A method for controlling a hydrogen circulation pump

Abstract

The present invention provides a hydrogen circulation pump control method, comprising: detecting the load state of a fuel cell system; determining whether the load increase value of the fuel cell system exceeds a preset load threshold; if so, detecting the outlet water temperature of the coolant of the fuel cell stack; determining whether the outlet water temperature is greater than or equal to a preset water temperature threshold; if so, controlling the speed of the hydrogen circulation pump to load the fuel cell stack according to a preset loading slope. This method has the advantages of reducing the number of low voltages experienced by individual cells during variable load conditions, allowing the fuel cell engine to operate normally; reducing the average and lowest cell voltage recovery times and the voltage difference between individual cells during variable load conditions, thereby improving the life of the fuel cell stack; and reducing the voltage fluctuation amplitude of the fuel cell stack during variable load operation, thereby facilitating stable operation of the fuel cell engine.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell vehicle control, and in particular to a hydrogen circulation pump control method. Background Art

[0002] Hydrogen fuel cells are power generation devices that convert the chemical energy generated by the reaction of hydrogen and oxygen directly into electrical energy through an electrochemical reaction. They offer advantages such as high power generation efficiency and minimal environmental pollution, leading to their widespread use in the automotive sector. Water management is crucial in the control of proton exchange membrane fuel cells. The proton exchange membrane must contain sufficient moisture. If the fuel cell is not adequately humidified, the membrane will dry out, significantly reducing the membrane's proton conductivity. In severe cases, this can degrade the performance of the fuel cell stack and lead to irreversible voltage loss. However, if the water generated by the cell cannot be properly drained, it can easily flood the electrodes, deactivating the catalyst and clogging the pores in the connected gas diffusion layer, resulting in a shortage of reactant gases at the reaction interface. Therefore, maintaining a good water balance is crucial.

[0003] The fuel cell's single cell near the end plate is significantly affected by ambient temperature. When the ambient temperature is low, liquid water is more likely to condense, causing water plugging. This is known as the stack end plate effect. The introduction of humidified hydrogen by the hydrogen circulation pump exacerbates this phenomenon, and water plugging is particularly severe under severe load fluctuations and complex driving conditions.

[0004] Currently, existing low-voltage fuel cell system technologies often employ self-humidification, connecting the outlet of a humidification return line to an inlet, and installing a hydrogen circulation pump and a gas-water separator on the line. A disadvantage of this approach is that, to reduce the complexity of system control, existing technical solutions fail to control and manage the humidity of the circulated hydrogen. When the ambient temperature is low, water vapor within the stack is first cooled at the end plates, quickly condensing into liquid water. This is especially true when the battery system's load suddenly increases, as the rapid increase in system power leads to a sharp increase in water production and exacerbates water vapor condensation. If the circulation pump continues to introduce wet hydrogen into the stack, severe water blockage may occur, leading to a drop in the voltage of the individual chips due to insufficient gas flow. The individual chips near the hydrogen circulation pump may also experience a severe end plate effect, which can even cause the fuel cell engine to malfunction.

[0005] In summary, it is necessary to provide a hydrogen circulation pump control method that can overcome the defects of the prior art. Summary of the Invention

[0006] The present invention aims to provide a hydrogen circulation pump control method that can overcome the defects of the prior art. The purpose of the present invention is achieved through the following technical solutions.

[0007] One embodiment of the present invention provides a hydrogen circulation pump control method, which includes multiple steps:

[0008] Step 1: Detect the load status of the fuel cell system;

[0009] Step 2: Determine whether the load increase value of the fuel cell system exceeds the preset load threshold.

[0010] If “yes”, go to step 3;

[0011] Step 3: Detecting the outlet water temperature of the coolant of the fuel cell stack;

[0012] Step 4: Determine whether the stack water temperature is greater than or equal to the preset water temperature threshold. If yes, proceed to step 5.

[0013] Step 5: Control the speed of the hydrogen circulation pump to load according to the preset loading slope.

[0014] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, step 2: determines whether the load increase value of the fuel cell system exceeds a preset load threshold. If "no", execute step 1 again.

[0015] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, step 4: determines whether the stack water temperature is greater than or equal to a preset water temperature threshold; if "no", execute step 3 again.

[0016] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, the speed loading slope of the hydrogen circulation pump is smaller than the power increase slope of the stack when the output power is increased due to the increase in the fuel cell system load.

[0017] The advantages of this hydrogen circulation pump control method are: it can reduce the number of times that the voltage of a single cell is low under variable load conditions, so that the fuel cell engine can pull the load normally; it can reduce the voltage recovery time of the average single cell and the lowest single cell and the voltage difference between the single cells under variable load conditions, which is beneficial to the life of the fuel cell stack; it can reduce the voltage fluctuation amplitude of the fuel cell stack during operation after variable load, which is beneficial to the stable operation of the fuel cell engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. Those skilled in the art will readily appreciate that these drawings are merely used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0019] Figure 1 A schematic diagram of a fuel cell hydrogen circulation system according to one embodiment of the present invention is shown;

[0020] Figure 2 Shown as Figure 1 The flowchart of the hydrogen circulation pump control method according to one embodiment of the present invention is shown;

[0021] Figure 3 Shown as Figure 2 The figure shows a schematic diagram comparing the effects of a hydrogen circulation pump control method according to one embodiment of the present invention and an existing hydrogen circulation system on the minimum single-chip voltage of a fuel cell stack. DETAILED DESCRIPTION

[0022] Figure 1-2 The following description describes alternative embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solutions of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or substitutions derived from these embodiments will fall within the scope of protection of the present invention. Those skilled in the art will understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following alternative embodiments, but is limited only by the claims and their equivalents.

[0023] Figure 1 FIG2 shows a schematic diagram of a fuel cell hydrogen circulation system according to an embodiment of the present invention. Figure 1 As shown, the fuel cell hydrogen circulation system includes a fuel cell stack 100, a first pipeline 101, a water separator 102, a second pipeline 103, a third pipeline 105, a hydrogen circulation pump 106, a fourth pipeline 107, a hydrogen spray 108, a fifth pipeline 109 and a sixth pipeline 110. The water separator 102 is connected to the hydrogen outlet of the fuel cell stack 100 through the first pipeline 101, the discharge port of the water separator 102 is connected to the mixing point 104 through the second pipeline 103, the hydrogen circulation pump 106 is connected to the exhaust port of the water separator 102 through the third pipeline 105, the first end of the hydrogen spray 108 is connected to the hydrogen circulation pump 106 through the fourth pipeline 107, the second end of the hydrogen spray 108 is connected to the external hydrogen source through the fifth pipeline 109, and the third end of the hydrogen spray 108 is connected to the hydrogen inlet of the fuel cell stack 100 through the sixth pipeline 110.

[0024] Figure 2 like Figure 1 Flowchart of a method for controlling a hydrogen circulation pump according to an embodiment of the present invention is shown in FIG. Figure 2 As shown, the hydrogen circulation pump control method includes multiple steps:

[0025] Step 1: Detect the load status of the fuel cell system;

[0026] Step 2: Determine whether the load increase value of the fuel cell system exceeds the preset load threshold.

[0027] If “yes”, go to step 3;

[0028] Step 3: Detecting the outlet water temperature of the coolant of the fuel cell stack;

[0029] Step 4: Determine whether the stack water temperature is greater than or equal to the preset water temperature threshold. If yes, proceed to step 5.

[0030] Step 5: Control the speed of the hydrogen circulation pump to load according to the preset loading slope.

[0031] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, step 2: determines whether the load increase value of the fuel cell system exceeds a preset load threshold. If "no", execute step 1 again.

[0032] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, step 4: determines whether the stack water temperature is greater than or equal to a preset water temperature threshold; if "no", execute step 3 again.

[0033] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, the speed loading slope of the hydrogen circulation pump is less than the power increase slope of the stack due to the increase in the fuel cell system load. The output voltage of the fuel cell stack of the fuel cell system generally remains stable, so the increase in the output power of the fuel cell system is generally achieved by increasing the output current of the stack. Therefore, the speed loading slope of the hydrogen circulation pump is also less than the current increase slope of the stack due to the increase in the fuel cell system load.

[0034] According to the hydrogen circulation pump control method provided by any one of the above embodiments of the present invention, the smaller the speed loading slope of the hydrogen circulation pump is, the longer it takes for the hydrogen circulation pump to increase from an initial speed to a target speed.

[0035] According to the hydrogen circulation pump control method provided by any one of the above-mentioned embodiments of the present invention, the greater the power increase slope of the stack output power, the shorter the time it takes for the stack output power to increase from the initial output power to the output rate required after the loading load increases.

[0036] Figure 3 Shown as Figure 2 The figure shows a schematic diagram comparing the effects of a hydrogen circulation pump control method according to one embodiment of the present invention and an existing hydrogen circulation system on the minimum single-chip voltage of a fuel cell stack. Figure 3 On the left Figure 3-1 A time-varying curve diagram of the stack output current, minimum single-chip voltage, outlet water temperature, and hydrogen circulation pump speed increase when the load of the existing hydrogen circulation system suddenly increases; Figure 3 on the right side Figure 3-2 This is a time-varying diagram of the stack output current, minimum single-chip voltage, outlet water temperature, and hydrogen circulation pump rate increase when the load suddenly increases after applying the hydrogen circulation pump control method according to one embodiment of the present invention.

[0037] like Figure 3-1 As shown in the figure, the loading slope of the circulating pump speed of the existing hydrogen circulation system is greater than the slope of the current increase, and the outlet water temperature is not judged before the circulating pump speed starts loading. At this time, the minimum single-chip voltage of the fuel cell system stack will repeatedly be low; Figure 3-2 As shown, after applying the hydrogen circulation pump control method of an embodiment of the present invention, the circulation pump starts to load after the water temperature out of the stack reaches the preset water temperature threshold, and the loading slope of the circulation pump speed is less than the slope of the current increase. At this time, the fluctuation frequency and amplitude of the lowest single-chip voltage of the fuel cell stack are significantly smaller than the fluctuation frequency and amplitude of the lowest single-chip voltage of the fuel cell stack using the existing hydrogen circulation system.

[0038] The advantages of this hydrogen circulation pump control method are: it can reduce the number of times that the voltage of a single cell is low under variable load conditions, so that the fuel cell engine can pull the load normally; it can reduce the voltage recovery time of the average single cell and the lowest single cell and the voltage difference between the single cells under variable load conditions, which is beneficial to the life of the fuel cell stack; it can reduce the voltage fluctuation amplitude of the fuel cell stack during operation after variable load, which is beneficial to the stable operation of the fuel cell engine.

[0039] It should be appreciated that although the foregoing description has been made by way of example of the present invention, such and other modifications and variations that will be apparent to those skilled in the art are to be considered within the broad scope of the invention as set forth herein. Therefore, although the invention has been described with reference to preferred embodiments, it is not intended that the novel device be limited thereby, but rather that it encompasses various modifications and equivalents that fall within the broad scope of the foregoing disclosure and claims.

Claims

1. A hydrogen circulation pump control method, characterized in that: The hydrogen circulation pump control method includes multiple steps: Step 1: Detect the load status of the fuel cell system; Step 2: Determine whether the load increase value of the fuel cell system exceeds a preset load threshold. If yes, proceed to step 3. Step 3: Detecting the outlet water temperature of the coolant of the fuel cell stack; Step 4: Determine whether the stack water temperature is greater than or equal to the preset water temperature threshold. If yes, proceed to step 5. Step 5: Control the speed of the hydrogen circulation pump to load according to the preset loading slope; The speed loading slope of the hydrogen circulation pump is smaller than the power increase slope of the stack due to the increase in the fuel cell system load. The increase in the output power of the fuel cell system is achieved by increasing the output current of the stack. The speed loading slope of the hydrogen circulation pump is still smaller than the current increase slope of the stack output current caused by the increase in the load of the fuel cell system. The smaller the speed loading slope of the hydrogen circulation pump, the longer it takes for the hydrogen circulation pump to increase from the initial speed to the target speed; the greater the power increase slope of the stack output power, the shorter the time it takes for the stack output power to increase from the initial output power to the output power rate required after the loading load increases.

2. The hydrogen circulation pump control method according to claim 1, characterized in that: Step 2: Determine whether the load increase value of the fuel cell system exceeds a preset load threshold. If "no", execute step 1 again.

3. The hydrogen circulation pump control method according to claim 1, characterized in that: Step 4: Determine whether the stack water temperature is greater than or equal to a preset water temperature threshold. If "no", execute step 3 again.

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