Distributed Power Systems

Abstract

To provide a technique capable of suppressing voltage reduction of a wire network even when a device responsible for maintaining voltage of the wire network is stopped.SOLUTION: A distributed power supply system includes a main machine connected to a wire network and capable of supplying and collecting DC power to and from the wire network, a sub machine connected to the wire network and capable of supplying DC power to the wire network, and one or more devices connected to the wire network and capable of collecting or supplying DC power by chemical reaction. The sub machine supplies DC power to the wire network when the voltage of the wire network becomes equal to or less than a set voltage, which is a preset voltage, along with an interruption of DC power supply from the main machine by maintaining the output voltage at the set voltage while the output voltage from the main machine is equal to or higher than the set voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distributed power supply system. [Background technology]

[0002] A distributed power supply system is a system in which power is supplied from multiple devices connected to an electric grid. Examples of connected devices include generators that use renewable energy, such as solar cells and wind turbines, power storage devices for stabilizing power, and fuel cells for supplementing power shortages. For example, the DC bus control system disclosed in Patent Document 1 is a distributed power supply system in which power is supplied from solar cells, wind turbines, multiple power storage devices, and fuel cells connected in parallel to an electric grid. In Patent Document 1, the power storage devices and fuel cells operate as power buffers to maintain the voltage in the electric grid within a certain range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6923231 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the voltage in the electric grid is maintained mainly by charging and discharging a power storage device. Because safety is a major consideration in the operation and control of such a power storage device, the operation of a distributed power system must also take into consideration the possibility of the power storage device shutting down for safety reasons (for example, to avoid high temperatures or overcharging). However, the technology described in Patent Document 1 did not fully consider operation when the device responsible for maintaining the voltage of the electric grid (the power storage device) shuts down. This posed a problem in that the voltage in the electric grid would drop if the device responsible for maintaining the voltage of the electric grid shuts down. Note that this problem is not limited to safety reasons, but is common to all cases in which the device responsible for maintaining the voltage of the electric grid shuts down.

[0005] The present invention has been made to solve at least some of the above-mentioned problems, and aims to provide a distributed power supply system that can suppress a drop in voltage in an electric power grid even if a device responsible for maintaining the voltage of the electric power grid stops. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a distributed power supply system including a main unit connected to an electric grid and capable of supplying and recovering DC power to the electric grid, a secondary unit connected to the electric grid and capable of supplying DC power to the electric grid, and one or more devices connected to the electric grid and capable of recovering or supplying DC power through a chemical reaction, wherein while DC power is being supplied from the main unit to the electric grid at an output voltage equal to or greater than a predetermined set voltage, the secondary unit maintains its output voltage at the set voltage, and supplies DC power to the electric grid when the voltage at the electric grid falls below the set voltage due to a stoppage of DC power supply from the main unit.

[0008] According to this configuration, while the output voltage from the main unit is equal to or higher than the set voltage, the auxiliary unit is controlled so that the output voltage from the auxiliary unit is maintained at the set voltage. Then, when the supply of DC power from the main unit to the electric grid is stopped and the voltage in the electric grid becomes equal to or lower than the set voltage, the auxiliary unit controls the output voltage from the auxiliary unit to the electric grid. Therefore, even if the supply of power from the main unit to the power grid is stopped, the output voltage of the secondary unit is maintained at a set voltage, so that the secondary unit can supply DC power to the power grid as soon as the voltage on the power grid drops below the set voltage. Therefore, even if the supply of power from the main unit (i.e., the device responsible for maintaining the voltage on the power grid) to the power grid is stopped, a drop in voltage on the power grid can be suppressed.

[0009] (2) In the distributed power supply system of the above form, the set voltage may be a voltage equal to or lower than a lower limit voltage of a voltage control range of the main unit, and the main unit may stop supplying DC power to the power grid when the output voltage from the main unit becomes equal to or lower than the lower limit voltage. According to this configuration, when the output voltage of the main unit falls below the lower limit voltage, the supply of DC power from the main unit to the power grid can be stopped. Even in such a case, the output voltage of the secondary unit is maintained at a preset voltage that is equal to or lower than the lower limit voltage, so that DC power can be supplied from the secondary unit to the power grid as soon as the voltage on the power grid falls below the preset voltage.

[0010] (3) In the distributed power supply system of the above form, the one or more devices may include a generation unit that recovers DC power from the power grid and generates a reactant through a chemical reaction, and the generation unit may stop generating the reactant when the main engine stops supplying DC power to the power grid. According to this configuration, the power consumed by the generating unit can be reduced, and therefore the progress of the voltage drop in the power grid caused by the interruption of the supply of DC power from the main engine can be slowed down.

[0011] (4) In the distributed power supply system of the above form, the one or more devices may include a power generation unit capable of supplying DC power generated using the reactant to the power grid, and the power generation unit may start generating power when the main engine stops supplying DC power to the power grid. According to this configuration, power is supplied from the power generation unit to the power grid, so that a voltage drop in the power grid caused by a stop in the supply of DC power from the main engine can be suppressed.

[0012] (5) In the distributed power supply system of the above form, the main unit includes a main unit control unit that controls the main unit, and the secondary unit includes a secondary unit control unit that controls the secondary unit, and the main unit control unit and the secondary unit control unit may be different from the control units that control the generation unit and the power generation unit. With this configuration, the main unit and the auxiliary unit are controlled individually by the main unit control unit and the auxiliary unit control unit, respectively, so the number of times the main unit and the auxiliary unit are controlled can be increased compared to when the main unit and the auxiliary unit are controlled by a control unit that simultaneously controls a large number of devices including the main unit and the auxiliary unit. Therefore, since the output voltage from the auxiliary unit can be accurately maintained at a set voltage, when the supply of DC power from the main unit is stopped, DC power can be quickly supplied to the power grid from the auxiliary unit, which becomes the new supply source.

[0013] (6) In the distributed power supply system of the above aspect, the DC power supplied from the secondary unit to the power grid may be derived from power generated using renewable energy. According to this configuration, it is possible to use electricity derived from renewable energy to suppress a voltage drop in the power grid caused by an interruption in the supply of DC power from the main engine.

[0014] (7) In the distributed power system of the above aspect, the DC power supplied from the sub-unit to the power grid may be derived from power supplied to the sub-unit from another distributed power system. According to this configuration, it is possible to suppress a voltage drop in the power grid caused by an interruption in the supply of DC power from the main unit by using power supplied to the secondary unit from another distributed power supply system.

[0015] (8) According to one aspect of the present invention, there is provided a distributed power supply system, comprising: a main unit connected to an electric power grid and capable of supplying and recovering AC power to and from the electric power grid; The power grid comprises a secondary unit connected to the power grid and capable of supplying AC power to the power grid, and one or more devices connected to the power grid and capable of recovering or supplying AC power through a chemical reaction, wherein the secondary unit maintains the frequency of the AC power it outputs at a preset frequency while the frequency of the AC power supplied from the main unit to the power grid is equal to or higher than a preset frequency, and supplies AC power to the power grid when the frequency of the AC power flowing through the power grid falls below the set frequency due to the stoppage of AC power supply from the main unit.

[0016] According to this configuration, the secondary unit is controlled to maintain the frequency of the AC power output from the secondary unit at the set frequency while the frequency of the AC power supplied from the main unit to the electric grid is equal to or higher than the set frequency. Then, when the supply of AC power from the main unit to the electric grid is stopped and the frequency of the AC power flowing through the electric grid falls below the set frequency, the secondary unit supplies AC power to the electric grid. Therefore, even when the supply of AC power from the main unit to the electric grid is stopped, the frequency of the AC power output from the secondary unit is already maintained at the set frequency. Therefore, as soon as the frequency of the AC power flowing through the electric grid falls below the set frequency, the secondary unit can supply AC power to the electric grid. Therefore, even when the supply of AC power from the main unit (i.e., the device responsible for maintaining the frequency in the electric grid) to the electric grid is stopped, a drop in the frequency in the electric grid can be suppressed.

[0017] (9) In the distributed power supply system of the above form, the set frequency may be a frequency that is equal to or lower than a lower limit frequency of a frequency control range of the main engine, and the main engine may stop supplying AC power to the power grid when the frequency of the AC power flowing through the power grid becomes equal to or lower than the lower limit frequency. According to this configuration, when the frequency of the AC power flowing through the electric grid falls below the lower limit frequency, the supply of AC power from the main unit to the electric grid can be stopped. Even in such a case, the frequency of the AC power output from the secondary unit is maintained at a set frequency that is set in advance to be below the lower limit frequency, so that AC power can be supplied from the secondary unit to the electric grid as soon as the frequency of the AC power flowing through the electric grid falls below the set frequency.

[0018] The present invention can be realized in various forms, for example, as a control method for a distributed power supply system, a computer program for controlling a distributed power supply system, a server device for distributing the computer program, a non-transitory storage medium on which the computer program is stored, etc. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is an explanatory diagram illustrating the configuration of a distributed power supply system according to a first embodiment; [Figure 2] FIG. 2 is an explanatory diagram schematically illustrating the voltage control range of each device. [Figure 3] FIG. 2 is an explanatory diagram illustrating output control in the main engine. [Figure 4] FIG. 4 is an explanatory diagram illustrating output control in the secondary machine. [Figure 5] FIG. 10 is an explanatory diagram schematically illustrating the voltage control range of each device in the second embodiment. [Figure 6] FIG. 10 is an explanatory diagram illustrating output control in the auxiliary unit of the second embodiment. [Figure 7] FIG. 10 is an explanatory diagram illustrating the configuration of a distributed power supply system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] First Embodiment FIG. 1 is an explanatory diagram illustrating the configuration of a distributed power supply system 1 according to one embodiment of the present invention. The distributed power supply system 1 is a system in which a main unit 10, a secondary unit 20, and one or more devices capable of recovering or supplying DC power through a chemical reaction are connected via an electric wire network NT. In the example of FIG. 1, the one or more devices include three devices, specifically, a first device 30, a second device 40, and a third device 60 ... This is a system in which the DC power to be supplied to the load 90 is shared and output by the main unit 10, the auxiliary unit 20, the first device 30, and the third device 60. The distributed power supply system 1 also includes a storage unit 50 and a device control unit 70.

[0021] The main engine 10 is a device connected to an electric power network NT and capable of supplying and recovering DC power to and from the electric power network NT. The main engine 10 includes a storage battery 12, a power converter 14, and a main engine control unit 16. The storage battery 12, which is a secondary battery, is connected to the electric power network NT via the power converter 14, which is a DC / DC converter. The main engine control unit 16, which controls the main engine 10, acquires the voltage in the electric power network NT and controls the switching of the power converter 14, thereby controlling the charging and discharging of the storage battery 12. In other words, the main engine control unit 16 controls the supply and recovery of DC power from the storage battery 12 to the electric power network.

[0022] The auxiliary unit 20 is a device connected to the electric power network NT and capable of supplying DC power to the electric power network NT. The auxiliary unit 20 includes a power converter 24 and an auxiliary unit control unit 26. The power converter 24 converts power supplied from a power source 80 and supplies the converted power to the electric power network NT. In this embodiment, the power source 80 is a wind power generator that generates AC power, and therefore the power converter 24 is an AC / DC converter. In other words, the DC power supplied from the auxiliary unit 20 to the electric power network NT is derived from power generated using renewable energy. The auxiliary unit control unit 26, which controls the auxiliary unit 20, controls the switching of the power converter 24.

[0023] The first device 30 is a device capable of supplying DC power to the electric wire network NT. The first device 30 includes a solar cell 32 and a power converter 34. The solar cell 32 is connected to the electric wire network NT via the power converter 34, which is a DC / DC converter. The power converter 34 converts the DC power supplied from the solar cell 32 and supplies it to the electric wire network NT.

[0024] The second device 40 is a device capable of recovering DC power from the electric wire network NT through a chemical reaction. The second device 40 includes a water electrolysis unit 42 and a power converter 44. The water electrolysis unit 42 is connected to the electric wire network NT via the power converter 44, which is a DC / DC converter. The power converter 44 converts the power recovered from the electric wire network NT and supplies the converted power to the water electrolysis unit 42. The water electrolysis unit 42 electrolyzes water using the DC power supplied from the electric wire network NT via the power converter 44. In other words, the water electrolysis unit 42 is a production unit that recovers DC power from the electric wire network NT and produces reactants through a chemical reaction. Hydrogen produced by the electrolysis of water is stored in the storage unit 50.

[0025] The third device 60 is a device capable of supplying DC power to the electric wire network NT through a chemical reaction. The third device 60 includes a fuel cell 62 and a power converter 64. The fuel cell 62 is connected to the electric wire network NT via the power converter 64, which is a DC / DC converter. The fuel cell 62 generates DC power using hydrogen and oxygen stored in the storage unit 50. The power converter 64 converts the DC power supplied from the fuel cell 62 and supplies it to the electric wire network NT. In other words, the fuel cell 62 is a power generation unit capable of supplying DC power generated using reactants to the electric wire network NT.

[0026] The equipment control unit 70 controls the first equipment 30, the second equipment 40, and the third equipment 60. The above-mentioned main equipment control unit 16 and auxiliary equipment control unit 26 are separate control units different from the equipment control unit 70. The equipment control unit 70 mainly controls the supply of DC power from the first equipment 30 and the third equipment 60 to the electric wire network NT, and the recovery of DC power from the electric wire network NT by the second equipment 40.

[0027] The output voltage from the first device 30 varies depending on the amount of solar radiation irradiating the solar cell 32. In the distributed power supply system 1, a main device 10 equipped with a storage battery 12 is provided in parallel via an electric wire network NT. The voltage in the electric wire network NT is maintained within a certain range (and at a voltage equal to or higher than a set voltage V1, which will be described later with reference to FIG. 4 ) by switching between charging and discharging by the main unit 10 in accordance with fluctuations in the output voltage from the first device 30. In other words, the main unit 10 is a device responsible for maintaining the voltage in the electric wire network NT. Typically, in the distributed power supply system 1, the DC power to be supplied to the load 90 via the electric wire network NT is shared and output mainly by the main unit 10 and the first device 30. At this time, the second device 40 appropriately recovers DC power from the electric wire network NT in accordance with the DC power supplied to the electric wire network NT, and stores the generated hydrogen in the storage unit 50. In this embodiment, while DC power is being supplied from the main unit 10 to the electric wire network NT, the supply of DC power from the third device 60 to the electric wire network NT is stopped.

[0028] FIG. 2 is an explanatory diagram showing a schematic diagram of the voltage control range of each device connected to the power network NT. The voltage V H ,V L ,V M and the voltage V shown on the right h ,V B are voltages that indicate the upper and lower limits of the voltage control range, and the voltage V H is the highest, and the voltage V B The voltage control range of the main engine 10 is L to voltage V H That is, the main engine 10 is in a state where the output voltage from the main engine 10 is a voltage V L or less, or voltage V H If the voltage V exceeds the upper or lower limit of the voltage control range set for each device, the device stops supplying or recovering DC power. The voltage control range for the first device 30 and the third device 60 is set to the voltage V M to voltage V H The voltage control range of the second device 40 is between the voltage V B to voltage V h The voltage control range of the auxiliary unit 20 is between voltage V B to voltage V L Until then.

[0029] 3 is an explanatory diagram for explaining output control in the main engine 10. When the voltage in the electric wire network NT is maintained within a certain range, the line segment M shown in FIG. NT The magnitude of the current flowing from the main machine 10 to the electric wire network NT or the magnitude of the current flowing from the electric wire network NT to the main machine 10 is determined using the above equation. In FIG. 3, the vertical axis Ax represents voltage, and the horizontal axis represents current. The voltage V shown in FIG. 3 H ,V L are the lower and upper limit voltages of the voltage control range of the main engine 10, as in Figure 2. 10 indicates the output voltage from the main unit 10, and the line segment M NT Along with this movement, the vertical axis Ax moves along the horizontal axis of Figure 3. That is, the line segment M NT The intersection point of and the vertical axis Ax is point V 10 Point V NT indicates the voltage in the power grid NT, and the line M NT Move up. Point V NT is located on the right side of the vertical axis Ax (i.e., point V 10 The voltage indicated by point V NT ), the main machine 10 (the storage battery 12) supplies DC power to the power grid NT. NT When is located as shown in Figure 3, the line segment M NT Using this, point V 10 and point V NT A current of magnitude S corresponding to the difference ΔV between the points V and V flows through the wire network NT. NT is located to the left of the vertical axis Ax (i.e., point V 10 The voltage indicated by < point V NT ), the main machine 10 (storage battery 12) recovers DC power from the electric wire network NT. At this time, the magnitude of the current flowing from the electric wire network NT to the storage battery 12 is the same as in the case of discharging, as shown by the line segment M NT and ΔV.

[0030] 4 is an explanatory diagram for explaining the output control in the auxiliary unit 20.NT The magnitude of the current flowing from the sub-machine 20 to the power grid NT is determined using the above equation. In FIG. 4, as in FIG. 3, the vertical axis Ax represents voltage and the horizontal axis represents current. The line segment M shown in FIG. 4 NT , voltage V H , voltage V L is the same as in Figure 3, but the line segment M NT In the distributed power supply system 1, as explained in FIGS. 2 and 3, the output voltage from the main engine 10 is within the voltage control range of voltage V L to voltage V H On the other hand, while the output voltage from the main unit 10 is maintained within the voltage control range, the auxiliary unit 20 maintains the output voltage at a set voltage V1 (shown in FIG. 4). In this embodiment, this set voltage V1 is equal to or less than the voltage V1, which is the lower limit voltage of the voltage control range of the main unit 10. L The lower limit voltage V L Since the output voltage from the main unit 10 is equal to or greater than the set voltage V1, the auxiliary unit 20 It can be said that the output voltage is maintained at the set voltage V1 during this period.

[0031] If the storage battery 12 becomes too hot or is overcharged, the supply of DC power from the main machine 10 is stopped to ensure safety. In such a case, the main machine control unit 16 receives information from various sensors (not shown) indicating that the storage battery 12 is in a hot or overcharged state, and then stops the supply of DC power from the main machine 10 by performing at least one of stopping the switching by the power converter 14 and opening a switch (not shown) that opens and closes the electrical connection between the main machine 10 and the electric wire network NT. In addition, the main machine 10 stops the supply of DC power from the main machine 10 when the output voltage from the main machine 10 reaches a lower limit voltage V L The supply of DC power to the power grid NT is also stopped if:

[0032] As the supply of DC power from the main unit 10 is stopped, the voltage in the electric wire network NT, which had been maintained within a certain range until then, begins to drop. After that, the auxiliary unit 20, which had been maintaining the output voltage at the set voltage V1, starts to supply DC power to the electric wire network NT when the voltage in the electric wire network NT falls below the set voltage V1. Referring to FIG. 4, when the voltage in the electric wire network NT is NT Of the voltages V1 to V B When the voltage V reaches the voltage between V1 and V2 (the voltage on the line segment sg), a current of a magnitude corresponding to the difference between the voltage V1 and V2 flows through the electric wire network NT, as explained in FIG. 3. Therefore, in order to have the auxiliary machine 20 supply DC power immediately after the supply of DC power from the main machine 10 is stopped, the set voltage V1 must be set to a value less than the voltage V L It is preferable to set the voltage to 90% or more of the above.

[0033] In this embodiment, when the main machine 10 stops supplying DC power to the electric wire network NT and when the auxiliary machine 20 starts supplying DC power to the electric wire network NT, the second machine 40 (water electrolysis unit 42) stops generating hydrogen (a reactant) and the third machine 60 (fuel cell 62) starts generating power. In such a case, the machine control unit 70 receives a signal from the main machine control unit 16 indicating that the main machine 10 has stopped supplying DC power, and detects a voltage transition (a slowdown in the rate of voltage increase or voltage decrease due to the DC power supply from the auxiliary machine 20) after the voltage in the electric wire network NT becomes equal to or lower than the set voltage V1, thereby stopping the generation of hydrogen by the second machine 40 and starting the power generation by the third machine 60. In this way, when the supply of DC power from the main machine 10 is stopped, the voltage in the electric wire network NT is maintained by the DC power output from the auxiliary machine 20, the first machine 30, and the third machine 60.

[0034] As described above, according to the distributed power system 1 of the first embodiment, the secondary unit 20 is controlled so that the output voltage from the secondary unit 20 is maintained at the set voltage V1 while the output voltage from the primary unit 10 is equal to or higher than the set voltage V1. Then, when the supply of DC power from the primary unit 10 to the electric wire network NT is stopped and the voltage in the electric wire network NT becomes equal to or lower than the set voltage V1, the secondary unit 20 supplies DC power to the electric wire network NT. Therefore, even when the supply of power from the primary unit 10 to the electric wire network NT is stopped, the output voltage of the secondary unit 20 is already maintained at the set voltage V1. Therefore, as soon as the voltage in the electric wire network NT becomes equal to or lower than the set voltage V1, the secondary unit 20 can supply DC power to the electric wire network NT. Therefore, even when the supply of power from the primary unit 10 to the electric wire network NT is stopped, a drop in the voltage in the electric wire network NT can be suppressed.

[0035] In the distributed power supply system 1 of the first embodiment, the output voltage from the main engine 10 is lower than the lower limit voltage V L If the voltage V L Since the voltage is maintained at the lower set voltage V1, DC power can be supplied from the secondary unit 20 to the power grid NT as soon as the voltage in the power grid NT falls below the set voltage V1.

[0036] Furthermore, in the distributed power supply system 1 of the first embodiment, when the main engine 10 stops supplying DC power to the electric wire network NT, the generation of reactants by the water electrolysis unit 42 is stopped. Since the power consumed by 42 can be reduced, the progress of the voltage drop in the power grid NT caused by the interruption of the supply of DC power from the main engine 10 can be delayed.

[0037] Furthermore, in the distributed power supply system 1 of the first embodiment, when the main engine 10 stops supplying DC power to the electric wire network NT, power generation is started by the fuel cell 62. Therefore, since power is supplied from the fuel cell 62 to the electric wire network NT, it is possible to suppress a voltage drop in the electric wire network NT caused by the stop of the supply of DC power from the main engine 10.

[0038] Furthermore, in the distributed power supply system 1 of the first embodiment, the main unit control unit 16 and the auxiliary unit control unit 26 are separate control units different from the equipment control unit 70. Therefore, the main unit 10 and the auxiliary unit 20 are individually controlled by the main unit control unit 16 and the auxiliary unit control unit 26, respectively, and therefore the number of times the main unit 10 and the auxiliary unit 20 are controlled can be increased compared to when the main unit 10 and the auxiliary unit 20 are controlled by a control unit that simultaneously controls a large number of devices including the main unit 10 and the auxiliary unit 20. Therefore, the output voltage from the auxiliary unit 20 can be accurately maintained at the set voltage V1, and therefore when the supply of DC power from the main unit 10 is stopped, DC power can be quickly supplied to the power grid NT from the auxiliary unit 20, which becomes a new supply source.

[0039] Furthermore, in the distributed power supply system 1 of the first embodiment, the DC power supplied from the secondary unit 20 to the power grid NT is derived from power generated using renewable energy. Therefore, by using the power derived from renewable energy, it is possible to suppress a voltage drop in the power grid NT caused by a stop in the supply of DC power from the primary unit 10.

[0040] Second Embodiment 5 is an explanatory diagram showing a schematic diagram of the voltage control range of each device connected to the power line network NT in a distributed power supply system 1a of the second embodiment. The distributed power supply system 1a of the second embodiment is the same as the distributed power supply system 1 of the first embodiment except that the voltage control range of the secondary device 20 is different from that of the distributed power supply system 1 of the first embodiment.

[0041] In the distributed power supply system 1 of the first embodiment, the voltage control range of the secondary unit 20 is B to voltage V LIn contrast, in the distributed power supply system 1a of the second embodiment, the voltage control range of the sub-unit 20 is between voltage V B to voltage V A (>Voltage V L ) The set voltage V1 is the lower limit voltage of the voltage control range of the main engine 10. L is the same magnitude of voltage.

[0042] 6 is an explanatory diagram illustrating output control in the secondary unit 20. In FIG. 6, as in FIG. 4, the vertical axis Ax represents voltage and the horizontal axis represents current. In the distributed power supply system 1a, as shown in FIG. 5, the output voltage from the primary unit 10 is controlled within the voltage control range of voltage V L to voltage V H On the other hand, the auxiliary unit 20 maintains the output voltage at a set voltage V1 (shown in FIG. 6) while the output voltage from the main unit 10 is maintained within the voltage control range. In the second embodiment, the set voltage V1 is set to a value equal to or greater than the voltage V L Since the voltage is the same as the voltage V L If the supply of DC power to the power grid NT is stopped because the voltage falls below the set voltage V1 (below the lower limit of the voltage control range), DC power will immediately be supplied to the power grid NT from the secondary unit 20, which has been maintaining the output voltage at the set voltage V1.

[0043] Similarly to the first embodiment, the distributed power supply system 1a of the second embodiment described above can also suppress a voltage drop in the electric wire network NT when the supply of power from the main machine 10 to the electric wire network NT is stopped. Furthermore, in the distributed power supply system 1a of the second embodiment, the set voltage V1 is set to the voltage V, which is the lower limit voltage of the voltage control range of the main machine 10. L Since the voltage is set to the same magnitude as the voltage V L If the supply of DC power to the power grid NT is stopped because the voltage falls below the lower limit of the voltage control range, , DC power can be instantly supplied from the sub-unit 20 to the power grid NT.

[0044] <Third embodiment> 7 is an explanatory diagram illustrating the configuration of a distributed power supply system 1b according to a third embodiment. The distributed power supply system 1b according to the third embodiment is the same as the distributed power supply system 1 according to the first embodiment, except that AC power flows through the power line network NT.

[0045] In the distributed power system 1b, AC power flows through the electric wire network NT, and therefore the power converters 14, 24, 34, 44, and 64 are DC / AC converters. The electric wire network NT is provided with a frequency sensor 77 that detects the frequency of the AC power flowing through the electric wire network NT. The main machine control unit 16 receives a signal indicating the frequency from the frequency sensor 77. In the distributed power system 1b of the third embodiment, the main machine 10 stops supplying AC power to the electric wire network NT when the frequency of the AC power flowing through the electric wire network NT falls below a lower limit frequency. The lower limit frequency is the lower limit frequency of the frequency control range of the main machine 10.

[0046] When the frequency of the AC power in the electric wire network NT is maintained within a certain range, the frequency of the AC power supplied from the main machine 10 to the electric wire network NT is maintained at a frequency equal to or higher than the set frequency F1. Meanwhile, while the frequency of the AC power supplied from the main machine 10 to the electric wire network NT is maintained at a frequency equal to or higher than the set frequency F1, the auxiliary machine 20 maintains the frequency of the AC power it outputs at the set frequency F1. In this embodiment, this set frequency F1 is a frequency set to be equal to or lower than the lower limit frequency of the main machine 10 described above.

[0047] If the storage battery 12 becomes too hot or is overcharged, or if the frequency of the AC power flowing through the electric wire network NT drops below a lower limit frequency due to a drop in the SOC (State of Charge) of the storage battery 12, the main machine 10 stops supplying AC power to the electric wire network NT. As the supply of DC power from the main machine 10 stops, the frequency of the AC power flowing through the electric wire network NT, which had been maintained within a certain range until then, drops. Thereafter, the auxiliary machine 20, which had been maintaining the frequency of the AC power it outputs at a set frequency F1, supplies AC power to the electric wire network NT when the frequency in the electric wire network NT drops below the set frequency F1. Therefore, in order to have the auxiliary machine 20 start supplying AC power immediately after the supply of AC power from the main machine 10 stops, it is preferable to set the set frequency F1 to a value close to the lower limit frequency of the main machine 10.

[0048] As described above, according to the distributed power supply system 1b of the third embodiment, the secondary unit 20 is controlled to maintain the frequency of the AC power output from the secondary unit 20 at the set frequency F1 while the frequency of the AC power supplied from the main unit 10 to the electric wire network NT is equal to or higher than the set frequency F1. Then, when the supply of AC power from the main unit 10 to the electric wire network NT is stopped and the frequency of the AC power flowing through the electric wire network NT becomes equal to or lower than the set frequency F1, the secondary unit 20 supplies AC power to the electric wire network NT. Therefore, even when the supply of AC power from the main unit 10 to the electric wire network NT is stopped, the frequency of the AC power output from the secondary unit 20 is maintained at the set frequency F1 in advance. Therefore, as soon as the frequency of the AC power flowing through the electric wire network NT becomes equal to or lower than the set frequency F1, the secondary unit 20 can supply AC power to the electric wire network NT. Therefore, even when the supply of AC power from the main unit 10 (i.e., the device responsible for maintaining the frequency in the electric wire network NT) to the electric wire network NT is stopped, a drop in the frequency in the electric wire network NT can be suppressed.

[0049] Furthermore, in the distributed power supply system 1b of the third embodiment, when the frequency of the AC power flowing through the electric wire network NT becomes equal to or lower than the lower limit frequency, the supply of AC power from the main unit 10 to the electric wire network NT can be stopped. Even if such a stop occurs, the frequency of the AC power output from the auxiliary unit 20 is maintained at the set frequency F1 that is set in advance to be equal to or lower than the lower limit frequency. Therefore, as soon as the frequency of the AC power flowing through the electric wire network NT becomes equal to or lower than the set frequency F1, AC power can be supplied from the auxiliary machine 20 to the electric wire network NT.

[0050] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0051] [Variation 1] In the above embodiment, the main engine 10 is equipped with the storage battery 12, which is a secondary battery, but this is not limited to this. For example, the main engine 10 may be equipped with an electric double layer capacitor, a capacitor, a flywheel battery, etc. instead of or in addition to the storage battery 12.

[0052] [Variation 2] In the above embodiment, the power supplied from the secondary unit 20 to the electric wire network NT is derived from power generated using renewable energy, but this is not limited to this. For example, the power supplied from the secondary unit 20 to the electric wire network NT may be derived from power supplied to the secondary unit 20 from another distributed power supply system. In such a distributed power supply system, a voltage (frequency) drop in the electric wire network NT caused by a stop of power supply from the main unit 10 can be suppressed by using the power supplied to the secondary unit 20 from the other distributed power supply system.

[0053] [Variation 3] In the above embodiment, the auxiliary machine 20 itself does not have a power supply, and supplies power to the power grid NT using power supplied from an external power supply 80, but this is not limited to this. For example, the auxiliary machine 20 itself may have a power supply, similar to the main machine 10, the first device 30, and the third device 60. In this case, the power supply may be any power supply, such as a storage battery, a solar cell, or a fuel cell. Furthermore, the power converter 24 is selected arbitrarily depending on whether the power supplied from the power supply is DC or AC.

[0054] [Variation 4] In the above embodiment, the water electrolysis unit 42 is provided as the generator, but this is not limited thereto. For example, the generator may be a generator that generates alcohol by performing carbon dioxide reduction, or a generator that generates ammonia by reducing nitrogen. In other words, the generator may generate any reactant as long as it generates a reactant using electric power and the power generation unit can generate electric power using the reactant.

[0055] [Variation 5] In the above embodiment, the power generation unit includes the fuel cell 62 that uses hydrogen and oxygen, but this is not limiting. For example, the power generation unit may be a fuel cell that uses alcohol or the like, or a power generation unit that burns chemical substances (hydrogen, alcohol, ammonia, etc.) to rotate a turbine or the like.

[0056] [Variation 6] In the above embodiment, the system includes the equipment control unit 70, the main unit control unit 16, and the auxiliary unit control unit 26, but this is not limited to this. For example, the system may include only the equipment control unit 70, and all of the equipment connected to the power line network NT may be controlled by the equipment control unit 70. Alternatively, each equipment may have its own control unit that controls it individually. Furthermore, the system may include a control unit that simultaneously controls the main unit 10 and the auxiliary unit 20, and a control unit that controls equipment other than the main unit 10 and the auxiliary unit 20.

[0057] [Variation 7] In the above embodiment, each device stops supplying DC power when the upper or lower limit of the voltage control range set for that device is exceeded. In addition, each device may suppress the supply of DC power when the voltage approaches the upper limit of the voltage control range set for that device, thereby preventing the voltage from exceeding the upper limit.

[0058] [Variation 8] In the above embodiment, while the main machine 10 supplies DC power to the electric wire network NT, the supply of DC power from the third device 60 to the electric wire network NT is stopped, but this is not limited to this. For example, while the main machine 10 supplies DC power to the electric wire network NT, the third device 60 may also supply DC power to the electric wire network NT. Then, when the main machine 10 stops supplying DC power to the electric wire network NT, after the auxiliary machine 20 starts supplying DC power to the electric wire network NT, the DC power supplied from the third device 60 may be increased compared to before the main machine 10 stopped.

[0059] [Variation 9] In the above embodiment, when the main machine 10 stops supplying DC power to the electric wire network NT and when the auxiliary machine 20 starts supplying DC power to the electric wire network NT, the second device 40 (water electrolysis unit 42) stops generating hydrogen (reactant) and the third device 60 (fuel cell 62) starts generating power. However, this is not limited to this. For example, the second device 40 (water electrolysis unit 42) may stop generating hydrogen (reactant) and the third device 60 (fuel cell 62) may start generating power, triggered only by the main machine 10 stopping supplying DC power to the electric wire network NT. In this case, in order to prevent the fuel cell 62 from starting generating power before the voltage in the electric wire network NT becomes equal to or lower than the set voltage V1, the set voltage V1 may be set equal to or lower than the voltage V2 as in the second embodiment. L or the voltage V L It is preferable that the voltage be set to a value as close as possible to the value of the reference voltage.

[0060] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate. [Explanation of symbols]

[0061] 1, 1a, 1b...Distributed power supply system 10…Main engine 12...Storage battery 14...Power converter 16…Main engine control section 20...auxiliary unit 24...Power converter 26...Auxiliary machine control unit 30...1st device 32...Solar cell 34...Power converter 40…Second device 42...Water electrolysis section 44...Power converter 50...Storage section 60...Third device 62…fuel cell 64...Power converter 70...Device control unit 77...Frequency sensor

Claims

1. A distributed power system, comprising: a main engine connected to an electric grid and capable of supplying and recovering DC power to and from the electric grid; a sub-unit connected to the power grid and capable of supplying DC power to the power grid; one or more devices connected to the power grid and capable of recovering or supplying DC power through a chemical reaction; The auxiliary machine is While the output voltage from the main engine is equal to or higher than a preset voltage, the output voltage is maintained at the preset voltage. A distributed power supply system that supplies DC power to the power grid when the voltage in the power grid falls below the set voltage due to the supply of DC power from the main engine being stopped.

2. 2. The distributed power supply system according to claim 1, the set voltage is a voltage equal to or lower than a lower limit voltage of a voltage control range of the main engine, The distributed power supply system, wherein the main engine stops supplying DC power to the power grid when the output voltage from the main engine falls below the lower limit voltage.

3. 3. The distributed power supply system according to claim 1 or 2, the one or more devices include a device including a generator that recovers DC power from the power grid and generates a reactant through a chemical reaction; The generation unit stops generating the reactant when the main engine stops supplying DC power to the power grid.

4. The distributed power supply system according to claim 3, the one or more devices include a device including a power generation unit capable of supplying DC power generated using the reactants to the power grid; The power generation unit starts generating power when the main engine stops supplying DC power to the power grid.

5. The distributed power supply system according to claim 4, The main engine includes a main engine control unit that controls the main engine, The auxiliary machine includes an auxiliary machine control unit that controls the auxiliary machine, A distributed power supply system in which the main unit control unit and the auxiliary unit control unit are different from equipment control units that control equipment including the generation unit and equipment including the power generation unit.

6. A distributed power supply system according to any one of claims 1 to 5, A distributed power system, wherein the DC power supplied from the secondary unit to the power grid is derived from power generated using renewable energy.

7. A distributed power supply system according to any one of claims 1 to 5, A distributed power system, wherein the DC power supplied from the secondary unit to the power grid is derived from power supplied to the secondary unit from another distributed power system.

8. A distributed power system, comprising: a main engine connected to an electric grid and capable of supplying and recovering AC power to and from the electric grid; a sub-unit connected to the power grid and capable of supplying AC power to the power grid; one or more devices connected to the power grid and capable of recovering or supplying AC power through a chemical reaction; The auxiliary machine is While the frequency of the AC power supplied from the main engine to the power grid is equal to or higher than a preset frequency, the frequency of the AC power to be output is maintained at the preset frequency, A distributed power supply system that supplies AC power to the power grid when the frequency of the AC power flowing through the power grid falls below the set frequency due to the supply of AC power from the main engine being stopped.

9. 9. The distributed power supply system according to claim 8, the set frequency is a frequency equal to or lower than a lower limit frequency of a frequency control range of the main engine, The main unit stops supplying AC power to the power grid when the frequency of the AC power flowing through the power grid becomes equal to or lower than the lower limit frequency.

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