JP2022086261A - Charge rate estimation device and charge rate estimation method for power storage elements - Google Patents

Abstract

To provide a charge rate estimation device and a charge rate estimation method, with which it is possible to estimate a charge rate with high reliability with regard to a power storage element in which a flat region where an open-circuit voltage change is small and a change region where said change is large appear in conjunction with a charge rate change.SOLUTION: A memory 51b constitutes an open-circuit voltage characteristic storage unit for storing open-circuit voltage characteristics and preliminarily stores an SOC-OCV table that correlates an OCV [mV] value to each SOC [%] value. A charge rate estimation unit 51d estimates the charge rate of each secondary battery 31. A charge rate compensation unit 51e compensates for the charge rate estimated referring to the open-circuit voltage characteristic. An internal resistance value calculation unit 51f calculates the direct-current internal resistance value of each secondary battery 31 from the current measured by a current sensor 4 and the inter-terminal voltage measured by a voltage detection circuit 52. A charge rate correction unit 51g adopts the charge rate estimated by the charge rate estimation unit 51d as a charge rate of the secondary battery 31 when the calculated direct-current resistance value is smaller than or equal to a prescribed value y.SELECTED DRAWING: Figure 1

Description

The present invention relates to a charge rate estimation device and a charge rate estimation method for a power storage element in which a flat region with a small change in open circuit voltage and a large change region appear with respect to a change in the charge rate.

Conventionally, as this kind of charge rate estimation device and charge rate estimation method, for example, there are a state estimation device and a state estimation method disclosed in Patent Document 1.

The state estimation device and state estimation method disclosed in the same document utilize the SOC-OCV characteristics of the secondary battery shown in FIG. 2 of the same document. The SOC-OCV characteristic is represented by an SOC (charge rate) on the horizontal axis and an OCV (open circuit voltage) on the vertical axis, and the OCV change with respect to the SOC change is represented as the open circuit voltage characteristic of the secondary battery. As shown in this SOC-OCV characteristic, the secondary battery has a flat region in which the OCV change with respect to the SOC change is relatively small and a large change region. In the state estimation device and state estimation method disclosed in the same document, as shown in FIG. 6 of the same document, in the change region where the OCV change with respect to the SOC change is large, the SOC estimated by the current integration method is subjected to the Kalman filter. to correct. Further, in a flat region where the OCV change with respect to the SOC change is small, the SOC estimated by the current integration method is not corrected, and the SOC estimated by the current integration method is used as the SOC at that time.

Further, as an actual operation of a battery pack using such a secondary battery as a power storage element, in each charge / discharge cycle in which charge / discharge is repeated with a pause period in between, the charge period or the timing of transition from the discharge period to the pause period OCV may be measured. Then, the SOC corresponding to the measured OCV is specified from the SOC-OCV correspondence table stored in advance, and the specified SOC is estimated to be the SOC at the end timing of the rest period, and the initial SOC at the rest period transition timing is estimated. SOC may be corrected.

Japanese Patent No. 6657967

However, the SOC-OCV characteristics of the secondary battery change significantly in the flat region where the OCV change with respect to the SOC change is relatively small in response to a slight change in the OCV. Further, the value of OCV causes hysteresis due to the history of charging / discharging of the secondary battery, and the measured value changes according to the number of elapsed cycles of charging / discharging due to the hysteresis. Therefore, if the SOC is estimated based on the SOC-OCV characteristics from the measured value of the OCV in the flat region where the OCV change is relatively small, an error occurs in the estimated SOC. This error is greatly affected by the above-mentioned hysteresis in each charge / discharge cycle, and greatly occurs in the estimated SOC.

This phenomenon is particularly remarkable in the olivine-based lithium-ion secondary battery, and in the flat region of the SOC-OCV characteristics of the olivine-based lithium-ion secondary battery, the OCV is only deviated by a few mV, and the SOC is tens of tens. % Error occurs. Therefore, in a flat region where the OCV change is relatively small, the SOC is estimated from the measured value of OCV based on the SOC-OCV characteristics, and the OCV characteristics of the secondary battery at that time are in the flat region based on the estimated SOC. If it is determined whether it is in the change area or not, the accurate determination cannot be made.

Therefore, a state estimation device and a state estimation method for estimating SOC based on whether the olivine-based lithium ion secondary battery is in the flat region or the changing region of the SOC-OCV characteristics disclosed in the above-mentioned conventional patent document 1. Then, the SOC cannot be estimated with high reliability.
Further, in the actual operation of the conventional battery pack, when the OCV value is measured in a flat region where the OCV change is relatively small, it is specified by the OCV measurement value from the SOC-OCV correspondence table stored in advance. SOC includes a large amount of error.

The present invention has been made in view of the above points, and is a charge rate estimation capable of estimating SOC with high reliability for a power storage element in which a flat region with a small OCV change and a large change region appear with respect to an SOC change. It is an object of the present invention to provide an apparatus and a method for estimating a charge rate.

To this end, the present invention
A current measuring unit that measures the current flowing through a power storage element having an open circuit voltage characteristic in which a relatively small flat region and a large change region of the open circuit voltage change appear with respect to a change in the charge rate.
A voltage measuring unit that measures the voltage between the terminals of the power storage element,
A charge rate estimation unit that estimates the charge rate of the power storage element,
A charge rate correction unit that corrects the charge rate of the power storage element estimated by the charge rate estimation unit, and a charge rate correction unit.
An internal resistance value calculation unit that calculates the internal resistance value of the power storage element from the current flowing through the power storage element measured by the current measurement unit and the voltage between the terminals of the power storage element measured by the voltage measurement unit.
When the internal resistance value calculated by the internal resistance value calculation unit is equal to or less than a predetermined value, the charge rate estimation of the power storage element including the charge rate correction unit using the charge rate estimated by the charge rate estimation unit as the charge rate of the power storage element. The device was configured.

Further, the present invention
A current measurement step in which a current measuring unit measures the current flowing through a power storage element having an open circuit voltage characteristic in which a relatively small flat region and a large change region of the open circuit voltage change appear with respect to a change in charge rate.
The charge rate estimation step for estimating the charge rate of the power storage element, and
A charge rate correction step that corrects the charge rate of the power storage element estimated in the charge rate estimation step, and a charge rate correction step.
An internal resistance value calculation step that calculates the internal resistance value of the power storage element from the current flowing through the power storage element measured by the current measurement unit and the voltage between the terminals of the power storage element measured by the voltage measurement unit.
When the internal resistance value calculated in the internal resistance value calculation step is equal to or less than a predetermined value, the charge rate estimation of the power storage element including the charge rate correction step in which the charge rate estimated in the charge rate estimation step is the charge rate of the power storage element. Constructed the method.

According to these configurations, when the internal resistance value calculated by the internal resistance value calculation unit or the internal resistance value calculation step is equal to or less than a predetermined value, the power storage element has a characteristic of the open circuit voltage with respect to the charge rate of the change in the open circuit voltage. It is judged to be in the state of a small flat area. In the flat region where the characteristic of the open circuit voltage with respect to the charge rate is small in the open circuit voltage change, the internal resistance value of the power storage element is smaller than in the change region in which the open circuit voltage change is large. Further, the internal resistance value of the power storage element does not have a large hysteresis due to the history of charge / discharge unlike the charge rate.

Therefore, according to this configuration, the calculated internal resistance value is compared with the predetermined value, so that the characteristic of the open circuit voltage with respect to the charge rate is in the state of the flat region where the change in the open circuit voltage is small or in the state of the large change region. Is accurately determined by the charge rate correction unit or the charge rate correction step. When it is determined that the characteristics of the open circuit voltage are in a flat region where the change in the open circuit voltage is small, the corrected charge rate obtained by being corrected by the charge rate correction unit or the charge rate correction step includes a large error. The charge rate estimated by the charge rate estimation unit or the charge rate estimation step is taken as the charge rate of the power storage element at that time.

For this reason, we provide a charge rate estimation device and a charge rate estimation method that can reliably estimate the charge rate for a power storage element in which a flat region with a small change in open circuit voltage and a large change region appear with respect to a change in the charge rate. It becomes possible to do.

Further, the present invention
A pause period determination unit that determines whether the storage element has entered a pause period without being measured by the current measuring unit for a predetermined period of time.
An estimated charge rate storage unit that stores the charge rate estimated by the charge rate estimation unit,
A corrected charge rate storage unit that stores the charge rate corrected by the charge rate correction unit,
It is equipped with a pause period end determination unit that measures whether the current starts to flow in the power storage element during the pause period and determines whether the pause period has ended.
The estimated charge rate storage unit stores the charge rate estimated by the charge rate estimation unit as the initial charge rate when the pause period determination unit determines that the power storage element has entered the pause period.
The internal resistance value calculation unit calculates the internal resistance value of the power storage element from the current that begins to flow in the power storage element during the pause period and the voltage between the terminals of the power storage element measured by the voltage measurement unit at that time.
When the internal resistance value calculated by the internal resistance value calculation unit is equal to or less than the predetermined value, the charge rate correction unit sets the initial charge rate stored in the estimated charge rate storage unit as the charge rate of the power storage element at the end of the pause period. It is characterized by the fact that.

Further, the present invention
A pause period determination step for determining whether the storage element has entered a pause period without being measured by the current measuring unit for a predetermined period of time, and a pause period determination step.
An estimated charge rate storage step that stores the estimated charge rate in the charge rate estimation step in the estimated charge rate storage unit, and an estimated charge rate storage step.
A correction charge rate storage step for storing the charge rate corrected in the charge rate correction step in the correction charge rate storage unit, and a correction charge rate storage step.
It is provided with a pause period end determination step in which it is measured by the current measuring unit that the current starts to flow in the power storage element during the pause period and it is determined whether the pause period has ended.
When the estimated charge rate storage step determines in the pause period determination step that the power storage element has entered the pause period, the charge rate estimated in the charge rate estimation step is stored as the initial charge rate.
The internal resistance value calculation step calculates the internal resistance value of the power storage element from the current that starts flowing to the power storage element during the pause period and the voltage between the terminals of the power storage element measured by the voltage measuring unit at that time.
When the internal resistance value calculated in the internal resistance value calculation step is equal to or less than the predetermined value in the charge rate correction step, the initial charge rate stored in the estimated charge rate storage unit is set to the charge rate of the power storage element at the end of the pause period. It is characterized by the fact that.

According to these configurations, the charge rate estimated by the charge rate estimation unit or the charge rate estimation step when it is determined by the pause period determination unit or the pause period determination step that the power storage element has entered the pause period is used as the initial charge rate. It is stored in the estimated charge rate storage unit. In addition, the internal resistance value when the pause period end determination unit or the pause period end determination step determines that the pause period has ended is calculated by the internal resistance value calculation unit or the internal resistance value calculation step, and the internal resistance is calculated. It is determined whether the value is equal to or less than the predetermined value. When it is determined that the internal resistance value is equal to or less than a predetermined value, the initial charge rate stored in the estimated charge rate storage unit is set as the charge rate of the power storage element at the end of the pause period by the charge rate correction unit or the charge rate correction step. To.

For this reason, in the actual operation of a battery pack composed of a storage element in which a flat region with a small change in the open circuit voltage and a large change region appear with respect to a change in the charge rate, charging at the end of the pause period of the battery pack The rate can be estimated with high reliability.

Further, the present invention
It is equipped with an open circuit voltage characteristic storage unit that stores the open circuit voltage characteristics as the value of the open circuit voltage for each charge rate value.
The charge rate estimation unit estimates the charge rate of the power storage element by the current integration method.
The charge rate correction unit converts the charge rate of the power storage element estimated by the charge rate estimation unit into the charge rate stored in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by the voltage measurement unit. It is characterized by correction.

Further, the present invention
It is equipped with an open circuit voltage characteristic storage step that stores the open circuit voltage characteristics as the open circuit voltage value for each charge rate value in the open circuit voltage characteristic storage unit.
The charge rate estimation step estimates the charge rate of the power storage element by the current integration method.
The charge rate correction step converts the charge rate of the power storage element estimated in the charge rate estimation step into the charge rate stored in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by the voltage measurement unit. It is characterized by correction.

According to these configurations, the charge rate correction by the charge rate correction unit or the charge rate correction step is such that the charge rate of the power storage element estimated by the current integration method by the charge rate estimation unit or the charge rate estimation step is the voltage measurement unit. It is performed by setting the charge rate stored in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by.

Further, the present invention
The charge rate estimation unit estimates the charge rate of the power storage element by the current integration method.
The charge rate correction unit is characterized in that the charge rate estimated by the charge rate estimation unit is corrected by using a Kalman filter.

Further, the present invention
The charge rate estimation step estimates the charge rate of the power storage element by the current integration method.
The charge rate correction step is characterized in that the charge rate estimated in the charge rate estimation step is corrected by using a Kalman filter.

According to these configurations, the charge rate is corrected by the charge rate correction unit or the charge rate correction step, and the charge rate of the power storage element estimated by the current integration method by the charge rate estimation unit or the charge rate estimation step uses the Kalman filter. It is done by being corrected.

According to the present invention, as described above, for a power storage element in which a flat region with a small change in open circuit voltage and a large change region appear with respect to a change in the charge rate, a charge rate estimation device and a charge capable of estimating the charge rate with high reliability. A rate estimation method can be provided.

It is a block diagram which shows the schematic structure of the battery pack provided with the charge rate estimation device of the power storage element by one Embodiment of this invention. It is a graph which shows the SOC-OCV characteristic of the secondary battery referred to in the charge rate estimation device of the power storage element and the charge rate estimation method according to one embodiment. It is a figure which shows the SOC-OCV table corresponding to the SOC-OCV characteristic shown in FIG. 2 stored in the charge rate estimation apparatus of the power storage element by one Embodiment. It is a graph showing the SOC-DCR curve of a secondary battery superimposed on the SOC-OCV curve shown in FIG. It is a flowchart which shows the outline of the process in the charge rate estimation method of the power storage element by one Embodiment of this invention.

Next, a charge rate estimation device and a charge rate estimation method for the power storage element according to the embodiment of the present invention will be described.

FIG. 1 is a block diagram showing a schematic configuration of a battery pack 2 including a charge rate estimation device 1 for a power storage element according to an embodiment.

The battery pack 2 supplies electric power to a power source operated by electric energy in, for example, an electric vehicle or a small ship. The battery pack 2 has an assembled battery 3, a current sensor 4, and a battery management unit (BMU) 5 that manages the assembled battery 3. These current sensors 4 and BMU 5 constitute a charge rate estimation device 1.

The assembled battery 3 is configured by laminating a plurality of laminated cells composed of a secondary battery 31 and connecting them in series, and each secondary battery 31 is used as a power storage element. In the present embodiment, each secondary battery 31 is an olivine-based (iron phosphate) lithium ion secondary battery (LFP), and the change in open circuit voltage (OCV) with respect to the change in charge rate (SOC) is shown in the graph of FIG. The SOC-OCV characteristics shown are shown. The horizontal axis of the graph is SOC [%], the vertical axis is OCV [mV], and the graph shows the SOC-OCV curve A. As shown in this SOC-OCV characteristic, each secondary battery 31 exhibits an open circuit voltage characteristic having a flat region L in which the OCV change with respect to the SOC change is relatively small and a flat region L in which the OCV change is large. The flat region L is set in a region where the OCV change with respect to the SOC change is, for example, 0.5 [mV /%] or less.

The charge rate is the ratio [%] of the remaining capacity to the fully charged capacity of the secondary battery 31, and is called SOC (State Of Charge). Further, the open circuit voltage is a voltage between terminals of the secondary battery 31 when no current is flowing through the secondary battery 31, and is called OCV (Open Circuit Voltage).

Each secondary battery 31 and the current sensor 4 are connected in series via wiring 6, for example, a charger 7 mounted on an electric vehicle or the like, or a load 7 such as a power source provided inside the electric vehicle or the like. Connected to. The charger 7 charges the assembled battery 3, and the load 7 receives electric power from the assembled battery 3 and consumes electric power.

The current sensor 4 constitutes a current measuring unit that measures the current flowing through each secondary battery 31. The current sensor 4 measures the current value of each secondary battery 31 at regular intervals, and transmits the measured current measurement value data to the control unit 51 in the BMU 5. The BMU 5 includes a control unit 51, a voltage detection circuit 52, and a temperature sensor 53. The control unit 51 includes a central processing unit (CPU) 51a, a memory 51b, and a communication unit 51c. The communication unit 51c communicates with an ECU (Electronic Control Unit) 8 mounted on an electric vehicle, a small ship, or the like, and transmits information about the secondary battery 31 to the ECU 8. The voltage detection circuit 52 is connected to both ends of each secondary battery 31 via a detection line, and constitutes a voltage measurement unit that measures the voltage between terminals of each secondary battery 31 in response to an instruction from the control unit 51. do. The temperature sensor 53 is a contact type or a non-contact type, and measures the temperature T [° C.] of each secondary battery 31.

In the memory 51b in the control unit 51, a computer program for executing the charge rate estimation method of the power storage element according to the embodiment and data necessary for executing the program are stored in advance. Various functional blocks are configured in the control unit 51 by controlling each part of the circuit of the CPU 51a according to this computer program. This functional block includes a charge rate estimation unit 51d, a charge rate correction unit 51e, an internal resistance value calculation unit 51f, and a charge rate correction unit 51g.

The charge rate estimation unit 51d functions to estimate the charge rate of each secondary battery 31. Further, the charge rate correction unit 51e fulfills a function of correcting the charge rate of each secondary battery 31 estimated by the charge rate estimation unit 51d. The internal resistance value calculation unit 51f is a DC of each secondary battery 31 from the current flowing through the secondary battery 31 measured by the current sensor 4 and the voltage between the terminals of the secondary battery 31 measured by the voltage detection circuit 52. It functions to calculate the internal resistance (DCR) value. When the DC internal resistance value calculated by the internal resistance value calculation unit 51f is equal to or less than a predetermined value y described later, the charge rate correction unit 51g sets the charge rate estimated by the charge rate estimation unit 51d as the charge rate of the secondary battery 31. It fulfills the function of.

Further, the memory 51b constitutes an estimated charge rate storage unit that stores the charge rate estimated by the charge rate estimation unit 51d, and a corrected charge rate storage unit that stores the charge rate corrected by the charge rate correction unit 51e. .. Further, the memory 51b constitutes an open circuit voltage characteristic storage unit that stores the open circuit voltage characteristic shown in FIG. 2, and the memory 51b has each charge rate (SOC [%]) as shown in FIG. The SOC-OCV table that associates the value of the open circuit voltage OCV [mV] with the value of is stored in advance. The flat region L shown in FIG. 2 corresponds to the characteristic represented by the value of each OCV [mV] when the SOC shown in the table is 40 to 70 [%]. Further, the memory 51b stores in advance an SOC-DCR table (not shown) that stores the value of the DC internal resistance (DCR) [mΩ] measured for each charge rate (SOC [%]) value. There is.

In the graph shown in FIG. 4, the SOC-DCR curve B plotted by each value of the SOC-DCR table stored in the memory 51b is superimposed on the SOC-OCV curve A shown in FIG. The SOC-OCV curve A is represented by a solid line, and the SOC-DCR curve B is represented by a broken line. The horizontal axis of the graph is SOC [%], the vertical axis on the left side is OCV [mV], and the vertical axis on the right side is DCR [mΩ]. The arrows in the graph indicate which of the left and right vertical axes each curve A or B corresponds to.

From the SOC-DCR curve B shown in the graph, the DC internal resistance value of the secondary battery 31 is smaller in the flat region L of the open circuit voltage than in the change region H of the open circuit voltage, and is a constant value y [mΩ. ] It is understood that it will be smaller. The flat region L is set in a region in the SOC-OCV curve A where the change in open circuit voltage with respect to the change in charge rate is within a predetermined range, for example, 0.5 [mV /%] or less. The constant value y [mΩ] defines the flat region L thus set in the SOC-OCV curve A in the SOC-DCR curve B, and in the present embodiment, the direct current to be compared by the charge rate correction unit 51 g. It is a predetermined value of the internal resistance value. However, in the present invention, the method of determining the predetermined value of the DC internal resistance value is not limited to this, and the secondary battery 31 exhibits in the SOC-DCR curve B in response to the change in the charge rate of the flat region L. , The predetermined value of the DC internal resistance value may be changed as necessary from the DC internal resistance value in the range smaller than the constant value y [mΩ].

Further, in the present embodiment, the charge rate estimation unit 51d estimates the charge rate of the secondary battery 31 by the current integration method. The charge rate correction unit 51e stores the charge rate of the secondary battery 31 estimated by the charge rate estimation unit 51d in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by the voltage detection circuit 52. The charge rate is corrected (see FIG. 3).

Further, in the present embodiment, the computer program stored in the memory 51b configures the functional blocks of the pause period determination unit 51h and the pause period end determination unit 51i in the control unit 51 as shown in FIG. The pause period determination unit 51h functions to determine whether the secondary battery 31 has entered the pause period without the current flowing through the secondary battery 31 being measured by the current sensor 4 over a predetermined period. The pause period end determination unit 51i functions to determine whether the pause period has ended by measuring that the current starts to flow in the secondary battery 31 during the pause period by the current sensor 4.

In the estimated charge rate storage unit, the charge rate estimated by the charge rate estimation unit 51d when the pause period determination unit 51h determines that the secondary battery 31 has entered the pause period is stored as the initial charge rate. The internal resistance value calculation unit 51f is a direct current of the secondary battery 31 from the current that starts to flow in the secondary battery 31 during the pause period and the voltage between the terminals of the secondary battery 31 measured by the voltage detection circuit 52 at that time. Calculate the internal resistance value. When the internal resistance value calculated by the internal resistance value calculation unit 51f is equal to or less than a predetermined value y, the charge rate correction unit 51g sets the initial charge rate stored in the estimated charge rate storage unit as the secondary battery at the end of the pause period. The charge rate is 31.

FIG. 5 is a flowchart showing an outline of the process of the charge rate estimation method of the power storage element according to the embodiment.

First, the CPU 51a acquires the current SOC value of each secondary battery 31 (see step 101). Next, the charge rate estimation unit 51d estimates the SOC value of each secondary battery 31 by the current integration method (see step 102). The charge rate estimated in the charge rate estimation step of this step 102 is stored in the estimated charge rate storage unit. Next, the current value flowing through each secondary battery 31 is measured and acquired by the current sensor 4 (see step 103). Then, the current flowing through each secondary battery 31 becomes zero over a predetermined period and is not measured by the current sensor 4, and whether or not each secondary battery 31 has entered the pause period is determined by the pause period determination unit 51h. (See step 104). In the present embodiment, whether or not the current value acquired in step 103 is zero for a certain period of time or more, for example, 2 hours or more is determined by a clock generated by a clock unit (not shown) in the control unit 51. If the current value acquired in step 103 is not zero for a certain period of time or more and the determination result in step 104 is No, the process returns to step 102 and the processes from step 102 to step 104 are repeated.

On the other hand, when the current value acquired in step 103 becomes zero for a certain period of time or more and the determination result in step 104 becomes Yes, it has already been determined that each secondary battery 31 has already entered the rest period. Whether or not it is determined (see step 105). When the process of step 105 is first executed, it is not determined that each secondary battery 31 has already entered the hibernation period, so the determination result of step 105 is No. In this case, it is determined in the pause period determination step of step 105 that each secondary battery 31 has entered the pause period. Then, the charge rate estimated in the charge rate estimation step of step 102 is acquired as the charge rate at the time of entering the pause period, and the acquired charge rate is stored in the estimated charge rate storage unit as the initial charge rate RSOC (step). 106). By this process of step 106, the charge rate SOC stored in the estimated charge rate storage unit is set as the initial charge rate RST (SOC = RSOC).

On the other hand, if it has already been determined that each secondary battery 31 has already entered the hibernation period and the determination result in step 105 is Yes, then from the voltage between terminals of the secondary battery 31 measured by the voltage detection circuit 52. , The open circuit voltage (OCV) value is acquired (see step 107). Next, the charge rate of each secondary battery 31 estimated in the charge rate estimation step of step 102 corresponds to the value of the open circuit voltage acquired in step 107, and the SOC-OCV characteristic is stored in the open circuit voltage characteristic storage unit. It is corrected to the charge rate VSOC stored as (see step 108). By this process of step 108, the charge rate SOC stored in the corrected charge rate storage unit is set as the corrected charge rate VSOC (SOC = VSOC). In step 108, a charge rate correction step for correcting the charge rate of the secondary battery 31 estimated in the charge rate estimation step of step 102, and a charge rate corrected in this charge rate correction step are stored in the corrected charge rate storage unit. Compute the correction charge rate storage step to be stored. In the open circuit voltage characteristic storage unit, the value of the open circuit voltage with respect to the value of each charge rate is stored in advance as the open circuit voltage characteristic for each secondary battery 31 in the open circuit voltage characteristic storage step (not shown). There is.

Next, it is measured by the current sensor 4 that the current starts to flow in each secondary battery 31 during the rest period, and it is determined whether or not the starting current has flowed in each secondary battery 31 (see step 109). This step 109 constitutes a pause period end determination step for determining whether or not the pause period of each secondary battery 31 has ended. If it is not detected that the starting current flows through each secondary battery 31 and the determination result in step 109 is No, the process returns to step 105 and the processes from step 105 to step 109 are repeated.

When the transient response caused by the flow of the starting current through each secondary battery 31 is detected and the determination result in step 109 is Yes, it is determined that the rest period of each secondary battery 31 has ended. In this case, next, the current flowing through the secondary battery 31 measured by the current sensor 4 and the voltage between the terminals of the secondary battery 31 measured by the voltage detection circuit 52 are seconded by the internal resistance value calculation unit 51f. The DC internal resistance value of the battery 31 is calculated (see step 110).

Next, the internal resistance value calculated in this internal resistance value calculation step of step 110 is a predetermined value y selected from the internal resistance values in the range presented by the secondary battery 31 corresponding to the change in the charge rate of the flat region L. It is determined whether or not it is as follows (see step 111). When the internal resistance value calculated in step 110 is a predetermined value y or less, the determination result in step 111 is Yes, and the charge rate SOC of the secondary battery 31 is stored in the estimated charge rate storage unit by the charge rate correction unit 51 g. The initial charge rate is RSOC (see step 112). If the internal resistance value calculated in step 110 is not equal to or less than the predetermined value y, the determination result in step 111 is No, and the charge rate SOC of the secondary battery 31 is corrected by the charge rate correction unit 51 g. It is set to the corrected charge rate VSOC stored in (see step 113). In steps 111 and 112, when the internal resistance value calculated in the internal resistance value calculation step of step 110 is a predetermined value y or less, the charge rate estimated in the charge rate estimation step of step 102 is the charge rate of the secondary battery 31. It constitutes a charge rate correction step.

According to the charge rate estimation device and the charge rate estimation method of the power storage element according to the present embodiment, the internal resistance value calculated by the internal resistance value calculation unit 51f and the internal resistance value calculation step of step 110 is a predetermined value y or less. In the case of, the secondary battery 31 is determined to be in the state of the flat region L in which the characteristic of the open circuit voltage with respect to the charge rate is a small change in the open circuit voltage. In the flat region L where the characteristic of the open circuit voltage with respect to the charge rate is small in the open circuit voltage change, the internal resistance value of the secondary battery 31 is higher than that in the change region H in which the open circuit voltage change is large, as shown in the graph of FIG. Becomes smaller. Further, the internal resistance value of the secondary battery 31 does not have a large hysteresis due to the history of charge / discharge unlike the charge rate.

Therefore, according to the charge rate estimation device and the charge rate estimation method of the power storage element according to the present embodiment, the calculated internal resistance value is compared with the predetermined value y, so that the characteristic of the open circuit voltage with respect to the charge rate becomes the open circuit voltage. Whether it is in the state of the flat region L with a small change or the state of the flat region H with a large change is accurately determined by the charge rate correction unit 51g and the charge rate correction steps of steps 111 and 112. The charge rate estimated by the current integration method in step 102 accumulates an error with the passage of time. In the present invention, for example, as in Patent Document 1, the region determination is performed as compared with the case where it is determined from the estimated charge rate whether the region is in the flat region L or the change region H by referring to the SOC-OCV characteristics. The accuracy can be improved. Then, when it is determined that the characteristic of the open circuit voltage is in the state of the flat region L where the change in the open circuit voltage is small, the corrected charge rate obtained by being corrected by the charge rate correction step of the charge rate correction unit 51e and step 108 is obtained. Is assumed to include a large error, and the charge rate estimated by the charge rate estimation unit 51d and the charge rate estimation step of step 102 is the charge rate of the secondary battery 31 at that time.

Therefore, for the secondary battery 31 in which the flat region L with a small change in the open circuit voltage and the flat region H with a large change in the open circuit appear with respect to the change in the charge rate, the charge rate estimation device and the charge rate capable of estimating the charge rate with high reliability. It becomes possible to provide an estimation method.

If the corrected charge rate obtained by being corrected by the charge rate correction unit 51e and the charge rate correction step of the charge rate correction unit 51e and step 108 is adopted when the characteristic of the open circuit voltage is in the state of the flat region L where the change in the open circuit voltage is small, The corrected charge rate includes a large error. That is, from the table shown in FIG. 3, when the OCV is measured as, for example, 3320 mV at the timing of transition from the charge period or the discharge period to the rest period, the SOC is corrected to 70%, and the number of cycles in which the secondary battery 31 is charged or discharged. After the repetition, if the OCV is measured as, for example, 3306 mV at the timing when the rest period ends, the SOC is corrected to 40%, and a large error of 30 [%] occurs in the corrected charge rate. This SOC error is due to the fact that the OCV shifts due to hysteresis in the flat region L for each charge / discharge cycle.

Further, according to the charge rate estimation device and the charge rate estimation method of the power storage element according to the present embodiment, when it is determined by the pause period determination unit 51h and the pause period determination step of step 105 that the secondary battery 31 has entered the pause period. The charge rate estimated by the charge rate estimation step 51d and the charge rate estimation step of step 102 is stored in the estimated charge rate storage unit as the initial charge rate RSOC. Further, the internal resistance value when it is determined by the pause period end determination unit 51i and the pause period end determination step of step 109 that the pause period has ended is the internal resistance value calculation step of the internal resistance value calculation unit 51f and step 108. It is determined whether or not the calculated internal resistance value is equal to or less than a predetermined value y. When the internal resistance value is determined to be equal to or less than the predetermined value y, the initial charge rate RSOC stored in the estimated charge rate storage unit is set at the end of the pause period by the charge rate correction unit 51 g and the charge rate correction steps of steps 111 and 112. It is the charge rate of the secondary battery 31 in.

Therefore, in the actual operation of the battery pack 20 in which the flat region L in which the open circuit voltage change is small and the flat region H in which the large change region H appears with respect to the change in the charge rate using the secondary battery 31, the battery pack 20 is suspended. The charge rate at the end of the period can be estimated with high reliability.

In the above embodiment, the correction of the charge rate by the charge rate correction step of the charge rate correction unit 51e and step 108 is estimated by the current integration method by the charge rate estimation step of the charge rate estimation unit 51d and step 102. The case where the charge rate of the next battery 31 is set to the charge rate stored in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by the voltage detection circuit 52 has been described. .. However, the correction of the charge rate by the charge rate correction step of the charge rate correction unit 51e and step 108 is the charge rate of the secondary battery 31 estimated by the current integration method by the charge rate estimation step of the charge rate estimation unit 51d and step 102. However, it may be configured to be performed by being corrected by using a Kalman filter. In this case, the "Kalman gain" and "Kalman gain" are used in the charge rate correction unit 51e and the charge rate correction step, as opposed to the "SOC pre-estimated value" which is the charge rate estimated in the charge rate estimation unit 51d and the charge rate estimation step. The "pre-estimated value of SOC" is corrected by adding the product of "prediction error of terminal voltage" by the Kalman filter. Even with such a configuration, the same operation and effect as those of the charge rate estimation device and the charge rate estimation method of the power storage element according to the above embodiment can be obtained.

The charge rate estimation device and the charge rate estimation method of the power storage element according to the above embodiment have described the case where the secondary battery 31 is an LFP. However, the present invention is not limited to the case where the secondary battery 31 is an LFP, and the open circuit voltage characteristic in which a relatively small flat region and a large change region of the open circuit voltage change appear with respect to the charge rate change. It can be similarly applied to other power storage elements having the above. Even in that case, the same effects as those of the charge rate estimation device and the charge rate estimation method of the power storage element according to the above embodiment are exhibited.

1: Charge rate estimation device 2: Battery pack 3: Assembly battery 31: Secondary battery (storage element)
4: Current sensor (current measuring unit)
5: Battery Management Unit (BMU)
51: Control unit 51a: CPU
51b: Memory (estimated charge rate storage unit, corrected charge rate storage unit, open circuit voltage characteristic storage unit)
51d: Charge rate estimation unit 51e: Charge rate correction unit 51f: Internal resistance calculation unit 51g: Charge rate correction unit 51h: Pause period determination unit 51i: Pause period end determination unit

Claims (8)

A current measuring unit that measures the current flowing through a power storage element having an open circuit voltage characteristic in which a relatively small flat region and a large change region of the open circuit voltage change appear with respect to a change in the charge rate.
A voltage measuring unit that measures the voltage between the terminals of the power storage element, and
A charge rate estimation unit that estimates the charge rate of the power storage element,
A charge rate correction unit that corrects the charge rate of the power storage element estimated by the charge rate estimation unit, and a charge rate correction unit.
An internal resistance value calculation unit that calculates the internal resistance value of the power storage element from the current flowing through the power storage element measured by the current measurement unit and the voltage between terminals of the power storage element measured by the voltage measurement unit.
When the internal resistance value calculated by the internal resistance value calculation unit is equal to or less than a predetermined value, the power storage element including the charge rate correction unit having the charge rate estimated by the charge rate estimation unit as the charge rate of the power storage element. Charge rate estimation device. A pause period determination unit that determines whether the current that flows through the storage element has entered the pause period without being measured by the current measuring unit over a predetermined period.
An estimated charge rate storage unit that stores the charge rate estimated by the charge rate estimation unit, and an estimated charge rate storage unit.
A corrected charge rate storage unit that stores the charge rate corrected by the charge rate correction unit,
A pause period end determination unit for determining whether or not the pause period has ended is provided by measuring that the current starts to flow in the power storage element during the pause period.
The estimated charge rate storage unit stores the charge rate estimated by the charge rate estimation unit as the initial charge rate when the power storage element is determined to have entered the pause period by the pause period determination unit.
The internal resistance value calculation unit calculates the internal resistance value of the power storage element from the current that starts to flow in the power storage element during the rest period and the voltage between terminals of the power storage element measured by the voltage measuring unit at that time. Calculate and
When the internal resistance value calculated by the internal resistance value calculation unit is equal to or less than the predetermined value, the charge rate correction unit sets the initial charge rate stored in the estimated charge rate storage unit at the end of the rest period. The charge rate estimation device for a power storage element according to claim 1, wherein the charge rate of the power storage element is used. It is provided with an open circuit voltage characteristic storage unit that stores the open circuit voltage characteristic as the value of the open circuit voltage with respect to the value of each charge rate.
The charge rate estimation unit estimates the charge rate of the power storage element by the current integration method, and determines the charge rate.
The charge rate correction unit stores the charge rate of the power storage element estimated by the charge rate estimation unit in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by the voltage measurement unit. The charge rate estimation device for a power storage element according to claim 1 or 2, wherein the charge rate is corrected to be adjusted. The charge rate estimation unit estimates the charge rate of the power storage element by the current integration method, and determines the charge rate.
The charge rate estimation device for a power storage element according to claim 1 or 2, wherein the charge rate correction unit corrects the charge rate estimated by the charge rate estimation unit using a Kalman filter. A current measurement step in which a current measuring unit measures the current flowing through a power storage element having an open circuit voltage characteristic in which a relatively small flat region and a large change region of the open circuit voltage change appear with respect to a change in charge rate.
The charge rate estimation step for estimating the charge rate of the power storage element, and
A charge rate correction step for correcting the charge rate of the power storage element estimated in the charge rate estimation step, and a charge rate correction step.
An internal resistance value calculation step of calculating the internal resistance value of the power storage element from the current flowing through the power storage element measured by the current measuring unit and the voltage between terminals of the power storage element measured by the voltage measuring unit.
When the internal resistance value calculated in the internal resistance value calculation step is equal to or less than a predetermined value, the power storage element including the charge rate correction step in which the charge rate estimated in the charge rate estimation step is used as the charge rate of the power storage element. Charge rate estimation method. A pause period determination step for determining whether the current that flows through the storage element has entered the pause period without being measured by the current measuring unit for a predetermined period, and a pause period determination step.
An estimated charge rate storage step for storing the estimated charge rate in the charge rate estimation step in the estimated charge rate storage unit, and an estimated charge rate storage step.
A correction charge rate storage step for storing the charge rate corrected in the charge rate correction step in the correction charge rate storage unit, and a correction charge rate storage step.
It is provided with a pause period end determination step in which it is measured by the current measuring unit that the current starts to flow in the power storage element during the pause period, and it is determined whether or not the pause period has ended.
The estimated charge rate storage step stores the charge rate estimated in the charge rate estimation step as the initial charge rate when it is determined in the pause period determination step that the power storage element has entered the pause period.
In the internal resistance value calculation step, the internal resistance value of the power storage element is calculated from the current that starts to flow in the power storage element during the rest period and the voltage between the terminals of the power storage element measured by the voltage measuring unit at that time. death,
In the charge rate correction step, when the internal resistance value calculated in the internal resistance value calculation step is equal to or less than the predetermined value, the initial charge rate stored in the estimated charge rate storage unit is set to the initial charge rate stored in the estimated charge rate storage unit at the end of the rest period. The method for estimating the charge rate of a power storage element according to claim 5, wherein the charge rate of the power storage element is used. The open circuit voltage characteristic storage step for storing the open circuit voltage characteristic as the open circuit voltage value for each charge rate value in the open circuit voltage characteristic storage unit is provided.
In the charge rate estimation step, the charge rate of the power storage element is estimated by the current integration method, and the charge rate is estimated.
In the charge rate correction step, the charge rate of the power storage element estimated in the charge rate estimation step is stored in the open circuit voltage characteristic storage unit corresponding to the value of the open circuit voltage measured by the voltage measuring unit. The method for estimating the charge rate of the power storage element according to claim 5 or 6, wherein the charge rate is corrected to be adjusted. In the charge rate estimation step, the charge rate of the power storage element is estimated by the current integration method, and the charge rate is estimated.
The charge rate estimation method for a power storage element according to claim 5 or 6, wherein the charge rate correction step corrects the charge rate estimated in the charge rate estimation step by using a Kalman filter.

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