JP7016704B2 - Rechargeable battery system - Google Patents

Description

The present invention relates to a secondary battery system.

In a power supply device using a power storage means such as a battery, a distributed power storage device, an electric vehicle, etc., a state detection device for detecting the state of the power storage means is used in order to use the power storage means safely and effectively. There is. The state of the power storage means includes a state of charge (State of Charge: SOC) indicating how much the charge is charged or how much charge is left to be discharged, and the temperature of the power storage device.

As one of the methods for estimating SOC, there is a method of measuring and integrating the current value in and out of the battery. However, this method also integrates the measurement error included in the measured value of the current, so that there is a problem that the SOC error increases with the passage of time.

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

The first SOC value is continuously calculated by integrating the charge / discharge currents of the secondary battery to obtain the first integrated value, and adding the result of dividing by the capacity value of the secondary battery 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 calculated as the second SOC value, and each time the second SOC value is calculated, The SOC initial value is updated with the second SOC value, and the integration operation of the first integrated value is restarted. As a result, the SOC error that increases as the current measurement values are integrated can be updated at the timing when charging / discharging is switched, so that the latest SOC value can be estimated accurately.

Japanese Patent No. 5051661

In the invention described in Patent Document 1, a correction value for correcting the terminal voltage obtained at the timing of switching between charging and discharging is calculated. Therefore, it is difficult to calculate the SOC when charging or discharging continues. Further, since an error occurs in the terminal voltage, it cannot be expected that the SOC error will be largely eliminated.

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

The secondary battery system of the present invention has a plurality of secondary batteries connected in series, a current detection unit, a voltage detection unit, and data on the initial value of the charged state and the initial value of the battery capacity of the secondary battery. A storage unit having a database including the battery, a temperature detection unit for measuring or estimating the temperature of a first secondary battery which is at least one secondary battery among a plurality of secondary batteries, and a control unit are provided. The control unit is internally calculated from the temperature of the first secondary battery acquired by the temperature detection unit, the current acquired by the current detection unit, and the voltage of the first secondary battery acquired by the voltage detection unit. The charge state of the first secondary battery is calculated from the resistance, and the initial value of the charge state of the second secondary battery, which is the secondary battery for which the temperature is not measured or estimated among the plurality of secondary batteries. And the charge state of the second secondary battery is calculated by using the data of the initial value of the battery capacity and the charge state of the first secondary battery.

According to the present invention, among a plurality of secondary batteries constituting a secondary battery system, it is possible to estimate the charge state of the secondary battery having no means for measuring or estimating the temperature with high accuracy. can.

It is a schematic diagram which shows the structure of the secondary battery system which concerns on this invention and its periphery. It is a schematic diagram which shows the circuit structure of the cell control unit of FIG. 1 and its surroundings. 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 the SOC and the temperature of each cell used in this invention.

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

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

FIG. 1 is a schematic configuration diagram showing a secondary battery system of the present invention and a device connected to the secondary battery system.

In this figure, the secondary battery system 100 is connected to the inverter 400 that PWM-controls the motor generator 410 via relays 300 and 310. Further, 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 cell 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 insulating element 170 typified by a photocoupler. There is.

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

The assembled battery 110 is composed of a plurality of cell cell groups. Here, two cell groups 112a and 112b are shown, but there may be three or more. The cell group 112a and 112b are each composed of a plurality of cell cells 111.

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

In the storage unit 180, the assembled battery 110, the cell 111, the cell groups 112a, 112b have a fully charged capacity (battery capacity), the correspondence between the SOC and the open circuit voltage (OCV: Open Circuit Voltage), and the SOC. Information such as various setting values required for estimation is stored. Further, characteristic information of the cell management unit 120, the cell control units 121a, 121b, the assembled battery control unit 150, and the like can also be stored in the storage unit 180 in advance. Even if the operation of the secondary battery system 100, the assembled battery control unit 150, or the like is stopped, various information stored in the storage unit 180 is retained. The storage unit 180 stores the SOC table as an indicator of the correspondence between the SOC and the open circuit voltage. The storage unit 180 has a database including data of the initial value of SOC of the cell 111 (secondary battery) and the initial value of the battery capacity. The database contains data on the SOC, internal resistance and battery capacity of the cell 111 under environmental conditions including multiple temperature conditions, in other words, data on a map showing the relationship between the SOC of the cell 111, internal resistance and temperature, and the data thereof. It is desirable to include data on the corresponding battery capacity. More details will be described in the description section of FIG.

The cell management unit 120 includes a cell control unit 121a corresponding to the cell group 112a and a cell control unit 121b corresponding to the cell group 112b. The unit cell control units 121a and 121b measure the battery voltage and temperature of the cell cells 111 constituting the cell cell groups 112a and 112b, respectively, and monitor whether or not an abnormality has occurred.

The cell management unit 120 indirectly manages the cell 111 by managing the cell control units 121a and 121b.

The assembled battery control unit 150 includes the battery voltage and temperature of the single battery 111 transmitted by the single battery management unit 120 via the insulating element 170, the current value flowing through the assembled battery 110 transmitted by the current detection unit 130, and the voltage detection unit 140. The voltage value of the assembled battery 110 to be transmitted, the command to be appropriately transmitted by the vehicle control unit 200, and the like are received as signals.

The assembled battery control unit 150 uses the above-mentioned signals received from the cell management unit 120, the current detection unit 130, the voltage detection unit 140, the vehicle control unit 200, the SOC table stored in the storage unit 180, and the like. , SOC, SOH of the assembled battery 110, current and power that can be charged / discharged, abnormal state, calculation for detecting charge / discharge amount, and the like are executed. Based on the above calculation result, the assembled battery control unit 150 transmits a command for the cell cell control units 121a and 121b to manage the cell cell 111 and the cell cell groups 112a and 112b to the cell cell management unit 120. Further, the assembled battery control unit 150 transmits the above-mentioned calculation result, a command based on the calculation result, and the like to the vehicle control unit 200, and stores the above-mentioned calculation result in the storage unit 180 as needed.

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

In the present embodiment, the charger 420 is configured to control the charging voltage, charging current, and the like based on the command from the vehicle control unit 200, but the control is performed based on the command from the assembled battery control unit 150. May be good. Further, the charger 420 may be installed inside the vehicle or outside the vehicle depending on the configuration of the vehicle, the performance of the charger 420, the purpose of use, the installation conditions of the external power source, and the like. ..

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

When a vehicle equipped with the secondary battery system 100 is connected to a household power source or an external power source represented by a charging stand, the vehicle is charged with the secondary battery system 100 based on the information transmitted by the vehicle control unit 200. The device 420 is connected, and the assembled battery 110 is charged until a predetermined condition is met. The energy stored in the assembled battery 110 by charging is used at the next vehicle running, or is also used to operate electrical components inside and outside the vehicle. Further, if necessary, it may be discharged to an external power source represented by a household power source.

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

In this figure, the 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 voltage between the terminals of each cell 111.

The temperature detection unit 125 measures or estimates the temperature of a part or all of the batteries of the cell group 112i, and handles the temperature as a representative temperature value of the cell 111 constituting the cell group 112i. The temperature measured by the temperature detection unit 125 is used for various calculations for detecting the state of the cell 111, the cell group 112i, or the assembled battery 110. Here, the cell 111, which is the target of temperature measurement or estimation by the temperature detection unit 125, is referred to as a "first secondary battery". On the other hand, the cell 111 that is not the target of temperature measurement or estimation by the temperature detection unit 125 is called a "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 assembled battery control unit 150 (FIG. 1) via the signal input / output circuit 124. 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 in and around the cell control unit 121i, that is, the circuit for equalizing the voltage and SOC variation between the cell 111 generated due to self-discharge and variation in current consumption, etc. The description is omitted.

In the above description, the secondary battery system according to the embodiment has a control unit such as a cell control unit 121i, a control circuit 123 included therein, and an assembled battery control unit 150. The control unit that performs control may be any of these. Therefore, when the term "control unit" is used generically in the present specification, it means any of the above-mentioned control units.

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

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

Here, a general SOC calculation method will be described as a premise for describing the SOC calculation method in the present invention.

The OCV of the cell 111 is acquired, and the SOC at the time _tn when the OCV is acquired is acquired from the SOC table shown in FIG. The SOC obtained from the SOC table is called "SOC _v ". SOC _v at time t _n is expressed by the following equation (1).

In the equation, Map represents the function corresponding to the curve in FIG.

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

Here, _Qi is the full charge capacity of the cell 111 (FIG. 1). Further, in the following, the integral value described in the above equation (2) (the integral value of the molecule in the equation, which is the change in charge in the time from time t _n to time t) is referred to as " _ΔSI " 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-mentioned general SOC calculation method includes the first SOC error and the second SOC error described below.

<About the first SOC error>
The current detection unit 130 detects the charge / discharge current I (t) including a measurement error. This means that the time-integrated value ΔSOC (t) of the charge / discharge current represented by the above equation (2) includes an error. Even if the charge / discharge current I (t) has a small error, the time-integrated value ΔSOC (t) of the charge / discharge current accumulates an error as the integrated time becomes longer, and may become a large error. In the present specification, the error included in ΔSOC (t) is referred to as “first SOC error”. As will be described later, the present invention eliminates the first SOC error.

<About the second SOC error>
OCV is defined as a terminal-to-terminal voltage in which no charge / discharge current is generated and there is no time variation. The voltage between terminals of the cell 111 measured when the relays 300, 310, 320, and 330 shown in FIG. 1 are open and the voltage of the cell 111 does not fluctuate with time is OCV. Further, although the relays 300, 310, 320, and 330 are closed, the charging / discharging of the assembled battery 110 has not started, or even after the charging / discharging has been started, the charging / discharging is stopped and then left for a long time, and the voltage of the cell 111 becomes high. The voltage between the terminals of the cell 111 measured when the time does not fluctuate can be regarded as OCV.

However, when the assembled battery 110 is used, the relays 300, 310, 320, and 330 are closed. In addition, it does not occur frequently that the above-mentioned charging / discharging is not performed at all. That is, there is almost no opportunity to acquire OCV as a result while using the assembled battery 110.

An object of the present invention is to remove the first SOC error included in ΔSOC (t). For this purpose, it is necessary to re-detect the SOC from the battery voltage while the assembled battery 110 is in use (the relays 300, 310, 320, and 330 are closed). However, as described above, there is little opportunity to acquire 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 acquired by a temperature sensor installed in the secondary battery or by estimation, and the SOC of all the secondary batteries (cells) is obtained. Think about getting it more accurately.

Hereinafter, an example in which the current, the voltage of the cell, and the temperature of the cell are input to acquire the SOC, temperature, DC resistance, etc. of all the cells will be described.

FIG. 4 is a flowchart showing a method of calculating the SOC and temperature of each of the assembled batteries composed of a plurality of secondary batteries (cells) connected in series.

First, a map (database) showing the relationship between the SOC of the secondary battery, the DC 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. In general, even if the secondary batteries correspond to a group of single batteries connected in series or in parallel, the concept shown in this figure can be similarly applied.

Further, the map may be a map obtained by, for example, testing an extracted cell cell at the time of product testing, collecting detailed data, and compiling it as a database. In this case, the extracted cell and the plurality of cells actually used for the assembled battery are strictly different from each other. Therefore, the values of SOC, resistance, temperature, etc. calculated using the values included in the database are different from the actual values of the cell, and strictly include errors. This error is different from the first SOC error described above. The error between such a map and the actual cell cell value will be referred to as the "second SOC error".

The DC resistance R _i of each secondary battery is obtained from the current _I flowing through the secondary battery and the voltage Vi at that time (S110). Here, the subscript i represents the i-th secondary battery in series. Further, it is desirable to use the measured values for the current _I and the voltage Vi as shown in FIGS. 1 and 2. The voltage V _i may be a value during energization, or an internal resistance may be acquired using a map and this may be used as a DC resistance R _i .

Next, the DC resistance R _i and the temperature T _{sensor, i} of a part or all of the secondary batteries obtained by actual measurement or estimation are input to the map, and the SOC _{sensor, i} is output (S120). This SOC _{sensor, i} is not an SOC obtained from the integration of charge / discharge currents in which errors are accumulated, but an SOC output from a map created based on the results measured in advance using an actual secondary battery. , It is a value that does not cause accumulation of error. It is desirable to measure the temperature T _{sensor, i} of the secondary battery using a temperature sensor. Further, "input to the map" or "output from the map" has the same meaning as "calculation using the 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 methods of the above equations (2) and (3) (S130). Hereinafter, the SOC calculated by the current integration method is referred to as “SOC _int ”. The SOC of the i-th secondary battery in series is called "SOC _{int, i} ".

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

Since each secondary battery constituting the secondary battery module is connected in series, the value of _ΔSI in each secondary battery is common, and it is possible to apply the corrected _ΔSI to all the batteries. .. Therefore, the SOC _{int, i} (i = 1, 2, 3, ...) Of each secondary battery can be obtained with high accuracy (S160). In other words, the SOC _{int, i} of all secondary batteries can be determined by the current integration method using the corrected values of _ΔSI .

Next, the SOC _{int, i and} DC resistance R _i of each secondary battery are input to the map, and the temperature Ti of each secondary battery is output (S170). In other words, by acquiring the map values (temperature _Ti ) corresponding to SOC _{int, i and} Ri, the temperature of the secondary battery without the temperature sensor can be estimated with high accuracy. In this case, the measured voltage _Vi may be used for the calculation.

As a result, the temperature of all the batteries can be grasped without installing the temperature sensor on all the batteries, and the cost can be reduced by reducing the temperature sensors. Further, since the current can be limited according to those temperatures, 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 realize a secondary battery system having a long life and low cost.

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

Although the present invention has been specifically described above based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be variously modified without departing from the gist thereof.

In addition, each of the above configurations, functions, processing units, etc. can be realized as hardware by designing all or part of them, for example, by an integrated circuit, and the processor executes a program that realizes each function. It can also be realized as software by doing so. Information such as programs and tables that realize each function 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 shown above, one lithium ion secondary battery (secondary battery) is used as a single battery, and the batteries are connected in series to form an assembled battery. However, one secondary battery in which the single batteries are connected in parallel is used. It may be regarded as a battery and connected in series to form an assembled battery, or a single battery connected in series may be connected in parallel to form an assembled battery. Including parallel connection, there is a possibility that the charge / discharge current flowing through the cell may vary from individual to individual. In that case, change the number of current detectors installed and the charge / discharge current value flowing for each cell. Is detected, or the average current flowing through the cell is obtained, and the SOC calculation may be performed based on this.

Therefore, in the present specification, what is regarded as a secondary battery constituting an assembled battery may be a cell or a cell group, and when collectively referred to as a "secondary battery", the term "secondary battery" is used. It shall include a group of cells considered to be one secondary battery.

Further, in the above-described embodiment, the present invention has been considered for detecting the SOC of the assembled battery, but the present invention can also be considered for a cell or a cell group.

In other words, the plurality of secondary batteries so that all the charge states of the plurality of secondary batteries reach a predetermined value based on the SOC _{int, i} (FIG. 4) calculated by the current integration method. It is desirable to charge each of the plurality of secondary batteries so that the charging states of the batteries are the same. As a result, the capacity that can be charged and discharged as 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 charge state of the first secondary battery calculated by the current integration method.

Further, the secondary battery (cell) can be replaced individually based on the determination result of the life of the secondary battery.

100: Secondary battery system, 110: Assembly 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 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 (7)

With multiple secondary batteries connected in series,
Current detector and
Voltage detector and
A storage unit having a database containing data of the initial value of the charge state of the secondary battery and the initial value of the battery capacity, and the storage unit.
A temperature detection unit that measures or estimates the temperature of the first secondary battery, which is at least one of the plurality of secondary batteries.
With a control unit,
The control unit includes 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. The charge state of the first secondary battery is calculated from the internal resistance calculated from the voltage of the above, and the second of the plurality of secondary batteries is the secondary battery for which the temperature is not measured or estimated. Using the data of the initial value of the charged state of the secondary battery and the initial value of the battery capacity and the charged state of the first secondary battery, the charged state of the second secondary battery can be determined. Secondary battery system to calculate. The control unit calculates the charging state of the first secondary battery by the current integration method, and the charging state of the first secondary battery calculated by the current integration method, the temperature, and the inside thereof. The integrated current value is corrected so that the difference from the charged state of the first secondary battery calculated from the resistance is equal to or less than a predetermined value, and the integrated current value is used to obtain the second secondary battery. The secondary battery system according to claim 1, wherein the charging state is calculated. Based on the charging state of the first secondary battery calculated by the current integration method, the first two so that the charging state of all of the plurality of secondary batteries reaches a predetermined value. The secondary battery system according to claim 2, wherein each of the 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 the 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 contains data on the state of charge, internal resistance and temperature of the secondary battery.
The secondary battery system according to claim 2, wherein the control unit calculates the charge state 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 state of charge of the second secondary battery.

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