JP6771962B2 - Fuel cell control device and control method and power generation system - Google Patents

Description

The present invention relates to a fuel cell control device, a control method, and a power generation system.

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 (oxidizing agent 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 hydrogen, city gas, natural gas, oil, methanol, and coal. It is a fuel cell that is operated by using gas produced from a carbonaceous raw material such as gasified gas by a gasification facility. 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 this 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 generated in the combustor is performed. By adiabatic expansion of the gas, the turbine of the MGT is rotationally driven and the generator is rotationally driven, so that power generation with high power generation efficiency is possible.

As such control at the time of starting SOFC, for example, Patent Document 1 proposes the following method. First, an oxidant gas was supplied to the air electrode side of the power generation chamber to raise the temperature of the power generation chamber, and when the air electrode reached a temperature at which catalytic combustion was possible (for example, 400 ° C.), fuel gas was subsequently added. By supplying the oxidant gas to the air electrode side of the power generation chamber, the temperature rise of the power generation chamber is promoted. Then, when the temperature of the power generation chamber reaches a predetermined temperature (for example, 750 ° C. or higher), the fuel gas is supplied to the fuel electrode side to start the power generation of the power generation cell, and the fuel gas supplied to the air electrode side is added. Gradually reduce the amount to zero.

Further, as a SOFC control method, for example, Patent Document 2 discloses that the fuel gas and the oxidant gas are feedforward-controlled so that the operating temperature of the SOFC changes at a preset temperature change rate. There is.
Further, for example, in Patent Document 3, when the SOFC is started, the flow rate adjusting valve is preliminarily feed-forward controlled by the gain associated with the recirculation flow rate and the gas density according to the cooperative operation state of the SOFC and the MGT. Is disclosed.

Japanese Patent No. 5601945 Japanese Unexamined Patent Publication No. 2003-223912 JP 2015-50106

By the way, the power generation chamber of the SOFC has a large heat capacity, and a response delay occurs when controlling the operation amount related to the temperature control of the power generation chamber. That is, it takes some time from issuing the command regarding the temperature control of the power generation chamber until the temperature of the power generation chamber actually changes and stabilizes. Therefore, for example, when the load increases, an overshoot in which each control amount exceeds a specified value may occur, and additional control is performed in order to damage a part of the SOFC or reduce the overshoot amount again. It may take some time. On the other hand, in order to avoid overshoot when the load rises, each control amount is issued in sequence, and after each control amount changes and stabilizes, a command for the next operation is issued. However, when such control is performed, it takes a considerably long time for the control amount to reach the target value and the operation to be completed.

The present invention has been made in view of such circumstances, and controls a fuel cell capable of shortening the time to reach a target while avoiding overshoot of a controlled amount when the load of the fuel cell increases. It is an object of the present invention to provide an apparatus, a control method, and a power generation system.

The present invention is a fuel cell control device 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, and a target load for setting a target load of the fuel cell. The setting unit, the output current command setting unit that sets the output current command of the fuel cell from the target load of the fuel cell set by the target load setting unit at predetermined repetition time intervals, and the output current command of the fuel cell. A control command setting unit that sets control commands for a plurality of control systems, a control command correction unit that increases or decreases at least one control command set by the control command setting unit, and the control command correction unit. The control unit includes a control unit that controls at least one operation amount of the control system based on the control command corrected by the above, and the control unit is brought into the operating state of the fuel cell when the load of the fuel cell is changed. Provided is a fuel cell control device including a gain adjusting unit that changes at least one gain of the control system accordingly.

Further, in the fuel cell control device, the gain adjusting unit may change at least one gain of the control system according to the gas type of the exhaust fuel gas that changes depending on the operating state of the fuel cell.

According to the present invention, the output current command is set to repeat from the target load at predetermined time intervals, and the control commands of a plurality of control systems are set using the output current command. At least one control command in the plurality of control systems is corrected in the increasing direction or the decreasing direction by the control command correction unit, and a predetermined operation amount is controlled by the control unit based on the corrected control command. Thereby, for example, the flow rate of the fuel gas supplied to the fuel electrode, the flow rate of the oxidant gas supplied to the air electrode, and the like are controlled. Here, for example, the exhaust fuel gas circulating in the recirculation line that recirculates the exhaust fuel gas reacted at the fuel electrode to the fuel electrode changes the operating state of the fuel cell corresponding to each temperature rise mode from the start. The composition of the exhaust fuel gas changes as the temperature of the power generation room rises and the load increases. The sensitivity (gain) of the control valve or the like that controls the differential pressure between the fuel electrode and the air electrode provided in the exhaust fuel gas line changes due to the change in the gas composition accompanying the change in the state of the fuel cell. Therefore, for example, the valve control can be stabilized by adjusting the sensitivity of the control valve or the like according to the operating state of the fuel cell, for example, the change in the composition of the exhaust fuel gas.

In the fuel cell control device, the control unit may set at least one of the control commands by using at least one of proportional control, integral control, and differential control, and the gain adjusting unit may set the control unit. The gain to be adjusted may be, for example, at least one of a proportional gain, an integral gain, and a differential gain.

In the fuel cell control device, the gain adjusting unit may increase the gain related to the differential pressure control valve for adjusting the differential pressure between the air electrode and the fuel electrode.

By increasing the gain related to the differential pressure control valve in this way, the differential pressure adjustment speed can be increased, and the follow-up delay of the differential pressure control valve can be suppressed.

In the fuel cell control device, the gain adjusting unit may reduce the gain increase range in response to an increase in the output current command of the fuel cell.

In this way, by reducing the gain increase range in response to the increase in the output current command, it is possible to prevent hunting of the differential pressure control valve and realize a stable load increase.

In the fuel cell control device, the control command correction unit reduces a fuel air differential pressure command for controlling the differential pressure between the air electrode and the fuel electrode by a predetermined amount when the load of the fuel cell increases. A differential pressure command correction unit may be provided.

By reducing the fuel air differential pressure command by a predetermined amount in this way, it is possible to operate on the safe side so that the differential pressure does not temporarily increase due to each control fluctuation due to the load change. This makes it possible to avoid damage to the equipment.

In the fuel cell control device, the control command correction unit increases a flammable gas flow rate command for controlling the flow rate of the flammable gas supplied to the fuel electrode by a predetermined amount when the load of the fuel cell increases. A flammable gas flow rate command correction unit may be provided.

By increasing the flammable gas flow rate command by a predetermined amount in this way, it is possible to avoid a situation in which the flammable gas is insufficient when the load is increased. This makes it possible to avoid damage to the equipment due to a lack of flammable gas.

In the fuel cell control device, the target load of the fuel cell may be set from the outside air temperature around the fuel cell.

As a result, changes in the temperature of the power generation chamber due to the outside air temperature can be suppressed, and stable temperature control can be performed.

In the fuel cell control device, the fuel cell is, for example, a solid oxide fuel cell.

In the fuel cell control device, the output current command setting unit sets the output current command of the fuel cell from the target load of the fuel cell at a predetermined repeating time interval by using a predetermined current change rate. May be good.
In the fuel cell control device, the plurality of control systems include fuel gas supply flow rate to the fuel electrode, fuel cell air electrode inlet temperature, micro gas turbine output, differential pressure between the fuel electrode and the air electrode, and recirculation blower rotation. It may include two or more of the number and the pure water flow rate.

The present invention comprises a fuel cell including a power generation chamber in which a plurality of power generation cells including a fuel electrode, a solid electrolyte, and an air electrode having oxidation catalyst performance are arranged, and a fuel cell control device according to any one of the above. To provide a power generation system equipped with.

The present invention is a method for controlling a fuel cell including a power generation chamber in which a plurality of power generation cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged, and a target load setting for setting a target load of the fuel cell. Control of a plurality of control systems by using a process, an output current command setting step of setting an output current command of the fuel cell from a target load of the fuel cell at a predetermined repeating time interval, and an output current command of the fuel cell. Based on the control command setting step of setting the command, the control command correction step of increasing or decreasing at least one control command set in the control command setting step, and the control command corrected by the control command correction step. It has a control step of controlling at least one operation amount of the control system, and in the control step, at least one of the control systems according to the operating state of the fuel cell when the load of the fuel cell changes. A method of controlling a fuel cell that changes the gain is provided.

According to the present invention, when the load of the fuel cell is increased, it is possible to shorten the time to reach the target while avoiding the overshoot of the controlled amount.

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 functional block diagram which expanded and showed the function provided with the control device which concerns on one Embodiment of this invention. It is a functional block diagram which expanded and showed the function of the load increase mode about the SOFC control apparatus which concerns on one Embodiment of this invention. It is a figure which showed an example of the target load information. It is a figure which showed an example of the fuel gas flow rate information. It is a figure which showed an example of the inlet air temperature information. It is a figure which showed an example of MGT output information. It is a figure which showed an example of the differential pressure information. It is a figure which showed an example of the rotation speed information. It is a figure which showed an example of pure water flow rate information. It is a figure for demonstrating the correction by a fuel gas flow rate command correction part. It is a figure for demonstrating the correction by a differential pressure command correction part. It is a figure which showed the schematic structure of the control part shown in FIG. It is a figure which showed the schematic structure of the differential pressure control part shown in FIG. It is a flowchart which showed the control procedure in the load increase mode which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of a fuel cell control device and a control method and a power generation system 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, and SOFC 13. 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.
Compressed air (hereinafter, simply referred to as “air”) A1 from the compressor 21 is supplied to the combustor 22 via the first air supply line 26, and fuel is supplied via the first fuel gas supply line 27. Gas L1 is supplied. 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.

Fuel gas L2 to the fuel gas L1 and later supplied to the combustor 22 is a combustible gas, for example, liquefied natural gas (LNG), city gas, hydrogen _{(H 2)} and carbon monoxide (CO), methane (CH Hydrocarbon gas such as ₄ ) and gas produced by gasification equipment for carbonaceous raw materials (oil, coal, etc.) are used.

The SOFC 13 is supplied with heated fuel gas L2 as a reducing agent and heated air (oxidizing agent gas) as an oxidizing agent gas, and reacts at a predetermined operating temperature to generate power. 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 generates electricity by supplying an oxidant gas to the air electrode 13B and supplying the fuel 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 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 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 section which is the introduction section 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 of the air A passing through the heat exchanger 58 and the air A bypassing the heat exchanger 58 is adjusted, and the air A is adjusted. The temperature of the air A1 supplied to the SOFC 13 through the second air supply line 31 which is a part of the above 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 that supplies 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 MGT 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 for supplying pure water for reforming the fuel gas L2 to the fuel electrode 13A. 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 amount of pure water 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 tube 103 in the longitudinal axis direction of the base tube 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 pole 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 above.

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 fuel gas L2 that can be supplied and used for the fuel electrode 13A of the SOFC 13 is hydrogen (H ₂ ), carbon monoxide (CO), methane (CH ₄ ) and other hydrocarbon gases, city gas, natural gas, as well as oil. Gas produced from carbonaceous raw materials such as methanol and coal gas by a gasification facility. The fuel gas L2 in the present embodiment uses a fuel gas containing methane as a main component such as city gas and hydrogen.

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 atmosphere and a reducing 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 107 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., it has resistance and corrosion resistance to an oxidizing agent gas such as oxygen contained in the oxidizing gas. The material that owns 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 is monitored by a temperature sensor 92 or the like described later, and 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 electric power led out to the outside of the SOFC cartridge 203 by the current collector rod is led out to the outside of the SOFC module 201, converted into predetermined AC power by an inverter (not shown) or the like, and supplied to the power load.

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 exchanges heat 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. 4, at least one temperature sensor 92 is arranged in each SOFC cartridge 203. For example, when the SOFC 13 is configured to include four SOFC cartridges 203, at least a total of four temperature sensors will be provided. The temperature sensor 92 is arranged at least in the central region of the cell stack 101 in the longitudinal direction in the power generation chamber 215. The central region in the present embodiment is a region including the position where the temperature becomes the highest when the temperature distribution in the longitudinal direction of the cell stack 101 is taken, and the lower portion of the cell stack 101 is 0% and the upper portion is 100%. In the case, it is in the range of about 30% to 65%. More preferably, the central region is in the range of about 45% to 55%.
Further, the SOFC 13 is provided with various sensors such as a differential pressure sensor 90 (see FIG. 1) that measures the differential pressure between the fuel pole 13A and the air pole 13B. The measured values of the various sensors 90 and 92 provided at each part of the SOFC 13 are transmitted to the control device 60.

Further, the power generation system 10 is provided with an outside air temperature sensor 94 (see FIG. 1) that measures the outside air temperature around the SOFC 13. In the present embodiment, the outside air temperature sensor 94 is provided near the suction port of the compressor 21 of the MGT 11 and measures the temperature of the air A sucked by the compressor 21. The measured value of the outside air temperature sensor 94 is transmitted to the control device 60.

Further, the power generation system 10 includes a temperature sensor (not shown) that measures the air temperature (inlet air temperature) supplied to the SOFC 13 through the second air supply line 31, and the exhaust gas L3 that circulates in the fuel gas recirculation line 49. A temperature sensor (not shown) or the like for measuring the temperature of the air is provided. The measured value of each temperature sensor is transmitted to the control device 60.

The control device 60 acquires measured values from various sensors, opening degree information of each shutoff valve, and the like, performs calculations based on the acquired information, and controls the operation of each part of the power generation system 10.

[How to operate the power generation system]
Next, in the power generation system 10 having the above configuration, the control executed by the control device 60 will be briefly described.

At the time of starting the power generation system 10, the control device 60 first starts the MGT 11, stabilizes the output of the MGT 11 with a certain load, and then supplies a part of the air supplied from the compressor 21 to the SOFC 13. Then, the air electrode 13B of the SOFC 13 can be pressurized. Further, the fuel electrode 13A is pressurized by using a mixed gas or the like in which a reducing gas such as H ₂ is added to an inert gas such as N ₂ until the temperature rises to a predetermined temperature at which the reforming reaction of the fuel gas is possible. I can go. Further, the temperature of the air A1 supplied to the air electrode 13B of the SOFC 13 is raised to 300 to 500 ° C. by the heat exchanger 58, and the air electrode is such that the combustion reaction of the fuel gas L2 added to the air A1 occurs. The temperature of the power generation chamber 215 can be raised to a temperature at which 13B functions as a catalyst.
When the SOFC 13 is pressurized to a predetermined pressure, the shutoff valve 38 is opened, the SOFC 13 and the MGT 11 are connected, and the state shifts to a combined state in which air is supplied to the combustor 22 of the MGT 11 via the SOFC 13.

After the transition to the combined state, the air flow rate supplied to the SOFC 13 to raise the temperature of the SOFC 13 is increased, and the air flow rate supplied to the combustor 22 by bypassing the SOFC 13 is decreased. Then, until the SOFC 13 starts power generation after a certain period of time, the total amount of the air A can be controlled to be supplied to the combustor 22 via the SOFC 13, and the SOFC 13 can be heated at a uniform temperature as quickly as possible. You may do so.

Next, the control device 60 according to the embodiment of the present invention will be described with reference to the drawings.
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. 5 is a functional block diagram showing an expanded function of the control device 60 according to the present embodiment. As shown in FIG. 5, the control device 60 includes an SOFC control device 60a for controlling the SOFC 13 and an MGT control device 60b for controlling the MGT 11. Information can be exchanged between the SOFC control device 60a and the MGT control device 60b.

When the SOFC 13 is started, the SOFC control device 60a executes the first temperature rise mode, the second temperature rise mode, and the load rise mode in order to raise the power generation chamber temperature to the rated temperature and raise the load to the target load. ..

First, in the first temperature raising mode, the temperature of the power generation chamber 215 is raised by supplying the air A1 heated by the heat exchange by the heat exchanger 58 to the air electrode 13B. When the temperature of the power generation chamber reaches the first temperature threshold value Tth1 by the first temperature raising mode, the first temperature rising mode is switched to the second temperature rising mode. Here, the first temperature threshold is a temperature at which the air electrode 13B functions as a catalyst for the combustion reaction with the fuel gas L2 as a flammable gas, and is set, for example, in the range of about 400 ° C. to 450 ° C. There is.

In the second temperature rising mode, the air A1 is supplied to the air electrode 13B as in the first temperature rising mode, and the fuel gas L2 is added to the air A1 by the air electrode fuel supply line 80 by opening the control valve 82. .. In the air electrode 13B into which the air A1 and the fuel gas L2 have flowed in, the fuel gas L2 is catalytically burned on the air electrode 13B by the catalytic action of the air electrode 13B, and combustion heat is generated. In this way, in the second temperature rising mode, the temperature of the power generation chamber is raised by using the heat generated by the catalyst combustion.
In the second temperature rising mode, the SOFC control device 60a controls the flow rate of the fuel gas L2 so that the temperature change rate of the power generation chamber temperature does not exceed the upper limit value. Further, the SOFC control device 60a controls the inlet temperature of the air A1 supplied to the air electrode 13B of the SOFC 13 by the control valve 66 of the bypass line 62 according to the temperature of the power generation chamber.
When the power generation chamber temperature reaches the second temperature threshold value Tth2, the SOFC control device 60a switches from the second temperature rise mode to the load increase mode.

In the load increase mode, it is possible to raise the temperature of the power generation room only by self-heating due to the power generation during the load increase, but since it takes a long time to raise the temperature, the air electrode is the same as in the first temperature rise mode. Air A1 is supplied to 13B, and fuel gas L2 and pure water supply line 44 supply pure water from the second fuel gas supply line 41 to the fuel electrode 13A to start power generation. In the load increase mode, the temperature of the power generation chamber is raised by the heat generated by the catalyst combustion by supplying the fuel gas L2 to the air electrode 13B and the heat generated by both the power generation. In the load increase mode, after the temperature of the power generation room of the SOFC 13 rises until the temperature can be maintained by self-heating due to power generation, the supply amount of the fuel gas L2 supplied to the air electrode 13B is gradually reduced. The supply of the fuel gas L2 to the air electrode 13B is controlled to be zero at the same time when the load is reached. Further, in the load increase mode, the temperature of the power generation chamber rises due to the catalytic combustion of the air electrode and the heat generated by applying a load to the SOFC 13, but the temperature of the power generation chamber rises later than the load rise.

The second temperature threshold value Tth2 is set to, for example, 750 ° C. or higher. This is because if the fuel gas L2 is charged to the fuel electrode 13A side when the fuel cell 105 has not reached a sufficient temperature, the fuel cell when the solid electrolyte 111 (see FIG. 2) is in a high resistance state. This is because the 105 is generated to generate power, and the electrode constituent material is structurally changed and deteriorated, which causes a deterioration in the performance of the fuel cell 105. If the power generation chamber temperature is 750 ° C. or higher, the performance deterioration of the fuel cell 105 as described above is unlikely to occur. Therefore, the second temperature threshold value Tth2 is preferably set to around 750 ° C.
In the load increase mode, when the power generation room temperature reaches the power generation room target temperature Ttag and the load reaches the target load such as the rated load, the start-up is completed. The target temperature Ttag of the power generation room is equal to or higher than the temperature at which the SOFC 13 can maintain the temperature by self-heating due to heat generated by power generation, and is set at, for example, 800 to 950 ° C.

Next, the control at startup executed by the SOFC control device 60a will be specifically described with reference to the drawings. Here, the load increase mode, which is a feature of the present invention, will be described in particular.

FIG. 6 is a functional block diagram showing the functions of the SOFC control device 60a according to the embodiment of the present invention in the load increase mode.
As shown in FIG. 6, the SOFC control device 60a includes a target load setting unit 51, an output current command setting unit 52, a control command setting unit 53, a control command correction unit 5, and a control unit 54.

The target load setting unit 51 has target load information in which the outside air temperature and the target load (= target output current) of the SOFC 13 are associated with each other. The target load setting unit 51 acquires the value of the target load corresponding to the outside air temperature measured by the outside air temperature sensor 94 from the target load information and sets it as the target load.
FIG. 7 is a diagram showing an example of target load information. In FIG. 7, the horizontal axis represents the outside air temperature, and the vertical axis represents the target load (= target output current). The target load information is, for example, created in advance based on the results of a simulation or an actual machine test, and is supplied to the air electrode 13B when the valve opening of the control valve 64 or the like is fully opened. When the flow rate of the air A1 is set to the maximum, the value of the maximum load (maximum current) that the SOFC 13 can output is set in association with the outside air temperature. When the valve opening degree of the control valve 64 or the like is the same, in other words, when the flow rate is the same but the outside air temperature is different, the amount of air supplied to the power generation chamber 215 of the SOFC 13 changes because the air density changes. For example, when the outside air temperature is low, the air density becomes high, and the discharge air flow rate of the compressor 21 of the MGT 11 increases. Since the air A1 supplied to the power generation chamber 215 functions as a coolant, the larger the amount of air, the larger the maximum load that the SOFC 13 can output. For this reason, as shown in FIG. 7, the target load information has a characteristic that the lower the outside air temperature, the larger the target load.

Further, as shown by the dotted line in FIG. 7, the target load information may have a predetermined margin with respect to the target load determined from the outside air temperature. When the temperature of the power generation chamber changes due to a change in the load of the SOFC 13, the temperature of the power generation chamber may have a temperature distribution. By providing a predetermined margin in this way, it is possible to prevent the temperature of a part of the power generation chamber from exceeding the temperature upper limit value determined from the heat resistant temperature of some members of the SOFC 13 as much as possible. .. In the present embodiment, the margin here is set in the range of about 0.5% or less with respect to the target load (= target output current), for example. If the margin exceeds 0.5% and further exceeds 1%, the current value reached with respect to the target load (= target output current) decreases, which is not preferable because it deviates from the purpose of increasing the output of SOFC13 as much as possible. .. Further, if it is less than 0.1%, it is not preferable because it falls within the control error range of a flow control device (mass flow controller, etc.) and does not have a substantial margin.

The output current command setting unit 52 sets the output current command at a predetermined repetition time interval at a predetermined current change rate based on the target output current determined from the target load. If the current change rate is not provided, the current changes instantaneously, the response of each control amount cannot be followed, and the fuel gas temporarily becomes excessive or deficient. As a result, the operation of the power generation system 10 may become unstable, or the SOFC cartridge 203 may be damaged. Here, the current change rate indicates the gradient of the current change amount (current increase amount) per hour. The predetermined repetition time interval is the time required to sequentially execute a series of control processing steps and perform a step of determining whether or not the output current command has reached the target current. For example, if the target output current is set to 90% of the rated current and the current change rate is set to 5% / min of the rated current, the output current command after 10 minutes becomes 50% of the rated current, which takes about 18 minutes. The load will be increased to the target output current.
The predetermined current change rate may be changed according to the difference between the output current value and the target output current. For example, when the difference is large, the output current command may be set with a relatively large current change rate, and the current change rate may be set to decrease as the difference becomes smaller. By changing the current change rate in this way, it is possible to shorten the time required to reach the target output current and suppress overshoot of the temperature of the power generation chamber.

The control command setting unit 53 sets a plurality of control system control commands for changing the load of the SOFC 13 by using the output current command set by the output current command setting unit 52. Here, the control commands are not issued after the individual control commands are issued and the changes in the output current and the temperature of the power generation chamber, which are the control amounts, are stabilized, and then the next control command is issued, but the control commands are issued almost at the same time. For example, the control command setting unit 53 sets the fuel gas flow rate setting unit 53a for setting the flow rate command of the fuel gas L2 supplied to the fuel electrode 13A, and the inlet air temperature setting for setting the inlet temperature command for the air A1 supplied to the air electrode 13B. Section 53b, MGT output setting section 53c that sets the MGT output command, differential pressure setting section 53d that sets the differential pressure command between the fuel pole 13A and the air pole 13B, and the recirculation flow rate that sets the rotation speed command of the recirculation blower 50. It includes a setting unit 53e and a pure water flow rate setting unit 53f for setting a flow rate command of pure water to be supplied to the fuel electrode 13A.

As shown in FIG. 8, for example, the fuel gas flow rate setting unit 53a has fuel gas flow rate information in which the output current command and the flow rate of the fuel gas L2 are associated with each other, and the fuel gas flow rate information is changed to the output current command. The flow rate of the corresponding fuel gas L2 is acquired, and the acquired flow rate of the fuel gas L2 is set as the fuel gas flow rate command.
As shown in FIG. 9, the inlet air temperature setting unit 53b has inlet air temperature information in which the output current command and the inlet air temperature of the SOFC 13 to the air electrode 13B are associated with each other, and the inlet air temperature information. The inlet air temperature corresponding to the output current command is acquired from, and the acquired inlet air temperature information is set as the inlet air temperature command.

As shown in FIG. 10, the MGT output setting unit 53c has MGT output information in which the output current command and the MGT output are associated with each other, and acquires the MGT output corresponding to the output current command from the MGT output information. Then, the acquired MGT output is set as the MGT output command. Here, the MGT output information may be set according to the outside air temperature taken in by the compressor 21 of the MGT 11. The outside air temperature is measured by, for example, the outside air temperature sensor 94. For example, the MGT output information is set so that the MGT output for the same output current command increases as the intake outside air temperature decreases. This is because the lower the outside air temperature, the higher the flow rate of the air A blown by the compressor 21, and the more the flow rate of the combustion gas G from the combustor 22 can be increased.

For example, as shown in FIG. 11, the differential pressure setting unit 53d has differential pressure information in which the output current command and the fuel air differential pressure, which is the differential pressure between the fuel pole 13A and the air pole 13B, are associated with each other. The fuel air differential pressure corresponding to the output current command is acquired from the differential pressure information, and the acquired fuel air differential pressure is set as the fuel air differential pressure command.
As shown in FIG. 12, for example, the recirculation flow rate setting unit 53e has rotation speed information associated with the output current command and the blower rotation speed, and discharges the fuel gas recirculation line 49 according to the blower rotation speed. The flow rate for recirculating a part of the fuel gas L3 is controlled. The rotation speed corresponding to the output current command is acquired from the rotation speed information, and the acquired blower rotation speed is set as the blower rotation speed command. Here, the rotation speed information may be set according to the outside air temperature taken in by the MGT. For example, as shown in FIG. 7, the SOFC target load changes depending on the outside air temperature. When the outside air temperature becomes low, the SOFC target load rises, so that the air flow rate supplied to the SOFC increases and the pressure inside the system rises. As a result, the recirculation gas density increases, so when the outside air temperature is low, the blower rotation speed required to achieve the same recirculation flow rate as when the outside air temperature is high is set to be low.

As shown in FIG. 13, the pure water flow rate setting unit 53f has, for example, pure water flow rate information in which the output current command and the pure water flow rate are associated with each other, and corresponds to the output current command from the pure water flow rate information. Acquire the pure water flow rate value and set the acquired pure water flow rate as the pure water flow rate command. Since the SOFC load increases as the output current increases, the supply amount of steam required for reforming supplied from the fuel gas recirculation line 49 increases, and the pure water flow rate required to be supplied from the outside decreases. To do. Further, when the output current is equal to or higher than the predetermined SOFC load, all the steam required for reforming is supplied from the fuel gas recirculation line 49, so that the supply of pure water becomes unnecessary.

Various control commands set by the control command setting unit 53 are input to the control command correction unit 5. The control command correction unit 5 includes a fuel gas flow command correction unit 5a that corrects the fuel gas flow command set by the fuel gas flow setting unit 53a in an increasing direction, and a fuel air differential pressure command set by the differential pressure setting unit 53d. It is provided with a differential pressure command correction unit 5d that corrects in the direction of decreasing.

For example, as shown by the dotted line in FIG. 14, the fuel gas flow rate command correction unit 5a makes a correction by adding a predetermined correction value α to the fuel gas flow rate command set by the fuel gas flow rate setting unit 53a, and after the correction, The fuel gas flow rate command is output to the control unit 54. Here, the correction value α is set to a value corresponding to the response delay of the control system of the control valve 42. Further, the fuel gas flow rate command correction unit 5a gradually lowers the correction value α toward zero after the output current command reaches the target output current. As a result, the reduction atmosphere of the fuel electrode 13A is lowered due to the lack of fuel gas, and the deterioration of the fuel electrode 13A is prevented from occurring.

For example, as shown by the dotted line in FIG. 15, the differential pressure command correction unit 5d makes a correction by subtracting a predetermined correction value β from the fuel air differential pressure command set by the differential pressure setting unit 53d, and the corrected fuel. The air differential pressure command is output to the control unit 54. Here, the correction value β is set to a value corresponding to the response delay of the control system of the control valve 47 that adjusts the differential pressure. Further, the differential pressure command correction unit 5d sets the correction value β to zero from a predetermined time before reaching the target output current so that the correction value β becomes zero when the output current command reaches the target output current. Gradually lower towards. As a result, the period during which the fuel air differential pressure makes the correction value β content small and strict is minimized, and the period required for stabilizing the fuel air differential pressure control system is reduced.

As shown in FIG. 16, the control unit 54 includes a fuel gas flow rate control unit 54a, an inlet air temperature control unit 54b, an MGT output control unit 54c, a differential pressure control unit 54d, a recirculation flow rate control unit 54e, and a pure water flow rate control unit. It has 54f.
The fuel gas flow rate control unit 54a adjusts the amount of fuel gas supplied to the fuel electrode 13A by controlling the valve opening degree of the control valve 42 based on the fuel gas flow rate command corrected by the fuel gas flow rate command correction unit 5a. To do.
The inlet air temperature control unit 54b adjusts the valve opening degrees of the control valves 64 and 66 based on the inlet air temperature command from the inlet air temperature setting unit 53b, so that the inlet temperature of the air A1 supplied to the air electrode 13B is adjusted. To control.
The MGT output control unit 54c controls the MGT output mainly by adjusting the valve openings of the control valve 65 and the control valve 70 based on the MGT output command from the MGT output setting unit 53c.

The differential pressure control unit 54d adjusts the opening degree of the control valve 47 based on the fuel air differential pressure command corrected by the differential pressure command correction unit 5d, so that the fuel electrode 13A side is within a predetermined range from the air electrode 13B side. The fuel air differential pressure in the power generation chamber 215 is controlled so as to increase at (for example, 0.1 to 1 kPa).
The recirculation flow rate control unit 54e controls the amount of exhaust fuel gas supplied to the fuel electrode 13A by controlling the rotation speed of the recirculation blower 50 based on the blower rotation speed command from the recirculation flow rate setting unit 53e.
The pure water flow rate control unit 54f controls the amount of pure water supplied to the fuel electrode 13A by adjusting the discharge flow rate of the pump 48 based on the pure water flow rate command from the pure water flow rate setting unit 53f.

For at least two control systems of the fuel gas flow rate control unit 54a, the inlet air temperature control unit 54b, the MGT output control unit 54c, the differential pressure control unit 54d, the recirculation flow rate control unit 54e, and the pure water flow rate control unit 54f. Is issued a control command almost at the same time. For example, by performing feedback control or feedforward control based on each input command, control is performed to match various control amounts with the control command. For example, various manipulated variables in the control commands of various control systems may be created in advance based on the results of a simulation or an actual machine test using the characteristics shown in FIGS. 8 to 13. By doing so, even if control commands are issued to a plurality of control systems almost at the same time, each control amount stably approaches the command value under appropriate control, and the temperature of the power generation room of SOFC 13 and the like. It is possible to stably approach the load (output current) to the target value. The various control quantities in the control commands of the various controls are created in advance based on the results of simulation or actual machine operation test of command settings as shown in FIGS. 8 to 13. Therefore, even if control commands are issued almost at the same time, all the controlled quantities stably approach the command values under appropriate control, and the SOFC13 power generation chamber temperature and load (output current) are stabilized at the target values. It is possible to bring it closer.

FIG. 17 shows a schematic configuration of the differential pressure control unit 54d. The differential pressure control unit 54d includes, for example, a feedback control unit 55a, a feedforward control unit 55b, and an addition unit 55c as main configurations. The feedback control unit 55a performs PID control on the outputs of the difference calculation unit 551 and the difference calculation unit 551 that calculate the difference between the fuel air differential pressure command and the measurement differential pressure measured by the differential pressure sensor 90, and provides feedback control. It includes a PID control unit 552 that outputs a value and a gain adjustment unit 553 that adjusts the gain of the PID control unit 552. The feedforward control unit 55b calculates and outputs a feedforward control value from the fuel air differential pressure command and a preset function or the like.

The feedback control value output from the feedback control unit 55a and the feedforward control value output from the feedforward control unit 55b are added by the addition unit 55c to generate a differential pressure control value. By controlling the valve opening degree of the control valve 47 that adjusts the differential pressure based on this differential pressure control value, the fuel air differential pressure, which is the differential pressure between the fuel electrode 13A side and the air electrode 13B side of the SOFC 13, is adjusted. Will be done.

In order to stably control the control valve 47 that adjusts the differential pressure, it is necessary to prevent the valve opening degree of the control valve 47 from changing significantly. Therefore, during normal operation, the parameters of the PID control unit 552 of the feedback control unit 55a are set to be small.
The gain adjusting unit 553 increases the gain of the PID control unit 552 when the load of the SOFC 13 changes. The gain adjusting unit 553 increases, for example, at least one of proportional gain, integrated gain, and differential gain. At this time, the gain adjusting unit 553 may change the gain correction value γ according to the output current command set by the output current command setting unit 52 (see FIG. 6). For example, when the load rises, the operating state of the SOFC 13 changes when the temperature of the power generation chamber is raised from the time of starting. For example, as the modes are changed in the order of the first temperature rise mode, the second temperature rise mode, and the load rise mode, the types of gas supplied to the fuel electrode 13A are also nitrogen (or nitrogen + hydrogen) and nitrogen +. It changes to pure water (or nitrogen + hydrogen + pure water), fuel gas L2 + pure water (+ hydrogen), and fuel gas L2.

In this way, by changing the type of gas supplied to the fuel electrode 13A, the fuel consumption inside the SOFC 13 changes, and the composition of the exhaust fuel gas L3 flowing through the fuel gas recirculation line 49 changes. go. Then, since the change in the composition of the exhaust fuel gas L3 affects the sensitivity of the control valve 47, the sensitivity (gain) of the control valve 47 is changed to the composition of the exhaust fuel gas L3 according to the operating state of the SOFC 13. It needs to be adjusted accordingly.
For example, the gain adjusting unit 553 of the control valve 47 is based on the gas composition of the exhaust fuel gas L3 preset according to the operating state of the SOFC 13 or the gas composition of the exhaust fuel gas L3 calculated from the measured values of various flow rates. The gain correction value γ is set in consideration of the followability.

Specifically, the fuel consumption in the SOFC 13 changes according to the load increase of the SOFC 13, and the composition of the exhaust fuel gas L3 changes accordingly. Therefore, the gain correction value of the control valve 47 changes according to the load increase. Decrease γ. Further, since the temperature of the power generation chamber also rises as the load increases, the gain may be set according to the temperature of the power generation chamber. Further, the CV value of the control valve 47 also changes due to the change in the gas composition of the exhaust fuel gas L3. In order to cope with this, the gain correction value γ may be gradually lowered according to the output current command. This makes it possible to prevent hunting of the differential pressure control valve and realize a stable load increase.
Further, the gain correction value γ may be set in consideration of the current change rate. As the current change rate increases, the rate of change of the fuel air differential pressure also increases, so that the response delay of the control valve 47 to this change can be suppressed.

Next, the control in the load increase mode executed by the SOFC control device 60a will be described with reference to FIG. FIG. 18 is a flowchart showing a control procedure in the load increase mode. The load increase mode is a control mode that is started when the temperature of the power generation chamber reaches the second temperature threshold value Tth2 in the second temperature rise mode described above.
First, the target load setting unit 51 sets the target load (= target output current) from the target load information shown in FIG. 7 based on the outside air temperature (step SA1). Subsequently, the output current command setting unit 52 sets the output current command from the target output current corresponding to the target load using a predetermined current change rate (for example, 5% / min of the rated current) (step SA2). ). Here, the predetermined current change rate may change according to the output current command.

Subsequently, the control command setting unit 53 sets the control command of each control system based on the output current command (step SA3), and the control command correction unit 5 corrects the fuel gas flow rate command and the fuel air differential pressure command. (Step SA4). Then, the control of each control system is performed at approximately the same time based on the corrected fuel gas flow rate command, fuel air differential pressure command, and other control commands set by the control command setting unit 53 (step SA5). ). As a result, the control amount of various control systems changes toward the target load at about the same time. Subsequently, it is determined whether or not the output current command is equal to or greater than the target output current corresponding to the target load (step SA6). As a result, if the output current command is less than the target output current (“NO” in step SA6), the process returns to step SA2 after a predetermined time elapses, the output current command based on the target load is set again, and the newly set output is output. Subsequent steps are performed sequentially based on the current command.
The determination in step SA6 is performed at predetermined repetition time intervals, and the setting of the output current command from the target output current corresponding to the target load is also performed at predetermined repetition time intervals. As a result, control commands of various control systems are appropriately executed at predetermined repetition time intervals, and based on this, control of each control system can be performed at approximately the same time, and the time until each control amount stabilizes. Can be shortened. Here, the predetermined repetition time interval is the time required to execute the control of each process from step SA2 to step SA6.

By repeating steps SA2 to SA6 in this way, the output current command gradually changes toward the target output current, and when the output current command reaches the target output current, it is determined as "YES" in step SA6. , End this process. After the output current command reaches the target output current, for example, control is performed to maintain the output current of the SOFC 13 at the target output current.

As described above, according to the fuel cell control device and control method and the power generation system according to the present embodiment, the fuel gas flow rate command correction unit 5a for correcting the fuel gas flow rate command in the increasing direction is provided in the load increase mode. Therefore, it is possible to avoid a situation in which fuel gas is depleted due to a change in each controlled amount when the load increases. This makes it possible to avoid damage to the equipment due to lack of fuel gas.
Further, in the load increase mode, the differential pressure command correction unit 5d for correcting the fuel air differential pressure in the decreasing direction is provided, so that the operation is performed on the safe side so that the differential pressure does not temporarily increase due to each control fluctuation due to the load change. It becomes possible to make it. This makes it possible to avoid damage to the equipment.

Further, the differential pressure control valve 47 that controls the fuel air differential pressure performs stable operation by setting the parameter of the PID control unit 552 of the feedback control unit 55a to be small during normal operation, and increases the control gain when the load changes. Since the gain adjusting unit 553 is provided, the differential pressure adjusting speed can be increased, and the follow-up delay of the differential pressure control valve can be reduced. Further, by reducing the gain increase range in response to the increase in the output current command, it is possible to prevent hunting of the differential pressure control valve and realize a stable load increase.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention, for example, by partially or wholly combining the above-described embodiments. Is.

5: Control command correction unit 5a: Fuel gas flow rate command correction unit 5d: Differential pressure command correction unit 10: Power generation system 13A: Fuel pole 13B: Air pole 49: Fuel gas recirculation line 51: Target load setting unit 52: Output current Command setting unit 53: Control command setting unit 53a: Fuel gas flow rate setting unit 53b: Inlet air temperature setting unit 53c: MGT output setting unit 53d: Differential pressure setting unit 53e: Recirculation flow rate setting unit 53f: Pure water flow rate setting unit 54 : Control unit 54a: Fuel gas flow rate control unit 54b: Inlet air temperature control unit 54c: MGT output control unit 54d: Differential pressure control unit 54e: Recirculation flow rate control unit 54f: Pure water flow rate control unit 55a: Feedback control unit 55b: Feed forward control unit 55c: Addition unit 60: Control device 60a: SOFC control device 90: Differential pressure sensor 92: Temperature sensor 94: Outside air temperature sensor 101: Cell stack 103: Base tube 105: Fuel cell 111: Solid oxide 201: SOFC module 203: SOFC cartridge 551: Difference calculation unit 552: PID control unit 553: Gain adjustment unit

Claims (12)

A fuel cell control device 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 target load setting unit that sets the target load of the fuel cell,
An output current command setting unit that sets an output current command of the fuel cell from the target load of the fuel cell set by the target load setting unit at predetermined repetition time intervals, and an output current command setting unit.
A control command setting unit that sets control commands for a plurality of control systems using the output current command of the fuel cell, and a control command setting unit.
A control command correction unit that increases or decreases at least one control command set by the control command setting unit,
A control unit that controls at least one operation amount of the control system based on the control command corrected by the control command correction unit is provided.
The control unit includes a gain adjusting unit that changes at least one gain of the control system according to the operating state of the fuel cell when the load of the fuel cell changes .
Wherein the control command correcting unit, at the time of load increase of the fuel cell, Ru with the differential pressure command correction unit that reduces a predetermined amount of fuel differential air pressure command for controlling the pressure difference between the air electrode and the fuel electrode Fuel cell control device. A fuel cell control device 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 target load setting unit that sets the target load of the fuel cell,
An output current command setting unit that sets an output current command of the fuel cell from the target load of the fuel cell set by the target load setting unit at predetermined repetition time intervals, and an output current command setting unit.
A control command setting unit that sets control commands for a plurality of control systems using the output current command of the fuel cell, and a control command setting unit.
A control command correction unit that increases or decreases at least one control command set by the control command setting unit,
A control unit that controls at least one operation amount of the control system based on the control command corrected by the control command correction unit.
With
The control unit includes a gain adjusting unit that changes at least one gain of the control system according to the operating state of the fuel cell when the load of the fuel cell changes.
The target load setting unit, the control device of the fuel cell from the outside air temperature around to set the target load of the fuel cell of the fuel cell. The fuel cell control device according to claim 1 or 2 , wherein the gain adjusting unit changes at least one gain of the control system according to a gas type of exhaust fuel gas that changes depending on the operating state of the fuel cell. The fuel cell control according to any one of claims 1 to 3, wherein the control unit sets at least one of the control commands by using at least one of proportional control, integral control, and differential control. apparatus. The fuel cell control device according to any one of claims 1 to 4 , wherein the gain adjusting unit increases the gain of a differential pressure control valve for adjusting the differential pressure between the air electrode and the fuel electrode. The fuel cell control device according to any one of claims 1 to 5 , wherein the gain adjusting unit reduces the gain increase range in response to an increase in the output current command of the fuel cell. The control command correction unit is a flammable gas flow rate command correction unit that increases a flammable gas flow rate command for controlling the flow rate of the flammable gas supplied to the fuel electrode by a predetermined amount when the load of the fuel cell increases. The fuel cell control device according to any one of claims 1 to 6. The fuel cell control device according to any one of claims 1 to 7 , wherein the fuel cell is a solid oxide fuel cell. Any one of claims 1 to 8 , wherein the output current command setting unit sets an output current command of the fuel cell from the target load of the fuel cell at a predetermined repeating time interval using a predetermined current change rate. The fuel cell control device described in. A fuel cell having a power generation chamber in which a plurality of power generation cells having a fuel electrode, a solid electrolyte, and an air electrode having oxidation catalytic performance are arranged, and a fuel cell.
A power generation system including the fuel cell control device according to any one of claims 1 to 9 . A method for controlling a fuel cell having a power generation chamber in which a plurality of power generation cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged.
The target load setting process for setting the target load of the fuel cell and
An output current command setting step of setting the output current command of the fuel cell from the target load of the fuel cell at predetermined repeating time intervals, and
A control command setting process for setting control commands for a plurality of control systems using the output current command of the fuel cell, and
A control command correction step of increasing or decreasing at least one control command set in the control command setting step, and a control command correction step.
It has a control step of controlling at least one operation amount of the control system based on the control command corrected by the control command correction step.
In the control step, when the load of the fuel cell changes, at least one gain of the control system is changed according to the operating state of the fuel cell .
The control command correction step is a fuel cell control method including a step of reducing a fuel air differential pressure command for controlling the differential pressure between the air electrode and the fuel electrode by a predetermined amount when the load of the fuel cell is increased. .. A method for controlling a fuel cell having a power generation chamber in which a plurality of power generation cells including a fuel electrode, a solid electrolyte, and an air electrode are arranged.
The target load setting process for setting the target load of the fuel cell and
An output current command setting process for setting the output current command of the fuel cell from the target load of the fuel cell at predetermined repeating time intervals, and an output current command setting process.
A control command setting process for setting control commands for a plurality of control systems using the output current command of the fuel cell, and
A control command correction step of increasing or decreasing at least one control command set in the control command setting step, and a control command correction step.
A control step that controls at least one operation amount of the control system based on the control command corrected by the control command correction step.
Have,
In the control step, when the load of the fuel cell changes, at least one gain of the control system is changed according to the operating state of the fuel cell.
The target load setting step is a fuel cell control method for setting a target load of the fuel cell from the outside air temperature around the fuel cell.

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