Diagnostic method for diagnosing state of electrochemical cell of electrochemical energy converter

Abstract

The invention relates to a diagnostic method (100) for diagnosing the state of an electrochemical cell (301) of an electrochemical energy converter (300), the diagnostic method (100) comprising: ascertaining (101) a change (201) of an electrical property of the electrochemical cell over time, determining (103) an evaluable data packet (205, 209), aggregating (105) at least one range (207, 211) of the evaluable data packet (205, 209) into an aggregated change process, and determining (105) the state of the electrochemical cell (301) of the electrochemical energy converter (300). The method comprises determining (107) a slope for at least one range of the aggregated change process, assigning (109) a characteristic value to the slope according to a predetermined assignment scheme in order to quantify the state of the electrochemical cell, outputting (111) the characteristic value on an output unit, the evaluable data packet (205, 209) comprising a plurality of data points, the values of the data points differ from one another at most by a predetermined threshold value at least for a predetermined duration.

Description

Technical Field

[0001] The invention relates to a diagnostic method for diagnosing the state of an electrochemical cell of an electrochemical energy converter, a computing unit and an electrochemical energy converter according to the appended claims. Background Art

[0002] A fuel cell is an electrochemical energy converter that converts, for example, hydrogen and oxygen into water, electricity and heat.

[0003] The porous electrodes of fuel cells, often called catalyst layers, usually consist of platinum particles supported on larger carbon particles. This carbon phase (Kohlenstoff phase) is responsible for the transport of electrons and heat. In addition, ionomers are also interspersed throughout the carbon phase to ensure proton conductivity.

[0004] Electrochemical reactions require three-phase boundaries, which are formed by the intersection of platinum, ionic polymers, and reactants.

[0005] The membrane is at the heart of the fuel cell and consists mainly of ionic polymers. It is the continuity of the ionic polymer phase of the electrode. The function of the membrane is to transfer hydrogen protons from the anode electrode to the cathode electrode as loss-free as possible, while separating the two gas spaces and acting as an electrical insulator. The proton conductivity of the membrane depends primarily on its temperature and water content.

[0006] During fuel cell operation, the aging of these various components causes fuel cell performance to degrade over time and must be monitored.

[0007] To monitor aging, known methods are to measure the current polarization course on a test bench, for example during maintenance, and compare it with a reference course, to carry out cyclic voltammetry, linear sweep voltammetry (LSV) measurements and / or to measure the discharge time, and / or to carry out electrochemical impedance spectroscopy.

[0008] However, these methods are too complex and time-consuming to be performed online and continuously during normal operation. Summary of the invention

[0009] Within the scope of the invention, a diagnostic method, a computing unit and a chemical energy converter are proposed. Further features and details of the invention are derived from the corresponding dependent claims, the description and the drawings. Of course, the features and details relating to the diagnostic method according to the invention also apply to the computing unit and the electrochemical energy converter according to the invention, and vice versa, so that the disclosures concerning the corresponding inventive aspects can always be cross-referenced.

[0010] The invention is used in particular for determining and quantifying the state of at least one electrochemical cell of an electrochemical energy converter.

[0011] According to a first aspect of the invention, a diagnostic method for diagnosing the state of an electrochemical cell of an electrochemical energy converter is proposed. The proposed diagnostic method comprises determining the change of an electrical property of the electrochemical cell over time, determining an evaluable data packet, aggregating at least a corresponding range of the evaluable data packet into an aggregated change process, determining the slope of at least one range of the aggregated change process, assigning a characteristic value to the slope according to a predetermined assignment scheme to quantify the state of the electrochemical cell, and outputting the characteristic value on an output unit, wherein the evaluable data packet includes a plurality of data points, the values ​​of which differ from each other by at most a predetermined threshold value at least within a predetermined time period.

[0012] In the context of the present invention, an evaluable data packet refers to a plurality of measured values ​​corresponding to a quasi-steady state.

[0013] The proposed diagnostic method is based on the following principle: the measured values ​​of the electrical properties of the electrochemical cell determined by the sensor are evaluated and only those measured values ​​that are relevant or representative for the state of the electrochemical cell are used to diagnose the state of the electrochemical cell. For this purpose, evaluable data packets are determined in the measured values, in particular those corresponding to a quasi-steady state, and these data packets are aggregated into an aggregated course of events. Thus, measured values ​​determined in non-steady states, in particular in the startup phase or the standby phase, are discarded and only measured values ​​determined in stable system states are used.

[0014] The predetermined duration provided in the invention provides a minimum time for the electrochemical energy converter to oscillate into the corresponding state, thereby minimizing the influence of external influences (eg load and / or temperature changes) and maximizing the signal response of the electrical properties of the electrochemical cell.

[0015] Based on the aggregate course of the evaluable data packets, the state of the electrochemical cell can be reliably determined by determining the slope of the aggregate course of change. For quantification, the slope is assigned a characteristic value, such as a numerical value on an ordinal scale or a color in a color scheme, in particular a traffic light scheme.

[0016] In order to ensure that the corresponding data in the evaluable data packets correspond to a quasi-steady state, ie are ascertained during a quasi-stationary state of the electrochemical energy converter, the evaluable data packets include only those data points which differ from one another by at most a predetermined threshold value at least for a predetermined period of time.

[0017] Furthermore, it can be provided that the evaluable data packet includes a range of data points whose values ​​differ from one another by at most a predetermined threshold value at least within a predetermined time period, wherein the range ends at the end of the evaluable data packet and is smaller than the evaluable data packet.

[0018] By selecting a range of a plurality of data points, the values ​​of which differ from one another by at most a predetermined threshold value at least within a predetermined duration, in particular in a later range after the predetermined duration, a particularly long oscillation of the state of the electrochemical energy converter is ensured, thereby minimizing the influence of changing conditions (e.g. temperature changes or load changes) on the aggregated course of change. The aggregated course of change thus reflects changes in the electrical properties of the electrochemical cell particularly effectively.

[0019] The electrical characteristic may be set to include at least one parameter from the following parameter list: current intensity, voltage, power.

[0020] Since the current intensity, voltage and power parameters of an electrochemical cell change with aging, these parameters are particularly suitable for determining the state of an electrochemical cell.

[0021] It can also be provided that the aggregated change process is extrapolated into the future, and the diagnostic method further comprises determining other slopes of at least one range of the extrapolated change process, assigning other characteristic values ​​to the other slopes according to a predetermined assignment scheme to quantify the future state of the electrochemical cell, and outputting the other characteristic values ​​on an output unit.

[0022] In order to predict the future state of the electrochemical cell and predict, for example, the time of discontinuation or the so-called "end of life", the course of the polymerization can be extrapolated. For this purpose, for example, a straight line with a slope determined for the course of the polymerization can be used, or a fitting function (for example, the method of least squares or a polynomial fit) can be used to determine the future course of the polymerization.

[0023] It can also be provided that in order to determine whether an evaluable data packet includes a plurality of data points whose values ​​differ from one another by at most a predetermined threshold value at least over a predetermined period of time, variances and / or derivatives of a plurality of data points are calculated.

[0024] It is also possible to filter the change process of the electrical characteristics through a filter so that only data points that meet predetermined filtering criteria are included in the change process, wherein the filtering criteria include that the operating temperature of the electrochemical energy converter is within a predetermined temperature range and / or the power of the electrochemical energy converter is not zero.

[0025] In particular, a zero power state of the electrochemical energy converter does not represent aging of the corresponding electrochemical cell of the electrochemical energy converter, so by filtering out the corresponding measured values, the validity of the remaining data after filtering can be maximized for determining the aging of the electrochemical cell.

[0026] According to a second aspect, the invention relates to a computing unit for diagnosing the state of an electrochemical energy converter. The computing unit is configured to determine an evaluable data packet from a course of change of the electrochemical energy converter ascertained by a sensor, aggregate at least corresponding ranges of the evaluable data packet into an aggregate course of change, determine a slope of at least one range of the aggregate course of change, assign a characteristic value to the slope according to a predetermined assignment scheme to quantify the state of the electrochemical cell, and output the characteristic value on an output unit, wherein the evaluable data packet includes a plurality of data points, the values ​​of which differ from one another by at most a predetermined threshold value at least for a predetermined duration.

[0027] In the context of the present invention, a computing unit refers to a computer, a server, a processor, a controller or any other programmable circuit.

[0028] In particular, the proposed computing unit can be a central server, which is communicatively connected to a plurality of electrochemical energy converters, in order to carry out the proposed diagnostic method, i.e. to receive measured values ​​of the respective electrochemical energy converters and to determine the respective characteristic values. Thus, the characteristic values ​​can be determined online without visiting a workshop.

[0029] Alternatively, the proposed computing unit can be part of a corresponding electrochemical energy converter, in particular part of a controller.

[0030] According to a third aspect, the invention relates to an electrochemical energy converter comprising a plurality of electrochemical cells, a sensor configured to measure an electrical property of at least one electrochemical cell of the plurality of electrochemical cells, and a communication interface, wherein the communication interface is configured to transmit the measured values ​​ascertained by the sensor to a possible configuration of the proposed computing unit.

[0031] The communication interface of the electrochemical energy converter may be a wireless interface for communicating with a central server or a cable for communicating with a controller.

[0032] According to a fourth aspect, the invention relates to a further electrochemical energy converter comprising a plurality of electrochemical cells, a sensor configured to measure an electrical property of at least one electrochemical cell of the plurality of electrochemical cells, and a possible configuration of the proposed calculation unit.

[0033] The electrochemical energy converter can carry out the proposed diagnostic method autonomously via its own, in particular local, computing unit.

[0034] It may be provided that the proposed electrochemical energy converter or another electrochemical energy converter is an electrolyser or a fuel cell system.

[0035] Further advantages, features and details of the invention emerge from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 shows a possible configuration of the proposed diagnostic method,

[0037] Figure 2 Show according to Figure 1 A detailed description of the diagnostic method,

[0038] Figure 3 shows a system having a possible configuration of the proposed electrolysis cell and a possible configuration of the proposed computing unit, DETAILED DESCRIPTION

[0039] exist Figure 1 , a diagnostic method 100 for diagnosing the state of an electrochemical cell of an electrochemical energy converter is shown. The diagnostic method 100 comprises a determination step 101, in which the course of an electrical property of the electrochemical cell over time is determined, for example by means of an electrical sensor.

[0040] Furthermore, diagnostic method 100 comprises a determination step 103 , in which evaluable data packets are ascertained from the profiles ascertained in ascertainment step 101 , and a grouping step 105 , in which at least corresponding ranges of the corresponding evaluable data packets ascertained in ascertainment step 103 are grouped into an aggregate profile.

[0041] Furthermore, the diagnostic method 100 comprises a further determination step 107, in which a slope of at least a range of the polymeric variation process is determined, an assignment step 109, in which a characteristic value is assigned to the slope according to a predetermined assignment scheme to quantify the state of the electrochemical cell, and an output step 111, in which the characteristic value is output on an output unit, such as a display or a loudspeaker.

[0042] According to the diagnostic method 100 , it is provided that the evaluable data packet includes a plurality of data points whose values ​​differ from one another by at most a predetermined threshold value at least over a predetermined period of time.

[0043] exist Figure 2 , a diagram 200 is shown with time on the horizontal axis and current intensity on the vertical axis. The course 201 corresponds to the current intensity values ​​measured by the sensor of the electrochemical energy converter for the electrochemical cell.

[0044] After the warm-up phase, the electrochemical energy converter (here, a fuel cell system, for example) is loaded, after which the electrochemical energy converter oscillates into the load and passes into a quasi-steady state 203, wherein the corresponding measured values ​​differ from each other by at most a predetermined threshold value, at least for a predetermined duration. Accordingly, the quasi-steady state 203 forms an evaluable data packet 205.

[0045] also, Figure 2 2 shows a range 207 consisting of a plurality of data points, the values ​​of which differ from one another by at most a predetermined threshold value at least for a predetermined duration. The range 207 corresponds to a portion of the evaluable data packet 205 and ends at the end of the evaluable data packet 205, wherein the length of the range 207 can be predetermined. Alternatively, the length of the range 207 can correspond to the length of the data packet 205. Thus, the measured values ​​or data points of the range 207 are determined when the electrochemical energy converter oscillates for a long time into a quasi-steady state and the variance of the measured values ​​is particularly small.

[0046] Due to a further load change, the change process 201 jumps into a further quasi-steady state and forms a further evaluable data packet 209 having a further range 211 .

[0047] By combining ranges 207 and 211 , a combined profile can be determined which relates only to the electrical properties of the electrochemical cell in the quasi-steady-state range and thus describes the aging of the electrochemical cell particularly effectively.

[0048] exist Figure 3 , an electrochemical energy converter 300 is shown. The electrochemical energy converter 300 includes a plurality of electrochemical cells 301, a sensor 303 configured to measure the electrical properties of at least one electrochemical cell 301 in the plurality of electrochemical cells 301, and a communication interface 305, which is configured to transmit the measured values ​​obtained by the sensor 303 to a computing unit 307, so as to implement the Figure 1 Diagnostic methods 100.

Claims

1. A diagnostic method (100) for diagnosing the state of an electrochemical cell (301) of an electrochemical energy converter (300), in, The diagnostic method (100) comprises: Obtaining (101) the change process (201) of the electrical characteristics of the electrochemical cell over time, determining (103) evaluable data packets (205, 209), Aggregating (105) at least one range (207, 211) of corresponding evaluable data packets (205, 209) into an aggregated change process, determining (107) a slope for at least one range of variation of the polymerization, assigning (109) a characteristic value to the slope according to a predetermined assignment scheme to quantify the state of the electrochemical cell, Outputting (111) the characteristic value on an output unit, The evaluable data packets (205, 209) comprise a plurality of data points, the values ​​of which differ from one another by at most a predetermined threshold value at least for a predetermined time period.

2. The diagnostic method (100) according to claim 1, It is characterized in that An evaluable data packet (205, 209) comprises a range (207, 211) consisting of a plurality of data points, the values ​​of which differ from one another by at most a predetermined threshold value at least for a predetermined duration, wherein the range (207, 211) ends at the end of the evaluable data packet (205, 209) and is smaller than the evaluable data packet (205, 209).

3. The diagnostic method (100) according to any one of the preceding claims, It is characterized in that The electrical characteristic comprises at least one parameter from the following parameter list: current intensity, voltage, power.

4. The diagnostic method (100) according to any one of the preceding claims, It is characterized in that The aggregated change process is extrapolated into the future, and the diagnostic method (100) further comprises: determining a further slope for at least one range of the extrapolated profile, assigning other characteristic values ​​to the other slopes according to a predetermined assignment scheme to quantify the state of the electrochemical cell in the future, The further characteristic value is outputted at the output unit.

5. The diagnostic method (100) according to any one of the preceding claims, It is characterized in that In order to determine whether an evaluable data packet (205, 209) includes a plurality of data points whose values ​​differ from one another by at most a predetermined threshold value at least over a predetermined time period, variances and / or derivatives of the plurality of data points are calculated.

6. The diagnostic method (100) according to any one of the preceding claims, It is characterized in that The change process of the electrical characteristic is filtered by means of a filter so that only data points that meet a predetermined filtering criterion are included in the change process (201), wherein the filtering criterion includes: the operating temperature of the electrochemical energy converter (300) is within a predetermined temperature range and / or the power of the electrochemical energy converter (300) is not zero.

7. A calculation unit (307) for diagnosing the state of the electrochemical energy converter (300), in, The computing unit (307) is configured to: determining an evaluable data packet (205, 209) from a course of change (201) ascertained by a sensor (303) of the electrochemical energy converter (300), Aggregating at least one range (207, 211) of corresponding evaluable data packets (205, 209) into an aggregated change process, determining a slope for at least one range of the variation of the polymerization, assigning a characteristic value to the slope according to a predetermined assignment scheme to quantify the state of the electrochemical cell (301) and outputting the characteristic value on an output unit, The evaluable data packets (205, 209) comprise a plurality of data points, the values ​​of which differ from one another by at most a predetermined threshold value at least for a predetermined time period.

8. Electrochemical energy converter (300), in, The electrochemical energy converter (300) comprises: a plurality of electrochemical cells (301), a sensor (303) configured to measure an electrical characteristic of at least one electrochemical cell (301) of the plurality of electrochemical cells (301), a communication interface (305), Therein, the communication interface (305) is configured to transmit the measured values ​​ascertained by the sensor (303) to a computing unit (307) according to claim 7.

9. Electrochemical energy converter (300), in, The electrochemical energy converter (300) comprises: a plurality of electrochemical cells (301), a sensor (303) configured to measure an electrical characteristic of at least one electrochemical cell (301) of the plurality of electrochemical cells (301), The calculation unit (307) according to claim 7.

10. The electrochemical energy converter (300) according to claim 8 or 9, It is characterized in that The electrochemical energy converter (300) is an electrolyser or a fuel cell system.

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