JP6804232B2 - Power generation system and its protection control method - Google Patents

Description

The present invention relates to a power generation system and a protection control method thereof.

A fuel cell is a power generation device that uses a power generation method based on an electrochemical reaction. It has a fuel electrode, which is an electrode on the fuel side, an air electrode, which is an electrode on the air (oxidant gas) side, and only ions between them. It is composed of an electrolyte through which it passes, and various types have been developed depending on the type of electrolyte.

Of these, for example, solid oxide fuel cells (Solid Oxide Fuel Cell: hereinafter referred to as "SOFC") use ceramics such as zirconia ceramics as an electrolyte, and coal gasification gas produced from a carbonaceous raw material by a gasification facility. It is a fuel cell operated by using gas such as hydrogen, city gas, natural gas, oil, methanol, etc. as fuel. This SOFC has a high operating temperature of about 700 to 1000 ° C. in order to increase ionic conductivity, and is known as a highly efficient high-temperature fuel cell.

A combined cycle system has been developed in which such an SOFC is combined with an internal combustion engine such as a micro gas turbine (hereinafter referred to as "MGT"). In the MGT, the compressed air discharged from the compressor is supplied to the air electrode of the SOFC, and the high-temperature exhaust fuel gas discharged from the SOFC is supplied to the combustor of the MGT for combustion, and the combustion gas generated in the combustor is used. The turbine of MGT is driven to rotate by adiabatic expansion. Then, by transmitting the rotational drive of the turbine to the generator to generate electricity, it is possible to generate electricity with high power generation efficiency.

Such SOFCs are designed to be urgently stopped from the viewpoint of safety when some abnormality such as a significant decrease in cell voltage or a sudden temperature rise in a power generation cell is detected.
For example, Patent Document 1 discloses that when an abnormality requiring the stop of SOFC occurs, an appropriate stop operation is performed according to an operating state (for example, blower operation and whether or not an inert gas can be supplied). ing.
Further, for example, Patent Document 2 discloses an emergency stop method in which the flow rates of air and water are reduced to prevent deterioration of the power generation cell when the load current is stopped due to the emergency stop of the SOFC. There is.
Further, Patent Document 3 discloses an energy removing device that reduces the energy stored in the power generation device in the case of a normal stop or a stop for safety. This energy removal device is a power generation device that draws current from a fuel cell by a resistor or the like when, for example, a normal stop occurs, a power adjustment system (PCS) fails, or the load of the power generation device is disconnected. It consumes the residual fuel inside and protects the fuel cell stack.

Japanese Unexamined Patent Publication No. 2014-146476 Japanese Unexamined Patent Publication No. 2012-216372 Special Table 2002-505509

For example, in the conventional SOFC, when an abnormality is detected, the operation of the SOFC is stopped and a cooling process using nitrogen or the like is performed. For this reason, even if the abnormality is resolved at an early stage after the operation is stopped, it takes a considerable amount of time to start the operation and restart the power generation because the SOFC has been temporarily stopped and cooled. Was there. That is, SOFC requires a temperature raising step of raising the temperature of the SOFC power generation chamber to a temperature at which power generation is possible at the time of starting or restarting, and it is necessary to start power generation after the temperature of the power generation chamber reaches a temperature at which power generation is possible. There is. The longer the elapsed time from the shutdown, the lower the temperature of the power generation room, and the longer the time required for the temperature rise process of the power generation room. In particular, when restarting from a cold start after the temperature of the power generation chamber has been cooled to a room temperature level, it may take one day or more to complete the start-up.

In addition, it is not an abnormality of the SOFC itself, but a load facility or power system that is the power supply destination of the power generated by the SOFC, or it is placed between the SOFC and the power system and converts DC power into AC power to the power system. When an abnormality occurs in the power conditioner or the like supplied to the power conditioner, the operation of the SOFC is stopped in the same manner, but the abnormality of the power conditioner may be resolved at a relatively early stage. Therefore, even in such a case, if the operation of the SOFC is stopped every time an abnormality occurs and the SOFC is cooled, the operating rate is lowered and more generated power is supplied. The result is that the purpose of the power generation system is met.

The present invention has been made in view of such circumstances, and when an abnormality is detected on the power supply destination side of the fuel cell power generation output end, from the elimination of the abnormality to the restart of the fuel cell power generation. It is an object of the present invention to provide a power generation system capable of shortening the time required for the operation and a protection control method thereof.

The present invention generates electricity with a fuel cell including a power generation chamber in which a plurality of fuel cell cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged, a control device for controlling the fuel cell, and the fuel cell. A power conversion device is provided between the power supply destination to which the power is supplied and the power generation output end of the fuel cell, and the control device is moved from the power generation output end of the fuel cell to the power supply destination side. An abnormality detection unit that detects an abnormality that has occurred and an output control unit that shifts the power generation chamber of the fuel cell to a power generation standby state that maintains a predetermined power generation possible temperature or higher are provided, and the abnormality detection unit detects the abnormality. Provided is a power generation system in which the fuel cell does not output power and is in a no-load state when the fuel cell is used.

According to the power generation system of the present invention, the fuel cell does not output power when an abnormality that occurs from the power generation output end of the fuel cell to the power supply destination side of the fuel cell body is detected by the abnormality detection unit. At the same time, the output control unit shifts the fuel cell to the power generation standby state. Here, the power generation standby state is a state in which the power generation chamber of the fuel cell is maintained at a predetermined power generation possible temperature or higher. As a result, when the abnormality is resolved, the fuel gas for the power generation reaction can be supplied to the fuel electrode in a short time, and the power generation can be started. As a result, it is possible to shorten the time required from the elimination of the abnormality to the power generation as compared with the conventional case.

The power generation system is connected to a switch provided between the power generation output end of the fuel cell and the power supply destination, and to open the switch when the abnormality is detected by the abnormality detection unit. It may be provided with a control unit.
According to such a configuration, when an abnormality is detected by the abnormality detecting unit, the fuel cell can be easily put into a no-load state.

In the power generation system, the output control unit may supply the oxidant gas and the first fuel gas to the air electrode and supply the second fuel gas to the fuel electrode in the power generation standby state.

According to the power generation system, the oxidant gas and the first fuel gas are supplied to the air electrode in the power generation standby state. As a result, the temperature of the power generation chamber can be maintained above a predetermined temperature at which power can be generated by the heat generated by the catalyst combustion. Further, since a predetermined amount of the second fuel gas is supplied to the fuel electrode, the fuel electrode can be maintained in the reducing gas atmosphere, and deterioration of the fuel cell can be prevented.
Here, the first fuel gas and the second fuel gas may be the same gas, or may be different gases.

The power generation system includes a micro gas turbine to which exhaust fuel and exhaust air from the fuel cell are supplied, and the control device operates the micro gas turbine when the abnormality is detected by the abnormality detection unit. May be continued.

According to the above power generation system, even after the abnormality is detected by the abnormality detection unit, the operation of the micro gas turbine is continued, so that the operation of the micro gas turbine is stopped, as compared with the conventional power generation system. , It is possible to increase the output of the power generation system as a whole.

The power generation system is an interconnection point in which a first power line that transmits the power generated by the fuel cell, a second power line that transmits the power generated by the microgas turbine, and the first power line and the second power line are connected. And a third power line connecting the interconnection point and the power supply destination, and the switch may be provided on the first power line.

According to such a configuration, the connection between the fuel cell and the power supply destination can be easily cut off by opening the switch, and the generated power generated by the micro gas turbine can be continuously used. It becomes possible to supply power to the power supply destination.

In the power generation system, in the control device, when the abnormality is detected by the abnormality detection unit, the operation mode of the micro gas turbine is set to a predetermined amount in which the supply amount of the third fuel gas to the combustor is preset. The high-efficiency operation mode is released when the operation mode determination unit that determines whether or not the high-efficiency operation mode is suppressed below the value and the operation mode determination unit determines that the high-efficiency operation mode is set. However, it may be provided with an operation mode switching unit for switching to another operation mode for supplying the third fuel gas to the combustor in a larger amount than the high efficiency operation mode.

According to the above power generation system, when an abnormality is detected by the abnormality detection unit and the operation mode of the micro gas turbine is a high efficiency operation mode for improving fuel efficiency, the high efficiency operation mode is canceled. It is possible to switch to another operation mode in which more third fuel gas is supplied to the combustor than in the high efficiency operation mode. This makes it possible to maintain stable combustion in the combustor.
The third fuel gas may be the same gas as at least one of the first fuel gas and the second fuel gas, or may be different from each other.

In the power generation system, the output control unit may supply reforming water to the fuel electrode when the abnormality is detected by the abnormality detection unit.
In this case, the output control unit supplies the reforming water having a preset minimum flow rate to the fuel electrode, and reaches the target flow rate after a predetermined time has elapsed from the start of supply of the reforming water. The supply amount of reforming water may be increased.

According to the above power generation system, when an abnormality is detected by the abnormality detection unit, reforming water for reforming is supplied to the fuel electrode, so that reforming water required for reforming is supplied in advance. It becomes possible to do. Furthermore, since the minimum flow rate is supplied at the start of supply of reforming water and the flow rate is increased to the target flow rate after a predetermined time has elapsed from the start of supply of reforming water, the pressure fluctuation and flow rate that occur at the start of supply of reforming water It is possible to suppress fluctuations.

The present invention is a protection control method for a power generation system including a fuel cell in which a plurality of fuel cell cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged in a power generation chamber, and the power generation of the fuel cell. The step of detecting an abnormality generated from the output end to the power supply destination side, the step of setting the fuel cell to a no-load state in which the fuel cell does not output power when the abnormality is detected, and the step of detecting the abnormality. Provided is a protection control method of a power generation system including a step of shifting the power generation chamber of a fuel cell to a power generation standby state for maintaining a predetermined power generation possible temperature or higher.
The protection control method of the power generation system may further include a step of raising the power generation chamber of the fuel cell to a target temperature and increasing the output of the fuel cell to the target output when the abnormality is resolved. ..

According to the present invention, when an abnormality is detected on the power supply destination side of the SOFC power generation output end, the time from the elimination of the abnormality to the restart of the SOFC power generation can be shortened.

It is a schematic block diagram which showed the schematic structure of the power generation system which concerns on one Embodiment of this invention. It is a figure which showed one aspect of the cell stack of SOFC which concerns on one Embodiment of this invention. It is a figure which showed one aspect of the SOFC module which concerns on one Embodiment of this invention. It is sectional drawing of one aspect of the SOFC cartridge which concerns on one Embodiment of this invention. It is a figure which showed the schematic structure of the PCS which concerns on one Embodiment of this invention, and one form of wiring between a power generation system and a power system. It is a functional block diagram which mainly developed and showed the function related to protection control among various functions provided in the control device which concerns on one Embodiment of this invention. It is a flowchart which showed the procedure of protection control of the power generation system which concerns on one Embodiment of this invention. It is a figure which compared the time transition of the various control amounts at the time of executing the protection control by the power generation system which concerns on one Embodiment of this invention, and the emergency stop control of a conventional power generation system.

Hereinafter, an embodiment of the power generation system and the protection control method thereof according to the present invention will be described with reference to the drawings.

[Power generation system configuration]
First, a schematic configuration of a power generation system according to an embodiment of the present invention will be described.
FIG. 1 is a schematic configuration diagram showing a schematic configuration of a power generation system 10 according to an embodiment of the present invention. As shown in FIG. 1, the power generation system 10 includes a micro gas turbine (hereinafter referred to as “MGT”) 11, a generator 12, SOFC 13, a power conditioner (power converter, hereinafter referred to as “PCS”) 120, and the like. ing. The power generation system 10 is configured to obtain high power generation efficiency by combining power generation by the MGT 11 and power generation by the SOFC 13.

The MGT 11 has a compressor 21, a combustor 22, and a turbine 23, and the compressor 21 and the turbine 23 are integrally rotatably connected by a rotating shaft 24. The compressor 21 is rotationally driven by the rotation of the turbine 23, which will be described later.
The compressor 21 compresses the air A taken in from the air take-in line 25. A part of compressed air (hereinafter, simply referred to as “air”) A from the compressor 21 is supplied to the combustor 22 via the first air supply line 26, and the first fuel gas supply line 27 is provided. The fuel gas L1 is supplied through the fuel gas L1. The first air supply line 26 is provided with a control valve 65 for adjusting the amount of air supplied to the combustor 22, and the first fuel gas supply line 27 adjusts the flow rate of fuel gas supplied to the combustor 22. A control valve 70 is provided for this purpose. Further, a part of the exhaust fuel gas L3 circulating in the fuel gas recirculation line 49 of the SOFC 13 described later is supplied to the combustor 22 through the exhaust fuel gas supply line 45. The exhaust fuel gas supply line 45 is provided with a control valve 47 for adjusting the amount of exhaust fuel gas supplied to the combustor 22. Further, a part of the exhaust air A2 used in the air electrode 13B of the SOFC 13 is supplied to the combustor 22 through the exhaust air supply line 36 described later.

The combustor 22 mixes and burns the fuel gas L1, a part of the air A, the exhaust fuel gas L3, and the exhaust air A2 to generate the combustion gas G. The combustion gas G is supplied to the turbine 23 through the combustion gas supply line 28. The turbine 23 rotates due to the adiabatic expansion of the combustion gas G, and the exhaust gas is discharged from the combustion exhaust gas line 55. The generator 12 is provided coaxially with the turbine 23, and generates electricity by rotationally driving the turbine 23.

The fuel gas L1 supplied to the combustor 22 and the fuel gas L2 described later are flammable gases, and for example, a gas such as coal gasification gas produced from a carbonaceous raw material (coal or the like) by a gasification facility, carbon monoxide ( Hydrocarbon gas such as CO) and methane (CH ₄ ), liquefied natural gas (LNG), city gas, hydrogen (H ₂ ), methanol, petroleum and the like are used. As the fuel gases L1 and L2 in the present embodiment, for example, city gas is used, and fuel gas containing methane as a main component is used. The fuel gas L1 and the fuel gas L2 may be the same gas or may be different gases.

The SOFC 13 is configured by accommodating a fuel electrode 13A, an air electrode 13B, and a solid electrolyte in a pressure vessel. The detailed configuration of SOFC 13 will be described later.
The SOFC 13 reacts at a predetermined operating temperature to generate power by supplying an oxidizing agent gas to the air electrode 13B and supplying a fuel gas (reducing agent gas) to the fuel electrode 13A.
The oxidant gas is, for example, a gas containing approximately 15% to 30% of oxygen, and air is typically preferable. However, in addition to air, a mixed gas of combustion exhaust gas and air or a mixed gas of oxygen and air is used. Etc. can be used. In the present embodiment, a case where at least a part (air A1) of the air A compressed by the compressor 21 is adopted as the oxidant gas supplied to the SOFC 13 will be illustrated and described.

Air (oxidizer gas) A1 is supplied to the SOFC 13 as an oxidant gas through the second air supply line 31 branched from the first air supply line 26 to the air supply unit which is the introduction portion of the air electrode 13B. The second air supply line 31 is provided with a control valve 64 for adjusting the flow rate of the supplied air A1. Further, in the first air supply line 26, a heat exchanger 58 is provided on the upstream side (in other words, the compressor 21 side) of the air A1 from the branch point of the second air supply line 31. In the heat exchanger 58, the air A is heat-exchanged with the exhaust gas discharged from the combustion exhaust gas line 55 to raise the temperature. Further, the second air supply line 31 is provided with a bypass line 62 that bypasses the heat exchanger 58. The bypass line 62 is provided with a control valve 66 so that the bypass flow rate of the air A can be adjusted. By controlling the opening degree of the control valves 64 and 66 by the control device 60 described later, the flow rate ratio between the air A passing through the heat exchanger 58 and the air A bypassing the heat exchanger 58 is adjusted, and the second The temperature of the air A1 supplied to the SOFC 13 through the air supply line 31 is adjusted.
The temperature of the air A1 supplied to the SOFC 13 has an upper limit of the temperature so as not to damage the constituent materials of the SOFC cartridge 203, including the air supply unit for introducing the air A1 into the SOFC cartridge 203 constituting the SOFC 13 and the air supply branch pipe. It is restricted.

Further, an air electrode fuel supply line 80 for supplying the fuel gas L2 as a flammable gas is connected to the second air supply line 31. The air electrode fuel supply line 80 is provided with a control valve 82 for adjusting the amount of fuel gas supplied to the second air supply line 31. By controlling the valve opening degree of the control valve 82 by the control device 60 described later, the supply amount of the fuel gas L2 added to the air A1 is adjusted. The amount of the fuel gas L2 added to the air A1 is supplied at a flammable limit concentration or less, and more preferably at 3% by volume or less.

An exhaust air discharge line 34 for discharging the exhaust air A2 used in the air electrode 13B is connected to the SOFC 13. An exhaust air supply line 36 for supplying the exhaust air A2 to the combustor 22 is connected to the exhaust air discharge line 34. The exhaust air supply line 36 is provided with a shutoff valve 38 for disconnecting the system between the SOFC 13 and the gas turbine 11.
Further, the exhaust air discharge line 34 is provided with a control valve (or shutoff valve) 37 for adjusting the amount of exhaust air discharged to the outside.

The SOFC 13 is further subjected to a second fuel gas supply line 41 for supplying the fuel gas L2 to the fuel gas supply unit 207 (see FIG. 3) which is an introduction unit of the fuel electrode 13A, and after being used for the reaction at the fuel electrode 13A. It is connected to the exhaust fuel gas line 43 that discharges the exhaust fuel gas L3. The second fuel gas supply line 41 is provided with a control valve 42 for adjusting the flow rate of the fuel gas L2 supplied to the fuel electrode 13A, and the exhaust fuel gas line 43 adjusts the amount of exhaust fuel gas discharged to the outside. A control valve (or shutoff valve) 46 is provided for this purpose. The excess pressure can be quickly adjusted by the control valve (or shutoff valve) 46 of the exhaust fuel gas line 43 and the control valve (or shutoff valve) 37 of the exhaust air discharge line 34. Further, the fuel air differential pressure between the fuel electrode 13A and the air electrode 13B of the SOFC 13 is controlled by the control valve 47 so that the fuel electrode 13A side becomes higher in a predetermined pressure range. Further, a fuel gas recirculation line 49 for recirculating the exhaust fuel gas L3 to the inlet of the fuel electrode 13A of the SOFC 13 is connected to the exhaust fuel gas line 43. The fuel gas recirculation line 49 is provided with a recirculation blower 50 for recirculating the exhaust fuel gas L3.

Further, the fuel gas recirculation line 49 is provided with a pure water supply line 44 that supplies pure water to the fuel electrode 13A as reforming water for reforming the fuel gas L2. A pump 48 is provided on the pure water supply line 44. By controlling the discharge flow rate of the pump 48 by the control device 60, the pure water flow rate supplied to the fuel electrode 13A is adjusted.

[SOFC configuration]
Next, the configuration of the SOFC 13 will be described with reference to FIGS. 2 to 4.
First, a cylindrical cell stack used for SOFC of the SOFC combined cycle power generation system (fuel cell combined cycle power generation system) according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram showing one aspect of the cell stack 101 according to the present embodiment. The cell stack 101 includes a cylindrical base tube 103, a plurality of fuel cell 105 formed on the outer peripheral surface of the base tube 103, and an interconnector 107 formed between adjacent fuel cell 105. The fuel cell 105 is formed by laminating a fuel electrode 13A, a solid electrolyte 111, and an air electrode 13B. Further, the cell stack 101 is an air electrode 13B of the fuel cell 105 formed at one end of the plurality of fuel cell 105 formed on the outer peripheral surface of the base pipe 103 in the longitudinal axis direction of the base pipe 103. The lead film 115 is electrically connected to the fuel cell 105 at the other end of the fuel cell 105, and is electrically connected to the fuel electrode 13A of the fuel cell 105 (not shown). To be equipped.

Substrate tube 103 is made of a porous material, for example, CaO-stabilized _ZrO 2 (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ + NiO) , or _Y 2 _{O 3} stabilized ZrO ₂ (YSZ), or The main component is MgAl ₂ O _{4 and the} like. The base tube 103 supports the fuel cell 105, the interconnector 107, and the lead film 115, and the fuel gas supplied to the inner peripheral surface of the base tube 103 is supplied to the inner peripheral surface of the base tube 103 through the pores of the base tube 103. It is diffused into the fuel electrode 13A formed on the outer peripheral surface of the fuel cell.

The fuel electrode 13A is composed of an oxide of a composite material of Ni and a zirconia-based electrolyte material, and for example, Ni / YSZ is used. The thickness of the fuel electrode 13A is 50 to 250 μm. In this case, in the fuel electrode 13A, Ni, which is a component of the fuel electrode 13A, has a catalytic action on the fuel gas. This catalytic action reacts a fuel gas supplied via the substrate tube 103, for example, a mixed gas of methane (CH ₄ ) and water vapor, and reforms it into hydrogen (H ₂ ) and carbon monoxide (CO). .. Further, the fuel electrode 13A is an interface between hydrogen (H ₂ ) and carbon monoxide (CO) obtained by reforming and oxygen ions (O ^2- ) supplied via the solid electrolyte 111 with the solid electrolyte 111. It reacts electrochemically in the vicinity to produce water (H ₂ O) and carbon dioxide (CO ₂ ). At this time, the fuel cell 105 generates electricity by the electrons emitted from the oxygen ions.

The solid electrolyte 111 is mainly composed of YSZ having airtightness that does not allow gas to pass through and high oxygen ion conductivity at high temperature. The solid electrolyte 111 moves oxygen ions (O ^2- ) generated in the air electrode 13B to the fuel electrode 13A. The film thickness of the solid electrolyte 111 located on the surface of the fuel electrode 13A is 10 to 100 μm.

The air electrode 13B is composed of, for example, a LaSrMnO _3- based oxide or a LaCoO _3- based oxide. The air electrode 13B dissociates oxygen in the supplied oxidant gas such as air in the vicinity of the interface with the solid electrolyte 111 to generate oxygen ions (O ^2- ). The air electrode 13B may have a two-layer structure. In this case, the air electrode layer (air electrode intermediate layer) on the solid electrolyte 111 side is made of a material having high ionic conductivity and excellent catalytic activity. The air electrode layer (air electrode conductive layer) on the air electrode intermediate layer may be composed of a perovskite-type oxide represented by Sr and Ca-doped LaMnO ₃ . By doing so, the power generation performance can be further improved.

The interconnector 107 is composed of a conductive perovskite-type oxide represented by M _1-x L _x TiO ₃ (M is an alkaline earth metal element and L is a lanthanoid element) such as SrTiO ₃ system. The interconnector 107 has a dense film so that the fuel gas and air do not mix with each other, and has stable durability and electrical conductivity in both an oxidizing gas atmosphere and a reducing gas atmosphere. In the adjacent fuel cell 105, the interconnector 107 electrically connects the air electrode 13B of one fuel cell 105 and the fuel electrode 13A of the other fuel cell 105, and the adjacent fuel cell 105 are connected to each other. Are connected in series. Since the lead film 115 needs to have electron conductivity and a coefficient of thermal expansion close to that of other materials constituting the cell stack 101, Ni such as Ni / YSZ and a zirconia-based electrolyte material are used. It is composed of a composite material. The lead film 115 derives the DC power generated by the plurality of fuel cell 105s connected in series by the interconnector to the vicinity of the end of the cell stack 101.

Next, the SOFC module and the SOFC cartridge according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a view showing one aspect of the SOFC module according to the present embodiment, and FIG. 4 is a cross-sectional view of one aspect of the SOFC cartridge according to the present embodiment.

As shown in FIG. 3, the SOFC module 201 includes, for example, a plurality of SOFC cartridges 203 and a pressure vessel 205 for accommodating the plurality of SOFC cartridges 203. Although FIG. 3 illustrates a cylindrical SOFC cell stack, this does not necessarily have to be the case, and for example, a flat cell stack may be used. Since the pressure vessel 205 is operated at an internal pressure of 0.1 MPa to about 1 MPa and an internal temperature of atmospheric temperature to about 550 ° C., the pressure vessel 205 is a material having resistance to oxygen and the like contained in the oxidant gas. Is used. For example, a stainless steel material such as SUS304 is suitable.

The SOFC module 201 includes a fuel gas supply unit 207 and a plurality of fuel gas supply branch pipes 207a, and a fuel gas discharge unit 209 and a plurality of fuel gas discharge branch pipes 209a. Further, the SOFC module 201 includes an air supply unit (not shown), an air supply branch pipe (not shown), an air discharge unit (not shown), and a plurality of air discharge branch pipes (not shown).

The fuel gas L2 from the second fuel gas supply line 41 (see FIG. 1) is supplied to the plurality of SOFC cartridges 203 through the fuel gas supply unit 207 and the plurality of fuel gas supply branch pipes 207a. The fuel gas supply branch pipe 207a guides the fuel gas L2 supplied through the fuel gas supply unit 207 to the plurality of SOFC cartridges 203 at a substantially equal flow rate, and substantially equalizes the power generation performance of the plurality of SOFC cartridges 203.

The exhaust fuel gas L3 discharged from the SOFC cartridge 203 is guided to the exhaust fuel gas line 43 (see FIG. 1) at a substantially equal flow rate by passing through the fuel gas discharge branch pipe 209a and the fuel gas discharge unit 209.

In the present embodiment, a mode in which a plurality of SOFC cartridges 203 are assembled and stored in the pressure vessel 205 is described, but the present invention is not limited to this, and for example, the SOFC cartridge 203 is not assembled and is stored in the pressure vessel 205. It may be stored inside.

As shown in FIG. 4, the SOFC cartridge 203 includes a plurality of cell stacks 101, a power generation chamber 215, a fuel gas supply chamber 217, a fuel gas discharge chamber 219, an air supply chamber 221 and an air discharge chamber 223. I have. Further, the SOFC cartridge 203 includes an upper tube plate 225a, a lower tube plate 225b, an upper heat insulating body 227a, and a lower heat insulating body 227b. In the present embodiment, the SOFC cartridge 203 is provided with the fuel gas by arranging the fuel gas supply chamber 217, the fuel gas discharge chamber 219, the air supply chamber 221 and the air discharge chamber 223 as shown in FIG. The structure is such that air as an oxidant gas flows opposite to the inside and outside of the cell stack 101, but the embodiment is not necessarily limited to this example, and for example, the inside and outside of the cell stack are parallel to each other. Or the air may flow in a direction orthogonal to the longitudinal axis direction of the cell stack.

The power generation chamber 215 is a region formed between the upper heat insulating body 227a and the lower heat insulating body 227b. The power generation chamber 215 is an area in which the fuel cell 105 of the cell stack 101 is arranged, and is an area in which fuel gas and air are electrochemically reacted to generate electricity. For example, the temperature near the central portion of the cell stack 101 in the power generation chamber 215 in the longitudinal direction becomes a high temperature atmosphere of about 700 ° C. to 1000 ° C. during steady operation of the SOFC module 201.

The fuel gas supply chamber 217 is an area surrounded by the upper casing 229a and the upper pipe plate 225a of the SOFC cartridge 203, and the fuel gas supply branch pipe 207a is provided by the fuel gas supply hole 231a provided above the upper casing 229a. Is communicated with. The plurality of cell stacks 101 are joined to the upper pipe plate 225a by the seal member 237a, and the fuel gas supply chamber 217 receives the fuel gas supplied from the fuel gas supply branch pipe 207a through the fuel gas supply hole 231a. It is guided inside the base tubes 103 of the plurality of cell stacks 101 at a substantially uniform flow rate, and the power generation performance of the plurality of cell stacks 101 is substantially made uniform.

The fuel gas discharge chamber 219 is an area surrounded by the lower casing 229b and the lower pipe plate 225b of the SOFC cartridge 203, and the fuel gas discharge branch pipe 209a is provided by the fuel gas discharge hole 231b provided in the lower part of the lower casing 229b. Is communicated with. The plurality of cell stacks 101 are joined by a lower pipe plate 225b and a sealing member 237b, and the fuel gas discharge chamber 219 passes through the inside of the base pipe 103 of the plurality of cell stacks 101 and is supplied to the fuel gas discharge chamber 219. The exhaust fuel gas L3 to be generated can be aggregated and led to the fuel gas discharge branch pipe 209a through the fuel gas discharge hole 231b.

The air supply chamber 221 is an area surrounded by the lower casing 229b, the lower pipe plate 225b, and the lower heat insulating body 227b of the SOFC cartridge 203, and is illustrated by the air supply hole 233a provided on the side surface of the lower casing 229b. Not communicated with the air supply branch pipe. The air supply chamber 221 can guide a predetermined flow rate of air supplied from an air supply branch pipe (not shown) through the air supply hole 233a to the power generation chamber 215 through the air supply gap 235a at a substantially uniform flow rate.

The air discharge chamber 223 is an area surrounded by the upper casing 229a of the SOFC cartridge 203, the upper pipe plate 225a, and the upper heat insulating body 227a, and is illustrated by the air discharge holes 233b provided on the side surface of the upper casing 229a. It is communicated with the air discharge branch pipe. The air discharge chamber 223 can guide the exhaust air supplied from the power generation chamber 215 to the air discharge chamber 223 through the air discharge gap 235b to an air discharge branch pipe (not shown) through the air discharge hole 233b.

The DC power generated in the power generation chamber 215 is led out to the vicinity of the end of the cell stack 101 by a lead film 115 (see FIG. 2) made of Ni / YSZ or the like provided in the plurality of fuel cell 105, and then the SOFC cartridge. The current is collected by the current collecting rod (not shown) of 203 via the current collecting plate (not shown), and is taken out to the outside of each SOFC cartridge 203. The DC power led out to the outside of the SOFC cartridge 203 is led out to the outside of the SOFC module 201, converted into AC power by the PCS (power conditioner) 120 (see FIG. 5) described later, and sent to the power supply destination. Is supplied. The power supply destination includes, for example, at least one of a power system and a load facility.

As described above, in the SOFC 13 according to the present embodiment, the fuel gas L2 and the air A1 flow so as to face the inside and the outside of the cell stack 101. As a result, the exhaust air A2 exchanges heat with the fuel gas L2 supplied to the power generation chamber 215 through the inside of the base pipe 103, and the upper pipe plate 225a and the like made of a metal material are deformed such as buckling. It is cooled to a temperature that does not allow it to be supplied to the air discharge chamber 223. Further, the fuel gas L2 is heated by heat exchange with the exhaust air A2 discharged from the power generation chamber 215 and supplied to the power generation chamber 215. As a result, the fuel gas L2 preheated to a temperature suitable for power generation can be supplied to the power generation chamber 215 without using a heater or the like. Further, the exhaust fuel gas L3 that has passed through the inside of the base pipe 103 and passed through the power generation chamber 215 is heat-exchanged with the air A1 supplied to the power generation chamber 215, and the lower pipe plate 225b and the like made of a metal material are formed. It is cooled to a temperature at which it does not deform such as buckling and is supplied to the fuel gas discharge chamber 219. Further, the air A1 is heated by heat exchange with the exhaust fuel gas L3 and supplied to the power generation chamber 215. As a result, air heated to a temperature required for power generation can be supplied to the power generation chamber 215 without using a heater or the like.

Further, as shown in FIG. 1, various sensors are provided in various places of the power generation system 10. For example, the SOFC 13 is provided with a differential pressure sensor 90 for measuring the differential pressure between the fuel electrode 13A and the air electrode 13B, a temperature sensor 92 for measuring the temperature of the power generation chamber, and the like. Further, an outside air temperature sensor 94 that measures the temperature of the air A sucked by the compressor 21 as the outside air temperature is provided near the suction port of the compressor 21 of the MGT 11.
Further, the power generation system 10 includes a temperature sensor (not shown) that measures the temperature (inlet air temperature) of the air A1 supplied to the SOFC 13 through the second air supply line 31, and exhaust fuel that circulates in the fuel gas recirculation line 49. A temperature sensor (not shown) or the like for measuring the temperature of the gas L3 is provided. Further, each control valve is provided with a valve opening degree detecting unit (not shown) for detecting the valve opening degree.
The measurement data detected by these various sensors and the valve opening degree detecting unit is transmitted to the control device 60.

The control device 60 controls the SOFC 13 and the MGT 11 in cooperation with the PCS 120 by using the measurement data measured by various sensors, the valve opening degree detecting unit, and the like. Specifically, arithmetic processing is performed based on the above-mentioned measurement data, and the operation of each part of the power generation system 10 is controlled so as to satisfy the required load. Further, the control device 60 executes protection control when an abnormality occurs in the PCS 120 or the like.

FIG. 5 is a diagram showing a schematic configuration of the PCS 120 and a form of wiring between the power generation output end of the SOFC 13 of the power generation system 10 and the power system 135. As shown in FIG. 5, the PCS 120 is an electric circuit using a semiconductor element or the like. For example, the booster circuit 122 that boosts the DC power output from the SOFC 13 and the DC power boosted by the booster circuit 122 are converted into AC power. It includes an inverter 123 for conversion, a filter circuit 124 for filtering AC power converted by the inverter 123, a switch 125 in a PCS, and the like.
In the present embodiment, the output of the SOFC 13 output from the PCS 120 is supplied to the power system 135, which is a predetermined power supply destination. In the present embodiment, the power system 135 is illustrated as a predetermined power supply destination, but instead or in addition to this, the generated power may be supplied to a specific load facility.

The AC power output from the PCS 120 is sent to the power transmission facility 130 through the power line C1. In the power transmission facility 130, the power line C1 and the power line C2 that transmits the generated power from the generator 12 of the MGT 11 are connected at the interconnection point X. The power line C3 between the interconnection point X and the power system 135 is provided with, for example, a system switch 131, a transformer 132, and the like.
With such a configuration, for example, the generated power of the SOFC 13 is boosted to a voltage corresponding to the output to the power transmission facility 130 by the booster circuit 122 in the PCS, and then converted from the DC power to the AC power by the inverter 123. The electric power output from the inverter 123 is filtered by the filter circuit 124 (for example, smoothing), and is supplied to the power transmission facility 130 via the closed PCS switch 125. The AC power from the PCS 120 and the AC power from the MGT 11 are superposed at the interconnection point X in the power transmission facility 130 and supplied to the power system 135 through the closed system switch 131 and the transformer 132.

The switch 125 in the PCS is a switch for switching the grid connection and disconnection between the SOFC 13 and the power system 135. Further, the system switch 131 is a switch for switching the grid connection and disconnection between the power generation system 10 and the power system 135.
Specifically, the switch 125 in the PCS is closed when the SOFC 13 and the power system 135 are connected, and is opened when the SOFC 13 is disconnected from the power system 135. Further, the system switch 131 is closed when the power generation system 10 and the power system 135 are connected, and is opened when the power generation system 10 is disconnected from the power system 135.
The opening / closing control of the switch 125 in the PCS and the system switch 131 is performed by the control device 60 or the PCS 120.
In the present embodiment, the switch 125 in the PCS is provided in the PCS, but the arrangement is not limited to this. That is, the switch for switching the grid connection and disconnection between the SOFC 13 and the power system 135 may be provided on the power line C1 connecting the power generation output end of the SOFC 13 and the interconnection point X. For example, the SOFC 13 It may be provided between the power generation output end of the PCS 120 and the PCS 120, or may be provided between the PCS 120 and the interconnection point X.

[Protective control of power generation system]
Next, the protection control executed by the control device 60 when a PCS abnormality occurs in the power generation system 10 having the above configuration will be described. The PCS abnormality is an abnormality in which the power generation output of the SOFC 13 cannot be normally transmitted to the power supply destination (in the present embodiment, the power system 135) as described later.
The control device 60 is, for example, a computer or a sequencer, and includes a CPU, a ROM (Read Only Memory) for storing programs executed by the CPU, and a RAM (Random Access Memory) that functions as a work area during execution of each program. ) Etc. are provided. A series of processing processes for realizing various functions described later is recorded in a recording medium or the like in the form of a program, and the CPU reads this program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions described later are realized.

FIG. 6 is a functional block diagram showing mainly the functions related to protection control among various functions included in the control device 60. As shown in FIG. 6, the control device 60 includes a PCS abnormality detection unit 140, a connection control unit 141, an output control unit 142, an operation mode determination unit 143, and an operation mode switching unit 144.

The PCS abnormality detection unit 140 detects the occurrence of a PCS abnormality. The PCS abnormality is an abnormality that occurs on the power supply destination side, which is the side that supplies power from the power generation output end of the SOFC 13. In the present embodiment, the PCS abnormality includes, for example, a power system abnormality, a PCS failure, and a power transmission / interconnection device failure. Examples of the power system abnormality include a power failure of the power system 135, a momentary power failure, a frequency fluctuation of a predetermined width or more, a voltage fluctuation of a predetermined value or more, a voltage drop of a predetermined value or less, and the like. Further, as a PCS failure, a failure or disconnection of each element or each component constituting the PCS 120, a communication abnormality between the PCS 120 and the control device 60 (for example, a PCS that cannot receive an answer from the PCS 120 to a request transmitted to the PCS 120). Answerback error) is an example. Further, as an example of equipment failure of power transmission / interconnection, failure or damage of each device such as power transmission equipment 130, system switch 131, transformer 132 installed between PCS 120 and power system 135, and power line is given as an example. Be done. The PCS abnormality is not limited to the above example, and is various abnormalities such that the generated power of the SOFC 13 cannot be normally transmitted to the power system 135, and it is necessary to detect the abnormality and perform SOFC protection control. To say.

When the PCS abnormality detection unit 140 detects the occurrence of a PCS abnormality, the connection control unit 141 switches the switch 125 in the PCS from the closed state to the open state, and disconnects the SOFC 13 from the power system 135. In other words, the SOFC 13 and the power supply destination are disconnected. As a result, the SOFC 13 is in a no-load state to which no load is connected. In SOFC13, the output current of power generation becomes zero, and open electromotive force is generated.

The output control unit 142 puts the SOFC 13 in the power generation standby state when the PCS abnormality detection unit 140 detects the PCS abnormality. Here, the power generation standby state is a state in which the temperature of the power generation room is maintained above a predetermined temperature at which power can be generated, and if a load is connected, power generation can be started in a short time.

Specifically, the output control unit 142 adjusts the opening degree of the control valve 82 and the valve opening degree of the control valves 64 and 66 in the power generation standby state to adjust the fuel gas L2 and the air (oxidizer gas) A1. It is supplied to the air electrode 13B. As a result, catalyst combustion is performed in the power generation chamber, and the heat generated by the catalyst combustion is used to maintain the temperature of the power generation chamber above a predetermined temperature at which power can be generated. When the fuel cell 105 has not reached a sufficient temperature, in other words, when the solid electrolyte 111 (see FIG. 2) is in a high resistance state, the fuel gas L2 is charged to the fuel electrode 13A side to push the fuel cell 105. This is because when power is generated, the electrode constituent material undergoes structural changes and deteriorates, which causes a decrease in the performance of the fuel cell 105. Here, the temperature at which power can be generated means, for example, 750 ° C. or higher.

The power generation room temperature is set to, for example, 80% or more of the rated operating temperature in order to prevent performance deterioration of the fuel cell 105. Specifically, the power generation room target temperature is self-heating due to heat generated by SOFC13. The temperature is set at a temperature higher than the temperature that can be maintained, for example, in a temperature range of 85% or more and 100% or less of the rated operating temperature.

Further, the output control unit 142 narrows the control valve 42 to a slightly open state close to the fully closed state in the power generation standby state, so that the supply of the fuel gas L2 to the fuel electrode 13A is significantly larger than the flow rate during the rated operation. The flow rate is reduced to a small amount. Here, when the control valve 42 is fully closed and the supply of the fuel gas L2 to the fuel electrode 13A is stopped, the fuel electrode 13A has an oxide gas atmosphere when there is oxygen entering from the air electrode 13B. This is because the fuel cell 105 may be deteriorated. In order to prevent deterioration of the fuel cell 105, a minute flow rate of fuel gas L2 is supplied to the fuel electrode 13A, and pure water, which is reforming water corresponding to the minute flow rate of fuel gas L2, is supplied from the pure water supply line 44. By doing so, the fuel gas L2 having a minute flow rate is reformed into a gas containing a large amount of hydrogen, and the reformed gas such as this hydrogen gas reacts with the oxygen entering from the air electrode 13B to reduce the fuel electrode 13A. Maintain a gas atmosphere.
The fuel gas L2 supplied to the fuel electrode 13A is the minimum flow rate required to maintain the fuel electrode 13A in the reducing gas atmosphere or a flow rate obtained by giving a predetermined margin to the flow rate, for example, the rating of SOFC13. It is set in the range of several% or more and 10% or less with respect to the flow rate during operation.
In the exhaust fuel gas line 43, the reformed gas of the fuel gas L2 having a minute flow rate and water vapor that has reacted with oxygen are discharged as the exhaust fuel gas, and the exhaust fuel gas L3 having a minute flow rate is the fuel electrode 13A of the SOFC 13. It is recirculated to the inlet by the fuel gas recirculation line 49 and the recirculation blower 50.

Further, the output control unit 142 supplies pure water to the fuel electrode 13A when the PCS abnormality detection unit 140 detects the PCS abnormality. This pure water is the water required for reforming. Here, in a normal load drop, the supply of pure water is started when the output of the SOFC 13 becomes equal to or less than a predetermined value. This is because the amount of steam generated by the power generation reaction is large in the load region where the output is equal to or higher than a predetermined value, so that the steam recirculated to the SOFC 13 through the fuel gas recirculation line 49 covers the steam required for reforming. Because it can be done. When the output of the SOFC 13 decreases, the amount of water vapor generated in the power generation reaction decreases, so that the amount of water vapor circulating in the fuel gas recirculation line 49 decreases, and the water vapor required for reforming cannot be supplied. Therefore, when the output of SOFC 13 is equal to or less than a predetermined value (for example, the predetermined value is set in the range of 40% or more and 50% or less of the rated output), pure water is supplied from the outside via the pure water supply line 44. Supply and replenish the shortage of water vapor.

In the present embodiment, when a PCS abnormality occurs, it is not necessary to supply pure water in a state where the output of SOFC 13 is equal to or higher than a predetermined value. However, when a PCS abnormality occurs, the output of the SOFC 13 drops rapidly in order to disconnect the SOFC 13 from the power system 135, and the output of a predetermined value (for example, 40% or more and 50% or less of the rated output) has not passed. The load state is reached, and the output of SOFC 13 becomes zero. Therefore, in anticipation of this situation, in the present embodiment, when the occurrence of a PCS abnormality is detected, the supply of pure water is started in advance.
Further, the output control unit 142 supplies the fuel electrode 13A with the minimum flow rate of pure water for stably starting the sudden pure water supply at the start of the pure water supply. Pure water is sprayed from a spray nozzle provided in the fuel gas recirculation line 49, and this spray nozzle is heated to a high temperature by the gas circulating in the fuel gas recirculation line 49. If a considerable amount of pure water is rapidly supplied to such a high-temperature spray nozzle, pressure fluctuations and flow rate fluctuations may occur, and auxiliary equipment such as the spray itself may be damaged. In order to prevent such pressure fluctuations, flow rate fluctuations, and spray damage, the lowest flow rate of pure water is supplied to the spray nozzle at the start of pure water supply, and a predetermined period from the start of pure water supply ( After (for example, several minutes) has passed and the spray nozzle is cooled to some extent, the pure water flow rate is gradually increased to the target pure water flow rate. Here, the minimum flow rate of pure water in the present embodiment is set in the range of several% or more and about 20% or less of the pure water flow rate supplied during operation when the output of SOFC 13 is less than a predetermined value, for example. Further, the target pure water flow rate is set to be equal to or higher than the flow rate at which carbon precipitation does not occur by appropriately performing the reforming reaction of the fuel gas L2 supplied to the fuel electrode 13A. For example, S / C (steam carbon ratio). ) Is set to a value in the range of about 3 or more and 5 or less.

The operation mode determination unit 143 determines whether or not the current operation mode of the MGT 11 is a high-efficiency operation mode when an abnormality is detected by the PCS abnormality detection unit 140. Here, the high-efficiency operation mode means that the fuel gas L1 supplied to the combustor 22 via the first fuel gas supply line 27 (see FIG. 1) is supplied through the exhaust fuel gas supply line 45 without using it as much as possible. This is an operation mode in which the flow rate of the fuel gas L1 is set to be equal to or less than a preset predetermined value so as to maximize the utilization of the exhaust fuel gas L3 as fuel to improve fuel efficiency.

When the operation mode switching unit 144 determines that the current operation mode is the high-efficiency operation mode, the operation mode switching unit 144 releases the high-efficiency operation mode, and more fuel gas L1 than the high-efficiency operation mode. Is switched to another operation mode for supplying the combustor 22. For example, the operation mode switching unit 144 determines the flow rate of the air A supplied from the compressor 21 based on the outside air temperature and the fuel cell load (= 0A) measured by the outside air temperature sensor 94, and controls the output of the MGT 11. Switch to operation mode.
In this way, when a PCS abnormality is detected, the operation mode is set in which the high-efficiency operation of suppressing the fuel gas L1 to improve fuel efficiency is released and the supply amount of the fuel gas L1 supplied to the combustor 22 is increased. By switching, it becomes possible to maintain stable combustion of the combustor 22.

Next, the procedure of protection control executed by the control device 60 according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing a procedure for protection control of the power generation system according to the present embodiment.
First, when a PCS abnormality is detected during operation of the power generation system (for example, rated operation, partial load operation, etc.) (“YES” in step SA1), the switch 125 in the PCS is switched from the closed state to the open state. , SOFC 13 is disconnected from the power system 135 (step SA2). Further, the SOFC 13 is set to a no-load state in which no power is output, so that the output of the SOFC 13 becomes zero. If no PCS abnormality is detected (“NO” in step A1), the operation of the power generation system (for example, rated operation, partial load operation, etc.) is continued.

Subsequently, each control valve or the like is controlled in order to shift to the power generation standby state (step SA3). Specifically, the amount of fuel gas L2 supplied to the fuel electrode 13A is reduced to the target flow rate by bringing the control valve 42 close to the closed state and making it slightly open. This target flow rate is set in the range of several% or more and 10% or less with respect to the flow rate during rated operation, for example. Further, as the fuel gas L2 decreases, the flow rate of the air A1 supplied to the air electrode 13B also decreases. The flow rate of the air A1 is controlled by, for example, controlling the valve opening degrees of the control valves 64 and 66. Further, by opening the control valve 82, the fuel gas L2 is added to the air A1, and the air A1 to which the fuel gas L2 is added is supplied to the air electrode 13B, so that the power generation room temperature is set to a predetermined temperature by heat generation due to catalytic combustion. Keep above.

Subsequently, it is determined whether or not the current operation mode of the MGT 11 is the high efficiency operation mode (step SA4), and if it is the high efficiency operation mode (“YES” in step SA4), the high efficiency operation mode is set. An operation mode in which the flow rate of the air A supplied from the compressor 21 is determined from another operation mode, for example, the SOFC load (0A) and the outside air temperature taken in by the outside air temperature sensor 94, and the target MGT output is set. Switch to (step SA5).
Subsequently, the supply of pure water is started (step SA6). Specifically, the pure water supply is started at the minimum flow rate for stable pure water supply, and then the pure water is increased to the target flow rate after a predetermined period (for example, after 3 to 4 minutes).
If it is determined in step SA4 that the current operation mode of the MGT 11 is not the high-efficiency operation mode (“NO” in step SA4), the operation mode is not switched and the process proceeds to step SA6 to pure water. Start supplying.

By executing various processes in this way, when a PCS abnormality is detected, the power generation standby state is maintained for the SOFC13, and the MGT11 is based on the outside air temperature and the SOFC load (= 0A). The output control of the MGT 11 is continuously performed. As a result, the SOFC 13 is maintained in a state where it can start power generation in a short time when the power generation is restarted, and the generated power generated by the generator 12 of the MGT 11 may be supplied to the power system 135.

Then, in the above state, when the PCS abnormality is resolved, the control device 60 starts the power generation of the SOFC 13. For example, the control device 60 sets a target output current according to the required load, and sets a control command for each control system based on the target output current. Then, various control systems are controlled based on the set control commands. For example, the control commands of each control system include a flow command of the fuel gas L2 supplied to the fuel pole 13A, an inlet air temperature command of the air A1 supplied to the air pole 13B, and a differential pressure command between the fuel pole 13A and the air pole 13B. , The rotation speed command of the recirculation blower 50, the flow rate command of pure water supplied to the fuel electrode 13A, the MGT output command, and the like.

In this way, control commands of various control systems are set based on the target output current, and control (for example, feedback control or feedforward control) is performed to match the outputs of various control systems with the set control commands. As a result, it is possible to change the control amounts of at least two or more control systems in each control system almost all at once toward the control command, and set the target of each control such as the temperature of the power generation room in a short time. As a result, the SOFC output and the temperature of the power generation chamber can be rapidly increased toward the target output and the target temperature, and the MGT output can be increased as the output of the SOFC 13 increases.

FIG. 8 shows the execution of protection control by the power generation system according to the present embodiment (hereinafter, simply referred to as “protection control”) and emergency stop control of the conventional power generation system (hereinafter, simply referred to as “emergency stop control”). It is a figure which compared and showed the time transition of various control amounts in the case of. The temporal transition of various control amounts is shown by a thick line for the protection control of the present embodiment and a thin line for the emergency stop control of the conventional power generation system.
FIG. 8A shows an example of the temporal transition of the SOFC output, the power generation room temperature, and the MGT output. 8 (b) to 8 (d) show the air flow rate of the air A1 supplied to the air electrode 13B, the fuel flow rate of the fuel gas L2 supplied to the fuel electrode 13A, and the net supply to the fuel electrode 13A. An example of the temporal transition of the water flow rate is shown.

As shown in FIG. 8, when a PCS abnormality is detected at time t1 when the SOFC 13 is operating at the rated output, the SOFC 13 is disconnected from the power system 135 in both protection control and emergency stop control, and the SOFC 13 is operated. The SOFC output becomes zero by setting the no-load state in which no power is output.
After the occurrence of the PCS abnormality, the emergency stop control stops the operation of the SOFC 13 and the MGT 11. As a result, the MGT output becomes zero as shown in FIG. 8 (a), and the air flow rate decreases in a short time toward a predetermined flow rate as shown in FIGS. 8 (b) and 8 (c), and the fuel The flow rate also drops to a predetermined value in a short time.

Then, in the emergency stop control, when a PCS abnormality is detected, the operation of the SOFC 13 is stopped to prepare for the transition to the cooling process. Therefore, as shown in time t1 to t2 of FIG. 8A, power generation is performed. The room temperature continues to drop. Then, when the PCS abnormality is resolved at time t2, the emergency stop control increases the air flow rate in order to raise the temperature of the power generation chamber to the temperature at which power can be generated (see FIG. 8B). Subsequently, in the emergency stop control, at time t3, the flow rate of fuel supplied to the air electrode 13B is increased (see FIG. 8C) to cause catalytic combustion to raise the temperature of the power generation chamber (FIG. 8 (a)). )reference). Then, at time t6, when the temperature of the power generation room reaches the temperature at which power can be generated, power generation is started (see FIG. 8A). As a result, the SOFC output increases after time t6. Further, in the emergency stop control, the pure water flow rate is gradually reduced after the flow rate of the fuel gas L2 to the air electrode 13B starts to increase at time t3 (see FIG. 8D). After that, in the emergency stop control, at time t7, the SOFC output reaches a predetermined output at which pure water supply is not required for fuel reforming, and at the subsequent time t8, the output of SOFC 13 reaches the rated load.
In this way, in the emergency stop control in the conventional power generation system, the power generation standby state is not executed. Therefore, even if the PCS abnormality is resolved at an early stage of time t2, the temperature that raises the power generation room temperature to the power generation possible temperature. Since the ascending step is required, it takes time from the resolution of the PCS abnormality to the start of power generation (for example, it takes time from time t2 to t6 in FIG. 8).

On the other hand, in the protection control of the present embodiment, when the PCS abnormality is detected at time t1, the SOFC 13 is maintained in the power generation standby state. That is, as shown in FIG. 8B, although the air flow rate drops to a constant flow rate in a short time when a PCS abnormality occurs, the flow rate required to maintain the power generation chamber temperature above the power generation possible temperature is constant. Further, as shown in FIG. 8C, a predetermined flow rate is maintained for the fuel flow rate in order to prevent deterioration of the fuel electrode 13A of the fuel cell. In addition, the pure water required for reforming is also started to be supplied in a short time (see FIG. 8D). Further, regarding the power generation operation of the MGT 11, power generation is continued in a state where the power generation output is reduced. At this time, another operation mode in which more fuel gas L1 is supplied to the combustor 22 than in the high efficiency operation mode is adopted, and stable combustion in the combustor 22 is maintained.
Subsequently, when the PCS abnormality is resolved at time t2, in the protection control, the pure water flow rate gradually decreases as the output of the SOFC 13 increases. Then, at time t4, when the SOFC output reaches a predetermined output at which pure water supply is not required for fuel reforming, the pure water flow rate is set to zero, and at the subsequent time t5, the SOFC output reaches the rated output.

As described above, as shown in the times t1 to t2 of FIG. 8A, the protection control makes it possible to maintain the temperature of the power generation room at or higher than the temperature at which power can be generated. As a result, for example, when the PCS abnormality is resolved at time t2, the power generation of the SOFC 13 is promptly started by promptly increasing the air flow rate and the fuel flow rate (see FIGS. 8B and 8C). It is possible to make it (Fig. 8 (a)). As described above, in the protection control, it is possible to eliminate the temperature rise process required in the conventional emergency stop control, and it is possible to start the power generation in a short time. Therefore, it is possible to shorten the time required to reach the target load as compared with the emergency stop control. Further, according to the protection control, as shown at times t1 to t2 in FIG. 8A, even if a PCS abnormality is detected, the operation of the MGT 11 is continued, so that the MGT output is continued to the power system 135. Can be supplied.

As described above, according to the power generation system 10 and its protection control method according to the present embodiment, when a PCS abnormality is detected, the SOFC 13 is disconnected from the power system 135 and the power generation standby state is entered. Let me. In the power generation standby state, catalyst combustion is generated by supplying air A1 and fuel gas L2 to the air electrode 13B, and this heat keeps the power generation chamber temperature of SOFC 13 above the power generation possible temperature and fuels the fuel electrode 13A. By supplying the gas L2, the fuel electrode 13A is maintained in a reducing gas atmosphere, and deterioration of the fuel cell 105 is prevented. By maintaining such a power generation standby state, it is possible to start power generation in a short time when the PCS abnormality is resolved. As a result, it is possible to shorten the time required from the elimination of the PCS abnormality to the start of power generation as compared with the conventional system in which the emergency stop control is performed.

Further, according to the present embodiment, since the operation of the MGT 11 is maintained even when a PCS abnormality is detected, it is possible to continue to supply the MGT output (for example, about several tens of kW) to the power system 135. Further, in this case, when the MGT 11 is operated in the high efficiency operation mode, the high efficiency operation mode is canceled and the operation mode is switched to the operation mode in which more fuel gas L1 is supplied to the combustor 22. It is possible to maintain stable combustion in the combustor 22 and stabilize the operation of the MGT 11.

Further, in the conventional emergency stop control, nitrogen may be supplied to the air electrode 13B in order to temporarily cool the SOFC 13 after the PCS abnormality is detected. However, according to the power generation system 10 according to the present embodiment. For example, the SOFC 13 is not cooled using nitrogen, and the SOFC 13 is held in the power generation standby state. This makes nitrogen unnecessary. Unlike city gas and the like, nitrogen is installed and used in a state of being stored in a tank or the like, so maintenance work such as tank replacement is required. According to the present embodiment, since the consumption of nitrogen can be suppressed, the frequency of nitrogen tank replacement can be reduced, and the work associated with tank replacement and the like can be reduced.

Further, according to the present embodiment, when a PCS abnormality is detected, the SOFC 13 stops power generation, but the power generation standby state is set so that the operation is not stopped, so that the number of heat cycles of the SOFC 13 can be reduced. As a result, deterioration of the cell stack can be suppressed, and the life of the cell stack can be extended.

10: Power generation system 11: MGT (micro gas turbine)
12: Generator 13: SOFC (fuel cell)
13A: Fuel pole 13B: Air pole 60: Control device 105: Fuel cell 111: Solid electrolyte 120: Power conditioner (PCS: Power converter)
125: Switch in PCS (switch)
135: Power system 140: PCS abnormality detection unit (abnormality detection unit)
141: Connection control unit 142: Output control unit 143: Operation mode determination unit 144: Operation mode switching unit (operation mode release unit)
215: Power generation room C1: Power line (first power line)
C2: Power line (second power line)
C3: Power line (third power line)
X: Interconnection point L1: Fuel gas (third fuel gas)
L2: Fuel gas (first fuel gas, second fuel gas)

Claims (10)

A fuel cell including a power generation chamber in which a plurality of fuel cell cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged.
A micro gas turbine to which the exhaust fuel and exhaust air from the fuel cell are supplied, and
A control device that controls the fuel cell and
It is provided with a power conversion device arranged between a power supply destination to which power generated by the fuel cell is supplied and a power generation output end of the fuel cell.
The control device is
An abnormality detection unit that detects an abnormality that has occurred from the power generation output end of the fuel cell to the power supply destination side,
When the abnormality is detected by the abnormality detection unit, the output control unit is provided to shift the power generation chamber of the fuel cell to a power generation standby state for maintaining the temperature above a predetermined power generation possible temperature.
A power generation system in which, when the abnormality is detected by the abnormality detection unit, the fuel cell is put into a no-load state in which no electric power is output, and the micro gas turbine is continuously operated . A fuel cell including a power generation chamber in which a plurality of fuel cell cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged.
A control device that controls the fuel cell and
A power conversion device arranged between a power supply destination to which the power generated by the fuel cell is supplied and a power generation output end of the fuel cell.
With
The control device is
An abnormality detection unit that detects an abnormality that has occurred from the power generation output end of the fuel cell to the power supply destination side,
When the abnormality is detected by the abnormality detection unit, the output control unit shifts the power generation chamber of the fuel cell to a power generation standby state for maintaining the temperature above a predetermined power generation possible temperature.
With
When the abnormality is detected by the abnormality detection unit, the fuel cell is set to a no-load state in which no electric power is output.
The output control unit is a power generation system that supplies reforming water to the fuel electrode when the abnormality is detected by the abnormality detection unit. A switch provided between the power generation output end of the fuel cell and the power supply destination,
The power generation system according to claim 1, further comprising a connection control unit that opens the switch when the abnormality is detected by the abnormality detection unit. The output control unit, in the power generation standby state, supplies the oxidant gas and the first fuel gas to the air electrode, the power generation system according to the second fuel gas to the請Motomeko 2 you supplied to the fuel electrode .. The first power line that transmits the generated power of the fuel cell and
The second power line that transmits the generated power of the micro gas turbine and
An interconnection point connecting the first power line and the second power line,
A third power line that connects the interconnection point and the power supply destination is provided.
The power generation system according to claim 3 , wherein the switch is provided on the first power line. The control device is
When the abnormality is detected by the abnormality detection unit, the operation mode of the micro gas turbine is a high-efficiency operation mode in which the supply amount of the third fuel gas to the combustor is suppressed to a predetermined value or less set in advance. An operation mode determination unit that determines whether or not there is,
When the operation mode determination unit determines that the high efficiency operation mode is set, the high efficiency operation mode is released and a larger amount of the third fuel gas than the high efficiency operation mode is supplied to the combustor. The power generation system according to claim 1, further comprising an operation mode switching unit for switching to another operation mode. When the abnormality is detected by the abnormality detection unit, the output control unit supplies the reforming water having a preset minimum flow rate to the fuel electrode, and is preset from the start of supply of the reforming water. The power generation system according to claim 2 , wherein the supply amount of the reforming water is increased to the target flow rate after a lapse of a predetermined time. A fuel cell in which a fuel cell, a solid electrolyte, and a plurality of fuel cell cells including an air electrode are arranged in a power generation chamber, and a micro gas turbine to which exhaust fuel and exhaust air from the fuel cell are supplied are provided. It is a protection control method for the power generation system
The process of detecting an abnormality that has occurred from the power generation output end of the fuel cell to the power supply destination side, and
When the abnormality is detected, the step of setting the fuel cell to a no-load state in which no electric power is output, and
When the abnormality is detected, a step of shifting the power generation chamber of the fuel cell to a power generation standby state for maintaining the temperature above a predetermined power generation possible temperature , and
A protection control method for a power generation system, which includes a step of continuously operating the micro gas turbine when the abnormality is detected, and a method of protecting and controlling the power generation system. The protection control method for a power generation system according to claim 8, further comprising a step of raising the power generation chamber of the fuel cell to a target temperature and increasing the output of the fuel cell to the target output when the abnormality is resolved. It is a protection control method for a power generation system including a fuel cell in which a plurality of fuel cell cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged in a power generation chamber.
The process of detecting an abnormality that has occurred from the power generation output end of the fuel cell to the power supply destination side, and
When the abnormality is detected, the step of setting the fuel cell to a no-load state in which no electric power is output, and
When the abnormality is detected, a step of shifting the power generation chamber of the fuel cell to a power generation standby state for maintaining the temperature above a predetermined power generation possible temperature, and
When the abnormality is detected, the step of supplying reforming water to the fuel electrode
Protective control methods for power generation systems, including.

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