JP7786271B2 - Distributed Power Systems - Google Patents

Description

The present invention relates to a distributed power supply system.

A distributed power supply system is a system in which power is supplied from multiple devices connected to an electric grid. 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, maintaining the voltage on the electric grid within a certain range.

Patent No. 6923231

In Patent Document 1, the voltage in the electric grid is maintained primarily by charging and discharging power storage devices. Because safety is a major consideration in the operation and control of such power storage devices, the operation of a distributed power system must also take into account 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. As a result, there was an issue of the voltage in the electric grid dropping when the device responsible for maintaining the voltage of the electric grid shuts down. This issue 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.

The present invention has been made to solve at least some of the above-mentioned problems, and aims to provide a distributed power generation system that can suppress voltage drops in the power grid even if the device responsible for maintaining the voltage in the power grid stops.

The present invention has been made to solve at least some of the above-mentioned problems, and can be realized in the following forms.

(1) According to one aspect of the present invention, a distributed power supply system is provided. The distributed power supply system includes 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. 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. When the voltage on the electric grid falls below the set voltage following the cessation of DC power supply from the main unit, the secondary unit supplies DC power to the electric grid.

According to this configuration, the secondary unit is controlled so that its output voltage is maintained at the set voltage while the output voltage from the main unit is equal to or greater than the set voltage. Then, when the supply of DC power from the main unit to the grid is stopped and the voltage on the grid falls below the set voltage, the secondary unit supplies DC power to the grid. Therefore, even if the supply of power from the main unit to the grid is stopped, the output voltage of the secondary unit is already maintained at the set voltage. Therefore, as soon as the voltage on the grid falls below the set voltage, the secondary unit can supply DC power to the grid. Therefore, even if the supply of power from the main unit (i.e., the device responsible for maintaining the voltage on the grid) to the grid is stopped, a drop in the voltage on the grid can be suppressed.

(2) In the distributed power supply system of the above form, the set voltage may be a voltage that is 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.

(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.

(4) In the distributed power supply system of the above aspect, 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.

(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, 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.

(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.

(7) In the distributed power system of the above aspect, the DC power supplied from the secondary unit to the power grid may be derived from power supplied to the secondary 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.

(8) According to one aspect of the present invention, there is provided a distributed power system, comprising: a main unit connected to an electric grid and capable of supplying and recovering AC power to and from the electric 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.

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

(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.

The present invention can be realized in various forms, such as a method for controlling a distributed power supply system, a computer program for controlling a distributed power supply system, a server device for distributing the computer program, and a non-transitory storage medium on which the computer program is stored.

1 is an explanatory diagram illustrating a configuration of a distributed power supply system according to a first embodiment; FIG. 2 is an explanatory diagram schematically illustrating the voltage control range of each device. FIG. 2 is an explanatory diagram illustrating output control in the main engine. FIG. 4 is an explanatory diagram illustrating output control in the secondary machine. FIG. 10 is an explanatory diagram schematically illustrating the voltage control range of each device according to the second embodiment. FIG. 10 is an explanatory diagram illustrating output control in the secondary unit of the second embodiment. FIG. 10 is an explanatory diagram illustrating the configuration of a distributed power supply system according to a third embodiment.

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. The distributed power supply system 1 is a system in which the DC power to be supplied to a load 90 via the electric wire network NT is shared and output by the main unit 10, the secondary unit 20, the first device 30, and the third device 60. The distributed power supply system 1 also includes a storage unit 50 and an device control unit 70.

The main engine 10 is connected to the power grid NT and is capable of supplying and recovering DC power to and from the power grid 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 power grid 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 on the power grid 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 power grid.

The auxiliary unit 20 is a device connected to the power grid NT and capable of supplying DC power to the power grid NT. The auxiliary unit 20 includes a power converter 24 and an auxiliary unit control unit 26. The power converter 24 converts the power supplied from the power source 80 and supplies it to the power grid 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 power grid 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.

The first device 30 is a device capable of supplying DC power to the power grid NT. The first device 30 includes a solar cell 32 and a power converter 34. The solar cell 32 is connected to the power grid 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 power grid NT.

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 it to the water electrolysis unit 42. The water electrolysis unit 42 electrolyzes water using 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. The hydrogen produced by the electrolysis of water is stored in the storage unit 50.

The third device 60 is a device capable of supplying DC power to the electrical grid 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 electrical grid 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 electrical grid NT. In other words, the fuel cell 62 is a power generation unit capable of supplying DC power generated using reactants to the electrical grid NT.

The equipment control unit 70 controls the first equipment 30, the second equipment 40, and the third equipment 60. The main equipment control unit 16 and the auxiliary equipment control unit 26 described above are separate control units that are distinct 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 power line network NT, and the recovery of DC power from the power line network NT by the second equipment 40.

The output voltage from the first device 30 fluctuates depending on the amount of solar radiation irradiating the solar cell 32. In the distributed power system 1, a main unit 10 equipped with a storage battery 12 is also provided via the electric wire network NT. The main unit 10 switches between charging and discharging depending on fluctuations in the output voltage from the first device 30, thereby maintaining the voltage of the electric wire network NT within a certain range (and a voltage equal to or greater than a set voltage _V1 , which will be described later with reference to FIG. 4 ). In other words, the main unit 10 is a device responsible for maintaining the voltage of the electric wire network NT. Typically, in the distributed power 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 depending on the DC power supplied to the electric wire network NT, and stores the produced hydrogen in a storage unit 50. In this embodiment, while DC power is being supplied from the main engine 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.

FIG. 2 is an explanatory diagram schematically illustrating the voltage control ranges of each device connected to the power line network NT. The voltages _VH , _VL , and _VM shown on the left side of FIG. 2 and the voltages _Vh and _VB shown on the right side represent the upper and lower limits of the voltage control range, with voltage _VH being the highest and voltage _VB being the lowest. The voltage control range of the main motor 10 is between voltage _VL and voltage _VH . That is, the main motor 10 stops supplying DC power to the power line network NT when the output voltage from the main motor 10 falls below voltage _VL or exceeds voltage _VH . In this way, each device connected to the power line network NT stops supplying or recovering DC power when the voltage exceeds the upper or lower limit of the voltage control range set for that device. The voltage control range of the first device 30 and the third device 60 is between voltage _VM and voltage _VH . The voltage control range of the second device 40 is between voltage _VB and voltage _Vh . The voltage control range of the auxiliary unit 20 is between voltage _VB and voltage _VL .

FIG. 3 is an explanatory diagram illustrating output control of the main engine 10. When maintaining the voltage in the electric wire network NT within a certain range, the magnitude of the current flowing from the main engine 10 to the electric wire network NT or the magnitude of the current flowing from the electric wire network NT to the main engine 10 is determined using the line segment _MNT shown in FIG. 3. In FIG. 3, the vertical axis Ax represents voltage, and the horizontal axis represents current. The voltages _VH and _VL shown in FIG. 3 are the lower and upper limit voltages of the voltage control range of the main engine 10, as in FIG. 2. Point _V10 represents the output voltage from the main engine 10 and moves on the line segment _MNT depending on the output voltage from the first device 30 (solar cell 32). Accordingly, the vertical axis Ax moves along the horizontal axis in FIG. 3. That is, point _V10 is the intersection of line segment _MNT and vertical axis Ax. Point _VNT represents the voltage in the electric wire network NT and moves on the line segment _MNT depending on fluctuations in that voltage. When point _VNT is located on the right side of the vertical axis Ax (i.e., when the voltage indicated by point _V10 is greater than the voltage indicated by point _VNT ), the main machine 10 (storage battery 12) supplies DC power to the electric wire network NT. For example, when point _VNT is located at the position shown in FIG. 3, a current of magnitude S corresponding to ΔV, which is the difference between points _V10 and _VNT, is caused to flow to the electric wire network _NT using the line segment MNT. On the other hand, when point _VNT is located on the left side of the vertical axis Ax (i.e., when the voltage indicated by point _V10 is less than the voltage indicated by point _VNT ), the main machine 10 (storage battery 12) recovers DC power from the electric wire network NT. In this case, the magnitude of the current flowing from the electric wire network NT to the storage battery 12 is calculated using the line segment _MNT and ΔV, as in the case of discharging.

FIG. 4 is an explanatory diagram illustrating output control in the secondary unit 20. The magnitude of the current flowing from the secondary unit 20 to the power line network NT is determined using the thick line segment S _NT shown in FIG. 4 . In FIG. 4 , as in FIG. 3 , the vertical axis Ax represents voltage, and the horizontal axis represents current. The line segments M _NT , V _H , and V _L shown in FIG. 4 are the same as in FIG. 3 , except that the line segment M _NT is indicated by a dashed line. As described with reference to FIGS. 2 and 3 , in the distributed power system 1, the output voltage from the primary unit 10 is maintained within the voltage control range, which is between voltage V _L and voltage V _H . Meanwhile, the secondary unit 20 maintains its output voltage at a set voltage V ₁ (shown in FIG. 4 ) while the output voltage from the primary unit 10 is maintained within the voltage control range. In this embodiment, this set voltage V ₁ is a voltage lower than voltage V _L , which is the lower limit voltage of the voltage control range of the primary unit 10. Furthermore, since the lower limit voltage _VL is a voltage equal to or greater than the set voltage _V1 , it can be said that the auxiliary unit 20 maintains the output voltage at the set voltage _V1 while the output voltage from the main unit 10 is equal to or greater than the set voltage _V1 .

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 indicating that the storage battery 12 is in a high temperature or overcharged state from various sensors (not shown), and then stops the supply of DC power from the main machine 10 by performing at least one of stopping 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 power grid NT. The main machine 10 also stops the supply of DC power to the power grid NT when the output voltage from the main machine 10 falls below a lower limit voltage _VL .

As the supply of DC power from the main machine 10 is stopped, the voltage in 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 its output voltage at the set voltage _V1 , supplies 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 falls between voltage _V1 and voltage _VB (the voltage on the line segment sg) on the thick line segment _SNT , a current of a magnitude corresponding to the difference between that voltage and point _V1 flows through the electric wire network NT, as in the description of 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, it is preferable to set the set voltage _V1 to a voltage equal to or greater than 90% of the voltage _VL .

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. The machine control unit 70 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 falls below the set voltage V1, thereby stopping the generation of hydrogen by the second machine 40 and starting the generation of power 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.

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 maintained at the set voltage _V1 in advance. 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.

Furthermore, in the distributed power system 1 of the first embodiment, when the output voltage from the main unit 10 falls below a lower limit voltage _VL , the supply of DC power from the main unit 10 to the power grid NT can be stopped. Even in such a case, the output voltage of the secondary unit 20 is maintained at a preset voltage _V1 that is lower than the voltage _VL , so that 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 preset voltage _V1 .

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. This reduces the power consumed by the water electrolysis unit 42, thereby slowing down the voltage drop in the electric wire network NT caused by the stop of the supply of DC power from the main engine 10.

Furthermore, in the distributed power generation system 1 of the first embodiment, when the main engine 10 stops supplying DC power to the power grid NT, power generation by the fuel cell 62 begins. Therefore, since power is supplied from the fuel cell 62 to the power grid NT, a voltage drop in the power grid NT caused by the stoppage of DC power supply from the main engine 10 can be suppressed.

Furthermore, in the distributed power 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. This increases the number of times the main unit 10 and the auxiliary unit 20 are controlled 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 , so that when the supply of DC power from the main unit 10 is stopped, DC power can be quickly supplied to the power line network NT from the auxiliary unit 20, which becomes a new supply source.

Furthermore, in the distributed power 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 power derived from renewable energy, it is possible to suppress a voltage drop in the power grid NT caused by an interruption in the supply of DC power from the primary unit 10.

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 the distributed power system 1a of the second embodiment. The distributed power system 1a of the second embodiment is the same as the distributed power 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 system 1 of the first embodiment.

In the distributed power supply system 1 of the first embodiment, the voltage control range of the secondary unit 20 is between voltage _VB and voltage _VL (see FIG. 2), whereas in the distributed power supply system 1a of the second embodiment, the voltage control range of the secondary unit 20 is between voltage _VB and voltage _VA (>voltage _VL ). In addition, the set voltage _V1 is the same as voltage _VL , which is the lower limit voltage of the voltage control range of the primary unit 10.

FIG. 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 system 1a, as shown in FIG. 5, the output voltage from the primary unit 10 is maintained within a voltage control range from voltage _VL to voltage _VH . Meanwhile, the secondary unit 20 maintains its output voltage at a set voltage _V1 (shown in FIG. 6) while the output voltage from the primary unit 10 is maintained within the voltage control range. In the second embodiment, the set voltage _V1 is the same as the voltage _VL. Therefore, if the supply of DC power to the power grid NT is stopped because the output voltage from the primary unit 10 falls below voltage _VL (below the lower limit of the voltage control range), the secondary unit 20, which has maintained its output voltage at the set voltage _V1 , immediately supplies DC power to the power grid NT.

As in the first embodiment, the distributed power system 1a of the second embodiment described above can also suppress a voltage drop in the power wire network NT when the supply of power from the main unit 10 to the power wire network NT is stopped. Furthermore, in the distributed power system 1a of the second embodiment, the set voltage _V1 is set to a voltage equal to the voltage _VL , which is the lower limit voltage of the voltage control range of the main unit 10. Therefore, when the supply of DC power to the power wire network NT is stopped because the output voltage from the main unit 10 falls below the voltage _VL (below the lower limit of the voltage control range), DC power can be immediately supplied to the power wire network NT from the secondary unit 20.

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.

In the distributed power system 1b, AC power flows through the power line network NT, and therefore the power converters 14, 24, 34, 44, and 64 are DC/AC converters. The power line network NT is provided with a frequency sensor 77 that detects the frequency of the AC power flowing through the power line network NT. The main machine control unit 16 receives a signal indicating this 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 power line network NT when the frequency of the AC power flowing through the power line 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.

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, the auxiliary machine 20 maintains the frequency of the AC power it outputs at the set frequency _F1 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 . 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.

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 decrease 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 has been maintaining the frequency of its output AC power 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 supply 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.

As described above, according to the distributed power supply system 1b of the third embodiment, 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 , the secondary unit 20 is controlled so that the frequency of the AC power output from the secondary unit 20 is maintained at 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 , AC power is supplied from the secondary unit 20 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 already maintained at the set frequency _F1 , so that AC power can be supplied from the secondary unit 20 to the electric wire network NT 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 . Therefore, even if the supply of AC power from the main machine 10 (i.e., the device responsible for maintaining the frequency in the power line network NT) to the power line network NT is stopped, a drop in the frequency in the power line network NT can be suppressed.

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 in such a case, the frequency of the AC power output from the secondary 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, and 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 secondary unit 20 to the electric wire network NT.

<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.

[Modification 1]
In the above embodiment, the main engine 10 is provided 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 provided with an electric double layer capacitor, a capacitor, a flywheel battery, or the like instead of or in addition to the storage battery 12.

[Modification 2]
In the above embodiment, the power supplied from the secondary machine 20 to the power grid NT is derived from power generated using renewable energy, but this is not limited to this. For example, the power supplied from the secondary machine 20 to the power grid NT may be derived from power supplied to the secondary machine 20 from another distributed power supply system. In such a distributed power supply system, the power supplied to the secondary machine 20 from the other distributed power supply system can be used to suppress a voltage (frequency) drop in the power grid NT caused by an interruption in the power supply from the main machine 10.

[Modification 3]
In the above embodiment, the auxiliary machine 20 itself does not have a power supply, and supplies power to the power line network NT using power supplied from the external power supply 80. However, 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 as appropriate depending on whether the power supplied from the power supply is direct current or alternating current.

[Modification 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. That is, 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.

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

[Modification 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.

[Modification 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.

[Modification 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 from that before the main machine 10 was stopped.

[Modification 9]
In the above embodiment, when the main engine 10 stops supplying DC power to the electric wire network NT and the auxiliary engine 20 starts supplying DC power to the electric wire network NT, the second equipment 40 (water electrolysis unit 42) stops generating hydrogen (reactant) and the third equipment 60 (fuel cell 62) starts generating power. However, this is not limited to this. For example, the second equipment 40 (water electrolysis unit 42) may stop generating hydrogen (reactant) and the third equipment 60 (fuel cell 62) may start generating power only when the main engine 10 stops supplying DC power to the electric wire network NT. In this case, to prevent the fuel cell 62 from starting generating power before the voltage in the electric wire network NT drops below the set voltage _V1 , it is preferable that the set voltage _V1 be set to a voltage equal to or as close as possible to _the voltage _VL , as in the second embodiment.

This aspect has been described above based on embodiments and variations, but 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 its spirit or the scope of the claims, and equivalents are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

REFERENCE SIGNS LIST 1, 1a, 1b... Distributed power supply system 10... Main unit 12... Storage battery 14... Power converter 16... Main unit control unit 20... Auxiliary unit 24... Power converter 26... Auxiliary unit control unit 30... First device 32... Solar cell 34... Power converter 40... Second device 42... Water electrolysis unit 44... Power converter 50... Storage unit 60... Third device 62... Fuel cell 64... Power converter 70... Device control unit 77... Frequency sensor

Claims (9)

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. 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. 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. 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. 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. 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. 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. 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. 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.