A method for diagnosing faults in a SOFC system based on an oxygen sensor

Abstract

This invention belongs to the field of high-temperature fuel cell technology, specifically relating to a fault diagnosis method for SOFC systems based on an oxygen sensor. The method includes adding an oxygen sensor at the cathode outlet of the fuel cell stack, measuring the oxygen concentration at the SOFC system cathode outlet using the oxygen sensor, calculating the theoretical value of the oxygen concentration at the SOFC system cathode outlet, and subtracting the measured value from the theoretical value. When the absolute value of the difference exceeds a predetermined threshold, a system fault is determined. This invention achieves the diagnostic effect of an SOFC system by adding only one oxygen sensor at the cathode outlet of the fuel cell stack, at extremely low cost. It utilizes the original system's state and data to accurately and efficiently identify system faults, and can effectively assist in verifying fault diagnosis for SOFC systems operating for extended periods.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature fuel cell technology, and more specifically, relates to a fault diagnosis method for SOFC systems based on oxygen sensors. Background Technology

[0002] Solid oxide fuel cell (SOFC) systems are energy conversion devices that directly convert the chemical energy of fuel into electrical energy. Because there is only one energy conversion process, SOFC systems have extremely high power generation efficiency. Compared to the 30-40% power generation efficiency of traditional thermal power generation, SOFC power generation efficiency can reach 50-60%. If combined heat and power (CHP) is implemented to further utilize the high-temperature exhaust gas, the total CHP efficiency can reach 80%. Furthermore, because SOFC electricity is generated through an electrochemical electron transfer process, it has advantages such as no combustion, no pollution, and no noise, making it an environmentally friendly power generation system. SOFC systems have a wide range of applications, and have already achieved significant success and practical application in military portable special equipment, residential SOFC CHP systems, large power plant units, and grid power compensation, with power levels ranging from W to MW. They are also involved in transportation, distributed generation, and other fields.

[0003] SOFC systems are highly efficient at generating electricity, but they need to operate in high-temperature environments of 600-1000℃, making system safety paramount. High temperatures introduce safety hazards and present new challenges for system maintenance. The safety of SOFC systems has always been a popular research area, as timely fault detection and effective fault location are crucial for the continuous operation of SOFC systems. Current mainstream research directions include determining whether a system fault has occurred, identifying the location of the fault, and determining the cause of the fault.

[0004] The core component of an SOFC system is the fuel cell stack. This stack not only operates under high-temperature conditions but is also a precision device. It serves as a container for the high-temperature electrochemical reactions and as a generator responsible for electron output and transfer. However, due to its intricate structure, the fuel cell stack is difficult to analyze and inspect. Faults can only be determined indirectly through other methods. Current indirect methods are often complex, requiring the establishment of mechanistic models or data-based equivalent models of the fuel cell stack. However, due to the large amount of data and high thermoelectric coupling in SOFC systems, these models cannot fully and accurately reflect the actual system's state. The simulated system cannot accurately reproduce the actual system's operating state in the field of fault identification. Currently, there is no diagnostic method for identifying and detecting system faults within the original system. Summary of the Invention

[0005] In response to the need for improvement in existing technologies, this invention provides a fault diagnosis method for SOFC systems based on oxygen sensors, with the aim of timely diagnosis and location of potential faults within the SOFC system.

[0006] To achieve the above objectives, according to one aspect of the present invention, a fault diagnosis method for an SOFC system based on an oxygen sensor is provided, comprising:

[0007] S1: Add an oxygen sensor at the cathode outlet of the SOFC system to be diagnosed, and use the actual oxygen concentration value measured by the oxygen sensor as the actual oxygen concentration value at the SOFC system outlet.

[0008] S2: Calculate the theoretical oxygen concentration at the cathode outlet of the SOFC system;

[0009] S3: Subtract the actual oxygen concentration value at the cathode outlet of the SOFC system from the treated oxygen concentration value at the cathode outlet of the SOFC system. If the absolute value of the difference is greater than a predetermined threshold, it is determined that the SOFC system has malfunctioned.

[0010] Furthermore, S2 includes the following steps:

[0011] S2.1: The net power of the SOFC system stack is calculated using the following formula (1), where U and I are the voltage and current during the electrochemical reaction process of the SOFC system:

[0012] P n =UI (Equation 1);

[0013] S2.2: Obtain the average input power Q of hydrogen fuel inf ;

[0014] S2.3: Assume Q f The molar calorific value of hydrogen under standard conditions, q vf The average volumetric flow rate of fuel under standard conditions, E fv The fuel energy per unit volume of hydrogen under standard conditions, due to Q inf =q vf E fv E can be calculated using the following formula (2). fv :

[0015] E fv =Q f / M (Formula 2);

[0016] Where M is the standard molar volume of an ideal gas;

[0017] S2.4: The molar flow rate q of hydrogen fuel consumed by the electrochemical reaction in the SOFC system can be obtained according to equations (1) and (2). conf It is the following formula (3):

[0018] q conf =UI / E fv (Equation 3);

[0019] S2.5: Using the electrochemical reaction equation 2H2 + O2 = 2H2O for hydrogen fuel, the molar flow rate of oxygen consumed by the SOFC system in the electrochemical reaction is calculated using the following formula (4):

[0020] q cona =UI / 2E fv (Equation 4);

[0021] S2.6: Obtain the molar flow rate q of the air introduced into the cathode of the SOFC system using a gas flow meter. air ;

[0022] S2.7: The theoretical oxygen concentration α at the cathode outlet of the SOFC stack is obtained by subtracting the molar flow rate of oxygen consumed by the electrochemical reaction during the operation of the SOFC system from the molar flow rate of oxygen introduced into the cathode of the SOFC system using the following formula (5). equ for:

[0023] α equ =(0.21*q) air -q cona ) / (q air -q cona (Equation 5).

[0024] Furthermore, the predetermined threshold in step S3 is 3-5%, preferably 3%.

[0025] According to another aspect of the present invention, the present invention also provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is executed by a processor, it controls the device where the storage medium is located to perform a fault diagnosis method for an SOFC system based on an oxygen sensor as described above.

[0026] According to another aspect of the present invention, the present invention also provides a fault diagnosis system for an SOFC system based on an oxygen sensor, comprising:

[0027] An oxygen sensor is used to measure the actual oxygen concentration at the cathode outlet of the SOFC system. The oxygen sensor is located at the cathode outlet of the SOFC system stack to be diagnosed.

[0028] The calculation module is used to calculate the theoretical oxygen concentration at the cathode outlet of the SOFC stack.

[0029] The diagnostic module is used to subtract the actual oxygen concentration value at the cathode outlet of the SOFC system from the treated oxygen concentration value at the cathode outlet of the SOFC system. If the absolute value of the difference is greater than a predetermined threshold, it is determined that the SOFC system has malfunctioned.

[0030] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0031] (1) As a timely fault diagnosis method, the present invention has a low dependence on the device. Only an oxygen sensor needs to be added at the cathode outlet of the fuel cell stack to realize real-time tracking of the SOFC system and detect system faults in the first time.

[0032] (2) In the process of obtaining the theoretical oxygen concentration at the cathode outlet of the SOFC stack, the present invention utilizes the visualized parameters in the SOFC system, such as voltage, current, average input power of fuel, fuel flow rate, air flow rate, etc., which is very convenient.

[0033] (3) The actual oxygen concentration value provided by the oxygen sensor of the present invention can not only serve as an important basis for system fault diagnosis, but also as basic data for subsequent system fault location determination. Attached Figure Description

[0034] Figure 1 This is a flowchart of a fault diagnosis method for an SOFC system based on an oxygen sensor, provided as an embodiment of the present invention.

[0035] Figure 2 The diagram shows the structure of an SOFC system provided in an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1

[0038] like Figure 1 As shown, this embodiment provides a fault diagnosis method for an SOFC system based on an oxygen sensor, including:

[0039] S1: Add an oxygen sensor at the cathode outlet of the SOFC system to be troubleshooted, such as... Figure 2As shown, the actual oxygen concentration value measured by the oxygen sensor is obtained, which is the actual oxygen concentration value at the cathode outlet of the SOFC system.

[0040] S2.1: The net power of the SOFC system stack is calculated using the following formula (1), where U and I are the voltage and current during the electrochemical reaction process of the SOFC system:

[0041] P n =UI (Equation 1);

[0042] S2.2: Obtain the average fuel input power Q inf ;

[0043] S2.3: Assume Q f Q is the molar calorific value of hydrogen under standard conditions. f =M·Q inf E fv q represents the fuel energy per unit volume of hydrogen under standard conditions. vf Given the average volumetric flow rate of fuel under standard conditions, since Q inf =q vf E fv Therefore, E can be calculated using the following formula (2). fv , with kJ / m 3 count:

[0044] E fv =Q f / M (Formula 2);

[0045] Where M is the standard molar volume of an ideal gas (2.2414 × 10⁻⁶). -2 m 3 / mol);

[0046] S2.4: Since the chemical energy of hydrogen fuel consumed in the electrochemical reaction of the SOFC system is converted into electrical energy, the molar flow rate q of the consumed hydrogen fuel can be obtained according to equations (1) and (2). conf It is the following formula (3):

[0047] q conf =UI / E fv (Equation 3);

[0048] S2.5: Using the electrochemical reaction equation 2H2 + O2 = 2H2O for hydrogen fuel, the molar flow rate of oxygen consumed by the SOFC system in the electrochemical reaction is calculated using the following formula (4):

[0049] q cona =UI / 2E fv (Equation 4);

[0050] S2.6: Obtain the molar flow rate q of the air introduced into the cathode of the SOFC system using a gas flow meter. air ;

[0051] S2.7: The theoretical oxygen concentration α at the cathode outlet of the SOFC stack is calculated by subtracting the molar flow rate of oxygen consumed by the electrochemical reaction during the operation of the SOFC system from the molar flow rate of oxygen introduced into the cathode of the SOFC system using the following formula (5). equ for:

[0052] α equ =(0.21*q) air -q cona ) / (q air -q cona (Equation 5);

[0053] S3: Treat the residual oxygen concentration α at the system cathode outlet. equ The oxygen concentration is subtracted from the oxygen concentration measured by the oxygen sensor. If the absolute value of the difference exceeds a set threshold of 3%, the SOFC system is considered to have malfunctioned.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fault diagnosis method for an SOFC system based on an oxygen sensor, characterized in that, include: S1: Add an oxygen sensor at the cathode outlet of the SOFC system to be diagnosed, and use the actual oxygen concentration value measured by the oxygen sensor as the actual oxygen concentration value at the cathode outlet of the SOFC system. S2: Calculate the theoretical oxygen concentration at the cathode outlet of the SOFC system; Step S2 consists of the following steps: S2.1: The net power of the SOFC system stack is calculated using the following formula (1), where U and I are the voltage and current during the electrochemical reaction process of the SOFC system: ； S2.2: Obtain the average input power of hydrogen fuel ; S2.3: Assumptions The molar calorific value of hydrogen under standard conditions, The average volumetric flow rate of fuel under standard conditions, The fuel energy per unit volume of hydrogen under standard conditions, due to The following formula (2) is used to calculate : (Equation 2); Where M is the standard molar volume of an ideal gas; S2.4: The molar flow rate of hydrogen fuel consumed by the electrochemical reaction in the SOFC system can be obtained according to equations (1) and (2). The following formula (3) is given: (Equation 3); S2.5: Electrochemical reaction equations using hydrogen fuel The molar flow rate of oxygen consumed by the electrochemical reaction in the SOFC system can be calculated using the following formula (4): (Equation 4); S2.6: Obtain the molar flow rate of the air introduced into the cathode of the SOFC system via a gas flow meter. ; S2.7: The theoretical oxygen concentration at the cathode outlet of the SOFC stack is obtained by subtracting the oxygen molar flow rate consumed by the electrochemical reaction during the operation of the SOFC system from the oxygen molar flow rate in the air introduced into the SOFC system cathode using the following formula (5). for: (Equation 5); S3: Subtract the actual oxygen concentration value at the cathode outlet of the SOFC system from the treated oxygen concentration value at the cathode outlet of the SOFC system. If the absolute value of the difference is greater than a predetermined threshold, it is determined that the SOFC system has malfunctioned.

2. The fault diagnosis method for an SOFC system based on an oxygen sensor according to claim 1, characterized in that, The predetermined threshold in step S3 is 3-5%.

3. The fault diagnosis method for an SOFC system based on an oxygen sensor according to claim 2, characterized in that, The predetermined threshold in step S3 is 3%.

4. A computer-readable storage medium comprising a stored computer program, wherein, When the computer program is run by the processor, it controls the device containing the storage medium to execute a fault diagnosis method for an SOFC system based on an oxygen sensor as described in any one of claims 1-3.

5. A fault diagnosis system for an SOFC system based on an oxygen sensor, characterized in that, include: An oxygen sensor is used to measure the actual oxygen concentration at the cathode outlet of the SOFC system. The oxygen sensor is located at the cathode outlet of the SOFC system stack to be diagnosed. The calculation module is used to calculate the theoretical oxygen concentration at the cathode outlet of the SOFC stack. The diagnostic module is used to subtract the actual oxygen concentration value at the cathode outlet of the SOFC system from the treated oxygen concentration value at the cathode outlet of the SOFC system. If the absolute value of the difference is greater than a predetermined threshold, it is determined that the SOFC system has malfunctioned.

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