A method for controlling a fuel cell system during cold start

Abstract

The application discloses a kind of fuel cell system cold machine operation control method.The method of the present application is: fuel cell system starts operation, real-time acquisition fuel cell into stack coolant temperature and preset temperature threshold T tar Real-time comparison is carried out;Current water temperature into stack ≤ preset temperature threshold, then enter cold machine state, water temperature into stack > preset temperature threshold, then enter hot machine state;When being in cold machine state, in response to the power request of whole vehicle corresponding power, power pull load will be carried out according to the single piece voltage variance V σ And single piece minimum voltage value V cell , corresponding restriction is carried out to power pull load;When hot machine state, do not make any restriction, real-time follow-up pull load is carried out in response to the power request of whole vehicle;The present application solves the problem that single piece voltage is too low to cause fault shutdown when following demand power pull load under the condition of fuel cell system cold machine state;Solve the problem that single piece consistency is poor when following demand power pull load under the condition of fuel cell system cold machine state.

Description

TECHNICAL FIELD

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

[0002] Hydrogen energy is a clean decarbonization secondary energy with rich application scenarios, and is also an ideal carrier and medium for renewable energy storage and conversion. The position of hydrogen energy will become increasingly important and will play an important role in decarbonization in traditional industries, transportation, construction and other fields, and a hydrogen fuel cell system is a power generation device that uses hydrogen as fuel and converts chemical energy in the fuel into electric energy through an electrochemical reaction, has the advantages of high energy conversion efficiency, zero emission and no noise, and corresponding technological progress can promote the development and upgrading of hydrogen production, storage and transportation technology systems. Under the drive of the new round of energy revolution, countries around the world attach great importance to hydrogen fuel cell technology to support the realization of low-carbon and clean development mode.

[0003] When the fuel cell system is at a low temperature of the cooling liquid, the activation voltage is high, resulting in a low output voltage, and the power will decrease under the same current. When the temperature is low, less water is carried out by exhaust gas, and local water flooding may occur, causing poor consistency of single cell voltage, and individual single cell voltage may be abnormally low, local current may be too high, hot spots may occur, and even reverse polarity may occur, resulting in failure of the stack. At the same time, when the temperature is low, the load power cannot be blindly increased, because when the temperature is low, the fuel cell reaction rate is slow, and the electricity that can be generated is small. If the load power is forced to increase, the fuel cell may have side reactions such as water electrolysis and carbon corrosion when it cannot meet the large load. Therefore, it is crucial to reasonably increase the load power and as quickly as possible to increase the temperature of the system stack when the fuel cell is in a cold state before reaching the rated operating temperature.

[0004] At present, fuel cell stacks generally have poor performance when the temperature of the cooling liquid is low. Most methods limit the current load by setting a constant current or by temperature to prevent the current load from being too large at low temperatures, which may cause poor consistency of the stack and low voltage of the single cell, resulting in shutdown. However, due to the differences in the environmental state of the system operation and the performance of each stack and the performance of the later stage, the method of simply limiting the current load by setting a constant current or by temperature may easily cause the stack to have poor consistency of the single cell voltage and low voltage of the single cell, resulting in the risk of shutdown.

[0005] In view of the above description, in the prior art, the fuel cell system stack coolant is heated until the entire fuel cell cooling water temperature reaches the rated operating temperature by running at a preset fixed current. This method only uses a low temperature operating condition point supported by most stacks based on empirical values to heat the engine, and cannot exclude the performance difference of individual stacks, the performance decay in the later period, and the low temperature running of the engine under different environments. Loading to the fixed current point to run the engine easily leads to poor consistency of the stacks and low single voltage failure shutdown. In the process of continuously rising water temperature, since the stack performance is getting better, it can continue to load larger power points to generate more heat to speed up the heating of the fuel cell cooling water. However, since there is only one single operating condition point, the overall heating time is too long. By limiting the corresponding load current according to the temperature, this method only uses a low temperature operating condition point supported by most stacks based on empirical values to heat the engine, and cannot exclude the performance difference of individual stacks, the performance decay in the later period, and the low temperature running of the engine under different environments. Loading to the preset corresponding current to heat the engine easily leads to poor consistency of the stacks and low single voltage failure shutdown. Moreover, the load current is limited at each temperature, which cannot fully improve the load power and heat the fuel cell system stack coolant, and the heating time is too long. SUMMARY

[0006] The present application overcomes the defects in the prior art and provides a fuel cell system cold start control method. The present application solves the problem of low single voltage leading to failure shutdown when following the demand power load in the cold state of the fuel cell system; solves the problem of poor single consistency when following the demand power load in the cold state of the fuel cell system; and solves the problem of long heating time of the fuel cell system.

[0007] The object of the present application is achieved at least by one of the following technical solutions.

[0008] A fuel cell system cold start control method, comprising the following steps:

[0009] (1) The fuel cell system starts to run, and the fuel cell inlet stack coolant temperature is collected in real time and compared with a preset temperature threshold T tar in real time;

[0010] (2) If the current inlet stack water temperature T stacKin ≤ preset temperature threshold T tar , the cold state is entered, and the inlet stack water temperature T stacKin > preset temperature threshold T tar , the heating state is entered;

[0011] (3) When the fuel cell system inlet stack water temperature T stacKin ≤ preset temperature threshold T tar, then in the cold state, when responding to the vehicle power request, the power pull load is limited according to the single piece voltage variance value V σ and the single piece minimum voltage value V cell issued by the stack inspection module; if not, then in the hot state, without any limit, responding to the vehicle power request for real-time follow-up load;

[0012] (4) judging the current power point, if the single piece voltage variance value V σ ≤ preset threshold V σ_min and the minimum single piece voltage value V cell ≥ preset threshold V cell_max , then responding to the vehicle power request for response load; if not, then entering step (5);

[0013] (5) judging the current power point, preset threshold V σ_max > single piece voltage variance V σ > preset threshold V σ_min or preset threshold V cell_min < minimum single piece voltage V cell < V cell_max, , then stay at the current power point; if not, then entering step (6);

[0014] (6) judging the current power point, single piece voltage variance V σ ≥ preset threshold V σ_max and minimum single piece voltage V cell ≤ preset threshold V cell_min， decrease load by the preset percentage power of the current power point for a preset time T, while recording the number N of times of decrease load under the current power point current, if the number of continuous decrease load under the same current is greater than or equal to the preset threshold N toal , then alarm and stop; if not, return to step (2).

[0015] In the above method, in step (1), the preset temperature threshold T tar is 60-65℃.

[0016] In the above method, the single piece voltage variance V σ is issued by the stack inspection module.

[0017] In the above method, in steps (4) and (5), the preset threshold V σ_min is 50-150.

[0018] In the above method, the minimum single piece voltage V cell is the real-time detection feedback value of the stack inspection module.

[0019] In the above method, in steps (4) and (5), the preset threshold V cell_max0.60~0.65V.

[0020] In the above method, in the step (5) and the step (6), the preset threshold value V cell_min 0.60~0.65V.

[0021] In the above method, in the step (5) and the step (6), the preset threshold value V σ_max 200~250.

[0022] In the above method, in the step (6), the preset threshold value N toal 0~10.

[0023] Compared with the prior art, the control method has the following advantages:

[0024] (1) The control method can effectively reduce the problem of poor consistency of single piece in the process of running or load pulling of the electric pile in the cold state of the system

[0025] (2) The control method can effectively reduce the problem of too low single piece in the process of running or load pulling of the electric pile in the cold state, which leads to shutdown alarm

[0026] (3) The control method can maximize the load pulling to the maximum allowable power point of the pile according to the real-time performance of the pile in the cold state, heat the cooling liquid of the pile, and shorten the warm-up time. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a flow chart of a fuel cell system cold running control method of the application;

[0028] Figure 2 is a flow chart in example 1 of the application;

[0029] Figure 3 is a flow chart in example 2 of the application;

[0030] Figure 4 is a flow chart in example 3 of the application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0032] Example 1

[0033] The flow chart in this example is shown in Figure 2 .

[0034] 1、Fuel cell system receives the whole vehicle starting signal and demand power, fuel cell system starts successfully to idle speed;

[0035] 2、Fuel cell system real-time acquisition of current fuel cell system into the stack water temperature T stacKin And compare ≤ preset temperature threshold T tar 63℃ and duration > 5S, judge whether the fuel cell system is in cold state;

[0036] 3、When fuel cell system into the stack water temperature T stacKin ≤ preset temperature threshold T tar 63℃ and duration > 5S ， Then in the cold state, in response to the corresponding power request of the whole vehicle, the power load will be limited according to the single piece voltage variance value V σ And the minimum single piece voltage value V cell , if not, enter the hot state, do not make any limit, respond to the power request of the whole vehicle for real-time follow-up load;

[0037] 4、In the process of power load, if the single piece voltage variance V σ ≤100 and the minimum single piece voltage value V cell ≥0.7 V, then respond to the power request of the whole vehicle, and respond to the load;

[0038] 5、In the process of power load, the current power point, 200 > single piece voltage variance V σ >100 or preset threshold 0.65V < minimum single piece voltage Vcell <0.7V, then keep the current power point continue to run, no longer respond to the power request of the whole vehicle;

[0039] 6、In the process of power load, when the single piece voltage variance V σ ≥200 and the minimum single piece voltage value V cell ≤0.65V, then load down to 90% power of the current power point for 30S, and record the occurrence frequency N under the current power current, when the continuous load down frequency N under the same stack current point is greater than 5 times, the system alarm stops, and the continuous load down frequency N is reset to 0

[0040] Example 2

[0041] The flow chart in this embodiment is shown in Figure 3 .

[0042] 1、Fuel cell system receives the whole vehicle starting signal and demand power, fuel cell system starts successfully to idle speed;

[0043] 2、Fuel cell system real-time acquisition of current fuel cell system into the stack water temperature T sta And compare ≤ preset temperature threshold Ttar 65℃ and duration > 5S, judge whether the fuel cell system is in cold state;

[0044] 3, when the fuel cell system enters the water temperature T stacKin ≤ preset temperature threshold T tar 65℃ and duration > 5S ， The cold state, in response to the vehicle power request for power pull load, will be limited according to the single chip voltage variance V σ And the minimum voltage value V cell , if not, enter the hot state, do not make any limit, respond to the vehicle power request for real-time follow-up load;

[0045] 4, in the process of power pull load, if the single chip voltage variance V σ ≤100 and the minimum single chip voltage value V cell ≥0.7 V, respond to the vehicle power request, and respond to the load;

[0046] 5, in the process of power pull load, the current power point, 200> single chip voltage variance V σ >100 or preset threshold 0.65V < minimum single chip voltage V cell <0.7V, then keep the current power point continue to run, no longer respond to the vehicle power request;

[0047] 6, in the process of power pull load, when the single chip voltage variance V σ ≥200 and the minimum single chip voltage value V cell ≤0.65V, then reduce the load to 90% of the current power point power for 30S, and record the occurrence frequency N under the current power current, when the continuous load reduction frequency N under the same stack current point is greater than 5 times, the system alarm stop, and the continuous load reduction frequency N is reset to 0

[0048] Example 3

[0049] The flow chart in this embodiment is shown in Figure 4 .

[0050] 1, the fuel cell system receives the vehicle starting signal and the demand power, and the fuel cell system starts successfully to idle speed;

[0051] 2, the fuel cell system real-time acquisition current fuel cell system into the water temperature T sta And compare ≤ preset temperature threshold T tar 60℃ and duration > 5S, judge whether the fuel cell system is in cold state;

[0052] 3, when the fuel cell system enters the water temperature T stacKin ≤ preset temperature threshold Ttar 60℃ and duration > 5S ， then in cold state, in response to the whole vehicle corresponding power request for power pull load, will be according to the single piece voltage variance value V σ and single piece minimum voltage value V cell , the power pull load corresponding limit; if not, into the hot state, do not make any limit, in response to the whole vehicle power request for real-time follow-up load;

[0053] 4, in the process of power pull load, if the single piece voltage variance V σ ≤100 and the minimum single piece voltage value V cell ≥0.72V, in response to the whole vehicle power request, for response load;

[0054] 5, in the process of power pull load, the current power point, 200 > single piece voltage variance V σ >100 or the preset threshold 0.65V < minimum single piece voltage V cell <0.72V, keep the current power point continue to run, no longer respond to the whole vehicle power request;

[0055] 6, in the process of power pull load, when the single piece voltage variance V σ ≥200 and the minimum single piece voltage value V cell ≤0.65V, load to the current power point 90% power operation 30S, and record the current power current under the number of occurrences N, when the same stack current point under continuous load down N is greater than 5 times, the system alarm stop, and the continuous load down N is reset to 0.

[0056] The technical features of the above embodiments can be combined arbitrarily, in order to make the description simple, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combination of these technical features does not exist contradictory, should be considered as the scope of the present application.

Claims

1. A method for controlling the cold start operation of a fuel cell system, characterized in that, Includes the following steps: (1) When the fuel cell system is started and running, the temperature of the fuel cell stack coolant and the preset temperature threshold T are collected in real time. tar Perform real-time comparisons; (2) Current influent water temperature T stacKin ≤Preset temperature threshold T tar Then it enters the chiller state, and the reactor water temperature T stacKin >Preset temperature threshold T tar Then it enters the hot engine state; (3) When the fuel cell system feed water temperature T stacKin ≤Preset temperature threshold T tar If the engine is in a cold state, when it responds to the power request of the vehicle and performs power load, it will adjust the power load based on the single-chip voltage variance value V issued by the fuel cell stack inspection module. σ and the lowest voltage value V of a single chip cell If the power load is not specified, the engine will enter a warm-up state without any restrictions and will respond to the vehicle's power request to perform real-time load loading. (4) Determine the current power point. If the single-chip voltage variance value V σ ≤Preset threshold V σ_min And the lowest single-chip voltage value V cell ≥Preset threshold V cell_max If yes, then respond to the vehicle power request and perform load response; otherwise, proceed to step (5). (5) Determine the current power point and preset the threshold V. σ_max >Single-chip voltage variance V σ >Preset threshold V σ_min Or a preset threshold V cell_min <Minimum single-chip voltage V cell <V cell_max, If not, then continue running at the current power point; otherwise, proceed to step (6). (6) Determine the current power point and the single-chip voltage variance V. σ ≥Preset threshold V σ_max And the lowest single-chip voltage V cell ≤Preset threshold V cell_min， The system operates at a preset percentage of power at the current power point for a preset time T, while simultaneously recording the number of times the load is reduced under the current at the current power point, N. If the number of consecutive load reductions under the same current is greater than or equal to a preset threshold N, the system will be considered a successor. toal If the alarm is triggered, the machine will shut down; otherwise, return to step (2).

2. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, In step (1), the preset temperature threshold T tar The temperature is 60~65℃.

3. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, The single-chip voltage variance V σ Issued by the fuel cell stack inspection module.

4. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, In steps (4) and (5), the preset threshold V σ_min The range is 50 to 150.

5. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, The lowest single-chip voltage V cell This provides real-time detection and feedback values ​​for the fuel cell stack inspection module.

6. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, In steps (4) and (5), the preset threshold V cell_max The voltage is 0.65~0.72V.

7. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, In steps (5) and (6), the preset threshold V cell_min The voltage is 0.60~0.65V.

8. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, In steps (5) and (6), the preset threshold V σ_max It is between 200 and 250.

9. The method for controlling the cold start operation of a fuel cell system according to claim 1, characterized in that, In step (6), the preset threshold N toal The range is 0 to 10.

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