KR100742301B1 - Fuel cell system and operating method thereof - Google Patents

Abstract

Provided are a fuel cell system, which prevents the production of electric power to be supplied to peripheral devices in an abnormal cell within a fuel cell stack, and thus supplies electric power stably, and an operating method thereof. The fuel cell system(100) comprises: a fuel cell stack(110) which produces direct electric power by an electrochemical reaction of hydrogen and oxygen; a fuel supply device(120) which supplies a hydrogen-containing reformed gas to the fuel cell stack(110); an oxidant supply device(130) which supplies an oxygen-containing oxidant to the fuel cell stack(110); many peripheral devices(BOP) which perform the start, stop, and generation-state maintenance operations of the system using electric power generated from the fuel cell stack(110); and a power distribution device(150) which distributes electric power generated from the fuel cell stack(110) to the many peripheral devices(BOP), respectively. The fuel cell stack(110) has current collectors which divide the many stacked unit cells into at least two regions, are placed at both ends of the unit cells, and collect an electric current generated by the unit cells between the both ends. The power distribution device(150) selectively distributes electric power of a specific region generated among at least two regions in the fuel cell stack(110), to the many peripheral devices(BOP).

Description

Fuel Cell System and Operating Method Thereof

1 is a schematic diagram of a fuel cell system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a first embodiment of a DC power source supplied by the fuel cell stack shown in FIG. 1.

FIG. 3 is a flowchart illustrating a method of distributing power depending on whether a specific cell is generated in the fuel cell stack illustrated in FIG. 2.

4 is a schematic diagram illustrating a second embodiment of a DC power source supplied by the fuel cell stack shown in FIG. 1.

FIG. 5 is a flowchart illustrating a method of distributing power according to whether a specific cell is generated in the fuel cell stack illustrated in FIG. 4.

FIG. 6 is a graph showing that the output cell voltage changes with time while changing the coolant temperature of the fuel cell stack shown in FIG. 1.

FIG. 7 is a graph showing that the output cell voltage changes with time while increasing the output power of the fuel cell stack shown in FIG.

FIG. 8 is a flowchart illustrating a process of predicting an abnormality of a specific cell in a fuel cell stack in advance by reflecting the results shown in FIGS. 6 and 7.

FIG. 9 is a graph showing an output voltage of a fuel cell stack implemented according to the operation step shown in FIG. 8.

10 is a schematic diagram of a fuel cell system according to the prior art.

※ Explanation of code about main part of drawing ※

100, 200: fuel cell system 110, 210: fuel cell stack

120, 220: fuel supply device 130, 230: oxidant supply device

140, 240: cooling device 150, 250: power distribution device

The present invention relates to a fuel cell system that generates electric power by an electrochemical reaction between hydrogen and oxygen, and more particularly, a fuel supplying stable power by preventing an excessive drop in voltage of a specific cell in a fuel cell stack. A battery system and a method of operating the same.

A polymer electrolyte fuel cell is a fuel cell using a polymer membrane having a hydrogen ion exchange characteristic as an electrolyte, and generates electricity and heat by causing an electrochemical reaction using a fuel gas containing hydrogen and air containing oxygen. Such a polymer electrolyte fuel cell has a fast starting capability and can be miniaturized, and thus, the polymer electrolyte fuel cell is widely used in various fields such as a mobile power source, an automotive power source, and a home cogeneration plant.

10 is a schematic diagram of a fuel cell system according to the prior art.

As shown in FIG. 10, the fuel cell system 200 according to the related art includes a fuel cell stack 210 for producing direct current power by an electrochemical reaction between hydrogen and oxygen, and natural gas (LNG) or liquefied petroleum gas. A fuel supply device 220 for reforming a hydrocarbon-based power source F, such as LPG, into hydrogen-rich gas and supplying the fuel cell stack 210 to the fuel cell stack 210, and an oxidant containing oxygen in the fuel cell stack 210. It is provided with an oxidant supply device 230 for supplying the cooling device, a cooling device 240 for cooling the fuel cell stack 210 as a main component, in addition to the controller for performing operations such as starting, stopping, maintaining the power generation state, Balance of Plants (BOPs) that require power, such as pumps, valves, sensors, and the like, are provided.

In addition, the conventional fuel cell system 200 includes a power distribution device 250 for distributing and supplying the power produced in the fuel cell stack 210 to a plurality of peripheral devices (BOPs) requiring power, respectively. An auxiliary power source such as an external AC power 260 or a battery 261 is also provided to provide starting power to the peripheral device BOP at the initial start-up and to stop the supply after the power is produced in the fuel cell stack 210. That is, in the fuel cell system 200 according to the related art, the auxiliary power supply provides the starting power of various peripheral devices (BOP) at the initial startup, and the fuel cell stack while the fuel supply device 220 and the cooling device 240 are stabilized. Various peripheral devices (BOPs) use the DC power generated at 210.

However, in the fuel cell system 200 according to the related art, when a voltage of a specific cell is lowered below a predetermined reference value during the operation maintenance operation and the operation is continued, the electrode of the corresponding cell is destroyed, and the specific cell is abnormal. Due to this problem, other adjacent cells are also weakened. Therefore, when there is a problem in a specific cell, measures such as reducing the output or stopping operation are necessary. However, in practice, the fuel cell system 200 according to the related art has an electrochemical reaction while the heat balance is shifted when the start-up and operation conditions are changed when there is an abnormality in a specific cell than when a voltage of a specific cell is continuously lowered. There is a problem that the generated water temporarily blocks the gas flow path. Thus, while conventionally reducing the output of the fuel cell stack 210 or stops the power production for a while, this also can not be a practical problem solving method because it can not supply a stable power.

The present invention has been proposed to solve the problems of the prior art as described above, two or more power sources supplied from the fuel cell stack to the power required by the various peripheral devices (BOP) that is a power consumption source through the power distribution device Provides a fuel cell system and a method of operating the same, by stably supplying generated power by preventing power generation for supplying to various peripheral devices (BOPs) in a specific cell in the fuel cell stack by configuring to be used selectively. Its purpose is to.

The fuel cell system of the present invention includes a fuel cell stack for producing direct current power by an electrochemical reaction between hydrogen and oxygen, a fuel supply device for supplying reformed gas containing hydrogen to the fuel cell stack, and a fuel cell stack for the fuel cell stack. An oxidant supply device for supplying an oxidant containing oxygen, and a plurality of BOPs (Balance of Balances) for starting, stopping, and maintaining a power generation state by using the power generated by the fuel cell stack, And a power distribution device configured to distribute and supply the power produced by the fuel cell stack to the plurality of peripheral devices (BOPs). In particular, the fuel cell stack is configured to divide the current generated by the unit cells of the corresponding region between both ends of the plurality of unit cells and the both ends of the plurality of unit cells sequentially stacked therein into two or more regions. The current collectors to be integrated are respectively located, and the power distribution unit selectively distributes and supplies power of a specific region to the plurality of peripheral devices (BOP) among powers produced in two or more regions in the fuel cell stack. It features.

In addition, the present invention preferably further includes an auxiliary power supply for providing initial starting power of the peripheral device (BOP) and stopping the power supply after the power is produced in the fuel cell stack.

In addition, the current collector of the present invention is preferably a material having a low contact resistance and a high allowable current.

In addition, the fuel cell stack of the present invention is composed of a plurality of fuel cell stacks connected in series or in parallel, the power distribution device is connected to each of the plurality of fuel cell stacks of the plurality of fuel cell stacks It is desirable to operate such that the load on the fuel cell stack in which an abnormality occurs or is predicted to occur is reduced.

As a method of operating the fuel cell system of the present invention, a method of distributing and supplying the peripheral device (BOP) to use the electric power produced by the fuel cell stack includes an abnormality among two or more regions partitioned by the current collector. The first step of selecting a region in which a specific cell is located or predicted to cause an abnormality, and the power generated in the remaining regions except for the region of the specific cell selected in the first stage, the peripheral device BOP. And a second step of distributing and connecting the power distribution unit so as to selectively use.

In addition, the present invention preferably searches first for an abnormality in the region where the first stacked cells and the last stacked cells are located in the first step.

In addition, the present invention preferably receives the initial starting power required by the peripheral device (BOP) from the external auxiliary power supply before the fuel cell stack generates power.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 is a schematic diagram of a fuel cell system according to an embodiment of the present invention.

As shown in FIG. 1, the fuel cell system 100 according to the present embodiment includes a fuel cell stack 110 for producing direct current power by an electrochemical reaction between hydrogen and oxygen, and a hydrogen-modified power source material F. A fuel supply device 120 for reforming gas to supply reformed gas to the fuel cell stack 110, an oxidant supply device 130 for supplying an oxidant containing oxygen to the fuel cell stack 110, and a fuel cell stack; Cooling device 140 for cooling 110, a power converter for converting the direct current (DC) power produced in the fuel cell stack 110 into alternating current (AC) power, and produced in the fuel cell stack 110 Balances of Plants (BOP), which perform start-up, stop, and maintenance of power generation systems using power, respectively, and power generated from the fuel cell stack 110 to a plurality of peripherals (BOP), respectively. A power distribution device 150 for distributing and supplying is provided. In addition, the fuel cell system 100 provides an initial starting power of the peripheral device (BOP) and the external AC power 160 or the battery 161 which stops the power supply after the power is produced in the fuel cell stack 110. The same auxiliary power supply is further provided.

FIG. 2 is a schematic view showing a first embodiment of a DC power supply supplied by the fuel cell stack shown in FIG. 1, and FIG. 3 is a distribution of power depending on an abnormality of a specific cell generated in the fuel cell stack shown in FIG. 2. It is a flowchart showing the method.

As shown in FIGS. 1 to 3, the fuel cell stack 110 of the present embodiment includes a plurality of unit current collectors disposed at both ends of the plurality of unit cells sequentially stacked therein and a current collector disposed between both ends thereof. The unit cells of are divided into two or more regions. The current collector is a means for integrating the currents produced by the unit cells in the area, but different forms or materials may be used depending on the operating conditions and specifications. However, if the current collector is not limited in shape and has a small contact resistance and a high allowable current, It may be a pin or a clip.

In FIG. 1 and FIG. 2, reference numeral 8 denotes the total voltage generated in the fuel cell stack 110, and 8-1 denotes a voltage generated in the first region when divided into three regions. -2 means a voltage generated in the second region, and 8-3 means a voltage generated in the third region. When a plurality of unit cells are partitioned into more than three, the n-th region is indicated by 8-n. In addition, the voltage generated in the fuel cell stack 110 is converted into a DC power source using a relay or semiconductor switching elements and an insulated DC / DC converter, and surrounds the fuel cell system 100 using the DC power source. Loads such as BOPs and power converters can be displayed broken down into 7-1, 7-2, ..., 7-m and the like.

In the fuel cell system of the present embodiment, a kind of load such as a peripheral device (BOP) selectively uses power generated by the fuel cell stack 110 according to the following method (see FIG. 3).

First of all, the fuel cell system 100 generates the starting power required by the loads 7-1, 7-2, ..., 7-m before power is produced in the fuel cell stack 110 during initial startup. A kind of load 7-1, 7-2, which is supplied from an auxiliary AC power source such as an external AC power 160 or a battery 161 and stably generates power in the fuel cell stack 110, and then is a peripheral device (BOP). , ..., 7-m) are supplied with the necessary power from the fuel cell stack 110.

Then, the fuel cell stack 110 is operated to search for an abnormality in a specific cell located in which of two or more regions partitioned by the current collector during power generation. Then, the power distribution unit 150 distributes and connects the power source generated in the remaining areas to selectively use the power source generated in the remaining areas, except in the region of the specific cell in which the abnormality occurs.

That is, by measuring whether the voltage 8-1 generated in the first region is lowered below a predetermined reference value and determining that there is an abnormality, the loads 7-1, 7-2,. One of the 7-m) is connected to use the voltage generated in one of the remaining regions 8-2, 8-3,..., 8-n. In the same process, it is determined whether an abnormality occurs from the voltage 8-2 generated in the second region to the voltage 8-n generated in the last region, and the load 7-1, of the fuel cell system 100 is determined. 7-2, ..., 7-m) are all supplied with power from the normal area.

However, one of the normal loads (7-1, 7-2, ..., 7-m) is for system users (eg DC / AC inverters, automotive motor drives), which is a power source It is not advisable to change this, except for this fixed load, only the remaining loads (m-1) can move the power source.

FIG. 4 is a schematic view showing a second embodiment of a DC power supply supplied by the fuel cell stack shown in FIG. 1, and FIG. 5 is a distribution of power depending on an abnormality of a specific cell generated in the fuel cell stack shown in FIG. 4. It is a flowchart showing the method.

In addition to the fuel cell stack 110 used in the fuel cell system 100 of the present embodiment, a general fuel cell stack may be a place where temporary abnormalities occur most frequently due to temporary excessive or insufficient humidification among a plurality of stacked unit cells. First and last unit cell. Therefore, in the present embodiment, as shown in FIG. 4, a current collector is positioned at both ends of a plurality of stacked unit cells, and the first and the last unit cells are divided between the plurality of unit cells so that each is divided into one region. The current collector is located. In the present embodiment, the switch 1 and the switch 2 are connected to a plurality of current collectors, respectively. Loads such as peripherals (BOPs) are interconnected. In this configuration, the fuel cell stack 110 illustrated in FIG. 4 may also be embodied in the same manner as illustrated in FIG. 2.

Herein, in the fuel cell stack 110 illustrated in FIG. 4, a plurality of unit cells except for a region where the first and last cells are located among the plurality of regions is set as one region. Then, when n = 3 and m = 2, 7-1 is the output of the fuel cell power generation system after power conversion, and 7-2 is used as starting power of the peripheral device (BOP) required for driving the system.

In addition, the fuel cell system 100 may selectively use power generated by the fuel cell stack 110 by loads of a kind such as a peripheral device (BOP) according to the following method (see FIG. 5).

First, the fuel cell system 100 may convert the starting power required by the loads 7-2 into the external AC power 160 or the battery 161 before power is produced in the fuel cell stack 110 at initial startup. It is supplied from the same auxiliary power supply.

Then, the fuel cell stack 110 is operated to measure whether the voltage of the region in which the first unit cell or the last unit cell is lowered during the power generation is measured, and when it is determined that both regions are abnormal. By operating the switch, the power supply 7-2 of the peripheral device BOP is connected to the region 8-3 of the unit cells except for the region where the first unit cell and the last unit cell are located. If it is determined that there is an error in the area where the first unit cell is located, the switch is operated to move the power supply 7-2 of the peripheral device to the area 8-1 of the unit cells except for the area where the first unit cell is located. Connect. If it is determined that there is an error in the region where the last unit cell is located, the switch is operated to connect the power supply 7-2 of the peripheral device to the region 8-2 of the unit cells except for the region where the last unit cell is located. .

As described above, the present embodiment reduces the burden caused by the power generation in the region determined to be abnormal, and waits for recovery of the unit cell in which the abnormality occurs, and then supplies the power supply 7-2 of the peripheral device to the fuel cell stack 110. The predetermined operation is completed by connecting to the entire area 8.

However, the output power 7-1 of the fuel cell system 100 is preferably connected to the entire region 8 of the fuel cell stack 110, and by operating a switch according to the state of the fuel cell stack 110. You may change it.

FIG. 6 is a graph showing that the output cell voltage changes with time while changing the coolant temperature of the fuel cell stack shown in FIG. 1, and FIG. 7 is a graph illustrating the output power of the fuel cell stack shown in FIG. This graph shows that the output cell voltage changes over time.

In general, a fuel cell system may have an equilibrium condition such as flow rate, pressure, temperature, etc. in a fuel cell stack due to factors such as generation power change or installation environment change during operation. In this transient state in which the operating conditions of the fuel cell system change, both cells stacked first and last of the fuel cell stack are most affected.

Referring to FIG. 6, in the fuel cell stack, as the temperature condition increases, the humidification condition is dried in a transient state where the temperature increases, and the last unit cell is affected, and as the temperature decreases, the first unit The cells are affected and eventually the voltages of the first and last unit cells tend to drop excessively. As shown in FIG. 7, the fuel cell stack has a tendency that the first and last unit cells are excessively lower than the average value as the output power condition required by the system increases. As shown in the above experiment, if the characteristics of the voltage change of the fuel cell stack are known in advance, unlike the method of FIG. 5, the fuel of the unit cell does not need to wait for the voltage of the unit cell to fall below a predetermined value as in FIG. 8. It would be more preferable to respond so that the voltage of the unit cell in which the abnormality is predicted before the operation condition of the battery stack changes is stabilized.

Thus, in the present embodiment, if data of a specific cell that is expected to cause an abnormal phenomenon is set according to the conditions of each flow rate, humidification condition, pressure, temperature, output power, etc., the specific cell predicted by referring to the data that has been previously possessed The power distribution device 150 is switched to operate in a direction to reduce the load on the region. Then, after a predetermined time elapses for the recovery of the specific cell with abnormality, the power distribution device 150 switches to the original connection state.

In addition, the present embodiment is a fuel cell stack including a specific cell that is expected to occur as described above, or even in the case of a fuel cell system in which a plurality of fuel cell stacks are connected in series or in parallel. The power distribution device is switched to operate in a direction to reduce the load, thereby producing stable power.

As a result, as shown in FIG. 9, it was confirmed that any unit cell did not drop excessively above the average cell voltage value, and the power could be stably supplied from the fuel cell stack.

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this, It can be variously modified and implemented in a claim, the detailed description of an invention, and the attached drawing, and this invention is also this invention. Naturally, it belongs to the range of.

As described in detail above, the fuel cell system and its operation method of the present invention can be configured to selectively use the power required by the various peripheral devices (BOP) that is the power consumption source from the two or more power supplied from the fuel cell stack As a result, a specific cell having an abnormality in the fuel cell stack is prevented from being continuously generated in power, thereby stably supplying power from the fuel cell stack.

Claims (7)

A fuel cell stack for producing direct current power by an electrochemical reaction between hydrogen and oxygen; A fuel supply device for supplying reformed gas containing hydrogen to the fuel cell stack; An oxidant supply device for supplying an oxidant containing oxygen to the fuel cell stack; A plurality of peripheral devices (BOPs) for performing a start, stop and power generation state maintenance operation of the system by using the electric power produced by the fuel cell stack; And It includes a power distribution device for distributing and supplying the power produced in the fuel cell stack to each of the plurality of peripheral devices (BOP), The fuel cell stack accumulates the current produced by the unit cells of the region between both ends of the plurality of unit cells and the ends of the plurality of unit cells so as to divide the plurality of unit cells sequentially stacked therein into two or more regions. Each current collector is located, The power distribution device selectively distributes and supplies power of a specific region to the plurality of peripheral devices (BOP) among powers produced in two or more regions in the fuel cell stack. The method of claim 1, And an auxiliary power supply for providing initial starting power of the peripheral device (BOP) and for stopping power supply after power is produced in the fuel cell stack. The method of claim 1, The current collector is a fuel cell system, characterized in that the material is low contact resistance and high allowable current. The method according to claim 1 or 2, The fuel cell stack includes a plurality of fuel cell stacks connected in series or in parallel, and the power distribution unit is connected to the plurality of fuel cell stacks, respectively, to cause an abnormality among the plurality of fuel cell stacks. A fuel cell system, characterized in that it is operated such that the load on the fuel cell stack expected to be generated is reduced. As a method of operating the fuel cell system according to claim 1, The peripheral device (BOP) is distributed and supplied to use the power produced in the fuel cell stack, A first step of selecting a particular cell in which two or more regions divided by the current collector are generated or are predicted to have an abnormality; And a second step of distributing and connecting the power distribution unit so that the peripheral device (BOP) selectively uses power generated in the remaining areas except for the region of the specific cell selected in the first step. How does it work? The method of claim 5, And first searching whether an abnormality occurs in an area in which the first stacked cell and the last stacked cell are located in the first step. The method of claim 5, A method of operating a fuel cell system, characterized in that the auxiliary power source is provided with initial starting power required by the peripheral device (BOP) before the fuel cell stack generates power.

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