Power system and control method thereof

Abstract

To provide a power system which is interconnected with a power system utilized for stable supply of power, and a control method therefor.SOLUTION: In a power system S1, a power facility 10 comprising a power supply device 11 and a power conditioner 21 has two operation modes of a first operation mode and a second operation mode. A system control device 50 supplies power from the power facility 10 to a load connected to an interconnection line L0 including at least a specific load 70B, by closing an interconnection switch 41 and interconnecting the power facility 10 to a power system 1 in the first operation mode, supplies power from the power facility 10 only to the specific load 70B by interconnecting to the power system 1 and controlling output power of the power facility 10 equal to or less than load power of the specific load 70B in the second operation mode, and continues power supply from the power facility 10 to the specific load 70B without interruption by opening the interconnection switch 41 and paralleling off the power facility 10 from the power system in a case where abnormality of the power system 1 is detected.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a power system that is interconnected with an electric power grid. [Background technology]

[0002] In order to reduce dependence on fossil fuels and address environmental issues, the introduction of distributed power sources, such as photovoltaic (PV) systems, is being promoted. PV systems convert the power generated by solar panels from direct current to alternating current using an inverter circuit and output the converted power. Patent Document 1 listed below discloses a photovoltaic power generation system that is connected to a power grid.

[0003] A power system (solar power generation system) connected to a power grid supplies power from power equipment (solar power generation panels) to a load, and if there is surplus power, it flows back to the power grid to sell the power. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-126110 Summary of the Invention [Problem to be solved by the invention]

[0005] The loads of a power system may include loads that require a stable supply of power. An object of the present invention is to enable a power system interconnected with a power grid to be used not only for energy conservation purposes but also for a stable supply of power. [Means for solving the problem]

[0006] The power system includes a power facility, an interconnection line that connects the power facility to a power grid, an interconnection switch located on the interconnection line, a specific load connected to the interconnection line, and a control device, and the power facility has two operating modes: a first operating mode and a second operating mode.

[0007] In the first operation mode, the control device closes the interconnection switch to interconnect the power equipment to the power grid, and supplies power from the power equipment to loads connected to the interconnection line including at least the specific load without being limited by the load power of the specific load.In the second operation mode, the control device closes the interconnection switch to interconnect the power equipment to the power grid, controls the output power of the power equipment to be equal to or less than the load power of the specific load, and supplies power from the power equipment only to the specific load.

[0008] When the control device detects an abnormality in the power grid during the second operation mode, it opens the interconnection switch to disconnect the power equipment from the power grid and continue the power supply from the power equipment to the specific load without interruption. The uninterruptible operation is a switching method in which the time when the voltage becomes zero on the AC output voltage waveform of the power equipment interconnected to the power grid is ¼ cycle or less.

[0009] This technology can be applied to a control method or a control program for a power system. [Effects of the Invention]

[0010] The power system, which is connected to the power grid, can be used not only for energy conservation purposes but also for ensuring a stable supply of electricity. [Brief explanation of the drawings]

[0011] [Figure 1] Power System Block Diagram [Figure 2] A diagram summarizing the switch status for each operating mode [Figure 3]A chart summarizing the inverter circuit control in each operating mode [Figure 4] Diagram showing the power flow during the first operating mode [Figure 5] Diagram showing the power flow during the first operating mode [Figure 6] Diagram showing the power flow during the second operating mode [Figure 7] A simplified version of Figure 6 [Figure 8] Diagram showing the flow of power during stand-alone operation of power facilities [Figure 9] Flowchart of operation mode switching process [Figure 10] 1 is a block diagram illustrating another embodiment of a power system. [Figure 11] 1 is a block diagram illustrating another embodiment of a power system. DETAILED DESCRIPTION OF THE INVENTION

[0012] The power system includes a power facility, an interconnection line that connects the power facility to a power grid, an interconnection switch located on the interconnection line, a specific load connected to the interconnection line, and a control device, and the power facility has two operating modes: a first operating mode and a second operating mode.

[0013] In the first operation mode, the control device closes the interconnection switch to interconnect the power equipment to the power grid, and supplies power from the power equipment to loads connected to the interconnection line including at least the specific load without being limited by the load power of the specific load.In the second operation mode, the control device closes the interconnection switch to interconnect the power equipment to the power grid, controls the output power of the power equipment to be equal to or less than the load power of the specific load, and supplies power from the power equipment only to the specific load.

[0014] If the control device detects an abnormality in the power system during the second operating mode, it opens the interconnection switch to disconnect the power equipment from the power system and continue to supply power from the power equipment to the specific load without interruption.

[0015] In this configuration, when the first operating mode is selected, the power facility supplies power to the loads connected to the interconnection line without being limited by the load power of the specific load. By supplying power from the power facility to the load, it is possible to utilize renewable energy such as solar power, contributing to energy savings in the power system.

[0016] In this configuration, when the second operation mode is selected, the output power of the power equipment is controlled to be equal to or less than the load power (load size) of the specific load, and the power equipment operates as a dedicated power source that supplies power only to the specific load. If an abnormality in the power grid is detected during the second operation mode, the power equipment continues to supply power to the specific load without interruption. This ensures that the power supply to the specific load is not interrupted, and a stable power supply can be provided to the specific load.

[0017] The embodiment of the present invention may be as follows. The control device may permit switching from the first operation mode to the second operation mode when the load power of the specific load is equal to or greater than a predetermined value.

[0018] If the transition to the second operation mode is permitted when the load power of the specific load is below a predetermined value, the output power of the power equipment cannot be controlled to be equal to or less than the load power, and there is a concern that the output power of the power equipment may exceed the load power of the specific load. If the output power of the power equipment exceeds the load power of the specific load, reverse power flow to the power grid may occur during the second operation mode. With this configuration, the transition to the second operation mode is permitted when the load power of the specific load is equal to or greater than a predetermined value, making it less likely that the output power of the power equipment will exceed the load power of the specific load. Therefore, it is possible to suppress the occurrence of reverse power flow to the power grid during the second operation mode.

[0019] The control device may further include a switching circuit that switches a connection point of the specific load to the interconnection line. In the first operation mode, the control device may use the switching circuit to connect the specific load to one of both end points of the interconnection switch that is on the power grid side. In the second operation mode, the control device may use the switching circuit to connect the specific load to one of both end points of the interconnection switch that is on the power equipment side.

[0020] In this configuration, the connection point of the specific load to the interconnection line can be switched depending on the operating mode. In the second operating mode, if the end point on the power equipment side of the interconnection switch is selected as the connection destination of the specific load, a path from the power equipment to the specific load can be maintained even if the interconnection switch is opened following the detection of an abnormality in the power system.

[0021] The power equipment may include a power supply device and an inverter circuit that converts DC power of the power supply device into AC power and outputs the AC power. The switching circuit may include a first switch and a second switch connected in series, the first switch being connected to one of both end points of the interconnection switch that is closer to the power grid, the second switch being connected to one of both end points of the interconnection switch that is closer to the power equipment, and the specific load being connected to a connection point between the first switch and the second switch.

[0022] The control device may close the second switch during the second operation mode, and current-control the inverter circuit so that the power supplied from the inverter circuit to the specific load via the second switch is smaller than the load power of the specific load, and if an abnormality occurs in the power grid during the second operation mode, keep the second switch closed and switch the inverter circuit from current control to voltage control. With this configuration, when an abnormality in the power grid is detected, the power equipment can transition to independent operation without momentary interruption, and continue to supply power to the specific load.

[0023] <Embodiment 1> 1. Description of power system S1 1 is a block diagram of a power system S1. The power system S1 includes a power facility 10, an interconnection line L0, branch lines L1 and L2, an interconnection switch 41, a switching circuit 45, a measurement unit 48, a control device 50, a display unit 61, an operation unit 65, a first load 70A, and a second load 70B.

[0024] The power facility 10 includes a power supply device 11 and a power conditioner 21. The power supply device 11 includes a generator 13 and a battery 15. The generator 13 may be a generator that uses renewable energy, such as a solar power generation panel PV. The battery 15 may be a secondary battery that can be repeatedly charged and discharged, such as a lithium-ion secondary battery.

[0025] The power conditioner 21 is a power conversion device and includes a first converter circuit 22, a second converter circuit 23, an inverter circuit 25, and a measurement unit 27.

[0026] The generator 13 is connected to the first converter circuit 22. The first converter circuit 22 is a DC / DC converter. The output of the generator 13 can be controlled by the first converter circuit 22. The first converter circuit 22 may be a chopper.

[0027] The battery 15 is connected to the second converter circuit 23. The second converter circuit 23 is a bidirectional DC / DC converter that discharges and charges the battery 15. The second converter circuit 23 can control the input and output of the battery 15. The second converter circuit 23 may be a bidirectional chopper.

[0028] The first converter circuit 22 and the second converter circuit 23 are each connected to an inverter circuit 25 .

[0029] The inverter circuit 25 is a bidirectional conversion circuit that selectively performs inverse conversion (inverter) that converts DC to AC and forward conversion (converter) that converts AC to DC. The inverter circuit 25 is connected to the power grid 1 via an interconnection line L0.

[0030] By causing the inverter circuit 25 to perform an inverse conversion operation, it is possible to convert the DC power input from the power supply device 11 into AC power and output it.

[0031] By operating the inverter circuit 25 in a forward conversion mode, AC power input from the power grid 1 can be converted into DC power and output. The battery 15 can be charged by the output DC power.

[0032] The measurement unit 27 measures the output voltage Vinv and the output current Iinv during the inverse conversion operation of the inverter circuit 25. The measurement unit 27 measures the input voltage Vinv and the input current Iinv during the forward conversion operation. The measurement results of the measurement unit 27 are input to the control device 50.

[0033] The interconnection line L0 connects the power equipment 10 to the power system 1. The interconnection switch 41 is installed on the interconnection line L0. By closing the interconnection switch 41, the power equipment 10 can be interconnected to the power system 1. By opening the interconnection switch 41, the power equipment 10 can be disconnected from the power system 1. The interconnection switch 41 is controlled to be closed when there is no abnormality in the power system 1.

[0034] The first branch line L1 is connected to the interconnection line L0 at point B. A first load 70A is connected to the first branch line L1.

[0035] The power system 1 is a system operated by an electric utility company and includes a system power source 3. A measuring instrument 5 is installed at a power receiving point A of the power system S1.

[0036] The measuring instrument 5 measures the received power Pgrid of the power system S1. The received power Pgrid is the power that the power system S1 receives from the power grid 1 (power at the power receiving point A). The measurement result Pgrid of the measuring instrument 5 is transmitted to the control device 50 via a communication line. The dashed line H shown in FIG. 1 indicates the boundary between the power grid 1 and the power system S1.

[0037] The switching circuit 45 is a circuit that switches the connection point of the second branch line L2 with respect to the interconnection line L0. The switching circuit 45 includes a first switch 46 and a second switch 47. The first switch 46 and the second switch 47 are connected in series.

[0038] The first switch 46 is connected to the end point D on the power grid 1 side of the interconnection switch 41, out of the end points D and E of the interconnection switch 41. The second switch 47 is connected to the end point E on the power conditioner 21 side of the interconnection switch 41, out of the end points D and E of the interconnection switch 41.

[0039] A second load 70B is connected to a connection point F of the two switches 46 and 47 via a second branch line L2.

[0040] By closing the first switch 46 and opening the second switch 47, the second load 70B can be connected to point D of the interconnection switch 41. By opening the first switch 46 and closing the second switch 47, the second load 70B can be connected to point E of the interconnection switch 41.

[0041] The second switch 47 is for independent operation, and the second load 70B is a specific load to which power is supplied by the independent operation of the power conditioner 21. The second load 70B is a load to which it is desirable to supply power to operate even during a power outage, such as a computer, elevator, refrigerator, or air conditioner.

[0042] The measurement unit 48 is installed at point C on the interconnection line L0. The measurement unit 48 measures the system voltage Vgrid of the power system 1. The measurement result of the measurement unit 48 is input to the control device 50.

[0043] The control device 50 includes a CPU 51 and a memory 53. The memory 53 stores a control program for the inverter circuit 25. In addition, the memory 53 stores data necessary for controlling the power system S1. The data includes data on the load power [kW] of the second load 70B.

[0044] The control device 50 can control switching between forward conversion operation and reverse conversion operation by issuing commands to the inverter circuit 25. The control device 50 monitors the output power Pinv of the inverter circuit 25 during reverse conversion operation and the input power Pinv during forward conversion operation, based on the measurement values ​​(Vinv, Iinv) of the measurement unit 27. The control device 50 operates the inverter circuit 25 in synchronization with the system power supply 3 during a first operation mode, which will be described later, based on the measurement values ​​of the measurement unit 48.

[0045] The control device 50 controls the connection state of the interconnection switch 41 to connect or disconnect the power equipment 10 to the power system 1. The control device 50 controls the switching circuit 45 to switch the connection point of the second load 70B to the interconnection line L0.

[0046] The display unit 61 displays various information relating to the operating state of the power conditioner 21, such as the output power Pinv [kW]. The operation unit 65 is used for input operations and selection operations for the power conditioner 21.

[0047] 2. Switching the operating mode The power equipment 10 has a first operation mode and a second operation mode. The manager of the power system S1 can use the operation unit 65 to select either operation mode.

[0048] <First operating mode> When the first operation mode is selected, the control device 50 controls the grid-connection switch 41 to be closed, as shown in Figures 2 and 4. Also, the control device 50 closes the first switch 46 of the switching circuit 45 and opens the second switch 47. By closing the first switch 46 and opening the second switch 47, the second load 70B is connected to point D of the grid-connection switch 41 via the second branch line L2.

[0049] When the first operation mode is selected, the control device 50 supplies power to the first load 70A and the second load 70B connected to the tie line L0 from the inverter circuit 25 without being limited to the load power X2 of the second load 70B. For example, the inverter circuit 25 converts the generator output into alternating current and outputs it so that the generator 13 achieves maximum efficiency. The load power X [kW] is the magnitude of the load.

[0050] The power flow of the power system S1 changes according to the magnitude relationship between the output power Pinv of the inverter circuit 25, the load power X1 of the first load 70A, and the load power X2 of the second load 70B.

[0051] When X2 < Pinv < X1 + X2, as shown in FIG. 4, the power flow at the power receiving point A is a forward power flow (a power flow from the power system 1 to the power system S1), and power is supplied to the first load 70A from both the power system 1 and the inverter circuit 25. Also, power is supplied to the second load 70B from the inverter circuit 25.

[0052] When X1 + X2 < Pinv, as shown in FIG. 5, the power flow at the power receiving point A is a reverse power flow (a power flow from the power system S1 to the power system 1), and power is supplied to the first load 70A from the inverter circuit 25. Also, power is supplied to the second load 70B from the inverter circuit 25.

[0053] During the selection of the first operation mode, the inverter circuit 25 can output without being limited to the load power X2 of the second load 70B. When X2 < Pinv, the inverter circuit 25 supplies power to the first load 70A and the second load 70B. Therefore, by utilizing renewable energy such as sunlight, the power system S1 can be energy - saved.

[0054] <When an abnormality in the power system is detected> If the control device 50 detects an abnormality in the power grid 1 during the first operation mode, for example, if it detects a voltage fluctuation or frequency fluctuation of a predetermined value or more from the measured value of the grid voltage Vgrid, it switches the interconnection switch 41 from closed to open and switches the first switch 46 of the switching circuit 45 from closed to open. In addition, the output of the inverter circuit 25 is stopped.

[0055] By opening the interconnection switch 41, the power equipment 10 can be protected by being disconnected from the power system 1 in which the abnormality has been detected. Similarly, by opening the first switch 46, the second load 70B can be protected by being disconnected from the power system 1 in which the abnormality has been detected.

[0056] <Second operating mode> When the second operation mode is selected, the control device 50 closes the grid-connection switch 41, as shown in Figures 2 and 6. Also, the control device 50 opens the first switch 46 of the switching circuit 45 and closes the second switch 47. By opening the first switch 46 and closing the second switch 47, the second load 70B is connected to point E of the grid-connection switch 41 via the second branch line L2.

[0057] When the second operation mode is selected, the control device 50 controls the output power Pinv [kW] of the inverter circuit 25 to be equal to or less than the load power X2 [kW] of the second load 70B (Pinv≦X2).

[0058] Specifically, during grid connection, the output voltage Vinv of the inverter circuit 25 is equal to the grid voltage Vgrid. Therefore, the control device 50 can control the output power Pinv of the inverter circuit 25 by controlling the output current Iinv of the inverter circuit 25 (current control).

[0059] 6, by controlling Pinv≦X2, the power flow at receiving point A becomes a forward power flow (a power flow from power system 1 toward power system S1), and power is supplied to first load 70A from power system 1. In addition, the power flow at point C on interconnection line L0 also becomes a forward power flow (a power flow from power system 1 toward power equipment 10), and power is supplied to second load 70B from both power system 1 and inverter circuit 25.

[0060] In other words, by controlling the output power Pinv of the inverter circuit 25 to be equal to or less than the load power X2 of the second load 70B, power is not supplied from the inverter circuit 25 to the first load 70A, and power is supplied only to the second load 70B.

[0061] During the second operation mode, as shown in FIG. 7, the power flow at point C is always forward, and therefore the entire power equipment 100 including the second load 70B can be regarded as a load from the perspective of the power system 1.

[0062] <When an abnormality is detected in the power grid> If the control device 50 detects an abnormality in the power grid 1 during the second operation mode, for example, if it detects a voltage fluctuation or frequency fluctuation of a predetermined value or more from the measured value of the grid voltage Vgrid, it switches the interconnection switch 41 from closed to open, as shown in FIG. 8, and keeps the second switch 47 of the switching circuit 45 closed.

[0063] By opening the interconnection switch 41, the power equipment 10 can be disconnected from the power system 1 in which the abnormality has been detected. By keeping the second switch 47 closed, the connection between the power equipment 10 and the second load 70B can be maintained.

[0064] In addition to controlling the interconnection switch 41 and the second switch 47, the control device 50 switches the inverter circuit 25 from current control to voltage control, and controls the output voltage Vinv of the inverter circuit 25 to a predetermined constant voltage such as 100V.

[0065] As a result, if an abnormality in the power grid 1 is detected during the second operation mode, the power equipment 10 transitions to independent operation without interruption, and can continue to supply power to the second load 70B. The uninterruptible switching is a method of switching in which the time it takes for the voltage to become zero on the AC output voltage waveform of the power equipment 10 interconnected with the power grid 1 is 1 / 4 cycle or less.

[0066] In this way, even if an abnormality occurs in the power system 1 while the second operation mode is selected, the power supply from the power equipment 10 to the second load 70B can continue without interruption, so that power can be stably supplied to the second load 70B.

[0067] The isolated operation refers to a state in which a distributed power source connected to a grid power source is disconnected from the grid and power is supplied from the distributed power source to a load on the customer premises. In this example, the power facility 10 is disconnected from the power grid 1 and power is supplied from the power facility 10 to a second load 70B corresponding to the load on the customer premises.

[0068] 4.Effectiveness This configuration allows the power system S1 interconnected with the power grid 1 to be used not only for energy conservation purposes (first operation mode) but also for a stable supply of power (second operation mode).

[0069] For example, if a solar power generation panel PV is used for the generator 13, the first operation mode can be selected during times when power generation is high (such as daytime), and the second operation mode can be selected during times when power generation is low (such as nighttime), thereby achieving energy conservation in the power system S1 and ensuring a stable supply of power to the second load 70B. In particular, because the power supply device 11 is equipped with a battery 15, power can be supplied to the second load 70B using the power of the battery 15 even during times when the generator 13 is not generating power. Furthermore, the selection of the operation mode is not limited to the above example, and different selections are also possible. For example, the first operation mode and the second operation mode may be selected on a daily or weekly basis.

[0070] <Embodiment 2> 9 is a flowchart of the operation mode switching process. The operation mode switching process can be performed at any time while the control device 50 is running. The initial setting of the operation mode is the first operation mode.

[0071] The operation mode switching process is made up of four steps S10 to S40. In S10, the control device 50 determines whether the second operation mode has been selected.

[0072] When the manager of the power system S1 performs a selection operation for the second operation mode using the operation unit 65, a YES determination is made in S10, and the process proceeds to S20.

[0073] In S20, the control device 50 accesses the memory 53 to read data on the load power X2 of the second load 70B, and determines whether the load power X2 [kW] of the second load 70B is equal to or greater than a predetermined value. The predetermined value can be set arbitrarily as long as it is equal to or greater than the minimum output [kW] of the power equipment 10.

[0074] If the load power X2 of the second load 70B is equal to or greater than the predetermined value, a YES determination is made in S20, and the process proceeds to S30. When the process proceeds to S30, the control device 50 switches the operation mode of the power equipment 10 from the initially set first operation mode to the second operation mode.

[0075] If the load power X2 of the second load 70B is less than the predetermined value, a NO determination is made in S20 and the process proceeds to S40. When the process proceeds to S40, the control device 50 maintains the operation mode of the power equipment 10 in the initially set first operation mode.

[0076] If the transition to the second operation mode is permitted when the load power X2 of the second load 70B is less than a predetermined value, the output power Pinv of the power equipment 10 cannot be controlled to a value lower than the load power X2 during the second operation mode, and there is a concern that the output power Pinv of the power equipment 10 may exceed the load power X2. If the output power Pinv of the power equipment 10 exceeds the load power X2 of the second load 70B, reverse power flow to the power grid 1 may occur during the second operation mode.

[0077] In this configuration, when the load power X2 of the second load 70B is equal to or greater than a predetermined value, the transition to the second operation mode is permitted, making it difficult for the output power Pinv of the power equipment 10 to exceed the load power X2 of the second load 70B. Therefore, it is possible to suppress the occurrence of reverse power flow to the power system 1 during the second operation mode.

[0078] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0079] (1) In the above embodiment, the power supply device 11 includes the generator 13 and the battery 15. The battery 15 may be omitted, and the power supply device 11 may include only the generator 13. The generator 13 may be omitted, and the power supply device 11 may include only the battery 15. The generator 13 may be configured by combining an AC generator and a rectifier. The battery 15 is not limited to a secondary battery, and may be a capacitor.

[0080] (2) In the first operation mode, the control device 50 may monitor the received power Pgrid of the power system S1 from the measurement results of the measurement unit 5, and control the output power Pinv of the inverter circuit 25 so that the received power Pgrid of the power system S1 is equal to or greater than a threshold. By making the received power Pgrid of the power system S1 equal to or greater than the threshold, the power flow at point A can be controlled to be a forward power flow.

[0081] (3) In the first embodiment, while the second operation mode is selected, the second switch 47 is always closed regardless of the state of the power grid 1, thereby enabling the power supply to the second load 70B to continue uninterrupted even if an abnormality occurs in the power grid 1. If the power supply to the second load 70B can continue uninterrupted even if an abnormality occurs in the power grid 1, power may be supplied to the second load 70B by a method different from that of the first embodiment. For example, while the second operation mode is selected, if there is no abnormality in the power grid 1, the first switch 46 is closed, and power is supplied to the second load 70B via a path passing through the first switch 46. If an abnormality in the power grid 1 is detected, the first switch 46 and the second switch 47 may be switched uninterruptedly, and thereafter power may be supplied to the second load 70B via a path passing through the second switch 47.

[0082] (4) In the first operation mode, it is sufficient if energy can be saved by supplying power from the power equipment 10 without being limited by the load power X2 of the second load 70B while closing the interconnection switch 41 and connecting to the power grid 1. If an abnormality in the power grid 1 is detected during the first operation mode, any control may be performed. As disclosed in the first embodiment, the power grid 10 may be disconnected from the power grid 1 to stop the output of the inverter circuit 25, or another control may be performed.

[0083] (5) In the first embodiment, an abnormality in the power grid 1 is detected based on the measured value of the grid voltage Vgrid by the measuring unit 48. The detection of an abnormality in the power grid 1 may be determined based on an external signal.

[0084] (6) In the second embodiment, when the second load 70B, which is a specific load, is equal to or greater than a predetermined value, switching from the first operating mode to the second operating mode is permitted. Switching from the first operating mode to the second operating mode may be permitted without being limited by the load power X2 of the second load 70B. In this case, if, during the second operating mode, it becomes impossible to control the output power of the power equipment 10 to be smaller than that of the second load 70B, switching from the second operating mode to the first operating mode may be permitted.

[0085] (7) Figure 10 is a block diagram of a power system S2. The power system S2 includes a power supply device 11, a power conditioner 121, a grid line L0, branch lines L1 and L2, a first load 70A, and a second load 70B. The power conditioner 121 includes a first converter circuit 22, a second converter circuit 23, an inverter circuit 25, a measurement unit 27, a grid-connection switch 41, a switching circuit 45, a measurement unit 48, a control device 50, a display unit 61, and an operation unit 65.

[0086] The power system S2 differs from the power system S1 in that the power conditioner 121 includes a grid-connected switch 41, a switching circuit 45, a measuring unit 48, a control device 50, a display unit 61, and an operation unit 65. The technology disclosed in this specification is not limited to the power system S1, but can be applied to the power system S2. The first load 70A may be omitted in the power systems S1 and S2.

[0087] (8) In the power systems S1 and S2, the switching circuit 45 is configured from a first switch 46 and a second switch 47. The switching circuit 45 may be a separate circuit as long as it can switch the connection point of the second load 70B to either of the end points D and E of the interconnection switch 41. Furthermore, as shown in the power system S3 (see FIG. 11), the switching function of the connection point of the second load 70B to the interconnection line L0 may be omitted, leaving only the second switch 47, and power may be supplied to the second load 70B via a path that passes through the second switch 47 not only in the second operating mode but also when the first operating mode is selected. [Explanation of symbols]

[0088] 1 Power system 3 grid power supply 10 Power equipment 11 Power supply 13. Generator 15 Battery 21 Power conditioner 25 Inverter circuit 41 Grid-connected switch 45 Switching circuit 46 First Switch 47 Second Switch 50 Control device 61 Display section 65 Operation section 70A 1st load 70B 2nd load (specific load) S1, S2 power systems

Claims

1. 1. An electric power system comprising: Electric power equipment and an interconnection line that connects the power facility to an electric power system; an interconnection switch located on the interconnection line; A specific load connected to the interconnection line; a control device; The operation modes of the power equipment include: There are two operation modes: the first operation mode and the second operation mode. The control device In the first operating mode, The interconnection switch is closed to interconnect the power equipment to the power grid; supplying power from the power facility to loads connected to the interconnection line including at least the specific load without being limited by the load power of the specific load; In the second operating mode, The interconnection switch is closed to interconnect the power equipment to the power grid; controlling the output power of the power facility to be equal to or less than the load power of the specific load, and supplying power from the power facility only to the specific load; When the control device detects an abnormality in the power system during the second operation mode, the control device opens the interconnection switch to disconnect the power equipment from the power system, and continues to supply power from the power equipment to the specific load without interruption.

2. 2. The power system of claim 1, The control device permits switching from the first operation mode to the second operation mode when the load power of the specific load is equal to or greater than a predetermined value.

3. The power system according to claim 1 or 2, a switching circuit that switches a connection point of the specific load to the interconnection line; The control device In the first operating mode, The switching circuit connects the specific load to one of the two end points of the interconnection switch on the power grid side; In the second operating mode, The power system connects the specific load to an end point on the power equipment side of the interconnection switch by the switching circuit.

4. 4. The power system of claim 3, The power equipment includes: a power supply; an inverter circuit that converts DC power from the power supply device into AC power and outputs the AC power, The switching circuit a first switch and a second switch connected in series; the first switch is connected to one of both end points of the interconnection switch on the power grid side; the second switch is connected to an end point of the interconnection switch on the power equipment side, the specific load is connected to a connection point between the first switch and the second switch, The control device During the second operation mode, the second switch is closed, and the inverter circuit is current-controlled so that the power supplied from the inverter circuit to the specific load via the second switch is smaller than the load power of the specific load; If an abnormality in the power grid is detected during the second operating mode, the second switch is kept closed to switch the inverter circuit from current control to voltage control.

5. A method for controlling a power system, comprising: The power system is Electric power equipment and an interconnection line that connects the power facility to an electric power system; an interconnection switch located on the interconnection line; a specific load connected to the interconnection line, The operation modes of the power equipment include: There are two operation modes: the first operation mode and the second operation mode. In the first operating mode, The interconnection switch is closed to interconnect the power equipment to the power grid; supplying power from the power facility to loads connected to the interconnection line including at least the specific load without being limited by the load power of the specific load; In the second operating mode, The interconnection switch is closed to interconnect the power equipment to the power grid; controlling the output power of the power facility to be equal to or less than the load power of the specific load, and supplying power from the power facility only to the specific load; When an abnormality in the power system is detected during the second operation mode, the interconnection switch is opened to disconnect the power equipment from the power system, and power supply from the power equipment to the specific load is continued without interruption.

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