JP2013143212A - Fuel cell power generation system and operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generation system that stably conducts a self-sustained operation when a commercial power source has a failure, and also suppresses the increase of a device cost.SOLUTION: A fuel cell power generation system conducts an interconnected operation interconnected with a commercial power source 105, and a self-sustained operation when the commercial power source 105 has a failure. The fuel cell power generation system comprises: a fuel cell power generation device 10 that generates electric power by the supply of air and fuel gas; an inverter 101 that converts direct-current power generated by the fuel cell power generation device 10, into alternating-current power; and a control part 100 that increases an amount of air or fuel gas to be supplied to a fuel cell in the fuel cell power generation device 10 when the power failure of the commercial power source 105 is detected.

Description

  Embodiments described herein relate generally to a fuel cell power generation system and an operation method thereof.

  The fuel cell power generation system directly converts the combined energy of hydrogen and oxygen generated by the fuel processor into electrical energy, and since it is a chemical reaction, it has high power generation efficiency and low environmental pollution. It is evaluated as an excellent power generation system.

  The fuel cell power generation system not only has a built-in fuel cell body, but also a fuel processing device for extracting hydrogen gas from hydrocarbon fuels typified by city gas and LP gas, and converts the output DC power to AC power. An electric control device (inverter), a heat utilization device that recovers heat generated by power generation, a control device for controlling the entire system, and the like are provided to transmit power to a general household. Usually, the fuel cell power generation system performs an operation linked to a commercial power source (interconnected operation).

  In recent years, when a power failure occurs in a commercial power source due to a disaster or the like, there is an increasing need for a self-sustained operation in which a fuel cell power generation system operates by generating an alternating voltage by itself and continues power transmission. During the self-sustained operation, the fuel cell power generation system transmits power used at home. For example, when a living room lighting is turned on, the amount of power used at home increases, and the power output of the fuel cell power generation system increases rapidly. Moreover, when the living room lights are turned off, the amount of power consumed at home decreases, and the power output of the fuel cell power generation system sharply decreases. The conventional fuel cell power generation system cannot cope with such a sudden change in load during the self-sustaining operation, and the fuel cell power generation system may stop generating power.

  By separately providing a battery (stabilizing storage battery) in the fuel cell power generation system, it is possible to cope with a sudden change in load, but there is a problem that the cost of the fuel cell power generation system is increased and the casing is enlarged.

JP 2008-152959 A

  The problem to be solved by the present invention is to provide a fuel cell power generation system capable of stably performing independent operation and suppressing cost increase during a power failure of a commercial power supply, and an operation method thereof.

  According to this embodiment, the fuel cell power generation system performs a self-sustained operation at the time of a grid connection operation linked to a commercial power source and a power failure of the commercial power source. This fuel cell power generation system is supplied with air and fuel gas, detects a fuel cell that generates power, an inverter that converts DC power generated by the fuel cell into AC power, and a power failure of the commercial power source, And a controller that increases the amount of air or fuel gas supplied to the fuel cell.

1 is a schematic configuration diagram of a fuel cell power generation system according to an embodiment. It is a schematic block diagram of the fuel cell power generator concerning this embodiment. It is a flowchart explaining the operating method of the fuel cell power generation system which concerns on this embodiment. It is a graph which shows an example of transition of output electric power at the time of interconnection operation, fuel utilization rate, and oxygen utilization rate of the fuel cell power generation system concerning this embodiment. It is a graph which shows an example of transition of output electric power at the time of self-sustained operation, fuel utilization rate, and oxygen utilization rate of a fuel cell power generation system concerning this embodiment.

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

  FIG. 1 shows a schematic configuration of a fuel cell power generation system according to this embodiment. The fuel cell power generation system includes a fuel cell power generation device 10, an inverter 101 that converts DC power output from the fuel cell power generation device 10 into AC power, a power transmission breaker 103, a system breaker 104, and a fuel cell power generation system. The control part 100 which controls the whole is provided. The inverter 101 is provided with a gate 102 composed of a semiconductor switch or the like.

  The fuel cell power generation system performs an interconnection operation synchronized with the voltage and frequency of the power system (commercial power source) 105. Further, the fuel cell power generation system performs a self-sustained operation at the time of a power failure of the power system 105.

As shown in FIG. 2, in the fuel cell power generation apparatus 10, the fuel supplied from the fuel blower 12 and the water supplied from the water tank 13 through the water pump 14 are mixed into the reformer 15 filled with the catalyst. And hydrogen is extracted from the fuel. The reformer 15 is supplied with burner air by a burner air blower 19 and rises to a temperature effective for taking out hydrogen-rich gas, and the following reforming reaction occurs.
2CH ₄ + 3H ₂ O → 7H ₂ + CO ₂ + CO

CO generated by the reforming reaction in the reformer 15 passes through the CO converter 16 and the CO selective oxidizer 17, and is reduced to a level of several ppm. In the CO transformer 16, the CO concentration is reduced by the following equilibrium reaction.
2CO + H ₂ O → H ₂ + CO ₂ + CO

In the CO selective oxidizer 17, the CO concentration is reduced to several ppm level by the following equilibrium reaction.
3CO + O ₂ → 2CO ₂ + CO

  The hydrogen-rich gas that has passed through the CO converter 16 and the CO selective oxidizer 17 is introduced into the fuel electrode of the fuel cell 11. Air (oxygen) is introduced into the oxidant electrode of the fuel cell 11 by the air blower 18. The fuel cell 11 has an electrolyte membrane (not shown), and a fuel electrode and an oxidant electrode that are provided to face each other with the electrolyte membrane interposed therebetween. When air is introduced into the oxidizer electrode and hydrogen-rich gas is introduced into the fuel electrode, electricity (DC power) and thermal energy are generated by an electrochemical reaction at both electrodes. Thermal energy is recovered by cooling water (not shown), and DC power is supplied to the inverter 101 in FIG.

  The surplus hydrogen rich gas in the fuel cell 11 is mixed with the burner air supplied by the burner air blower 19 and supplied to the reformer 15.

  As shown in FIG. 1, the inverter 101 converts DC power output from the fuel cell 11 of the fuel cell power generation apparatus 10 into AC power, supplies power to the power load 106 via the power transmission breaker 103, and transmits power. Power is supplied to the power load 107 through the circuit breaker 103 and the system circuit breaker 104. The power load 106 is a load that supplies power by a self-sustained operation of the fuel cell power generation system at the time of a power failure of the power system 105. The power load 106 is, for example, a personal computer for acquiring disaster information, a television set, lighting for daily life, or the like. On the other hand, the power load 107 is a load to which power is not supplied from the fuel cell power generation system that operates independently during a power failure of the power load 105.

  The control unit 100 monitors the power system 105 and switches the disconnection / connection of the gate 102, the power transmission circuit breaker 103, and the system circuit breaker 104. For example, when detecting a power failure in the power system 105, the control unit 100 disconnects the gate 102, the power transmission circuit breaker 103, and the system circuit breaker 104, performs a gate block, then closes the gate 102 and releases the gate block. The fuel cell power generation system performs idle operation. Here, idle operation refers to an operation state only for self-power supply.

  In addition, the control unit 100 connects the power transmission circuit breaker 103 when the power supply of the power load 106 is detected during a power failure of the power system 105 or when a power supply is requested by the user, and the fuel cell power generator The power generated by 10 is supplied to the power load 106 so that the fuel cell power generation system performs a self-sustaining operation. The control unit 100 compares the flow rate of the fuel gas (hydrogen-rich reformed gas) and / or air supplied to the fuel cell power generation apparatus 10 when the fuel cell power generation system performs a self-sustained operation with that during the interconnection operation. And increase. Specifically, the control unit 100 controls the fuel blower 102 and / or the air blower 108 to increase the supply amount of fuel gas and / or air.

  By increasing the flow rate of the fuel gas and / or air, the fuel utilization rate / oxygen utilization rate in the fuel cell power generation apparatus 10 decreases, and the fuel utilization rate / oxygen utilization rate is allowed even if the power consumption of the power load 106 changes suddenly. It is possible to prevent the upper limit from being exceeded. Here, the fuel utilization rate refers to the rate at which fuel is consumed for power generation, and the oxygen utilization rate refers to the rate at which oxygen in the air is consumed for power generation.

  In addition, when the power system 105 returns from a power failure, the control unit 100 connects the system circuit breaker 104 so that the fuel cell power generation system performs the interconnection operation. At this time, the control unit 100 reduces the flow rate of the fuel gas and / or air supplied to the fuel cell power generation apparatus 10 as compared with the self-sustained operation. That is, the flow rate of the fuel gas and / or air supplied to the fuel cell power generator 10 when the power system 105 is in the normal state is restored.

  Next, the operation method of the fuel cell power generation system from the occurrence of a power failure of the power system 105 to the recovery from the power failure will be described using the flowchart shown in FIG.

  (Step S <b> 101) When the power system 105 is in a normal state, the fuel cell power generation system performs an interconnection operation synchronized with the voltage and frequency of the power system 105. FIG. 4 shows an example of the transition of output power, fuel utilization rate, and oxygen utilization rate during the interconnected operation of the fuel cell power generation system. As shown in FIG. 4, it can be seen that power generation is performed in the vicinity of the allowable upper limit of the fuel utilization rate and oxygen utilization rate (dashed line in the figure) during the interconnected operation. This is because the output control of the fuel cell power generation system is gently performed by supplying power from the power system 105 to the power loads 106 and 107 to cope with variations in the power used. The reason for setting the allowable upper limit is that the power generation efficiency can be kept high by reducing the amount of fuel used.

  (Step S102) When a power failure occurs in the power system 105, the process proceeds to Step S103.

  (Step S103) The control unit 100 opens the gate 102 and performs gate block.

  (Step S <b> 104) The control unit 100 disconnects the power breaker 103 and the system breaker 104.

  (Step S105) The control unit 100 connects the gate 102 and releases the gate block. Thereby, the fuel cell power generation system performs idle operation.

  (Step S106) When power is supplied to the power load 106, the process proceeds to Step S107.

  (Step S107) The control unit 100 connects the power breaker 103. Thereby, the fuel cell power generation system performs a self-sustained operation.

  At this time, the control unit 100 increases the flow rate of the fuel gas and / or air supplied to the fuel cell power generation device 10. During the independent operation, the on / off operation of the power load 106 directly affects the operation of the fuel cell power generation apparatus 10.

  FIG. 5 shows an example of changes in output power, fuel utilization rate, and oxygen utilization rate when the operation is switched from the grid operation to the independent operation through the idle operation. Unlike the interconnected operation shown in FIG. 4, during the independent operation, the fuel utilization rate and the oxygen utilization rate are not stable due to the influence of the on / off operation of the power load 106. When the flow rate of the fuel gas and / or air supplied to the fuel cell power generation apparatus 10 is the same as that in the interconnected operation, if the power consumption of the power load 106 increases rapidly, the fuel utilization rate and the oxygen utilization rate exceed the allowable limits. Then, power generation in the fuel cell power generation device 10 is stopped. However, in the present embodiment, during the self-sustained operation, the flow rate of the fuel gas and / or air supplied to the fuel cell power generation apparatus 10 is increased, so that the fuel utilization rate and the oxygen utilization rate are given a margin. Even if the power consumption increases rapidly, it is possible to prevent the fuel utilization rate and the oxygen utilization rate from exceeding the allowable limits and to continue the independent operation stably.

  (Step S108) When the power system 105 is recovered from the power failure, the process proceeds to Step S109.

  (Step S109) The control unit 100 opens the gate 102 and performs gate block.

  (Step S110) The inverter 101 outputs AC power synchronized with the voltage and frequency of the power system 105.

  (Step S111) The control unit 100 connects the gate 102 and releases the gate block.

  (Step S <b> 112) The control unit 100 connects the system breaker 104. Thereby, the interconnection operation of the fuel cell power generation system is resumed.

  As described above, according to the present embodiment, even if the power consumption of the power load 106 changes suddenly by increasing the flow rate of the fuel gas and / or air supplied to the fuel cell power generation apparatus 10 during the self-sustaining operation, It is possible to prevent the rate and the oxygen utilization rate from exceeding the allowable limit, and to continue the independent operation stably. Therefore, it is possible to stably carry out independent operation at the time of a power failure of the commercial power source. Moreover, since it is not necessary to provide a battery separately, an increase in apparatus cost can be suppressed.

  In the above embodiment, the control unit 100 connects the power transmission circuit breaker 103 and the system circuit breaker 104. However, these may be configured by a breaker or the like so that the user can connect them.

  In the above embodiment, it goes without saying that increasing the flow rate of the fuel gas and / or air is increasing the flow rate of hydrogen introduced into the fuel electrode and / or oxygen introduced into the oxidizer electrode.

  Although the embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Fuel cell power generation device 11 Fuel cell 12 Fuel blower 13 Water tank 14 Water pump 15 Reformer 16 CO converter 17 CO selective oxidizer 18 Air blower 19 Burner air blower 100 Control unit 101 Inverter 102 Gate 103 Transmission breaker 104 System Circuit breaker 105 Power system 106, 107 Power load

Claims (5)

A fuel cell power generation system that performs a self-sustained operation at the time of a power failure of the commercial power supply and the commercial power supply,
A fuel cell that is supplied with air and fuel gas to generate electricity;
An inverter that converts DC power generated by the fuel cell into AC power;
A control unit that increases the amount of air or fuel gas supplied to the fuel cell when a power failure of the commercial power source is detected;
A fuel cell power generation system comprising: A first circuit breaker connected to the inverter;
A second circuit breaker provided between the first circuit breaker and the commercial power source;
Further comprising
The control unit disconnects the first circuit breaker and the second circuit breaker when detecting a power failure of the commercial power supply, and connects the first circuit breaker when performing a self-sustaining operation. The fuel cell power generation system according to claim 1.   The control unit returns the supply amount of air or fuel gas to the fuel cell to the supply amount of air or fuel gas during the interconnection operation when detecting recovery from a power failure of the commercial power source. The fuel cell power generation system according to claim 1 or 2. An operation method of a fuel cell power generation system that performs a grid-operated operation linked to a commercial power source and a self-sustained operation at the time of a power failure of the commercial power source,
Supplying air and fuel gas to the fuel cell to generate DC power; and
A step of converting DC power generated by the fuel cell into AC power by an inverter;
Monitoring the commercial power source;
Increasing the supply amount of air or fuel gas to the fuel cell when detecting a power failure of the commercial power source;
A method of operating a fuel cell power generation system comprising:   The method further comprises the step of returning the supply amount of air or fuel gas to the fuel cell to the supply amount of air or fuel gas at the time of the interconnection operation when the recovery from the power failure of the commercial power source is detected. The operation method of the fuel cell power generation system according to claim 4.

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