JP2013029445A - Battery management device and power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery management device enabling proper charging and discharging control of a storage battery by determining whether the calculated SOC can be reliable or not.SOLUTION: A battery management device for managing one or a plurality of storage batteries includes: a SOC (State of Charge) reliability calculation part for calculating SOC reliability which is an index expressing the reliability of the calculated SOC of a storage battery; and a SOC reliability determination part for determining whether the SOC calculated on the basis of the calculation result by the SOC reliability calculation part can be reliable or not.

Description

  The present invention relates to a battery management device that manages storage batteries.

  Due to the high performance of electronic devices using batteries and the diversification of applications, the power consumption of electronic devices is expanding at a pace exceeding the high performance of batteries. In recent years, the capacity of storage batteries has been increased, and the introduction of power supply systems that store power consumed in buildings, factories, stores, homes, and the like has been promoted.

  Therefore, the importance of calculating SOC (State Of Charge) is increasing for appropriate charge / discharge control of the storage battery. The SOC is a parameter representing the ratio of the dischargeable capacity (remaining capacity) to the full charge capacity (FCC) in percentage. Accurate calculation of SOC becomes difficult due to deterioration due to repeated charging and discharging (deterioration of discharge characteristics), so electronic devices and power supply systems that use storage batteries communicate with battery packs that contain storage batteries, and are obtained by calculation The life determined from the SOC and power consumption is displayed.

  The difficulty in calculating the SOC occurs because the full charge capacity decreases due to deterioration such as an increase in the internal resistance of the storage battery. For example, at a standard temperature, the full charge capacity is reduced by about 0.05% after one cycle of use when the remaining amount is 0% after full charge.

  Thus, for example, Patent Document 1 discloses a method for calculating the SOC with high accuracy by measuring an accurate open circuit voltage (OCV).

  Also, for example, Patent Document 2 discloses a method for accurately calculating the SOC by correcting the full charge capacity based on the number of times that the accumulated value of the charge capacity reaches the learning capacity at that time and the external condition in which the storage battery is left unattended. Is disclosed.

Japanese Patent No. 4472733 JP 2002-236154 A

  However, although Patent Documents 1 and 2 disclose a method for calculating the SOC with high accuracy, it is not determined whether or not the calculated SOC is reliable. It was unclear whether to do it.

  Therefore, an object of the present invention is to provide a battery management device that enables appropriate charge / discharge control of a storage battery by determining whether or not the calculated SOC can be trusted.

In order to achieve the above object, the present invention provides a battery management apparatus for managing one or a plurality of storage batteries,
An SOC reliability calculation unit that calculates an SOC reliability that is an index indicating the reliability of the calculated SOC (State Of Charge) of the storage battery;
An SOC reliability determination unit that determines whether or not the SOC calculated based on the calculation result by the SOC reliability calculation unit can be trusted;
It is set as the structure provided with.

  Further, in the above configuration, the SOC reliability calculation unit is a calculation unit that calculates an SOC reliability based on a parameter accumulated in the storage battery, and a calculation unit that calculates an SOC reliability based on a parameter not accumulated in the storage battery. There may be.

  In any one of the above-described configurations, when the SOC reliability determination unit determines that the SOC can be trusted, the SOC use range for performing charge / discharge control of the storage battery is set wide, and the SOC reliability determination unit If the SOC is determined to be unreliable, an SOC usage range setting unit that narrows the SOC usage range may be provided.

  In any of the above-described configurations, when the SOC reliability determination unit determines that the SOC is unreliable, a charging prohibition threshold that is an SOC threshold for prohibiting charging of the storage battery is set to be smaller than normal, and the storage battery You may make it provide the charging / discharging prohibition threshold value setting part which sets the discharge prohibition threshold value which is an SOC threshold value which prohibits discharge larger than usual.

  In any one of the above configurations, a learning process start control unit that starts a learning process for learning the full charge capacity of the storage battery when the SOC reliability determination unit determines that the SOC is unreliable is provided. Also good.

  Moreover, the power supply system of the present invention has one or a plurality of storage batteries, a battery management device having any one of the above configurations, and a power conversion unit connected to the one or more storage batteries. To do.

  According to the present invention, it is possible to perform appropriate charge / discharge control of a storage battery by determining whether or not the calculated SOC is reliable.

It is a figure showing the whole electric power supply system composition concerning one embodiment of the present invention. It is a figure which shows the internal structure of BMU (Battery Management Unit) concerning one Embodiment of this invention. It is a figure which shows the internal structure of the control part which BMU which concerns on one Embodiment of this invention has. It is an example of the table which shows the correspondence of the cycle number of a battery pack, and SOC reliability C1. It is an example of the table which shows the correspondence of the temperature of a battery pack, and SOC reliability C2. It is an example of the straight line which shows the relationship between the cycle number of a battery pack, and SOC reliability C1. It is an example of the quadratic function which shows the relationship between the temperature of a battery pack, and SOC reliability C2. It is a figure which shows the state transition in the control using SOC reliability C2.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a power supply system according to an embodiment of the present invention. However, in FIG. 1, a thin solid line indicates a signal line, and a thick solid line indicates a power line. The power supply system shown in FIG. 1 includes a master controller 1, a PCS (Power Conditioning System) management unit 2, a PCS 3, a BMU (Battery Management Unit) 4, and an assembled battery 5. The master controller 1 and the PCS management unit 2 are not necessarily separate and may be integrated.

  The master controller 1 receives a charge / discharge control command from the host, creates a charge / discharge control command for each of the plurality of assembled batteries 5, and sends it to the PCS management unit 2. The PCS management unit 2 has a function of receiving the charge / discharge control command from the master controller 1 and managing the operation of a plurality of PCSs 3 provided. The assembled battery 5 is connected to the PCS 3 through the power line for each PCS 3. The PCS 3 has a function of performing power conversion between the external commercial power source 100 and the assembled battery 5 or power conversion between the assembled battery 5 and an external load (not shown), and is a bidirectional AC / DC converter. is there. When a solar cell is used as an external power source instead of the external commercial power supply 100, the PCS 3 may be a bidirectional DC / DC converter.

  The PCS management unit 2 is positioned lower than the master controller 1 and controls the operation of the PCS 3 based on the charge / discharge control command so that the electric power of the external commercial power supply 100 is temporarily stored in the assembled battery 5 or the stored power is externally stored. It has a function to perform power management for discharging to the load.

  The assembled battery 5 includes a plurality of battery packs 50 connected in series. The battery pack 50 includes a plurality of storage battery cells such as lithium ion batteries and a communication unit (all not shown). The battery pack 50 sends various parameters (number of cycles, elapsed time, temperature, voltage, etc.) for calculating the SOC reliability described later to the BMU 4 in response to a request from the BMU 4. Further, the battery pack 50 sends various parameters (full charge voltage, current voltage, full charge capacity and remaining capacity) for calculating the SOC to the BMU 4 in response to a request from the BMU 4.

  The internal configuration of the BMU 4 is shown in FIG. As illustrated in FIG. 2, the BMU 4 includes a first communication unit 41, a control unit 42, and a second communication unit 43. The control unit 42 transmits a data request command to the assembled battery 5 via the first communication unit 41 and acquires data from the assembled battery 5. Further, the control unit 42 communicates with the master controller 1 via the second communication unit 43.

  The internal configuration of the control unit 42 is shown in FIG. As shown in FIG. 3, the control unit 42 includes an SOC calculation unit 421, an SOC reliability C1 calculation unit 422, an SOC reliability C1 determination unit 423, an SOC reliability C2 calculation unit 424, and an SOC reliability C2 determination. Unit 425, charge / discharge control unit 426, and BMU normal control unit 427.

  Here, the calculation of the SOC will be described. First, when the BMU normal control unit 427 makes a data request to each battery pack 50 (FIG. 1) included in the assembled battery 5 via the first communication unit 41, each battery pack. Data for calculating the SOC is sent from 50 to the first communication unit 41. When the full charge voltage and the current voltage are sent as data for calculating the SOC, the SOC calculation unit 421 calculates the SOC as SOC = current voltage / full charge voltage × 100 (%). When the full charge capacity and the remaining capacity are sent as data for calculating the SOC, the SOC calculation unit 421 calculates the SOC as SOC = residual capacity / full charge capacity × 100 (%). Furthermore, the SOC may be calculated by weighted addition of the SOCs calculated by both methods.

  Hereinafter, calculation of the SOC reliability by the control unit 42 and control using the calculated SOC reliability will be described.

<Calculation of SOC reliability>
When the BMU normal control unit 427 makes a data request to each battery pack 50 (FIG. 1) included in the assembled battery 5 via the first communication unit 41, each battery pack 50 sends a request to the first communication unit 41. Data is sent. This data includes parameters that are accumulated and parameters that are not accumulated.

  As the accumulated parameter, for example, any one of the number of cycles in which charging / discharging is one cycle, the elapsed time, SOH (State of Health), or the accumulated amount of charging / discharging can be adopted. The SOC reliability C1 calculation unit 422 receives parameters accumulated from the first communication unit, and calculates the SOC reliability C1 based on the parameters.

  Here, the SOC reliability is an index such that when the value is high, the calculated error of the SOC is small, and when the value is low, the error of the actual SOC is large.

  In the case of adopting the number of cycles as the accumulated parameter, for example, the SOC reliability C1 may be calculated using a table showing the correspondence between the number of cycles and the SOC reliability C1 as shown in FIG. Alternatively, for example, the SOC reliability C1 may be calculated based on a straight line indicating the relationship between the number of cycles and the SOC reliability C1 as shown in FIG. When the number of cycles increases, the storage battery deteriorates and the full charge capacity of the storage battery decreases. Therefore, it is considered that the difference between the full charge capacity used for the SOC calculation and the actual full charge capacity becomes large, and an error between the calculated SOC and the actual SOC becomes large. Therefore, in the table shown in FIG. 4 and the straight line shown in FIG. 6, the value of the SOC reliability C1 decreases as the number of cycles increases.

  As the parameter that is not accumulated, for example, any one of temperature, charge rate, discharge rate, or voltage can be adopted. The SOC reliability C2 calculation unit 424 receives parameters not accumulated from the first communication unit, and calculates the SOC reliability C2 based on the parameters. In addition, when employ | adopting a voltage as a parameter, after calculating the variation in the voltage of each battery pack 50 contained in the assembled battery 5, SOC reliability C2 is calculated based on the calculated variation.

  In the case of an example in which the temperature is used as a parameter that is not accumulated, the SOC reliability C2 may be calculated using a table showing the correspondence between the temperature and the SOC reliability C2 as shown in FIG. Alternatively, for example, the SOC reliability C2 may be calculated based on a quadratic function indicating the relationship between the temperature and the SOC reliability C2 as shown in FIG. In the table of FIG. 5 and the quadratic function of FIG. 7, the room temperature is set to 20 ° C., and the value of the SOC reliability C2 is reduced when the room temperature deviates from the room temperature. When measuring the voltage of the storage battery based on the normal temperature, if the temperature of the storage battery rises from the normal temperature, the internal resistance of the storage battery increases, and the accurate voltage of the storage battery cannot be measured. Then, since the voltage value is used to calculate the SOC, it is considered that an error between the calculated SOC and the actual SOC becomes large. It is assumed that the same is true when the temperature of the storage battery drops from room temperature. For example, when the voltage is measured based on a high temperature, the reliability of the SOC is high at a high temperature, and the reliability of the SOC is lowered when the voltage deviates from the high temperature.

  In the above description, one SOC reliability C1 and C2 is calculated for each one type of parameter. However, a plurality of SOC reliability C1 and C2 are calculated for each of a plurality of types of parameters. Also good.

Further, as shown in the following formula (1), the SOC reliability C1 and the SOC reliability C2 may be weighted and added to calculate the SOC reliability C3.
C3 = k.C1 + (1-k) .C2 (1)
Here, k is a weighted addition coefficient.

<Control using SOC reliability>
(SOC usage range switching control)
First, a control example using the SOC reliability C1 calculated from the accumulated parameters (for example, the number of cycles) will be described. The SOC reliability C1 calculation unit 422 starts calculating the SOC reliability C1 every second at a certain time of the day (once a day), for example. And the SOC reliability C1 determination part 423 takes the average of the SOC reliability C1 calculated in 1 minute. Since the SOC reliability C1 is calculated for each of the plurality of battery packs 50 included in the assembled battery 5, a plurality of average values are also calculated for each battery pack 50. The SOC reliability C1 determination unit 423 further calculates the average of the plurality of average values calculated or determines the minimum value of the plurality of average values calculated. Then, the SOC reliability C1 determination unit 423 determines whether or not the calculated SOC can be trusted by determining whether or not the average value or the minimum value is equal to or greater than a predetermined threshold value.

  When it is determined that the calculated SOC is reliable, the charge / discharge control unit 426 sets the master controller 1 to widen the SOC usage range for the corresponding assembled battery 5 via the second communication unit 43. As an example of the wider SOC usage range, it may be 10 to 90%. On the other hand, when it is determined that the calculated SOC is not reliable, the charge / discharge control unit 426 sets the master controller 1 to narrow the SOC usage range for the corresponding assembled battery 5 via the second communication unit 43. To do. As an example of the narrow SOC usage range, it may be 20 to 80%.

  The master controller 1 includes the SOC of each battery pack 50 included in the assembled battery 5 calculated by the SOC calculating unit 421 of each BMU 4, the SOC usage range set for each assembled battery 5 by each BMU 4, and the upper level. The charge / discharge control command for each assembled battery 5 is created on the basis of the charge / discharge control command from, and sent to the PCS management unit 2. Then, the PCS management unit 2 controls each PCS 3 to control charging / discharging of each assembled battery 5. Thereby, it becomes possible to control charging / discharging of each assembled battery 5 safely.

(Charge / discharge prohibition threshold switching control)
Next, an example of control using the SOC reliability C2 calculated from a non-cumulative parameter (for example, temperature) will be described. Here, the state transition as shown in the state transition diagram shown in FIG. 8 is always performed. The SOC reliability C2 calculation unit 424 starts calculating the SOC reliability C2 every second, for example. Then, the SOC reliability C2 determination unit 425 takes an average of the SOC reliability C2 calculated for 10 seconds. Since the SOC reliability C2 is calculated for each of the plurality of battery packs 50 included in the assembled battery 5, a plurality of average values are also calculated for each battery pack 50. The SOC reliability C2 determination unit 425 further takes an average of the calculated plurality of average values or determines a minimum value of the calculated plurality of average values. Then, the SOC reliability C2 determination unit 425 determines whether or not the calculated SOC can be trusted by determining whether or not the average value or the minimum value is equal to or greater than a predetermined threshold (state transition in FIG. 8). State S1) in the figure. That is, the SOC reliability C2 is determined once every 10 seconds. Further, using the SOC reliability C1 calculation unit 422 and the SOC reliability C1 determination unit 423, the SOC reliability C1 is similarly determined once every 10 seconds.

  Here, the charge / discharge control unit 426 compares the SOC of each battery pack 50 included in the assembled battery 5 calculated by the SOC calculation unit 421 with the charge prohibition threshold and the discharge prohibition threshold, and the SOC is equal to or higher than the charge prohibition threshold ( If it becomes 90% or more, for example, the master controller 1 is instructed to prohibit charging via the second communication unit 43, and if the SOC is equal to or lower than the discharge inhibition threshold (for example, 10% or less), the master communicates via the second communication unit 43. Command controller 1 to prohibit discharge. When the master controller 1 receives the charge / discharge prohibition command, the master controller 1 sends a charge / discharge prohibition command to the PCS management unit 2, and the PCS management unit 2 that has received the charge / discharge prohibition command responds to the received battery pack 5 according to the received command. Prohibit charging or discharging.

  In the above description, when it is determined that the calculated SOC is reliable for both of the SOC reliability levels C1 and C2 (transition to state S2 in FIG. 8), the charge / discharge control unit 426 sets the charge prohibition threshold to the normal value ( For example, the discharge prohibiting threshold value is set to a normal value (for example, 10%). Then, SOC reliability C1 and C2 determination is performed once every 10 seconds (transition to state S1 in FIG. 8).

  On the other hand, when it is determined that the SOC calculated for at least one of the SOC reliability levels C1 and C2 is not reliable (transition to the state S3 in FIG. 8), the charge / discharge control unit 426 sets the charge prohibition threshold from the normal value. A small value is set (for example, 70%), and the discharge prohibition threshold is set to be larger than a normal value (for example, 30%). And here, SOC reliability C1 and C2 determination are performed once every 300 seconds (transition to state S1 in FIG. 8). The SOC reliability C1 and C2 determination once every 300 seconds means the SOC reliability C1 and C2 calculated in 300 seconds instead of 10 seconds in the above-described SOC reliability C1 and C2 determination once every 10 seconds. The average is taken.

  As described above, when the reliability of the SOC becomes low, the charge prohibition threshold and the discharge prohibition threshold are set to the safe side, so that charging / discharging can be prohibited immediately in a dangerous state. In addition, when the reliability of the SOC is high, the determination frequency is set to be higher than when the reliability is low (once every 300 seconds) as the determination once every 10 seconds. This is because the threshold value is set to a normal value, and it is possible to prevent the dangerous state from continuing even though the reliability of the SOC is lowered in the middle.

  When it is determined that the SOC calculated as described above is not reliable, the charge / discharge control unit 426 instructs the master controller 1 to limit the charge / discharge rate via the second communication unit 43, and the PCS management unit 2. The charge / discharge rate of the corresponding assembled battery 5 may be limited by the control of the PCS 3 via the.

(Full charge capacity learning)
Next, full charge capacity learning using the SOC reliability C1 calculated from the accumulated parameters (for example, the number of cycles) will be described. Here, it is assumed that the SOC reliability C1 determination unit 423 determines whether or not the SOC can be trusted at a certain frequency (for example, once-daily SOC reliability C1 determination as described above). .

  If it is determined that the SOC is not reliable, the charge / discharge control unit 426 instructs the full charge capacity learning of the assembled battery 5 corresponding to the master controller 1 via the second communication unit 43. Then, the master controller 1 controls the PCS 3 corresponding to the assembled battery 5 to be subjected to learning processing via the PCS management unit 2 and fully charges the assembled battery 5 to be subjected to learning processing. The full charge of the assembled battery 5 means that one or more of the battery packs 50 included in the assembled battery 5 are fully charged.

  And the master controller 1 controls PCS3 corresponding to the assembled battery 5 used as the object of a learning process via the PCS management part 2, and discharges the assembled battery 5 used as the object of a learning process to a predetermined level. That is, discharging is performed until one or more of the battery packs 50 included in the assembled battery 5 to be subjected to learning processing reach a predetermined level. At this time, each battery pack 50 included in the assembled battery 5 to be subjected to the learning process calculates the full charge capacity by integrating the discharge current from full charge, and updates the full charge capacity of each battery pack 50. . The predetermined level should be essentially a level corresponding to complete discharge. However, when the drive power of the communication unit of the battery pack 50 is supplied from the storage battery cell, complete discharge is performed. If this happens, communication between the BMU 4 and the battery pack 50 will be interrupted, so it is desirable to set the state where some charge remains to a predetermined level. When the full charge capacity learning is completed, the accumulated parameter (for example, the number of cycles) of each battery pack 50 included in the assembled battery 5 that is the object of the learning process is reset.

  As described above, when the reliability of the SOC becomes low, the SOC can be calculated with high accuracy by learning the full charge capacity. In the above, the full charge capacity learning is performed by fully discharging (or discharging close to it) after fully charging, but conversely, it is fully charged by fully discharging (or discharging close to it) and then fully charging. You may make it perform charge capacity learning.

  The embodiment of the present invention has been described above, but the embodiment can be variously modified within the scope of the gist of the present invention.

1 Master Controller 2 PCS Management Unit 3 PCS
4 BMU
41 first communication unit 42 control unit 43 second communication unit 421 SOC calculation unit 422 SOC reliability C1 calculation unit 423 SOC reliability C1 determination unit 424 SOC reliability C2 calculation unit 425 SOC reliability C2 determination unit 426 charge / discharge control unit (SOC usage range setting unit, charge / discharge inhibition threshold setting unit, learning process start control unit)
427 BMU normal control unit 5 battery pack 50 battery pack 100 external commercial power supply

Claims (6)

A battery management device for managing one or more storage batteries,
An SOC reliability calculation unit that calculates an SOC reliability that is an index indicating the reliability of the calculated SOC (State Of Charge) of the storage battery;
An SOC reliability determination unit that determines whether or not the SOC calculated based on the calculation result by the SOC reliability calculation unit can be trusted;
A battery management device comprising:   The SOC reliability calculation unit is a calculation unit that calculates an SOC reliability based on a parameter accumulated in the storage battery, and a calculation unit that calculates an SOC reliability based on a parameter not accumulated in the storage battery. The battery management apparatus according to claim 1.   When it is determined that the SOC is reliable by the SOC reliability determination unit, the SOC use range when performing charge / discharge control of the storage battery is set wide, and the SOC reliability determination unit determines that the SOC cannot be trusted. 3. The battery management device according to claim 1, further comprising: an SOC usage range setting unit configured to set the SOC usage range to be narrow.   When the SOC reliability determination unit determines that the SOC is not reliable, a discharge prohibition threshold that is an SOC threshold for prohibiting charging of the storage battery is set smaller than normal, and a discharge that is an SOC threshold for prohibiting discharge of the storage battery. The battery management apparatus according to any one of claims 1 to 3, further comprising a charge / discharge prohibition threshold setting unit configured to set the prohibition threshold to be larger than normal.   The learning process start control part which starts the learning process which learns the full charge capacity | capacitance of the said storage battery, when it determines with SOC not being reliable by the said SOC reliability determination part, The learning process start control part is provided. The battery management apparatus in any one of.   It has one or a plurality of storage batteries, the battery management device according to any one of claims 1 to 5, and a power conversion unit connected to the one or more storage batteries. Power supply system.

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