CN112086668B

CN112086668B - Multiphase load-changing method for starting and stopping fuel cell

Info

Publication number: CN112086668B
Application number: CN202011021276.XA
Authority: CN
Inventors: 林瑞; 余行; 楼狄明; 陈亮; 石秀勇
Original assignee: Nanchang Intelligent New Energy Vehicle Research Institute
Current assignee: Nanchang Intelligent New Energy Vehicle Research Institute
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2023-04-21
Anticipated expiration: 2040-09-25
Also published as: CN112086668A

Abstract

The invention relates to the field of fuel cells, in particular to a multiphase load changing method for starting and stopping a fuel cell, which provides four basic multiphase auxiliary load changing modes for changing the time-varying process of a load, wherein one or more of a large load, a linear descending load, a two-phase ladder load, a linear descending load, a small load and a three-phase load are respectively designed, and the 4 load changing modes are combined to be matched with the cathode side air consumption process in the starting and stopping depressurization process of the fuel cell, so that the extra performance attenuation caused by the connection of the auxiliary load is avoided, and the durability and the service life of the fuel cell are improved. The control strategy of the multiphase load-changing form can flexibly regulate the fuel cell depressurization time by regulating parameters of multiphase loads, and provides a larger degree of control freedom for achieving the fuel cell depressurization time under specific requirements.

Description

Multiphase load-changing method for starting and stopping fuel cell

Technical Field

The invention relates to the field of fuel cells, in particular to a multiphase load-changing method for starting and stopping a fuel cell.

Background

The fuel cell has the advantages of high energy conversion efficiency, environmental friendliness, high starting speed and the like, and is considered as an ultimate solution of a vehicle. For this reason, various governments and enterprises have proposed development schemes such as the fuel cell partner program (CaFCP), the european urban clean traffic program (cut), the japan hydrogen energy and fuel cell car demonstration program (JHFC), etc. in california.

However, the current Proton Exchange Membrane Fuel Cell (PEMFC) has the disadvantages of high manufacturing cost, short life, poor stability, etc., which prevent large-scale commercial popularization and application of the PEMFC because of its bad and unfavorable operating conditions and transients occurring during normal driving of the vehicle, and PEMFC technology has great challenges in terms of durability. Hydrogen-based fuel cell power transmission systems for electric vehicles must achieve high durability while maintaining high power efficiency and fuel economy to achieve range and life of the internal combustion engine vehicle. The technology also needs to meet cost targets to make fuel cell vehicles (FCEVs) commercially successful.

The durability of the fuel cell is greatly affected by the working condition, and particularly, the durability of the fuel cell for the vehicle can be permanently damaged by frequent start-up and shutdown working conditions or starting after long-time shutdown. For a vehicle-mounted fuel cell engine, various different types of working conditions, such as a start-stop working condition and the like, are frequently experienced. The research result shows that the start-stop working condition has great influence on the service life of the fuel cell and is inferior to the variable load working condition.

Patent CN101159334a published in 4 and 9 in 2008 proposes a method for improving the service life of a fuel cell, which is to add a nitrogen electromagnetic valve and a bottle body filled with nitrogen in front of an anode air inlet of the fuel cell. Before the fuel cell is started, firstly, a nitrogen electromagnetic valve is electrified, nitrogen is sent to an anode cavity of the fuel cell, air permeated in the anode cavity is discharged, and then the nitrogen electromagnetic valve is closed; when the fuel cell stops working, the working electromagnetic valve is closed, the nitrogen electromagnetic valve is opened, nitrogen is fed into the anode cavity of the fuel cell, and residual hydrogen in the anode cavity is discharged. The contact reaction of hydrogen in the anode cavity and permeated air is effectively prevented, and the start-stop durability of the fuel cell is improved. However, the method requires an additional nitrogen cylinder and an electromagnetic valve, which increases the structural complexity of the fuel cell device.

Patent CN103259031B published in 2015, 9 and 30 provides a method for controlling start-up and stop of proton exchange membrane fuel cell. The method is characterized in that a modularized discharging circuit and an air purging device are added on the basis of an original fuel cell system to control, the whole fuel cell stack is divided into a plurality of cell modules, each cell module is connected with a modularized discharging circuit formed by connecting a control switch, an auxiliary load and a transistor diode in series, each discharging circuit and a main load circuit are connected in parallel at two ends of a cathode and an anode of the fuel cell, the control switch controls the connection of the auxiliary load, and the transistor diode controls the on voltage of the whole discharging circuit; the method effectively realizes the safe starting and stopping of the proton exchange membrane fuel cell system, but the method has a plurality of components, and the load is an auxiliary load in a single form, namely, a constant load is connected when the fuel cell is stopped, and the method can not completely fit the internal gas consumption process when the fuel cell is stopped. The constant load commonly used may cause air starvation and counter-electrode phenomena of the fuel cell at the later stages of auxiliary load connection.

Disclosure of Invention

The invention provides a multiphase load-changing form aiming at the starting and stopping conditions of a fuel cell, aims to fit the cathode side air consumption process in the shutdown depressurization process of the fuel cell, avoids the extra performance attenuation caused by air starvation and opposite polarity of an auxiliary load, improves the durability and service life of the fuel cell, and simultaneously provides more flexible shutdown depressurization time.

The aim of the invention is achieved by the following technical scheme: a multiphase load-changing method for starting and stopping a fuel cell, wherein the multiphase load-changing method comprises a plurality of loads with different attributes, and the loads change with time course, and the method specifically comprises one or more of the following 4 methods: high-order load + linear falling load, two-phase ladder load, linear falling load + low-order load, three-phase load.

The load connection means that the cathode side oxygen is consumed by the auxiliary load through the cathode-anode connection after shutdown, only nitrogen is left, the anode side cannot cause a hydrogen/air interface when the next startup/shutdown cycle begins, and the carbon carrier of the cathode catalytic layer is protected from corrosion in the startup process. The multiphase variable load is characterized in that the type, the initial value, the connection time and the linear descending time of the load are changed, the load value in the first stage of multiphase variable load is set larger and bears most of the gas consumption task, and then the descending load connected is used for consuming the gas diffusion layer of the battery and the residual oxygen attached to the catalytic layer, so that the oxygen in the fuel cell is ensured to be exhausted, and the generation of a hydrogen/air interface in the next starting process is further prevented.

The two-phase auxiliary load form of high-order load and linear descending load means that a load of 100-300 mA/cm < 2 > is connected after shutdown, the load is linearly descending to 0 after 5-15 s, and finally unloading is carried out.

The two-phase ladder load control strategy specifically comprises the steps of connecting a high-level load of 100-300 mA/cm < 2 > after stopping, maintaining the suddenly reduced load to be a low-level load of 0-100 mA/cm < 2 > in the moment after the platform period of 1-5 s, and unloading after the platform period of 5-15 s.

The specific form of the linear descending load and low-level load control strategy is to connect the linear descending load after stopping until the low-level load with the size of 0-100 mA/cm < 2 > is reached, and then to maintain the load for 5-15 s in the load platform period and then to unload the load.

The three-phase load control strategy specifically refers to unloading after a combination of three different sequences of high-order load with a platform period of 1-5 s, low-order load with a platform period of 5-15 s and linear load with a platform period of 5-15 s after shutdown.

The invention has the advantages that: (1) The auxiliary load after shutdown consumes oxygen on the cathode side and only nitrogen exists, so that the anode side cannot cause a hydrogen/air interface at the beginning of the next startup/shutdown cycle, and the carbon carrier of the cathode catalytic layer is protected from corrosion in the startup process.

(2) After the auxiliary load is connected in the shutdown process, the reaction gas in the fuel cell is gradually reduced, the gas consumption process is slow and then fast during the shutdown, the demand on the discharge load is gradually reduced, and the load is continuously reduced along with the shutdown. The invention is more suitable for the cathode side air consumption process in the start-stop depressurization process of the fuel cell, avoids the extra performance attenuation caused by air starvation and counter electrode because of connecting auxiliary loads, and improves the durability and service life of the fuel cell.

(3) The control strategy of the multiphase load-changing type can flexibly regulate the fuel cell depressurization time by regulating the parameters of the multiphase load, and provides a larger degree of control freedom for achieving the fuel cell depressurization time under specific requirements.

(4) The auxiliary load mode is simpler to realize for the proton exchange membrane fuel cell system of the vehicle, and the control mode can be integrated on the vehicle control system.

Drawings

FIG. 1 heavy load+linearly decreasing load control method example;

FIG. 2 illustrates an example two-phase ladder load control method;

FIG. 3 illustrates an example linear droop load + low load control method;

FIG. 4 is an example three-phase load control method;

FIG. 5 is a schematic illustration of a temporary shutdown-startup cycle of a fuel cell non-protection load shutdown strategy;

FIG. 6 is a schematic illustration of a temporary shutdown-startup cycle of a two-phase auxiliary load shutdown strategy for a fuel cell;

FIG. 7 is a graph comparing voltage response over time with one shutdown of the unprotected control group and the two-phase auxiliary load group.

Detailed Description

The invention is further described below with reference to the drawings.

A multiphase load-changing method for starting and stopping a fuel cell, wherein the multiphase load-changing method comprises a plurality of loads with different attributes, and the loads change with time course, and the method specifically comprises one or more of the following 4 methods: high load + linear descent load; two-phase ladder loading; linear descent load + low load; a three-phase load.

Example 1

FIG. 1 shows a high-order load+linear descent load control method in a multiphase load-changing method, and the adjustable change parameters of the auxiliary load form are as follows: an initial high load value, a high load time, and a load linear fall time.

Example 2

FIG. 2 is a schematic diagram showing a two-phase ladder load control method in a multiphase load varying method, wherein the auxiliary load type can adjust the variation parameters as follows: high load, high load time, low load, and low load time.

Example 3

FIG. 3 shows a linear descent load+low-order load control strategy in a multiphase load variation method, and the adjustable variation parameters of the auxiliary load form are as follows: high load, high load time, low load, and low load time.

Example 4

FIG. 4 shows an example of a three-phase control strategy in a multiphase load-varying method, where the auxiliary load type can adjust the variation parameters as follows: high load, high load time, medium load time, low load, and low load time.

As shown in fig. 5, the gas consumption process is slow and then fast when the fuel cell is stopped, the demand for discharging load is gradually reduced, and the load should be continuously reduced along with the stop. As shown in fig. 6, the linear two-phase auxiliary load is connected in the shutdown process, and the load is reduced to the low-level load for a certain time. The internal reaction gas of the fuel cell is gradually reduced, and the two-phase auxiliary load strategy is more suitable for the cathode side air consumption process in the start-stop depressurization process of the fuel cell, so that the extra performance attenuation caused by air starvation and opposite polarity due to the connection of auxiliary loads is avoided, and the durability and the service life of the fuel cell are improved.

FIG. 7 is an enlarged comparison of the time course of the voltage drop of the unprotected control group and the two-phase auxiliary load group over time, showing that the voltage of the battery without the auxiliary load drops slowly over time and then quickly over time after shutdown, the voltage drops to 0.1V for about 160s; the cathode oxygen is consumed rapidly by the initial high-level load in the two-phase auxiliary load strategy, the voltage drop speed is higher, the voltage is reduced from the open-circuit voltage to 0.1V for about 20s after the shutdown, and when the low-level load of the two-phase auxiliary load strategy is connected, the voltage drop speed is slowed down, so that air starvation caused by the connection of the auxiliary load can be avoided.

Claims

1. The multiphase load changing method for starting and stopping the fuel cell is characterized in that the multiphase load changing method comprises 3 loads with different attributes, the loads change along with time course, and particularly comprise a high-order load, a low-order load and a linear load, the loads are unloaded after being combined in different sequences, and the depressurization time of the fuel cell is flexibly regulated and controlled by regulating parameters of the multiphase loads.

2. The multiphase load-changing method for starting and stopping fuel cell according to claim 1, wherein the high-order load has a value ranging from 100ma/cm to 300ma/cm ² The value range of the low-order load is 0-100 mA/cm ² The high-order load can be maintained for a period of time, the platform period range is 1-10 s, the low-order load can be maintained for a period of time, the platform period range is 5-20 s, and the change time history from the high-order load to the low-order load is characterized by linearity or stepThe time history of the ladder abrupt change and the linear change is characterized by 3-15 s.

3. The multiphase load changing method for starting and stopping a fuel cell according to claim 1, wherein the control strategy of the three-phase load is that the three-phase load is a combination of three different orders of a high-level load with a platform period of 1-10 s, a low-level load with a platform period of 5-20 s and a linear load with a platform period of 3-15 s after stopping.