Power interchange system and control method

Abstract

To provide a system capable of continuing power interchange control even if an abnormality or the like occurs in a master unit and communication apparatuses between nodes, at low cost.SOLUTION: In a power interchange system (100) according to one aspect of the present invention, first to fourth power distribution units (1-4) are connected to a common distribution line (L). The first to fourth power distribution units (1-4) include a master unit (1) that controls power distribution to the second to fourth power distribution units (2-4) and slave units (2-4) composed of the second to fourth power distribution units (2-4), and switch the master unit (1) to one of the slave units (2-4) based on a voltage change of the distribution line (L).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power interchange system and a control method for the power interchange system. [Background technology]

[0002] In recent years, power interchange systems that exchange power between autonomous microgrids have become known. In relation to this type of power interchange system, for example, Patent Document 1 proposes a power interchange system that combines a photovoltaic power generation facility, a DC-DC converter, a storage battery, etc. into one node (unit) and interchanges power between a plurality of nodes. In this power interchange system, a central control device receives information on the power state of each node and transmits power interchange information to each node, thereby controlling the power interchange between the nodes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 199604 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, it is necessary to install a central control device to control the power interchange between the nodes and sensors to detect the power flow of each node. This poses the problem of high costs for system construction. In addition, if an abnormality occurs in the master device such as the central control device or the control devices between the nodes, the system may not function properly.

[0005] One aspect of the present invention has been made in consideration of the above-mentioned problems in the conventional technology, and its object is to realize a system at low cost that can continue to control power interchange even if an abnormality or the like occurs in the master unit. [Means for solving the problem]

[0006] In order to solve the above problems, a power interchange system according to one embodiment of the present invention is a power interchange system in which a plurality of power distribution units are connected to a common power distribution line, the plurality of power distribution units including a master unit constituted by one of the plurality of power distribution units and controlling power interchange to other power distribution units, and a slave unit constituted by the other power distribution unit, and the master unit is switched to one of the slave units based on a voltage change on the power distribution line.

[0007] In order to solve the above problems, a control method according to one embodiment of the present invention is a control method for a power interchange system in which a plurality of power distribution units are connected to a common power distribution line, the plurality of power distribution units including a master unit constituted by one of the plurality of power distribution units and controlling power distribution to other power distribution units, and a slave unit constituted by the other power distribution unit, and switching the master unit to one of the slave units based on a voltage change on the power distribution line. Effect of the Invention

[0008] According to one aspect of the present invention, a system capable of continuing power interchange control even when an abnormality or the like occurs in the master device can be realized at low cost. [Brief description of the drawings]

[0009] [Figure 1] 1 is a conceptual diagram showing a schematic configuration of a power interchange system according to an embodiment of the present invention. [Diagram 2] 2 is a block diagram showing a main configuration of the power interchange system shown in FIG. 1. [Diagram 3] 4 is a timing chart showing the basic operation of the master device (first power distribution unit) and the slave devices (second power distribution unit to fourth unit). [Figure 4] 10 is a timing chart showing a power interchange operation between a master device (first power distribution unit) and a slave device (third power distribution unit). [Diagram 5]5 is a flowchart showing a basic operation and a power interchange operation of the master machine. [Figure 6] 5 is a flowchart showing a basic operation and a power interchange operation of a slave machine. [Figure 7] 10 is a timing chart showing a switching operation of a master device (first power distribution unit) and slave devices (second to fourth power distribution units). [Figure 8] 10 is a timing chart showing a switching operation of the master device from the first power distribution unit to the third power distribution unit. [Figure 9] 10 is a flowchart showing a master device switching operation in the master device. [Figure 10] 10 is a flowchart showing steps of a master device switching operation in a slave device. [Figure 11] FIG. 2 is a state transition diagram of the power interchange system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present invention (hereinafter, also referred to as "the present embodiment") will be described below with reference to the drawings. However, the following description is an example of a power interchange system according to the present invention, and the technical scope of the present invention is not limited to the illustrated example. Note that the same or corresponding parts in the drawings are given the same reference numerals, and their description will not be repeated.

[0011] [Outline of the power interchange system] First, an overview of a power interchange system 100 according to this embodiment will be described. Fig. 1 is a conceptual diagram showing a schematic configuration of the power interchange system 100 according to this embodiment. As shown in Fig. 1, the power interchange system 100 includes a plurality of power distribution units connected to a common power distribution line L. In the illustrated example, the power interchange system 100 includes four power distribution units, namely a first power distribution unit 1, a second power distribution unit 2, a third power distribution unit 3, and a fourth power distribution unit, as the plurality of power distribution units. Note that the number of power distribution units connected to the common power distribution line L may be at least two or more.

[0012] The first power distribution unit 1 to the fourth power distribution unit 4 are DC power distribution units installed for each of the consumers C1 to C4. The first power distribution unit 1 to the fourth power distribution unit 4 exchange power among the consumers C1 to C4. Each of the consumers C1 to C4 may be an independent microgrid.

[0013] These first power distribution unit 1 to fourth power distribution unit 4 include a master unit that is composed of one of the first power distribution unit 1 to fourth power distribution unit 4 and controls power interchange (power distribution) to the other power distribution units, and slave units that are composed of the other power distribution units excluding the master unit. For example, when the first power distribution unit 1 operates as the master unit, the remaining second power distribution unit 2 to fourth power distribution unit 4 operate as slave units.

[0014] In the power interchange system 100 according to this embodiment, the master unit can be switched to one of the slave units based on a voltage change in the power distribution line L. Therefore, even if an abnormality or the like occurs in the power distribution unit operating as the master unit, the master unit can be switched to another power distribution unit, making it possible to continue control of power interchange.

[0015] [Configuration of the power interchange system] Fig. 2 is a block diagram showing a main configuration of the power interchange system 100 shown in Fig. 1. As shown in Fig. 2, in the power interchange system 100, a first power distribution unit 1 to a fourth power distribution unit 4 are connected to a common power distribution line L.

[0016] The power distribution line L is a power line that electrically connects each of the first power distribution unit 1 to the fourth power distribution unit 4 without passing through a commercial power system. In this embodiment, the power distribution line L is formed of a DC (Direct Current) power distribution line that transmits direct current power.

[0017] The first power distribution unit 1 to the fourth power distribution unit 4 mutually supply and demand DC power therebetween via a common power distribution line L, thereby exchanging power. Each of the first power distribution unit 1 to the fourth power distribution unit 4 has a common configuration and function. For this reason, in the following, a configuration example of the first power distribution unit 1 will be described, and a description of configuration examples of the second power distribution unit 2 to the fourth power distribution unit 4 will be omitted.

[0018] (Power distribution unit configuration) The first power distribution unit 1 includes a solar power generation device 11, a storage battery 12, a DC-DC converter 13, a voltage sensor 14, a current sensor 15, a storage unit 16, and a control unit 17.

[0019] The solar power generation device 11 is a power generation device having a photoelectric conversion element that converts sunlight into DC power. The solar power generation device 11 generates DC power according to the amount of solar radiation. Note that the first power distribution unit 1 may include a power generation device that generates power using natural energy or renewable energy other than sunlight, instead of the solar power generation device 11 that generates power using sunlight, or in addition to the solar power generation device 11.

[0020] The storage battery 12 is a battery that charges and discharges DC power. The storage battery 12 is composed of a secondary battery such as a lithium ion battery, a NaS (sodium-sulfur) battery, a redox flow battery, a lead storage battery, etc. The DC power stored in the storage battery 12 is supplied to the second power distribution unit 2 to the fourth power distribution unit 4, etc. via a DC-DC converter 13. The DC power stored in the storage battery 12 is also supplied to a load 20, etc., installed in the consumer C1.

[0021] The load 20 is an electrical load such as an electrical device installed in the consumer C1. In this embodiment, the load 20 is, for example, a DC load that operates on DC power. However, the load 20 may be an AC load that operates on AC power converted by a DC-AC inverter or the like that converts DC power into AC power.

[0022] The DC-DC converter 13 is a converter that converts the voltage of DC power. In this embodiment, the DC-DC converter 13 is provided in the first power distribution unit 1 as a converter for power interchange. The DC-DC converter 13 changes the voltage and current on the power distribution line L side in accordance with a control signal from the control unit 17, thereby supplying and demanding power between the second power distribution unit 2 to the fourth power distribution unit 4.

[0023] The voltage sensor 14 is a sensor that detects the voltage on the distribution line L side of the DC-DC converter 13. The voltage sensor 14 outputs the detected voltage value to the control unit 17.

[0024] The current sensor 15 is a sensor that detects a current from the power distribution line L of the DC-DC converter 13. The current sensor 15 outputs the detected current value to the control unit 17.

[0025] The storage unit 16 is a storage device that stores a control program, parameters, and the like used for controlling power interchange. The storage unit 16 stores, for example, a specific voltage and the like that is assigned (set) in advance to each of the first power distribution unit 1 to the fourth power distribution unit 4. The specific voltage will be described later.

[0026] The control unit 17 is a control device that comprehensively controls each part of the first power distribution unit 1. The control unit 17 is configured by a processor such as a CPU (Central Processing Unit), or is configured by a logic circuit formed in an integrated circuit (IC chip) or the like. The control unit 17 includes a determination unit 171 and a device control unit 172.

[0027] The determination unit 171 acquires, for example, the amount of charge of the storage battery 12, the voltage value output from the voltage sensor 14, or the current value output from the current sensor 15, and determines whether or not these values ​​are equal to or greater than a predetermined value. The determination unit 171 outputs the determination result to the device control unit 172.

[0028] The equipment control unit 172 controls the operation of each part of the first power distribution unit 1 based on the determination result input from the determination unit 171, and causes the operation of power interchange to be performed.

[0029] [Operation of the power interchange system] Next, an operation example of the power interchange system 100 will be described with reference to Fig. 3 to Fig. 6. As described above, in the power interchange system 100, one of the first power distribution unit 1 to the fourth power distribution unit 4 operates as a master unit, and the other power distribution units operate as slave units. Depending on the situation, the master unit can be switched to one of the slave units.

[0030] Therefore, each of the first power distribution unit 1 to the fourth power distribution unit 4 can operate both as a master unit and as a slave unit, and switches between these operations depending on the situation. Therefore, a power distribution unit that operates as a master unit in one situation can operate as a slave unit in another situation.

[0031] The master unit controls the voltage of the power distribution line L by voltage control, and controls the power interchange with the slave units in an integrated manner. The master unit discharges power from its own storage battery 12 or outputs power from its own solar power generation device 11, and outputs power to the slave units. In this way, the master unit charges the storage battery 12 of the slave units. Also, the slave units charge power to their own storage battery 12 or supply power to their own units while following the master unit by current control. An example of the operation of the power interchange system will be specifically described below.

[0032] In the following, a basic operation will be described in which the first power distribution unit 1 is the master unit and the second power distribution unit 2 to the fourth power distribution unit 4 are slave units. Also, the voltages on the power distribution line L side of the DC-DC converter 13 of the first power distribution unit 1 are denoted as Vdc1 to Vdc4, and the currents are denoted as Idc1 to Idc4 (see FIG. 1).

[0033] [Basic operation] First, the basic operations of the master unit and the slave units will be described. Fig. 3 is a timing chart showing the basic operations of the master unit (first power distribution unit 1) and the slave units (second power distribution unit 2 to fourth power distribution unit 4). The upper part of Fig. 3 is a timing chart of the master unit (first power distribution unit 1), and the lower part of Fig. 3 is a timing chart of the slave units (second power distribution unit 2 to fourth power distribution unit 4).

[0034] In the power interchange system 100, a different unique voltage is assigned in advance to each of the first power distribution unit 1 to the fourth power distribution unit 4. In this embodiment, a unique voltage V1 is assigned in advance to the first power distribution unit 1, a unique voltage V2 is assigned to the second power distribution unit 2, a unique voltage V3 is assigned to the third power distribution unit 3, and a unique voltage V4 is assigned to the fourth power distribution unit 4. In this embodiment, the unique voltages V1 to V4 are set so that the voltage values ​​increase stepwise in the order of the unique voltage V1, the unique voltage V2, the unique voltage V3, and the unique voltage V4. These unique voltages V1 to V4 are stored in the memory units 16 of the first power distribution unit 1 to the fourth power distribution unit 4.

[0035] In basic operation, the first power distribution unit 1, which is the master device, repeatedly changes Vdc1 in the order of the specific voltage V2, specific voltage V3, and specific voltage V4 assigned to the slave devices. In other words, the master device performs repetitive control to gradually change the voltage of the power distribution line L to the specific voltages V2, V3, and V4, excluding the specific voltage V1 assigned to the device itself.

[0036] Specifically, as shown in the upper part of Fig. 3, at time t11, the first power distribution unit 1 changes Vdc1 to the inherent voltage V2 of the second power distribution unit 2. Next, at time t12 after a predetermined time T1, the first power distribution unit 1 starts control to change Vdc1 to the inherent voltage V3 of the third power distribution unit 3, and Vdc1 is changed to the inherent voltage V3 at time t13. Next, at time t14 after the predetermined time T1, the first power distribution unit 1 starts control to change Vdc1 to the inherent voltage V4 of the fourth power distribution unit 4, and Vdc1 is changed to the inherent voltage V4 at time t15. Next, at time t16 after the predetermined time T1, the first power distribution unit 1 starts control to change Vdc1 to the inherent voltage V2 of the second power distribution unit 2, and Vdc1 is changed to the inherent voltage V1 at time t17. Thereafter, the first power distribution unit 1 continues the repetitive control of changing Vdc1 to the intrinsic voltages V2, V3, and V4 until Idc1 equal to or greater than the predetermined value is detected.

[0037] Each of the second to fourth power distribution units 2 to 4, which are slave devices, detects the voltage of the power distribution line L by a voltage sensor 14. When the voltage sensor 14 detects the specific voltage V2 assigned to the second power distribution unit 2, the second power distribution unit 2 determines whether or not power interchange (charging) from the master device is necessary. This determination is made based on the amount of power generated by the solar power generation device 11, the amount of power stored in the storage battery 12, etc.

[0038] When it is determined that power interchange from the master device is not required, the second power distribution unit 2 performs a first constant current control, controlling the current of its own device to Idc2 = 0 A. The third power distribution unit 3 and the fourth power distribution unit 4 also perform the same control as the second power distribution unit 2. When all of the second power distribution unit 2 to the fourth power distribution unit 4 have determined that power interchange is not required, as shown in the lower part of Fig. 3, the voltages Vdc2 to Vdc4 detected by each slave device repeatedly change stepwise between the intrinsic voltages V2, V3, and V4.

[0039] [Power interchange operation] Next, a power interchange operation in which power is interchanged from the master device to the slave device will be described. Fig. 4 is a timing chart showing the charging operation of the master device and the slave device when power is interchanged (charged) from the first power distribution unit 1, which is the master device, to the third power distribution unit 3, which is the slave device.

[0040] As shown in FIG. 4, at time t21, when the voltage sensor 14 detects the intrinsic voltage V3 of the third power distribution unit 3 which is a slave device, the third power distribution unit 3 determines whether or not power interchange (charging) is necessary.

[0041] When it is determined that power interchange is necessary, at time t22, the third power distribution unit 3 performs second constant current control to control the current Idc3 of its own device to a predetermined value (Icc) that is not 0. As a result, power is supplied from the first power distribution unit 1 to the third power distribution unit 3, and the storage battery 12 of the slave device is charged.

[0042] If the current sensor 15 detects a current of a predetermined value (Icc) while the first power distribution unit 1, which is the master device, is controlling the voltage of the power distribution line L to the inherent voltage V3 of the third power distribution unit 3, the first power distribution unit 1 determines that the third power distribution unit 3 has started the second constant current control. As a result, the first power distribution unit 1 interrupts the repetitive control and maintains the inherent voltage V3 of the slave device (third power distribution unit 3) that wishes to be charged (first constant voltage control).

[0043] At time t23, the third power distribution unit 3 that is performing charging switches to the first constant current control when the storage battery 12 of the slave device is sufficiently charged and charging is to be terminated.

[0044] As a result, at time t24, current sensor 15 of first power distribution unit 1 detects 0 A, and the master device determines that the slave device has finished charging, and switches to repetitive control.

[0045] [Flowchart for master unit basic operation and power interchange] The above basic operation and each step of power interchange will be described with reference to a flowchart. Fig. 5 is a flowchart showing the basic operation and power interchange operation of the first power distribution unit 1, which is the master device.

[0046] In S11, the first power distribution unit 1, which is the master device, performs repetitive control and changes Vdc1 of the first power distribution unit 1 to V2, V3, and V4 in turn (see the upper part of FIG. 3). This repetitive control is performed by the device control unit 172 of the master device controlling the DC-DC converter 13 with reference to the specific voltages V1 to V4 stored in the memory unit 16.

[0047] Next, in S12, the determination unit 171 of the first power distribution unit 1 determines whether or not a current equal to or greater than a predetermined value is detected by the current sensor 15 during the repetitive control (see time t21 in FIG. 4). If not detected (No in S12), the device control unit 172 of the first power distribution unit 1 returns to S11 and continues the repetitive control. On the other hand, if detected (Yes in S12), the process proceeds to S13.

[0048] Next, in S13, the device control unit 172 of the first power distribution unit 1 ends the repetitive control, and switches to the first constant voltage control that maintains the voltage at the time of S12 (see time t22 in FIG. 4).

[0049] Next, in S14, the determination unit 171 of the first power distribution unit 1 determines whether or not a current less than a predetermined value is detected by the current sensor 15 (see times t22 to t23 in FIG. 4). If not detected (No in S14), the process returns to S13. On the other hand, if detected (Yes in S14), the process proceeds to S15.

[0050] Next, in S15, the device control unit 172 of the first power distribution unit 1 ends the first constant voltage control and switches to repetitive control (see time t24 in FIG. 4). That is, Vdc1 is changed from the inherent voltage V3 of the third power distribution unit 3 that was initially charged to the inherent voltage V4 of the fourth power distribution unit 4.

[0051] [Flowchart for basic operation and power interchange of slave units] FIG. 6 is a flowchart showing the basic operation and power interchange operation of the third power distribution unit 3, which is a slave device.

[0052] In S21, the third power distribution unit 3 performs the first constant current control using the current sensor 15 so that the current Idc3 becomes 0 A. Vdc3 of the third power distribution unit 3 becomes substantially equal to Vdc1 of the first power distribution unit 1, which is the master device (see the lower part of FIG. 3).

[0053] Next, in S22, the determination unit 171 of the third power distribution unit 3 determines whether or not the intrinsic voltage V3 of the device itself has been detected by the voltage sensor 14 (see time t21 in FIG. 4). If not detected (No in S22), the process returns to S21 and continues the first constant current control. On the other hand, if detected (Yes in S22), the process proceeds to S23.

[0054] Next, in S23, the determination unit 171 of the third power distribution unit 3 acquires the amount of electricity stored in the storage battery 12 of its own device, and determines whether charging (power interchange) is necessary (see time t21 in FIG. 4). If charging is not necessary (No in S23), the process returns to S21 and the first constant current control is continued. On the other hand, if charging is necessary (Yes in S23), the process proceeds to S24.

[0055] Next, in S24, the device control unit 172 of the slave device switches the DC-DC converter 13 to the second constant current control in order to perform charging, and controls Idc3 to Icc, thereby performing charging (see time t21 in FIG. 4).

[0056] Next, in S25, the determination unit 171 of the slave device checks the storage battery 12 of its own device and determines whether a predetermined amount of power is charged (see times t22 to t23 in FIG. 4). If the amount of power is insufficient (No in S25), the process returns to S24. If the amount of power is sufficient (Yes in S25), the process proceeds to S26.

[0057] Finally, in S26, the device control unit 172 of the slave device ends the second constant current control, and switches the DC-DC converter 13 to the first constant current control (see time t23 in FIG. 4).

[0058] [Switching operation] Next, a switching (handover) operation of the master device for switching the master device to one of the slave devices will be described using as an example a case where the master device is switched from the first power distribution unit 1, which is the master device, to the second power distribution unit 2, which is the slave device.

[0059] FIG. 7 is a timing chart showing the switching operation of the master unit and the slave units when the first power distribution unit 1 is the master unit and the second power distribution unit 2 to the fourth power distribution unit 4 are slave units.

[0060] At time t31, if the first power distribution unit 1, which is the master device, can no longer continue to operate as the master device due to, for example, a lack of stored power in the storage battery 12 or a malfunction, the first power distribution unit 1 terminates the repetitive control and performs a second constant voltage control in which Vdc1 is controlled to the inherent voltage V1 of the device itself.

[0061] At time t32, the second power distribution unit 2, which is a slave unit, detects that the voltage of the power distribution line L has become the inherent voltage (V1) of the first power distribution unit 1, which was the previous master unit, and recognizes that the first power distribution unit 1 can no longer continue to operate as the master unit. After that, among the slave units, the unit next to the master unit (the second power distribution unit 2 next to the first power distribution unit 1) determines whether it can operate as a master unit.

[0062] At time t33, the second power distribution unit 2, which was a slave unit until time t32, finds that it can operate as a master unit and starts operating as the master unit. The second power distribution unit 2, which has become the master unit, starts repetitive control and attempts to change Vdc2 to the inherent voltage (V3) of the unit next to its own device.

[0063] At time t34, the second power distribution unit 2 passes a current toward the power distribution line L to change the voltage of the power distribution line L to Vdc2 (V3). The current sensor 15 of the first power distribution unit 1, which was the master unit, detects that the absolute value of the current has changed to or exceeds a predetermined value (Icc). After that, the first power distribution unit 1 starts operating as a slave unit and starts the first constant current control.

[0064] At time t35, the second power distribution unit 2 that has become the master device sequentially changes the voltage at regular time intervals by repetitive control. During this time, the slave devices (including the first power distribution unit 1) perform the first constant current control.

[0065] Next, the switching operation of the master unit and the slave unit will be explained based on the process of changing the master unit from the first power distribution unit 1, which is the master unit, to the third power distribution unit 3, which is the slave unit. At this time, since the second power distribution unit 2 cannot operate as the master unit, the third power distribution unit 3, which is the next unit, operates as the master unit.

[0066] FIG. 8 is a timing chart showing the switching operation of the master unit and the slave unit when the first power distribution unit 1 is the master unit, the second power distribution unit 2 is a slave unit that cannot operate as a master unit, and the third power distribution unit 3 is a slave unit that can operate as a master unit.

[0067] Times t31 and t32 are omitted because they are the same as those in Fig. 7. At time t43, the second power distribution unit 2, which was the slave unit until time t32, realizes that it cannot continue to operate as the master unit. The second power distribution unit 2 ends the first constant current control, switches to the second constant voltage control, and attempts to change Vdc2 to V2 (the inherent voltage of its own device).

[0068] At time t44, the current sensor 15 of the first power distribution unit 1 detects that the absolute value of the current has changed to or exceeds a predetermined value (Icc). After that, the first power distribution unit 1 starts operating with itself as a slave device, and starts the first constant current control.

[0069] At time t45, the third power distribution unit 3, which is a slave device, measures that the voltage detected by the voltage sensor 14 is V2 during the first constant current control, and thereby determines whether or not the device itself can operate as a master device.

[0070] At time t46, the third power distribution unit 3, which was a slave unit until time t45, finds out that it can operate as a master unit and starts operating as the master unit. The third power distribution unit 3, which has become the master unit, starts repetitive control and changes Vdc3 to the inherent voltage (V4) of the unit next to its own device.

[0071] At time t47, the second power distribution unit 2 detects that the absolute value of the current has changed to or exceeds a predetermined value, and thereby starts operating as a slave device, and switches to the first constant current control.

[0072] At time t48, the third power distribution unit 3 sequentially changes the voltage at regular time intervals by repetitive control. During this time, the slave devices (including the first power distribution unit 1 and the second power distribution unit 2) perform the first constant current control.

[0073] [Flowchart of switching operation in the master unit] FIG. 9 is a flow chart showing the steps of the master device switching operation in the first power distribution unit 1 which is the master device.

[0074] In S31, the determination unit 171 of the first power distribution unit 1, which is the master unit, determines whether or not it is possible to continue operating as the master unit (see time t31 in FIG. 7 and FIG. 8). If it is possible to continue (Yes in S31), S31 is repeated. On the other hand, if it is not possible to continue (No in S31), the process proceeds to S32.

[0075] Next, in S32, the device control section 172 of the first power distribution unit 1 performs the second constant voltage control in which Vdc1=V1 (see time t31 to time t32 in FIG. 7 and FIG. 8).

[0076] Next, in S33, the determination unit 171 of the first power distribution unit 1 detects an output current whose absolute value is equal to or greater than a predetermined value by the current sensor 15 (see times t32 to t33 in FIG. 7 and times t32 to t43 in FIG. 8). If the output current is not detected (No in S33), S33 is repeated. On the other hand, if the output current is detected (Yes in S33), the process proceeds to S34.

[0077] Next, in S34, the first power distribution unit 1 becomes a slave device, and the device control unit 172 of the first power distribution unit 1 starts the first constant current control (see time t34 in FIG. 7 and time t47 in FIG. 8).

[0078] [Flowchart of switching operation in slave device] FIG. 10 is a flow chart showing the steps of a switching operation of the master device in the second power distribution unit 2 or the third power distribution unit 3 which is a slave device.

[0079] In S41, the second power distribution unit 2 or the third power distribution unit 3, which is a slave device, infers the device number of the current master device (first power distribution unit 1) from the voltage change of the power distribution line L. The determination unit 171 of the second power distribution unit 2 or the third power distribution unit 3 checks whether the measurement value of the voltage sensor 14 is the inherent voltage (V1) of the current master device (first power distribution unit 1) (see time t33 in FIG. 7 and time t43 in FIG. 8). If the measurement value of the voltage sensor 14 is not the voltage of the current master device (No in S61), S61 is repeated. On the other hand, if the measurement value of the voltage sensor 14 is the voltage of the current master device (Yes in S61), the process proceeds to S62.

[0080] Next, in S42, the determination unit 171 of the second power distribution unit 2 or the third power distribution unit 3 determines whether the own device is the next device after the current master device (first power distribution unit 1) (see time t33 in FIG. 7 and time t43 in FIG. 8). If the own device is not the next device (No in S42), the process returns to S41. On the other hand, if the own device is the next device (Yes in S42), the process proceeds to S43.

[0081] Next, in S43, the determination unit 171 of the second power distribution unit 2 or the third power distribution unit 3 determines whether its own device can operate as a master device (see time t33 in FIG. 7 and time t43 in FIG. 8). If it can operate (Yes in S43), the process proceeds to S44. On the other hand, if it cannot operate (No in S43), the process proceeds to S45.

[0082] Next, in S44, the equipment control unit 172 of the second power distribution unit 2 or the third power distribution unit 3 starts operating as a master unit, and starts repetitive control to output the unique voltage of the next unit of its own device (see time t33 in Figure 7 and time t46 in Figure 8).

[0083] Next, in S45, the device control unit 172 of the second power distribution unit 2 starts the second constant voltage control to output the inherent voltage of its own device (see time t43 in FIG. 8). At this time, although the second power distribution unit 2 is a slave device, it becomes the master device until a master device that can continue to operate is determined, and provisionally controls the voltage of the power distribution line L.

[0084] Next, in S46, the determination unit 171 of the second power distribution unit 2 checks, using the current sensor 15 of its own device, whether an output current has an absolute value equal to or greater than a predetermined value (see time t46 to time t47 in FIG. 8). If the output current is not checked (No in S46), S46 is repeated. On the other hand, if the output current is checked (Yes in S46), the process proceeds to S47.

[0085] Next, in S47, the second power distribution unit 2 ends the second constant voltage control and switches to the first constant current control (see time t47 in FIG. 8). At this time, the second power distribution unit 2 determines that a new master unit has been decided, and ends its role of provisionally controlling the voltage of the power distribution line L in place of the master unit, even though it is a slave unit.

[0086] [State transition diagram] FIG. 11 is a state transition diagram of the power interchange system according to the embodiment.

[0087] 11, the master unit waits in state A for a response from the slave unit as to whether or not it needs to exchange power, and if power exchange is necessary, transitions to state B. In state B, the master unit discharges power to the slave unit and charges the slave unit. As the master unit discharges power, its own stored power decreases, making it unable to operate as a master unit, and it transitions to state C and starts operating as a slave unit.

[0088] The slave device waits in state C for a response from the master device regarding whether or not it needs to interchange power, and if it does, it transitions to state D. The slave device charges with power from the master device in state D. Also, in state C, the slave device can transition to state A in response to a request from the master device and start operating as the master device.

[0089] In this way, in a power interchange system, the master device discharges power and the slave devices charge power. In a power interchange system, if the master device discharges power and is no longer able to function as the master device, one of the slave devices will operate as the master device, and the master device will dynamically switch, allowing the power interchange system to continue operating.

[0090] [Effects of the power interchange system] Thus, the power interchange system 100 according to this embodiment is a power interchange system in which the first power distribution unit 1 to the fourth power distribution unit 4 are connected to a common power distribution line L. In the power interchange system 100, the first power distribution unit 1 to the fourth power distribution unit 4 are each composed of one of the first power distribution unit 1 to the fourth power distribution unit 4, and include a master device that controls power distribution to the other power distribution units, and a slave device composed of the other power distribution units, and the master device is switched to one of the slave devices based on a voltage change in the power distribution line L.

[0091] In the power interchange system 100, the master device can be switched to one of the slave devices based on a voltage change in the power distribution line L. Therefore, even if an abnormality occurs in the master device, control of power interchange can be continued. Furthermore, unlike the conventional system, there is no need to install a central control device or the like for controlling power interchange between a plurality of power distribution units (nodes). Therefore, the cost required for constructing the power interchange system 100 is reduced.

[0092] Therefore, according to this embodiment, it is possible to realize at low cost the power interchange system 100 that can continue to control power interchange even if an abnormality occurs in the master unit.

[0093] Of the multiple power distribution units, one operates as a master unit, and the other units operate as slave units subordinate to the master unit. Any power distribution unit can operate as both a master unit and a slave unit. Therefore, there is no need for a dedicated central control device to control multiple power distribution units.

[0094] The first power distribution unit 1 to the fourth power distribution unit 4 determine the state of the power interchange system and operate based on information measured by their own sensors. Therefore, there is no need for communication lines to know the state of the other power distribution units and use them for control.

[0095] In addition, one of the multiple power distribution units operates as a master unit, and the other units operate as slave units subordinate to the master unit. Any power distribution unit can operate as both a master unit and a slave unit. Therefore, there is no need for a dedicated central control device to control multiple power distribution units.

[0096] The first power distribution unit 1 to the fourth power distribution unit 4 determine the state of the power interchange system 100 and operate based on information measured by their own sensors. Therefore, there is no need for communication lines to know the states of the other power distribution units and use them for control.

[0097] Since the power distribution line L is common to the power distribution units 1 to 4, power can be exchanged between the power distribution units 1 to 4.

[0098] In addition, one of the multiple power distribution units operates as a master unit, and the other units operate as slave units subordinate to the master unit. Any power distribution unit can operate as both a master unit and a slave unit. Therefore, there is no need for a dedicated central control device to control multiple power distribution units.

[0099] 〔summary〕 The power interchange system according to aspect 1 of the present invention is a power interchange system in which a plurality of power distribution units are connected to a common power distribution line, the plurality of power distribution units including a master unit constituted by one of the plurality of power distribution units and controlling power interchange to other power distribution units, and a slave unit constituted by the other power distribution unit, and switching the master unit to one of the slave units based on a voltage change on the power distribution line.

[0100] According to the above configuration, the master unit can be switched to a slave unit based on a change in the voltage of the power distribution line, so that control of power interchange can be continued even if an abnormality or the like occurs in the master unit.

[0101] In the power interchange system of aspect 2 of the present invention, in the above aspect 1, each of the plurality of power distribution units is pre-assigned a different inherent voltage, and the master unit is switched to one of the slave units by changing the voltage of the power distribution line based on the inherent voltage.

[0102] According to the above configuration, the state of each power distribution unit can be managed by using the inherent voltage of the power distribution unit for control.

[0103] A power interchange system according to a third aspect of the present invention is configured in such a way that, when the master device is unable to continue operating as the master device, the master device changes the voltage of the distribution line to the specific voltage assigned to the device itself.

[0104] According to the above configuration, the master device can notify the slave devices that it can no longer continue to operate as the master device by changing the voltage of the power distribution line to the specific voltage assigned to the master device itself.

[0105] In the power interchange system of aspect 4 of the present invention, in aspect 3 above, the slave unit determines whether or not it can switch to become the master unit when the voltage of the distribution line changes to the specific voltage assigned to the master unit.

[0106] According to the above configuration, when the master device is unable to continue its operation, it is possible to cause the slave device to determine whether or not it is capable of taking over the operation as the master device.

[0107] In a power interchange system according to aspect 5 of the present invention, in any of aspects 2 to 4 above, the master unit changes the voltage of the distribution line based on the specific voltage assigned to the slave unit when the master unit is able to continue operating as the master unit.

[0108] According to the above configuration, the master device can notify the slave device that it can continue to operate as the master device, and can wait for the start of power interchange with the slave device.

[0109] A sixth aspect of the present invention relates to a power interchange system, in which, in the fifth aspect described above, when there are multiple slave units, the master unit switches the voltage of the distribution line in stages based on the specific voltages assigned to the slave units.

[0110] According to the above configuration, it is possible to explicitly notify a plurality of slave devices of which slave device a response is currently being waited for.

[0111] In the power interchange system according to aspect 7 of the present invention, in aspect 6 above, the slave device determines whether or not to receive power interchange from the master device when the voltage on the distribution line changes to the specific voltage assigned to the slave device.

[0112] According to the above configuration, the slave device can recognize that the master device is waiting for a response from the slave device.

[0113] A control method according to another aspect of the present invention is a control method for a power interchange system in which a plurality of power distribution units are connected to a common power distribution line, the plurality of power distribution units including a master unit constituted by one of the plurality of power distribution units and controlling power distribution to other power distribution units, and a slave unit constituted by the other power distribution units, and including a switching step of switching the master unit to one of the slave units based on a voltage change on the power distribution line.

[0114] [Software implementation example] The control block (particularly the control unit 17 and the storage unit 16) of each of the power distribution units 1 to 4 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

[0115] In the latter case, each of the power distribution units 1 to 4 includes a computer that executes instructions of a program, which is software that realizes each function. The computer includes, for example, one or more processors, and a computer-readable recording medium that stores the program. The computer achieves the object of the present invention by having the processor read the program from the recording medium and execute it. The processor may be, for example, a CPU (Central Processing Unit). The recording medium may be a "non-transient tangible medium," such as a ROM (Read Only Memory), tape, disk, card, semiconductor memory, programmable logic circuit, or the like. The computer may further include a RAM (Random Access Memory) that expands the program. The program may be supplied to the computer via any transmission medium (such as a communication network or broadcast waves) that can transmit the program. Note that one aspect of the present invention may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

[0116] [Additional Notes] 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]

[0117] 1. First Power Distribution Unit 2. Second Power Distribution Unit 3. Third Power Distribution Unit 4. Fourth Power Distribution Unit 100 Power Exchange System L distribution line

Claims

1. A power interchange system in which a plurality of power distribution units are connected to a common power distribution line, the plurality of power distribution units include a master unit configured as one of the plurality of power distribution units and configured to control power interchange with other power distribution units by voltage control that controls a voltage of the power distribution line, and a slave unit configured as the other power distribution unit; Each of the plurality of power distribution units is assigned a unique voltage different from each other in advance, When the master device cannot continue to operate as the master device, the master device changes the voltage of the power distribution line to the specific voltage assigned to the master device itself; A power interchange system that switches the master device to one of the slave devices so that one of the slave devices takes over the voltage control based on a voltage change in the power distribution line.

2. The power interchange system according to claim 1 , wherein the slave device determines whether or not the slave device can switch to the master device when a voltage on the power distribution line changes to the specific voltage assigned to the master device.

3. The power interchange system according to claim 1 , wherein the master device, when capable of continuing to operate as the master device, changes a voltage of the power distribution line based on the specific voltage assigned to the slave device.

4. The power interchange system according to claim 3 , wherein when there are a plurality of the slave devices, the master device switches the voltage of the power distribution line in stages based on the plurality of unique voltages assigned to the slave devices.

5. The power interchange system according to claim 4 , wherein the slave device determines whether or not to receive power interchange from the master device when a voltage on the power distribution line changes to the specific voltage assigned to the slave device.

6. A control method for a power interchange system in which a plurality of power distribution units are connected to a common power distribution line, comprising: the plurality of power distribution units include a master unit configured from one of the plurality of power distribution units and configured to control power distribution to other power distribution units by voltage control that controls a voltage of the power distribution line, and a slave unit configured from the other power distribution unit; Each of the plurality of power distribution units is assigned a unique voltage different from each other in advance, When the master device cannot continue to operate as the master device, the master device changes the voltage of the power distribution line to the specific voltage assigned to the master device itself; A control method comprising: switching the master unit to one of the slave units based on a voltage change in the power distribution line such that one of the slave units takes over the voltage control.

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