Rapid low-temperature starting system and method for direct methanol fuel cell power station

Abstract

The invention relates to the technical field of fuel cell low-temperature starting control, in particular to a direct methanol fuel cell (DMFC) power station rapid low-temperature starting system and method. The system comprises a main controller, a methanol supply subsystem, an electric pile, a lithium battery heating subsystem and a temperature detection subsystem. The main controller constructs a thermal state vector and predicts temperature change based on a discrete thermal network model, the optimal heat supply power meeting energy budget and thermal safety constraint is solved in a prediction window, the optimal heat supply power is mapped into pulse frequency, duty ratio and heat supply routing variables, and partition heat supply of the methanol hot area and the electric pile hot area is achieved; and meanwhile, the lithium battery pack is subjected to self-preheating under the low-temperature condition, and pipeline freezing and air blocking are prevented through emptying and reperfusion closed-loop control. Smooth temperature rise and accurate power distribution can be achieved in the low-temperature environment, starting energy consumption and battery impact are reduced, the safety of the electric pile and the starting success rate are improved, and the method is suitable for reliable operation of a power station-level DMFC system.

Description

Technical Field

[0001] This invention relates to the field of low-temperature start-up control technology for fuel cell power plants, and in particular to a rapid low-temperature start-up system and method for a direct methanol fuel cell power plant. Background Technology

[0002] Direct methanol fuel cells (DMFCs) generate electricity directly using methanol as fuel, making them suitable for distributed power plants and emergency power supply scenarios. However, in environments below 0°C, the viscosity of the methanol solution increases and may even undergo a phase change, reducing the reactivity of the fuel cell stack. Simultaneously, the internal resistance of lithium batteries increases at low temperatures, posing safety risks for direct high-power discharge. Existing low-temperature start-up methods often employ constant-power heating or simple temperature threshold control, failing to consider thermal coupling, environmental heat dissipation, and the latent heat of phase change, resulting in high energy consumption, long start-up times, and insufficient reliability. Therefore, a low-temperature start-up control system that balances safety, energy efficiency, and reliability is needed. Summary of the Invention

[0003] The present invention aims to provide a rapid low-temperature start-up system and method for a direct methanol fuel cell power plant, which can achieve rapid, safe and low-energy start-up in low-temperature environments.

[0004] To achieve the aforementioned objective, this invention provides a rapid cryogenic start-up system for a direct methanol fuel cell power station, comprising a main controller, a direct methanol fuel cell stack, a methanol supply subsystem, a lithium battery heating subsystem, and a temperature detection subsystem; wherein the lithium battery heating subsystem converts DC power into a frequency of [frequency missing] according to instructions from the main controller. Duty cycles are respectively , The pulsed electrical energy, and according to the heating routing vector The pulsed electrical energy is selectively coupled to at least one of a first heating end for heating the methanol supply subsystem and a second heating end for heating the fuel cell stack; the temperature detection subsystem is used to collect ambient temperature. Methanol temperature and fuel cell temperature And output to the main controller; the main controller is configured to construct a thermal state vector:

[0005]

[0006] And the predicted temperature is calculated based on the heat dissipation network model:

[0007] ,

[0008] These correspond to the equivalent heating power of the first heating end and the second heating end, respectively; A represents the thermal inertia matrix; B is the input matrix; This is the equivalent heat loss matrix. This is a latent heat compensation term for phase change. For discrete time steps, The main controller is further configured to be a unit column vector in the prediction window. Internally solve for the objective function that satisfies both energy budget and thermal security constraints. To obtain optimal heating power and will Mapping to a set of parameters The lithium battery heating subsystem is controlled to implement closed-loop heating of the methanol hot zone and the fuel cell hot zone according to the strategy of "self-preheating - zoned heating - gradual withdrawal".

[0009] To achieve the aforementioned objective, the present invention also provides a method for rapid low-temperature start-up of a direct methanol fuel cell power plant, comprising:

[0010] S2-1: Temperature Acquisition: Acquisition And build ;

[0011] S2-2: Predictive Power Allocation: Based on predictions from the heat dissipation network model In the prediction window The inner solution of the optimization problem satisfying the constraints of lower temperature limit, upper power limit, energy budget and temperature rise rate yields the following results. ;

[0012] S2-3: Pulse Mapping and Closed-Loop Heating: [The following text appears to be incomplete and requires further context:] Mapped to The lithium battery pack is controlled to preheat itself first, then provide heat in zones and gradually withdraw until the temperature of the methanol hot zone and the stack hot zone reaches the start-up threshold.

[0013] Compared with existing technologies, the rapid low-temperature start-up system and method for direct methanol fuel cell power plants provided by this invention have the following beneficial effects: By establishing a thermal network prediction model and combining pulse power modulation with dynamic switching of the heating path, this invention achieves rapid, low-energy, and safe start-up of direct methanol fuel cell power plants in low-temperature environments; while ensuring the safety of the battery and stack, it improves the system's start-up reliability and operational stability. Attached Figure Description

[0014] Figure 1 This is a block diagram of the rapid low-temperature start-up system for a direct methanol fuel cell power plant provided by the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to embodiments. It should be understood that the following embodiments are used to explain the present invention and not to limit the scope of protection of the present invention; in the absence of conflict, the embodiments and technical features disclosed in this specification can be combined with each other.

[0016] The present invention will be further described below with reference to embodiments. It should be understood that the following embodiments are used to explain the present invention and not to limit the scope of protection of the present invention; in the absence of conflict, the embodiments and technical features disclosed in this specification can be combined with each other.

[0017] Figure 1 This is a block diagram of the rapid cryogenic start-up system for a direct methanol fuel cell power plant provided by the present invention. Figure 1 As shown, the rapid cryogenic start-up system for a direct methanol fuel cell power station provided by the present invention includes a direct methanol fuel cell stack, a methanol supply subsystem, a lithium battery heating subsystem, a temperature detection subsystem, and a main controller. The lithium battery heating subsystem converts DC power into frequency power according to instructions from the main controller. Duty cycles respectively , The pulsed electrical energy, and according to the heating routing variables The pulsed electrical energy is selectively coupled to at least one of a first heating end for heating the methanol supply subsystem and a second heating end for heating the fuel cell stack; the temperature detection subsystem is used to collect ambient temperature. Methanol temperature and fuel cell temperature And output to the main controller.

[0018] In this invention, the direct methanol fuel cell stack is composed of multiple stacked single-cell units. Each single-cell unit includes a membrane electrode assembly, a bipolar plate, and a sealing structure. The bipolar plate forms an anode flow channel and a cathode flow channel. The anode flow channel is used to introduce methanol-water solution and discharge carbon dioxide, while the cathode flow channel is used to introduce air and discharge generated water and exhaust gas. The stack generates protons and electrons through the methanol oxidation reaction at the anode. Protons are conducted to the cathode via a proton exchange membrane, and electrons are output through an external circuit to form an electric current. An oxygen reduction reaction occurs at the cathode to generate water, thereby converting the chemical energy of methanol into electrical energy output. A stack temperature sensor is installed in the stack to collect the stack temperature. It works in conjunction with the second heating end to achieve closed-loop temperature control during the low-temperature start-up process.

[0019] In this invention, the methanol supply subsystem includes a methanol storage tank, a transfer pump, a pipeline system, and a venting subsystem. The methanol storage tank stores methanol solution and supplies it to the anode channel via the transfer pump. The venting subsystem vents residual liquid in the pipeline during shutdown and performs closed-loop control of refilling and venting during startup. The methanol pipeline flow rate is monitored. Methanol pipeline The system combines temperature rise consistency with other parameters to improve low-temperature start-up reliability and fuel utilization. The venting subsystem includes a vent valve and a storage tank. The vent valve is connected to the methanol supply subsystem pipeline and controlled by the main controller. During shutdown, the main controller shuts down the delivery pump and opens the vent valve for a preset time to drain residual methanol solution from the pipeline into the storage tank, thereby reducing the risk of low-temperature freezing and blockage. During startup, the main controller starts the delivery pump at a low flow rate and periodically opens and closes the vent valve to execute a closed-loop venting process. When the pipeline pressure difference meets the specified requirements... Traffic requirements are met Furthermore, the stack temperature rise rate is consistent with the model prediction. Once the venting is complete, the vent valve is closed, and normal liquid supply resumes. The temperature rise rate of the fuel cell stack is predicted based on the heat dissipation network model; This is the threshold for temperature rise consistency. This is the differential pressure threshold. This is the lower limit threshold for traffic flow.

[0020] The main controller calculates the temperature model residuals. And combined with the excitation response of the test opening and closing of the vent valve The system determines whether the pipeline is frozen or blocked. If the anomaly is confirmed, the main controller switches the heating routing variable. This improves the reliability and robustness of the low-temperature start-up phase by redirecting to a backup heating path or redistributing heating power.

[0021] In this invention, the lithium battery heating subsystem includes a lithium battery pack, a pulse power modulator, and an electronic switching device, wherein the output voltage of the lithium battery pack is... The output current is The pulse power modulator converts the DC power of the lithium battery pack into a frequency converter according to the instructions of the main controller. These correspond to the duty cycles of the first heating end and the second heating end, respectively. The pulsed electrical energy, the electronic transfer switch according to the heating route variables Pulsed electrical energy is coupled to a first heating end and a second heating end. The first heating end is located on the outer wall of the storage tank or the outer periphery of the pipeline in the methanol supply subsystem to provide heat to reduce methanol viscosity or prevent freezing. The second heating end is located on the outside of the fuel cell stack casing to provide heat to increase the fuel cell stack operating temperature.

[0022] The temperature detection subsystem includes at least: a first temperature sensor, a second temperature sensor, a third temperature sensor, and a signal conditioning and acquisition module. The first temperature sensor is located on the outside of the power plant casing or near the air inlet and is used to measure the ambient temperature. The second temperature sensor is placed on the outer or inner wall of the methanol storage tank or at a critical location in the methanol pipeline (such as near the pump inlet) to measure the methanol temperature. The third temperature sensor is located on the surface of the fuel cell stack, near the clamping plate, end plate, or at a pre-reserved temperature measurement hole inside the fuel cell stack, and is used to measure the temperature of the fuel cell stack. The signal conditioning and acquisition module includes filters, amplifiers, A / D converters, and / or digital acquisition interfaces, used to convert sensor signals into data that the main controller can recognize.

[0023] In this invention, the main controller is configured to construct a thermal state vector based on the temperature information received from the temperature detection subsystem, and to calculate the predicted temperature based on the heat dissipation network model. It is further configured to... (The sentence is incomplete and requires more context to translate accurately.) Internally solve the optimization problem that satisfies energy budget constraints and thermal security constraints to obtain the optimal heating power. and will The parameters are mapped to a set of pulse power modulator parameters to control the lithium battery heating subsystem to implement closed-loop heating of the methanol hot zone and the fuel cell hot zone according to the strategy of "self-preheating - zoned heating - gradual withdrawal".

[0024] Specifically, it includes:

[0025] The S1-1 main controller operates with discrete time steps. Periodically receive ambient temperature Methanol temperature and fuel cell temperature Construct the thermal state vector: ,in, This represents the discrete time step, typically ranging from 0.5s to 2s. To reduce noise, the original temperature signal can be processed using a moving average or exponential filtering.

[0026] S1-2 calculates and predicts the temperature based on the heat dissipation network model:

[0027]

[0028] Where Δt is the discrete time step; A represents the thermal inertia of the thermal region itself and the coupling effect:

[0029]

[0030] The equivalent heat capacity of the methanol hot zone; This represents the equivalent heat capacity of the fuel cell stack's hot zone. The heat transfer coefficient of the methanol thermal zone to the environment; The heat transfer coefficient of the fuel cell stack's hot zone to the environment; This refers to the external heat dissipation area of ​​the methanol storage tank. This refers to the heat dissipation area of ​​the fuel cell stack casing; The thermal conductivity effect of the fuel cell stack on the methanol hot zone; The effect of the methanol hot zone on the thermal conductivity of the fuel cell stack.

[0031] In this invention, This refers to the equivalent heating power of the first heating end and the second heating end; Here is the input matrix, representing the effect of unit power input on temperature rise:

[0032] .

[0033] In this invention, This is the heat loss matrix, used to characterize the impact of environmental heat dissipation:

[0034] ,

[0035] in, The convective heat transfer coefficient is... For heat exchange area, For equivalent heat capacity, .

[0036] This is a bold statement. It is a unit column vector.

[0037] In this invention, For phase transition compensation terms:

[0038]

[0039] in: , Latent heat of phase transition; Phase transition mass change rate; Phase transition region indicator function.

[0040] Enabled in the phase transition temperature region; otherwise, it is a zero vector.

[0041] S1-3 in the prediction window Solving the optimization problem internally yields the current optimal heating power. Prediction window Typical range is 5 ~20 .

[0042] An example of the objective function J is:

[0043]

[0044] And satisfy: Temperature constraint: Power constraints: Energy constraints: Temperature rise rate constraint: ;in, , , Budget for available energy; This indicates that the power sequence for a future period of time is optimized within the prediction window; Indicates from the current moment arrive The power sequence; To predict the number of steps; Represents the target temperature vector; This represents the weighted temperature error squared term; This represents the squared term of the weighted power change. To activate the minimum safe temperature threshold; This represents the maximum allowable heating power at one end. This represents the maximum permissible rate of temperature rise.

[0045] The main controller only executes the current cycle. And recalculate in the next cycle to achieve rolling optimization control; the available energy budget satisfies:

[0046]

[0047] in, For discharge efficiency, This is the rated voltage of the lithium battery pack. The rated capacity of the lithium battery, and The health status meets

[0048] ,in, The initial internal resistance, , is a coefficient.

[0049] S1-4 maps the optimal heating power to a set of pulse modulation parameters:

[0050] ,in, For optimal frequency, These are the optimal duty cycles. This is the optimal heating route vector.

[0051] In this invention, the duty cycle is calculated as follows:

[0052]

[0053] The pulse frequency satisfies: The typical range is ; And the heating routing variable Used to limit the output current within the same control cycle , These are the minimum and maximum values ​​of the frequency, respectively. Rated heating power

[0054] S1-5 When the ambient temperature meets the following conditions: And the temperature of the lithium battery: At that time, the main controller controls the lithium battery pack to perform self-preheating. Specifically: Typical values ​​range from -20℃ to -10℃; the self-preheating method involves applying a pulsed current to the battery preheating circuit. At that time, the zoned heating phase begins, supplying heat to the methanol heating zone and the electric stack heating zone respectively. This is the low-temperature switching threshold temperature; This refers to the current temperature of the lithium battery. The minimum operating temperature threshold for safe battery discharge.

[0055] S1-6 When the temperature of the hot zone reaches the start-up threshold, the main controller gradually reduces the duty cycle and performs a gradual exit:

[0056] in: The duty cycle decreases in increments, typically ranging from 0.02 to 0.1. Throughout the startup process, the main controller updates the temperature data and re-solves the optimization problem each cycle, forming a closed-loop control.

[0057] The present invention also provides a method for rapid low-temperature start-up of a direct methanol fuel cell power plant, comprising:

[0058] S2-11: Temperature Acquisition: Acquisition And build ;

[0059] S2-2: Predictive Power Allocation: Based on predictions from the heat dissipation network model In the prediction window The inner solution of the optimization problem satisfying the constraints of lower temperature limit, upper power limit, energy budget and temperature rise rate yields the following results. ;

[0060] S2-3: Pulse Mapping and Closed-Loop Heating: [The following text appears to be incomplete and requires further context:] Mapped to The lithium battery pack is controlled to preheat itself first, then heat in sections and gradually withdraw until the temperature of the methanol hot zone and the stack hot zone reaches the start-up threshold.

[0061] S2-4: Priming and Venting: Start the delivery pump at a low flow rate and periodically open and close the vent valve to perform a closed-loop venting process until the required conditions are met. , and temperature rise consistency threshold;

[0062] S2-5: Anomaly Diagnosis and Degradation: When the model residuals and differential pressure test responses meet the icing / blockage criteria, switch the heating routing variables. To the backup heating path.

[0063] This invention achieves precise temperature control of the methanol hot zone and the fuel cell stack hot zone by constructing a thermal state vector and predicting temperature changes based on a heat dissipation network model. It introduces a phase change latent heat compensation term to correct temperature prediction errors when methanol or water is in the phase change range, avoiding misjudgment of heating effect. By employing a "self-preheating—zoned heating—gradual withdrawal" strategy, the system can smoothly enter the working state even in extremely low temperature environments. Therefore, this invention can stably start up under even lower ambient temperatures (e.g., -30℃ and below).

[0064] This invention solves for the optimal heating power within a predictive window, avoiding ineffective and excessive heating; it introduces energy budget constraints to ensure the heating process operates within the tolerance range of the lithium battery; and it achieves continuously adjustable power output through duty cycle and frequency modulation, improving energy utilization efficiency. Therefore, it can reduce overall energy consumption while meeting startup time requirements.

[0065] This invention suppresses thermal shock and reduces stress damage to the membrane electrode structure and seals by setting a temperature rise rate constraint; it performs self-preheating of the lithium battery at low temperatures to avoid performance degradation caused by high-current discharge at low temperatures; and it employs a gradual withdrawal mechanism to smoothly reduce heating power and prevent temperature overshoot. This extends the lifespan of the battery stack and the battery itself.

[0066] This invention improves fault identification accuracy by jointly determining icing or blockage events through temperature model residuals and the test opening and closing response of the vent valve. When an anomaly is detected, the heating path is automatically switched or the heating power is reallocated, achieving reconfigurable heating paths. Closed-loop control of venting and refilling effectively eliminates the risks of airlocks and freezing. Thus, the system can adaptively adjust under abnormal operating conditions, improving overall reliability.

[0067] This invention adopts a modular design, with the main controller, heating subsystem, methanol supply subsystem, and venting subsystem being relatively independent; the control logic is clear, and parameters can be obtained through calibration or online identification; it does not rely on complex reforming or hydrogen production devices and is suitable for direct methanol fuel cell systems.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A rapid cryogenic start-up system for a direct methanol fuel cell power station, comprising a main controller, a direct methanol fuel cell stack, a methanol supply subsystem, a lithium battery heating subsystem, and a temperature detection subsystem; wherein, The lithium battery heating subsystem converts DC power into a frequency of [frequency value] according to the instructions of the main controller. Duty cycles are respectively , The pulsed electrical energy, and according to the heating routing vector The pulsed electrical energy is selectively coupled to at least one of a first heating end for heating the methanol supply subsystem and a second heating end for heating the fuel cell stack; the temperature detection subsystem is used to collect ambient temperature. Methanol temperature and fuel cell temperature And output to the main controller; characterized in that the main controller is configured to construct a thermal state vector: And the predicted temperature is calculated based on the heat dissipation network model: ， These correspond to the equivalent heating power of the first heating end and the second heating end, respectively; A represents the thermal inertia matrix; B is the input matrix; This is the equivalent heat loss matrix. This is a latent heat compensation term for phase change. For discrete time steps, The main controller is further configured to be a unit column vector in the prediction window. Internally solve for the objective function that satisfies both energy budget and thermal security constraints. To obtain optimal heating power and will Mapping to a set of parameters The lithium battery heating subsystem is controlled to implement closed-loop heating of the methanol hot zone and the fuel cell hot zone according to the strategy of "self-preheating - zoned heating - gradual withdrawal".

2. The system according to claim 1, characterized in that, The objective function for: And satisfy the constraints: , , , ,in , , Budget for available energy; This indicates that the power sequence for a future period of time is optimized within the prediction window; Indicates from the current moment arrive The power sequence; To predict the number of steps; Represents the target temperature vector; This represents the weighted temperature error squared term; This represents the squared term of the weighted power change; To activate the minimum safe temperature threshold; This represents the maximum allowable heating power at one end. This represents the maximum permissible rate of temperature rise.

3. The system according to claim 2, characterized in that, The heat loss matrix for: , in, The convective heat transfer coefficient is... For heat exchange area, For equivalent heat capacity, .

4. The system according to claim 3, characterized in that, The latent heat compensation term for phase change satisfies: in: , Latent heat of phase transition; Phase transition mass change rate; Phase transition region indicator function, For equivalent heat capacity, .

5. The system according to claim 4, characterized in that, , For optimal frequency, These are the optimal duty cycles. This is the optimal heating route vector, where, ; For the first Each heating end at time The optimal equivalent heating power; For the first The rated heating power of each heating end.

6. The system according to claim 5, characterized in that, when At that time, the main controller controls the lithium battery pack to perform self-preheating until the lithium battery temperature reaches a certain level. Then switch to zoned heating for the methanol hot zone and the fuel cell stack hot zone; when It will directly enter the zone heating system; This is the low-temperature switching threshold temperature; This refers to the current temperature of the lithium battery. The minimum operating temperature threshold for safe battery discharge.

7. The system according to claim 6, characterized in that, It also includes the venting subsystem, which comprises a venting valve and a storage tank. The venting valve is connected to the methanol supply subsystem pipeline and controlled by the main controller. It is used to vent residual methanol solution from the pipeline into the storage tank during shutdown and to refill the methanol solution in the storage tank into the pipeline during startup. The completion criteria for the refilling and venting loop are satisfied as follows: ,in This refers to the pressure difference in the methanol pipeline. This refers to the methanol pipeline flow rate; The temperature rise rate of the fuel cell stack is predicted based on the heat dissipation network model; This is the threshold for temperature rise consistency. This is the differential pressure threshold. This is the lower limit threshold for traffic flow.

8. The system according to claim 7, characterized in that, The main controller is based on the temperature model residual. and the pressure difference change after the test opening and closing excitation of the vent valve. Determine if an icing or blockage event occurs, and based on... Switching between pulsed electrical energy.

9. The system according to claim 2, characterized in that, The available energy budget satisfies: in, For discharge efficiency, This is the rated voltage of the lithium battery pack. The rated capacity of the lithium battery, and The health status meets ， in The initial internal resistance, , is a coefficient.

10. A method for rapid cryogenic start-up of a direct methanol fuel cell power station using the system described in any one of claims 1 to 9, characterized in that, include: S2-1: Temperature Acquisition: Acquisition And build ; S2-2: Predictive Power Allocation: Based on predictions from the heat dissipation network model In the prediction window The inner solution of the optimization problem satisfying the constraints of lower temperature limit, upper power limit, energy budget and temperature rise rate yields the following results. ; S2-3: Pulse Mapping and Closed-Loop Heating: [The following text appears to be incomplete and requires further context:] Mapped to The lithium battery pack is controlled to preheat itself first, then provide heat in zones and gradually withdraw until the temperature of the methanol hot zone and the stack hot zone reaches the start-up threshold.

Images