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 test system for the internal resistance and voltage of a fuel cell stack single-chip battery, which includes a test unit, a program-controlled AC current excitation source, a DC blocking capacitor, a current detection module, a keyboard, a liquid crystal display unit, and a storage unit, and is characterized in that: The program-controlled AC current excitation source is connected in series with a DC blocking capacitor and then connected in parallel with the output of the fuel cell. The test unit periodically controls the frequency and amplitude of the AC current excitation source through the communication interface, and sequentially collects the voltage and current signals of each single cell and performs Internal resistance calculation; the current detection module, keyboard, liquid crystal display unit, and storage unit are respectively connected to the test unit, and the test unit communicates with the main controller of the stack or other equipment through the communication interface. The invention has simple and clear circuit, high reliability, moderate cost, high measurement accuracy, fast speed, abundant interfaces and easy expansion, and meets the needs of real-time and high-precision testing of the internal resistance and voltage of a single-chip battery of a fuel cell stack.

Description

An online test system for the internal resistance and voltage of a fuel cell stack monolithic battery

technical field

The invention belongs to a system for testing the internal resistance and voltage of a series power supply unit, in particular to an on-line testing system for the internal resistance and voltage of a fuel cell stack monolithic battery. the

Background technique

A fuel cell is a device that converts chemical energy stored in fuel and oxidant into electrical energy through an electrochemical reaction. The biggest feature of this device is that no combustion is involved in the reaction process, so its energy conversion efficiency is not limited by the "Carnot cycle", and the actual efficiency is 2 to 3 times that of ordinary internal combustion engines. In addition, it also has the advantages of high energy, low noise, no pollution, and zero emissions. Therefore, countries all over the world regard it as one of the major research projects to solve the problems of environment and energy shortage. According to the fuel cell power requirements in practical applications, the fuel cell stack is usually composed of several to hundreds of single cells in series. During the operation of the fuel cell, the abnormality of a single cell will affect the performance and safety of the entire stack. In order to ensure For the normal operation of the fuel cell and to evaluate its performance, the operating parameters must be monitored in real time. There is no doubt that the voltage of a single cell is the most direct reflection of the battery's power generation performance, so it must be monitored in real time. The internal resistance is the main factor to measure the difficulty of electron and proton transmission in the electrode, and also the key parameter to determine the power generation efficiency of the fuel cell, and the humidity and temperature of the fuel cell have a strong coupling relationship with its internal resistance, which can be realized through the internal resistance test The soft measurement of humidity and temperature provides reference for the control of parameters such as humidity and temperature. Therefore, in order to ensure the safe, stable and efficient operation of fuel cells, it is necessary to monitor the internal resistance of each single fuel cell in real time. However, since the internal resistance of the fuel cell can be capacitive, inductive and purely resistive, the internal resistance of a single chip is only in the order of μΩ and mΩ, and it changes in real time. It is generally impossible to measure it accurately with existing ordinary instruments. the

The AC impedance of current fuel cells can only be tested with complex experimental setups consisting of many interconnected subsystems. These devices generally include high-end and complex instruments such as fuel cell test benches, electronic loads, and frequency analyzers, and require technicians to correctly configure their hardware connections, software programs, and interface communication protocols, etc., which makes this type of test platform very complex and expensive. very high. Relevant patents show that the hardware of the fuel cell AC impedance online test system needs to be equipped with controllable electronic loads, frequency analyzers, GPIB interfaces, current and voltage waveform acquisition equipment, etc., and the test software requires special data analysis software and various instrument drivers. For example: Patents WO02/27342 and WO2003/083498 of the Clean Energy Company of Ontario, Canada; patent WO2003/098769 of the Green Light Power Technology Company of British Columbia, Canada. These devices test the internal resistance of the fuel cell by controlling the electronic load. Since the load carried by the actual fuel cell stack cannot be controlled according to the test requirements, their method cannot be used for online testing. the

Most of the above-mentioned testers also have the function of testing the voltage of a fuel cell single cell, but the single cell impedance test and the single cell voltage test are performed separately, which also limits its function. the

Contents of the invention

The object of the present invention is to provide a simple and reliable on-line testing system for the internal resistance and voltage of a fuel cell stack single-chip battery, so as to overcome the shortcomings of the existing testing system. the

In order to achieve the above object, the present invention includes a program-controlled alternating current excitation source, a DC blocking capacitor, a current detection module, a keyboard and a liquid crystal display unit, a storage unit, and at least one test unit. The battery output terminals are connected in parallel, and the test unit periodically controls the frequency and amplitude of the AC current excitation source through the communication interface, sequentially collects the voltage and current signals of each single battery and calculates the internal resistance; the current detection module, keyboard and liquid crystal display unit, The storage unit (through the USB interface) is connected to the test unit respectively, and the liquid crystal display unit displays the internal resistance and voltage of each single battery, and alarms the battery with abnormal internal resistance or voltage; the test unit communicates with the main controller of the stack or other Device communication, multiple test units are connected through a communication network to perform single-chip internal resistance and voltage tests on any number of fuel cell stacks. the

It is characterized in that: test unit is made of controller MCU, multi-channel analog switch, signal conditioning circuit, two alternating and direct current separation circuits, phase difference detection circuit, two effective value measurement circuits, A/D converter, communication interface and Composed of at least one instrumentation amplifier, in which the controller MCU communicates with the AC current excitation source through a communication interface. The two input terminals of each instrumentation amplifier are respectively connected to the two ends of the corresponding single cells, and the outputs of multiple instrumentation amplifiers are connected to a multi-channel The input terminals of the analog switches are connected, the output terminals of the multi-channel analog switches are connected with the input terminals of the AC-DC separation circuit 1 of the voltage acquisition channel, and the control terminals of the multi-channel analog switches are connected with the I/O port of the controller MCU; the AC-DC separation The AC output terminal of the circuit 1 is connected to the input terminal of the effective value measurement circuit 1 and the input terminal of the phase difference detection circuit; the input terminal of the signal conditioning circuit is connected to the output terminal of the current detection module, and the output terminal of the signal conditioning circuit is connected to the current acquisition channel The input end of the AC-DC separation circuit 2 is connected, the AC output end of the AC-DC separation circuit 2 is connected with the input end of the effective value measurement circuit 2 and the input end of the phase difference detection circuit; the DC output ends of the two AC-DC separation circuits and the two The output end of the effective value measurement circuit and the output end of the phase difference detection circuit and the output ends of the two effective value measurement circuits and the output end of the phase difference detection circuit are respectively connected to the controller MCU through the A/D converter, and the phase difference detection circuit also has an output end Connect with the controller MCU.

The above-mentioned current detection circuit is composed of a precision closed-loop Hall current sensor and a precision sampling resistor to realize precise I/V conversion, and its output terminal is connected to the input terminal of the signal conditioning circuit of the test unit. the

The above AC current excitation source is controlled by the controller MCU in real time, its output current amplitude is not greater than 5% of the stack current, and its output current frequency changes periodically between 100Hz-20kHz. the

The signal conditioning circuit in the above test unit consists of an instrumentation amplifier and precision resistors. the

The two AC-DC separation circuits in the above test unit are composed of a second-order high-pass active filter circuit, a voltage follower, and a second-order low-pass active filter circuit. The DC output terminal is composed of a current-limiting resistor R and a voltage regulator tube D. Output protection circuit, the AC output terminal is composed of a current limiting resistor R and a transient voltage suppressor TVS to form a limiting output protection circuit. the

The phase difference detection circuit in the above test unit is composed of phase difference absolute value detection and phase difference sign detection. The phase difference absolute value detection introduces a voltage comparison unit, an exclusive OR gate circuit, a low-pass active filter circuit, and a limiter output protection circuit. Its output terminal is connected to the input terminal of the A/D converter; the phase difference sign detection is composed of a voltage comparison unit, a voltage follower, an exclusive OR gate circuit, an RC differential circuit and a D latch, and its output terminal is connected to the I of the controller MCU. /O port connection. the

The A/D converter in the above test unit is an A/D converter with 14-bit resolution. It communicates with the controller MCU through SPI, that is, it receives control signals and sends analog-to-digital conversion results. It has 8 analog channels and built-in 4V Reference and conversion clock and 8×FIFO, and can also use an external voltage reference (the present invention uses an external +5V as a voltage reference), which has the advantages of short conversion time, high precision, and flexible use. There is a photoelectric isolation circuit between the controller MCU and the A/D converter, multi-channel analog switch, phase difference detection circuit, and communication interface to avoid external noise interference and ensure the stable operation of the test unit. the

The storage unit in the above test unit is connected to the controller MCU in the test unit through the USB interface, the controller MCU is connected to the program-controlled AC current excitation source through the RS485 communication interface, and the test unit is connected to the stack main controller through the CAN, RS232/485 communication interface Or other equipment communication, multiple test units are connected through the CAN communication network to perform single-chip internal resistance and voltage tests on any number of fuel cell stacks. the

Compared with the prior art, the invention has the advantages that the measurement system has strong practicability and does not affect the normal operation of the fuel cell during the testing process. The invention has simple and clear circuit, high reliability, moderate cost, high measurement accuracy, fast speed, abundant interfaces and easy expansion, and meets the needs of real-time and high-precision testing of the internal resistance and voltage of a single-chip battery of a fuel cell stack. the

Description of drawings

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

Fig. 2 is a schematic block diagram of a fuel cell stack with any number of pieces tested by multiple test units of the present invention. the

Fig. 3 is a schematic diagram of the AC-DC separation circuit in the test unit of the present invention. the

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

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but these embodiments should not be construed as limiting the present invention. the

The invention includes a test unit, a program-controlled AC current excitation source and a DC blocking capacitor, a current detection module, a keyboard, a liquid crystal display unit, and a storage unit, wherein the test unit is composed of a controller MCU, an instrument amplifier, a multi-channel analog switch, a signal conditioning circuit, and an AC Composed of DC separation circuit, phase difference detection circuit, effective value measurement circuit, A/D converter, RS232/485 communication interface and CAN (Control Local Area Network) communication interface (Figure 1), in which the program-controlled AC current excitation source is connected in series with a DC blocking capacitor Then it is connected in parallel with the fuel cell stack, so that a sinusoidal AC signal is superimposed on each single fuel cell. The voltage at both ends of each cell is respectively amplified 10 times by the instrumentation amplifier AD621 and then connected to the input terminal of the multi-channel analog switch. The multi-channel analog switch is controlled by the controller MCU to output one of the voltages, and the voltage enters the AC-DC separation of the voltage acquisition channel. Circuit 1. The stack current is collected in real time by a precision closed-loop Hall current sensor and a precision sampling resistor. The voltage at both ends of the sampling resistor is amplified 4 times by the instrument amplifier AD620 and then enters the AC-DC separation circuit 2 of the current acquisition channel. The AC output terminals of the two AC-DC separation circuits are respectively connected to the input terminals of the two effective value measurement chips AD536 and the input terminal of the phase difference detection circuit, and the DC output terminals and the output terminals of the effective value measurement chip AD536 are directly connected to the A/D converter TLC3548 for analog Input channel connections. The A/D converter TLC3548 sends the analog-to-digital conversion result to the controller MCU in SPI mode. The controller MCU calculates the phase difference α of the AC voltage and current according to the phase difference sign and the analog-to-digital conversion result, and calculates the current phase difference α according to the analog-to-digital conversion result. Stack AC current I _AC , DC current I _DC , AC voltage V AC and _DC voltage V _DC of the monolithic battery, combined with the phase difference α to calculate the internal resistance Z of the monolithic battery:

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; AC</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; AC</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>$

The controller MCU sends the measured internal resistance Z and voltage V _DC of the single battery to the liquid crystal display unit for real-time display, and displays an alarm for batteries whose internal resistance is greater than the warning value or whose voltage is lower than the warning value.

The plurality of test units of the present invention can be connected through the CAN communication network to perform single-chip internal resistance and voltage tests on any number of fuel cell stacks. Multiple single-chip batteries in the fuel cell stack are connected to the input end of a test unit, and all single-chip The slice battery is connected to the input terminals of n test units, the program-controlled AC current excitation source and the DC blocking capacitor are connected in parallel with the output terminals of the fuel cell stack, and the current detection module is connected to the test unit 1 (Fig. 2). While testing the internal resistance and voltage of multiple single-chip batteries, the test unit 1 also controls the program-controlled AC current excitation source in real time through the RS485 communication interface, collects the stack current, and sends the current value to other test units through the CAN communication network. Test unit 2 ～The internal resistance and voltage values of multiple single-chip batteries tested by test unit n are sent to test unit 1 through the CAN communication network, and test unit 1 transmits the internal resistance and voltage values of all single-chip batteries to the liquid crystal display unit for display, and displays all The internal resistance and voltage values of the single battery are sent to the storage unit for storage through the USB interface, and the test system communicates with the PC or other devices through the RS232/485 communication interface of the test unit 1. the

The AC-DC separation circuit 1 of the voltage acquisition channel of the present invention is the same as the AC-DC separation circuit 2 of the current acquisition channel. The AC-DC separation circuit is composed of a second-order high-pass active filter circuit, a voltage follower, and a second-order low-pass active filter circuit. AC channel and DC channel (Figure 3). the

1. The AC channel of the AC-DC separation circuit is composed of a second-order high-pass active filter circuit and a second-order low-pass active filter circuit, so that it can output 100Hz-20kHz signals, and its output terminal has a current-limiting resistor R12 and a transient voltage suppressor TVS The limiting output protection circuit constituted makes its output clamp between -V _T to +V _T , and protects the safety of the effective value measurement chip AD536 and subsequent devices. The transfer function of the second-order high-pass active filter circuit is:

${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="S"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png,H200710169083720080324E000011.png"\; state="\{\{state\}\}">S</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png,H200710169083720080324E000011.png"\; state="\{\{state\}\}">C</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 3</span>}}}$

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

Lower limit frequency: $f_{\mathrm{no}}=\frac{1}{2\mathrm{\&pi;}\sqrt{R1R2C2\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">C</figure-callout>}3}}$

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

According to A _F (∞)=-1, f _n ＝100Hz, ε＝0.707 and the actual resistance and capacitance parameters, take C1＝C2＝C3＝0.1μF, R1＝7.5kΩ, R2＝36kΩ, the actual second-order high-pass has The source filter circuit A _F (∞)=-1, f _n =97Hz, ε=0.685, which can meet the system's 100Hz high-pass filter requirements. The second-order low-pass active filter circuit and the second-order high-pass active filter circuit have duality, and the second-order low-pass active filter can be obtained by replacing the resistor in the second-order high-pass active filter circuit with a capacitor, and replacing the capacitor with a resistor. The circuit also determines the actual parameters of each resistor and capacitor according to the passband gain, the upper limit frequency, and the damping coefficient.

2. The DC channel of the AC-DC separation circuit is composed of a voltage follower U3, a second-order low-pass active filter circuit and an amplifier circuit. The limiting output protection circuit composed of a current-limiting resistor R13 and a voltage regulator tube D1 at the output end makes it The output is clamped between -0.7V and +V _D to protect the safety of A/D converter TLC3548 and subsequent devices, so as not to damage the circuit and chip. The second-order low-pass active filter circuit and the second-order high-pass active filter circuit have duality, and the resistance and capacitance parameters in the second-order low-pass active filter circuit are determined by referring to the parameters of the second-order high-pass active filter circuit of the AC channel.

The phase difference test circuit of the present invention adopts the voltage comparator LM311 to carry out shaping to the sinusoidal AC voltage signal V(t) and the current signal V _i (t), and V(t) and V _i (t) are output after being shaped by the voltage comparator LM311 Square waves A, B, A and B pass through the XOR gate circuit to output C pulse (Figure 4), and its Fourier series expression is:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 5</span>}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; +</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; n\&omega;t</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; n\&omega;t</span>}<span\; class="notranslate">\; )</span>$

Among them, q is the duty cycle of C pulse, ω=400π～12000π, a _n and b _n are constants. C pulse elapsed time constant RC≥10T (T=2π/ω is the cycle of C pulse, T _max ≤0.005S, here choose R26=100kΩ, C10=1μF can meet the requirements of 1.59Hz low-pass filter, fully meet the system requirements) The low-pass active filter circuit outputs a stable voltage U _F , which is the average value of U _C (t):

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 5</span>}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; |</span>}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 5</span>}\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; )</span>$

U _F passes through the limiting output protection circuit composed of current limiting resistor R27 and voltage regulator tube D3. Its output is clamped between -0.7V and +V _D , and then enters TLC3548 for analog-to-digital conversion. The resolution is:

5/2 ¹⁴ ＝0.305mV

according to $\left|\mathrm{\&alpha;}\right|=\frac{\mathrm{\&pi;}{\mathrm{<figure-callout\; id="5"\; label="u\; f"\; filenames="DEST\_PATH\_RE-S2007101690837E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_f}{5}$ It can be seen that the resolution of the phase difference |α| is 6.1π×10 ^-5 radians. Use RC differential circuit and D latch to judge the sign of phase difference between A and B, and the output Q of D latch is connected to the input I/O port of controller MCU through optical isolation 6N137. Q=1 means that the voltage is ahead of the current, and the sign of the phase difference is positive; Q=0 means that the sign of the phase difference is negative, which actually means that the internal resistance of the fuel cell is inductive, capacitive or purely resistive.

The accuracy of this phase difference test method is as high as 6.1π×10 ^-5 radians, and the accuracy is not affected by the frequency of the input signal, which is very suitable for the situation where the signal frequency varies in a large range in this system. Its test range is -π～π, and there is no test dead angle.

The content not described in detail in this specification belongs to the prior art known to those skilled in the art. the

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.

Images