KR102829876B1 - Control system and method of hydrogen purge valve - Google Patents

Abstract

The present invention relates to a control system and a control method for a hydrogen purge valve, and more particularly, to control of a hydrogen purge valve for discharging hydrogen in a fuel cell system. A control method for a hydrogen purge valve according to some embodiments of the present invention includes: a step of determining an operating range of a fuel cell system; a step of determining an operating condition of a hydrogen purge valve according to the operating range; and a step of operating the hydrogen purge valve according to the determined operating condition.

Description

Control system and method of hydrogen purge valve {CONTROL SYSTEM AND METHOD OF HYDROGEN PURGE VALVE}

The present invention relates to a control system and control method for a hydrogen purge valve, and more specifically, to control of a hydrogen purge valve for discharging hydrogen in a fuel cell system.

Fuel cells are energy sources that produce electricity through the electrochemical reaction of hydrogen and oxygen. Due to the environmental friendliness of fuel cells, research on fuel cells has been actively conducted recently. Among them, interest in vehicles that use fuel cells is growing in the automobile industry.

In vehicles, fuel cell stacks are applied by stacking multiple unit cells. In the fuel cell stack, air and hydrogen gas are supplied to both sides of the EGA (Electricity-Generating Assembly), which is the power generation part of the unit cell. The supplied air and hydrogen are ionized at the air electrode and the hydrogen electrode, respectively, and an electrochemical reaction occurs to produce electricity.

One of the main roles of the EGA when the fuel cell is in operation is to prevent the air and hydrogen gas supplied to both sides of the EGA from mixing with each other so that they can ionize at the electrodes on both sides and undergo an electrochemical reaction. If the air and hydrogen gas flow to opposite sides due to deterioration of the EGA, it can have a negative effect on the output of the fuel cell, ultimately shortening the performance and life of the fuel cell. Specifically, the output of the fuel cell deteriorates as the voltage generated is lowered by various chemical reactions, such as direct combustion reactions of the hydrogen that flows to the cathode. In addition, the performance and life of the fuel cell can be shortened as the ambient temperature rapidly increases due to the exothermic reaction of the hydrogen that flows to the cathode.

Therefore, if we discover the cause of hydrogen and oxygen moving to opposite poles and devise a solution for this, it will be helpful in improving the durability of fuel cells.

Patent Registration No. 10-1113649 (Registration Date: 2012.02.01)

The present invention has been devised to solve the above-described problems,

The present invention aims to provide a method for controlling a hydrogen purge valve that can improve the durability of a fuel cell.

The purpose of the present invention is not limited to the purposes mentioned above, and other purposes not mentioned can be clearly understood by a person having ordinary knowledge in the technical field to which the present invention belongs (hereinafter referred to as 'ordinary skilled worker') from the description below.

In order to achieve the purpose of the present invention as described above and to perform the characteristic functions of the present invention described below, the features of the present invention are as follows.

A method for controlling a hydrogen purge valve according to some embodiments of the present invention comprises: a step of determining an operating range of a fuel cell system; a step of determining an operating condition of a hydrogen purge valve according to the operating range; and a step of operating the hydrogen purge valve according to the determined operating condition.

A control system for a hydrogen purge valve according to some embodiments of the present invention includes a hydrogen purge valve configured to open for a predetermined period of time and then close at predetermined intervals to discharge hydrogen within a fuel cell system; and a controller configured to control an operating condition of the hydrogen purge valve according to an operating range of the fuel cell system.

According to the present invention, a method for controlling a hydrogen purge valve capable of improving the durability of a fuel cell is provided.

The effects of the present invention are not limited to those described above, and other effects not mentioned will be clearly recognized by those skilled in the art from the description below.

Figure 1 illustrates the pressure change of a fuel cell during hydrogen purge.
Figure 2 illustrates a configuration diagram of a hydrogen purge valve control system according to the present invention.
Figure 3 illustrates the operation method of a conventional hydrogen purge valve.
Figure 4 illustrates a flow chart of a method for controlling a hydrogen purge valve according to some embodiments of the present invention.
Figure 5 illustrates a control element of a control method according to the present invention.
Figures 6 to 9 illustrate application examples in which the control method according to the present invention is applied to various operating areas of a fuel cell system.
Figure 10 illustrates the pressure change of a fuel cell during hydrogen purging by a control method according to the present invention.

The specific structural and functional descriptions presented in the embodiments of the invention are merely exemplified for the purpose of explaining embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention may be implemented in various forms. In addition, it should not be construed as being limited to the embodiments described in this specification, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Meanwhile, in the present invention, the terms first and/or second, etc. may be used to describe various components, but the components are not limited to the terms. The terms are used only for the purpose of distinguishing one component from other components, for example, within the scope of the rights according to the concept of the present invention, the first component may be named the second component, and similarly, the second component may also be named the first component.

When it is said that an element is "connected" or "connected" to another element, it should be understood that it may be directly connected or connected to that other element, but that there may be other elements in between. On the other hand, when it is said that an element is "directly connected" or "in direct contact with" another element, it should be understood that there are no other elements in between. Other expressions used to describe the relationship between elements, such as "between" and "directly between" or "adjacent to" and "directly adjacent to", should be interpreted similarly.

Like reference numerals throughout the specification represent like elements. Meanwhile, the terminology used herein is for the purpose of describing embodiments only and is not intended to limit the present invention. In the present specification, the singular also includes the plural unless specifically stated otherwise. The terms "comprises" and/or "comprising" as used herein do not exclude the presence or addition of one or more other elements, steps, operations, and/or elements mentioned.

Hereinafter, the present invention will be described in detail with reference to the attached drawings.

The present applicant operated a fuel cell for a long period of time to simulate the deterioration phenomenon of the Electricity-Generating Assembly (EGA) and examined the state of the EGA.

Here, it was confirmed that deterioration progresses from local deterioration of the air inlet section where air is introduced into the EGA. It was confirmed that the deteriorated area of the air inlet section of the air side where air is introduced is larger than that of the hydrogen side. Through this, it was confirmed that deterioration starts at the air inlet section and, as the electrode is lost, electrode deterioration of the opposite hydrogen side progresses. In this case, it was confirmed that the durable sealing characteristics are broken through the deteriorated section, causing the gases of each side to exchange with each other, ultimately resulting in a decrease in performance. In addition, if this deterioration rapidly increases and a hole is formed, the local temperature increases due to the rapid reaction between hydrogen and oxygen. This may form a hole in the separator, making operation of the fuel cell no longer possible.

The reason why the air inlet deteriorates in this way is that, first of all, the point where the oxygen partial pressure is the highest in the EGA is the air inlet where the air pressure is the highest. Therefore, the amount of oxygen that crosses over to the hydrogen electrode cannot but be greater than at other points. The oxygen that crosses over through the membrane generates oxygen radicals at the platinum (Pt) catalyst of the hydrogen electrode. The generated oxygen radicals promote the deterioration of the ionomer, and the electrolyte membrane becomes thinner and thinner, and the sealing properties deteriorate.

In addition, if oxygen passes through the membrane to the hydrogen electrode, it can cause electrode corrosion on the air electrode side. If oxygen and hydrogen coexist in the hydrogen electrode due to the oxygen passing to the hydrogen electrode, a local voltage increase occurs at the air electrode. This can cause corrosion of the air electrode and cause local electrode detachment at the air inlet.

In addition, pressure drop due to hydrogen purge can be cited. When the fuel cell is operated, nitrogen diffuses from the air electrode to the hydrogen electrode, and the concentration of the hydrogen electrode gradually decreases. If the concentration of the hydrogen electrode decreases, a local hydrogen shortage phenomenon may occur, causing electrode deterioration and performance degradation. Therefore, in order to maintain the concentration of the hydrogen electrode above a certain concentration, the fuel cell system performs hydrogen purge (H ₂ purge) that periodically discharges hydrogen gas.

The valves used for hydrogen purge are mainly solenoid valves, motor-driven rotary solenoids, etc. Through ON/OFF control of the valve, the valve is opened momentarily, and hydrogen and other gases on the hydrogen electrode side are discharged. At this time, the pressure is momentarily lowered due to the flow of gas discharged momentarily, and hydrogen is supplied through the hydrogen supply valve to compensate for the lowered pressure.

Since the hydrogen supplied in this way has a concentration of 100%, the hydrogen concentration inside the fuel cell can be maintained above a certain level. However, with this ON/OFF type valve control, the pressure of the hydrogen outlet pressure is reduced, as shown in Fig. 1. The reduction in the pressure of the hydrogen outlet pressure reduces the pressure difference between the air inlet pressure and the hydrogen outlet pressure, thereby creating an environment in which oxygen on the air electrode side can easily pass through the membrane toward the hydrogen outlet. Since the hydrogen purge is necessarily operated periodically while the fuel cell is operating, an environment in which air continuously passes through the hydrogen outlet portion of the hydrogen electrode is created. This influence causes deterioration of the membrane at the air inlet portion, which reduces the durability and marketability of the fuel cell.

In addition, a rapid pressure drop on the hydrogen electrode side due to rapid purge can cause physical deformation from the air electrode side to the hydrogen electrode side. This can be a factor causing a decrease in the durability of the EGA, such as electrode detachment and partial shape deformation.

Ultimately, the air inlet is under relatively vulnerable conditions compared to other parts of the EGA. Therefore, there is no major problem during the initial operation of the fuel cell, but deterioration of the air inlet appears during long-term operation.

In particular, as the fuel cell system changes to a high-output driving system centered on pressurized driving, the pressure on the hydrogen electrode side increases, so control of the pressure drop at the hydrogen electrode due to rapid purge is becoming an essential element.

Accordingly, the present invention seeks to improve the durability of a fuel cell through a method for controlling a hydrogen purge valve that can prevent a rapid pressure drop on the hydrogen electrode side due to rapid purge and prevent oxygen at the air inlet from flowing to the hydrogen electrode side.

As shown in FIG. 2, the control system of the hydrogen purge valve according to the present invention includes a controller (100) and a hydrogen purge valve (200).

The controller (100) is configured to control at least one of the maximum opening area (A), opening ratio (B), and opening time (C) of the hydrogen purge valve (200). The controller (100) may be a controller of a fuel cell system, or may be a controller separately provided for controlling the hydrogen purge valve (200).

The hydrogen purge valve (200) is configured to purge hydrogen of the fuel cell system by operation. According to the present invention, the hydrogen purge valve (200) may be any type of valve in which the opening ratio, opening time, and opening area can be controlled by the controller (100). According to some embodiments of the present invention, the hydrogen purge valve (200) is a PWM (Pulse Width Modulation) solenoid valve. According to some embodiments of the present invention, the hydrogen purge valve (200) is a rotary solenoid valve.

The conventional purge control method instantaneously opens the valve by ON/OFF control of the valve to discharge hydrogen and other gases. As illustrated in Fig. 3, at a specific point in time, the opening area of the valve instantaneously becomes 100%, and the valve is closed after maintaining the open state for a preset time. However, according to the present invention, the opening area of the valve is gradually increased during hydrogen purge. Therefore, according to the present invention, a gas including hydrogen or the like (hereinafter, “discharged gas”) is gradually discharged, and a gas such as hydrogen that is required to be discharged can be discharged without a significant change in pressure.

A method for controlling a hydrogen purge valve according to some embodiments of the present invention is configured to control at least one of a maximum opening area (A), a change in the opening area over time (hereinafter, an opening ratio (B)), and an opening time (C) of a hydrogen purge valve (200) according to the output of a fuel cell system.

Referring to Fig. 4, first, the controller (100) detects the operating range of the fuel cell system (S20). The operating range of the fuel cell system may be an output request input to the fuel cell system from the outside. For example, the operating range may be determined based on the vehicle driver's will to accelerate, etc.

According to an embodiment of the present invention, the operating range includes at least a portion of low power, medium-low power, medium-high power, and high power ranges. The low power range is a range in which the maximum output of the fuel cell system is the lowest, the medium-low power range is a range in which the maximum output is higher than that of the low power range, and the medium-high power range is a range in which the maximum output is higher than that of the medium-low power range but lower than that of the high power range. As a non-limiting example, the low power range can be classified as having a maximum output of about 30% or less, the medium-low power range as having a maximum output of about 30 to 60%, the medium-high power range as having a maximum output of about 60 to 90%, and the high power range as having a maximum output of about 90 to 100%.

The controller (100) determines the maximum opening area (A), opening ratio (B), or opening time (C) of the hydrogen purge valve (200) during hydrogen purge according to the detected operating area (S40). The maximum opening area (A), opening ratio (B), or opening time (C), which are the operating conditions of the hydrogen purge valve (200) for each output area, can be determined in advance and stored in the storage (120). The controller (100) can obtain the operating conditions suitable for the corresponding operating area from the storage (120).

Referring to FIG. 5, the maximum opening area (A) is the maximum opening area that can be opened when purging hydrogen in the corresponding output area. The maximum opening area (A) can be 100%, 80%, or other sizes as determined in advance. In other words, the maximum opening area (A) refers to the area that the hydrogen purge valve (200) can open to the maximum for purging hydrogen. If the maximum opening area (A) is large, a large amount of exhaust gas can be discharged.

The opening ratio (B) can be defined as the amount of change in the opening area over time. In particular, it means the speed at which the hydrogen purge valve (200) will be opened over time at the beginning or end of the hydrogen purge. The smaller the opening ratio (B), the more slowly the hydrogen purge valve (200) opens. This can reduce the fluctuation range of the hydrogen pressure during the purge and can stably maintain the hydrogen pressure.

The opening time (C) is the total time that the hydrogen purge valve (200) remains open. In other words, it refers to the time from the time the hydrogen purge valve (200) starts to open to the time it closes again. The opening time (C) determines the amount of purge, and therefore the hydrogen concentration of the fuel cell system.

When the operating conditions of the hydrogen purge valve (200) are determined, the controller (100) operates the hydrogen purge valve (200) with the determined operating conditions (S60). Hereinafter, the control when operating the hydrogen purge valve (200) with exemplary operating conditions will be examined.

Figures 6 to 9 illustrate exemplary control diagrams for each operating region. The controller (100) can stably supply hydrogen without a large fluctuation in hydrogen pressure during purge in the fuel cell system by controlling the maximum opening area (A), opening ratio (B), or opening time (C) for each output or operating region.

Figure 6 corresponds to the low-power region. In the low-power region where the maximum output is low, the hydrogen pressure within the fuel cell system is low. Therefore, the opening ratio (B) is large so that hydrogen can escape at a fast rate, and the maximum opening area (A) is also made to reach 100%.

Figure 7 illustrates the control of the medium-low power region. In the medium-low power region, the maximum opening area (A) is set to 100%, but since the hydrogen pressure is higher than in the low power region, the opening ratio (B) is made small to prevent rapid changes in hydrogen pressure and the opening time (C) is extended so that sufficient exhaust gas can be discharged.

Figure 8 illustrates the control of the medium-high output region. In the medium-high output region, the hydrogen pressure will be relatively high, so the maximum opening area (A) is reduced to 80%. In addition, the opening ratio (B) is also made smaller than in the medium-low output region to prevent rapid changes in hydrogen pressure.

Fig. 9 illustrates the control of the high-power region. In the high-power operation region, since the hydrogen pressure is high, even if the opening area is small, the amount of hydrogen discharged increases. Therefore, the maximum opening area (A) can be set to only about 40%. In addition, in order to prevent rapid fluctuations in hydrogen pressure, the opening ratio (B) is made relatively gentle and small. However, in this case, since the hydrogen purge amount may be small, the opening time (C) is adjusted to a relatively long time to prevent a decrease in hydrogen concentration, so that the hydrogen concentration can be controlled during fuel cell operation. In other words, three factors can be appropriately controlled.

In the case of fuel cell systems, especially in the case of vehicle fuel cell systems, the current consumed is determined according to the operating range of the fuel cell system or the output of the vehicle. And the amount of hydrogen and oxygen consumed is determined according to the current consumed. In order to smoothly supply the hydrogen and oxygen, which are the fuels consumed, an operating method is used that increases the hydrogen pressure and air pressure as the current consumed increases.

Therefore, if only the opening area is controlled, proper control cannot be achieved in a system where the hydrogen pressure varies depending on the current. For example, if the hydrogen pressure is low when the control speed or the opening area is the same, the hydrogen discharge flow rate will be small and the hydrogen pressure fluctuation when the purge valve is opened will be small. However, if the hydrogen pressure is high when the control speed or the opening area is the same, the hydrogen discharge flow rate will be large and the hydrogen pressure fluctuation will be relatively very large.

Accordingly, the present invention controls not only the maximum opening area of the hydrogen purge valve, but also the change in the opening area over time and the opening time differently according to the output or operating range of the fuel cell system, thereby preventing a rapid change in hydrogen pressure depending on the size of the hydrogen pressure.

According to the present invention, when the opening area of the hydrogen purge valve (200) is changed over time, the discharge speed of the exhaust gas can be controlled, so that the exhaust gas can be prevented from escaping rapidly, and a rapid decrease in the hydrogen outlet pressure can be prevented. As shown in Fig. 10, according to the present invention, there is no significant change in the hydrogen outlet pressure during hydrogen purge. Compared to Fig. 1, which shows a change in the conventional outlet pressure, the present invention can prevent a rapid change in the hydrogen outlet pressure, and thus solve the accompanying problems.

The present invention described above is not limited to the above-described embodiments and the attached drawings, and it will be apparent to a person skilled in the art to which the present invention pertains that various substitutions, modifications, and changes are possible within a scope that does not depart from the technical spirit of the present invention.

100: Controller 120: Storage
200: Hydrogen purge valve A: Maximum opening area
B: Opening rate C: Opening time

Claims (13)

A step for determining an operating range of a fuel cell system, wherein the operating range includes a plurality of operating ranges divided according to the maximum output of the fuel cell system;
A step for determining an operating condition of a hydrogen purge valve according to the above-mentioned operating range, wherein the operating condition includes at least a part of a maximum opening area of the hydrogen purge valve determined according to the above-mentioned operating range, an opening ratio, a change in the opening area according to time, or an opening time; and
A step of operating a hydrogen purge valve according to the determined operating conditions;
Including,
The steps for operating the above hydrogen purge valve are:
A method for controlling a hydrogen purge valve, comprising a step of reducing the opening ratio as the operating range in which the maximum output of the fuel cell system is greater among the plurality of operating ranges. delete delete A method for controlling a hydrogen purge valve according to claim 1, wherein the maximum opening area is an area at which the hydrogen purge valve opens to the maximum during a specific purge. A method for controlling a hydrogen purge valve according to claim 1, wherein the opening time is the total time that the hydrogen purge valve remains open during purge. A method for controlling a hydrogen purge valve according to claim 1, wherein the plurality of driving regions include a low output region and a high output region, and the high output region is a region in which the maximum output of the fuel cell system is greater than that of the low output region. A method for controlling a hydrogen purge valve according to claim 6, wherein the opening ratio is made smaller in the high output range than in the low output range. A method for controlling a hydrogen purge valve according to claim 6, wherein the maximum opening area is made smaller in the high output region than in the low output region. A method for controlling a hydrogen purge valve according to claim 6, wherein the opening time is made longer in the high output range than in the low output range. A method for controlling a hydrogen purge valve according to claim 6, wherein the plurality of driving regions further include a medium power region between a high power region and a low power region. A method for controlling a hydrogen purge valve according to claim 10, wherein in the medium power range, the opening ratio and maximum opening area are made smaller and the opening time is adjusted to be longer than in the low power range. A hydrogen purge valve configured to open and close for a certain period of time at regular intervals to discharge hydrogen within the fuel cell system; and
A controller configured to control the operating conditions of a hydrogen purge valve according to the operating range of the above fuel cell system;
, and the controller comprises:
Determining the operating range of the above fuel cell system;
Determine the operating conditions of the hydrogen purge valve according to the above operating range; and
It is configured to operate the hydrogen purge valve according to the determined operating conditions,
The above driving range includes multiple driving ranges divided according to the maximum output of the fuel cell system,
The above operating conditions include at least a portion of the maximum opening area of the hydrogen purge valve, the change in the opening area over time, which is the opening ratio, or the opening time, which is determined according to the operating range.
The above controller,
A control system for a hydrogen purge valve configured to reduce the opening ratio as the operating range in which the maximum output of the fuel cell system is greater among the above-mentioned multiple operating ranges. delete

Images