JP2014128152A - Charge and discharge controller, charge and discharge control system and charge and discharge control method - Google Patents

Abstract

A charge / discharge control device capable of efficiently controlling charging and discharging of a plurality of power storage devices is provided.
A condition storage unit configured to store a charging condition indicating a bus voltage condition for charging and a discharging condition indicating a bus voltage condition for discharging, which are set for each power storage device, and a condition storage unit Whether or not to charge each of the power storage devices based on the voltage fluctuation of the DC bus and the charging and discharging conditions. Determine.
[Selection] Figure 3

Description

  The present invention relates to a technique for controlling charging and discharging of a plurality of storage batteries.

In recent years, there are power storage systems in which a power storage unit is provided in a building such as a general household, an office building, or a factory, and the power stored in the power storage unit is supplied to a load. In a power storage system, for example, power supplied from a commercial power system and power supplied from a power generation device using natural energy such as sunlight are stored in a power storage unit.
In Patent Document 1, the voltage of the DC bus connected to the power storage unit is monitored, and when the voltage of the DC bus increases, the power storage unit is charged, and when the voltage of the DC bus decreases, the power storage unit is discharged. Technology is disclosed. Thereby, since the voltage of the DC bus is maintained within a certain range, it is possible to stabilize power supply from the power storage unit to the load via the DC bus.

JP 2006-129585 A

In a conventional power storage system, when a plurality of power storage units are mounted, a technique for efficiently controlling charging and discharging of each power storage unit is required.
The present invention has been made in view of such circumstances, and an object thereof is to provide a charge / discharge control device, a charge / discharge control system, and a charge / discharge control method that can efficiently control charging and discharging of a plurality of power storage units. And

  In order to achieve the above object, a charge / discharge control device according to the present invention is a charge / discharge control device that controls charging and discharging of a plurality of power storage devices connected to the DC bus in accordance with voltage fluctuations of the DC bus. A bus voltage acquisition unit that acquires a bus voltage indicating a current voltage of the DC bus, and a charging condition and a discharge condition that are set in each of the power storage devices and indicate a condition of the bus voltage for charging. A condition storage unit that stores a discharge condition indicating a condition of the bus voltage, a condition update unit that updates a charge condition and a discharge condition of each of the power storage devices stored in the condition storage unit, the bus voltage and the power storage It is determined whether to charge each of the power storage devices based on the charging conditions of each device, and based on the bus voltage and the discharge conditions of each of the power storage devices Characterized in that it comprises a discharge determining unit that determines whether to discharge for each collector.

  The charge / discharge system according to the present invention includes a DC bus, a plurality of power storage devices connected to the DC bus, and a charge / discharge control that controls charging and discharging of the plurality of power storage devices according to voltage fluctuations of the DC bus. An electric storage system comprising: a device, wherein the charge / discharge control device performs a charge set in each of the electric storage device and a bus voltage acquisition unit that acquires a bus voltage indicating a current voltage of the DC bus A condition storage unit for storing a charge condition indicating the bus voltage condition and a discharge condition indicating the bus voltage condition for discharging, and a charge condition and a discharge for each of the power storage devices stored in the condition storage unit Determining whether to charge each of the power storage devices based on the bus voltage and the charging conditions of each of the power storage devices; Scan voltage and the electric storage device based on the respective discharge conditions, characterized in that it comprises a discharge determining unit that determines whether to discharge for each of the power storage device.

  In addition, the charge / discharge control method according to the present invention includes a charge condition indicating a voltage condition of the DC bus for performing charging set for each of the plurality of power storage devices connected to the DC bus, and the charge for discharging A condition storage unit for storing a discharge condition indicating a voltage condition of the DC bus is provided, and charging and discharging of each of the power storage devices are controlled based on voltage fluctuation of the DC bus and charging and discharging conditions of each of the power storage devices. A charge / discharge control method used in a charge / discharge control device, comprising: a condition update step for updating a charge condition and a discharge condition of each of the power storage devices stored in the condition storage unit; and a current voltage of the DC bus A bus voltage acquisition step for acquiring a bus voltage, and charging for each of the power storage devices based on the bus voltage and a charging condition of each power storage device Determines Ukaina, characterized in that it comprises a said bus voltage and charge-discharge judgment step of judging whether to discharge for each of the power storage device based on the discharge conditions of the battery storages.

According to the above configuration, the charging condition for charging and the discharging condition for discharging are individually set for each power storage device (power storage unit). Thereby, it becomes possible to preferentially charge or discharge a specific power storage device.
Further, by updating the charging condition and the discharging condition, it is possible to efficiently control charging and discharging of a plurality of power storage devices by switching power storage devices that are preferentially charged or discharged.

The figure which shows an example of the charge operation sequence according to the voltage rise of a DC bus, and the threshold value of an electrical storage unit Block diagram showing schematic configuration of power storage system Block diagram showing an example of the functional configuration of a DC / DC converter The block diagram which shows an example of a function structure of a charging / discharging threshold value update part The figure which shows an example of the relationship between an open circuit voltage and a battery remaining capacity Flow chart showing an example of the operation of the DC / DC converter The flowchart which shows an example of charging / discharging determination processing The figure which shows an example of the charge period and discharge period of the electrical storage unit accompanying the voltage fluctuation of a DC bus The block diagram which shows an example of a function structure of a charging / discharging threshold value update part Diagram showing an example of the relationship between internal resistance and health The figure which shows an example of the correspondence information which shows the correspondence of a health degree and a threshold value The figure which shows an example of the charge period and discharge period of the electrical storage unit accompanying the voltage fluctuation of a DC bus The block diagram which shows an example of a function structure of a charging / discharging threshold value update part The figure which shows an example of the scheduling information which prescribed | regulated the change order of a priority The figure which shows an example of the corresponding information which shows the correspondence of a priority and a threshold value Flow chart showing an example of the operation of the DC / DC converter Block diagram showing schematic configuration of power storage system Block diagram showing an example of the functional configuration of the charge / discharge controller Flow chart showing an example of the operation of the DC / DC converter The figure which shows an example of the charge period and discharge period of the electrical storage unit accompanying the voltage fluctuation of a DC bus The figure which shows an example of the charge period and discharge period of the electrical storage unit accompanying the voltage fluctuation of a DC bus The flowchart which shows an example of charging / discharging determination processing

(Knowledge that became the basis of the invention)
The conventional power storage system monitors the voltage of the DC bus, charges the power storage unit when the voltage of the DC bus exceeds the threshold value, and discharges the power storage unit when the voltage of the DC bus falls below the threshold value. Yes.
Consider a case where a plurality of power storage units are mounted in a power storage system in order to increase output. Here, the output of the power storage system is the amount of charge that can be charged or discharged per unit time.

  When a plurality of power storage units are mounted in a power storage system, charging and discharging are generally controlled uniformly among the power storage units, that is, using the same threshold value in the plurality of power storage units. However, when a plurality of power storage units are mounted in a power storage system, even if charge and discharge control is uniformly performed between the power storage units, a difference in the remaining battery capacity may occur due to a deviation in the initial characteristics of the power storage units. . Even if the initial characteristics of the power storage units are uniform, the degree of aging deterioration may differ due to differences in the temperature environment of each power storage unit, and a difference in battery remaining capacity may occur. Therefore, in order to level the dynamically changing battery remaining capacity and the degree of deterioration between the energy storage units, charging and discharging of some energy storage units are given priority over charging and discharging of other energy storage units. It may be better to do it.

The inventors of the present invention have intensively studied the case where a plurality of power storage units are mounted in a power storage system, and found the following. Here, it is assumed that two power storage units A and B are mounted in the power storage system.
FIG. 1 is a diagram illustrating an example of a charging operation sequence according to a voltage increase of a DC bus and a threshold value of a power storage unit. In the figure, the graph shows the voltage fluctuation of the DC bus over time, T _CA shows the threshold value for starting and stopping charging in the power storage unit A, and T _CB starts and stops charging in the power storage unit B. It shows the threshold value for

Suppose that the voltage fluctuation of the DC bus has occurred as shown in the figure with the threshold value set as described above. In this case, the power storage system, the voltage of the DC bus begin charging the power storage unit A at time T1 which exceeds the threshold value T _CA, the charging of the electricity storage unit B at time T2 in which the voltage of the DC bus exceeds the threshold value T _CB Start. Thereafter, the power storage system stops the charging of the power storage unit A at time T4 when the voltage of the DC bus stops charging of the electricity storage unit B at time T3 drops below the threshold value T _CB, the voltage of the DC bus falls below the threshold value T _CA To do.

  Accordingly, the lower the threshold value for starting charging (hereinafter referred to as the charging start threshold value), the earlier the charging start of the corresponding power storage unit becomes, and the threshold value for stopping charging (hereinafter referred to as the charging stop threshold value). It can be said that the charging stop of the corresponding power storage unit is delayed as the value is set lower. Therefore, by setting the charging start threshold and the charging stop threshold low, the corresponding power storage unit can be preferentially charged. Similarly, regarding discharge, a threshold value for starting discharge (hereinafter referred to as a discharge start threshold value) and a threshold value for stopping discharge (hereinafter referred to as a discharge stop threshold value) are set high. The power storage unit can be preferentially discharged.

Based on the above knowledge, the inventors of the present invention have conceived the present invention that eliminates a deviation between power storage units by dynamically controlling a threshold value for each power storage unit, thereby enabling a long life of the power storage system. It is a thing. Hereinafter, embodiments of the present invention will be described.

(Embodiment 1)
<1-1. Overview>
In the first embodiment, a threshold value for charging and a threshold value for discharging are set based on the battery remaining capacity of each power storage unit, and the battery remaining capacity of each power storage unit is leveled so as to equalize the battery remaining capacity of each power storage unit. The structure which controls charge and discharge is shown.

The remaining battery capacity of the power storage unit is a percentage of the current amount of charge that can be discharged with reference to the amount of charge that can be discharged when fully charged.
<1-2. Configuration>
<Power storage system>
FIG. 2 is a block diagram showing a schematic configuration of the power storage system according to Embodiment 1 of the present invention. The power storage system according to Embodiment 1 of the present invention includes a power generation device 10, a DC / DC converter 20, a power storage unit 30, a DC / AC converter 40, an AC power supply 50, a load 60, and a DC bus 70.

The power generation device 10 is, for example, a solar cell that converts sunlight into electric power by the photovoltaic effect. The DC / DC converter 20 boosts the power supplied from the power generator 10 and outputs the boosted power to the DC bus 70. At that time, the DC / DC converter 20 performs MPPT (Maximum Power Point Tracking) control and outputs so that the generated power in the power generation apparatus 10 becomes maximum.
The power storage unit 30 includes a plurality of power storage units 31 (31A, 31B, ..., 31N) and a DC / DC converter 100 (100A, 100B, ..., 100N). As shown in the figure, the power storage units 31 are connected to the DC bus 70 via the corresponding DC / DC converters 100, respectively.

Each power storage unit 31 includes a secondary battery that can be repeatedly charged and discharged, such as a lithium ion battery.
Each of the DC / DC converters 100 monitors the voltage of the DC bus 70, and when the voltage of the DC bus 70 exceeds a threshold value, supplies power from the DC bus 70 to the corresponding storage unit 31, and the voltage of the DC bus 70 is This is a bidirectional converter that supplies power from the power storage unit 31 to the DC bus 70 corresponding to a case where the threshold value is below the threshold value. Details of the DC / DC converter 100 will be described later.

The DC / AC converter 40 converts the DC power supplied from the DC bus 70 into AC power having a predetermined voltage and supplies the AC power to the load 60. The AC power supply 50 supplies AC power having a predetermined voltage to the load 60.
<DC / DC converter 100>
Next, details of the DC / DC converter 100 will be described. Here, DC / DC converter 100A corresponding to power storage unit 31A will be described as an example. The configuration of the other DC / DC converter 100 (100B,..., 100N) is substantially the same as that of the DC / DC converter 100A, and the description thereof is omitted.

FIG. 3 is a block diagram showing a functional configuration of the DC / DC converter 100A. As illustrated, the DC / DC converter 100A includes a bus voltage acquisition unit 101A, a charge / discharge threshold update unit 102A, a charge / discharge threshold storage unit 103A, a charge / discharge determination unit 104A, and a charge / discharge control unit 105A.
The bus voltage acquisition unit 101A is a voltage sensor that measures the voltage of the DC bus.

The charge / discharge threshold update unit 102A calculates the battery remaining capacity of the corresponding power storage unit 31A, determines a threshold for charging the power storage unit 31A and a threshold for discharging based on the calculated battery remaining capacity, This is stored in the discharge threshold storage unit 103A. Details of the charge / discharge threshold update unit 102A will be described later.
The charge / discharge determination unit 104A uses the DC bus voltage measured by the bus voltage acquisition unit 101A and the threshold value stored in the charge / discharge threshold value storage unit 103A to determine whether to charge the power storage unit 31A and It is determined whether or not the unit 31A is discharged. Thereafter, the charge / discharge determination unit 104A outputs a charge flag and a discharge flag indicating the determination result to the charge / discharge control unit 105A.

The charge / discharge control unit 105A charges and discharges the power storage unit 31A based on the charge flag and the discharge flag input from the charge / discharge determination unit 104A. That is, the charge / discharge control unit 105A supplies the power of the DC bus 70 to the power storage unit 31A when the charge flag is ON, and supplies the power of the power storage unit 31A to the DC bus 70 when the discharge flag is ON.
<Charging / Discharging Threshold Update Unit 102>
FIG. 4 is a block diagram illustrating a functional configuration of the charge / discharge threshold update unit 102A. As shown in the figure, the charge / discharge threshold update unit 102A includes a battery information acquisition unit 111A, a battery state calculation unit 112A, a battery characteristic storage unit 113A, a time information acquisition unit 114A, and a charge / discharge threshold setting unit 115A.

Battery information acquisition unit 111A measures the open circuit voltage of power storage unit 31A. Battery information acquisition unit 111A measures the open circuit voltage of power storage unit 31A after the end of charging and discharge of power storage unit 31A, and stores the acquired open circuit voltage in a storage unit (not shown). Shall.
Battery state calculation unit 112A calculates the remaining battery capacity of power storage unit 31A in response to a threshold update instruction from time information acquisition unit 114A. Battery state calculation unit 112A calculates the battery remaining capacity of power storage unit 31A based on the open circuit voltage of power storage unit 31A measured by battery information acquisition unit 111A and the battery characteristic information stored in battery characteristic storage unit 113A.

In the present embodiment, the battery characteristic information is information indicating the relationship between the open circuit voltage and the remaining battery capacity. In general, it is known that there is a relationship as shown in FIG. 5 between the open circuit voltage and the battery remaining capacity. Thereby, the battery state calculation unit 112A can calculate the battery remaining capacity from the open circuit voltage.
114 A of time information acquisition parts generate | occur | produce a clock signal of a predetermined period (for example, 2 hours), and output the produced | generated clock signal to battery state calculation part 112A as a threshold value update instruction | indication mentioned above. The time information acquisition unit 114A is configured using, for example, a crystal resonator.

Each time the battery remaining capacity is input from the battery state calculation unit 112A, the charge / discharge threshold setting unit 115A receives the charge start threshold, the charge stop threshold, the discharge start threshold, and the discharge of the power storage unit 31A according to the input battery remaining capacity. The stop threshold value is calculated, and each calculated threshold value is stored in the charge / discharge threshold value storage unit 103A. When the bus voltage target value is V _s , the difference between the upper limit of the threshold and the bus voltage target value is V _Max [V], and the remaining battery capacity of the power storage unit 31A is a [%], the charge / discharge threshold setting unit 115A The start threshold value V _CA is calculated as shown in the following formula (1).

V _CA = V _s + V _Max × a / 100 (1)

When the difference between the lower limit of the threshold and the bus voltage target value is V _Min [V], the charge / discharge threshold setting unit 115A calculates the discharge start threshold V _DA as shown in the following equation (2).

V _DA = V _s −V _Min × (100−a) / 100 (2)

The bus voltage target value is the voltage value of the DC bus to be maintained. The bus voltage target value, the difference between the upper limit of the threshold and the bus voltage target value, and the difference between the lower limit of the threshold and the bus voltage target value are determined in advance.

The charge stop threshold is the same value as the charge start threshold, and the discharge stop threshold is the same value as the discharge start threshold.

<1-3. Operation>
Next, the operation of the DC / DC converter 100 will be described. Here, the DC / DC converter 100A will be described as an example. The operations of the other DC / DC converters 100 (100B,..., 100N) are substantially the same as those of the DC / DC converter 100A, and a description thereof will be omitted.

FIG. 6 is a flowchart showing the operation of the DC / DC converter 100A.
First, the battery information acquisition unit 111A measures battery information (open circuit voltage) of the power storage unit 31A (step S11).
Battery state calculation unit 112A calculates the battery state (battery remaining capacity) of power storage unit 31A based on the battery information output from battery information acquisition unit 111A and the battery characteristic information in battery characteristic storage unit 113A (step S12). .

The charge / discharge threshold setting unit 115A determines the charge start threshold, the charge stop threshold, the discharge start threshold, and the discharge stop threshold of the power storage unit 31A from the battery state calculated by the battery state calculator 112A, and the charge / discharge threshold is determined by the determined threshold. The threshold value of the storage unit 103A is updated (step S13).
The charge / discharge determination unit 104A uses the charge start threshold, the charge stop threshold, the discharge start threshold, and the discharge stop threshold stored in the charge / discharge threshold storage unit 103A, and the DC bus voltage detected by the bus voltage acquisition unit 101A. Based on this, a charge / discharge determination process to be described later is performed, and a charge flag and a discharge flag as determination results are output to the charge / discharge control unit 105A (step S14).

The charge / discharge control unit 105A controls charging and discharging of the power storage unit based on the charge flag and the discharge flag (step S15).
The battery state calculation unit 112A determines whether or not there is a threshold update instruction from the time information acquisition unit 114A (step S16). If there is a threshold update instruction (step S16: Yes), the process returns to step S11, and the threshold update instruction If there is no (step S16: No), the process returns to step S14.
<Charge / discharge determination process>
Next, the charge / discharge determination process in step S14 of FIG. 6 performed by the charge / discharge determination unit 104A will be described in detail.

FIG. 7 is a flowchart showing details of the charge / discharge determination process performed by the charge / discharge determination unit 104A. Note that the initial values of the charge flag and the discharge flag are OFF.
When the charge / discharge determination process is started, the charge / discharge determination unit 104A instructs the bus voltage acquisition unit 101A to acquire the current value of the DC bus voltage (referred to as the bus voltage current value) (step S201).

Next, the charge / discharge determination unit 104A determines whether or not the discharge flag is ON (step S202).
When the discharge flag is ON (step S202: Yes), the charge / discharge determination unit 104A determines whether the current bus voltage value is larger than the discharge stop threshold stored in the charge / discharge threshold storage unit 103A ( Step S203).

When the discharge flag is ON and the current bus voltage value is larger than the discharge stop threshold stored in the charge / discharge threshold storage unit 103A (step S203: Yes), the charge / discharge determination unit 104A sets the discharge flag to OFF (step S203). S204) The charge / discharge determination process is terminated.
When the discharge flag is ON and the current bus voltage value is less than or equal to the discharge stop threshold stored in the charge / discharge threshold storage unit 103A (step S203: No), the charge / discharge determination unit 104A ends the charge / discharge determination process.

When the discharge flag is OFF (step S202: No), the charge / discharge determination unit 104A determines whether the charge flag is ON (step S205).
When the charge flag is ON (step S205: Yes), the charge / discharge determination unit 104A determines whether the current bus voltage value is smaller than the charge stop threshold stored in the charge / discharge threshold storage unit 103A ( Step S206).

When the charge flag is ON and the current bus voltage value is smaller than the charge stop threshold value stored in the charge / discharge threshold value storage unit 103A (step S206: Yes), the charge / discharge determination unit 104A sets the charge flag to OFF (step S206). S207) The charge / discharge determination process is terminated.
When the charge flag is ON and the current bus voltage value is equal to or greater than the charge stop threshold value stored in the charge / discharge threshold value storage unit 103A (step S206: No), the charge / discharge determination unit 104A ends the charge / discharge determination process.

When the charge flag is OFF (step S205: No), the charge / discharge determination unit 104A determines whether or not the bus voltage current value is larger than the charge start threshold stored in the charge / discharge threshold storage unit 103A ( Step S208).
When the current bus voltage value is larger than the charging start threshold value stored in the charging / discharging threshold value storage unit 103A (step S208: Yes), the charging / discharging determination unit 104A sets the charging flag to ON (step S209). End the process.

When the current bus voltage value is less than or equal to the charging start threshold value stored in the charging / discharging threshold value storage unit 103A (step S208: No), the charging / discharging determination unit 104A stores the current bus voltage value in the charging / discharging threshold value storage unit 103A. It is determined whether it is smaller than the discharge start threshold value (step S210).
When the current bus voltage value is smaller than the discharge start threshold value stored in the charge / discharge threshold value storage unit 103A (step S210: Yes), the charge / discharge determination unit 104A sets the discharge flag to ON (step S211). The process ends.

When the current bus voltage value is greater than or equal to the discharge start threshold stored in the charge / discharge threshold storage unit 103A (step S210: No), the charge / discharge determination unit 104A ends the charge / discharge determination process.
After the charge / discharge determination process, the charge / discharge determination unit 104A outputs a charge flag and a discharge flag, which are determination results, to the charge / discharge control unit 105A.
<1-4. Summary>
The power storage system according to the present embodiment periodically measures the battery remaining capacity of each power storage unit 31, and the charge start threshold, charge stop threshold, discharge start threshold of each power storage unit 31 according to the measured battery remaining capacity, And the setting of the discharge stop threshold is repeated. At this time, the discharge start threshold value of the power storage unit having a high battery remaining capacity is set high, and the charge start threshold value of the power storage unit having a low battery remaining capacity is set low.

FIG. 8 is a diagram illustrating an example of a charging period and a discharging period of each power storage unit accompanying a voltage variation of the DC bus when the remaining battery capacity is large in the order of power storage units 31A, 31B, and 31C (descending order).
Here, T _CA indicates the charge start threshold value and the charge stop threshold value of the power storage unit 31A, T _CB indicates the charge start threshold value and the charge stop threshold value of the power storage unit 31B, and T _CC indicates the charge start threshold value of the power storage unit 31C. And the charge stop threshold. T _DA indicates the discharge start threshold and discharge stop threshold of the power storage unit 31A, T _DB indicates the discharge start threshold and discharge stop threshold of the power storage unit 31B, and T _DC indicates the discharge start threshold of the power storage unit 31C and Indicates the discharge stop threshold.

As shown in the figure, the storage unit with a higher battery remaining capacity has a longer discharge period, and the storage unit with a lower battery remaining capacity has a longer charging period.
As a result, the power storage system controls charging and discharging of each power storage unit 31 so that the battery remaining capacity of each power storage unit is leveled even if the battery remaining capacity between the power storage units varies for some reason. can do.

Furthermore, the power storage system according to the present embodiment can solve the following problems by leveling the battery remaining capacity of each power storage unit.
For example, in a secondary battery such as a lithium ion battery or a lead storage battery, it is known that the deterioration of the battery increases as the depth of discharge per discharge cycle increases. With this characteristic, when the discharge depth per cycle of some of the power storage units becomes extremely deep, the deterioration of the part of the power storage units is promoted, and the life of the entire power storage system is shortened.

On the other hand, in the power storage system of the first embodiment, each power storage unit battery remaining capacity is leveled, so that charging and discharging of each power storage unit is performed uniformly. The discharge depth per discharge cycle is less likely to be biased. Thereby, the electrical storage system can suppress that deterioration of a one part electrical storage unit is accelerated | stimulated.

(Embodiment 2)
<2-1. Overview>
In the first embodiment, the configuration is shown in which the threshold is set based on the battery remaining capacity of the power storage unit, thereby realizing the leveling of the battery remaining capacity of the power storage unit. In the second embodiment, a configuration is shown in which a threshold value is set based on a health level that is an index indicating the degree of deterioration of each power storage unit, thereby extending the life of the power storage system.

<2-2. Configuration>
The power storage system of the second embodiment is different from the power storage system of the first embodiment only in the configuration of the charge / discharge threshold update unit 102. The description of the same components as those in Embodiment 1 is omitted.

FIG. 9 is a block diagram showing a configuration of the charge / discharge threshold update unit 102A in the second embodiment. As shown in the figure, the charge / discharge threshold update unit 102A in the second embodiment includes a battery information acquisition unit 121A, a battery state calculation unit 122A, a battery characteristic storage unit 123A, a time information acquisition unit 124A, a charge / discharge threshold setting unit 125A, And a correspondence information storage unit 126A.
Battery information acquisition unit 121A measures the internal resistance of power storage unit 31A. For example, the internal resistance R1 of the power storage unit 31A uses the voltage V1 and the current I1 when current is flowing through the power storage unit 31A during charging, and the voltage V2 when no current flows through the power storage unit 31A after charging. Thus, it is obtained by the following equation (3).

R1 = (V1-V2) / I1 (3)

In the present embodiment, the battery information acquisition unit 121A measures the voltages V1 and V2 and the current I1 to determine the internal resistance R1 before and after the end of charging of the power storage unit 31A.

Battery state calculation unit 122A calculates the health level of power storage unit 31A in response to a threshold update instruction from time information acquisition unit 124A. The battery state calculation unit 122A calculates the health level of the power storage unit 31A based on the internal resistance of the power storage unit 31A obtained by the battery information acquisition unit 121A and the battery characteristic information stored in the battery characteristic storage unit 123A.
In the present embodiment, the battery characteristic information is information indicating the relationship between the internal resistance and the health level. For example, by defining the relationship between the internal resistance and the health level as shown in FIG. 10, the battery state calculation unit 122A can calculate the health level from the internal resistance.

The time information acquisition unit 124A generates a clock signal having a predetermined period, and outputs the generated clock signal to the battery state calculation unit 122A as the above-described threshold update instruction.
The charge / discharge threshold value setting unit 125A uses the health level input from the battery state calculation unit 122A and the correspondence information stored in the correspondence information storage unit 126A, and the charge start threshold, the charge stop threshold, and the discharge start of the power storage unit 31A. The threshold value and the discharge stop threshold value are determined, and each of the determined threshold values is stored in the charge / discharge threshold value storage unit 103A.

FIG. 11 is a diagram illustrating an example of correspondence information stored in the correspondence information storage unit 126A. Here, V _s in the figure is a predetermined bus voltage target value. As shown in the figure, in the correspondence information, a charge start threshold value, a charge stop threshold value, a discharge start threshold value, and a discharge stop threshold value corresponding to the health level are determined in advance. Therefore, the charge / discharge threshold setting unit 125A can determine each threshold corresponding to the health level input from the battery state calculation unit 122A by referring to the correspondence information.

The above is a configuration different from that of the first embodiment.
<2-3. Operation>
Next, the operation of the DC / DC converter 100 according to the present embodiment will be briefly described with respect to differences from the first embodiment.
In step S11, battery information acquisition unit 121A measures battery information (internal resistance) of power storage unit 31A.

In step S12, battery state calculation unit 122A calculates the battery state (health level) of power storage unit 31A based on the battery information output from battery information acquisition unit 121A and the battery characteristic information in battery characteristic storage unit 123A.
In step S13, the charge / discharge threshold value setting unit 125A determines the charge start threshold value, the charge stop threshold value, the discharge start threshold value, and the discharge stop threshold value of the power storage unit 31A from the battery state calculated by the battery state calculation unit 122A. The threshold value of the charge / discharge threshold value storage unit 103A is updated.

The above is the operation different from the first embodiment.
<2-4. Summary>
The power storage system according to the present embodiment periodically measures the health level of each power storage unit 31, and the charge start threshold, the charge stop threshold, the discharge start threshold, and the discharge of each power storage unit 31 according to the measured health level Repeat the setting of the stop threshold. At this time, the charging start threshold value of the power storage unit having a high health level (small deterioration) is set low and the discharging start threshold value is set high, and the charging start threshold value of the power storage unit having a low health level (high deterioration) is set high. Set.

FIG. 12 is a diagram illustrating an example of a charging period and a discharging period of each power storage unit accompanying a voltage variation of the DC bus when the health level is large in the order (descending order) of the power storage units 31A, 31B, and 31C.
Here, T _CA indicates the charge start threshold value and the charge stop threshold value of the power storage unit 31A, T _CB indicates the charge start threshold value and the charge stop threshold value of the power storage unit 31B, and T _CC indicates the charge start threshold value of the power storage unit 31C. And the charge stop threshold. T _DA indicates the discharge start threshold and discharge stop threshold of the power storage unit 31A, T _DB indicates the discharge start threshold and discharge stop threshold of the power storage unit 31B, and T _DC indicates the discharge start threshold of the power storage unit 31C and Indicates the discharge stop threshold.
As shown in the figure, the charge period and the discharge period become longer as the power storage unit has a higher health level. In addition, the power storage unit having a lower health level has a shorter charging period and discharging period. That is, the power storage system preferentially charges and discharges power storage units having a high health level, and controls charging and discharging of each power storage unit 31 so as to equalize the health level.

Thereby, the power storage system according to the second embodiment suppresses the deterioration of a part of the power storage units and realizes a long life of the power storage system.
In the power storage system of the second embodiment, the average of the charge start threshold value and the discharge start threshold value of one power storage unit is set to match the bus voltage target value. According to this configuration, when the average of the voltage of the DC bus matches the bus voltage target value, the power storage system can make the charging depth and the discharging depth of the power storage unit substantially the same.

(Embodiment 3)
<3-1. Overview>
In the first and second embodiments, the configuration is shown in which charging and discharging of each power storage unit are efficiently controlled by setting a threshold based on the battery remaining capacity and health level of the power storage unit. Embodiment 3 shows a configuration in which threshold values are updated based on scheduling, and power storage units that are preferentially charged and discharged are sequentially switched.

<3-2. Configuration>
The power storage system of the third embodiment is different from the power storage system of the first embodiment only in the configuration of the charge / discharge threshold update unit 102. The description of the same components as those in Embodiment 1 is omitted. Here, four power storage units 31 (A, B, C, D) are mounted in the power storage system, and charging / discharging of each power storage unit is performed by DC / DC converters 100A, 100B, 100C, 100D, respectively. Shall be controlled.

FIG. 13 is a block diagram illustrating a functional configuration of the charge / discharge threshold update unit 102A according to the third embodiment. As shown in the figure, the charge / discharge threshold update unit 102A in the third embodiment includes a priority determination unit 131A, a time information acquisition unit 132A, a change order storage unit 133A, a charge / discharge threshold setting unit 134A, and a correspondence information storage unit 135A. Is provided.
The priority determination unit 131A calculates the priority of the power storage unit 31A based on the current time output from the time information acquisition unit 132A and the scheduling information stored in the change order storage unit 133A.

The time information acquisition unit 132A includes, for example, a crystal oscillator and outputs information indicating the current time together with a threshold update instruction to the priority determination unit 131A at a predetermined period (for example, 3 hours).
Next, the scheduling information stored in the change order storage unit 133 will be described. FIG. 14 shows an example of scheduling information stored in the change order storage unit 133. As shown in the figure, the scheduling information is information in which the time zone is associated with the priority. Then, the change order storage unit 133 of each DC / DC converter 100A stores only scheduling information related to the corresponding power storage unit 31. That is, the change order storage unit 133A of the DC / DC converter 100A stores scheduling information related to the power storage unit 31A, the change order storage unit 133B of the DC / DC converter 100B stores scheduling information related to the power storage unit 31B, and The change order storage unit 133C of the DC converter 100C stores scheduling information related to the power storage unit 31C, and the change order storage unit 133D of the DC / DC converter 100D stores scheduling information related to the power storage unit 31D. Therefore, the priority determination unit 131A determines the priority of the power storage unit 31A corresponding to the current time input from the time information acquisition unit 132A by referring to the scheduling information stored in the change order storage unit 133A. Can do.

Note that the scheduling information is predetermined for each power storage unit so that the priority of some power storage units is determined to be different from the priority of other power storage units in the same time zone.
The charge / discharge threshold setting unit 134A uses the priority input from the priority determination unit 131A and the correspondence information stored in the correspondence information storage unit 135A, and the charge start threshold, the charge stop threshold, and the discharge start of the power storage unit 31A. The threshold value and the discharge stop threshold value are determined, and each of the determined threshold values is stored in the charge / discharge threshold value storage unit 103A.

FIG. 15 is a diagram illustrating an example of correspondence information stored in the correspondence information storage unit 135A. Here, V _s in the figure is a predetermined bus voltage target value. As shown in the figure, in the correspondence information, a charge start threshold value, a charge stop threshold value, a discharge start threshold value, and a discharge stop threshold value corresponding to the priority are determined in advance. Therefore, the charge / discharge threshold setting unit 134A can determine each threshold according to the priority input from the priority determination unit 131A by referring to the correspondence information.

The above is a configuration different from that of the first embodiment.
<3-3. Operation>
Next, the operation of the DC / DC converter 100 of the third embodiment will be described. FIG. 16 is a flowchart showing the operation of the DC / DC converter 100 of the third embodiment. As shown in the figure, the DC / DC converter 100 of the third embodiment performs steps S31 and S32 instead of steps S11, S12, and S13 in the operation of the DC / DC converter 100 of the first embodiment.

In step S31, the priority determination unit 131A determines the priority of the power storage unit 31A based on the current time.
In step S32, the charge / discharge threshold setting unit 125A determines the charge start threshold, the charge stop threshold, the discharge start threshold, and the discharge stop threshold of the power storage unit 31A from the priority determined by the priority determination unit 131A. The threshold value of the charge / discharge threshold value storage unit 103A is updated.

After updating each threshold value in step S32, the operations in steps S14 to S16 are performed in the same manner as the DC / DC converter 100 described in the first embodiment.
<3-4. Summary>
The power storage system of the third embodiment updates the threshold based on the scheduling and sequentially switches the power storage units to be operated with priority. According to this configuration, the operating power storage unit and the standby power storage unit are sequentially switched according to the scheduling, so that deterioration of each power storage unit can be delayed. As a result, the life of the power storage system can be extended.

(Embodiment 4)
<4-1. Overview>
In the first to third embodiments, the configuration of the autonomous distributed power storage system in which the DC / DC converter 100 corresponding to each power storage unit 31 sets a threshold value has been described. In the fourth embodiment, a configuration is shown that includes a charge / discharge controller that integrates and sets threshold values that have been distributed and performed in each of the plurality of DC / DC converters 100.

<4-2. Configuration>
The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
<Power storage system>
FIG. 17 is a block diagram showing a schematic configuration of the power storage system in the fourth embodiment. The power storage system of the fourth embodiment includes a power storage unit 200 instead of power storage unit 30 in the power storage system of the first embodiment.

The power storage unit 200 includes a plurality of power storage units 31 (31A, 31B,..., 31N), a DC / DC converter 300 (300A, 300B,..., 300N), and a charge / discharge controller 210. As shown in the figure, the power storage units 31 are connected to the DC bus 70 and the charge / discharge controller 210 via the corresponding DC / DC converters 300, respectively.
Each DC / DC converter 300 is configured by removing bus voltage acquisition unit 101, charge / discharge threshold update unit 102, charge / discharge threshold storage unit 103, and charge / discharge determination unit 104 from DC / DC converter 100 of the first embodiment. It is.

<Charge / Discharge Controller 210>
The charge / discharge controller 210 has functions corresponding to the bus voltage acquisition unit 101, the charge / discharge threshold update unit 102, the charge / discharge threshold storage unit 103, and the charge / discharge determination unit 104 of each DC / DC converter 100 according to the first embodiment. .
FIG. 18 is a block diagram showing a functional configuration of the charge / discharge controller 210. As shown in the figure, the charge / discharge controller 210 includes a bus voltage acquisition unit 211, a charge / discharge threshold update unit 212, a charge / discharge threshold storage unit 213, and a charge / discharge determination unit 214.

The bus voltage acquisition unit 211 is a voltage sensor that measures the voltage of the DC bus 70 similar to the bus voltage acquisition unit 101.
The charge / discharge threshold update unit 212 calculates the remaining battery capacity of each power storage unit 31, and individually determines the threshold for charging and discharging each of the power storage units 31 based on the calculated remaining battery capacity. And stored in the charge / discharge threshold storage unit 213. Details of the charge / discharge threshold update unit 212 will be described later.

  Whether charging / discharging determination unit 214 charges each power storage unit 31 using the voltage of DC bus measured by bus voltage acquisition unit 211 and the threshold value of each power storage unit 31 stored in charge / discharge threshold storage unit 213. It is determined individually whether or not each of the power storage units 31 is discharged. Thereafter, the charge / discharge determination unit 214 outputs a charge flag and a discharge flag indicating the determination result to each charge / discharge control unit 105.

<Charging / Discharging Threshold Update Unit 212>
As shown in FIG. 18, the charge / discharge threshold update unit 212 includes a battery information acquisition unit 221, a battery state calculation unit 222, a time information acquisition unit 223, a battery characteristic storage unit 224, a priority determination unit 225, and a charge / discharge threshold setting unit. 226 and a correspondence information storage unit 227.
The battery information acquisition unit 221 measures the open circuit voltage of each power storage unit 31. The battery information acquisition unit 221 measures the open circuit voltage of the corresponding power storage unit 31 after completion of charging and discharging of each power storage unit 31, and stores the measured open circuit voltage in a storage unit (not shown). It shall be.

  The battery state calculation unit 222 calculates the remaining battery capacity of each power storage unit 31 according to the threshold update instruction from the time information acquisition unit 223. The battery state calculation unit 222 calculates the remaining battery capacity of each power storage unit 31 based on the open circuit voltage of each power storage unit 31 measured by the battery information acquisition unit 221 and the battery characteristic information stored in the battery characteristic storage unit 224. To do.

The time information acquisition unit 223 generates a clock signal having a predetermined period (for example, 2 hours), and outputs the generated clock signal to the battery state calculation unit 222 as the above-described threshold update instruction.
The battery characteristic storage unit 224 stores battery characteristic information indicating the relationship between the open circuit voltage corresponding to each power storage unit 31 and the remaining battery capacity.
The priority determination unit 225 determines the priority of each power storage unit every time the battery remaining capacity of each power storage unit is input from the battery state calculation unit 222. Specifically, the priority determination unit 225 ranks the storage units based on the remaining battery capacity of each storage unit 31 calculated by the battery state calculation unit 222, and sets the rank as a priority to the charge / discharge threshold setting unit. Output.

The charge / discharge threshold setting unit 226 uses the priority of each power storage unit 31 input from the priority determination unit 225 and the correspondence information stored in the correspondence information storage unit 227, and the charge start threshold for each power storage unit 31. The charge stop threshold value, the discharge start threshold value, and the discharge stop threshold value are determined, and the determined threshold values are stored in the charge / discharge threshold value storage unit 213.
The correspondence information storage unit 227 stores correspondence information in which a charge start threshold value, a charge stop threshold value, a discharge start threshold value, and a discharge stop threshold value corresponding to the priority are determined.

<4-3. Operation>
Next, the operation of the power storage system of Embodiment 4 will be described. FIG. 19 is a flowchart showing operations of charge / discharge controller 210 and DC / DC converter 300 of the fourth embodiment.
First, the battery information acquisition part 221 measures the battery information (open circuit voltage) of each electrical storage unit 31 (step S41).

The battery state calculation unit 222 calculates the battery state (remaining battery capacity) of each power storage unit 31 based on the battery information output from the battery information acquisition unit 221 and the battery characteristic information in the battery characteristic storage unit 224 (step S42). ).
The priority determination unit 225 determines the priority of each power storage unit 31 based on the battery state of each power storage unit 31 calculated by the battery state calculation unit 222 (step S43).

The charge / discharge threshold setting unit 226 determines a charge start threshold, a charge stop threshold, a discharge start threshold, and a discharge stop threshold for each power storage unit 31 based on the priority of each power storage unit 31 determined by the priority determination unit 225. The threshold values of the charge / discharge threshold value storage unit 213 are updated with the determined threshold values (step S44).
The charge / discharge determination unit 214 includes a charge start threshold, a charge stop threshold, a discharge start threshold, and a discharge stop threshold stored in the charge / discharge threshold storage unit 213, and the voltage of the DC bus 70 detected by the bus voltage acquisition unit 211. Based on the above, charge / discharge determination processing is performed for each power storage unit 31, and a charge flag and a discharge flag as determination results are output to each charge / discharge control unit 105 (step S14).

Each charging / discharging control unit 105 controls charging and discharging of the corresponding power storage unit 31 based on the charging flag and discharging flag input from charging / discharging determination unit 214 (step S15).
The battery state calculation unit 222 determines whether or not there is a threshold update instruction from the time information acquisition unit 223 (step S16). If there is a threshold update instruction (step S16: Yes), the process returns to step S41, and the threshold update instruction If there is no (step S16: No), the process returns to step S14.

<4-4. Summary>
In the above, the structure of the electrical storage system provided with the charging / discharging controller which integrates the setting of each threshold value of the some electrical storage unit 31 was shown. The effects produced by this configuration will be described in comparison with the configuration of the first embodiment.
In the configuration of the first embodiment, based on only the battery residual image capacity of one power storage unit, the threshold value of the one power storage unit is determined regardless of the battery remaining capacity of the other power storage unit. On the other hand, in the configuration of the fourth embodiment, the priority of the one power storage unit is determined based on the battery residual image capacity of one power storage unit and the battery remaining capacity of another power storage unit. Accordingly, it is possible to set the threshold value of the one power storage unit based on the relative relationship between the battery remaining capacity of one power storage unit and the battery remaining capacity of another power storage unit.

(Modification)
Although the power storage system according to the present invention has been described according to Embodiments 1 to 4, the present invention is not limited to this. Hereinafter, various modifications included as the idea of the present invention will be described.
<Modification 1-1>
In the above embodiment, the charge start threshold and the charge stop threshold are the same value, but the charge start threshold and the charge stop threshold may be different values. Similarly, the discharge start threshold value and the discharge stop threshold value may be different values.

For example, the charge stop threshold value and the discharge start threshold value may be the same as the bus voltage target value. FIG. 20 shows an example of the charging period and discharging period of the power storage unit accompanying the voltage fluctuation of the DC bus when the charge stop threshold and the discharge start threshold are the same as the bus voltage target value. In Figure, T _C denotes a charge start threshold of the power storage unit, T _D indicates the discharge starting threshold of the power storage unit.

As shown in the figure, when the charge stop threshold is the same as the bus voltage target value, the power storage unit continues to be charged until the DC bus voltage exceeds the charge start threshold and falls below the bus voltage target value. In addition, when the discharge stop threshold is equal to the bus voltage target value, the power storage unit continues to discharge until the DC bus voltage falls below the discharge start threshold and exceeds the bus voltage target value.
Thus, when the charge stop threshold and the discharge start threshold are the same as the bus voltage target value, once charging or discharging of the power storage unit is started, the power storage unit is charged or discharged until the voltage reaches the bus voltage target value. Continuation improves the convergence of the DC bus voltage to the bus voltage target value.

In the case where the charge start threshold is equal to or higher than the charge stop threshold and the discharge start threshold is equal to or lower than the discharge stop threshold as in the case where the charge stop threshold and the discharge start threshold are the same as the bus voltage target value, FIG. By performing the processing according to the flowchart shown, it is possible to appropriately determine whether or not the power storage unit should be charged and whether or not the discharge should be performed.
<Modification 1-2>
Next, the case where the charge stop threshold value larger than a charge start threshold value or the discharge stop threshold value smaller than a discharge start threshold value is included is demonstrated.

The threshold value as described above is set, for example, when it is desired to align the charging depth or the discharging depth with a plurality of power storage units. Here, the power storage system will be described assuming that two power storage units A and B are mounted.
FIG. 21 shows an example of the charging period and discharging period of the power storage unit accompanying the voltage fluctuation of the DC bus when a plurality of power storage units are desired to have the same charging depth and discharging depth. In the figure, the threshold value T _C1 indicates the charge start threshold value of the power storage unit A and the charge stop threshold value of the power storage unit B, and the threshold value T _C2 indicates the charge stop threshold value of the power storage unit A and the charge start threshold value of the power storage unit B. . The threshold value T _D1 indicates the discharge start threshold value of the power storage unit A and the discharge stop threshold value of the power storage unit B, and the threshold value T _D2 indicates the discharge stop threshold value of the power storage unit A and the discharge start threshold value of the power storage unit B.

  When the charge start threshold, the charge stop threshold, the discharge start threshold, and the discharge stop threshold are set in this way, as shown in the figure, the order in which charging is started and the order in which charging is stopped are determined in the power storage units A and B. Thus, the order of starting discharge coincides with the order of stopping discharge. Therefore, by setting the threshold value in this way, it is possible to align the charging depth and the discharging depth in the power storage units A and B.

More generally, a storage unit with a lower charge start threshold is set to a higher charge stop threshold, and a storage unit with a lower discharge start threshold is set to a higher discharge stop threshold to charge a plurality of storage units. It becomes possible to arrange the depth and the discharge depth.
By the way, when the charging stop threshold value larger than the charging start threshold value or the discharge stop threshold value smaller than the discharge start threshold value is included, in the flowchart shown in FIG. It is not possible to appropriately determine whether or not to perform the operation. This is because the output of the charge / discharge determination unit becomes unstable when the voltage of the DC bus is larger than the charge start threshold and smaller than the charge stop threshold, and when the voltage of the DC bus is smaller than the discharge start threshold and larger than the charge stop threshold. Because.

Therefore, whether the storage unit should be charged and whether the storage unit should be discharged even when the charge start threshold is smaller than the charge stop threshold or the discharge start threshold is larger than the discharge stop threshold. FIG. 22 is a flowchart of charge / discharge determination processing that can appropriately determine the above. It is assumed that the initial values of the charge flag and the discharge flag are OFF, and the initial values of the variables V _old and V _now are the bus voltage target values.

When the charge / discharge determination process is started, the charge / discharge determination unit instructs the bus voltage acquisition unit to acquire the current value of the DC bus voltage (referred to as bus voltage current value), and to the variable V _old as the variable V _old . The value of _now is substituted and the current bus voltage value is substituted for variable V _now (step S301).
Next, the charge / discharge determination unit determines whether or not the discharge flag is ON (step S202).

When the discharge flag is ON (step S202: Yes), the charge / discharge determination unit determines whether the variable V _now is larger than the variable V _old (step S302), and the variable V _now is equal to or less than the variable V _old . If there is (step S302: No), the charging / discharging process is terminated. If the variable V _now is greater than the variable V _old (step S302: Yes), the charge and discharge determination unit determines whether the variable V _now is greater than the discharge-stop threshold value, the variable V _now following discharge stop threshold In the case (step S303: No), the charge / discharge determination process is terminated. When the variable V _now is larger than the discharge stop threshold (step S303: Yes), the charge / discharge determination unit turns off the discharge flag (step S204) and ends the charge / discharge determination process.

When the discharge flag is OFF (step S202: No), the charge / discharge determination unit determines whether or not the charge flag is ON (step S205).
When the charge flag is ON (step S205: Yes), the charge / discharge determination unit determines whether or not the variable V _now is smaller than the variable V _old (step S304), and the variable V _now is greater than or _equal to the variable V _old . If present (step S304: No), the charge / discharge process is terminated. If the variable V _now is less than the variable V _old (step S304: Yes), the charge and discharge determination unit determines whether the variable V _now is less than the charging stop threshold value, the variable V _now is more than the charging stop threshold value In the case (step S305: No), the charge / discharge determination process is terminated. When the variable V _now is smaller than the charge stop threshold (step S305: Yes), the charge / discharge determination unit turns off the charge flag (step S207) and ends the charge / discharge determination process.

When the charge flag is OFF (step S205: No), the charge / discharge determination unit determines whether or not the variable V _now is larger than the variable V _old (step S306).
If the variable V _now is greater than the variable V _old (step S306: Yes), the charge and discharge determination unit determines whether the variable V _now is greater than the charge start threshold, the variable V _now following charge start threshold In the case (step S307: No), the charge / discharge determination process is terminated. When the variable V _now is larger than the charge start threshold (step S307: Yes), the charge / discharge determination unit sets the charge flag to ON (step S209) and ends the charge / discharge determination process.

When the discharge flag is OFF and the variable V _now is less than the variable V _old (step S306: No), the charge / discharge determination unit determines whether the variable V _now is smaller than the variable V _old (step S308).
If the variable V _now is less than the variable V _old (step S308: Yes), the charge and discharge determination unit determines whether the variable V _now is less than the discharge start threshold, the variable V _now is more than the discharge start threshold In the case (step S309: No), the charge / discharge determination process is terminated. When the variable V _now is smaller than the discharge start threshold (step S309: Yes), the charge / discharge determination unit turns on the discharge flag (step S211) and ends the charge / discharge determination process.

When the variable V _now is greater than or equal to the variable V _old (step S308: No), the charge / discharge determination unit ends the charge / discharge determination process.
The charge / discharge determination unit outputs a charge flag and a discharge flag, which are determination results, to the charge / discharge control unit after the charge / discharge determination process.
Here, in steps S302, S304, S306, and S308, it is determined whether the DC bus voltage is rising or falling by comparing the current value of the DC bus voltage with the previous value. doing. This stabilizes the output of the charge / discharge determination unit by limiting the start of charge and stop of discharge while the DC bus voltage is rising and the stop of charge and start of discharge are limited to when the DC bus voltage is falling. Yes.

By performing the processing in this manner, whether or not the power storage unit should be charged and discharged when the charge start threshold is smaller than the charge stop threshold or the discharge start threshold is larger than the discharge stop threshold. It is possible to appropriately determine whether or not.
<Modification 2>
In the above embodiment, the charge stop threshold value for stopping the charging of the power storage unit is set, but the charge stop threshold value may not be set. In this case, for example, the charge / discharge determination unit further includes a configuration for measuring the amount of charge charged by the corresponding power storage unit, and the charge amount charged by the corresponding power storage unit after the charge flag is turned on exceeds a predetermined amount. In this case, the charging flag may be turned off. Further, the charge / discharge determination unit may be configured to turn off the charge flag after a predetermined time has elapsed since the charge flag was turned on.

  In addition, for example, the charge / discharge determination unit further includes a configuration for measuring the amount of charge discharged by the corresponding power storage unit, and when the amount of charge discharged by the corresponding power storage unit exceeds a predetermined amount after turning on the discharge flag Alternatively, the discharge flag may be turned off. Further, the charge / discharge determination unit may be configured to turn off the discharge flag after a predetermined time has elapsed since the discharge flag was turned on.

<Modification 3>
In the above embodiment, the time information acquisition unit outputs a threshold update instruction for updating the charging condition (charging start threshold and charging stop threshold) and discharging condition (discharge starting threshold and discharge stop threshold) at a predetermined cycle. The threshold update instruction may not be a predetermined cycle. For example, the power storage system further includes a configuration for measuring an increase or decrease associated with charging or discharging of the amount of charge accumulated in the power storage unit, and the amount of charge accumulated in the power storage unit after updating the charging condition and discharging condition When the increase / decrease in the number exceeds a predetermined value, the charging condition and discharging condition of the power storage unit may be updated.

<Modification 4>
In the third embodiment, the scheduling information is information in which the time zone is associated with the priority. However, the scheduling information is not limited to this. The scheduling information may be information indicating the priority change order, and may not be associated with the time zone. In that case, every time the priority determination unit 131 acquires a threshold update instruction from the time acquisition unit, the priority determination unit 131 may update the priority of the corresponding power storage unit according to the priority change order indicated by the scheduling information.

Note that the scheduling information in this case is such that the priority of some power storage units and the priority of other power storage units are determined to be different values at the same time. It is assumed that a priority change order different from the priority change order of the power storage units is set in advance.
Further, the scheduling information may be information for determining charging conditions and discharging conditions instead of information for determining priority. That is, the scheduling information may be information indicating the change order of the charging condition and discharging condition of each power storage device. The charging / discharging threshold value setting unit only needs to update the charging condition and discharging condition of the corresponding power storage unit in accordance with the changing order of the charging condition and discharging condition indicated by the scheduling information each time a threshold update instruction is acquired from the time acquisition unit. .

  Note that the scheduling information in this case is a part of power storage so that the charging conditions and discharging conditions of some power storage units and the charging conditions and discharging conditions of other power storage units are determined to be different values at the same time. It is assumed that a charging condition and discharging condition changing order different from the changing order of charging conditions and discharging conditions of other power storage units is set in advance for the unit.

<Modification 5>
In the above embodiment, the power storage unit is composed of a secondary battery that can be repeatedly charged and discharged, such as a lithium ion battery. Secondary batteries that can be repeatedly charged and discharged include lead-acid batteries, nickel-hydrogen batteries, nickel-cadmium batteries, and the like in addition to lithium ion batteries. The power storage unit may be configured using a capacitor such as a lithium ion capacitor or an electric double layer capacitor. The power storage unit may be a flywheel battery or the like that converts electrical energy into kinetic energy for storage.

Each power storage unit may be configured by connecting a plurality of power storage devices (secondary battery, capacitor, flywheel battery, etc.) in series, or may be configured by connecting a plurality of power storage devices in parallel. Alternatively, a plurality of power storage devices connected in series may be further connected in parallel.
<Modification 6>
Each functional component (charge / discharge threshold update unit, charge / discharge threshold storage unit, charge / discharge determination unit, etc.) shown in the above-described embodiment may be realized as a circuit that performs the function, IC, LSI, or the like. It may be configured as an integrated circuit package. This package is incorporated into various devices (DC / DC converters) and used for use, whereby the various devices realize each function as shown in each embodiment.

Note that the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology.
(Supplement)
Hereinafter, the configuration of the charge / discharge control device as one embodiment of the present invention and the effects of the modified examples will be described.

  <A> A charge / discharge control apparatus according to an embodiment of the present invention is a charge / discharge control apparatus that controls charging and discharging of a plurality of power storage devices connected to the DC bus according to voltage fluctuations of the DC bus. A bus voltage acquisition unit that acquires a bus voltage indicating a current voltage of the DC bus, and a charging condition and a discharge condition that are set in each of the power storage devices and indicate a condition of the bus voltage for charging A condition storage unit that stores a discharge condition indicating a condition of the bus voltage; a condition update unit that updates a charge condition and a discharge condition of each of the power storage devices stored in the condition storage unit; and the bus voltage and the power storage device It is determined whether to charge each of the power storage devices based on the respective charging conditions, and the power storage devices are determined based on the bus voltage and the discharge conditions of the power storage devices. Characterized in that it comprises a discharge determining unit that determines whether to discharge of respectively.

According to the above configuration, the charging condition for charging and the discharging condition for discharging are individually set for each power storage device (power storage unit). Thereby, it becomes possible to preferentially charge or discharge a specific power storage device.
Further, by updating the charging condition and the discharging condition, it is possible to efficiently control charging and discharging of a plurality of power storage devices by switching power storage devices that are preferentially charged or discharged.

  <B> In the charge / discharge control device according to the embodiment (A), each of the charging conditions includes a charging start threshold value indicating a magnitude of the bus voltage for starting charging, and each of the discharging conditions is A discharge start threshold value indicating a magnitude of the bus voltage for starting discharge, wherein the condition update unit sets a charge start threshold value of each power storage device to be larger than a target value of the bus voltage, and starts discharge of each power storage device The threshold is updated to be smaller than the target value, and the charge / discharge determination unit determines that the bus voltage exceeds the charge start threshold of the one power storage device when the one power storage device is not being charged or discharged. Is detected to start charging the one power storage device, and when the one power storage device is not being charged or discharged, the bus voltage is below the discharge start threshold of the one power storage device. When it is detected that may determine to start the discharge of the one of the power storage device.

According to the above configuration, the charging start threshold value larger than the bus voltage target value is set as the charging condition, and the discharging start threshold value smaller than the bus voltage target value is set as the discharging condition. Thereby, the subject shown below can be solved.
When each storage unit is equipped with a voltage sensor that acquires the voltage of the DC bus, it is difficult to completely eliminate an error between the plurality of voltage sensors. It is determined whether or not charging should be performed and whether or not discharging should be performed. In this case, depending on the voltage measurement error, it may be determined that some of the power storage units should be charged while the other power storage units should be discharged. Thus, if the charge / discharge directions are different between the power storage units in the power storage system, the power simply moves between the power storage units, which promotes power loss and deterioration of the power storage units.

  In response to this problem, according to the configuration in which the charge start threshold value larger than the bus voltage target value and the discharge start threshold value smaller than the bus voltage target value are set, the detection error of the bus voltage acquisition unit is The charge / discharge directions of the respective power storage devices can be aligned within a range not exceeding the difference between the charge start threshold and the discharge start threshold. That is, charging and discharging of each power storage unit can be controlled so that the power storage unit that performs charging and the power storage that performs discharging do not coexist.

  <C> In the charge / discharge control device according to the embodiment (B), the condition update unit updates the charge condition and the discharge condition with a storage state calculation unit that calculates the remaining capacity of each of the power storage devices. The discharge start threshold of the one power storage device is set to a higher value as the remaining capacity of the one power storage device increases, and the charge start threshold of the one power storage device is set to a lower value as the remaining capacity of the one power storage device decreases. A charge / discharge threshold setting unit to be set may be provided.

According to the above configuration, charging and discharging of each power storage device can be controlled so that the remaining battery capacity of each power storage device is leveled.
<D> In the charge / discharge control device according to the embodiment (B), the condition update unit updates the charge condition and the discharge condition with a storage state calculation unit that calculates the degree of deterioration of each of the power storage devices. The charging start threshold of the one power storage device is set to a higher value as the one power storage device deteriorates, and the discharge start threshold of the one power storage device is set to a lower value as the one power storage device deteriorates. A charge / discharge threshold setting unit to be set may be provided.

According to the above configuration, charging and discharging of each power storage device can be controlled so that the degree of deterioration of each power storage device is leveled.
<E> In the charge / discharge control device of the embodiment (B), the condition update unit stores correspondence information in which a plurality of priorities are associated with charge conditions and discharge conditions, and the correspondence information storage unit and the power storage A priority determination unit that determines the priority of each device such that the priority of some power storage devices is different from the priority of other power storage devices, and the priority when the priority changes before and after the determination. And a condition setting unit that updates the charging condition and discharging condition of the power storage device having changed to the charging condition and discharging condition corresponding to the priority after the change with reference to the correspondence information.

According to the above configuration, charging and discharging of each power storage device can be controlled based on the priority of each power storage device.
<F> In the charge / discharge control device according to the embodiment (E), the condition update unit is set so that the priority change order of some power storage devices is different from the priority change order of other power storage devices. A change order storage unit that stores change order information indicating a change order of priority for each of the power storage devices, and the priority determination unit is configured to change according to the change order indicated by the change order information of each of the power storage devices. The priority of each power storage device may be determined.

  According to the above configuration, the priority of each power storage device can be updated in the change order indicated by the predetermined change order information. Thereby, the charging and discharging of each power storage device can be performed in advance by determining change order information in accordance with environmental changes that can be predicted in advance (for example, voltage fluctuations of the DC bus or changes in the power storage state of the power storage devices). Can be appropriately controlled with respect to changes in the environment that can be predicted.

In addition, by determining the change order information so that the power storage devices that are preferentially charged and discharged are sequentially switched, deterioration of each power storage device can be delayed.
<G> In the charge / discharge control device of the above embodiment (B), the condition update unit includes a change order of charge conditions and discharge conditions of some power storage devices and a change order of charge conditions and discharge conditions of other power storage devices. Is set to be different from each other, according to a change order storage unit that stores change order information indicating a change order of charge conditions and discharge conditions for each power storage device, and a change order indicated by the change order information of each of the power storage devices, You may provide the condition setting part which sets the charge condition and discharge condition of each said electrical storage apparatus.

  According to the above configuration, updating the charging conditions (charging start threshold and charging stop threshold) and discharging conditions (discharging start threshold and discharge stop threshold) of each power storage device in the change order indicated by the predetermined change order information. it can. Thereby, the charging and discharging of each power storage device can be performed in advance by determining change order information in accordance with environmental changes that can be predicted in advance (for example, voltage fluctuations of the DC bus or changes in the power storage state of the power storage devices). Can be appropriately controlled with respect to changes in the environment that can be predicted.

In addition, it is possible to delay the deterioration of each power storage device by determining the change order information so that the power storage devices that are preferentially charged and discharged are sequentially switched.
<H> In addition, a charge / discharge system according to an embodiment of the present invention includes a DC bus, a plurality of power storage devices connected to the DC bus, charging of the plurality of power storage devices according to voltage fluctuations of the DC bus, and A storage system comprising a charge / discharge control device that controls discharge, wherein the charge / discharge control device is set in each of the storage device and a bus voltage acquisition unit that acquires a bus voltage indicating a current voltage of the DC bus A condition storage unit for storing a charge condition indicating a condition of the bus voltage for charging and a discharge condition indicating a condition of the bus voltage for discharging, and the power storage stored in the condition storage unit Whether to charge each of the power storage devices based on a condition update unit that updates the charging conditions and discharging conditions of each device, and the bus voltage and the charging conditions of each of the power storage devices Or it determines, characterized in that it comprises said bus voltage and the energy storage device discharge determining unit that determines whether to discharge for each of the power storage device based on the respective discharge conditions.

According to the above configuration, the charging condition for charging and the discharging condition for discharging are individually set for each power storage device. Thereby, it becomes possible to preferentially charge or discharge a specific power storage device.
Further, by updating the charging condition and the discharging condition, it is possible to efficiently control charging and discharging of a plurality of power storage devices by switching power storage devices that are preferentially charged or discharged.

  <I> In the charge / discharge system of the above embodiment (H), the condition update unit calculates a storage state of each of the power storage devices, a priority of one power storage device, and sets the priority of the one power storage device. A priority determination unit that determines the power storage state of the device and the power storage state of another power storage device, and when the priority changes before and after the determination, the charge condition and discharge condition of the power storage device whose priority has changed A condition setting unit that refers to the correspondence information and updates the changed priority to the corresponding charging condition and discharging condition may be provided.

According to the above configuration, the threshold value of the one power storage device is set based on the relative relationship between the power storage state (battery remaining capacity, deterioration degree, etc.) of the one power storage device and the battery remaining capacity of the other power storage device. Is possible.
<J> In the charge / discharge system according to the embodiment (H), the charge / discharge control device includes a plurality of power conversion units corresponding to the plurality of power storage devices, and each of the power conversion units includes the bus voltage acquisition unit. A storage unit that stores a charging condition and a discharging condition of the corresponding power storage device among the condition storage unit, and a charging condition and a discharging condition of the corresponding power storage device stored in the storage unit among the condition update unit And a determination unit that determines whether or not to charge the corresponding power storage device and whether or not to discharge the corresponding power storage device among the charge / discharge determination units. May be.

The above configuration is a configuration that autonomously controls charging and discharging of each of the power storage devices existing in a distributed manner. Therefore, according to the above configuration, an autonomous distributed power storage system can be realized.
<K> A charge / discharge control method according to an embodiment of the present invention includes a charge condition and a discharge condition indicating a voltage condition of the DC bus for charging each of the plurality of power storage devices connected to the DC bus. A condition storage unit that stores a discharge condition indicating a voltage condition of the DC bus for performing charging, and charging each of the power storage devices based on a voltage fluctuation of the DC bus and a charge condition and a discharge condition of each of the power storage devices And a charge / discharge control method used in a charge / discharge control device for controlling discharge, a condition update step for updating a charge condition and a discharge condition of each of the power storage devices stored in the condition storage unit; A bus voltage acquisition step for acquiring a bus voltage indicating a current voltage, and for each power storage device based on the bus voltage and a charging condition of each power storage device. Charging / discharging determination step of determining whether or not to perform discharging for each of the power storage devices based on the bus voltage and a discharge condition of each power storage device. And

According to the above configuration, the charging condition for charging and the discharging condition for discharging are individually set for each power storage device. Thereby, it becomes possible to preferentially charge or discharge a specific power storage device.
Further, by updating the charging condition and the discharging condition, it is possible to efficiently control charging and discharging of a plurality of power storage devices by switching power storage devices that are preferentially charged or discharged.

  The present invention can efficiently control charging and discharging of a plurality of power storage units, and is useful for use in a power storage system such as a distributed power supply device or an uninterruptible power supply device.

30, 200 Power storage unit 31 Power storage unit 70 DC bus 100, 300 DC / DC converter 101, 211 Bus voltage acquisition unit 102, 212 Charge / discharge threshold update unit (condition update unit)
103, 213 Charge / discharge threshold storage unit (condition storage unit)
104, 214 Charge / discharge determination unit 105 Charge / discharge control unit 111, 121, 221 Battery information acquisition unit 112, 122, 222 Battery state calculation unit (power storage state calculation unit)
113, 123, 224 Battery characteristic storage unit 114, 124, 132, 223 Time information acquisition unit 115, 125, 134, 226 Charge / discharge threshold setting unit (condition setting unit)
126, 135, 227 Corresponding information storage unit 131, 225 Priority determination unit 133 Change order storage unit 210 Charge / discharge controller

Claims (11)

A charge / discharge control device for controlling charging and discharging of a plurality of power storage devices connected to the DC bus according to voltage fluctuation of the DC bus,
A bus voltage acquisition unit for acquiring a bus voltage indicating a current voltage of the DC bus;
A condition storage unit configured to store a charging condition indicating a condition of the bus voltage for charging and a discharging condition indicating a condition of the bus voltage for discharging, which are set in each of the power storage devices;
A condition updating unit for updating the charging condition and discharging condition of each of the power storage devices stored in the condition storage unit;
It is determined whether to charge each of the power storage devices based on the bus voltage and the charging conditions of each of the power storage devices, and for each of the power storage devices based on the bus voltage and the discharge conditions of each of the power storage devices. A charge / discharge control apparatus comprising: a charge / discharge determination unit that determines whether or not to perform discharge. Each of the charging conditions includes a charging start threshold value indicating a magnitude of the bus voltage for starting charging,
Each of the discharge conditions includes a discharge start threshold value indicating the magnitude of the bus voltage for starting discharge,
The condition update unit updates the charging start threshold of each power storage device to be larger than the target value of the bus voltage, and updates the discharge start threshold of each power storage device to be smaller than the target value.
The charge / discharge determination unit
When one power storage device is not being charged or discharged, if it is detected that the bus voltage exceeds a charge start threshold of the one power storage device, it is determined to start charging the one power storage device;
When it is detected that the bus voltage is lower than the discharge start threshold of the one power storage device when the one power storage device is not being charged or discharged, it is determined that the discharge of the one power storage device is started.

The charge / discharge control apparatus according to claim 1. The condition update unit
A storage state calculation unit for calculating a remaining capacity of each of the storage devices;
When the charge condition and the discharge condition are updated, the discharge start threshold of the one power storage device is set to a higher value as the remaining capacity of the one power storage device is larger, and the remaining capacity of the one power storage device is smaller. The charge / discharge control apparatus according to claim 2, further comprising: a charge / discharge threshold setting unit that sets a charge start threshold of one power storage device to a low value. The condition update unit
A power storage state calculation unit for calculating the degree of deterioration of each of the power storage devices;
When updating the charging condition and the discharging condition, the charging start threshold of the power storage device is set to a higher value as the power storage device is deteriorated, and the power storage device is deteriorated as the power storage device is deteriorated. The charge / discharge control apparatus according to claim 2, further comprising: a charge / discharge threshold setting unit that sets a discharge start threshold of one power storage device to a low value. The condition update unit
A correspondence information storage unit for storing correspondence information in which each of a plurality of priorities is associated with a charging condition and a discharging condition; a priority of each of the power storage devices; a priority of some power storage devices is a priority of other power storage devices A priority determination unit that determines a degree different from the degree,
When the priority changes before and after the determination, the charging condition and discharging condition of the power storage device whose priority has changed are updated to the charging condition and discharging condition corresponding to the changed priority with reference to the correspondence information. The charge / discharge control apparatus according to claim 2, further comprising: a condition setting unit that performs the operation. The condition update unit indicates a priority change order for each of the power storage devices set so that a priority change order of some power storage devices is different from a priority change order of other power storage devices. A change order storage unit for storing change order information;
The charge / discharge control apparatus according to claim 5, wherein the priority determination unit determines a priority of each of the power storage devices according to a change order indicated by change order information of each of the power storage devices. The condition update unit
Change order of charge conditions and discharge conditions for each power storage device, in which the change order of charge conditions and discharge conditions for some power storage devices is different from the change order of charge conditions and discharge conditions for other power storage devices A change order storage unit for storing change order information indicating
The charge / discharge control apparatus according to claim 2, further comprising: a condition setting unit configured to set a charging condition and a discharging condition of each of the power storage devices according to a change order indicated by the change order information of each of the power storage devices. A power storage system comprising a DC bus, a plurality of power storage devices connected to the DC bus, and a charge / discharge control device that controls charging and discharging of the plurality of power storage devices according to voltage fluctuations of the DC bus,
The charge / discharge control device comprises:
A bus voltage acquisition unit for acquiring a bus voltage indicating a current voltage of the DC bus;
A condition storage unit configured to store a charging condition indicating a condition of the bus voltage for charging and a discharging condition indicating a condition of the bus voltage for discharging, which are set in each of the power storage devices;
A condition updating unit for updating the charging condition and discharging condition of each of the power storage devices stored in the condition storage unit;
It is determined whether to charge each of the power storage devices based on the bus voltage and the charging conditions of each of the power storage devices, and for each of the power storage devices based on the bus voltage and the discharge conditions of each of the power storage devices. A charge / discharge control system comprising: a charge / discharge determination unit that determines whether or not to perform discharge. The condition update unit
A power storage state calculation unit for calculating a power storage state of each of the power storage devices;
A priority determination unit that determines the priority of one power storage device using the power storage state of the one power storage device and the power storage state of another power storage device;
When the priority changes before and after the determination, the charging condition and discharging condition of the power storage device whose priority has changed are updated to the charging condition and discharging condition corresponding to the changed priority with reference to the correspondence information. The charge / discharge control system according to claim 8, further comprising: a condition setting unit that performs: The charge / discharge control device comprises:
A plurality of power conversion units corresponding to the plurality of power storage devices;
Each of the power converters
The bus voltage acquisition unit;
Among the condition storage units, a storage unit that stores a charging condition and a discharging condition of a corresponding power storage device, and
Among the condition update units, an update unit that updates the charging conditions and discharge conditions of the corresponding power storage device stored in the storage unit,
The charging / discharging determination unit includes a determination unit that determines whether or not to charge the corresponding power storage device and whether or not to discharge the corresponding power storage device. 8. The charge / discharge control system according to 8. A charging condition indicating a voltage condition of the DC bus for charging and a discharging condition indicating a voltage condition of the DC bus for discharging are set for each of a plurality of power storage devices connected to the DC bus. And a charge / discharge control method used in a charge / discharge control device that controls charging and discharging of each of the power storage devices based on voltage fluctuations of the DC bus and charging and discharging conditions of each of the power storage devices. There,
A condition update step of updating the charging condition and discharging condition of each of the power storage devices stored in the condition storage unit;
A bus voltage acquisition step of acquiring a bus voltage indicating a current voltage of the DC bus;
It is determined whether or not to charge each of the power storage devices based on the bus voltage and the charging conditions of each power storage device, and the discharge of each of the power storage devices is discharged based on the bus voltage and the discharge conditions of each power storage device. A charge / discharge control method comprising: a charge / discharge determination step for determining whether or not to perform.

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