JP2009238609A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cost and save electric power of a fuel cell system used for a distributed power source. <P>SOLUTION: A generator 1 equipped with a fuel cell 11 generates power by controlling operation with a power generation control part 4. An inverter 2 converts DC power output from the generator 1 into AC power. The AC power output from the inverter 2 is transmitted to a house 9 through a power transmission line 6. A distribution line 8 is connected to the power transmission line 6, and a current sensor 5 is installed in the power distribution line 8. A reverse power flow prevention control part 3 detects reverse power flow based on the measured value with the current sensor 5 and executes the prescribed treatment for obstructing the reverse power flow when the reverse power flow is detected. A sensor input change-over part 10 is connected to the current sensor 5 and sends the measured value of the current sensor 5 to either one of the reverse power flow prevention control part 3 and the power generation control part 4 after changing over it under the prescribed condition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system used as a distributed power source.

  In recent years, fuel cell systems that generate electricity by chemically reacting hydrogen extracted from natural gas and the like with oxygen in the air have attracted attention as distributed power sources, and are expected to spread to general households.

  A power generation system using such a fuel cell system is linked to a commercial power system such as an electric power company. Therefore, even if the power consumption in the demand area (home) exceeds the power generation output (for example, 1 kW at the maximum) of the fuel cell system, it can be supplemented with the power from the commercial power source.

  On the other hand, when the power generation output of the fuel cell system exceeds the power consumption in the demand area, the surplus power is reversely flowed to the commercial power source. Therefore, in the fuel cell system used as a distributed power source in the home as described above, measures have been conventionally taken to monitor and prevent reverse power flow (for example, Patent Document 1).

  A general method for preventing reverse power flow in a conventional fuel cell system will be briefly described below. The fuel cell system shown in FIG. 5 includes a generator 1, an inverter 2, a reverse power flow prevention control unit 3, a power generation control unit 4, and current sensors 5a and 5b. The generator 1 generates DC power using a fuel cell (not shown). The inverter 2 converts the DC power supplied from the generator 1 into AC power and outputs it. The AC power output from the inverter 2 is transmitted to the house 9 via the transmission line 6 and consumed by a load device (not shown). Further, a distribution line 8 from a commercial power source 7 such as an electric power company is connected to the transmission line 6.

  The reverse flow prevention control unit 3 monitors the measurement value of the current sensor 5 a provided in the distribution line 8 to detect the presence or absence of reverse flow. And if generation | occurrence | production of reverse power flow is detected, control (for example, reduction of the output electric power of the inverter 2, etc.) for preventing reverse power flow will be performed. The power generation control unit 4 controls the operation of the power generator 1 in accordance with the previously generated power generation plan. The power generation control unit 4 creates a power generation plan using the output power value of the inverter 2 transmitted from the reverse power flow prevention control unit 3 and the power consumption value in the house 9 during power generation. On the other hand, at the time of non-power generation, a power generation plan is created using the power consumption value calculated based on the measured value of the current sensor 5b provided in the distribution line 8.

  FIG. 6 is a diagram showing the configuration of another example fuel cell system. As shown in FIG. 6, in the fuel cell system of this example, there is one current sensor provided on the distribution line 8 (only the current sensor 5a), and the measured value is not directly input to the power generation control unit 4. . Therefore, the power generation control unit 4 of this example needs to receive the power consumption value in the house 9 via the reverse power flow prevention control unit 3 even during non-power generation.

As described above, the fuel cell system of FIG. 6 requires only one current sensor for measuring the value of the electric power supplied from the commercial power supply 7, and therefore requires two current sensors. Compared to the system, the cost can be reduced. On the other hand, in the fuel cell system of FIG. 5, the operation of the reverse power flow prevention control unit 3 can be stopped when the generator 1 is not generating power (that is, when the fuel cell system is on standby), and always requires operation. Compared to the fuel cell system of FIG. 6, power saving during standby can be achieved.
JP 2002-281672 A

  In the above two conventional examples, each fuel cell system has advantages and disadvantages compared to the other. Therefore, realization of a new fuel cell system having each merit is desired.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel cell system capable of reducing cost and saving power.

  A fuel cell system according to the present invention includes a generator that generates power using a fuel cell, an inverter that converts DC power output from the generator into AC power, an electric wire between the inverter and a demand area, and a commercial power source. Based on the current sensor provided in the connection line connecting between the current sensor, based on the measured value of the current sensor, detecting a reverse power flow in which power is supplied from the inverter to the commercial power source, and detecting the reverse power flow, A reverse flow prevention control unit that executes a predetermined process for preventing the reverse flow, a power generation control unit that controls the operation of the generator, and the current sensor, and the measurement value of the current sensor is transmitted to the reverse flow And a switching unit that switches to and transmits to either one of the prevention control unit or the power generation control unit under a predetermined condition.

  The switching unit preferably performs the switching according to an operating state of the generator.

  In this case, more specifically, the switching unit transmits the measured value of the current sensor to the reverse power flow prevention control unit when power generation is performed by the power generator, and the power generation is not performed. It is preferable to transmit to the power generation control unit.

  Preferably, the reverse power flow prevention control unit stops its operation when the power generation is not performed.

  In addition, the reverse power flow prevention control unit, when the power generation is being performed, the output power value of the inverter and the value of the commercial power supplied from the commercial power source calculated based on the measured value of the current sensor May be transmitted to the power generation control unit.

  In the above case, the power generation control unit is calculated based on the output power value of the inverter transmitted from the reverse power flow prevention control unit or the output power value of the inverter and the value of the commercial power. A power generation plan serving as a guideline for controlling the operation of the power generator may be created using at least one of the power consumption values in FIG.

  Further, when the power generation is not performed, the power generation control unit uses the power consumption value in the demand area calculated based on the measurement value of the current sensor transmitted from the switching unit. A power generation plan can be created as a guideline for controlling the operation of the generator.

  As described above, according to the present invention, it is possible to reduce the cost and save power of the fuel cell system used as a distributed power source.

  Hereinafter, an embodiment of a fuel cell system according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing the overall configuration of the fuel cell system of the present embodiment. The fuel cell system of this embodiment is used as a home-use distributed power source, and is incorporated in a cogeneration system that uses exhaust heat generated during power generation for hot water supply, heating, and the like. The fuel cell system includes a power generator 1, an inverter 2, a reverse power flow prevention control unit 3, a power generation control unit 4, a current sensor 5, and a sensor input switching unit 10.

  The power generator 1 includes a fuel cell 11 and a reformer 12 that generates a reformed gas to be supplied to the fuel cell 11. The fuel cell 11 is a polymer electrolyte fuel cell, for example, and is generally called a fuel cell stack (FC stack). The fuel cell 11 has a configuration in which a plurality of cells are stacked, and one cell is not shown, but a pair of electrodes each composed of a fuel electrode (anode) and an air electrode (cathode) are disposed between the electrodes. It has a configuration in which an intervening polymer film is sandwiched between separators. The fuel cell 11 generates power using fuel gas (reformed gas) supplied from the reformer 12 to the anode and oxidant gas (air) supplied from an air supply source (not shown) to the cathode.

  The reformer 12 steam-reforms a raw fuel gas such as natural gas supplied from a raw fuel gas supply source (not shown) to generate a hydrogen-rich reformed gas. Then, after reducing the carbon monoxide concentration in the reformed gas (about 10 ppm or less), the reformed gas is supplied to the fuel cell 11.

  The DC power output from the generator 1 is converted into AC power by the inverter 2 and transmitted to the house 9 (demand area) via the transmission line 6. The transmitted AC power is supplied to and consumed by various load devices 90 (for example, a light, a refrigerator, a television, etc.) installed in the house 9. In addition, a commercial power source 7 such as an electric power company is connected to the power transmission line 6 via a distribution line 8 (connection line). Therefore, even if the total power consumption of the load equipment in the house 9 exceeds the power output from the inverter 2 (for example, 1 kW at the maximum), the power from the commercial power supply 7 (commercial power) can be compensated. .

  The reverse power flow prevention control unit 3 calculates the measured value of the current sensor 5 provided on the distribution line 8 (specifically, based on the measured value of the current sensor 5) during operation of the generator 1 (that is, during power generation). The presence or absence of reverse power flow is detected by monitoring the commercial power value (commercial power value). And if a reverse power flow is detected, the predetermined process (reverse power flow response process) for preventing it will be performed. As shown in FIG. 2, the reverse power flow prevention control unit 3 functionally includes a data acquisition unit 30, a result data transmission unit 31, a determination unit 32, and a reverse power flow correspondence unit 33.

  The data acquisition unit 30 acquires the measurement value of the current sensor 5 via the sensor input switching unit 10. Here, the current sensor 5 is, for example, a clamp-type alternating current sensor. The data acquisition unit 30 calculates the commercial power value based on the measured value of the current sensor 5 and the supply voltage (system voltage) from the inverter 2. The actual data transmission unit 31 transmits the commercial power value calculated by the data acquisition unit 30 and the output power value of the inverter 2 to the power generation control unit 4 as actual data.

  The determination unit 32 determines whether a reverse power flow has occurred based on the commercial power value calculated by the data acquisition unit 30. Specifically, when power of a predetermined value (for example, 50 W) or more is supplied to the distribution line 8, it is determined that a reverse power flow has occurred.

  The reverse power flow corresponding unit 33 executes processing for preventing the generated reverse power flow (reverse power flow response processing). Specifically, the reverse power flow corresponding unit 33 performs control for supplying surplus power to an auxiliary heating device (not shown). The auxiliary heating device is a heating device that is used supplementarily to make up for the shortage, such as when exhaust heat is insufficient during power generation. Further, the reverse power flow correspondence unit 33 transmits instruction data for reducing the output power to the power generation control unit 4 and the inverter 2.

  As described above, the reverse power flow prevention control unit 3 includes the reverse power flow composed of the processing for detecting the presence or absence of reverse power flow (reverse power flow detection processing) and the corresponding processing at the time of reverse power flow detection (reverse power flow response processing). Perform prevention processing. As a matter of course, the reverse power flow prevention process of the reverse power flow prevention control unit 3 only needs to be performed during operation of the power generator 1 (power generation). Therefore, the reverse power flow prevention control unit is not in power generation (standby mode). 3 stops its operation.

  The power generation control unit 4 controls the operation of the power generator 1 according to a power generation plan created in advance. The power generation control unit 4 creates a power generation plan using a power generation result (that is, output power value), a demand result (power consumption value in the house 9), and the like. The actual demand is obtained by adding the output power value and the commercial power value.

  As described above, the power generation control unit 4 receives the output power value and the commercial power value as actual data from the reverse power flow prevention control unit 3 during power generation. On the other hand, during non-power generation (standby), a power consumption value (in this case, equal to the commercial power value) is calculated based on the measurement value of the current sensor 5 input via the sensor input switching unit 10. Use this to create a power generation plan.

  In addition, when the reverse power flow is detected and an output power reduction instruction is received from the reverse power flow prevention control unit 3, the power generation control unit 4 controls the power generator 1 so that the output power does not exceed the power consumption. For example, the power generation control unit 4 adjusts the amount of raw fuel gas and air supplied to the power generator 1.

  The sensor input switching unit 10 is composed of, for example, a mechanical relay. The sensor input switching unit 10 is connected to the current sensor 5, the reverse power flow prevention control unit 3, and the power generation control unit 4. The signal transmission direction of the sensor input switching unit 10 is switched between power generation and standby. Specifically, the sensor input switching unit 10 sends the input measurement value (indicating signal) of the current sensor 5 to the reverse flow prevention control unit 3 during power generation, and the power generation control unit 4 during standby. To send.

  Next, the procedure of the reverse power flow prevention process by the reverse power flow prevention control unit 3 will be described with reference to the flowchart of FIG. The reverse power flow prevention process is started when power generation by the power generator 1 is started, and thereafter, the following process is repeatedly performed until the power generation is stopped.

  First, the data acquisition unit 30 acquires the measurement value of the current sensor 5 from the sensor input switching unit 10 (step S101). Further, the data acquisition unit 30 calculates a commercial power value based on the system voltage measured by the inverter 2 and the acquired measured value of the current sensor 5 (step S102).

  The determination unit 32 determines whether a reverse power flow has occurred based on the calculated commercial power value (step S103). The determination part 32 determines with the reverse power flow having generate | occur | produced, for example, when the electric power of 50 W or more is supplied to the distribution line 8. FIG. As a result, if it is determined that a reverse power flow has occurred (YES in step S103), the reverse power flow response unit 33 executes the above-described reverse power flow processing (step S104). On the other hand, when it is determined that no reverse flow has occurred (NO in step S103), the process proceeds to step S105.

  The performance data transmission unit 31 transmits the commercial power value calculated by the data acquisition unit 30 and the output power value of the inverter 2 to the power generation control unit 4 as performance data (step S105). The actual data is used when the power generation control unit 4 creates a power generation plan.

  The above process is repeated until power generation is stopped (YES in step S106).

  As described above, in the fuel cell system of the present embodiment, only one current sensor (current sensor 5) is installed for detecting a reverse power flow. In addition, the sensor input switching unit 10 can be configured with very inexpensive parts such as a mechanical relay. Therefore, the fuel cell system of this embodiment can reduce the cost as compared with the conventional fuel cell system (see FIG. 5) that requires two current sensors.

  Furthermore, since the operation of the reverse power flow prevention control unit 3 can be stopped during non-power generation (standby), compared with the conventional fuel cell system (see FIG. 6) that always requires operation, Power saving can be achieved.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  For example, although the current sensor 5 is provided in the distribution line 8 in the above embodiment, it may be installed on the downstream side after the interconnection point P of the transmission line 6 as shown in FIG. In this case, the reverse power flow prevention control unit 3 compares the power consumption value calculated based on the measurement value of the current sensor 5 with the output power value of the inverter 2 to detect the presence or absence of the reverse power flow.

  Further, in the above embodiment, when the reverse power flow occurs, surplus power is supplied to an auxiliary heating device (not shown), but the load device that supplies the surplus power is not limited to the auxiliary heating device, and various types of cogeneration systems are provided. Can be supplied to various load devices.

  Moreover, each process in the flowchart demonstrated by the said embodiment is not limited to the order, In the range which does not deviate from the meaning of this invention, an order can be changed arbitrarily.

1 is a diagram illustrating an overall configuration of a fuel cell system according to an embodiment of the present invention. It is a figure which shows the functional structure of the reverse power flow prevention control part of FIG. It is a flowchart which shows the procedure of a reverse power flow prevention process. It is a figure which shows the whole structure of the fuel cell system which concerns on other embodiment. It is a figure which shows the whole structure (two current sensors) of the conventional fuel cell system. It is a figure which shows the whole structure (one electric current sensor) of the conventional fuel cell system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generator 2 Inverter 3 Reverse power flow prevention control part 4 Power generation control part 5 Current sensor 6 Transmission line (electric wire)
8 Distribution lines (connection lines)
9 Houses (demand areas)
10 Sensor input switching part (switching part)
11 Fuel cell

Claims (7)

A generator for generating electricity using a fuel cell;
An inverter that converts DC power output from the generator into AC power;
A current sensor provided on a connecting line connecting the electric wire between the inverter and the place of demand and a commercial power source;
Based on the measured value of the current sensor, a reverse power flow in which electric power is supplied from the inverter to the commercial power supply is detected. A prevention control unit;
A power generation control unit for controlling the operation of the power generator;
A switching unit that is connected to the current sensor, and that switches and transmits a measured value of the current sensor to either the reverse power flow prevention control unit or the power generation control unit under a predetermined condition;
A fuel cell system. The switching unit performs the switching according to the operation state of the generator.
The fuel cell system according to claim 1. The switching unit transmits the measured value of the current sensor to the reverse power flow prevention control unit when power generation is performed by the power generator, and transmits to the power generation control unit when the power generation is not performed. To
The fuel cell system according to claim 2. The reverse power flow prevention control unit stops its operation when the power generation is not performed.
The fuel cell system according to claim 3. The reverse power flow prevention control unit, when the power generation is performed, outputs the output power value of the inverter and the value of the commercial power supplied from the commercial power source calculated based on the measured value of the current sensor. Send to the power generation control unit,
The fuel cell system according to claim 3. The power generation control unit is an output power value of the inverter transmitted from the reverse power flow prevention control unit or a power consumption value in the demand area calculated based on the output power value of the inverter and the value of the commercial power A power generation plan that serves as a guideline for controlling the operation of the generator using at least one of the following:
The fuel cell system according to claim 5. The power generation control unit uses the power consumption value in the demand area calculated based on the measurement value of the current sensor transmitted from the switching unit when the power generation is not performed. Create a power generation plan that will guide you in controlling your operation,
The fuel cell system according to claim 3.

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