CN1750304A - A control method that can improve the stability of fuel cell start-up and shutdown operation - Google Patents

Abstract

This invention relates to a control method for increasing the stable start and close down operation including designing a control system, which operates especially when the generation system of a fuel battery stats and stops according to the time interval of the stop including controlling the H supply and circulation and air supply and discharge for 3~300 seconds 5~20 times of the normal metering ratio of 1.2, 20~2.5 each time when starts and ready to close down the generation system and the system tests itself normal and enters into the idle speed, which can eliminate the water gathering phenomenon in the battery.

Description

A control method that can improve the stability of fuel cell start-up and shutdown operation

technical field

The invention relates to a fuel cell, in particular to a control method capable of improving the stability of the fuel cell for start-up and shutdown operation.

Background technique

An electrochemical fuel cell is a device that converts hydrogen and oxidants into electrical energy and reaction products. The internal core component of the device is the membrane electrode (Membrane Electrode Assembly, referred to as MEA). The membrane electrode (MEA) is composed of a proton exchange membrane and two porous conductive materials, such as carbon paper, sandwiched between the two sides of the membrane. On the two boundary surfaces of the membrane and the carbon paper, there are even and finely dispersed catalysts for initiating electrochemical reactions, such as metal platinum catalysts. Conductive objects can be used on both sides of the membrane electrode to draw the electrons generated during the electrochemical reaction through an external circuit to form a current loop.

At the anode end of the membrane electrode, the fuel can permeate through the porous diffusion material (carbon paper), and an electrochemical reaction occurs on the surface of the catalyst, losing electrons and forming positive ions, which can migrate through the proton exchange membrane, Reach the cathode end of the other end of the membrane electrode. At the cathode end of the membrane electrode, a gas containing an oxidant (such as oxygen), such as air, penetrates through the porous diffusion material (carbon paper), and electrochemically reacts on the surface of the catalyst to obtain electrons to form negative ions. Anions formed at the cathode end react with positive ions migrating from the anode end to form reaction products.

In a proton exchange membrane fuel cell that uses hydrogen as fuel and air containing oxygen as the oxidant (or pure oxygen as the oxidant), the catalytic electrochemical reaction of fuel hydrogen in the anode region produces positive hydride ions (or protons). The proton exchange membrane facilitates the migration of positive hydride ions from the anode region to the cathode region. In addition, the proton exchange membrane separates the hydrogen-containing fuel gas stream from the oxygen-containing gas stream so that they do not mix with each other and cause an explosive reaction.

In the cathode area, oxygen gets electrons on the surface of the catalyst to form negative ions, and reacts with positive hydrogen ions migrated from the anode area to generate water as a reaction product. In a proton exchange membrane fuel cell using hydrogen and air (oxygen), the anode reaction and cathode reaction can be expressed by the following equation:

Anode reaction:

Cathode reaction:

In a typical proton exchange membrane fuel cell, the membrane electrode (MEA) is generally placed between two conductive plates, and the surface of each guide plate in contact with the membrane electrode is formed by die-casting, stamping or mechanical milling to form at least More than one diversion groove. These current guide plates can be made of metal or graphite. The fluid channels and flow guide grooves on these guide plates guide the fuel and oxidant into the anode area and the cathode area on both sides of the membrane electrode respectively. In the structure of a single proton exchange membrane fuel cell, there is only one membrane electrode, and the two sides of the membrane electrode are the deflectors of the anode fuel and the cathode oxidant respectively. These deflectors are not only used as current collectors, but also as mechanical supports on both sides of the membrane electrodes. The guide grooves on the deflectors are also used as passages for fuel and oxidant to enter the anode and cathode surfaces, and as a way to take away fuel cells during the operation of the fuel cell. Channels for the resulting water.

In order to increase the total power of the entire proton exchange membrane fuel cell, two or more single cells can usually be stacked in series to form a battery pack or connected in a tiled manner to form a battery pack. In direct-stacked and series-connected battery packs, there can be diversion grooves on both sides of a pole plate, one of which can be used as the anode diversion surface of one membrane electrode, and the other side can be used as the cathode of another adjacent membrane electrode. The diversion surface, this kind of plate is called a bipolar plate. A series of cells are connected together in a certain way to form a battery pack. The battery pack is usually fastened together by the front end plate, the rear end plate and the tie rods to form a whole.

A typical battery pack usually includes: (1) diversion inlet and diversion channel of fuel and oxidant gas, fuel (such as hydrogen, methanol or methanol, natural gas, hydrogen-rich gas obtained by reforming gasoline) and oxidant (mainly Oxygen or air) is evenly distributed into the diversion grooves of each anode and cathode surface; (2) the inlet and outlet of the cooling fluid (such as water) and the diversion channel, the cooling fluid is evenly distributed into the cooling channels in each battery pack, Absorb the heat generated by the electrochemical exothermic reaction of hydrogen and oxygen in the fuel cell and take it out of the battery pack for heat dissipation; (3) the outlet of the fuel and oxidant gas and the corresponding guide channel, when the fuel gas and oxidant gas are discharged, can Carry out the liquid and vapor state water generated in the fuel cell. Usually, the inlets and outlets of all fuels, oxidants, and cooling fluids are opened on one or both end plates of the fuel cell stack.

Proton exchange membrane fuel cells can be used as the power system of vehicles, ships and other vehicles, and can also be used as mobile and fixed power generation devices.

When the proton exchange membrane fuel cell can be used as a vehicle, ship power system or mobile and fixed power station, it must include battery stack, fuel hydrogen supply system, air supply subsystem, cooling and heat dissipation subsystem, automatic control and power output. .

Fig. 1 is a fuel cell power generation system. In Fig. 1, 1 is a fuel cell stack, 2 is a hydrogen storage bottle or other hydrogen storage device, 3 is a pressure reducing valve, 4 is an air filter device, 5 is an air compression supply device, 6' , 6 is a water-steam separator, 7 is a water tank, 8 is a cooling fluid circulation pump, 9 is a radiator, 10 is a hydrogen circulation pump, 11, 12 are humidification devices.

According to the operating principle or principle of the above-mentioned typical fuel cell power generation system at present, for example, the invention patent of Shanghai Shenli Technology Co., Ltd. "A fuel cell with dynamic control device", the Chinese patent application number is 200410016609.4; 200420020471.0. The controller in the fuel cell power generation system monitors and calculates the operating temperature and output power requirements of the fuel cell to determine the control of the hydrogen flow and air flow, so that the fuel cell stack can achieve any power output requirements: 1 .Associated control of output power and working temperature; 2.Associated control of output power, hydrogen flow, and air flow, in which hydrogen flow and air flow are controlled at 1.2 and 2.0 respectively according to output power requirements; 3. Hydrogen flow and air flow Link dynamic control with corresponding humidification devices that can realize dynamic humidification adjustment and control, so that the hydrogen and air entering the fuel cell stack at any flow rate can maintain the best relative humidity (somewhere between 70% and 95%) 4. According to the temperature and humidity of the outside weather, the adjustment and control method is the same as point (3), and achieves the same purpose as point (3). The ultimate goal is to enable the fuel cell stack to achieve high-efficiency operation and operate under optimal working conditions under any power output requirement, and the fuel cell stack can have the best fuel efficiency.

The principle and principle of the dynamic control of the above-mentioned fuel cell power generation system is to realize automatic monitoring and calculation according to the operating parameters of the fuel cell in different operating temperatures, environments, power output requirements, etc., and to control according to the set target value to achieve the fuel cell. Batteries run at optimum working conditions and with high efficiency.

Among them, the correlation control between output power, hydrogen flow and air flow, hydrogen flow is required by the output power with a metering ratio of 1.2; air flow is controlled according to the output power required metering ratio of 2.0 to 2.5 is very important, otherwise it will take a long time to Running for a long time will not only reduce the overall efficiency of the entire fuel cell power generation system, but also make the operating conditions of the fuel cell abnormal. In severe cases, the performance of the fuel cell will be reduced or even irreversibly lost.

Although the dynamic target control of the above-mentioned fuel cell power generation system can ensure the long-term operation of the entire fuel cell and achieve high efficiency, it also has the following technical defects:

1. When the fuel cell power generation system starts and then enters the idling state (at this time, the output power of the entire power generation system is zero), the dynamic target control of the fuel cell power generation system requires that the air and hydrogen flow in the fuel cell power generation system are very small, and only the power generation system is supported. Some power consuming devices run by themselves. When the fuel cell power generation system stops working for a long time and restarts, it is very likely that the air and hydrogen supply and discharge of the fuel cell power generation system will condense and accumulate water inside the circulation subsystem due to temperature changes in the weather environment. At this time, the fuel cell power generation system is still in the idling state after starting, and the hydrogen supply cycle, air supply, and discharge are very small, and the internal water cannot be discharged.

2. When the fuel cell power generation system produces a large amount of product water after high-power operation but quickly enters the idling state and then shuts down, the air, hydrogen supply and discharge of the fuel cell power generation system, and the product water inside the circulation subsystem are not Drain clean, it will accumulate inside the fuel cell.

The above two conditions will cause water accumulation inside the fuel cell, and in severe cases, some air and hydrogen guide grooves in the fuel cell stack will be blocked, thereby affecting the operation stability of the fuel cell. Water blockage in the hydrogen diversion groove or air diversion groove in a single cell will cause the single cell to be starved of fuel hydrogen or insufficient air supply, and the performance of the single cell will drop sharply, and in severe cases it will lead to the The electrode is reversed and burned.

Contents of the invention

The object of the present invention is to provide a kind of control method that can improve the fuel cell stability start-up and shutdown operation in order to overcome the above-mentioned defects in the prior art. Operational stability of fuel cells.

The purpose of the present invention can be achieved through the following technical solutions: a control method that can improve the stability of the fuel cell starting and shutting down operation, it is characterized in that the method includes designing a control system, and the control system is based on the shutdown of the fuel cell power generation system The time interval is to carry out specific operation operations when the fuel cell power generation system is started and stopped. The specific operation operation includes the hydrogen supply and Circulation, air supply and discharge are controlled to run for 3 to 300 seconds according to 5 to 20 times the normal metering ratio of 1.2, 2.0 to 2.5.

The control system includes CAN/CAN protocol converter, command controller, CAN/485 converter, air pump frequency converter, air pump, single-chip controller, hydrogen drainage solenoid valve, hydrogen circulation pump, CAN card, monitoring PC, The CAN/CAN protocol converter transmits data between the internal CAN2 bus of the fuel cell power generation system and the CAN1 bus of the upper controller of the fuel cell power generation system, and the command controller controls the reception of data from the CAN/CAN protocol converter to control the entire The fuel cell power generation system starts and shuts down, the air frequency converter receives commands from the command controller through the CAN/485 converter to control the speed of the air pump, and the single-chip controller receives commands from the command controller to control the hydrogen drainage solenoid valve The hydrogen circulation speed of the switch and the hydrogen circulation pump, the monitoring PC receives and records the operation data of the command controller through the CAN card and provides manual monitoring.

The CAN/CAN protocol converter is also called a network bridge. The baud rate and data format of the CAN1 network of the upper controller are different from those of the internal CAN2 network of the fuel cell power generation system, including the upper controller sending start and stop signals and transmitting fault codes. All must be converted by the bridge.

The command controller detects the control signal of the CAN2 network to distinguish between short-term shutdown and long-term shutdown. When the fuel cell power generation system is started, if the upper controller sends a short-term shutdown command, the command controller executes a short-term air pump and hydrogen Circulation pump speed-up operation, if the upper controller sends a long-time shutdown command, the instruction controller will perform long-term air pump speed-up and hydrogen circulation pump speed-up operations.

The monitoring PC can accept manual operation instructions, and sends operation instructions to the instruction controller through the CAN card to increase the speed of the air pump, the hydrogen circulation pump, and switch the solenoid valve for hydrogen drainage.

The control method of the present invention performs special operation control when the fuel cell power generation system starts and stops according to the shutdown time interval of the fuel cell power generation system. Generally speaking, every time the fuel cell power generation system is started, after the system self-checks to be normal and enters the idle state, the hydrogen supply and circulation, air supply and discharge will be controlled and operated at 5 to 20 times the normal metering ratio of 1.2, 2.0 to 2.53 seconds to 300 seconds to ensure that all accumulated water in the hydrogen and air subsystems of the fuel cell power generation system is carried out by the large flow of hydrogen and air without causing stagnation.

Description of drawings

1 is a schematic diagram of an existing fuel cell power generation system;

Fig. 2 is a schematic diagram of the operation of the control method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 2, a control method that can improve the stability of fuel cells starting and shutting down, the method includes designing a control system, the control system includes CAN/CAN protocol converter, command controller, CAN/485 converter , Air pump (controlling motor speed) frequency converter, air pump M1 (motor), microcontroller controller, hydrogen drainage solenoid valve, hydrogen circulation pump M2, CAN card, monitoring (computer) PC, etc. The CAN/CAN protocol converter is also called a network bridge, which is used to transmit data between the internal CAN2 bus of the fuel cell power generation system and the CAN1 bus of the upper controller of the fuel cell power generation system. The baud rate and data format of the CAN1 network of the upper controller are different from those of the CAN2 network inside the fuel cell power generation system. For example, the upper controller sends start and stop signals and transmits fault codes, etc., all need bridge conversion. The air pump inverter can receive commands from the command controller to control the speed of the air pump motor through the CAN/485 converter. The controller controls the data received from the CAN/CAN protocol converter to control the start-up and shutdown and operating status of the entire fuel cell power generation system, and transmits it to the monitoring PC through the CAN card to record operating data and provide manual monitoring.

The command controller detects the control signal of the CAN2 network to distinguish between temporary shutdown and long-term shutdown. Due to the temporary shutdown controlled by the upper controller, the controller is instructed to execute a very short speed-up program of the air pump M1 and the hydrogen circulation pump M2 at the next startup. The upper controller thinks that the cold machine starts after a long shutdown, and automatically controls when it is turned on and off. The air pump inverter increases the air flow, and executes the long-term air pump speed-up and hydrogen pump speed-up procedures. In special cases, the speed of the air pump can be increased at any time by monitoring the PC to bring out excess liquid water. At the same time, the single-chip controller can be controlled to drive the hydrogen circulation pump and the hydrogen drainage solenoid valve to increase the hydrogen flow.

This embodiment 1 is a control method for starting and stopping operation of a 50KW fuel cell power generation system. According to the normal flow metering ratio of hydrogen: 1.2; air 2.0 implements flow target control; The total flow in the stack is 20 liters/minute and 100 liters/minute respectively; when the output is 50KW at full load, they are 600 liters/minute and 2.5 cubic meters/minute respectively. When the control system detects that the shutdown time of the fuel cell power generation system has exceeded 12 hours, when the power generation system is restarted, when the system controller self-tests to be normal, and then enters the idle state, the controller immediately starts a special program. Increase the flow rate of hydrogen and air to 400 L/min and 2000 L/min for 60 seconds. When the fuel cell power generation system detects that the shutdown time is 5 minutes, after restarting, the system controller self-tests to be normal, and then enters the idle state, and immediately starts a special program to increase the hydrogen and air flow to 400 liters/ minutes, 2000 liters/minute, and a duration of 3 seconds.

Each time before the fuel cell power generation system shuts down, enter the idling state and increase the flow of hydrogen and air to 400 liters/minute and 2000 liters/minute for 10 seconds, and then shut down.

Example 2

As shown in FIG. 2 , a control method for improving the stability of fuel cell start-up and shutdown operation includes designing a control system, which is basically the same as that of Embodiment 1. The difference is: when the control system detects that the shutdown time of the fuel cell power generation system is about 6 hours, when the power generation system restarts, when the system controller self-tests to be normal, and then enters the idle state, the controller immediately starts a special program , at idle speed, increase the hydrogen and air flow rates to 100 liters/minute and 500 liters/minute for 180 seconds. When the fuel cell power generation system detects that the shutdown time is 5 minutes, after restarting, the system controller self-tests to be normal, and then enters the idle state, and immediately starts a special program to increase the hydrogen and air flow to 100 liters/ minutes, 500 liters/minute, and a duration of 12 seconds. Each time before the fuel cell power generation system shuts down, it enters the idle state and increases the flow of hydrogen and air to 100 liters/minute and 500 liters/minute for 40 seconds.

Example 3

As shown in FIG. 2 , a control method for improving the stability of fuel cell start-up and shutdown operation includes designing a control system, which is basically the same as that of Embodiment 1. The difference is: when the control system detects that the shutdown time of the fuel cell power generation system has exceeded 24 hours, when the power generation system is restarted, when the system controller self-tests to be normal, and then enters the idle state, the controller immediately starts a special program , at idle speed, increase the hydrogen and air flow rates to 400 liters/minute and 2000 liters/minute for 300 seconds.

Claims (5)

1. A control method capable of improving stability of fuel cell starting and shutdown operation is characterized by comprising the step of designing a control system, wherein the control system carries out specific operation according to the shutdown time interval of a fuel cell power generation system when the fuel cell power generation system is started and shut down, the specific operation comprises the steps of starting and preparing to shut down the fuel cell power generation system each time, hydrogen is supplied and circulated after the power generation system is self-checked to normally enter an idling state, and air supply and discharge are controlled to operate for 3-300 seconds according to 5-20 times of a normal metering ratio of 1.2 and 2.0-2.5.

2. The method as claimed in claim 1, wherein the control system comprises a CAN/CAN protocol converter, a command controller, a CAN/485 converter, an air pump inverter, an air pump, a single chip microcomputer controller, a hydrogen drain solenoid valve, a hydrogen circulation pump, a CAN card, and a monitor PC, the CAN/CAN protocol converter transmits data between a CAN2 bus inside the fuel cell power generation system and a CAN1 bus of an upper controller of the fuel cell power generation system, the command controller controls the whole fuel cell power generation system to start and shut down, the air inverter receives a command from the command controller through the CAN/485 converter to control the rotation speed of the air pump, and the single chip microcomputer controller receives a command from the command controller to control the switching of the hydrogen drain solenoid valve and the hydrogen circulation pump And the monitoring PC receives and records the operation data of the command controller through the CAN card and provides manual monitoring.

3. The method as claimed in claim 2, wherein the CAN/CAN protocol converter is also called a bridge, baud rate and data format of the CAN1 network of theupper layer controller are different from those of the CAN2 network in the fuel cell power system, and the upper layer controller is required to transmit start and stop signals and transmit fault codes.

4. The method as claimed in claim 2, wherein the command controller detects the control signal of the CAN2 network to distinguish between short-time shutdown and long-time shutdown, and when the fuel cell power generation system is started, if the upper controller issues the short-time shutdown command, the command controller executes the short-time air pump and hydrogen circulation pump speed-up operation, and if the upper controller issues the long-time shutdown command, the command controller executes the long-time air pump speed-up and hydrogen circulation pump speed-up operation.

5. The method as claimed in claim 2, wherein the monitoring PC receives manual operation commands and sends operation commands to the command controller via the CAN card to activate the air pump, the hydrogen circulation pump and the hydrogen drain solenoid valve.

Images