Power supply system

Abstract

To provide a power supply system that can improve the ability of power supply to follow demand changes.SOLUTION: A power supply system 1000 comprises a plurality of power generation units 100 and a system controller 18. Each power generation unit 100 includes a power generation module 20, a power conditioner 16, and a local controller 17. In each power generation unit 100, the local controller 17 is configured to be able to execute output adjustment control, and the output adjustment control includes heteronomous output adjustment control for adjusting output power in a heteronomous manner and autonomous output adjustment control for autonomously adjusting output power. The system controller 18 divides all of the power generation units 100 into groups of output adjusters that execute output adjustment control, and, based on first information regarding power purchased from a commercial power system 500, coordinates the heteronomous output adjustment control and the autonomous output adjustment control so as to substantially equalize the output power of each output adjuster.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power supply system using a fuel cell or the like.

Background Art

[0002] It is expected that by switching part of the commercial power purchased by consumers from the power company to self-generated power, it will lead to a reduction in carbon dioxide emissions. For example, the primary energy efficiency of thermal power generation using coal or LNG as fuel is about 40%, while the primary energy efficiency of a solid oxide fuel cell (SOFC) that generates power by reforming city gas mainly composed of methane can be expected to be 50% - 65%. Therefore, increasing the proportion of self-generated power can contribute to reducing the environmental load.

[0003] In addition, it is expected that by realizing a system that can maintain power supply independently when a power outage occurs due to a natural disaster, the adverse effects on social life and economic activities can be reduced. For example, a solid oxide fuel cell (SOFC) can generate power independently and supply power to the outside as long as the supply of city gas is not interrupted. In the case of an earthquake, the gas infrastructure may be damaged depending on the scale, but in the case of a typhoon, it can be said that there is almost no impact on the gas infrastructure, so power supply can be continued.

[0004] Patent Documents 1 and 2 disclose a power supply system (fuel cell system) that operates in parallel with a commercial power supply system and supplies power to power demand facilities. When there is a large demand during operation, such as in a power demand facility in a factory or the like, the power supply system is composed of a plurality of power generation units (for example, fuel cell units).

[0005] In addition, in the power supply system, it is not recognized to cause reverse power flow to the commercial power supply system side regardless of the number of installed power generation units. Therefore, a response of always purchasing power from the commercial power supply system is required.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2016-019430 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2016-019431 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] The demand of power demand facilities varies depending on the operating conditions of factories and the like. The demand increases during the operating hours and decreases during the shutdown hours. Reducing the number of operating power generation units during the low demand period may impair the followability of power supply to the demand change.

[0008] For example, since the SOFC unit operates the power generation module at 600 to 800°C, if it becomes cold due to the operation stop, it takes a very long time to restart. Also, if the power generation module is kept warm and waiting for operation, not only the power generation efficiency is reduced due to the fuel loss, but also a certain amount of time is required from the release of standby to obtaining the minimum output power. Therefore, it is not recommended to stop the operation or wait for operation of a part of the power generation unit during the low demand period.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a power supply system capable of enhancing the followability of power supply to demand changes. [Means for Solving the Problems]

[0010] The power supply system according to the present invention includes a plurality of power generation units operated in parallel with a commercial power supply system, and a system controller that comprehensively controls the control states of the plurality of power generation units. Each of the plurality of power generation units includes a power generation module, a power conditioner that converts the generated power of the power generation module into output power corresponding to the AC power of the commercial power supply system, and a local controller that controls the output power by controlling the generated power of the power generation module. In the plurality of power generation units, each of the local controllers is configured to be capable of executing output adjustment control for adjusting the output power within a range of not more than the rated output power and not less than the minimum output power. The output adjustment control includes heteronomous output adjustment control for adjusting the output power heteronomously and autonomous output adjustment control for adjusting the output power autonomously. The system controller divides all of the plurality of power generation units into a group of output adjusters that execute the output adjustment control, and comprehensively controls the heteronomous output adjustment control and the autonomous output adjustment control so that the output power of each of the output adjusters is made substantially equal based on first information regarding the purchased power from the commercial power supply system.

Effect of the Invention

[0011] According to the present invention, there is provided a power supply system capable of enhancing the followability of power supply with respect to demand changes.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] 1.1 Outline of the Configuration of the Power Generation Unit First, an outline of the configuration of the power generation unit used in the power supply system according to the present embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of the power generation unit according to the present embodiment. As shown in FIG. 1, the power generation unit 100 is of a type using a fuel cell, and includes a plurality of cell stacks 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a CO oxidizer (carbon monoxide oxidizer) 8, a condensate recovery tank 9, a first raw fuel blower 10, a first air blower 11, a water pump 12, a second raw fuel blower 13, a second air blower 14, a third air blower 15, a power conditioner 16, and a local controller 17.

[0015] In the example of the present embodiment, a total of eight cell stacks 1 are provided, including those not shown in FIG. 1.

[0016] The power generation unit 100 also includes lines (pipelines) such as a raw fuel line La, a mixed gas line Lb, an anode fuel line Lc, an anode off-gas line Ld, a cathode air line Le, a cathode off-gas line Lf, a combustion gas line Lg, a burner cooling air line Lh, a reformed water line Li, a startup air line Lj, a cooling air line Lk, and a condensate recovery line Lw.

[0017] The anode fuel line Lc includes a first distribution manifold Ma that serves as the main pipe for introducing anode fuel, and the cathode air line Le includes a second distribution manifold Mb that serves as the main pipe for introducing cathode air. These distribution manifolds Ma and Mb have an inlet and a plurality of outlets corresponding to each cell stack 1, and cause the fluid flowing into the inlet to flow out from each of the outlets.

[0018] The anode off-gas line Ld includes a first collection manifold Mc that serves as the main pipe for discharging anode off-gas, and the cathode off-gas line Lf includes a second collection manifold Md that serves as the main pipe for discharging cathode off-gas. These collection manifolds Mc and Md have a plurality of inlets and outlets corresponding to each cell stack 1, and cause the fluid flowing into each inlet to flow out from the outlet.

[0019] The combustion gas line Lg includes a heat radiation cylinder Za and a combustion gas pipe Zb. The cooling air line Lk includes a cooling pipe Zc and a collection pipe Lk1.

[0020] The raw fuel line La is a pipe connecting the fuel intake port E1 and the burner 3, and a second raw fuel blower 13 is disposed in this pipe. The second raw fuel blower 13 is a device that pressurizes the raw fuel gas Gf (for example, methane-containing gas such as city gas 13A) taken in from the fuel intake port E1 and sends it to the downstream side of the raw fuel line La. Typically, it is driven during the startup operation of the power generation unit 100.

[0021] The mixed gas line Lb is a pipe connecting the fuel intake port E2 and the reformer 2, and in this pipe, in order from the upstream side, a first raw fuel blower 10, an evaporator 4, and a first bellows type expansion joint B1 are disposed. The first raw fuel blower 10 is a device that pressurizes the raw fuel gas Ga taken in from the fuel intake port E2 and sends it to the downstream side of the mixed gas line Lb. Typically, it is driven during the power generation operation of the power generation unit 100.

[0022] The anode fuel line Lc is a pipeline connecting the reformer 2 and the anodes of each cell stack 1. More specifically, the anode fuel line Lc includes, in order from the upstream side, a pipeline connecting the reformer 2 and the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipelines (the branch pipes of the first distribution manifold Ma) connecting the outlets of the first distribution manifold Ma and the anodes of each cell stack 1.

[0023] The anode off-gas line Ld is a pipeline connecting the anodes of each cell stack 1 and the burner 3. More specifically, the anode off-gas line Ld includes, in order from the upstream side, eight pipelines (the branch pipes of the first collection manifold Mc) connecting the anodes of each cell stack 1 and the inlets of the first collection manifold Mc, the first collection manifold Mc, and a pipeline (hereinafter referred to as "pipeline Ld1") connecting the outlet of the first collection manifold Mc and the burner 3. In the middle of the pipeline Ld1, a second bellows expansion joint B2, an anode off-gas cooler 6, an anode off-gas condenser 7, and a gas-liquid separation section Sa are arranged in order from the upstream side.

[0024] The cathode air line Le is a pipeline connecting the air inlet E3 and the cathodes of each cell stack 1. More specifically, the cathode air line Le includes, in order from the upstream side, a pipeline (hereinafter referred to as "pipeline Le1") connecting the air inlet E3 and the inlet of the second distribution manifold Mb, the second distribution manifold Mb, and eight pipelines (the branch pipes of the second distribution manifold Mb) connecting the outlets of the second distribution manifold Mb and the cathodes of each cell stack 1.

[0025] In the middle of pipeline Le1, in order from the upstream side, a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows-type expansion joint B3 are arranged. The first air blower 11 is a device that pressurizes the air Aa taken in from the air intake E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during the power generation operation of the power generation unit 100. Further, in the pipeline Le1, a bypass path Le2 that bypasses the anode off-gas cooler 6 and the air preheater 5 is provided so as to connect the midpoint between the air intake E3 and the anode off-gas cooler 6 and the midpoint between the air preheater 5 and the third bellows-type expansion joint B3.

[0026] The cathode off-gas line Lf is a pipeline that connects the cathode of each cell stack 1 and the burner 3. More specifically, the cathode off-gas line Lf includes, in order from the upstream side, eight pipelines (branch pipes of the second collection manifold Md) that connect the cathode of each cell stack 1 and the inlets of the second collection manifold Md, the second collection manifold Md, and a pipeline (hereinafter referred to as "pipeline Lf1") that connects the outlet of the second collection manifold Md and the burner 3.

[0027] The combustion gas line Lg is a pipeline that connects the burner 3 and the gas discharge port E6. More specifically, the combustion gas line Lg includes, in order from the upstream side, a heat radiation cylinder Za, a pipeline that connects the heat radiation cylinder Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipeline (hereinafter referred to as "pipeline Lg1") that connects the combustion gas pipe Zb and the gas discharge port E6. In the middle of the pipeline Lg1, in order from the upstream side, a fourth bellows-type expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4 are arranged.

[0028] The burner cooling air line Lh is a pipe connecting the pipe line Le1 and the starting air line Lj, and a flow rate adjusting means (such as an orifice) (not shown) is provided in this pipe line. More specifically described, the burner cooling air line Lh branches at an intermediate point of the pipe line Le1 connecting the first air blower 11 and the anode off-gas cooler 6, and merges into the starting air line Lj on the downstream side of the second air blower 14. It is configured such that a minute flow rate of air Ab flows toward the burner 3 when the first air blower 11 is driven.

[0029] The cooling air line Lk is a pipe connecting the air intake E5 and a predetermined location of the pipe line Lg1 (a location between the evaporator 4 and the gas discharge port E6), and in this pipe line, a third air blower 15 and a cooling pipe Zc are arranged in order from the upstream side. The third air blower 15 is a device that boosts the cooling air Ad taken in from the air intake E5 and sends it to the downstream side of the cooling air line Lk.

[0030] The reformed water line Li is a pipe connecting the condensed water recovery tank 9 and the evaporator 4, and a water pump 12 is arranged in this pipe line. The water pump 12 is a device that sends the condensed water Wb stored in the condensed water recovery tank 9 as reformed water Wa to the downstream side of the reformed water line Li.

[0031] The starting air line Lj is a pipe connecting the air intake E4 and the pipe line Lf1, and a second air blower 14 is arranged in this pipe line. The second air blower 14 is a device that boosts the air Ac taken in from the air intake E4 and sends it to the downstream side of the starting air line Lj, and is typically driven during the startup operation of the power generation unit 100.

[0032] The condensate recovery line Lw is a pipeline that connects the gas-liquid separation section Sa disposed in the middle of the pipeline Ld1 and the condensate recovery tank 9. The gas-liquid separation section Sa is a member that separates the condensate Wb generated in the anode off-gas condenser 7 from the anode off-gas Gd, and the separated condensate Wb flows down in the condensate recovery line Lw. The tip of the condensate recovery line Lw is opened to the gas phase portion without being immersed in the aqueous phase portion of the condensate recovery tank 9 so that the condensate amount does not increase or decrease under the influence of the water temperature of the stored condensate Wb. Note that the tip of the condensate recovery line Lw is not immersed in the aqueous phase portion in order not to change the flow rate of the anode off-gas Gd sent to the burner 3. In particular, this configuration is effective when the anode off-gas Gd after separating the condensate Wb is recycled to the primary side of the cell stack or used for power generation in the subsequent cell stack. For the gas-liquid separation section Sa, for example, a T-shaped pipe in which a straight pipe section is arranged horizontally and a branch pipe section is arranged downward is used. Also, a small-capacity cylindrical container erected in the vertical direction can be used as the gas-liquid separation section Sa.

[0033] The cell stack 1 is a power generation body composed of a solid oxide fuel cell (SOFC). The solid oxide fuel cell is a high-temperature operating fuel cell in which the solid electrolyte, anode, and cathode constituting the power generation cell are all ceramics, and a power generation unit in which a predetermined number of power generation cells are integrated via a metal interconnect material (also referred to as a separator material) is called a cell stack. The battery output of the cell stack 1 is fed after being adjusted by the power conditioner 16.

[0034] The reformer 2 reforms the raw fuel gas Ga using steam to generate a reformed gas Gc and sends it to the subsequent stage side. The reformer 2 has a catalyst for steam reforming, reacts methane contained in the raw fuel gas Ga with steam, and generates a reformed gas Gc containing carbon monoxide and hydrogen. Although steam reforming is an endothermic reaction, the reformer 2 can stably generate the reformed gas Gc by heat supply from the burner 3.

[0035] The burner 3 burns the inflowing gas to generate heat, and discharges the combustion gas Gg generated by combustion into the combustion gas line Lg. The evaporator 4 is a device that indirectly heat-exchanges the reformed water Wa and the combustion gas Gg (heat source fluid), and plays a role of evaporating the reformed water Wa and heating the raw fuel gas Ga simultaneously by heat-exchanging with the combustion gas Gg.

[0036] The air preheater 5 and the anode off-gas cooler 6 are both heat exchangers that indirectly heat-exchange a low-temperature fluid and a high-temperature fluid. The air preheater 5 plays a role of preheating the air Aa in the cathode air line Le by heat-exchanging with the combustion gas Gg, and the anode off-gas cooler 6 plays a role of cooling the anode off-gas Gd by heat-exchanging with the air Aa in the cathode air line Le.

[0037] The anode off-gas condenser 7 uses the fan 7a to cool the anode off-gas Gd and condenses the water vapor contained in the anode off-gas Gd. Note that the anode off-gas condenser 7 of this embodiment is an air-cooled heat exchanger, but instead, a water-cooled heat exchanger may be adopted, and thus it may be a cogeneration type power generation unit in which heat recovery is performed.

[0038] The CO oxidizer 8 is a device that brings the harmful carbon monoxide contained in the combustion gas Gg into contact with a catalyst and converts it into harmless carbon dioxide. The CO oxidizer 8 does not operate when the oxidation reaction in the burner 3 is complete, and operates only when the oxidation reaction in the burner 3 is incomplete.

[0039] The condensate recovery tank 9 recovers the condensate Wb discharged from the gas-liquid separation section Sa and serves to make it reusable as reformed water Wa. The condensate recovery tank 9 is provided with a water level detector Sb and a drain valve Sc in order to adjust the water level of the stored reformed water Wa within a predetermined range. When the water level detector Sb detects the upper limit water level, the drain valve Sc is opened, while when the water level detector Sb detects the lower limit water level, the drain valve Sc is closed. In this way, the condensate recovery tank 9 is ensured to have the required amount of reformed water Wa. In addition, in order to prevent the anode off-gas Gd from leaking to the outside during the drainage operation of the reformed water Wa, the drainage position by the drain valve Sc is set near the bottom of the condensate recovery tank 9.

[0040] Also, as shown by the dashed-line frame in FIG. 1, each cell stack 1, reformer 2, burner 3, each manifold Ma to Md, heat radiation cylinder Za, combustion gas pipe Zb, and cooling pipe Zc are arranged in the first region R1. The first region R1 is maintained at a temperature exceeding 600°C during the power generation operation of the power generation unit 100 and independently maintains the heat balance of heat absorption and heat generation. On the other hand, the evaporator 4, air preheater 5, anode off-gas cooler 6, and CO oxidizer 8 are arranged in the second region R2. The second region R2 is maintained at a temperature lower than that of the first region R1 and higher than room temperature during the power generation operation of the power generation unit 100. The first region R1 and the second region R2 are each surrounded by a heat insulation box, and the power generation module 20 is formed by integrating the two heat insulation boxes. The anode off-gas condenser 7, condenser fan 7a, condensate recovery tank 9, each blower 10, 11, 13, 14, 15, water pump 12, power conditioner 16, and local controller 17 are arranged outside the power generation module 20 (room temperature region). Note that each of the above-mentioned bellows-type expansion pipe joints B1 to B4 is used to absorb the expansion and contraction of the piping caused by the temperature change between the cold state and the operation state.

[0041] FIG. 2 is a schematic diagram showing the configuration of the power conditioner 16 according to the present embodiment, and shows the internal configuration of the power conditioner 16 and the connection state to peripheral devices. The power generation module 20 is configured to include elements such as the cell stack 1 as described above. Further, the auxiliary machine 30 for operating the power generation module 20 includes components such as the raw fuel blowers 10 and 13, the air blowers 11, 14, and 15, the water pump 12, and the fan 7a of the anode off-gas condenser 7.

[0042] The power conditioner 16 converts the generated power of the power generation module 20 into output power corresponding to the AC power of the commercial power supply system 500. The power conditioner 16 includes DC / DC converters 16a and 16b, a smoothing capacitor 16c, a grid-connected inverter 16d, switches 16e and 16f, and control circuits 16g and 16h.

[0043] The DC / DC converter 16a boosts and converts the DC power from the power generation module 20 (boosting circuit). The smoothing capacitor 16c smooths the output power of the DC / DC converter 16a. The grid-connected inverter 16d converts the output power of the DC / DC converter 16a into AC power equivalent to the commercial power supply system.

[0044] The output side of the grid-connected inverter 16d is electrically connected to, for example, a distribution board 610 for receiving commercial power installed in a building. The grid-connected inverter 16d and the distribution board 610 can be switched between a parallel state and a disconnection state via the switch 16e. The commercial power supply system 500 and the power demand equipment 600 are electrically connected to the distribution board 610. The power demand equipment 600 includes a plurality of sub-distribution boards, and load devices such as lighting fixtures, power devices, or outlets used in the building are electrically connected to each sub-distribution board.

[0045] In addition, the grid-connected inverter 16d is electrically connected to the independent power outlet 300. The grid-connected inverter 16d and the independent power outlet 300 can be switched between a connected state and a disconnected state via the switch 16f. The independent power outlet 300 is composed of a plurality of outlets into which the power plugs of various electrical equipment can be inserted.

[0046] The DC / DC converter 16b and the control circuit 16g function as a drive power supply unit that supplies drive power to the auxiliary machine 30. The DC / DC converter 16b adjusts the DC voltage boosted by the DC / DC converter 16a to a DC voltage suitable for driving the auxiliary machine 30. The control circuit 16g supplies the DC voltage adjusted by the DC / DC converter 16b to the auxiliary machines 30 to appropriately drive the auxiliary machine 30. The above-mentioned auxiliary machine 30 is driven using commercial power during the startup operation and shutdown operation of the power generation unit 100, and is driven using the generated power during the power generation operation of the power generation unit 100.

[0047] The DC / DC converter 16a and the control circuit 16h function as an operating power supply unit that supplies operating power to the load module 40. The load module 40 is configured to include an electric heater 41 and a radiator fan 42. In the independent operation mode of the power generation unit 100, the load module 40 causes the electric heater 41 to generate heat to consume the surplus generated power of the cell stack 1, and the radiator fan 42 sends an air flow to the electric heater 41 to promote heat dissipation. Note that the load module 40 is disposed, for example, inside or outside the casing of the power generation unit 100.

[0048] The local controller 17 controls the operation of the power generation unit 100 according to a control program created and stored in advance. The local controller 17 is provided with a communication unit 17a that communicates with the outside of the power generation unit 100. In addition, a current sensor 200, which will be described later, is connected to the local controller 17. Details of the local controller 17 will be described later as needed.

[0049] 1.2 Outline of the operation of the power generation unit Next, the general operation of the power generation unit 100 will be described with reference to FIG. 1. The raw fuel gas Ga supplied into the mixed gas line Lb from the fuel inlet E2 is sent to the downstream side by the action of the first raw fuel blower 10. In parallel with the supply of the raw fuel gas Ga, the reformed water Wa supplied into the reformed water line Li from the condensate recovery tank 9 has its water volume adjusted by the water pump 12 and flows into the mixed gas line Lb.

[0050] The reformed water Wa flows into the evaporator 4 together with the raw fuel gas Ga in the mixed gas line Lb, and is heated by heat exchange in the evaporator 4 to become water vapor (superheated steam). The water vapor is mixed with the heated raw fuel gas Ga and flows into the reformer 2 as the mixed gas Gb.

[0051] The reformer 2 reforms the raw fuel gas Ga using the water vapor in the mixed gas Gb, generates the reformed gas Gc, and sends it to the downstream side. The reformed gas Gc sent out from the reformer 2 is distributed to the anodes of the respective cell stacks 1 through the anode fuel line Lc.

[0052] On the other hand, in parallel with the supply of the above-described raw fuel gas Ga, air Aa is supplied into the cathode air line Le from the air inlet E3. The air Aa in the cathode air line Le is sent to the downstream side by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6 and further heated by heat exchange in the air preheater 5, and then distributed to the cathodes of the respective cell stacks 1. Note that, for temperature adjustment of the air Aa, etc., a part of the air Aa, i.e., the air Aa1, can also be made to flow into the cathodes of the respective cell stacks 1 through the bypass path Le2.

[0053] Furthermore, in synchronization with the supply of the air Aa to the cathode, air Ab is supplied into the burner cooling air line Lh. The air Ab in the burner cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant for reducing the combustion temperature of the burner 3.

[0054] Each cell stack 1 generates electricity using the reformed gas Gc flowing into the anode and the air Aa flowing into the cathode. When current sweeping by the power conditioner 16 is executed with the reformed gas Gc and the air Aa supplied to the cell stack 1, power generation (electrochemical reaction between the reformed gas and oxygen) of the cell stack 1 is started. During the power generation operation of the cell stack 1, the anode off-gas Gd is discharged from the anode to the anode off-gas line Ld, and the cathode off-gas Ge is discharged from the cathode to the cathode off-gas line Lf. The anode off-gas Gd contains the reformed gas that was unreacted at the anode, and the cathode off-gas Ge contains the oxygen that was unreacted at the cathode.

[0055] The anode off-gas Gd discharged from each cell stack 1 to the anode off-gas line Ld is collected in the first collection manifold Mc, then cooled by heat exchange in the anode off-gas cooler 6, and flows into the anode off-gas condenser 7. In the anode off-gas condenser 7, the anode off-gas Gd is cooled to below the dew point temperature, and the water vapor contained in the anode off-gas Gd condenses.

[0056] The anode off-gas Gd that has passed through the anode off-gas condenser 7 is sent to the gas-liquid separation section Sa for gas-liquid separation, and the condensed water Wb is recovered in the condensed water recovery tank 9. The condensed water Wb recovered in the condensed water recovery tank 9 is reused as the reformed water Wa as described above. Note that the non-condensed portion (the anode off-gas Gd after gas-liquid separation) in the anode off-gas Gd is sent to the burner 3.

[0057] The cathode off-gas Ge discharged from each cell stack 1 to the cathode off-gas line Lf is collected in the second collection manifold Md, then mixed with the air Ab flowing in through the burner cooling air line Lh in the pipeline Lf1, and sent to the burner 3. Also, to the burner 3, according to the operating state of the power generation unit 100, the raw fuel gas Gf supplied from the fuel inlet E1 is sent through the raw fuel line La, and the air Ac supplied from the air inlet E4 is sent through the starting air line Lj.

[0058] The burner 3 has the gas Gx for the first burner, which is the raw fuel gas Gf and / or the anode off-gas Gd, and the gas Gy for the second burner, which is the air Ac and / or the cathode off-gas Ge, flowing into it, and burns these to generate heat. That is, the gas Gx for the first burner is a mixture of the raw fuel gas Gf and the anode off-gas Gd, or is in the state of either the raw fuel gas Gf or the anode off-gas Gd, and which state it is in can vary depending on the operating state of the power generation unit 100, etc. Also, the gas Gy for the second burner is a mixture of the air Ac and the cathode off-gas Ge, or is in the state of either the air Ac or the cathode off-gas Ge, and which state it is in can vary depending on the operating state of the power generation unit, etc. That is, according to the startup operation, power generation operation (full load operation or partial load operation), shutdown operation, etc. of the power generation unit 100, the supply gas to the burner 3 changes its state as appropriate.

[0059] Note that the raw fuel gas Gf is a type of hydrocarbon-containing gas. On the other hand, the air Ac is a type of oxidant-containing gas. During the combustion operation of the burner 3, air Ab is continuously supplied from the burner cooling air line Lh, and the combustion temperature is adjusted.

[0060] The combustion gas Gg generated by the combustion in the burner 3 is sent to the combustion gas line Lg, passes through the heat radiation cylinder Za, the combustion gas pipe Zb, the air preheater 5, the CO oxidizer 8, and the evaporator 4 in sequence, and is discharged from the gas discharge port E6 to the outside of the power generation module 20. The heat radiation cylinder Za and the combustion gas pipe Zb are arranged so as to be able to effectively heat the reformer 2 using the combustion gas Gg. Also, the combustion gas Gg in the combustion gas line Lg is used for heat exchange when passing through the air preheater 5 and the evaporator 4, and when carbon monoxide is contained, the carbon monoxide is converted to carbon dioxide when passing through the CO oxidizer 8.

[0061] Also, the cooling air Ad supplied from the air intake E5 to the cooling air line Lk serves to cool the interior of the power generation module 20 when passing through the cooling pipe Zc. As will be described later, the cooling pipe Zc is installed in the vicinity of the cell stack 1, and the cell stack 1 can be effectively cooled by the cooling air Ad. Then, the cooling air Ad finally passes through the collecting pipe Lk1 and is discharged to the outside of the power generation module 20 from the gas outlet E6 together with the combustion gas Gg.

[0062] Also, in the power generation unit 100, the amount of heat (temperature) inside the power generation module 20 is controlled by adjusting the flow rate of the cooling air Ad introduced into the cooling pipe Zc. As an example, when the discharge temperature of the cathode off-gas Ge flowing out from the cell stack 1 exceeds the upper limit temperature, the local controller 17 drives the third air blower 15, and controls the rotation speed of the third air blower 15 so that the discharge temperature of the cathode off-gas Ge becomes the target temperature (a temperature lower than the upper limit temperature by a predetermined temperature). The greater the rotation speed of the third air blower 15 increases, the greater the flow rate of the cooling air Ad introduced into the cooling pipe Zc. Also, when the rotation speed below the lower limit value continues for a predetermined time, the local controller 17 stops the third air blower 15.

[0063] Note that the cooling pipe Zc installed near the cell stack 1 can also be used to heat up the cell stack 1 during the startup operation of the power generation unit 100. Specifically, in the startup operation of the power generation unit 100, first, the second raw fuel blower 13 and the second air blower 14 are driven to burn the burner 3. The combustion gas Gg generated by this combustion flows through the heat radiation cylinder Za and the combustion gas pipe Zb, while heating the cold reformer 2 from the outside by radiative heat transfer to increase its temperature. Further, the combustion gas Gg becomes the heat source of the evaporator 4, generating steam from the reforming water Wa. This steam flows through the cold reformer 2 and the cell stack 1 in sequence, heating these devices from the inside by heat conduction to increase their temperature. If there is waste heat in the combustion gas Gg discharged from the evaporator 4, the combustion gas Gg is made to flow from the pipeline Lg1 into the collection pipe Lk1. As a result, since the combustion gas Gg flows through the cooling pipe Zc, the cold cell stack 1 can be heated from the outside by radiative heat transfer to increase its temperature.

[0064] In the power generation operation of the power generation unit 100, balancing the heat balance among the heat generation due to the electrochemical reaction between the reformed gas Gc and oxygen in the cell stack 1, the heat generation due to the combustion reaction between the anode off-gas Gd and the cathode off-gas Ge in the burner 3, and the heat absorption due to the steam reforming reaction between the raw fuel gas Ga and steam (reforming water Wa) in the reformer 2 is called "thermal self-sufficiency". Also, recovering the water (reforming water Wa) generated by the electrochemical reaction between the reformed gas Gc and oxygen and repeatedly using it in the steam reforming reaction is called "water self-sufficiency".

[0065] In the power generation operation of the power generation unit 100, the output power of the grid-connected inverter 16d is equal to the value obtained by subtracting the total power losses due to the operation of the auxiliary machine 30, the power losses due to the operation of the power conditioner 16, and the power losses due to the operation of the load module 40. The load module 40 operates in the self-sustaining operation mode described later.

[0066] When the power generation unit 100 is operated at full load with the rated output power, the local controller 17 sets the scavenging current value for the cell stack 1 to the rated current value and supplies the corresponding amount of raw fuel gas Ga. When the power generation unit 100 is operated at a partial load below the rated output power and above the minimum output power, the local controller 17 sets the scavenging current value for the cell stack 1 to a range below the rated current value and above the lower limit current value, and supplies the corresponding amount of raw fuel gas Ga. When the power generation unit 100 is put on standby with zero output power, the local controller 17 sets the scavenging current value for the cell stack 1 to the value corresponding to the operating power of the auxiliary machine 30, and supplies the minimum amount of raw fuel gas Ga while keeping the power generation module 20 warm. Note that the state in which the power generation unit 100 is put on standby with zero output power is referred to as "hot standby".

[0067] The power generation operation of the power generation unit 100 includes a grid-connected operation mode and an independent operation mode. In the grid-connected operation mode, as shown in FIG. 2, the switch 16e is controlled to be in the on state and the switch 16f is controlled to be in the off state. Thereby, the power generation unit 100 is operated in parallel with the commercial power supply system 500. In the independent operation mode, conversely to FIG. 2, the switch 16e is controlled to be in the off state and the switch 16f is controlled to be in the on state. Thereby, the power generation unit 100 is operated in a disconnected state from the commercial power supply system 500.

[0068] The local controller 17 constantly monitors the presence or absence of a power outage in the commercial power supply system 500, and when a power outage is detected, it shifts the power generation unit 100 from the grid-connected operation mode to the independent operation mode. In the independent operation mode, when an electrical device is connected to the independent outlet 300, it is possible to supply the output power of the grid-connected inverter 16d as the independent operation power to the electrical device. When the commercial power supply system 500 resumes power after a power outage, the local controller 17 shifts the power generation unit 100 from the independent operation mode to the grid-connected operation mode.

[0069] When the supply amount of the self-driving power exceeds the consumption amount in the self-driving mode, the power generation unit 100 causes the load module 40 to consume the surplus of the self-driving power. The adjustment of the power consumption amount of the load module 40 can be realized by adjusting the calorific value of the electric heater 41 (for example, the number of heaters to be energized, or the adjustment of the on / off duty ratio of the energization).

[0070] 2.1 Configuration Overview of Power Supply System Next, the configuration overview of the power supply system according to the present embodiment will be described. FIG. 3 is a schematic diagram showing the configuration of the power supply system according to the present embodiment. As shown in FIG. 3, the power supply system (fuel cell system) 1000 includes a plurality of power generation units 100 operated in parallel (system connection mode) with respect to the commercial power supply system 500, and a system controller 18 that comprehensively controls the control states of each machine. The power supply system 1000 supplies the total output power obtained by adding up the output powers of each power generation unit 100 to the power demand facility 600.

[0071] In the present embodiment, the power supply system 1000 includes a first power generation unit 101, a second power generation unit 102, a third power generation unit 103, and a fourth power generation unit 104. Each of the power generation units 101 to 104 has the same rated output power. For example, if the rated output power of each is 6 kW, the power supply system 1000 can supply a total output power of up to 24 kW.

[0072] <Number of Installation Platforms of Power Generation Unit> The number of power generation units 100 installed, N, is determined so as not to generate reverse power flow in a state where all the power generation units 100 are operating at their rated output power (i.e., a state where the power supply system 1000 is operating at the maximum power supply capacity). Specifically, for each rated output power of the power generation unit 100 being Qr [W], the reference purchase power Qs [W] preset to be constantly purchased from the commercial power supply system 500, and the minimum demand power D [W] during a predetermined period in the power demand facility 600, when the natural number obtained by truncating the decimal part of the value obtained by the calculation (D - Qs) / Qr is n, it is determined to satisfy the following formula (1). 2 ≤ N ≤ n …(1)

[0073] For example, when the rated output power Qr = 6 kW, the reference purchase power Qs = 2 kW, and the minimum demand power D = 27 kW, n is calculated to be 4. Therefore, according to formula (1), the number of installed units N is estimated to be 2 to 4 units. Here, in order to take advantage of the merit of self-generation of minimizing the purchase power cost, it is desirable to select the maximum number of units n, which is 4, within the estimated range of the number of installed units N.

[0074] When the actual number of installed units N is the maximum number n, the reference purchase power Qs is set to a predetermined positive value that is less than the difference value obtained by subtracting the maximum power supply capacity obtained by multiplying the maximum number n by the rated output power Qr from the minimum demand power D.

[0075] Note that the predetermined period for grasping the minimum demand power D targets at least one week and at most one year, and it is desirable not to include low-demand periods (nighttime and holidays) when the operation of factories, etc. is suspended. By grasping the minimum demand power D for high-demand periods when the operation of factories, etc. is being carried out, four power generation units 100 can be operated at their rated output power during high-demand periods.

[0076] <Operation as an output adjuster> As described above, the power generation unit 100 can be operated at the rated output power under full load, at a partial load below the rated output power and equal to or higher than the minimum output power, or in hot standby with the output power being zero. That is, each of the power generation units 101 to 104 can be operated as an output adjuster that operates within the range of equal to or lower than the rated output power and equal to or higher than the minimum output power. Note that since the power generation module 20 in the present embodiment includes the SOFC cell stack, the minimum output power in partial load operation is set based on the minimum fuel supply amount that can maintain the thermal self-sufficiency of the power generation module 20 and the minimum fuel utilization rate that can maintain the water self-sufficiency of the power generation module 20.

[0077] The maximum output power of the power generation unit 100 in the parallel operation mode is equivalent to the rated output power (6 kW). Also, the minimum output power of the power generation unit 100 in the parallel operation mode is set as the lower limit value at which, in addition to achieving both thermal self-sufficiency and water self-sufficiency, the decrease in the power generation efficiency during partial load operation does not occur with respect to the power generation efficiency during full load operation. In this case, the minimum output power is, for example, equivalent to 50% (3 kW) of the rated output power (6 kW). Note that when output adjustment below the minimum output power is required, the operation will shift to hot standby.

[0078] The output adjuster adjusts the output power from the power conditioner 16 by performing an operation of increasing or decreasing the output current from the grid-connected inverter 16d. The local controller 17 increases the sweep current value for the cell stack 1 in parallel with the increase in the output current and increases the supply amount of the raw fuel gas Ga. Also, the local controller 17 decreases the sweep current value for the cell stack 1 in parallel with the decrease in the output current and decreases the supply amount of the raw fuel gas Ga. Thereby, the power generation power of the power generation module 20 increases or decreases as the output current increases or decreases.

[0079] <Local Controller> Each of the local controllers 17 installed in the power generation units 101 to 104 is constituted by a programmable logic controller (PLC). The PLC has an arithmetic unit, a storage unit, an input unit, an output unit, and a power supply unit, and executes required arithmetic operations and sequence control using a processing program created and stored in advance. Note that a current sensor 200, which will be described later, is connected to the input unit of the PLC.

[0080] Each of the local controllers 17 is configured to be able to execute output adjustment control for adjusting the output power of the power conditioner 16 within a range equal to or lower than the rated output power and equal to or higher than the minimum output power based on first information regarding purchased power from the commercial power supply system 500. The output adjustment control includes heteronomous output adjustment control for heteronomously adjusting the output power and autonomous output adjustment control for autonomously adjusting the output power. Details of the heteronomous output adjustment control and the autonomous output adjustment control will be described later.

[0081] <System controller> Each of the local controllers 17 installed in the power generation units 101 to 104 has a system control unit that can function as a system controller 18. This system control unit is a functional block incorporated in the PLC.

[0082] In the present embodiment, the power generation units 101 to 104 are classified into one master unit and the remaining slave units. Specifically, the first power generation unit 101 is the master unit, and the second power generation unit 102, the third power generation unit 103, and the fourth power generation unit 104 are the slave units.

[0083] The system control unit in the first power generation unit 101 designated as the master unit is activated as the system controller 18. On the other hand, each of the system control units in the second power generation unit 102, the third power generation unit 103, and the fourth power generation unit 104 designated as the slave units is deactivated as the system controller 18. As a result, the system controller 18 of the master unit has a configuration for overall controlling the control states of the master unit itself and the slave units.

[0084] <Information and communication function> The system controller 18 of the master unit and the local controller 17 of the master unit can exchange information with each other inside the PLC. Also, the system controller 18 of the master unit and the local controller 17 of the slave unit can communicate with each other via the communication unit 17a attached to the PLC.

[0085] Each of the local controllers 17 continuously transmits information regarding its own control state and output state (for example, the sweeping current value for the cell stack 1, the output power of the grid-connected inverter 16d, etc.) to the system controller 18. The system controller 18 uses this information received from each of the local controllers 17 to coordinate the heteronomous output adjustment control and autonomous output adjustment control of the output adjuster.

[0086] <Current sensor> The power supply system 1000 includes a current sensor 200 that detects the forward power flow current flowing from the commercial power supply system 500 to the power demand facility 600. The current sensor 200 consists of a first current sensor 201 associated with the first power generation unit 101 which is the master unit, a second current sensor 202 associated with the second power generation unit 101 which is a slave unit, a third current sensor 203 associated with the third power generation unit 103 which is a slave unit, and a fourth current sensor 204 associated with the fourth power generation unit 104 which is a slave unit. The detection parts of the current sensors 201 to 204 are disposed on the power transmission cable from the commercial power supply system 500 to the power demand facility 600, and are upstream of the connection points P1 to P4 of the output cables of the power generation units 101 to 104.

[0087] The detection information (current value information) of each of the current sensors 201 to 204 is input to the local controller 17 of the corresponding power generation unit 101 to 104. In the master unit, the detection information is shared between the local controller 17 and the system controller 18.

[0088] 2.2 Outline of control of power supply system The power supply system 1000 uses the setting information regarding the reference purchased power to execute output adjustment control for each of the power generation units 101 to 104. FIG. 4 is an explanatory diagram showing the relationship between the actually purchased power Qm from the commercial power supply system 500 and the reference purchased power in the output adjustment control. When the actually purchased power Qm is on the positive side, it indicates that a forward current is flowing from the commercial power supply system 500 to the power demand facility 600, and when the actually purchased power Qm is on the negative side, it indicates that a reverse current is flowing from the power supply system 1000 to the commercial power supply system 500.

[0089] For each of the system controller 18 and the local controller 17, a first reference purchased power Q1 and a second reference purchased power Q2 higher than this are set. Also, for each of the local controllers 17, a third reference purchased power Q3 lower than the second reference purchased power Q2 is set.

[0090] The first reference purchased power Q1 is a set value (for example, 2 kW) corresponding to the reference purchased power Qs used to determine the number of installed units of the power generation unit 100. The first reference purchased power Q1 is a standard margin for not generating a reverse current not only when all the units of the power generation unit 100 are operating at full load but also when operating at partial load, and is a set value for determining a relatively slow demand decrease below the minimum demand power D.

[0091] The second reference purchased power Q2 is a set value that becomes the target value when decreasing the output power of the power generation unit 100 to increase the actually purchased power Qm. The second reference purchased power Q2 is preferably determined so that one decrease operation is completed within a predetermined time regardless of the number of installed units of the power generation unit 100. For example, when the decrease rate of the output current of each machine is the same, if the second reference purchased power Q2 is too large, the smaller the number of installed units, the longer it takes for the decrease operation to end, and the responsiveness to demand changes deteriorates. Therefore, the second reference purchased power Q2 is set to a smaller value as the number of installed units of the power generation unit 100 is smaller, so that the difference from the first reference purchased power Q1 does not become excessive.

[0092] In addition, the two-reference purchased power Q2 also needs to be determined according to the maximum detected current of the current sensor 200. For example, if the AC voltage value of the commercial power supply system 500 is 100 V and the maximum detected current of the current sensor 200 is 100 A, the detection upper limit of the actual purchased power Qm is 10 kW. Therefore, the second-reference purchased power Q2 should be set to a value (e.g., 8 kW) below this detection upper limit.

[0093] The third-reference purchased power Q3 is the marginal margin to prevent reverse power flow even when all the power generation units 100 are operating at partial load, and it is a set value for determining a relatively rapid demand decrease below the minimum required power D. It is desirable that the third-reference purchased power Q3 be set to a value (e.g., 0.5 kW) that can ensure a time margin until the occurrence of reverse power flow even if there is a slight response delay in suppressing the output of the power generation unit 100.

[0094] Hereinafter, the heteronomous output adjustment control and the autonomous output adjustment control executed by each of the local controllers 17 will be described with reference to the flowcharts shown in FIGS. 5 to 7. FIG. 5 is a flowchart of the overall control in the system controller 18, and FIGS. 6 and 7 are flowcharts of the output adjustment control in the local controller 17.

[0095] <Overall Control of System Controller Based on First Information> First, the overall control will be described according to the flowchart of FIG. 5. In step ST101, the system controller 18 divides all of the power generation units 101 to 104 into groups of output adjusters that execute output adjustment control, and transmits an execution permission signal for output adjustment control to each of the local controllers 17. By receiving the execution permission signal, each of the local controllers 17 can execute output adjustment control within the range of the rated output power or less and the minimum output power or more.

[0096] In step ST102, the system controller 18 calculates, in real time, a monitored value of the actual purchased power Qm from the commercial power supply system 500 based on the detection information (current value information) input from the corresponding current sensor 201 and the AC voltage value (e.g., 100 V) of the commercial power supply system 500. This actual purchased power Qm is used as the first information for output adjustment control.

[0097] In step ST103, the system controller 18 determines whether any of the power generation units 101 to 104 is executing the second output reduction control described below. If it is executing (YES in step ST103), the process proceeds to step ST104. On the other hand, if it is not executing (NO in step ST103), the process proceeds to step ST109.

[0098] In step ST104, the system controller 18 determines whether it has received an end report of the second output reduction control from all of the power generation units 101 to 104. If it has received (YES in step ST104), the process proceeds to step ST105. On the other hand, if it has not received (NO in step ST104), the process loops through step ST104.

[0099] In step ST105, the system controller 18 transmits a third output reduction request to all of the power generation units 101 to 104. The third output reduction request is information for causing each of the local controllers 17 to execute the third output reduction control described below. Further, the third output reduction request includes output reduction width information (downward output current width) individually assigned to each of the local controllers 17. This output reduction width information is for increasing the actual purchased power Qm immediately after the execution of the second output reduction control to a state substantially equal to the second reference purchased power Q2, and is also information for making the output powers of the respective output regulators substantially equal when the third output reduction control ends. That is, when each output regulator performs output adjustment by the specified unique downward output current width, the actual purchased power Qm becomes substantially equal to the second reference purchased power Q2, and at the same time, the output powers of the respective output regulators become substantially equal.

[0100] In step ST106, the system controller 18 determines whether the actually purchased power Qm is less than the first reference purchased power Q1. If it is less (YES in step ST106), the process proceeds to step ST107. On the other hand, if it is not less (NO in step ST106), the process proceeds to step ST108.

[0101] In step ST107, the system controller 18 sends a first output reduction request to all of the power generation units 101 to 104. The first output reduction request is information for causing each of the local controllers 17 to execute a first output reduction control described later. Further, the first output reduction request includes output reduction width information (downward output current width) evenly assigned to each of the local controllers 17. This output reduction width information is information for increasing the actually purchased power Qm in a state where it is less than the first reference purchased power Q1 to a state substantially equal to the second reference purchased power Q2, and is information for making the output powers of the output regulators substantially equal when the first output reduction control ends. That is, when each output regulator performs output adjustment by the same downward output current width specified, the actually purchased power Qm becomes substantially equal to the second reference purchased power Q2, and at the same time, the output powers of the output regulators become substantially equal.

[0102] In step ST108, the system controller 18 determines whether a state where the actually purchased power Qm exceeds the second reference purchased power Q2 has continued for a predetermined time. If it has exceeded (YES in step ST108), the process proceeds to step ST113. On the other hand, if it has not exceeded (NO in step ST108), the process returns to step ST102.

[0103] In step ST109, the system controller 18 transmits an output increase request to all of the power generation units 101 to 104. The output increase request is information for causing each of the local controllers 17 to execute output increase control described later. The output increase request also includes output increase width information (increased output current width) equally allocated to each of the local controllers 17. This output increase width information is for reducing the actual purchased power Qm in a state where it exceeds the second reference purchased power Q2, and is also for making the output power of each of the output regulators substantially equal. That is, when each output regulator performs output adjustment by the same increased output current width specified, the output power of the output regulators is maintained in a substantially equal state, and the actual purchased power Qm decreases toward the first reference purchased power Q1.

[0104] In step ST110, the system controller 18 determines whether the actual purchased power Qm is within the range from the first reference purchased power Q1 to the second reference purchased power Q2. If it is within the range (YES in step ST110), the transmission of the output increase request is stopped and the process ends. On the other hand, if it is not within the range (NO in step ST110), the process returns to step ST109 and the output increase width information (additional increased output current width) is continuously transmitted. At the end of step ST110, the actual purchased power Qm enters the range from the first reference purchased power Q1 to the second reference purchased power Q2 (for example, a state slightly below the second reference purchased power Q2), and at the same time, the output power of each output regulator becomes substantially equal. Also, in step ST110, when all the output regulators have reached the rated output power, the process may end without making a determination regarding the actual purchased power Qm.

[0105] Note that in step ST108, if a predetermined time (for example, 10 minutes) has not elapsed since the end of the previous first output decrease control or second output decrease control, the process may be made to wait before proceeding to step ST109. By providing such a waiting time, the induction of an unintended reverse power flow due to increasing the output power in a situation where the demand fluctuates violently is avoided.

[0106] <Output Adjustment Control of Local Controller Based on First Information> Next, output adjustment control will be described with reference to the flowcharts of FIGS. 6 and 7. In step ST201, the local controller 17 calculates, in real time, a monitored value of the actual purchased power Qm from the commercial power supply system 500 based on the detection information (current value information) input from the corresponding current sensors 201 to 204 and the AC voltage value (e.g., 100 V) of the commercial power supply system 500. This actual purchased power Qm is used for output adjustment control as the first information.

[0107] In step ST202, the local controller 17 determines whether the actual purchased power Qm is less than the third reference purchased power Q3. If it is less (YES in step ST202), the process proceeds to step ST203. On the other hand, if it is not less (NO in step ST202), the process proceeds to step ST209.

[0108] In step ST203, the local controller 17 executes second output reduction control. The second output reduction control belongs to autonomous output adjustment control that does not depend on the request from the system controller 18, and gradually reduces the output current from the system connection inverter 16d by a predetermined adjustment width.

[0109] In step ST204, the local controller 17 determines whether the actual purchased power Qm has reached the third reference purchased power Q3 due to the output reduction operation of its own device. If it has reached (YES in step ST204), the process proceeds to step ST205. On the other hand, if it has not reached (NO in step ST204), the process returns to step ST203 to continue the second output reduction control.

[0110] In step ST205, the local controller 17 ends the second output reduction control, fixes the output current, and transmits a report of the end of the second output reduction control to the system controller 18. Note that at the end of the second output reduction control, the output power of each output adjuster is non-uniform.

[0111] In step ST206, the local controller 17 determines whether it has received a third output decrease request from the system controller 18. If received (YES in step ST206), the process proceeds to step ST207. On the other hand, if not received (NO in step ST206), the process loops in step ST206 and waits for the reception of the third output decrease request.

[0112] In step ST207, the local controller 17 executes third output decrease control. The third output decrease control belongs to the heteronomous output adjustment control according to the request from the system controller 18, and based on the output decrease width information (downward output current width) included in the third output decrease request, the output current from the system connection inverter 16d is gradually decreased in a predetermined adjustment width step by step.

[0113] In step ST208, the local controller 17 determines whether it has reached the downward output current width (output decrease width) assigned to itself. If reached (YES in step ST208), the process ends. On the other hand, if not reached (NO in step ST208), the process returns to step ST207 and continues the third output decrease control.

[0114] In step ST209, the local controller 17 determines whether it has received a first output decrease request from the system controller 18. If received (YES in step ST209), the process proceeds to step ST210. On the other hand, if not received (NO in step ST209), the process proceeds to step ST212.

[0115] In step ST210, the local controller 17 executes first output decrease control. The first output decrease control belongs to the heteronomous output adjustment control according to the request from the system controller 18, and based on the output decrease width information (downward output current width) included in the first output decrease request, the output current from the system connection inverter 16d is gradually decreased in a predetermined adjustment width step by step.

[0116] In step ST211, the local controller 17 determines whether the output current reduction width (output reduction width) assigned to its own device has been reached. If it has been reached (YES in step ST211), the process ends. On the other hand, if it has not been reached (NO in step ST211), the process returns to step ST210 and continues the first output reduction control.

[0117] In step ST212, the local controller 17 determines whether an output increase request has been received from the system controller 18. If it has been received (YES in step ST212), the process proceeds to step ST213. On the other hand, if it has not been received (NO in step ST212), the process returns to step ST201.

[0118] In step ST213, the local controller 17 executes output increase control. The output increase control belongs to heteronomous output adjustment control that follows a request from the system controller 18, and based on the output increase width information (output current increase width) included in the output increase request, the output current from the system connection inverter 16d is gradually increased in a predetermined adjustment width.

[0119] In step ST214, the local controller 17 determines whether the output increase request from the system controller 18 has stopped. If it has stopped (YES in step ST214), the process ends. On the other hand, if it has not stopped (NO in step ST214), the process proceeds to step ST215.

[0120] In step ST215, the local controller 17 determines whether the rated output power has been reached by the output increase operation of its own device. If it has been reached (YES in step ST215), the process ends. On the other hand, if it has not been reached (NO in step ST215), the process returns to step ST213 and continues the output increase control.

[0121] The above-described first output reduction control is executed in a situation where a relatively slow demand decrease occurs that is below the minimum required power D. By reducing the output power of the power generation unit 100 at an early stage when the demand is trending downward and sufficiently recovering the actual purchased power Qm, the occurrence of reverse power flow is prevented. On the other hand, the second output reduction control and the subsequent third output reduction control are executed in a situation where a relatively rapid demand decrease occurs that is below the minimum required power D. When an unexpected rapid decrease in demand occurs, the occurrence of reverse power flow is avoided by quickly recovering the actual purchased power Qm through a two-stage output adjustment.

[0122] <Output Adjustment Control of Local Controller Based on Second Information> Each of the local controllers 17 can be configured to be capable of executing autonomous output adjustment control based on second information regarding the cooperation state between itself and the commercial power supply system 500. The control based on the second information has priority over the control based on the first information.

[0123] 〔Control Example A Based on Second Information〕 When the inter-terminal voltage on the output side of the power conditioner 16 of the local controller 17 exceeds the set value, the local controller 17 executes a power factor constant control that outputs reactive power so that the power factor becomes constant with respect to the generated power (active power) of the power generation module 20. This power factor constant control is an operation for suppressing the increase in the system voltage. If the inter-terminal voltage does not become below the set value even after executing the power factor constant control for a predetermined time, the local controller 17 executes the above-described second output reduction control and forcibly shifts the power generation unit 100 to partial load operation. The end condition of the second output reduction control is when the inter-terminal voltage becomes below the set value.

[0124] 〔Control Example B Based on Second Information〕 When the local controller 17 detects a reverse power flow current by means of the corresponding current sensors 201 to 204 (for example, when Qm ≤ -200 [W]), the power generation unit 100 is shifted to the hot standby described above. In the present embodiment, the reverse power flow due to an unexpected rapid decrease in demand is basically avoided by the second output decrease control described above. Therefore, the shift to the hot standby is an emergency measure when the second output decrease control does not function sufficiently.

[0125] <Output adjustment control of local controller based on the third information> Each of the local controllers 17 can be configured to be capable of executing autonomous output adjustment control based on the third information regarding the internal temperature of the power conditioner 16 dedicated to the own device. The control based on the third information has priority over the control based on the first information.

[0126] 〔Control example based on the third information〕 The grid-connected inverter 16d is provided with a function of monitoring the temperature abnormality of the switching element in order to prevent damage to the switching element such as an IGBT constituting the power module due to overheating. When the internal temperature of the power conditioner 16, that is, the temperature of the switching element exceeds the upper limit value, the local controller 17 executes the second output decrease control described above and forcibly shifts the power generation unit 100 to partial load operation. The end condition of the second output decrease control is when the internal temperature falls below the upper limit value.

[0127] <Output adjustment control of local controller based on the fourth information> Each of the local controllers 17 can be further configured to be capable of executing autonomous output adjustment control based on the fourth information regarding the thermal balance of the power generation module 20 dedicated to the own device. The control based on the fourth information has priority over the control based on the first information.

[0128] 〔Control example A based on the fourth information〕 During the power generation operation of the power generation module 20, the local controller 17 adjusts the rotation speed of the fan 7a so that the cooling temperature of the anode off-gas Gd flowing out from the anode off-gas condenser 7 becomes a target temperature below the dew point at which condensation of water vapor occurs. When this rotation speed exceeds the upper limit value, the local controller 17 executes the second output reduction control described above and forcibly shifts the power generation unit 100 to partial load operation. The end condition of the second output reduction control is when the rotation speed of the fan 7a falls below the upper limit value.

[0129] When the temperature of the cooling air (outside air) sent by the fan 7a is high and the anode off-gas Gd cannot be cooled below the dew point, the amount of condensed water Wb generated decreases and water self-sufficiency cannot be maintained. Therefore, by reducing the power generation power of the power generation module 20, the discharge temperature of the anode off-gas Gd flowing out from the cell stack 1 is lowered so that it can be cooled below the dew point even in a situation where the temperature of the cooling air is high.

[0130] 〔Control Example B Based on the Fourth Information〕 During the power generation operation of the power generation module 20, the local controller 17 adjusts the rotation speed of the third air blower 15 so that the discharge temperature of the cathode off-gas Ge flowing out from the cell stack 1 becomes the target temperature. When this rotation speed exceeds the upper limit value, the local controller 17 executes the second output reduction control described above and forcibly shifts the power generation unit 100 to partial load operation. The end condition of the second output reduction control is when the operation amount falls below the upper limit amount.

[0131] The discharge temperature of the cathode off-gas Ge flowing out from the cell stack 1 reflects the operating temperature of the cell stack 1. When the operating temperature of the cell stack 1 is too high even when the cooling air Ad is passed through the cooling pipe Zc, there is a risk of deteriorating the fuel utilization rate or accelerating the deterioration of the power generation cells. Therefore, by reducing the power generation power of the power generation module 20, the reaction heat of the reformed gas and oxygen is reduced to lower the operating temperature of the cell stack 1.

[0132] <Exclusion Process from the Output Adjuster> When there is a power generation unit 100 that is performing autonomous output adjustment control based on any one of the second information, the third information, and the fourth information, the system controller 18 divides the remaining power generation units 100, excluding these, into the group of output adjusters in step ST101. Note that since the output power of the power generation unit 100 excluded from the output adjusters is determined by the output adjustment control led by the local controller 17, only the group of output adjusters is the target for equalizing the output power.

[0133] 3. Other Modification Examples The cell stack 1 constituting the power generation module 20 may be a molten carbonate fuel cell (MCFC) instead of a solid oxide fuel cell (SOFC). The MCFC is a high-temperature operating fuel cell like the SOFC and has high power generation efficiency.

[0134] The power generation module 20 using a fuel cell is not limited to the type that generates power with a single-stage cell stack 1, and may be of the type that generates power with two or more stages of cell stacks 1. Specifically, water vapor is removed from the anode off-gas discharged from the previous-stage cell stack to generate a reformed gas, and this reformed gas is supplied to the anode of the next-stage cell stack. In addition, when generating the reformed gas, carbon dioxide contained in the anode off-gas may be removed using a separation membrane, an absorbent, or the like. By configuring to generate power with two or more stages of cell stacks, the fuel utilization rate can be significantly increased.

[0135] The power generation module 20 using a fuel cell is not limited to the configuration of supplying reformed gas to the cell stack, and may be configured to supply pure hydrogen gas. Specifically, hydrogen gas supplied from an external hydrogen production site through a transportation infrastructure is introduced into the anode of the cell stack. When using hydrogen gas as the primary fuel, components (reformer 2, evaporator 4, anode off-gas condenser 7, gas-liquid separation section Sa, condensate recovery tank 9, water pump 12, etc.) required for steam reforming and water self-sufficiency can be omitted.

[0136] The power generation unit 100 is not limited to the type using a fuel cell and can be changed to other types. The power generation unit may be of a type using a solar cell, or may be of a type that rotates a generator using an organic Rankine cycle, a steam turbine, a gas turbine, or a gas engine.

[0137] The system controller 18 may be a functional block incorporated in the local controller 17 (PLC), but can also be an independent controller separated from the local controller 17. In this case, each of the local controllers 17 is connected to the system controller 18 via the communication unit 17a.

[0138] The power supply system 1000 can also be provided with an additional second current sensor, separately from the first current sensors 201 to 204 connected to the local controllers 17 of the respective power generation units 101 to 104. This additional second current sensor is connected to the system controller 18 of the master unit.

[0139] A part of the control function executed by the local controller 17 (PLC) can also be configured to be executed by the built-in controller equipped in the power conditioner 16. In this case, the built-in controller is substantially a component of the local controller 17. For example, the above-described second output drop control, control examples A and B based on the second information, and control example based on the third information may be control functions executed by the built-in controller. Furthermore, monitoring of power outage and power restoration, and transition instructions between the parallel operation mode and the independent operation mode may be control functions executed by the built-in controller.

[0140] According to the power supply system 1000 of the present embodiment described above, the following effects are obtained.

[0141] (1) The power supply system 1000 includes a plurality of power generation units 100 operating in parallel with the commercial power supply system 500, and a system controller 18 that overall controls the control states of the plurality of power generation units 100. Each of the plurality of power generation units 100 includes a power generation module 20, a power conditioner 16 that converts the generated power of the power generation module 20 into output power corresponding to the AC power of the commercial power supply system 500, and a local controller 17 that controls the output power by controlling the generated power of the power generation module 20. In the plurality of power generation units 100, each local controller 17 is configured to be capable of executing output adjustment control for adjusting the output power within a range not less than the minimum output power and not more than the rated output power. The output adjustment control includes heteronomous output adjustment control (constant speed output decrease control A, constant speed output decrease control C, constant speed output increase control) for heteronomously adjusting the output power, and autonomous output adjustment control (constant speed output decrease control B) for autonomously adjusting the output power. The system controller 18 divides all of the plurality of power generation units 100 into a group of output adjusters, and overall controls the heteronomous output adjustment control and the autonomous output adjustment control so that the output power of each output adjuster is made substantially equal based on the first information regarding the purchased power from the commercial power supply system 500.

[0142] The plurality of power generation units 100 are basically configured to perform full load operation or partial load operation in a grid-connected operation mode. The system controller 18 divides all of the power generation units 100 into a group of output adjusters, and overall controls the heteronomous output adjustment control and the autonomous output adjustment control by the local controller 17. As a result, all of the power generation units 100 are always operated as output adjusters, so that the followability of the power supply to demand changes can be enhanced. Since all of the power generation units 100 in the power supply system 1000 of this operation mode are output adjusters, it is suitable for power supply to a power demand facility 600 having a relatively large demand fluctuation range between a high demand period and a low demand period.

[0143] In addition, the system controller 18 coordinates the heteronomous output adjustment control and autonomous output adjustment control by the local controller 17 so as to make the output power of each output adjuster substantially equal. Since the output power of each power generation unit 100 is substantially equal, the loads on the power generation modules 20 and auxiliary machines 30 are also generally equal, and there are few variations in the degree of degradation and remaining life. Therefore, maintenance such as component replacement can be planned and carried out at the same timing for all the power generation units 100.

[0144] (2) In the power supply system 1000 of (1), a current sensor 200 for detecting a forward power flow current flowing from the commercial power supply system 500 to the power demand facility 600 is provided. The system controller 18 calculates the actual purchased power Qm from the detection information of the current sensor 200 as the first information. When the actual purchased power Qm is lower than the first reference purchased power Q1, the system controller 18 causes each of the local controllers 17 to execute the first output decrease control with an output decrease width equally allocated to each of them so that the actual purchased power Qm becomes approximately equal to the second reference purchased power Q2, which is higher than the first reference purchased power Q1. When the actual purchased power Qm exceeds the second reference purchased power Q2, the system controller 18 causes each of the local controllers 17 to execute the output increase control with an output increase width equally allocated to each of them until the actual purchased power Qm falls within the range from the first reference purchased power Q1 to the second reference purchased power Q2.

[0145] When the system controller 18 determines that a relatively slow demand decrease in which the actual purchased power Qm falls below the minimum demand power D due to the actual purchased power Qm falling below the first reference purchased power Q1, the system controller 18 causes each of the local controllers 17 to execute the first output decrease control heteronomously so as to increase the actual purchased power Qm to the second reference purchased power Q2. Thereby, while making the power supply follow the demand decrease, the generation of reverse power flow can be effectively prevented.

[0146] In addition, when the system controller 18 determines an increase in demand because the actually purchased power Qm exceeds the second reference purchased power Q2, it heteronomously causes each of the local controllers 17 to execute output increase control so as to reduce the actually purchased power Qm to within the range from the first reference purchased power Q1 to the second reference purchased power Q2. Thereby, while making the power supply follow the increase in demand, it is possible to aim to return to the full-load operation of each power generation unit 100.

[0147] Furthermore, the system controller 18 causes each of the local controllers 17 to execute the first output decrease control with an equally assigned output decrease width, while executing the output increase control with an equally assigned output increase width. Thereby, during the partial load operation of each of the power generation units 101 to 104, the output power can always be equalized.

[0148] (3) In the power supply system 1000 of (2), each of the local controllers 17 calculates the actually purchased power Qm from the detection information of the current sensor 200 as the first information, and when the actually purchased power Qm is lower than the third reference purchased power Q3 which is lower than the first reference purchased power Q1, executes the second output decrease control so that the actually purchased power Qm becomes approximately equal to the third reference purchased power Q3. After the second output decrease control is executed, the system controller 18 causes each of the local controllers 17 to execute the third output decrease control with an output decrease width individually assigned to each of them so that the actually purchased power Qm becomes approximately equal to the second reference purchased power.

[0149] When each of the local controllers 17 determines a relatively rapid decrease in demand such that the actually purchased power Qm falls below the minimum required power D because the actually purchased power Qm is lower than the third reference purchased power Q3, it autonomously executes the second output decrease control to recover the actually purchased power Qm to the third reference purchased power Q3. Thereafter, the system controller 18 heteronomously causes each of the local controllers 17 to execute the third output decrease control to increase the actually purchased power Qm to the second reference purchased power Q2. Thereby, it is possible to surely prevent the occurrence of reverse power flow even against a sudden decrease in demand.

[0150] Further, the system controller 18 causes each of the local controllers 17 to execute third output reduction control with an individually assigned output reduction width. As a result, at the end of the second output reduction control, the uneven output power of each machine can be returned to an equalized state, and the partial load operation can be continued.

[0151] (4) In the power supply system 1000 of (2) or (3), the plurality of power generation units 100 have the same rated output power, and the first reference purchase power Q1 is a predetermined positive value that is less than the difference value obtained by subtracting the maximum power that can be supplied by multiplying the rated output power A by the number of installed power generation units N from the minimum demand power D during a predetermined period in the power demand facility 600.

[0152] When the first reference purchase power Q1 is set in this way, during the high demand period when an operation such as in a factory is being carried out, all the power generation units 100 will be operated at the rated output power. Therefore, the merit of self-generation of minimizing the purchase power cost can be enjoyed.

[0153] In addition, since each of the power generation units 101 to 104 is operated based on full load operation, if the first output reduction control and the output increase control are executed with an equally assigned output adjustment width, the output power during partial load operation will always be maintained in an equalized state. As a result, after the trial operation of the power supply system 1000, the maintenance cycles of each machine can be made to coincide.

[0154] (5) In the power supply system 1000 of (2) or (3), each of the local controllers 17 continuously transmits the current output information of its own machine (sweeping current value for the cell stack 1, output power of the grid-connected inverter 16d, etc.) to the system controller 18, and the system controller 18 uses the output information received from each machine to overall control the heteronomous output adjustment control (constant speed output reduction control A, constant speed output reduction control C, constant speed output increase control) and the autonomous output adjustment control (constant speed output reduction control B).

[0155] When the local controller 17 is executing the constant-speed output decrease controls A to C and the constant-speed output increase control, the system controller 18 acquires the output information of each machine at any time and monitors the progress of the output adjustment. When the output information cannot be acquired, there is a risk of reverse power flow due to the inability to respond to demand changes, but such a risk can be judged at an early stage.

[0156] Also, when the local controller 17 finishes the constant-speed output decrease controls A and C and the constant-speed output increase control, the system controller 18 acquires the output information of each machine at any time and calculates the output allocation amounts for the power generation units 101 to 104. Thereby, the output powers of the power generation units 101 to 104 can be quickly equalized.

[0157] (6) In the power supply system 1000 of (2) or (3), each of the local controllers 17 has a system control unit that can function as the system controller 18. A plurality of power generation units 100 are classified into one master unit and the remaining slave units. The system control unit in the power generation unit 101 designated as the master unit is activated as the system controller 18, and the system control units in the power generation units 102 to 104 designated as the slave units are deactivated as the system controller 18.

[0158] The plurality of power generation units 101 to 104 are configured such that the activation / inactivation of the system control unit incorporated in the local controller 17 can be switched. By activating only the system control unit of the power generation unit 101 designated as the master unit as the system controller 18, it becomes unnecessary to install an independent system controller. Therefore, the introduction cost (equipment cost, construction cost, etc.) of the power supply system 1000 can be minimized.

[0159] In the power supply system 1000 of (7)(6), the current sensor 200 includes a plurality of first current sensors 201 to 204 (first current sensors) respectively associated with each of the local controllers 17 of the master unit and the slave units, and a single second current sensor associated with the system controller 18 of the master unit, and the second current sensor can be selectively equipped.

[0160] The plurality of first current sensors 201 to 204 are provided corresponding to the plurality of power generation units 101 to 104. Therefore, each local controller 17 can grasp the actually purchased power Qm in real time. Therefore, the local controller 17 can execute the second output reduction control without delay in response to a sudden decrease in demand.

[0161] Also, when an additional second current sensor is equipped, the system controller 18 can independently calculate the monitored value of the actually purchased power Qm. Therefore, when causing each of the local controllers 17 to execute the first output reduction control and the third output reduction control, the system controller 18 can generate highly accurate assigned output reduction width information. Similarly, when causing each of the local controllers 17 to execute the output increase control, the system controller 18 can generate highly accurate assigned output reduction width information.

[0162] (8) In the power supply system 1000 of (1) to (3), each of the local controllers 17 is further configured to be able to execute autonomous output adjustment control based on any one of the second information regarding the cooperation state between its own device and the commercial power supply system 500, the third information regarding the internal temperature of the power conditioner 16 exclusive to its own device, and the fourth information regarding the thermal balance of the power generation module 20 exclusive to its own device. The system controller 18 divides the remaining power generation units 100 excluding the power generation unit 100 that is executing the autonomous output adjustment control based on any one of the second information, the third information, and the fourth information into a group of output adjusters that execute the heteronomous output adjustment control (constant speed output decrease control A, constant speed output decrease control C, constant speed output increase control) and the autonomous output adjustment control (constant speed output decrease control B) based on the first information.

[0163] Each of the local controllers 17 autonomously executes the output adjustment control based on the second information, the third information, and the fourth information with priority over the output adjustment control based on the first information. By preferentially executing the output adjustment control based on the second information, the occurrence of unexpected reverse power flow is avoided. As a result, it is possible to prevent adverse effects on the commercial power supply system 500 operated by the power company. By preferentially executing the output adjustment control based on the third information, damage to switching elements such as IGBTs that constitute the power module of the system connection inverter 16d due to overheating is prevented. As a result, the frequency of stopping the power generation module 100 due to abnormal occurrences other than regular maintenance can be reduced. By preferentially executing the output adjustment control based on the fourth information, the water self-sufficiency of the power generation module 20 is maintained, and deterioration of fuel utilization efficiency and deterioration of the power generation cells are prevented. As a result, high-efficiency power generation operation can be continued.

[0164] Also, when there is a power generation unit 100 that is executing the autonomous output adjustment control based on any one of the second information, the third information, and the fourth information, the system controller 18 divides the remaining power generation units 100 excluding these into a group of output adjusters. Therefore, while utilizing the output adjusters, the power supply amount can be made to follow the demand change.

[0165] (9) In the power supply system 1000 of (1) to (3), in a plurality of power generation units 100, each of the power generation modules 20 includes a cell stack 1 in which solid oxide fuel cells are integrated.

[0166] The power supply system 1000 performs self-generation by the power generation unit 100 of the type using SOFC and supplies the self-generated power to consumers. Since SOFC has a higher primary energy efficiency than thermal power generation, by switching a part of the commercial power purchased by consumers from the power company to self-generated power, it is possible to reduce carbon dioxide emissions.

[0167] Also, the plurality of power generation units 100 can shift from the grid-connected operation mode to the stand-alone operation mode when a power outage occurs in the commercial power supply system 500. By realizing a system that maintains power supply independently during a power outage due to natural disasters or the like, it is possible to reduce the adverse effects on social life and economic activities.

[0168] As described above, the embodiments of the present invention have been described. However, the configuration of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. That is, the above embodiments should be considered as illustrative in all respects and not restrictive. The technical scope of the present invention is shown not by the description of the above embodiments but by the claims, and it should be understood that all modifications belonging to the meaning and scope equivalent to the claims are included.

[0169] 〔Contribution to the Sustainable Development Goals (SDGs) led by the United Nations〕 The power generation unit and power supply system according to the present disclosure reduce carbon dioxide emissions by improving the primary energy efficiency, and can contribute to the achievement of Goal 13, "Take urgent action to combat climate change" of the SDGs (Sustainable Development Goals). Further, the power generation unit and power supply system according to the present disclosure can independently maintain power supply in the event of a power outage due to a natural disaster, and can contribute to the achievement of Goal 11, "Sustainable cities and communities" of the SDGs.

Explanation of symbols

[0170] 1 Cell stack 2 Reformer 3 Burner 4 Evaporator 5 Air preheater 6 Anode off-gas cooler 7 Anode off-gas condenser 7a Fan 8 CO oxidizer (carbon monoxide oxidizer) 9 Condensate recovery tank 10 First primary fuel blower 11 First air blower 12 Water pump 13 Second primary fuel blower [[ID=3)]]14 Second air blower 15 Third air blower 16 Power conditioner 16a, 16b DC / DC converter 16c Smoothing capacitor 16d Grid connection inverter 16e, 16f Switch 16g, 16h Control circuit 17 Local controller 17a Communication unit 18 System controller 20 Power generation module 30 Auxiliary equipment 40 Load module 41 Electric heater 42 Heat dissipation fan 100 Power generation unit 101 First power generation unit 102 Second power generation unit 103 Third power generation unit 104 Fourth power generation unit 200 Current sensor 201 First current sensor 202 Second current sensor 203 Third current sensor 204 Fourth current sensor 300 Self - contained socket 500 Commercial power supply system 600 Power demand equipment 610 Switchboard 1000 Power supply system Aa, Ab, Ac Air Ad Cooling air B1 First bellows type expansion joint B2 Second bellows type expansion joint B3 Third bellows type expansion joint B4 Fourth bellows type expansion joint E1, E2 Fuel inlet E3, E4, E5 Air inlet E6 Gas outlet Ga, Gf Raw fuel gas Gb Mixed gas Gc Reformed gas Gd Anode off - gas Ge Cathode off - gas Gg Combustion gas La Raw fuel line Lb Mixed gas line Lc Anode fuel line Ld Anode off - gas line Le Cathode air line Lf Cathode off - gas line Lg Combustion gas line Lh Burner cooling air line Li Reformed water line Lj Starting air line Lk Cooling air line Lk1 Collector pipe Lw Condensate Recovery Line Ma First Distribution Manifold Mb Second Distribution Manifold Mc First Collection Manifold Md Second Collection Manifold R1 First Region R2 Second Region Sa Gas-Liquid Separation Section Sb Water Level Detector Sc Drain Valve Wa Treated Water Wb Condensate Za Heat Radiation Tube Zb Combustion Gas Pipe Zc Cooling Pipe

Claims

1. A plurality of power generation units operated in parallel with respect to a commercial power supply system, and a system controller that comprehensively controls the control states of the plurality of power generation units, wherein each of the plurality of power generation units includes a power generation module, a power conditioner that converts the generated power of the power generation module into output power corresponding to the AC power of the commercial power supply system, and a local controller that controls the output power by controlling the generated power of the power generation module, in the plurality of power generation units, each of the local controllers is configured to be capable of executing output adjustment control for adjusting the output power within a range of not less than the minimum output power and not more than the rated output power, the output adjustment control includes heteronomous output adjustment control for heteronomously adjusting the output power, and autonomous output adjustment control for autonomously adjusting the output power, the system controller divides all of the plurality of power generation units into a group of output adjusters that execute the output adjustment control, and based on first information regarding the purchased power from the commercial power supply system, comprehensively controls the heteronomous output adjustment control and the autonomous output adjustment control so that the output power of each of the output adjusters is made substantially equal. A power supply system.

2. Comprising a current sensor for detecting a forward current flowing from the commercial power supply system to a power demand facility, the system controller calculates the actual purchased power from the detection information of the current sensor as the first information, when the actual purchased power is less than a first reference purchased power, executes first output reduction control with an output reduction width equally allocated to each of the local controllers so that the actual purchased power becomes substantially equal to a second reference purchased power higher than the first reference purchased power, when the actual purchased power exceeds the second reference purchased power, executes output increase control with an output increase width equally allocated to each of the local controllers until the actual purchased power falls within the range from the first reference purchased power to the second reference purchased power. The power supply system according to Claim 1.

3. Each of the local controllers calculates the actual purchased power from the detection information of the current sensor as the first information, When the actual purchased power is lower than a third reference purchased power that is lower than the first reference purchased power, second output reduction control is executed so that the actual purchased power becomes approximately equal to the third reference purchased power. The system controller After the second output reduction control is executed, third output reduction control is executed with an output reduction width individually assigned to each of the local controllers so that the actual purchased power becomes approximately equal to the second reference purchased power. The power supply system according to claim 2.

4. The plurality of power generation units have the same rated output power. The first reference purchased power is a predetermined positive value that is lower than a difference value obtained by subtracting the maximum power that can be supplied, which is the rated output power multiplied by the number of installed power generation units, from the minimum required power during a predetermined period in the power demand facility. The power supply system according to claim 2 or 3.

5. Each of the local controllers continuously transmits the current output information of its own unit to the system controller. The system controller uses the output information received from each unit to coordinate the heteronomous output adjustment control and the autonomous output adjustment control. The power supply system according to claim 2 or 3.

6. Each of the local controllers has a system control unit that can function as the system controller. The plurality of power generation units are divided into one master unit and the remaining slave units. The system control unit in the power generation unit designated as the master unit is activated as the system controller. The system control unit in the power generation unit designated as the slave unit is deactivated as the system controller. The power supply system according to claim 2 or 3.

7. The current sensor includes a plurality of first current sensors associated with each of the local controllers of the master unit and the slave units, and a single second current sensor associated with the system controller of the master unit. The second current sensor can be selected whether or not to be equipped. The power supply system according to claim 6.

8. ​ Each of the local controllers is further configured to be able to execute the autonomous output adjustment control based on any one of second information regarding the coordination state between the own device and the commercial power supply system, third information regarding the internal temperature of the power conditioner exclusive to the own device, and fourth information regarding the thermal balance of the power generation module exclusive to the own device. The system controller divides the remaining power generation units excluding the power generation unit that is executing the autonomous output adjustment control based on any one of the second information, the third information, and the fourth information into a group of output adjusters that execute the heteronomous output adjustment control and the autonomous output adjustment control based on the first information. The power supply system according to any one of claims 1 to 3.

9. In the plurality of power generation units, each of the power generation modules is configured to include a cell stack integrating solid oxide fuel cells. The power supply system according to any one of claims 1 to 3.

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