JP7256724B2 - Storage system and management method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electric storage system and a management method.

BACKGROUND Conventionally, a power storage system is known in which two or more power storage devices are connected in parallel to one power converter (PCS; Power Conditioning System). In such a power storage system, the power storage device with the lowest voltage value or the power storage device with the highest voltage value is first connected to the power converter, and then the difference with respect to the output voltage of the power converter is equal to or less than a predetermined difference. A device is connected to a power conversion device (for example, Patent Document 1).

JP 2016-119839 A

By the way, in the power storage system described above, it is possible to individually measure the state of charge (SOC; State Of Charge) of two or more power storage devices. is. As a result of intensive studies, the inventors have found that, assuming such a case, it is necessary to devise various ways of deriving the state of charge of the entire power storage system from the state of charge of each power storage device. I found out.

Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electricity storage system and a management method capable of appropriately managing the state of charge of the entire electricity storage system. .

In the power storage system according to the first feature, two or more power storage devices are connected in parallel to one power conversion device. The power storage system includes a management unit that manages information specifying two or more individual states of charge corresponding to the two or more power storage devices and information specifying an overall state of charge of the power storage system. The management unit manages a highest individual state of charge selected from the two or more individual states of charge as the overall state of charge when the reference overall state of charge of the power storage system belongs to a first range. and managing the state of charge calculated based on the two or more individual states of charge as the state of charge when the reference overall state of charge of the power storage system belongs to a second range lower than the first range. and if the reference overall state of charge of the power storage system belongs to a third range lower than the second range, the lowest individual state of charge selected from among the two or more individual state of charge is selected. A third process for managing the overall state of charge is performed.

A management method according to a second feature is a method used in a power storage system in which two or more power storage devices are connected in parallel to one power conversion device. The management method includes a step A of managing information identifying two or more individual states of charge corresponding to the two or more power storage devices respectively, and a step B managing information identifying an overall state of charge of the power storage system. , provided. In step B, if the reference overall state of charge of the power storage system belongs to a first range, managing the highest individual state of charge selected from among the two or more individual states of charge as the overall state of charge. and managing the state of charge calculated based on the two or more individual states of charge as the overall state of charge when the reference overall state of charge of the power storage system belongs to a second range lower than the first range. , when the reference overall state of charge of the power storage system belongs to a third range lower than the second range, the lowest individual state of charge selected from the two or more individual state of charge is managed as the overall state of charge. and

ADVANTAGE OF THE INVENTION According to this invention, the electrical storage system and management method which enable it to manage the charge state of the whole electrical storage system appropriately can be provided.

FIG. 1 is a diagram showing a power storage system 100 according to an embodiment. FIG. 2 is a diagram for explaining the capacity of the power storage device 110 according to the embodiment. FIG. 3 is a diagram for explaining charging and discharging of two or more power storage devices 110 according to the embodiment. FIG. 4 is a diagram for explaining management of the state of charge according to the embodiment. FIG. 5 is a diagram showing a management method according to the embodiment.

Embodiments will be described below with reference to the drawings. In addition, in the following description of the drawings, the same or similar reference numerals are given to the same or similar parts. However, the drawings are schematic.

(electricity storage system)
A power storage system according to an embodiment will be described below with reference to FIG. As shown in FIG. 1 , the power storage system 100 includes two or more power storage devices 110, two or more sensors 111, two or more switching units 120, a PCS (Power Conditioning System) 130, a sensor 131, and a control unit. 210 , a management unit 220 , an output unit 230 and a storage unit 240 .

Power storage device 110 is a device that stores electric power. Specifically, power storage device 110 has two or more power storage cells that store power. Two or more storage cells constitute a cell string connected in series with each other. Power storage device 110 may have two or more cell strings connected in parallel. The power storage device 110 has a discharge resistor connected to each of the two or more power storage cells, and has a function of suppressing variations in voltage values of the two or more power storage cells by discharging from the power storage cells to the discharge resistors (hereinafter referred to as , cell balance function). The voltage values of the storage cells are equalized by repeating charging or discharging of the storage device 110 .

In FIG. 1, as power storage devices 110, power storage devices 110A to 110C are illustrated. Two or more power storage devices 110 are connected in parallel to one PCS 130 .

Sensor 111 is provided at the output end of power storage device 110 and detects the state of power storage device 110 . The state of power storage device 110 includes the voltage value at the output terminal of power storage device 110 . The state of power storage device 110 may include the current value of power discharged from power storage device 110 or the current value of power charged to power storage device 110 .

Here, the term “output end” means an output end of electric power in discharging the power storage device 110 . Therefore, the “output end” is synonymous with the power input end in charging the power storage device 110 . Hereinafter, for convenience of explanation, in the discharge of power storage device 110, the side to which power is output will be referred to as the "output end", and the side to which power will be input will be referred to as the "input end".

In FIG. 1, as the sensor 111, sensors 111A to 111C are illustrated. Sensor 111A detects the state of power storage device 110A. Similarly, sensor 111B detects the state of power storage device 110B, and sensor 111C detects the state of power storage device 110C.

Switching unit 120 switches electrical connection between power storage device 110 and PCS 130 . Specifically, the switching unit 120 switches connection or disconnection of the power line that connects the power storage device 110 and the PCS 130 . Hereinafter, the state in which power storage device 110 and PCS 130 are electrically connected is referred to as "ON", and the state in which power storage device 110 and PCS 130 are electrically disconnected is referred to as "OFF". Although not particularly limited, the switching unit 120 may be a mechanical relay mechanism. The switching unit 120 may be a relay circuit configured by switching elements.

In FIG. 1, as the switching section 120, switching sections 120A to 120C are illustrated. The switching unit 120A switches ON/OFF of the power storage device 110A. Similarly, the switching unit 120B switches ON/OFF of the power storage device 110B, and the switching unit 120C switches ON/OFF of the power storage device 110C.

The PCS 130 is a power conversion device that converts DC power discharged from the power storage device 110 into AC power, and converts the DC power charged in the power storage device 110 into AC power. An input terminal of PCS 130 is connected to power storage device 110 via a power line. The output end of the PCS 130 is connected to the power grid via a power line. The output end of the PCS 130 may be connected via a power line to a device (other distributed power source or load, etc.) provided in the facility that includes the power storage system 100 . Here, PCS 130 may have a terminal (self-sustaining terminal) that connects PCS 130 to a device provided in a facility in a state in which power storage system 100 is disconnected from the power system (hereinafter referred to as a self-sustaining state).

A sensor 131 is provided at the output end of the PCS 130 and detects the state of the PCS 130 . The state of PCS 130 includes the voltage value at the output of PCS 130 . The state of PCS 130 may include the current value of power output from PCS 130 when power storage device 110 is discharged, and may include the current value of power input to PCS 130 when power storage device 110 is charged.

Control unit 210 may include at least one processor. The at least one processor may be comprised of a single integrated circuit (IC) or may be comprised of multiple circuits (such as integrated circuits and/or discrete circuits) communicatively coupled.

Control unit 210 is connected to components provided in power storage system 100 via signal lines. Here, the controller 210 is connected to the sensor 111, the PCS 130, and the sensor 131 via signal lines. Control unit 210 controls charging or discharging of power storage device 110 under the control of PCS 130 . Control unit 210 acquires the state of power storage device 110 from sensor 111 . Control unit 210 acquires the state of PCS 130 from sensor 131 .

Management unit 220 manages information about power storage system 100 . For example, the management unit 220 is configured by a memory such as a nonvolatile memory and/or a storage medium such as a HDD (Hard disc drive). More specifically, management unit 220 manages information specifying two or more individual states of charge (hereinafter referred to as individual SOCs (States of Charge)) corresponding to two or more power storage devices 110, respectively. Management unit 220 manages information specifying the overall state of charge (hereinafter referred to as overall SOC) of power storage system 100 . Details of the SOC will be described later (see FIG. 2).

Output unit 230 outputs information managed by management unit 220 . Specifically, the output unit 230 outputs the overall SOC. The output unit 230 may output the individual SOC. Although not particularly limited, the form of output may be display or voice. For example, the output unit 230 may be configured by a display, or may be configured by a speaker. Alternatively, the output unit 230 may be configured by a communication module and transmit information managed by the management unit 220 to an external device. The communication module may be a wireless communication module conforming to standards such as IEEE802.11a/b/g/n, ZigBee, Wi-SUN, and LTE, or a wired communication module conforming to standards such as IEEE802.3. may The external device may be a user terminal such as a personal computer or a smart phone, or may be an EMS (Energy Management System) provided in a facility including the power storage system 100 .

Storage unit 240 stores information managed by management unit 220 as a log. The storage unit 240 is configured by a memory such as a nonvolatile memory and/or a storage medium such as a HDD (Hard disc drive). The storage unit 240 stores the transition of the overall SOC as a log. The storage unit 240 may store the transition of the individual SOC as a log. The storage unit 240 may store the transition of the operating state (charging, discharging, standby, etc.) of the PCS 130 as a log.

(capacity of power storage device)
The capacity of the power storage device 110 according to the embodiment will be described below with reference to FIG. 2 .

As shown in FIG. 2 , the capacity of power storage device 110 includes an unusable capacity in which use of power storage device 110 is restricted from the viewpoint of suppressing deterioration of power storage device 110 . The threshold TH ₁ is a threshold for specifying the unusable capacity (on the upper limit side), and the threshold TH ₂ is a threshold for specifying the unusable capacity (on the lower limit side). The capacity of the power storage device 110 includes an emergency capacity (BCP; Business Continuity Plan) capacity for emergency situations such as disasters. Threshold TH ₃ is a threshold that specifies the BCP capacity.

In the following description, it is assumed that the total capacity of power storage device 110 is the capacity excluding the unusable capacity. Since the BCP capacity is not used in a normal state other than an emergency, the capacity that can be discharged from power storage device 110 (dischargeable capacity) is obtained by subtracting the BCP capacity from the power (remaining power storage amount) accumulated in power storage device 110. value. The chargeable capacity (chargeable capacity) of the power storage device 110 is a value obtained by subtracting the remaining power storage amount from the total capacity. For convenience, the sum of the remaining amount of power storage and the unusable capacity (lower limit side) will be referred to as the power storage capacity.

The SOC of power storage device 110 may be determined based on the capacity between TH ₁ and TH ₂ (that is, the total capacity of power storage device 110). Specifically, the SOC of power storage device 110 is represented by the ratio of the power storage capacity of power storage device 110 to the total capacity of power storage device 110 . The upper limit SOC is specified by the threshold _TH1 described above. The lower SOC is specified by threshold _TH3 .

In such a case, the SOC measurement method may be a method using a curve representing the relationship between SOC and OCV (Open Circuit Voltage) (hereinafter referred to as SOC-OCV curve). With such a method, the SOC can be measured by detecting the voltage value at the output end of power storage device 110 . However, the method of measuring the SOC is not limited to this, and may be a method using integration of current accompanying charging or discharging of power storage device 110 .

Furthermore, due to regular maintenance of power storage device 110, remeasurement of the total capacity is performed. Specifically, re-measurement is performed by discharging power storage device 110 from a fully charged state to a predetermined discharged state. The predetermined discharge state is a state in which the BCP capacity is discharged. However, discharge is not performed until the unusable capacity (lower limit side) is discharged. When the SOC is measured using the SOC-OCV curve, such maintenance redefines the voltage values corresponding to the upper limit SOC and lower limit SOC.

Although the capacity and SOC of one power storage device 110 have been described in FIG. 2, the same applies to the capacity and SOC of two or more power storage devices 110 connected in parallel. Therefore, its details are omitted.

(charging and discharging)
Charging and discharging of two or more power storage devices 110 according to the embodiment will be described below with reference to FIG. 3 . Here, description will be made on the premise that all of power storage devices 110A to 110C are ON.

In FIG. 3, the voltage value corresponding to the remaining power storage capacity of the power storage device 110C is the maximum voltage value (V _MAX ), the voltage value corresponding to the remaining power storage capacity of the power storage device 110B is the minimum voltage value (V _MIN ), A case is exemplified where the voltage value corresponding to the remaining amount of power storage of the power storage device 110A is an intermediate voltage value (V _MID ) between V _MAX and V _MIN .

In such a case, in order to suppress deterioration of power storage devices 110 caused by cross currents in two or more power storage devices 110, in a state where the difference (V _DIF ) between V _MAX and V _MIN is a threshold (TH _DIF ), Two or more power storage devices 110 are charged or discharged.

As shown in FIG. 3, by charging or discharging two or more power storage devices 110, the voltage variation (V _DIF described above) of each power storage device 110 may be reduced. However, V _DIF may increase due to variations in the internal resistance of each power storage device 110 . Furthermore, if time elapses without charging or discharging of each power storage device 110, it is conceivable that V _DIF will increase due to natural discharge or the like.

(Management of charging status)
Management of the state of charge according to the embodiment will be described below with reference to FIG. 4 . Here, a case is illustrated in which the individual SOC of the power storage device 110C is the highest and the individual SOC of the power storage device 110B is the lowest.

As described above, the management unit 220 manages the individual SOC and the overall SOC. Under such a premise, the management unit 220 manages the overall SOC as follows.

First, when the reference overall state of charge (hereinafter referred to as reference SOC) of power storage system 100 belongs to the first range, management unit 220 sets the highest individual SOC selected from two or more individual SOCs to the overall SOC. A first process of managing as That is, when the reference SOC belongs to the first range, the individual SOC of power storage device 110C is managed as the overall SOC.

Second, management unit 220 performs a second process of managing the SOC calculated based on two or more individual SOCs as the overall SOC when the reference SOC belongs to a second range lower than the first range. That is, when the reference SOC belongs to the third range, the SOC calculated based on the individual SOCs of power storage devices 110A to 110C is managed as the overall SOC.

Third, when the reference SOC belongs to a third range lower than the second range, the management unit 220 performs a third process of managing the lowest individual SOC selected from two or more individual SOCs as the overall SOC. I do. That is, when the reference SOC belongs to the third range, the individual SOC of power storage device 110B is managed as the overall SOC.

As shown in FIG. 4, a first range is defined by threshold TH ₁₁ , a second range is defined by thresholds TH ₁₁ and TH ₁₂ , and a third range is defined by threshold TH _12. As shown in FIG. In other words, the first range is the range in which the reference SOC is higher than the threshold _TH11 . The second range is a range that is higher than the threshold _TH12 and equal to or lower than the threshold _TH11 . A third range is a range in which the reference SOC is equal to or less than the threshold _TH12 .

In such a case, the reference SOC may be a common SOC throughout the first to third processes. For example, the average value of the individual SOCs of power storage devices 110A to 110C may be used as the reference SOC. Alternatively, the reference SOC may be different SOCs throughout the first to third processes. For example, the highest individual SOC may be used as the reference SOC in the first process, and the lowest individual SOC may be used as the reference SOC in the third process. Furthermore, in the second process, both the highest individual SOC and the lowest individual SOC are used as reference SOCs. That is, when the highest individual SOC exceeds the threshold _TH11 , the second process is switched to the first process, and when the lowest individual SOC is below the threshold _TH12 , the second process is switched to the third process.

Here, the lower limit state of charge (that is, the lower limit SOC described with reference to FIG. 3) that specifies the remaining capacity (that is, the BCP capacity described with reference to FIG. 3) that should be secured for emergencies in power storage system 100 is determined. Against this background, control unit 210 controls discharging of power storage system 100 so that the overall SOC managed by the second process does not fall below the lower limit SOC. In other words, the lower limit SOC is determined to belong to the second range and is higher than the threshold _TH12 described in FIG.

Furthermore, the overall SOC used in the second process may be the average of two or more individual SOCs. Here, the average may be a simple average of two or more individual SOCs or a weighted average of two or more individual SOCs. A weighted average of two or more individual SOCs is calculated by weighting relatively higher individual SOCs as the reference SOC approaches the threshold TH ₁₁ , and relatively lower as the reference SOC approaches the threshold TH ₁₂ . It is calculated by weighting the individual SOC.

(Management method)
A management method according to the embodiment will be described below with reference to FIG. FIG. 5 explains the operation of the management unit 220 described above. The flow shown in FIG. 5 is periodically repeated.

As shown in FIG. 5 , management unit 220 manages the individual SOCs of two or more power storage devices 110 in step S10. For example, management unit 220 calculates the individual SOC by acquiring voltage values at the output terminals of two or more power storage devices 110 . Further, management unit 220 identifies the above-described reference SOC based on the individual SOC.

In step S11, the management unit 220 determines whether or not the reference SOC is greater than the threshold _TH11 . The management unit 220 proceeds to the process of step S13 when the determination result is YES, and proceeds to the process of step S12 when the determination result is NO.

In step S12, the management unit 220 determines whether or not the reference SOC is greater than the threshold _TH12 . The management unit 220 proceeds to the process of step S14 when the determination result is YES, and proceeds to the process of step S15 when the determination result is NO.

In step S13, the management unit 220 performs a first process of managing the highest individual SOC selected from two or more individual SOCs as the overall SOC.

In step S14, the management unit 220 performs a second process of managing the SOC calculated based on two or more individual SOCs as the overall SOC.

In step S15, the management unit 220 performs a third process of managing the lowest individual SOC selected from two or more individual SOCs as the overall SOC.

(Action and effect)
In the embodiment, the power storage system 100 performs the first process of managing the highest individual SOC as the overall SOC when the reference SOC belongs to the first range. According to such a configuration, it is possible to prevent the SOC from reaching the upper limit SOC more easily than in the case where the simple average of two or more individual SOCs is managed as the overall SOC. For example, when the overall SOC is output, the user's sense of incongruity is reduced, and when the transition of the overall SOC is stored as a log, the unnaturalness of the log is reduced.

In the embodiment, the power storage system 100 performs the third process of managing the lowest individual SOC as the overall SOC when the reference SOC belongs to the third range. According to such a configuration, the risk of using the BCP capacity or unusable capacity (lower limit side) is reduced compared to the case where the simple average of two or more individual SOCs is managed as the overall SOC. Alternatively, although the simple average of two or more individual SOCs is managed as the overall SOC, any one of the power storage devices stops discharging so as to avoid using the BCP capacity or the unusable capacity (lower limit side). The user's sense of discomfort is reduced, and the unnaturalness of the log is reduced, compared to the case where the configuration is adopted.

In the embodiment, when the reference SOC belongs to the second range, the power storage system 100 performs the second process of managing the SOC calculated based on two or more individual SOCs as the overall SOC. Furthermore, the lower limit SOC specifying the BCP capacity is determined to belong to the second range. According to such a configuration, it is possible to accurately leave the remaining power storage amount to be secured as the BCP capacity.

[Other embodiments]
Although the present invention has been described by the above-described embodiments, the statements and drawings forming part of this disclosure should not be construed as limiting the present invention. Various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art from this disclosure.

Although not specifically mentioned in the embodiment, at least one of the control unit 210, the management unit 220, the output unit 230, and the storage unit 240 may be the PCS 130, and is provided in an EMS provided in a facility that includes the power storage system 100. good too. EMS may be provided by a cloud service.

Although not particularly mentioned in the embodiment, the signal line provided in the power storage system 100 may be wired or wireless.

Although not specifically mentioned in the embodiment, the control unit 210 may control charging or discharging of the power storage system 100 based on the overall SOC managed by the management unit 220 . For example, control unit 210 may stop charging power storage system 100 when the overall SOC reaches the upper limit SOC. Similarly, control unit 210 may stop discharging power storage system 100 when the overall SOC reaches the lower limit SOC.

In the embodiment, the capacity of power storage device 110 includes the BCP capacity, and the lower limit SOC specifies the BCP capacity. However, embodiments are not so limited. Lower limit SOC may specify the unusable capacity (lower limit side) without the capacity of power storage device 110 including the BCP capacity.

DESCRIPTION OF SYMBOLS 100... Power storage system, 110... Power storage apparatus, 111... Sensor, 120... Switching part, 130... PCS, 210... Control part, 220... Management part, 230... Output part, 240... Storage part

Claims (7)

A power storage system in which two or more power storage devices are connected in parallel to one power converter,
a management unit that manages information specifying two or more individual states of charge corresponding to each of the two or more power storage devices and information specifying an overall state of charge of the power storage system ;
A difference between a maximum voltage value among voltage values corresponding to the remaining power levels of the two or more power storage devices and a minimum voltage value among voltage values corresponding to the remaining power levels of the two or more power storage devices reaches a threshold. a control unit that performs charging or discharging of the two or more power storage devices when
The management department
performing a first process of managing, as the overall state of charge, the highest individual state of charge selected from among the two or more individual state of charge when the reference overall state of charge of the power storage system belongs to a first range;
A second process of managing the state of charge calculated based on the two or more individual states of charge as the state of charge when the reference overall state of charge of the power storage system belongs to a second range lower than the first range. and
When the reference overall state of charge of the power storage system belongs to a third range lower than the second range, the lowest individual state of charge selected from the two or more individual states of charge is managed as the overall state of charge. A power storage system that performs a third process. 2. The power storage system according to claim 1, wherein said power storage system is connected via a power line to a device provided in a facility including said power storage system. 3. The power storage system according to claim 1, further comprising an output unit that outputs said overall state of charge. 4. The power storage system according to any one of claims 1 to 3, further comprising a storage unit that stores a transition of said overall state of charge as a log. A lower limit state of charge for specifying the remaining capacity to be secured for emergency use as the power storage system is defined,
5. The power storage system according to any one of claims 1 to 4 , further comprising a control unit that controls discharging of the power storage system so that the overall state of charge managed by the second process does not fall below the lower limit state of charge. storage system. The power storage system according to any one of claims 1 to 5 , wherein the overall state of charge managed by the second process is an average of the two or more individual states of charge. A management method used in a power storage system in which two or more power storage devices are connected in parallel to one power conversion device,
a step A of managing information specifying two or more individual states of charge corresponding to each of the two or more power storage devices;
a step B of managing information specifying the overall state of charge of the power storage system;
A difference between a maximum voltage value among voltage values corresponding to the remaining power levels of the two or more power storage devices and a minimum voltage value among voltage values corresponding to the remaining power levels of the two or more power storage devices reaches a threshold. and a step C of performing charging or discharging of the two or more power storage devices in the case of
The step B is
managing the highest individual state of charge selected from among the two or more individual states of charge as the overall state of charge when the reference state of charge of the power storage system belongs to a first range;
managing a state of charge calculated based on the two or more individual states of charge as the overall state of charge when the reference overall state of charge of the power storage system belongs to a second range lower than the first range;
When the reference overall state of charge of the power storage system belongs to a third range lower than the second range, the lowest individual state of charge selected from the two or more individual states of charge is managed as the overall state of charge. A method of administration, including steps.

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