Fixed type high-temperature solid oxide fuel cell heat and power cogeneration system

Abstract

The invention discloses a fixed type high-temperature solid oxide fuel cell heat and power cogeneration system. The system comprises a gas control unit, a heat management unit, a fuel cell power generation unit and a user side unit, the gas control unit comprises a hydrogen control unit, a nitrogen control unit and a compressed air three-way control unit; the thermal management unit comprises a hydrogen preheater, a cathode air preheater, a starting burner and a cooling unit; the fuel cell power generation unit comprises a high-temperature solid oxide fuel cell stack, a collector channel module and a rear combustor. The high-power solid oxide fuel cell has the characteristics of long service life, high-efficiency application and low noise, and can meet the high-power power utilization requirements of users in different application scenes. The invention can be widely applied to the technical field of solid oxide fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells, and in particular to a fixed high-temperature solid oxide fuel cell cogeneration system. Background Art

[0002] Traditional thermal power plants and power equipment first convert chemical energy into thermal energy through the combustion of fuel, then convert thermal energy into mechanical energy, and finally convert mechanical energy into electrical energy. Due to the constraints of the Carnot cycle, the energy conversion rate is only 35% under the best conditions, and less than 20% in actual conditions. Fuel cells are a new type of power generation technology after hydropower, thermal power, and nuclear power generation technologies. It is an efficient power generation device that directly converts chemical energy into electrical energy without fuel combustion. Compared with gas turbines and thermal power boilers, hydrogen-to-electricity conversion through fuel cells has the advantages of flexibility (fast start and stop, support for small power output), cleanliness (no NOx emissions), and low noise. Fuel cell power generation technology is generally used for distributed power sources ranging from 0.5 kilowatts to 2 megawatts, and application scenarios include micro-cogeneration systems, uninterruptible power supplies, and power generation devices of power companies in residential and commercial buildings.

[0003] Compared with other types of fuel cells, the main advantages of solid oxide fuel cells (SOFC) are: ① strong fuel applicability, hydrogen can be used, and methane, carbon monoxide, biogas, diesel, gasoline, methanol and other traditional fossil fuels and their industrial by-products can all be used as fuel for solid oxide fuel cells; ② all-solid ceramic structure, with better structural stability; ③ high power generation efficiency. This allows solid oxide fuel cells to meet power needs of different scales and levels, especially for distributed power generation systems of offshore oil platforms and communication base stations. It can also be used as a portable power source and auxiliary power unit (APU), as well as the power systems of trains and ships, the silent submarine power systems in military applications, and the mobile power sources of battlefield command centers, becoming the most promising green power generation system in the 21st century.

[0004] Because it is not limited by the Carnot cycle, the theoretical thermal efficiency of the combined heat and power system based on solid oxide fuel cells is over 80%, and the actual power generation efficiency can reach 50%-60%. It has the advantages of high energy conversion efficiency, low noise, low infrared radiation, low emissions, and wide fuel adaptability, which can meet the security needs at the social level. At the same time, the solid oxide fuel cell can realize regional combined heat and power, further improve the energy conversion efficiency of the fuel, and improve the comprehensive utilization rate of the waste heat of the fuel and the system.

[0005] However, the existing solid oxide fuel cell cogeneration system has problems such as short life of the battery stack during long-term operation and poor control of the system gas heat and power balance. These two problems restrict the application and development of fixed solid oxide fuel cell cogeneration systems. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a fixed high-temperature solid oxide fuel cell cogeneration system that has the characteristics of long life, high efficiency, low noise, and can meet the high-power electricity demand of users in different application scenarios.

[0007] The technical solution adopted by the present invention is: a fixed high-temperature solid oxide fuel cell cogeneration system, a gas control unit, a thermal management unit, a fuel cell power generation unit and a user side unit, wherein:

[0008] The gas control unit includes a hydrogen control unit, a nitrogen control unit and a compressed air three-way control unit;

[0009] The thermal management unit includes a hydrogen preheater, a cathode air preheater, a start-up burner and a cooling unit;

[0010] The fuel cell power generation unit comprises a high temperature solid oxide fuel cell stack, a collector module and a post-burner;

[0011] The hydrogen control unit, the nitrogen control unit and the hydrogen preheater are connected via a three-way valve, and are used to mix hydrogen and nitrogen to generate a nitrogen-hydrogen mixed gas. During the heating and cooling stages, the nitrogen-hydrogen mixed gas provides a reducing atmosphere protection for the high-temperature solid oxide fuel cell stack in a high-temperature state, thereby preventing the battery stack from being damaged due to oxidation cracking; the hydrogen preheater is used to preheat the nitrogen-hydrogen mixed gas;

[0012] The three-way compressed air control unit is respectively connected to the cathode air preheater, the starting burner and the afterburner; the cathode air preheater is used to preheat the first-way compressed air input; the starting burner is used to perform startup combustion heating for the system and continuously heat up the system in the early startup stage; the afterburner is used to perform high-temperature supplementary combustion reaction to provide a heat source for maintaining the normal operating temperature of the system.

[0013] The high-temperature solid oxide fuel cell stack is connected to the hydrogen preheater to receive the preheated nitrogen-hydrogen mixture; the high-temperature solid oxide fuel cell stack is connected to the cathode air preheater to receive the preheated first compressed air; the high-temperature solid oxide fuel cell stack generates cathode tail gas and first anode tail gas by electrochemical reaction of the preheated nitrogen-hydrogen mixture and the preheated first compressed air; the high-temperature solid oxide fuel cell stack is connected to the start-up burner to input the first anode tail gas into the start-up burner for system startup combustion heating and obtain the second anode tail gas; the high-temperature solid oxide fuel cell stack is connected to the cooling unit to cool the cathode tail gas; the high-temperature solid oxide fuel cell stack is connected to the user-side unit to transmit the electrical energy generated by the electrochemical reaction to the user side for use;

[0014] The hydrogen preheater is connected to the start-up burner, and uses the second anode tail gas generated by the start-up burner to preheat the hydrogen preheater; the hydrogen preheater is connected to the post-burner, and is used to input the second anode tail gas into the post-burner for high-temperature supplementary combustion reaction to obtain a third anode tail gas;

[0015] The cooling unit is connected to the post-burner and is used to cool the third anode tail gas; the cooling unit is connected to the user-side unit and is used to transport the hot water generated by the cooling unit to the user side for use;

[0016] The collecting channel module is located inside the high-temperature solid oxide fuel cell stack and is used for preheating and evenly distributing the airflow on the fuel side and the air side to achieve a balance in the electrical performance of each cell stack.

[0017] Further, the hydrogen control unit includes a one-way valve, a pressure sensor, a mass flow controller, a solenoid valve and a gas rotary valve, wherein:

[0018] Hydrogen enters the system pipeline through a one-way valve to prevent hydrogen backflow; then the pressure sensor monitors the pressure feedback of the low-temperature section, and then the mass flow controller controls the flow, passes through the solenoid valve and the gas rotary valve in turn, and enters the hydrogen preheater through the three-way valve.

[0019] Further, the nitrogen control unit includes a pressure reducing valve, a pressure sensor, a mass flow controller and a solenoid valve, wherein:

[0020] The nitrogen enters the system pipeline after being reduced in pressure by the pressure reducing valve, and the pressure sensor monitors the pressure of the low-temperature section for feedback, and then the flow rate is regulated by the mass flow controller, and then enters the hydrogen preheater through the solenoid valve and the three-way valve in turn.

[0021] Further, the three-way compressed air control unit includes a first-way compressed air control module, a second-way compressed air control module and a third-way compressed air control module, wherein:

[0022] The first compressed air control module includes a mass flow controller, an air filter, a one-way valve, a pressure sensor, a solenoid valve and a temperature sensor;

[0023] The compressed air passes through a three-way valve to generate a first-path compressed air, and the first-path compressed air is flow-controlled by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the first-path compressed air, and to filter out dust and solid impurities in the air; then passes through a one-way valve to prevent the filtered first-path compressed air from flowing back, and then the pressure sensor monitors and feeds back the pressure of the low-temperature section; then passes through an electromagnetic valve, and finally the filtered first-path compressed air flows back through a temperature sensor for temperature monitoring and feedback before entering the cathode air preheater;

[0024] The second compressed air control module includes a mass flow controller, an air filter, a one-way valve, a pressure sensor and a solenoid valve;

[0025] The compressed air passes through a three-way valve to generate a second compressed air, and the second compressed air is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the second compressed air, and filter out dust and solid impurities in the air; then passes through a one-way valve to prevent the filtered second compressed air from flowing back, and then the pressure sensor monitors the pressure of the low-temperature section for feedback; finally, the filtered second compressed air flows back through a solenoid valve and enters the start-up burner;

[0026] The third compressed air control module includes a mass flow controller, an air filter and a solenoid valve;

[0027] The compressed air passes through a three-way valve to generate a third-way compressed air, the flow of the third-way compressed air is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the third-way compressed air, and filter out dust and solid impurities in the air; finally, the filtered third-way compressed air flows back through a solenoid valve and enters the post-burner.

[0028] Further, the cooling unit includes a manual stop valve, a temperature sensor, a three-way valve, a first heat exchanger, a second heat exchanger, a third heat exchanger, a hot water tank, an auxiliary cooling fan and a water storage tank, wherein:

[0029] The cooling pure water enters the system pipeline through a manual stop valve, and then passes through a temperature sensor for temperature monitoring and feedback, and then is divided into a first path of cooling pure water and a second path of cooling pure water through a three-way valve; the first path of cooling pure water exchanges heat with the cathode tail gas through the first heat exchanger, and then outputs hot water and enters the hot water tank; the second path of cooling pure water exchanges heat with the third anode tail gas through the second heat exchanger, and then outputs hot water and enters the hot water tank; after the third anode tail gas is cooled in the second heat exchanger, it is input into the third heat exchanger for energy exchange cooling with the cooling water input from the water storage tank again, and the finally cooled third anode tail gas is discharged by the auxiliary cooling fan, and the cooling water generated after the condensation of the third anode tail gas is input into the water storage tank for recycling.

[0030] Furthermore, the user side unit includes a DC / AC grid-connected inverter unit and a fuel cell control unit, wherein:

[0031] The DC / AC grid-connected inverter unit includes an IGBT inverter unit and an inverter control module;

[0032] The IGBT inverter unit includes an IGBT inverter;

[0033] The inverter control module includes an auxiliary power supply, a control protection board and a drive board, and a control circuit;

[0034] The control circuit includes a power / voltage outer loop and an inductor current inner loop;

[0035] Under the control and drive of the control protection board and the drive board, the IGBT inverter inverts the input stable and smooth DC into an SVPWM wave, and filters the SVPWM wave into a pure sine wave through LC filtering and transformer transformation to supply power to the load; the auxiliary power supply is used to provide working power for the IGBT inverter, the control protection board and the drive board;

[0036] The fuel cell control unit is used to monitor and control the gas control unit, the thermal management unit, and the fuel cell power generation unit in real time, thereby preventing the system from malfunctioning and ensuring that the system is in the best operating state.

[0037] Furthermore, the fuel cell control unit includes a signal conditioning module, a frequency signal sampling module, a multi-way switch and an A / D module, an ARM module, a D / A module, an OD output module, and a communication module, wherein:

[0038] The signal conditioning module is used to sample the sensor feedback analog quantity;

[0039] The frequency signal sampling module is used to measure the state of the execution component;

[0040] The multi-way switch and A / D module are used for multi-way analog quantity sampling;

[0041] The ARM module is used to perform control and logic operations;

[0042] The D / A module is used to output analog control quantity;

[0043] The OD output module is used to output switching value;

[0044] The communication module is used to establish a communication channel between the power supply and the human-machine interactive touch screen, the inspection instrument and the energy storage battery pack.

[0045] Furthermore, the control process of the fuel cell control unit includes power-on software initialization and while main loop, wherein:

[0046] The power-on software initialization includes initialization of each MCU status bit, IO port, and sampling amount;

[0047] The while main loop includes a semaphore sampling and measuring subroutine, a data receiving and processing subroutine, a system fault state detection subroutine, a system working state switching subroutine, a system control state updating subroutine, a host computer data sending subroutine, and a watchdog feeding subroutine;

[0048] The signal quantity sampling and measurement subroutine completes the sampling and data processing of each signal quantity of the system;

[0049] The receiving data and processing subroutine processes the data received by the CVM, BMS, DC / DC, DC / AC and HMI screens;

[0050] The system fault status detection subroutine detects the fault status of the system according to the current parameters of the system;

[0051] The system working state switching subroutine switches the working state of the system according to the host computer instruction and the signal quantity sampling result;

[0052] The system control state updating subroutine updates the control state of each control component according to the working state switching result.

[0053] Furthermore, the system control state update subroutine considers the instantaneous optimization of the solid oxide fuel cell working efficiency range during control, distributes the output power of the solid oxide fuel cell and the lithium battery in real time within the entire operating condition for different states and load states, and gives the optimal operating point setting value of the solid oxide fuel cell through iterative optimization.

[0054] Furthermore, a composite method of feedforward control and anti-saturation PID feedback control is used to manipulate the control variables so that the state variables of the solid oxide fuel cell cogeneration system are as close as possible to the optimal operating point set value.

[0055] The beneficial effects of the present invention are as follows: the present invention achieves low-temperature clean emissions by performing multi-stage heat exchange balance on the exhaust gas generated by the high-temperature solid oxide fuel cell stack, only produces a small amount of water vapor and cooling water for discharge, and produces high-temperature hot water for supply to residents and commercial users; combines the compressed air three-way control unit to perform multi-stage utilization of the waste heat of the front-end system to achieve efficient power generation of fuel cells; proposes a fuel cell control unit and control flow for the operating conditions of the cogeneration system, performs real-time analysis and adjustment of the system stack, so that the system and the stack can respond efficiently and promptly, effectively reduce the failure rate, and increase the service life of the system and the stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a structural block diagram of a fixed high-temperature solid oxide fuel cell cogeneration system of the present invention;

[0057] Figure 2 This is a structural diagram of a gas control unit of a fixed high-temperature solid oxide fuel cell cogeneration system of the present invention;

[0058] Figure 3 This is a structural diagram of a thermal management unit of a fixed high-temperature solid oxide fuel cell cogeneration system of the present invention;

[0059] Figure 4 This is a structural diagram of a fuel cell power generation unit of a fixed high-temperature solid oxide fuel cell cogeneration system of the present invention;

[0060] Figure 5 This is a user side unit structure diagram of a fixed high temperature solid oxide fuel cell cogeneration system of the present invention;

[0061] Figure 6 This is a structural diagram of a fuel cell control unit of a fixed high-temperature solid oxide fuel cell combined heat and power system of the present invention;

[0062] Figure 7 This is a control flow chart of a fuel cell control unit of a fixed high-temperature solid oxide fuel cell combined heat and power system of the present invention;

[0063] Figure 8 It is a basic energy management strategy flow chart of a fixed high-temperature solid oxide fuel cell cogeneration system of the present invention. DETAILED DESCRIPTION

[0064] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0065] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 The present invention provides a fixed high-temperature solid oxide fuel cell cogeneration system, including a gas control unit, a thermal management unit, a fuel cell power generation unit and a user side unit, wherein:

[0066] The gas control unit includes a hydrogen control unit, a nitrogen control unit and a compressed air three-way control unit;

[0067] The thermal management unit includes a hydrogen preheater, a cathode air preheater, a start-up burner and a cooling unit;

[0068] The fuel cell power generation unit comprises a high temperature solid oxide fuel cell stack, a collector module and a post-burner;

[0069] The hydrogen control unit, the nitrogen control unit and the hydrogen preheater are connected through a three-way valve, and are used to mix hydrogen and nitrogen to generate a nitrogen-hydrogen mixed gas. During the heating and cooling stages, the nitrogen-hydrogen mixed gas provides a reducing atmosphere protection for the high-temperature solid oxide fuel cell stack at a high temperature of 750° C., thereby preventing the battery stack from being damaged due to oxidation cracking; the hydrogen preheater is used to preheat the nitrogen-hydrogen mixed gas and heat the gas temperature to 600° C.;

[0070] The three-way compressed air control unit is respectively connected to the cathode air preheater, the starting burner and the afterburner; the cathode air preheater is used to preheat the first-way compressed air input; the starting burner is used to perform startup combustion heating for the system, and continuously heats the system to 750°C in the early startup stage; the afterburner is used to perform high-temperature supplementary combustion reaction to provide a heat source for maintaining the normal operating temperature of the system.

[0071] The high-temperature solid oxide fuel cell stack is connected to the hydrogen preheater to receive the preheated nitrogen-hydrogen mixture; the high-temperature solid oxide fuel cell stack is connected to the cathode air preheater to receive the preheated first compressed air; the high-temperature solid oxide fuel cell stack generates cathode tail gas and first anode tail gas by electrochemical reaction of the preheated nitrogen-hydrogen mixture and the preheated first compressed air; the high-temperature solid oxide fuel cell stack is connected to the start-up burner to input the first anode tail gas into the start-up burner for system startup combustion heating and obtain the second anode tail gas; the high-temperature solid oxide fuel cell stack is connected to the cooling unit to cool the cathode tail gas; the high-temperature solid oxide fuel cell stack is connected to the user-side unit to transmit the electrical energy generated by the electrochemical reaction to the user side for use;

[0072] The hydrogen preheater is connected to the start-up burner, and uses the second anode tail gas generated by the start-up burner to preheat the hydrogen preheater; the hydrogen preheater is connected to the post-burner, and is used to input the second anode tail gas into the post-burner for high-temperature supplementary combustion reaction to obtain a third anode tail gas;

[0073] The cooling unit is connected to the post-burner and is used to cool the third anode tail gas; the cooling unit is connected to the user-side unit and is used to transport the hot water generated by the cooling unit to the user side for use;

[0074] The collecting channel module is located inside the high-temperature solid oxide fuel cell stack and is used for preheating and evenly distributing the airflow on the fuel side and the air side to achieve a balance in the electrical performance of each cell stack.

[0075] Preferably, the hydrogen control unit includes a one-way valve, a pressure sensor, a mass flow controller, a solenoid valve and a gas rotary valve, wherein:

[0076] Hydrogen enters the system pipeline through a one-way valve to prevent hydrogen backflow; then the pressure sensor monitors the pressure feedback of the low-temperature section, and then the flow is regulated by a mass flow controller, and then passes through the solenoid valve and the gas rotary valve in turn, and enters the hydrogen preheater through the three-way valve.

[0077] Preferably, the nitrogen control unit includes a pressure reducing valve, a pressure sensor, a mass flow controller and a solenoid valve, wherein:

[0078] The nitrogen enters the system pipeline after being reduced in pressure by the pressure reducing valve, and the pressure sensor monitors the pressure of the low-temperature section for feedback, and then the flow rate is regulated by the mass flow controller, and then enters the hydrogen preheater through the solenoid valve and the three-way valve in turn.

[0079] Preferably, the three-way compressed air control unit comprises a first-way compressed air control module, a second-way compressed air control module and a third-way compressed air control module, wherein:

[0080] The first compressed air control module includes a mass flow controller, an air filter, a one-way valve, a pressure sensor, a solenoid valve and a temperature sensor;

[0081] The compressed air passes through a three-way valve to generate a first-path compressed air, the flow of which is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the first-path compressed air, and to filter out dust and solid impurities in the air; then passes through a one-way valve to prevent the filtered first-path compressed air from flowing back, and then a pressure sensor monitors and feedbacks the pressure of the low-temperature section; then passes through a solenoid valve, and finally the filtered first-path compressed air flows back through a temperature sensor for temperature monitoring and feedback before entering the cathode air preheater, exchanging the temperature of the first-path compressed air to 600°C.

[0082] The second compressed air control module includes a mass flow controller, an air filter, a one-way valve, a pressure sensor and a solenoid valve;

[0083] The compressed air passes through a three-way valve to generate a second compressed air, and the second compressed air is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the second compressed air, and filter out dust and solid impurities in the air; then passes through a one-way valve to prevent the filtered second compressed air from flowing back, and then the pressure sensor monitors the pressure of the low-temperature section for feedback; finally, the filtered second compressed air flows back through a solenoid valve and enters the start-up burner;

[0084] The third compressed air control module includes a mass flow controller, an air filter and a solenoid valve;

[0085] The compressed air passes through a three-way valve to generate a third-way compressed air, the flow of the third-way compressed air is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the third-way compressed air, and filter out dust and solid impurities in the air; finally, the filtered third-way compressed air flows back through a solenoid valve and enters the post-burner.

[0086] Preferably, the cooling unit includes a manual stop valve, a temperature sensor, a three-way valve, a first heat exchanger, a second heat exchanger, a third heat exchanger, a hot water tank, an auxiliary cooling fan and a water storage tank, wherein:

[0087] The cooling pure water enters the system pipeline through a manual stop valve, and then passes through a temperature sensor for temperature monitoring and feedback, and then is divided into a first path of cooling pure water and a second path of cooling pure water through a three-way valve; the first path of cooling pure water exchanges heat with the cathode tail gas through the first heat exchanger, and then outputs hot water and enters the hot water tank; the second path of cooling pure water exchanges heat with the third anode tail gas through the second heat exchanger, and then outputs hot water and enters the hot water tank; after the third anode tail gas is cooled in the second heat exchanger, it is input into the third heat exchanger for energy exchange cooling with the cooling water input from the water storage tank again, and the finally cooled third anode tail gas is discharged by the auxiliary cooling fan, and the cooling water generated after the condensation of the third anode tail gas is input into the water storage tank for recycling.

[0088] Preferably, the user-side unit includes a DC / AC grid-connected inverter unit and a fuel cell control unit, wherein:

[0089] The DC / AC grid-connected inverter unit includes an IGBT inverter unit and an inverter control module;

[0090] The IGBT inverter unit includes an IGBT inverter;

[0091] The inverter control module includes an auxiliary power supply, a control protection board and a drive board, and a control circuit;

[0092] The control circuit includes a power / voltage outer loop and an inductor current inner loop; the outer loop does not directly participate in active power regulation, it follows the active power output of the DC / DC in the networking mode; in the island mode, it provides voltage and frequency reference for the microgrid.

[0093] Under the control and drive of the control protection board and the drive board, the IGBT inverter inverts the input stable and smooth DC into an SVPWM wave, and filters the SVPWM wave into a pure sine wave through LC filtering and transformer transformation to supply power to the load; the auxiliary power supply is used to provide working power for the IGBT inverter, the control protection board and the drive board;

[0094] The fuel cell control unit is used to measure the status of each sensor and actuator in the system, and to monitor and control the gas control unit, thermal management unit, and fuel cell power generation unit in real time through an internal control algorithm to prevent system failures while ensuring that the system is in the best operating state.

[0095] Preferably, refer to Figure 6 The fuel cell control unit includes a signal conditioning module, a frequency signal sampling module, a multi-way switch and an A / D module, an ARM module, a D / A module, an OD output module, and a communication module, wherein:

[0096] The signal conditioning module is used to sample the sensor feedback analog quantity;

[0097] The frequency signal sampling module is used to measure the state of the execution component;

[0098] The multi-way switch and A / D module are used for multi-way analog quantity sampling;

[0099] The ARM module is used to perform control and logic operations;

[0100] The D / A module is used to output analog control quantity;

[0101] The OD output module is used to output switching value;

[0102] The communication module is used to establish a communication channel between the power supply and the human-machine interactive touch screen, the inspection instrument and the energy storage battery pack.

[0103] Preferably, refer to Figure 7 The control process of the fuel cell control unit includes power-on software initialization and while (1) main loop, wherein:

[0104] The power-on software initialization includes initialization of each MCU status bit, IO port, and sampling amount;

[0105] The while (1) main loop includes a semaphore sampling and measuring subroutine, a data receiving and processing subroutine, a system fault state detection subroutine, a system working state switching subroutine, a system control state updating subroutine, a host computer data sending subroutine, and a watchdog feeding subroutine;

[0106] The signal quantity sampling and measurement subroutine completes the sampling and data processing of each signal quantity of the system;

[0107] The receiving data and processing subroutine processes the data received by the CVM, BMS, DC / DC, DC / AC and HMI screens;

[0108] The system fault status detection subroutine detects the fault status of the system according to the current parameters of the system;

[0109] The system working state switching subroutine switches the working state of the system according to the host computer instruction and the signal quantity sampling result;

[0110] The system control state updating subroutine updates the control state of each control component according to the working state switching result.

[0111] Reference Figure 8, for each 12kW power generation system, its control strategy is independent of each other. The control goal of the system control strategy is to take power control as the fundamental purpose, while limiting safety factors such as temperature and fuel utilization rate within a certain working range to ensure the safety of the system, and to increase the fuel utilization rate as much as possible during the adjustment process to improve the system efficiency. Therefore, the system control state update subroutine of the present invention considers the instantaneous optimization of the solid oxide fuel cell working efficiency range during control, and distributes the output power of the solid oxide fuel cell and the lithium battery in real time within the entire working condition for different states and load states. The optimal operating point setting value of the solid oxide fuel cell is given through iterative optimization to achieve instantaneous optimization of system performance. The optimal operating point of the solid oxide fuel cell includes: stack temperature, fuel utilization rate and air oxygen ratio.

[0112] In view of the coupling characteristics of the cogeneration system, the present invention regards the changes in the remaining control loop parameters as a kind of interference, and uses a composite method of feedforward control and anti-saturation PID feedback control to manipulate the control variables, so that the state variables of the solid oxide fuel cell cogeneration system are as close as possible to the optimal operating point setting value, and track the optimal operating point of the solid oxide fuel cell. Feedforward control is used to respond to the demand for rapid power changes in a timely manner, and PID feedback control is to make additional fine adjustments to the control quantity to improve control accuracy.

[0113] The fixed high-temperature solid oxide fuel cell cogeneration system of the specific embodiment of the present invention is designed for an output power of 10kW, and the DC / AC grid-connected inverter unit is designed with a rated power of 10kW, an output voltage of three-phase AC380V, and a power factor>0.95; to ensure system efficiency, the DC / AC grid-connected inverter unit is designed to have an efficiency of 93%. The minimum bus voltage of the DC / AC grid-connected inverter unit is 220V*1.414*2=622V, so the DC bus voltage rating is 700V, and the DC / DC unidirectional energy adapter unit output voltage rating is 700V; each solid oxide fuel cell power generation unit has 50-60 series of stacks, and every two series of single cells are connected in series for sampling. The number of sampling channels of the inspection instrument is 60 / 2*6=180, and the open circuit voltage of each single cell is 1.15V.

[0114] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A stationary high-temperature solid oxide fuel cell combined heat and power system, It is characterized in that It includes a gas control unit, a thermal management unit, a fuel cell power generation unit and a user side unit, wherein: The gas control unit includes a hydrogen control unit, a nitrogen control unit and a compressed air three-way control unit; The thermal management unit includes a hydrogen preheater, a cathode air preheater, a start-up burner and a cooling unit; The fuel cell power generation unit comprises a high temperature solid oxide fuel cell stack, a collector module and a post-burner; The hydrogen control unit, the nitrogen control unit and the hydrogen preheater are connected via a three-way valve, and are used to mix hydrogen and nitrogen to generate a nitrogen-hydrogen mixed gas. During the heating and cooling stages, the nitrogen-hydrogen mixed gas provides a reducing atmosphere protection for the high-temperature solid oxide fuel cell stack in a high-temperature state, thereby preventing the battery stack from being damaged due to oxidation cracking; the hydrogen preheater is used to preheat the nitrogen-hydrogen mixed gas; The three-way compressed air control unit is respectively connected to the cathode air preheater, the starting burner and the afterburner; the cathode air preheater is used to preheat the first-way compressed air input; the starting burner is used to perform startup combustion heating for the system and continuously heat up the system in the early startup stage; the afterburner is used to perform high-temperature supplementary combustion reaction to provide a heat source for maintaining the normal operating temperature of the system. The high-temperature solid oxide fuel cell stack is connected to the hydrogen preheater to receive the preheated nitrogen-hydrogen mixture; the high-temperature solid oxide fuel cell stack is connected to the cathode air preheater to receive the preheated first compressed air; the high-temperature solid oxide fuel cell stack generates cathode tail gas and first anode tail gas by electrochemical reaction of the preheated nitrogen-hydrogen mixture and the preheated first compressed air; the high-temperature solid oxide fuel cell stack is connected to the start-up burner to input the first anode tail gas into the start-up burner for system startup combustion heating and obtain the second anode tail gas; the high-temperature solid oxide fuel cell stack is connected to the cooling unit to cool the cathode tail gas; the high-temperature solid oxide fuel cell stack is connected to the user-side unit to transmit the electrical energy generated by the electrochemical reaction to the user side for use; The hydrogen preheater is connected to the start-up burner, and uses the second anode tail gas generated by the start-up burner to preheat the hydrogen preheater; the hydrogen preheater is connected to the post-burner, and is used to input the second anode tail gas into the post-burner for high-temperature supplementary combustion reaction to obtain a third anode tail gas; The cooling unit is connected to the post-burner and is used to cool the third anode tail gas; the cooling unit is connected to the user-side unit and is used to transport the hot water generated by the cooling unit to the user side for use; The collecting channel module is located inside the high-temperature solid oxide fuel cell stack and is used for preheating and evenly distributing the airflow on the fuel side and the air side to achieve a balance in the electrical performance of each cell stack.

2. According to claim 1, a fixed high-temperature solid oxide fuel cell combined heat and power system, It is characterized in that The hydrogen control unit includes a one-way valve, a pressure sensor, a mass flow controller, a solenoid valve and a gas rotary valve, wherein: Hydrogen enters the system pipeline through a one-way valve to prevent hydrogen backflow; then the pressure sensor monitors the pressure feedback of the low-temperature section, and then the mass flow controller controls the flow, passes through the solenoid valve and the gas rotary valve in turn, and enters the hydrogen preheater through the three-way valve.

3. According to claim 1, a fixed high temperature solid oxide fuel cell cogeneration system, It is characterized in that The nitrogen control unit includes a pressure reducing valve, a pressure sensor, a mass flow controller and a solenoid valve, wherein: The nitrogen enters the system pipeline after being reduced in pressure by the pressure reducing valve, and the pressure sensor monitors the pressure of the low-temperature section for feedback, and then the flow rate is regulated by the mass flow controller, and then enters the hydrogen preheater through the solenoid valve and the three-way valve in turn.

4. According to claim 1, a fixed high-temperature solid oxide fuel cell combined heat and power system, It is characterized in that The three-way compressed air control unit comprises a first-way compressed air control module, a second-way compressed air control module and a third-way compressed air control module, wherein: The first compressed air control module includes a mass flow controller, an air filter, a one-way valve, a pressure sensor, a solenoid valve and a temperature sensor; The compressed air passes through a three-way valve to generate a first-path compressed air, and the first-path compressed air is flow-controlled by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the first-path compressed air, and to filter out dust and solid impurities in the air; then passes through a one-way valve to prevent the filtered first-path compressed air from flowing back, and then the pressure sensor monitors and feeds back the pressure of the low-temperature section; then passes through an electromagnetic valve, and finally the filtered first-path compressed air flows back through a temperature sensor for temperature monitoring and feedback before entering the cathode air preheater; The second compressed air control module includes a mass flow controller, an air filter, a one-way valve, a pressure sensor and a solenoid valve; The compressed air passes through a three-way valve to generate a second compressed air, and the second compressed air is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the second compressed air, and filter out dust and solid impurities in the air; then passes through a one-way valve to prevent the filtered second compressed air from flowing back, and then the pressure sensor monitors the pressure of the low-temperature section for feedback; finally, the filtered second compressed air flows back through a solenoid valve and enters the start-up burner; The third compressed air control module includes a mass flow controller, an air filter and a solenoid valve; The compressed air passes through a three-way valve to generate a third-way compressed air, the flow of the third-way compressed air is regulated by a mass flow controller, and then passes through an air filter to separate liquid water and liquid oil droplets in the third-way compressed air, and filter out dust and solid impurities in the air; finally, the filtered third-way compressed air flows back through a solenoid valve and enters the post-burner.

5. According to claim 1, a fixed high-temperature solid oxide fuel cell combined heat and power system, It is characterized in that The cooling unit includes a manual stop valve, a temperature sensor, a three-way valve, a first heat exchanger, a second heat exchanger, a third heat exchanger, a hot water tank, an auxiliary cooling fan and a water storage tank, wherein: The cooling pure water enters the system pipeline through a manual stop valve, and then passes through a temperature sensor for temperature monitoring and feedback, and then is divided into a first path of cooling pure water and a second path of cooling pure water through a three-way valve; the first path of cooling pure water exchanges heat with the cathode tail gas through the first heat exchanger, and then outputs hot water and enters the hot water tank; the second path of cooling pure water exchanges heat with the third anode tail gas through the second heat exchanger, and then outputs hot water and enters the hot water tank; after the third anode tail gas is cooled in the second heat exchanger, it is input into the third heat exchanger for energy exchange cooling with the cooling water input from the water storage tank again, and the finally cooled third anode tail gas is discharged by the auxiliary cooling fan, and the cooling water generated after the condensation of the third anode tail gas is input into the water storage tank for recycling.

6. A fixed high temperature solid oxide fuel cell combined heat and power system according to claim 1, It is characterized in that The user side unit includes a DC / AC grid-connected inverter unit and a fuel cell control unit, wherein: The DC / AC grid-connected inverter unit includes an IGBT inverter unit and an inverter control module; The IGBT inverter unit includes an IGBT inverter; The inverter control module includes an auxiliary power supply, a control protection board and a drive board, and a control circuit; The control circuit includes a power / voltage outer loop and an inductor current inner loop; Under the control and drive of the control protection board and the drive board, the IGBT inverter inverts the input stable and smooth DC into an SVPWM wave, and filters the SVPWM wave into a pure sine wave through LC filtering and transformer transformation to supply power to the load; the auxiliary power supply is used to provide working power for the IGBT inverter, the control protection board and the drive board; The fuel cell control unit is used to monitor and control the gas control unit, the thermal management unit, and the fuel cell power generation unit in real time, thereby preventing the system from malfunctioning and ensuring that the system is in the best operating state.

7. A fixed high temperature solid oxide fuel cell combined heat and power system according to claim 6, It is characterized in that The fuel cell control unit includes a signal conditioning module, a frequency signal sampling module, a multi-way switch and an A / D module, an ARM module, a D / A module, an OD output module, and a communication module, wherein: The signal conditioning module is used to sample the sensor feedback analog quantity; The frequency signal sampling module is used to measure the state of the execution component; The multi-way switch and A / D module are used for multi-way analog quantity sampling; The ARM module is used to perform control and logic operations; The D / A module is used to output analog control quantity; The OD output module is used to output switching value; The communication module is used to establish a communication channel between the power supply and the human-machine interactive touch screen, the inspection instrument and the energy storage battery pack.

8. A fixed high temperature solid oxide fuel cell combined heat and power system according to claim 6, It is characterized in that The control process of the fuel cell control unit includes power-on software initialization and while main loop, wherein: The power-on software initialization includes initialization of each MCU status bit, IO port, and sampling amount; The while main loop includes a semaphore sampling and measuring subroutine, a data receiving and processing subroutine, a system fault state detection subroutine, a system working state switching subroutine, a system control state updating subroutine, a host computer data sending subroutine, and a watchdog feeding subroutine; The signal quantity sampling and measurement subroutine completes the sampling and data processing of each signal quantity of the system; The receiving data and processing subroutine processes the data received by the CVM, BMS, DC / DC, DC / AC and HMI screens; The system fault status detection subroutine detects the fault status of the system according to the current parameters of the system; The system working state switching subroutine switches the working state of the system according to the host computer instruction and the signal quantity sampling result; The system control state updating subroutine updates the control state of each control component according to the working state switching result.

9. A fixed high temperature solid oxide fuel cell combined heat and power system according to claim 8, It is characterized in that The system control state update subroutine considers the instantaneous optimization of the solid oxide fuel cell working efficiency range during control, distributes the output power of the solid oxide fuel cell and the lithium battery in real time within the entire working condition for different states and load states, and gives the optimal operating point setting value of the solid oxide fuel cell through iterative optimization.

10. A fixed high temperature solid oxide fuel cell combined heat and power system according to claim 9, It is characterized in that The control variables are manipulated by a composite method of feedforward control and anti-saturation PID feedback control, so that the state variables of the solid oxide fuel cell cogeneration system are as close as possible to the optimal operating point set value.

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