JP2008305647A - Fuel cell power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute stable power generation operation by improving control accuracy even if fuel cell bodies have different individual characteristics and different deterioration states. <P>SOLUTION: A fuel cell power generation system is composed of: a fuel cell body; a fuel processor for supplying hydrogen to an anode of the fuel cell body; an air supply device for supplying oxygen to a cathode of the fuel cell body; and a controller for controlling the fuel processor and the air supply device. The controller is provided with: a calculation means 52, which obtains a relationship between a power generation voltage and a current by calculation using least-squares while taking in a voltage and a current of the fuel cell body detected by a detection means; a memory 53, which tabulates the relationship between the voltage and the current obtained by the calculation means at fixed intervals so as to always store it as the newest IV characteristic; and a determination means 54 that compares the newest IV characteristic stored in the memory with a present operating voltage of the fuel cell body 1 so as to transmit control output when a difference between them is larger than a threshold set in consideration of the newest IV characteristic. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell power generation system capable of stable power generation operation.

  Conventionally, a fuel cell is known as a system for directly converting chemical energy of a raw fuel containing hydrocarbons into electricity. This fuel cell is the one that takes out electricity directly by electrochemically reacting hydrogen as fuel and oxygen as oxidant. It can take out electric energy with high efficiency, and at the same time, it is quiet and harmful exhaust gas. It is a system that has an environmentally friendly feature that does not emit light.

  Until recently, relatively large PAFC (phosphoric acid type) has been mainly developed, but recently, the development of small PEFC (solid polymer fuel cell) has become active, and the popularization of household fuel cell systems is coming soon. It has become a situation.

  By the way, this household fuel cell system needs cost reduction for the spread, and as a part of it, efforts to simplify the system and reduce the size of the equipment are being made by various manufacturers.

  On the other hand, these challenges have an essential problem that there is a possibility of losing the stability and robustness of the device, and the improvement of the robustness by devising the control without adding the device is an important point.

  In addition, PEFC has low resistance to CO due to low-temperature operation, so there is a possibility that the voltage may temporarily drop due to increase in CO accompanying fluctuations in the fuel processing system, etc., and this response will affect the reliability of operation. There is a face.

  FIG. 4 is a configuration diagram of a typical fuel cell power generation system.

  As shown in FIG. 4, the fuel cell power generation system includes a fuel cell main body 1 composed of an anode 1a and a cathode 1b, a fuel processing device 2 for supplying hydrogen-rich fuel to the anode 1a of the fuel cell main body 1, and a fuel cell main body 1. Cathode air supply device 3 for supplying air to the cathode 1b of the battery, an inverter 4 for converting the output power generated by the fuel cell main body 1 into alternating current and supplying it to the AC system, and these fuel cell main body 1, fuel processing device 2, cathode The air supply device 3 and the control device 5 for controlling the inverter 4 are configured, and these are housed in a fuel cell package (not shown).

  Here, the fuel processing device 2 includes a fuel supply system 6, a steam supply system 7, a reformer device 8 including a reformer and a CO converter, a CO removal air supply system 9, and a CO remover 10. .

  In the fuel cell power generation system having such a configuration, when an abnormality occurs in the output voltage of the fuel cell main body 1 during power generation, an interlock operation as shown in FIG. 5 is normally performed. Specifically, as shown in FIG. 5, a recovery operation is performed when the battery voltage during power generation becomes a constant voltage, for example, 50 V or less, and even if the battery voltage falls to 45 V or less without being restored, an alarm is issued and the battery voltage further decreases. In general, the protection is stopped when the voltage becomes 40 V or less. These are usually determined by using a constant voltage value as a threshold value.

Incidentally, in a fuel cell system, there is a fuel cell system that accurately determines the deterioration of the cathode catalyst when the fuel cell voltage decreases and executes cathode recovery to recover the cathode catalyst from the deteriorated state (for example, Patent Document 1). .
JP-A-2005-174643

  By the way, since the conventional fuel cell power generation system described above does not have a function of controlling the IV characteristic of the real-time battery characteristic, it is difficult to determine an abnormality when the voltage drops.

  Normally, as described above, recovery operation, alarm operation, or protection operation is performed when the battery voltage falls below a certain voltage. In this case, however, the margin between the rated output and the minimum output (as normal) The difference in the setting value at the time of abnormality is greatly different, and it cannot be said that proper control can be performed.

  Here, an example of performing the recovery operation will be described with reference to the IV characteristic diagram shown in FIG.

  The initial IV characteristic 20 is the initial operating voltage-current characteristic of the battery, and the IV characteristic 21 after 10,000 h operation is the operating voltage-current characteristic after 10,000 h operation. The operating points of the rated and minimum outputs on the initial IV characteristic 20 and the IV characteristic 21 after 10,000 hours of operation are as shown in the figure.

  As shown in FIG. 6, when the recovery threshold value 26 is a constant value, the tolerance 22 up to the threshold value at the initial minimum output, the tolerance 23 up to the threshold value at the minimum output after 10000h operation, and the threshold value at the initial rating The tolerance 24 up to and the tolerance 25 up to the threshold after driving for 10,000 hours are greatly different.

  Accordingly, in some cases, the recovery function operates quickly, and in other cases, the recovery function does not work unless the abnormality further progresses. Although this is not appropriate, it is a widely used method as a simple means.

  In the above-mentioned Patent Document 1, reference is made to the recovery operation, but ON / OFF related to the recovery operation is performed by simple voltage fixed setting monitoring.

  As a means for avoiding such problems, it can be said that it is relatively effective to prepare standard IV characteristics and predict the current IV characteristics based on the operation time and use them for protection. It is not possible to cope with differences in individual characteristics and deterioration conditions.

  The present invention has been made to solve the above-described problems. By learning the IV characteristics of the fuel cell main body, the fuel that can improve the accuracy of these controls and perform stable power generation operation. An object is to provide a battery power generation system.

  In order to achieve the above object, the present invention provides a fuel cell main body, a reformer that steam-reforms the raw fuel to generate a hydrogen-rich gas, and a CO-rich gas from the hydrogen-rich gas reformed by the reformer. A fuel processing device including a CO remover that supplies air to the anode of the fuel cell main body and supplies air to the anode of the fuel cell main body, an air supply device that supplies oxygen to the cathode of the fuel cell main body, In a fuel cell system comprising a device and a control device for controlling the air supply device, a voltage and current detection means for detecting a voltage and a current during operation of the fuel cell main body are provided, and the control device includes the voltage And calculation means for taking in the voltage data and current data detected by the current detection means and learning the relationship between the generated voltage and current of the fuel cell main body by calculation using the least square method; The relationship between the voltage data and the current data obtained by the calculation means is tabulated at a constant period, and is always stored as the latest IV characteristics, the latest IV characteristics stored in the storage means, and the voltage detection means. And determining means for sending a control output when the difference is greater than a threshold value set in consideration of the latest IV characteristics.

  The present invention also provides a fuel cell main body, a fuel processing device for supplying hydrogen to the anode of the fuel cell main body, an air supply device for supplying oxygen to the cathode of the fuel cell main body, the fuel processing device, In a fuel cell system comprising a control device for controlling the air supply device, a voltage and current detection means for detecting a voltage and a current during operation of the fuel cell main body are provided, and the control device includes the voltage and current. Calculation means that takes in the voltage data and current data detected by the detection means and learns the relationship between the power generation voltage and current of the fuel cell main body by calculation using the least square method, and voltage data and current obtained by the calculation means A storage means that tabulates the data relationship at a fixed period and always stores it as the latest IV characteristics, and the latest IV characteristics stored in the storage means. And a determination means for sending a control output when the difference is greater than a threshold value set in consideration of the latest IV characteristics, and a current operating voltage of the fuel cell body detected by the voltage detection means. Prepare.

  According to the present invention, the IV characteristics are learned from the generated voltage and current of the fuel cell body, and the threshold value is always set in consideration of the latest IV characteristics. Even if they are different, the control accuracy can be increased, and stable power generation operation can be performed.

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

  FIG. 1 is a block diagram showing the main part of the inside of the control device in the first embodiment of the fuel cell system according to the present invention, and the overall configuration of the fuel cell power generation system is the same as FIG. To do.

  In the present embodiment, the power generation voltage data V and current data I of the fuel cell body 1 detected by a voltage detection means and a current detection means (not shown) are taken in via the input / output means (I / O) 51, and the least square method is used. The calculation means 52 for constantly learning the relationship between the generated voltage and current of the fuel cell main body 1 by executing the calculation according to the above, and the relationship between the generated voltage data and the current data obtained by the calculation means 52 is tabulated at a constant cycle, The memory 53 that stores the latest IV characteristics, the latest IV characteristics stored in the memory 53, and the current operating voltage of the fuel cell main body 1 captured via the input / output means (I / O) 51 To determine whether or not the difference exceeds a threshold set as an interlock level in consideration of the latest IV characteristics. And a stage 54.

  In this case, the memory 53 continuously stores characteristics over the entire output of the fuel cell main body 1, which are obtained by the computing means 52 by the least square method. Therefore, since this characteristic is an average characteristic in units of several days, rapid deterioration in several hours can be detected by deviation from this curve.

  Further, the determination means 54 uses, for example, the latest IV characteristic −5V for the recovery operation, the latest IV characteristic −10V for the alarm, and the latest IV characteristic −15V for the protection stop as the threshold of the interlock level. Are set, and when the difference between the current battery voltage and the latest IV characteristic exceeds these protection threshold values, the control output of recovery operation, alarm, and protection stop is transmitted.

  Next, the operation of this embodiment will be described with reference to FIGS.

  Assuming that the fuel cell system is in operation, the power generation voltage and current of the fuel cell body 1 are detected by voltage detection means and current detection means (not shown), and the voltage data and current data are transmitted via the I / O 51. Then, the calculation means 52 executes the calculation by the least square method and learns the relationship between the power generation voltage and current of the fuel cell main body 1 and stores the power generation voltage data and current data in the memory 53. The relationship is tabulated at a fixed period and stored as the latest IV characteristics.

  On the other hand, the determination means 54 compares the latest IV characteristic stored in the memory 53 with the current operating voltage of the fuel cell main body 1, and the difference is set according to the interlock level considering the latest IV characteristic. It is determined whether or not a threshold value to be exceeded is exceeded, and if so, a control output as shown in FIG. 2 is sent according to the interlock level.

  That is, as shown in FIG. 2, first, when the current operating voltage V is smaller than the latest IV characteristic −5V, the recovery operation is controlled. When the characteristic becomes lower than −10V, an alarm is controlled. Further, when the current operation voltage V becomes lower than the latest IV characteristic −15V without returning, the protection stop operation is controlled.

  FIG. 3 shows the relationship between the initial IV characteristic, the IV characteristic after 10,000 hours of operation, and the recovery operation threshold value 31 set in consideration of these IV characteristics.

  Since the recovery operation threshold value 26 for the conventional initial IV characteristic and the IV characteristic after 10000h operation shown in FIG. 6 is set as a fixed value, there is a margin for the interlock operation depending on the operation time and output band of the fuel cell body 1. In this embodiment, as apparent from FIG. 3, the output operation and the operation are compared by comparing the recovery operation threshold value 31 considering the latest IV characteristics with the current operation voltage of the fuel cell body 1. It can be seen that the tolerance to the interlock operation can be made constant regardless of the time and the degradation rate.

  Therefore, since a suitable interlock level can be secured at all times without depending on the output and deterioration state of the fuel cell main body 1, a highly robust fuel cell system can be obtained.

  Here, the following five methods can be considered as recovery methods.

  One is to lower the output of the fuel cell body to a certain level, and the second is to control the steam supply system 7 shown in FIG. 5 to increase the reformed steam flow rate. Since CO suppression is aimed at by these, if it is the influence by temporary CO rise, possibility that it can improve is high.

  Further, the third is to control the cathode air device 3 shown in FIG. 5 to increase the air flow rate to the cathode. If the cause of the decrease in battery voltage is due to the cathode utilization factor, this operation can be improved.

  The fourth is to control the CO removal air supply system 9 shown in FIG. 5 to increase the amount of CO removal air. If the voltage drop is caused by a shortage of CO removal air, an improvement can be expected.

  Further, as a fifth method, there is a method of increasing the fuel flow rate by controlling the fuel supply system 6 shown in FIG. If the voltage drops due to the fuel flow rate, recovery can be expected.

  Further, it is effective to perform these recovery operations successively in a short time and hold and continue items for which voltage recovery of the fuel cell main body 1 has been observed.

  Thus, according to the present embodiment, the risk of a temporary increase in CO concentration can be reduced by these recovery operations, and a highly reliable fuel cell system can be obtained.

  In the first embodiment described above, the case where the present invention is applied to a fuel cell system (PAFC, SOFC, PEFC, etc.) equipped with a reformer such as a steam reformer or autothermal has been described. The present invention can be applied to a fuel cell system.

  In this case, operations and effects similar to those of the first embodiment can be obtained except that steam control and CO remover control cannot be performed during the recovery operation.

  Further, in the first embodiment, the interlock operation is performed by the total voltage of the fuel cell main body 1. However, the voltage of the cell or cell block constituting the fuel cell is monitored by the control device 5, and the voltage of the cell or cell block is monitored. By learning the IV characteristic, it is possible to perform control with higher reliability and higher accuracy.

The block block diagram which shows the principal part inside the control apparatus in 1st Embodiment of the fuel cell system by this invention. The figure which shows the flowchart of the battery voltage interlock in the determination means in the embodiment. In the same embodiment, the graph which shows the relationship between the initial IV characteristic and IV characteristic after 10000h driving | operation, and the recovery operation | movement threshold value each set in consideration of these IV characteristics. Configuration diagram showing a typical fuel cell power generation system The figure which shows the flowchart of the conventional battery voltage interlock. The graph which shows the relationship between the conventional initial IV characteristic and IV characteristic after 10,000-h driving | operation, and a recovery operation | movement threshold value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body, 1a ... Anode, 1b ... Cathode, 2 ... Fuel processing device, 3 ... Cathode air supply device, 4 ... Inverter, 5 ... Control device, 51 ... Input / output means, 52 ... Calculation means by least square method 53 ... Memory, 54 ... Determination means, 6 ... Fuel supply system, 7 ... Steam supply system, 8 ... Reformer and CO converter, 9 ... CO removal air supply system, 10 ... CO remover

Claims (10)

A fuel cell body, a reformer for steam reforming the raw fuel to generate a hydrogen-rich gas, and CO from the hydrogen-rich gas reformed by the reformer to remove the CO to the anode of the fuel cell body A fuel processing apparatus having a CO remover by supplying air to be supplied, an air supplying apparatus for supplying oxygen to the cathode of the fuel cell main body, each device in the fuel processing apparatus, and a control device for controlling the air supplying apparatus In a fuel cell system composed of
A voltage and current detection means for detecting the voltage and current during operation of the fuel cell body is provided;
The control device includes calculation means for taking in voltage data and current data detected by the voltage and current detection means, and learning a relationship between the power generation voltage and current of the fuel cell main body by calculation using a least square method, and the calculation The relationship between the voltage data and current data obtained by the means is tabulated at a fixed period, and is always stored as the latest IV characteristics, and the latest IV characteristics stored in the storage means and the voltage detection means are detected. And determining means for sending a control output when the difference is larger than a threshold value set in consideration of the latest IV characteristics. Fuel cell power generation system. The fuel cell power generation system according to claim 1,
The determination means sets a threshold value set in consideration of the latest IV characteristics to a first level at which a voltage can be recovered by a recovery operation, and sends a control output of the recovery operation when the current operating voltage is lower than the level. A fuel cell power generation system. The fuel cell power generation system according to claim 2, wherein
The control output of the recovery operation is any one of output suppression of the fuel cell main body, output increase of the reforming steam flow rate, increase of the CO supply air supply, increase of air supplied to the cathode, and increase of raw fuel. A fuel cell power generation system. The fuel cell power generation system according to claim 2, wherein
The determination means sets a threshold value set in consideration of the latest IV characteristics to a second level smaller than the first level, and sends an alarm control output when the current operating voltage is lower than the first level. A fuel cell power generation system. The fuel cell power generation system according to claim 4, wherein
The determination means sets a threshold value set in consideration of the latest IV characteristics to a third level smaller than the second level, and sends a control output of the protection stop operation when the current operating voltage is lower than the second level. A fuel cell power generation system. Controlling the fuel cell body, a fuel processing device for supplying hydrogen to the anode of the fuel cell body, an air supply device for supplying oxygen to the cathode of the fuel cell body, the fuel processing device and the air supply device A fuel cell system comprising a control device for
A voltage and current detection means for detecting the voltage and current during operation of the fuel cell body is provided;
The control device includes calculation means for taking in voltage data and current data detected by the voltage and current detection means, and learning a relationship between the power generation voltage and current of the fuel cell main body by calculation using a least square method, and the calculation The relationship between the voltage data and current data obtained by the means is tabulated at a fixed period, and is always stored as the latest IV characteristics, and the latest IV characteristics stored in the storage means and the voltage detection means are detected. And determining means for sending a control output when the difference is larger than a threshold value set in consideration of the latest IV characteristics. Fuel cell power generation system. The fuel cell power generation system according to claim 6, wherein
The determination means sets a threshold value set in consideration of the latest IV characteristics to a first level at which a voltage can be recovered by a recovery operation, and sends a control output of the recovery operation when the current operating voltage is lower than the level. A fuel cell power generation system. The fuel cell power generation system according to claim 7, wherein
A fuel cell power generation system characterized in that the control output of the recovery operation is any one of output suppression of the fuel cell main body, increase of air supplied to the cathode, and increase of raw fuel. The fuel cell power generation system according to claim 7, wherein
The determination means sets a threshold value set in consideration of the latest IV characteristics to a second level smaller than the first level, and sends an alarm control output when the current operating voltage is lower than the first level. A fuel cell power generation system. The fuel cell power generation system according to claim 9, wherein
The determination means sets a threshold value set in consideration of the latest IV characteristics to a third level smaller than the second level, and sends a control output of the protection stop operation when the current operating voltage is lower than the second level. A fuel cell power generation system.

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