A fuel cell system loading control method

Abstract

The present invention discloses a method for dynamic loading control of a fuel cell system, comprising: obtaining a voltage signal value and a requested power value of an accelerator pedal of a whole vehicle; determining a power loading rate coefficient according to an accelerator pedal voltage feedback signal and a voltage signal change rate; determining a loading rate according to the power loading rate coefficient, and obtaining air flow, air pressure, tail exhaust valve opening time, and reflux pump speed compensation values ​​according to the loading rate and the loading request power; in a dynamic loading process of the fuel cell system, adjusting the air pressure flow, tail exhaust valve opening time, and reflux pump speed in real time according to the compensation values, and performing real-time regulation on a gas shortage phenomenon caused by insufficient reaction gas during the loading process and a flooding phenomenon caused by excessive and untimely drainage of instantaneously generated liquid water, so as to improve the dynamic response characteristics of the fuel cell system.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fuel cell system loading control method. Background Art

[0002] Hydrogen fuel cells are a new type of electrochemical power generation device that can continuously generate electricity as long as the required hydrogen and oxygen are provided. Fuel cell systems have the advantages of high energy conversion efficiency, zero emissions, and no noise. They have good low-temperature starting characteristics at low temperatures and are very suitable for providing power for vehicles. In recent years, the development momentum of fuel cell systems is booming. The main development directions include fuel cell systems for buses, fuel cell systems for heavy trucks, and fuel cell systems for ships. In particular, automotive fuel cell systems have the longest development time. There are already automotive fuel cell systems developed by many companies on the market that are officially in operation. Fuel cell systems have entered a new stage of development.

[0003] However, with the actual application of fuel cell systems, the life decay of fuel cells has become a bottleneck in the development of fuel cell systems. There are many factors that cause the life decay of fuel cells. Among them, the decay rate of fuel cells under different working conditions during the use of fuel cells varies to a certain extent. The working conditions that cause the most serious life decay of fuel cells are the start-stop process and loading process of the fuel cell. Other operating conditions have relatively little effect on the life of the fuel cell.

[0004] In the actual operation of fuel cell vehicles, frequent loading operations are inevitable. When the fuel cell is loaded, if the loading strategy is not set properly, it will cause local hydrogen and oxygen deficiency in the fuel cell, and even cause more serious voltage drop and voltage reversal, thereby causing irreversible damage to the fuel cell catalyst layer, and ultimately leading to the fuel cell life decay. On the other hand, the dynamic response speed of the fuel cell system has always been a very important key indicator of the fuel cell system, which directly affects the acceleration and safety of the vehicle. How to ensure the dynamic performance of the fuel cell and speed up the dynamic response speed of the fuel cell system without causing the fuel cell life decay has always been a technical problem in the fuel cell engine industry.

[0005] At present, the more common solution is to use an extended-range solution to increase the power battery capacity of the vehicle. The power battery provides the power required for the operation of the vehicle, and the fuel cell system charges the power battery under several fixed working conditions most of the time. This solution can effectively avoid the frequent changes in the working conditions of the fuel cell system and improve the stability and service life of the fuel cell system, but the disadvantage is also obvious, that is, the cost of the whole vehicle has increased significantly, which is not conducive to the commercialization of fuel cell vehicles. Another solution is to optimize the control strategy of the fuel cell system, increase the reaction gas pressure and flow rate of the loading condition, and promptly discharge the liquid water generated during the loading process to avoid gas shortage and flooding. This can not only ensure that the fuel cell system can meet the needs of the vehicle's rapid output power, but also avoid irreversible damage to the stack caused by rapid loading.

[0006] There are many factors that affect the dynamic characteristics of the loading process, including loading rate, loading current and amplitude, fuel cell operating temperature, anode and cathode gas pressure, cathode gas flow and humidity, and liquid water distribution, etc. Therefore, the current compensation method of fixed air flow and pressure values ​​cannot meet all conditions. If the influencing factors change, the loading compensation effect will be unsatisfactory.

[0007] The dynamic control methods for fuel cell systems in the prior art generally reduce the loading rate and extend the loading time to ensure that the loading process does not damage the fuel cell, thereby improving the reliability of the fuel cell system, but sacrificing the dynamic performance indicators of the system. In addition, by compensating the flow and pressure of the reaction gas during the loading process, the dynamic performance, stability and reliability of the fuel cell system can be improved to a certain extent. However, this simple quantitative compensation method is too simple and does not have closed-loop monitoring capabilities. If the external environment or the state of the battery and components of the fuel cell system changes, the compensation value will be unreasonable and the loading control effect will deteriorate. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention discloses a method for dynamic loading control of a fuel cell system, which specifically includes the following steps:

[0009] Get the vehicle's accelerator pedal voltage signal value and requested power value;

[0010] Determine the power loading rate coefficient according to the accelerator pedal voltage feedback signal and the voltage signal change rate;

[0011] Determine the loading rate according to the power loading rate coefficient, and obtain the air flow, air pressure, tail exhaust valve opening time and reflux pump speed compensation value according to the loading rate and the loading request power;

[0012] During the dynamic loading process of the fuel cell system, the air flow, air pressure, tail valve opening time and reflux pump speed are adjusted in real time according to the compensation value, and the phenomenon of insufficient reaction gas during the loading process and excessive liquid water generated instantaneously and untimely drainage are controlled in real time to improve the dynamic response characteristics of the fuel cell system.

[0013] The urgency of the vehicle power demand is judged according to the accelerator pedal voltage feedback signal and the voltage signal change rate, and the power loading rate coefficient is determined. The power loading rate coefficient is multiplied by the maximum allowable loading rate of the fuel cell system to obtain the loading rate;

[0014] The air flow compensation status table is queried according to the loading rate and the loading request power. If it is 0, it means that the current air flow compensation value is optimal and there is no need to increase or decrease the compensation value according to the step size. If it is 1, it means that the current air flow compensation value is inappropriate and the air flow compensation value needs to be increased according to the step size. If it is 2, it means that the compensation value needs to be reduced according to the step size. The sum of the basic air flow compensation value and the flow compensation correction value obtained from the table is the actual air flow compensation value for this loading. The air pressure compensation, tail exhaust time compensation and reflux pump speed compensation do not need to be corrected, and the loading process is directly executed according to the basic value in the table. After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are executed according to the comparison result until the optimal air flow compensation value for that point is found.

[0015] The air pressure compensation status table is queried according to the loading rate and the loading request power. If it is 0, it means that the current air pressure compensation value is optimal and there is no need to increase or decrease the compensation value according to the step size. If it is 1, it means that the current air pressure compensation value is inappropriate and the air pressure compensation value needs to be increased according to the step size. If it is 2, it means that the compensation value needs to be reduced according to the step size. The sum of the basic air pressure compensation value and the pressure compensation correction value obtained by looking up the table is the actual air pressure compensation value for this loading. The air flow compensation, tail exhaust time compensation and reflux pump speed compensation do not need to be corrected, and the loading process is directly executed according to the basic value in the table. After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are executed according to the comparison result until the optimal air pressure compensation value for the point is found.

[0016] The tail exhaust time compensation status table is queried according to the loading rate and the loading request power. If it is 0, it means that the current tail exhaust time compensation value is optimal and there is no need to increase or decrease the compensation value according to the step size. If it is 1, it means that the current tail exhaust time compensation value is inappropriate and the compensation value needs to be increased according to the step size. If it is 2, it means that the compensation value needs to be reduced according to the step size. The sum of the tail exhaust time basic compensation value and the tail exhaust time compensation correction value obtained by looking up the table is the actual compensation value of the tail exhaust time for this loading. The air flow compensation, air pressure compensation and reflux pump speed compensation do not need to be corrected, and the loading process is directly executed according to the basic value in the table. After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are executed according to the comparison result until the optimal tail exhaust time compensation value for the point is found.

[0017] The reflux pump speed compensation status table is queried according to the loading rate and the loading request power. If it is 0, it means that the current reflux pump speed compensation value is optimal and there is no need to increase or decrease the compensation value according to the step size. If it is 1, it means that the current reflux pump speed compensation value is inappropriate and the compensation value needs to be increased according to the step size. If it is 2, it means that the compensation value needs to be reduced according to the step size. The sum of the basic compensation value of the reflux pump speed and the correction value of the reflux pump speed compensation obtained by looking up the table is the actual compensation value of the reflux pump speed for this loading. The air flow compensation, air pressure compensation and tail exhaust time compensation do not need to be corrected, and the loading process is directly executed according to the basic value in the table. After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are executed according to the comparison result until the optimal reflux pump speed compensation value for this point is found.

[0018] When external conditions change or the state of the battery stack changes, if the original compensation value does not meet the requirements, the feedback value of the monitoring evaluation index is used to determine whether the compensation value meets the requirements. If it does not meet the requirements, the compensation value is corrected and adjusted.

[0019] When determining the power loading rate coefficient, the horizontal axis of the loading rate coefficient table is the accelerator pedal voltage amplitude, and the vertical axis is the accelerator pedal voltage signal change rate.

[0020] During the dynamic loading process of the fuel cell system: compensation is performed on the air flow, air pressure, tail valve opening time and reflux pump speed, wherein the compensation value includes a basic compensation value and a modified compensation value. The basic compensation value is obtained by looking up the table based on the loading rate and the loading target power, and the modified compensation value is obtained by adjusting the loading target feedback value.

[0021] According to the fuel cell loading characteristics, the loading voltage is lowered to the amplitude V f , battery mean square error S and lower range R are used as evaluation indicators for evaluating fuel cell loading performance.

[0022] Whether the air flow compensation value needs to be corrected is determined according to the corresponding evaluation index value during the loading process. If correction is required, positive correction or reverse correction is performed according to the step size until the optimal air flow compensation value is found; the same processing method is used when correcting the air pressure compensation value, the tail exhaust valve opening time compensation value and the reflux pump speed compensation value.

[0023] Due to the adoption of the above technical solution, the present invention provides a method for dynamic loading control of a fuel cell system. The method uses a method of adjusting the air flow, air pressure, tail valve opening time and reflux pump speed during the loading process to increase the flow and pressure of the reaction gas during the loading process, solve the problem of local gas shortage caused by the uniform distribution of the reaction gas, increase the tail valve start time to improve the drainage capacity of the fuel cell during the loading process, and solve the problem of excessive liquid water generation at the moment of loading and untimely drainage causing local flooding. In addition, the compensation values ​​of the air flow, air pressure, tail valve opening time and reflux pump speed during the loading process are self-learned and corrected to ensure that the fuel cell system dynamically adjusts the above compensation values ​​when its own performance changes or the external environment changes, so that it can meet the loading requirements and improve the dynamic loading performance and service life of the system.

[0024] This method also determines the driver's intention based on the amplitude of the accelerator pedal feedback voltage signal and the signal change rate, quantifies the urgency of the vehicle's power demand, and then dynamically adjusts the fuel cell system loading rate. This can not only meet the driver's needs and ensure the drivability and safety of the vehicle, but also slow down the loading rate when emergency loading is unnecessary, minimize the performance degradation of the fuel cell caused by emergency loading, and extend the service life of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a specific flow chart of the dynamic loading control method of the fuel cell system in the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention:

[0028] like Figure 1A flow chart of a dynamic loading control method for a fuel cell system is shown, which is used to improve the dynamic performance of fuel cells and increase the service life of fuel cells. The control process includes: obtaining the accelerator pedal voltage signal value and the requested power value of the whole vehicle, determining the power loading rate coefficient according to the accelerator pedal voltage feedback signal and the voltage signal change rate, and determining the loading rate according to the power loading coefficient. According to the loading rate and the loading request power, the air flow, air pressure, tail exhaust valve opening time and reflux pump speed compensation values ​​are obtained. During the loading process, the air pressure flow, tail exhaust valve opening time and reflux pump speed are adjusted in time according to the compensation values, and the control is closed in the loop to solve the problem of insufficient reaction gas during the loading process, and excessive liquid water is generated instantly and the drainage is not timely. Improve the dynamic response characteristics and stability of the system and extend the service life of the system.

[0029] The specific control steps are as follows:

[0030] First, the fuel cell system is tested under standard environmental conditions (on the system bench) for the best air flow compensation value under different loading rates and target power conditions, as well as the best air pressure compensation value, tail valve opening time compensation value and best reflux pump speed compensation value, and the initial data calibration of the air flow, air pressure, tail valve opening time and reflux pump speed compensation table is completed. At the same time, the S value, R value, V f value, complete the loading evaluation index S value table, R value table and V f Each compensation table and evaluation index table is automatically maintained when the system is running.

[0031] This patent evaluates the dynamic performance of the fuel cell system loading mainly using the battery voltage undershoot amplitude V f , the standard deviation S and lower range R of the battery are defined as follows:

[0032] The battery voltage undershoot amplitude is expressed as:

[0033] V f =V s One V l

[0034] Where V f is the battery voltage undershoot amplitude; V s is the voltage stability value after loading; V l It is the minimum value of the loading voltage undershoot.

[0035] The battery standard deviation is expressed as:

[0036]

[0037] Where S is the standard deviation of the voltage of each battery; n is the number of cells in the battery stack; u i is the output voltage of the single cell in section i; It is the average voltage of all cells in the stack.

[0038] The battery lower range is expressed as:

[0039]

[0040] Where R is the lower range; is the average voltage of all cells in the stack; u min is the lowest single cell voltage.

[0041] In the vehicle operation scenario, the accelerator pedal voltage feedback signal and the vehicle power request value are obtained, and the loading rate coefficient is determined according to the accelerator pedal voltage signal change rate and the feedback amplitude. The horizontal axis of the loading rate coefficient table is the accelerator pedal voltage amplitude, and the vertical axis is the accelerator pedal voltage signal change rate.

[0042] The loading rate is determined according to the loading rate coefficient, and the loading rate is the product of the loading rate coefficient and the maximum allowable loading rate of the system.

[0043] According to the loading rate and the power request value, the air flow compensation table, the air pressure compensation table, the tail exhaust valve opening time compensation table, and the reflux pump speed compensation table are checked; the air flow compensation basic value, the air pressure compensation basic value, the tail exhaust valve opening time compensation basic value, and the reflux pump speed compensation basic value are obtained.

[0044] During the dynamic loading process of the fuel cell system, the air pressure and flow, tail valve opening time and reflux pump speed are adjusted in real time according to the compensation value, and the insufficient reaction gas pressure and flow, and the instantaneous excessive liquid water generated during the dynamic loading process and the untimely drainage are regulated in real time to improve the dynamic response characteristics of the fuel cell system.

[0045] The compensation status table of air flow, air flow, tail valve opening time and reflux pump speed indicates the effective status of the compensation value, providing a basis for how to correct the compensation value when loading next time. The program will automatically maintain the table when it is running, and the initial value can be set to 0.

[0046] The urgency of the vehicle power demand is judged according to the accelerator pedal voltage feedback signal and the voltage signal change rate, and the loading rate coefficient is determined, the value range is between 0 and 1, and the power loading coefficient is multiplied by the maximum allowable loading rate of the fuel cell system to obtain the loading rate;

[0047] S100, query the air flow compensation state table according to the loading rate and the loading request power. If the table value is 0, it means that the current air flow compensation value is appropriate and there is no need to increase or decrease the compensation value. Then, execute S200.

[0048] S110, if the table value is not 0, it means that the current compensation gas volume value is inappropriate and the flow rate needs to be increased or decreased for compensation correction.

[0049] S120, if the table value is 1, it means that the flow compensation value needs to be increased, and if it is 2, it means that the flow compensation value needs to be decreased, and the flow correction step length of increase or decrease is 1, that is, each increase or decrease is 1g / s. The actual compensation value of the air flow rate loaded this time is obtained by adding or subtracting the flow correction step length from the basic compensation value of the air flow rate; the flow correction step length can be adjusted according to the actual situation.

[0050] S130, there is no need to judge whether the air pressure compensation, tail exhaust time compensation and reflux pump speed compensation need to be corrected. The compensation value is directly given according to the table value. The air flow is compensated according to the actual compensation value obtained in step S120, and the loading process is executed.

[0051] S140, after the loading process is completed, the loading process is evaluated, and the battery voltage standard deviation S value of this loading process is compared with the S value in the table according to the loading rate and the loading request power.

[0052] If the S value is smaller than the S value in the table, it is considered that the current compensation is effective and there is room for optimization. The compensation value should be increased or decreased in the same direction. S150 is executed to update the air flow compensation table to the current compensation value and the S table to the current S value. S160 is executed to update the air flow compensation state table. If the compensation value is increased this time, the compensation will continue to be increased next time, and the air flow compensation state table is set to 1; if the compensation value is reduced this time, the compensation will continue to be reduced next time, and the air flow compensation state table is set to 2; until the S value is equal to the S value in the table.

[0053] If the standard deviation S value is equal to the table lookup S value, and the current compensation direction is the same as the previous compensation direction, it is considered that the current correction is invalid and the next correction should be made in the opposite direction. Execute S160 and update the air flow compensation status table to 1 or 2.

[0054] If the standard deviation S value is equal to the table lookup S value, and the current compensation direction is opposite to the previous compensation direction, it is considered that the previous compensation was very appropriate and there is no need to correct the compensation value. S160 is executed to update the air flow compensation status table to 0.

[0055] If the standard deviation S value is larger than the S value in the table, and the current compensation direction is the same as the previous compensation direction, it means that the current air flow is over-compensated and should be corrected in the opposite direction next time. Execute S160 and update the air flow compensation status table to 1 or 2.

[0056] If the standard deviation S value is larger than the S value in the table, and the current compensation is in the opposite direction to the previous compensation, it means that the forward and reverse compensation effects are not ideal. The original state can be maintained, and S160 is executed to update the air flow compensation state table to 0.

[0057] Further, the air flow compensation state table is queried according to the loading rate and the loading request power. If the table value is 0, it means that the current air flow compensation value is appropriate, and then S200 is executed.

[0058] S200, query the air pressure compensation state table according to the loading rate and the loading request power. If the table value is 0, it means that the current air pressure compensation value is appropriate and there is no need to increase or decrease the compensation value. Then, S300 is executed.

[0059] S210: If the table value is not 0, it means that the current compensation gas volume value is inappropriate and the flow rate needs to be increased or decreased for compensation correction.

[0060] S220, if the table value is 1, it means that the pressure compensation value needs to be increased, and if it is 2, it means that the pressure compensation value needs to be decreased, and the pressure correction step length of increase or decrease is 1Kpa, that is, increase or decrease 1Kpa each time. The actual compensation value of the air pressure for this loading is obtained by adding or subtracting the pressure correction step length from the basic air pressure compensation value; the pressure correction step length can be appropriately adjusted according to the change in the rated power of the system.

[0061] S230: air flow compensation, tail exhaust time compensation and reflux pump speed compensation do not need to be judged whether they need to be corrected, and are directly compensated according to the table value. The air pressure is compensated according to the actual compensation value obtained in step S220, and the loading process is executed.

[0062] S240, after the loading process is completed, the loading process is evaluated, and the battery voltage drop amplitude V f According to the loading rate and loading request power, V f The values ​​are compared.

[0063] If V f Value comparison table V f If the value is small, it is considered that the current compensation is effective and there is still room for optimization. The compensation value should be increased or decreased in the same direction. S250 is executed to update the air pressure compensation table to the current compensation value and update V f The table is V f Execute S260, update the air pressure compensation status table, if the compensation value is increased this time, the compensation will continue to increase next time, and the air pressure compensation status table is set to 1; if the compensation value is reduced this time, the compensation will continue to decrease next time, and the air pressure compensation status table is set to 2; until V f Value and Lookup Table V f Until the value remains the same.

[0064] If V f Value and Lookup Table V fIf the values ​​are the same and the current compensation direction is the same as the previous compensation direction, the current correction is considered invalid and the next time correction should be made in the opposite direction. S260 is executed to update the air pressure compensation status table to 1 or 2.

[0065] If V f Value and Lookup Table V f If the values ​​are the same and the current compensation direction is opposite to the previous compensation direction, it is considered that the previous compensation was very appropriate and there is no need to correct the compensation value. S260 is executed to update the air pressure compensation state table to 0.

[0066] If V f Value comparison table V f If the value is large and the current compensation direction is the same as the previous compensation direction, it means that the current air pressure is over-compensated and should be corrected in the opposite direction next time. Execute S260 and update the air pressure compensation status table to 1 or 2.

[0067] If V f Value comparison table V f If the value is large and the current compensation is in the opposite direction to the previous compensation, it means that the forward and reverse compensation effects are not ideal. Just keep the original state and execute S260 to update the air pressure compensation state table to 0.

[0068] Further, the air flow compensation state table and the air pressure compensation state table are queried according to the loading rate and the loading request power. If the table values ​​are all 0, it means that the current air flow and pressure compensation values ​​are appropriate, and then S300 is executed.

[0069] S300, querying the tail-row time compensation state table according to the loading rate and the loading request power, if the table value is 0, it means that the current tail-row time compensation value is appropriate, and there is no need to increase or decrease the compensation value, then executing S400.

[0070] If the table lookup value is not 0, S310 is executed, indicating that the current tail exhaust time compensation value is inappropriate and the tail exhaust time needs to be increased or decreased for compensation correction.

[0071] S320, if the table value is 1, it means that the tail exhaust time compensation value needs to be increased, and 2 means that the tail exhaust time compensation value needs to be decreased, and the time correction step of increase or decrease is 0.1s, that is, the tail exhaust opening time increases or decreases by 0.1s. The actual compensation value of the tail exhaust time for this loading is obtained by adding or subtracting the time correction step from the tail exhaust time basic compensation value; the tail exhaust time correction step can be appropriately adjusted according to the change in the rated power of the system.

[0072] S330: There is no need to judge whether the air flow compensation, air pressure compensation and reflux pump speed compensation need to be corrected. Compensation can be performed by directly looking up the table. The tail exhaust time is compensated according to the actual compensation value obtained in step S320, and the loading process is executed.

[0073] S340, after the loading process is completed, the loading process is evaluated, and the battery lower range R of this loading process is compared with the R value in the table according to the loading rate and the loading request power.

[0074] If the R value is smaller than the R value in the table, it is considered that the current compensation is effective and there is room for optimization. The compensation value should be increased or decreased in the same direction. S350 is executed to update the tail-displacement time compensation table to the current compensation value and the R table to the current R value. S360 is executed to update the tail-displacement time compensation status table. If the compensation value is increased this time, the compensation will continue to be increased next time, and the tail-displacement time compensation status table is set to 1; if the compensation value is reduced this time, the compensation will continue to be reduced next time, and the tail-displacement time compensation status table is set to 2; until the R value is equal to the R value in the table.

[0075] If the R value is equal to the R value in the table, and the current compensation direction is the same as the previous compensation direction, it is considered that the current correction is invalid and the next correction should be made in the opposite direction. S360 is executed to update the tail exhaust time compensation status table to 1 or 2.

[0076] If the R value is equal to the R value in the table, and the current compensation direction is opposite to the previous compensation direction, it is considered that the previous compensation was very appropriate and there is no need to correct the compensation value. S360 is executed to update the tail-displacement time compensation status table to 0.

[0077] If the R value is larger than the R value in the table, and the current compensation direction is the same as the previous compensation direction, it means that the current tail exhaust time compensation is over-compensated and the next time it should be corrected in the opposite direction. Execute S360 and update the tail exhaust time compensation status table to 1 or 2.

[0078] If the R value is larger than the R value in the table, and the current compensation is in the opposite direction to the previous compensation, it means that the forward and reverse compensation effects are not ideal. The original state can be maintained, and S360 is executed to update the tail exhaust time compensation state table to 0.

[0079] Furthermore, the air flow compensation status table, air pressure compensation status table and tail exhaust time compensation status table are queried according to the loading rate and the loading request power. If the table values ​​are all 0, it means that the current air flow, pressure and tail exhaust time compensation values ​​do not need to be corrected, and then S400 is executed.

[0080] S400, query the reflux pump speed compensation state table according to the loading rate and the loading request power. If the table value is 0, it means that the current reflux pump speed compensation value is appropriate and there is no need to increase or decrease the compensation value. Then execute S500.

[0081] If the table lookup value is not 0, S410 is executed, indicating that the current reflux pump speed compensation value is inappropriate and the speed needs to be increased or decreased for compensation correction.

[0082] S420, if the table value is 1, it means that the speed compensation value needs to be increased, and 2, it means that the speed compensation value needs to be decreased, and the speed correction step length of increase or decrease is 300rpm, that is, the speed is increased or decreased by 300rpm each time. The actual compensation value of the speed of the reflux pump for this loading is obtained by adding or subtracting the speed correction step length of the reflux pump from the basic compensation value of the speed of the reflux pump; the speed correction step length of the reflux pump can be appropriately adjusted according to the change of the rated power of the system.

[0083] S430: air flow compensation, air pressure compensation and tail exhaust time compensation do not need to be judged whether they need to be corrected, and are directly given according to the table value. The reflux pump speed compensation is compensated according to the actual compensation value obtained in step S320, and the loading process is executed.

[0084] S440, after the loading process is completed, the loading process is evaluated, and the standard deviation S value of the current loading voltage is compared with the S value in the table.

[0085] If the S value is smaller than the S value in the table, it is considered that the current compensation is effective and there is room for optimization. The compensation value should be increased or decreased in the same direction. S450 is executed to update the reflux pump speed compensation table to the current compensation value and the S table to the current S value. S460 is executed to update the reflux pump speed compensation state table. If the compensation value is increased this time, the compensation will continue to be increased next time, and the reflux pump speed compensation state table is set to 1; if the compensation value is reduced this time, the compensation will continue to be reduced next time, and the reflux pump speed compensation state table is set to 2; until the S value is equal to the S value in the table.

[0086] If the S value is equal to the S value in the table, and the current compensation direction is the same as the previous compensation direction, the current correction is considered invalid and the next correction should be made in the opposite direction. Execute S460 and update the reflux pump speed compensation status table to 1 or 2.

[0087] If the S value is equal to the S value in the table, and the current compensation direction is opposite to the previous compensation direction, it is considered that the previous compensation was very appropriate and there is no need to correct the compensation value. S460 is executed to update the reflux pump speed compensation status table to 0.

[0088] If the S value is larger than the S value in the table, and the current compensation direction is the same as the previous compensation direction, it means that the current reflux pump speed compensation is over-compensated and should be corrected in the opposite direction next time. Execute S460 and update the reflux pump speed compensation status table to 1 or 2.

[0089] If the S value is larger than the S value in the table, and the current compensation is in the opposite direction to the previous compensation, it means that the forward and reverse compensation effects are not ideal. Just keep the original state and execute S460 to update the reflux pump speed compensation state table to 0.

[0090] Furthermore, the air flow compensation status table, air pressure compensation status table, tail exhaust time compensation status table and reflux pump speed compensation status table are queried according to the loading rate and the loading request power. If the table values ​​are all 0, it means that the current air flow, air pressure, tail exhaust time and reflux pump speed compensation values ​​do not need to be corrected. Simply look up the table to obtain the basic compensation value for compensation, execute S500, and execute the loading process.

[0091] S510, after the loading process is completed, the loading process indicator V f , S, and R are evaluated and compared with the corresponding table values. If the three indicators are equal, the current cycle is exited. If not, S520 is executed.

[0092] If this load V f Value greater than or less than the lookup table V f value, then update V f The table value is V f If the S value of this loading is greater than or less than the S value in the table, the S table value is updated to be the S value of this time, the air flow compensation state table and the return pump speed compensation state table are updated to be set to 1, and the air flow and return pump speed compensation values ​​are optimized for the next loading; if the R value of this loading is greater than or less than the R value in the table, the R table value is updated to be the R value of this time, the tail exhaust time compensation state table is updated to be set to 1, and the tail exhaust time compensation value is optimized for the next loading. After executing S520, exit this loop.

[0093] Repeated polling and confirmation of the above process ensures that the air flow, air pressure, tail valve opening time and reflux pump speed compensation value are always in the optimal state during loading, ensuring the dynamic loading effect of the system.

[0094] Furthermore, when external conditions change or the state of the battery stack changes, if the original compensation value does not meet the requirements, the feedback value of the monitoring evaluation index is used to determine whether the compensation value meets the requirements. If it does not meet the requirements, the compensation value is corrected and adjusted.

[0095] Furthermore, during the dynamic loading process of the fuel cell system: compensation is performed on the air flow, air pressure, tail valve opening time and reflux pump speed, wherein the compensation value includes a basic compensation value and a corrected compensation value, the basic compensation value is obtained by looking up the table based on the loading rate and the loading target power, and the corrected compensation value is obtained by judging and adjusting the feedback value of the loading evaluation index.

[0096] Furthermore, according to the fuel cell loading characteristics, the loading voltage is lowered to a value V f , battery mean square error S and lower range R are used as evaluation indicators for evaluating fuel cell loading performance.

[0097] Furthermore, it is determined whether the air flow compensation value needs to be corrected according to the corresponding evaluation index value during the loading process. If correction is required, positive correction or reverse correction is performed according to the step size until the optimal air flow compensation value is found; the same processing method is used when correcting the air pressure compensation value, the tail exhaust valve opening time compensation value and the reflux pump speed compensation value.

[0098] The present invention discloses a dynamic loading control method for a fuel cell system. In this method, a dynamic loading rate and a dynamic compensation method are adopted, which can meet the performance indicators to the greatest extent possible, improve the system life, reduce the power loss of the system BOP components, make the loading control compensation more accurate, avoid over-compensation or under-compensation, and improve the system efficiency.

[0099] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A fuel cell system dynamic loading control method, characterized in that include: Get the vehicle's accelerator pedal voltage signal value and requested power value; Determine the power loading rate coefficient according to the accelerator pedal voltage feedback signal and the voltage signal change rate; Determine the loading rate according to the power loading rate coefficient, and obtain the air flow, air pressure, tail exhaust valve opening time and reflux pump speed compensation value according to the loading rate and the loading request power; During the dynamic loading process of the fuel cell system, the air flow, air pressure, tail valve opening time and reflux pump speed are adjusted in real time according to the compensation value, and the insufficient reaction gas in the loading process, excessive liquid water generated instantaneously and the untimely drainage are regulated in real time to improve the dynamic response characteristics of the fuel cell system.

2. A fuel cell system dynamic loading control method according to claim 1, characterized in that: The urgency of the vehicle power demand is judged according to the accelerator pedal voltage feedback signal and the voltage signal change rate, and the power loading rate coefficient is determined. The power loading rate coefficient is multiplied by the maximum allowable loading rate of the fuel cell system to obtain the loading rate; Query the air flow compensation status table according to the loading rate and loading request power. If it is 0, it means that the current air flow compensation value is optimal and there is no need to increase or decrease the compensation value according to the step length. If it is 1, it means that the current air flow compensation value is not appropriate and the air flow compensation value needs to be increased according to the step length. If it is 2, it means that the compensation value needs to be decreased according to the step length. The sum of the basic air flow compensation value and the flow compensation correction value obtained by looking up the table is the actual air flow compensation value for this loading. The air pressure compensation, tail exhaust time compensation and reflux pump speed compensation do not need to be corrected, and the loading process is directly executed according to the basic value of the table. After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are performed according to the comparison result until the optimal air flow compensation value at that point is found.

3. A fuel cell system dynamic loading control method according to claim 1, characterized in that: Query the air pressure compensation status table according to the loading rate and loading request power. If it is 0, it means that the current air pressure compensation value is optimal and there is no need to increase or decrease the compensation value according to the step length. If it is 1, it means that the current air pressure compensation value is not appropriate and the air pressure compensation value needs to be increased according to the step length. If it is 2, it means that the compensation value needs to be decreased according to the step length. The sum of the basic air pressure compensation value and the pressure compensation correction value obtained by looking up the table is the actual air pressure compensation value for this loading. The air flow compensation, tail exhaust time compensation and reflux pump speed compensation do not need to be corrected, and the loading process is directly executed according to the basic value in the table. After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are performed according to the comparison result until the optimal air pressure compensation value of the point is found.

4. A fuel cell system dynamic loading control method according to claim 1, characterized in that: Query the tail row time compensation status table according to the loading rate and loading request power. If it is 0, it means that the current tail row time compensation value is optimal and there is no need to increase or decrease the compensation value according to the step length. If it is 1, it means that the current tail row time compensation value is not appropriate and the compensation value needs to be increased according to the step length. If it is 2, it means that the compensation value needs to be decreased according to the step length. The sum of the tail row time basic compensation value and the tail row time compensation correction value obtained by querying the table is the actual tail row time compensation value for this loading. Air flow compensation, air pressure compensation and reflux pump speed compensation do not need to be corrected, and the loading process is directly executed according to the basic value of the table lookup; After the loading process is completed, the loading process evaluation index is compared with the table value, and different processing steps are performed according to the comparison result until the optimal tail discharge time compensation value of the point is found.

5. A fuel cell system dynamic loading control method according to claim 1, characterized in that: Query the reflux pump speed compensation status table according to the loading rate and loading request power. If it is 0, it means that the current reflux pump speed compensation value is optimal and there is no need to increase or decrease the compensation value according to the step length. If it is 1, it means that the current reflux pump speed compensation value is not appropriate and the compensation value needs to be increased according to the step length. If it is 2, it means that the compensation value needs to be decreased according to the step length. The sum of the reflux pump speed basic compensation value and the reflux pump speed compensation correction value obtained by looking up the table is the actual compensation value of the reflux pump speed for this loading. The air flow compensation, air pressure compensation and tail exhaust time compensation do not need to be corrected, and the loading process is directly executed according to the basic value in the table. After the loading process is completed, the evaluation index of the loading process is compared with the previous one, and different processing steps are performed according to the comparison results until the optimal reflux pump speed compensation value at that point is found.

6. A fuel cell system dynamic loading control method according to any one of claims 1 to 5, characterized in that: When external conditions change or the state of the battery stack changes, if the original compensation value does not meet the requirements, the feedback value of the monitoring evaluation index is used to determine whether the compensation value meets the requirements. If it does not meet the requirements, the compensation value is corrected and adjusted.

7. A fuel cell system dynamic loading control method according to claim 6, characterized in that: When determining the power loading rate coefficient, the horizontal axis of the loading rate coefficient table is the accelerator pedal voltage amplitude, and the vertical axis is the accelerator pedal voltage signal change rate.

8. A fuel cell system dynamic loading control method according to claim 7, characterized in that: During the dynamic loading process of the fuel cell system: compensation is performed on the air flow, air pressure, tail valve opening time and reflux pump speed, wherein the compensation value includes a basic compensation value and a modified compensation value. The basic compensation value is obtained by looking up the table based on the loading rate and the loading target power, and the modified compensation value is obtained by adjusting the loading target feedback value.

9. A fuel cell system dynamic loading control method according to claim 8, characterized in that: According to the fuel cell loading characteristics, the loading voltage is lowered to the amplitude V f , battery mean square error S and lower range R are used as evaluation indicators for evaluating fuel cell loading performance.

10. A fuel cell system dynamic loading control method according to claim 9, characterized in that: According to the value of the mean square error S of the battery cells during the evaluation loading process, it is determined whether the air flow compensation value needs to be corrected. If correction is required, a positive correction or a reverse correction is performed according to the step size until the optimal air flow compensation value is found; according to the voltage drop amplitude V during the evaluation loading process f , determine whether the air pressure compensation value needs to be corrected; determine whether the tail valve opening time compensation value needs to be corrected according to the value of the lower range R during the evaluation loading process; determine whether the reflux pump speed compensation value needs to be corrected according to the value of the battery mean square error S during the evaluation loading process. The correction method for the air pressure, tail valve opening time and reflux pump speed compensation values ​​is the same as the air flow compensation value correction method.

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