Power system and power system control method

Abstract

To suppress the spread range of an accident in a bus for supplying power by direct current in a tree shape.SOLUTION: A power system includes: a bus provided in a tree shape to supply power by direct current; and a first block part which is provided in each node of the bus to block connection between an upstream side and a downstream side of the node having itself, and blocks the upstream side and the downstream side of the node having itself in the case that a state in which a current value of current flowing through itself is equal to or more than a threshold due to an accident in the bus continues for a blocking time or more for each direction of the current. At least the first block part provided by a node closest on an upstream side more than an occurrence position of the accident in the bus and the first block part provided by a node closest on a downstream side more than the occurrence position of the accident in the bus perform blocking between the upstream side and the downstream side of the nodes having themselves.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a system for isolating a faulted section of a power distribution line. In this system, multiple circuit breakers are installed on a normally closed, two-circuit loop power distribution line. When detecting a fault on one side of the loop power distribution line, the closer the circuit breaker is to the end of that side, the shorter the interruption time it takes to shut off the line. When detecting a fault on the other side of the loop power distribution line, the closer the circuit breaker is to the end of that side, the shorter the interruption time it takes to shut off the line. Therefore, in the system disclosed in Patent Document 1, even if a fault occurs on the power distribution line, the circuit breakers closest to the fault on either side of the fault will shut off the line the fastest, preventing power outages in other sections. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-309552 Summary of the Invention [Problem to be solved by the invention]

[0004] As an alternative to large-scale power networks that rely on fossil and nuclear energy, power networks that use locally produced and consumed electricity are attracting attention. A wide variety of devices will be connected to power networks that use locally produced and consumed electricity, including photovoltaic (PV) power generation devices that generate electricity using renewable energy, stationary energy storage devices, and electric vehicles (EVs). As each of these devices uses a direct current (DC) power source, studies are underway to build a direct current (DC) power network (DC grid).

[0005] One example of a DC grid configuration is a tree-shaped bus configuration. In a tree-shaped DC grid, if an accident such as a short circuit or a ground fault occurs, it is desirable to isolate the faulted section to minimize the area of ​​the power outage and maximize the number of devices that continue to operate, similar to the system disclosed in Patent Document 1. However, because the system disclosed in Patent Document 1 is designed for loop-shaped distribution lines, it cannot be applied to a DC grid with a tree-shaped configuration, and therefore cannot minimize the area of ​​the power outage.

[0006] The present invention has been made in view of the above, and has an object to limit the extent of the impact of an accident in a tree-shaped bus that supplies power by DC. [Means for solving the problem]

[0007] One aspect of the present invention is a power system comprising: a bus arranged in a tree shape and supplying power via direct current; and a first interrupter unit provided at each node of the bus, which connects and disconnects between the upstream and downstream sides of the node to which it belongs, and which disconnects between the upstream and downstream sides of the node to which it belongs when an accident in the bus causes the current value of the current flowing through the bus to exceed a threshold value and continues for longer than a disconnection time specified for each direction of the current, and at least the first interrupter unit provided in the nearest node upstream of the location of the accident on the bus and the first interrupter unit provided in the nearest node downstream of the location of the accident on the bus disconnect between the upstream and downstream sides of the node to which it belongs.

[0008] In a power system according to one embodiment of the present invention, the terminal node is a power converter that converts input power and outputs it, and a power element that can supply, consume, or charge power is connected to the power converter, and if the location of the accident is between the terminal node and the power element, the first interrupter of the terminal node may interrupt the connection between the upstream and downstream sides of the node.

[0009] In addition, in a power system according to one embodiment of the present invention, the route of the bus is connected to another bus, and the route is provided with a second disconnection unit that connects and disconnects between one of the connected buses and the other bus, and the second disconnection unit may disconnect between the one bus and the other bus if the location of the accident is upstream of the terminal node of the bus.

[0010] In the power system according to an aspect of the present invention, the first interrupter may connect between the upstream side and the downstream side of the node in which the first interrupter is located in response to an external command.

[0011] In the power system according to one aspect of the present invention, the interruption time may differ depending on the hierarchy of the node.

[0012] A control method for a power system according to one embodiment of the present invention is a control method for a power system having buses arranged in a tree shape and supplying power via direct current, and a circuit breaker provided at each node of the bus, which performs connection and disconnection between the upstream and downstream sides of the node to which it belongs, and which disconnects between the upstream and downstream sides of the node to which it belongs when a state in which the current value of a current flowing through the bus due to an accident is above a threshold continues for more than a disconnection time specified for each direction of the current, and at least the circuit breaker provided in the node nearest to the location of the accident on the bus upstream and the circuit breaker provided in the node nearest to the location of the accident downstream of the bus disconnect between the upstream and downstream sides of the node to which it belongs. [Effects of the Invention]

[0013] According to the present invention, it is possible to limit the extent of the impact of an accident in a tree-shaped bus that supplies power by DC. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing the configuration of a power system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of the blocking unit according to the embodiment. [Figure 3] FIG. 3 is a diagram for explaining the first operation example. [Figure 4] FIG. 4 is a diagram for explaining the second operation example. [Figure 5] FIG. 5 is a diagram for explaining the third operation example. [Figure 6] FIG. 6 is a diagram for explaining the fourth operation example. [Figure 7] FIG. 7 is a diagram for explaining the fifth operation example. [Figure 8] FIG. 8 is a diagram for explaining the sixth operation example. [Figure 9] FIG. 9 is a diagram for explaining the seventh operation example. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment described below. Furthermore, in the description of the drawings, the same parts are appropriately designated by the same reference numerals.

[0016] <Power system configuration> 1 is a diagram showing the configuration of a power system according to an embodiment of the present invention. The power system 1 includes multiple DC grids, which are power transmission networks, and an EMS (Energy Management System). The EMS is an example of a central control device.

[0017] The DC grids GR1 and GR2 are power networks that supply DC power. Although FIG. 1 illustrates the DC grids GR1 and GR2, the power system 1 may be configured to include three or more DC grids. A protection device PR that controls power interchange between the DC grids GR1 and GR2 is provided between the DC grids GR1 and GR2. The protection device PR includes a breaker that connects and disconnects the DC grids GR1 and GR2, and has a function of communicating information via wire or wirelessly. The breaker that the protection device PR includes will be described later.

[0018] The DC grids GR1 and GR2 are laid out in a tree shape and include a bus BUS that supplies DC power. Note that the configuration of the DC grid GR2 is the same as that of the DC grid GR1, so the following description will explain the configuration of the DC grid GR1 as a representative, and will omit the explanation of the DC grid GR2.

[0019] The DC grid GR1 includes first protection devices P11 and P12, second protection devices P21-P24, and power converters C1-C8, which are nodes of the bus BUS. The DC grid GR1 also includes a plurality of power elements EL1-EL4. For ease of explanation, the root side of the tree-shaped bus BUS will be referred to as the upstream side, and the leaf side will be referred to as the downstream side. In other words, the protection device PR side, which is the root side, will be referred to as the upstream side, and the power converters C1-C8 side, which are the leaf side, will be referred to as the downstream side.

[0020] The first protection devices P11 and P12 are connected to a protection device PR located upstream of the first protection devices P11 and P12. The first protection device P11 is connected to second protection devices P21 and P22 located downstream of the first protection device P11 on the bus BUS, and the first protection device P12 is connected to second protection devices P23 and P24 located downstream of the first protection device P12 on the bus BUS. The first protection devices P11 and P12 have the function of performing wired or wireless information communication. The first protection device P11 is equipped with a breaker unit that connects and disconnects between the protection device PR and the second protection devices P21 and P22, and the first protection device P12 is equipped with a breaker unit that connects and disconnects between the protection device PR and the second protection devices P23 and P24. The breakers equipped in the first protection devices P11 and P12 will be described later.

[0021] The second protection device P21 is connected to the first protection device P11 and also to power converters C1 and C2 downstream of the second protection device P21 on the bus BUS, and the second protection device P22 is connected to the first protection device P11 and also to power converters C3 and C4 downstream of the second protection device P22 on the bus BUS. The second protection device P21 has a breaker unit that connects and disconnects between the first protection device P11 and the power converters C1 and C2, and the second protection device P22 has a breaker unit that connects and disconnects between the first protection device P11 and the power converters C3 and C4. The second protection device P23 is connected to the first protection device P12 and also to power converters C5 and C6 downstream of the second protection device P23 on the bus BUS, and the second protection device P24 is connected to the first protection device P12 and also to power converters C7 and C8 downstream of the second protection device P24 on the bus BUS. The second protection device P23 has a circuit breaker that connects or disconnects the first protection device P12 and the power converters C5 and C6, and the second protection device P24 has a circuit breaker that connects or disconnects the first protection device P12 and the power converters C7 and C8. The second protection devices P21 to P24 have a function of performing wired or wireless information communication. The circuit breakers provided in the second protection devices P21 to P24 will be described later.

[0022] The power converters C1 to C8 are DC / DC converters that convert so-called direct current voltages. Each of the power converters C1 to C8 has a circuit breaker that connects or disconnects the upstream and downstream sides of itself, and has the function of performing wired or wireless information communication. The circuit breakers that the power converters C1 to C8 have will be described later.

[0023] The power element EL1 is, for example, a stationary power storage device that can supply, consume, and charge power, and is connected to power converters C1 and C5. The stationary power storage device is an example of a permanently installed power storage device. The power converters C1 and C5 have the function of converting the voltage of the DC power supplied by the power element EL1 and outputting it to the bus BUS, and also converting the voltage of the DC power supplied from the bus BUS and outputting it to the power element EL1, thereby charging it.

[0024] The power element EL2 is, for example, a solar power generation device capable of generating and supplying power, and is connected to power converters C2 and C6. A solar power generation device is an example of a power generation device that generates power using renewable energy. The power converters C2 and C6 have the function of converting the voltage of the DC power supplied by the power element EL2 and outputting it to the bus BUS.

[0025] The power element EL3 is, for example, an on-board power storage device capable of supplying, consuming, and charging power, and is connected to power converters C3 and C7. The on-board power storage device is mounted on an electric vehicle EV and is an example of a mobile, non-stationary power storage device. The power converters C3 and C7 have the function of converting the voltage of the DC power supplied by the power element EL3 and outputting it to the bus BUS, and also converting the voltage of the DC power supplied from the bus BUS and outputting it to the power element EL3 for charging. The power converters C3 and C7 are provided, for example, in a charging station or residential charging equipment, but may also be mounted on the electric vehicle EV.

[0026] As an example, power element EL4 is a ZEH (Net Zero Energy House) that can supply, consume, and charge power, and is connected to power converters C4 and C8. The ZEH has, for example, a solar power generation device, a storage battery, and electrical appliances such as an air conditioner and a refrigerator as power loads. Power converters C4 and C8 have the function of converting the voltage of the DC power supplied by power element EL4 and outputting it to the bus BUS, and also converting the voltage of the DC power supplied from the bus BUS and outputting it to power element EL4, charging the storage battery, and operating the power load.

[0027] The EMS 10 has a function of comprehensively managing the state of the power system 1. The EMS 10 includes a control unit 11, a storage unit 12, and a communication unit 13.

[0028] The control unit 11 performs various arithmetic processing to realize the functions of the EMS 10, and is configured to include processors such as a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), and a GPU (Graphics Processing Unit). The functions of the control unit 11 are realized as functional units by the control unit 11 reading and executing various programs from the storage unit 12.

[0029] The storage unit 12 includes, for example, a ROM (Read Only Memory) that stores various programs and data used by the control unit 11 to perform arithmetic processing. The storage unit 12 also includes, for example, a RAM (Random Access Memory) that is used as a workspace for the control unit 11 to perform arithmetic processing and for storing the results of the arithmetic processing of the control unit 11. The storage unit 12 may include an auxiliary storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The control unit 11 executes the programs stored in the storage unit 12 to realize a function of controlling the protection device PR, first protection devices P11, P12, second protection devices P21 to P24, and breaker units provided in the power converters C1 to C8.

[0030] The communication unit 13 includes a communication module that performs wired or wireless information communication. The communication unit 13 performs information communication with the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the power converters C1 to C8 via a network NW that is configured from an internet network, a mobile phone network, etc.

[0031] <Configuration of the interrupter> Next, the specific configuration of the breaker units provided in the protection device PR, first protection devices P11, P12, second protection devices P21 to P24, and power converters C1 to C8 will be described. Fig. 2 is a diagram showing the configuration of a breaker unit 100 provided in the protection device PR, first protection devices P11, P12, second protection devices P21 to P24, and power converters C1 to C8. The breaker unit 100 includes terminals T1 and T2, a control unit 101, a measurement unit 102, a switching unit 103, and a communication unit 104. The breaker units 100 provided in the first protection devices P11, P12, second protection devices P21 to P24, and power converters C1 to C8 are an example of a first breaker unit, and the breaker unit 100 provided in the protection device PR is an example of a second breaker unit.

[0032] Terminal T1 is connected to the bus BUS on the upstream side as viewed from the circuit breaker 100, and terminal T2 is connected to the bus BUS on the downstream side as viewed from the circuit breaker 100. In the circuit breaker 100 provided in the protection device PR, for example, terminal T1 is connected to the bus BUS on the DC grid GR1 side, and terminal T2 is connected to the bus BUS on the DC grid GR2 side. In addition, in the circuit breaker 100 provided in each of the power converters C1 to C8, for example, terminal T1 is connected to the bus BUS on the DC grid GR1 side, and terminal T2 is connected to the power element.

[0033] The switching unit 103 is connected to the terminal T1 and the terminal T2, and is controlled by the control unit 101 to connect and disconnect between the terminal T1 and the terminal T2. In the circuit breaker 100 of the first protection devices P11, P12 and the second protection devices P21 to P24, when the switching unit 103 is in a closed state, the bus BUS on the upstream side as viewed from the circuit breaker 100 is connected to the bus BUS on the downstream side, and when the switching unit 103 is in an open state, the bus BUS on the upstream side as viewed from the circuit breaker 100 is disconnected from the bus BUS on the downstream side. In the circuit breaker 100 of the protection device PR, when the switching unit 103 is in a closed state, the bus BUS of the DC grid GR1 is connected to the bus BUS of the DC grid GR2, and when the switching unit 103 is in an open state, the bus BUS of the DC grid GR1 is disconnected from the bus BUS of the DC grid GR2. In the disconnection section 100 of the power converters C1 to C8, when the switching section 103 is in the closed state, the bus BUS and the power element are connected, and when the switching section 103 is in the open state, the bus BUS and the power element are disconnected.

[0034] The measurement unit 102 is a so-called current measuring device, and measures the current value of the current flowing through the bus BUS and the direction of the current flowing through the bus BUS. The measurement unit 102 outputs the measurement results of the current value and current direction to the control unit 101. Note that the measurement unit 102 may also measure the voltage value and power value of the bus BUS.

[0035] The communication unit 104 includes a communication module for performing information communication via wire or wirelessly, and performs information communication with the EMS 10 via a network NW configured from the Internet network, a mobile phone network, etc. The communication unit 104, for example, receives commands from the EMS 10 and outputs them to the control unit 101, and transmits information about the bus BUS input from the control unit 101 to the EMS 10.

[0036] The control unit 101 includes a processor and a storage unit that perform various arithmetic operations to realize the functions of disconnecting and connecting the bus BUS. The processor and storage unit may use the configurations exemplified as the control unit 11 and storage unit 12, respectively. The functions of the control unit 101 are realized by the processor reading and executing various programs from the storage unit. The control unit 101 controls the opening / closing unit 103 based on, for example, the measurement results of the measurement unit 102 and commands from the EMS 10.

[0037] Specifically, the control unit 101 controls the switching unit 103 to a closed state when the current value measured by the measurement unit 102 is less than a predetermined threshold value stored in the storage unit. Furthermore, the control unit 101 controls the switching unit 103 to an open state when the state in which the current value measured by the measurement unit 102 is equal to or greater than the predetermined threshold value continues for a predetermined breaking time or longer. That is, the breaking units 100 provided in the protection device PR, first protection devices P11, P12, second protection devices P21 to P24, and power converters C1 to C8 each break or connect the bus BUS in an autonomous and decentralized manner.

[0038] The threshold value and the breaking time used by the control unit 101 when controlling the switching unit 103 are stored in the storage unit, and the breaking time is set according to predetermined rules. Specifically, in this embodiment, breaking times t1 to t5 are set, and the breaking times t1 to t5 are set based on the following rules (1) to (3). (1) When a fault occurs downstream of the power converters C1 to C8, the fault does not spread to the upstream side of the power converters C1 to C8. (2) When an accident occurs within a DC grid, the accident does not spread to other connected DC grids. (3) Limiting the extent of interruption within the DC grid when an accident occurs.

[0039] The breaking times are stored for the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the power converters C1 to C8. The breaking time t2 is stored for the protection device PR. The breaking time t1 and the breaking time t5 are stored for the power converters C1 to C8. The breaking time t1 is used when the measured current direction is downstream, and the breaking time t5 is used when the measured current direction is upstream. The first protection devices P11, P12 and the second protection devices P21 to P24 are stored with the breaking times t3 and t4. The breaking time t4 is used when the measured current direction is downstream, and the breaking time t3 is used when the current direction is upstream. In the case of the power system 1 shown in FIG. 1, the relationship between the interruption times t1 to t5 is set to be interruption time t1<interruption time t2<interruption time t3<interruption time t4<interruption time t5 based on the rules (1) to (3).

[0040] <Example of power system operation> (First operation example) Next, an operation example of the power system 1 will be described. Fig. 3 is a diagram for explaining an operation example when a short circuit occurs at position S1 between the power converter C2 and the power element EL2. In Fig. 3, the components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in Fig. 3, the network NW and EMS 10 are omitted from illustration.

[0041] When a short circuit occurs at position S1, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S1 in bus BUS. As a result, in protection device PR, the current flows toward DC grid GR1, and in first protection device P11, second protection device P21, and power converter C2, the current flows downstream. In addition, in first protection device P12, second protection devices P22 to P24, and power converters C1, C3 to C8, the current flows upstream.

[0042] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S1 and the measured current value exceeds a threshold value, the control unit 101 starts measuring the elapsed time since the current value exceeded the threshold value.

[0043] First, in the circuit breaker 100 of power converter C2, the direction of the current flowing is downstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t1 stored in the memory unit. In the circuit breaker 100 of power converter C2, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the breaking time t1, and the control unit 101 controls the switching unit 103 to open it. As a result, the short-circuit position S1 downstream of the power converter C2 is disconnected from the bus BUS. Because the position S1 is disconnected from the power converter C2, the current value of the current flowing through the bus BUS becomes less than the threshold value.

[0044] Furthermore, in the circuit breaking unit 100 of the protection device PR, the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t2 stored in the memory unit. Here, in the circuit breaking unit 100 of the protection device PR, because the position S1 is disconnected from the bus BUS, the current value measured by the measurement unit 102 becomes equal to or less than the threshold value before the measured elapsed time becomes equal to or greater than the breaking time t2. In the circuit breaking unit 100 of the protection device PR, the state in which the current value is equal to or greater than the threshold value does not continue for equal to or greater than the breaking time t2, so the control unit 101 closes the switching unit 103.

[0045] Furthermore, in the circuit breakers 100 of the first protection device P12 and the second protection devices P22 to P24, the direction of current flow is upstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t3 stored in the memory unit. Here, in the circuit breakers 100 of the first protection device P12 and the second protection devices P22 to P24, position S1 is disconnected from the bus BUS, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time becomes equal to or greater than the breaking time t3. In the circuit breakers 100 of the first protection device P12 and the second protection devices P22 to P24, the state in which the current value is equal to or greater than the threshold does not continue for equal to or greater than the breaking time t3, so the control unit 101 closes the switching unit 103.

[0046] Furthermore, in the circuit breaking units 100 of the first protection device P11 and the second protection device P21, the direction of current flow is downstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t4 stored in the memory unit. Here, in the circuit breaking units 100 of the first protection device P11 and the second protection device P21, position S1 is disconnected from the bus BUS, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time becomes equal to or greater than the breaking time t4. In the circuit breaking units 100 of the first protection device P11 and the second protection device P21, the state in which the current value is equal to or greater than the threshold does not continue for equal to or greater than the breaking time t4, so the control unit 101 closes the switching unit 103.

[0047] Furthermore, in the breaker units 100 of the power converters C1, C3 to C8, the direction of current flow is upstream, so the control unit 101 determines whether to open or close the switching unit 103 using the interruption time t5 stored in the memory unit. Here, in the breaker units 100 of the power converters C1, C3 to C8, position S1 is disconnected from the bus BUS, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time reaches or exceeds the interruption time t5. In the breaker units 100 of the power converters C1, C3 to C8, the state in which the current value is equal to or greater than the threshold does not continue for or exceeds the interruption time t5, so the control unit 101 closes the switching unit 103.

[0048] As described above, when a short circuit occurs at position S1, the circuit breaker 100 included in power converter C2, which is the nearest node upstream of position S1, breaks the connection between the upstream and downstream sides of power converter C2. When a short circuit occurs at position S1, only the downstream side of power converter C2 is disconnected in DC grid GR1, so components not hatched in Fig. 3 can exchange power via bus BUS. Furthermore, in the circuit breaker 100 of protection device PR, the control unit 101 does not open the switching unit 103, so the connection between DC grid GR1 and DC grid GR2 can continue.

[0049] (Second operation example) Fig. 4 is a diagram for explaining an example of operation when a short circuit occurs at position S2 between the power converters C1, C2 and the second protection device P21. In Fig. 4, the components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in Fig. 4, the network NW and EMS 10 are omitted from illustration.

[0050] If a short circuit occurs at position S2, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S2 in bus BUS. Therefore, in protection device PR, the current flows toward DC grid GR1, and in first protection device P11 and second protection device P21, the current flows downstream. Also, in power converters C1 to C8, first protection device P12, and second protection devices P22 to P24, the current flows upstream.

[0051] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S2 and the measured current value exceeds a threshold value, the control unit 101 starts measuring the elapsed time since the current value exceeded the threshold value.

[0052] First, in the circuit breaker 100 of the protection device PR, the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t2 stored in the memory unit. In the circuit breaker 100 of the protection device PR, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the breaking time t2, and the control unit 101 controls the switching unit 103 to open it. This disconnects the DC grid GR2 from the DC grid GR1.

[0053] Next, in the circuit breaker 100 of the first protection device P12 and the second protection devices P22 to P24, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3 stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection device P12 and the second protection devices P22 to P24, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3, and the control unit 101 controls the switching unit 103 to open it.

[0054] Next, in the circuit breaker 100 of the first protection device P11 and the second protection device P21, the direction of the current flow is downstream, so the control unit 101 uses the circuit breaker time t4 stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection device P11 and the second protection device P21, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t4, and the control unit 101 controls the switching unit 103 to open it.

[0055] Next, in the circuit breaker 100 of the power converters C1 and C2, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t5 stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the power converters C1 and C2, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t5, and the control unit 101 controls the switching unit 103 to open it.

[0056] In the circuit breakers 100 of the power converters C3 to C8, the direction of current flow is upstream, so the control unit 101 uses the breaking time t5 stored in the memory unit to determine whether to open or close the switching unit 103. Here, in the circuit breakers 100 of the power converters C3 to C8, the circuit breakers 100 of the second protection devices P23 and P24 open the switching unit 103 at breaking time t3, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time reaches or exceeds breaking time t5. In the circuit breakers 100 of the power converters C3 to C8, the state in which the current value is equal to or greater than the threshold does not continue for or exceeds breaking time t5, so the control unit 101 closes the switching unit 103.

[0057] As described above, when a short circuit occurs at position S2, at least the circuit breaker 100 included in the second protection device P21, which is the nearest node upstream of position S2, and the circuit breaker 100 included in the power converters C1 and C2, which are the nearest nodes downstream of position S2, break the connection between their own upstream and downstream sides. When a short circuit occurs at position S2, in DC grid GR1, the switching units 103 of the circuit breakers 100 in power converters C3 to C8 are closed, so that power can be exchanged between power converters C3 and C4, between power converters C5 and C6, and between power converters C7 and C8, which are not hatched in Fig. 4.

[0058] (Third operation example) Fig. 5 is a diagram for explaining an example of operation when a short circuit occurs at position S3 between the first protection device P11 and the second protection devices P21 and P22. In Fig. 5, the components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in Fig. 5, the network NW and EMS 10 are omitted from illustration.

[0059] When a short circuit occurs at position S3, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S3 in bus BUS. As a result, in protection device PR, the current flows toward DC grid GR1, and in first protection device P11, the current flows downstream. In addition, in power converters C1 to C8, first protection device P12, and second protection devices P21 to P24, the current flows upstream.

[0060] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S3 and the measured current value exceeds a threshold value, the control unit 101 begins measuring the elapsed time since the current value exceeded the threshold value.

[0061] First, in the breaker unit 100 of the protection device PR, as in the second operation example, the elapsed time measured by the measuring unit 102 becomes equal to or greater than the breaker time t2, and the control unit 101 controls the switching unit 103 to open the switching unit 103. This disconnects the DC grid GR2 from the DC grid GR1.

[0062] Next, in the breaker units 100 of the first protection device P12 and the second protection devices P21 to P24, the direction of the current flow is upstream, so the control unit 101 uses the breaking time t3 stored in the memory unit to determine whether to open or close the switching unit 103. In the breaker units 100 of the first protection device P12 and the second protection devices P21 to P24, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the breaking time t3, and the control unit 101 controls the switching unit 103 to open it.

[0063] Next, in the circuit breaker 100 of the first protection device P11, the direction of the current flow is downstream, so the control unit 101 uses the circuit breaker time t4 stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection device P11, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t4, and the control unit 101 controls the switching unit 103 to open it.

[0064] In the circuit breaker 100 of each of the power converters C1 to C8, the direction of current flow is upstream, so the control unit 101 uses the breaking time t5 stored in the memory unit to determine whether to open or close the switching unit 103. Here, in the circuit breaker 100 of each of the power converters C1 to C8, the circuit breaker 100 of each of the second protection devices P21 to P24 opens the switching unit 103 at breaking time t3, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold value before the measured elapsed time reaches or exceeds breaking time t5. In the circuit breaker 100 of each of the power converters C1 to C8, the state in which the current value is equal to or greater than the threshold value does not continue for or exceeds breaking time t5, so the control unit 101 closes the switching unit 103.

[0065] As described above, when a short circuit occurs at position S3, at least the circuit breaker 100 included in the first protection device P11, which is the nearest node upstream of position S3, and the circuit breaker 100 included in the second protection devices P21 and P22, which are the nearest nodes downstream of position S3, break the connection between their upstream and downstream sides. When a short circuit occurs at position S3, in DC grid GR1, the switching units 103 of the circuit breakers 100 in power converters C1 to C8 are closed, so that power can be exchanged between power converters C1 and C2, between power converters C3 and C4, between power converters C5 and C6, and between power converters C7 and C8, which are not hatched in Fig. 5.

[0066] (Fourth operation example) Fig. 6 is a diagram for explaining an example of operation when a short circuit occurs at position S4 between the protection device PR and the first protection devices P11 and P12. In Fig. 6, the components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in Fig. 6, the network NW and EMS 10 are omitted from the illustration.

[0067] When a short circuit occurs at position S4, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S4 in bus BUS. As a result, in protection device PR, a current flows toward DC grid GR1. Furthermore, in power converters C1 to C8, first protection devices P11 and P12, and second protection devices P21 to P24, a current flows upstream.

[0068] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S4 and the measured current value exceeds a threshold value, the control unit 101 begins measuring the elapsed time since the current value exceeded the threshold value.

[0069] First, in the protection device PR, as in the second operation example, the elapsed time measured by the measurement unit 102 of the breaker unit 100 becomes equal to or greater than the breaker time t2, and the control unit 101 controls the switching unit 103 to open the switching unit 103. This disconnects the DC grid GR2 from the DC grid GR1.

[0070] Next, in the circuit breakers 100 of the first protection devices P11, P12 and the second protection devices P21 to P24, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3 stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breakers 100 of the first protection devices P11, P12 and the second protection devices P21 to P24, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3, and the control unit 101 controls the switching unit 103 to open it.

[0071] In the circuit breaker 100 of each of the power converters C1 to C8, the direction of current flow is upstream, so the control unit 101 uses the breaking time t5 stored in the memory unit to determine whether to open or close the switching unit 103. Here, in the circuit breaker 100 of each of the power converters C1 to C8, the circuit breaker 100 of each of the second protection devices P21 to P24 opens the switching unit 103, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold value before the elapsed time being measured reaches or exceeds the breaking time t5. In the circuit breaker 100 of each of the power converters C1 to C8, the state in which the current value is equal to or greater than the threshold value does not continue for or exceeds the breaking time t5, so the control unit 101 closes the switching unit 103.

[0072] As described above, when a short circuit occurs at position S4, at least the circuit breaker 100 included in the protection device PR that is the nearest node upstream of position S4 and the circuit breaker 100 included in the first protection devices P11 and P12 that are the nearest nodes downstream of position S4 break the connection between their own upstream and downstream sides. When a short circuit occurs at position S4, in DC grid GR1, the switching units 103 of the circuit breakers 100 in power converters C1 to C8 are closed, so that power can be exchanged between power converters C1 and C2, between power converters C3 and C4, between power converters C5 and C6, and between power converters C7 and C8, which are not hatched in Fig. 6.

[0073] It should be noted that the interruption times stored in the control unit 101 are not limited to the interruption times t1 to t5. In the above-described configuration, the first protection devices P11, P12 and the second protection devices P21 to P24 store the interruption time t3, but for example, the interruption time t3 stored in the first protection devices P11, P12 may be referred to as the interruption time t3a, and the interruption time t3 stored in the second protection devices P21 to P24 may be referred to as the interruption time t3b. Also, in the above-described configuration, the first protection devices P11, P12 and the second protection devices P21 to P24 store the interruption time t4, but the interruption time t4 stored in the first protection devices P11, P12 may be referred to as the interruption time t4b, and the interruption time t4 stored in the second protection devices P21 to P24 may be referred to as the interruption time t4a. In this modification, the relationship between the shutoff times t1, t2, t3a, t3b, t4a, t4b, and t5 is set as follows: shutoff time t1<shutoff time t2<shutoff time t3a<shutoff time t3b<shutoff time t4a<shutoff time t4b<shutoff time t5. An example of operation in this modification will be described below.

[0074] (5th operation example) 7 is a diagram illustrating an example of operation when a short circuit occurs at position S5 between the power converters C1 and C2 and the second protection device P21, where the interruption times are t1, t2, t3a, t3b, t4a, t4b, and t5. In FIG. 7, the components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in FIG. 7, the network NW and EMS 10 are not shown.

[0075] When a short circuit occurs at position S5, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S5 in bus BUS. Therefore, in protection device PR, the current flows toward DC grid GR1, and in first protection device P11 and second protection device P21, the current flows downstream. In addition, in power converters C1 to C8, first protection device P12, and second protection devices P22 to P24, the current flows upstream.

[0076] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S5 and the measured current value exceeds a threshold value, the control unit 101 begins measuring the elapsed time since the current value exceeded the threshold value.

[0077] First, in the breaker unit 100 of the protection device PR, as in the second operation example, the elapsed time measured by the measuring unit 102 becomes equal to or greater than the breaker time t2, and the control unit 101 controls the switching unit 103 to open the switching unit 103. This disconnects the DC grid GR2 from the DC grid GR1.

[0078] Next, in the circuit breaker 100 of the first protection device P12, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3a stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection device P12, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3a, and the control unit 101 controls the switching unit 103 to open it.

[0079] Next, in the circuit breaker 100 of the second protection device P22, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3b stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the second protection device P22, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3b, and the control unit 101 controls the switching unit 103 to open it.

[0080] In the circuit breaker 100 of the second protection devices P23 and P24, the direction of current flow is upstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t3b stored in the memory unit. Here, in the circuit breaker 100 of the second protection devices P23 and P24, the first protection device P12 opens the switching unit 103 in the circuit breaker 100, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the elapsed time being measured becomes equal to or greater than the breaking time t3b. In the circuit breaker 100 of the second protection devices P23 and P24, the state in which the current value is equal to or greater than the threshold does not continue for equal to or greater than the breaking time t3b, so the control unit 101 closes the switching unit 103.

[0081] Next, in the circuit breaker 100 of the second protection device P21, the direction of the current flow is downstream, so the control unit 101 uses the circuit breaker time t4a stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the second protection device P21, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t4a, and the control unit 101 controls the switching unit 103 to open it.

[0082] In the circuit breaker 100 of the power converters C1 and C2, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t5 stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the power converters C1 and C2, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t5, and the control unit 101 controls the switching unit 103 to open it.

[0083] In the circuit breaker 100 of the power converters C3 to C8, the direction of current flow is upstream, so the control unit 101 uses the breaking time t5 stored in the memory unit to determine whether to open or close the switching unit 103. Here, in the circuit breaker 100 of the power converters C3 to C8, the circuit breaker 100 of the first protection device P12 opens the switching unit 103, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time reaches or exceeds the breaking time t5. In the circuit breaker 100 of the power converters C3 to C8, the state in which the current value is equal to or greater than the threshold does not continue for or exceeds the breaking time t5, so the control unit 101 closes the switching unit 103.

[0084] As described above, when a short circuit occurs at position S5, at least the circuit breaker 100 included in the second protection device P21, which is the nearest node upstream of position S5, and the circuit breaker 100 included in the power converters C1 and C2, which are the nearest nodes downstream of position S5, break the connection between their upstream and downstream sides. When a short circuit occurs at position S5, in DC grid GR1, the switching units 103 of the circuit breakers 100 in the second protection devices P23 and P24 and the power converters C3 to C8 are closed, so that power can be exchanged between the power converters C3 and C4, which are not hatched in Fig. 7, and between the power converters C5 to C8.

[0085] (6th operation example) 8 is a diagram illustrating an example of operation when a short circuit occurs at position S6 between the first protection device P11 and the second protection devices P21 and P22, assuming that the interruption times are t1, t2, t3a, t3b, t4a, t4b, and t5. In FIG. 8, the components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in FIG. 8, the network NW and EMS 10 are not shown.

[0086] If a short circuit occurs at position S6, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S6 in bus BUS. Therefore, in protection device PR, the current flows toward DC grid GR1, and in first protection device P11, the current flows downstream. Furthermore, in power converters C1 to C8, first protection device P12, and second protection devices P21 to P24, the current flows upstream.

[0087] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S6 and the measured current value exceeds a threshold value, the control unit 101 starts measuring the elapsed time since the current value exceeded the threshold value.

[0088] First, in the breaker unit 100 of the protection device PR, as in the second operation example, the elapsed time measured by the measuring unit 102 becomes equal to or greater than the breaker time t2, and the control unit 101 controls the switching unit 103 to open the switching unit 103. This disconnects the DC grid GR2 from the DC grid GR1.

[0089] Next, in the circuit breaker 100 of the first protection device P12, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3a stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection device P12, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3a, and the control unit 101 controls the switching unit 103 to open it.

[0090] Next, in the circuit breaker 100 of the second protection devices P21 and P22, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3b stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the second protection devices P21 and P22, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3b, and the control unit 101 controls the switching unit 103 to open it.

[0091] In the circuit breaker 100 of the second protection devices P23 and P24, the direction of current flow is upstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t3b stored in the memory unit. Here, in the circuit breaker 100 of the second protection devices P23 and P24, the first protection device P12 opens the switching unit 103 in the circuit breaker 100, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the elapsed time being measured becomes equal to or greater than the breaking time t3b. In the circuit breaker 100 of the second protection devices P23 and P24, the state in which the current value is equal to or greater than the threshold does not continue for equal to or greater than the breaking time t3b, so the control unit 101 closes the switching unit 103.

[0092] Next, in the circuit breaker 100 of the first protection device P11, the direction of the current flow is downstream, so the control unit 101 uses the circuit breaker time t4b stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection device P11, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t4b, and the control unit 101 controls the switching unit 103 to open it.

[0093] In the circuit breakers 100 of the power converters C1 to C8, the direction of current flow is upstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t5 stored in the memory unit. Here, in the circuit breakers 100 of the power converters C1 and C2, the circuit breaker 100 of the second protection device P21 opens the switching unit 103, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time reaches or exceeds the breaking time t5. In the circuit breakers 100 of the power converters C1 and C2, the state in which the current value is equal to or greater than the threshold does not continue for or exceed the breaking time t5, so the control unit 101 closes the switching unit 103.

[0094] In the circuit breaker 100 of the power converters C3 and C4, the circuit breaker 100 of the second protection device P22 opens the switching unit 103, so that the current value measured by the measuring unit 102 falls below the threshold before the measured elapsed time reaches or exceeds the interruption time t5. In the circuit breaker 100 of the power converters C3 and C4, the state in which the current value is above the threshold does not continue for or exceed the interruption time t5, so the control unit 101 closes the switching unit 103.

[0095] Furthermore, in the circuit breaker 100 of the power converters C5 to C8, the circuit breaker 100 of the first protection device P12 opens the switching unit 103, so that the current value measured by the measurement unit 102 becomes equal to or less than the threshold value before the measured elapsed time reaches or exceeds the interruption time t5. In the circuit breaker 100 of the power converters C5 to C8, the state in which the current value is equal to or greater than the threshold value does not continue for or exceeds the interruption time t5, so the control unit 101 closes the switching unit 103.

[0096] As described above, when a short circuit occurs at position S6, at least the circuit breaker 100 included in the first protection device P11, which is the nearest node upstream of position S6, and the circuit breaker 100 included in the second protection devices P21 and P22, which are the nearest nodes downstream of position S6, break the connection between their upstream and downstream sides. When a short circuit occurs at position S6, in DC grid GR1, the switching units 103 of the circuit breakers 100 in the second protection devices P23 and P24 and the power converters C1 to C8 are closed, so that power can be exchanged between power converters C1 and C2, between power converters C3 and C4, and between power converters C5 to C8, which are not hatched in Fig. 8.

[0097] (7th operation example) 9 is a diagram illustrating an example of operation when a short circuit occurs at position S7 between protection device PR and first protection devices P11 and P12, with interruption times being t1, t2, t3a, t3b, t4a, t4b, and t5. In FIG. 9, components that open the switching unit 103 due to the occurrence of a short circuit and the interruption time are indicated by hatching. Also, in FIG. 9, the network NW and EMS 10 are omitted from illustration.

[0098] When a short circuit occurs at position S7, a current having a value equal to or greater than the threshold stored in control unit 101 flows toward position S7 in bus BUS. As a result, a current flows downstream in protection device PR. Furthermore, a current flows upstream in power converters C1 to C8, first protection devices P11 and P12, and second protection devices P21 to P24.

[0099] In the protection device PR, the first protection devices P11, P12, the second protection devices P21 to P24, and the circuit breaker 100 of the power converters C1 to C8, when a short circuit occurs at position S7 and the measured current value exceeds a threshold value, the control unit 101 begins measuring the elapsed time since the current value exceeded the threshold value.

[0100] First, in the breaker unit 100 of the protection device PR, as in the second operation example, the elapsed time measured by the measuring unit 102 becomes equal to or greater than the breaker time t2, and the control unit 101 controls the switching unit 103 to open the switching unit 103. This disconnects the DC grid GR2 from the DC grid GR1.

[0101] Next, in the circuit breaker 100 of the first protection devices P11 and P12, the direction of the current flow is upstream, so the control unit 101 uses the circuit breaker time t3a stored in the memory unit to determine whether to open or close the switching unit 103. In the circuit breaker 100 of the first protection devices P11 and P12, the elapsed time measured by the measurement unit 102 becomes equal to or greater than the circuit breaker time t3a, and the control unit 101 controls the switching unit 103 to open it.

[0102] In the circuit breakers 100 of the second protection devices P21 to P24, the direction of current flow is upstream, so the control unit 101 determines whether to open or close the switching unit 103 using the breaking time t3b stored in the memory unit. Here, in the circuit breakers 100 of the second protection devices P21 to P24, the circuit breakers 100 of the first protection devices P11 and P12 open the switching unit 103, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time reaches or exceeds the breaking time t5. In the circuit breakers 100 of the second protection devices P21 to P24, the state in which the current value is equal to or greater than the threshold does not continue for or exceed the breaking time t3b, so the control unit 101 closes the switching unit 103.

[0103] Furthermore, in the circuit breaker 100 of the power converters C1 to C8, the direction of current flow is upstream, so the control unit 101 uses the breaking time t5 stored in the memory unit to determine whether to open or close the switching unit 103. Here, in the circuit breaker 100 of the power converters C1 to C8, the circuit breaker 100 of the first protection devices P11, P12 opens the switching unit 103, so the current value measured by the measurement unit 102 becomes equal to or less than the threshold before the measured elapsed time reaches or exceeds the breaking time t5. In the circuit breaker 100 of the power converters C1 to C8, the state in which the current value is equal to or greater than the threshold does not continue for or exceed the breaking time t5, so the control unit 101 closes the switching unit 103.

[0104] As described above, when a short circuit occurs at position S7, at least the circuit breaker 100 included in the protection device PR that is the nearest node upstream of position S7 and the circuit breaker 100 included in the first protection devices P11 and P12 that are the nearest nodes downstream of position S7 break the connection between their upstream and downstream sides. When a short circuit occurs at position S7, in DC grid GR1, the switching units 103 of the circuit breakers 100 in the second protection devices P21 to P24 and the power converters C1 to C8 are closed, so that power can be exchanged between the power converters C1 to C4 that are not hatched in Fig. 9 and the power converters C5 to C8.

[0105] As described above, according to this embodiment, when an accident occurs downstream of the power converters C1 to C8, it is possible to prevent the accident from spreading upstream of the power converters C1 to C8. Furthermore, according to this embodiment, when an accident occurs on a bus BUS in a DC grid, it is possible to prevent the accident from spreading to buses BUS of other DC grids connected to the bus BUS of the DC grid where the accident occurred. Furthermore, according to this embodiment, when an accident occurs on a bus BUS in a DC grid, it is possible to suppress the spread of the accident and maximize the number of power elements that continue to operate.

[0106] It should be noted that the present invention is not limited to the above-described embodiments. The present invention also includes configurations in which the above-described components are appropriately combined. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments, and various modifications are possible.

[0107] In the above-described embodiment, when the bus BUS recovers from a short-circuit accident, a command to close the switching unit 103 is sent from the EMS 10, and the device that receives this command may close the switching unit 103 in response to the command.

[0108] In the above-described embodiment, the circuit breaker 100 that has closed the switching unit 103 may transmit an identifier for identifying itself and information indicating that the switching unit 103 has been closed to the EMS 10. This configuration makes it possible to know which component in the DC grids GR1 and GR2 has cut off the power supply, and to know the location of the accident.

[0109] In the above-described embodiment, the tree-shaped bus BUS has a three-layer configuration downstream of the protection device PR, but it may have two or four or more layers. Also, in the above-described embodiment, the tree-shaped bus BUS branches from one node to two nodes, but it may also branch from one node to three or more nodes. Also, downstream of the second protection devices P21 to P24, there may be at least one power storage device or power generation device for each of the second protection devices P21 to P24.

[0110] In the above-described embodiment, the power system 1 includes the DC grid GR1 and the DC grid GR2, but may also be configured without the DC grid GR2.

[0111] In the above-described embodiment, a commercial power system may be connected to the bus BUS via a power converter capable of converting AC power to DC power and DC power to AC power. Preferably, the power converter to which the commercial power system is connected also includes the circuit breaker 100. [Explanation of symbols]

[0112] 1. Power System 10 EMS 11 Control section 12 Storage section 13 Communications Department 100 Breaker 101 Control section 102 Measuring part 103 Opening and Closing Section 104 Communications Department BUS C1~C8 Power converters EL1~EL4 power elements EV Electric Vehicle GR1, GR2 DC grid NW Network P11, P12 1st protection device P21~P24 2nd protection device PR protection device T1 and T2 terminals

Claims

1. a bus provided in a tree shape and supplying power by DC; a first interruption unit provided for each node of the bus, which performs connection and disconnection between the upstream side and downstream side of the node that includes the first interruption unit, and which disconnects the upstream side and downstream side of the node that includes the first interruption unit when a state in which a current value flowing through the first interruption unit is equal to or greater than a threshold due to an accident on the bus continues for a disconnection time determined for each direction of the current; and The bus route is connected to other buses, the route includes a second interruption unit that connects and interrupts the connection between one of the connected buses and the other of the connected buses; the second cutoff unit cuts off communication between the one bus and the other bus when the location of the fault is upstream of a terminal node of the bus; At least the first cutoff unit provided in the nearest node on the upstream side of the location of the accident on the bus and the first cutoff unit provided in the nearest node on the downstream side of the location of the accident on the bus cut off between the upstream side and downstream side of the node that includes them. Power system.

2. the terminal node is a power converter that converts input power and outputs the converted power, a power element capable of supplying, consuming, or charging power is connected to the power converter; When the location of the fault is between the terminal node and the power element, the first interrupter of the terminal node interrupts the connection between the upstream side and the downstream side of the node. The power system of claim 1 .

3. The first cutoff unit connects between the upstream side and the downstream side of the node having the first cutoff unit in response to an external command. The power system according to claim 1 or 2.

4. The blocking time varies depending on the hierarchy of the node. The power system according to any one of claims 1 to 3.

5. a bus provided in a tree shape and supplying power by DC; a first interruption unit provided for each node of the bus, which performs connection and disconnection between the upstream side and downstream side of the node that includes the first interruption unit, and which disconnects the upstream side and downstream side of the node that includes the first interruption unit when a state in which a current value flowing through the first interruption unit is equal to or greater than a threshold due to an accident on the bus continues for a disconnection time determined for each direction of the current; and The bus route is connected to other buses, The route includes a second disconnection unit that connects and disconnects the bus between the connected bus and the other bus. A control method for a power system comprising: the second cutoff unit cuts off communication between the one bus and the other bus when the location of the fault is upstream of a terminal node of the bus; At least the first cutoff unit provided in the nearest node on the upstream side of the location of the accident on the bus and the first cutoff unit provided in the nearest node on the downstream side of the location of the accident on the bus cut off between the upstream side and downstream side of the node that includes them. Power system control methods.

Images