KR-102962104-B1 - FUEL CELL SYSTEM AND CONTROL METHOD THEREOF

KR102962104B1KR 102962104 B1KR102962104 B1KR 102962104B1KR-102962104-B1

Abstract

The present invention relates to a fuel cell system and a control method thereof. The fuel cell system comprises a fuel cell stack including a fuel electrode and an air electrode; a recirculation line for recirculating gas discharged from the fuel cell stack back to the fuel cell stack; an air discharge line connected to the air electrode and configured to discharge air discharged from the air electrode to the outside; a purge line having one end connected to the fuel electrode or the recirculation line and the other end connected to the air discharge line, for discharging a fluid inside the fuel electrode through the air discharge line; a control valve unit having a first control valve installed on the air discharge line and installed downstream of the purge line, and a second control valve installed upstream of the purge line; and a control unit that controls the opening and closing of the first control valve and the second control valve by considering the hydrogen concentration inside the fuel electrode, the pressure of the fuel electrode, and the pressure of the air electrode.

Inventors

심선보
장인우

Assignees

현대자동차주식회사
기아 주식회사

Dates

Publication Date: 20260511
Application Date: 20201211

Claims (16)

A fuel cell stack including a fuel electrode and an air electrode; A recirculation line for recirculating gas discharged from the above fuel cell stack to the above fuel cell stack; An air discharge line connected to the air electrode and configured to discharge air discharged from the air electrode to the outside; A purge line having one end connected to the fuel electrode or the recirculation line and the other end connected to the air discharge line, for discharging fluid inside the fuel electrode through the air discharge line; A control valve unit having a first control valve installed on the air discharge line and located downstream of the purge line, and a second control valve installed upstream of the purge line; A pressure acquisition unit for acquiring the pressure at both ends of the above purge line and the pressure of the above air electrode; and It includes a control unit that controls the opening and closing of the first control valve and the second control valve by taking into account the hydrogen concentration inside the fuel electrode, the pressure of the fuel electrode, and the pressure of the air electrode. The above control unit A fuel cell system that controls the opening and closing of the second control valve so that the pressure inside the air electrode is maintained within a predetermined range, taking into account the pressure of the air electrode received from the pressure acquisition unit and the opening and closing of the first control valve.
In paragraph 1, The above control unit A fuel cell system that controls the first control valve to regulate the pressure difference between the two ends of the purge line so that a predetermined amount of fluid is discharged from the fuel electrode in consideration of the hydrogen concentration inside the fuel electrode, and controls the second control valve so that the pressure inside the air electrode is maintained within a predetermined range.
In paragraph 2, A fuel cell system further comprising a concentration acquisition unit for acquiring hydrogen concentration within the above fuel electrode.
In paragraph 3, The above control unit A fuel cell system that calculates a target purge flow rate, which is the flow rate of a fluid to be discharged through the purge line, in order to bring the acquired hydrogen concentration, which is the hydrogen concentration obtained from the concentration acquisition unit, into the reference hydrogen concentration range, which is a preset hydrogen concentration range, when the acquired hydrogen concentration exceeds the reference hydrogen concentration range.
In paragraph 4, The above control unit A fuel cell system that receives the pressure at both ends of the purge line obtained from the pressure acquisition unit and controls the opening and closing of the first control valve so that the pressure difference at both ends of the purge line is adjusted so that the target purge flow rate can be discharged.
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In paragraph 1, It includes a humidifier connected to the air discharge line and an air supply line for supplying air to the air electrode, and humidifies the air supplied to the air supply line using the air discharged from the air electrode and supplies it to the air electrode. The above pressure acquisition unit is configured to acquire pressure on the upstream side of the humidifier in the air discharge line, and the second control valve is installed on the downstream side of the humidifier in the air discharge line, in a fuel cell system.
In paragraph 3, It further includes a shut-off valve installed in the purge line to open or close the purge line, and A fuel cell system in which the control unit controls the shut-off valve to open when the fuel cell system starts and controls the shut-off valve to close when the fuel cell system ends.
In paragraph 8, When the end of the two ends of the above purge line connected to the above recirculation line is called the front end, and the end connected to the above air discharge line is called the rear end, The above control unit receives the pressure at both ends of the purge line obtained from the pressure acquisition unit, and controls the shut-off valve to close when the pressure at the rear end of the purge line is higher than the pressure at the front end of the purge line.
In paragraph 8, The above control unit A fuel cell system that controls the shut-off valve to close when the acquired hydrogen concentration, which is the hydrogen concentration obtained from the concentration acquisition unit, reaches the lowest limit hydrogen concentration range, which is the lowest hydrogen concentration in the fuel electrode that is preset.
A recirculation line for recirculating gas discharged from a fuel cell stack including a fuel electrode and an air electrode to the fuel cell stack, and An air discharge line connected to the air electrode and configured to discharge air discharged from the air electrode to the outside, and A purge line having one end connected to the fuel electrode or the recirculation line and the other end connected to the air discharge line, for discharging fluid inside the fuel electrode through the air discharge line, and A control method for a fuel cell system applied to a fuel cell system comprising a first control valve installed on the air discharge line and installed downstream of the purge line, and a second control valve installed upstream of the purge line. A first step of obtaining a hydrogen concentration within the above fuel electrode; A second step of calculating a target purge flow rate, which is the flow rate of a fluid to be discharged from the recirculation line, in order to bring the acquired hydrogen concentration, which is the hydrogen concentration obtained in the first step, within the reference hydrogen concentration range, if the acquired hydrogen concentration, which is the hydrogen concentration obtained in the first step, exceeds the reference hydrogen concentration range, which is a preset hydrogen concentration range; and A third step comprising adjusting the first control valve to generate a pressure difference at both ends of the purge line to discharge the target purge flow rate, and A control method for a fuel cell system, wherein the third step further comprises a step of controlling the opening and closing of the second control valve so that the pressure inside the air electrode is maintained within a predetermined range, taking into account the pressure of the air electrode and the opening and closing of the first control valve.
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In Paragraph 11, It further includes a shut-off valve installed in the purge line and opening or closing the purge line, A method for controlling a fuel cell system, further comprising a shut-off valve opening step of opening the shut-off valve when starting the fuel cell system before the first step, and a shut-off valve closing step of closing the shut-off valve when the fuel cell system is terminated after the third step.
In Paragraph 13, A control method for a fuel cell system comprising the additional step of closing a shut-off valve when the pressure at the rear end of the purge line is higher than the pressure at the front end of the purge line, wherein the end connected to the recirculation line is called the front end and the end connected to the air discharge line is called the rear end.
In Paragraph 13, A control method for a fuel cell system further comprising the step of closing the shut-off valve when the hydrogen concentration obtained in the first step reaches a minimum limit hydrogen concentration range, which is a preset minimum hydrogen concentration range within the fuel electrode.
In Paragraph 11, A method for controlling a fuel cell system that returns to the first step when the fuel cell system is in operation after the third step.

Description

Fuel cell system and control method thereof The present invention relates to a fuel cell system and a method for controlling the same, and more specifically, to a fuel cell system and a method for controlling the same that improves the performance and durability of a fuel cell. Fuel cells produce electricity through the reaction between hydrogen supplied to the fuel electrode (also called the anode or hydrogen electrode) and oxygen supplied to the air electrode (also called the cathode or oxygen electrode), and moisture is generated as a byproduct. A portion of the moisture circulates inside the fuel electrode in gaseous form. In addition, a polymer electrolyte membrane is installed inside the fuel cell to block gases and selectively permeate and transmit ions. Due to the material properties of the electrolyte membrane, nitrogen moves from the air electrode to the fuel electrode through the membrane caused by the pressure difference and nitrogen concentration difference between the fuel electrode and the air electrode. During the operation of a fuel cell system, the hydrogen concentration inside the anode continuously decreases due to the accumulation of water vapor (gaseous moisture) and nitrogen, which is a major cause of reduced performance and durability. To prevent this, the fuel cell system increases the hydrogen concentration in the anode by periodically exhausting a mixed gas containing hydrogen and supplying additional hydrogen through hydrogen purge control. There is a risk of explosion if the hydrogen-containing gas mixture inside the fuel electrode is purged directly into the atmosphere during purging. Therefore, in conventional fuel cell systems, the hydrogen-containing gas mixture is purged through an exhaust line connected to the outlet of the air electrode, sufficiently mixed and diluted with exhaust air, and then released into the atmosphere. In order for the fuel electrode mixture to be released into the exhaust line using the conventional method, a condition must be maintained at the time of purging where the pressure at both ends of the purge valve is greater than the pressure at the air electrode. However, while a high hydrogen concentration within the fuel electrode is advantageous in terms of fuel cell performance and durability, the difference in hydrogen concentration between the fuel electrode and the air electrode causes an increased amount of hydrogen to move to the air electrode through the electrolyte membrane, leading to a problem that reduces the efficiency of the fuel cell system. Thus, when purging is performed using conventional methods, there are limitations in minimizing the variability of hydrogen concentration in the fuel electrode, and a problem of reduced efficiency in the fuel cell system may occur at the time of purging. Therefore, there is a need to improve the technology for performing purging while maintaining the hydrogen concentration within the anode as low as possible, within a range that minimizes the impact on the performance and durability of the fuel cell system. FIG. 1 is a block diagram illustrating the configuration of a fuel cell system according to a first embodiment of the present invention. FIG. 2 is a flowchart of a control method for a fuel cell system according to a first embodiment of the present invention. FIG. 3 is a block diagram illustrating the configuration according to a second embodiment of the present invention. FIG. 4 is a flowchart of a control method for a fuel cell system according to a second embodiment of the present invention. Hereinafter, embodiments of the present invention will be described in detail according to the attached drawings. First, the embodiments described below are suitable for illustrating the technical features of the fuel cell system and the control method thereof according to the present invention. However, the present invention is not limited to the embodiments described below, nor are the technical features of the present invention limited by the described embodiments; various modifications are possible within the technical scope of the present invention. FIG. 1 is a block diagram illustrating the configuration of a fuel cell system according to a first embodiment of the present invention, and FIG. 2 is a flowchart of a control method for a fuel cell system according to a first embodiment of the present invention. Referring to FIGS. 1 and 2, a fuel cell system (1) according to a first embodiment of the present invention includes a fuel cell stack (10), a recirculation line (72), an air discharge line (74), a purge line (75), a control valve section, and a control section (60). The fuel cell stack (10) includes a fuel electrode (11) and an air electrode (12). The fuel cell system produces electrical energy by converting chemical energy into electrical energy using the oxidation-reduction reaction of hydrogen supplied to the fuel electrode (11) and oxygen supplied to the air electrode (12). The fuel cell sys