Load tracking and temperature control system and method of SOFC (solid oxide fuel cell) system

Abstract

The invention discloses a load tracking and temperature control system and method of an SOFC (Solid Oxide Fuel Cell) system. The system comprises a first controller and a third controller, the third controller takes the current of the electric pile as a control variable, takes a fuel component at the outlet of the electric pile as a controlled variable, or takes the voltage of the electric pile as a controlled variable; when the third controller takes the fuel component at the outlet of the galvanic pile as a controlled variable, the fuel component at the outlet of the galvanic pile is collected by a fuel component sensor at the outlet of the anode of the galvanic pile, and the deviation between the fuel component and a target value of the fuel component is compared, so that a control signal is generated and transmitted to a DC / DC conversion unit, and the current of the galvanic pile is adjusted through the DC / DC conversion unit; the first controller takes the fuel gas flow as a control variable and the electric pile current as a controlled variable, and the first controller generates a control signal to adjust the opening degree of the fuel gas adjusting valve by comparing the deviation between an electric pile current set value and the electric pile current adjusted by the third controller, so that the fuel gas flow fed into the two-stage heat exchanger is dynamically adjusted.

Description

Technical Field

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

[0002] Compared to traditional gas turbine power generation, solid oxide fuel cells (SOFCs) convert chemical energy to electrical energy directly through electrochemical reactions, bypassing intermediate processes such as thermal and mechanical energy. This reduces environmental pollution and improves fuel efficiency. Compared to other fuel cells, such as proton exchange membrane fuel cells (PFMFCs) and molten carbonate fuel cells (MCFCs), SOFCs utilize a solid-state structure that requires no precious metals, offering advantages such as environmental friendliness and high efficiency. SOFCs have attracted widespread attention in the fields of distributed energy and clean power generation. SOFCs operate at high temperatures of approximately 750°C. If the stack temperature and temperature gradient exceed safe limits, thermal stress can damage the stack. During power following, rapid changes in current cause transient changes in the electrochemical reaction, and untimely fuel supply can lead to irreversible degradation, such as cell perforation. The challenge and difficulty of SOFC system control research is to achieve effective control solutions for load following and thermal management.

[0003] Traditional SOFC load tracking and temperature control often target specific system models, employing a parameter exhaustive optimization method to determine a safe temperature range. These parameters, such as fuel flow rate, air ratio, and bypass ratio, are then adjusted based on power requirements. This approach has limited universality and can often only achieve good results for specific models. It also suffers from poor anti-interference capabilities in industrial environments with various disturbances and degradation. Most existing technologies fail to effectively coordinate the relationships between multiple factors, such as fuel flow rate, stack current, and temperature. During load changes, the stack is prone to fuel starvation, temperature overshoot, and excessive temperature gradients, which can impact the safety and service life of the SOFC.

[0004] SOFCs convert the chemical energy of fuel gas into electricity through electrochemical reactions. To track power demand, the fuel gas flow rate must be continuously adjusted to ensure sufficient fuel within the SOFC stack and prevent fuel starvation. Excess fuel burns in the combustion chamber, producing high-temperature exhaust gases. This high-temperature exhaust gas then passes through a preheater to heat the gases (fuel gas and air) entering the stack. The stack's gas inlet temperature must be kept constant, as must the temperature difference between the gas inlet and outlet to prevent thermal stress and potential damage caused by variations in stack temperature and temperature gradients. A portion of the fuel gas entering the stack is converted into electricity, while a portion is maintained at a constant stack inlet temperature by heat generated by combustion. Current control methods primarily rely on the fuel gas tracking power demand. Under wide power fluctuations, this tracking effect is poor, as electrochemical reactions consume fuel at a millisecond-level, while the fuel gas tracking speed is in seconds. Consequently, temperature control is also ineffective. Summary of the Invention

[0005] The object of the present invention is to provide a load tracking and temperature control system for a SOFC system, which adopts a traditional PID method to solve the technical problems existing in the background technology.

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

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

[0008] When the SOFC system is operating, 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 for heating. They are then sent to the anode and cathode of the fuel cell stack respectively. After the reaction in the fuel cell stack is completed, the current generated by the reaction is processed by the DC / DC conversion unit and output, which is called the fuel cell current. The gas containing unburned fuel discharged from the fuel cell stack enters the combustion chamber. After being completely burned in the combustion chamber, the gas is sent to the two-stage heat exchanger and discharged as exhaust gas after heat exchange.

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

[0010] The third controller uses the stack current as a controlled variable and the fuel composition at the stack outlet as a controlled variable, or uses the stack voltage as a controlled variable;

[0011] When the third controller uses the fuel composition at the stack outlet as a controlled variable, the fuel composition at the stack outlet is collected by a fuel composition sensor at the stack anode outlet, and the deviation is compared with the target fuel composition value. Based on the collected information, a control signal is generated to the DC / DC converter unit, which then adjusts the stack current through the DC / DC converter unit.

[0012] When the third controller uses the stack voltage as the controlled variable, it collects the stack voltage through the voltage sensor and compares the deviation with the stack voltage target value, and generates a control signal to the DC / DC conversion unit based on the collected data, thereby adjusting the stack current through the DC / DC conversion unit;

[0013] The first controller uses the fuel gas flow rate as the control variable and the stack current as the controlled variable. The first controller 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, thereby dynamically adjusting the fuel gas flow rate sent to the two-stage heat exchanger.

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

[0015] One end of the bypass valve loop 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, part of the 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 stack cathode inlet temperature 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 stack cathode inlet temperature and the temperature set value.

[0017] In some embodiments, a fourth controller is further included, wherein the fourth controller uses the opening of the bypass valve as a controlled variable;

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

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

[0020] If the third controller uses the stack voltage as the controlled variable, the fourth controller uses the stack voltage target value as the controlled variable;

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

[0022] In some embodiments, further comprising a fifth controller;

[0023] The fifth controller uses air flow as a control variable and the stack outlet temperature as a controlled variable. The fifth controller 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 set value.

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

[0025] The sixth controller is used to calculate the air flow safety value according to the real-time fuel gas flow and the 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 air flow safety 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 air flow safety value.

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

[0028] When the SOFC system is operating, 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 for heating. They are then sent to the anode and cathode of the fuel cell stack respectively. After the reaction in the fuel cell stack is completed, the current generated by the reaction is processed by the DC / DC conversion unit and output, which is called the fuel cell current. The gas containing unburned fuel discharged from the fuel cell stack enters the combustion chamber. After being completely burned in the combustion chamber, the gas is sent to the two-stage heat exchanger and discharged as exhaust gas after heat exchange.

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

[0030] The third controller collects the fuel composition at the stack outlet through the fuel composition sensor at the stack anode outlet, compares the deviation with the fuel composition target value, and generates a control signal to the DC / DC conversion unit based on the collected data, thereby adjusting the stack current through the DC / DC conversion unit;

[0031] Alternatively, the third controller collects the stack voltage through a voltage sensor and compares the deviation with the stack voltage target value, and accordingly generates a control signal to the DC / DC conversion unit, thereby regulating the stack current through the DC / DC conversion unit;

[0032] The first controller 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, thereby dynamically adjusting the fuel gas flow rate sent to the two-stage heat exchanger.

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

[0034] One end of the bypass valve loop 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, part of the 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 temperature setting value.

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

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

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

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

[0040] The fifth controller 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 setting value.

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

[0042] The sixth controller is used to calculate the air flow safety value according to the real-time fuel gas flow and the 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 air flow safety 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 air flow safety value.

[0044] Compared to the prior art, the load tracking and temperature control system and method for a SOFC system provided by the present invention utilizes multiple, coordinated controllers within the SOFC system, employing traditional PID methods to overcome the prior art issues of delayed fuel response during load changes, leading to fuel deficit and fuel allocation for power generation and temperature control. This enables multivariable coordinated control of stack current, fuel flow, and temperature. By integrating multi-layer closed-loop feedback and feedforward regulation mechanisms, including cascade control, valve position control, and override control, the system rapidly and accurately matches fuel supply with load demand, effectively preventing issues such as fuel deficit, temperature overruns, and temperature gradient overruns. This significantly improves the SOFC system's dynamic response capability, operational safety, and stack lifespan. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution in this embodiment, the following is a brief introduction to the drawings required for describing the embodiment. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

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

[0047] Figure 2 Schematic diagram of a load tracking and temperature control system of a SOFC system in another embodiment.

[0048] Explanation of the accompanying drawings: 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 conversion unit. DETAILED DESCRIPTION

[0049] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the following further describes how the present invention is implemented in conjunction with the accompanying drawings and specific implementation methods.

[0050] In the first embodiment, referring to Figure 1 As shown, the present invention provides a load tracking and temperature control system for a SOFC system. In addition to the aforementioned reference numerals, those skilled in the art will appreciate that CC represents a current controller, VPC represents a valve position controller, AC represents a fuel composition controller, AT represents a fuel composition 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-level selector.

[0051] The SOFC system includes a two-stage heat exchanger 1, an SOFC stack 2, a combustion chamber 3 and a DC / DC conversion unit 10. When the SOFC system is operating, the fuel gas and air are controlled by the fuel gas regulating valve and the air regulating valve respectively, and are sent to the two-stage heat exchanger 1 for heating, and then sent to the anode and cathode of the stack respectively. After the reaction in the stack is completed, the current generated by the reaction is processed by the DC / DC conversion unit 10 and output, which is called the stack current. The gas containing unburned fuel discharged from the stack enters the combustion chamber 3. The gas that has been completely burned in the combustion chamber 3 is sent to the two-stage heat exchanger 1 and discharged as exhaust gas after heat exchange.

[0052] 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 a control variable and the fuel composition at the stack outlet as a controlled variable. The third controller 6 collects the fuel composition at the stack outlet via a fuel composition sensor at the stack anode outlet, compares the deviation with the target fuel composition value, and generates a control signal based on the obtained value 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] First controller 4 uses the fuel gas flow rate as the controlled variable and the stack current as the controlled variable. By comparing the deviation between the stack current set value and the stack current adjusted by third controller 6, first controller 4 generates a control signal to adjust the opening of the fuel gas regulating valve, thereby dynamically adjusting the fuel gas flow rate supplied to the two-stage heat exchanger 1. In first controller 4, when the stack current is lower than the set value, the opening of the fuel gas regulating valve is increased; when the stack current is higher than the set value, 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, the first controller 4 implements feedback tracking control of the stack current, and the third controller 6 implements feedback control of the fuel composition at the stack outlet. The circuit corresponding to the third controller 6 implements effective control of the internal fuel composition to ensure that there is no fuel deficit inside the stack; the circuit corresponding to the first controller 4 implements tracking of the fuel flow rate to the current setting value to meet the stack power tracking requirements. The construction of the first controller 4 and the third controller 6 effectively solves the problem of rapid tracking under rapid load changes and possible fuel deficits. The first controller 4 cooperates with the third controller 6. When the stack current setting value increases, the first controller 4 will adjust the fuel gas flow rate to track the stack current. The change in fuel gas flow rate causes the third controller 6 to automatically adjust the stack current after detecting a change in the fuel composition, and eventually reach the set value of the stack current.

[0055] Furthermore, the load tracking and temperature control system of the 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. When the bypass valve is opened, part of the air does not pass through the two-stage heat exchanger 1 and directly enters the cathode of the stack. The second controller 5 uses the bypass air flow rate as the control variable and the cathode inlet temperature of the 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 stack and the temperature set value. In the second controller 5, when the cathode inlet temperature of the stack is lower than the set value, the opening of the bypass valve is reduced; when the cathode inlet temperature of the stack is higher than the set value, the opening of the bypass valve is increased.

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

[0057] In this embodiment, the second controller 5, the fourth controller 7 and the third controller 6 construct a 'temperature-fuel composition-stack current' multi-variable cascade feedback + valve position control structure, which realizes the decoupling control of fuel on power and temperature through the control of stack current, and can ensure that the temperature of the stack is always effectively controlled under rapid load changes, solving the problem of response hysteresis of conventional solutions.

[0058] Specifically, for example, under the initial conditions, the stack current and the 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 bypass valve opening, causing the stack cathode inlet temperature to rise, bringing the cathode inlet temperature close to the set value. At the same time, because the bypass valve opening decreases to below the set value, the fourth controller 7 increases the fuel composition target value. If the fuel composition target value increases, causing the fuel composition at the stack outlet to fall below the target value, the third controller 6 reduces the stack current. Because the stack current falls below the set value, the first controller 4 increases the fuel gas regulating valve opening, thereby increasing the fuel composition at the stack outlet. At the same time, after the fuel composition at the stack outlet increases, the temperature of the post-combustion gas produced by the combustion chamber increases, and is then fed into the bipolar heat exchanger 1, causing the stack cathode inlet temperature to increase.

[0059] It can be seen that the decrease in the bypass valve opening and the increase in the fuel composition at the stack outlet both increase the stack cathode inlet temperature to approach the set value. Once the temperature rises above the set value, the second controller 5 increases the bypass valve opening to approach the set value through a control cycle opposite to the previous one. Once the bypass valve opening exceeds the set value, the fourth controller 7 reduces the target fuel composition. If the reduction in the target fuel composition 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 fuel component target value is continuously adjusted according to environmental changes during the control process. Through effective control of the fuel component, the stack current, bypass valve opening and stack cathode inlet temperature all respond quickly to approach the set value.

[0061] Furthermore, the SOFC system's load tracking and temperature control system also includes a fifth controller 8 . The fifth controller 8 uses air flow as a control variable and the stack outlet temperature as a controlled variable to implement feedback tracking control of the stack outlet temperature. 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 set point. It is understandable that because some air passes through the bypass valve and not through the two-stage heat exchanger 1 and is delivered to the stack 2, the air temperature at the stack 2 inlet is lower than the fuel temperature. Given an adequate air supply, the greater the air flow, the lower the stack outlet temperature. Therefore, in the fifth controller 8 , when the stack outlet temperature is lower than the set point, the air flow input is reduced; when the stack outlet temperature is higher than the set point, the air flow 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 air flow safety value based on the real-time fuel gas flow 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 air flow safety 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 air flow safety value, thereby preventing insufficient air supply during the operation of the fuel cell stack.

[0063] The fifth controller 8 uses air flow-temperature closed-loop control and integrates the safety protection mechanism of the high-level selector and the sixth controller 9. The temperature-air flow closed-loop receives the stack outlet temperature and the set cathode outlet temperature, and adjusts the air flow input of the blower through the deviation signal to ensure that the stack outlet temperature is stable at the target set value. The high-level selector monitors the ratio of fuel flow to air flow in real time. When the air flow tends to be too low due to temperature feedback, it automatically switches to the safety lower limit to avoid insufficient oxygen supply and ensure the stability and safety of the chemical reaction in the stack.

[0064] In addition, the second controller 5 and the fifth controller 8 control the inlet temperature and outlet temperature of the fuel cell stack, so that the temperature of the fuel cell stack is controlled within a suitable range, while solving the problem of excessive temperature difference of the fuel cell stack, which can effectively improve the life of the fuel cell stack.

[0065] Through such a structure, the present invention not only achieves the effective decoupling of SOFC stack fuel gas power tracking and temperature control, but also significantly improves the system's ability to quickly respond to dynamic changes in temperature and fuel components, ensures the unity of temperature safety and fuel utilization, and greatly enhances the operational stability and safety of the stack system.

[0066] In addition, in the second embodiment, referring to Figure 2 As shown in the figure, VC represents a voltage controller and VT represents a voltage sensor. The difference from the first embodiment is that the third controller 6 uses the stack voltage as the controlled variable, rather than the fuel composition at the stack outlet. It is understandable that the fuel state inside the stack is not necessarily reflected by the fuel composition. When the air supply is sufficient, 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 with the stack voltage target value, thereby generating a control signal to the DC / DC conversion unit 10, and then adjusting the stack current through the DC / DC conversion unit 10.

[0068] Correspondingly, the fourth controller 7 uses the stack voltage target value as a control variable; the fourth controller 7 generates the stack voltage target value 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 can be achieved similar to that of the first embodiment, with the only difference being that the current fuel state inside the stack is reflected through the stack voltage rather than the fuel composition.

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

[0071] The third controller 6 collects the fuel composition at the outlet of the fuel stack through the fuel composition sensor at the anode outlet of the fuel stack, and compares the deviation with the fuel composition target value, 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; or, the third controller 6 collects the fuel stack voltage through the voltage sensor, and compares the deviation with the target value of the fuel stack voltage, 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; 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 adjusted by the third controller 6, thereby dynamically adjusting the fuel gas flow rate sent to the two-stage heat exchanger 1.

[0072] Furthermore, a bypass valve loop and a second controller 5 are provided in the SOFC system; one end of the bypass valve loop is located in front of the air inlet of the two-stage heat exchanger 1, and the other end is located behind the air outlet of the two-stage heat exchanger 1, so that when the bypass valve is opened, part of the 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 temperature set value.

[0073] Furthermore, a fourth controller 7 is provided in the SOFC system; the fourth controller 7 generates a fuel component target value 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 fuel stack voltage target value 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 provided 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 setting value.

[0075] Furthermore, a sixth controller 9 and a high-level selector are provided 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 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 air flow safety 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 air flow safety value.

[0076] Compared to the prior art, the load tracking and temperature control system and method for a SOFC system provided by the present invention utilizes multiple, coordinated controllers within the SOFC system, employing traditional PID methods to overcome the prior art issues of delayed fuel response during load changes, leading to fuel deficit and fuel allocation for power generation and temperature control. This enables multivariable coordinated control of stack current, fuel flow, and temperature. By integrating multi-layer closed-loop feedback and feedforward regulation mechanisms, including cascade control, valve position control, and override control, the system rapidly and accurately matches fuel supply with load demand, effectively preventing issues such as fuel deficit, temperature overruns, and temperature gradient overruns. This significantly improves the SOFC system's dynamic response capability, operational safety, and stack lifespan.

[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 structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in 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 conversion 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 are sent to the two-stage heat exchanger (1) for heating, and then sent to the anode and cathode of the stack respectively. After the stack completes the reaction, the current generated by the reaction is processed by the DC / DC conversion unit (10) and output, which is called the stack current. The gas containing unburned fuel discharged from the stack enters the combustion chamber (3). The gas that has been completely burned in the combustion chamber (3) is sent to the two-stage heat exchanger (1) and discharged as exhaust gas after heat exchange. It is characterized by: 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 a controlled variable and the fuel composition at the stack outlet as a controlled variable, or uses the stack voltage as a controlled variable; When the third controller (6) uses the fuel composition at the outlet of the stack as a controlled variable, it collects the fuel composition at the outlet of the stack through a fuel composition sensor at the outlet of the stack anode, compares the deviation with the target value of the fuel composition, and generates a control signal to the DC / DC conversion unit (10) based on the deviation, thereby adjusting the stack current through the DC / DC conversion unit (10); When the third controller (6) uses the stack voltage as a controlled variable, it collects the stack voltage through a voltage sensor and compares the deviation with the stack voltage target value, thereby generating a control signal to the DC / DC conversion unit (10), thereby regulating the stack current through the DC / DC conversion unit (10); The first controller (4) uses the fuel gas flow rate as a control variable and the stack current as a 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).

2. The load tracking and temperature control system of the SOFC system according to claim 1, characterized in that: Also includes a bypass valve circuit 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 opened, part of the 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 a control variable and the stack cathode inlet temperature as a controlled variable. The second controller (5) generates a control signal to adjust the opening of the bypass valve by comparing the deviation between the stack cathode inlet temperature and a temperature setting value.

3. The load tracking and temperature control system of the SOFC system according to claim 2, characterized in that: It also includes a fourth controller (7), wherein the fourth controller (7) uses the bypass valve opening as a controlled variable; If the third controller (6) uses the fuel composition at the stack outlet as a controlled variable, the fourth controller (7) uses the fuel composition target value as a controlled variable; The fourth controller (7) generates a fuel composition target value by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides the target value to the third controller (6); If the third controller (6) uses the stack voltage as a controlled variable, the fourth controller (7) uses the stack voltage target value as a controlled variable; 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 for the bypass valve opening, and provides the target value for the stack voltage to the third controller (6).

4. The load tracking and temperature control system of the SOFC system according to claim 3, characterized in that: Also included is a fifth controller (8); The fifth controller (8) uses the air flow rate as a control variable and the stack outlet temperature as a 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 stack outlet temperature and the temperature set value.

5. The load tracking and temperature control system of the SOFC system according to claim 4, characterized in that: Also includes a sixth controller (9) and a high position selector; The sixth controller (9) is used to calculate the air flow safety value according to the real-time fuel gas flow and a preset ratio; The high-order selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller (8) with the air flow safety 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 air flow safety value.

6. 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 conversion 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 are sent to the two-stage heat exchanger (1) for heating, and then sent to the anode and cathode of the stack respectively. After the stack completes the reaction, the current generated by the reaction is processed by the DC / DC conversion unit (10) and output, which is called the stack current. The gas containing unburned fuel discharged from the stack enters the combustion chamber (3). The gas that has been completely burned in the combustion chamber (3) is sent to the two-stage heat exchanger (1) and discharged as exhaust gas after heat exchange. It is characterized by: A first controller (4) and a third controller (6) are provided in the SOFC system; The third controller (6) collects the fuel composition at the outlet of the fuel stack through the fuel composition sensor at the outlet of the fuel stack anode, compares the deviation with the target value of the fuel composition, and generates a control signal to the DC / DC conversion unit (10) based on the collected data, thereby adjusting the current of the fuel stack through the DC / DC conversion unit (10); Alternatively, the third controller (6) collects the stack voltage through a voltage sensor and compares the deviation with the stack voltage target value, thereby generating a control signal to the DC / DC conversion unit (10), thereby regulating the stack current through the DC / DC conversion 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 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).

7. The load tracking and temperature control method of the SOFC system according to claim 6, characterized in that: A bypass valve loop and a second controller (5) are also provided 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, part of the 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 stack and the temperature setting value.

8. The load tracking and temperature control method of the SOFC system according to claim 7, characterized in that: A fourth controller (7) is also provided in the SOFC system; The fourth controller (7) generates a fuel composition target value by comparing the deviation between the current bypass valve opening and the set value of the bypass valve opening, and provides the target value 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 for the bypass valve opening, and provides the target value for the stack voltage to the third controller (6).

9. The load tracking and temperature control method of the SOFC system according to claim 8, characterized in that: A fifth controller (8) is also provided 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 setting value.

10. The load tracking and temperature control method of the SOFC system according to claim 9, characterized in that: A sixth controller (9) and a high-level selector are also provided in the SOFC system; The sixth controller (9) is used to calculate the air flow safety value according to the real-time fuel gas flow and a preset ratio; The high-order selector is used to compare the air flow value corresponding to the control signal generated by the fifth controller (8) with the air flow safety 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 air flow safety value.

Images