CN100464195C - A safe and accurate fuel cell voltage monitoring device - Google Patents

Abstract

The invention relates to a safe and exact fuel battery voltage detect device, which include single battery voltage detect device, fuel battery controller. The single battery voltage detect device include some difference amplifiers, some multiple-way switch, SCM having CAN bus communication interface. The SCM include an ADC and CPU. The difference amplifiers connect with single battery one by one corresponding, to measure the voltage difference between the two single poles of the fuel battery galvanic pile. The multiple-way switch is on or off by the control of the CPU. The ADC transforms the voltage signals outputted from the difference amplifiers to digital signals. The CPU analyzes the digital signals and gets the monitoring information, then the SCM sends the information out to fuel battery controller.

Description

A safe and accurate fuel cell voltage monitoring device

technical field

The invention relates to fuel cells, in particular to a safe and accurate fuel cell voltage monitoring device.

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: H ₂ → 2H ⁺ +2e

Cathode reaction: 1/2O ₂ +2H ⁺ +2e→H ₂ O

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 not only as power systems for vehicles, ships and other vehicles, but also as mobile or fixed power stations.

Proton exchange membrane fuel cells are generally composed of several single cells. These single cells are connected in series or parallel to form a proton exchange membrane fuel cell stack, and the proton exchange membrane fuel cell stack is combined with other operating support systems to form the entire proton exchange membrane fuel cell stack. Exchange membrane fuel cell power generation system.

Since each proton exchange membrane fuel cell stack module is generally composed of several single cells connected in series or in parallel, it is particularly important to monitor and automatically control the working voltage of the fuel cell, especially the working voltage of all single cells, and the safety alarm. Because any abnormal situation of the entire fuel cell power generation system, such as overcurrent, exceeding the normal operating temperature, etc., will show that the operating voltage of some single cells is in an abnormal state. Especially when electrode breakdown occurs, the output voltage of the single cell where the electrode is located will reach an abnormal value, such as close to zero, or even a negative value, while the output voltage of other normal single cells is generally between 1.2 and 0.5V. Electrodes running at negative values for a long time will cause permanent damage and unsafe factors. Therefore, it is very important to monitor the single cells of each module of the fuel cell stack. When the working voltage of individual or some single cells is lower than the normal working voltage of other single cells, the control subsystem of the fuel cell power generation system should alarm in time, and even execute shutdown , cut off the load, cut off the hydrogen supply and other commands.

See Figure 1, Figure 2. FIG. 1 is an electrical block diagram of an existing fuel cell voltage single-cell voltage detector, including a fuel cell stack 101 , several photoelectric switches 102 , A/D converters 103 and a CPU 104 . FIG. 2 is a schematic diagram of an existing fuel cell voltage monitoring device, including a fuel cell stack 201 , a fuel cell voltage single cell voltage detector 202 , a fuel cell controller 203 , and a CAN bus 204 .

As shown in Figure 2, in the traditional control mode, after the fuel cell voltage monitor measures the voltage of the monitoring point, the measured value of each monitoring point is sent to the controller through the CAN bus. Due to the constraints of the CAN bus communication rate and the operating conditions of dozens to hundreds of single electrodes that need to be monitored by each fuel cell, the voltage of each monitoring point is usually sent to the fuel cell controller by means of cycle interval transmission. value, the controller analyzes all the data to find out whether the performance of the fuel cell electrode is normal. Usually there is a way to increase the number of fuel cell electrodes monitored by monitoring points to make up for the lack of communication speed. There are following deficiencies in the above approach:

1. Since all the monitoring point voltages are sent to the controller, the time difference between the two voltage values obtained by the controller before and after each monitoring point is often hundreds of milliseconds to more than 1000 milliseconds. The controller cannot judge in real time whether the electrodes of the fuel cell are working normally.

2. A large amount of data is transmitted on the CAN bus, which reduces the reliability of communication.

3. The controller needs to process a large amount of monitoring point voltage data.

4. Increasing the number of monitoring points cannot fully make up for the lack of communication speed, and will cause when the fuel cell electrode fails, because one monitoring point measures too many electrodes, it is impossible to determine which electrode fails.

Shanghai Shenli Company "A voltage monitoring and monitoring device suitable for large-scale integrated fuel cells" (invention patent application number: 2004100175089; utility model application number: 2004200216703). The technical problem to be solved by the patented invention is to provide a voltage monitoring and monitoring device suitable for large-scale integrated fuel cells. The single-cell voltage monitor used in the device includes a single-chip microcomputer with a controller area bus (CAN bus) communication interface, a number of photoelectric switch devices, and the photoelectric switch devices are connected with the single cells to be monitored one by one, and the output signal of the single-chip microcomputer is circuit controlled. The corresponding photoelectric switch device is turned on or closed, and the collected value is filtered and processed and sent to the analysis controller through the CAN bus. The schematic diagram of the single cell voltage monitor is shown in Fig. 2 .

Although this patented technology can monitor the output voltage of a single cell or a group of single cells in a large-scale integrated fuel cell, it also has some technical defects. Switch the corresponding photoelectric switch off or on. When the CPU is working, it is necessary to ensure that only 2 adjacent photoelectric switches are turned on each time. The voltage difference between the adjacent 2 single electrodes is sent to the A/D converter in the microcontroller for Analog-to-digital conversion, the CPU corresponds the converted digital quantity to the voltage value, so as to obtain the monitoring point voltage. However, when the single-chip CPU is disturbed, the signal on the I/O port controlling the photoelectric switch may be reversed, changing from 0 to 1 or from 1 to 0. When the signal is changed from 0 to 1, it will cause The two electrodes whose signals are both 1 are short-circuited, so that the single-electrode voltage of this road is also connected to the CPU in series. The higher voltage is added to the CPU, which may cause the CPU to burn out, or cause the electrodes to burn out.

Contents of the invention

The object of the present invention is to provide a safe and accurate fuel cell voltage monitoring device in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions: a safe and accurate fuel cell voltage monitoring device, characterized in that the device includes a single cell voltage detector and a fuel cell controller, and the described single cell voltage detector includes Some differential amplifiers, some multi-way switches, a single-chip microcomputer with a controller area bus (CAN bus) communication interface, the single-chip microcomputer includes an A/D converter and a CPU, and the several differential amplifiers and the single cells that need to be monitored one by one Corresponding to the connection, monitor the voltage difference between the two single electrodes of the fuel cell stack, the multi-way switch is switched off or on in turn under the control of the CPU, and the A/D converter turns the multi-way switch into The obtained differential amplifier output voltage signal is converted into a digital signal, the CPU obtains the digital signal and analyzes it to obtain the monitoring information of the fuel cell voltage, and the single chip microcomputer sends the monitoring information to the fuel cell controller through the CAN bus.

The differential amplifier is a precise low-power unity-gain differential amplifier, which has a relatively large input range in the normal mode. Accurate 1V/1 differential gain and high rejection ratio in common mode, excellent temperature characteristic curve of resistor network, suitable for industrial field environments from -40°C to +85°C.

Every two adjacent single electrodes of the fuel cell use a differential amplifier, and when monitoring the fuel cell stack voltage with multiple single electrodes, multiple differential amplifiers are used sequentially; the differential amplifier has two low and high Voltage signal input terminal Vin-, Vin+, an output terminal V _o ; each single electrode of the fuel cell has a voltage output terminal; the voltage output terminal of the first single electrode in the fuel cell stack is only connected to the first differential amplifier The low-voltage input terminal Vin- is connected, the voltage output terminal of the last single electrode is only connected to the high-voltage input terminal Vin+ of the last differential amplifier, and the voltage output terminals of each other single electrode are divided into two circuits, respectively connected to the adjacent The high and low voltage input ends of the two differential amplifiers are connected.

The input terminals of the multi-way switch are correspondingly connected to the output ends of the differential amplifiers. When the number of the differential amplifiers exceeds the number of connections of the input terminals of a multi-way switch, a plurality of multi-way switches are used, and the multi-way switches take turns under the control of the CPU. conduction.

The input end of the A/D converter is connected to the output end of the multi-way switch, and when multiple multi-way switches are used, correspondingly multiple A/D converters are used.

The fuel cell stack can be provided with one or more such fuel cell voltage monitors according to the total number of composed cells.

The monitoring device can analyze the performance of the monitored fuel cell electrodes in real time. The analysis information of the monitoring points includes the number and voltage value of one or several monitoring points with the lowest voltage. When the voltage of a certain monitoring point Shutdown information generated when it is lower than the allowable limit value of the fuel cell electrode and exceeds the allowable time, and the fault information generated when the voltage of a certain monitoring point is lower than the allowable fault value of the fuel cell electrode and exceeds the allowable time, all monitoring points the total voltage value.

The monitoring device can optionally send the voltage values of all monitoring points.

Due to the adoption of the above technical solutions, the present invention overcomes the defects in the prior art. Compared with the prior art, the present invention has the following advantages:

1. Since a differential amplifier is used between every two electrodes, there will be no short circuit between the electrodes, ensuring the safety of the electrodes and the CPU.

2. Due to the use of a high-precision differential operational amplifier, the measurement accuracy of the battery voltage is improved.

3. The controller can obtain the working performance of the electrode in real time.

4. The amount of data communication is reduced.

5. The amount of data processing of the controller is greatly reduced. Each voltage monitor analyzes the voltage of the monitoring point and informs the controller whether to perform emergency shutdown, fault handling and other actions.

6. The position of the faulty electrode can be known quickly.

Description of drawings

Fig. 1 is the electrical block diagram of the original fuel cell voltage single cell voltage detector;

Figure 2 is a schematic diagram of the original fuel cell voltage monitoring device;

Fig. 3 is the electric block diagram of existing fuel cell voltage single-cell voltage detector;

Fig. 4 is a schematic diagram of the existing fuel cell voltage monitoring device;

FIG. 5 is a schematic diagram of the input and output ports of the differential operational amplifier.

Detailed ways

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

See Figure 3, Figure 4. Fig. 3 is the electric block diagram of a kind of example of fuel cell voltage cell voltage detector of the present invention, comprises several differential amplifiers 302, several multiplex switches 303, the A/D converter 304 and CPU 305 that comprise in the one-chip computer, several The differential amplifier 302 is connected to the single cells 301 that need to be monitored one by one, and monitors the voltage difference between the two single electrodes of the fuel cell stack 301. The multi-way switch 303 is switched off or on in turn under the control of the CPU 305, A The /D converter 304 converts the output voltage signal of the differential amplifier obtained when the multi-way switch 303 is turned on into a digital signal, and the CPU 305 obtains the digital signal and analyzes it to obtain monitoring information on the voltage of the fuel cell. Referring to FIG. 4 , the single-chip microcomputer in the fuel cell voltage single-cell voltage detector sends the monitoring information to the fuel cell controller 403 through the CAN bus 404 . In this figure, the device detects a total of 32 single cells.

Referring to Figure 5, it is a schematic diagram of the input and output ports of the differential operational amplifier, Vin+ and Vin- are the two high and low voltage input terminals of the differential amplifier, and V _o is the voltage output terminal of the differential amplifier.

Example 1

The method of the present invention is further described in conjunction with specific component models.

Combined with Figure 2, the differential amplifier adopts INA148±200V common-mode voltage differential amplifier, and the CPU adopts LPC2119 single-chip 32-bit ARM chip of PHILIPS Company, which has 4 A/D converters and CAN bus interface, and the multi-channel switch adopts 74HC4051 Eight-channel multiplexer, its working process is as follows:

1. Use INA148 to measure the voltage difference V _o between two electrodes = (Vin+)—(Vin-)

2. Use 8 to 1 multi-way switch to switch between 8 electrodes in turn.

3. Send V _o to A/D for conversion.

4. Correspond the converted digital quantity with the voltage value.

5. Repeat the above steps 1-4 to get the voltage value of 32 electrodes.

6. Add the voltage difference between each electrode to get the total voltage by program.

Example 2

The method of the present invention will be further described in conjunction with the embodiment of measuring the voltage difference between the 4th and 5th electrodes of the fuel cell stack.

Combined with Figure 2, when it is necessary to measure the voltage difference between the 4 and 5 electrodes of the fuel cell stack, the working process is as follows:

1. The INA148 connected between the two electrodes 4 and 5 obtains the analog signal V _o = (Vin+)-(Vin-) of the voltage difference between electrode 4 and electrode 5.

2. Use the three I/O ports P0.16, P0.17, and P0.18 of LPC2119 to gate the multi-way switch 1, and the gate status table is as follows:

P0.18 P0.17 P0.16 Gated electrode electrode voltage difference 0 0 0 1, 2 electrode voltage difference 0 0 1 2, 3 electrode voltage difference 0 1 0 3, 4 electrode voltage difference 0 1 1 4, 5 electrode voltage difference 1 0 0 5, 6 electrode voltage difference

1 0 1 6, 7 electrode voltage difference 1 1 0 7, 8 electrode voltage difference 1 1 1 8, 9 electrode voltage difference

Compilation of software program control can make P0.18=0, P0.17=1, P0.16=1, select multi-way switch.

3. Use A/D1 to convert V _o from digital to analog.

4. Correspond the converted digital quantity with the voltage value.

5. Obtain the voltage difference between the two electrodes 4 and 5.

Example 3

The method of the present invention will be further described in conjunction with the embodiment in which the single-chip computer analyzes the monitoring information of the fuel cell voltage.

Combined with Figure 4, the specific implementation process of the single-chip microcomputer analyzing the monitoring information of the fuel cell voltage is as follows:

1. Sampling filter

The single-chip microcomputer selects the measurement point through chip selection, and samples each monitoring point in the fuel cell stack 301 once every 5 ms, that is, 200 samples per second. For every 20 measured values, remove the maximum value and the minimum value and calculate the average value by weighting to obtain the measured value. In this way, a measured value is obtained every 100ms.

2. Data communication

First add up the above measured values to get the total voltage. Calculate the serial number and voltage value of the monitoring point with the lowest voltage value according to the above measured values. When the voltage of a certain monitoring point is lower than the allowable limit value of the fuel cell electrode and exceeds the allowable time, a shutdown message is generated. When the voltage of a monitoring point is lower than the allowable fault value of the fuel cell electrode and exceeds the allowable time, a fault message is generated. Send the above information to the CAN bus through one frame (multi-frame) data.

3. Other

When using activated electrodes and other occasions where the voltage of each monitoring point needs to be known, the user is allowed to activate the function of sending the voltage values of all monitoring points.

For example, in a 50KW fuel cell power station, there are 480 electrodes in total, and each voltage monitoring point monitors 2 electrodes, and there are 240 voltage monitoring points in total. The fuel cell is divided into four modules, using four voltage monitors, and each voltage monitor monitors 60 voltage monitoring points. Using the above method, each voltage monitor sends the monitored fuel cell electrode operating conditions at the voltage monitoring point to the controller at intervals of 0.2s. The four voltage monitors send a total of 20 frames of CAN data to the controller. (Usually, if the controller is notified of all the voltage monitoring points once in 0.2s, at least 300 frames of CAN data need to be sent. Voltage monitoring points/CAN maximum voltage monitoring point data per frame/time interval)

Claims (7)

1. A safe and accurate fuel cell voltage monitoring device is characterized in that the device includes a single cell voltage detector and a fuel cell controller, and the described single cell voltage detector includes several differential amplifiers, some multi-way switches, The single-chip microcomputer of controller area bus (CAN bus) communication interface, described single-chip microcomputer comprises A/D converter and CPU, and described several differential amplifiers are connected with the single cells that need to be monitored one by one, and monitor the two fuel cell stacks. The voltage difference between the single electrodes of the chip, the multi-way switch is switched off or on in turn under the control of the CPU, and the A/D converter converts the output voltage signal of the differential amplifier obtained when the multi-way switch is turned on It is a digital signal, and the CPU obtains the digital signal and obtains the monitoring information of the fuel cell voltage through analysis, and the single-chip microcomputer sends the monitoring information to the fuel cell controller through the CAN bus; the monitoring device can monitor the monitored information in real time. The performance of the fuel cell electrode is analyzed. The analysis information of the monitoring points includes the number and voltage value of one or several monitoring points with the lowest voltage. When the voltage of a certain monitoring point is lower than the limit value allowed by the fuel cell electrode and Shutdown information generated when the allowable time is exceeded, fault information generated when the voltage of a certain monitoring point is lower than the allowable fault value of the fuel cell electrode and exceeds the allowable time, and the total voltage value of all monitoring points. 2. A safe and accurate fuel cell voltage monitoring device according to claim 1, wherein the differential amplifier is an accurate low power consumption unity gain differential amplifier, which has a larger Input range, which consists of an ultra-precision bipolar operational amplifier with an ultra-high-precision thin-film resistor network, has a more accurate 1V/V differential gain and a higher rejection ratio in common mode, and the resistor network has excellent temperature characteristics The curve is suitable for industrial site environments from -40°C to +85°C. 3. A safe and accurate fuel cell voltage monitoring device according to claim 1 or 2, characterized in that, every two adjacent single electrodes of the fuel cell use a differential amplifier to monitor When the fuel cell stack voltage is high, multiple differential amplifiers are used sequentially; the differential amplifier has two voltage signal input terminals Vin-, Vin+ and an output terminal V _o for low and high voltage signals; each single electrode of the fuel cell has a Voltage output terminal; the voltage output terminal of the first single electrode in the fuel cell stack is only connected to the low voltage input terminal Vin- of the first differential amplifier, and the voltage output terminal of the last single electrode is only connected to the last differential amplifier The high-voltage input terminal Vin+ of each single electrode is connected to each other, and the voltage output terminal of each other single electrode is divided into two circuits, which are respectively connected to the high-voltage and low-voltage input terminals of two adjacent differential amplifiers. 4. A safe and accurate fuel cell voltage monitoring device according to claim 1, characterized in that the input terminals of the multi-way switch are correspondingly connected to the output terminals of the differential amplifiers, and when the number of differential amplifiers exceeds one or more When the number of input terminals of the multi-way switch is connected, multiple multi-way switches are used, and the multi-way switches are turned on in turn under the control of the CPU. 5. A safe and accurate fuel cell voltage monitoring device according to claim 1, characterized in that the input end of the A/D converter is connected to the output end of the multi-way switch. When switching, a plurality of A/D converters are used correspondingly. 6. A safe and accurate fuel cell voltage monitoring device according to claim 1, characterized in that, the fuel cell stack is set with one or more single cell voltages according to the total number of single cells formed Detector. 7. A safe and accurate fuel cell voltage monitoring device according to claim 1, characterized in that said monitoring device can optionally send voltage values of all monitoring points.

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