CN106324355A - AC impedance test system and method for electrochemical device - Google Patents

Abstract

The invention provides an AC impedance test system for an electrochemical device, comprising an electrochemical device, a control device, a DC adjustment branch, and a disturbance adjustment branch connected in parallel with the DC adjustment branch. The electrochemical device is connected with the control device. The DC adjustment branch includes a first output load. The disturbance adjustment branch includes a current disturbance device used for producing disturbance current and a second output load. The control device is used for, after making the current disturbance device opened, adjusting the input current of the current disturbance device to a preset disturbance current, and calculating an AC impedance corresponding to the disturbance frequency of the preset disturbance current according to the output current and output voltage of a to-be-tested single chip of the electrochemical device. The invention further provides an AC impedance test method for an electrochemical device. According to the AC impedance test system and the AC impedance test method for an electrochemical device, the circuit structure is simple, the commonality is strong, and the performance of the test system is improved.

Description

AC impedance testing system and method for electrochemical device

Technical Field

The invention relates to the technical field of electrochemical devices, in particular to an alternating current impedance testing system and method of an electrochemical device.

Background

A hydrogen-oxygen Proton Exchange Membrane Fuel Cell (PEMFC) is an electrochemical device, which directly converts chemical energy into electric energy, and the energy conversion of a traditional internal combustion engine is limited by carnot cycle, while the energy conversion of the hydrogen-oxygen Proton Exchange Membrane Fuel Cell is not limited by carnot cycle, and theoretically, the energy conversion efficiency is higher. Because the substances participating in the reaction are hydrogen and air, the reaction product is water, and no harmful emissions are generated, the method is favored by people and is gradually applied to the fields of standby power stations, transportation, mobile power supplies and the like.

The output characteristic of the proton exchange membrane fuel cell is direct current, the output voltage of a single piece of the proton exchange membrane fuel cell is less than 1V, typically 0.7V, and in order to provide higher voltage, a plurality of fuel cell single pieces are required to be connected in series to form a fuel cell stack, and the output power is correspondingly improved. The fuel cell single chip is composed of an anode Gas Diffusion Layer (GDL), a Membrane Electrode Assembly (MEA), and a cathode Gas Diffusion Layer.

The fuel cell stack is a core component of a fuel cell power generation system, and a plurality of accessory systems are arranged at the periphery of the stack to assist the fuel cell stack to work, wherein the accessory systems comprise an air system, a hydrogen system, a cooling system, a power regulation system, a humidification system, a control system and the like. The air system is responsible for providing a proper amount of oxidant namely air for the galvanic pile, and the temperature, the pressure and the flow of the air entering the galvanic pile need to be adjusted according to the working condition; the hydrogen system is responsible for supplying hydrogen to the galvanic pile, and the pressure and the flow of the hydrogen entering the galvanic pile need to be adjusted according to the working condition; the cooling system keeps the temperature of the galvanic pile at a proper level in a coolant circulation mode, so that the stable and reliable operation of the galvanic pile is ensured; the power regulating system enables the output characteristic of the fuel cell system to meet the load requirement in a mode of regulating the output voltage or the output current of the fuel cell stack; the humidifying system is responsible for adjusting the humidity of air entering the galvanic pile, and over-drying or over-wetting has adverse effects on a proton exchange membrane and the galvanic pile, so that the humidity of the air entering the galvanic pile needs to be controlled; the control system is the brain of the whole fuel cell power generation system, and particularly performs optimal control on each subsystem at the periphery of the galvanic pile, so that the galvanic pile is in an optimal working state, and the long-term stable and reliable operation of the galvanic pile is ensured.

Fig. 1 shows a typical fuel cell system, in which ambient air is compressed by an air compressor, enters a radiator, is cooled by the radiator, enters a humidifier for humidification, enters an electric stack after humidification, and undergoes an electrochemical reaction, oxygen on a cathode side reacts with hydrogen ions from an anode to produce water (in a gaseous or liquid state) while outputting electric energy, and most of the water flows out from the cathode air side, so that the oxygen content in the cathode air participating in the reaction is reduced, the water content (humidity) is increased, and the air at the outlet of the electric stack is discharged into the environment through a flow control valve 2 after moisture is recovered by a condenser. The air system can control the air flow and the air pressure entering the electric pile through the coordination control of the air compressor and the flow control valves 1 and 2, can adjust the air inlet temperature through the radiator, and controls the air inlet humidity through the humidifier.

According to the operating principle and performance characteristics of PEMFCs, since water (gas or liquid) generated by the reaction inside the stack needs to be carried out through the cathode reaction channel, if the generated liquid water is not removed in time, the generated water may block the flow channel, i.e., so-called flooding phenomenon, which may cause the performance degradation of the stack and affect the use of the fuel cell. In order to improve the drainage capacity, it is necessary to increase the flow rate or flow velocity of air so as to smoothly blow off liquid water. When idling or small load, because the generated water quantity is small, if the air flow is always kept large, the water on the surfaces of the flow channel and the proton exchange membrane is easy to be dried, so that the membrane is over-dried and the performance is reduced; if the air flow rate is kept small all the time, liquid water in the flow passage is not easy to blow away, and flooding is caused.

In a fuel cell control system, based on the existing sensor configuration, including cathode and anode inlet temperature and pressure sensors, cathode and anode outlet temperature and pressure sensors, and cathode inlet and outlet humidity sensors, the operating state inside a fuel cell stack is usually observed by adopting a lumped parameter model, but because the fuel cell stack is formed by connecting a plurality of single sheets in series and is limited by the structure of a stack gas supply system, the inlet pressure, the temperature, the humidity and the inlet components of each fuel cell single sheet are different, the voltage of the single sheet is inconsistent due to the difference of the gas supply state and the temperature difference of the single sheets, and when the structure of a system is unreasonable and the number of the single sheets is increased, the voltage inconsistency of the single sheets is more obvious. Because the working state of the fuel cell single chip cannot be observed in real time, and particularly, whether the single chip is flooded or dry membrane cannot be effectively judged in time, the internal working state of the fuel cell can be adjusted by controlling the gas supply system and the humidification system of the fuel cell, so that the phenomenon of flooding or dry membrane of the local fuel cell single chip is difficult to avoid, and the improvement of the performance of the fuel cell system is very unfavorable.

However, with the progress of science and technology, through continuous and intensive research, it is found that the performance characteristics of the fuel cell can be researched in an equivalent circuit mode, and the operating state of the fuel cell and the impedance element in the equivalent circuit have a certain corresponding relationship. According to the relation between the fuel cell equivalent circuit and the performance of the fuel cell and the corresponding relation between the resistance element and the capacitance element of the fuel cell equivalent circuit and the states of different components of the fuel cell stack, the working state of a fuel cell single chip and the whole working state of the fuel cell stack can be accurately predicted by acquiring the impedance value changes of the resistance element and the capacitance element in the fuel cell equivalent circuit in real time.

In order to obtain resistance and capacitance parameters in an equivalent circuit of a fuel cell, alternating current impedance research needs to be carried out, the price of commercial alternating current impedance analysis equipment in the current market is more than one hundred thousand RMB, the working voltage range and the current range of the commercial alternating current impedance analysis equipment cannot meet the wide application requirements of the existing fuel cell, particularly, the number of single fuel cells of a fuel cell stack can be changed from one to hundreds of single fuel cells, and the area of the single fuel cell can be changed from several square centimeters to hundreds of square centimeters. Although commercial ac impedance analysis devices have a wide range of frequency measurements, it has been shown from literature research that the acceptable frequency band for performing fuel cell ac impedance analysis is not as broad as those described for these instruments.

Disclosure of Invention

In view of the problems of high cost and poor versatility of the commercial ac impedance analysis equipment, the present invention aims to provide an ac impedance testing system and method for an electrochemical device, wherein the testing system has low cost and high versatility.

In order to achieve the purpose, the invention adopts the following technical scheme:

an alternating current impedance testing system of an electrochemical device comprises the electrochemical device, a control device, a direct current regulating branch and a disturbance regulating branch connected with the direct current regulating branch in parallel, wherein the electrochemical device is connected with the control device;

the direct current regulating branch comprises a first output load, the input end of the first output load is connected to the electrochemical device, the output end of the first output load is in signal connection with the control device, and the control device monitors the working state of the first output load;

the disturbance regulating branch comprises a current disturbance device and a second output load, wherein the current disturbance device is used for generating disturbance current, the input end of the current disturbance device is connected to the electrochemical device, the output end of the current disturbance device is connected to the second output load, and the current disturbance device and the second output load are both connected to the control device;

the control device is used for adjusting the input current of the current disturbance device to a preset disturbance current after controlling the current disturbance device to be started, and calculating alternating current impedance corresponding to the disturbance frequency of the preset disturbance current according to the output current and the output voltage of the to-be-detected single chip of the electrochemical device.

In one embodiment, the control device comprises a controller and a voltage inspection device for monitoring the output voltage of each single chip to be tested of the electrochemical device;

the voltage measuring end of each single chip of the electrochemical device is connected to the voltage inspection device, the voltage inspection device is connected to the controller, the controller is used for selecting the single chip to be detected and controlling the voltage inspection device to collect the selected output voltage of the single chip to be detected.

In one embodiment, the voltage inspection device comprises a single chip gating module and a signal processing module which are connected with each single chip of the electrochemical device;

the single chip gating module is used for acquiring the output voltage of the single chip to be tested according to the control signal of the controller; the signal processing module is connected with the controller and used for transmitting the output voltage of the single chip to be tested to the controller.

In one embodiment, the device further comprises a first voltage detection device and a first current detection device for detecting the output current of the electrochemical device;

the input end of the first voltage detection device is connected to the output end of the electrochemical device, and the output end of the first voltage detection device is connected to the common end of the voltage inspection device and the controller; the first current detection device is arranged at the output end of the electrochemical device in series and is connected to the common end of the voltage inspection device and the controller.

In one embodiment, the dc regulating branch further comprises a second current detecting device for detecting an input current of the first output load, and the second current detecting device is connected to the controller.

In one embodiment, the disturbance adjusting branch further includes a third current detection device for detecting an input current of the current disturbance device, the third current detection device is connected to the controller, and the controller is further configured to adjust a time for turning on or off the current disturbance device according to the detected input current of the current disturbance device by the third current detection device, so that the input current of the current disturbance device reaches the preset disturbance current.

In one embodiment, the input current of the current perturbation device comprises an alternating perturbation current and a direct perturbation current, and the amplitude of the alternating perturbation current is smaller than that of the direct perturbation current;

the control device is further used for adjusting the disturbance frequency and the disturbance amplitude of the alternating current disturbance current and the amplitude of the direct current disturbance current so as to obtain the preset disturbance current.

In one embodiment, the disturbance adjusting branch further comprises a second voltage detection device for detecting the output voltage of the current perturbation device and a fourth current detection device for detecting the output current of the current perturbation device;

the second voltage detection device and the fourth current detection device are both connected to the controller, and the controller is used for adjusting the voltage range or the resistance value of the second output load according to the output voltage and the output current of the current disturbance device.

In one embodiment, the current perturbation device is a Boost type DC/DC converter, a Buck type Buck DC/DC converter or a DC/AC converter.

The invention also provides an alternating current impedance testing method of the electrochemical device, which is used for the alternating current impedance testing system of the electrochemical device, and the method comprises the following steps:

controlling the first output load to start, and enabling the electrochemical device to work normally;

judging whether to perform an alternating current impedance test; when the alternating current impedance test is judged to be carried out, the following steps are carried out:

controlling the current perturbation device and the second output load to start;

adjusting a voltage range or a resistance value of the second output load;

adjusting the input current of the current disturbance device to be a preset disturbance current;

acquiring the output current and the output voltage of a to-be-detected single chip of the electrochemical device;

calculating alternating current impedance corresponding to the disturbance frequency of the preset disturbance current according to the output current and the output voltage of the single chip to be tested;

changing the disturbance frequency of the preset disturbance current to obtain an updated preset disturbance current;

calculating alternating current impedance corresponding to the updated disturbance frequency according to the output current and the output voltage of the single chip to be tested;

and obtaining an alternating current impedance map of the electrochemical device according to a plurality of different disturbance frequencies and corresponding alternating current impedances thereof.

In one embodiment, the method further comprises:

obtaining disturbance frequency and disturbance amplitude of alternating disturbance current in the disturbance current;

obtaining the amplitude of the direct current disturbance current in the disturbance current;

obtaining a preset disturbance current according to the disturbance frequency and the disturbance amplitude of the alternating current disturbance current and the amplitude of the direct current disturbance current;

and adjusting the on-off time of the current disturbance device, and adjusting the input current of the current disturbance device to be the preset disturbance current.

In one embodiment, the method further comprises the steps of:

and when the alternating current impedance test is judged not to be carried out, controlling the first output load to be in an opening state and controlling the current disturbance device to be closed.

The invention has the beneficial effects that:

according to the alternating current impedance testing system and method of the electrochemical device, the electrochemical device is enabled to normally work through the first output load adjustment, when the current disturbance device is started, the input current of the current disturbance device is adjusted through the second output load and the current disturbance device, so that the output current of the electrochemical device is superposed with the alternating current disturbance current on the basis of the direct current, the alternating current impedance of the electrochemical device can be detected, the circuit structure is simple, the universality is high, and the cost of the alternating current impedance testing system is reduced. And the performance of the test system is further improved through the first output load and the second output load which are relatively independently arranged.

Drawings

FIG. 1 is a system diagram of a PEM fuel cell according to an embodiment;

FIG. 2 is an equivalent circuit diagram of an electrochemical device;

FIG. 3 is an AC impedance spectrum of an electrochemical device;

FIG. 4 is a system diagram of an AC impedance testing system of an electrochemical device in accordance with one embodiment of the present invention;

FIG. 5 is a circuit diagram of one embodiment of the current perturbation device of FIG. 4;

FIG. 6 is a circuit diagram of another embodiment of the current perturbation device of FIG. 4;

FIG. 7 is a schematic diagram of one embodiment of the voltage inspection device of FIG. 4;

FIG. 8 is a graph of the input current and corresponding voltage signal of the current perturbation device in the single frequency AC impedance measurement mode;

fig. 9 is a flowchart illustrating an ac impedance testing method of an electrochemical device according to an embodiment of the present invention.

Detailed Description

In order to make the technical solution of the present invention clearer, the ac impedance testing system and method of the electrochemical device of the present invention are further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

As shown in fig. 4, the ac impedance testing system of the electrochemical device 100 according to an embodiment of the present invention includes the electrochemical device 100, a control device, a dc regulating branch, a disturbance regulating branch connected in parallel with the dc regulating branch, a first voltage detecting device 500, and a first current detecting device 600. Here, the first voltage detection device 500 may be a voltage sensor, and the first current detection device 600 may be a current sensor or a current transformer, etc. The electrochemical device 100, the direct current regulation branch and the disturbance regulation branch are all connected to the control device.

Wherein the electrochemical device 100 is connected to a control device for controlling the operating conditions of the electrochemical device 100. Generally, the output voltage of the electrochemical device 100 is a dc voltage, and the output current is a dc current. The electrochemical device 100 may include one or more monoliths that generate electrical energy through chemical reactions. Each monolithic piece includes a positive electrode, a negative electrode, and a dielectric separator disposed between the positive and negative electrodes. As shown in FIG. 2, each of the monolithic performance characteristics of the electrochemical device 100 may be equated with an equivalent circuit that includes a Steve voltage E_NernstAnd an anode double electric layer capacitor C_dl,AAnode resistance R_f,ACathode double electric layer capacitor C_dl,CACathode resistance R_f,CAAnd proton exchangeFilm resistance R_Ω. Wherein the anode double electric layer capacitor C_dl,AAnd anode resistance R_f,AAn anode RC circuit and a cathode double electric layer capacitor C are formed in parallel_dl,CAAnd the cathode resistance R_f,CAParallel to form a cathode RC circuit, a stedt voltage E_NernstAnode RC circuit, proton exchange membrane resistor R_ΩAnd a cathode RC circuit is arranged in series.

FIG. 3 is an AC impedance spectrum corresponding to the equivalent circuit of each chip of the electrochemical device 100, wherein the horizontal axis Z is_reRepresenting the real part of the impedance, the vertical axis Z_imRepresenting the imaginary part of the impedance: wherein,

$Z_{FC}\left(\mathrm{\ω}\right)=R_{\mathrm{\Ω}}+\frac{R_{f,A}}{1+{\mathrm{j\ωR}}_{f,A}{C}_{dl,A}}+\frac{R_{f,CA}}{1+{\mathrm{j\ωR}}_{f,CA}{C}_{dl,CA}}---\left(1\right)$

$\underset{\mathrm{\ω}\→\mathrm{\∞}}{\lim }{Z}_{FC}\left(\mathrm{\ω}\right)=R_{\mathrm{\Ω}}---\left(2\right)$

Z_FC(0)＝R_Ω+R_f,A+R_f,CA＝R_internal(3)

wherein Z is_FC(ω) represents the AC impedance of the single piece of the electrochemical device 100, ω represents the frequency of the AC perturbation current, j represents the imaginary unit, R_internalWhich represents the total internal resistance exhibited when the single-chip output signal of the electrochemical device 100 is a dc signal.

Therefore, as can be seen from fig. 3 and the above equations (1) to (3), the operating environment states (such as temperature, humidity, etc.) of the components of the electrochemical device 100 can be determined by detecting the impedances in the equivalent circuit during the operation of the electrochemical device 100, so as to dynamically adjust the operating environment states to improve the efficiency of the electrochemical device 100. In this embodiment, the electrochemical device 100 may be a power battery such as a low-temperature proton exchange membrane fuel cell, a lithium ion battery, or a lithium iron phosphate battery, and of course, the electrochemical device 100 may also adopt a super capacitor or the like.

The control device includes a controller 210 and a voltage inspection device 220 connected to the controller 210, in this embodiment, the controller 210 and the voltage inspection device 220 are connected via a bus, and the electrochemical device 100, the first output load 300, the current perturbation device 410 and the second output load 420 are all connected to the controller 210. The controller 210 is used for controlling the operations of the above components. In this embodiment, the controller 210 may be determined according to the type of the electrochemical device 100. For example, the controller 210 may include a hydrogen system, an air system, a cooling system, a recovery system, a temperature and humidity measurement system, and the like. In other embodiments, when the electrochemical device 100 is a lithium ion battery pack, the controller 210 can be a lithium ion battery management device.

The voltage patrol apparatus 220 is connected to the electrochemical apparatus 100 for monitoring the output voltage of each individual chip of the electrochemical apparatus 100. As shown in fig. 7, the voltage inspection device 220 includes a single chip gating module 221 and a signal processing module 222, wherein the voltage measuring end of each single chip of the electrochemical device 100 is connected to the single chip gating module 221 of the voltage inspection device 220, the controller 210 is configured to select the single chip to be tested, and the single chip gating module 221 is configured to collect the output voltage of the selected single chip to be tested according to the control signal of the controller 210. The signal processing module 222 is connected to the controller 210, and configured to transmit the acquired output voltages of the multiple to-be-tested singlechips to the controller 210 after a certain number of output voltages of the to-be-tested singlechips are acquired. Specifically, the signal processing module 222 transmits the detected output voltages of the plurality of test slices to the controller 210 through the communication bus. The monolithic gating module 221 and the signal processing module 222 may be constituted by electronic circuit devices.

In this embodiment, the voltage sampling rate of the voltage inspection device 220 is as high as tens of kilohertz, so the ac impedance testing system of this embodiment can measure the voltage signal within a wide range of frequency, and the versatility of the ac impedance testing system can be improved.

In other embodiments, the controller 210 may control the voltage inspection device 220 to collect the output voltages of multiple chips simultaneously. For example, the single chip gating module can gate one or more single chips to be tested according to the control signal of the controller 210, and the voltage inspection device 220 can perform synchronous sampling on the output voltage of each single chip to be tested, so that the ac impedance testing efficiency of the electrochemical device 100 is improved.

The dc regulating branch comprises a first output load 300 and a second current detecting device 310, an input terminal of the first output load 300 is connected to the electrochemical device 100, an output terminal of the first output load 300 is in signal connection with a control device, specifically, an output terminal of the first output load 300 is in signal connection with the controller 210, and the controller 210 is configured to monitor an operating state of the first output load and enable the electrochemical device 100 to output a dc current by regulating the first output load 300. In this embodiment, the first output load 300 may be an electronic load or a motor. When the current perturbation device 410 is turned off, the controller 210 controls the first output load 300 to be turned on, so that the electrochemical device 100 and the first output load 300 form a loop, and the current perturbation device 410 can work normally. At this time, the electrochemical device 100 may be tested in various conditions, and the voltage inspection device 220 may be controlled to monitor the output voltage of each single chip of the electrochemical device 100.

The second current detecting device 310 is disposed at an input terminal of the first output load 300, and is used for detecting an input current of the first output load 300, and the second current detecting device 310 is connected to the controller 210 and transmits the detected input current of the first output load 300 to the controller 210. The second current detection device 310 may be a current sensor or a current transformer.

The disturbance adjusting branch circuit is connected in parallel with the dc adjusting branch circuit, and is configured to generate a disturbance current, and includes a current disturbance device 410 and a second output load 420, an input end of the current disturbance device 410 is connected to the electrochemical device 100, an output end of the current disturbance device 410 is connected to the second output load 420, and the current disturbance device 410 and the second output load 420 are both connected to the control device, specifically, the current disturbance device 410 and the second output load 420 are both connected to the controller 210. The controller 210 can control the on/off of the current perturbation device 410, adjust the input current of the current perturbation device 410 to a preset perturbation current by controlling the on/off time of the current perturbation device 410, and adjust a preset perturbation frequency by adjusting the perturbation amplitude and the perturbation frequency of the alternating perturbation current, thereby implementing the adjustment of the input current of the current perturbation device 410, and further implementing the alternating current impedance test on the electrochemical device 100 by including an alternating perturbation current in the output current of the electrochemical device 100. At this time, the output voltage of the electrochemical device 100 also generates a signal corresponding to the voltage of the ac perturbation current, wherein the relationship between the input current of the current perturbation device 410 and the corresponding voltage signal in the single-frequency ac impedance measurement mode is shown in fig. 8.

Meanwhile, the controller 210 is further configured to adjust an output voltage or a resistance value of the second output load 420, so that the second output load 420 is adapted to the output of the current perturbation device 410 to further control the input current of the current perturbation device 410. The performance of the test system is further improved by the first output load 300 and the second output load 420 which are arranged relatively independently. When the current perturbation device 410 is turned on, the input current of the perturbation adjusting branch circuit is the sum of the ac perturbation current and the dc perturbation current, which can be specifically referred to the description below.

The current perturbation device 410 may be a Boost type DC/DC converter, a Buck type Buck DC/DC converter, or a DC/AC converter. The controller 210 may control the turning on or off of the current perturbation device 410 by controlling the turning on or off of the switching devices in the converter. The second output load 420 may be a resistive load or an electronic load.

Further, the input terminal of the first voltage detection device 500 is connected to the output terminal of the electrochemical device 100, and the output terminal of the first voltage detection device 500 is connected to the common terminal of the voltage inspection device 220 and the controller 210, as shown in fig. 4, the output terminal of the first voltage detection device 500 is connected to the connection line between the voltage inspection device 220 and the controller 210, so that the controller 210 and the voltage inspection device 220 can both obtain the output voltage of the single chip to be tested through the first voltage detection device 500, the circuit structure is simplified, and the use is convenient. The first voltage detection device 500 may be a voltage sensor.

The connection of the first current detection means 600 is at the output terminal of the electrochemical device 100 and the first current detection means 600 is connected to the control means, and in particular, the first current detection means 600 is connected to the common terminal of the voltage inspection device 220 and the controller 210, as shown in fig. 4, and the output terminal of the first current detection means 600 is connected to the connection line between the voltage inspection device 220 and the controller 210. The first current detecting device 600 may be a current sensor or a current transformer for detecting the output current of each chip to be tested of the electrochemical device 100 and transmitting the detected output current of the electrochemical device 100 to the control device.

The controller 210 is further configured to calculate an ac impedance corresponding to a disturbance frequency of the current ac disturbance current according to the output current and the output voltage of each single chip to be measured of the electrochemical device 100 after the current disturbance device 410 is turned on. Here, the output current of the electrochemical device 100 may be obtained by the first current detecting device 600, and the output voltage of the electrochemical device 100 may be obtained by the first voltage detecting device 500.

Further, the disturbance frequency and the disturbance amplitude of the alternating disturbance current are both controllable values, and the controller 210 can adjust the disturbance frequency of the alternating disturbance current and determine the disturbance amplitude corresponding to the disturbance frequency, so as to determine the preset alternating disturbance current according to the disturbance frequency and the disturbance amplitude. The controller 210 is further configured to change the disturbance amplitude and the disturbance frequency of the ac disturbance current, update the ac disturbance current, and calculate an ac impedance corresponding to the updated disturbance frequency according to the output current of the electrochemical device 100 corresponding to the updated ac disturbance current and the output power source, so as to obtain an ac impedance spectrum of the electrochemical device 100. Thus, the disturbance frequency of the ac disturbance current is changed, and the ac impedance value of the electrochemical device 100 at different disturbance frequencies is measured, so that the frequency spectrum of the ac impedance can be drawn. The circuit has the advantages of simple structure and strong universality, and reduces the cost of the alternating current impedance test system.

In one embodiment, the disturbance adjustment branch further comprises a third current detection device 430, a fourth current detection device 440, and a second voltage detection device 430. Wherein, the third current detection device 430 is disposed at the input end of the current perturbation device 410, and is used for detecting the input current of the current perturbation device 410 in real time. The third current detecting device 430 is connected to the controller 210, and the controller 210 may adjust the input current of the current perturbation device 410 according to the current signal detected by the third current detecting device 430, and specifically, the controller 210 may adjust the time when the current perturbation device 410 is turned on or off according to the current signal detected by the third current detecting device 430, so that the input current of the current perturbation device 410 reaches the preset perturbation current. When the current perturbation device 410 is turned on, the input current of the current perturbation device 410 comprises an AC perturbation current and a DC perturbation current, i.e.

Where I represents the input current of the current perturbation device 410, I₁Representing a direct disturbance current, I₂Representing the alternating disturbance current, a representing the disturbance amplitude of the alternating disturbance current, f representing the disturbance frequency of the alternating disturbance current,representing the initial phase angle of the ac perturbation current and t representing time.

The disturbance frequency of the alternating disturbance current can be single frequency or multiple frequencies. When the disturbance frequency of the AC disturbance current is multiple frequencies, the AC disturbance current I₂The calculation method of (c) is as follows:

wherein A is₁Andrespectively the disturbance frequency f₁Corresponding disturbance amplitude and initial phase, A₂Andrespectively the disturbance frequency f₂Corresponding disturbance amplitude and initial phase, A₁Andrespectively the disturbance frequency f₁Corresponding disturbance amplitude and initial phase, A_NAndrespectively the disturbance frequency f_NCorresponding perturbation amplitude and initial phase. In this embodiment, AC disturbance current I₂The disturbance amplitude and the disturbance frequency at any frequency can be set by the controller 210, that is, the disturbance amplitude and the disturbance frequency of the ac disturbance current can be adjusted on line by the controller 210, which mainly depends on the requirements of the application object of the current disturbance device 410. Therefore, when the ac disturbance current has multiple frequencies, the controller 210 first determines the amplitude and the initial phase corresponding to each disturbance frequency, and then calculates the ac disturbance current I according to the above formula₂。

Further, when the current perturbation device 410 adopts a DC/DC converter or a DC/AC converter, the amplitude of the alternating current perturbation current is smaller than that of the direct current perturbation current, so as to ensure that the input current of the current perturbation device 410 is greater than 0, so as to ensure that the current perturbation device 410 can work normally. When the ac disturbing current has multiple frequencies, the amplitude of the ac disturbing current at each frequency should be smaller than the amplitude of the dc disturbing current, i.e. the maximum amplitude of the ac disturbing current should be smaller than the amplitude of the dc disturbing current, so as to ensure that the current disturbing apparatus 410 can work normally.

The second voltage detection device 430 and the fourth current detection device 440 are disposed at the output end of the current perturbation device 410, specifically, the second voltage detection device 430 and the fourth current detection device 440 are disposed between the current perturbation device 410 and the second output load 420, and the second voltage detection device 430 and the fourth current detection device 440 are connected to the controller 210. The second voltage detecting device 430 is used for detecting the output voltage of the current perturbation device 410 (i.e. the input voltage of the second output load 420), and transmitting the detected output voltage of the current perturbation device 410 to the controller 210. The fourth current detecting device 440 is used for detecting the output current of the current perturbation device 410 (i.e. the input voltage of the second output load 420) and transmitting the detected output current of the current perturbation device 410 to the controller 210. In this embodiment, the second voltage detection device 430 may be a voltage sensor, and the third current detection device 430 and the fourth current detection device 440 may be a current sensor or a current transformer, etc.

The controller 210 adjusts the output characteristics of the current perturbation device 410 according to the output current and the output voltage of the current perturbation device 410, mainly adjusting the output voltage of the current perturbation device 410. The controller 210 may then match the second output load 420 to the output of the current perturbation device 410 by adjusting the voltage range or resistance value of the second output load 420. Accordingly, the control of the input current of the current perturbation device 410 can be realized according to the detection values of the third current detection device 430, the fourth current detection device 440 and the second voltage detection device 430.

In one embodiment, the current perturbation device 410 comprises a switching device, and the controller 210 is configured to control the switching device to be turned on or off to control the current perturbation device 410 to be turned on or off, and can enable the input current of the current perturbation device 410 to reach the preset perturbation current by controlling the on or off time of the switching device.

As shown in fig. 5, the current perturbation device 410 is a Boost type DC/DC converter, and includes an inductor L1, a diode D1, a switching device G1, and a capacitor C1, wherein the switching device G1 may be an IGBT (Insulated Gate Bipolar Transistor), a MOS (field effect Transistor), a BJT (Bipolar Junction Transistor), or the like. One end of the inductor L1 is connected to the anode of the input power supply, the other end of the inductor L1 is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the anode of the output power supply, and the input power supply and the output power supply share the cathode. The collector of the switching device is connected to the common terminal between the inductor L1 and the diode D1, the emitter of the switching device G1 is connected to the cathode of the input power source, the gate of the switching device G1 is connected to the controller 210, and the controller 210 controls the switching device G1 to be turned on or off. The capacitor C1 is connected between the positive pole and the negative pole of the output power source, i.e. one end of the capacitor C1 is connected to the cathode of the diode D1, and the other end of the capacitor C1 is connected to the negative pole of the output power source.

When the switching device G1 is turned on, the current generated by the input power flows through the inductor L1, the current flowing through the inductor L1 increases linearly according to the physical characteristics of the inductor, the electric energy is stored in the inductor L1, the inductor L1 and the switching device G1 form a conducting loop, the anode of the diode D1 is connected between the cathode of the input power and the anode of the output power, and the diode D1 is turned off in the reverse direction. When the switching device G1 is turned from on to off, the current flowing through the inductor L1 cannot change abruptly according to the physical characteristics of the inductor, so that an electromotive force is generated, the direction of the electromotive force is the same as the direction of the input power, the electric energy stored in the inductor L1 is continuously discharged, the capacitor C1 is charged through the diode D1, and the energy is supplied to the second output load 420, and at this time, the inductor L1, the diode D1, the capacitor C1, and the second output load 420 form a loop. When the switching device G1 is periodically controlled to be turned on and off, energy transfer from the input power source to the output power source is realized. The controller 210 may generate the ac perturbation signal by controlling the on or off state of the switching device G1 at different times.

As shown in fig. 6, the current perturbation device 410 may also adopt a Buck DC/DC converter, which includes a switching device G2, an inductor L2, a diode D2 and a capacitor C2, wherein the switching device G2 may be an IGBT (Insulated Gate Bipolar Transistor), a MOS (field effect Transistor) or a BJT (Bipolar Junction Transistor), etc. The gate of the switching device G2 is connected to the controller 210, the collector of the switching device G2 is connected to the positive electrode of the input power supply, the emitter of the switching device G2 is connected in series with the inductor L2 and then connected to the positive electrode of the output power supply, and the output power supply and the input power supply share a negative electrode. An anode of the diode D2 is connected to a cathode of the output power source, and a cathode of the diode D2 is connected to a corresponding common terminal between an emitter of the switching device G2 and the inductor L2. The capacitor C2 is connected between the positive pole and the negative pole of the output power source, i.e. one end of the capacitor C2 is connected to the inductor L1, and the other end of the capacitor C2 is connected to the positive pole of the diode D2.

When the controller 210 controls the switching device G2 to be turned on, the cathode of the diode D2 is connected to the anode of the input power source, the anode of the diode D2 is connected to the cathode of the input power source, and the diode D2 is turned off. The input power supplies charge the inductor L2 through the switching device G2. When the controller 210 controls the switching device G2 to turn off, the inductor L2 charges the capacitor C2, thereby realizing the transfer of the input power to the output power.

The working principle of the ac impedance testing system of the electrochemical device 100 in this embodiment is as follows:

1) non-ac impedance test mode:

when the controller 210 determines that the ac impedance analysis is not to be performed, the controller 210 controls the current perturbation device 410 to be turned off. At this time, the controller 210 first adjusts the operating conditions of the electrochemical device 100 such that the electrochemical device 100 establishes an open-circuit voltage, and then controls the first output load 300 to be activated such that the electrochemical device 100 starts to operate normally, and both the output voltage and the output current of the electrochemical device 100 are dc signals. Meanwhile, the voltage of each single chip of the electrochemical device 100 is monitored through the voltage inspection device 220, and the output current of the electrochemical device 100 is monitored through the first current detection device 600, so that various operation conditions of the electrochemical device 100 can be tested.

2) AC impedance test mode

When the controller 210 determines to perform the ac impedance analysis, the controller 210 controls the current perturbation device 410 and the second output load 420 to be activated. The controller 210 adjusts the second output load 420 to a suitable voltage range or resistance value, and the controller 210 obtains a preset disturbance current by adjusting an alternating current disturbance current and a direct current disturbance current of the disturbance current, specifically, the controller 210 selects a disturbance frequency of the alternating current disturbance current, determines a disturbance amplitude corresponding to the disturbance frequency, obtains the preset disturbance current, and adjusts the input current of the current disturbance device 410 to be the preset disturbance current, wherein the input current of the current disturbance device 410 is equal to the sum of the alternating current disturbance current and the direct current disturbance current, and the amplitude of the alternating current disturbance current is always smaller than the amplitude of the direct current disturbance current by adjusting the output of the second output load 420.

Thus, the output current of the electrochemical device 100 includes an ac perturbation current, and the output voltage of the electrochemical device 100 generates a voltage response signal corresponding to the ac perturbation current. At this time, the output voltage of the selected cell of the electrochemical device 100 is detected by the first voltage detection device 500, and the output current of the cell is synchronously detected by the first current detection device 600. After the output voltage and the output current of a certain number of the single chips to be tested are collected, the single chip inspection device transmits the output voltage and the output current to the controller 210.

The controller 210 performs signal processing on the acquired output voltage and output current of the multiple single chips to be tested, and calculates the ac impedance at the disturbance frequency of the current ac disturbance current. Thereafter, the controller 210 changes the disturbance frequency and the disturbance amplitude of the ac disturbance current, obtains an updated ac disturbance current, and calculates the ac impedance at the disturbance frequency of the updated ac disturbance current according to the above manner. The frequency spectrum of the alternating current impedance can be drawn through the alternating current impedances corresponding to a plurality of different disturbance frequencies. Thereafter, the controller 210 controls the current perturbation device 410 to be turned off.

In addition, as shown in fig. 9, an embodiment of the present invention further provides an ac impedance testing method for an electrochemical device, which is used in the ac impedance testing system for an electrochemical device, and includes the following steps:

s100, controlling the first output load to start to enable the electrochemical device to work normally; in this embodiment, the electrochemical device may be caused to output a direct current by adjusting the first output load.

S200, judging whether to perform an alternating current impedance test; the controller can judge whether to perform the alternating current impedance test according to whether the test trigger signal is received or not, and can also judge whether to perform the alternating current impedance test according to the current working condition of the alternating current impedance system, for example, when the working condition of the alternating current impedance test system reaches the preset working condition, the controller controls the test system to perform the alternating current impedance test; otherwise, the AC impedance test is not performed.

When the alternating current impedance test is judged to be needed, namely when the alternating current impedance test system is in an alternating current impedance test mode, the following steps are executed:

s300, controlling the current disturbance device and the second output load to start; when the alternating current impedance test is needed, the disturbance adjusting branch is communicated with the output end of the electrochemical device, so that disturbance current can be superposed at the output end of the electrochemical device, and the alternating current impedance test is realized. After the current perturbation device and the second output load are started, the alternating current impedance test is carried out according to the following steps:

s400, adjusting the voltage range or the resistance value of the second output load; the voltage range or the resistance value of the second output load is adapted to the output of the current perturbation device by adjusting the second output load. In this embodiment, the control of the output voltage of the current perturbation device may be achieved by the detection values of the second voltage detection device and the fourth current detection device disposed between the second output load and the current perturbation device.

S500, adjusting the input current of the current disturbance device to be a preset disturbance current; specifically, when the input current of the current perturbation device does not reach the preset perturbation current, the controller may regulate and control the on/off time of the switching device in the current perturbation device, so that the input current of the current perturbation device reaches the preset perturbation current.

The preset disturbance current can be obtained in an online adjustment mode, and the method specifically comprises the following steps:

obtaining disturbance frequency and disturbance amplitude of alternating disturbance current in the disturbance current; the controller firstly determines the disturbance frequency of the alternating current disturbance current, and then determines the disturbance amplitude corresponding to the disturbance frequency, so that the current alternating current disturbance current is obtained. When the disturbance frequency is multi-frequency, firstly, determining each disturbance frequency and the corresponding disturbance amplitude, and then forming a preset disturbance current according to superposition of each sub-disturbance current.

Obtaining the amplitude of the direct current disturbance current in the disturbance current; i.e. the dc disturbing current in the disturbing current may be set by on-line.

And obtaining a preset disturbance current according to the disturbance frequency and the disturbance amplitude of the alternating current disturbance current and the amplitude of the direct current disturbance current. Wherein,

wherein I represents a preset disturbance current, I₁Representing a direct disturbance current, I₂Representing the alternating disturbance current, a representing the disturbance amplitude of the alternating disturbance current, f representing the disturbance frequency of the alternating disturbance current,representing the initial phase angle of the ac perturbation current and t representing time.

S600, obtaining the output current and the output voltage of a to-be-detected single chip of the electrochemical device; in this embodiment, can obtain the output voltage of the monolithic that awaits measuring through first voltage detection device and voltage inspection device, obtain the output current of the monolithic that awaits measuring through first current detection device synchronization.

S700, calculating alternating current impedance corresponding to disturbance frequency of preset disturbance current according to output current and output voltage of the single chip to be tested;

s800, changing the disturbance frequency of the preset disturbance current to obtain an updated preset disturbance current; the disturbance amplitude and the disturbance frequency of the alternating disturbance current are controllable and can be adjusted on line through the controller.

S900, calculating alternating current impedance corresponding to the updated disturbance frequency according to the output current and the output voltage of the single chip to be tested; after step S800, the process returns to step S500, and steps S500 to S800 are repeated until a plurality of different disturbance frequencies and corresponding ac impedances are obtained. The specific implementation manner is described in the above.

S1000, obtaining an alternating current impedance spectrum of the electrochemical device according to a plurality of different disturbance frequencies and corresponding alternating current impedances thereof. Therefore, the disturbance frequency of the alternating disturbance current is changed, and the alternating impedance value of the electrochemical device at different disturbance frequencies is measured, so that the frequency spectrum graph of the alternating impedance can be drawn. The circuit has the advantages of simple structure and strong universality, and reduces the cost of the alternating current impedance test system.

In one embodiment, the method further comprises the steps of:

when the controller determines that the alternating current impedance test is not needed, that is, the alternating current impedance test system works in the non-alternating current impedance test mode, step S1001 is executed to control the current perturbation device to be turned off, control the first output load to be in the on state, and control the output power of the first output load to enable the electrochemical device to work normally. Specifically, when the current perturbation device is turned off, the controller controls the first output load to be started, so that the electrochemical device and the first output load form a loop, and the current perturbation device can work normally. Therefore, the electrochemical device can be tested under various working conditions, and the voltage inspection device is controlled to monitor the output voltage of each single chip of the electrochemical device.

The ac impedance testing method of this embodiment is consistent with the working principle of the ac impedance testing system in the above embodiment, and the specific implementation process may be referred to the above description.

According to the alternating current impedance testing system and method of the electrochemical device, the electrochemical device is enabled to normally work through the first output load adjustment, when the current disturbance device is started, the input current of the current disturbance device is adjusted through the second output load and the current disturbance device, so that the output current of the electrochemical device is superposed with the alternating current disturbance current on the basis of the direct current, the alternating current impedance of the electrochemical device can be detected, the circuit structure is simple, the universality is high, and the cost of the alternating current impedance testing system is reduced. And the performance of the test system is further improved through the first output load and the second output load which are relatively independently arranged.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (12)

1. The alternating current impedance testing system of the electrochemical device is characterized by comprising the electrochemical device, a control device, a direct current regulating branch and a disturbance regulating branch connected with the direct current regulating branch in parallel, wherein the electrochemical device is connected with the control device;

the direct current regulating branch comprises a first output load, the input end of the first output load is connected to the electrochemical device, the output end of the first output load is in signal connection with the control device, and the control device is used for monitoring the working state of the first output load;

the disturbance regulating branch comprises a current disturbance device and a second output load, wherein the current disturbance device is used for generating disturbance current, the input end of the current disturbance device is connected to the electrochemical device, the output end of the current disturbance device is connected to the second output load, and the current disturbance device and the second output load are both connected to the control device;

the control device is used for adjusting the input current of the current disturbance device to a preset disturbance current after controlling the current disturbance device to be started, and calculating alternating current impedance corresponding to the disturbance frequency of the preset disturbance current according to the output current and the output voltage of the to-be-detected single chip of the electrochemical device.

2. The ac impedance testing system of an electrochemical device according to claim 1, wherein the control device comprises a controller and a voltage inspection device for monitoring the output voltage of each of the individual test pieces of the electrochemical device;

the voltage measuring end of each single chip of the electrochemical device is connected to the voltage inspection device, the voltage inspection device is connected to the controller, the controller is used for selecting the single chip to be detected and controlling the voltage inspection device to collect the selected output voltage of the single chip to be detected.

3. The ac impedance testing system of an electrochemical device according to claim 2, wherein the voltage inspection device comprises a single chip gating module and a signal processing module connected to respective single chips of the electrochemical device;

the single chip gating module is used for acquiring the output voltage of the single chip to be tested according to the control signal of the controller; the signal processing module is connected with the controller and used for transmitting the output voltage of the single chip to be tested to the controller.

4. The ac impedance testing system of an electrochemical device according to claim 2, further comprising a first voltage detecting means and a first current detecting means for detecting an output current of the electrochemical device;

the input end of the first voltage detection device is connected to the output end of the electrochemical device, and the output end of the first voltage detection device is connected to the common end of the voltage inspection device and the controller; the first current detection device is arranged at the output end of the electrochemical device in series and is connected to the common end of the voltage inspection device and the controller.

5. The ac impedance testing system of claim 2, wherein the dc regulation branch further comprises a second current detection device for detecting the input current of the first output load, the second current detection device being connected to the controller.

6. The ac impedance testing system of claim 2, wherein the disturbance adjusting branch further comprises a third current detection device for detecting the input current of the current perturbation device, the third current detection device is connected to the controller, and the controller is further configured to adjust the time for turning on or off the current perturbation device according to the detected input current of the current perturbation device by the third current detection device, so that the input current of the current perturbation device reaches the preset disturbance current.

7. The alternating current impedance testing system of the electrochemical device according to claim 6, wherein the input current of the current perturbation device comprises an alternating current perturbation current and a direct current perturbation current, and the amplitude of the alternating current perturbation current is smaller than the amplitude of the direct current perturbation current;

the control device is further used for adjusting the disturbance frequency and the disturbance amplitude of the alternating current disturbance current and the amplitude of the direct current disturbance current so as to obtain the preset disturbance current.

8. The ac impedance testing system of claim 6, wherein the disturbance adjusting branch further comprises a second voltage detection device for detecting the output voltage of the current perturbation device and a fourth current detection device for detecting the output current of the current perturbation device;

the second voltage detection device and the fourth current detection device are both connected to the controller, and the controller is used for adjusting the voltage range or the resistance value of the second output load according to the output voltage and the output current of the current disturbance device.

9. The alternating current impedance testing system of an electrochemical device according to claim 1, wherein the current perturbation device is a Boost type DC/DC converter, a Buck type Buck DC/DC converter, or a DC/AC converter.

10. An ac impedance testing method of an electrochemical device, characterized by being used in the ac impedance testing system of the electrochemical device according to claim 1, the method comprising the steps of:

controlling the first output load to start, and enabling the electrochemical device to work normally;

judging whether to perform an alternating current impedance test;

when the alternating current impedance test is judged to be carried out, the following steps are carried out:

controlling the current perturbation device and the second output load to start;

adjusting a voltage range or a resistance value of the second output load;

adjusting the input current of the current disturbance device to be a preset disturbance current;

acquiring the output current and the output voltage of a to-be-detected single chip of the electrochemical device;

calculating alternating current impedance corresponding to the disturbance frequency of the preset disturbance current according to the output current and the output voltage of the single chip to be tested;

changing the disturbance frequency of the preset disturbance current to obtain an updated preset disturbance current;

calculating alternating current impedance corresponding to the updated disturbance frequency according to the output current and the output voltage of the single chip to be tested;

and obtaining an alternating current impedance map of the electrochemical device according to a plurality of different disturbance frequencies and corresponding alternating current impedances thereof.

11. The method for testing ac impedance of an electrochemical device of claim 10, further comprising:

obtaining disturbance frequency and disturbance amplitude of alternating disturbance current in the disturbance current;

obtaining the amplitude of the direct current disturbance current in the disturbance current;

obtaining a preset disturbance current according to the disturbance frequency and the disturbance amplitude of the alternating current disturbance current and the amplitude of the direct current disturbance current;

and adjusting the on-off time of the current disturbance device, and adjusting the input current of the current disturbance device to be the preset disturbance current.

12. The ac impedance testing method of claim 10, further comprising the steps of:

and when the alternating current impedance test is judged not to be carried out, controlling the first output load to be in an opening state and controlling the current disturbance device to be closed.