WO2019142550A1

WO2019142550A1 - Secondary battery system

Info

Publication number: WO2019142550A1
Application number: PCT/JP2018/045603
Authority: WO
Inventors: ソクチョル申; 耕平本蔵; 鈴木　修一
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2018-01-18
Filing date: 2018-12-12
Publication date: 2019-07-25
Also published as: JP7016704B2; JP2019124612A

Abstract

The present invention highly accurately estimates the state of charge of a secondary battery, from among a plurality of secondary batteries composing a secondary battery system, that is not provided with a means for measuring or estimating temperature. This secondary battery system comprises a plurality of secondary batteries connected in series, a current detection unit, a voltage detection unit, a storage unit having a database including data for the initial state-of-charge and battery-capacity values of the secondary batteries, a temperature detection unit for measuring or estimating the temperature of at least one first secondary battery from among the plurality of secondary batteries, and a control unit. The control unit calculates the state of charge of the first secondary battery from the temperature of the first secondary battery acquired from the temperature detection unit and an internal resistance calculated from a current acquired by the current detection unit and the voltage of the first secondary battery acquired by the voltage detection unit, and uses the data for the initial state-of-charge and battery-capacity values of a second secondary battery, from among the plurality of secondary batteries, in which the temperature is not measured or estimated and the state of charge of the first secondary battery to calculate the state of charge of the second secondary battery.

Description

Secondary battery system

The present invention relates to a secondary battery system.

In a power supply device using a storage means such as a battery, a distributed power storage device, an electric car, etc., a state detection device for detecting the state of the storage means is used to use the storage means safely and effectively. There is. The state of the storage means includes a state of charge (SOC) indicating how much the battery has been charged or how much the amount of charge that can be discharged remains, the temperature of the storage device, and the like.

One method of estimating the SOC is to measure and integrate the current value into and out of the battery. However, in this method, since the measurement error included in the measured value of the current is also integrated, there is a problem that the SOC error increases with the passage of time.

As means for solving the above problems, Patent Document 1 discloses the following invention.

The first SOC value is continuously calculated by integrating the charge / discharge current of the secondary battery to obtain the first integrated value and dividing the result by the capacity value of the secondary battery and adding it to the SOC initial value. . After correcting the terminal voltage of the secondary battery obtained at the timing of switching between charging and discharging to approach the open circuit voltage, the SOC at that time is determined as the second SOC value, and each time the second SOC value is determined, The SOC initial value is updated with the second SOC value to restart the integration calculation of the first integrated value. As a result, the SOC error, which expands as the current measurement values are integrated, can be updated at the timing when charging and discharging are switched, so that the latest SOC value can be accurately estimated.

Patent No. 5051661 gazette

In the invention described in Patent Document 1, the correction value for correcting the terminal voltage obtained at the timing when charge and discharge are switched is calculated. Therefore, it is difficult to calculate the SOC when charging or discharging continues. Furthermore, since an error also occurs in the terminal voltage, it can not be expected to substantially eliminate the SOC error.

An object of the present invention is to estimate with high accuracy the state of charge of a secondary battery not provided with means for measuring or estimating temperature among a plurality of secondary batteries constituting a secondary battery system. is there.

The secondary battery system of the present invention comprises data of a plurality of secondary batteries connected in series, a current detection unit, a voltage detection unit, and an initial value of the charge state of the secondary battery and an initial value of the battery capacity. And a control unit for measuring or estimating the temperature of the first secondary battery that is at least one of the plurality of secondary batteries, and a control unit. The controller calculates the temperature of the first secondary battery acquired by the temperature detector, the current calculated by the current detector, and the internal calculated from the voltage of the first secondary battery acquired by the voltage detector. From the resistance, the charge state of the first secondary battery is calculated, and among the plurality of secondary batteries, the initial value of the charge state of the second secondary battery, which is a secondary battery that does not measure or estimate the temperature And data of initial value of battery capacity and charging of first secondary battery Using state, and calculates the state of charge of the second secondary battery.

According to the present invention, among the plurality of secondary batteries constituting the secondary battery system, it is possible to estimate with high accuracy the state of charge of the secondary battery not provided with means for measuring or estimating temperature. it can.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the secondary battery system which concerns on this invention, and the structure of the periphery of it. It is the schematic which shows the cell control part of FIG. 1, and the circuit structure of the periphery of it. It is a graph which shows the example of the SOC table used in this invention. It is a flowchart which shows the method of calculating SOC and temperature of each single battery used in this invention.

Hereinafter, a secondary battery system according to an embodiment of the present invention will be described.

Embodiment
The secondary battery system is suitably applied to a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), an electric vehicle (EV) and the like.

FIG. 1 is a schematic configuration view showing a secondary battery system of the present invention and devices connected thereto.

In the figure, secondary battery system 100 is connected to an inverter 400 that performs PWM control of motor generator 410 via

relays

300 and 310. Also, the secondary battery system 100 is connected to the charger 420 via the

relays

320 and 330.

The secondary battery system 100 includes an assembled battery 110, a single battery management unit 120, a current detection unit 130, a voltage detection unit 140, an assembled battery control unit 150, a storage unit 180, and an insulation element 170 represented by a photocoupler. There is.

The vehicle control unit 200 can communicate with the battery pack control unit 150, the charger 420 and the inverter 400.

The battery assembly 110 is composed of a plurality of unit cell groups. Here, although two

unit cell groups

112a and 112b are shown, three or more may be sufficient. Each of the

unit cell groups

112 a and 112 b is configured of a plurality of unit cells 111.

The current detection unit 130 detects the current flowing to the battery assembly 110. The voltage detection unit 140 detects the voltage of the assembled battery 110.

In the storage unit 180, the fully charged capacity (battery capacity) of the battery pack 110, the cells 111, and the

cell groups

112a and 112b, the correspondence relationship between the SOC and the open circuit voltage (OCV), the SOC Information such as various setting values necessary for estimation is stored. Furthermore, characteristic information of the unit cell management unit 120, the unit

cell control units

121a and 121b, and the assembled battery control unit 150 can also be stored in the storage unit 180 in advance. Even if the operations of the secondary battery system 100, the assembled battery control unit 150, etc. are stopped, various information stored in the storage unit 180 is held. Note that the storage unit 180 stores an SOC table as indicating the correspondence between the SOC and the open circuit voltage. The storage unit 180 has a database including data of the initial value of the SOC of the unit cell 111 (secondary battery) and the initial value of the battery capacity. The database is data of SOC of unit cell 111, internal resistance and battery capacity under environmental conditions including a plurality of temperature conditions, in other words, map data showing the relationship of SOC of unit cell 111, internal resistance and temperature, and It is desirable to include corresponding battery capacity data. Further details will be described in the explanation of FIG.

The unit cell management unit 120 includes a unit cell control unit 121a corresponding to the unit cell group 112a and a unit cell control unit 121b corresponding to the unit cell group 112b. The single

cell control units

121a and 121b respectively measure the battery voltage and temperature of the single cells 111 constituting the

single cell groups

112a and 112b, monitor whether or not an abnormality has occurred, and the like.

The unit cell management unit 120 indirectly manages the unit cell 111 by managing the unit

cell control units

121a and 121b.

In the battery pack control unit 150, the battery voltage or temperature of the battery 111 transmitted by the battery management unit 120 via the insulating element 170, the current value flowing to the battery assembly 110 transmitted by the current detector 130, the voltage detector 140 A voltage value of the battery pack 110 to be transmitted, a command appropriately transmitted by the vehicle control unit 200, and the like are received as signals.

The battery pack control unit 150 uses the unit cell management unit 120, the current detection unit 130, the voltage detection unit 140, the above-described signal received from the vehicle control unit 200, the SOC table stored in the storage unit 180, and the like. An operation for detecting the SOC, SOH, chargeable / dischargeable current or power, abnormal condition, charge / discharge amount, etc. of the assembled battery 110 is executed. The assembled battery control unit 150 transmits a command for the single

cell control units

121 a and 121 b to manage the single cells 111 and the

single battery groups

112 a and 112 b to the single cell management unit 120 based on the above calculation result. Further, the battery pack control unit 150 transmits the above-described calculation result and a command based on the calculation result to the vehicle control unit 200, and stores the above-described calculation result in the storage unit 180 as necessary.

Vehicle control unit 200 controls inverter 400 and charger 420 using the information received from battery pack control unit 150. While the vehicle is traveling, secondary battery system 100 is connected to inverter 400, and uses the energy stored in assembled battery 110 to drive motor generator 410. At the time of charging, the secondary battery system 100 is connected to the charger 420 and charged by the power supply from a household power supply or a charging stand. At this time, the power from the charger 420 is stored in the battery pack 110.

In the present embodiment, the charger 420 is configured to control the charging voltage, the charging current, and the like based on a command from the vehicle control unit 200, but the control is performed based on the command from the assembled battery control unit 150. It is also good. In addition, the charger 420 may be installed inside the vehicle or may be installed outside the vehicle according to the configuration of the vehicle, the performance of the charger 420, the purpose of use, the installation condition of the external power supply, etc. .

When the vehicle system having the secondary battery system 100 starts and travels, the secondary battery system 100 is connected to the inverter 400 under the management of the vehicle control unit 200, and the energy stored in the battery pack 110 is stored. Is used to drive the motor generator 410. At the time of regeneration, the battery pack 110 is charged by the power generated by the motor generator 410.

When the vehicle provided with the secondary battery system 100 is connected to a household power supply or an external power supply represented by a charging stand, charging with the secondary battery system 100 is performed based on the information transmitted by the vehicle control unit 200. The battery 420 is connected to charge the battery pack 110 until predetermined conditions are met. The energy stored in the battery pack 110 by charging is used during the next travel of the vehicle or is also used to operate electrical components and the like inside and outside the vehicle. Furthermore, if necessary, it may be released to an external power source represented by a household power source.

FIG. 2 is a schematic configuration view showing one unit cell control unit.

In the figure, the unit cell control unit 121i includes a voltage detection circuit 122 (voltage detection unit), a control circuit 123, a signal input / output circuit 124, and a temperature detection unit 125.

The voltage detection circuit 122 measures the inter-terminal voltage of each unit cell 111.

The temperature detection unit 125 measures or estimates the temperature of part or all of the unit cell group 112i, and handles the temperature as a temperature representative value of the unit cells 111 constituting the unit cell group 112i. The temperature measured by the temperature detection unit 125 is used for various calculations for detecting the state of the unit cell 111, the unit cell group 112i, or the assembled battery 110. Here, the unit cell 111 which is the target of measurement or estimation of the temperature by the temperature detection unit 125 is referred to as “first secondary battery”. On the other hand, the unit cell 111 which is not a target of measurement or estimation of the temperature by the temperature detection unit 125 is referred to as “second secondary battery”.

The control circuit 123 receives the measurement result from the voltage detection circuit 122 and the temperature detection unit 125, and transmits the measurement result to the battery pack control unit 150 (FIG. 1) via the signal input / output circuit 124. In addition, it is also possible to transmit information to the voltage detection circuit 122 and the temperature detection unit 125 based on the information from the signal input / output circuit 124. The balancing circuit generally mounted on the cell control unit 121i and the periphery thereof, that is, a circuit for equalizing the voltage or SOC variation among the cell 111 generated due to self discharge, current consumption variation, etc. The description was omitted.

In the above description, the secondary battery system according to the embodiment includes the control unit such as the unit cell control unit 121i, the control circuit 123 included in the unit cell, and the battery pack control unit 150. The control unit that performs control may be any of these. Therefore, when collectively referred to as “control unit” in the present specification, any one of the control units described above is referred to.

FIG. 3 is a graph of an example of the SOC table (database) stored in the storage unit 180 of FIG. The horizontal axis represents the SOC of the unit cell 111 shown in FIG. 1, and the vertical axis represents the OCV of the unit cell 111.

Although the data format is arbitrary, it is shown here in graph format for the convenience of explanation. Although the data table is used in the present embodiment, the correspondence relationship between the OCV and the SOC can also be expressed by using a mathematical expression or the like. Other methods may be used as long as the method can convert OCV to SOC or SOC to OCV.

Here, a general SOC calculation method will be described on the assumption that the SOC calculation method in the present invention is described.

The OCV of the unit cell 111 is acquired, and the SOC at time t _{n when the} OCV is acquired from the SOC table shown in FIG. 3 is acquired. The SOC acquired from the SOC table is called "SOC _v ". The SOC _{v at} time t _n is represented by the following equation (1).

Where Map represents a function corresponding to the curve of FIG.

Only the above equation (1) can only obtain the SOC at time t _n . Therefore, as shown in the following equation (2), change amount ΔSOC (t) of SOC in the time from time t _n to time t is calculated using the integrated value of the charge and discharge current. Then, by adding ΔSOC (t) to SOC _v (t _n ), as shown in the following equation (3), SOC at time t which is momentarily after time t _n (hereinafter referred to as “SOC _i ” Get).

Here, Q _i is the full charge capacity of the unit cell 111 (FIG. 1). Also, in the following, the integral value (the value of the integral of the numerator in the equation, which is the change in charge in the time from time t _n to time t) described in the above equation (2) is “ΔS _I ” or It is called "current integrated value".

The above is a general SOC calculation method, which is called a current integration method.

The SOC _i obtained by the above-described general SOC calculation method includes a first SOC error and a second SOC error described below.

<About the first SOC error>
The current detection unit 130 detects the charge / discharge current I (t) in a form including a measurement error. This means that the time integration value ΔSOC (t) of the charge and discharge current shown in the above equation (2) includes an error. Even if the charging / discharging current I (t) is a small error, as the integration time ΔSOC (t) is longer, the error is accumulated as the integration time ΔSOC (t) becomes, and a large error may occur. In the present specification, an error included in ΔSOC (t) is referred to as a “first SOC error”. As described later, in the present invention, the first SOC error is removed.

<About the second SOC error>
OCV is defined as an inter-terminal voltage in which no charge / discharge current occurs and no time variation occurs. When the

relays

300, 310, 320, and 330 shown in FIG. 1 are open and the voltage of the unit cell 111 does not change with time, the inter-terminal voltage of the unit cell 111 is OCV. Also, if the

relays

300, 310, 320, 330 are closed but charging / discharging of the assembled battery 110 is not started, or even after it is started, it is left for a long time after charging / discharging is stopped. The terminal-to-terminal voltage of the unit cell 111 can be regarded as OCV when the time does not change.

However, when using the assembled battery 110, the

relays

300, 310, 320, 330 are closed. In addition, it is not frequent that the above-described charge and discharge are not performed at all. That is, while using the battery pack 110, there is almost no opportunity to acquire an OCV as a result.

An object of the present invention is to remove the first SOC error included in ΔSOC (t). For this purpose, it is necessary to redetect the SOC from the battery voltage during use of the battery assembly 110 (the

relays

300, 310, 320, and 330 are closed). However, as described above, there is little opportunity to acquire an OCV with the

relays

300, 310, 320, 330 closed.

Therefore, the temperature of at least one secondary battery constituting the assembled battery (secondary battery module) is obtained by the temperature sensor installed in the secondary battery or by estimation, and the SOCs of all the secondary batteries (unit cells) are obtained. Think about getting more accurate.

Hereinafter, an example will be described in which the current, the voltage of the unit cell, and the temperature of the unit cell are input, and the SOC, temperature, direct current resistance, and the like of all unit cells are acquired.

FIG. 4 is a flow chart showing a method of calculating the SOC and temperature of each unit cell in a battery pack composed of a plurality of secondary batteries (unit cells) connected in series.

First, a map (database) indicating the relationship between the SOC of the secondary battery, the direct current resistance R, and the temperature T is prepared (S100). This map preferably corresponds to the deterioration of the battery. Here, the secondary battery is a single battery. Generally, even if the secondary batteries correspond to a unit cell group connected in series or in parallel, the concept shown in the figure can be applied similarly.

In addition, the map may be, for example, a test performed on the extracted single battery at the time of the product test, collecting detailed data, and collecting it as a database. In this case, the extracted single battery and each of the plurality of single batteries actually used for the assembled battery are strictly different. For this reason, the values of SOC, resistance, temperature and the like calculated using the values contained in the database differ from the actual values of single cells, and strictly include errors. This error is different from the above first SOC error. An error between such a map and the value of an actual single cell will be referred to as a "second SOC error".

The direct current resistance R _i of each secondary battery is determined from the current I flowing to the secondary battery and the voltage V _{i at} that time (S 110). Here, the subscript i represents the i-th secondary battery in series. Further, as the current I and the voltage V _i , it is desirable to use values measured as shown in FIGS. 1 and 2. The voltage V _i may be a value during energization, or a map may be used to obtain the internal resistance, which may be used as the direct current resistance R _i .

Next, DC resistance R _i and temperature T _{sensor, i of} a part or all of the secondary battery obtained by measurement or estimation are input to a map, and SOC _{sensor, i} is output (S120). This SOC _{sensor, i} is not the SOC obtained from the integration of the charge / discharge current at which the error is accumulated, but the SOC output from the map created based on the result of measurement in advance using an actual secondary battery. , Is a value that does not cause accumulation of errors. The temperature T _{sensor, i} of the secondary battery is preferably measured using a temperature sensor. Also, "input to map" or "output from map" has the same meaning as "calculate using a map (database)".

On the other hand, the SOC of the same secondary battery as that targeted in S120 is separately calculated by the current integration method of the above formulas (2) and (3) (S130). Hereinafter, the SOC calculated by the current integration method is referred to as "SOC _int ". Also, the SOC of the i-th secondary battery in series is called "SOC _{int, i} ".

Then, SOC _{sensor, i} is compared with SOC _{int, i} (S140). If the values are not equal (if the difference between the values exceeds a predetermined value), the current integration value ΔS _I of the above equation (2) is corrected so that the difference is less than or equal to the predetermined value ( S150). In other words, the error of ΔS _I due to the error of the current detection unit (current sensor) is reduced. The correction method may be such that SOC _{int, i} which is the result of SOC calculation (S130) by the current integration method is replaced with SOC _{sensor, i} , and the current integration value is calculated backward.

Since the respective secondary batteries constituting the secondary battery module are connected in series, the value of ΔS _I in each secondary battery is common, and it is possible to apply the corrected ΔS _I to all the batteries . Accordingly, SOC _{int, i} (i = 1, 2, 3,...) Of each secondary battery can be obtained with high accuracy (S 160). In other words, SOC _{int, i} of all the secondary batteries can be determined by the current integration method using the corrected value of ΔS _I.

Then, the SOC _{int, i} and the direct current resistance R _i of each secondary battery are input to the map, and the temperature T _i of each secondary battery is output (S170). In other words, the temperature of the secondary battery in which the temperature sensor is not provided can be estimated with high accuracy by acquiring the values of the map (temperature T _i ) corresponding to the SOC _{int, i} and R _i . In this case, the measured voltage V _i may be used for the calculation.

Thus, the temperature of all the batteries can be grasped without installing the temperature sensors in all the batteries, and the cost can be reduced by reducing the temperature sensors. In addition, since the current can be limited in accordance with the temperature, it is possible to realize a highly safe and long-life secondary battery system. Furthermore, by grasping the temperature of each battery, it is possible to efficiently cool the battery and to realize a long life and low cost secondary battery system.

In the present invention, the process of S130, S140, S150 and S160 shown in FIG. 4 is omitted, and the data of SOC _{sensor, i} obtained in the process of S120 is used instead of SOC _{int, i} in S170. The temperature T _i may be obtained using a map in the process. However, in this case, it is conceivable to increase the allowable value for the difference between SOC _{sensor, i} and SOC _{int, i} to be compared in the process of S140 because the process of correction of S150 or the like has not been performed. Although the error of the temperature T _i tends to be large because the correction is not made, the method of the present invention can be applied.

As mentioned above, although this invention was concretely demonstrated based on embodiment, this invention is not limited to the above-mentioned embodiment, It can not be overemphasized that it can change variously in the range which does not deviate from the summary.

In addition, each configuration, function, processing unit, etc. can be realized as hardware by designing all or part of them with, for example, an integrated circuit, or a processor executes a program that realizes each function. It can also be realized as software by doing this. Programs for realizing the respective functions, and information such as a table can be stored in a storage device such as a memory or a hard disk, or a storage medium such as an IC card or a DVD.

In the embodiment described above, although a single lithium ion secondary battery (secondary battery) is used as a single battery and this is connected in series to form a battery assembly, one secondary battery in which single batteries are connected in parallel is used as one secondary battery It may be regarded as a battery, and may be connected in series to constitute a battery assembly, or a series connected battery may be connected in parallel to constitute a battery assembly. If parallel connection is included, there is a possibility that individual differences may occur in the charge and discharge current flowing in the unit cells, but in that case, the charge and discharge current value flowing in each unit cell is changed by changing the number of installed current detection units. The SOC calculation may be performed based on the detected current or the average current flowing to the unit cell.

Therefore, in the present specification, what is regarded as a secondary battery constituting the assembled battery may be a single battery or a single battery group, and when collectively referred to as "secondary battery", It shall contain a single battery group regarded as one secondary battery.

Further, in the embodiment described above, the present invention is considered to detect the SOC of the battery pack, but the present invention can be considered to be a single battery or a single battery group.

In addition, based on the SOC _{int, i} (FIG. 4) calculated by the current integration method, in other words, a plurality of secondary batteries are set so that all charge states of the plurality of secondary batteries reach a predetermined value. It is desirable to charge each of the plurality of secondary batteries so that the charge states of Thereby, the chargeable / dischargeable capacity of the entire secondary battery system can be increased.

Further, according to the present invention, the life of the secondary battery can be determined based on the change in the state of charge of the first secondary battery calculated by the current integration method.

Furthermore, based on the determination result of the life of the secondary battery, it is possible to individually replace the secondary battery (unit cell).

100: secondary battery system, 110: assembled battery, 111: single battery, 112a, 112b, 112i: single battery group, 120: single battery management unit, 121a, 121b, 121i: single battery control unit, 122: voltage detection circuit , 123: control circuit, 124: signal input / output circuit, 125: temperature detection unit, 130: current detection unit, 140: voltage detection unit, 150: battery pack control unit, 170: insulation element, 180: storage unit, 200: Vehicle control unit, 300, 310, 320, 330: relay, 400: inverter, 410: motor generator, 420: charger.

Claims

A plurality of secondary batteries connected in series;
A current detection unit,
A voltage detection unit,
A storage unit having a database including data of an initial value of a state of charge of the secondary battery and an initial value of a battery capacity;
A temperature detection unit that measures or estimates the temperature of a first secondary battery that is at least one of the plurality of secondary batteries;
And a control unit,
The control unit controls the temperature of the first secondary battery acquired by the temperature detection unit, the current acquired by the current detection unit, and the first secondary battery acquired by the voltage detection unit. A second battery which is a secondary battery which does not measure or estimate the temperature among the plurality of secondary batteries, from the internal resistance calculated from the voltage of The charging state of the second secondary battery is determined using the initial value of the charging state of the secondary battery and the data of the initial value of the battery capacity and the charging state of the first secondary battery. Calculate a secondary battery system.
The control unit calculates the charge state of the first secondary battery by a current integration method, and the charge state of the first secondary battery calculated by the current integration method, the temperature, and the inside The current integrated value is corrected so that the difference between the charge state of the first secondary battery calculated from the resistance and the charge state is equal to or less than a predetermined value, and using the current integrated value, the second secondary battery is The secondary battery system according to claim 1, wherein the state of charge is calculated.
The first two of the plurality of secondary batteries are arranged such that the state of charge reaches a predetermined value based on the state of charge of the first secondary battery calculated by the current integration method. The secondary battery system according to claim 2, wherein each of a secondary battery and the second secondary battery is charged.
The secondary battery system according to claim 2, wherein the life of the secondary battery is determined based on a change in the state of charge of the first secondary battery calculated by the current integration method.
The secondary battery system according to claim 4, wherein the secondary batteries are individually replaced based on the determination result of the life.
The database includes data of charge state, internal resistance and temperature of the secondary battery,
The secondary battery system according to claim 2, wherein the control unit calculates the state of charge of the first secondary battery using the data.
The secondary battery system according to claim 6, wherein the control unit calculates the temperature of the second secondary battery from the charge state of the second secondary battery.