JP2014197459A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent power generation from stopping by operating a flame rod which detects flame even when power failure continues during power generation.SOLUTION: A fuel cell system includes: a stack 2 for generating power by reacting fuel gas and oxidant gas; a hydrogen generator 1 for generating fuel gas by being supplied with raw material; a combustor for burning combustible gas to heat the hydrogen generator; an inverter 5 for converting DC power generated by the stack 2 into AC power; a flame rod 4 for detecting an ignition condition of the combustor; and a DC/AC converter 6 disposed on an electric wire branched from a power source between the stack 2 and the inverter 5 and converting DC power of the stack 2 into AC power to be supplied to the flame rod 4, in which since being supplied with power by AC power converted from DC power generated by the stack 2, the flame rod 4 can be operated without stopping power generation.

Description

  The present invention relates to a fuel cell system.

  Conventionally, in this type of fuel cell system, when the flame that has been detected by the flame detection means is no longer detected, the combustor is ignited again, so that even if the flame disappears during combustion, it automatically burns again. (See, for example, Patent Document 1).

  FIG. 5 shows the fuel cell system disclosed in the publication. A fuel cell system is a system that generates electricity by causing an electrochemical reaction between fuel gas and oxidant gas from the outside, and at the same time, recovers the heat generated by the reaction and stores it as hot water in a hot water storage tank, effectively using the recovered heat. is there. The hydrogen-containing gas used during power generation is generated by a reforming reaction between the raw material and water by a hydrogen generator. Carbon monoxide contained in the generated hydrogen-containing gas is reduced inside the hydrogen generator and supplied to the stack. Most of the supplied hydrogen-containing gas is consumed in the stack, but the remaining hydrogen-containing gas is supplied to a combustor provided in the hydrogen generator in order to heat the reformer of the hydrogen generator. Here, if the combustor misfires and the combustion raw material and the remaining fuel gas are not supplied to the combustor and continue to be supplied to the combustor, the gas leaks and becomes unsafe. In order to check the younger state of this combustor, a flame rod is installed in the combustor, and this flame rod applies an alternating voltage to the flame to ionize hydrocarbons and flow toward the burner. Therefore, it is determined whether the combustor is ignited or misfired. In addition to the flame rod, there are thermocouples for flame detection. However, when using a thermocouple, it takes several seconds from the misfire to detect it to obtain a high misfire response. There is a fear that it is not possible. On the other hand, when a flame rod is used, the combustion state can be detected more sensitively and the misfire response is high. Further, since the flame has a flame rectification characteristic, it is possible to detect a short of the frame rod itself by setting the voltage applied to the frame rod to an AC voltage. For these reasons, flame rod detection using an alternating voltage is very effective in preventing gas leakage.

Japanese Patent Laid-Open No. 01-155119

  However, in the conventional configuration, when the flame disappears during power generation due to an instantaneous power failure or the like, the combustor can be continuously burned by an ignition instruction from the controller, but the power failure seems to continue. In such a case, since the power supply from the system to the frame rod is cut off and the frame rod cannot operate, there is a problem that misfire is erroneously detected and power generation stops.

  The present invention solves the above-mentioned conventional problems, and it is possible to maintain power generation even when a power failure continues by supplying power to a frame rod that operates with AC power using DC power generated during power generation. For the purpose.

In order to solve the conventional problems, a fuel cell system of the present invention includes a stack that generates power by reacting a fuel gas and an oxidant gas, a hydrogen generator that is supplied with raw materials and generates fuel gas, and A combustor that burns a combustible gas to heat a hydrogen generator, an inverter that converts DC power generated by the stack into AC power, a frame rod that detects the ignition state of the combustor, and a stack and an inverter And a DC / AC converter that is arranged on an electric wire branched from a power source between the two and that converts the DC power of the stack into AC power and supplies the AC power to the frame rod. As a result, even if the power outage continues during power generation and power cannot be supplied from the grid to the frame rod, AC power is generated from DC power generated by power generation, and the frame rod is operated by supplying AC power to the frame rod. Therefore, the combustion state can be detected correctly and power generation can be continued.

  The fuel cell system of the present invention can operate without stopping power generation even when a power failure continues during power generation.

Configuration diagram of a fuel cell system in an embodiment of the present invention 1 is a configuration diagram of a fuel cell system including a controller according to an embodiment of the present invention. The figure which shows the table | surface of the circuit failure of the frame rod circuit in embodiment of this invention Graph chart of flame strength and current value in the embodiment of the present invention Conventional fuel cell system configuration diagram

  According to a first aspect of the present invention, there is provided a stack for generating power by reacting a fuel gas and an oxidant gas, a hydrogen generator for generating fuel gas supplied with raw materials, and a hydrogen generator for burning a combustible gas. The combustor to be heated, the inverter that converts the DC power generated by the stack into AC power, the frame rod that detects the ignition state of the combustor, and the electric wire branched from the power source between the stack and the inverter The DC / AC converter converts the DC power into AC power and supplies it to the frame rod. Therefore, even if the power failure continues during power generation, the frame rod is converted from the DC power generated by the stack. Since power is supplied by AC power, the combustion state can be detected correctly, and operation can be performed without stopping power generation.

  The second aspect of the invention further includes a controller for controlling the operation of the fuel cell system, particularly the fuel cell system of the first aspect of the invention, and the frame rod receives a frame rod circuit that receives AC power supplied from a DC / AC converter. If the DC / AC converter cuts off the power supply to the frame rod circuit, the frame rod OFF signal is sent from the frame rod circuit to the controller, so the system stops and operates on the safe side. I can do it.

  In the third aspect of the invention, particularly in the fuel cell system of the first or second aspect of the invention, the controller operates the DC / AC converter to detect a failure of the frame rod circuit when the combustor is not ignited. It can be confirmed whether the flame rod circuit is normal before the ignition operation.

  According to a fourth aspect of the present invention, in particular, in the fuel cell system according to any one of the first to third aspects, when the combustor is ignited, the controller stops the DC / AC converter to cause a failure of the frame rod circuit. Since the detection is performed, it is possible to always check whether the frame rod circuit has an ON failure.

  The fifth aspect of the invention is particularly the fuel cell system of any one of the first to fourth aspects of the invention, because the DC / AC converter converts the alternating current power so that the direct current power of the stack becomes equal to or higher than the first predetermined voltage. By setting the voltage higher than the commercial AC voltage, the detection accuracy of the frame rod signal can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 shows a configuration diagram of a fuel cell system according to an embodiment of the present invention.

  In FIG. 1, a fuel cell system 10 includes a hydrogen generator 1 that extracts hydrogen from a fuel gas, a stack 2 that reacts a fuel gas and an oxidant gas to generate DC power, and a DC power that is generated in the stack 2. An inverter 5 that converts AC to AC power, a combustor 3 that performs an ignition operation to generate heat necessary for power generation, a flame rod 4 that detects the ignition state of the combustor 3 and operates with AC power, and a stack 2 And a DC / AC converter 6 that branches from an electric wire arranged between the inverter 5 and converts the DC power generated by the stack 2 into AC power.

  About the fuel cell system comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The fuel cell system 10 generates electricity by causing an electrochemical reaction between a fuel gas and an oxidant gas from the outside, and at the same time, recovers heat generated by the reaction and stores it as hot water in a hot water storage tank to effectively use the recovered heat. It is. The hydrogen-containing gas used during power generation is generated by a reforming reaction between the raw material and water by the hydrogen generator 1. Carbon monoxide contained in the generated hydrogen-containing gas is reduced inside the hydrogen generator 1 and supplied to the stack 2. Most of the supplied hydrogen-containing gas is consumed in the stack 2, but the remaining hydrogen-containing gas is supplied to the combustor 3 provided in the hydrogen generator 1 in order to heat the reformer of the hydrogen generator 1. Supplied. Here, if the combustor 3 misfires and the combustion raw material and the remaining fuel gas are not supplied to the combustor 3 without being burned, the gas leaks and becomes unsafe. In order to confirm the combustion state of the combustor 3, a flame rod 4 is installed in the combustor 3. The flame rod 4 applies an alternating voltage in the flame to ionize hydrocarbons, Since a minute current flowing in the direction is measured, ignition and misfire of the combustor 3 are determined using this current value. As for flame detection, there are thermocouples in addition to the frame rod 4, but when using a thermocouple, it takes several seconds from the misfire to detect it in order to use the temperature change of the flame, and high misfire responsiveness. There is a risk that it will not be obtained. On the other hand, when the flame rod 4 is used, the combustion state can be detected more sensitively and the misfire response is high. Further, since the flame has a flame rectification characteristic, it is possible to detect a short circuit of the frame rod 4 itself by setting the voltage applied to the frame rod 4 to an AC voltage. For these reasons, flame rod detection based on AC voltage is very effective in preventing gas leakage.

  Next, the operation of the frame rod detection circuit will be described in detail.

  When the fuel cell system 10 is stopped, on standby, or started, AC power is supplied from the system 9 to the power supply 12, and the AC power is converted into DC power by the power supply 12. The power source 12 outputs the DC power to the DC / AC converter 6, and the DC / AC converter 6 converts the DC power into AC power and supplies it to the frame rod circuit. When shifting to power generation, the power source 12 converts the DC power generated from the stack 2 into DC power different from the DC power and outputs it to the DC / AC converter 6. The DC / AC converter 6 converts DC power into AC power and supplies it to the frame rod circuit 8.

  Here, when the power failure continues during power generation, the power of the grid 9 is cut off, so the power supply from the grid 9 to the power supply 12 is not performed, but the power supply 12 uses the DC power generated by the stack 2. Since DC power is output to the DC / AC converter 6, the DC / AC converter 6 can continuously supply AC power to the frame rod circuit 8 even during a power failure.

  As described above, in the present embodiment, since a flame can be detected even if a power failure continues during power generation, misfire is not erroneously detected and the system does not stop.

  In FIG. 2, a frame rod circuit 8 that operates with AC power is provided between the DC / AC converter 6 and the frame rod 4, and a controller 7 that controls the frame rod circuit 8 is further provided. As a result, when the power supply from the DC / AC converter 6 to the frame rod circuit 8 is interrupted, the signal sent from the frame rod circuit 8 to the controller 7 is normally interrupted. An abnormality of the DC / AC converter 6 can be detected.

  Further, the controller 7 detects a circuit failure of the frame rod circuit 8 as shown in FIG. First, when the combustor 3 is ignited, it is normal when the DC / AC converter 6 is ON (power is supplied to the frame rod circuit 8) and the frame rod circuit 8 outputs ON. However, when the frame rod circuit 8 outputs OFF, a circuit failure occurs, and the frame rod circuit 8 outputs ON while the DC / AC converter 6 is OFF (power supply to the frame rod circuit 8 is cut off). If it is, the circuit is faulty. If it is OFF, it is normal. Next, when the combustor 3 is not ignited, regardless of whether the DC / AC converter 6 is ON or OFF, when the frame rod circuit 8 is ON output, the circuit has failed and is output OFF. The case is normal.

  Therefore, when the combustor 3 is not ignited, the DC / AC converter 6 is turned on and off, so that a circuit failure of the frame rod circuit 8 can be detected before the ignition is performed. I can do it. In addition, when the combustor 3 is ignited, it is possible to confirm the ON failure of the frame rod circuit 8 by turning off the DC / AC converter 6 when ignited. A circuit to perform can be provided.

  FIG. 4 is a graph of the detection accuracy of the frame rod signal, with the horizontal axis representing the flame strength and the vertical axis representing the current value.

  When the first predetermined voltage 11 output from the DC / AC converter 6 is 200V AC, the graph moves downward as compared with AC 200V as shown in FIG. 4, and the graph is compared with AC 200V when AC 250V. Move upward. The current threshold at which the flame rod signal can be detected differs depending on the circuit. However, if the flame rod signal can be detected at a threshold A or higher, the flame strength can be detected only at B or higher at AC 200V. It can be seen that when the voltage is AC250V, the strength of the flame can be detected at A or higher, so that the detection accuracy increases when the voltage is increased. However, when the voltage exceeds AC300V in accordance with Japanese regulations, the insulation voltage needs to be set larger than the case where the insulation distance is less than that. Therefore, the output voltage of the DC / AC converter 6 is set to AC290V lower than AC300V. It is good.

  As described above, the fuel cell system according to the present invention can generate AC power with DC power generated from the stack even when power outage continues during power generation, so that it can be used for a fuel cell cogeneration system. Applicable.

DESCRIPTION OF SYMBOLS 1 Hydrogen generator 2 Stack 3 Combustor 4 Flame rod 5 Inverter 6 DC / AC converter 7 Controller 8 Flame rod circuit 9 System | strain 10 Fuel cell system 11 1st predetermined voltage 12 Power supply

Claims (5)

A stack that generates power by reacting fuel gas and oxidant gas;
A hydrogen generator for supplying the raw material to produce the fuel gas;
A combustor for burning the combustible gas to heat the hydrogen generator;
An inverter that converts DC power generated by the stack into AC power;
A flame rod for detecting the ignition state of the combustor;
A DC / AC converter that is disposed on an electric wire branched from a power source between the stack and the inverter, and that converts DC power of the power source into AC power and supplies the AC power to the frame rod;
A fuel cell system comprising: A controller for controlling the operation of the fuel cell system;
The frame rod includes a frame rod circuit that receives AC power supplied from the DC / AC converter,
The frame rod circuit is configured to send an OFF signal to the controller when AC power is not supplied from the DC / AC converter.
The fuel cell system according to claim 1. The controller operates the DC / AC converter to detect a failure of the frame rod circuit when the combustor is not ignited.
The fuel cell system according to claim 1 or 2. The controller, when the combustor is ignited, stops the DC / AC converter and detects a failure of the frame rod circuit.
The fuel cell system according to claim 1. The DC / AC converter converts the direct current power of the stack into alternating current power so as to be a voltage equal to or higher than a first predetermined voltage.
The fuel cell system according to claim 1.

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