CN105938181B - Storage element management device, management method, module, recording medium, and moving object - Google Patents

Abstract

The invention provides an electric storage element management device, an electric storage element management method, an electric storage element management program, an electric storage element module, and a mobile body, wherein the SOC of an electric storage element can be acquired with high precision. A current accumulation method for determining the SOC of an electric storage element from the time accumulation of the current flowing through the electric storage element and an OCV method for determining the SOC based on the V-SOC correlation between the voltage of the electric storage element and the state of charge can be executed, and when the V-SOC correlation is divided into a plurality of SOC regions, a given value in the second SOC region is adopted as an SOC estimation value when a first SOC region, which is an SOC region to which the SOC determined according to the current accumulation method belongs, and a second SOC region, which is an SOC region to which the SOC determined according to the OCV method belongs, are different from each other. The given value is set between a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area and an intermediate value of the second SOC area.

Description

Storage element management device, management method, module, recording medium, and moving object

Technical Field

The technology disclosed in the present specification relates to technology for acquiring a State Of Charge (SOC) Of an electric storage element such as a lithium ion battery.

Background

Conventionally, in an electric storage device such as a secondary battery used by repeating charge and discharge, a current integration method is an example of a method of estimating the SOC at an arbitrary time point. This is a method of measuring the amount of power to be supplied to and discharged from the battery by constantly measuring the charge/discharge current of the battery, and determining the SOC by adding or subtracting the amount of power from the initial capacity. This method has an advantage of being able to estimate the SOC even when the battery is in use. However, on the other hand, since the amount of charge/discharge power is always accumulated by measuring the current, there is a drawback that the accumulation of measurement errors of the current sensor and the like gradually becomes inaccurate.

For this reason, an OCV method using a SOC determination method based on, for example, the Open Circuit Voltage (OCV) of the battery has been developed. The method comprises the following steps: the open-circuit voltage, which is the battery voltage when no current flows in the battery, is measured by using the characteristic that the OCV and the SOC have a correlation with relatively good accuracy when no current flows in the battery, the SOC corresponding to the measured OCV is obtained by referring to the correlation between the OCV and the SOC stored in advance, and the SOC estimated by the current integration method is corrected. This can cut off the accumulation of errors, and thus can improve the accuracy of SOC estimation by the current integration method.

In recent years, however, a lithium ion battery using lithium iron phosphate as a positive electrode active material has attracted attention. In such a lithium ion battery, as shown in fig. 1, for example, the OCV-SOC characteristic is in a flat region (voltage flat region) in which the OCV hardly changes even though the SOC changes in a wide range. This means that it is difficult to improve the error of SOC estimation even by the OCV method in such a lithium ion battery.

That is, in the case of a lithium ion battery having OCV-SOC characteristics as shown in fig. 1, for example, when OCV is about 3.33V, which is expressed as a voltage flat region, SOC can be said to be almost anywhere from 15% to 95%. Therefore, in such a battery, the SOC correction based on the OCV can be performed only in a voltage gradient region where the OCV is inclined to some extent in the OCV-SOC characteristic, and since the frequency of the SOC correction based on the OCV becomes low, there is a limit to improve the accuracy of SOC estimation.

Such an error in SOC estimation may cause an undesirable situation such as a shortage of electric power particularly in an electric vehicle using a battery as a drive source, and it is therefore desirable to eliminate the situation.

In contrast, for example, in the technique disclosed in japanese patent application laid-open No. 2010-266221, when it is detected that the SOC has changed from a place lower than the lower limit value of the voltage flat region into the voltage flat region due to charging, the SOC is reset to the lower limit value of the voltage flat region.

Patent document

Patent document 1: japanese patent laid-open publication No. 2010-266221

Problems to be solved by the invention

However, in the technique of the above-mentioned japanese patent application laid-open No. 2010-266221, when the battery is discharged to a considerable extent, the timing at which the SOC changes from a place lower than the lower limit value of the voltage flat region to the voltage flat region is captured, and therefore the frequency thereof is not necessarily high, and there is still a limit to the improvement of the accuracy.

Disclosure of Invention

In the present specification, a technique is disclosed that can accurately acquire the SOC of an electric storage element.

Means for solving the problems

An electric storage element management method according to the technology disclosed in the present specification for determining an SOC estimation value that is a value indicating a state of charge of an electric storage element is characterized in that a first SOC determination method and a second SOC determination method for determining an SOC of the electric storage element by different methods are respectively executable, and when a V-SOC correlation between a voltage of the electric storage element and a state of charge is divided into a plurality of SOC ranges, a predetermined value is adopted as the SOC estimation value when a first SOC range that is an SOC range to which the SOC determined by the first SOC determination method belongs and a second SOC range that is an SOC range to which the SOC determined by the second SOC determination method belongs are different from each other, and the predetermined value is set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

Further, the electric storage element management device according to the technology disclosed in the present specification is characterized in that it is provided with: an information processing unit capable of executing a first SOC determination method and a second SOC determination method for determining the SOC of the electric storage element by different methods, respectively, wherein when dividing a V-SOC correlation between a voltage and a state of charge of the electric storage element into a plurality of SOC ranges, if a first SOC range, which is an SOC range to which the SOC determined by the first SOC determination method belongs, and a second SOC range, which is an SOC range to which the SOC determined by the second SOC determination method belongs, are different from each other, a given value is adopted as the SOC estimation value, and the given value is set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

Further, in the case where the first SOC determination method is a method of determining the SOC of the electric storage element using data obtained by measuring the current flowing through the electric storage element, and the second SOC determination method is a method of determining the SOC of the electric storage element using data obtained by measuring the voltage of the electric storage element, it is possible to effectively utilize the advantage of the temporal property of the first SOC determination method using the data obtained by measuring the current, and it is possible to obtain the advantage of improving the accuracy with reference to the value obtained by the second SOC determination method using the data obtained by measuring the voltage.

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

The technology disclosed in the present specification can be implemented as a power storage element management device and a power storage element management method, and a power storage element module, a mobile body, or a program in which these devices or methods are installed.

Effects of the invention

According to the technology of the present specification, since the SOC obtained by the two methods is used as a reference, an estimation error of the SOC of the electric storage element can be suppressed.

Drawings

Fig. 1 is a graph showing an example of OCV-SOC characteristics of a lithium ion battery.

Fig. 2 is a graph showing an example of the OCV-SOC characteristic of the lithium ion battery according to the present embodiment.

Fig. 3 is a block diagram showing a configuration of a battery module according to an embodiment.

Fig. 4 is a flowchart showing a flow of the SOC determination process.

Description of the symbols

10: load, 30: secondary battery (electric storage device), 40: current sensor, 50: storage battery manager (storage element management apparatus), 60: control unit, 61: information processing unit, 70: a voltage measuring part.

Detailed Description

(outline of the present embodiment)

First, an outline of the power storage element management method and the device thereof according to the present embodiment will be described. The present technology is for determining an SOC estimation value that is a value indicating a state of charge of an electric storage element such as a lithium ion battery, and includes: a current sensor that detects a current flowing in the electric storage element; and a voltage sensor that detects a voltage when no current or a minute current flows in the power storage element. The power storage element is mounted on a mobile body such as a vehicle, an electric train, a ship, or an aircraft.

On the other hand, among various power storage elements, there are power storage elements such as lithium ion batteries, for example, which have a correlation between a voltage (V) and a state of charge (SOC) with relatively high reproducibility. For this reason, the correlation is tabulated as a V-SOC correlation in advance for such an electric storage element and stored in a memory. Further, for example, an information processing unit having a CPU and a memory storing a necessary operation program is provided, and the information processing unit is capable of executing: a current integration method for determining the SOC of the storage element by obtaining the amount of charge/discharge power by integrating the time of the current detected by the current sensor; and an OCV method for determining SOC based on the V-SOC correlation relationship based on a detection result of the voltage sensor.

The SOC estimation value is determined according to the relationship of the SOCs determined by the respective methods. In this case, the V-SOC correlation is divided into a plurality of SOC ranges, and it is determined to which SOC range each SOC determined by the current accumulation method and the OCV method belongs, and the SOC estimation value is determined as follows depending on whether the SOC ranges are the same or different. (1) That is, when the SOC range to which the SOC determined by the current integration method belongs (this is referred to as "first SOC range") and the SOC range to which the SOC determined by the OCV method belongs (this is referred to as "second SOC range") are the same, the SOC determined by the current integration method is adopted as the SOC estimation value. (2) Further, in the case where the first SOC range and the second SOC range become ranges different from each other, a given value, which is set between a boundary value on a side close to the first SOC range and an intermediate value of the second SOC range among boundary values that demarcate the second SOC range, among the second SOC range (the range to which the SOC obtained based on the OCV method belongs), among the second SOC range is caused to be employed as the SOC estimation value.

For example, in the SOC that is desirable for the power storage element, when there is an SOC region 1 in which the change of the voltage (V) with respect to the SOC change is larger than a predetermined value in a region from a region where the SOC is small to a region where the SOC is large, then there is an SOC region 2 (voltage flat region) in which the change of the voltage (V) with respect to the SOC change is smaller than the predetermined value, and then there is an SOC region 3 in which the change of the voltage (V) with respect to the SOC change is larger than the predetermined value, there are 9 modes of mode 1 to mode 9 in the SOC (hereinafter referred to as SOC (i)) determined by the current integration method and the SOC (hereinafter referred to as SOC (V)) determined by the OCV method belonging to each region as shown in table 1 below.

In each of these embodiments, the SOC estimation value used is as described in the column of "used SOC estimation value" at the right end of table 1, based on the conditions (1) and (2) described above. Here, "SOC (i)" represents SOC determined based on the current integration method.

"upper half value of region 1" means a given value from the middle SOC (middle value) of the region among the SOCs belonging to SOC region 1 to the upper limit value which is the boundary value on the region 2 side to which SOC (i) belongs.

"lower half value of region 2" means a given value from the SOC (middle value) in the middle of the region to the lower limit value that is the boundary value on the region 1 side to which SOC (i) belongs, among the SOCs belonging to SOC region 2.

"upper half value of region 2" means a given value from the middle SOC (middle value) of the region among the SOCs belonging to SOC region 2 to a lower limit value that is a boundary value on the region 3 side to which SOC (i) belongs.

The "lower half value of region 3" is a given value from the middle SOC (middle value) of the region to the lower limit value that is the boundary value on the region 2 side to which SOC (i) belongs, among SOCs belonging to SOC region 3.

[ Table 1]

	SOC region 1	SOC region 2	SOC region 3	SOC estimation value adopted in Xin
					Mode 1	SOC(V)&SOC(I)			SOC(1)
Mode 2	SOC(V)	SOC(I)		Upper half of area 1
					Mode 3	SOC(V)		SOC(I)	Upper half of area 1
Mode 4	SOC(I)	SOC(V)		Lower half value of region 2
					Mode 5		SOC(V)&SOC(I)		SOC(I)
Mode 6		SOC(V)	SOC(I)	Upper half of area 2
					Mode 7	SOC(I)		SOC(V)	Lower half value of region 3
Mode 8		SOC(I)	SOC(V)	Lower half value of region 3
					Mode 9			SOC(V)&SOC(I)	SOC(I)

According to the method for determining the SOC estimation value, the following advantages can be obtained.

As in the embodiments 1, 5, and 9, when the region (first SOC region) to which the SOC (i) obtained by the current integration method belongs and the region (second SOC region) to which the SOC (v) obtained by the OCV method belongs are the same, the value of SOC (i) can be trusted, and therefore, the SOC (i) is directly used as the SOC estimation value, and the SOC is not corrected by the OCV.

As in the embodiments 2 and 3, when the area (second SOC area) to which SOC (v) belongs is SOC area 1 and the area (first SOC area) to which SOC (i) belongs is an area (SOC area 2 or area 3) different from SOC area 1, there is a high possibility that an error is accumulated in the calculation by the current integration method. Therefore, in this case, the SOC based on the OCV is corrected by a predetermined value (upper half value of region 1) from the middle SOC (middle value) of SOC region 1 as the second SOC region to the upper limit value that is the boundary value on the region 2 or region 3 side of the first SOC region to which SOC (i) belongs, thereby eliminating the accumulated error. The reason for this correction is that the SOC is indicated in SOC range 1 by the OCV method and the SOC greater than this is indicated by the current integration method, and therefore the estimated SOC value is considered to be closest to the true value if it is set to the upper half value of SOC range 1. As the upper half value of the region I, the upper limit value or a value close thereto is preferable.

On the other hand, as in embodiment 4, when the area (second SOC area) to which SOC (v) belongs is SOC area 2 and the area (first SOC area) to which SOC (i) belongs is SOC area 1, there is a high possibility that an error is accumulated in the calculation by the current integration method. Therefore, in this case, the SOC based on the OCV is corrected by a predetermined value (lower half value of region 2) from the SOC (intermediate value) in the middle of the region to the lower limit value that is the boundary value on the SOC region 2 side to which the SOC (i) belongs among the SOCs belonging to the SOC region 2 that is the second SOC region, and the accumulated error can be eliminated.

Conversely, as in embodiment 6, when the SOC range to which the second SOC range (SOC (v)) belongs) is the SOC range 2 and the first SOC range (SOC range to which the SOC (i)) belongs) is the SOC range 3, there is a high possibility that an error is accumulated in the calculation by the current integration method. In this case, therefore, the SOC is corrected by the OCV at a given value (upper half value of region 2) between the SOC belonging to the second SOC region (SOC region 2) and the upper limit value that is the boundary value on the SOC region 3 side to which the first SOC region (SOC) (i) belongs.

As in embodiments 7 and 8, when the second SOC area to which SOC (v) belongs is SOC area 3 and the first SOC area to which SOC (i) belongs is SOC area 1 or area 2, there is a high possibility that an error is accumulated in the calculation by the current integration method. In this case, therefore, the SOC based on the OCV is corrected by a predetermined value (lower half value of region 3) between the SOC (intermediate value) in the middle of the region among the SOCs belonging to SOC region 3 as the second SOC region and the lower limit value that is the boundary value on the SOC region 1 or 2 side as the first SOC region, thereby eliminating the accumulated error. The reason for this correction is that the SOC is indicated in SOC range 3 by the OCV method and the SOC smaller than this is indicated by the current integration method, and therefore the estimated SOC value is considered to be closest to the true value if it is set to the lower half value of SOC range 3. As the lower half value of the region 3, the lower limit value or a value close thereto is preferable.

Accordingly, while the SOC is determined by the current accumulation type SOC determination process, the SOC can be corrected frequently by the reset process in the case where the SOC areas to which the SOC (i) and the SOC (v) belong are different, and therefore the following advantages can be obtained: the SOC can be determined even when the electric storage element is in use, and accumulation of errors, which is a drawback of the current integration method, can be prevented, so that the accuracy of the SOC estimation value becomes high. In order to accurately determine the SOC of a battery having a plateau region by the current integration method, it is necessary to use a current measuring means having good measurement accuracy and perform a high-speed current integration process so that the current value is not missed. Further, in order to improve the accuracy of SOC estimation of a battery having a plateau region, a method of performing dV/dQ calculation to capture an inflection point in OCV-SOC characteristics has been proposed, but when this method is installed, a high degree of calculation processing and a large capacity of memory are required to capture the inflection point, which also increases the cost for realizing these points, and it is expected that a large amount of time is required for verification work. In contrast to these aspects, the present invention is a method for determining whether or not the SOC has entered the SOC range for the SOC including the error of the current measurement means, and therefore, a highly accurate current measurement means is not required, and the processing is simpler than the method for calculating dV/dQ.

The power storage element management device according to the technology disclosed in the present specification is suitable for managing a power storage element having a characteristic of a voltage flat region in a V-SOC correlation, and therefore a lithium ion battery using an iron phosphate-based positive electrode active material can be exemplified as a management target. In particular, it is most suitable for estimating the state of charge of a lithium ion battery of a type in which a plurality of voltage flat regions are present. The presence of a plurality of voltage flat regions means that there are voltage gradient regions between these regions, and the reset process can be performed at high frequency by utilizing the difference in the results of the current integration method and the OCV method, and the accuracy of the SOC estimation value increases.

(details of the embodiment)

Hereinafter, an embodiment in which the technology disclosed in the present specification is applied to a battery module for driving an electric vehicle such as an EV, an HEV, or a PHEV will be described in detail with reference to fig. 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 the secondary batteries 30, and a current sensor 40 that detects a current flowing in the secondary batteries 30. BM50 is an example of the "power storage element management device".

The secondary battery 30 is an example of an "electric storage device", and is charged by a charger (not shown) to supply 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 of a graphite-based material and a positive electrode active material of an iron phosphate system such as LiFePO4, and has a correlation (referred to as "V-SOC correlation" herein) shown in fig. 2 between, for example, an Open Circuit Voltage (OCV) and a state of charge (SOC). In the V-SOC correlation, the state of charge of the secondary battery 30 is considered by being divided into 5 regions as follows.

In 3 of these ranges I, III, and V, the OCV curve of the battery corresponding to the SOC has a slope that rises to the right to some extent, i.e., the change in voltage (OCV) with respect to the change in state of charge (SOC) is relatively large and is a predetermined value or more. For this reason, these regions are referred to as "voltage gradient regions" I, III, V.

In contrast, in the regions (regions II and IV) other than the voltage gradient regions I, III and V, the inclination of the OCV curve of the battery corresponding to the SOC thereof is extremely small, that is, the voltage (OCV) changes to the predetermined value or less with respect to the change in the state of charge (SOC). For this reason, these regions are referred to as "voltage flat regions" II, IV.

The BM50 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 a CPU)61 as an information processing unit and a memory 63. Various programs for controlling the operation of the BM50 are stored in the memory 63, and the CPU61 executes SOC determination processes including "current accumulation type SOC determination processing", "voltage reference type SOC determination processing", "first reset processing", "second reset processing", and "third reset processing" described later in accordance with the programs read out from the memory 63. The memory 63 stores data necessary for executing the SOC determination process, such as a tabulated V-SOC correlation of the secondary battery 30, upper and lower limit values of the state of charge of each of the regions I to V, and a state of charge as an initial value of the secondary battery 30.

The voltage measuring unit 70 is connected to both ends of the secondary battery 30 via voltage probe lines, and functions to measure the voltage V of each secondary battery 30 at predetermined intervals. The current measuring unit 80 has a function of measuring the current flowing through the secondary battery 30 via the current sensor 40.

An SOC determination process of determining the SOC of the secondary battery 30 is described next with reference to fig. 4. The SOC determination process is started by, for example, the BM50 receiving an execution command from an ECU (not shown) mounted on the vehicle, and after the start, the series of steps shown in fig. 4 are repeatedly executed at a predetermined cycle T in accordance with the command of the control unit 60.

When the SOC determination process is started, first, a process of measuring the voltage of each secondary battery 30 by the voltage measurement unit 70 is executed in accordance with the instruction of the control unit 60 (S1). Then, the control unit 60 gives a command to the current measuring unit 70 to perform a process of measuring the current flowing through the secondary battery 30 by the current sensor 40 (S2). The voltage value measured at S1 and the current value measured at S2 are converted into digital values and stored in the memory 63.

Then, the process proceeds to S3, and the control unit 60 multiplies the current value I measured in S2 by a predetermined period T to calculate the current integrated value ZI as shown in the following expression (1) and expression (2). The calculated current integrated value ZI is added to or subtracted from the remaining capacity W3 at this time point according to the current flow, thereby calculating a new remaining capacity W3 of the secondary battery 30. That is, each time the SOC determination process is performed once, the value of the remaining capacity W3 is updated by adding or subtracting the current integrated value ZI to or from the remaining capacity (previous value) W3.

ZI＝I×T········(1)

W3＝W3+ZI····(2)

Then, the process proceeds to S4, where it is determined whether or not a current is flowing in the secondary battery 30 at that point in time, but if a current is flowing in the secondary battery 30 during charging or discharging, the current value exceeds the determination reference value, and therefore it is determined as no in S4. If it is determined at S4 that the determination is no, the process proceeds to S5. At S5, the control unit 60 executes a process of estimating the SOC of the secondary battery 30 by the current integration method. Specifically, as shown in the following expression (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 processing of S1, S2, S3, and S5 corresponds to processing for determining the state of charge of the secondary battery 30 by obtaining the amount of charge/discharge power by integrating the time of the current. Thereafter, the SOC having the specific value determined by this S5 is labeled as SOC (i).

Then, the process of S5 is completed and the process of one cycle is ended. Then, the SOC determination process is repeatedly executed at a predetermined cycle T. While the discharge or charge of the secondary battery 30 continues, the processes of S1 to S5 are repeatedly executed at a predetermined cycle T, the values of the voltage value V, the current value I, and the remaining capacity W3 of the secondary battery 30 are updated every time (S1 to S3), and the SOC is calculated every time by the current integration method (S5).

Then, if the current I flowing through the secondary battery 30 is smaller than the predetermined value (the value at which the current is substantially zero) due to completion of charging or completion of discharging of the secondary battery 30, it is determined as yes in S4, and the process proceeds to S6. In S6, a process of calculating the elapsed time from when no current has flowed in the secondary battery 30 is executed.

Then, the process proceeds to S7, and the control unit 60 executes a process of determining whether or not a settling time (a predetermined time period set in advance) has elapsed. The stabilization time is a time for waiting for the OCV (open circuit voltage) of the secondary battery 30 to stabilize, and if the elapsed time measured at S7 becomes the stabilization time, it is determined as yes at S7, and the process proceeds to S8.

At S8, control unit 60 determines the SOC of secondary battery 30 based on the OCV method. Specifically, first, the voltage measurement unit 70 measures the OCV (open circuit voltage in a state where no current flows) of the secondary battery 30. Then, based on the measured OCV, the SOC is determined with reference to the correlation characteristics of V-OCV shown in fig. 2. S8 corresponds to a process of determining the state of charge based on the V-SOC correlation based on the detection result of the voltage sensor. Thereafter, the SOC having the specific value determined by S8 is labeled as SOC (v).

Then, the process proceeds to S9, where it is determined to which region I to V the soc (V) value belongs. If it is determined that SOC (V) belongs to any of voltage gradient regions I, III, and V, the process proceeds to S10, and a first reset process is performed in which SOC (I) acquired by the current accumulation SOC determination process is replaced with SOC (V) determined by the voltage reference SOC determination process of S8. This is because in the voltage gradient regions I, III, and V, since OCV and SOC have a correlation with good accuracy, SOC (I) acquired by the current integration type SOC determination processing of S5 can be corrected to a value with higher accuracy, and the accuracy in the SOC determination process is increased.

On the other hand, when it is determined in S9 that the SOC region (second SOC region) to which SOC (v) belongs is voltage flat region II, IV, it is next determined whether or not the region matches the SOC region (first SOC region) to which SOC (i) belongs (S11). Here, if the areas of the two SOCs coincide, that is, if SOC (i) exists between the lower limit value and the upper limit value of voltage flat area II or IV, correction based on the V-SOC correlation is not performed, and the process returns. Therefore, the SOC (i) obtained by the current integration SOC determination process at S5 is used continuously. This is because, in these voltage flat regions II and IV, since there is a high possibility that relatively large errors are included in SOC (V) due to the flatness in the V-SOC correlation, if correction is performed based on the V-SOC correlation as in the conventional technique, the errors increase conversely.

In S11, although it is determined from soc (v) that voltage flat regions II and IV are present, if it is determined that the value of soc (i) is greater than the upper limit values of both voltage flat regions II and IV, the process proceeds to S12, and the value of soc (i) is replaced with the upper limit value of these regions (second reset process).

For example, if SOC (V) indicates that the SOC 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 is the original SOC (if the determination is made, the error may become large). However, if SOC (i) is 66% or more, which is the upper limit SOC of region II, the possibility that the original SOC is around 66% is extremely high. Therefore, the SOC is corrected to the upper limit value of 66% in this region II. If SOC (v) indicates that the area IV is located and SOC (i) is 95% or more, which is the upper limit SOC of the area IV, the possibility that the original SOC is around 95% is extremely high. Therefore, the SOC is corrected to 95% of the upper limit value of the region IV. This can reduce the error included in soc (i).

On the contrary, in S11, although it is determined that the voltage flat regions II and IV are present from the soc (v), if it is determined that the value of soc (i) is smaller than the lower limit values of the two voltage flat regions II and IV, the process proceeds to S13, and the value of soc (i) is replaced with the lower limit value of these regions (third replacement processing).

For example, if SOC (V) indicates that the SOC 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 is the original SOC (if the determination is made, the error may become large). However, if SOC (i) is 30% or less, which is the lower limit SOC of region II, the possibility that the original SOC is in the vicinity of 30% is extremely high. For this reason, the SOC is corrected to 30% of the lower limit value of this region II. Further, if SOC (V) indicates that the SOC is in region IV, the original SOC should be in any of 68% to 95% based on the V-SOC correlation, but which value cannot be determined (if the determination is made, the error still increases). 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 extremely high. For this reason, the SOC is corrected to 68% of the lower limit value of the region IV. This can reduce the error included in soc (i).

< other embodiment >

The present invention is not limited to the embodiments described above and illustrated in the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the above-described embodiment, the lithium ion secondary battery using the iron phosphate-based positive electrode active material is exemplified as an example of the electric storage element, but the present invention is not limited thereto. The present invention may be applied to a case where a secondary battery other than a lithium ion secondary battery, a capacitor involving an electrochemical phenomenon, or the like has a voltage flat region in a V-SOC correlation, and the voltage flat region is not limited to a case where two voltage flat regions exist, and may be a type of electric storage element having only one voltage flat region as shown in fig. 1, or may be a type of electric storage element having three or more voltage flat regions.

(2) In the above embodiment, the CPU61 is exemplified as an example of the control unit 60. The control unit 60 may be configured to include a plurality of CPUs, a hardware Circuit such as an ASIC (Application Specific Integrated Circuit), an MPU, a microcomputer, a programmable PLD, or an FPGA, or both a hardware Circuit and a CPU. In short, the control unit may be any unit that executes the SOC determination process described above by software processing or/and a hardware circuit. When the present invention is implemented using software, the software (computer program) can be recorded in a storage medium such as a semiconductor memory and distributed, or can be stored in a storage device of a computer via a wired or wireless communication line.

(3) In the above embodiment, when it is determined in S9 what region in the V-SOC correlation the state of charge of secondary battery 30 is in, SOC is determined from OCV measured and it is determined which region is the SOC, but when OCV and SOC have a unique correspondence relationship, the region may be determined directly from 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 described in the above embodiment, and a method of estimating the OCV from the charge and discharge I, V and R, or the kalman method may be employed. The former method is a method of calculating OCV based on the internal resistance R of the battery, the terminal voltage V of the battery, and the charge/discharge current I, and based on the relationship between OCV and RI. The kalman method is a method of creating an equivalent circuit model of a battery, sequentially estimating circuit parameters of the model using a kalman filter, calculating OCV from the estimated circuit parameters, and further calculating SOC, as disclosed in, for example, japanese patent laid-open No. 2004 and 514249, and japanese patent laid-open No. 2012 and 47580.

(5) Further, the method of determining the SOC of the power storage element using the data obtained by measuring the current flowing through the power storage element is not limited to the so-called current integration method of measuring the current flowing through the power storage element at a fixed cycle and calculating the SOC by adding or subtracting IT obtained by multiplying the measured current value I by the cycle T to the initial capacity x (ah), and a time integration method may be employed when a certain current value can be regarded as constant. The time integration method mentioned here is a method of measuring a time T during which a current value flowing through the power storage element stays within a predetermined range that can be regarded as constant, and adding or subtracting a value obtained by multiplying the current I regarded as constant by the time T to the initial capacity x (ah) to obtain the SOC.

(6) In the above embodiment, when the first SOC range and the second SOC range are the same, that is, when the range to which the SOC determined by the current integration method belongs and the range to which the SOC determined by the OCV method belongs are the same, the SOC itself determined by the current integration method is used as the SOC estimation value. Further, which value of the SOC estimated by the first and second SOC determination methods is used may be determined based on the temperature and current value of the power storage element.

(7) In addition, when the SOC of the power storage element is estimated using data obtained by measuring the current flowing through the power storage element, if the SOC is smaller than the lower limit of the assumed SOC range, it is considered that the SOC estimation value is deviated in the discharging direction. Therefore, in this case, the accuracy of SOC estimation can be improved by shifting the current measurement value to the charging side. On the other hand, when the estimated value of the SOC exceeds the upper limit of the SOC range, the accuracy of SOC estimation can be improved by shifting the current measurement value to the discharge side. In addition, when the SOC range is not changed in a manner of being deviated despite the deviation of the current measurement value, it may be determined that the current measurement unit is abnormal.

(8) In the above-described embodiment, the example in which the power storage element is mounted on the mobile body such as an electric vehicle has been described, but the power storage element is not limited to the member mounted on the mobile body, and may be a power storage device provided in a stationary-type apparatus. Examples of stationary equipment include uninterruptible power supply devices and emergency power supply devices installed in factories, homes, and offices, and power storage devices connected to a power transmission system for power distribution and power load balancing.

Claims (13)

1. An electric storage element management method for determining an SOC estimation value that is a value indicating a state of charge of an electric storage element,

the first SOC determination method and the second SOC determination method 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 electric storage element and the state of charge is divided into a plurality of SOC regions, if a first SOC region, which is an SOC region to which the SOC determined by the first SOC determination method belongs, and a second SOC region, which is an SOC region to which the SOC determined by the second SOC determination method belongs, are different from each other, a given value is adopted as the SOC estimation value,

the given values are set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

2. The power storage element management method according to claim 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 determining the SOC of the power storage element using data obtained by measuring a voltage of the power storage element.

3. The power storage element management method according to claim 1 or 2,

when the first SOC range and the second SOC range are the same, the SOC determined based on the first SOC determination method is used as the SOC estimation value.

4. The power storage element management method according to claim 1 or 2,

one of the SOC regions is a region corresponding to a voltage flat region in which a change in voltage of the electric storage element with respect to a change in SOC in the V-SOC correlation relationship is smaller than other regions.

5. An electric storage element management device that outputs an SOC estimation value that is a value indicating a state of charge of an electric storage element,

the power storage element management device includes: an information processing unit capable of executing a first SOC determination method and a second SOC determination method for determining the SOC of the power storage element by different methods,

the information processing unit adopts a given value as the SOC estimation value when a first SOC range, which is an SOC range to which the SOC determined by the first SOC determination method belongs, and a second SOC range, which is an SOC range to which the SOC determined by the second SOC determination method belongs, are different from each other when dividing the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC ranges,

the given values are set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

6. The storage element management device according to claim 5,

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 determining the SOC of the power storage element using data obtained by measuring a voltage of the power storage element.

7. The electrical storage element management device according to claim 5 or 6,

when the first SOC range and the second SOC range are the same, the SOC determined based on the first SOC determination method is used as the SOC estimation value.

8. The electrical storage element management device according to claim 5 or 6,

one of the SOC regions is a voltage flat region in which a change in voltage of the electrical storage element with respect to a change in SOC in the V-SOC correlation is smaller than other regions.

9. The storage element management device according to claim 8,

the V-SOC correlation relationship includes information related to a plurality of the voltage plateau regions.

10. The electrical storage element management device according to claim 5 or 6,

the storage element is a lithium ion battery containing an iron phosphate-based positive electrode active material.

11. An electricity storage element module is characterized by comprising:

an electric storage element; and

an information processing unit capable of executing a first SOC determination method and a second SOC determination method for determining the SOC of the power storage element by different methods,

the information processing unit adopts a given value as the SOC estimation value when a first SOC range, which is an SOC range to which the SOC determined by the first SOC determination method belongs, and a second SOC range, which is an SOC range to which the SOC determined by the second SOC determination method belongs, are different from each other when dividing the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC ranges,

the given values are set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

12. A computer-readable recording medium having a storage element management program recorded thereon for causing a computer for controlling a storage element to determine an SOC estimation value that is a value indicating a state of charge of the storage element,

the computer is enabled to execute a first SOC determination method and a second SOC determination method for determining the SOC of the power storage element by different methods,

when the V-SOC correlation between the voltage of the electric storage element and the state of charge is divided into a plurality of SOC regions, if a first SOC region, which is an SOC region to which the SOC determined by the first SOC determination method belongs, and a second SOC region, which is an SOC region to which the SOC determined by the second SOC determination method belongs, are different from each other, a process of using a given value as the SOC estimation value is performed,

the given values are set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

13. A movable body is provided with:

an electric storage element; and

a storage element management device that outputs an SOC estimation value that is a value indicating a state of charge of the storage element,

the moving body is characterized in that the moving body,

the power storage element management device includes: an information processing unit capable of executing a first SOC determination method and a second SOC determination method for determining the SOC of the power storage element by different methods,

the information processing unit adopts a given value as the SOC estimation value when a first SOC range, which is an SOC range to which the SOC determined by the first SOC determination method belongs, and a second SOC range, which is an SOC range to which the SOC determined by the second SOC determination method belongs, are different from each other when dividing the V-SOC correlation between the voltage of the power storage element and the state of charge into a plurality of SOC ranges,

the given values are set as: a value close to a boundary value on a side close to the first SOC area among boundary values that demarcate the second SOC area or a value between the boundary value and a middle value of the second SOC area.

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