Method and system for controlling output current of fuel cell

Abstract

The invention discloses a control method and system for output current of a fuel cell. The method includes: determining total power required to be output by a fuel cell; after the total current required by the DCDC high-voltage side is determined, the difference value between the total current and the actual current value output by the DCDC high-voltage side is calculated, and after the difference value is compared with the maximum allowable current difference value of the DCDC high-voltage side, the target output current of the DCDC low-voltage side is adjusted; comparing the target output current of the DCDC low-voltage side after each adjustment with the maximum allowable current of the DCDC low-voltage side, and taking the minimum value of the two as a new target output current of the DCDC low-voltage side; and calculating a difference value between the target output current of the DCDC low-voltage side and the actual current value of the low-voltage side, comparing the difference value with a current threshold value, and controlling the adjustment process of the target output current of the DCDC low-voltage side according to a comparison result. The current can be accurately set for a long time, and the power requirement of the whole vehicle is met on the premise that reliable and safe operation of the fuel cell is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fuel cell, and particularly relates to a control method and system of fuel cell output current. BACKGROUND

[0002] Fuel cell needs to respond to the power request of the whole vehicle during operation. At present, the main logic on the vehicle is that the whole vehicle sends a power request or a current request. After receiving the power request, the fuel cell system obtains the current of the corresponding point according to the polarization curve measured previously, and then adjusts the current in combination with the efficiency of the DC system. The current is the set current of the low-voltage side of the fuel cell. After the current is set, the flow and pressure are responded according to the value. Since the current value is taken from the polarization curve, it is relatively accurate in the early stage of operation. However, in the middle and late stages of fuel cell operation, the materials inside the fuel cell are affected by the environment such as long-time work, high temperature and high humidity, and phenomena such as aging and corrosion occur, resulting in performance degradation.

[0003] Due to performance degradation, the polarization curve measured in the early stage will change, and the efficiency of the DCDC converter will change with time and temperature, which will significantly affect the efficiency of the DCDC converter. Therefore, the open-loop method of directly looking up the table to obtain the low-voltage side current will become less and less accurate over time.

[0004] To help understanding, the polarization curve of the fuel cell is a curve describing the relationship between the output voltage of the fuel cell and the current density, reflecting the performance of the fuel cell under different working conditions. For example, if the polarization curve is measured, when the current is 110A, the average voltage of the single cell is 0.727. If the vehicle is set to 80kw, and the efficiency of the DCDC converter is 100%, the current of 110A can meet the power demand of the vehicle.

[0005] According to the polarization curve test, only the target output current of 110A needs to be set to meet the power demand of the vehicle. However, with the aging and performance degradation of the fuel cell, the overall characteristics of the fuel cell are that the greater the current, the lower the single cell voltage. The average voltage of the single cell corresponding to 110A has drifted to 0.7V. If the current is still set to 110A, the actual power is only 77kw, which cannot meet the demand of 80kw of the system. Therefore, this method is not suitable. Long-term use will greatly affect the driving experience and even safety.

[0006] Therefore, the present application provides a control method and system of fuel cell output current. SUMMARY

[0007] The present invention aims to overcome the shortcomings of the prior art and proposes a method and system for controlling the output current of a fuel cell, so as to achieve the following objectives: to accurately set the current for a long time, and to meet the power requirements of the whole vehicle while ensuring the reliable and safe operation of the fuel cell.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a method for controlling the output current of a fuel cell, the method comprising the following steps:

[0009] Step S1: Confirm the total power P that the fuel cell needs to output. 总 ;

[0010] Step S2: Based on the total power P 总 Determine the total current I required on the high-voltage side of the DC-DC converter. 总 It also monitors the actual current value I0 output from the high-voltage side of the DC-DC converter in real time and calculates the total current I. 总 The difference between I and the actual current value I0 delta1 ;

[0011] Step S3: Convert the difference I delta1 The difference between the preset maximum allowable current on the high-voltage side of the DC-DC converter and the current I is... Diff The comparison was performed, and the fuel cell current was applied in step I by superimposing the output values. Step Adjust the target output current on the low-voltage side of the DC-DC converter;

[0012] Step S4: Compare the adjusted target output current on the low-voltage side of the DC-DC converter with the preset maximum allowable current I on the low-voltage side of the DC-DC converter. m The two values ​​are compared, and the minimum value is taken as the corresponding target output current I on the low-voltage side of the DC-DC converter. n ;

[0013] Step S5: Monitor the actual current value I1 of the current DC-DC low-voltage side output in real time, and calculate the target output current I of the DC-DC low-voltage side. n The difference between I1 and the actual current value delta2 and the difference I delta2 With the preset current threshold I k The comparison is performed, and the adjustment process of the target output current on the low-voltage side of the DC-DC converter is controlled based on the corresponding comparison results.

[0014] Preferably, in step S1, the fuel cell needs to output a total power P. 总 Power required for the whole vehicle P Veh Total power consumed by fuel cell system accessories P AUX sum.

[0015] Preferably, the fuel cell system accessories include air compressor, circulation pump, water pump, PTC heater, and the corresponding fuel cell system accessories consume total power P AUX = P ACP + P ARB + P CWP + P PTC .

[0016] Preferably, the total power P 总 required to be output by the fuel cell is compared with the preset maximum allowable output power P alow of the fuel cell, and the minimum value is taken as the new total power P 总 required to be output by the fuel cell.

[0017] Preferably, the preset maximum allowable output power P alow of the fuel cell is related to the fuel cell system fault level.

[0018] Preferably, the fuel cell system fault level is divided into four levels according to the fault severity, wherein, in the first level fault, the power is not limited; in the second level fault, the current allowable output power is limited to 75% of the rated power; in the third level fault, the maximum current allowable output power is limited to 50% of the rated power; and in the fourth level fault, the fuel cell no longer responds to the external power request.

[0019] Preferably, in the step S3:

[0020] If I delta1 > I Diff > 0, the fuel cell current loading step I Step is set to a positive value and is continuously superimposed on the DCDC low-voltage side target output current until 0 < I delta1 < I Diff. .

[0021] If I delta1 < 0 and |I delta1 | > I Diff , the fuel cell current loading step I Step is set to a negative value and is continuously superimposed on the DCDC low-voltage side target output current until I delta1 < 0 and |I delta1 | < I Diff .

[0022] Preferably, the fuel cell current loading step I Step is compared with the preset maximum allowable loading step, and the absolute value of the smaller one is taken as the new fuel cell current loading step I Step .

[0023] Preferably, in the step S5:

[0024] If I delta2 > 0, control the DCDC low-voltage side target output current to stop superimposing the fuel cell current loading step I k , until 0 < I Step , resume superimposition. delta2 k If I delta2 < 0 and |I delta2 | > I k , control the DCDC low-voltage side target output current to stop superimposing the fuel cell current loading step I Step , until I delta2 < 0 and |I delta2 | < I Diff , resume superimposition.

[0025] If I delta2 < 0 and |I delta2 | > I k , control the DCDC low-voltage side target output current to stop superimposing the fuel cell current loading step I Step , until I delta2 < 0 and |I delta2 | < I Diff , resume superimposition.

[0026] The application also proposes a fuel cell output current control system using the above-mentioned fuel cell output current control method, the system comprising a vehicle controller, a fuel cell, a battery management system, a fuel cell system accessory, and a DCDC converter, wherein the battery management system is in communication connection with the vehicle controller and the fuel cell system accessory respectively; the fuel cell output end is connected to the low-voltage side of the DCDC converter, and the high-voltage side of the DCDC converter is connected in parallel to the vehicle power grid.

[0027] The vehicle controller is used to send a vehicle demand power request to the battery management system.

[0028] The battery management system is used to determine the DCDC low-voltage side target output current according to the fuel cell output current control method of any one of claims 1-9 after receiving the vehicle demand power request.

[0029] The technical effects of the application are:

[0030] The application calculates the difference I delta1 between the high-voltage side demand current and the actual current in real time, dynamically adjusts the low-voltage side target current by superimposing the step I Step , and solves the problem of relying on the fixed polarization curve in the traditional method. This method can automatically adapt to changes such as stack performance degradation and system efficiency decline, and ensures that the fuel cell accurately matches the vehicle power demand throughout the life cycle.

[0031] The application compares the difference I delta2 between the low-voltage side target current and the actual current in real time, sets a threshold Ik for resuming superimposition, pauses the step superimposition when the actual current does not reach the current target, avoids short-term current surge, and restores adjustment after the difference is reduced, balances response speed and stability, and improves system robustness. Attached Figure Description

[0032] Figure 1 A flowchart of a fuel cell output current control method provided in an embodiment of the present invention. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. This is to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solutions of the present invention, and to facilitate its implementation. It should be noted that the terms "first," "second," etc., used in this application are only for the convenience of describing the technical solutions and to distinguish components; the corresponding component configurations may be the same or different, and are not intended to limit the scope of this application. To make the technical solutions of the present invention clearer, the present invention will be explained and illustrated through the following embodiments.

[0034] The fuel cell system includes a fuel cell, a battery management system, fuel cell system accessories, and a DC-DC converter. The battery management system is communicatively connected to both the vehicle controller and the fuel cell system accessories. The fuel cell output is electrically connected to the low-voltage side of the DC-DC converter, and the high-voltage side of the DC-DC converter is connected in parallel to the vehicle's power grid. The fuel cell output is also electrically connected to the fuel cell system accessories. In operation, the fuel cell system's battery management system responds to the vehicle controller's power demand request and sets the target output current on the low-voltage side of the DC-DC converter.

[0035] Correspondingly, this embodiment provides a method for controlling the output current of a fuel cell, used to accurately control the target output current on the low-voltage side of the DC-DC converter over a long period of time, so as to ensure the reliable operation of the fuel cell and meet the power requirements of the vehicle. Figure 1 As shown, the method includes the following steps:

[0036] Step S1: Confirm the total power P that the fuel cell needs to output. 总 ;

[0037] Step S2: Based on the total power P 总 Determine the total current I required on the high-voltage side of the DC-DC converter. 总 It also monitors the actual current value I0 output from the high-voltage side of the DC-DC converter in real time and calculates the total current I. 总 The difference between I and the actual current value I0 delta1 ;

[0038] Step S3: Convert the difference I delta1 The difference between the preset maximum allowable current on the high-voltage side of the DC-DC converter and the current I is... Diff The comparison was performed, and the fuel cell current was applied in step I by superimposing the output values.Step Adjust the target output current on the low-voltage side of the DC-DC converter;

[0039] Step S4: Compare the adjusted target output current on the low-voltage side of the DC-DC converter with the preset maximum allowable current I on the low-voltage side of the DC-DC converter. m The two values ​​are compared, and the minimum value is taken as the corresponding target output current I on the low-voltage side of the DC-DC converter. n ;

[0040] Step S5: Monitor the actual current value I1 of the current DC-DC low-voltage side output in real time, and calculate the target output current I of the DC-DC low-voltage side. n The difference between I1 and the actual current value delta2 and the difference I delta2 With the preset current threshold I k The comparison is performed, and the adjustment process of the target output current on the low-voltage side of the DC-DC converter is controlled based on the corresponding comparison results.

[0041] In simple terms, the control principle of this application is as follows: First, the target current of the low-voltage side of the DC-DC converter is set according to the actual demand current and actual current of the high-voltage side. Second, the actual current of the low-voltage side of the DC-DC converter is detected in real time to see if it reaches the target current of the low-voltage side. If not, the superposition of the target current of the low-voltage side of the DC-DC converter is stopped. After the target current of the low-voltage side of the DC-DC converter is reached, the target current of the low-voltage side of the DC-DC converter is increased / decreased to meet the current power requirements of the vehicle.

[0042] Specifically, referring to step S1, this embodiment first determines the total power P that the fuel cell needs to output. 总 The fuel cell needs to output a total power P. 总 Power required for the whole vehicle P Veh Total power consumed by fuel cell system accessories P AUX sum.

[0043] In this embodiment, fuel cell system accessories refer to components that consume significant power, while low-pressure components with lower power consumption can be ignored. The fuel cell system accessories in this embodiment include an air compressor, a circulation pump, a water pump, and a PTC heater. The total power consumed by these fuel cell system accessories is P. AUX =P ACP +P ARB +P CWP +P PTC , where P ACP Indicates the air compressor power, P ARB Indicates the power of the circulating pump, P CWP Indicates the power of the water pump, P PTCPTC heater power, which can be obtained by multiplying the output current and voltage of the corresponding accessory monitored by the battery management system, or directly obtained by the battery management system communicating with the corresponding accessory.

[0044] In actual process, the total power P 总 required to be output by the fuel cell is not only the power required by the vehicle, but also the actual working condition constraint of the fuel cell system. Therefore, the total power P 总 required to be output by the fuel cell is compared with the preset maximum allowable output power P alow of the fuel cell, and the minimum value is taken as the new total power P 总 required to be output by the fuel cell. The preset maximum allowable output power P alow of the fuel cell is affected by the water temperature at the water outlet of the fuel cell stack, the average voltage of the single cell, etc. In specific implementation, the size of P alow can be flexibly set according to actual conditions. It is worth noting that the various preset values described in the present application are not fixed and can change in each cycle of the method of the present application, which will not be described in detail hereinafter.

[0045] In the present embodiment, the preset maximum allowable output power P alow of the fuel cell is also related to the fault level of the fuel cell system, so as to ensure the safe operation of the fuel cell. Specifically, the fault level of the fuel cell system in the present embodiment is divided into four levels from low to high according to the severity of the fault, i.e., level one, level two, level three and level four. In level one, the power is not limited; in level two, the current allowable output power is limited to 75% of the rated power; in level three, the maximum current allowable output power is limited to 50% of the rated power; and in level four, the fuel cell system no longer responds to the external power request and the power output is prohibited. In specific implementation, the number of fault levels and the size of the corresponding limited power can be flexibly set according to actual conditions.

[0046] In summary, the total power P 总 required to be output by the fuel cell is P Veh + P AUX . Referring to step S2, the total current I 总 required by the high-voltage side of the DCDC can be determined according to the total power P 总 , i.e., the platform voltage U 总 of the vehicle power grid is fixed, and the total current required by the high-voltage side of the DCDC is I 总 = P 总 / U 总 . At the same time, the actual current value I0 output by the high-voltage side of the DCDC is monitored in real time, and the total current I 总 is calculated.总 the difference I between the actual current value I0 and the target current value I delta1 , i.e. I delta1 = I 总 - I0.

[0047] According to the difference I delta1 , the DCDC low-voltage side target output current can be adjusted. Referring to step S3, the difference I delta1 is compared with a preset DCDC high-voltage side maximum allowable current difference I Diff , so as to adjust the DCDC low-voltage side target output current by superimposing the fuel cell current loading step I Step on the premise of safety. The preset DCDC high-voltage side maximum allowable current difference I Diff is also related to the water temperature at the water outlet of the stack, the average voltage of the single cell, etc. Specifically, the step S3 comprises:

[0048] If I delta1 > I Diff > 0, it indicates that the actual current value I0 output by the DCDC high-voltage side has not reached the target current of the DCDC high-voltage side, and the actual current value I0 needs to be increased. Correspondingly, according to the relationship between the currents on both sides of the DCDC converter, the DCDC low-voltage side current is increased, and the DCDC high-voltage side current is increased synchronously. Therefore, the actual current value I0 is increased by increasing the DCDC low-voltage side current target output current in the embodiment, i.e. the fuel cell current loading step I Step is set to be positive, and is continuously superimposed on the DCDC low-voltage side target output current until I delta1 < I Diff. , and then the superimposition is stopped, and the system starts to operate stably.

[0049] Similarly, if I delta1 < 0 and |I delta1 | > I Diff , the actual current value I0 output by the DCDC high-voltage side has far exceeded the target current of the DCDC high-voltage side, and thus the actual current value I0 output by the DCDC high-voltage side needs to be reduced. At this time, the fuel cell current loading step I Step is set to be negative, and is continuously superimposed on the DCDC low-voltage side target output current until I delta1 < 0 and |I delta1 | < I Diff , and then the superimposition is stopped, and the system starts to operate stably.

[0050] In summary, the method of this invention enables dynamic setting of the target output current on the low-voltage side of the DC-DC converter, which can cover the entire life cycle of the fuel cell. At the same time, by continuously superimposing data, it finds the accurate target output current on the low-voltage side of the DC-DC converter under different battery conditions to meet the vehicle power requirements. It does not rely on traditional polarization curves and effectively solves the problem of current setting not meeting requirements due to stack degradation and reduced system efficiency, thus solving the problem of abnormal current and power setting throughout the entire life cycle of the fuel cell.

[0051] In addition, considering system safety during the adjustment of the target output current on the low-voltage side of the DC-DC converter, this embodiment also specifies the fuel cell current loading step size I. Step The new fuel cell current loading step I is determined by comparing the new step size with the preset maximum allowable loading step size and taking the smaller absolute value of the two. Step The preset maximum allowable loading step size is also related to the water temperature at the fuel cell stack inlet and the average voltage of the individual cells. In actual implementation, it can be flexibly set according to the actual situation.

[0052] Referring to step S4, the adjusted target output current on the low-voltage side of the DCDC is not applied directly, but rather compared with the preset maximum allowable current I on the low-voltage side of the DCDC. m The two values ​​are compared, and the minimum value is taken as the corresponding target output current I on the low-voltage side of the DC-DC converter. n Among them, the preset maximum allowable current I on the low-voltage side of the DC-DC converter. m Similarly, it is related to the water temperature at the fuel cell stack inlet and the average voltage of the individual cells, and can be flexibly set according to the actual situation during implementation. Step S4 is used to protect the system and prevent over-discharge caused by low system voltage and low temperature, forming a double protection with the previous step protection.

[0053] Furthermore, referring to step S5, after each superposition, the target output current on the low-voltage side of the DC-DC converter is also monitored in real time to determine the actual current value I1 of the current output on the low-voltage side of the DC-DC converter, and the current target output current I on the low-voltage side of the DC-DC converter is calculated. n The difference between I1 and the actual current value delta2 , that is I delta2 =I n -I1, and the difference I delta2 With the preset current threshold I k The comparison process, based on the corresponding comparison results, controls the adjustment of the target output current on the low-voltage side of the DC-DC converter. The specific process is as follows:

[0054] If I delta2 >I k> 0, indicating that the stack output power has not reached the target power, even if the high-voltage side target current has not been reached, the low-voltage side target current is no longer increased, that is, the DCDC low-voltage side target output current stops superimposing the fuel cell current loading step I Step , until 0 < I delta2 < I k , the superposition is resumed;

[0055] Similarly, if I delta2 < 0 and |I delta2 | > I k , the DCDC low-voltage side target output current is controlled to stop superimposing the fuel cell current loading step I Step , until I delta2 < 0 and |I delta2 | < I Diff , the superposition is resumed.

[0056] In summary, according to the difference I delta2 , the adjustment process of the DCDC low-voltage side target output current is controlled, so that the change of the actual current output by the DCDC low-voltage side is progressive. If the actual current output by the DCDC low-voltage side does not reach the current target current, and the target current is further increased, it may cause the actual current output by the DCDC low-voltage side to increase sharply in a short time, thereby causing safety risks such as battery damage.

[0057] The application also provides a fuel cell output current control system using the above-mentioned fuel cell output current control method. The system comprises a vehicle controller, a fuel cell, a battery management system, a fuel cell system accessory, and a DCDC converter. The battery management system is in communication connection with the vehicle controller and the fuel cell system accessory. The fuel cell output end is electrically connected to the low-voltage side of the DCDC converter, and the high-voltage side of the DCDC converter is connected in parallel to the vehicle power grid.

[0058] The vehicle controller is used to send a vehicle demand power request to the battery management system.

[0059] The battery management system is used to receive the vehicle demand power request and determine the DCDC low-voltage side target output current according to the fuel cell output current control method of the application.

[0060] The application is described above in conjunction with the drawings. Obviously, the specific implementation of the application is not limited by the above method. As long as various non-essential improvements are made using the method concept and technical solution of the application, or the above-mentioned concept and technical solution of the application is directly applied to other occasions without improvement, they are all within the protection scope of the application.

Claims

1. A method for controlling the output current of a fuel cell, characterized in that: The method includes the following steps: Step S1: Confirm the total power P that the fuel cell needs to output. 总 ; Step S2: Based on the total power P 总 Determine the total current I required on the high-voltage side of the DC-DC converter. 总 It also monitors the actual current value I0 output from the high-voltage side of the DC-DC converter in real time and calculates the total current I. 总 The difference between I and the actual current value I0 delta1 ; Step S3: Convert the difference I delta1 The difference between the preset maximum allowable current on the high-voltage side of the DC-DC converter and the current I is... Diff The comparison was performed, and the fuel cell current was applied in step I by superimposing the output values. Step Adjust the target output current on the low-voltage side of the DC-DC converter; Step S4: Compare the adjusted target output current on the low-voltage side of the DC-DC converter with the preset maximum allowable current I on the low-voltage side of the DC-DC converter. m The two values ​​are compared, and the minimum value is taken as the corresponding target output current I on the low-voltage side of the DC-DC converter. n ; Step S5: Monitor the actual current value I1 of the current DC-DC low-voltage side output in real time, and calculate the target output current I of the DC-DC low-voltage side. n The difference between I1 and the actual current value delta2 and the difference I delta2 With the preset current threshold I k The comparison is performed, and the adjustment process of the target output current on the low-voltage side of the DC-DC converter is controlled based on the corresponding comparison results.

2. The method for controlling the output current of a fuel cell according to claim 1, characterized in that: The total power P that the fuel cell needs to output in step S1 总 Power required for the whole vehicle P Veh Total power consumed by fuel cell system accessories P AUX sum.

3. The method for controlling the output current of a fuel cell according to claim 2, characterized in that: The fuel cell system accessories include an air compressor, a circulation pump, a water pump, and a PTC heater. The total power consumed by the corresponding fuel cell system accessories is P. AUX =P ACP +P ARB +P CWP +P PTC .

4. A method for controlling the output current of a fuel cell according to claim 2 or 3, characterized in that: The total power P that the fuel cell needs to output 总 Compared with the preset maximum allowable output power P of the fuel cell alow The two values ​​are compared, and the minimum value is taken as the total power P that the new fuel cell needs to output. 总 .

5. The method for controlling the output current of a fuel cell according to claim 4, characterized in that: The preset maximum allowable output power P of the fuel cell alow This is related to the fault level of the fuel cell system.

6. The method for controlling the output current of a fuel cell according to claim 5, characterized in that: The fault levels of the fuel cell system are divided into four levels according to the severity of the fault. Level 1 faults do not limit the power output; Level 2 faults limit the current allowed output power to 75% of the rated power; Level 3 faults limit the current allowed maximum output power to 50% of the rated power; and Level 4 faults stop responding to external power requests.

7. The method for controlling the output current of a fuel cell according to claim 1, characterized in that: In step S3: If I delta1 >I Diff If the value is greater than 0, then the fuel cell current loading step size I is set. Step It is a positive value, and it is continuously added to the target output current on the low-voltage side of the DC-DC converter until 0 < I. delta1 <I Diff. ; If I delta1 <0 and |I delta1 |>I Diff Then set the fuel cell current loading step size I. Step It is a negative value, and it continuously adds to the target output current on the low-voltage side of the DC-DC converter until I... delta1 <0 and |I delta1 |<I Diff .

8. The method for controlling the output current of a fuel cell according to claim 7, characterized in that: The fuel cell current loading step size I Step The new fuel cell current loading step I is determined by comparing the new step size with the preset maximum allowable loading step size and taking the smaller absolute value of the two. Step .

9. A method for controlling the output current of a fuel cell according to any one of claims 1, 7, and 8, characterized in that: In step S5: If I delta2 >I k If the value is greater than 0, then the target output current on the low-voltage side of the DC-DC converter will stop being superimposed with the fuel cell current loading step size I. Step until 0 < I delta2 <I k At that time, restore the overlay; If I delta2 <0 and |I delta2 |>I k Then, control the target output current on the low-voltage side of the DC-DC converter to stop superimposing the fuel cell current loading step size I. Step until I delta2 <0 and |I delta2 |<I Diff At that time, the overlay is restored.

10. A control system for the output current of a fuel cell, using a control method for the output current of a fuel cell according to any one of claims 1-9, characterized in that: The system includes a vehicle controller, a fuel cell, a battery management system, fuel cell system accessories, and a DC-DC converter. The battery management system is communicatively connected to the vehicle controller and the fuel cell system accessories. The output of the fuel cell is connected to the low-voltage side of the DC-DC converter, and the high-voltage side of the DC-DC converter is connected in parallel to the vehicle's power grid. The vehicle controller is used to send a power demand request for the vehicle to the battery management system; The battery management system is used to receive the power demand request from the vehicle. A method for controlling the output current of a fuel cell according to any one of claims 1-9 determines the target output current on the low-voltage side of a DC-DC converter.

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