CN101221223B - Single slice battery essential resistance and voltage on-line testing system for fuel cell pile - Google Patents

Abstract

The invention relates to an online system for testing the essential resistance and the voltage of a single cell of a fuel cell stack, comprising a testing unit, a programmed AC driving source, a blocking condenser, an electric current detecting module, a keyboard, an LCD unit and a storage unit, which is characterized in that the programmed AC driving source is serially connected with the blocking condenser and then parallel connected with an output end of a fuel cell, and the testing unit is used for controlling the frequency and the amplitude value of the AC driving source periodically through a communication interface and collecting the voltage and the electric current signals of each single cell in order for computing essential resistance; the electric current detecting module, the keyboard, the LCD unit and the storage unit are respectively connected with the testing unit which communicates with a main controller of galvanic pile and other equipments through the communication interface. The online system has compact and legible circuit, high reliability, moderate cost, high measurement precision, quick measurement speed and ample and scalable interfaces, and the invention satisfies the requirements of the real-time and high-precision testing of the essential resistance and the voltage of the single cell of the fuel cell stack.

Description

A kind of fuel cell pack single slice battery essential resistance and voltage on-line testing system

Technical field

The invention belongs to internal resistance of a kind of series electrical source monomer and voltage testing system, particularly a kind of fuel cell pack single slice battery essential resistance and voltage on-line testing system.

Background technology

Fuel cell is a kind ofly will be stored in the device that chemical energy in fuel and the oxygenant converts electric energy to by electrochemical reaction.The maximum characteristics of this device are not relate to burning in the course of reaction, so its energy conversion efficiency is not subjected to the restriction of " Carnot cycle ", and actual service efficiency then is 2～3 times of ordinary internal combustion engine.In addition, advantage such as energy height, noise are little, pollution-free, zero-emission that it also has, so countries in the world all are considered as it one of great brainstorm project that solves environment and energy shortage problem.According in the practical application to the fuel battery power requirement; usually fuel cell pack is composed in series to hundreds of sheet monocell by several; in the fuel cell operation process; the performance and the safety that can influence whole stack unusually of monolithic battery; in order to ensure the operate as normal of fuel cell and assess its performance, must monitor in real time operational factor.Undoubtedly, monolithic battery voltage is the most direct reflection of cell power generation performance, so monitoring in real time.Internal resistance is measurement electronics and proton transmit complexity in electrode a principal element, it also is the key parameter of decision fuel cell power generation efficient, and fuel cell humidity and temperature and its internal resistance have stronger coupled relation, test the soft measurement that can realize by internal resistance, for humidity, the isoparametric control of temperature provide reference to humidity and temperature.Therefore, in order to ensure safe, stable, the efficient operation of fuel cell, must monitor in real time each monolithic internal resistance of fuel cell.But because internal resistance of fuel cell can be capacitive, perception and pure resistive, monolithic internal resistance size is only in μ Ω, m Ω level, and real-time change, and existing General Instrument generally can't accurately be measured it.

The AC impedance of current fuel cell can only be tested by the experimental facilities of complexity, and these equipment comprise the subsystem of many interconnection.These equipment generally comprise high-grade complex instrument such as fuel battery test platform, electronic load, frequency analyzer, and needing the technician correctly to dispose their hardware line, software program and interface communications protocol etc., this makes, and such test platform is very complicated, cost is very high.About patent shows that needing to dispose controlled electron load, frequency analyzer, gpib interface, electric current and voltage waveform on the fuel cell AC impedance Online Transaction Processing hardware obtains equipment etc., testing software needs exclusive data analysis software and various instrument drive programs etc.For example: patent WO02/27342 of Ontario, Canada Hydrogenics Corp and WO2003/083498; The patent WO2003/098769 of Columbia Province of Britain, Canada Greenlight Power Technologies.These equipment come the test fuel cell internal resistance by the control to electronic load, owing to natural fuel battery pile institute bringing onto load can not be controlled by test request, so their method can not be carried out on-line testing.

The above tester also has fuel cell monolithic battery voltage tester function mostly, but the monolithic battery testing impedance separates with the monolithic battery voltage tester and carry out, and this has also limited the performance of its function.

Summary of the invention

The object of the present invention is to provide a kind of simple, reliable fuel cell pack single slice battery essential resistance and voltage on-line testing system, to overcome the deficiency of existing test macro.

To achieve these goals, the present invention includes program control alternating current driving source, capacitance, current detection module, keyboard and liquid crystal display, storage unit, at least one test cell, in parallel with the fuel cell output terminal again behind the program control alternating current driving source serial connection capacitance, test cell is periodically controlled the frequency and the amplitude of alternating current driving source by communication interface, gathers each monolithic battery voltage and current signal successively and carries out internal resistance and calculate; Current detection module, keyboard and liquid crystal display, storage unit (through USB interface) are connected with test cell respectively, and liquid crystal display shows each single slice battery essential resistance and voltage, and to the battery alarm of internal resistance or electric voltage exception; Test cell is communicated by letter with pile master controller or miscellaneous equipment by communication interface, and a plurality of test cells carry out monolithic internal resistance and voltage tester by the fuel cell pack that communication network connects any sheet number.

[0008Be characterized in: test cell is by controller MCU, multiway analog switch, signal conditioning circuit, two alternating current-direct current separation circuits, phase difference detecting circuit, two effective value metering circuits, A/D converter, communication interface and at least one instrument amplifier are formed, its middle controller MCU realizes communicating by letter by communication interface and alternating current driving source, two input ends of each instrument amplifier connect respectively with corresponding each monocell two ends, the output of a plurality of instrument amplifiers links to each other with the input end of a multiway analog switch, the output terminal of multiway analog switch is connected with the input end of the alternating current-direct current separation circuit 1 of voltage acquisition passage, and the control end of multiway analog switch is connected with the I/O mouth of controller MCU; The ac output end of alternating current-direct current separation circuit 1 is connected with the phase difference detecting circuit input end with the input end of effective value metering circuit 1; The input end of signal conditioning circuit links to each other with the output terminal of current detection module, the output terminal of signal conditioning circuit is connected with the input end of the alternating current-direct current separation circuit 2 of current acquisition passage, and the ac output end of alternating current-direct current separation circuit 2 is connected with the phase difference detecting circuit input end with the input end of effective value metering circuit 2; The dc output end of two alternating current-direct current separation circuits and two effective value metering circuit output terminals are connected with controller MCU by A/D converter respectively with the phase difference detecting circuit output terminal with phase difference detecting circuit output terminal and two effective value metering circuit output terminals, and phase difference detecting circuit also has an output terminal to be connected with controller MCU.

Above-mentioned current detection circuit is made up of precise closed-loop Hall current sensor and accurate sampling resistor, realizes accurate I/V conversion, and its output terminal is connected with the signal conditioning circuit input end of test cell.

The controlled device MCU of above-mentioned alternating current driving source controls in real time, and its output current amplitude is not more than 5% of pile electric current, and its output current frequency cycle between 100Hz-20kHz changes.

Signal conditioning circuit is made of instrument amplifier and precision resistance in the above-mentioned test cell.

Two alternating current-direct current separation circuits are made up of second order high pass active filter circuit, voltage follower, step low-pass active filter circuit respectively in the above-mentioned test cell; dc output end constitutes the amplitude limit output protection circuit by current-limiting resistance R, stabilivolt D, and ac output end constitutes the amplitude limit output protection circuit by current-limiting resistance R, Transient Voltage Suppressor TVS.

Phase difference detecting circuit is detected with the phase differential symbol detection by the phase differential absolute value and forms in the above-mentioned test cell, the phase differential absolute value detects and has introduced voltage comparison unit, NOR gate circuit, low pass active filter circuit, amplitude limit output protection circuit, and its output terminal is connected with the A/D converter input end; The phase differential symbol detection is made up of voltage comparison unit, voltage follower, NOR gate circuit, RC differentiating circuit and D-latch, and its output terminal is connected with the I/O mouth of controller MCU.

A/D converter is the A/D converter of 14 bit resolutions in the above-mentioned test cell, it is communicated by letter by the SPI mode with controller MCU, promptly receive control signal and send the analog to digital conversion result, it has 8 analog channels, built-in 4V benchmark and change over clock and 8 * FIFO, and can use external voltage reference (the present invention adopts outside+5V to make voltage reference), have switching time short, precision is high, use advantage flexibly.Between controller MCU and A/D converter, multiway analog switch, phase difference detecting circuit, the communication interface photoelectric isolating circuit is arranged, avoid external noise to disturb, guarantee test cell stable operation.

Storage unit links to each other with test cell middle controller MCU through USB interface in the above-mentioned test cell, controller MCU joins by RS485 communication interface and program control alternating current driving source, test cell is communicated by letter with pile master controller or miscellaneous equipment by CAN, RS232/485 communication interface, and a plurality of test cells carry out monolithic internal resistance and voltage tester by the fuel cell pack that the CAN communication network connects any sheet number.

The present invention compared with prior art, its beneficial effect be measuring system practical, in test process, do not influence the fuel cell operate as normal.Circuit of the present invention is succinct, clear, the reliability height, and cost is moderate, and measuring accuracy height, speed are fast, and the needs that fuel cell pack single slice battery essential resistance and voltage real-time high-precision are tested are satisfied in rich interface and easily expansion.

Description of drawings

Fig. 1 is a structural principle block diagram of the present invention.

Fig. 2 tests any sheet for a plurality of test cells of the present invention and counts the fuel cell pack theory diagram.

Fig. 3 is an alternating current-direct current separation circuit schematic diagram in the test cell of the present invention.

Fig. 4 is a phase difference detecting circuit schematic diagram in the test cell of the present invention.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples, but this embodiment should not be construed as limitation of the present invention.

The present invention includes test cell, program control alternating current driving source and capacitance, current detection module, keyboard and liquid crystal display, storage unit, wherein test cell is by controller MCU, instrument amplifier, multiway analog switch, signal conditioning circuit, the alternating current-direct current separation circuit, phase difference detecting circuit, the effective value metering circuit, A/D converter, RS232/485 communication interface and CAN (control area net) communication interface is formed (Fig. 1), in parallel with fuel cell pack again behind the wherein program control alternating current driving source serial connection capacitance, thus on each monolithic fuel cell, superposeed sinusoidal ac signal.Each monocell both end voltage links to each other with the multiway analog switch input end after instrument amplifier AD621 amplifies 10 times respectively, multiway analog switch controlled device MCU control output road voltage wherein, this road voltage enters the alternating current-direct current separation circuit 1 of voltage acquisition passage.The pile electric current is gathered in real time by precise closed-loop Hall current sensor and accurate sampling resistor, and the sampling resistor both end voltage enters the alternating current-direct current separation circuit 2 of current acquisition passage after instrument amplifier AD620 amplifies 4 times.The ac output end of two alternating current-direct current separation circuits is connected with the phase difference detecting circuit input end with two effective value measured chip AD536 input ends respectively, and dc output end and effective value measured chip AD536 output terminal directly are connected with A/D converter TLC3548 analog input channel.A/D converter TLC3548 sends the analog to digital conversion result for controller MCU in the SPI mode, and controller MCU obtains the phase differential α of alternating voltage electric current according to phase differential symbol and analog to digital conversion result, and obtains pile alternating current I according to the analog to digital conversion result _AC, DC current I _DC, monolithic battery alternating voltage V _ACDC voltage V _DC, calculate single slice battery essential resistance Z in conjunction with phase differential α again:

$Z=\frac{V_{\mathrm{AC}}}{I_{\mathrm{AC}}}(\cos \mathrm{\α}+j\sin \mathrm{\α})$

Controller MCU surveys single slice battery essential resistance Z and voltage V with institute _DCIssue liquid crystal display and show in real time, and internal resistance is shown greater than early warning value or the voltage battery alarm less than warning value.

A plurality of test cell of the present invention connects and can carry out monolithic internal resistance and voltage tester to the fuel cell pack of any sheet number by the CAN communication network, a plurality of monolithic batteries in the fuel cell pack are connected with a test cell input end, all monolithic battery is connected with n test cell input end, program control alternating current driving source and capacitance series connection back are in parallel with the fuel cell pack output terminal, and current detection module is connected (Fig. 2) with test cell 1.Also control program control alternating current driving source in real time in the time of test cell 1 a plurality of single slice battery essential resistances of test and voltage by the RS485 communication interface, gather the pile electric current, and current value sent to other test cell by the CAN communication network, the a plurality of single slice battery essential resistances and the magnitude of voltage of test cell 2～test cell n test send to test cell 1 by the CAN communication network, test cell 1 sends whole single slice battery essential resistances and magnitude of voltage to liquid crystal display and shows, and whole single slice battery essential resistances and magnitude of voltage are sent to cell stores by USB interface, test macro is communicated by letter with PC or miscellaneous equipment by the RS232/485 communication interface of test cell 1.

Voltage acquisition passage alternating current-direct current separation circuit 1 of the present invention is identical with current acquisition passage alternating current-direct current separation circuit 2, the alternating current-direct current separation circuit is made up of second order high pass active filter circuit, voltage follower, step low-pass active filter circuit, forms communication channel and direct current channel (Fig. 3).

1, the communication channel of alternating current-direct current separation circuit is made up of second order high pass active filter circuit and step low-pass active filter circuit; make its output 100Hz-20kHz signal; the amplitude limit output protection circuit that its output terminal has current-limiting resistance R12, Transient Voltage Suppressor TVS to constitute makes its output clamper at-V _TTo+V _TBetween, the safety of protection effective value measured chip AD536 and subsequent device.Second order high pass active filter circuit transport function is:

$A_F\left(s\right)=\frac{-\frac{C1}{C3}{S}^2}{{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png,H200710169083720080324E000011.png"\; state="\{\{state\}\}">S</figure-callout>}}^2+\frac{1}{R2}(\frac{C1}{C2\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}+\frac{1}{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png,H200710169083720080324E000011.png"\; state="\{\{state\}\}">C</figure-callout>}2}+\frac{1}{C3})S+\frac{1}{R1R2C2\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}}$

Passband gain wherein: $A_F(\&infin;)=-\frac{C1}{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}$

Lower frequency limit: $f_n=\frac{1}{2\mathrm{\&pi;}\sqrt{R1R2C2\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}}$

Ratio of damping: $\mathrm{\&epsiv;}=\frac{1}{2}\sqrt{\frac{R1}{R2}}(\frac{C1}{\sqrt{C2\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}}+\sqrt{\frac{C2}{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}}+\sqrt{\frac{C3}{C2}})$

According to A _F(∞)=-1, f _n=100Hz, ε=0.707 and actual resistance, capacitance parameter restriction are got C1=C2=C3=0.1 μ F, R1=7.5k Ω, R2=36k Ω, actual second order high pass active filter circuit A _F(∞)=-1, f _n=97Hz, the 100Hz of system high-pass filtering requirement can be satisfied in ε=0.685.Step low-pass active filter circuit and second order high pass active filter circuit have duality, resistance in the second order high pass active filter circuit is replaced to electric capacity, electric capacity replaces to resistance, just the step low-pass active filter circuit be can get, each resistance, electric capacity actual parameter determined according to passband gain, upper limiting frequency, ratio of damping equally.

2, the direct current channel of alternating current-direct current separation circuit is made up of voltage follower U3, step low-pass active filter circuit and amplifying circuit, and the amplitude limit output protection circuit that its output terminal has current-limiting resistance R13, stabilivolt D1 to constitute makes its output arrive+V at clamper-0.7V _DBetween, the safety of protection A/D converter TLC3548 and subsequent device is in order to avoid damage circuit and chip.Step low-pass active filter circuit and second order high pass active filter circuit have duality, and resistance, capacitance parameter are determined with reference to above-mentioned communication channel second order high pass active filter circuit parameter in the step low-pass active filter circuit.

Phase differential test circuit of the present invention adopts voltage comparator LM311 offset of sinusoidal ac voltage signal V (t), current signal V _i(t) carry out shaping, V (t) and V _i(t) output square wave A, B after over-voltage comparator LM311 shaping, A and B are through NOR gate circuit output C pulse (Fig. 4), and its fourier series expression formula is:

$U_C\left(t\right)=5q+\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}(a_n\cos \mathrm{n\&omega;t}+b_n\sin \mathrm{n\&omega;t})$

Wherein q is C duty of ratio, ω=400 π～12000 π, a _nAnd b _nBe constant.(T=2 π/ω is the cycle of C pulse to C pulse elapsed time constant RC 〉=10T, T _Max≤ 0.005S selects R26=100k Ω, C10=1 μ F can satisfy the requirement of 1.59Hz low-pass filtering herein, satisfies system requirements fully) low pass active filter circuit output burning voltage U _F, i.e. U _C(t) mean value:

$U_F=5q=\frac{5\left|\mathrm{\&alpha;}\right|}{\mathrm{\&pi;}},(0\&le;U\&le;5V)$

U _FBy the amplitude limit output protection circuit that current-limiting resistance R27, stabilivolt D3 constitute, its output clamper at-0.7V to+V _DBetween, entering TLC3548 then and carry out analog to digital conversion, its resolution is:

5/2 ¹⁴＝0.305mV

According to $\left|\mathrm{\&alpha;}\right|=\frac{\mathrm{\&pi;}{\mathrm{<figure-callout\; id="5"\; label="U\; F"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">U</figure-callout>}}_F}{5}$ Phase differential as can be known | α | resolution be 6.1 π * 10 ^-5Radian.Utilize RC differentiating circuit and D-latch to judge the phase differential symbol of A and B, the output Q of D-latch links to each other with the input I/O mouth of controller MCU every 6N137 through light.Q=1 represents that voltage is ahead of electric current, and the phase differential symbol is for just; Q=0 represents the phase differential symbol for negative, and in fact this represented that internal resistance of fuel cell is perception, capacitive or pure resistive.

This phase differential method of testing precision is up to 6.1 π * 10 ^-5Radian, and precision do not influence by the frequency input signal size, is fit to very much the situation of signal frequency wide variation in the native system.Its test specification is-π～π not have the test dead angle.

The content that is not described in detail in this instructions belongs to this area professional and technical personnel's known prior art.

Claims (5)

1. fuel cell pack single slice battery essential resistance and voltage on-line testing system, comprise program control alternating current driving source, capacitance, current detection module, keyboard and liquid crystal display, storage unit, at least one test cell, test cell is communicated by letter with pile master controller or miscellaneous equipment by communication interface, it is characterized in that: test cell is by controller MCU, multiway analog switch, signal conditioning circuit, two alternating current-direct current separation circuits, phase difference detecting circuit, two effective value metering circuits, A/D converter, communication interface and at least one instrument amplifier are formed, its middle controller MCU realizes communicating by letter by communication interface and alternating current driving source, two input ends of each instrument amplifier connect respectively with corresponding each monocell two ends, the output of a plurality of instrument amplifiers links to each other with the input end of a multiway analog switch, the output terminal of multiway analog switch is connected with the input end of the alternating current-direct current separation circuit 1 of voltage acquisition passage, and the control end of multiway analog switch is connected with the I/O mouth of controller MCU; The ac output end of alternating current-direct current separation circuit 1 is connected with the phase difference detecting circuit input end with the input end of effective value metering circuit 1; The input end of signal conditioning circuit links to each other with the output terminal of current detection module, the output terminal of signal conditioning circuit is connected with the input end of the alternating current-direct current separation circuit 2 of current acquisition passage, and the ac output end of alternating current-direct current separation circuit 2 is connected with the phase difference detecting circuit input end with the input end of effective value metering circuit 2; The dc output end of two alternating current-direct current separation circuits and two effective value metering circuit output terminals are connected with controller MCU by A/D converter respectively with the phase difference detecting circuit output terminal, and phase difference detecting circuit also has an output terminal to be connected with controller MCU.

2. fuel cell pack single slice battery essential resistance as claimed in claim 1 and voltage on-line testing system is characterized in that: signal conditioning circuit is made of instrument amplifier and precision resistance in the test cell.

3. fuel cell pack single slice battery essential resistance as claimed in claim 1 and voltage on-line testing system; it is characterized in that: two alternating current-direct current separation circuits are made up of second order high pass active filter circuit, voltage follower, step low-pass active filter circuit respectively in the test cell; dc output end constitutes the amplitude limit output protection circuit by current-limiting resistance R, stabilivolt D, and ac output end constitutes the amplitude limit output protection circuit by current-limiting resistance R, Transient Voltage Suppressor TVS.

4. fuel cell pack single slice battery essential resistance as claimed in claim 1 and voltage on-line testing system, it is characterized in that: phase difference detecting circuit is detected with the phase differential symbol detection by the phase differential absolute value and forms in the test cell, the phase differential absolute value detects and has introduced voltage comparison unit, NOR gate circuit, low pass active filter circuit, amplitude limit output protection circuit, and its output terminal is connected with the A/D converter input end; The phase differential symbol detection is made up of voltage comparison unit, voltage follower, NOR gate circuit, RC differentiating circuit and D-latch, and its output terminal is connected with the I/O mouth of controller MCU.

5. fuel cell pack single slice battery essential resistance as claimed in claim 1 and voltage on-line testing system, it is characterized in that: A/D converter is the A/D converter of 14 bit resolutions in the test cell, it is communicated by letter by the SPI mode with controller MCU, between controller MCU and A/D converter, multiway analog switch, phase difference detecting circuit, the communication interface photoelectric isolating circuit is arranged.

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