A cathode closed air-cooled double-stack cathode parallel load distribution control method

Abstract

The application provides a cathode closed air-cooled double-stack cathode parallel collaborative load distribution control method, which can realize intelligent and dynamic load distribution between double stacks of a cathode parallel structure, ensures efficient, stable and reliable operation of the system, and effectively prolongs the overall service life of the system; comprising: S1, constructing a double-stack fuel cell system, the double-stack fuel cell system comprising a parallel first stack and a second stack, the first stack and the second stack being connected to a lithium battery through corresponding DC / DC converters respectively, and a load being connected to the lithium battery; S2, based on the charging and discharging power and the capacity SOC variation trend of the lithium battery, determining a single-stack output request power P_req through an energy management strategy; S3, determining an expected total power P_total of stack output according to the single-stack output request power P_req, and then performing synchronous or asynchronous switching start on the first stack and the second stack based on the expected total power P_total, so as to optimize the output power distribution between the first stack and the second stack, thereby realizing stable power output of each stack.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to a method for parallel cooperative load distribution control of dual-stack cathodes in a closed-loop air-cooled cathode configuration. Background Technology

[0002] Currently, connecting multiple fuel cell stacks in parallel is a common technical solution to improve the output power of fuel cell systems. In small and medium power applications, closed-cathode air-cooled fuel cells are favored due to their simple structure and low cost. In existing technologies, multiple stacks are typically connected in parallel using the following methods: (1) Direct parallel connection method: The output terminals of multiple fuel cells are directly connected together. This method has the simplest structure, but there are unavoidable performance differences between fuel cells (such as internal resistance and output voltage), which will lead to serious imbalance of output current and the system cannot work stably. At the same time, the direct parallel connection scheme will generate circulating current due to the differences in fuel cell characteristics, resulting in energy loss, accelerating fuel cell aging, and even causing safety accidents. (2) Simple current sharing method based on DC / DC: Each stack is equipped with a DC / DC converter, and the output current of each branch is forced to be consistent through the current sharing controller. Although this method solves the current balancing problem of direct parallel connection, it has the following problems: a. Low overall system efficiency: The strategy is simple, only pursuing equal current, without considering the efficiency characteristics of each stack and the power consumption of auxiliary equipment (BOP), making it difficult to achieve the optimal overall system efficiency. That is, the simple current sharing strategy cannot make each stack work at its highest efficiency point. Especially for air-cooled systems, the power consumption of auxiliary equipment (such as blowers and fans) accounts for a large proportion. The current sharing strategy that ignores the power consumption of auxiliary equipment may lead to a decrease in the net output power of the system. b. Auxiliary machine control is disconnected from the stack load: In the existing control scheme, the auxiliary machine control is often independent of the load distribution strategy. When the load changes dynamically, the air supply and heat dissipation may not be matched in time, and the best working environment for the air-cooled stack may not be provided, resulting in a shortage of reactants or overheating in the stack, which affects performance and lifespan. c. Lack of life balance management: The differences in aging levels between individual fuel cells are not considered. Long-term operation will accelerate the widening of these differences, thereby shortening the lifespan of the entire system. Therefore, there is an urgent need for a closed-loop air-cooled dual-reactor parallel cooperative load distribution control method to solve the above-mentioned technical problems. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a cathode-closed air-cooled dual-stacking cathode parallel cooperative load distribution control method, which can realize intelligent and dynamic load distribution between dual stacks with parallel cathode structure, ensuring efficient, stable and reliable system operation, and effectively extending the overall system lifespan.

[0004] This invention adopts the following technical solution: a method for parallel coordinated load distribution control of cathodes in a closed-loop air-cooled dual-reactor configuration, comprising the following steps: S1. Construct a dual-stack fuel cell system, wherein the dual-stack fuel cell system includes a first stack and a second stack connected in parallel, the first stack and the second stack are respectively connected to the lithium battery through corresponding DC / DC converters, and the load is connected to the lithium battery; S2. Based on the changing trends of the lithium battery's charging and discharging power and SOC capacity, determine the single-stack output request power P_req through an energy management strategy; S3. Determine the expected total output power P_total of the stack based on the single stack output request power P_req. Then, based on the expected total power P_total, start the first stack and the second stack synchronously or asynchronously to optimize the output power distribution between the first stack and the second stack, thereby achieving stable power output of each stack.

[0005] Furthermore, the dual-stack fuel cell system also includes an air filter, a blower, a first inlet pressure sensor P1, a first outlet pressure sensor P2, a second inlet pressure sensor P3, a second outlet pressure sensor P4, a first back pressure valve K1, and a second back pressure valve K2; the DC / DC converter is divided into a first DC / DC converter and a second DC / DC converter; air passes through the air filter and is connected to the blower, the output end of the blower is connected to the inlets of both the first and second fuel cell stacks, the outlet of the first fuel cell stack is connected to the first back pressure valve K1, the outlet of the second fuel cell stack is connected to the second back pressure valve K2, the first inlet pressure sensor P1 is connected to the connecting pipe between the blower and the first fuel cell stack, the second inlet pressure sensor P3 is connected to the connecting pipe between the blower and the second fuel cell stack; the first outlet pressure sensor P2 is connected to the connecting pipe between the first fuel cell stack and the first back pressure valve K1, and the second outlet pressure sensor P4 is connected to the connecting pipe between the second fuel cell stack and the second back pressure valve K2; Furthermore, step S2 also includes the following steps: S2.1 Real-time monitoring of the lithium battery's SOC (State of Charge). The lithium battery is divided into three working zones according to its SOC: a high-capacity zone, a medium-capacity zone, and a low-capacity zone. S2.2. Based on the SOC region of the lithium battery, trigger the corresponding capacity change trend judgment logic: when the SOC is in the high range, execute the first capacity change trend judgment logic. When the capacity SOC is in the middle range, execute the second or third capacity change trend judgment logic; When the capacity SOC is in the low range, execute the fourth capacity change trend judgment logic; wherein, the capacity change trend is determined as a dynamic change trend of the state of charge (SOC) of the lithium battery within a preset time window, and the change trend includes rising, falling or unchanged; S2.3, determining an energy management strategy for stack power based on a corresponding capacity change trend determination logic; further, in said step S2.1, the capacity SOC state is divided into a high region, a middle region and a low region according to a preset first SOC threshold X1%, a second SOC threshold X2%, a third SOC threshold X3% and a fourth SOC threshold X4%, wherein X1>X2>X3>X4; the high region is where the capacity SOC is greater than or equal to X1%; the middle region is where the capacity SOC is between X1% and X4%; the low region is where the capacity SOC is less than or equal to X4%; further, in said step S2.2, when the capacity SOC is in the middle region, the capacity SOC is compared with the second SOC threshold X2% and the third SOC threshold X3% for further determination; if X1%>SOC>X2%, it indicates that the capacity SOC is in the upper part of the middle region at this time; if X2%≥SOC≥X3%, it indicates that the capacity SOC is in the middle part of the middle region at this time; if X4%<SOC<X3%, it indicates that the capacity SOC is in the lower part of the middle region at this time; further, the first SOC threshold X1% is that the capacity SOC is between 75% and 95%; the second SOC threshold X2% is that the capacity SOC is between 60% and 80%; the third SOC threshold X3% is that the capacity SOC is between 20% and 40%; the fourth SOC threshold X4% is that the capacity SOC is between 10% and 20%; further, in said step S2.3, when the capacity SOC is in the high region, the energy management comprises the following steps: S2.3.11, if the capacity SOC shows an upward trend, acquiring a first target power value P_tag1, that is P_tag1=P_mid–aC; if the capacity SOC shows an unchanged trend or a downward trend, keeping the first target power value P_tag1 equal to the output requested power P_req of the single stack; wherein, P_mid is the median value of the load power within a set time; a is the step size of power regulation; C is the discharge rate of the lithium battery; S2.3.12 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag1 = P_load – 1 / 2aC, and then proceed to step S2.3.13; if not, then proceed to step S2.3.13. Where P_load is the load power; S2.3.13. Maintain the first target power value P_tag1 in step S2.3.12 as the current single stack output requested power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the upper part of the middle region, the following energy management steps are included: S2.3.21 If the capacity SOC shows an upward trend, then obtain the second target power value P_tag2, that is, P_tag2=P_mid+1 / 4aC; If the SOC of the capacity remains unchanged or decreases, then the second target power value P_tag2 is kept as the single stack output requested power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.22 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag2 = P_load – 1 / 2aC, and then proceed to step S2.3.23; if not, then proceed to step S2.3.23. Where P_load is the load power; S2.3.23. Maintain the second target power value P_tag2 in step S2.3.22 as the current single-pile output requested power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the lower part of the middle region, the following energy management steps are included: S2.3.31. If the capacity SOC shows a decreasing trend, then obtain the third target power value P_tag3, that is, P_tag3=P_mid+1 / 2aC; If the SOC (State of Charge) remains unchanged or increases, then the third target power value P_tag3 is kept at the single stack output request power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.32 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag3 = P_load + 1 / 2aC, and then proceed to step S2.3.33; if not, then proceed to step S2.3.33. Where P_load is the load power; S2.3.33. Keep the third target power value P_tag3 in step S2.3.32 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the low range, the following energy management steps are included: S2.3.41 If the capacity SOC shows a decreasing trend or remains unchanged, then obtain the fourth target power value P_tag4, that is, P_tag4=P_mid+aC; If the SOC of the capacity is increasing, then the fourth target power value P_tag4 is kept as the single stack output request power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.42 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag4 = P_load + 1 / 2aC, and then proceed to step S2.3.43; if not, then proceed to step S2.3.43. Where P_load is the load power; S2.3.43. Maintain the fourth target power value P_tag4 in step S2.3.42 as the current single-pile output requested power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the middle of the median region, the following energy management steps are included: S2.3.51, Keep the fifth target power value P_tag5 as the single-pile output requested power P_req; S2.3.52 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag5=P_load, and then proceed to step S2.3.53; if not, then proceed to step S2.3.53. Where P_load is the load power; S2.3.53. Maintain the fifth target power value P_tag5 in step S2.3.52 as the current single-pile output requested power P_req, and then wait for the next cycle of energy management adjustment; Further, in step S3, the expected total output power P_total of the fuel cell stack is determined based on the single fuel cell stack output request power P_req, i.e., P_total = P_sys + P_req; where P_sys is the sum of the power of the sampling blower, air filter, back pressure valve, and DC / DC converter. Furthermore, step S3 also includes the following power allocation optimization step: S3.1 Determine whether the SOC capacity of the lithium battery is greater than the second SOC threshold X2%. If yes, start the high-healthy battery stack and then proceed to step S3.2; if no, start the first and second battery stacks simultaneously and then proceed to step S3.3. S3.2 Determine whether the expected total power output P_total of the battery stack meets the requirements of not exceeding the rated power P of the single battery stack and the discharge power of the lithium battery being less than 3aC. If yes, the expected total power P_total is the single battery stack output request power P_req, and then proceed to step S3.5; if no, start another battery stack, and then proceed to step S3.3. S3.3 The first and second electric stacks are synchronously loaded with the same current slope until the single stack output requested power P_req of each electric stack is P_total / 2, that is, the sum of the output power of the first and second electric stacks is equal to the expected total power P_total. Then the load change stops and step S3.4 is performed. S3.4 Determine whether the lithium battery capacity SOC meets the requirement of being greater than or equal to the first SOC threshold X1% and the voltage of a single cell of the battery stack is higher than the set value. If yes, proceed to step S3.5; otherwise, end the process and wait for the next cycle of power allocation optimization. S3.5. Shut down the low-healthy fuel cell stacks, and the system enters single-stack operation, then waits for the next cycle of power allocation optimization; Furthermore, in step S3, when the lithium battery capacity SOC is greater than or equal to the first SOC threshold X1%, the low-health stack is shut down, and the system enters single-stack operation. The expected total power P_total is the single-stack output request power P_req of the high-health stack.

[0006] The beneficial effects of this invention are that by monitoring the charging and discharging power and power change trends of lithium batteries in real time, and through energy management strategies, it enables the capacity and power of lithium batteries to be in the highest efficiency range. At the same time, it controls the power during the synchronous and asynchronous start-up process of the battery stacks, optimizes the output power distribution between the first and second battery stacks, thereby achieving stable power output of each battery stack, thus ensuring the efficient, stable and reliable operation of the system, and effectively extending the overall lifespan of the system. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a flowchart of the present invention; Figure 3 This is a flowchart of energy management in this invention. Detailed Implementation

[0008] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention provides a cathode-closed air-cooled dual-reactor parallel cooperative load distribution control method, comprising the following steps: S1. Construct a dual-stack fuel cell system, wherein the dual-stack fuel cell system includes a first stack and a second stack with cathodes (air path) connected in parallel. The first stack and the second stack are respectively connected to the lithium battery through corresponding DC / DC converters, and the load is connected to the lithium battery. Furthermore, the dual-stack fuel cell system also includes an air filter, a blower, a first inlet pressure sensor P1, a first outlet pressure sensor P2, a second inlet pressure sensor P3, a second outlet pressure sensor P4, a first back pressure valve K1, and a second back pressure valve K2; the DC / DC converter is divided into a first DC / DC converter and a second DC / DC converter; air passes through the air filter and is connected to the blower, the output end of the blower is connected to the inlets of both the first and second fuel cell stacks, the outlet of the first fuel cell stack is connected to the first back pressure valve K1, the outlet of the second fuel cell stack is connected to the second back pressure valve K2, the first inlet pressure sensor P1 is connected to the connecting pipe between the blower and the first fuel cell stack, the second inlet pressure sensor P3 is connected to the connecting pipe between the blower and the second fuel cell stack; the first outlet pressure sensor P2 is connected to the connecting pipe between the first fuel cell stack and the first back pressure valve K1, and the second outlet pressure sensor P4 is connected to the connecting pipe between the second fuel cell stack and the second back pressure valve K2; S2. Based on the changing trends of lithium battery charging and discharging power and capacity SOC, the output request power P_req of a single battery stack is determined through energy management strategies; where P_req refers to the power that the energy management part expects the battery stack to output, which is the energy management part's request for the battery stack output power. Furthermore, step S2 also includes the following steps: S2.1 Real-time monitoring of lithium battery capacity SOC. The lithium battery is divided into three working zones according to its capacity SOC state: high zone, medium zone, and low zone. The capacity SOC status is divided into high, medium and low zones according to the preset first SOC threshold X1%, second SOC threshold X2%, third SOC threshold X3% and fourth SOC threshold X4%, where X1>X2>X3>X4. The first SOC threshold X1% is when the capacity SOC is between 75% and 95%; The second SOC threshold X2% is when the capacity SOC is between 60% and 80%; The third SOC threshold X3% represents the capacity SOC being between 20% and 40%; The fourth SOC threshold, multiplied by 4%, represents a capacity SOC between 10% and 20%. The first SOC threshold X1% is usually set at a high point after the start of the constant voltage charging stage of the lithium battery. Above this value, the charging acceptance of the lithium battery drops sharply. If it continues to be charged strongly, it will lead to a decrease in coulombic efficiency, faster temperature rise, and accelerated life decay. It can be determined by consulting the cell datasheet to find the start point SOC of the constant voltage stage (CV) in the standard charging curve and taking a safety margin (such as 5%) downward. For example, if a cell enters constant voltage charging at 90% SOC, the first SOC threshold X1% can be set to 85%. It can also be determined by observing the inflection point of voltage rise during constant power charging at different SOCs through experiments. The second SOC threshold of 2% and the third SOC threshold of 3% define the high-efficiency and low-degradation operating window of a lithium battery. Within this range, the battery's internal resistance is relatively stable and low, the charge and discharge efficiency is high, and the impact on lifespan is minimal. By plotting the internal resistance-SOC curve and the charge and discharge efficiency-SOC curve of a lithium battery at different SOCs, the second SOC threshold of 2% should be set before the inflection point where the internal resistance begins to increase significantly and the efficiency begins to decrease significantly, usually between 60% and 80% SOC. The third SOC threshold X3% should be set after the inflection point in the discharge curve where the voltage plateau period ends and the discharge curve enters a faster decline phase, and is usually between 20% and 40% of SOC. The goal of this patent is to maintain the system's operating state within this "sweet zone" (X3 ~ X2) most of the time; The fourth SOC threshold X4% is the discharge cutoff protection point of a lithium battery. If the SOC is lower than this value, over-discharge of the lithium battery will cause irreversible capacity loss and even damage to the battery. The SOC value corresponding to the discharge cutoff voltage specified in the cell specification can be directly referred to, and a safety margin (e.g., 5%-10%) is added upward. For example, if the SOC corresponding to the cutoff voltage is 5%, the fourth SOC threshold X4% can be set to 15%; and the high region is where the capacity SOC is greater than or equal to X1%; the middle region is where the capacity SOC is between X1% and X4%; the low region is where the capacity SOC is less than or equal to X4%; when the capacity SOC is in the middle region, the capacity SOC is compared with the second SOC threshold X2% and the third SOC threshold X3% again for judgment; if X1%>SOC>X2%, it indicates that the current capacity SOC is in the upper part of the middle region; if X2%≥SOC≥X3%, it indicates that the current capacity SOC is in the middle part of the middle region, and the current power request of the stack is maintained; if X4%<SOC<X3%, it indicates that the current capacity SOC is in the lower part of the middle region; S2.2, trigger a corresponding capacity change trend judgment logic according to the region where the capacity SOC of the lithium battery is located: when the capacity SOC is in the high region, execute the first capacity change trend judgment logic; when the capacity SOC is in the middle region, execute the second or third capacity change trend judgment logic; when the capacity SOC is in the low region, execute the fourth capacity change trend judgment logic; wherein the capacity change trend judgment refers to the dynamic change trend of the capacity SOC of the lithium battery within a preset time window, and the change trends include rising, falling or unchanged; S2.3, make a decision on the energy management strategy for stack power according to the corresponding capacity change trend judgment logic; further, in step S2.3, when the capacity SOC is in the high region, the following energy management steps are included: S2.3.11, if the capacity SOC shows an upward trend, acquire the first target power value P_tag1, that is P_tag1=P_mid–aC; if the capacity SOC has an unchanged trend or a falling trend, keep the first target power value P_tag1 as the output requested power P_req of the single stack; wherein P_mid is the median value of the load power within a set time (e.g., 2 seconds); a is the step size for power regulation; C is the discharge rate of the lithium battery; The value 'a' determines the value of 'aC', which affects the target power in the energy management process and thus the power request. When determining 'a', it can be based on the lithium battery's charge and discharge capacity. For example, the power corresponding to the value of 'a' should not exceed the power calculated by the lithium battery at the maximum sustainable charging rate (e.g., 0.3C) under the corresponding SOC, i.e., 'a' ≤ battery capacity (Ah) * 0.3C. Other methods can also be used to determine 'a', but the determination of 'a' is not the focus of this patent, therefore other methods will not be elaborated further. S2.3.12 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag1 = P_load – 1 / 2aC, and then proceed to step S2.3.13; if not, then proceed to step S2.3.13. Where P_load is the load power; S2.3.13. Keep the first target power value P_tag1 in step S2.3.12 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the upper part of the middle region, the following energy management steps are included: S2.3.21 If the capacity SOC shows an upward trend, then obtain the second target power value P_tag2, that is, P_tag2=P_mid+1 / 4aC; If the SOC of the capacity remains unchanged or decreases, then the second target power value P_tag2 is kept as the single stack output requested power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.22 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag2 = P_load – 1 / 2aC, and then proceed to step S2.3.23; if not, then proceed to step S2.3.23. Where P_load is the load power; S2.3.23. Keep the second target power value P_tag2 in step S2.3.22 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the middle of the median region, the following energy management steps are included: S2.3.51. Maintain the fifth target power value P_tag5 as the single stack output request power P_req; that is, the fifth target power value P_tag5 at this time is the current power request of the stack. S2.3.52 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag5=P_load, and then proceed to step S2.3.53; if not, then proceed to step S2.3.53. Where P_load is the load power; S2.3.53. Maintain the fifth target power value P_tag5 in step S2.3.52 as the current single-pile output requested power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the lower part of the middle region, the following energy management steps are included: S2.3.31. If the capacity SOC shows a decreasing trend, then obtain the third target power value P_tag3, that is, P_tag3=P_mid+1 / 2aC; If the SOC (State of Charge) remains unchanged or increases, then the third target power value P_tag3 is kept at the single stack output request power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.32 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag3 = P_load + 1 / 2aC, and then proceed to step S2.3.33; if not, then proceed to step S2.3.33. Where P_load is the load power; S2.3.33, Keep the third target power value P_tag3 in step S2.3.32 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment; Furthermore, in step S2.3, when the capacity SOC is in the low range, the following energy management steps are included: S2.3.41 If the capacity SOC shows a decreasing trend or remains unchanged, then obtain the fourth target power value P_tag4, that is, P_tag4=P_mid+aC; If the SOC of the capacity is increasing, then the fourth target power value P_tag4 is kept as the single stack output request power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.42 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag4 = P_load + 1 / 2aC, and then proceed to step S2.3.43; if not, then proceed to step S2.3.43. Where P_load is the load power; S2.3.43. Keep the fourth target power value P_tag4 in step S2.3.42 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment; S3. Determine the expected total output power P_total of the stack based on the single stack output request power P_req. Then, based on the expected total power P_total, start the first stack and the second stack synchronously or asynchronously to optimize the output power distribution between the first stack and the second stack, thereby achieving stable power output of each stack. Further, in step S3, the expected total output power P_total of the fuel cell stack is determined based on the single fuel cell stack output request power P_req, i.e., P_total = P_sys + P_req; where P_sys is the sum of the power of other BOP auxiliary components such as the sampling blower, air filter, back pressure valve, and DC / DC converter. Furthermore, step S3 also includes the following power allocation optimization step: S3.1 Determine whether the SOC capacity of the lithium battery is greater than the second SOC threshold X2%. If yes, start the high-healthy battery stack and then proceed to step S3.2; if no, start the first and second battery stacks simultaneously and then proceed to step S3.3. Among them, high-healthy fuel cell stacks have better degradation, while low-healthy fuel cell stacks have more severe degradation. The degree of fuel cell degradation can be quantified by monitoring the internal resistance of the fuel cell stack and the voltage under specific operating conditions. S3.2 Determine whether the expected total power output P_total of the battery stack meets the requirements of not exceeding the rated power P of the single battery stack and the discharge power of the lithium battery being less than 3aC. If yes, the expected total power P_total is the single battery stack output request power P_req, and then proceed to step S3.5; if no, start another battery stack, and then proceed to step S3.3. S3.3 The first and second electric stacks are synchronously loaded with the same current slope. If the high-power electric stack is deloaded, the newly started electric stack is loaded until the single-stack output requested power P_req of each electric stack is P_total / 2, that is, the sum of the output power of the first and second electric stacks is equal to the expected total power P_total. Then, the current of the other electric stack is pulled to the same level with the target current of the electric stack with the larger output current. Then, step S3.4 is performed. During this process, the total airflow corresponding to the change in the total output power of the fuel cell stack also needs to be adjusted accordingly. The blower controls the total flow rate. Therefore, the blower can be adjusted in real time according to the existing calibrated relationship between the total output power of the fuel cell stack and the blower speed. After the blower is adjusted to the appropriate position, the back pressure valves K1 and K2 of each branch are adjusted to maintain the pressure difference between P1 and P2, and between P3 and P4. This pressure difference is provided by the fuel cell stack manufacturer. Generally speaking, the fuel cell stack will maintain different pressure differences at different power levels. S3.4 Determine whether the lithium battery capacity SOC meets the requirement of being greater than or equal to the first SOC threshold X1% and the voltage of a single cell of the battery stack is higher than the set value (e.g., the value range is 0.8~0.85). If yes, it means that the lithium battery is in a charging state, and proceed to step S3.5; otherwise, end the process and wait for the next cycle of power allocation optimization. S3.5. Shut down the low-healthy fuel cell stacks, and the system enters single-stack operation, then waits for the next cycle of power allocation optimization; Furthermore, in step S3, when the lithium battery capacity SOC is greater than or equal to the first SOC threshold X1%, the low-health stack is shut down because the stack output power is low at this time. Directly shutting down one of the low-health stacks will not affect the power output. The system enters single-stack operation, and the expected total power P_total is the single-stack output request power P_req of the high-health stack.

[0009] This invention optimizes the auxiliary system control strategy, reduces the use and power proportion of BOP auxiliary components, and optimizes the lithium battery charging and discharging logic, making it more suitable for mild hybrid systems. In terms of fuel cell protection, the optimized multi-machine control logic eliminates the problem of inconsistent fuel cell degradation in traditional multi-machine parallel solutions. Specifically, through step S2, the real-time state of charge (SOC) and dynamic performance (capacity change rate) of the lithium battery are coupled to achieve maximum optimization of the depth and frequency of fuel cell power regulation, while keeping the capacity and power of the lithium battery in the highest efficiency range. This enables precise management of fuel cell power with predictive and adaptive capabilities, effectively improving the efficiency, response speed, and lifespan of the hybrid power system.

[0010] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0011] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for controlling the parallel coordinated load distribution of cathodes in a closed-loop air-cooled dual-reactor configuration, characterized in that: Includes the following steps: S1. Construct a dual-stack fuel cell system, wherein the dual-stack fuel cell system includes a first stack and a second stack connected in parallel, the first stack and the second stack are respectively connected to the lithium battery through corresponding DC / DC converters, and the load is connected to the lithium battery; S2. Based on the changing trends of the lithium battery's charging and discharging power and SOC capacity, determine the single-stack output request power P_req through an energy management strategy; S3. Determine the expected total output power P_total of the stack based on the single stack output request power P_req. Then, based on the expected total power P_total, start the first stack and the second stack synchronously or asynchronously to optimize the output power distribution between the first stack and the second stack, thereby achieving stable power output of each stack. Step S2 further includes the following steps: S2.1 Real-time monitoring of the lithium battery's SOC (State of Charge). The lithium battery is divided into three working zones according to its SOC: a high-capacity zone, a medium-capacity zone, and a low-capacity zone. S2.

2. Based on the SOC region of the lithium battery, trigger the corresponding capacity change trend judgment logic; Among them, the capacity change trend judgment is the dynamic change trend of lithium battery capacity SOC within a preset time window, and the change trend includes rising, falling or remaining unchanged. S2.

3. Based on the corresponding capacity change trend, determine the energy management strategy for the stack power.

2. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 1, characterized in that: The dual-stack fuel cell system also includes an air filter, a blower, a first inlet pressure sensor P1, a first outlet pressure sensor P2, a second inlet pressure sensor P3, a second outlet pressure sensor P4, a first back pressure valve K1, and a second back pressure valve K2; the DC / DC converter is divided into a first DC / DC converter and a second DC / DC converter. Air passes through the air filter and is then connected to the blower. The output of the blower is connected to the inlets of both the first and second fuel cell stacks. The outlet of the first fuel cell stack is connected to the first back pressure valve K1, and the outlet of the second fuel cell stack is connected to the second back pressure valve K2. The first inlet pressure sensor P1 is connected to the connecting pipe between the blower and the first fuel cell stack, and the second inlet pressure sensor P3 is connected to the connecting pipe between the blower and the second fuel cell stack. The first outlet pressure sensor P2 is connected to the connecting pipe between the first fuel cell stack and the first back pressure valve K1, and the second outlet pressure sensor P4 is connected to the connecting pipe between the second fuel cell stack and the second back pressure valve K2.

3. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 2, characterized in that: Trigger the corresponding capacity change trend judgment logic: When the SOC capacity is in the high range, execute the first capacity change trend judgment logic; When the capacity SOC is in the middle range, execute the second or third capacity change trend judgment logic; When the SOC (State of Charge) is in the low range, the fourth logic for judging the capacity change trend is executed.

4. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 3, characterized in that: In said step S2.1, the capacity SOC state is divided into a high region, a middle region and a low region according to a preset first SOC threshold X1%, a second SOC threshold X2%, a third SOC threshold X3% and a fourth SOC threshold X4%, wherein X1>X2>X3>X4; The high region is where the capacity SOC is greater than or equal to X1%; The middle region is where the capacity SOC is between X1% and X4%; The low region is where the capacity SOC is less than or equal to X4%.

5. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 4, characterized in that: In said step S2.2, when the capacity SOC is in the middle region, the capacity SOC is judged again with the second SOC threshold X2% and the third SOC threshold X3%; if X1%>SOC>X2%, it indicates that the capacity SOC is in the upper part of the middle region at this time; if X2%≥SOC≥X3%, it indicates that the capacity SOC is in the middle part of the middle region at this time; if X4%<SOC<X3%, it indicates that the capacity SOC is in the lower part of the middle region at this time.

6. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 4, characterized in that: The first SOC threshold X1% is that the capacity SOC is 75%~95%; The second SOC threshold X2% is that the capacity SOC is 60%~80%; The third SOC threshold X3% is that the capacity SOC is 20%~40%; The fourth SOC threshold X4% is that the capacity SOC is 10%~20%.

7. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 3, characterized in that: In said step S2.3, when the capacity SOC is in the high region, the following energy management steps are included: S2.3.11, if the capacity SOC shows an upward trend, acquire a first target power value P_tag1, that is, P_tag1=P_mid–aC; If the trend of the capacity SOC remains unchanged or decreases, keep the first target power value P_tag1 as the output requested power P_req of the single stack; Wherein, P_mid is the median value of the load power within a set time; a is the step size of power regulation; C is the discharge rate of the lithium battery; S2.3.12, judge whether it is satisfied that the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC, if yes, perform power regulation, that is P_tag1=P_load–1 / 2aC, then proceed to step S2.3.13; if no, proceed to step S2.3.13; Wherein, P_load is the load power; S2.3.13, keep the first target power value P_tag1 in said step S2.3.12 as the current output requested power P_req of the single stack, then wait for the next cycle of energy management regulation.

8. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 5, characterized in that: In said step S2.3, when the capacity SOC is in the upper part of the middle region, the following energy management steps are included: S2.3.21, if the capacity SOC shows an upward trend, acquire a second target power value P_tag2, that is, P_tag2=P_mid+1 / 4aC; If the trend of the capacity SOC remains unchanged or decreases, keep the second target power value P_tag2 as the output requested power P_req of the single stack; Wherein, P_mid is the median value of the load power within a set time; a is the step size of power regulation; C is the discharge rate of the lithium battery; S2.3.22 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag2 = P_load – 1 / 2aC, and then proceed to step S2.3.23; if not, then proceed to step S2.3.

23. Where P_load is the load power; S2.3.

23. Keep the second target power value P_tag2 in step S2.3.22 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment.

9. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 5, characterized in that: In step S2.3, when the capacity SOC is in the lower part of the middle region, the following energy management steps are included: S2.3.

31. If the capacity SOC shows a decreasing trend, then obtain the third target power value P_tag3, that is, P_tag3=P_mid+1 / 2aC; If the SOC (State of Charge) remains unchanged or increases, then the third target power value P_tag3 is kept at the single stack output request power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.32 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag3 = P_load + 1 / 2aC, and then proceed to step S2.3.33; if not, then proceed to step S2.3.

33. Where P_load is the load power; S2.3.

33. Keep the third target power value P_tag3 in step S2.3.32 at the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment.

10. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 3, characterized in that: In step S2.3, when the capacity SOC is in the low range, the following energy management steps are included: S2.3.41 If the capacity SOC shows a decreasing trend or remains unchanged, then obtain the fourth target power value P_tag4, that is, P_tag4=P_mid+aC; If the SOC of the capacity is increasing, then the fourth target power value P_tag4 is kept as the single stack output request power P_req. Where P_mid is the midpoint of the load power within the set time; a is the step size of power adjustment; and C is the lithium battery discharge rate. S2.3.42 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharging power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag4 = P_load + 1 / 2aC, and then proceed to step S2.3.43; if not, then proceed to step S2.3.

43. Where P_load is the load power; S2.3.

43. Keep the fourth target power value P_tag4 in step S2.3.42 as the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment.

11. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 5, characterized in that: In step S2.3, when the capacity SOC is in the middle of the median region, the following energy management steps are included: S2.3.51, Keep the fifth target power value P_tag5 as the single-pile output requested power P_req; S2.3.52 Determine whether the instantaneous charging power of the lithium battery is greater than aC and the discharge power is greater than 3aC. If yes, then perform power adjustment, i.e., P_tag5=P_load, and then proceed to step S2.3.53; if not, then proceed to step S2.3.

53. Where P_load is the load power; S2.3.

53. Keep the fifth target power value P_tag5 in step S2.3.52 as the current single stack output request power P_req, and then wait for the next cycle of energy management adjustment.

12. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 4, characterized in that: In step S3, the expected total output power P_total of the fuel cell stack is determined based on the single fuel cell stack output request power P_req, i.e., P_total = P_sys + P_req; where P_sys is the sum of the power of the sampling blower, air filter, back pressure valve, and DC / DC converter.

13. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 12, characterized in that: Step S3 also includes the following power allocation optimization steps: S3.1 Determine whether the SOC capacity of the lithium battery is greater than the second SOC threshold X2%. If yes, start the high-healthy battery stack and then proceed to step S3.2; if no, start the first and second battery stacks simultaneously and then proceed to step S3.

3. S3.2 Determine whether the expected total power output P_total of the battery stack meets the requirements of not exceeding the rated power P of the single battery stack and the discharge power of the lithium battery being less than 3aC. If yes, the expected total power P_total is the single battery stack output request power P_req, and then proceed to step S3.5; if no, start another battery stack, and then proceed to step S3.

3. S3.3 The first and second electric stacks are synchronously loaded with the same current slope until the single stack output requested power P_req of each electric stack is P_total / 2, that is, the sum of the output power of the first and second electric stacks is equal to the expected total power P_total. Then the load change stops and step S3.4 is performed. S3.4 Determine whether the lithium battery capacity SOC meets the requirement of being greater than or equal to the first SOC threshold X1% and the voltage of a single cell of the battery stack is higher than the set value. If yes, proceed to step S3.5; otherwise, end the process and wait for the next cycle of power allocation optimization. S3.

5. Shut down the low-healthy fuel cell stacks, and the system enters single-stack operation, then waits for the next cycle of power allocation optimization.

14. The cathode closed-loop air-cooled dual-reactor parallel cooperative load distribution control method according to claim 12, characterized in that: In step S3, when the lithium battery capacity SOC is greater than or equal to the first SOC threshold X1%, the low-health stack is shut down and the system enters single-stack operation. The expected total power P_total is the single-stack output request power P_req of the high-health stack.

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