Inverter power system for SOFC stacks and methods of using the same
By employing independent DC/DC power conversion modules and a central control unit in the SOFC fuel cell stack system, electrical isolation and independent regulation of multiple fuel cell stacks are achieved, solving the complexity and reliability issues of the fuel cell stack system and improving the system's safety and efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI INSTITUTE OF APPLIED PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2026-03-13
- Publication Date
- 2026-06-19
AI Technical Summary
In existing SOFC fuel cell stack systems, the operation of multiple stacks in series and parallel presents problems such as high electrical system complexity, low safety and reliability, especially performance degradation caused by interference and improper control due to poor stack consistency, insulation degradation or local faults.
Multiple independent SOFC stack modules are connected to the DC/DC power conversion module. Electrical isolation is achieved through a high-frequency isolation transformer, and the module is coordinated and controlled by a central control unit. Each module supports hot-swapping and N-1 redundant operation. A multi-operation mode collaborative control strategy is adopted to achieve independent adjustment and fault isolation.
This system enables independent access and electrical isolation of multiple SOFC stacks, avoiding interference between stacks, reducing system complexity and the impact of faults, improving system reliability and availability, and reducing system size and manufacturing costs.
Smart Images
Figure CN122246836A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fuel cells, specifically relating to an inverter power supply system for SOFC stacks and its usage method, which features multi-channel and isolation characteristics. Background Technology
[0002] Solid oxide fuel cells (SOFCs) are electrochemical power generation devices that operate under high-temperature conditions. They have advantages such as high power generation efficiency, strong fuel adaptability, and high waste heat quality, and have received widespread attention in distributed energy, microgrids, and multi-energy complementary systems in recent years.
[0003] Due to limitations in individual battery power, stack sealing structure, and thermoelectric management, the rated power of a single SOFC stack is typically small at present, making it difficult to directly meet the needs of large-scale SOFC combined heat and power. Therefore, multiple stacks are usually connected in series, parallel, or a series-parallel combination to construct multi-stack high-power stack modules, thereby expanding the system power level and improving redundancy operation capabilities.
[0004] However, operating multiple SOFC stacks in series and parallel significantly increases the complexity of the electrical system. On the one hand, different SOFC stacks inevitably differ in manufacturing consistency, operating temperature, and dynamic response characteristics, and the output voltage, current, and power capacity of each stack change asynchronously with operating conditions. On the other hand, if multiple stacks are directly coupled electrically, a single stack malfunction can easily trigger a cascading effect, reducing the safety and reliability of the system. Therefore, in multiple SOFC stack systems, the stacks are typically divided into multiple stack groups for electrical control. This requires multiple independent inverter power supply units to convert the low-voltage DC power output from multiple SOFC stacks into AC power that meets the requirements of the power grid or load, and in this process, achieve independent control and effective decoupling of each stack.
[0005] Currently, large SOFC systems contain numerous fuel cell stacks. To facilitate stack management and reduce system downtime, stacks are typically grouped and integrated. Within each stack group, stacks can be connected in series or parallel, or both simultaneously, as long as the overall operating voltage, current, and power of the stack group are within the inverter power supply system's specifications. However, due to performance differences between stacks and uneven fuel distribution, connecting multiple stacks in series or parallel can lead to instability issues.
[0006] The main reasons for using series connection of fuel cell stacks in current technology are as follows: 1. Series circuits can maintain equal current in each fuel cell stack, achieving low-current, high-voltage operation and reducing ohmic energy consumption; 2. Current control can be uniformly adjusted according to the performance of the fuel cell stacks, with strong targeting and fast adjustment speed, and it is also convenient to protect the fuel cell stacks from overvoltage. However, series connection of fuel cell stacks also has the disadvantage of accelerated degradation of the poor-performing stacks if not controlled properly, and the performance of the fuel cell stack group is determined by the worst-performing stack; at the same time, high voltage also places higher requirements on the internal insulation of the fuel cell stack and the insulation between the fuel cell stack and ground.
[0007] In existing technologies, one approach involves multiple SOFC stacks connected in parallel, forming an inverter power system with multiple DC inputs, DC power collection, and centralized inversion. Multiple DC power sources are connected to the same DC bus via DC / DC power conversion modules, and then connected to the grid or operated off-grid via a centralized DC / AC inverter module. This type of technology has been applied in photovoltaic power generation and energy storage systems, enabling the collection and unified inversion of energy from multiple DC power sources.
[0008] However, the existing solutions mentioned above are mainly designed for photovoltaic modules or battery energy storage systems. Their DC source characteristics are relatively stable and they are less sensitive to current change rate and electrical shock. They do not fully consider the application background that SOFC single stacks have small power and must be operated in series and parallel by multiple stacks. They also do not specifically optimize for the differences, independence and safety decoupling requirements in multi-SOFC stack parallel systems.
[0009] The existing technology has at least the following shortcomings:
[0010] (1) Although multiple DC inputs can be connected to the same DC bus, the electrical isolation levels between different inputs are insufficient. When a SOFC stack experiences performance degradation, voltage abnormality, or failure to shut down, it is easy to cause interference to other stacks through the DC bus or control loop.
[0011] (2) The control strategy lacks a control mechanism that coordinates with the operation stages of SOFC stack startup, steady-state operation and power regulation, making it difficult to take into account the stability of multiple stacks operating in parallel;
[0012] (3) During power regulation or operation mode switching, the rate of change of current and voltage is usually guided by the response of the power electronic system, without fully considering the SOFC stack's ability to withstand the rate of change of current and thermal stress.
[0013] Therefore, there is an urgent need for an inverter power supply system that can enable independent access, electrical isolation, safe decoupling, and stable coordinated operation of multiple SOFC stacks to meet the needs of engineering and large-scale application of high-power SOFC combined heat and power systems. Summary of the Invention
[0014] The purpose of this invention is to provide an inverter power supply system for SOFC stacks and its usage method, so as to realize independent adjustment of different SOFC stacks and avoid interference problems caused by poor stack consistency, insulation degradation or local faults in the traditional multi-stack direct series and parallel connection method.
[0015] To achieve the above objectives, the present invention provides an inverter power supply system for SOFC stacks, characterized in that it includes multiple independent SOFC stack modules, DC / DC power conversion modules configured one-to-one with each SOFC stack module to form power supply channels, a DC / AC inverter module connected to the output terminals of all DC / DC power conversion modules via a high-voltage DC bus, a load connected to the output terminal of the DC / AC inverter module, and a central control unit connected to all SOFC stack modules, DC / DC power conversion modules, DC / AC inverter modules, and the load; the central control unit performs parameter control on the corresponding DC / DC power conversion module according to the operating conditions of each SOFC stack module.
[0016] The load is either connected to the grid or consumed off-grid.
[0017] Each DC / DC power conversion module includes a BOOST circuit, an LLC resonant converter, and an output rectifier circuit connected in sequence. The LLC resonant converter achieves electrical isolation between the input and output through a high-frequency isolation transformer, so that there is no direct electrical connection between the input sides of each DC / DC power conversion module.
[0018] The independent power supply channels consisting of the SOFC stack module and the DC / DC power conversion module both support hot-swapping and N-1 redundancy operation.
[0019] The DC / DC power conversion module boosts the DC output from the corresponding SOFC stack module to a high voltage DC of 600–900V and then connects it to the high voltage DC bus.
[0020] The parameters collected by the central control unit include: open-circuit voltage and real-time current from the SOFC stack module; input voltage, input current, output voltage, output current, and module status from the DC / DC power conversion module; AC output voltage, AC output current, active power, reactive power, and frequency from the DC / AC inverter module; and grid voltage, frequency, and load power demand from the grid and off-grid consumption.
[0021] The command parameters issued by the central control unit include: commands sent to the DC / DC power conversion module: operating mode, target current / voltage / power value; commands sent to the DC / AC inverter module: grid-connected / off-grid mode switching, output voltage / frequency setting value; system-level commands: start / stop, fault reset, mode switching.
[0022] On the other hand, the present invention provides a method of using an inverter power supply system for SOFC stacks, comprising:
[0023] Step S1: Build the inverter power supply system for SOFC stacks as described above; after the inverter power supply system is started, the central control unit initializes each SOFC stack module, each DC / DC power conversion module, and the DC / AC inverter module, and establishes communication connections; the central control unit collects parameters from each SOFC stack module, each DC / DC power conversion module, and the DC / AC inverter module in real time, and judges the operating condition of the inverter power supply system based on the collected parameters;
[0024] Step S2: During the startup phase, based on the operating conditions, select a constant current, constant voltage, or constant power operating mode for each DC / DC power conversion module, and then input the control setpoint and parameter adjustment rules corresponding to the operating mode.
[0025] Step S3: The central control unit performs linear or quasi-linear ramp adjustment of the current, voltage or power according to the parameter adjustment rules, so that the current, voltage or power is smoothly adjusted and ultimately maintained at the control setpoint.
[0026] Step S4: When any SOFC stack module or its corresponding DC / DC power conversion module is detected to be in an abnormal operating state, a fault handling procedure is executed to isolate the faulty power supply channel. The fault handling procedure includes: controlling the DC / DC power conversion module to gradually reduce its output and disconnect it from the high-voltage DC bus, while the remaining DC / DC power conversion modules continue to operate.
[0027] Step S5: When the system shutdown conditions are met, the shutdown phase begins. Based on the system's operating mode before shutdown, the output of each channel is gradually reduced according to the corresponding parameter adjustment rules to achieve a safe shutdown of the system.
[0028] The parameter adjustment rules for different operating modes include:
[0029] In constant current operation mode, the control setpoint is the target current value and the time required for the zero current to rise to the target current value. The parameter adjustment rule is to keep the output current constant, and the initial setting method is to linearly increase or decrease the output current according to the target current value and time.
[0030] In constant voltage operation mode, the control setpoint is the target voltage value and the time required for the voltage to rise from zero to the target voltage value. The parameter adjustment rule is to keep the output voltage constant, and the initial setting method is to linearly increase or decrease the output voltage according to the set target current and time.
[0031] In constant power operation mode, the control setpoint is the target power value, the time required for the power to rise from zero to the target power value, the parameter adjustment rule is to keep the output power constant, and the initial setting method is to linearly increase or decrease the output power according to the set target current and time.
[0032] The methods for judging abnormal operating states of SOFC stack modules are as follows: If it is operating under constant current, when the voltage of the SOFC stack module drops below the safe voltage, it is considered to be an abnormal operating state; if it is operating under constant voltage, when the current of the SOFC stack module drops sharply by 20%, it is considered to be an abnormal operating state; if it is operating under constant power, when the current of the SOFC stack module rises sharply by 20% or the voltage of the SOFC stack module drops below the safe voltage, it is considered to be an abnormal operating state.
[0033] Compared with existing single-channel power supply systems, the inverter power supply system proposed in this invention uses multiple independent and electrically isolated DC / DC power conversion modules connected to each SOFC stack respectively. This allows multiple SOFC stacks with smaller power and different performance to be independently connected to the same inverter power supply system and realize independent adjustment of different SOFC stacks. This avoids the interference problems caused by poor stack consistency, insulation degradation or local faults in the traditional multi-stack direct series and parallel connection method.
[0034] The DC / DC power conversion module employs an isolated resonant converter topology, achieving electrical isolation between the SOFC stack side and the high-voltage DC bus side. This effectively suppresses the impact of stack-side faults and voltage fluctuations on the DC bus and other stacks, while also reducing high-frequency losses and electromagnetic interference. Each DC / DC power conversion module in this invention boosts the DC output from the corresponding SOFC stack module to a high-voltage DC of 600–900V, then converges it all to the high-voltage bus for centralized inversion. Compared to direct low-voltage DC inversion or distributed inversion schemes, this significantly reduces the DC-side current level, decreases the size of power devices, inductors, and bus structures, thereby reducing system size, transmission losses, and overall manufacturing costs, while increasing system power density.
[0035] The multi-mode collaborative control strategy proposed in this invention supports constant current, constant voltage, and constant power operation modes for each DC / DC power conversion module, and achieves adaptive switching of operation modes through a central control unit. Simultaneously, linear or quasi-linear ramp control is employed during power regulation and mode switching to effectively mitigate abrupt changes in the stack's operating state. Furthermore, when any SOFC stack or its corresponding DC / DC module malfunctions, this invention can independently disconnect the faulty path while the remaining stacks continue operating, providing continuous operation or N-1 redundancy capability, significantly improving the system's reliability and availability. Attached Figure Description
[0036] Figure 1 This is a schematic diagram of an inverter power supply system for SOFC stacks according to the present invention.
[0037] Figure 2 Is it like this? Figure 1 The diagram shows a block diagram of a DC / DC power conversion module for an inverter power supply system used in SOFC stacks.
[0038] Figure 3 Is it like this? Figure 1 The diagram shows a control logic diagram of an inverter power supply system for SOFC stacks.
[0039] Figure 4 Is it like this? Figure 1 The flowchart shown illustrates a method of using an inverter power supply system for an SOFC stack. Detailed Implementation
[0040] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0041] This invention provides an inverter power supply system for SOFC fuel cell stacks. For example... Figure 1 As shown, the inverter power supply system mainly includes multiple independent SOFC stack modules 10, DC / DC power conversion modules 20 arranged one-to-one with each SOFC stack module 10 to form power supply channels, a DC / AC inverter module 40 connected to the output terminals of all DC / DC power conversion modules 20 via a high-voltage DC bus 30, a load connected to the output terminal of the DC / AC inverter module 40, and a central control unit 60 connected to all SOFC stack modules 10, DC / DC power conversion modules 20, DC / AC inverter module 40, and the load. The load can be the grid 51 or off-grid power supply 52. The central control unit 60 controls the parameters of the corresponding DC / DC power conversion module 20 according to the operating conditions of each SOFC stack module 10.
[0042] like Figure 2 As shown, each DC / DC power conversion module 20 has an isolated structure, comprising a BOOST circuit 21, an LLC resonant converter 22, and an output rectifier circuit 23 connected in sequence to achieve electrical isolation between the input and output. The BOOST circuit 21 acts as the front-end, boosting the low-voltage DC output from the SOFC stack module 10. The LLC resonant converter 22 acts as the rear-end, achieving electrical isolation between the input and output through a high-frequency isolation transformer and transferring energy. It also features soft-switching characteristics, improving efficiency and reducing electromagnetic interference. The output rectifier circuit 23 rectifies the output to obtain a stable high-voltage DC.
[0043] Because the input side (low-voltage side) and output side (high-voltage DC bus side) of each DC / DC power conversion module 20 are electrically isolated through the isolation transformer of the LLC resonant converter 22, there is no direct electrical connection between the input sides of each DC / DC power conversion module 20, i.e., there is no direct electrical connection between each SOFC stack module 10. A fault in any SOFC stack module 10 (such as a short circuit or open circuit) will not affect other SOFC stack modules 10 through the DC bus, preventing electrical interference to other SOFC stack modules 10 and the high-voltage DC bus 30 caused by insulation degradation, abnormal voltage, or fault shutdown of any SOFC stack module 10. Furthermore, the number of DC / DC power conversion modules 20 can be expanded according to the number of independent stack modules in the SOFC system. The independent power supply channels composed of SOFC stack modules 10 and DC / DC power conversion modules 20 both support hot-swapping and N-1 redundancy operation.
[0044] In addition, the DC / DC power conversion module 20 boosts the DC power output from the corresponding SOFC stack module 10 to a high voltage DC of 600–900V and then collects it to the high voltage DC bus 30 to reduce the current on the DC side and reduce the size and transmission loss of the inverter power supply system.
[0045] The DC / AC inverter module 40 has an internal digital signal processor (DSP). The DSP is the control chip of the DC / AC inverter module 40, used to realize the DC / AC conversion of the DC / AC inverter module 40.
[0046] The central control unit 60 is an independent hardware device responsible for the coordinated control, mode switching, and fault handling of the entire system. The parameters collected by the central control unit 60 include: open-circuit voltage and real-time current from the SOFC stack module 10; input voltage, input current, output voltage, output current, and module status (normal / fault / communication interruption) from the DC / DC power conversion module 20; and AC output voltage (U) from the DC / AC inverter module 40. abU bc U ca AC output current (I) a I b I c ), active power, reactive power, frequency; grid voltage, frequency, and load power demand from the grid and off-grid consumption (if it is off-grid mode).
[0047] The command parameters issued by the central control unit 60 include: commands sent to the DC / DC power conversion module 20: operating mode (constant current / constant voltage / constant power), target current / voltage / power value; commands sent to the DC / AC inverter module 40: grid-connected / off-grid mode switching, output voltage / frequency setting value (off-grid mode); system-level commands: start / stop, fault reset, mode switching (grid-connected / off-grid).
[0048] Therefore, during normal system operation, each DC / DC power conversion module 20 independently controls its input current according to the instructions of the central control unit 60. Simultaneously, it boosts the voltage to obtain the output voltage (high-voltage direct current) of the DC / DC power conversion module 20. This boosted output voltage is then connected in parallel to the high-voltage direct current bus 30. By boosting the voltage at the DC / DC power conversion module 20 before connecting it to the high-voltage direct current bus 30, the bus current is effectively reduced, minimizing system transmission losses. The electrical energy on the high-voltage direct current bus 30 is then inverted by the DC / AC inverter module 40 and connected to the grid or off-grid for absorption, outputting AC power that meets the requirements of grid connection or off-grid absorption, thus enabling the SOFC system to supply power to the external grid or local loads.
[0049] During operation control, depending on the different operating conditions of the SOFC stack module 10, such as startup, steady-state operation, or power regulation, each DC / DC power conversion module 20 can select a constant current, constant voltage, or constant power operating mode and dynamically adjust its own output current, output voltage, or output power.
[0050] like Figure 3 and Figure 4 As shown, the method of using the inverter power supply system for SOFC stacks according to the present invention includes:
[0051] Step S1: Build the inverter power supply system for SOFC stacks as described above; after the inverter power supply system is started, the central control unit 60 initializes each SOFC stack module 10, each DC / DC power conversion module 20, and DC / AC inverter module 40, and establishes communication connections; the central control unit 60 collects parameters from each SOFC stack module 10, each DC / DC power conversion module 20, and DC / AC inverter module 40 in real time, and judges the operating condition of the inverter power supply system based on the collected parameters;
[0052] The parameters collected by the central control unit 60 include: open-circuit voltage and real-time current from the SOFC stack module 10; input voltage, input current, output voltage, output current, and module status from the DC / DC power conversion module 20; AC output voltage, AC output current, active power, reactive power, and frequency from the DC / AC inverter module 40; and grid voltage, frequency, and load power demand from the grid and off-grid consumption.
[0053] Step S2: During the startup phase, based on the operating conditions, select a constant current, constant voltage, or constant power operating mode for each DC / DC power conversion module 20, and then input the control setpoint and parameter adjustment rules corresponding to the operating mode.
[0054] The constant current, constant voltage, or constant power operating modes are determined by factors such as the performance of the SOFC stack module 10 and stack safety. The inverter system of the present invention can realize the use and switching of these three functions for the power generation system according to actual needs.
[0055] The parameter adjustment rules for different operating modes are shown in Table 1.
[0056] Table 1: Parameter Adjustment Rules under Different Operating Modes
[0057]
[0058] Step S3: The central control unit 60 performs linear or quasi-linear ramp adjustment of the current, voltage or power according to the parameter adjustment rules, so that the current, voltage or power is smoothly adjusted and ultimately maintained at the control setpoint.
[0059] The command parameters issued by the central control unit 60 include: commands sent to the DC / DC power conversion module 20: operating mode, target current / voltage / power value; commands sent to the DC / AC inverter module 40: grid-connected / off-grid mode switching, output voltage / frequency setting value; system-level commands: start / stop, fault reset, mode switching.
[0060] Specifically, the current, voltage, or power obtained through linear or quasi-linear ramp-up regulation is sent to the corresponding DC / DC power conversion module 20 to control the output voltage of the DC / DC power conversion module 20. For example, in constant voltage mode, by setting the output voltage to the target voltage value, the increase in the output voltage of the DC / DC power conversion module 20 will affect the output current of the SOFC stack module 10. The increase in current leads to a decrease in voltage. At the same time, the inverter system will collect the output voltage of the DC / DC power conversion module 20 in real time and compare it with the target voltage value. Then, the adjustment command is returned to the inverter system. The entire setting-adjustment-data acquisition-comparison-adjustment process can be completed in milliseconds, which is the same as the cascade control principle of flow, thus making the output voltage change linearly.
[0061] Therefore, when adjusting power or switching operating modes, the central control unit 60 gradually changes the control commands for current, voltage or power using a linear or quasi-linear ramping method. The rate of change is set according to the actual operating conditions of the SOFC stack module 10, thereby reducing the electrochemical stress and thermal shock caused by sudden current changes and ensuring the stability and safety of the SOFC stack module 10 operation.
[0062] Quasi-linearity is the mathematical definition of a function, which simply means that the slope of each sampling point is basically the same. In this invention, quasi-linearity means that the slope of each sampling point differs by less than 5%.
[0063] Step S3 further includes: if it is determined that the startup phase is not underway, then steps S2 and S3 are stopped, and a fault handling process is executed.
[0064] Step S4: When any SOFC stack module 10 or its corresponding DC / DC power conversion module 20 is detected to be in an abnormal operating state, a fault handling procedure is executed to isolate the faulty power supply channel. The fault handling procedure includes: controlling the DC / DC power conversion module 20 to gradually reduce its output and disconnect it from the high-voltage DC bus 30, while the remaining DC / DC power conversion modules 20 continue to operate, thereby enabling the multi-stack system to continue to supply power or operate with N-1 redundancy under abnormal conditions, and improving the overall reliability and availability of the system.
[0065] This invention primarily detects the current, voltage, and power of the SOFC stack module 10 to determine faults. Faults in the DC / DC power conversion module 20 are detected by the device's own parameters, and the fault signals are provided by the equipment supplier, which are not within the scope of this invention. The method for determining abnormal operating states of the SOFC stack module 10 is as follows: If operating under constant current, an abnormal operating state is considered to have occurred when the voltage of the SOFC stack module 10 drops below the safe voltage. This safe voltage needs to be calculated based on the specifications of the SOFC stack module 10 and the series / parallel connection method of multiple SOFC stack modules 10. If operating under constant voltage, an abnormal operating state is considered to have occurred when the current of the SOFC stack module 10 drops sharply by 20%. If operating under constant power, an abnormal operating state is considered to have occurred when the current of the SOFC stack module 10 rises sharply by 20% or the voltage of the SOFC stack module 10 drops below the safe voltage.
[0066] Abnormal operating conditions may include, for example, the voltage of the SOFC stack module 10 exceeding the stop voltage. This is one type of abnormal operating condition that can occur in the SOFC stack module 10.
[0067] Step S5: When the system shutdown conditions are met, the shutdown phase begins. Based on the system's operating mode before shutdown, the output of each channel is gradually reduced according to the corresponding parameter adjustment rules to achieve a safe shutdown of the system.
[0068] In constant current operation mode, the parameter adjustment rules are the same as those for current ramping: set the target current reduction value, the rate of current reduction, and the reduction time. In constant power operation mode, the requirements are the same as for power ramping: set the target power reduction value, the rate of power reduction, and the reduction time.
[0069] Step S5 may further include: if it is determined that the system is not in the shutdown phase, then step S5 is stopped and a fault handling process is executed.
[0070] Compared with existing single-channel power supply systems, the inverter power supply system for SOFC stacks proposed in this invention uses multiple independent and electrically isolated DC / DC power conversion modules connected to each SOFC stack respectively. This allows multiple SOFC stacks with smaller power and different performance to be independently connected to the same inverter power supply system and enables independent adjustment of different SOFC stacks. This avoids the interference problems caused by poor stack consistency, insulation degradation or local faults in the traditional multi-stack direct series and parallel connection method.
[0071] The DC / DC power conversion module employs an isolated resonant converter topology, achieving electrical isolation between the SOFC stack side and the high-voltage DC bus side. This effectively suppresses the impact of stack-side faults and voltage fluctuations on the DC bus and other stacks, while also reducing high-frequency losses and electromagnetic interference. Each DC / DC power conversion module in this invention boosts the DC output from the corresponding SOFC stack module to a high-voltage DC of 600–900V, then converges it all to the high-voltage bus for centralized inversion. Compared to direct low-voltage DC inversion or distributed inversion schemes, this significantly reduces the DC-side current level, decreases the size of power devices, inductors, and bus structures, thereby reducing system size, transmission losses, and overall manufacturing costs, while increasing system power density.
[0072] The multi-mode collaborative control strategy proposed in this invention supports constant current, constant voltage, and constant power operation modes for each DC / DC power conversion module, and achieves adaptive switching of operation modes through a central control unit. Simultaneously, linear or quasi-linear ramp control is employed during power regulation and mode switching to effectively mitigate abrupt changes in the stack's operating state. Furthermore, when any SOFC stack or its corresponding DC / DC module malfunctions, this invention can independently disconnect the faulty path while the remaining stacks continue operating, providing continuous operation or N-1 redundancy capability, significantly improving the system's reliability and availability.
[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. All simple and equivalent changes and modifications made in accordance with the claims and description of this application fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.
Claims
1. An inverter power supply system for SOFC fuel cell stacks, characterized in that, It includes multiple independent SOFC stack modules, DC / DC power conversion modules that correspond one-to-one with each SOFC stack module to form a power supply channel, a DC / AC inverter module connected to the output terminals of all DC / DC power conversion modules via a high-voltage DC bus, a load connected to the output terminal of the DC / AC inverter module, and a central control unit connected to all SOFC stack modules, DC / DC power conversion modules, DC / AC inverter modules, and load; the central control unit controls the parameters of the corresponding DC / DC power conversion module according to the operating conditions of each SOFC stack module.
2. The inverter power supply system for SOFC stacks according to claim 1, characterized in that, The load is either connected to the grid or consumed off-grid.
3. The inverter power supply system for SOFC stacks according to claim 1, characterized in that, Each DC / DC power conversion module includes a BOOST circuit, an LLC resonant converter, and an output rectifier circuit connected in sequence. The LLC resonant converter achieves electrical isolation between the input and output through a high-frequency isolation transformer, so that there is no direct electrical connection between the input sides of each DC / DC power conversion module.
4. The inverter power supply system for SOFC stacks according to claim 1, characterized in that, The independent power supply channels consisting of the SOFC stack module and the DC / DC power conversion module both support hot-swapping and N-1 redundancy operation.
5. The inverter power supply system for SOFC stacks according to claim 1, characterized in that, The DC / DC power conversion module boosts the DC output from the corresponding SOFC stack module to a high voltage DC of 600–900V and then connects it to the high voltage DC bus.
6. The inverter power supply system for SOFC stacks according to claim 1, characterized in that, The parameters collected by the central control unit include: open-circuit voltage and real-time current from the SOFC stack module; input voltage, input current, output voltage, output current, and module status from the DC / DC power conversion module; AC output voltage, AC output current, active power, reactive power, and frequency from the DC / AC inverter module; and grid voltage, frequency, and load power demand from the grid and off-grid consumption. The command parameters issued by the central control unit include: commands sent to the DC / DC power conversion module: operating mode, target current / voltage / power value; commands sent to the DC / AC inverter module: grid-connected / off-grid mode switching, output voltage / frequency setting value; system-level commands: start / stop, fault reset, mode switching.
7. A method of using an inverter power supply system for an SOFC fuel cell stack, characterized in that, include: Step S1: Construct the inverter power supply system for SOFC stacks as described in any one of claims 1-6; after the inverter power supply system is started, the central control unit initializes each SOFC stack module, each DC / DC power conversion module, and the DC / AC inverter module, and establishes communication connections; the central control unit collects parameters from each SOFC stack module, each DC / DC power conversion module, and the DC / AC inverter module in real time, and determines the operating condition of the inverter power supply system based on the collected parameters; Step S2: During the startup phase, based on the operating conditions, select a constant current, constant voltage, or constant power operating mode for each DC / DC power conversion module, and then input the control setpoint and parameter adjustment rules corresponding to the operating mode. Step S3: The central control unit performs linear or quasi-linear ramp adjustment of the current, voltage or power according to the parameter adjustment rules, so that the current, voltage or power is smoothly adjusted and ultimately maintained at the control setpoint. Step S4: When any SOFC stack module or the corresponding DC / DC power conversion module is detected to be in an abnormal operating state, the fault handling procedure is executed to isolate the faulty power supply channel. The fault handling procedure includes: controlling the DC / DC power conversion module of that circuit to gradually reduce its output and disconnect it from the high-voltage DC bus, while the remaining DC / DC power conversion modules continue to operate; Step S5: When the system shutdown conditions are met, the shutdown phase begins. Based on the system's operating mode before shutdown, the output of each channel is gradually reduced according to the corresponding parameter adjustment rules to achieve a safe shutdown of the system.
8. The method of using the inverter power supply system for SOFC stacks according to claim 7, characterized in that, The parameter adjustment rules for different operating modes include: In constant current operation mode, the control setpoint is the target current value and the time required for the zero current to rise to the target current value. The parameter adjustment rule is to keep the output current constant, and the initial setting method is to linearly increase or decrease the output current according to the target current value and time. In constant voltage operation mode, the control setpoint is the target voltage value and the time required for the voltage to rise from zero to the target voltage value. The parameter adjustment rule is to keep the output voltage constant, and the initial setting method is to linearly increase or decrease the output voltage according to the set target current and time. In constant power operation mode, the control setpoint is the target power value and the time required for the power to rise from zero to the target power value. The parameter adjustment rule is to keep the output power constant, and the initial setting method is to linearly increase or decrease the output power according to the set target current and time.
9. The method of using the inverter power supply system for SOFC stacks according to claim 7, characterized in that, The methods for judging abnormal operating states of SOFC stack modules are as follows: If it is operating under constant current, when the voltage of the SOFC stack module drops below the safe voltage, it is considered to be an abnormal operating state; if it is operating under constant voltage, when the current of the SOFC stack module drops sharply by 20%, it is considered to be an abnormal operating state; if it is operating under constant power, when the current of the SOFC stack module rises sharply by 20% or the voltage of the SOFC stack module drops below the safe voltage, it is considered to be an abnormal operating state.