

  When the SOC determination sequence starts, first, a process of measuring the voltage of each secondary battery 30 is executed by the voltage measuring unit 70 in accordance with an instruction from the control unit 60 (S1). Next, the control unit 60 gives a command to the current measurement unit 70 and performs a process of measuring the current flowing through the secondary battery 30 by the current sensor 40 (S2). The voltage value measured in S <b> 1 and the current value measured in S <b> 2 are converted into digital values and stored in the memory 63.

  Thereafter, the process proceeds to S3, and the control unit 60 multiplies the current value I measured in S2 by the specified period T to obtain the current integrated value ZI as shown in the following equations (1) and (2). calculate. Further, a new remaining capacity W3 of the secondary battery 30 is calculated by adding or subtracting the calculated current integrated value ZI to the remaining capacity W3 at that time according to the direction of the current. That is, each time the SOC determination sequence is performed once, the value of the remaining capacity W3 is updated by adding / subtracting the current integrated value ZI to the remaining capacity (previous value) W3.

ZI = I × T (1)
W3 = W3 + ZI (2)
Thereafter, the process proceeds to S4, where it is determined whether or not current is flowing through the secondary battery 30. At this point, when the secondary battery 30 is being charged or discharged and current is flowing. Since the current value exceeds the determination reference value, NO is determined in S4. If NO is determined in S4, the process proceeds to S5. In S <b> 5, a process for estimating the SOC of the secondary battery 30 by the current integration method is executed by the control unit 60. Specifically, as shown in the following equation (3), the SOC value is obtained by dividing the remaining capacity W3 calculated in S3 by the full charge capacity W4 stored in the memory 63.

SOC = W3 / W4 (3)
The process through S1, S2, S3, and S5 corresponds to a process of determining the charge state of the secondary battery 30 by obtaining the charge / discharge power amount by time integration of current. Hereinafter, the SOC having the specific value determined in S5 is referred to as SOC (i).

  And the process for one period is complete | finished with the completion of the process of S5. Thereafter, the SOC determination sequence is repeatedly executed at a specified period T. During the period in which the secondary battery 30 is continuously discharged or charged, the processes of S1 to S5 are repeated at the specified period T, and the voltage value V, current value I, and remaining capacity W3 of the secondary battery 30 are determined. Is updated each time (S1 to S3), and the SOC is also calculated each time using the current integration method (S5).

  If the current I flowing through the secondary battery 30 becomes smaller than a predetermined value (a value at which the current can be regarded as substantially zero) due to completion of charging or discharging of the secondary battery 30, a YES determination is made in S4, and the process proceeds to S6. To do. In S6, a process of counting the elapsed time after the current stops flowing in the secondary battery 30 is executed.

  Thereafter, the process proceeds to S <b> 7, and a process for determining whether or not a stable time (a predetermined time set in advance) has elapsed is executed by the control unit 60. The stabilization time is a time for waiting for the OCV (open circuit voltage) of the secondary battery 30 to stabilize. When the elapsed time measured in S7 becomes the stabilization time, YES is determined in S7, and the process proceeds to S8. Transition.

  In S <b> 8, processing for determining the SOC of the secondary battery 30 based on the OCV method is executed by the control unit 60. Specifically, first, a process of measuring the OCV (open voltage in a state where no current flows) of the secondary battery 30 is executed by the voltage measurement unit 70. Then, the SOC is determined by referring to the measured OCV and the correlation characteristic of V-OCV shown in FIG. This S8 corresponds to processing for determining the state of charge based on the V-SOC correlation from the detection result of the voltage sensor. Hereinafter, the SOC having the specific value determined in S8 is referred to as SOC (v).

  Thereafter, the process proceeds to S9, and it is determined which of the regions I to V the SOC (v) value belongs to. Here, when it is determined that the SOC (v) belongs to any one of the voltage gradient regions I, III, and V, the process proceeds to S10 and the SOC (i obtained by the above-described current integration type SOC determination process is obtained. ) Is replaced with the SOC (v) determined by the voltage reference type SOC determination process of S8. In the voltage gradient regions I, III, and V, since there is a precise correlation between the OCV and the SOC, the SOC (i) acquired by the current integration type SOC determination process in S5 is corrected to a more accurate value. This is because the accuracy in the SOC determination sequence is high.

  On the other hand, if it is determined in S9 that the SOC region (second SOC region) to which the SOC (v) belongs is the voltage flat regions II and IV, this is continued to the SOC region (first first) to which the SOC (i) belongs. It is determined whether or not it coincides with the (SOC region) (S11). Here, if both SOC regions match, that is, if SOC (i) exists between the lower limit value and the upper limit value of the voltage flat region II or IV, correction based on the V-SOC correlation is performed. Without any return. Therefore, the SOC (i) acquired by the current integration type SOC determination process in S5 is used as the SOC. In these voltage flat regions II and IV, because of the flatness in the V-SOC correlation, there is a high possibility that a relatively large error is included in the SOC (v), and the V-SOC correlation is uniform as in the prior art. This is because if the correction is performed based on the relationship, the error increases.

  In S11, the SOC (i) value is larger than the upper limit values of the two voltage flat regions II and IV, although it is determined that the voltage flat regions II and IV are in accordance with the SOC (v). If it is determined, the process proceeds to S12, and the value of SOC (i) is replaced with the upper limit value of those areas (second reset process).

  For example, if the SOC (v) indicates that it is in region II, the original SOC should be in any of 30% to 66% based on the V-SOC correlation, but it cannot be determined which value (If specified, the error may spread.) However, if the SOC (i) is 66% or more, which is the upper limit SOC of the region II, the possibility that the original SOC is around 66% is very high. Therefore, the SOC is corrected to the upper limit value 66% of the region II. If SOC (v) indicates that the region is in the region IV while SOC (i) is 95% or more which is the upper limit SOC of the region IV, the original SOC may be around 95%. Is extremely expensive. Therefore, the SOC is corrected to the upper limit value 95% of the region IV. Thereby, the error included in SOC (i) can be reduced.

  Conversely, in S11, although it is determined that the voltage flat regions II and IV are in accordance with the SOC (v), the value of SOC (i) is lower than the lower limit value of both voltage flat regions II and IV. If it is smaller, the process proceeds to S13, and the value of SOC (i) is replaced with the lower limit value of those areas (third reset process).

  For example, if the SOC (v) indicates that it is in region II, the original SOC should be in any of 30% to 66% based on the V-SOC correlation, but it cannot be determined which value (If specified, the error may spread.) However, if SOC (i) is 30% or less, which is the lower limit SOC of region II, the possibility that the original SOC is around 30% is very high. Therefore, the SOC is corrected to the lower limit value 30% of the region II. Also, if the SOC (v) indicates that it is in the region IV, the original SOC should be in any of 68% to 95% based on the V-SOC correlation. Can't (specifically, the error spreads). However, if SOC (i) is 68% or less, which is the lower limit SOC of region IV, the possibility that the original SOC is around 68% is very high. Therefore, the SOC is corrected to 68% of the lower limit value of the region IV. Thereby, the error included in SOC (i) can be reduced.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) Although the lithium ion secondary battery using the iron phosphate positive electrode active material is illustrated as an example of the power storage element in the above embodiment, the present invention is not limited thereto. It may be a secondary battery other than a lithium ion secondary battery, a capacitor with an electrochemical phenomenon, etc., and is suitable for a battery having a voltage flat region in the V-SOC correlation, and the voltage flat region is in two places. It is not limited to a certain type, but may be a power storage element having only one type of voltage flat region as shown in FIG. 1, or may be a power storage element having three or more types of voltage flat regions. .

  (2) In the above embodiment, the CPU 61 is taken as an example of the control unit 60. The control unit 60 may have a configuration including a plurality of CPUs, a configuration including hardware circuits such as an application specific integrated circuit (ASIC), an MPU, a microcomputer, a programmable PLD, and an FPGA, or a configuration including both hardware circuits and CPUs. . In short, the control unit only needs to execute the SOC determination sequence using software processing or / and a hardware circuit. When the present invention is implemented using software, the software (computer program) is recorded and distributed on a storage medium such as a semiconductor memory, or the computer is connected via a wired or wireless communication line. It can be stored in a storage device.

  (3) In the above embodiment, in determining in which region the charge state of the secondary battery 30 is in the V-SOC correlation in S9, the SOC is obtained from the measured OCV, and in which region. However, if the OCV and the SOC have a unique correspondence, the area may be determined directly from the OCV.

  (4) The method of determining the SOC of the power storage element using the data obtained by measuring the voltage of the power storage element is not limited to the OCV method exemplified in the above embodiment, and the OCV is estimated from charge / discharge I, V and R. And the Kalman method can be adopted. Here, the former refers to a method of calculating the OCV based on the relationship OCV = V−RI based on the internal resistance R of the battery, the terminal voltage V of the battery, and the charge / discharge current I. Also, the Kalman method, for example, as disclosed in JP-T-2004-514249, JP-A-2012-47580, etc., creates an equivalent circuit model of a battery and uses the Kalman filter to model circuit parameters. Is sequentially estimated, and OCV and thus SOC are calculated from the estimated circuit parameters.

  (5) Further, as a method of determining the SOC of the power storage element using data obtained by measuring the current flowing through the power storage element, the current flowing through the power storage element is measured at a constant period, and the measured current value I is multiplied by the period T. In addition to the so-called current integration method in which the combined IT is added to or subtracted from the initial capacity X (Ah) to obtain the SOC, the time integration method can also be adopted when any current value can be considered constant. Here, the time integration method is to measure a time T staying within a predetermined range in which the value of the current flowing through the electric storage element can be regarded as constant, and to calculate a value obtained by multiplying the assumed constant current I by the time T. A method for obtaining the SOC by adjusting the initial capacity X (Ah).

  (6) In the above embodiment, the first SOC region and the second SOC region are the same, that is, the region to which the SOC determined by the current integration method belongs and the region to which the SOC determined by the OCV method belongs are the same. In some cases, the SOC itself determined based on the current integration method is adopted as the SOC estimation value. However, the present invention is not limited to this, and the SOC determined based on the current integration method is not limited to this. For example, a value obtained by correcting according to the SOC determined by the OCV method may be used as the estimated SOC value. Also, which of the SOCs estimated by the first and second SOC determination methods is to be adopted can be determined according to the temperature and current value of the storage element.

  (7) When the SOC of the electricity storage device is estimated using data obtained by measuring the current flowing through the electricity storage device, the estimated SOC value is shifted in the discharge direction when the SOC is less than the lower limit of the assumed SOC range. It is thought that. Therefore, in this case, the accuracy of SOC estimation can be improved by offsetting the current measurement value to the charging side. On the contrary, when the estimated value of SOC exceeds the upper limit of the SOC range, the accuracy of SOC estimation can be improved by offsetting the current measurement value to the discharge side. In addition, even when the current measurement value is offset in this way, it may be determined that the current measurement unit is abnormal when the SOC range does not change.

  (8) In the above embodiment, an example in which a power storage element is mounted on a moving body such as an electric vehicle has been described. However, the power storage element is not limited to that mounted on the mobile body, and is provided in a stationary device. It may be a power storage device. Examples of stationary devices include uninterruptible power supplies installed in factories, homes, and offices, emergency power supplies, or power storage devices connected to the power transmission system for power distribution and power load leveling Can do.

  10: Load, 30: Secondary battery (storage element), 40: Current sensor, 50: Battery manager (storage element management device), 60: Control unit, 61: Information processing unit, 70: Voltage measurement unit

Claims (13)

A method for determining an estimated SOC value, which is a value indicating a state of charge of a storage element,
The first and second SOC determination methods for determining the SOC of the power storage element by different methods can be executed,
When the V-SOC correlation between the voltage of the storage element and the state of charge is divided into a plurality of SOC regions,
The first SOC region that is the SOC region to which the SOC determined by the first SOC determination method belongs and the second SOC region that is the SOC region to which the SOC determined by the second SOC determination method belong to each other If they are different, a predetermined value is adopted as the SOC estimated value,
The predetermined value is a value close to a boundary value closer to the first SOC region, or a value between the boundary value and an intermediate value of the second SOC region, among boundary values dividing the second SOC region. The storage element management method set to 1.   The first SOC determination method is a method of determining the SOC of the power storage element using data obtained by measuring a current flowing through the power storage element, and the second SOC determination method is a method of measuring a voltage of the power storage element. The storage element management method according to claim 1, wherein the storage element management method is a method of determining an SOC of the storage element using the obtained data.   The SOC determined based on the first SOC determination method is used as the estimated SOC value when the first SOC region and the second SOC region are the same. Item 3. The storage element management method according to Item 2.   One of the SOC regions is a region corresponding to a voltage flat region in which the voltage of the power storage element corresponds to a change in voltage with respect to a change in SOC in the V-SOC correlation is smaller than the others. The electrical storage element management method as described in any one of Claims 1 thru | or 3. An information processing unit that outputs an estimated SOC value that is a value indicating a state of charge of a storage element, and that can respectively execute a first SOC determination method and a second SOC determination method that determine the SOC of the storage element by different methods. With
When the information processing unit divides the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC regions,
The first SOC region that is the SOC region to which the SOC determined by the first SOC determination method belongs and the second SOC region that is the SOC region to which the SOC determined by the second SOC determination method belong to each other If they are different, a predetermined value is adopted as the SOC estimated value,
The predetermined value is a value close to a boundary value closer to the first SOC region, or a value between the boundary value and an intermediate value of the second SOC region, among boundary values dividing the second SOC region. The storage element management device set to 1.   The first SOC determination method is a method of determining the SOC of the power storage element using data obtained by measuring a current flowing through the power storage element, and the second SOC determination method is a method of measuring a voltage of the power storage element. The storage element management device according to claim 5, wherein the stored data is used to determine the SOC of the storage element.   The SOC determined based on the first SOC determination method is used as the estimated SOC value when the first SOC region and the second SOC region are the same. Item 7. The storage element management device according to Item 6.   6. One of the SOC regions is a voltage flat region in which the voltage of the power storage element is smaller in voltage change with respect to the change in SOC in the V-SOC correlation. The electrical storage element management apparatus as described in any one of claim | item 7.   The storage element management apparatus according to claim 8, wherein the V-SOC correlation includes information on a plurality of the voltage flat regions.   The power storage element management device according to any one of claims 4 to 10, wherein the power storage element is a lithium ion battery including an iron phosphate-based positive electrode active material. An energy storage device, and an information processing unit capable of respectively executing first and second SOC determination methods for determining the SOC of the energy storage device by different methods,
When the information processing unit divides the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC regions,
The first SOC region that is the SOC region to which the SOC determined by the first SOC determination method belongs and the second SOC region that is the SOC region to which the SOC determined by the second SOC determination method belong to each other If they are different, a predetermined value is adopted as the SOC estimated value,
The predetermined value is a value close to a boundary value closer to the first SOC region, or a value between the boundary value and an intermediate value of the second SOC region, among boundary values dividing the second SOC region. The storage element module set to. A program for causing a computer that controls a storage element to determine an estimated SOC value that is a value indicating a state of charge of the storage element,
The first and second SOC determination methods for determining the SOC of the power storage element by different methods can be executed,
When the V-SOC correlation between the voltage of the storage element and the state of charge is divided into a plurality of SOC regions,
The first SOC region that is the SOC region to which the SOC determined by the first SOC determination method belongs and the second SOC region that is the SOC region to which the SOC determined by the second SOC determination method belong to each other If they are different, a process of adopting a predetermined value as the SOC estimation value is performed,
The predetermined value is a value close to a boundary value closer to the first SOC region, or a value between the boundary value and an intermediate value of the second SOC region, among boundary values dividing the second SOC region. The storage element management program set to. A mobile unit comprising: a storage element; and a storage element management device that outputs an SOC estimated value that is a value indicating a state of charge of the storage element,
The power storage element management device includes information processing units capable of respectively executing first and second SOC determination methods for determining the SOC of the power storage element by different methods.
When the information processing unit divides the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC regions,
The first SOC region that is the SOC region to which the SOC determined by the first SOC determination method belongs and the second SOC region that is the SOC region to which the SOC determined by the second SOC determination method belong to each other If they are different, a predetermined value is adopted as the SOC estimated value,
The predetermined value is a value close to a boundary value closer to the first SOC region, or a value between the boundary value and an intermediate value of the second SOC region, among boundary values dividing the second SOC region. A moving object set to.

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