JP2007194080A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of conducting stable operation independent of kinds of an oxidant gas compressor. <P>SOLUTION: When the output of a fuel cell stack 5 is dropped, an oxidant gas flow rate and pressure ratio of the oxidant gas compressor 2 are estimated, and when the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are present in a surging region, an oxidant gas pressure holding valve 3 and an oxidant gas outlet pressure control valve 6 are shut off, the oxidant gas pressure in the fuel cell stack 5 is held, and in this state, operation of the oxidant gas compressor 2 is stopped, and after the stop of the operation of the oxidant gas compressor 2, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas are estimated, and when the flow rate of the oxidant gas and the the pressure ratio of the oxidant gas compressor are out of the surging region, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure control valve 6 are opened, and the operation of the oxidant gas compressor 2 is resumed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system capable of stable operation regardless of the type of oxidant gas compressor.

  The fuel cell system supplies hydrogen as a fuel gas to the fuel electrode of the fuel cell, supplies air as the oxidant gas to the oxidant electrode of the fuel cell, and causes the hydrogen and oxygen in the air to react electrochemically. To obtain generated power. Such a fuel cell system is highly expected to be put into practical use, for example, as a power source for automobiles, and research and development for practical use are being actively carried out.

  As a fuel cell used in a fuel cell system. For example, a solid polymer type fuel cell is known as being suitable for mounting in an automobile. A solid polymer type fuel cell is provided with a solid polymer membrane as an electrolyte membrane between a fuel electrode and an oxidant electrode. In this solid polymer type fuel cell, the solid polymer membrane functions as an ion conductor, a reaction occurs in which hydrogen is separated into hydrogen ions and electrons at the fuel electrode, and oxygen and hydrogen in the air at the oxidant electrode. A reaction for generating water from ions and electrons is performed.

  In such a fuel cell system, when the load of the fuel cell decreases, the required oxidant gas flow rate decreases and the discharge flow rate decreases. In this case, if the discharge pressure is kept constant, the oxidant gas compression is reduced. A surging phenomenon (a phenomenon in which the oxidant gas (air) is not compressed) may occur in the machine.

In order to cope with such a problem, for example, in the “pressure control method for a fuel cell power generation system” disclosed in Japanese Patent Publication No. 62-60791, the load current of the fuel cell is detected, and based on the decrease in the load current. There has been proposed a method of stabilizing the operation of the oxidant gas compressor by reducing the rotational speed of the oxidant gas compressor and the oxidant gas discharge pressure of the oxidant gas compressor to optimize the operation pressure.
Japanese Examined Patent Publication No. 62-60791

  However, the technique disclosed in Patent Document 1 described above reduces the rotational speed of the oxidant gas compressor and the oxidant gas discharge pressure of the oxidant gas compressor based on the decrease in load current, but the output decreases. Sometimes the oxidant gas pressure could not be reduced until the fuel gas pressure at the anode decreased. For this reason, an oxidant gas compressor is required to operate at a high pressure and a low flow rate. This operating condition is severe for an oxidant gas compressor, and stable operation is difficult depending on the type of the oxidant gas compressor. For this reason, some fuel cells cannot be used.

  At the same time, the operation of the oxidant gas compressor at a high pressure and a low flow rate is also in an operating range where the operating efficiency is poor, and has been a factor of a decrease in the operating efficiency of the fuel cell system.

  The present invention has been made in view of the above-described conventional circumstances, avoids the operation of the oxidant gas compressor at a high pressure and a low flow rate, and operates stably regardless of the type of the oxidant gas compressor. An object of the present invention is to provide a fuel cell system capable of the following.

  Another object of the present invention is to provide a fuel cell system that improves the operation efficiency by avoiding the operation of the oxidant gas compressor at a high pressure and a low flow rate.

  In order to solve the above-described object, the present invention provides a fuel cell that generates power by supplying fuel gas and oxidant gas, and a fuel gas that supplies fuel gas to the fuel cell while adjusting fuel gas pressure by a fuel gas supply valve. Oxidant gas supply for supplying oxidant gas to the fuel cell while adjusting the pressure of the oxidant gas supplied from the supply means and the oxidant gas compressor with an oxidant gas pressure holding valve and an oxidant gas outlet pressure regulating valve And when the output of the fuel cell is reduced, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor are estimated, and the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor are When within the predetermined range, the oxidant gas pressure maintaining valve and the oxidant gas outlet pressure regulating valve are shut off, and the oxidant gas compressor is stopped while maintaining the oxidant gas pressure in the fuel cell. Characterized in that it comprises control means for the.

  In the fuel cell system according to the present invention, when the output of the fuel cell is reduced, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor are estimated, and the oxidant gas flow rate and the oxidant gas compressor pressure ratio are estimated. Is in the respective predetermined range (surging region in which the oxidant gas compressor may cause surging), the control means shuts off the oxidant gas pressure holding valve and the oxidant gas outlet pressure regulating valve, and the fuel cell Since the operation of the oxidant gas compressor is stopped while maintaining the oxidant gas pressure inside, the operation of the oxidant gas compressor at a high pressure and a low flow rate is avoided, and depending on the type of the oxidant gas compressor. Therefore, stable operation is possible and operation efficiency can be improved.

  Hereinafter, Examples 1 to 4 of the fuel cell system of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. The fuel cell system of the present embodiment is used as a driving power source of a fuel cell vehicle, for example, and as shown in FIG. 1, a fuel that generates power by supplying fuel gas (hydrogen) and oxidant gas (air). A battery stack 5 is provided.

  Further, as an oxidant gas supply means, an oxidant gas supply device 1, an oxidant gas compressor 2, an oxidant gas supply channel, an oxidant gas pressure holding valve 3, an oxidant gas pressure sensor 4, an oxidant gas exhaust flow. A fuel gas supply device 7, a fuel gas supply valve 8, a fuel gas supply flow path, a fuel gas pressure sensor 9, and a fuel gas circulation flow path. Furthermore, it is the structure provided with the controller 10 which controls each component based on the detection signal from various sensors, such as the fuel cell stack 5, oxidant gas supply means, and fuel gas supply means.

  The fuel cell stack 5 includes a fuel cell (anode) supplied with hydrogen as a fuel gas and an oxidant electrode (cathode) supplied with air as an oxidant gas with an electrolyte interposed therebetween to form a power generation cell. In addition, it has a stack structure in which a plurality of power generation cells are stacked in multiple stages, and converts chemical energy into electrical energy by an electrochemical reaction based on hydrogen and oxygen in the air. In each power generation cell of the fuel cell stack 5, a reaction occurs in which hydrogen supplied to the fuel electrode is separated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte, and the electrons pass through an external circuit to generate power. , Move to the oxidizer electrode. At the oxidizer electrode, hydrogen in the supplied air reacts with hydrogen ions and electrons that have moved through the electrolyte to produce water, which is discharged to the outside.

  For example, a solid polymer electrolyte membrane is used as the electrolyte of the fuel cell stack 5 in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte membrane is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water.

  In order to generate power in the fuel cell stack 5, it is necessary to supply hydrogen as fuel gas or air as oxidant gas to the fuel electrode (anode) or oxidant electrode (cathode) of each power generation cell. Then, an oxidant gas supply means and a fuel gas supply means are provided as mechanisms for that purpose.

  In the fuel gas supply means, the fuel gas supplied from the fuel gas supply device 7 such as a hydrogen tank as a fuel gas supply source is decompressed by the fuel gas supply valve 8, and the fuel gas supply flow path and ejector (not shown) The fuel cell stack 5 is fed to the fuel electrode through the fuel cell stack 5. The fuel electrode pressure of the fuel cell stack 5 is detected by the fuel gas pressure sensor 9 or predicted based on the output of the fuel cell stack 5 currently taken out, and the controller 10 feeds back the detected value or the predicted value. Thus, by controlling the operation of the fuel gas supply valve 8, the fuel electrode pressure of the fuel cell stack 5 is maintained at a desired pressure.

  Further, in the fuel cell stack 5, not all of the supplied fuel gas is consumed, and the remaining fuel gas (hydrogen discharged from the fuel electrode of the fuel cell stack 5) is newly supplied from the fuel gas supply device 7. The supplied fuel gas flowing through the fuel gas supply channel is mixed with the ejector and supplied again to the fuel electrode of the fuel cell stack 5. For this reason, a fuel gas circulation passage is connected to the fuel electrode outlet side of the fuel cell stack 5, and the fuel gas discharged from the fuel electrode of the fuel cell stack 5 passes through the fuel gas circulation passage and the ejector to form a fuel. The battery stack 5 is circulated.

  On the other hand, in the oxidant gas supply means, the oxidant gas is supplied from the oxidant gas supply device 1, and after being compressed and increased in pressure by the oxidant gas compressor 2, the oxidant gas is supplied via the oxidant gas pressure holding valve 3. Air is fed into the gas supply flow path and supplied to the oxidant electrode of the fuel cell stack 5.

  Further, an oxidant gas exhaust passage for discharging the oxidant gas from the fuel cell stack 5 is connected to the oxidant electrode outlet side of the fuel cell stack 5, and was not consumed by the fuel cell stack 5. Oxidant gas (oxygen and other components in the air) is discharged out of the system through the oxidant gas outlet pressure regulating valve 6 and the oxidant gas exhaust passage. The oxidant extreme pressure of the fuel cell stack 5 is detected by the oxidant gas pressure sensor 4 or predicted based on the output of the fuel cell stack 5 currently taken out, and the controller 10 detects the detected value or the By feeding back the predicted values and controlling the operations of the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6, the oxidant electrode pressure of the fuel cell stack 5 is maintained at a desired pressure.

  The cooling mechanism and the humidifying means are omitted because they are not directly related to the characteristic part of the present invention. FIG. 1 shows a configuration applicable to each of the first to fourth embodiments. In the first embodiment, the oxidizing gas pressure sensor 4 and the fuel gas pressure sensor 9 are not used, and the oxidation is performed. In this configuration, the agent gas pressure sensor 4 and the fuel gas pressure sensor 9 are not provided. Therefore, the pressure control of the fuel gas and the oxidant gas by the controller 10 described above is performed based on the predicted value.

  Furthermore, the controller 10 is configured as a microcomputer having, for example, a CPU, a ROM, a RAM, a peripheral interface, and the like, reads the detection values of various sensors, and based on the determination, calculation result, or prediction value for the detection values, Various control signals are output to control the operation of each part of the fuel cell system.

  The characteristic control in the controller 10 of this embodiment is that the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated when the output of the fuel cell stack 5 decreases, When the pressure ratio of the oxidant gas compressor 2 is within the predetermined range, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off to hold the oxidant gas pressure in the fuel cell stack 5. Then, the operation of the oxidant gas compressor 2 is stopped, and after the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated, and the oxidant gas When the gas flow rate and the oxidant gas compressor pressure ratio are out of the predetermined ranges, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened to operate the oxidant gas compressor 2. The point is to resume.

  Here, the predetermined range of the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 is such that the oxidant gas compressor 2 undergoes surging on the plane of the oxidant gas flow rate to the pressure ratio of the oxidant gas compressor 2. This is a possible surging area. Specifically, in the explanatory diagrams of FIGS. 3 and 4, the outside of the (triangular) area SA is the surging area of the oxidant gas compressor 2, and the inside of the area SA is the surging area of the oxidant gas compressor 2. This is an area where stable operation is possible outside.

  Next, the operation at the time of operation of the fuel cell system of the present embodiment configured as described above will be described with reference to FIGS. Here, FIG. 2 is a flowchart for explaining operation control in the fuel cell system of the first embodiment, and FIGS. 3 and 4 are oxidant gas on the plane of the ratio of the oxidant gas flow rate to the pressure ratio of the oxidant gas compressor 2. FIG. 4 is an explanatory diagram for explaining the transition of operating points of the compressor 2.

  First, in response to an output reduction instruction (output fluctuation) of the fuel cell stack 5 in normal operation (step S101), the controller 10 estimates the current flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2. (Step S102).

  Here, when the output currently taken out from the fuel cell stack 5 is determined, the pressure and flow rate at the inlet of the fuel cell stack 5 are determined, and the pressure loss characteristics of each part up to the inlet of the fuel cell stack 5 are also determined in advance. Since it is known, the pressure (pressure ratio) required at the outlet of the oxidant gas compressor 2 can also be calculated. At this time, the pressure loss calculation of the temperature of the oxidant gas is required, but it can be calculated from the pressure ratio of the oxidant gas compressor 2. That is, if the pressure ratio and the temperature of the oxidant gas compressor 2 outlet are repeatedly calculated, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 can be predicted by calculation.

  That is, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated according to the following procedure.

Procedure 1: Based on the output of the fuel cell stack 5, the flow rate (NL / min) of the oxidant gas at the inlet of the fuel cell stack 5 and the required oxidant gas pressure at the inlet of the fuel cell stack 5 are obtained with reference to a predetermined map table. .

Procedure 2: The approximate pressure ratio of the oxidant gas compressor 2 is calculated from the required oxidant gas pressure at the inlet of the fuel cell stack 5.

Procedure 3: The oxidant gas temperature at the outlet of the oxidant gas compressor 2 is calculated from the approximate pressure ratio of the oxidant gas compressor 2.

Procedure 4: The pressure loss of each component is obtained from the approximate pressure ratio of the oxidant gas compressor 2 and the oxidant gas temperature at the outlet of the oxidant gas compressor 2.

Procedure 5: Calculate the oxidant gas pressure at the inlet of the fuel cell stack 5 based on the pressure loss of each component, and compare it with the required oxidant gas pressure at the inlet of the fuel cell stack 5.

Procedure 6: Based on the comparison, the pressure ratio of the oxidant gas compressor 2 is corrected, and the oxidant gas temperature at the outlet of the oxidant gas compressor 2 is calculated.

Procedure 7: The oxidant gas pressure at the inlet of the fuel cell stack 5 is calculated from the corrected pressure ratio of the oxidant gas compressor 2 and the oxidant gas temperature at the outlet of the oxidant gas compressor 2, and the oxidant at the inlet of the fuel cell stack 5 is calculated. Compare with gas demand pressure.

(Repeat step 6 and step 7.)
When the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated in this manner, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are then calculated in the surging region (FIG. It is determined whether or not the area is within the hatched area outside area 3 (step S105).

  On the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the estimated flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is the surging region. When it is outside (in the area SA), the process returns to step S102 and the normal operation of the oxidant gas compressor 2 is continued.

  When the operating point of the oxidant gas compressor 2 (the estimated flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is within the surging region (outside the region SA), the oxidant gas compressor 2 (Step S106), the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off (step S107), and the oxidant gas pressure in the fuel cell stack 5 is maintained. .

  After the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas is lowered and the pressure ratio of the oxidant gas compressor 2 is also lowered as shown by the broken line in FIG. Then, the current flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated (step S108).

  Similarly to step S105, it is determined whether or not the estimated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are within the surging region (outside the region SA) (step S111). On the plane of the flow ratio to the pressure ratio of the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the estimated flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is within the surging region (region). If it is outside (SA), the process returns to step S108 and the oxidant gas compressor 2 is kept stopped.

  When the operating point of the oxidant gas compressor 2 (the estimated flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is outside the surging region (inside the region SA), the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened (step S112), the oxidant gas compressor 2 is started and the operation is restarted (step S113).

  With the above procedure, on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 3), the operating point of the oxidant gas compressor 2 is determined from the PQ1 to the target oxidant gas flow rate and The pressure ratio of the oxidant gas compressor 2 changes to PQt.

  As described above, in the fuel cell system of the present embodiment, when the output of the fuel cell stack 5 decreases, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated, and the flow rate of the oxidant gas When the pressure ratio of the oxidant gas compressor 2 is in the surging region, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off to maintain the oxidant gas pressure in the fuel cell stack 5. Then, the operation of the oxidant gas compressor 2 is stopped, and after the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated, and the oxidant gas When the gas flow rate and the pressure ratio of the oxidant gas compressor are out of the surging region, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened, and the operation of the oxidant gas compressor 2 is resumed. Because we decided to do so, oxidant gas compression Avoiding operation of the oxidant gas compressor at a high pressure and a low flow rate when 2 is in a surging region (an unstable operation region or a stall region of the oxidant gas compressor 2) that may cause surging, It is possible to improve the driving efficiency by enabling the stable driving and avoiding the driving under the low driving efficiency.

  In this embodiment, a turbo compressor is used as the oxidant gas compressor 2 and its surging area is illustrated in FIG. 3, but the surging area in the case of using a Rishorum compressor is a broken line in FIG. It is outside the (triangular) area SB indicated by. That is, in FIG. 4, when the Rishorum type compressor is used, when the operating point of the oxidant gas compressor 2 is changed from PQ1 to PQt, the operating point of the oxidant gas compressor 2 changes outside the surging region. However, when a turbo compressor is used, the oxidant gas compressor 2 passes through a surging region where surging may occur. That is, according to the present embodiment, a stable operation can be performed regardless of the type of the oxidant gas compressor 2.

  Next, a fuel cell system according to Example 2 of the present invention will be described. The configuration of the fuel cell system of Example 2 is the same as that of Example 1 (FIG. 1), and a specific description of each component is omitted.

  However, in Example 2, the oxidant gas pressure sensor 4 is used, but the fuel gas pressure sensor 9 is not used, and the fuel gas pressure sensor 9 is not provided. Therefore, the pressure control of the fuel gas by the controller 10 is performed based on the predicted value.

  The characteristic control in the controller 10 of the second embodiment is that the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 based on the detection result of the oxidant gas pressure sensor 4 when the output of the fuel cell stack 5 decreases. And the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off when the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are within the respective predetermined ranges. Then, the operation of the oxidant gas compressor 2 is stopped while the oxidant gas pressure in the fuel cell stack 5 is maintained, and after the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas and the oxidant gas compressor 2 and when the oxidant gas flow rate and the oxidant gas compressor pressure ratio deviate from their respective predetermined ranges, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 Open the oxidant gas pressure There is a point to resume the operation of the machine 2.

  The oxidant gas compressor 2 may cause surging within a predetermined range of the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 on the plane of the oxidant gas flow rate to the pressure ratio of the oxidant gas compressor 2. The characteristic surging area (outside the area SA) is the same as that of the first embodiment (see FIGS. 3 and 4).

  Next, the operation at the time of operation of the fuel cell system of the present embodiment will be described with reference to FIG. 3 and FIG. Here, FIG. 5 is a flowchart for explaining operation control in the fuel cell system of the second embodiment.

  First, when an output reduction instruction (output fluctuation) of the fuel cell stack 5 is given in normal operation (step S201), the controller 10 determines the current flow rate of the oxidant gas based on the detection result of the oxidant gas pressure sensor 4. The pressure ratio of the oxidant gas compressor 2 is calculated (step S202).

  Next, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are within the surging region (the hatched region outside the region SA in FIG. 3) (step S205).

  On the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is outside the surging region ( When in the area SA), the process returns to step S202, and the normal operation of the oxidant gas compressor 2 is continued.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is within the surging region (outside the region SA), the operation of the oxidant gas compressor 2 is performed. (Step S206), the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off (step S207), and the oxidant gas pressure in the fuel cell stack 5 is maintained.

  After the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas is lowered and the pressure ratio of the oxidant gas compressor 2 is also lowered thereafter, as shown by the broken line in FIG. Then, based on the detection result of the oxidant gas pressure sensor 4, the current flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are calculated (step S208).

  Similarly to step S205, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are within the surging region (outside the region SA) (step S211). On the plane of the pressure ratio of the flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is within the surging region (outside the region SA). ), The process returns to step S208, and the oxidant gas compressor 2 is stopped.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) is outside the surging region (inside the region SA), the oxidant gas pressure holding valve 3 and The oxidant gas outlet pressure regulating valve 6 is opened (step S212), the oxidant gas compressor 2 is started, and the operation is restarted (step S213).

  With the above procedure, on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 3), the operating point of the oxidant gas compressor 2 is determined from the PQ1 to the target oxidant gas flow rate and The pressure ratio of the oxidant gas compressor 2 changes to PQt.

  As described above, in the fuel cell system of this embodiment, when the output of the fuel cell stack 5 decreases, the flow rate of the oxidant gas and the pressure of the oxidant gas compressor 2 are determined based on the detection result of the oxidant gas pressure sensor 4. When the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are in the surging region, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off. While maintaining the oxidant gas pressure in the fuel cell stack 5, the operation of the oxidant gas compressor 2 is stopped. After the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas and the oxidant gas compressor 2 are stopped. When the oxidant gas flow rate and the oxidant gas compressor pressure ratio deviate from the surging region, the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened. The oxidant gas compressor 2 Therefore, when the oxidant gas compressor 2 is in a surging region (an unstable operation region or a stall region of the oxidant gas compressor 2) in which surging may occur, the pressure is high and the flow rate is low. This avoids the operation of the oxidizer gas compressor, enables stable operation regardless of the type of oxidizer gas compressor, and improves operation efficiency by avoiding operation under poor operating efficiency. Can be made.

  In addition, compared with the first embodiment, more accurate oxidant gas flow rate and pressure ratio of the oxidant gas compressor 2 can be obtained based on the detection result of the oxidant gas pressure sensor 4, and thus more accurate. It becomes possible to control the operation of the oxidant gas compressor 2 in the surging region, and the operation time of the oxidant gas compressor 2 can be reduced by shortening the stop time of the oxidant gas compressor 2. Can be resumed.

  Next, a fuel cell system according to Example 3 of the present invention will be described. The configuration of the fuel cell system of Example 3 is the same as that of Example 1 (FIG. 1), and a specific description of each component is omitted.

  However, in the third embodiment, the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9 are not used, but the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9 are provided. Therefore, the pressure control of the fuel gas and the oxidant gas by the controller 10 is performed based on the actually measured values.

  The characteristic control in the controller 10 of the third embodiment is that the flow rate of the oxidant gas and the oxidant are determined based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9 when the output of the fuel cell stack 5 decreases. The pressure ratio in consideration of the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the gas compressor 2 is calculated, and the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are in respective predetermined ranges. The oxidant gas pressure maintaining valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off, and the oxidant gas compressor 2 is stopped while maintaining the oxidant gas pressure in the fuel cell stack 5. After the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated, and the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor are Out of range Occasionally, opens the oxidant gas pressure holding valve 3 and the oxidant gas outlet regulating valve 6 lies in that to resume the operation of the oxidizing gas compressor 2.

  The oxidant gas compressor 2 may cause surging within a predetermined range of the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 on the plane of the oxidant gas flow rate to the pressure ratio of the oxidant gas compressor 2. The characteristic surging area (outside the area SA) is the same as that of the first embodiment (see FIGS. 3 and 4).

  Next, the operation at the time of operation of the fuel cell system of the present embodiment will be described with reference to FIG. 3 and FIG. Here, FIG. 6 is a flowchart for explaining operation control in the fuel cell system of the third embodiment.

  First, when the output reduction instruction (output fluctuation) of the fuel cell stack 5 is given in the normal operation (step S301), the controller 10 determines the oxidant based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9. A gas flow rate and a pressure ratio in consideration of the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the oxidant gas compressor 2 are calculated (steps S302 and S303).

  Next, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure) are within the surging region (the shaded region outside the region SA in FIG. 3) ( Step S305).

  On the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) ) Is outside the surging area (in the area SA), the process returns to step S302 and the normal operation of the oxidant gas compressor 2 is continued.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) is within the surging region (outside the region SA), the oxidant The operation of the gas compressor 2 is stopped (step S306), the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off (step S307), and the oxidant gas pressure in the fuel cell stack 5 is held. Keep it.

  After the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas is lowered and the pressure ratio of the oxidant gas compressor 2 is also lowered thereafter, as shown by the broken line in FIG. Similarly, based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9, the flow rate of the oxidant gas and the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the oxidant gas compressor 2 are considered. The calculated pressure ratio is calculated (steps S308 and S309).

  Similarly to step S305, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure) are within the surging region (outside the region SA) (step 305). S311), on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (differential pressure) Is taken into the surging area (outside the area SA), the process returns to step S308 and the oxidant gas compressor 2 is kept stopped.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) is outside the surging region (inside the region SA), the oxidant The gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened (step S312), the oxidant gas compressor 2 is started, and the operation is restarted (step S313).

  With the above procedure, on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 3), the operating point of the oxidant gas compressor 2 is determined from the PQ1 to the target oxidant gas flow rate and The pressure ratio of the oxidant gas compressor 2 changes to PQt.

  As described above, in the fuel cell system of this embodiment, when the output of the fuel cell stack 5 decreases, the flow rate of the oxidant gas and the oxidant are determined based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9. The pressure ratio in consideration of the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the gas compressor 2 is calculated, and the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are in the surging region. Sometimes, the operation of the oxidant gas compressor 2 is stopped while the oxidant gas pressure maintaining valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off and the oxidant gas pressure in the fuel cell stack 5 is maintained. After the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated, and the oxidant gas flow rate and the oxidant gas compressor pressure ratio are out of the surging region. When the acid Since the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened and the operation of the oxidant gas compressor 2 is resumed, surging that may cause the oxidant gas compressor 2 to perform surging. Avoid operating the oxidant gas compressor at high pressure and low flow rate when it is in the region (unstable operating region or stalled region of the oxidant gas compressor 2), regardless of the type of oxidant gas compressor In addition to enabling stable operation, it is possible to improve operation efficiency by avoiding operation under conditions where operation efficiency is poor.

  Compared with the first and second embodiments, the pressure of the oxidant gas compressor 2 in consideration of the differential pressure that the electrolyte membrane in the fuel cell stack 5 can withstand based on the detection result of the fuel gas pressure sensor 9. The ratio is obtained, the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 6 is anticipated, and the operation of the oxidant gas compressor 2 is restarted. The operation in the surging region of 2 can be reliably avoided, and the stop time of the oxidant gas compressor 2 can be shortened and the operation of the oxidant gas compressor 2 can be restarted.

  Next, a fuel cell system according to Example 4 of the present invention will be described. The configuration of the fuel cell system of Example 4 is the same as that of Example 1 (FIG. 1), and a specific description of each component is omitted.

  However, in Example 4, the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9 are not used, but the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9 are provided. Therefore, the pressure control of the fuel gas and the oxidant gas by the controller 10 is performed based on the actually measured values.

  Similarly to the third embodiment, when the output of the fuel cell stack 5 decreases, the flow rate of the oxidant gas and the fuel of the oxidant gas compressor 2 are determined based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9. The pressure ratio in consideration of the differential pressure that can be withstood by the electrolyte membrane in the battery stack 5 is calculated, and when the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 are in the respective predetermined ranges, oxidation is performed. The operation of the oxidant gas compressor 2 is stopped while the oxidant gas pressure maintaining valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off and the oxidant gas pressure in the fuel cell stack 5 is maintained, and the oxidant gas compressor is stopped. 2 when the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 are estimated and the oxidant gas flow rate and the oxidant gas compressor pressure ratio deviate from their predetermined ranges. In addition, the oxidant gas pressure holding valve 3 The oxidant gas outlet pressure regulating valve 6 is opened, and the operation of the oxidant gas compressor 2 is resumed. The characteristic control in the controller 10 of the fourth embodiment is performed while the oxidant gas compressor 2 is stopped. When the output request is changed, the opening degree of the oxidant gas pressure holding valve 3, the oxidant gas outlet pressure regulating valve 6 and the fuel gas supply valve 8 is adjusted, and the operation of the oxidant gas compressor 2 is resumed. is there.

  Here, when the oxidant gas pressure predicted based on the changed required output is higher than the oxidant gas pressure at the oxidant electrode of the current fuel cell stack 5, the oxidant gas pressure holding valve 3, the oxidant gas While adjusting the opening degree of the outlet pressure regulating valve 6 and the fuel gas supply valve 8, the oxidant gas compressor 2 is returned to the normal operation state.

  Further, when the oxidant gas pressure predicted based on the changed required output is lower than the oxidant gas pressure at the oxidant electrode of the current fuel cell stack 5, and the required output is larger than the initial target required output. The oxidant gas pressure holding valve 3, oxidation is performed so that the operation of the oxidant gas compressor 2 is resumed at the minimum oxidant gas flow rate that remains at the current pressure ratio of the oxidant gas compressor 2 and out of the predetermined range. The opening degree of the agent gas outlet pressure regulating valve 6 and the fuel gas supply valve 8 is adjusted.

  Further, when the oxidant gas pressure predicted based on the changed required output is lower than the oxidant gas pressure at the oxidant electrode of the current fuel cell stack 5, and the required output is smaller than the initial target required output. Oxidant gas pressure holding valve 3, oxidant gas outlet pressure regulating valve 6 and fuel gas supply valve so as to restart the operation of oxidant gas compressor 2 at a pressure ratio of oxidant gas compressor 2 outside the predetermined range. Adjust the opening of 8.

  The oxidant gas compressor 2 may cause surging within a predetermined range of the oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 on the plane of the oxidant gas flow rate to the pressure ratio of the oxidant gas compressor 2. The characteristic surging region (outside the region SA in FIG. 9) is the same as that of the first embodiment (see FIGS. 3 and 4).

  Next, the operation at the time of operation of the fuel cell system of the present embodiment will be described with reference to FIG. 7, FIG. 8, and FIG. 7 and 8 are flowcharts for explaining the operation control in the fuel cell system of the third embodiment. FIG. 9 is an oxidant gas on the plane of the ratio of the oxidant gas flow rate to the pressure ratio of the oxidant gas compressor 2. FIG. 4 is an explanatory diagram for explaining the transition of operating points of the compressor 2.

  First, when an output reduction instruction (output fluctuation) of the fuel cell stack 5 is given in normal operation (step S401), the controller 10 determines the oxidant based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9. A gas flow rate and a pressure ratio in consideration of the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the oxidant gas compressor 2 are calculated (steps S402 and S403).

  Next, it is determined whether or not there is a change in the target output (step S404). If there is a change in the target output, the process shifts to a process for canceling the output fluctuation operation shown in FIG. 8 (step S415), and the target output. If there is no change, the process proceeds to step S405 as in the third embodiment.

  In step S405, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure) are within the surging area (the hatched area outside the area SA in FIG. 9). .

  On the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) ) Is outside the surging area (in the area SA), the process returns to step S402 and the normal operation of the oxidant gas compressor 2 is continued.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) is within the surging region (outside the region SA), the oxidant The operation of the gas compressor 2 is stopped (step S406), the oxidant gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are shut off (step S407), and the oxidant gas pressure in the fuel cell stack 5 is held. Keep it.

  After the operation of the oxidant gas compressor 2 is stopped, the flow rate of the oxidant gas is lowered and the pressure ratio of the oxidant gas compressor 2 is also lowered thereafter, as shown by the broken line in FIG. Similarly, based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9, the flow rate of the oxidant gas and the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the oxidant gas compressor 2 are considered. The calculated pressure ratio is calculated (steps S408 and S409).

  Further, similarly to step S405, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure) are within the surging region (outside the region SA) (step 405). S411), on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (differential pressure) Is taken into the surging area (outside the area SA), the process returns to step S408 and the oxidant gas compressor 2 is kept stopped.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) is outside the surging region (inside the region SA), the oxidant The gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened (step S412), the oxidant gas compressor 2 is started, and the operation is restarted (step S413).

  With the above procedure, on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 9), the operating point of the oxidant gas compressor 2 is determined from the PQ1 to the target oxidant gas flow rate and The pressure ratio of the oxidant gas compressor 2 changes to PQt.

  Next, the process of canceling the output fluctuation operation that is performed when the target output fluctuates in step S404 will be described with reference to FIG.

  If the target output varies, first, the oxidant gas flow rate with respect to the target output and the pressure ratio of the oxidant gas compressor 2 are calculated (step S502).

  Next, whether or not the oxidant gas pressure predicted based on the changed required output is higher than the oxidant gas pressure of the oxidant electrode of the fuel cell stack 5 based on the detection result of the current oxidant gas pressure sensor 4. Is determined (step S503).

  When the oxidant gas pressure predicted based on the changed required output is higher than the oxidant gas pressure at the oxidant electrode of the current fuel cell stack 5, the oxidant gas pressure holding valve 3, the oxidant gas outlet pressure regulating valve 6 and the opening degree of the fuel gas supply valve 8 (step S504), the oxidant gas compressor 2 is started (step S505) and returned to the normal operation state (step S506).

  With the above procedure, the target output fluctuates at the operating point PQc of the oxidant gas compressor 2 on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 9). The operating point of the gas compressor 2 changes to a target operating point (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) PQf1 with respect to the required output changed from PQ1.

  In step S503, when the oxidant gas pressure predicted based on the changed required output is lower than the oxidant gas pressure of the oxidant electrode of the current fuel cell stack 5, the required output is set to the initial target. It is determined whether the output is larger than the requested output (step S511).

  When the required output is larger than the initial target required output, the oxidant gas compression is performed at the minimum oxidant gas flow rate that remains at the current pressure ratio of the oxidant gas compressor 2 and that is outside the surging region (outside the region SA). The opening degree of the oxidant gas pressure holding valve 3, the oxidant gas outlet pressure regulating valve 6 and the fuel gas supply valve 8 is adjusted so as to resume the operation of the machine 2 (steps S512 and S513), and the normal operation state is restored ( Step S514).

  With the above procedure, the target output fluctuates at the operating point PQc of the oxidant gas compressor 2 on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 9). The operation of the oxidant gas compressor 2 is resumed at the lowest oxidant gas flow rate that increases only the flow rate of the oxidant gas while maintaining the pressure ratio of the oxidant gas compressor 2 and deviates from the surging region (outside the region SA). The operating point of the oxidant gas compressor 2 changes to a target operating point (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) PQf2 with respect to the required output changed from PQ1.

  In step S511, if the required output is smaller than the initial target output, the oxidant is detected based on the detection results of the oxidant gas pressure sensor 4 and the fuel gas pressure sensor 9 as in steps S402 and S403. A gas flow rate and a pressure ratio in consideration of the differential pressure that can be withstood by the electrolyte membrane in the fuel cell stack 5 of the oxidant gas compressor 2 are calculated (steps S521 and S522).

  Further, it is determined whether or not there is a change in the target output (step S523). If there is a change in the target output, the process returns to the beginning of the output change operation stop process (step S502) again, and there is no change in the target output. In that case, the process proceeds to step S524.

  In step S524, as in step S405, it is determined whether or not the calculated oxidant gas flow rate and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure) are within the surging region (outside the region SA). On the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2, the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure) )) Is within the surging area (outside the area SA), the process returns to step S521 and the oxidant gas compressor 2 is stopped.

  When the operating point of the oxidant gas compressor 2 (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2 (considering the differential pressure)) is outside the surging region (inside the region SA), the oxidant The gas pressure holding valve 3 and the oxidant gas outlet pressure regulating valve 6 are opened (step S525), the oxidant gas compressor 2 is started and the operation is restarted (step S526).

  With the above procedure, the target output fluctuates at the operating point PQc of the oxidant gas compressor 2 on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 (see FIG. 9), and then the fuel The oxidant gas pressure at the oxidant electrode of the battery stack 5 decreases, and the operation of the oxidant gas compressor 2 is restarted at the pressure ratio of the oxidant gas compressor 2 out of the surging region (outside the region SA). The operating point of the oxidant gas compressor 2 changes to a target operating point (the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor 2) PQf3 with respect to the required output changed from PQ1.

  As described above, in the fuel cell system of this embodiment, when the output request is changed while the oxidant gas compressor 2 is stopped, the oxidant gas pressure holding valve 3, the oxidant gas outlet pressure regulating valve 6, and The operation of the oxidant gas compressor 2 is resumed by adjusting the opening degree of the fuel gas supply valve 8 and an instruction to resume operation is given when the output request is changed while the oxidant gas compressor 2 is stopped. Since it is the structure which can be performed, operation | movement can be restarted again even if the oxidizing gas compressor 2 stops.

  Further, in the fuel cell system of the present embodiment, when the oxidant gas pressure predicted based on the changed required output is higher than the oxidant gas pressure of the oxidant electrode of the current fuel cell stack 5, the oxidant gas Since the oxidant gas compressor 2 is returned to the normal operation state while adjusting the opening degree of the pressure holding valve 3, the oxidant gas outlet pressure regulating valve 6 and the fuel gas supply valve 8, the oxidant gas compressor 2 is stopped. In particular, driving can be resumed.

  Further, in the fuel cell system of this embodiment, the oxidant gas pressure predicted based on the changed required output is lower than the oxidant gas pressure of the oxidant electrode of the current fuel cell stack 5, and the required output is initially When it is larger than the target required output, the operation of the oxidant gas compressor 2 is resumed at the minimum oxidant gas flow rate that remains at the current pressure ratio of the oxidant gas compressor 2 and out of the predetermined range. Since the opening degree of the oxidant gas pressure holding valve 3, the oxidant gas outlet pressure regulating valve 6 and the fuel gas supply valve 8 is adjusted, the operation is restarted even when the oxidant gas compressor 2 is stopped, and the oxidant gas compression is performed. The machine 2 can return to the normal operation mode.

  Furthermore, in the fuel cell system of the present embodiment, the oxidant gas pressure predicted based on the changed required output is lower than the oxidant gas pressure of the oxidant electrode of the current fuel cell stack 5, and the required output is initially When the output is smaller than the target required output, the oxidant gas pressure holding valve 3 and the oxidant gas are restarted so that the operation of the oxidant gas compressor 2 is resumed at the pressure ratio of the oxidant gas compressor 2 outside the predetermined range. Since the opening degree of the outlet pressure regulating valve 6 and the fuel gas supply valve 8 is adjusted, the operation can be resumed even when the oxidant gas compressor 2 is stopped, and the normal operation mode of the oxidant gas compressor 2 can be returned. .

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. 3 is a flowchart for explaining operation control in the fuel cell system according to the first embodiment. It is explanatory drawing explaining transition of the operating point of the oxidant gas compressor 2 on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2. FIG. 6 is an explanatory diagram (by type) illustrating the transition of the operating point of the oxidant gas compressor 2 on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2. 6 is a flowchart illustrating operation control in the fuel cell system according to the second embodiment. 6 is a flowchart illustrating operation control in the fuel cell system of Example 3. 7 is a flowchart (No. 1) for explaining operation control in the fuel cell system of Embodiment 4. 10 is a flowchart (part 2) illustrating operation control in the fuel cell system of Example 4. FIG. 10 is an explanatory diagram for explaining the transition of the operating point of the oxidant gas compressor 2 on the plane of the pressure ratio of the oxidant gas flow rate to the oxidant gas compressor 2 of Example 4;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oxidant gas supply device 2 Oxidant gas compressor 3 Oxidant gas pressure holding valve 4 Oxidant gas pressure sensor 5 Fuel cell stack 6 Oxidant gas outlet pressure regulating valve 7 Fuel gas supply device 8 Fuel gas supply valve 9 Fuel gas pressure Sensor 10 Controller

Claims (9)

A fuel cell that generates power by supplying fuel gas and oxidant gas;
Fuel gas supply means for supplying fuel gas to the fuel cell while adjusting fuel gas pressure by a fuel gas supply valve;
An oxidant gas supply means for supplying an oxidant gas to the fuel cell while adjusting the pressure of the oxidant gas supplied from the oxidant gas compressor by an oxidant gas pressure holding valve and an oxidant gas outlet pressure regulating valve;
When the output of the fuel cell is reduced, the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor are estimated, and the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor are within respective predetermined ranges. Control means for shutting down the operation of the oxidant gas compressor while maintaining the oxidant gas pressure in the fuel cell by shutting off the oxidant gas pressure holding valve and the oxidant gas outlet pressure regulating valve at a certain time When,
A fuel cell system comprising:   The control means estimates the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor after the operation of the oxidant gas compressor is stopped, and the oxidant gas flow rate and the oxidant gas compressor are estimated. The operation of the oxidant gas compressor is resumed by opening the oxidant gas pressure holding valve and the oxidant gas outlet pressure regulating valve when the pressure ratio is out of a predetermined range. Item 4. The fuel cell system according to Item 1. The oxidant gas supply means has an oxidant gas pressure sensor at the oxidant electrode inlet of the fuel cell,
3. The control unit according to claim 1, wherein the control unit calculates the flow rate of the oxidant gas and the pressure ratio of the oxidant gas compressor based on a detection result of the oxidant gas pressure sensor. The fuel cell system according to item. The fuel gas supply means has a fuel gas pressure sensor at the fuel electrode inlet of the fuel cell,
The control means calculates a pressure ratio of the oxidant gas compressor as a pressure ratio considering a differential pressure that can be withstood by the electrolyte membrane in the fuel cell, based on a detection result of the fuel gas pressure sensor. The fuel cell system according to any one of claims 1 to 3.   The predetermined range of the oxidant gas flow rate and the oxidant gas compressor pressure ratio may cause the oxidant gas compressor to surging on a plane of the oxidant gas flow rate to the oxidant gas compressor pressure ratio. The fuel cell system according to any one of claims 1 to 4, wherein the fuel cell system is a surging region.   The control means adjusts the opening degrees of the oxidant gas pressure holding valve, the oxidant gas outlet pressure regulating valve, and the fuel gas supply valve when an output request is changed while the oxidant gas compressor is stopped. The fuel cell system according to any one of claims 1 to 5, wherein the operation of the oxidant gas compressor is resumed.   When the oxidant gas pressure predicted based on the changed required output is higher than the oxidant gas pressure at the oxidant electrode of the current fuel cell, the control means is configured to provide the oxidant gas pressure holding valve, the oxidant The fuel cell system according to claim 6, wherein the oxidant gas compressor is returned to a normal operation state while adjusting an opening degree of a gas outlet pressure regulating valve and the fuel gas supply valve.   The control means is configured such that the oxidant gas pressure predicted based on the changed demand output is lower than the oxidant gas pressure at the oxidant electrode of the current fuel cell, and the demand output is larger than the originally desired demand output. The oxidant gas pressure holding valve, the oxidant gas pressure holding valve, so as to restart the operation of the oxidant gas compressor at a minimum oxidant gas flow rate that remains at the current oxidant gas compressor pressure ratio and is out of the predetermined range. The fuel cell system according to claim 6, wherein the opening degree of the oxidant gas outlet pressure regulating valve and the fuel gas supply valve is adjusted.   The control means is configured such that the oxidant gas pressure predicted based on the changed required output is lower than the oxidant gas pressure of the oxidant electrode of the current fuel cell, and the required output is smaller than the initial target required output. The oxidant gas pressure holding valve, the oxidant gas outlet pressure regulating valve, and the fuel gas supply so as to resume the operation of the oxidant gas compressor at an oxidant gas compressor pressure ratio outside the predetermined range. The fuel cell system according to claim 6, wherein the opening of the valve is adjusted.

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