A method and apparatus for starting a fuel cell system

Abstract

The application provides a starting method and device of a fuel cell system, and relates to the technical field of fuel cells, in particular to: opening an anode inlet hydrogen supply valve and an anode outlet purge valve, so that hydrogen enters the fuel cell and purges the anode; when the anode purge is completed and the air flow of an air compressor reaches a first threshold value, opening a cathode inlet isolation valve and a cathode outlet isolation valve; opening and closing the anode outlet purge valve according to a first switching period and opening and closing an anode outlet drain valve according to a second switching period, wherein the first switching period is much smaller than the second switching period; obtaining a voltage value of a fuel cell stack, and if the voltage value reaches a second threshold value, connecting a high-voltage DC-DC as a load to the fuel cell, wherein the second threshold value is greater than the working voltage of the high-voltage DC-DC. The application can improve the starting speed of the fuel cell system, thereby improving fuel utilization and system efficiency and achieving lower battery performance degradation.

Description

Technical Field

[0001] This application relates to the field of fuel cell system technology, and in particular to a method and apparatus for starting a fuel cell system. Background Technology

[0002] Removing water and inert gases is a necessary step before a fuel cell system outputs current. This mitigates carbon corrosion of the catalyst support layer in a proton exchange fuel cell and prevents premature degradation of battery performance, which can negatively impact the system's performance over time. Therefore, removing water and inert gases from both sides of the proton exchange membrane helps meet automotive industry standards for rated power operation and low-voltage start-stop cycles of fuel cell systems.

[0003] Currently, commonly used fuel cell system startup strategies follow two principles:

[0004] 1. During startup and shutdown, the time spent at the hydrogen-air interface is reduced by using anodic and cathode purging. Anode purging uses hydrogen from the hydrogen storage system (H2 tank), while cathode purging is achieved using either nitrogen or air.

[0005] 2. Reduce the potential during startup and shutdown by applying a virtual load, an external load, or by creating an internal short circuit in the fuel cell.

[0006] Because nitrogen for cathode purging is difficult to obtain in passenger or commercial vehicles, it is challenging to establish an N2 / H2 interface during vehicle parking, even though air purging consumes most of the oxygen during parking. Using current cathode isolation valves, maintaining the N2 / H2 interface across the proton exchange membrane remains difficult during extended vehicle parking periods.

[0007] Existing fuel cell systems suffer from problems such as slow start-up speed and easy degradation of battery performance. Summary of the Invention

[0008] In view of this, this application provides a method and apparatus for starting a fuel cell system to solve the above-mentioned technical problems.

[0009] In a first aspect, embodiments of this application provide a method for starting a fuel cell system, the fuel cell system comprising: an air compressor, a cathode inlet isolation valve, a cathode outlet isolation valve, an anode inlet hydrogen supply valve, an anode outlet purge valve, an anode outlet drain valve, a fuel cell stack, and a high-voltage DC-DC converter; the starting method includes:

[0010] Open the hydrogen supply valve at the anode inlet and the purging valve at the anode outlet to allow hydrogen to enter the fuel cell and purge the anode;

[0011] When the anode purging is complete and the air flow rate of the air compressor reaches the first threshold, open the cathode inlet isolation valve and the cathode outlet isolation valve.

[0012] The anode outlet purge valve is opened and closed according to the first switching cycle, and the anode outlet drain valve is opened and closed according to the second switching cycle, wherein the first switching cycle is much shorter than the second switching cycle;

[0013] Obtain the voltage value of the fuel cell stack. If the voltage value reaches the second threshold, connect the high-voltage DC-DC converter as a load to the fuel cell. The second threshold is greater than the operating voltage of the high-voltage DC-DC converter.

[0014] Furthermore, the method also includes: closing the cathode inlet isolation valve and the cathode outlet isolation valve when the fuel cell system is in a shut-off state.

[0015] Furthermore, the fuel cell system further includes: an air splitter valve; the method further includes:

[0016] First, open the air distribution valve, then turn on the air compressor and set the air compressor to high-speed mode.

[0017] Furthermore, the first switching cycle includes: a first opening time and a first closing time; the first opening time is greater than or equal to 1s and less than or equal to 2s, and the first closing time is greater than or equal to 0.5s and less than or equal to 1s.

[0018] The second switching cycle includes: a second opening time and a second closing time; the second opening time is greater than or equal to 1s and less than or equal to 2s, and the second closing time is greater than or equal to 5s and less than or equal to 10s.

[0019] Secondly, embodiments of this application provide a starting device for a fuel cell system, applied to a fuel cell system comprising: an air compressor, a cathode inlet isolation valve, a cathode outlet isolation valve, an anode inlet hydrogen supply valve, an anode outlet purge valve, an anode outlet drain valve, a fuel cell stack, and a high-voltage DC-DC converter; the starting device comprises:

[0020] The anode purging start-up module is used to open the anode inlet hydrogen supply valve and the anode outlet purging valve, allowing hydrogen to enter the fuel cell and purge the anode;

[0021] The cathode purging start module is used to open the cathode inlet isolation valve and the cathode outlet isolation valve when the anode purging is completed and the air flow of the air compressor reaches the first threshold.

[0022] The anode outlet control module is used to open and close the anode outlet purge valve according to a first switching cycle and to open and close the anode outlet drain valve according to a second switching cycle, wherein the first switching cycle is much shorter than the second switching cycle;

[0023] The load connection module is used to obtain the voltage value of the fuel cell stack. If the voltage value reaches a second threshold, the high-voltage DC-DC converter is connected to the fuel cell as a load. The second threshold is greater than the operating voltage of the high-voltage DC-DC converter.

[0024] Furthermore, the device also includes a first control module, used to close the cathode inlet isolation valve and the cathode outlet isolation valve when the fuel cell system is in a shut-off state.

[0025] Furthermore, the fuel cell system also includes an air splitter valve; the device also includes a first control module, used to first open the air splitter valve, then turn on the air compressor, and set the air compressor operating mode to high-speed mode.

[0026] Furthermore, the first switching cycle includes: a first opening time and a first closing time; the first opening time is greater than or equal to 1s and less than or equal to 2s, and the first closing time is greater than or equal to 0.5s and less than or equal to 1s.

[0027] The second switching cycle includes: a second opening time and a second closing time; the second opening time is greater than or equal to 1s and less than or equal to 2s, and the second closing time is greater than or equal to 5s and less than or equal to 10s.

[0028] The beneficial effects of this application include the following three aspects: First, by using short, high-frequency anode purging instead of long, constant anode purging, hydrogen utilization during purging is optimized or reduced, thereby improving fuel utilization and system efficiency and achieving lower battery performance degradation; second, by using high-flow cathode purging instead of the existing low / medium-flow cathode purging, faster cathode purging is achieved, thereby improving the system start-up speed; in addition, by using high-voltage DC-DC as a "smart" load, the low potential of the fuel cell can be maintained, and the overall system efficiency can be improved. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 A flowchart of a startup method for a fuel cell system provided in an embodiment of this application;

[0031] Figure 2 This is a functional structure diagram of the starting device of the fuel cell system provided in the embodiments of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0034] First, a brief introduction to the design concept of the embodiments of this application will be given.

[0035] The fuel cell system of this application embodiment includes: an air compressor, a cathode inlet isolation valve, a cathode outlet isolation valve, an anode inlet hydrogen supply valve, an anode outlet purge valve, an anode outlet drain valve, a fuel cell stack, and a high-voltage DC-DC converter.

[0036] Existing fuel cell systems suffer from problems such as slow start-up speed and easy degradation of battery performance.

[0037] To address the aforementioned technical issues, this application provides an efficient and rapid start-up method for fuel cell systems, applicable to buses and commercial vehicles. By controlling the cathode and anode purging processes, using high-frequency anode purging and low-frequency anode venting to remove unwanted gases and condensate, using high-flow gas to quickly and effectively purge the cathode, and utilizing a high-voltage DC-DC converter as a "smart" load, all of these methods enable more energy-efficient startup of the fuel cell system (FCS) while preventing fuel cell performance degradation.

[0038] Among them, the combination of high-frequency purging of the anode and high-flow purging of the cathode under cathode shutdown is the key technical point of this application. High-voltage DC-DC is used as a "smart" load, which is the opposite of the "virtual" load used in the traditional FCS startup process.

[0039] After introducing the application scenarios and design concepts of the embodiments of this application, the technical solutions provided by the embodiments of this application will be described below.

[0040] like Figure 1 As shown in the figure, this application provides a method for starting a fuel cell system, including:

[0041] Step 101: Open the hydrogen supply valve at the anode inlet and the purge valve at the anode outlet to allow hydrogen to enter the fuel cell and purge the anode;

[0042] Before the fuel cell system is started (in the off state), the cathode inlet isolation valve and cathode outlet isolation valve are closed during long-term shutdown; the cathode is airtight by closing the cathode inlet and outlet air flow paths, and they remain closed during the fuel cell system startup to maintain the N2 / H2 interface.

[0043] Step 102: When the anode purging is completed and the air flow rate of the air compressor reaches the first threshold, open the cathode inlet isolation valve and the cathode outlet isolation valve;

[0044] Before this step, open the air diversion valve, then turn on the air compressor and set its operating mode to high speed. The airflow initially bypasses the cathode. Once a high airflow rate is reached (the first threshold, which is calculated specifically for different system designs, but is commonly around 80 g / s), open the cathode inlet and cathode outlet isolation valves to rapidly purge the cathode without electrical load.

[0045] Step 103: Open and close the anode outlet purge valve according to the first switching cycle, and open and close the anode outlet drain valve according to the second switching cycle, wherein the first switching cycle is much shorter than the second switching cycle;

[0046] The anode outlet purge valve is used to remove the inert gas accumulated on the anode, and the anode outlet drain valve is used to remove the condensate on the anode.

[0047] Periodic anode purging is achieved by using a rapidly opening / closing frequency to control the anode outlet of the anode purge valve, and a slower opening / closing frequency to control the anode discharge valve of the anode outlet. The purpose is to move water and unwanted gases from the front end of the fuel cell to the purge / discharge back end.

[0048] The first switching cycle includes: a first opening time and a first closing time; preferably, the first opening time is greater than or equal to 1s and less than or equal to 2s, and the first closing time is greater than or equal to 0.5s and less than or equal to 1s.

[0049] The second switching cycle includes a second opening time and a second closing time; preferably, the second opening time is greater than or equal to 1s and less than or equal to 2s, and the second closing time is greater than or equal to 5s and less than or equal to 10s.

[0050] Step 104: Obtain the voltage value of the fuel cell stack. If the voltage value reaches the second threshold, connect the high-voltage DC-DC converter as a load to the fuel cell.

[0051] When hydrogen and air are supplied to the anode and cathode respectively, the fuel cell outputs current. The voltage value of the fuel cell is obtained through a high-voltage DC-DC converter. When a preset condition (a second threshold, which is slightly higher than the operating voltage of the high-voltage DC-DC converter itself) is reached, the high-voltage DC-DC converter is connected to the fuel cell as soon as possible. The high-voltage DC-DC converter can act as an electrical load, maintaining a potential lower than the open circuit voltage (OCV) during the start-up phase, while recovering the electrical energy used to charge the high-voltage battery, thereby improving the efficiency of the entire system and vehicle, as well as fuel economy.

[0052] Based on the above embodiments, this application provides a starting device for a fuel cell system, see below. Figure 2 As shown, the starting device 200 for a fuel cell system provided in this application embodiment includes:

[0053] The anode purging start-up module 201 is used to open the anode inlet hydrogen supply valve and the anode outlet purging valve, so that hydrogen enters the fuel cell and purges the anode;

[0054] The cathode purging start module 202 is used to open the cathode inlet isolation valve and the cathode outlet isolation valve when the anode purging is completed and the air flow of the air compressor reaches the first threshold.

[0055] The anode outlet control module 203 is used to open and close the anode outlet purge valve according to a first switching cycle and to open and close the anode outlet drain valve according to a second switching cycle, wherein the first switching cycle is much shorter than the second switching cycle;

[0056] The load access module 204 is used to obtain the voltage value of the fuel cell stack. If the voltage value reaches a second threshold, the high-voltage DC-DC converter is connected to the fuel cell as a load. The second threshold is greater than the operating voltage of the high-voltage DC-DC converter.

[0057] In one possible implementation, the device further includes: a first control module, configured to close the cathode inlet isolation valve and the cathode outlet isolation valve when the fuel cell system is in a shut-off state.

[0058] As one possible implementation, the fuel cell system further includes an air splitter valve; the device further includes a first control module, configured to first open the air splitter valve, then turn on the air compressor, and set the air compressor operating mode to high-speed mode.

[0059] As one possible implementation, the first switching cycle includes: a first opening time and a first closing time; the first opening time is greater than or equal to 1s and less than or equal to 2s, and the first closing time is greater than or equal to 0.5s and less than or equal to 1s.

[0060] As one possible implementation, the second switching cycle includes: a second opening time and a second closing time; the second opening time is greater than or equal to 1s and less than or equal to 2s, and the second closing time is greater than or equal to 5s and less than or equal to 10s.

[0061] Furthermore, although the operations of the method of this application are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0062] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for starting a fuel cell system, the fuel cell system comprising: An air diversion valve, an air compressor, a cathode inlet isolation valve, a cathode outlet isolation valve, an anode inlet hydrogen supply valve, an anode outlet purge valve, an anode outlet drain valve, a fuel cell stack, and a high-voltage DC-DC converter; characterized in that it includes: Open the hydrogen supply valve at the anode inlet and the purging valve at the anode outlet to allow hydrogen to enter the fuel cell and purge the anode; First open the air distribution valve, then turn on the air compressor and set the air compressor to high-speed mode; The anode outlet purge valve is opened and closed according to the first switching cycle, and the anode outlet drain valve is opened and closed according to the second switching cycle to perform high-frequency anode purging. The first switching cycle is much shorter than the second switching cycle. When the anode purging is completed and the air flow rate of the air compressor reaches the first threshold, open the cathode inlet isolation valve and the cathode outlet isolation valve to perform high-flow cathode purging. Obtain the voltage value of the fuel cell stack. If the voltage value reaches the second threshold, connect the high-voltage DC-DC converter as a load to the fuel cell. The second threshold is greater than the operating voltage of the high-voltage DC-DC converter.

2. The start-up method for a fuel cell system according to claim 1, characterized in that, The method further includes closing the cathode inlet isolation valve and the cathode outlet isolation valve when the fuel cell system is in a shut-off state.

3. The start-up method for a fuel cell system according to claim 1, characterized in that, The first switching cycle includes: a first opening time and a first closing time; the first opening time is greater than or equal to 1s and less than or equal to 2s, and the first closing time is greater than or equal to 0.5s and less than or equal to 1s.

4. The start-up method for a fuel cell system according to claim 1, characterized in that, The second switching cycle includes: a second opening time and a second closing time; the second opening time is greater than or equal to 1s and less than or equal to 2s, and the second closing time is greater than or equal to 5s and less than or equal to 10s.

5. A starting device for a fuel cell system, applied to a fuel cell system, the fuel cell system comprising: An air diversion valve, an air compressor, a cathode inlet isolation valve, a cathode outlet isolation valve, an anode inlet hydrogen supply valve, an anode outlet purge valve, an anode outlet drain valve, a fuel cell stack, and a high-voltage DC-DC converter; characterized in that it includes: The anode purging start-up module is used to open the anode inlet hydrogen supply valve and the anode outlet purging valve, allowing hydrogen to enter the fuel cell and purge the anode; The first control module is used to first open the air diversion valve, then open the air compressor, and set the working mode of the air compressor to high-speed mode; The anode outlet control module is used to open and close the anode outlet purge valve according to the first switching cycle and open and close the anode outlet drain valve according to the second switching cycle to perform high-frequency anode purging, wherein the first switching cycle is much shorter than the second switching cycle; The cathode purging start module is used to open the cathode inlet isolation valve and the cathode outlet isolation valve to perform high-flow cathode purging when the anode purging is completed and the air flow of the air compressor reaches the first threshold. The load connection module is used to obtain the voltage value of the fuel cell stack. If the voltage value reaches a second threshold, the high-voltage DC-DC converter is connected to the fuel cell as a load. The second threshold is greater than the operating voltage of the high-voltage DC-DC converter.

6. The starting device for a fuel cell system according to claim 5, characterized in that, The device further includes: a first control module, used to close the cathode inlet isolation valve and the cathode outlet isolation valve when the fuel cell system is in a shut-off state.

7. The starting device for a fuel cell system according to claim 5, characterized in that, The first switching cycle includes: a first opening time and a first closing time; the first opening time is greater than or equal to 1s and less than or equal to 2s, and the first closing time is greater than or equal to 0.5s and less than or equal to 1s.

8. The starting device for a fuel cell system according to claim 5, characterized in that, The second switching cycle includes: a second opening time and a second closing time; the second opening time is greater than or equal to 1s and less than or equal to 2s, and the second closing time is greater than or equal to 5s and less than or equal to 10s.

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