JP4263401B2 - Fuel cell power generation system and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generation system and a control method thereof.
[0002]
[Prior art]
Conventionally, a fuel cell power generation system of this type has been proposed that converts DC power from a fuel cell into AC power identical to that of a commercial power supply and supplies it to an auxiliary machine driven by AC power (for example, (Kaihei 8-315842). In this system, the output terminal of the fuel cell is connected to the power line from the commercial power source to the load and the auxiliary machine used for the operation of the fuel cell via the inverter, and the auxiliary machine using the AC power converted by the inverter. Is driving.
[0003]
[Problems to be solved by the invention]
However, in such a fuel cell power generation system, the efficiency of the entire system may be reduced. Since electric power generated by the fuel cell is used to supply power to the auxiliary machine used to operate the fuel cell, it is necessary to perform DC / AC conversion in order to supply power to the auxiliary machine driven by AC power. The efficiency of the entire system is reduced along with the conversion efficiency by the DC / AC conversion.
[0004]
One object of the fuel cell power generation system and the control method thereof according to the present invention is to improve the efficiency of the entire system. Another object of the fuel cell power generation system and control method thereof according to the present invention is to stably operate the fuel cell.
[0005]
[Means for solving the problems and their functions and effects]
The fuel cell power generation system and the control method thereof according to the present invention employ the following means in order to achieve at least a part of the above object.
[0006]
The fuel cell power generation system of the present invention comprises:
A fuel cell power generation system including a fuel cell that generates power by receiving fuel supply,
A DC / DC converter for load connected to the output terminal of the fuel cell and an inverter connected to the DC / DC converter for load, and using DC power from the fuel cell to a load from another system power source Power supply means for other systems capable of supplying power to the power supply line of
A fuel constituted by an auxiliary DC / DC converter connected to a power line between the fuel cell and the load DC / DC converter, and driven by a predetermined DC power using the DC power from the fuel cell. Auxiliary power supply means for supplying the predetermined DC power to the auxiliary machine for the battery power generation system;
Current detection means for detecting an output current from the fuel cell;
The auxiliary power supply means is controlled so that the auxiliary-side voltage of the auxiliary DC / DC converter is maintained at a predetermined voltage, and the output current detected by the current detection means is output from the fuel cell. Power supply control means for controlling the power supply means for the other system so that power is supplied to the power supply line as a current within a predetermined range from the target current to be
It is a summary to provide.
[0007]
In the fuel cell power generation system of the present invention, the predetermined DC power is supplied to an auxiliary machine for the fuel cell power generation system driven by the predetermined DC power using the DC power from the fuel cell. Therefore, since DC / AC conversion is not required for power supply to the auxiliary machine, the efficiency of the entire system can be improved as compared with a system that requires DC / AC conversion. Of course, it is possible to supply power to the power supply line from the other system power source to the load using the DC power from the fuel cell. Here, “auxiliary equipment” includes equipment necessary for system operation.
[0010]
The fuel cell power generation system of the present invention may include a reforming unit that reforms a hydrocarbon-based fuel into a hydrogen-rich fuel and supplies the fuel as fuel supplied to the fuel cell. If it carries out like this, it can generate electric power using hydrocarbon fuel. In this aspect of the fuel cell power generation system of the present invention, the hydrocarbon fuel may be city gas or propane gas. In this way, the fuel cell system can be made suitable for installation in a general household.
[0011]
The fuel cell power generation system according to the present invention may include a hot water storage unit that stores at least water that is heated using heat from the fuel cell. In this way, since the heat from the fuel cell can be used, the energy efficiency of the system can be improved. Of course, heat other than the heat from the fuel cell may be used.
[0012]
The control method of the fuel cell power generation system of the present invention includes:
A fuel cell that generates power upon supply of fuel; a load DC / DC converter connected to the output terminal of the fuel cell; and an inverter connected to the load DC / DC converter. Connected to the power line between the fuel cell and the load DC / DC converter, and the power supply means for the other system capable of supplying power to the power supply line from the other system power supply to the load using DC power Auxiliary power supply for supplying a predetermined DC power to an auxiliary machine for a fuel cell power generation system configured by a DC / DC converter for an auxiliary machine and driven by a predetermined DC power using the DC power from the fuel cell A fuel cell power generation system control method comprising:
(A) detecting an output current from the fuel cell;
(B) The auxiliary power supply means is controlled so that the auxiliary side voltage of the auxiliary DC / DC converter is maintained at a predetermined voltage, and the output current detected by the current detection means is the fuel. The gist is to control the power supply means for the other system so that power is supplied to the power supply line from a target current to be output from the battery within a predetermined range .
[0013]
According to the control method of the fuel cell power generation system of the present invention, since direct current alternating current conversion is not performed for supplying power to the auxiliary machine, the efficiency of the entire system can be improved as compared with the case of performing direct current alternating current conversion. . Further, since the output current from the fuel cell is controlled to be stabilized at the target current, the operating state of the fuel cell can be maintained in a stable state. Of course, it is possible to supply power to the power supply line from the other system power source to the load using the DC power from the fuel cell. Here, “auxiliary equipment” includes equipment necessary for system operation.
[0014]
In the control method of the fuel cell power generation system according to the present invention, the step (b) includes the step of supplying the predetermined DC power to the auxiliary machine by the auxiliary machine power supply unit by the other system power supply unit. It may be a step of controlling to give priority to the supply of power to the power supply line. In this way, since the power supply to the auxiliary machine is given priority, the system can be operated stably.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described using examples. FIG. 1 is a configuration diagram showing an outline of the configuration of a fuel cell power generation system 20 according to an embodiment of the present invention. As shown in the figure, the fuel cell power generation system 20 of the embodiment includes a reformer 30 that receives supply of city gas (13A) from a gas pipe 22 and reforms the city gas into hydrogen-rich reformed gas, and a reformer. A CO selective oxidation unit 34 that reduces carbon monoxide in the gas and uses it as a fuel gas, a fuel cell 40 that receives supply of the fuel gas and air, and generates power by an electrochemical reaction, and a cooling water and hot water storage for the fuel cell 40 A heat exchanger 42 that performs heat exchange with the low-temperature water in the tank 44, a DC / DC converter 52 for load that adjusts the voltage and current of the DC power from the fuel cell 40 and converts it into desired DC power, and The inverter 54 that supplies the power line 12 through the circuit breaker 55 to the AC power having the same phase as that of the commercial power supply 10 and supplies power from the commercial power supply 10 to the load 16 through the circuit breaker 14; Fuel cell 4 A DC / DC converter 56 for auxiliary equipment that converts DC power from the power into predetermined DC power to be supplied to the auxiliary equipment, a load power meter 58 that detects load power consumed by the load 16, and an electronic device that controls the entire system And a control unit 60.
[0016]
The reformer 30 has the following equation (1) based on city gas supplied from the gas pipe 22 through the control valve 24, the booster pump 26, and the desulfurizer 27 excluding sulfur, and water vapor supplied through a pipe (not shown). And the hydrogen-rich reformed gas is generated by the steam reforming reaction and shift reaction of the following formula (2). The reformer 30 is provided with a combustion section 32 that supplies heat necessary for such a reaction. The combustion section 32 is supplied with city gas from a gas pipe 22 through a control valve 24 and a booster pump 28. It has become so. Further, the exhaust gas on the anode side of the fuel cell 40 is supplied to the combustion unit 32 so that unreacted hydrogen in the anode off-gas can be used as fuel.
[0017]
[Expression 1]
CH ₄ + H ₂ O → CO + 3H ₂ (1)
CO + H ₂ O → CO ₂ + H ₂ (2)
[0018]
The CO selective oxidation unit 34 is modified by a carbon monoxide selective oxidation catalyst (for example, a catalyst made of an alloy of platinum and ruthenium) that receives supply of air from a pipe (not shown) and selects and oxidizes carbon monoxide in the presence of hydrogen. Carbon monoxide in the gas is selectively oxidized to obtain a hydrogen-rich fuel gas having a very low carbon monoxide concentration (about several ppm in the embodiment).
[0019]
The fuel cell 40 comprises a single cell comprising an electrolyte membrane, an anode electrode and a cathode electrode sandwiching the electrolyte membrane, a fuel gas and air to the anode electrode and the cathode electrode, and a separator that forms a partition between the cells. It is configured as a solid polymer fuel cell formed by stacking a plurality of layers, and generates power by an electrochemical reaction between hydrogen in the fuel gas from the CO selective oxidation unit 34 and oxygen in the air from the blower 41. The fuel cell 40 is formed with a circulating cooling water flow path, and is maintained at an appropriate temperature (in the embodiment, about 80 to 90 ° C.) by circulating the cooling water. A heat exchanger 42 is provided in the cooling water circulation flow path, and the low temperature water supplied from the hot water storage tank 44 by the pump 46 is heated by heat exchange with the cooling water of the fuel cell 40 so that the hot water storage tank. The hot water is stored in 44.
[0020]
An output terminal (not shown) of the fuel cell 40 is connected to the power line 12 from the commercial power supply 10 to the load 16 via a load DC / DC converter 52, an inverter 54, and a circuit breaker 55. The electric power is converted into AC power having the same phase as that of the commercial power supply 10, added to the AC power from the commercial power supply 10, and supplied to the load 16. Since the load DC / DC converter 52 and the inverter 54 are configured as a general DC / DC converter circuit and an inverter circuit, detailed description thereof is omitted. The load 16 is connected to the power line 12 via the circuit breaker 18.
[0021]
The output terminal of the fuel cell 40 is also connected to the auxiliary DC / DC converter 56 via the diode 51. The auxiliary DC / DC converter 56 is a predetermined auxiliary machine required for the operation of the fuel cell power generation system 20 such as the actuator of the control valve 24 driven by predetermined DC power, the booster pumps 26 and 28, the blower 41, and the pump 46. DC power is supplied.
[0022]
The electronic control unit 60 is configured as a microprocessor centered on the CPU 62. In addition to the CPU 62, a ROM 64 for storing processing programs, a RAM 66 for temporarily storing data, an input / output port and a communication port (not shown) Is provided. The electronic control unit 60 includes an output current i from a current sensor 50 attached to an output terminal of the fuel cell 40, an output current and voltage from a current sensor and voltage sensor (not shown) in the inverter 54, and a load wattmeter 58. Load power Po, each temperature from a temperature sensor (not shown) attached to the reformer 30, the CO selective oxidation unit 34, and the fuel cell 40 are input via an input port. In addition, the electronic control unit 60 provides drive signals to the actuator of the control valve 24, the boost pumps 26 and 28, the blower 41, the circulation pump 43, the pump 46, the load DC / DC converter 52, and the auxiliary DC / DC. A control signal to the converter 56, a switching control signal to the inverter 54, a drive signal to the circuit breaker 55, and the like are output via the output port.
[0023]
Next, the operation of the fuel cell power generation system 20 configured as described above, particularly the operation related to the operation of the system will be described. FIG. 2 is a flowchart illustrating an example of an operation control routine executed by the electronic control unit 60 of the embodiment. This routine is repeatedly executed every predetermined time (for example, every 8 msec) after the system is activated.
[0024]
When the operation control routine is executed, the CPU 62 of the electronic control unit 60 first determines whether or not the operation mode is being changed (step S100). The operation mode is set based on the power consumption of the load detected by the load wattmeter 58 by an operation mode setting routine (not shown). In the embodiment, the high mode of the high load, the mid mode of the medium load, It is set in any one of the three stages of the low load low mode and written to a predetermined address in the RAM 66. Note that the operation mode may be set based on the sum of the power consumption of the load and the power consumed by the auxiliary device for operating the system. Even when the operation mode is set, the operation state corresponding to the operation mode in which the reformer 30 or the fuel cell 40 is set cannot be immediately set. The change of the operation mode is performed by an operation control routine at the time of operation mode change (not shown). In this routine, whether or not to perform control in this routine is determined based on whether or not the operation mode is being changed. Therefore, when the operation mode is being changed, this routine is terminated without doing anything.
[0025]
When the operation mode is not being changed, that is, when the reformer 30 and the fuel cell 40 are operating in an operation state corresponding to the operation mode, the currently set operation mode is read from a predetermined address in the RAM 66. At the same time (step S102), a target current i * corresponding to the read operation mode is derived (step S104). The target current i * is set as the output current of the fuel cell 40 when the system can be operated efficiently when operated in the set operation mode. In the embodiment, the output current of the fuel cell 40 that allows the system to operate efficiently when operating in each operation mode by experiment or the like is obtained and stored in advance in the ROM 64 as a map, and when the operation mode is given, it corresponds from the map. The output current was derived as the target current i *.
[0026]
Next, the output current i of the fuel cell 40 is read from the current sensor 50 attached to the output terminal of the fuel cell 40 (step S106), and the deviation Δi is calculated by subtracting the read output current i from the target current i * ( In step S108, the calculated deviation Δi is compared with a positive / negative threshold value iref (step S110). The positive / negative threshold value iref is set as an allowable range of the output current i from the target current i *, and is determined by the characteristics of the system. When the deviation Δi is outside the allowable range set by the positive / negative threshold value iref, the load DC is set so that the current to the inverter 54 side changes by the deviation Δi in a direction to cancel the deviation Δi between the output current i and the target current i *. / DC converter 52 is controlled (step S112), and this routine is terminated. On the other hand, when the deviation Δi is within the allowable range, this routine is terminated as it is. Here, the auxiliary machine DC / DC converter 56 is controlled so that the output side maintains a predetermined voltage suitable for driving the auxiliary machine in order to supply electric power necessary for the auxiliary machine. In this operation control, the load DC / DC converter 52 is controlled so that the output current i of the fuel cell 40 is within the allowable range of the target current i *. It can be said that it has priority over the power supplied to the plant.
[0027]
According to the fuel cell power generation system 20 of the embodiment described above, the direct current power from the fuel cell 40 is supplied to the auxiliary equipment necessary for the operation of the system by the auxiliary equipment DC / DC converter 56 as the predetermined direct current power. The efficiency of the system can be improved as much as the DC / AC conversion is not performed, compared to the case where the DC / AC converted power is supplied to the auxiliary machine. In addition, the auxiliary DC / DC converter 56 is controlled to maintain a predetermined voltage suitable for driving the auxiliary machine, that is, the power supplied to the auxiliary machine is controlled with priority over the power supplied to the load 16 side. Therefore, the system can be operated stably.
[0028]
In the fuel cell power generation system 20 of the embodiment, the auxiliary DC / DC converter 56 is controlled so that the output side voltage of the auxiliary DC / DC converter 56 is maintained at a predetermined voltage suitable for driving the auxiliary machine. It is not necessary to perform constant voltage control, and DC power may be supplied to the auxiliary machine as necessary.
[0029]
In the fuel cell power generation system 20 according to the embodiment, when the deviation Δi between the output current i of the fuel cell 40 and the target current i * is outside the allowable range set by the positive / negative threshold value iref, the load is set to cancel the deviation. Although the control DC / DC converter 52 is controlled, it may be controlled by combining proportional control, integral control, differential control, etc. so that the output current i of the fuel cell 40 becomes the target current i *.
[0030]
In the fuel cell power generation system 20 of the embodiment, the load DC / DC converter 52 is controlled so that the output current i of the fuel cell 40 is maintained at the target current i * corresponding to the operation mode. The system operating state that is the utilization factor is detected, and the current output from the fuel cell 40 at that time is set as the target current i *, so that the output current i from the fuel cell 40 is maintained at the target current i *. The DC converter 52 may be controlled.
[0031]
In the fuel cell power generation system 20 of the embodiment, the operation mode has three levels of High mode, Mid mode, and Low mode, but the operation mode may be two levels, or four or more levels.
[0032]
In the fuel cell power generation system 20 of the embodiment, a solid polymer type fuel cell is used as the fuel cell 40, but it is not limited to a solid polymer type fuel cell, and any type of fuel cell may be used.
[0033]
In the fuel cell power generation system 20 of the embodiment, the city gas (13A) is supplied to the reformer 30 to generate the hydrogen-rich fuel gas. However, the city gas (12A) or the propane gas filled in the gas cylinder is used. May be supplied to the reformer 30 to generate fuel gas.
[0034]
In the fuel cell power generation system 20 of the embodiment, the city gas is supplied to the fuel cell 40 as the hydrogen-rich fuel gas by the reformer 30 and the CO selective oxidation unit 34. However, the hydrogen-rich fuel gas or pure hydrogen is used. It is good also as what supplies to the fuel cell 40 from the hydrogen tank which accumulates.
[0035]
In the fuel cell power generation system 20 of the embodiment, the hot water storage tank 44 that stores water by heating water using the heat of the fuel cell 40 is provided. However, the hot water storage tank 44 may be omitted.
[0036]
The embodiments of the present invention have been described using the embodiments. However, the present invention is not limited to these embodiments, and can be implemented in various forms without departing from the gist of the present invention. Of course you get.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system 20 according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an example of an operation control routine executed by the electronic control unit 60 of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Commercial power supply, 12 Electric power line, 14 Circuit breaker, 16 Load, 18 Circuit breaker, 20 Fuel cell power generation system, 22 Gas piping, 24 Control valve, 26, 28 Booster pump, 27 Desulfurizer, 30 Reformer, 32 Combustion Part, 34 CO selective oxidation part, 40 fuel cell, 41 blower, 42 heat exchanger, 43 circulation pump, 44 hot water tank, 46 pump, 50 current sensor, 52 DC / DC converter, 54 inverter, 55 circuit breaker, 56 DC / DC converter, 58 load power meter, 60 electronic control unit, 62 CPU, 64 ROM, 66 RAM, 68 timer.

Claims (5)

A fuel cell power generation system including a fuel cell that generates power by receiving fuel supply,
A DC / DC converter for load connected to the output terminal of the fuel cell and an inverter connected to the DC / DC converter for load, and using DC power from the fuel cell to a load from another system power source Power supply means for other systems capable of supplying power to the power supply line of
A fuel constituted by an auxiliary DC / DC converter connected to a power line between the fuel cell and the load DC / DC converter, and driven by a predetermined DC power using the DC power from the fuel cell. Auxiliary power supply means for supplying the predetermined DC power to the auxiliary machine for the battery power generation system;
Current detection means for detecting an output current from the fuel cell;
The auxiliary power supply means is controlled so that the auxiliary-side voltage of the auxiliary DC / DC converter is maintained at a predetermined voltage, and the output current detected by the current detection means is output from the fuel cell. Power supply control means for controlling the power supply means for the other system so that power is supplied to the power supply line as a current within a predetermined range from the target current to be
A fuel cell power generation system comprising: The fuel cell power generation system according to claim 1, wherein by reforming hydrocarbon-based fuel into hydrogen-rich fuel comprises a reforming unit for supplying a fuel to be supplied to the fuel cell. The fuel cell power generation system according to claim 2 , wherein the hydrocarbon fuel is city gas or propane gas. The fuel cell power generation system according to any one of claims 1 to 3, further comprising hot water storage means for storing hot water that has been heated using at least heat from the fuel cell. A fuel cell that generates power upon supply of fuel; a load DC / DC converter connected to the output terminal of the fuel cell; and an inverter connected to the load DC / DC converter. Connected to the power line between the fuel cell and the load DC / DC converter, and the power supply means for the other system capable of supplying power to the power supply line from the other system power supply to the load using DC power Auxiliary power supply for supplying a predetermined DC power to an auxiliary machine for a fuel cell power generation system configured by a DC / DC converter for an auxiliary machine and driven by a predetermined DC power using the DC power from the fuel cell A fuel cell power generation system control method comprising:
(A) detecting an output current from the fuel cell;
(B) The auxiliary power supply means is controlled so that the auxiliary side voltage of the auxiliary DC / DC converter is maintained at a predetermined voltage, and the output current detected by the current detection means is the fuel. A control method for a fuel cell power generation system, wherein the power supply means for other system is controlled so that power is supplied to the power supply line from a target current to be output from the battery within a predetermined range .

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