Power distribution system and control method for cluster

Abstract

To realize a power distribution system capable of mitigating excess or deficiency in power demand within a cluster through cooperation between the clusters.SOLUTION: In a power distribution system (100) in which a plurality of clusters (1A, 1B, 1C) are connectable to each other via an interconnection bus (9), a control device (10A) of the cluster (1A) independently operates its own cluster by controlling a switch (50A) to be in an open state under normal conditions, controls a power storage device (20A) so that voltage of a DC bus becomes a predetermined transmission request voltage, temporarily turns the switch into the closed state to apply the voltage of the DC bus to the interconnection bus as a power transmission request signal when voltage of the DC bus reaches or exceeds a predetermined upper limit voltage, controls the switch to be in the closed state, and operates its own cluster in cooperation with another cluster when the other cluster that responds to the power transmission request signal exists.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power distribution system consisting of a plurality of clusters and a method for controlling the clusters. [Background technology]

[0002] A power distribution system equipped with distributed power sources has been proposed. Patent Document 1 discloses a technique relating to an operation method of an energy system as such a power distribution system, in which a power generation device, a power storage device, and a load are connected to a direct current line (DC bus). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-92363 Summary of the Invention [Problem to be solved by the invention]

[0004] A series of such local power systems in which power generation devices, power storage devices, loads, etc. are connected to a DC bus is also called a cluster. Because such clusters are relatively small systems, there may be a surplus or shortage of power supply and demand within the cluster that cannot be handled by the cluster alone. In view of this problem, one aspect of the present disclosure aims to realize a power distribution system that can reduce the surplus or shortage of power supply and demand within a cluster by enabling power interchange between clusters when necessary. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, a power distribution system according to one embodiment of the present disclosure is a power distribution system in which multiple clusters are connected to each other via an interconnection bus, and the clusters include a DC bus, a power generation device, a power storage device, and a load connected to the DC bus, a switch that opens and closes the connection between the DC bus and the interconnection bus, and a control device. The control device normally controls the switch to an open state to operate the own cluster independently, and when the voltage of the DC bus reaches or exceeds a predetermined upper limit voltage, if no voltage is applied to the interconnection bus, the control device controls the power storage device to make the voltage of the DC bus a predetermined power transmission request voltage and then temporarily closes the switch to apply the voltage of the DC bus to the interconnection bus. If there is another cluster that has responded to the power transmission request signal, the control device controls the switch to a closed state to operate the own cluster in cooperation with the other cluster.

[0006] In order to solve the above problem, a cluster control method according to one embodiment of the present disclosure is a control method for a cluster in a power distribution system in which a plurality of clusters are connected to each other via a coordination bus, wherein the cluster includes a DC bus, a power generation device, a power storage device, and a load connected to the DC bus, and a switch that opens and closes the DC bus and the coordination bus. Under normal circumstances, the switch is controlled to an open state to operate the cluster independently. When the voltage of the DC bus reaches or exceeds a predetermined upper limit voltage, if no voltage is applied to the coordination bus, the switch controls the power storage device to raise the voltage of the DC bus to a predetermined power transmission request voltage, and then temporarily closes the switch to apply the voltage of the DC bus to the coordination bus. If there is another cluster that has responded to the power transmission request signal, the switch is controlled to a closed state to operate the cluster in coordination with the other cluster. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to realize a power distribution system that can reduce excesses and shortages in power supply and demand within a cluster through cooperation between clusters. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 illustrates a power distribution system according to an embodiment of the present disclosure. [Figure 2] 2 is a diagram for explaining the relationship between a cluster voltage (voltage of a DC bus) and the operation of each device in a cluster that constitutes the power distribution system. FIG. [Figure 3] 10 is a flowchart illustrating the operation of the cluster. [Figure 4] This is a subroutine of the power reception request mode in the flowchart. [Figure 5] This is a subroutine of the power transmission request mode in the flowchart. [Figure 6] This is a subroutine of the basic mode in the above flowchart. [Figure 7] FIG. 10 is a diagram showing the transition of cluster voltages in relation to the operation of a power transmission request. [Figure 8] FIG. 10 is a diagram for explaining operations regarding a power transmission request in each cluster. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below. However, the following description is merely an example of a power distribution system according to the present invention, and the technical scope of the present invention is not limited to the following description and the contents of the drawings.

[0010] <Outline of Power Distribution System 100> Fig. 1 is a block diagram showing an outline of the configuration of a power distribution system 100 according to one embodiment of the present invention. The power distribution system 100 is composed of a plurality of clusters 1 and a linking bus 9 that can connect the clusters 1. Of the plurality of clusters 1 included in the power distribution system 100, Fig. 1 shows cluster 1A, cluster 1B, and cluster 1C.

[0011] The notation "cluster 1" also collectively refers to cluster 1A, cluster 1B, and cluster 1C. In the following, when the symbols indicating the parts of a cluster end with letters A to C, they represent the parts of clusters 1A to 1C, respectively. When the symbols indicating the parts of a cluster do not end with letters A to C, they are collectively referred to as the parts, just like the notation "cluster 1."

[0012] <Configuration of Cluster 1> The configuration of cluster 1A will be explained in detail below, but the configurations of the other clusters are similar to that of cluster 1A.

[0013] Cluster 1A includes a control device 10A that controls each part of cluster 1A. Cluster 1A includes a DC bus 90A, which is a direct current circuit, and a switch 50A that opens and closes between the interconnection bus 9 and the DC bus 90A. The opening and closing operation of switch 50A is controlled by the control device 10A.

[0014] When the switch 50A is open, the DC bus 90A of cluster 1A is disconnected from the interconnection bus 9, and cluster 1A operates independently from other clusters (1B, 1C, etc.). When the switch 50 is open in all clusters 1 connected to the interconnection bus 9, there is no power source that applies voltage to the interconnection bus 9, and the grid voltage Vg, which is the voltage of the interconnection bus 9, is 0.

[0015] A first measuring instrument 91A is provided on the interconnection bus 9 side of the switch 50A to measure the grid voltage Vg, which is the voltage of the interconnection bus 9, and the current flowing in and out of the DC bus 90A from the interconnection bus 9. A second measuring instrument 92A is also provided on the DC bus 90A to measure the cluster voltage Vc, which is the voltage of the DC bus 90A. The control device 10A can obtain the grid voltage Vg from the first measuring instrument 91A and the cluster voltage Vc of the cluster 1A from the second measuring instrument 92A.

[0016] The measurement of the current Idc flowing in and out of the coordination bus 9 to the DC bus 90A may be performed by the second measuring instrument 92A instead of the first measuring instrument 91A. The control device 10A may acquire the current Idc using the first measuring instrument 91A or the second measuring instrument 92A. When the control device 10A detects the current flowing from the DC bus 90A to the coordination bus 9 as the current Idc, it determines that the transmission power Pout transmitted by the cluster 1A to the coordination bus 9 side is positive. When the control device 10A detects the current flowing from the coordination bus 9 to the DC bus 90A as the current Idc, it determines that the receiving power Pin received by the cluster 1A from the coordination bus 9 side is positive.

[0017] Cluster 1A also includes a power storage device 20A, a solar power generation device 30A (an example of a power generation device), and an EV system 40A (an example of a load), all of which are connected to a DC bus 90A. Note that, in addition to the devices shown in FIG. 1, many more devices, such as loads and other power generation devices, may be connected to DC bus 90A of cluster 1A.

[0018] The power storage device 20A is a device that receives power from the DC bus 90A, stores the power, and supplies the stored power to the DC bus 90A. The power storage device 20A has a switch 21A, a DC-DC converter 22A connected to the DC bus 90A via the switch 21A, and a storage battery 23A that charges and discharges under the control of the DC-DC converter 22A.

[0019] The power storage device 20A has a function of measuring the cluster voltage Vc of the connected DC bus 90A, and can autonomously determine an operation based on the measured cluster voltage Vc and perform charging and discharging operations. Alternatively, the power storage device 20A can operate according to instructions from the control device 10A. Note that the power storage device 20A may be configured to acquire the cluster voltage Vc measured by the second measuring device 92A, rather than measuring the cluster voltage Vc by itself.

[0020] The solar power generation device 30A is a device that can supply power generated by a solar panel 33A to a DC bus 90A. The solar power generation device 30A has a switch 31A, a DC-DC converter 32A connected to the DC bus 90A via the switch 31A, and a solar panel 33A that receives sunlight and generates power under the control of the DC-DC converter 32A.

[0021] The solar power generation apparatus 30A has a function of measuring the cluster voltage Vc of the connected DC bus 90A, and can autonomously determine the amount of power generation to be output to the DC bus 90A. Alternatively, the solar power generation apparatus 30A can operate according to instructions from the control apparatus 10A. Note that instead of measuring the cluster voltage Vc by itself, the solar power generation apparatus 30A may be configured to acquire the cluster voltage Vc measured by the second measuring instrument 92A.

[0022] As described above, EV system 40A is an example of a load, and consumes power received from DC bus 90A. EV system 40A has switch 41A, charging control unit 42A connected to DC bus 90A via switch 41A, and secondary battery 43A that is charged under the control of charging control unit 42A. In EV system 40A, secondary battery 43A is mounted on an electric vehicle (EV), and charging control unit 42A is mounted on the electric vehicle (EV) or EV charging equipment.

[0023] The EV system 40A has a function for measuring the cluster voltage Vc of the connected DC bus 90A and can determine whether or not to receive power from the DC bus 90A based on the cluster voltage Vc. Alternatively, the EV system 40A can determine whether or not to receive power in accordance with instructions from the control device 10A. Note that the EV system 40A may be configured to acquire the cluster voltage Vc measured by the second measuring device 92A, rather than measuring the cluster voltage Vc itself.

[0024] <Basic operation> When each cluster 1 is operated independently from other clusters 1, if the power supply and demand within the cluster 1 tends to be insufficient, the cluster voltage Vc drops, and if the power supply and demand within the cluster 1 tends to be in surplus, the cluster voltage Vc rises. Each device connected to the DC bus 90 in each cluster 1 is set to perform a basic operation according to the cluster voltage Vc having such characteristics. Figure 2 is a diagram for explaining the definition of such a basic operation.

[0025] When the cluster voltage Vc deviates from a predetermined range, each device connected to the DC bus 90, such as the power storage device 20, the solar power generation device 30, and the EV system 40, stops operating to protect the grid. As shown in FIG. 2, this predetermined range is equal to or greater than the device shutdown low voltage Vstlow and less than the device shutdown high voltage Vsthigh.

[0026] The EV system 40, which is a load, is allowed to receive power from the DC bus 90 and consume the received power to operate when the cluster voltage Vc is within the specified range. When the cluster voltage Vc deviates from the specified range, at least one of the switch 21 of the power storage device 20, the switch 31 of the solar power generation device 30, and the switch 41 of the EV system 40 may be configured to be open (OFF).

[0027] When the cluster voltage Vc is within the above-mentioned predetermined range, the power storage device 20 supplies power from the storage battery 23 to the DC bus 90 by discharging the storage battery 23 if the cluster voltage Vc is relatively low, and charges the storage battery 23 by receiving power from the DC bus 90 if the cluster voltage Vc is relatively high. More specifically, the power storage device 20 discharges from the storage battery 23 when the condition of Vstlow≦Vc<V1 (where V1 is the discharge limit voltage) is satisfied, and charges the storage battery 23 when the condition of V2≦Vc<Vsthigh (where V2 is the charge limit voltage) is satisfied.

[0028] Here, the discharge limit voltage V1 is a voltage slightly lower than the rated voltage of the DC bus 90, and the charge limit voltage V2 is a voltage slightly higher than the rated voltage. Therefore, the power storage device 20 basically switches the charging and discharging operations so that the voltage of the DC bus 90 of cluster 1 (cluster voltage Vc) is maintained at the rated voltage.

[0029] When the cluster voltage Vc is within the above-mentioned predetermined range, the solar power generation device 30 operates to generate power according to solar radiation, except when the cluster voltage Vc becomes high up to near the upper limit of the above-mentioned predetermined range. Here, generating power according to solar radiation means that the solar panel 33 is controlled to generate power under the maximum efficiency condition according to solar radiation, that is, Maximum Power Point Tracking (MTTP) control is performed. Thus, in cluster 1, a principle is determined to utilize the power generation capacity of the solar power generation device 30 as much as possible, except when the cluster voltage Vc approaches the device stop high voltage Vsthigh.

[0030] More specifically, the solar power generation device 30 generates power according to solar radiation when the condition of Vstlow≦Vc<Vdisch (where Vdisch is the upper limit voltage) is satisfied, and suppresses power generation when the condition of Vdisch≦Vc<Vsthigh is satisfied. As described above, since the upper limit voltage Vdisch is a voltage close to the device stop high voltage Vsthigh, it is set to a voltage higher than the charge limit voltage V2. <0000​FIG. 2 also shows the state (mode) of cluster 1 recognized by the control device 10 when the cluster voltage Vc reaches each voltage value. Details of the state (mode) of cluster 1 will be described later.

[0032] <Outline of operation considering inter-cluster cooperation> Except when it is determined that power sharing with other clusters is better, the control device 10 of each cluster 1 sets the switch 50 to the open (OFF) state and operates its own cluster independently from other clusters. In this case, the control device 10 basically entrusts each device connected to the DC bus 90 to execute the above-described autonomous operation as defined. In this case, even if the control device 10 controls each device connected to the DC bus 90 by a centralized control method to make each device perform the same operation as the above-described autonomous operation, the operation of each device in cluster 1 may remain unchanged.

[0033] On the other hand, when the control device 10 determines, by monitoring the cluster voltage Vc and the grid voltage Vg, that its own cluster is in a situation where power sharing with other clusters is better, it attempts power sharing with other clusters and actually executes power sharing depending on the situation. The operation of cluster 1 under the control of such a control device will be described in detail using the flowcharts of FIGS. 3 to 6, but the outline is as follows. Hereinafter, cluster 1A will be described as the own cluster.

[0034] When the power in cluster 1A is insufficient and the cluster voltage Vc drops to a state close to the equipment stop low voltage Vstlow, the control device 10A shifts the operation mode of cluster 1A to the power reception request mode. More specifically, when the condition of Vstlow ≦ Vc < Vch (where Vch is the lower limit voltage) is satisfied, the control device 10A shifts the operation mode to the power reception request mode.

[0035] In the power reception request mode, cluster 1A sends a power reception request signal to the cooperation bus 9. If there are other clusters that respond to the power reception request signal, it connects to the other cluster via the cooperation bus 9 to cover the power shortage of cluster 1A. Thus, in the power distribution system 100, when a power shortage occurs in cluster 1A that is operating independently, power lending from other clusters is executed if possible. Note that since the lower limit voltage Vch is a voltage close to the device stop low voltage Vstlow, it is set to a voltage lower than the discharge limit voltage V1.

[0036] When the power is surplus within cluster 1A and the cluster voltage Vc rises until it approaches the device stop high voltage Vsthigh, the control device 10A shifts the operation mode of cluster 1A to the power transmission request mode. More specifically, when the condition of Vdisch ≦ Vc < Vsthigh is satisfied, the control device 10A shifts the operation mode to the power transmission request mode.

[0037] In the power transmission request mode, when power lending via the cooperation bus 9 by other clusters is not being performed, cluster 1A sends a power transmission request signal to the cooperation bus 9. If there are other clusters that respond to the power transmission request signal, it connects to the other cluster. The other cluster that responds to the power transmission request signal can be cluster 1 where the cluster voltage Vc is less than the upper limit voltage Vdisch. In the power transmission request mode, when other clusters are already performing power lending via the cooperation bus 9, the DC bus 90A of cluster 1A also connects to the cooperation bus 9 to participate in the power lending.

[0038] Thus, in the power distribution system 100, when power surplus occurs in the independently operated cluster 1A, it is attempted to supply power to other clusters as much as possible and make the most of the power generation opportunity of the solar power generation device 30 in cluster 1A. Also, in the power distribution system 100, even without a central control device that integrally controls each cluster 1, the power distribution system 100 composed of multiple clusters 1 is configured to function as a whole based on the judgment of the control device 10 of each cluster 1. Further, in the power distribution system 100, a dedicated communication line for linking the control devices 10 of each cluster 1 is not necessarily required, and the power distribution system is configured to function as a whole.

[0039] From the above, summarizing the magnitude relationship of each voltage value defined for the cluster voltage Vc, which is the voltage of the DC bus 90A of cluster 1, it becomes as follows as shown in FIG. 2. Vstlow (equipment stop low voltage) < Vch (lower limit voltage) < V1 (discharge limit voltage) < V2 (charge limit voltage) < Vdisch (upper limit voltage) < Vsthigh (equipment stop high voltage).

[0040] <Cluster operation: General> Next, referring to FIGS. 3 to 8, the details of the operation of cluster 1 (cluster 1A as the self-cluster) will be described. FIG. 3 is the main routine of the flowchart for explaining the operation of cluster 1A. FIG. 4 is the subroutine of the power reception request mode in the flowchart of FIG. 3. FIG. 5 is the subroutine of the power transmission request mode in the flowchart of FIG. 3. FIG. 6 is the subroutine of the basic mode in the flowchart of FIG. 3.

[0041] The power storage device 20A, the solar power generation device 30A, and the EV system 40A, which are devices connected to the DC bus 90A of cluster 1A, operate according to the above-described basic operation as a premise unless there is a direct instruction from the control device 10A. Therefore, the flowcharts in FIGS. 3 to 6 mainly describe the operation of the control device 10A and the operations other than the above-described basic operations of the devices connected to the DC bus 90A. When cluster 1A is in operation, cluster 1A repeatedly executes the operations shown in the flowchart of FIG. 3. At the start of the flowchart of FIG. 3, cluster 1A is operating independently from other clusters.

[0042] Step S1: First, the control device 10A determines whether the cluster voltage Vc is less than the device stop low voltage Vstlow. If it is determined that the cluster voltage Vc is less than the device stop low voltage Vstlow, the flow proceeds to step S2 (YES in S1). Otherwise, the flow proceeds to step S3 (NO in S1).

[0043] Step S2: The control device 10A recognizes that cluster 1A is in the low voltage stop mode ("low voltage stop" in FIG. 2). Since cluster 1A is in the state of Vc < Vstlow, each device connected to the DC bus 90A has autonomously stopped, and the control device 10A does not need to particularly control the operations of these devices. Next, the flow ends.

[0044] Step S3: The control device 10A determines whether the cluster voltage Vc is less than the lower limit voltage Vch. If it is determined that the cluster voltage Vc is less than the lower limit voltage Vch, the flow proceeds to step S4 (YES in S3). Otherwise, the flow proceeds to step S5 (NO in S3).

[0045] Step S4: At the transition to this step, it is in the state of Vstlow ≤ Vc < Vch ("power reception request" in FIG. 2), and the subroutine of the power reception request mode shown in FIG. 4 is executed. Next, the flow ends.

[0046] Step S5: The control device 10A determines whether the cluster voltage Vc is less than the upper limit voltage Vdisch. If it is determined that the cluster voltage Vc is less than the upper limit voltage Vdisch, the flow proceeds to step S6 (YES in S5). Otherwise, the flow proceeds to step S7 (NO in S5).

[0047] Step S6: When transitioning to this step, it is in the state of Vch ≦ Vc < Vdisch (the "basic" in FIG. 2), and the subroutine of the basic mode shown in FIG. 6 is executed. Next, the flow ends.

[0048] Step S7: The control device 10A determines whether the cluster voltage Vc is less than the device stop high voltage Vsthigh. If it is determined that the cluster voltage Vc is less than the device stop high voltage Vsthigh, the flow proceeds to step S8 (YES in S7). Otherwise, the flow proceeds to step S9 (NO in S7).

[0049] Step S8: When transitioning to this step, it is in the state of Vdisch ≦ Vc < Vsthigh (the "power transmission request" in FIG. 2), and the subroutine of the power transmission request mode shown in FIG. 5 is executed. Next, the flow ends.

[0050] Step S9: The control device 10A recognizes that cluster 1A is in the overvoltage stop mode (the "overvoltage stop" in FIG. 2). Since cluster 1A is in the state of Vsthigh ≦ Vc, each device connected to the DC bus 90A stops autonomously, and the control device 10A does not need to perform any special control on the operation of these devices. Next, the flow ends.

[0051] <Operation of the Cluster: Power Reception Request Mode> Step S401: At the beginning of the power reception request mode, the control device 10A determines whether a voltage is applied to the communication bus 9, that is, whether Vg > 0. If it is determined that Vg > 0, the subroutine of the power reception request mode ends (YES in S401). Otherwise, the flow proceeds to step S402 (NO in S401).

[0052] It is determined that a voltage is applied to the cooperation bus 9 when power sharing between other clusters via the cooperation bus 9 is being performed and when another cluster responds to a power transmission request (when reaching step S605). In the power distribution system 100, when performing cooperation between clusters 1, the number of clusters on the power receiving side is limited to one.

[0053] Step S402: The control device 10A controls the switch 50A to be closed (ON) to connect the DC bus 90A of cluster 1A to the cooperation bus 9. When reaching step S4 in the subroutine of the power receiving request mode, the cluster voltage Vc in the range of Vstlow ≤ Vc < Vch is applied to the cooperation bus 9. Such a voltage signal of the cooperation bus 9 is recognized as a power receiving request signal indicating a request for power supply to cluster 1 from another cluster 1.

[0054] When reaching step S605 in the subroutine of the power receiving request mode, the cluster voltage Vc in the range of Vch ≤ Vc < Vdisch is applied to the cooperation bus 9. Such a voltage signal of the cooperation bus 9 is recognized as a signal indicating a response to a power transmission request signal from another cluster (step S812).

[0055] Also, the control device 10A waits for a time required until another cluster recognizes a signal indicating a response to such a power receiving request signal or such a power transmission request signal from cluster 1A and the power supply from the other cluster via the cooperation bus 9 starts. When the power supply from the other cluster starts, a current flows from the cooperation bus 9 to the DC bus 90A. At this time, cluster 1A with insufficient power and another cluster 1 in a power surplus state are cooperatively operated as if they were one cluster while being connected via the cooperation bus 9.

[0056] Step S403: Next, the control device 10A determines whether the cluster 1A is receiving power from the coordination bus 9, that is, whether the received power Pin exceeds 0. If the received power Pin exceeds 0, step S403 is repeated (YES in S403). Otherwise, the flow proceeds to step S404 (NO in S403). Here, when the received power Pin is 0, this includes the case where there is no other cluster that responds to the power reception request signal, and the case where the received power Pin becomes 0 while coordinated operation is being performed.

[0057] Step S404: Next, the control device 10A controls the switch 50A to open (OFF) and disconnects the DC bus 90A of the cluster 1A from the coordination bus 9. In other words, the coordinated operation of the cluster 1A with other clusters ends. Next, the power request mode ends.

[0058] <Cluster Operation: Power Transmission Request Mode> Step S801: At the beginning of the power transmission request mode, the control device 10A determines whether a voltage equal to or higher than the device stop low voltage Vstlow is applied to the coordination bus 9, that is, whether Vstlow≦Vg. If it is determined that Vstlow≦Vg, the flow proceeds to step S802 (YES in S801). Otherwise, the flow proceeds to step S810 (NO in S801).

[0059] Here, cases where Vstlow≦Vg include the following: When power interchange is being performed between other clusters via the cooperation bus 9. When there is another cluster that has responded to the power transmission request signal from cluster 1A (step S605). In these cases, power transmission from cluster 1A to the other cluster can be executed in step S802 and thereafter.

[0060] Step S802: The control device 10A forcibly controls the power storage device 20A to control the voltage of the DC bus 90A so that the cluster voltage Vc coincides with the grid voltage Vg.

[0061] Step S803: When the cluster voltage Vc matches the grid voltage Vg, subsequently, the control device 10A controls the switch 50A to close (ON), and conducts the DC bus 90A of cluster 1A to the cooperation bus 9. At this time, since the voltage of the DC bus 90A of cluster 1A that starts to be connected to the cooperation bus 9 matches the grid voltage Vg, no sudden voltage fluctuations will occur in the DC bus 90 of the other cluster 1 that is already conducting with the cooperation bus 9.

[0062] Step S804: Subsequently, the control device 10A terminates the forced control of the power storage device 20A and returns the operation of the power storage device 20A to the original operation. In this way, cluster 1A with surplus power, the cooperation bus 9 including other clusters in a power shortage state, and other clusters that are already conducting will be operated integrally in a state connected via the cooperation bus 9.

[0063] Step S805: Subsequently, the control device 10A determines whether cluster 1A is transmitting power to the cooperation bus 9, that is, whether the transmitted power Pout exceeds 0. If the transmitted power Pout exceeds 0, step S805 is repeated (YES in S805). Otherwise, the flow proceeds to step S805 (NO in S805).

[0064] Step S806: The control device 10A controls the switch 50A to open (OFF) and disconnects the DC bus 90A of cluster 1A from the cooperation bus 9. That is, the cooperative operation of cluster 1A with other clusters ends. Next, the subroutine of the power transmission request mode ends.

[0065] Step S810: The control device 10A determines whether the cluster voltage Vc is greater than or equal to the upper limit voltage Vdisch and less than the device stop high voltage Vsthigh, that is, whether it satisfies Vdisch ≤ Vc < Vsthigh. If it is determined that this condition is satisfied, the flow proceeds to step S811 (YES in S810). Otherwise, the subroutine of the power transmission request mode ends (NO in S810).

[0066] [[ID=I9]] Step S811: The control device 10A forcibly controls the power storage device 20A to control the voltage of the DC bus 90A so that the cluster voltage Vc becomes the power transmission request voltage Vdisch_sig. Here, the power transmission request voltage Vdisch_sig is a voltage lower than the lower limit voltage Vch and is a predetermined voltage lower than the device stop low voltage Vstlow.

[0067] Step S812: When the cluster voltage Vc becomes the power transmission request voltage Vdisch_sig, the control device 10A then controls the switch 50A to temporarily close (ON) to connect the DC bus 90A of cluster 1A to the coordination bus 9. That is, the control device 10A closes (ON) the switch 50A, and then controls it to open (OFF) again after a predetermined time. In this way, the cluster voltage Vc, which has become the power transmission request voltage Vdisch_sig, is temporarily applied to the coordination bus 9. Such a voltage signal of the coordination bus 9 is recognized as a power transmission request signal, which is a signal indicating that other clusters are requested to accept power for transmission from cluster 1A.

[0068] Step S813: Subsequently, the control device 10A ends the forced control of the power storage device 20A, and returns the operation of the power storage device 20A to the normal operation.

[0069] 7 is a graph showing an example of the transition of the cluster voltage Vc of cluster 1A, including the period from step S810 to step S813. In FIG. 7, at time t1, voltage control of the DC bus 90A by the power storage device 20A is started (step S811). Also in FIG. 7, at time t2 after the cluster voltage Vc reaches the power transmission request voltage Vdisch_sig, the switch 50A is closed (ON), and at time t3, a predetermined time later, the switch 50A is opened (OFF). Thereafter, the voltage control operation of the power storage device 20A in response to a forced instruction from the control device 10A is released (step S813), and FIG. 7 shows how the cluster voltage Vc returns to a value close to that at time t1.

[0070] Step S814: Next, the control device 10A monitors the grid voltage Vg. When the control device 10A detects that a voltage has been applied to the coordination bus 9, i.e., that Vg > 0, the flow immediately returns to step S801. Such application of a voltage to the coordination bus 9 is a response from one of the other clusters in response to the power transmission request signal (step S605). Next, when the flow returns to step S801 and the condition Vstlow ≦ Vg is confirmed, power transmission from cluster 1A is executed in step S802 and thereafter. Note that in this step, if the grid voltage Vg remains 0 even after a predetermined time has elapsed, i.e., if no other cluster has responded to the power transmission request signal, the flow also returns to step S801.

[0071] <Cluster operation: Basic mode> Step S601: At the beginning of the basic mode, the control device 10A determines whether a voltage is applied to the coordination bus 9, i.e., whether Vg>0. If it is determined that Vg>0, the flow proceeds to step S602 (YES in S601). Otherwise, the basic mode subroutine ends (NO in S601).

[0072] Step S602: The control device 10A determines whether the grid voltage Vg is less than the device stop low voltage Vstlow. If it is determined that the grid voltage Vg is less than the device stop low voltage Vstlow, the flow proceeds to step S603 (YES in S602). Otherwise, the basic mode subroutine ends (NO in S602). Here, the grid voltage Vg is less than the device stop low voltage Vstlow when a power transmission request signal is output from another cluster (step S812).

[0073] Step S603: The control device 10A waits for a time period according to the cluster voltage Vc of the cluster 1A. Here, the wait time is set to be shorter as the cluster voltage Vc is lower, that is, as the power is insufficient.

[0074] Step S604: Subsequently, the control device 10A determines whether a voltage is applied to the cooperation bus 9, that is, whether Vg > 0. If it is determined that Vg > 0, the subroutine of the basic mode ends (YES in S604). Otherwise, the flow proceeds to step S605 (NO in S604). Here, when a voltage is applied to the cooperation bus 9, it means that there is another cluster that responded to the power transmission request signal earlier than cluster 1A, that is, there is another cluster that has a greater power shortage than cluster 1A.

[0075] Step S605: The subroutine of the power reception request mode shown in FIG. 4 is executed. The flow reaches step S605 when cluster 1A responds to the power transmission request signal. Thus, there is only one cluster 1 that can receive power from other clusters in response to the power transmission request signal. Next, the subroutine of the basic mode ends.

[0076] <Operation of each cluster regarding power transmission request> FIG. 8 is a diagram for schematically explaining the operations of each cluster 1 related to the operation of the power transmission request in time series. In reference numeral 801p in FIG. 8, cluster 1A is the cluster that executes the power transmission request and is in a state where Vdisch ≦ Vc. Also, cluster 1B and cluster 1C are clusters 1 that are operating independently at this point and are in a state where Vch ≦ Vc < Vdisch.

[0077] Next, as shown by reference numeral 802p in FIG. 8, cluster 1A operates the switch 50A to temporarily apply the power transmission request voltage Vdisch_sig to the cooperation bus 9, thereby sending out the power transmission request signal (step S812).

[0078] Next, as shown by reference numeral 803p in FIG. 8, clusters 1B and 1C that detected the power transmission request signal (YES in step S602) wait for a time corresponding to their own cluster voltage Vc, that is, perform a countdown (step S603).

[0079] 8, cluster 1B, which had the lower cluster voltage Vc, finishes the countdown first and operates switch 50B to connect DC bus 90B to interconnection bus 9 (steps S605 and S402). When the other cluster 1C detects that Vg > 0 at the end of the countdown, it cannot respond to the power transmission request signal and maintains independent operation (YES in step S604).

[0080] [Software implementation example] The functions of the control device 10 (hereinafter referred to as "device") can be realized by a program that causes a computer to function as the device. In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The functions described in each of the above embodiments are realized by executing the program using the control device and storage device.

[0081] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium. Furthermore, some or all of the functions of each of the control blocks may be realized by a logic circuit. For example, an integrated circuit in which a logic circuit functioning as each of the control blocks is formed is also included in the scope of the present invention. Alternatively, the functions of each of the control blocks may be realized by, for example, a quantum computer.

[0082] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0083] 〔summary〕 A first aspect of the present disclosure is a power distribution system in which multiple clusters are connected to each other via an interconnection bus, wherein the clusters include a DC bus, a power generation device, a power storage device, and a load connected to the DC bus, a switch that opens and closes the connection between the DC bus and the interconnection bus, and a control device. The control device normally controls the switch to an open state to operate its own cluster independently, and when the voltage of the DC bus exceeds a predetermined upper limit voltage, if no voltage is applied to the interconnection bus, the control device controls the power storage device to make the voltage of the DC bus a predetermined transmission request voltage and then temporarily closes the switch to apply the voltage of the DC bus to the interconnection bus. If there is another cluster that has responded to the power transmission request signal, the control device controls the switch to a closed state to operate its own cluster in cooperation with the other cluster.

[0084] The power distribution system of aspect 2 of the present disclosure may be configured in such a way that, in aspect 1 above, when the control device detects that the power transmission request signal has been output from another cluster to the coordination bus during the normal operation, it responds to the power transmission request signal by controlling the switch to a closed state if no voltage is applied to the coordination bus after a waiting time corresponding to the voltage of the DC bus.

[0085] The power distribution system of aspect 3 of the present disclosure may be configured in the above-mentioned aspect 1 or 2 such that, when the voltage of the DC bus becomes equal to or higher than a predetermined upper limit voltage, if a voltage is applied to the interconnection bus, the control device controls the storage device to make the voltage of the DC bus equal to the voltage of the interconnection bus, and then controls the switch to a closed state.

[0086] The power distribution system of aspect 4 of the present disclosure may be configured in any one of aspects 1 to 3 above, such that when the voltage of the DC bus falls below a predetermined lower limit voltage and no voltage is applied to the coordination bus, the control device closes the switch to apply the voltage of the DC bus to the coordination bus as a power receiving request signal, which is a signal indicating a request to another cluster to supply power to the own cluster, and if there is another cluster that responds to the power receiving request signal, continues to control the switch to the closed state to operate the own cluster in coordination with the other cluster.

[0087] A fifth aspect of the present disclosure provides a power distribution system in the fourth aspect, wherein the requested power transmission voltage is lower than the lower limit voltage.

[0088] In a power distribution system according to a sixth aspect of the present disclosure, in the fourth or fifth aspect described above, the power storage device may normally discharge when the voltage of the DC bus is below a predetermined discharge limit voltage and charge when the voltage is equal to or higher than a predetermined charge limit voltage, the discharge limit voltage being higher than the lower limit voltage, and the charge limit voltage being higher than the discharge limit voltage and lower than the upper limit voltage.

[0089] A seventh aspect of the present disclosure is a method for controlling a cluster in a power distribution system in which multiple clusters are connected to each other via an interconnection bus, wherein the cluster includes a DC bus, a power generation device, a power storage device, and a load connected to the DC bus, and a switch that opens and closes the DC bus and the interconnection bus. Under normal circumstances, the switch is controlled to an open state to operate the cluster independently. When the voltage of the DC bus reaches or exceeds a predetermined upper limit voltage, if no voltage is applied to the interconnection bus, a power transmission request signal is sent to another cluster requesting acceptance of power for transmission from the cluster, and the switch is then controlled to make the voltage of the DC bus a predetermined power transmission request voltage, and the switch is then temporarily closed to apply the voltage of the DC bus to the interconnection bus. If there is another cluster that has responded to the power transmission request signal, the switch is controlled to a closed state to operate the cluster in cooperation with the other cluster.

[0090] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0091] 100 Power Distribution System 1(1A, 1B, 1C) cluster 10 (10A, 10B, 10C) Control device 20(20A, 20B, 20C) Power storage device 30 (30A, 30B, 30C) Solar power generation equipment (power generation equipment) 40(40A, 40B, 40C) EV system (load) 50(50A, 50B, 50C) Switch 90 (90A, 90B, 90C) DC bus 91 (91A, 91B, 91C) First Measuring Instrument 92 (92A, 92B, 92C) Second measuring instrument 9. Linked bus Vg Grid voltage (voltage of interconnected bus) Vc Cluster voltage (DC bus voltage) Vsthigh Equipment shutdown high voltage Vdisch upper limit voltage V2 Charging limit voltage V1 Discharge limit voltage Vch lower limit voltage Vstlow Equipment shutdown low voltage Vdisch_sig Transmission demand voltage

Claims

1. A power distribution system in which a plurality of clusters can be connected to each other via a coordination bus, The clusters are DC bus and a power generation device, a power storage device, and a load connected to the DC bus; a switch that opens and closes the DC bus and the interconnection bus; a control device; and The control device In normal operation, the switch is controlled to an open state to operate the cluster independently, When the voltage of the DC bus reaches or exceeds a predetermined upper limit voltage, if no voltage is applied to the interconnection bus, the storage device controls the voltage of the DC bus to a predetermined transmission request voltage, and then temporarily closes the switch to apply the voltage of the DC bus to the interconnection bus as a transmission request signal, which is a signal indicating a request to another cluster to accept power for transmission from the cluster in question, and if there is another cluster that responds to the transmission request signal, the switch is controlled to a closed state, allowing the cluster in question to operate in cooperation with the other cluster.

2. The control device When it is detected that the power transmission request signal is output from another cluster to the coordination bus during the normal operation, 2. The power distribution system according to claim 1, wherein the power transmission request signal is responded to by controlling the switch to a closed state if no voltage is applied to the interconnection bus after a waiting time corresponding to the voltage of the DC bus.

3. The control device 3. The power distribution system according to claim 1, wherein when the voltage of the DC bus becomes equal to or higher than a predetermined upper limit voltage, if a voltage is applied to the interconnection bus, the power storage device is controlled to make the voltage of the DC bus equal to the voltage of the interconnection bus, and then the switch is controlled to a closed state.

4. The control device 4. The power distribution system according to claim 3, wherein when the voltage of the DC bus falls below a predetermined lower limit voltage, if no voltage is applied to the coordination bus, the switch is closed to apply the voltage of the DC bus to the coordination bus as a power reception request signal, which is a signal indicating that another cluster is requested to supply power to the cluster, and if there is another cluster that responds to the power reception request signal, the switch is continued to be controlled to the closed state to operate the cluster in coordination with the other cluster.

5. The power distribution system according to claim 4 , wherein the requested power transmission voltage is lower than the lower limit voltage.

6. The power storage device is In normal operation, when the voltage of the DC bus is less than a predetermined discharge limit voltage, discharging is performed, and when the voltage is equal to or greater than a predetermined charge limit voltage, charging is performed. The power distribution system according to claim 4 , wherein the discharge limit voltage is higher than the lower limit voltage, and the charge limit voltage is higher than the discharge limit voltage and lower than the upper limit voltage.

7. 1. A method for controlling a plurality of clusters in a power distribution system in which the clusters can be connected to each other via a linking bus, comprising: The clusters are DC bus and a power generation device, a power storage device, and a load connected to the DC bus; a switch that opens and closes the DC bus and the interconnection bus, In normal operation, the switch is controlled to an open state to operate the cluster independently, When the voltage of the DC bus reaches or exceeds a predetermined upper limit voltage, if no voltage is applied to the interconnection bus, the storage device is controlled to raise the voltage of the DC bus to a predetermined transmission request voltage, and then the switch is temporarily closed to apply the voltage of the DC bus to the interconnection bus as a transmission request signal, which is a signal indicating a request to another cluster to accept power for transmission from the own cluster, and if there is another cluster that responds to the transmission request signal, the switch is controlled to the closed state, so that the own cluster operates in cooperation with the other cluster.

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