CN111919355B

CN111919355B - Power storage system and measurement method

Info

Publication number: CN111919355B
Application number: CN201980022857.4A
Authority: CN
Inventors: 可知纯夫; 中村秀人; 手塚涉
Original assignee: Furukawa Electric Co Ltd; Furukawa Battery Co Ltd
Current assignee: Furukawa Electric Co Ltd; Furukawa Battery Co Ltd
Priority date: 2018-03-28
Filing date: 2019-03-25
Publication date: 2024-02-20
Anticipated expiration: 2039-03-25
Also published as: JPWO2019188890A1; JP7317801B2; CN111919355A; WO2019188890A1

Abstract

In an electric storage system including a plurality of parallel battery modules (2), connection between battery packs is performed safely with a simpler configuration. The power storage system (100) comprises: a multi-parallel battery module (2) formed by connecting a plurality of battery packs (20_1-20_n) in parallel, wherein the battery packs (20_1-20_n) comprise at least one lead battery cell (200); an ac/dc conversion device (3) that controls the power transmission/reception of the multi-parallel battery modules; switches (4_1-4_n) provided for each of the battery packs and connected in series between the corresponding battery pack and the ac/dc conversion device; and a control device (1, 1A) that, when the split battery packs are connected in parallel to each other, controls on/off of the switch corresponding to the battery pack that is the connection object, based on a measured value (delta V, T) associated with the voltage of the battery pack that is the connection object.

Description

Power storage system and measurement method

Technical Field

The present invention relates to a power storage system and a method for measuring an internal resistance of a battery, and for example, to a power storage system for controlling charge and discharge of a lead battery and a method for measuring an internal resistance of a lead battery.

Background

In recent years, since lead storage batteries are required to have a larger capacity, a large-sized power storage system is being popularized, which includes a multi-parallel battery module formed by connecting a plurality of battery packs (strings) in parallel, the battery packs being formed by connecting a single lead storage battery cell (single cell) or a plurality of lead storage battery cells in series.

In such a power storage system, in charge/discharge control of the battery packs, switching control for connecting and disconnecting the battery packs to/from each other may be performed. When the disconnected battery packs are reconnected, a circulating current flows between the battery packs immediately after the reconnection in the case that a voltage difference exists between the battery packs. It is known that when such a circulating current is a large current, the life of the battery is shortened.

In addition, it is known that when the circulating current flowing when the battery packs are reconnected to each other exceeds the allowable current of battery peripheral devices such as cables and circuit breakers connected to the multi-parallel battery modules, the power module is damaged or deteriorated due to heat generation.

In order to prevent the adverse effect of the circulating current on the battery and the battery peripheral devices, various methods have been studied. For example, patent document 1 discloses a power storage system including a 1 st circuit that connects a plurality of battery packs via a resistive element, and a 2 nd circuit that directly connects a plurality of battery packs without via a resistive element. In this power storage system, when the battery packs are connected to each other, first, the 1 st circuit is selected, the battery packs are connected to each other via the resistive element, the circulating current is suppressed, the voltage difference between the battery packs is reduced, and when the voltage difference is reduced, the 2 nd circuit is selected, and the battery packs are connected to each other without via the resistive element. Thus, the battery is prevented from being adversely affected by the large circulating current.

Knowing the internal resistance of the battery, the magnitude of the circulating current flowing when the battery pack having the voltage difference is connected can be found from ohm's law. As a method for calculating the internal resistance of the battery pack, the following method is known.

For example, patent document 2 discloses the following method: the internal resistance was obtained from the voltage and current of the battery during operation. Specifically, a measuring resistor element of a predetermined size is connected to the battery during the operation of the battery, and a change Δv in the voltage and a change Δi in the current of the measuring resistor element are measured. Then, the internal resistance R of the battery is calculated according to a calculation formula (r=Δv/Δi).

Further, it is known that the internal resistance of a battery has a frequency dependency, and non-patent document 1 discloses a technique for evaluating the internal resistance of a battery using a Cole-Cole diagram.

Here, the cole-cole diagram is a diagram in which the horizontal axis represents the real part of the internal resistance of the battery and the vertical axis represents the imaginary part of the internal resistance, and a trace is plotted when the frequency swings from 0.1Hz to several tens kHz.

For example, in the cole-cole diagram of a lead acid battery, the trace contacts the horizontal axis around a 1kHz frequency. The value at this time does not include an imaginary part of the impedance, and thus can be understood to represent the direct-current internal resistance of the lead-acid battery. Accordingly, the discharge current of the lead storage battery was controlled using the tester so that the lead storage battery flowed an alternating current Δi=io·sin (ωt) of about 1kHz, and the voltage change at this time was measured Then, the internal resistance of the lead-acid battery can be obtained from the ratio of the effective values of the ac current Δi and the voltage change Δv.

(prior art literature)

(patent literature)

Patent document 1: JP patent No. 6004350;

patent document 2: JP-A-63-12981.

(non-patent literature)

Non-patent document 1: plate wall chang et al, "relation between electrochemical impedance and reaction rate of diffusion-charge transfer hybrid control system", zairyo-to-Kankyo,51, 410-417, 2002. Non-patent document 2: daniel rouu et al, "12V battery modeling: model development, simulation and verification ", IEEE, month 6, 15 of 2017.

Disclosure of Invention

(problem to be solved by the invention)

However, the above prior art does not disclose any insight as to how small the voltage difference between the battery packs is to become a safe circulating current.

Further, in the technique disclosed in patent document 1, in order to suppress the circulating current, a plurality of circuits need to be prepared for each battery pack, which causes a problem that the system configuration becomes complicated and the cost increases.

Further, as shown in non-patent document 2, it is known that the internal resistance of the battery has a different value at the time of discharging and at the time of charging. Therefore, according to the method disclosed in patent document 2, although the resistance at the time of discharge can be measured, the resistance at the time of charge cannot be measured, and thus it cannot be said that the internal resistance of the battery can be accurately measured. Therefore, even if the value of the circulating current is estimated using the internal resistance measured by the method disclosed in patent document 2, the estimated value becomes a value that deviates from the value of the circulating current flowing when the battery packs are actually connected to each other.

Further, the present inventors have found that the circulation current actually flowing between the battery packs is very small, and is only a fraction of the predicted value, compared with the predicted value of the circulation current obtained based on the internal resistance measured by the technique disclosed in non-patent document 1. That is, it was found that the estimated circulating current is larger than the actual current when the internal resistance is found using the existing measurement method.

The present invention has been made in view of the above-described problems, and an object of the present invention is to securely connect battery packs to each other with a simpler configuration in a power storage system including a plurality of parallel battery modules.

(solution for solving the problem)

The power storage system according to the representative embodiment of the present invention includes: a multi-parallel battery module formed by connecting a plurality of battery packs in parallel, the battery packs including at least one lead battery cell; an ac/dc conversion device that controls the power transmission/reception of the multi-parallel battery modules; a switch provided corresponding to each of the battery packs, and connected in series between the corresponding battery pack and the ac/dc conversion device; and a control device that monitors a state of the battery pack for each of the battery packs, and controls on/off of the switch; the control device may control on/off of the switch corresponding to the battery pack as the connection target based on a measured value associated with the voltage of the battery pack as the connection target when the separated battery packs are connected in parallel with each other.

(effects of the invention)

According to the power storage system having the multi-parallel battery modules according to the present invention, the connection of the battery packs to each other can be performed safely with a simpler configuration.

Drawings

Fig. 1 is a graph showing a relationship between voltage and current at the time of equalizing charge of a lead acid battery.

Fig. 2 is a graph showing a circulating current generated due to a difference in voltage decay states of the battery pack.

Fig. 3 is a graph showing a circulating current generated by a difference in SOC of the battery pack.

Fig. 4 is a diagram showing a configuration of the power storage system according to embodiment 1.

Fig. 5 is a diagram showing a hardware configuration of the monitor.

Fig. 6 is a flowchart showing a flow of a method for controlling connection between battery packs in the power storage system according to embodiment 1.

Fig. 7 is a flowchart showing a flow of connection availability determination processing (step S2) of the battery pack according to embodiment 1.

Fig. 8 is a diagram for explaining a method of measuring the internal resistance of the battery according to embodiment 1.

Fig. 9 is a flowchart showing a flow of a method for measuring the internal resistance of the battery according to embodiment 1.

Fig. 10 is a diagram showing a configuration of a power storage system according to embodiment 2.

Fig. 11 is a diagram for explaining the stable reference time Ts.

Fig. 12 is a flowchart showing a flow of connection availability determination processing (step S2) of the battery pack according to embodiment 2.

Detailed Description

1. Summary of the embodiments

First, a representative embodiment of the invention disclosed in the present application will be described in brief. In the following description, reference numerals corresponding to the components of the invention are given to brackets in the drawings as an example.

The power storage system (100, 100A) according to the representative embodiment of the present invention is characterized by comprising: a multi-parallel battery module (2) formed by connecting a plurality of battery packs (20_1-20_n) in parallel, wherein the battery packs comprise at least one lead battery cell; an ac/dc conversion device (3) that controls the power transmission/reception of the multi-parallel battery modules; switches (4_1-4_n) provided for each of the battery packs and connected in series between the corresponding battery pack and the ac/dc conversion device; and a control device (1, 1A) that monitors the state of the battery pack for each of the battery packs and controls on/off of the switch, wherein the control device controls on/off of the switch corresponding to the battery pack as the connection object based on a measured value (delta V, T) associated with the voltage of the battery pack as the connection object when the separated battery packs are connected in parallel with each other.

In the above power storage system, the measurement value related to the voltage of the battery pack may be a voltage difference (Δv) between the battery packs as a connection target.

In the above power storage system, the control device may include: a storage unit (14) that stores a value of internal resistances (R, R, R2) of the battery packs measured in advance, and an allowable current (Iper) of a circulating current that flows when the battery packs are connected to each other; a judging unit (12) that judges whether or not the battery packs are connectable to each other; and a switch control unit (13) that switches on/off of the switch based on a result of the determination by the determination unit, wherein the determination unit calculates an estimated value (Ice) of a circulating current flowing when the battery packs, which are the connection targets, are connected to each other based on the voltage difference calculated from the measured value of the voltage of the battery pack, which is the connection target, and the value of the internal resistance stored in the storage unit, and instructs the switch control unit to allow the battery packs to be connected to each other when the estimated value is smaller than the allowable current stored in the storage unit, and instructs the switch control unit to not allow the battery packs to be connected to each other when the estimated value is larger than the allowable current stored in the storage unit.

In the above power storage system, the internal resistance stored in the storage unit may include a 1 st resistance (R1) and a 2 nd resistance (R2), and the determination unit may determine a state of the battery pack as the connection target, calculate the estimated value using the 1 st resistance when the battery pack as the connection target is in the 1 st state in which the voltage difference occurs due to a difference in a voltage decay state (see fig. 2), and calculate the estimated value using the 2 nd resistance when the battery pack as the connection target is in the 2 nd state in which the voltage difference occurs due to a difference in a charge state (see fig. 3).

In the above power storage system, the value of the internal resistance stored in the storage unit may be a value calculated based on a measured value of a peak value (Ip) of a circulating current flowing when the battery packs are connected to each other and a measured value of the voltage difference (Δv) before connection.

In the above power storage system, the internal resistance stored in the storage unit may be a combined resistance of a resistance at the time of charging and a resistance at the time of discharging, the resistance at the time of charging may be calculated based on a change amount of a voltage of the battery pack and a charging current when the battery pack is charged with a constant current, and the resistance at the time of discharging may be calculated based on a change amount of a voltage of the battery pack and a discharging current when the battery pack is discharged with a constant current.

In the above power storage system, the allowable current stored in the storage unit may be a value corresponding to a maximum value of a current allowed by the battery pack or a value corresponding to a maximum value of a current allowed by a device connected to the battery pack.

In the above power storage system, the measurement value of the battery pack related to the voltage may be an elapsed time (T) after the end of charging and after the end of discharging of the battery pack, which is a connection object.

In the above power storage system (100A), the control device (1A) may include: a storage unit (14A) that stores a stabilization reference time (Ts) that indicates a reference value of time until the voltage of the battery pack stabilizes after the end of charging and after the end of discharging of the battery pack; a judging unit (12A) that judges whether or not the battery packs are connectable to each other; and a switch control unit (13) that controls on/off of the switch based on a result of the determination by the determination unit, wherein the determination unit measures an elapsed time (T) that has elapsed after the end of charging and after the end of discharging of the battery pack as a connection target, and instructs the switch control unit to permit the battery packs to be connected to each other when the measured value of the elapsed time is greater than the stable reference time stored in the storage unit, and instructs the switch control unit to not permit the battery packs to be connected to each other when the measured value of the elapsed time is less than the stable reference time stored in the storage unit.

[ 10 ] A method for measuring internal resistances (R, R1, R2) of battery packs (20_1 to 20_n) including at least one lead storage battery cell (200), the method comprising: a voltage difference measurement step (S51) in which a voltage difference (Δv) between two of the battery packs is measured; a circulating current measuring step (S52) in which a peak value (Ip) of a circulating current flowing when the two battery packs have been connected to each other is measured; and an internal resistance calculation step (S53) of calculating the internal resistance of the battery pack based on the voltage difference measured by the voltage difference measurement step and the circulating current measured by the circulating current measurement step.

In the above measurement method, the internal resistance calculation step may further include: and a step of calculating an internal resistance of the battery pack based on a slope of a curve representing a relationship between a peak value of the circulating current measured by the circulating current measuring step and the voltage difference measured by the voltage difference measuring step.

2. Detailed description of the embodiments

Specific examples of the embodiments of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals are given to the components common to the respective embodiments, and overlapping description is omitted. In addition, the drawings are schematic, and it should be noted that dimensional relationships of elements, ratios of elements, and the like may be different from actual ones. The drawings may include portions having different dimensional relationships and ratios.

Summary of connection control between storage battery packs according to the present invention

An outline of connection control between battery packs according to the present invention will be described.

First, the principle of generation of the circulating current will be briefly described.

For the circulating current, the following two cases are considered: due to a difference in the decay state of the voltage after the charge or discharge of the battery pack, and due to a difference in the SOC of the connected battery pack. Hereinafter, each case will be described with reference to fig. 1 to 3.

First, a case where a circulating current is generated due to a difference in the decay state of the voltage of the battery pack will be described.

In general, it is known that the voltage of a battery changes and converges to a certain value (voltage decay) after the charge or discharge of the battery is stopped. Here, the charge equalization of the battery will be described as an example.

In fig. 1, the vertical axis represents the current (charge current) of the lead storage battery and the voltage (output voltage) of the lead storage battery flowing during the charge equalization, and the horizontal axis represents time.

Here, the equalization charge is a charge control for charging the lead storage battery to a full charge state at a predetermined period to eliminate sulfation, which is one of the causes of deterioration of the lead storage battery. As a method of equalizing charge, for example, a constant current-constant voltage charge (CCCV) method and a multi-stage charge method are known.

The constant current-constant voltage charging mode is a charging mode as follows: first, the lead-acid battery is charged at a constant current value (hereinafter, also referred to as "constant current charge" or "CC charge"), and after the battery voltage reaches a predetermined threshold value, the lead-acid battery is returned to a full charge state by constant voltage charge (hereinafter, also referred to as "constant voltage charge" or "CV charge").

The multi-stage charging method is as follows: firstly, constant-current charging is carried out, when the voltage of the storage battery reaches a specified threshold value, the constant-current charging is carried out with a current value lower than the previous value, the process is repeated for a plurality of times, and finally, constant-voltage charging is carried out with the specified voltage, so that the lead storage battery is restored to a full-charge state.

In any charging mode, constant voltage charging is performed in the latter half of equalizing charge. Fig. 1 shows, as an example, a time change in the charge current and voltage of the lead-acid battery when the charge is balanced by the constant-current-constant-voltage charging method.

As shown in fig. 1, in the lead storage battery, the state of charge (SOC) is not necessarily proportional to the voltage. For example, the voltage rapidly increases in the final period of equalizing charge, and after stopping charging, the voltage decays over a long period of time and converges to a predetermined voltage Veq.

Fig. 2 is a graph showing a circulating current generated due to a difference in voltage decay states of the battery pack. The graph shows the circulating current flowing when two battery packs are connected after the end of equalizing charge in the constant-current-constant-voltage charging system, and the voltage of each battery pack.

In fig. 2, the vertical axis represents current and voltage, respectively, and the horizontal axis represents time. In the figure, reference numeral 301 denotes a time change in the voltage of the 1 st battery pack that completes the equalization charge (CV charge) first among the two battery packs to be connected, and reference numeral 302 denotes a time change in the voltage of the 2 nd battery pack that completes the equalization charge (CV charge) after among the two battery packs to be connected. Further, reference numeral 401 denotes a temporal change in current (circulating current) flowing between the 1 st battery pack and the 2 nd battery pack.

As described above, the output voltage of the lead storage battery charged uniformly decays for a long time. As shown in fig. 2, when the 1 st and 2 nd battery packs end the equalizing charge at different times, the decay state of the voltage of the 1 st battery pack is different from the decay state of the voltage of the 2 nd battery pack, so a voltage difference Δv is generated between the voltage of the 1 st battery pack and the voltage of the 2 nd battery pack. Therefore, in this decay period, if the 1 st battery pack and the 2 nd battery pack are connected, a large circulating current may flow.

Next, a case where a circulating current is generated due to a difference in SOC of the battery pack will be described.

Fig. 3 is a graph showing a circulating current generated by a difference in SOC of the battery pack. In the figure, the circulating current and voltage flowing when two battery packs having different SOCs are connected are shown.

In fig. 3, the vertical axis represents current and voltage, and the horizontal axis represents time.

In the figure, reference numeral 311 denotes a time change in the voltage of the 1 st battery pack having a high SOC among the two battery packs to be connected, and reference numeral 312 denotes a time change in the voltage of the 2 nd battery pack having a low SOC among the two battery packs to be connected. Further, reference numeral 411 denotes a temporal change in current (circulating current) flowing between the 1 st battery pack and the 2 nd battery pack.

When a plurality of battery packs are connected at the time of initial introduction or restart of the power storage system, the SOCs of the battery packs may be different from each other, and the voltages of the battery packs may be different from each other. For example, as shown in fig. 3, when the 1 st battery pack and the 2 nd battery pack having different SOCs (voltages) are connected, a large circulating current may flow.

As described above, the circulating current is classified into a case due to a difference in the decay state of the voltage of the connected battery pack and a case due to a difference in the SOC of the connected battery pack, but in either case, the magnitude of the circulating current is determined by the magnitude of the voltage difference Δv between the battery packs and the internal resistance.

As shown in fig. 2 and 3, the present inventors have found that the actual measurement value of the circulating current flowing when the battery packs of different voltages are connected to each other is smaller than expected and decays relatively quickly.

Therefore, in the connection control between battery packs according to the present invention, in the power storage system, when the split battery packs are connected in parallel to each other, it is determined whether or not the battery packs can be connected to each other based on the measured value of the voltage correlation of the battery packs to be connected.

Here, examples of the measurement value of the voltage of the battery string include a voltage difference between the battery packs to be connected, an elapsed time after the end of charging and after the end of discharging of the battery packs to be connected, and the like.

In this specification, as embodiment 1, a power storage system that controls connection of battery packs based on a voltage difference between battery packs to be connected is exemplified, and as embodiment 2, a power storage system that controls connection of battery packs based on an elapsed time after completion of charging and after completion of discharging of the battery packs is exemplified, a connection control between battery packs according to the present invention will be described in detail.

Embodiment 1

The power storage system 100 shown in the figure is a power storage system including, for example, a lead storage battery that is recycled. The power storage system 100 supplies power to the load 7 from the power supply unit 6 (commercial power supply) during normal operation, for example, and supplies power to the load 7 from a lead-acid battery as a backup power supply when a power failure occurs.

The power supply unit 6 is a functional unit that supplies power to the power storage system 100 and the load 7. The power supply unit 6 is, for example, a commercial power supply. The power supply unit 6 may include a power generation facility that generates power based on renewable energy sources such as solar Power (PV) and the like, in addition to the commercial power source.

The power storage system 100 includes a battery module 2, an ac/dc converter 3, switches 4_1 to 4_n (n is an integer of 2 or more), breakers 5_1 to 5_n, and a control device 1.

The battery module 2 includes a lead storage battery configured to be chargeable and dischargeable. The battery module 2 is a multi-parallel battery module in which a plurality of battery packs including at least one lead battery cell are connected in parallel.

Specifically, as shown in fig. 4, the battery module 2 has a structure in which a plurality of battery packs 20_1 to 20—n, each of which is formed by connecting m (m is an integer of 1 or more) lead battery cells 200 in series, are connected in parallel. Hereinafter, the battery module 2 is also referred to as "multi-parallel battery module 2". When it is not necessary to distinguish between the battery packs 20_1 to 20—n, it is sometimes merely referred to as "battery pack 20".

The battery module 2 further includes a voltage sensor 201 in each of the battery packs 20_1 to 20—n, and the voltage sensor 201 measures the output voltage (battery voltage) of each of the battery packs 20_1 to 20—n. Further, a current sensor may be provided to measure the charge current and the discharge current of each of the battery packs 20_1 to 20—n.

An ac/dc conversion device (hereinafter also referred to as "PCS (Power Conditioning System, power control system)") 3 is a power conversion unit controlled by a control device 1 described later, converts power between a power supply unit 6, a battery module 2, and a load 7, and controls transmission and reception of power between the power supply unit 6, the battery module 2, and the load 7.

For example, the PCS3 converts Alternating Current (AC) power of the power supply portion 6 into Direct Current (DC) power and supplies the same to the battery module 2. The PCS3 is constituted by, for example, a DC/DC converter, an AC/DC converter (AC/DC), a switching circuit, and the like.

The switches 4_1 to 4_n are devices for switching connection and disconnection between the PCS3 and the multi-parallel battery module 2. As shown in fig. 4, the switches 4_1 to 4_n are provided corresponding to each of the battery packs 20_1 to 20—n, and are connected in series between the corresponding battery pack 20_1 to 20—n and the PCS 3. The switches 4_1 to 4_n are, for example, electromagnetic switches (relays).

The on/off of the switches 4_1 to 4_n is controlled by a control device 1 described later. Thereby, connection and disconnection between each of the battery packs 20_1 to 20—n and the PCS3 can be switched.

When it is not necessary to distinguish between the switches 4_1 to 4_n, it is sometimes merely referred to as "switch 4".

The circuit breakers 5_1 to 5_n are devices provided in each of the battery packs 20_1 to 20—n, and are configured to disconnect the PCS3 from each of the battery packs 20_1 to 20—n when an overcurrent flows between the PCS3 and each of the battery packs 20_1 to 20—n. Specifically, the circuit breakers 5_1 to 5_n are connected in series with the switches 4_1 to 4_n, respectively.

When it is not necessary to distinguish between the individual circuit breakers 5_1 to 5_n, it is sometimes merely referred to as "circuit breaker 5".

The control device 1 is a device that integrally controls the entire power storage system 100. The control device 1 monitors the state of each of the battery packs 20_1 to 20—n, and controls on/off of the switches 4_1 to 4_n.

As shown in fig. 4, the control device 1 includes a battery management unit 10 and a monitoring unit 11.

The battery management unit 10 is a device that integrally controls each component of the power storage system 100. The battery management unit 10 is, for example, EMS (Energy Management System).

The method for realizing the battery management unit 10 is as follows: for example, in a data processing apparatus including a processor such as a CPU (central processing unit) as a hardware resource, a storage device such as a RAM (Random access Memory) and a ROM (Read Only Memory), and a peripheral circuit such as an I/F circuit, the processor executes various operations in accordance with a program stored in the storage device to control the peripheral circuit.

The battery management unit 10 controls the charge and discharge of the multi-parallel battery module 2 by driving the PCS 3. For example, the battery management unit 10 performs balanced charging of the multi-parallel battery module 2 in various charging methods such as constant current-constant voltage charging (CCCV) based on the monitoring result of the multi-parallel battery module 2 by the monitoring unit 11.

The monitoring unit 11 is a data processing device that sequentially acquires physical quantities measured by the voltage sensors 201 and the like of the multi-parallel battery modules 2, and monitors the state of the multi-parallel battery modules 2 based on the physical quantities. The monitor 11 is, for example, a BMU (Battery Management Unit ).

Specifically, the monitoring unit 11 monitors the state of each of the battery packs 20_1 to 20—n, and controls the on/off of the switches 4_1 to 4_n. More specifically, when the split battery packs 20 are connected in parallel, the monitoring unit 11 controls the on/off of the switch 4 corresponding to the battery pack 20 to be connected based on the measured value associated with the voltage of the battery pack 20 to be connected.

As shown in fig. 4, the monitor unit 11 includes a switch control unit 13, a determination unit 12, and a storage unit 14 as main functional blocks. These functional blocks are realized by hardware resources and software provided in the data processing device as the monitor unit 11.

The hardware configuration of the monitor 11 will be described.

Fig. 5 is a diagram showing a hardware configuration of the monitor 11.

The monitor 11 includes, as hardware resources, a computing device 101, a storage device 102, a bus 103, a digital touch input output circuit (DIO) 104, and an analog input circuit (AI) 105.

The arithmetic device 101 is configured by a processor such as a CPU or DSP (digital signal processor). The storage device 102 is configured by, for example, ROM, RAM, HDD, a flash memory, and the like, and has a storage area in which a program 1021 for causing the arithmetic device 101 to execute various data processing, and data 1022 such as parameters and operation results for data processing according to the arithmetic device 101 are stored.

The program for controlling the connection between the battery packs according to the present embodiment is stored in the storage device 102 as a program 1021, for example.

The bus 103 is a functional unit that connects the arithmetic device 101, the storage device 102, the digital touch input/output circuit 104, and the analog input circuit 105 to each other, and can transmit and receive data between these devices.

The digital touch input output circuit (DIO) 104 is a circuit for inputting a digital signal output from an external device provided outside the monitor portion 11 and outputting the digital signal to the external device. For example, the digital touch input output circuit 104 may output a digital signal for controlling on/off of the switches 4_1 to 4_n.

An analog input circuit (AI) 105 is a circuit that inputs an analog signal output from an external device and converts it into a digital signal. For example, the analog input circuit 105 inputs an analog signal indicating the voltage of each of the battery packs 20_1 to 20—n detected by the voltage sensor 201, converts the analog signal into a digital signal, and stores the digital signal in the storage device 102 or the like via the bus 103.

The data processing device as the monitor unit 11 performs an operation by the operation device 101 in accordance with a program 1021 stored in the storage device 102, and controls the storage device 102, the bus 103, the digital touch input/output circuit 104, and the analog input circuit 105, thereby realizing the respective functional units shown in fig. 4, that is, the determination unit 12, the switch control unit 13, and the storage unit 14.

Next, each functional block of the monitor 11 will be described in detail.

In fig. 4, the storage unit 14 is a functional unit that stores various data for connection control between battery packs. For example, the storage unit 14 stores internal resistance information 141 and allowable current information 142.

The internal resistance information 141 is information indicating a value of the internal resistance R of the battery pack 20 measured in advance. The method of measuring the internal resistance R will be described below.

The allowable current information 142 is information indicating an allowable value of the circulating current (hereinafter also referred to as "allowable current Iper") which becomes a reference for determining whether or not connection between the battery packs 20 is possible.

The allowable current Iper is preferably a value corresponding to, for example, the maximum value of the current (charging current and discharging current) allowed by the battery pack 20 or the maximum value (rated constant current) of the current allowed by the device connected to the battery pack 20 such as the cable, the terminal block, the switch 4 (relay), and the breaker 5. An example is shown below.

For example, the multi-parallel battery module 2 has a structure in which 10 (n=10) battery packs 20_1 to 20_10 are connected in parallel, and the battery packs 20_1 to 20_10 are formed by connecting 196 (m=196) lead battery cells 200 in series, and the maximum charge current and the maximum discharge current of the lead battery permitted in a range that does not affect the cycle life are 200A and 400A. The input voltage range of the ac/dc converter 3 is 300V at the maximum, the rated constant current is 1000A, and the rated constant currents of the circuit breakers 5_1 to 5_n are 200A.

In this case, the ac/dc conversion device 3 has 1000A for the rated constant current, and 10 battery packs 20_1 to 20_10 are connected in parallel, so that the maximum allowable current for each row of battery packs 20 can be calculated to be 100A.

However, in the power storage system 100, it is necessary that a predetermined output (kW) be generated even when the parallel number becomes equal to or smaller than the initial setting due to some reason that a part of the battery packs 20_1 to 20—n are separated. Therefore, the allowable current Iper of the battery pack 20 corresponds to the maximum current (the charge current 200A, the discharge current 400A) of the lead-acid battery allowed in a range that does not affect the cycle life. That is, the allowable current Iper is "200A" at this time.

In this case, a device having a constant current (200A) equal to or greater than the allowable current Iper is also used as a device such as a cable or a junction block connected to the ac/dc converter 3 and the circuit breakers 5_1 to 5_n.

The determination unit 12 is a functional unit that determines whether or not the battery packs 20 can be connected to each other.

The determination unit 12 calculates an estimated value Ice of the circulating current flowing when the connected battery packs 20 are connected to each other, based on the voltage difference Δv between the connected battery packs 20 calculated from the measured value of the voltage of the connected battery packs 20 and the internal resistance R stored in the storage unit 14.

When the estimated value Ice of the circulating current is smaller than the allowable current Iper stored in the storage section 14, the judgment section 12 instructs the switch control section 13 to allow the battery packs 20 to be connected to each other, and when the estimated value Ice of the circulating current is larger than the allowable current Iper stored in the storage section 14, the judgment section 12 instructs the switch control section 13 not to allow the battery packs 20 to be connected to each other.

The switch control unit 13 is a functional unit for switching on/off of the switches 4_1 to 4_n in response to an instruction (determination result) from the determination unit 12. For example, when the switches 4_1 to 4_n are relays, the switch control unit 13 outputs a drive signal for switching on/off of the relays to the switches 4_1 to 4_n in response to an instruction from the monitoring unit 11 or the battery management unit 10.

Next, a flow of a connection control method between the control device 1 and the battery pack will be described.

Fig. 6 is a flowchart showing a flow of a method for controlling connection between battery packs in the power storage system 100 according to embodiment 1.

Here, as an example, a case will be described in which the switch 4 is controlled in sequence from the battery packs 20 that have completed the charge equalization to disconnect them from the PCS3, and when all the battery packs 20 have completed the charge equalization, the respective battery packs 20 are connected.

In fig. 6, first, the control device 1 determines whether or not the battery packs 20_1 to 20—n need to be reconnected (step S1). For example, when the equalization charge of all the battery packs 20_1 to 20—n is not completed, the control device 1 determines that the reconnection of the battery packs 20_1 to 20—n should not be performed, and waits until the equalization charge of all the battery packs 20_1 to 20—n is completed.

On the other hand, in step S1, when the equalization charge of all the battery packs 20_1 to 20—n is completed, the control device 1 determines that the disconnected battery packs 20_1 to 20—n need to be reconnected, and performs connection availability determination processing of the battery packs (step S2).

In step S2, first, the control device 1 calculates a voltage difference Δv between the battery packs 20 to be connected (step S21).

For example, in fig. 4, a case is considered in which battery pack 20_1 and battery pack 20_2 are connected. In this case, first, the determination unit 12 of the control device 1 acquires the measured value of the voltage V1 of the battery pack 20_1 measured by the voltage sensor 201 and the measured value of the voltage V2 of the battery pack 20_2 measured by the voltage sensor 201. Then, the determination unit 12 calculates a voltage difference Δv (= |v1-v2|) between the battery pack 20_1 and the battery pack 20_2 based on the measured value of the voltage V1 of the battery pack 20_1 and the measured value of the voltage V2 of the battery pack 20_2.

After step S21, the control device 1 calculates an estimated value Ice of the circulating current flowing between the battery packs 20 to be connected (step S22). In the above example, the judgment unit 12 calculates the estimated value Ice of the circulating current flowing between the battery pack 20_1 and the battery pack 20_2 based on the voltage difference Δv calculated in step S21 and the internal resistance R stored in the storage unit 14. For example, the determination unit 12 calculates the estimated value Ice of the circulating current based on the equation (ice=Δv/R).

Next, the judgment unit 12 of the control device 1 compares the estimated value Ice of the circulating current with the allowable current Iper stored in the storage unit 14 (step S23).

For example, in the above example, when the estimated value Ice of the circulating current flowing between the battery pack 20_1 and the battery pack 20_2 is smaller than the allowable current Iper, the judgment section 12 judges that the battery pack 20_1 and the battery pack 20_2 can be connected (step S24).

On the other hand, when the estimated value Ice of the circulating current flowing between the battery pack 20_1 and the battery pack 20_2 is larger than the allowable current Iper, the determination unit 12 determines that the battery pack 20_1 and the battery pack 20_2 cannot be connected (step S25).

Through the above steps, the connection availability determination process of the battery pack is performed (step S2).

In fig. 6, after step S2, the control device 1 performs connection control of the battery packs 20 based on the determination result of the connection availability determination process of the battery packs (step S2) (step S3).

For example, in the above example, when it is determined that the battery pack 20_1 and the battery pack 20_2 can be connected by the connection availability determination process (in the case of step S24), the determination unit 12 instructs the switch control unit 13 to allow connection of the battery pack 20_1 and the battery pack 20_2, and instructs the switch control unit 13 to turn on the switches 4_1, 4_2 (step S4). Thus, the switch control unit 13 can turn on the switch 4_1 corresponding to the battery pack 20_1 and the switch 4_2 corresponding to the battery pack 20_2, respectively.

On the other hand, in the above example, when it is determined that the battery pack 20_1 and the battery pack 20_2 are not connectable by the connection availability determination process (in the case of step S25), the determination unit 12 instructs the switch control unit 13 not to allow connection of the battery pack 20_1 and the battery pack 20_2, and instructs the switch control unit 13 to turn off the switches 4_1, 4_2 (step S5). Thereby, the switch control unit 13 keeps the switch 4_1 corresponding to the battery pack 20_1 and the switch 4_2 corresponding to the battery pack 20_2 in the off state.

Through the above steps, the control device 1 performs connection control between the battery packs.

Next, a method for measuring the internal resistance of the battery according to embodiment 1 will be described.

Fig. 8 is a diagram for explaining a method of measuring the internal resistance of the battery according to embodiment 1. Fig. 9 is a flowchart showing a flow of a method for measuring the internal resistance of the battery according to embodiment 1.

As shown in fig. 8 and 9, first, two lead storage batteries having different voltages are prepared (step S50). For example, two lead storage batteries of the same kind as those used in the target power storage system are prepared, and it takes a sufficient time to fully charge the prepared two lead storage batteries. Then, each lead storage battery was discharged at different times with a current corresponding to 0.1CA, and after the discharge was completed, the lead storage batteries were left for a predetermined time (for example, 16 hours) until the battery voltages of the two lead storage batteries stabilized. Thus, two lead storage batteries having different SOCs can be prepared.

Then, the voltages Vs1, vs2 of the respective lead storage batteries placed for a predetermined time are measured, and a voltage difference Δvs (= |vs1-Vs 2|) is obtained (step S51).

Next, these lead storage batteries are connected to each other, and the peak value Ip of the circulating current flowing between the lead storage batteries is measured (step S52).

Finally, the internal resistance of the lead storage battery is calculated (step S53). For example, steps S50 to S52 are repeatedly performed, a curve (function) showing the relationship between the voltage difference Δv and the peak value Ip of the circulating current is created, and the internal resistance R is calculated based on the slope of the curve.

Through the above steps, the internal resistance R of the battery can be measured.

The internal resistance R measured by the above-described measurement method reflects the resistance values of both the lead storage battery on the charging side (lead storage battery with low voltage) and the lead storage battery on the discharging side (lead storage battery with high voltage). Further, the internal resistance R measured by this measurement method is more accurate than the internal resistance value measured by the conventional method because it is based on the measured value of the circulating current actually generated using the same kind of battery as the battery applied in the power storage system 100.

The internal resistance R measured in the above example corresponds to the internal resistance of the lead-acid battery in a state where the lead-acid battery is not charged or discharged for a predetermined time or longer, such as at the time of initial introduction or at the time of periodic inspection of the power storage system 100.

That is, the internal resistance measured in the above example (fig. 8 and 9) corresponds to the internal resistance R1 when the circulating current is generated due to the difference in SOC of the battery pack (refer to fig. 3).

On the other hand, when a circulating current is generated due to a difference in the state of decay of the voltage of the battery pack (see fig. 2), the internal resistance R2 can be obtained by the following method. For example, in step S50 of the flowchart shown in fig. 9, two lead storage batteries whose voltages are in a decayed state after the stop of charging or after the stop of discharging are prepared, and the processes of steps S51 to S53 are performed using these lead storage batteries. Thus, the internal resistance R2 in the case where a circulating current is generated due to a difference in the attenuation state of the voltages of the connected battery packs (see fig. 2) can be obtained.

The value of the internal resistance R measured by the above method is stored in the storage unit 14 in advance as the internal resistance information 141, and is used for the connection availability determination processing (refer to fig. 7) of the connection control (refer to fig. 6) between the battery packs. For example, any one of the internal resistances R1 and R2 may be stored in the storage unit 14 as the internal resistance R, or an average value of the internal resistances R1 and R2 may be stored in the storage unit 14 as the internal resistance R. Alternatively, both the internal resistor R1 and the internal resistor R2 may be stored in the storage unit 14.

When storing both the internal resistance R1 and the internal resistance R2 as the internal resistance information 141, the control device 1 may execute the connection availability determination processing by using the internal resistance R1 and the internal resistance R2 separately, for example (step S2). Hereinafter, the description will be made specifically.

For example, when calculating the estimated value Ice of the circulating current in step S22 of the connection availability determination process (step S2), it is determined in which of the 1 st state due to the decaying state of the voltage of the battery pack and the 2 nd state due to the SOC of the battery pack is present, and in the 1 st state, the estimated value Ice (=Δv/R1) of the circulating current is calculated using the internal resistor R1 in step S22, and in the 2 nd state, the estimated value Ice (=Δv/R2) of the circulating current is calculated using the internal resistor R2 in step S22.

As described above, the power storage system 100 according to embodiment 1 includes: a multi-parallel battery module 2 formed by connecting a plurality of battery packs 20_1 to 20—n in parallel; switches 4_1 to 4_n provided for each of the battery packs 20_1 to 20—n and connected in series between the corresponding battery pack 20 and the ac/dc conversion device 3; and a control device 1. When the split battery packs 20 are connected in parallel, the control device 1 controls the on/off of the switch 4 corresponding to the battery pack 20 to be connected based on the measured value related to the voltage of the battery pack 20 to be connected.

Thus, it is not necessary to provide a plurality of circuits for each battery pack to suppress the circulating current as in the prior art, and therefore, the connection of the battery packs to each other can be performed safely with a simpler configuration.

For example, by measuring the voltage difference Δv between the battery packs 20 to be connected as a measurement value related to the voltage of the battery packs 20 to be connected and by knowing the state in which the voltage difference Δv between the battery packs 20 is small based on this information, the battery packs 20 are connected to each other, and thus, it is possible to prevent the adverse effect of the circulating current on the battery and the battery peripheral devices without employing a complicated circuit configuration as in the conventional art.

Specifically, in the power storage system 100, the determination unit 12 calculates an estimated value Ice of the circulating current flowing when the connected battery packs 20 are connected to each other based on the voltage difference Δv calculated from the measured value of the voltage of the connected battery pack and the value of the prestored internal resistance R, and when the estimated value Ice is smaller than the prestored allowable current Iper, the determination unit 12 instructs the switch control unit 13 to allow the battery packs 20 to be connected to each other, and when the estimated value Ice is larger than the allowable current Iper, the determination unit 12 instructs the switch control unit 13 not to allow the battery packs 20 to be connected to each other.

Thus, when the power storage system 100 is operated, the behavior of connecting the battery packs to each other under the condition that a large circulating current adversely affecting the battery and the battery peripheral devices flows can be prevented with certainty.

As described above, in the power storage system 100, the internal resistance stored in the storage unit 14 includes the internal resistance R1 (1 st resistance) in the 1 st state in which the voltage decay state of the battery pack 20 is poor, and the internal resistance R2 (2 nd resistance) in the 2 nd state in which the SOC of the battery pack is poor, and the determination unit 12 calculates the estimated value Ice of the circulating current using the internal resistance R1 when it is determined that the battery pack 20 to be connected is in the 1 st state, and calculates the estimated value Ice of the circulating current using the internal resistance R2 when it is determined that the battery pack 20 to be connected is in the 2 nd state.

Accordingly, the circulating current is estimated by distinguishing the case where the voltage of the battery pack is attenuated from the case where the SOC of the battery pack is attenuated, and therefore, the battery packs can be connected to each other more safely.

In addition, in power storage system 100, the value of the internal resistance stored in storage unit 14 is a value calculated based on the measured value of the peak value of the circulating current flowing when battery packs 20 are connected to each other and the measured value of voltage difference Δv between battery packs 20 before connection.

As described above, the internal resistance is measured more accurately than in the conventional method, and therefore, the circulating current can be estimated more accurately and the connection of the battery packs to each other can be performed more safely.

In the above embodiment, the method of actually generating the circulating current to measure the internal resistance has been described, but the present invention is not limited to this. For example, a constant current source may be connected to one battery (battery pack) of the same type as the battery used in the power storage system 100, the resistance of the battery during charging may be calculated based on the amount of change in voltage and the charging current during constant current charging, an electronic load may be connected to the same battery (battery pack), and the resistance of the battery during discharging may be calculated based on the amount of change in voltage and the discharging current during constant current discharging. Then, the calculated combined resistance (sum of resistances) of the resistance at the time of charging and the resistance at the time of discharging is taken as the internal resistance R.

Thus, the circulating current can be estimated using a more accurate internal resistance, and thus the connection of the battery packs to each other can be performed more safely.

In the power storage system 100, the allowable current Iper used for the connection availability determination process of the battery pack (step S2) is preferably set to a value corresponding to the maximum value of the current (charging current and discharging current) allowed by the battery pack 20 or a value corresponding to the maximum value of the current (rated constant current) allowed by the equipment (the circuit breaker 5, the cable, the terminal board, etc.) connected to the battery pack 20. Thus, the circulating current can be prevented from adversely affecting the battery and the battery peripheral equipment.

Embodiment 2

The power storage system 100A shown in the figure differs from the power storage system of embodiment 1 in that the connection of the battery packs is controlled based on the elapsed time after the end of charge and after the end of discharge of the battery packs, rather than based on the voltage difference Δv between the battery packs to be connected, and is otherwise identical to the power storage system 100A of embodiment 1.

In power storage system 100A, stability reference time information 143 is stored in advance in storage unit 14A of control device 1. The stability reference time information 143 is information of a reference value (also referred to as "stability reference time Ts") of a time period after the end of charging and after the end of discharging of the battery pack 20 until the voltage of the battery pack 20 stabilizes.

Fig. 11 is a diagram for explaining the stable reference time Ts.

In the figure, the horizontal axis represents time and the vertical axis represents voltage. Reference numeral 601 denotes a change in voltage of the lead storage battery with time after completion of the equalizing charge in the constant-current-constant-voltage charging manner.

As shown in fig. 11, the voltage of the lead-acid battery, which has been subjected to equalizing charge at time t1, decays over a long period of time and converges to a predetermined voltage Veq. That is, even if the plurality of battery packs end the charge equalization at different times, the voltage difference Δv between the battery packs is continuously reduced as time passes. Therefore, in the power storage system 100A according to embodiment 2, control is performed such that after the end of charging and after the end of discharging, the voltage of the battery pack 20 to be connected is waited until the allowable voltage Vper is reduced, and then the battery packs are allowed to be connected to each other.

The stable reference time Ts can be measured by the method shown below.

First, two lead storage batteries having different voltages are prepared. For example, two lead storage batteries of the same type as the lead storage battery used in the target power storage system are prepared, and the prepared two lead storage batteries are simultaneously started to be charged. Then, one lead storage battery is stopped to be charged, and after a certain time, the other lead storage battery is stopped to be discharged.

Then, the internal resistance R of the lead storage battery is calculated. Specifically, during the voltage decay period of the two lead storage batteries, the voltage difference Δv between the two lead storage batteries is measured, and the two lead storage batteries are connected to each other, and the peak value Ip of the circulating current is measured. Then, based on the ratio of the measured voltage difference Δv to the peak value Ip of the circulating current (r=Δv/Ip), the internal resistance R of the lead storage battery is calculated.

Then, an allowable voltage difference Δvpin between the two lead secondary batteries is calculated. Specifically, based on the allowable current Iper similar to embodiment 1 and the internal resistance R calculated by the above method, the allowable voltage difference Δvpin is calculated according to the equation (Δvpin=iper×r).

In addition, the voltage Veq of the lead storage battery after the decay was measured. For example, after the lead storage battery is charged uniformly, the voltage of the lead storage battery after 16 hours has elapsed is measured, and the measured value is set as the voltage Veq.

Then, after the end of the charge of the lead storage battery, the time required until the allowable voltage Vper is reduced is measured.

Here, the allowable voltage Vper is a voltage represented by vper=veq+Δvber as shown in fig. 11, and is also a voltage that is a reference for determining that if the voltage of the lead storage battery is reduced to this voltage, the lead storage battery and the like will not be adversely affected even if a circulating current flows.

Specifically, the time is counted at the time point (t 1) when the equalization charge of one lead storage battery is completed, and the elapsed time when the voltage of the lead storage battery reaches Vper is set as the stable reference time Ts. Therefore, when the battery packs are connected to each other after the stable reference time Ts has elapsed, the circulating current is equal to or less than the allowable current Iper, and thus the adverse effect of the circulating current on the battery and the battery peripheral devices can be prevented.

The information of the stable reference time Ts measured by the above method is stored in advance as stable reference time information 143 in the storage unit 14A of the control device 1A.

The method described above is a method for measuring the stable reference time Ts during charging of the battery, and the stable reference time Ts during discharging of the battery may be measured in the same manner. That is, the internal resistance R, the voltage Veq, the allowable voltage Vper, and the allowable voltage difference Δvpin after the discharge of the lead storage battery are calculated, and then the stable reference time Ts at the time of the discharge of the storage battery may be measured in the same manner as described above.

In power storage system 100A according to embodiment 2, determination unit 12A measures elapsed time T after the end of charge and after the end of discharge of battery pack 20 to be connected, and instructs switch control unit 13 to permit connection of battery packs 20 when the measured value of elapsed time T is greater than stabilization reference time Ts stored in storage unit 14, and instructs switch control unit 13 to not permit connection of battery packs 20 when the measured value of elapsed time T is less than stabilization reference time Ts.

For example, the determination unit 12A detects the stop of the charging and discharging of each of the battery packs 20_1 to 20—n from the monitoring results of the current (charging current and discharging current) and the voltage of each of the battery packs 20_1 to 20—n and the communication with the PSC 3. The determination unit 12A starts timing for each of the battery packs 20_1 to 20—n in response to detection of the stop of the charge and discharge, and measures the elapsed time T after the charge and discharge of each of the battery packs 20_1 to 20—n. When it is necessary to connect the battery pack 20 to be monitored to another battery pack 20, the elapsed time T of the battery pack 20 to be monitored is compared with the stabilization reference time Ts, and the connection of the battery pack 20 to be monitored to another battery pack 20 is prohibited until the elapsed time T exceeds the stabilization reference time Ts.

Next, a flow of a method for controlling connection between battery packs according to embodiment 2 will be described.

The overall flow of the method for controlling connection between battery packs according to embodiment 2 is the same as that of embodiment 1 (see fig. 6), and the content of the connection availability determination process (step S2) for battery packs is different from that of embodiment 1. Therefore, the flow of the connection availability determination process (step S2) of the battery pack according to embodiment 2 will be described below.

Here, in fig. 10, a case is considered in which battery pack 20_2 is connected to battery pack 20_1 in a state of equilibrium (voltage: veq) after the voltage decay is completed.

First, in the connection availability determination process of the battery pack in step S2, the determination unit 12A of the control device 1A determines whether or not the elapsed time T after the end of the charge (equalization charge) of the battery pack 20_2 reaches the stabilization reference time Ts (step S21A).

In step S21A, when the elapsed time T of the battery pack 20_2 reaches the stable reference time Ts, the determination unit 12A determines that the battery pack 20_1 and the battery pack 20_2 are connectable (step S22A).

On the other hand, when the elapsed time T of the battery pack 20_2 does not reach the stable reference time Ts, the determination unit 12A determines that the battery pack 20_1 and the battery pack 20_2 are not connectable (step S23A).

According to the above steps, the connection availability determination processing of step S2 is performed.

The other processes are the same as those of the power storage system 100 according to embodiment 1 (see fig. 6).

As described above, according to the power storage system 100A according to embodiment 2, the connection between the battery packs can be performed safely with a simpler configuration, as in the power storage system 100 according to embodiment 1.

For example, as the measured value related to the voltage of the battery pack 20 to be connected, the elapsed time T after the end of charge and after the end of discharge of the battery pack 20 to be connected is measured, and the state in which the voltage difference Δv between the battery packs is small is known based on the information, and the battery packs are connected to each other, so that it is possible to prevent the adverse effect of the circulating current on the battery and the battery peripheral devices without employing a complicated circuit configuration as in the conventional art.

More specifically, in power storage system 100, determination unit 12A measures elapsed time T after the end of charge and after the end of discharge of battery pack 20 to be connected, and instructs switch control unit 13 to permit connection of battery packs 20 to each other when the measured value of elapsed time T is greater than stabilization reference time Ts stored in storage unit 14A, and instructs switch control unit 13 to not permit connection of battery packs 20 to each other when the measured value of elapsed time T is less than stabilization reference time Ts stored in storage unit 14.

As a result, as in the case of the power storage system 100 according to embodiment 1, the connection between the battery packs can be prevented with certainty even in a situation where a large circulating current adversely affecting the battery and the battery peripheral equipment flows. In addition, thereby, the voltage difference Δv does not need to be measured.

In embodiment 2, since it is not necessary to measure the voltage of the battery, the decay time until the virtual voltage difference Δv reaches the allowable voltage difference Δvpin is set to Ts (see fig. 11). That is, since the voltage of the battery pack to be charged (low voltage) when the connected batteries are not lower than the attenuated voltage Veq, the voltage Veq is set to the voltage of the battery pack on the charging side, and the time when the voltage of the battery pack on the discharging side (high voltage) is sufficiently close to the voltage Veq is set to Ts, but the present invention is not limited thereto.

For example, it is also possible to determine whether or not the battery packs are connectable to each other by predicting the voltage based on the elapsed time after stopping charging or discharging, that is, the elapsed time after disconnection, for the battery pack on the charging side, and comparing the difference between the voltage and the voltage of the battery pack on the charging side and the allowable voltage Δvper.

Extension of embodiments

The present invention has been specifically described based on the embodiments, but the present invention is not limited to the embodiments, and various modifications are of course possible within the scope of the present invention.

For example, in embodiments 1 and 2, when software for controlling the digital touch input/output circuit (DIO) 104 by a trigger of some sort is executed, the software is configured by a software module related to the interlock, and when it is predicted that a circulating current exceeding the allowable current Iper flows, or when the elapsed time T after the end of charging (after the end of discharging) reaches the stable reference time Ts, the operation of connecting the battery packs in parallel is not performed, but the present invention is not limited thereto.

For example, in embodiment 1, a relay may be arranged between the control coil serving as a relay of the switch 4 and the control device 1, and the switch 4 and the control device 1 may be disconnected by the relay before the voltage difference Δv of the battery pack 20 becomes equal to or smaller than a predetermined voltage, thereby realizing physical interlocking.

In embodiment 2, for example, a timer relay may be arranged between the control coil serving as a relay of the switch 4 and the control device 1, and the switch 4 and the control device 1 may be disconnected by the timer relay until the elapsed time T after the end of charging and after the end of discharging of the battery pack 20 exceeds the stable reference time Ts, thereby realizing physical interlocking.

Description of the markers

1. 1A control device; 2 multiple parallel battery modules; 3 an AC/DC conversion device; 4. 4_1 to 4_n switches; 5. 5_1 to 5_n circuit breakers; 6 a power supply part; 7, loading; 10 a battery management unit; 11 a monitoring unit; 12. 12A judgment unit; 13 a switch control part; 14. 14A storage unit; 20. 20_1 to 20_n storage battery packs; 100. a 100A electrical storage system; 141 internal resistance information (R, R1, R2); 142 allow current information (Iper); 143 stabilizing the reference time information (Ts); a 200 lead storage battery unit; 201 voltage sensor.

Claims

1. An electric storage system, characterized by comprising:

a multi-parallel battery module formed by connecting a plurality of battery packs in parallel, wherein the battery packs comprise at least one lead battery cell;

an ac/dc conversion device that controls the power transmission/reception of the multi-parallel battery modules;

a switch provided corresponding to each of the battery packs and connected in series between the corresponding battery pack and the ac/dc conversion device; and

a control device that monitors a state of the battery pack for each of the battery packs and controls on/off of the switch,

the control means controls on/off of the switch corresponding to the connection object, i.e., the battery pack, based on a measured value associated with the voltage of the connection object, i.e., the battery pack, when the split battery packs are connected in parallel with each other,

The measured value associated with the voltage of the battery pack is the voltage difference between the connection objects that are the battery packs,

the control device comprises:

a storage unit that stores a value of an internal resistance of the battery pack measured in advance and an allowable current of a circulating current flowing when the battery packs are connected to each other;

a judging unit that judges whether or not the battery packs are connectable to each other; and

a switch control unit that switches on/off of the switch based on a result of the judgment by the judgment unit,

the judgment section calculates an estimated value of a circulating current flowing when the battery packs as the connection target are connected to each other based on the voltage difference calculated from the measured value of the voltage of the battery pack as the connection target and the value of the internal resistance stored in the storage section, allows the battery packs to be connected to each other with respect to the switch control section when the estimated value is smaller than the allowable current stored in the storage section, does not allow the battery packs to be connected to each other with respect to the switch control section when the estimated value is larger than the allowable current stored in the storage section,

the internal resistance stored in the memory portion includes a 1 st resistance and a 2 nd resistance,

The determination unit determines a state of the battery pack as a connection target, calculates the estimated value using the 1 st resistor when the battery pack as a connection target is in the 1 st state in which the voltage difference is generated due to a difference in the voltage decay state, and calculates the estimated value using the 2 nd resistor when the battery pack as a connection target is in the 2 nd state in which the voltage difference is generated due to a difference in the charge state.

2. An electric storage system, characterized by comprising:

the control device comprises:

the value of the internal resistance stored in the storage unit is a value calculated based on a measured value of a peak value of a circulating current flowing when the battery packs are connected to each other and a measured value of the voltage difference before connection.

3. The electricity storage system according to claim 1, wherein,

the internal resistance stored in the storage unit is a combined resistance of a resistance at the time of charging and a resistance at the time of discharging, the resistance at the time of charging is calculated based on a change amount of a voltage of the battery pack and a charging current when the battery pack is charged with a constant current, and the resistance at the time of discharging is calculated based on a change amount of a voltage of the battery pack and a discharging current when the battery pack is discharged with a constant current.

4. The power storage system according to any one of claim 1 to 3, wherein,

the allowable current stored in the storage unit is a value corresponding to a maximum value of a current allowable by the battery pack or a value corresponding to a maximum value of a current allowable by a device connected to the battery pack.