JP6643938B2 - Distributed power generation system - Google Patents

Description

  The present invention relates to a distributed power generation system including a power generation device capable of switching between a grid-connected operation connected to a power system and a self-sustaining operation not connected to a power system.

  Patent Literature 1 discloses a distributed power generation system including a power generation device capable of switching between an interconnected operation connected to an electric power system and an independent operation not connected to the electric power system. This distributed power generation system is configured to consume the output power of the power generator at the time of self-sustained operation using an independent load connected to the independent operation outlet, and to consume surplus power that cannot be consumed by the independent load. Internal load. That is, such an internal load is used as an electric heater for consuming excess power.

If reverse power flow from the power generator to the power system is prohibited, the surplus power is used for surplus power consumption even when the output power of the power generator is generated even during the interconnection operation. Must be consumed by electric heaters.
As described above, when the reverse power flow from the power generation device to the power system is prohibited, the surplus power of the power generation device is consumed regardless of whether the power generation device is performing the interconnected operation or the independent operation. Requires a large-capacity electric heater.

JP-A-2015-15669

  If a reverse power flow from the power generator to the power system is permitted, even if a surplus occurs in the output power of the power generator, the surplus power may be caused to flow back into the power system. For this reason, an electric heater for consuming the surplus electric power of the power generator is unnecessary only in the interconnection operation. However, when surplus electric power is generated during the self-sustaining operation, an electric heater for consuming the surplus electric power is required.

  As described above, in the conventional distributed power generation system, it is necessary to provide a large-capacity electric heater at least for processing surplus power during self-sustaining operation, regardless of whether or not reverse power flow to the power system is permitted. was there.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a distributed power generation system that can perform processing of surplus power without having a large-capacity electric heater. .

In order to achieve the above object, the distributed power generation system according to the present invention has a characteristic configuration including a power generation unit, and power conversion for converting the generated power of the power generation unit into a desired power by switching a plurality of semiconductor elements and outputting the desired power. A power generation device having a unit, and a control device,
The control device supplies power to the power consuming device from at least one of the power system and the power generation device when the power generation device is connected to the power system. A distributed power generation system that supplies power from the power generation device to a consumer device,
A temperature adjustment unit that adjusts the temperature of the power conversion unit,
The control device includes:
When it is determined that the excess power condition in which the generated power of the power generation unit becomes excessive is not satisfied, the switching of the plurality of semiconductor elements is performed at a predetermined timing, so that the power conversion unit performs power conversion. To do
When it is determined that the excess power condition is satisfied, the switching of the plurality of semiconductor elements is performed at a timing when the loss in the power conversion unit is larger than when the normal loss operation is performed, whereby the power conversion unit to perform the lossy operation to perform power conversion by,
When the control device determines that the excess power condition is satisfied, the control device operates the temperature adjustment unit such that the temperature of the power conversion unit is higher than when determining that the excess power condition is not satisfied. It is in the point to let .

According to the characteristic configuration, when the control device determines that the excess power condition in which the generated power of the power generation unit becomes excessive is satisfied, the timing at which the loss in the power conversion unit becomes larger than when the normal loss operation is performed. The power consumed by the power converter is relatively increased by the large-loss operation in which the plurality of semiconductor elements are switched. On the other hand, when the control device determines that the excess power condition in which the generated power of the power generation unit becomes excessive is not satisfied, the power conversion unit performs the normal loss operation of switching the plurality of semiconductor elements at a predetermined timing. To make the power consumed relatively small. That is, even if the power generated by the power generation unit of the power generation device is the same, the output power of the power generation device (that is, the output power after power conversion by the power conversion unit) is better when the large-loss operation is performed. , Which is smaller than when normal loss operation is performed. As described above, the control device adjusts the magnitude of the output power output from the power generation device by the power conversion unit inside the power generation device. The role of the electric heater for consumption is reduced.
Therefore, it is possible to provide a distributed power generation system capable of processing surplus power without a large-capacity electric heater.
In addition, the control device operates the temperature adjustment unit such that the temperature of the power conversion unit when it is determined that the excess power condition is satisfied is higher than when it is determined that the excess power condition is not satisfied. That is, the electric resistance of the power converter when the excess power condition is satisfied is increased, so that the loss in the power converter can be increased.

  Another characteristic configuration of the distributed power generation system according to the present invention is that the control device satisfies the excess power condition when a surplus occurs in the output power of the power generation device when the normal loss operation is performed. Is determined, and when there is no surplus in the output power of the power generator when the normal loss operation is performed, it is determined that the excess power condition is not satisfied.

  According to the characteristic configuration, when a surplus occurs in the output power of the power generation device when the normal loss operation is performed, the large loss operation is performed such that the loss in the power conversion unit of the power generation device increases. In other words, even if a surplus occurs in the output power of the power generator when the normal loss operation is performed, the output power of the power generator is reduced by performing the large loss operation and increasing the loss in the power converter. be able to.

  Still another characteristic configuration of the distributed power generation system according to the present invention is that the control device is configured to output the power generation device when the normal loss operation is performed in a state where the interconnection operation of the power generation device is not performed. When a surplus occurs in the power, it is determined that the excess power condition is satisfied, and the output power of the power generation device when the normal loss operation is performed in a state where the interconnection operation of the power generation device is not performed. The point is that it is determined that the excess power condition is not satisfied when no surplus occurs or when the interconnection operation of the power generation device is performed.

In a state where the power generation device is not connected to the power supply, if a surplus occurs in the output power of the power generation device, the surplus power must be consumed by some device.
Therefore, in this characteristic configuration, the control device satisfies the excess power condition when a surplus occurs in the output power of the power generation device when the normal loss operation is performed without performing the interconnection operation of the power generation device. Is determined and the loss in the power converter is increased by the large loss operation, thereby reducing the output power of the power generator. As a result, surplus power that must be consumed by some device can be reduced.

On the other hand, when there is no surplus in the output power of the power generator when the normal loss operation is performed in a state where the power generator is not connected, there is surplus power that must be consumed by some device. do not do. In addition, if the power generation device is in the interconnection operation, even if a surplus occurs in the output power of the power generation device, the surplus power can be flown backward to the power system.
Therefore, in the present characteristic configuration, the control device is configured to operate when the output power of the power generation device does not generate a surplus when the normal loss operation is performed in a state where the power generation device is not connected to the power generation device, or when the power generation device is not connected. When the system operation is being performed, it is determined that the excess power condition is not satisfied, and the large loss operation is not performed.

  Still another characteristic configuration of the distributed power generation system according to the present invention includes a consumption unit that can consume the power generated by the power generation unit, and the control device determines that the excess power condition is satisfied, This is to increase power consumption in the consuming unit.

  According to the above configuration, when the control device determines that the excess power condition is satisfied, the control device increases the power consumption in the consuming unit, thereby making it difficult to generate a surplus in the output power of the power generation device.

It is a figure showing composition of a distributed type power generation system. It is a figure showing composition of a power converter. It is a figure showing composition of a power generation unit and an exhaust heat recovery unit. FIG. 4 is a diagram illustrating an example of an output waveform of a power conversion unit. FIG. 4 is a diagram illustrating an example of an output waveform of a power conversion unit. FIG. 4 is a diagram illustrating an example of an output waveform of a power conversion unit.

<First embodiment>
Hereinafter, a distributed power generation system according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a distributed power generation system. FIG. 2 is a diagram illustrating a configuration of the power conversion unit. FIG. 3 is a diagram illustrating a configuration of the power generation unit and the exhaust heat recovery unit. As illustrated, the distributed power generation system includes a power generation unit 10 (an example of a power generation device of the present invention) and a control device C. The power generation unit 10 converts the power generated by the fuel cell unit 12 into a desired power (for example, a desired voltage, frequency, phase, etc.) by switching the plurality of semiconductor elements. ) And outputs the converted power.

[Power generation unit]
In the present embodiment, the fuel cell unit 12 as a power generation unit has a cell stack in which a plurality of cells having a fuel electrode 33 to which a fuel gas such as hydrogen is supplied and an air electrode 32 to which oxygen is supplied are stacked. It is composed. The fuel cell unit 12 can be configured using various types of cells, such as a polymer electrolyte cell and a solid oxide cell. Further, the power generation unit 10 of the present embodiment further includes a fuel reforming unit 13 for supplying a fuel gas (hydrogen or the like) generated by steam reforming of a hydrocarbon or the like to the fuel cell unit 12. I have.

  The power generated by the fuel cell unit 12 is output to one of the interconnected power line 4 and the independent power line 5 via the power converter 11 having an inverter or a converter and an inverter. In the following description, the power output from the fuel cell unit 12 is referred to as generated power, and the power output from the power generation unit 10 is referred to as output power. The state in which output power is supplied from the power conversion unit 11 to the interconnection power line 4 can be said to be a state in which the power generation unit 10 is performing interconnection operation. On the other hand, a state in which output power is supplied from the power conversion unit 11 to the independent power line 5 can be said to be a state in which the power generation unit 10 is performing an independent operation. The interconnection power line 4 is connected to an AC line 2 connected to the power system 1, and the AC line 2 is connected to a changeover switch 6. The independent power line 5 is connected to the changeover switch 6 separately from the AC line 2. The changeover switch 6 operates to switch the power supply source for the exhaust heat recovery unit 20 to one of the power supplied through the AC line 2 and the power supplied through the independent power line 5. The operation of the changeover switch 6 may be controlled by the control device C or automatically changed according to a change in the power supply destination from the power generation unit 10 (that is, whether or not power is supplied via the independent power line 5). A configuration in which the switch 6 operates may be used.

  As shown in FIG. 2, the power conversion unit 11 has a switching circuit unit 11a and a smoothing circuit unit 11b. The control device C controls the ON timing and the OFF timing of the switching elements included in the switching circuit unit 11a to adjust the rectangular wave output to the smoothing circuit unit 11b. In the smoothing circuit unit 11b, the rectangular wave obtained in the switching circuit unit 11a is smoothed, and power having a waveform close to the target waveform is obtained.

  The control device C performs an interconnection operation of supplying the output power of the power generation unit 10 to the AC line 2 when a normal state where the power supply from the power system 1 to the AC line 2 is performed normally is performed. When the power supply to the power supply 2 is not performed normally, the power supply unit 2 is configured to perform an independent operation in which the output power of the power generation unit 10 is supplied to the independent power line 5 that is electrically disconnected from the power system 1 in an abnormal state. In the present embodiment, the control device C is in a normal state in which the power supply from the power system 1 to the AC line 2 is normally performed, or the power supply from the power system 1 to the AC line 2 is normally performed. It is determined whether there is any abnormal state, for example, by referring to the voltage of the AC line 2 detected by the instrument transformer VT. That is, if the detected voltage value is equal to or higher than the set lower limit voltage, the control device C determines that the power supply from the power system 1 to the AC line 2 is in a normal state and the detected voltage value is normal. If the value is less than the set lower limit voltage, it is determined that the power supply from the power system 1 to the AC line 2 is not performed normally and is in an abnormal state.

  In this manner, the control device C supplies power to the power consuming device from at least one of the power system 1 and the power generation unit 10 during the interconnection operation of the power generation unit 10 to the power system 1, and the power generation unit 10 During the self-sustaining operation, the power is supplied from the power generation unit 10 to the power consuming device. The power consuming device at the time of the interconnection operation includes the general power load device 3 connected to the AC line 2 and the exhaust heat recovery unit 20. On the other hand, the power consuming device at the time of the independent operation includes the independent load device 9 and the exhaust heat recovery unit 20.

  In addition, at the time of the independent operation in which the output power of the power generation unit 10 is supplied to the independent power line 5, the idling operation of the power generation unit 10 as one form of the independent operation may be performed. Specifically, in a state where the output power of the power generation unit 10 is supplied to the independent power line 5, the control device C controls the power consumption device (the independent load device 9 and the exhaust heat recovery) measured by the current transformer CT2. When the power consumption of the unit 20) becomes larger than the output power of the power generation unit 10, the switch 16 is temporarily opened to perform an idling operation such that the power supply to the independent load device 9 is temporarily stopped. Sometimes.

[Exhaust heat recovery unit]
The exhaust heat recovery unit 20 is configured to recover exhaust heat from the power generation unit 10. For example, the exhaust heat recovery unit 20 recovers the heat of the cooling water for cooling the cell stack of the fuel cell unit 12 (that is, for recovering the exhaust heat from the fuel cell unit 12), and (An example of the heat storage device of the present invention) is configured to store the recovered heat. Therefore, the exhaust heat recovery unit 20 is provided with a hot water storage tank 21 for storing heat, a circulation path of cooling water, a heat medium that exchanges heat with the cooling water, and a heat path provided in the middle of the circulation path of the heat medium. It is composed of an auxiliary device 23 such as an electric pump for flowing the medium and an electromagnetic valve. Therefore, in the exhaust heat recovery unit 20, in order to cool the cell stack of the fuel cell unit 12, the exhaust heat is collected both during the interconnection operation of the power generation unit 10 and during the independent operation. It is necessary to perform an operation to recover heat, and as a result, power is consumed in the accessory device 23. Power supply to the exhaust heat recovery unit 20 is performed via an internal power line 17 connected to the changeover switch 6.

  In the system shown in FIG. 1, the general power load device 3 and the independent load device 9 are described. The general power load device 3 is electrically connected to the AC line 2 connected to the power system 1. Therefore, the general power load device 3 can receive power supply in a normal state where power supply from the power system 1 to the AC line 2 is performed normally, but power supply from the power system 1 to the AC line 2 In the abnormal state where the operation is not performed normally, power cannot be supplied. Therefore, the general power load device 3 referred to in the present embodiment is a device that does not need to be supplied with power in an abnormal state (for example, some lighting devices).

  On the other hand, the independent load device 9 can receive power supply from the power generation unit 10 in an abnormal state in which power supply from the power system 1 to the AC line 2 is not performed normally, as described later. Power is supplied to the independent load device 9 when power is supplied to the electrical outlet 7 via the independent power line 5 and the electrical plug 8 is connected to the electrical outlet 7. . The self-supporting load device 9 is a highly important device that the user wants to use even in an abnormal state where power supply from the power system 1 to the AC line 2 is not performed normally (for example, some lighting devices, refrigerators, and the like). ).

FIG. 3 is a diagram illustrating the configuration of the power generation unit 10 and the exhaust heat recovery unit 20.
The main components of the power generation unit 10 include a fuel reforming unit 13 and a fuel cell unit 12.
In the fuel reforming section 13, raw fuel is supplied to the reformer 30 through the raw fuel flow path L1, and the reformed gas generated in the reformer 30 passes through the reformed gas flow path L2 in the fuel cell section. The fuel is supplied to twelve fuel electrodes 33. Oxygen (air) is supplied to the air electrode 32 of the fuel cell unit 12 through a power generation air flow path L8. Then, power generation is performed in the fuel cell unit 12.
The amount of oxygen supplied to the cathode 32 is adjusted by the control device C controlling the operation of the blower B2.

The fuel cell unit 12 includes a plurality of stacked cells each having an electrolyte membrane (not shown) sandwiched between a fuel electrode 33 and an air electrode 32. FIG. 3 shows only a single cell for simplification. Further, the fuel cell unit 12 includes a cooling unit 34 that cools the fuel cell unit 12 by collecting heat generated during power generation. In the present embodiment, a water-cooled cooling unit 34 is provided. Specifically, water (hereinafter, referred to as “recovered water”) that circulates in a battery cooling water passage L6 described later is supplied to the cooling unit 34 to cool the fuel cell unit 12. The recovered water whose temperature has increased by passing through the cooling unit 34 flows into the exhaust heat recovery heat exchanger 38 provided in the middle of the battery cooling water flow path L6. Although the details will be described later, in the exhaust heat recovery heat exchanger 38, the recovered water exchanges heat with the hot water flowing through the exhaust heat recovery flow path L10 and transfers the waste heat recovered from the fuel cell unit 12 to the hot water. Hot water is stored in a hot water storage tank 21 as a heat storage device, where heat is stored.
The amount of cooling water flowing through the cooling unit 34 is adjusted by the control device C controlling the operation of the pump P4.

The reformer 30 is supplied with a raw fuel containing a hydrocarbon (for example, a city gas containing methane). Further, the recovered water stored in a battery cooling water tank 35 described later is supplied to the steam generator 41 by a pump P6 through a reforming water flow path L13, and the steam generator 41 is supplied to the reformer 30. Is supplied through the reforming water flow path L13. The reformer 30 performs steam reforming of raw fuel by using combustion heat given from a combustion chamber 31 provided therewith. The fuel gas containing hydrogen as a main component obtained by the steam reforming in the reformer 30 is supplied to the fuel electrode 33 through the reformed gas passage L2.
The amount of raw fuel supplied to the reformer 30 is adjusted by the control device C controlling the operation of the blower B3, and the amount of steam supplied to the reformer 30 is controlled by the control device C using the pump P6. The amount of the reformed gas supplied to the anode 33 is adjusted by controlling the operation.

At the fuel electrode 33, not all the supplied fuel gas is consumed by the power generation reaction. Therefore, fuel gas components such as hydrogen remain in the fuel electrode exhaust gas discharged from the fuel electrode 33. Therefore, the fuel electrode exhaust gas is used as the combustion gas in the combustion chamber 31. Specifically, the fuel electrode 33 supplies the fuel electrode exhaust gas to the combustion chamber 31 via the fuel electrode exhaust gas flow path L3. Further, oxygen used for combustion in the combustion chamber 31 is supplied to the combustion chamber 31 through the combustion air flow path L9. Then, the combustion exhaust gas after being burned in the combustion chamber 31 is discharged outside through the combustion exhaust gas passage L4. The cathode exhaust gas after being used in the cathode 32 is discharged through the cathode exhaust gas passage L5.
The amount of air supplied to the combustion chamber 31 is adjusted by the control device C controlling the operation of the blower B1.

  The combustion exhaust gas and the cathode exhaust gas contain moisture. Therefore, for the purpose of collecting the water, the flue gas passage L4 and the cathode exhaust passage L5 are joined at the portion of the composite heat exchanger 39, and the exhaust heat recovery for cooling the combustion exhaust gas and the cathode exhaust gas. The flow path L10 passes through the composite heat exchanger 39. That is, the water contained in the combustion exhaust gas and the air electrode exhaust gas is cooled and condensed in the combined heat exchanger 39 by the hot and cold water flowing through the exhaust heat recovery passage L10, and the condensed water is recovered as recovered water in the recovered water tank 36. Is done.

As described above, the recovered water stored in the recovered water tank 36 is dissolved in the electrolyte or water because the water contained in the fuel electrode exhaust gas and the water contained in the combustion exhaust gas are mixed. It is assumed that impurities and the like are included. Therefore, the recovered water is configured to be treated by the ion exchange resin 37 provided in the middle of the recovered water flow path L7. The recovered water after being treated by the ion exchange resin 37 is stored in a battery cooling water tank 35. Then, as described above, the water flowing from the battery cooling water tank 35 to the battery cooling water flow path L6 is supplied to the cooling unit 34, and flows out from the battery cooling water tank 35 to the reforming water flow path L13. Water is supplied to the steam generator 41.
The amount of recovered water flowing through the recovered water flow path L7, that is, the amount of recovered water treated by the ion exchange resin 37, is adjusted by the control device C controlling the operation of the pump P3.

The exhaust heat recovery unit 20 has an exhaust heat recovery flow path L10 in which hot water stored in the hot water storage tank 21 circulates between the hot water storage tank 21 and the heat exchanger 38 for exhaust heat recovery. Specifically, the hot and cold water is discharged from the hot water storage tank 21 so as to return to the hot water storage tank 21 via the composite heat exchanger 39, the exhaust heat recovery heat exchanger 38, and the surplus power consuming heater 22. A heat recovery channel L10 is provided. As a result, the waste heat recovered from the recovered water in the waste heat recovery heat exchanger 38 (that is, the waste heat recovered from the power generation unit 10) is given to the hot water flowing through the waste heat recovery flow path L10, and the hot water is stored. It is stored in the tank 21. Also, the heat generated by the surplus power consuming heater 22 that consumes the surplus power of the output power of the power generation unit 10 is also given to the hot water flowing through the exhaust heat recovery passage L <b> 10, and the hot water is stored in the hot water storage tank 21. The flow rate of the hot and cold water in the exhaust heat recovery passage L10 is adjusted by the pump P2.
The amount of hot water flowing through the exhaust heat recovery flow path L10 is adjusted by the control device C controlling the operation of the pump P2.

  The power consumption of the surplus power consumption heater 22 included in the exhaust heat recovery unit 20 is controlled by the control device C. That is, the control device C can adjust the power consumption of the exhaust heat recovery unit 20 as the power consumption device of the present invention by adjusting the power consumption of the surplus power consumption heater 22. For example, the control device C adjusts the power consumption of the surplus power consumption heater 22 so that the received power from the power system 1 that can be derived based on the detection result of the current transformer CT1 becomes zero or more. By performing such control, it is possible to prevent reverse power flow from the power generation unit 10 to the power system 1 from occurring.

  The exhaust heat recovery unit 20 has a hot water supply passage L12 that flows when hot water stored in the hot water storage tank 21 is supplied to the heat load device 24 via the heat source device 40. Although not shown, the heat source device 40 is a device that generates heat by burning fuel using oxygen (air) supplied by a blowing fan or the like. Further, the exhaust heat recovery unit 20 has a water supply passage L11 that supplies water to the hot water storage tank 21. The water supply channel L11 branches at a branch portion 25 into a water supply channel L11a connected to the hot water storage tank 21 and a water supply channel L11b not connected to the hot water storage tank 21. The water supply passage L11b is connected to the hot water supply passage L12 at a junction 27 on the upstream side of the heat source device 40. Further, at a branch portion 26 in the middle of the water supply passage L11b, a water supply passage L11c connected to the downstream side of the heat source device 40 branches. The water supply passage L11c is connected to the hot water supply passage L12 at a junction 28 downstream of the heat source device 40. As described above, by adopting a configuration in which water can be added to the hot water supplied from the hot water storage tank 21 and the hot water heated by the heat source device 40, hot water of an appropriate temperature is supplied to the heat load device 24. Can supply. In the case where the heat load device 24 is a floor heating device or the like using only the heat of hot water, the hot water after the heat is used by the heat load device 24 returns to the hot water storage tank 21. Alternatively, when the heat load device 24 is a hot water supply device using hot water itself, hot water does not return to the hot water storage tank 21. The heat source device 40 is used when the temperature of hot water required by the heat load device 24 is increased to a predetermined temperature and then supplied to the heat load device 24.

  As described above, the power generation unit 10 includes the blowers B1, B2, B3, the pumps P2, P3, P4, and the like as the accessory devices 14. Further, the exhaust heat recovery unit 20 includes a blower fan or the like of the heat source device 40 as the accessory device 23.

[Operation of power conversion unit]
In the present embodiment, the control device C is configured to switch the operation of the power conversion unit 11 depending on whether or not an excess power condition in which the generated power of the fuel cell unit 12 (power generation unit) becomes excessive is satisfied. I have. Specifically, when the control device C determines that the excess power condition is not satisfied, the control device C performs the normal loss operation in which the power conversion by the power conversion unit 11 is performed by switching the plurality of semiconductor elements at a predetermined timing. Let it do. On the other hand, when the control device C determines that the excess power condition is satisfied, the control device C switches the plurality of semiconductor elements at a timing when the loss in the power conversion unit 11 becomes larger than when the normal loss operation is performed. Thus, a large-loss operation in which power conversion by the power conversion unit 11 is performed is performed.

  4 to 6 are diagrams illustrating examples of output waveforms of the power conversion unit 11. FIG. For example, FIG. 4 shows an output waveform example when the control device C causes the power conversion unit 11 to perform power conversion by normal loss operation. On the other hand, FIG. 5 and FIG. 6 are examples of output waveforms when the control device C causes the power conversion unit 11 to perform power conversion by large loss operation. In the example of FIG. 5, the control device C sets the number of on / off times of the switching element to be larger than that in the normal loss operation shown in FIG. As a result, the switching loss in the switching circuit unit 11a becomes larger than in the normal loss operation. Further, in the example of FIG. 6, the control device C sets the number of on / off times of the switching element to be smaller than that in the normal loss operation shown in FIG. As a result, the loss in the coil of the smoothing circuit unit 11b becomes larger than in the normal loss operation.

  As described above, the control device C switches whether to cause the power conversion unit 11 to perform the power conversion by the normal loss operation or the power conversion by the large loss operation even if the power generation output of the fuel cell unit 12 is the same. Thus, the output power of the power generation unit 10 can be made different.

[Excessive power conditions]
In the present embodiment, the excess power condition is that a surplus occurs in the output power of the power generation unit 10 when the normal loss operation is performed. That is, the control device C determines that the excess power condition is satisfied when the output power of the power generation unit 10 when the normal loss operation is performed, and determines that the power generation unit when the normal loss operation is performed. When no surplus occurs in the output power of No. 10, it is determined that the excess power condition is not satisfied.

  It should be noted that the criterion used when the control device C determines that the output power of the power generation unit 10 when the normal loss operation is performed has a surplus can be set as appropriate. For example, the control device C determines that surplus occurs when the output power of the power generation unit 10 when the normal loss operation is performed becomes larger than the power consumption of the power consumption device, and the output power of the power generation unit 10 is It may be determined that no surplus occurs when the power consumption is equal to or less than the power consumption of the consuming device. Alternatively, the control device C determines whether the output power of the power generation unit 10 when the normal loss operation is performed is larger than the power consumption of the power consuming device, or the output of the power generation unit 10 when the normal loss operation is performed. When the power is equal to or less than the power consumption of the power consuming device but the difference is less than a predetermined value, it may be determined that a surplus occurs.

  Specifically, when the power generation unit 10 is generating power and outputting power, the control device C knows the output power from the power generation unit 10 based on the current and voltage output from the power conversion unit 11. Can be. Further, in the case of the interconnection operation, the control device C uses the power consumption device (the general power load device 3 and The power consumption of the exhaust heat recovery unit 20) can be known. Alternatively, in the case of the self-sustaining operation, the control device C uses the power consumption device (the self-sustaining load device 9 and the exhaust heat The power consumption of the recovery unit 20) can be known.

  As described above, in the distributed power generation system of the present embodiment, even if the power generated by the fuel cell unit 12 included in the power generation unit 10 is the same, the output power of the power generation unit 10 (that is, the power conversion by the power conversion unit 11) The later output power) is smaller when the large loss operation is performed than when the normal loss operation is performed. Note that, even if the power conversion unit 11 performs the large-loss operation, if the output power of the power generation unit 10 still generates a surplus, the control device C may use the surplus power by the surplus power consumption heater 22. Good. As described above, since the control device C adjusts the magnitude of the output power output from the power generation unit 10 by the power conversion unit 11 inside the power generation unit 10, at least a part of the output power of the power generation unit 10 is controlled. For consumption, the role of the surplus power consuming heater 22 is reduced. Therefore, it is possible to provide a distributed power generation system that can perform processing of surplus power without having a large-capacity surplus power consumption heater 22.

<Second embodiment>
The decentralized power generation system according to the second embodiment is different from the above-described embodiment in the content of the excess power condition. Hereinafter, the distributed power generation system according to the second embodiment will be described, but the description of the same configuration as the above embodiment will be omitted.

  In the present embodiment, reverse power flow from the power generation unit 10 to the power system 1 is allowed. Therefore, even if a surplus occurs in the output power of the power generation unit 10 while the power generation unit 10 is performing the interconnection operation, the surplus power may be caused to flow backward. That is, unlike the first embodiment, the control device C reduces the power received from the power system 1 that can be derived based on the detection result of the current transformer CT1 (that is, the power supplied to the power system 1 becomes negative). Even if a reverse power flow occurs), the surplus power consuming heater 22 need not consume power.

  The control device C determines that the excess power condition is satisfied when a surplus occurs in the output power of the power generation unit 10 when the normal loss operation is performed without the interconnection operation of the power generation unit 10. That is, during the self-sustained operation, the power cannot be reversely flown to the power system 1, and therefore the control device C sets the above-described large value when the output power of the power generation unit 10 during the normal loss operation is generated. The output power of the power generation unit 10 is reduced by increasing the loss in the power conversion unit 11 due to the loss operation.

  On the other hand, when there is no excess in the output power of the power generation unit 10 when the normal loss operation is performed in a state where the power generation unit 10 is not connected to the interconnection operation, or when the interconnection operation of the power generation unit 10 is not performed. When it is in the state of performing, it is determined that the excess power condition is not satisfied. That is, the control device C may operate the power converter 11 by the normal loss operation.

<Third embodiment>
The distributed power generation system according to the third embodiment is different from the above embodiment in the operation control of the power generation unit 10 when the excess power condition is satisfied. The distributed power generation system according to the third embodiment will be described below, but the description of the same configuration as the above embodiment will be omitted.

  In the distributed power generation system of the present embodiment, the power generation unit 10 has a cooling fan 15 as a temperature control unit that controls the temperature of the power conversion unit 11. Further, when the temperature of the power conversion unit 11 increases, the electric resistance in the power conversion unit 11 increases, and the loss in the power conversion unit 11 increases. That is, the output power of the power generation unit 10 can be changed by changing the temperature of the power conversion unit 11.

Therefore, when the control device C determines that the excess power condition is satisfied, the control device C rotates the cooling fan 15 so that the temperature of the power conversion unit 11 becomes higher than when it determines that the excess power condition is not satisfied. Set the speed lower than the reference rotation speed. As a result, the electric resistance of the power conversion unit 11 when the excess power condition is satisfied increases, the loss in the power conversion unit 11 increases, and the output power of the power generation unit 10 decreases.
On the other hand, when determining that the excess power condition is not satisfied, the control device C may set the rotation speed of the cooling fan 15 to the reference rotation speed.

<Fourth embodiment>
The distributed power generation system of the fourth embodiment is different from the above embodiment in the operation control of the power generation unit 10 and the exhaust heat recovery unit 20 when the excess power condition is satisfied. Hereinafter, the distributed power generation system according to the fourth embodiment will be described, but the description of the same configuration as the above embodiment will be omitted.

  In the above embodiment, when the excess power condition is satisfied, the power consumption of another device may be increased. For example, the distributed power generation system includes a consuming unit that can consume the power generated by the fuel cell unit 12. As such a consuming unit, the auxiliary equipment 14 provided in the power generation unit 10 (such as the blowers B1, B2, and B3 and the pumps P2, P3, and P4) and the auxiliary equipment 23 provided in the exhaust heat recovery unit 20 (Such as a blower fan of the heat source device 40). Then, when determining that the excess power condition is satisfied, the control device C may increase the power consumption in such a consuming unit. By performing such control, it is possible to make it difficult to generate a surplus in the output power of the power generation unit 10.

<Another embodiment>
<1>
In the above embodiment, the configuration of the distributed power generation system of the present invention has been described with a specific example. However, the configuration can be appropriately changed.
For example, FIG. 2 illustrates an example of a circuit of an inverter included in the power conversion unit 11, but an inverter having another configuration or a power conversion unit 11 including a converter and an inverter may be used.
In the above-described embodiment, the example in which the power generation unit is the fuel cell unit 12 has been described. However, another device such as a device in which the power generation unit includes an engine and a generator driven by the engine is used. May be configured.

  In addition, devices other than those described above as the auxiliary device 14 of the power generation unit 10 and the auxiliary device 23 of the exhaust heat recovery unit 20 may be mounted on the distributed power generation system, and the devices may be used as the above-described consuming units. For example, a ventilation fan for exchanging air inside and outside the housing of the power generation unit 10, an electric heater for adjusting the temperature of the reformer 30, and a liquid for preventing various liquids flowing inside the power generation unit 10 from freezing. Various devices such as electric heaters of the above may be used as the above-mentioned consuming unit. Similarly, various devices such as an electric heater for preventing freezing of various liquids flowing inside the exhaust heat recovery unit 20 and a pump for flowing the various liquids inside the exhaust heat recovery unit 20 are provided. It may be used as a consumer.

<2>
In the above-described embodiment, the location provided with the surplus power consuming heater 22 is not limited to the inside of the exhaust heat recovery unit 20, and may be appropriately changed in the power generation unit 10 or outside the power generation unit 10 and the exhaust heat recovery unit 20. It is possible. Further, as a device for cooling the power generation unit 10, a unit for cooling exhaust heat such as a radiator may be used instead of the exhaust heat recovery unit 20.

<3>
The configuration disclosed in the above embodiment (including another embodiment, hereinafter the same) can be applied in combination with the configuration disclosed in the other embodiment unless there is a contradiction, and is disclosed in the present specification. The embodiment is an exemplification, and the embodiment of the present invention is not limited to this, and can be appropriately modified without departing from the object of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a distributed power generation system that can perform processing of surplus power without having a large-capacity electric heater.

1 power system 3 general power load device (power consumption device)
9 Independent load device (power consumption device)
10 Power generation unit (power generation device)
11 Power conversion unit 12 Fuel cell unit (power generation unit)
14. Attached equipment (consumption department)
15 Cooling fan (temperature control part)
20 Exhaust heat recovery unit (power consumption device)
21 Hot water storage tank (heat storage device)
23 Auxiliary equipment (consumption department)
C control device

Claims (4)

A power generation unit, and a power generation device having a power conversion unit that converts the power generated by the power generation unit into a desired power by switching a plurality of semiconductor elements and outputs the power, and a control device.
The control device supplies power to the power consuming device from at least one of the power system and the power generation device when the power generation device is connected to the power system. A distributed power generation system that supplies power from the power generation device to a consumer device,
A temperature adjustment unit that adjusts the temperature of the power conversion unit,
The control device includes:
When it is determined that the excess power condition in which the generated power of the power generation unit becomes excessive is not satisfied, the switching of the plurality of semiconductor elements is performed at a predetermined timing, so that the power conversion unit performs power conversion. To do
When it is determined that the excess power condition is satisfied, the switching of the plurality of semiconductor elements is performed at a timing when the loss in the power conversion unit is larger than when the normal loss operation is performed, whereby the power conversion unit to perform the lossy operation to perform power conversion by,
The control device operates the temperature adjustment unit such that when it is determined that the excess power condition is satisfied, the temperature of the power conversion unit is higher than when it is determined that the excess power condition is not satisfied. distributed power generation system that makes. The control device includes:
When a surplus occurs in the output power of the power generator when the normal loss operation is performed, it is determined that the excess power condition is satisfied,
The distributed power generation system according to claim 1, wherein the excess power condition is determined not to be satisfied when no surplus occurs in the output power of the power generation device when the normal loss operation is performed. The control device includes:
When a surplus occurs in the output power of the power generator when the normal loss operation is performed in a state where the interconnection operation of the power generator is not performed, it is determined that the excess power condition is satisfied,
When no surplus occurs in the output power of the power generation device when the normal loss operation is performed in a state where the interconnection operation of the power generation device is not performed, or by performing the interconnection operation of the power generation device. The decentralized power generation system according to claim 1, wherein it is determined that the excess power condition is not satisfied when the power generation device is in the on state. Comprising a consuming unit capable of consuming the power generated by the power generating unit,
The distributed power generation system according to any one of claims 1 to 3, wherein the control device increases power consumption in the consuming unit when determining that the excess power condition is satisfied.

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