JP5481528B2 - Fuel cell control device - Google Patents

Description

  The present invention relates to a fuel cell control device capable of operating a fuel cell in a stable state at all times.

  Recently, fuel cells that generate electricity using hydrogen obtained from raw fuel such as natural gas and propane gas and oxygen in the air are highly efficient, environmentally friendly, and can use both electric energy and thermal energy at the same time. The spread to the home is spreading.

  When this fuel cell is installed in a home, high reliability is required as in a gas water heater, and it is important that the system does not stop even if there is some disturbance.

  However, since a fuel cell is a system that generates DC power by an electrochemical reaction between hydrogen and oxygen, the supply of raw fuel and water necessary for generating hydrogen and the supply of oxygen, that is, air, may fluctuate even slightly. The direct current voltage generated from the fuel cell is greatly reduced.

  Conventionally, as a countermeasure when the direct current voltage of the fuel cell decreases, a control device for a fuel cell system has been proposed which suppresses an increase in direct current generated with a decrease in the direct current voltage of the fuel cell (Patent Document). 1).

  The control device of this fuel cell system suppresses the direct current value at the stage where the direct current voltage of the fuel cell is starting to decrease at the stage where the direct current power generated from the fuel cell is converted into alternating current power. This reduces the burden on the fuel cell and improves the durability.

JP 2004-327055 A

  However, in such a conventional fuel cell system control device, it is possible to reduce the influence on the fuel cell against a gradual voltage drop due to deterioration of the fuel cell over time, etc., and to continue the operation of the system. In the case of a sudden voltage drop, DC power is excessively taken out, so that the characteristics of the fuel cell are deteriorated or the operation cannot be continued due to the voltage drop, and the system may be stopped.

  The present invention has been made to solve the above-described problems, and provides a stable fuel cell control device that is excellent in durability against rapid voltage drop of a fuel cell and can cope with deterioration with time. With the goal.

  In order to achieve the above object, the present invention constitutes a fuel cell control device by the following means.

The invention corresponding to claim 1 includes a hydrogen generator, a fuel cell stack that generates direct-current power by reacting a hydrogen-rich gas generated by the hydrogen generator and an oxidant gas, and the fuel cell stack. A power converter that converts the generated DC power into AC power and outputs it to the grid, a process system necessary for power generation, a control means for controlling the power converter, and a generated voltage of the fuel cell stack. a DC voltage measuring means for inputting to the control means Te, the control means is configured to power control the power conversion device by power generation command value, the power generation of the fuel cell stack measured at the DC voltage measuring means When the voltage drops below the set value, increasing of the power generation voltage of the fuel cell stack by controlling the power converting device operable minimum value as power generation command value That.

According to a second aspect of the present invention, in the fuel cell control apparatus according to the first aspect of the present invention, the control means includes a number of times recording means, and the number of times recording means is adapted to recover from a DC voltage drop to a steady operation state. When the number of repetitions is recorded and the number exceeds the predetermined number, the operation is continued with the generated power command value given to the power conversion device as the lowest outputable value.

  According to the present invention, the fuel cell is excellent in durability against a rapid voltage drop, and can be stable so as to cope with deterioration over time.

1 is a block configuration diagram showing a first embodiment of a fuel cell control device according to the present invention. FIG. The block circuit diagram which shows the internal structure of the power converter device in the embodiment. The figure which shows the relationship between the switching gate ON / OFF signal in the same embodiment, and the input / output of a power converter device. The figure which shows the example of the change of the switching gate ON / OFF signal and output change in 2nd Embodiment of the fuel cell control apparatus by this invention. The block block diagram which shows 3rd Embodiment of the fuel cell control apparatus by this invention. The block block diagram which shows 4th Embodiment of the fuel cell control apparatus by this invention. The block block diagram which shows 5th Embodiment of the fuel cell control apparatus by this invention. The characteristic view which shows the relationship between the direct current and direct-current voltage in the embodiment. The block block diagram which shows 6th Embodiment of the fuel cell control apparatus by this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a first embodiment of a fuel cell control device according to the present invention.

  In FIG. 1, reference numeral 1 denotes a hydrogen generator that is supplied with raw fuel such as natural gas or propane gas, reforms the raw fuel to generate a hydrogen-rich gas, 2 is a blower that takes in air, and 3 is a hydrogen generator. 1 is a fuel cell stack that is supplied with the hydrogen-rich gas generated in 1 and the air taken in by the blower 2 and generates electric energy and thermal energy by an electrochemical reaction, and these constitute a fuel cell.

  Also, 4 is a hot water storage tank connected to a hot water line that recovers thermal energy generated in the fuel cell stack 3, 5 is input DC power generated as electrical energy in the fuel cell stack 3, and this DC power is converted into AC power. It is the power converter device which converts.

  On the other hand, 6 is a control device, and this control device 6 sends and receives signals to and from equipment necessary for supplying and controlling raw fuel, air, hydrogen-rich gas, and the like to the fuel cell stack 3. Although it is comprised from the power control means to perform transmission / reception of the signal between the equipment control means to perform and the power converter device 5, it demonstrates focusing on the power control means to perform transmission / reception of the signal between the power converter devices 5 here. .

  Reference numeral 9 denotes a DC voltage detecting means provided on the DC line connecting the fuel cell stack 3 and the power converter 5 to the control device 6. The DC voltage signal 9a detected by the DC voltage detecting means 9 is Input to the power conversion device 5 and the control device 6 respectively.

  Here, as shown in FIG. 2, the power converter 5 is provided on the input side of a power converter 5a that converts DC power into AC power, a controller 5b that controls the power converter 5a, and the power converter 5a. Switching circuit 5c.

  The control device 6 outputs the generated power command value 7 to the control unit 5b of the power conversion device 5, and the DC voltage signal 9a detected by the DC voltage detection means 9 is supplied to the switching circuit 5c of the power conversion device 5. When it falls below the set value, it has a function of outputting a switching gate ON / OFF signal 8.

  Next, the operation of the fuel cell control device configured as described above will be described.

  First, the normal operation will be described.

  In FIG. 1, raw fuel such as natural gas or propane gas is reformed into a hydrogen-rich gas by the hydrogen generator 1 and supplied to the fuel cell stack 3. At the same time, air is supplied to the fuel cell stack 3 by the blower 2, and electricity and heat are generated from hydrogen and oxygen in the air by an electrochemical reaction.

  The heat generated in the fuel cell stack 3 is collected through a hot water circulation line, stored in a hot water storage tank 4, and used as a household heat load.

  On the other hand, the DC power generated in the fuel cell stack 3 is converted into AC power by the power converter 5, operates in an interconnected manner with a commercial power system, and is consumed by a household power load.

  During power generation, each device and process, such as supply of an appropriate amount of raw fuel and air, temperature control of the hydrogen generator 1, exhaust heat recovery, change of output power of the power conversion device 5, etc., by the device control means of the control device 6 Control the amount.

  The power conversion device 5 during normal operation receives the generated power command value 7 from the control device 6, and performs power control according to the generated power command value by the control of the power conversion unit 5a by the control unit 5b.

  When such control is performed, if the direct-current voltage output from the fuel cell stack 3 suddenly decreases due to fluctuations in raw fuel, air, hydrogen, etc., the control device 6 switches to the switching circuit 5c of the power conversion device 5. A switching gate ON / OFF signal as shown in FIG. 3 is input, and the input of DC power to the power conversion unit 5a is intermittently stopped.

  Then, the output voltage of the fuel cell stack 3 gradually rises, and when the voltage rises to a predetermined voltage, the switching gate ON / OFF signal is always turned on to restore the normal operation state.

  Note that the switching gate pulse for power conversion for controlling the power conversion unit 5a from the control unit 5b is a high-speed ON / OFF signal of several kHz to several tens of kHz, but here the switching gate ON / OFF signal 8 Represents that the time for performing high-speed switching of the power conversion unit 5a by the control unit 5b is ON and the time for not performing the switching is OFF.

  As described above, according to the first embodiment, when the DC voltage of the fuel cell stack 3 sharply decreases, the switching gate ON / OFF signal 8 is output from the control device 6 and the switching circuit 5c of the power conversion device 5 is activated. By performing the switching control, the input current of the power conversion device 5, that is, the output current of the fuel cell stack 3 can be suppressed, so that the DC voltage of the fuel cell stack 3 increases. For example, when the switching gate ON / OFF is performed at a cycle of 1 millisecond, the direct current decreases to ½, and the direct current voltage increases to a voltage at which stable operation is possible.

  At this time, since the ON / OFF cycle is shortened, hydrogen deficiency, oxygen deficiency, etc. due to promotion of local electrochemical reaction inside the fuel cell stack 3 do not occur, and the characteristics of the fuel cell stack 3 are affected. Never give.

  Further, the output current of the fuel cell stack 3 can be changed to any level by changing the ON / OFF interval and cycle of the switching gate ON / OFF signal 8. For example, by repeating OFF for 1 millisecond and ON for 3 milliseconds, the output current of the fuel cell stack 3 becomes 75% before the start of the change.

  Although the above has described the case where the switching circuit 5c is provided on the input side of the power conversion unit 5a controlled by the control unit 5b of the power conversion device 5, the switching circuit 5c is provided on the output side of the power conversion unit 5a. Even when the output power of 5 is limited, the same effect as described above can be obtained.

  The switching gate ON / OFF signal 8 can be input to the control unit 5b of the power converter 5 and the switching circuit 5c can be operated via the control unit 5b to obtain the same effect.

  Further, since the DC voltage signal 9a is input to the control unit 5b of the power conversion device 5, the same operation and effect can be achieved even when the control unit 5b makes a determination instead of the control device 6 and operates the switching circuit 5c. Can be obtained.

(Second Embodiment)
FIG. 4 is a diagram showing a switching gate ON / OFF signal for explaining a second embodiment of the fuel cell control apparatus according to the present invention. Since the configuration of the fuel cell control device is the same as that in FIG. 1, the description thereof is omitted here.

In the second embodiment, the ON / OFF interval is set as the switching gate ON / OFF signal output from the control device 6 to the switching circuit 5c of the power conversion device 5 when the DC voltage output from the fuel cell stack 3 decreases. For example, as shown in FIG. 4, it is gradually changed to restore the normal operating state.

That is, first, the control device as a S w Tchingugeto ON / OFF signal given to the switching circuit 5c of the power converter 5 from 6, to repeat the 1 millisecond OFF and ON of 1 millisecond as shown in FIG. 4 (a) As a result, the output current of the fuel cell stack 3 is set to 50% before the start of the change, and then, as shown in FIG. The output current is set to 66%, and thereafter, the output current of the fuel cell stack 3 is set to 75% by repeating the OFF for 1 millisecond and the ON for 3 milliseconds as shown in FIG. As shown in (1), the output current of the fuel cell stack 3 is changed to 80% by repeating the OFF of 1 millisecond and the ON of 4 milliseconds, thereby returning to the normal operation.

  By gradually changing the ON / OFF interval of the switching gate ON / OFF signal in this way, the change in the generated power of the fuel cell stack 3 until returning to the normal operation state becomes slower than in the first embodiment, The durability can be further increased.

  In the above embodiment, the ON / OFF interval of the switching gate ON / OFF signal is changed, but the same effect can be obtained even if the ON / OFF cycle is gradually changed.

(Third embodiment)
FIG. 5 is a block diagram showing a third embodiment of the fuel cell control device according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and different parts will be described here.

  In the first embodiment or the second embodiment described above, if the decrease in the DC voltage of the fuel cell stack 3 is repeated a predetermined number of times within a predetermined time, a cause of some non-temporary DC voltage decrease has occurred. It is possible that

  In the third embodiment, as shown in FIG. 5, the control device 6 is provided with a number recording means 10 for recording the number of occurrences of the decrease in the DC voltage of the fuel cell stack 3, and the number recording means 10 records within a predetermined time. When the number of occurrences of the DC voltage drop exceeds a predetermined number, the ON / OFF operation of the switching gate ON / OFF signal 8 is continued, and the operation is continued with the power generation output of the fuel cell stack 3 lowered. It is made to let you.

  In the fuel cell control device having such a configuration, when the direct-current voltage of the fuel cell stack 3 suddenly decreases, the switching gate output from the control device 6 to the switching circuit 5c of the power converter 5 as in the first embodiment. After the DC voltage of the fuel cell stack 3 rises to the set voltage due to the ON / OFF signal, the switching gate ON / OFF signal is always turned on to restore the normal operation state.

  After that, when the DC voltage of the fuel cell stack 3 drops below the set voltage again, the operation in which the DC voltage of the fuel cell stack 3 rises to the set voltage due to ON / OFF of the switching gate ON / OFF signal is repeated as described above. When the number of times of decrease in the DC voltage is recorded by the number of times recording means 10 and the predetermined number of times is exceeded within a predetermined time, the ON / OFF operation of the switching gate ON / OFF signal is continued, and the power generation output of the fuel cell stack 3 Continue driving in a state where

  In this way, the ON / OFF operation of the switching gate ON / OFF signal is continued and the power generation output of the fuel cell stack 3 is reduced when the number of DC voltage drops exceeds a predetermined number within a predetermined time. By continuing the operation, it becomes possible to eliminate unreasonable output fluctuations, and to minimize the influence on the fuel cell stack 3 and other failure points.

(Fourth embodiment)
FIG. 6 is a block diagram showing a fourth embodiment of the fuel cell control apparatus according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof will be omitted, and different parts will be described here.

  In the fourth embodiment, as shown in FIG. 6, the time is measured when the DC voltage of the fuel cell stack 3 falls below the set value in the control device 6 and the switching gate ON / OFF signal is turned on / off. When the DC voltage of the fuel cell stack 3 does not rise to a voltage equal to or higher than the set voltage even when the measurement time by the time measurement means 11 has exceeded a predetermined time, the generated power command value 7 is set. The operation is continued in a state in which the power generation output of the fuel cell stack 3 is lowered by lowering it according to the output reduction rate determined from the ON / OFF interval or cycle of the switching gate ON / OFF signal.

  In this way, the operation of the fuel cell stack 3 can be continued with an output capable of stable operation without continuing the operation of the first embodiment or the second embodiment described above. Further, even when the direct current voltage of the fuel cell stack 3 decreases with time, stable operation can be continued with the output of the fuel cell stack 3 lowered.

(Fifth embodiment)
FIG. 7 is a block diagram showing a fifth embodiment of the fuel cell control apparatus according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and different parts will be described here.

  In the fifth embodiment, the power conversion device 5 is not provided with a switching circuit, and the control device 6 is set with a minimum output power command value 7a that can be operated, and the DC voltage of the fuel cell stack 3 is lower than the set value. Then, the generated power command value 7a that should be the minimum output that can be operated from the control device 6 to the conversion unit of the power conversion device 5 is given to the control unit.

  In the fuel cell control device having such a configuration, during normal operation, power control according to the command value is performed by the generated power command value 7 given from the control device 6 to the control unit of the power conversion device 5.

  FIG. 8 is a characteristic diagram showing the relationship between the direct current and direct current voltage of the fuel cell stack 3.

  Now, when the operation is performed at the point (a) in FIG. 8 by the power control of the power converter 5, if the DC voltage is suddenly lowered due to fluctuations in raw fuel, air, hydrogen, etc., the operation point is changed to ( From point a) to point (b), the direct current increases at the same time as the direct current voltage drops.

  Then, when the control device 6 transmits the generated power command value 7a, which is the minimum controllable output, to the power conversion device 5 in the DC current-DC voltage characteristics shown in FIG. C) Move to point. If the cause of the voltage drop is temporary, the operating point shifts from point (c) to point (d) while operating for a certain period of time at the minimum output at point (c).

  After a certain period of time has elapsed since this operating point shifted to point (d), the generated power command value 7 transmitted from the control device 6 to the power converter 5 is returned to the original value, and the operating state at point (a) is reached. Revive.

  According to the present embodiment, when the DC voltage is suddenly reduced due to fluctuations in raw fuel, air, hydrogen, etc., during normal operation, the generated power is reduced to the minimum output to reduce the direct current of the fuel cell stack 3. Since the voltage increases, continuous operation can be performed.

  Further, if the DC voltage is temporarily decreased, the operation can be continued with the previous output set value even after the generated power command value 7 is returned to the original value.

  Note that even if the DC voltage drops further, even if it is the lowest controllable output, it will stop because it cannot continue operation, but it will automatically stop even if it cannot be detected by other protection systems. Therefore, it can be set as a highly safe system.

(Sixth embodiment)
FIG. 9 is a block diagram showing a sixth embodiment of the fuel cell control device according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and different parts will be described here.

  In the sixth embodiment, as shown in FIG. 9, the power conversion device 5 is not provided with a switching circuit, and the control device 6 is set with a minimum output power generation command value 7a that can be operated. A number recording means 10 is provided for recording the number of repetitions of the decrease in the DC voltage below the set value and the return to the steady operation state, and the number of repetitions recorded in the number recording means 10 within a predetermined time exceeds the predetermined number. In such a case, the controller 7 of the power converter 5 is provided with the generated power command value 7a that can be made the minimum output that can be operated from the control device 6, and the operation is continued with the power generation output of the fuel cell stack 3 as the minimum value. It is a thing.

  In the fuel cell control device having such a configuration, when the normal operation is performed by the power control of the power conversion device 5, if the direct current voltage is suddenly lowered due to fluctuations in raw fuel, air, hydrogen, etc., the fifth embodiment Similarly, the DC voltage of the fuel cell stack 3 is restored with the generated power command value 7 as the lowest controllable output. Then, after returning to the original generated power command value 7 after a lapse of a certain time, the DC voltage is again lowered below the set value, and when the operation of reducing the generated power command value to the lowest operable output is repeated, The number of times that the generated power command value has been reduced to the minimum operable output is recorded in the frequency recording means 10, and when the number of times the generated power command value has been reduced to the minimum output within a predetermined time exceeds the predetermined number, the generated power command value 7a is given to the power converter 5 to continue the operation at the lowest output that can be operated, and the operation is continued with the power generation output of the fuel cell stack 3 lowered.

  According to the present embodiment, when the operation of the fifth embodiment is repeated a predetermined number of times within a predetermined time, it is assumed that some cause of a decrease in DC voltage that is not temporary has occurred, and an unreasonable output fluctuation By stopping the operation, the influence on the fuel cell stack 3 and other failure points can be minimized. Furthermore, even when the direct current voltage has decreased due to the change with time of the fuel cell stack 3, the output of the power conversion device 5 can be lowered to continue the stable operation.

  DESCRIPTION OF SYMBOLS 1 ... Hydrogen generator, 2 ... Blower, 3 ... Fuel cell stack, 4 ... Hot water storage tank, 5 ... Power converter, 6 ... Control apparatus, 7, 7a ... Generated power command value, 8 ... Switching gate ON / OFF signal, DESCRIPTION OF SYMBOLS 9 ... DC voltage detection means, 9a ... DC voltage detection signal, 10 ... Count recording means, 11 ... Time measurement means

Claims (2)

A hydrogen generator, a fuel cell stack that generates direct-current power by reacting a hydrogen-rich gas generated by the hydrogen generator and an oxidant gas, and converts the direct-current power generated from the fuel cell stack into alternating current power A power converter that interconnects and outputs to the grid, a process system necessary for power generation and a control means that controls the power converter, and a DC voltage that measures the power generation voltage of the fuel cell stack and inputs it to the control means Measuring means,
It said control means generating as well as power controlling the power converter by power generation command value, when the generated voltage of the fuel cell stack measured at the DC voltage measuring means is lower than a set value, the operation lowest possible value A fuel cell control device that raises the power generation voltage of the fuel cell stack by controlling the power conversion device as a power command value . The fuel cell control device according to claim 1, wherein
The control means includes a number of times recording means, and records the number of repetitions of the return from the DC voltage drop to the steady operation state in the number of times recording means, and when the number of times exceeds a predetermined number, gives the power converter A fuel cell control device characterized in that the operation is continued with the generated power command value as a minimum value that can be output.

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