JP2016015820A - Battery controller and battery control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery controller and a battery control system capable of suppressing deterioration of a secondary battery effectively.SOLUTION: A battery controller includes upper and lower limit voltage calculation means for calculating the upper and lower limit voltage range including the total voltage V of a power storage device or the use upper limit value and the use lower limit value of the battery voltage V of a secondary battery in the power storage device, storage electric energy calculation means for calculating the available storage electric energy when the power storage device operates in the upper and lower limit voltage range, and charge and discharge instruction means for instructing charge and discharge to the charge and discharge device with the upper and lower limit voltage range. The upper and lower limit voltage calculation means calculates an upper and lower limit voltage range by using the V-dQ/dV characteristics obtained from the total voltage V or the battery voltage V and the capacity Q of the power storage device. When the storage electric energy goes below a predetermined value, the upper and lower limit voltage calculation means calculates an upper and lower limit voltage range so that the storage electric energy goes above a predetermined value.

Description

  The present invention relates to a battery control device and a battery control system that control charging and discharging of a secondary battery, and more particularly to a battery control device and a battery control system that suppress deterioration of a secondary battery.

  In recent years, secondary batteries such as lithium ion batteries have been used in various places due to the improvement of energy density. Higher volume density of the battery and lower power consumption of the device have made it possible to reduce the size and performance of portable devices such as mobile phones, while the higher energy weight density of the battery has made it possible to extend the travel distance of electric vehicles and the like. . At the same time, the use of natural energy such as wind power, solar power, and geothermal heat has attracted attention, and the method of smoothing and supplying the large fluctuations of electricity generated by charging and discharging of batteries has attracted attention.

  However, since the storage capacity of the secondary battery that can be charged / discharged is deteriorated depending on the number of times of charging / discharging, a deterioration suppressing technique and a long life extending technique are important.

  The progress of deterioration of the secondary battery constituting the power storage unit varies depending on the usage history such as the number of times of charging / discharging, the storage voltage, and the storage period. In particular, the progress of deterioration increases when the charge upper limit voltage of the secondary battery is high and when the discharge lower limit voltage is low. In the existing deterioration suppression technology, the lower the charging upper limit voltage, the more the deterioration is suppressed. Therefore, the deterioration is suppressed by lowering the charging upper limit voltage and limiting the storage capacity.

Patent Document 1 describes the following secondary battery system. The V-dQ / dV curve representing the relationship between the battery voltage V and the value dQ / dV obtained by dividing the change in the battery capacity Q by the change in the battery voltage V has first and second peaks. The internal state of the secondary battery (internal resistance increase, poor connection, occurrence of internal minute short circuit) is determined based on the actually measured voltage difference value that is the voltage between the peaks. Furthermore, by preventing the charge / discharge voltage of the secondary battery from exceeding the voltage corresponding to the second peak (the peak with the higher battery voltage), elution of Mn ²⁺ from the positive electrode is suppressed.

  Further, in Patent Document 2, when the deterioration amount D exceeds a predetermined value, the usage range of the upper limit voltage is increased, thereby extending the battery performance life. Patent Document 2 does not mention dQ / dV.

Japanese Patent No.5287872 JP 2012-085452 JP

  In patent document 1, it controls so that it may become below the battery voltage corresponded to the 2nd peak of dQ / dV. However, no attention is paid to the lower limit of the battery voltage.

  An object of the present invention is to provide a battery control device and a battery control system capable of effectively suppressing deterioration of a secondary battery by controlling charge / discharge conditions of a power storage unit by paying attention to upper and lower limits of the battery voltage. is there.

  The present invention relates to a battery control device that controls charging / discharging of a charging / discharging device using information on a total voltage or a battery voltage from a power storage device, the battery voltage of the power storage device or a battery of the battery included in the power storage device Upper / lower limit voltage calculation means for calculating an upper / lower limit voltage range including an upper limit value and a lower limit value for use of voltage V, and an amount of stored stored energy when the power storage device operates within the upper / lower limit voltage range A charge / discharge instruction means for instructing charge / discharge devices to charge / discharge within a range of the upper / lower limit voltage range, and the upper / lower limit voltage calculation means includes the total voltage V or the battery voltage V. And the upper and lower limit voltage range using the V-dQ / dV characteristic obtained from the capacity Q of the power storage device, and the upper and lower limit voltage calculation means when the stored power amount falls below a predetermined value Is determined in advance. A battery control unit for calculating the upper and lower limit voltage range to exceed the obtained values.

  ADVANTAGE OF THE INVENTION According to this invention, the battery control apparatus and battery control system which suppressed the deterioration of the secondary battery effectively can be provided.

It is the figure which showed the structure of the battery control apparatus which concerns on 1st Embodiment also including the use environment. It is a control flowchart which the battery control apparatus which concerns on 1st Embodiment performs. It is a figure for demonstrating how the battery control apparatus which concerns on 1st Embodiment determines an upper / lower limit total voltage. It is a figure for demonstrating that the battery control apparatus which concerns on 1st Embodiment calculates V-dQ / dV sequentially. It is a figure for demonstrating the reset when the capacity | capacitance _QLOW required by the charge / discharge conditions using the initially set upper and lower limit total voltage range cannot be maintained because a secondary battery deteriorates with time. It is a figure explaining the method of calculating | requiring V-dQ / dV characteristic about each secondary battery, and calculating | requiring an upper / lower limit voltage.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.
(First embodiment)
The present inventor paid attention to the slope dQ / dV of the stored power amount Q (hereinafter also referred to as storage capacity or capacity) with respect to the voltage V in order to determine the effect of suppressing deterioration. dQ / dV represents a storage capacity that can be stored in a certain voltage range. Generally, dQ / dV of a secondary battery including a lithium ion secondary battery has a plurality of peaks. This peak is attributed to a chemical reaction during charging or discharging, and the position, number, and size vary depending on the positive electrode, the negative electrode, the composition of the electrolytic solution, the charge / discharge current, and the like. There is a valley between these peaks, and in this voltage range, chemical reactions corresponding to the peaks on both sides occur at the same time, causing unintended chemical reactions and accelerating degradation. I thought.

  In other words, the present inventor uses the voltage range selected so that the fluctuation of dQ / dV with respect to the voltage V includes a peak and does not include a valley as much as possible, among the voltage range in which the power consumption of the secondary battery can be maintained. Thus, the inventors have found that the deterioration of the secondary battery can be suppressed while maintaining the minimum necessary capacity. The present inventor presumes that the chemical reaction corresponding to the peaks on both sides occurs simultaneously at the valley voltage between the peaks, so that an unintended chemical reaction occurs and the deterioration is promoted.

  FIG. 1 is a diagram showing a battery control system 10 according to the first embodiment together with its use environment. The battery control system 10 includes a power storage device 100 composed of a plurality of secondary batteries, a charge / discharge device 200 that charges and discharges the power storage device 100, and a control device 300 that controls them. FIG. 1 also shows an external system 500 that gives a control command to an external power network 400 and a control device 300 connected to the charge / discharge device 200. The use environment here refers to an external power network and an external control system.

  The power storage device 100 includes a power storage unit 102, a battery voltage measurement unit 103, and a total voltage measurement unit 104 in which a plurality of secondary batteries 101 are connected in series. The power storage means 102 is composed of a chargeable / dischargeable power storage component such as a lithium ion secondary battery, and has a function of changing the power storage amount and voltage by exchanging charge / discharge power with the charge / discharge device 200.

  The battery voltage measuring means 103 is composed of, for example, a voltage sensor, an operational amplifier, etc., and has a function of individually measuring the voltage of the secondary battery. The total voltage measuring means 104 is composed of, for example, a voltage sensor, an operational amplifier, etc., and has a function of measuring a total voltage that is a total value of the voltages of the secondary batteries connected in series. In addition, the power storage device 100 exchanges information with the control device 300.

  The charging / discharging device 200 includes charging / discharging means 201. Charging / discharging means 201 includes an ACDC converter, a DCDC converter, a PCS (Power Condition Subsystem), and the like, and exchanges power between power storage device 100 and external power network 400 in accordance with a charge / discharge instruction from control device 300.

  The control device 300 includes charge / discharge instruction means 301, upper / lower limit total voltage storage means 302, upper / lower limit total voltage calculation means 303, and stored power amount calculation means 304. While following the control command from external system 500, control device 300 controls charge / discharge device 200 according to the state of power storage device 100, that is, issues a charge / discharge instruction from charge / discharge instruction means 301.

  FIG. 2 is an example of a control flowchart performed by the control system according to the first embodiment.

When the charging / discharging operation is started (A1), the upper and lower limit total voltage calculating means 303 requests the battery in consideration of characteristics such as the battery voltage of the secondary battery 101 and the total voltage of the power storage device given in advance from the power storage device 100 Calculate the upper and lower total voltage range that can secure the capacity Q _LOW . The upper and lower limit total storage means 302 stores the calculation result (A2). A method for determining the upper and lower limit total voltage range is shown in FIGS.

  The QV characteristic indicating the relationship between the charge / discharge capacity Q of the secondary battery and the cell voltage V is shown on the right side of FIG. This Q-V characteristic is modified to obtain the V-dQ / dV characteristic shown on the left side of FIG. FIG. 3B is the same view as the left side of FIG. The V-dQ / dV characteristic usually has a plurality of peaks. V-dQ / dV may be abbreviated as dQ / dV hereinafter. V used here is preferably a cell voltage, but may be the total voltage of the power storage device.

When there are multiple peaks in dQ / dV, there are multiple voltages with the same dQ / dV. Among these, an upper limit value and a lower limit value that are closest to the voltage at which dQ / dV is maximized are selected. By charging / discharging the power storage device 100 in the vicinity of a voltage having a large dQ / dV, the upper and lower limit total voltage range of the secondary battery can be narrowed. Here, it is preferable to set an upper and lower limit total voltage range in which the voltage difference is as small as possible within a range in which a predetermined charge / discharge power capacity Q _LOW can be maintained including a voltage at which dQ / dV is maximized. At this time, the upper and lower limit total voltage range may be different between charging and discharging. The reason why the voltage range including the voltage at which dQ / dV is maximized is set because the voltage range has the largest capacity. If the voltage difference is the same, it is better to use a large capacity range. On the other hand, if it is the same capacity, it is better to use it in a narrow voltage range.

In the case of FIG. 1, the predetermined charge / discharge power capacity Q _LOW is a power capacity required by the secondary battery system 10 from the external power network 400 or a value set at the time of shipment.

  As shown in FIG. 2, after setting the upper and lower limit total voltage range, the charging / discharging device 200 continues the charging / discharging operation in accordance with an instruction from the external system 500, actually according to an instruction from the charging / discharging instruction unit 301 (A 3). In the case where a constant current operation or a constant power operation is performed at or below a predetermined power or current in a period longer than a predetermined time during the charge / discharge operation while performing the charge / discharge operation, the stored energy calculation means 304 stores the information, that is, the stored electric energy Q, and sequentially calculates and stores dQ / dV (A4). The dQ / dV characteristics are gradually completed as the usage time increases. For example, when a constant current operation for 1 hour or more is continued at a discharge rate of 1/10 C, the stored energy calculation means 304 calculates and stores dQ / dV for that period. FIG. 4 is a diagram showing this state. On the upper side of FIG. 4, an example of the usage history of the cell voltage and current rate is shown. Here, 1 C is a current value at which discharge is finished in just one hour (1 h) after rated discharge of a battery having a nominal capacity.

Here, the current rate is indicated by a positive numerical value during charging and a negative numerical value during discharging. From the usage history, extract the electric energy calculated from the voltage and current value when the current rate of ± 1C or less continues for 1 hour, and calculate dQ / dV. The lower diagram of FIG. 4 reproduces the V-dQ / dV characteristics by combining these dQ / dV fragments. Using the V-dQ / dV characteristics calculated in this way, it is possible to maintain the predetermined charge / discharge power capacity Q _LOW including the voltage at which dQ / dV is maximized, and the range is as small as possible. It is preferable to set the total voltage range. The reason why it is preferable that the range is as small as possible is that if the valley of dQ / dV is included, the range of the upper and lower limit voltages is widened, so that the deterioration is considered to be large. In order to reduce deterioration, it is desirable that the voltage difference is small.

  Thereafter, when there is a charge / discharge stop instruction from the charge / discharge instruction means 301 (Yes in A5), the charge / discharge operation is stopped (A7).

When there is no charge / discharge stop instruction from the charge / discharge instruction means 301 (No in A5), the charge / discharge is continued. The stored power amount calculation means 304 checks at an appropriate timing whether the stored power amount Q is below the above-described predetermined charge / discharge power capacity Q _LOW . If not lower (No in A6), the charge / discharge operation is continued (A3). When it falls below (Yes of A6), the stored energy calculation means 304 resets the upper and lower limit total voltage range set at the beginning of operation. This resetting will be described below.

The dQ / dV characteristics change due to reasons such as deterioration of the secondary battery 101 over time. As a result, the required capacity Q _LOW cannot be maintained under the charge / discharge conditions using the initially set upper and lower limit total voltage range. In that case, the dQ / dV characteristic is measured again, and based on this, the upper and lower limit total voltage range calculation means 303 recalculates and resets the upper and lower limit total voltage (A6 in FIG. 2). For example, the reset is centered on the voltage at which dQ / dV is maximum, and dQ / dV is equal to at least one of the upper limit value and the lower limit value of the upper and lower total voltage until the required capacity Q _LOW is satisfied. Thus, the upper and lower limit total voltage range is changed. Normally, the upper and lower total voltage range is expanded.

FIGS. 3C and 3D show the upper and lower limit total voltage ranges in time series in this order when dQ / dV changes due to deterioration. In the figure, dQ / dV changes in the order of a dotted line, a broken line, and an alternate long and short dash line. The charge / discharge range is changed each time the voltage at which dQ / dV is maximized changes. Set the upper and lower total voltage range that minimizes deterioration while maintaining the capacity Q _LOW or higher.

FIGS. 5A and 5B are the same as FIGS. 3C and 3D. In the dQ / dV indicated by the broken line in FIG. 5 (a), the maximum peak value is lower than the dotted line, and the upper and lower total voltage ranges are such that the valleys on both sides are not included around the voltage at which dQ / dV is maximum. When is set, Q _LOW is not satisfied (“Total upper and lower voltage range where required capacity is insufficient” in the figure). For this reason, the lower limit value is expanded to a voltage having the same dQ / dV that is second closest to the voltage that maximizes dQ / dV (“upper and lower limit total voltage range that satisfies the required capacity” in the figure). As a result, if the storage capacity of the upper / lower limit total voltage range satisfies Q _LOW , the upper / lower limit total voltage range is used, and if not, the upper limit value or lower limit value is updated again. In FIG. 5 (a), the updated upper and lower total voltage range includes one dQ / dV characteristic trough. By minimizing the number of troughs included, the secondary battery can be prevented from being degraded as much as possible. To do.

  FIG. 5B shows a case where the secondary battery 101 is further deteriorated and the dQ / dV characteristic changes as indicated by a one-dot chain line. The peak on the lowest voltage side is the voltage at which dQ / dV is maximum. In this case, the lower limit total voltage is expanded to include the maximum peak, and the upper limit total voltage is set slightly lower than that in FIG.

  The upper and lower limit total voltage range set here is a guideline for suppressing deterioration, and can be ignored when there is a high charge request / discharge request in an emergency or the like.

  Although the resetting timing may be arbitrary, for example, when the actual usable capacity falls below a certain threshold, the control device 300 determines that the capacity is insufficient and instructs the resetting. Other timing may be performed periodically (every 6 months, every year, etc.) or at a timing at which operation with a constant current at which a dQ / dV fragment is obtained.

  The system philosophy changes depending on whether the upper limit range is expanded or the lower limit range is expanded. By expanding the upper limit value to be higher, the lower limit value can be increased, and the remaining amount equal to or lower than the lower limit value can be used in an emergency. On the other hand, by expanding the lower limit value to be lower, the upper limit value can be lowered and deterioration can be suppressed.

As described above, by calculating the V-dQ / dV characteristic of the secondary battery and setting a voltage range in which a large dQ can be obtained, the secondary battery accompanying the charge / discharge operation is maintained while maintaining the necessary capacity. Can be effectively suppressed. The battery control system of this embodiment looks like a system with little deterioration while ensuring a constant capacity when viewed from the outside. Moreover, it looks like a system that minimizes the difference between the upper and lower limit voltages while maintaining the storage capacity Q.
(Second Embodiment)
In the first embodiment, “V used here is preferably a cell voltage, but may be a total voltage of a power storage device”. If the dQ / dV characteristics of each secondary battery 101 are ideal, the total voltage is the same as the cell voltage. However, if there are variations in secondary batteries due to changes over time or the like, first, valley voltages are obtained individually from dQ / dV of all secondary batteries 101. The voltage range including the maximum peak and between the valleys (inner) closest to the maximum peak is defined as the upper and lower limit voltages. In FIG. 6, the upper and lower limit voltages when there are three secondary batteries are obtained. Three maximum peaks of each secondary battery 101 overlap, and a narrow voltage range including the highest peak and not including valleys on both sides is set as the upper and lower limit voltages. FIG. 6 shows the voltage between the longest vertical thin lines. A method for resetting the upper and lower limit voltages when the dQ / dV characteristic changes due to deterioration or the like is the same as that in the first embodiment.

When dQ / dV is calculated from the total voltage, the valley voltage is wider than that obtained individually. Therefore, charging and discharging is performed with a wider upper and lower limit voltage than the valley voltage obtained individually in some cells (secondary batteries). Is done. Therefore, the deterioration is accelerated as compared with the case of obtaining individually. In order to further suppress the deterioration, it is preferable to obtain the individual cell voltage. However, if the dQ / dV of all cells cannot be obtained individually or if it is desired to simplify the calculation, the total voltage dQ / dV is used instead.
(Other embodiments)
Describe the resetting. In the first embodiment, the resetting is performed in a situation where the secondary battery satisfies Q _LOW in the initial operation, but dQ / dV changes due to deterioration and is no longer satisfied. However, if the required Q _LOW is high, there is a case where Q _LOW is not satisfied even if calculation is performed in the initial stage of use of the power storage device. Even in that case, the resetting may be performed similarly.

  In the first embodiment, the upper and lower limit total voltage storage unit 302 and the upper and lower limit total voltage calculation unit 303 are provided separately. However, if the upper and lower limit total voltage calculation unit 303 has a storage function, the upper and lower limit total voltage storage unit 302 is provided. Can be omitted.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

DESCRIPTION OF SYMBOLS 10 Battery control system 100 Power storage device 101 Secondary battery 102 Power storage means 103 Battery voltage measurement means 104 Total voltage measurement means 200 Charge / discharge device 201 Charge / discharge means 300 Control device 301 Charge / discharge instruction means 302 Upper / lower limit total voltage storage means 303 Upper / lower limit Total voltage calculation means 304 Charged energy calculation means 400 External power network 500 External system

Claims (10)

A battery control device that controls charging / discharging of the charging / discharging device using information on the total voltage or battery voltage from the power storage device,
Upper and lower limit voltage calculating means for calculating an upper and lower limit voltage range including a use upper limit value and a use lower limit value of the total voltage V of the power storage device or the battery voltage V of the battery included in the power storage device;
A storage power amount calculating means for calculating a usable stored power amount when the power storage device operates within the upper and lower limit voltage range;
Charge / discharge instruction means for instructing charge / discharge to the charge / discharge device within the range of the upper and lower limit voltage ranges;
With
The upper and lower limit voltage calculating means calculates the upper and lower limit voltage range using a V-dQ / dV characteristic obtained from the total voltage V or the battery voltage V and the capacity Q of the power storage device,
The battery control apparatus that calculates the upper and lower limit voltage ranges so that the stored power amount exceeds a predetermined value when the stored power amount falls below a predetermined value. The battery control device according to claim 1, wherein the upper and lower limit voltage calculating means calculates a voltage range including a maximum peak of V-dQ / dV characteristics.   The battery control device according to claim 1, wherein the upper and lower limit total voltage does not include a valley region of the V-dQ / dV characteristic.   3. The battery control device according to claim 2, wherein a region of a valley of the V-dQ / dV characteristic is included as the upper and lower limit total voltage when the stored electric energy is lower than a predetermined value.   When a constant current operation or a constant power operation below a predetermined power or current during a charge / discharge operation is performed, the information is stored and V-dQ / dV is sequentially calculated. The battery control device according to any one of 4.   6. The battery control device according to claim 5, wherein dQ / dV is partially obtained by using the total voltage V or battery voltage V during operation, and V-dQ / dV characteristics are calculated by combining them.   The current and voltage data at the time of constant current charge or constant current discharge equal to or lower than a predetermined current from current and voltage data obtained during operation are used for calculating V-dQ / dV. Battery control device.   The battery control device according to any one of claims 1 to 7, wherein the upper and lower limit voltage ranges are calculated and set again due to deterioration with time of V-dQ / dV characteristics. When calculating the upper and lower limit voltage range by obtaining the V-dQ / dV characteristics using the battery voltage V,
9. The battery control device according to claim 2, wherein a voltage range that includes a maximum peak and does not include a valley among the V-dQ / dV characteristics of each of the batteries is the upper and lower limit voltage range. Using the battery control device according to any one of claims 1 to 9,
The power storage device includes power storage means in which a plurality of secondary batteries are connected in series, battery voltage measurement means for measuring the battery voltage value of the secondary battery, and total voltage for measuring the total voltage value of the power storage means. Measuring means,
The charging / discharging device is a battery control system including charging / discharging means for charging / discharging the power storage device in accordance with an instruction from the battery control device.

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