JP6712802B2 - Power storage system, control device, and power storage device - Google Patents

Description

The present invention relates to a power storage system including a plurality of power storage devices and a control device connected in parallel, a control device, and a power storage device.

In recent years, a separate type power storage system has become widespread. In the separated type power storage system, a plurality of power storage devices connected in parallel are installed at positions distant from the power conditioner. In addition, a plurality of power storage devices connected in parallel may be installed at separate positions. In a power storage system including a plurality of power storage devices connected in parallel, it is required to manage the state of charge (SOC) between the power storage devices as uniformly as possible in order to secure the maximum output capacity of the system. As a method for equalizing SOC, some methods have been proposed in which the charge/discharge amount is distributed to each power storage device according to the SOC among a plurality of power storage devices.

For example, the discharge distribution ratio is calculated from the ratio of the discharge allowable amount of each power storage device, and the power command value according to the discharge distribution ratio is set in each power storage device. Similarly, the charge distribution ratio is calculated from the ratio of the charge allowable amount of each power storage device, and the power command value corresponding to the charge distribution ratio is set in each power storage device (see, for example, Patent Document 1). In order to perform such control, it is necessary for a control device that manages a plurality of power storage devices to grasp the SOC of each power storage device and give a command value to each power storage device individually.

JP, 2008-109840, A

However, in a separate type power storage system, it is necessary to give a command value by communication, and the communication amount increases in a system in which the command value is not common and is individually generated for each power storage device. The communication amount increases as the number of connected devices increases, and it may occur that the command value cannot be sent to all the power storage devices within the set period depending on the communication specifications.

The present invention has been made in view of the above circumstances, and an object thereof is a power storage system and a control device capable of distribution control of charge/discharge amount according to S0C while suppressing an increase in communication amount in a distributed power storage system. And providing a power storage device.

In order to solve the above problems, an electricity storage system according to an aspect of the present invention is configured such that a plurality of electricity storage devices connected in parallel are connected to the plurality of electricity storage devices via a communication line, and the plurality of electricity storage devices are charged or charged. A reference value corresponding to the amount of electric power obtained by dividing the total amount of electric power to be discharged by the number of the plurality of power storage devices is transmitted to the plurality of power storage devices, and each of the values determined based on the state of charge of the plurality of power storage devices A control device that transmits a correction value for correcting the reference value for the power storage device to each power storage device. The control device transmits the correction value less frequently than the reference value.

According to the present invention, in a distributed power storage system, it is possible to perform charge/discharge amount distribution control according to S0C while suppressing an increase in communication amount.

It is a figure which shows the structural example of the electrical storage system 1 which cooperated with the solar power generation system based on embodiment of this invention. FIG. 5 is a diagram illustrating an example of a command value notification timing from the common control unit to the first SB control unit and the second SB control unit according to the first embodiment. FIGS. 3A and 3B are diagrams illustrating current command values for the first power storage device and the second power storage device according to the first embodiment. FIGS. 4A and 4B are diagrams illustrating current command values for the first power storage device and the second power storage device according to the second embodiment. FIG. 11 is a diagram illustrating an example of a command value notification timing from the common control unit to the first SB control unit and the second SB control unit according to the third embodiment. 6A and 6B are diagrams illustrating current command values of the first power storage device and the second power storage device according to the third embodiment. The figure which shows an example of the command value notification timing from the common control unit to the first SB control unit and the second SB control unit and the SOC notification timing from the first SB control unit and the second SB control unit to the common control unit according to the fourth embodiment. Is. FIGS. 8A to 8C are transition examples of SOC_1 of the first power storage unit and SOC_2 of the second power storage unit and updating of current command values of the first power storage device and the second power storage device according to the fourth embodiment. It is a figure which shows an example. FIG. 16 is a diagram illustrating an example of a command value notification timing from the common control unit to the first SB control unit and the second SB control unit according to the fifth embodiment. FIG. 13 is a diagram showing current command values of a first power storage device and a second power storage device according to a fifth embodiment. FIG. 16 is a diagram illustrating current command values for the first power storage device and the second power storage device according to the sixth embodiment. 12A to 12C are diagrams showing current command values of the first power storage device and the second power storage device according to the first modification. 13A and 13B are diagrams showing current command values of the first power storage device and the second power storage device according to the second modification. It is a figure which shows another structural example of the electrical storage system which cooperated with the photovoltaic power generation system which concerns on embodiment of this invention.

FIG. 1 is a diagram showing a configuration example of a power storage system (creation and storage cooperation system) 1 that cooperates with a photovoltaic power generation system 10 according to an embodiment of the present invention. The power storage system 1 includes a plurality of power storage devices 20 connected in parallel to a DC bus 40 and one power conversion device 30. Hereinafter, in the present embodiment, it is assumed that the two power storage devices 20 of the first power storage device 20a and the second power storage device 20b are connected in parallel. The first power storage device 20a, the second power storage device 20b, and the power conversion device 30 are installed in separate housings and are connected by a communication line 50. Further, the solar power generation system 10 is connected to the DC bus 40 in parallel with the plurality of power storage devices 20.

The solar power generation system 10 includes a solar cell 11, a DC-DC converter 12, and a control unit 13. The DC-DC converter 12 converts the DC power supplied from the solar cell 11 into DC power of another voltage, and outputs the converted DC power to the DC bus 40. The DC-DC converter 12 can be composed of, for example, a step-up chopper.

The control unit 13 controls the DC-DC converter 12 so that the output power of the solar cell 11 is maximized. The configuration of the control unit 13 can be realized by cooperation of hardware resources and software resources, or only by hardware resources. As hardware resources, analog elements, microcomputers, DSPs, ROMs, RAMs, FPGAs, and other LSIs can be used. A program such as firmware can be used as a software resource.

The control unit 13 detects the input voltage and the input current of the DC-DC converter 12, which are the generated voltage and the generated current of the solar cell 11. Control unit 13 generates a command value for maintaining the generated power of solar cell 11 measured based on the detected input voltage and input current at the maximum power point (optimal operating point). Specifically, the operating point voltage is changed in a predetermined step width according to the hill climbing method to search for the maximum power point, and a command value for maintaining the maximum power point is generated. The DC-DC converter 12 operates according to the drive signal based on the generated command value.

The first power storage device 20a includes a power storage unit 21a, a DC-DC converter 22a, and a control unit 23a. The configuration of the control unit 23a can also be realized by cooperation of hardware resources and software resources, or only by hardware resources. The power storage unit 21a includes a storage battery 211a and a monitoring unit 212a. The storage battery 211a is composed of a plurality of storage battery cells connected in series or in series/parallel. A lithium ion storage battery, a nickel hydrogen storage battery, or the like can be used as the storage battery cell. A capacitor such as an electric double layer capacitor or a lithium ion capacitor may be used instead of the storage battery 211a. The monitoring unit 212a monitors the voltages, currents, and temperatures of the plurality of storage battery cells, and transmits the monitoring data of the plurality of storage battery cells to the control unit 23a.

The DC-DC converter 22a is a bidirectional converter that is connected between the power storage unit 21a and the DC bus 40 and charges and discharges the power storage unit 21a. The control unit 23a controls the DC-DC converter 22a based on the command value to charge/discharge the power storage unit 21a with a constant current (CC)/constant voltage (CV). In the present embodiment, consider a situation where charging/discharging is performed with a constant current (CC) based on a current command value received from the control unit 32 of the power conversion device 30 via the communication line 50.

The control unit 23a estimates the SOC of the storage battery 211a based on the voltage and current of the storage battery 211a received from the monitoring unit 212a. The SOC of the storage battery 211a can be estimated by the current integration method or the OCV method. The control unit 23a periodically transmits the estimated SOC to the control unit 32 of the power conversion device 30 via the communication line 50. The second power storage device 20b also has basically the same configuration as the first power storage device 20a.

The power conversion device 30 includes an inverter 31 and a control unit 32, and serves as a power conditioner system (PCS) of the power storage system 1. The configuration of the control unit 32 can also be realized by cooperation of hardware resources and software resources, or only by hardware resources.

The control unit 32 of the power conversion device 30 (hereinafter referred to as the common control unit 32) controls the control unit 23a of the first power storage device 20a (hereinafter referred to as the first SB control unit 23a) and the second power storage device 20b. The unit 23b (hereinafter, referred to as the second SB control unit 23b) and the control unit 13 of the photovoltaic power generation system 10 are connected by the communication line 50. For example, they are connected by a cable compatible with the RS-485 standard, and serial communication is performed according to a communication system compliant with the standard. Alternatively, the communication network may conform to the TCP/IP and Ethernet (registered trademark) standards. The DC-DC converter 12 and the control unit 13 of the solar power generation system 10 may be installed in the housing of the power conversion device 30, and in that case, the common control unit 32 and the control unit 13 of the solar power generation system 10. Can be directly connected by a signal line without using communication. In the present embodiment, the common control unit 32 serves as a common management unit that manages the first SB control unit 23a, the second SB control unit 23b, and the control unit 13 of the photovoltaic power generation system 10.

The inverter 31 converts the DC power input from the DC bus 40 into AC power, and supplies the converted AC power to the grid 4 or the load 5. Further, the inverter 31 converts the AC power supplied from the grid 4 into DC power and outputs the converted DC power to the DC bus 40. The common control unit 32 detects the voltage of the DC bus 40 and generates a command value for matching the detected bus voltage with the target value. The inverter 31 operates according to the drive signal based on the generated command value.

In the power storage system 1 shown in FIG. 1, the power output from the photovoltaic power generation system 10 to the DC bus 40, the power output from the first power storage device 20a to the DC bus 40 (negative power in the case of charging), and the second power storage device. It is necessary that the total of the power output to the DC bus 40 by the 20b (negative power in the case of charging) and the power output from the inverter 31 to the grid 4 or the load 5 are balanced. When the former becomes larger than the latter, the voltage of the DC bus 40 rises, and when the latter becomes larger than the former, the voltage of the DC bus 40 falls. Electric power on the DC side of the inverter 31 (electric power of the DC bus 40) mainly fluctuates depending on the power generation amount of the solar cell 11. The power on the AC side of the inverter 31 mainly fluctuates depending on the power consumption of the load 5.

When the power on the DC side of the inverter 31 is higher, the common control unit 32 instructs the first SB control unit 23a and the second SB control unit 23b to decrease the discharge amount or increase the charge amount. On the other hand, when the power on the AC side of the inverter 31 is higher, the common control unit 32 instructs the first SB control unit 23a and the second SB control unit 23b to increase the discharge amount or decrease the charge amount.

Conventionally, the common control unit 32 divides the surplus power or the insufficient power of the DC bus 40 by the number of connected power storage devices 20, and the power value to be discharged or charged by each power storage device 20 according to the SOC ratio of each power storage device 20. Had been decided. The common control unit 32 generates a current command value according to the determined discharge amount or charge amount of each power storage device 20, and transmits the current command value to each power storage device 20 via the communication line 50. Since the current command value is transmitted at each update timing of the command value, when the number of connected power storage devices 20 is N, N times the command value is transmitted. Hereinafter, a method of reducing the communication load by compressing the amount of data required to transmit the command value will be described.

(Example 1)
In the first embodiment, the common control unit 32 acquires the SOC of the power storage unit 21a from the first SB control unit 23a and the SOC of the power storage unit 21b from the second SB control unit 23b at regular intervals (for example, at 1 sec intervals). The common control unit 32 has a total amount of electric power to be charged or discharged by the first power storage device 20a and the second power storage device 20b (that is, an amount of power required to balance the power of the DC bus 40 and the power consumption of the load 5). To decide. The common control unit 32 calculates the respective current command values of the first power storage device 20a and the second power storage device 20b according to the acquired ratio of the SOC of the power storage unit 21a and the acquired SOC of the power storage unit 21b and the determined total power amount. To do. For example, when the SOC of the power storage unit 21a is 60% and the SOC of the power storage unit 21b is 40%, the total power amount is distributed at 3:2 for discharging, and the total power amount is 2:3 for charging. Distribute.

The common control unit 32 generates a reference command value corresponding to the amount of power obtained by dividing the total amount of power by the number of connected units. This reference command value becomes a current command value common to the first power storage device 20a and the second power storage device 20b. Further, the common control unit 32 generates a correction value 1 for the first power storage device 20a defined by the difference (offset) between the reference command value and the current command value for the first power storage device 20a, and similarly, the reference command value and the first correction value 2 The correction value 2 of the second power storage device 20b, which is defined by the difference from the current command value of the power storage device 20b, is generated. The common control unit 32 transmits the reference command value to the first power storage device 20a and the second power storage device 20b via the communication line 50 at a predetermined transmission frequency, and corrects the first power storage device 20a and the second power storage device 20b. The values 1 and 2 are transmitted at a frequency lower than the frequency of transmission of the reference command value.

The first SB control unit 23a receives the reference command value and the correction value 1, and adds the correction value 1 to the reference command value to restore the current command value for itself. The first SB control unit 23a controls the DC-DC converter 22a based on the restored current command value. Similarly, the second SB control unit 23b receives the reference command value and the correction value 2, and adds the correction value 2 to the reference command value to restore the current command value for itself. The second SB control unit 23b controls the DC-DC converter 22b based on the restored current command value.

FIG. 2 is a diagram illustrating an example of a command value notification timing from the common control unit 32 to the first SB control unit 23a and the second SB control unit 23b according to the first embodiment. In the example shown in FIG. 2, the common control unit 32 notifies the reference command value to the first SB control unit 23a and the second SB control unit 23b at, for example, 100 msec intervals. In addition, the common control unit 32 notifies the correction value 1 and the correction value 2 to the first SB control unit 23a and the second SB control unit 23b, for example, at intervals of several minutes.

FIGS. 3A and 3B are diagrams showing current command values of the first power storage device 20a and the second power storage device 20b according to the first embodiment. FIG. 3A is a diagram showing the relationship between the reference command value, the correction value 1 and the correction value 2 generated when the first power storage device 20a and the second power storage device 20b are instructed to discharge. FIG. 3B is a diagram showing a relationship between the reference command value, the correction value 1 and the correction value 2 generated when the first power storage device 20a and the second power storage device 20b are instructed to charge. The horizontal axis represents the total discharge power/total charge power required for the first power storage device 20a and the second power storage device 20b, and the vertical axis represents the discharge power required for each of the first power storage device 20a and the second power storage device 20b. The charging power is shown.

In the example shown in FIGS. 3A and 3B, it is premised that the SOC of power storage unit 21a is larger than the SOC of power storage unit 21b. On this premise, in the case of the discharge instruction, the correction value 1 becomes a positive value and the correction value 2 becomes a negative value. In the case of charging instructions, the opposite relationship is true.

As described above, according to the first embodiment, a situation in which the maximum output is always maintained by balancing the SOC between the power storage devices 20 while suppressing an increase in the amount of data notified to the power storage devices 20. it can.

(Example 2)
The process according to the second embodiment is the same as the process according to the first embodiment until the reference command values for the first power storage device 20a and the second power storage device 20b are generated. The common control unit 32 generates the correction value 1 of the first power storage device 20a defined by the ratio of the reference command value and the current command value of the first power storage device 20a, and similarly, the reference command value and the second power storage device 20b. The correction value 2 of the second power storage device 20b defined by the ratio with the current command value of is generated. The common control unit 32 transmits the reference command value to the first power storage device 20a and the second power storage device 20b at a predetermined transmission frequency via the communication line 50, and corrects the first power storage device 20a and the second power storage device 20b. The value 1 and the correction value 2 are transmitted at a frequency less than that of the reference command value.

The first SB control unit 23a receives the reference command value and the correction value 1, and multiplies the reference command value by the correction value 1 to restore the current command value for itself. The first SB control unit 23a controls the DC-DC converter 22a based on the restored current command value. Similarly, the second SB control unit 23b receives the reference command value and the correction value 2, and multiplies the reference command value by the correction value 2 to restore the current command value for itself. The second SB control unit 23b controls the DC-DC converter 22b based on the restored current command value. The command value notification timing from the common control unit 32 to the first SB control unit 23a and the second SB control unit 23b according to the second embodiment is the same as in FIG.

FIGS. 4A and 4B are diagrams illustrating current command values for the first power storage device 20a and the second power storage device 20b according to the second embodiment. FIG. 4A is a diagram showing the relationship between the reference command value, the correction value 1 and the correction value 2 which are generated when the first power storage device 20a and the second power storage device 20b are instructed to discharge. FIG. 4B is a diagram showing the relationship between the reference command value, the correction value 1 and the correction value 2 generated when the first power storage device 20a and the second power storage device 20b are instructed to charge.

Similarly to the examples shown in FIGS. 3A and 3B, the examples shown in FIGS. 4A and 4B also assume that the SOC of power storage unit 21a is larger than the SOC of power storage unit 21b. On this assumption, in the case of the discharge instruction, the correction value 1 becomes a value exceeding 1 and the correction value 2 becomes a value less than 1. The correction value 1 may be defined by a value obtained by subtracting 1 from the value obtained by dividing the current command value of the first power storage device 20a by the reference command value (+X [%]). Similarly, the correction value 2 may be defined by a value obtained by subtracting 1 from the value obtained by dividing the current command value of the second power storage device 20b by the reference command value (-X [%]). In the case of the charging instruction, the relationship between the correction value 1 and the correction value 2 is reversed.

As described above, according to the second embodiment, the same effect as that of the first embodiment is obtained. Further, compared to the first embodiment, it is possible to notify the first power storage device 20a and the second power storage device 20b of a more accurate current command value. Common to the first and second embodiments, the transmission frequency of the correction value 1 and the correction value 2 is lower than the transmission frequency of the reference command value. Therefore, when the total discharge power or the total charge power required for the first power storage device 20a and the second power storage device 20b changes, the change is reflected early in the reference command value, but in the correction value 1 and the correction value 2. Changes will be reflected later.

For example, when the total discharge power greatly decreases, the reference command value greatly decreases after at least 100 msec, but the correction value 1 and the correction value 2 do not change until after a few minutes. During this period, the correction value 1 and the correction value 2 are given as constants in the first embodiment, so the current command value of the first power storage device 20a obtained by adding the correction value 1 to the reference command value becomes excessive, and the correction value 2 Is added to the reference command value, the current command value of the second power storage device 20b obtained is too small. On the other hand, in the second embodiment, since the correction value 1 and the correction value 2 are given in the ratio, the current command value of the first power storage device 20a obtained by multiplying the reference command value by the correction value 1 and the correction value 2 The current command value of the second power storage device 20b obtained by multiplying the reference command value by can maintain a value close to an appropriate value.

(Example 3)
The processing according to the third embodiment is the same as the processing according to the first embodiment and the processing until the reference command values for the first power storage device 20a and the second power storage device 20b are generated. The common control unit 32 generates SOC_1 obtained by averaging SOC_1 acquired from the first SB control unit 23a and SOC_2 acquired from the second SB control unit 23b, as a common correction value. The common control unit 32 transmits the reference command value to the first power storage device 20a and the second power storage device 20b at a predetermined transmission frequency via the communication line 50, and is common to the first power storage device 20a and the second power storage device 20b. The correction value is transmitted less frequently than the reference command value.

The first SB control unit 23a receives the reference command value and the common correction value SOC_0, and generates its own current command value based on the received reference command value, common correction value SOC_0, and its own SOC_1. The first SB control unit 23a controls the DC-DC converter 22a based on the generated current command value. Specifically, in the case of a discharge instruction, the reference command value is multiplied by the correction value 1 (SOC_1/SOC_0) to calculate the current command value. In the case of the charging instruction, the reference command value is multiplied by the correction value 1 (SOC_0/SOC_1) or the correction value 1 (2-SOC_1/SOC_0) to generate the current command value. Similarly, the second SB control unit 23b receives the reference command value and the common correction value SOC_0, and generates its own current command value based on the received reference command value, common correction value SOC_0, and its own SOC_2. The second SB control unit 23b controls the DC-DC converter 22b based on the generated current command value.

FIG. 5 is a diagram illustrating an example of a command value notification timing from the common control unit 32 to the first SB control unit 23a and the second SB control unit 23b according to the third embodiment. In the example shown in FIG. 5, the common control unit 32 notifies the reference command value to the first SB control unit 23a and the second SB control unit 23b at, for example, 100 msec intervals. In addition, the common control unit 32 notifies the first SB control unit 23a and the second SB control unit 23b of the common correction value, for example, at intervals of several minutes.

FIGS. 6A and 6B are diagrams illustrating current command values for the first power storage device 20a and the second power storage device 20b according to the third embodiment. FIG. 6A is a diagram showing the relationship between the reference command value, the correction value 1 and the correction value 2 generated when the first power storage device 20a and the second power storage device 20b are instructed to perform a discharge. FIG. 6B is a diagram showing the relationship between the reference command value, the correction value 1 and the correction value 2 generated when the first power storage device 20a and the second power storage device 20b are instructed to charge.

In the example shown in FIGS. 6A and 6B, the SOC of the power storage unit 21a is the same as that in FIGS. 3A and 3B and FIGS. 4A and 4B. It is assumed that the state is larger than the SOC of. On this assumption, in the case of a discharge instruction, the correction value 1 is defined by the ratio (SOC_1/SOC_0) of the SOC_1 of the power storage unit 21a to the common correction value SOC_0, and the correction value 2 is the ratio of the SOC_2 of the power storage unit 21b to the common correction value SOC_0 ( SOC_2/SOC_0). In the case of the charge instruction, correction value 1 is defined by the ratio (SOC_0/SOC_1) of common correction value SOC_0 to SOC_1 of power storage unit 21a, and correction value 2 is the ratio (SOC_0/SOC_2) of common correction value SOC_0 to SOC_2 of power storage unit 21b. ).

As described above, according to the third embodiment, the same effect as that of the second embodiment is obtained. Further, since the correction value can be made common, the communication amount can be further compressed as compared with the first and second embodiments.

(Example 4)
The process according to the fourth embodiment is the same as the process according to the third embodiment until the reference command values for the first power storage device 20a and the second power storage device 20b are generated. The common control unit 32 generates SOC_0 obtained by averaging SOC_1 acquired from the first SB control unit 23a and SOC_2 acquired from the second SB control unit 23b as a common correction value. In the fourth embodiment, a new common correction value is generated when at least one of SOC_1 and SOC_2 used at the time of generating the previous common correction value changes by a predetermined value or more. Therefore, a new common correction value is not generated while the changes in the values of SOC_1 and SOC_2 are small.

The common control unit 32 transmits the reference command value to the first power storage device 20a and the second power storage device 20b via the communication line 50 at a predetermined transmission frequency. Further, when the new common correction value SOC_0 is generated, the common control unit 32 transmits the common correction value SOC_0 to the first power storage device 20a and the second power storage device 20b.

FIG. 7 illustrates a command value notification timing from the common control unit 32 to the first SB control unit 23a and the second SB control unit 23b, and a common control unit 32 from the first SB control unit 23a and the second SB control unit 23b according to the fourth embodiment. It is a figure which shows an example of the SOC notification timing to. In the example shown in FIG. 7, the common control unit 32 notifies the reference command value to the first SB control unit 23a and the second SB control unit 23b at, for example, 100 msec intervals. The first SB control unit 23a and the second SB control unit 23b notify the common control unit 32 of SOC_1 and SOC_2, for example, at 1 second intervals. When the change in at least one of SOC_1 and SOC_2 becomes larger than a predetermined value, the common control unit 32 generates a common correction value SOC_0 and notifies the first SB control unit 23a and the second SB control unit 23b.

FIGS. 8A to 8C are transition examples of SOC_1 of the power storage unit 21a and SOC_2 of the power storage unit 21b and updating of current command values of the first power storage device 20a and the second power storage device 20b according to the fourth embodiment. It is a figure which shows an example. 8B shows current command values of the first power storage device 20a and the second power storage device 20b before the command value is updated, and FIG. 8C shows the first power storage device 20a and the second power storage after the command value is updated. The respective current command values of the device 20b are shown. When common control unit 32 detects that SOC_1 of power storage unit 21a shown in FIG. 8A has decreased by a predetermined value (ΔSOC), common control unit 32 generates a new common correction value SOC_0, and first SB control unit 23a and second SB control are performed. Notify the section 23b.

As described above, according to the fourth embodiment, the same effect as that of the third embodiment can be obtained. Further, the correction value is updated and notified not when the SOC is regulated but when the SOC changes by a predetermined value or more. Therefore, while suppressing an increase in communication amount, it is possible to accurately follow the SOC variation and accurately distribute the required total charge/discharge amount between the first power storage device 20a and the second power storage device 20b.

(Example 5)
In the fifth embodiment, when one of the power storage devices 20 cannot be charged/discharged according to the command value, the common control unit 32 determines the necessary total charge/discharge amount according to the SOC of the power storage unit 21a and the power storage unit 21b. The command value is updated by redistribution to the power storage unit 21b. The common control unit 32 notifies the updated reference command value and correction value to the first power storage device 20a and the second power storage device 20b. The case where the power storage device 20 cannot be charged/discharged according to the command value means that the charge/discharge amount reaches the upper limit value or the lower limit value and is operated by being clipped at the upper limit value or the lower limit value, or the protection of the power storage device 20 side is performed. Depending on the function, the case where charging is prohibited or discharging is prohibited is applicable.

The common control unit 32 recognizes the state in which the power storage device 20 cannot be charged/discharged according to the command value by receiving a notification from the power storage device 20. In addition, by managing the SOC of each power storage device 20 on the side of the common control unit 32, it is possible to estimate whether or not the device cannot operate according to the command value.

When the charge/discharge amount of the first power storage device 20a or the second power storage device 20b is clipped to the upper limit value or the lower limit value and is operating, the common control unit 32 sets the charge/discharge amount of the clipped power storage device 20. With the upper limit value or the lower limit value fixed, the current command values for the first power storage device 20a and the second power storage device 20b are recalculated and the correction values are updated.

FIG. 9 is a diagram illustrating an example of a command value notification timing from the common control unit 32 to the first SB control unit 23a and the second SB control unit 23b according to the fifth embodiment. In the example shown in FIG. 9, the common control unit 32 notifies the reference command value to the first SB control unit 23a and the second SB control unit 23b at, for example, 100 msec intervals. Further, when the common control unit 32 receives from the first SB control unit 23a a limit notification indicating that the upper limit value or the lower limit value is reached and the clip operation is switched to, the common control unit 32 changes the current command value of the first power storage device 20a to the upper limit value or the lower limit value. To the value corresponding to. The common control unit 32 updates the current command value of the second power storage device 20b by subtracting the updated current command value of the first power storage device 20a from the current command value corresponding to the required total charge/discharge amount. The common control unit 32 updates the correction value 1 based on the reference command value and the current command value of the first power storage device 20a, and the correction value 2 based on the reference command value and the current command value of the second power storage device 20b. And the updated correction value 1 and correction value 2 are notified to the first SB control unit 23a and the second SB control unit 23b, respectively.

FIG. 10 is a diagram illustrating current command values for the first power storage device 20a and the second power storage device 20b according to the fifth embodiment. In the region where the discharge power of the first power storage device 20a is clipped to the upper limit value, the increase of the total discharge power is entirely covered by the increase of the discharge power of the second power storage device 20b.

When the number of power storage devices 20 is three or more, the increase in the total discharge power is covered by the increase in the discharge power of two or more power storage devices 20 that are not clipped. At that time, the two or more power storage devices 20 that are not in the clipping operation may increase the discharge power according to the SOC ratio, or the power storage device 20 with the highest SOC may increase the increase in the discharge power. You may pay. In the case of charging, power storage device 20 with the lowest SOC may cover all the increase in charging power.

As described above, according to the fifth embodiment, the same effect as that of the first embodiment can be obtained. Furthermore, in the fifth embodiment, even if the power storage device 20 that has reached the upper limit value or the lower limit value of the charge/discharge amount occurs, the required total charge/discharge amount can be secured.

(Example 6)
In the sixth embodiment, when the charging/discharging power of any one of the power storage devices 20 reaches the predetermined lower limit value, the common control unit 32 excludes the power storage device 20 that has reached the lower limit value from the distribution target, and the remaining power storage devices. At 20, the command value for distributing the required total charge/discharge amount is updated. For example, when the number of connected power storage devices 20 is N and one unit reaches the lower limit, the common control unit 32 divides the required total charge/discharge amount by (N-1) to obtain a new reference command value. To generate. Further, the common control unit 32 generates, based on the new reference command value, each correction value of the power storage device 20 according to each SOC of the (N-1) power storage devices 20 that have not reached the lower limit value. To do. It should be noted that power storage device 20 that has reached the lower limit may be notified of a stop instruction or a current command value of O[A].

The lower limit value of the charging/discharging power according to the sixth embodiment is not a value based on the battery specifications shown in the fifth embodiment, but is set to a value considering the power consumption for driving the DC-DC converter 22. For example, in the configuration in which the drive power of the DC-DC converter 22 is supplied from the power storage unit 21, when the drive power amount of the DC-DC converter 22 is larger than the power amount of the power storage unit 21, the charging operation is performed. This is a negative operation for power storage unit 21. Therefore, the lower limit value of the charging/discharging power according to the sixth embodiment is set to a value higher than at least the power consumption of the DC-DC converter 22.

FIG. 11 is a diagram illustrating current command values for the first power storage device 20a and the second power storage device 20b according to the sixth embodiment. In the region where the discharge power of the second power storage device 20b is lower than the lower limit value, the increase of the total discharge power is entirely covered by the increase of the discharge power of the first power storage device 20a. If the number of power storage devices 20 is three or more, the increase in the total discharge power is covered by the increase in the discharge power of two or more power storage devices 20 that have not reached the lower limit value. At that time, the two or more power storage devices 20 that have not reached the lower limit may increase the discharge power in accordance with the SOC ratio, or the power storage device 20 with the highest SOC may increase the discharge power. You may cover all. In the case of charging, power storage device 20 with the lowest SOC may cover all the increase in charging power.

As described above, according to the sixth embodiment, the same effect as that of the first embodiment can be obtained. Further, in the sixth embodiment, it is possible to prevent the efficiency of the entire system from being lowered due to the occurrence of the power storage device 20 whose charge/discharge power is lower than the lower limit value.

The present invention has been described above based on the embodiment. It is understood by those skilled in the art that the embodiments are exemplifications, that various modifications can be made to the combinations of the respective constituent elements and the respective processing processes, and that the modifications are within the scope of the present invention. ..

12A to 12C are diagrams showing current command values of the first power storage device 20a and the second power storage device 20b according to the first modification. Modification 1 is an example in which the first embodiment is improved. As shown in FIG. 12A, in the first embodiment, in the area A1 where the charging/discharging power is close to 0, power interchange (cross current) occurs between the first power storage device 20a and the second power storage device 20b. That is, a part of the electric power discharged by the first power storage device 20a is charged in the second power storage device 20b. Although the power interchange contributes to the leveling of the SOC, a loss occurs in the DC-DC converter 22a and the DC-DC converter 22b, so that the total amount of stored electricity decreases before and after the interchange.

Therefore, as shown in FIG. 12B, in a region A1 where electric power is exchanged between the first power storage device 20a and the second power storage device 20b, a correction value generated by reducing the offset amount at a predetermined ratio is used. Further, the correction value generated by the processing according to the second embodiment may be used. As a result, it is possible to prevent power interchange between the first power storage device 20a and the second power storage device 20b. Further, since it is not necessary to stop the power storage device 20 in order to prevent power interchange, a delay due to start/stop at the time of charging/discharging transition does not occur, and seamless operation is possible.

FIG. 12C is an example in which the region where the correction value generated by subtracting the offset amount at a predetermined ratio is used is set to a region A2 wider than the region A1 where power interchange occurs. In this example, before the discharge power of the first power storage device 20a reaches the power corresponding to the total current target value, the control is switched to the control using the correction value generated by subtracting the offset amount at a predetermined ratio. Accordingly, it is possible to more reliably prevent power interchange between the first power storage device 20a and the second power storage device 20b, and it is possible to perform a more seamless operation.

13A and 13B are diagrams showing current command values of the first power storage device 20a and the second power storage device 20b according to the second modification. Modification 2 is another modification of the first embodiment. As shown in FIG. 13A, when the discharge power of the first power storage device 20a becomes larger than the maximum output point, the total current target value and the total discharge amount of the first power storage device 20a and the second power storage device 20b are actually discharged. The electric current deviates.

Therefore, as shown in FIG. 13B, when the current command value generated by adding the received reference command value and correction value 1 exceeds the maximum output point, the first power storage device 20a maximizes its own charge/discharge power. Clip to the output point. That is, its own input/output power is saturated. In a region where the reference command value and the correction value 1 exceed the maximum output of the first power storage device 20a, the common control unit 32 compensates the charge/discharge amount of the first power storage device 20a due to the saturation of the first power storage device 20a. The shortage is assigned to the second power storage device 20b. Accordingly, it is possible to prevent the deviation between the total current target value and the total current that the first power storage device 20a and the second power storage device 20b are actually discharged, and realize linear control.

FIG. 14: is a figure which shows another structural example of the electrical storage system 1 which cooperated with the photovoltaic power generation system 10 which concerns on embodiment of this invention. In the configuration shown in FIG. 1, the example in which the common control unit is provided in the power conversion device 30 has been described, but the common control unit may be provided in the control device 60 independent of the power conversion device 30. Further, the common control unit may be provided in the first power storage device 20a or the second power storage device 20b.

In the above embodiment, when excess power is generated in the DC bus 40, excess power is generated by instructing the first SB control unit 23a and the second SB control unit 23b to decrease the discharge amount or increase the charge amount when the excess power is generated. The control for canceling the electric power has been described. In this respect, the control unit 13 of the solar power generation system 10 may be instructed to suppress the power generation amount of the solar cell 11. In this case, the total amount of charge/discharge required to charge/discharge the first power storage device 20a and the second power storage device 20b is a value after subtracting the power generation amount suppression amount of the solar cell 11.

Further, in the above embodiment, an example in which the power storage system 1 cooperates with the solar power generation system 10 has been described. In this respect, the above control can be applied even in a configuration that does not cooperate with the solar power generation system 10. In this case, the power storage unit 21a and the power storage unit 21b are charged only from the grid 4.

The embodiment may be specified by the following items.

[Item 1]
A plurality of power storage devices (20a, 20b) connected in parallel,
The plurality of power storage devices (20a, 20b) are connected to the plurality of power storage devices (20a, 20b) by a communication line (50), and the total amount of electric power to be charged or discharged by the plurality of power storage devices (20a, 20b) is determined by the plurality of power storage devices (20a, 20b) Each power storage device determined based on the state of charge of the plurality of power storage devices (20a, 20b) while transmitting to the plurality of power storage devices (20a, 20b) a reference value corresponding to the amount of power divided by the number of A control device (32/60) for transmitting a correction value for correcting the reference value for (20a, 20b) to each power storage device (20a, 20b),
The power storage system (1), wherein the control device (32/60) transmits the correction value at a frequency lower than the frequency of transmission of the reference value.
According to this, it is possible to control the distribution of the charge/discharge amount according to the charge state while suppressing an increase in the communication amount.
[Item 2]
The control device (32/60) determines a correction ratio with respect to the reference value of each power storage device (20a, 20b) based on the charge states of the plurality of power storage devices (20a, 20b), and the determined correction ratio To each power storage device (20a, 20b),
The power storage system according to item 1, wherein each power storage device (20a, 20b) determines a charge/discharge amount based on a reference value and a correction ratio received from the control device (32/60). 1).
According to this, by defining the correction value as a ratio, it is possible to issue a command with higher accuracy than in the case of defining by the difference.
[Item 3]
The control device (32/60) generates a common correction value that averages the state of charge of the plurality of power storage devices (20a, 20b), and uses the generated common correction value as the plurality of power storage devices (20a, 20a, 20b). 20b),
Each of the power storage devices (20a, 20b) is characterized by determining the charge/discharge amount based on the reference value received from the control device (32/60), a common correction value, and its own charge state. The power storage system (1) according to item 1.
According to this, the communication amount can be further compressed by making the correction value common in addition to the reference value.
[Item 4]
Each of the plurality of power storage devices (20a, 20b) periodically transmits its own charge state to the control device (32/60),
The control device (32/60) generates the correction value when the state of charge of at least one power storage device (20a, 20b) changes by a predetermined value or more, and the generated correction value is used as the plurality of power storage devices (20a). 20b), the power storage system (1) according to any one of Items 1 to 3.
According to this, the frequency of transmission of the correction value can be reduced, and the communication amount can be further compressed.
[Item 5]
When the charging/discharging amount of one of the power storage devices (20a) is clipped to the upper limit value or the lower limit value, the control device (32/60) sets the charging/discharging amount of the power storage device (20) to the upper limit value or the upper limit value. The power storage system (1) according to any one of items 1 to 3, wherein the reference value and the correction value are generated in a state of being fixed to the lower limit value.
According to this, even when the charging/discharging amount of any one of the power storage devices (20a) is clipped to the upper limit value or the lower limit value, the entire charging/discharging amount can be maintained at a desired power amount.
[Item 6]
When one of the power storage devices (20b) is stopped or the charge/discharge amount of the power storage device (20b) is lower than the lower limit, the control device (32/60) excludes the power storage device (20b) from the reference value. 4. The power storage system (1) according to any one of items 1 to 3, wherein the correction value is generated.
According to this, even if one of the power storage devices (20b) is stopped or the charge/discharge amount of the power storage device (20b) is lower than the lower limit value, the entire charge/discharge amount is maintained at a desired power amount. You can
[Item 7]
A control device (32/60) connected to a plurality of power storage devices (20a, 20b) connected in parallel by a communication line (50),
The reference value corresponding to the electric energy obtained by dividing the total electric energy to be charged or discharged by the plurality of power storage devices (20a, 20b) by the number of the plurality of power storage devices (20a, 20b) is set to the plurality of power storage devices (20a). , 20b), and a correction value for correcting the reference value for each power storage device determined based on the state of charge of the plurality of power storage devices (20a, 20b) from the transmission frequency of the reference value. A control device (32/60) characterized by transmitting to each power storage device (20a, 20b) with low frequency.
According to this, it is possible to control the distribution of the charge/discharge amount according to the charge state while suppressing an increase in the communication amount.
[Item 8]
A power storage device (20a) connected in parallel to at least one other power storage device (20b) and connected to a control device (32/60) by a communication line (50),
It corresponds to the amount of electric power obtained by dividing the total amount of electric power to be charged or discharged by the plurality of power storage devices (20a, 20b) by the number of the plurality of power storage devices (20a, 20b) from the control device (32/60). A correction value for receiving the reference value and correcting the reference value for each power storage device (20a, 20b) determined based on the state of charge of the plurality of power storage devices (20a, 20b) is used as the reference value. The power storage device (20a), wherein the power storage device (20a) is characterized in that it is received at a frequency lower than the reception frequency and the charge/discharge amount is determined based on the received reference value and correction value.
According to this, it is possible to control the distribution of the charge/discharge amount according to the charge state while suppressing an increase in the communication amount.

DESCRIPTION OF SYMBOLS 1 power storage system, 4 systems, 5 load, 10 solar power generation system, 11 solar cell, 12 DC-DC converter, 13 control part, 20a 1st power storage device, 21a power storage part, 211a storage battery, 212a monitoring part, 22a DC- DC converter, 23a control unit, 20b second power storage device, 21b power storage unit, 211b storage battery, 212b monitoring unit, 22b DC-DC converter, 23b control unit, 30 power conversion device, 31 inverter, 32 control unit, 40 DC bus, 50 communication lines, 60 control devices.

Claims (8)

A plurality of power storage devices connected in parallel to the DC bus ,
An inverter connected between the DC bus and the power system,
The plurality of power storage devices are connected to the plurality of power storage devices by a communication line, and a reference value corresponding to a power amount obtained by dividing a total power amount to be charged or discharged by the plurality of power storage devices by the number of the plurality of power storage devices. And a control device for transmitting to each power storage device a correction value for correcting the reference value of each power storage device determined based on the state of charge of the plurality of power storage devices,
The power storage system, wherein the control device transmits the correction value with a frequency less than the frequency with which the reference value is transmitted. The control device determines a correction ratio for the reference value of each power storage device based on the state of charge of the plurality of power storage devices, and transmits the determined correction ratio to each power storage device,
The power storage system according to claim 1, wherein each power storage device determines a charge/discharge amount based on a reference value and a correction ratio received from the control device. The control device generates a common correction value that averages the charging states of the plurality of power storage devices, and transmits the generated common correction value to the plurality of power storage devices,
The power storage system according to claim 1, wherein each power storage device determines a charge/discharge amount based on a reference value received from the control device, a common correction value, and its own charge state. Each of the plurality of power storage devices periodically transmits its own charge state to the control device,
The control device generates the correction value when the state of charge of at least one power storage device changes by a predetermined value or more, and transmits the generated correction value to the plurality of power storage devices. The power storage system according to any one of 3 above. When the charge/discharge amount of one of the power storage devices is clipped to the upper limit value or the lower limit value, the control device fixes the charge/discharge amount of the power storage device to the upper limit value or the lower limit value, and the reference The power storage system according to claim 1, wherein a value and the correction value are generated. The control device generates the reference value and the correction value excluding the power storage device when one of the power storage devices is stopped or the charge/discharge amount of the power storage device is lower than a lower limit value. Item 5. The power storage system according to any one of items 1 to 3. A control device in which a DC bus connected to an inverter connected to a power system is connected to a plurality of power storage devices connected in parallel by a communication line,
Charging the plurality of power storage devices while transmitting to the plurality of power storage devices a reference value corresponding to the amount of power obtained by dividing the total amount of power to be charged or discharged by the plurality of power storage devices by the number of the plurality of power storage devices. A control device, wherein a correction value for correcting the reference value for each power storage device determined based on a state is transmitted to each power storage device at a frequency lower than the frequency of transmitting the reference value. A power storage device, which is connected in parallel to at least one other power storage device to a DC bus to which an inverter connected to a power system is connected, and is connected to a control device via a communication line,
From the control device, a reference value corresponding to the amount of electric power obtained by dividing the total amount of electric power to be charged or discharged by the plurality of power storage devices by the number of the plurality of power storage devices is received, and the charging states of the plurality of power storage devices are received. The correction value for correcting the reference value for each power storage device determined based on is received at a frequency less than the reception frequency of the reference value, and the charge/discharge amount is received based on the received reference value and the correction value. A power storage device characterized by determining.

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