Load tracking and temperature control system and method for a SOFC system

Abstract

The application discloses a load tracking and temperature control system and method of a SOFC system, wherein the system comprises a first controller and a third controller; the third controller takes the stack current as a control variable, takes the fuel component at the stack outlet as a controlled variable, or takes the stack voltage as a controlled variable; when the third controller takes the fuel component at the stack outlet as a controlled variable, the fuel component at the stack outlet is collected through a fuel component sensor at the stack anode outlet, and a deviation from a target value of the fuel component is compared, and a control signal is generated to a DC / DC conversion unit, and the stack current is adjusted through the DC / DC conversion unit; the first controller takes the fuel gas flow as a control variable and takes the stack current as a controlled variable, and the first controller compares a deviation between a set value of the stack current and the stack current adjusted through the third controller, generates a control signal to adjust the opening degree of a fuel gas adjusting valve, and dynamically adjusts the fuel gas flow into the two-stage heat exchanger.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell system control, in particular to a load tracking and temperature control system and method for SOFC system. BACKGROUND

[0002] Compared with traditional gas turbine power generation, solid oxide fuel cell (SOFC) directly realizes the conversion of chemical energy to electrical energy through electrochemical reaction, skipping the intermediate process of heat and mechanical energy, reducing environmental pollution and improving fuel utilization. Compared with other fuel cells such as proton exchange membrane fuel cell (PEMFC) and molten carbonate fuel cell (MCFC), SOFC adopts a solid-state structure without noble metal, has the advantages of environmental protection and high efficiency, and is widely concerned in the field of distributed energy and clean power generation. SOFC needs to work at a high temperature of about 750℃, and if the temperature of the stack and the temperature gradient exceed the safe range, thermal stress will cause damage to the stack; during the power following process of SOFC, the rapid change of current leads to instantaneous change of electrochemical reaction, and if the fuel supply is not timely, it will cause irreversible degradation such as cell perforation. How to realize the load following and thermal management of SOFC through effective control scheme is the challenge and difficulty of the current SOFC system control research.

[0003] The load tracking and temperature control of traditional SOFC often aims at a specific system model, adopts a parameter exhaustive optimization method to obtain a temperature safety interval, and adjusts fuel flow, air ratio and bypass ratio and other parameters according to the power demand. The universality of this method is poor, and it can only obtain a good result for a specific model, and has the problem of poor anti-interference ability for industrial environment containing various disturbances and characteristic degradation. Most of the existing technologies fail to effectively coordinate the relationship among fuel flow, stack current and temperature, and in the process of load change, the stack is prone to problems such as fuel shortage, temperature overrun and excessive temperature gradient, thereby affecting the safety and service life of SOFC.

[0004] SOFC converts the chemical energy of fuel gas into electricity through electrochemical reaction. In order to track the power demand, the fuel gas flow needs to be adjusted constantly to ensure the fuel inside the SOFC stack is sufficient, preventing the problem of fuel shortage. The remaining fuel is burned in the combustor to produce high-temperature exhaust gas, which is used to heat the gas (fuel gas and air) entering the stack through the preheater. The gas inlet temperature of the stack needs to be kept constant, and the temperature difference between the gas inlet and outlet of the stack also needs to be kept constant, preventing thermal stress changes caused by changes in stack temperature and temperature gradient, which can damage the stack. Part of the fuel gas entering the stack is converted into electricity, and part of the heat generated by burning is used to ensure the constant temperature of the stack inlet gas. The current control method mainly uses fuel gas to track the power demand. Under large power fluctuations, the consumption rate of fuel by electrochemical reaction is in milliseconds, while the tracking rate of fuel gas is in seconds, resulting in poor tracking effect, and thus poor temperature control effect. SUMMARY

[0005] The purpose of the present application is to provide a load tracking and temperature control system for SOFC system, which uses traditional PID method to solve the technical problems in the background art.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows:

[0007] A load tracking and temperature control system for SOFC system, the SOFC system comprising a two-stage heat exchanger, a SOFC stack, a combustor and a DC / DC conversion unit;

[0008] When the SOFC system is working, the fuel gas and air are controlled by the fuel gas regulating valve and the air regulating valve respectively, and then sent to the two-stage heat exchanger for heating, and then sent to the anode and cathode of the stack respectively. The current formed by the reaction in the stack is output after being processed by the DC / DC conversion unit, which is called stack current. The gas containing unburned fuel discharged from the stack enters the combustor, and the gas after complete combustion in the combustor is sent to the two-stage heat exchanger and discharged as exhaust gas after heat exchange;

[0009] The load tracking and temperature control system for the SOFC system comprises a first controller and a third controller;

[0010] The third controller takes the stack current as the control variable, and takes the fuel component at the stack outlet as the controlled variable, or takes the stack voltage as the controlled variable;

[0011] When the third controller uses the fuel composition at the fuel stack outlet as the controlled variable, it collects the fuel composition at the fuel stack outlet through the fuel composition sensor at the fuel anode outlet of the fuel stack, compares the deviation with the target value of the fuel composition, and generates a control signal to the DC / DC conversion unit accordingly, and then adjusts the fuel stack current through the DC / DC conversion unit.

[0012] When the third controller uses the fuel cell stack voltage as the controlled variable, it acquires the fuel cell stack voltage through a voltage sensor and compares the deviation with the target value of the fuel cell stack voltage. Based on this, it generates a control signal to the DC / DC conversion unit, and then adjusts the fuel cell stack current through the DC / DC conversion unit.

[0013] The first controller uses fuel gas flow rate as the control variable and fuel cell stack current as the controlled variable. The first controller generates a control signal by comparing the deviation between the fuel cell stack current set value and the fuel cell stack current adjusted by the third controller to adjust the opening of the fuel gas regulating valve, thereby dynamically adjusting the fuel gas flow rate fed into the two-stage heat exchanger.

[0014] In some embodiments, a bypass valve circuit and a second controller are also included;

[0015] One end of the bypass valve circuit is located before the air inlet of the two-stage heat exchanger, and the other end is located after the air outlet of the two-stage heat exchanger, so that when the bypass valve is opened, some air does not pass through the two-stage heat exchanger and directly enters the cathode of the fuel cell stack.

[0016] The second controller uses the bypass air flow rate as the control variable and the cathode inlet temperature of the fuel cell stack as the controlled variable. The second controller generates a control signal to adjust the opening of the bypass valve by comparing the deviation between the cathode inlet temperature of the fuel cell stack and the temperature setpoint.

[0017] In some embodiments, a fourth controller is also included, wherein the bypass valve opening degree is the controlled variable;

[0018] If the third controller uses the fuel composition at the stack outlet as the controlled variable, then the fourth controller uses the target value of the fuel composition as the control variable.

[0019] The fourth controller generates a target value for fuel composition by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller.

[0020] If the third controller uses the fuel cell stack voltage as the controlled variable, then the fourth controller uses the fuel cell stack voltage target value as the control variable.

[0021] The fourth controller generates a target value for the fuel cell voltage by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller.

[0022] In some embodiments, a fifth controller is also included;

[0023] The fifth controller uses airflow as the control variable and fuel cell outlet temperature as the controlled variable. The fifth controller generates a control signal to adjust the airflow input of the blower by comparing the deviation between the fuel cell outlet temperature and the temperature setpoint.

[0024] In some embodiments, a sixth controller and a high-order selector are also included;

[0025] The sixth controller is used to calculate the safe airflow value based on the real-time fuel gas flow rate and a preset ratio.

[0026] The high-level selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller with the safe air flow value obtained by the sixth controller, and select the higher value between the two to adjust the air flow input of the blower to ensure that the air flow is not lower than the safe air flow value.

[0027] Another aspect of the present invention provides a load tracking and temperature control method for an SOFC system, the SOFC system comprising a two-stage heat exchanger, an SOFC stack, a combustion chamber and a DC / DC converter unit;

[0028] When the SOFC system is working, the fuel gas and air are controlled by the fuel gas regulating valve and the air regulating valve respectively, and then sent to the two-stage heat exchangers for heating. They are then sent to the anode and cathode of the fuel cell stack respectively, where the reaction is completed. The current generated by the reaction is processed by the DC / DC converter unit and output as the fuel cell stack current. The gas containing unburned fuel discharged from the fuel cell stack enters the combustion chamber. After complete combustion in the combustion chamber, the gas is sent to the two-stage heat exchangers and discharged as exhaust gas after heat exchange.

[0029] Configure a first controller and a third controller in the SOFC system;

[0030] The third controller collects the fuel composition at the fuel composition sensor at the fuel composition outlet of the fuel stack, compares the deviation with the target value of the fuel composition, and generates a control signal to the DC / DC converter unit accordingly, thereby adjusting the fuel stack current through the DC / DC converter unit.

[0031] Alternatively, the third controller acquires the stack voltage through a voltage sensor, compares the deviation from the target value of the stack voltage, and generates a control signal to the DC / DC converter unit accordingly, thereby adjusting the stack current through the DC / DC converter unit.

[0032] The first controller generates a control signal by comparing the deviation between the setpoint of the fuel cell stack current and the fuel cell stack current regulated by the third controller, thereby adjusting the opening of the fuel gas regulating valve and thus dynamically regulating the flow rate of fuel gas fed into the two-stage heat exchanger.

[0033] In some embodiments, a bypass valve circuit and a second controller are also provided in the SOFC system;

[0034] One end of the bypass valve circuit is located before the air inlet of the two-stage heat exchanger, and the other end is located after the air outlet of the two-stage heat exchanger, so that when the bypass valve is opened, some air does not pass through the two-stage heat exchanger and directly enters the cathode of the fuel cell stack.

[0035] The second controller generates a control signal to adjust the opening of the bypass valve by comparing the deviation between the cathode inlet temperature of the fuel cell stack and the set temperature value.

[0036] In some embodiments, a fourth controller is also provided in the SOFC system;

[0037] The fourth controller generates a target value for the fuel composition by comparing the deviation between the current bypass valve opening and its set value, and provides this value to the third controller; or

[0038] The fourth controller generates a target value for the fuel cell voltage by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller.

[0039] In some embodiments, a fifth controller is also provided in the SOFC system;

[0040] The fifth controller generates a control signal to adjust the airflow input of the blower by comparing the deviation between the fuel cell outlet temperature and the set temperature value.

[0041] In some embodiments, a sixth controller and a high-order selector are also provided in the SOFC system;

[0042] The sixth controller is used to calculate the safe airflow value based on the real-time fuel gas flow rate and a preset ratio.

[0043] The high-level selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller with the safe air flow value obtained by the sixth controller, and select the higher value between the two to adjust the air flow input of the blower to ensure that the air flow is not lower than the safe air flow value.

[0044] Compared with existing technologies, the load tracking and temperature control system and method for SOFC systems provided by this invention overcomes the problems of fuel shortage caused by untimely fuel response during load changes and the allocation of fuel for power generation and temperature control in existing technologies by setting up multiple cooperating controllers in the SOFC system and using the traditional PID method. This achieves multi-variable coordinated control of stack current, fuel flow, and temperature. By integrating multi-layer closed-loop feedback and feedforward regulation mechanisms such as cascade control, valve position control, and override control, it can quickly and accurately match fuel supply and load demand, effectively preventing problems such as fuel shortage, temperature over-limit, and temperature gradient over-limit, significantly improving the dynamic response capability, operational safety, and stack life of the SOFC system. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in this embodiment, the accompanying drawings used in the description of the embodiment will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 A schematic diagram of the load tracking and temperature control system of an SOFC system in one embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the load tracking and temperature control system of an SOFC system in another embodiment.

[0048] Explanation of reference numerals in the attached diagram: 1. Two-stage heat exchanger; 2. SOFC stack; 3. Combustion chamber; 4. First controller; 5. Second controller; 6. Third controller; 7. Fourth controller; 8. Fifth controller; 9. Sixth controller; 10. DC / DC converter unit. Detailed Implementation

[0049] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following description, in conjunction with the accompanying drawings and specific embodiments, further explains how this invention is implemented.

[0050] In the first embodiment, refer to Figure 1 As shown, this invention provides a load tracking and temperature control system for an SOFC system. Except as otherwise provided in the foregoing description of reference numerals, those skilled in the art will understand that in the figures, CC represents a current controller, VPC represents a valve position controller, AC represents a fuel component controller, AT represents a fuel component sensor, TC represents a temperature controller, TT represents a temperature sensor, FT represents a flow transmitter, FC represents a flow controller, and HS represents a high-position selector.

[0051] The SOFC system includes a two-stage heat exchanger 1, an SOFC stack 2, a combustion chamber 3, and a DC / DC converter unit 10. When the SOFC system is working, the fuel gas and air are fed into the two-stage heat exchanger 1 for heating, controlled by the fuel gas regulating valve and the air regulating valve, respectively. Then, they are fed into the anode and cathode of the stack, respectively, where the reaction is completed. The current generated by the reaction is processed by the DC / DC converter unit 10 and output as the stack current. The gas containing unburned fuel discharged from the stack enters the combustion chamber 3. After complete combustion in the combustion chamber 3, the gas is sent back to the two-stage heat exchanger 1 and discharged as exhaust gas after heat exchange.

[0052] The load tracking and temperature control system of this SOFC system includes a first controller 4 and a third controller 6. The third controller 6 uses the stack current as the control variable and the fuel composition at the stack outlet as the controlled variable. The third controller 6 collects the fuel composition at the stack outlet through a fuel composition sensor at the anode outlet of the stack, compares the deviation with the target value of the fuel composition, and generates a control signal to the DC / DC converter unit 10, which then adjusts the stack current. In the third controller 6, when the fuel composition is lower than the target value, the stack current is reduced; when the fuel composition is higher than the target value, the stack current is increased.

[0053] The first controller 4 uses the fuel gas flow rate as the control variable and the fuel cell stack current as the controlled variable. The first controller 4 generates a control signal by comparing the deviation between the setpoint of the fuel cell stack current and the current regulated by the third controller 6, thereby adjusting the opening of the fuel gas regulating valve and dynamically regulating the fuel gas flow rate fed into the two-stage heat exchanger 1. In the first controller 4, when the fuel cell stack current is lower than the setpoint, the opening of the fuel gas regulating valve is increased; when the fuel cell stack current is higher than the setpoint, the opening of the fuel gas regulating valve is decreased.

[0054] In this embodiment, the first controller 4 and the third controller 6 together constitute a cascade control system. The first controller 4 implements feedback tracking control of the fuel cell stack current, and the third controller 6 implements feedback control of the fuel cell stack outlet fuel composition. The loop corresponding to the third controller 6 effectively controls the internal fuel composition, ensuring that no fuel shortage occurs inside the fuel cell stack. The loop corresponding to the first controller 4 tracks the fuel flow rate to the current setpoint, meeting the fuel cell stack power tracking requirements. The combination of the first controller 4 and the third controller 6 effectively solves the problem of rapid tracking under rapid load changes and the potential for fuel shortage. The first controller 4 and the third controller 6 work together; when the fuel cell stack current setpoint increases, the first controller 4 adjusts the fuel gas flow rate to track the fuel cell stack current. The change in fuel gas flow rate causes the third controller 6 to automatically adjust the fuel cell stack current after detecting a change in fuel composition, ultimately reaching the setpoint of the fuel cell stack current.

[0055] Furthermore, the load tracking and temperature control system of this SOFC system also includes a bypass valve loop and a second controller 5. One end of the bypass valve loop is located before the air inlet of the two-stage heat exchanger 1, and the other end is located after the air outlet of the two-stage heat exchanger 1, so that when the bypass valve is open, some air bypasses the two-stage heat exchanger 1 and directly enters the cathode of the fuel cell stack. The second controller 5 uses the bypass air flow rate as the control variable and the fuel cell stack cathode inlet temperature as the controlled variable. The second controller 5 generates a control signal to adjust the opening degree of the bypass valve by comparing the deviation between the fuel cell stack cathode inlet temperature and the temperature setpoint. In the second controller 5, when the fuel cell stack cathode inlet temperature is lower than the setpoint, the opening degree of the bypass valve is reduced; when the fuel cell stack cathode inlet temperature is higher than the setpoint, the opening degree of the bypass valve is increased.

[0056] Furthermore, the load tracking and temperature control system of this SOFC system also includes a fourth controller 7. The fourth controller 7 uses the bypass valve opening as the controlled variable and the target value of the fuel composition as the control variable. The fourth controller 7 generates the target value of the fuel composition by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller 6. In the fourth controller 7, when the bypass valve opening is lower than the set value, the target value of the fuel composition is increased; when the bypass valve opening is higher than the set value, the target value of the fuel composition is decreased.

[0057] In this embodiment, the second controller 5, the fourth controller 7, and the third controller 6 construct a multivariate cascade feedback structure of 'temperature-fuel composition-stack current' + valve position control. By controlling the stack current, the fuel achieves decoupled control of power and temperature, which enables the stack to maintain effective temperature control under rapid load changes and solves the problem of response lag in conventional solutions.

[0058] Specifically, for example, under initial conditions, the stack current and bypass valve opening are both equal to their set values. If the current stack cathode inlet temperature is lower than the set value, the second controller 5 reduces the opening of the bypass valve, causing the stack cathode inlet temperature to rise and approach the set value. Simultaneously, because the bypass valve opening decreases to below the set value, the fourth controller 7 increases the target value of the fuel composition. The increase in the target value of the fuel composition causes the fuel composition at the stack outlet to be lower than the target value, so the third controller 6 reduces the stack current. Because the stack current decreases to below the set value, the first controller 4 increases the opening of the fuel gas regulating valve, thereby increasing the fuel composition at the stack outlet. Simultaneously, after the fuel composition at the stack outlet increases, the temperature of the combustion gas generated in the combustion chamber rises, and it is then sent to the two-stage heat exchanger 1, causing the stack cathode inlet temperature to rise.

[0059] It is evident that both the decrease in the bypass valve opening and the increase in fuel composition at the stack outlet cause the stack cathode inlet temperature to rise, approaching the set value. Once the temperature rises above the set value, after the reverse control process, the second controller 5 increases the bypass valve opening to approach the set value; once the bypass valve opening exceeds the set value, the fourth controller 7 lowers the target fuel composition value. If the decrease in the target fuel composition value causes the fuel composition at the stack outlet to exceed the target value, the third controller 6 increases the stack current to approach the set value.

[0060] Through the above cyclic control, the target value of fuel composition is continuously adjusted according to environmental changes during the control process. By effectively controlling the fuel composition, the stack current, bypass valve opening and stack cathode inlet temperature can all respond quickly to approach the set value.

[0061] Furthermore, the load tracking and temperature control system of this SOFC system also includes a fifth controller 8. The fifth controller 8 uses airflow as the control variable and the stack outlet temperature as the controlled variable to achieve feedback tracking control of the stack outlet temperature. The fifth controller 8 generates a control signal to adjust the airflow input of the blower by comparing the deviation between the stack outlet temperature and the set temperature. It is understood that because some air passes through the bypass valve and bypasses the two-stage heat exchanger 1 before entering the stack 2, the air temperature at the inlet of stack 2 is lower than the fuel temperature. Under the premise of sufficient air supply, a higher airflow results in a lower stack outlet temperature. Therefore, in the fifth controller 8, when the stack outlet temperature is lower than the set value, the airflow input is reduced; when the stack outlet temperature is higher than the set value, the airflow input is increased.

[0062] Furthermore, the load tracking and temperature control system of the SOFC system also includes a sixth controller 9 and a high-level selector; the sixth controller 9 is used to calculate the safe air flow value based on the real-time fuel gas flow rate and a preset ratio; the high-level selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller 8 with the safe air flow value obtained by the sixth controller 9, and select the higher value between the two to adjust the air flow input of the blower, so as to ensure that the air flow rate is not lower than the safe air flow value and prevent insufficient air supply during stack operation.

[0063] The fifth controller 8 employs an airflow-temperature closed-loop control system and integrates a high-level selector with the safety protection mechanism of the sixth controller 9. The temperature-airflow closed-loop system receives the stack outlet temperature and the set cathode outlet temperature, adjusting the blower's airflow input via a deviation signal to ensure the stack outlet temperature remains stable at the target setpoint. The high-level selector monitors the fuel flow rate to airflow ratio in real time. When the airflow rate becomes too low due to temperature feedback, it automatically switches to the safety lower limit to prevent insufficient oxygen supply and ensure the stability and safety of the stack's chemical reaction.

[0064] Furthermore, the second controller 5 and the fifth controller 8 control the inlet and outlet temperatures of the fuel cell stack, keeping the stack temperature within a suitable range and solving the problem of excessive temperature difference, thus effectively improving the lifespan of the fuel cell stack.

[0065] With this structure, the present invention not only achieves effective decoupling of SOFC fuel gas power tracking and temperature control, but also significantly improves the system's rapid response capability to dynamic changes in temperature and fuel composition, ensuring the balance between temperature safety and fuel utilization, and greatly enhancing the operational stability and safety of the fuel cell system.

[0066] In addition, in the second embodiment, refer to Figure 2 As shown in the figure, VC represents the voltage controller and VT represents the voltage sensor. The difference from the first embodiment is that the third controller 6 uses the stack voltage as the controlled variable, not the fuel composition at the stack outlet. It is understandable that the fuel state inside the stack does not necessarily need to be reflected by the fuel composition. With sufficient air supply, the fuel composition at the stack outlet is positively correlated with the stack voltage; therefore, the stack voltage can also reflect the current fuel state inside the stack.

[0067] In this embodiment, the third controller 6 collects the stack voltage through a voltage sensor and compares the deviation from the target value of the stack voltage. Based on this, it generates a control signal to the DC / DC converter unit 10, and then adjusts the stack current through the DC / DC converter unit 10.

[0068] Accordingly, the fourth controller 7 uses the target value of the fuel cell voltage as the control variable; the fourth controller 7 generates the target value of the fuel cell voltage by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller 6.

[0069] In this embodiment, the overall effect is similar to that of the first embodiment, except that the fuel state inside the fuel stack is reflected by the stack voltage rather than the fuel composition.

[0070] Another aspect of the present invention provides a load tracking and temperature control method for an SOFC system, comprising: setting a first controller 4 and a third controller 6 in the SOFC system;

[0071] The third controller 6 collects the fuel composition at the fuel stack outlet through a fuel composition sensor at the anode outlet of the fuel stack, compares the deviation from the target value of the fuel composition, and generates a control signal to the DC / DC converter unit 10 accordingly, thereby adjusting the fuel stack current through the DC / DC converter unit 10; or, the third controller 6 collects the fuel stack voltage through a voltage sensor, compares the deviation from the target value of the fuel stack voltage, generates a control signal to the DC / DC converter unit 10 accordingly, thereby adjusting the fuel stack current through the DC / DC converter unit 10; the first controller 4 generates a control signal to adjust the opening of the fuel gas regulating valve by comparing the deviation between the fuel stack current set value and the fuel stack current adjusted by the third controller 6, thereby dynamically adjusting the fuel gas flow rate fed into the two-stage heat exchanger 1.

[0072] Furthermore, a bypass valve loop and a second controller 5 are also set in the SOFC system; one end of the bypass valve loop is located before the air inlet of the two-stage heat exchanger 1, and the other end is located after the air outlet of the two-stage heat exchanger 1, so that when the bypass valve is opened, some air does not pass through the two-stage heat exchanger 1 and directly enters the cathode of the fuel cell stack; the second controller 5 generates a control signal to adjust the opening degree of the bypass valve by comparing the deviation between the cathode inlet temperature of the fuel cell stack and the temperature set value.

[0073] Furthermore, a fourth controller 7 is also provided in the SOFC system; the fourth controller 7 generates a target value for fuel composition by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller 6; or the fourth controller 7 generates a target value for the stack voltage by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller 6.

[0074] Furthermore, a fifth controller 8 is also set in the SOFC system; the fifth controller 8 generates a control signal to adjust the air flow input of the blower by comparing the deviation between the stack outlet temperature and the temperature setpoint.

[0075] Furthermore, a sixth controller 9 and a high-level selector are also set in the SOFC system; the sixth controller 9 is used to calculate the safe air flow value based on the real-time fuel gas flow rate and the preset ratio; the high-level selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller 8 with the safe air flow value obtained by the sixth controller 9, and select the higher value between the two to adjust the air flow input of the blower to ensure that the air flow is not lower than the safe air flow value.

[0076] Compared with existing technologies, the load tracking and temperature control system and method for SOFC systems provided by this invention overcomes the problems of fuel shortage caused by untimely fuel response during load changes and the allocation of fuel for power generation and temperature control in existing technologies by setting up multiple cooperating controllers in the SOFC system and using the traditional PID method. This achieves multi-variable coordinated control of stack current, fuel flow, and temperature. By integrating multi-layer closed-loop feedback and feedforward regulation mechanisms such as cascade control, valve position control, and override control, it can quickly and accurately match fuel supply and load demand, effectively preventing problems such as fuel shortage, temperature over-limit, and temperature gradient over-limit, significantly improving the dynamic response capability, operational safety, and stack life of the SOFC system.

[0077] Finally, it should be noted that the above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A load tracking and temperature control system for an SOFC system, the SOFC system comprising a two-stage heat exchanger (1), an SOFC stack (2), a combustion chamber (3), and a DC / DC converter unit (10). When the SOFC system is working, the fuel gas and air are controlled by the fuel gas regulating valve and the air regulating valve respectively and sent to the two-stage heat exchanger (1) for heating. Then they are sent to the anode and cathode of the fuel cell stack respectively. The reaction is completed in the fuel cell stack. The current generated by the reaction is processed by the DC / DC conversion unit (10) and output as the fuel cell stack current. The gas containing unburned fuel discharged from the fuel cell stack enters the combustion chamber (3). The gas after complete combustion in the combustion chamber (3) is sent to the two-stage heat exchanger (1) and discharged as exhaust gas after heat exchange. Its features are, The load tracking and temperature control system of the SOFC system includes a first controller (4) and a third controller (6). The third controller (6) uses the stack current as the control variable, the fuel composition at the stack outlet as the controlled variable, or the stack voltage as the controlled variable. When the third controller (6) takes the fuel composition at the fuel stack outlet as the controlled variable, it collects the fuel composition at the fuel stack outlet through the fuel composition sensor at the fuel anode outlet of the fuel stack, compares the deviation with the target value of the fuel composition, and generates a control signal to the DC / DC conversion unit (10) accordingly, and then adjusts the fuel stack current through the DC / DC conversion unit (10). When the third controller (6) uses the stack voltage as the controlled variable, it collects the stack voltage through a voltage sensor and compares the deviation with the target value of the stack voltage. Based on this, it generates a control signal to the DC / DC converter unit (10) and then adjusts the stack current through the DC / DC converter unit (10). The first controller (4) uses the fuel gas flow rate as the control variable and the stack current as the controlled variable. The first controller (4) generates a control signal to adjust the opening of the fuel gas regulating valve by comparing the deviation between the stack current set value and the stack current adjusted by the third controller (6), thereby dynamically adjusting the fuel gas flow rate fed into the two-stage heat exchanger (1). The load tracking and temperature control system of the SOFC system also includes a bypass valve circuit, a second controller (5) and a fourth controller (7). One end of the bypass valve circuit is located before the air inlet of the two-stage heat exchanger (1), and the other end is located after the air outlet of the two-stage heat exchanger (1), so that when the bypass valve is opened, some air does not pass through the two-stage heat exchanger (1) and directly enters the cathode of the fuel cell stack. The second controller (5) uses the bypass air flow rate as the control variable and the cathode inlet temperature of the fuel cell stack as the controlled variable. The second controller (5) generates a control signal to adjust the opening of the bypass valve by comparing the deviation between the cathode inlet temperature of the fuel cell stack and the temperature setpoint. The fourth controller (7) uses the bypass valve opening degree as the controlled variable; If the third controller (6) uses the fuel composition at the stack outlet as the controlled variable, then the fourth controller (7) uses the target value of the fuel composition as the control variable. The fourth controller (7) generates a target value for fuel components by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller (6). If the third controller (6) uses the stack voltage as the controlled variable, then the fourth controller (7) uses the stack voltage target value as the control variable; The fourth controller (7) generates a target value for the fuel cell voltage by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller (6).

2. The load tracking and temperature control system for the SOFC system according to claim 1, characterized in that, It also includes the fifth controller (8); The fifth controller (8) uses air flow as the control variable and the fuel cell outlet temperature as the controlled variable. The fifth controller (8) generates a control signal to adjust the air flow input of the blower by comparing the deviation between the fuel cell outlet temperature and the temperature set value.

3. The load tracking and temperature control system of the SOFC system according to claim 2, characterized in that, It also includes a sixth controller (9) and a high-order selector; The sixth controller (9) is used to calculate the air flow safety value based on the real-time fuel gas flow rate and the preset ratio; The high-level selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller (8) with the safe air flow value obtained by the sixth controller (9), and select the higher value between the two to adjust the air flow input of the blower to ensure that the air flow is not lower than the safe air flow value.

4. A load tracking and temperature control method for an SOFC system, the SOFC system comprising a two-stage heat exchanger (1), an SOFC stack (2), a combustion chamber (3), and a DC / DC converter unit (10). When the SOFC system is working, the fuel gas and air are controlled by the fuel gas regulating valve and the air regulating valve respectively and sent to the two-stage heat exchanger (1) for heating. Then they are sent to the anode and cathode of the fuel cell stack respectively. The reaction is completed in the fuel cell stack. The current generated by the reaction is processed by the DC / DC conversion unit (10) and output as the fuel cell stack current. The gas containing unburned fuel discharged from the fuel cell stack enters the combustion chamber (3). The gas after complete combustion in the combustion chamber (3) is sent to the two-stage heat exchanger (1) and discharged as exhaust gas after heat exchange. Its features are, In the SOFC system, a first controller (4) and a third controller (6) are set up. The third controller (6) collects the fuel composition at the fuel composition sensor at the anode outlet of the fuel stack and compares the deviation with the target value of the fuel composition. Based on this, it generates a control signal to the DC / DC converter unit (10) and then adjusts the fuel stack current through the DC / DC converter unit (10). Alternatively, the third controller (6) collects the stack voltage through a voltage sensor and compares the deviation from the target value of the stack voltage, thereby generating a control signal to the DC / DC converter unit (10), and then adjusts the stack current through the DC / DC converter unit (10); The first controller (4) generates a control signal to adjust the opening of the fuel gas regulating valve by comparing the deviation between the set value of the fuel stack current and the fuel stack current regulated by the third controller (6), thereby dynamically adjusting the flow rate of fuel gas fed into the two-stage heat exchanger (1). A bypass valve circuit, a second controller (5), and a fourth controller (7) are also set up in the SOFC system. One end of the bypass valve circuit is located before the air inlet of the two-stage heat exchanger (1), and the other end is located after the air outlet of the two-stage heat exchanger (1), so that when the bypass valve is opened, some air does not pass through the two-stage heat exchanger (1) and directly enters the cathode of the fuel cell stack. The second controller (5) generates a control signal to adjust the opening of the bypass valve by comparing the deviation between the cathode inlet temperature of the fuel cell stack and the set temperature value. The fourth controller (7) generates a target value for the fuel composition by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller (6); or The fourth controller (7) generates a target value for the fuel cell voltage by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides it to the third controller (6).

5. The load tracking and temperature control method for an SOFC system according to claim 4, characterized in that, Also, a fifth controller (8) is set up in the SOFC system; The fifth controller (8) generates a control signal to adjust the airflow input of the blower by comparing the deviation between the fuel cell outlet temperature and the temperature setpoint.

6. The load tracking and temperature control method for an SOFC system according to claim 5, characterized in that, A sixth controller (9) and a high-order selector are also set in the SOFC system; The sixth controller (9) is used to calculate the air flow safety value based on the real-time fuel gas flow rate and the preset ratio; The high-level selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller (8) with the safe air flow value obtained by the sixth controller (9), and select the higher value between the two to adjust the air flow input of the blower to ensure that the air flow is not lower than the safe air flow value.

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