Shared electrolyzer monitoring system and method

Abstract

The invention relates to a shared electrolyser monitoring system and method. Electrochemical impedance spectroscopy (EIS) systems and methods are described herein that facilitate the distribution of a single excitation generator across a plurality of electrolyzer stacks, each electrolyzer stack including a set of electrochemical cells. By distributing excitation signals, impedance data of the cells in each electrolyzer stack can be measured, e.g., assessed their condition or the condition of the stack, without the need for a separate excitation block for each electrolyzer stack. In various embodiments, a shared excitation generator is achieved by sequentially directing excitation signals to different stacks. A final response signal indicative of the impedance of the cell or the entire cell stack is locally processed on each respective electrolyzer stack. Advantageously, the excitation generator can be remotely positioned, for example, in a location constrained by less strict security measures, thereby reducing equipment and operating costs.

Description

Technical Field

[0001] The present invention relates generally to electrolyzer systems and methods. More particularly, the present invention relates to shared excitation in an EIS monitoring system for an electrolyzer measurement system and a method for monitoring and controlling the performance of electrochemical cells within an electrolyzer stack. Background Art

[0002] Electrochemical Impedance Spectroscopy (EIS) monitoring systems for water electrolyzers are used to study the impedance of electrochemical cells that produce primarily hydrogen and oxygen. Such systems are often used for hydrogen production in fuel cells and energy storage to analyze and optimize cell performance. Measuring the impedance of the cells in any given stack typically involves superimposing a known excitation signal on a DC signal at the operating point of the cell stack. The response is measured and the impedance, which is heavily dependent on the operating point, is calculated over a range of frequencies.

[0003] Electronic equipment near the electrolyzer stack is subject to additional safety protocols, such as ATEX compliance, to ensure the safety of equipment operating in environments subject to explosion risks caused by flammable gases, vapors, mists, or dust. This places additional constraints on hardware development, especially since the EIS measurement equipment must be placed relatively close to its respective stack to minimize unwanted side effects, such as wiring impedance and parasitics, which would otherwise negatively affect the accuracy or resolution of the measurement. In addition, traditional EIS methods use dedicated stimulus generation blocks for each stack, which results in high system costs, as the EIS stimulus generation block tends to be one of the most expensive components in the hardware system.

[0004] Therefore, there is a need for systems and methods that overcome such limitations present in conventional designs. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Reference will be made to embodiments of the present invention, examples of which may be shown in the accompanying drawings. These figures are intended to illustrate rather than limit. Although the present invention is generally described in the context of these embodiments, it should be understood that this is not meant to limit the scope of the present invention to these specific embodiments. The items in the drawings are not drawn to scale.

[0006] FIG1 shows a conventional EIS monitoring system.

[0007] Figure 2 An electrolyzer system according to various embodiments of the present disclosure is shown.

[0008] Figure 3 is an exemplary block diagram illustrating distances for a hydrogen generation plant layout according to various embodiments of the present disclosure.

[0009] Figure 4 is a schematic diagram of illustrative electrical interconnections of an exemplary system according to various embodiments of the present disclosure.

[0010] Figure 5 is a flow chart of an illustrative process for sharing an EIS according to various embodiments of the present disclosure. DETAILED DESCRIPTION

[0011] In the following description, for the purpose of explanation, specific details are set forth to provide an understanding of the present disclosure. However, it is apparent to those skilled in the art that the present disclosure can be implemented without these details. In addition, those skilled in the art will recognize that the embodiments of the present disclosure described below can be implemented in various ways, such as a process, apparatus, system / device, or method on a tangible computer-readable medium.

[0012] The components or modules shown in the figures are illustrations of exemplary embodiments of the present disclosure and are intended to avoid obfuscation of the present disclosure. It should be understood that throughout the discussion, components may be described as separate functional units, which may include subunits, but those skilled in the art will recognize that various components or parts thereof may be divided into separate components or may be integrated, including, for example, in a single system or component. It should be noted that the functions or operations discussed herein may be implemented as components. Components may be implemented in software, hardware, or a combination thereof.

[0013] Furthermore, the connections between components or systems in the diagrams are not limited to direct connections. Rather, data between these components may be modified, reformatted, or otherwise altered by intermediate components. Furthermore, additional or fewer connections may be used. It should also be noted that the terms "coupled," "connected," "communicatively coupled," "interface," "port," or any derivatives thereof, should be understood to include direct connections, indirect connections through one or more intermediate devices, and wireless connections. It should also be noted that any communication, such as signals, responses, replies, confirmations, messages, inquiries, etc., may include one or more information exchanges.

[0014] References in the specification to "one or more embodiments", "preferred embodiments" or "embodiments" etc. mean that the specific features, structures, characteristics or functions described in conjunction with the embodiments are included in at least one embodiment of the present disclosure and may be included in multiple embodiments. In addition, the above phrases appearing in various places in the specification do not necessarily refer to the same one or more embodiments.

[0015] Certain terms are used in various places in the specification for the purpose of explanation and should not be interpreted as limiting. The terms "include", "comprising", "consisting of", "consisting of" and any variations thereof should be understood as open terms, and any examples or lists of items are provided by way of illustration and should not be used to limit the scope of the present disclosure.

[0016] Any headings used herein are for organizational purposes only and shall not be used to limit the scope of the specification or claims.The entire contents of each reference / document mentioned in this patent document are incorporated herein by reference.

[0017] It should be noted that the embodiments described herein are constructed in the context of a shared electrochemical impedance spectroscopy (EIS) monitoring system and method, but those skilled in the art will recognize that the concepts of the present disclosure are not limited to these applications and can be used in other contexts as well. For example, another implementation can integrate the EIS excitation generation block into the stacked power supply.

[0018] In this document, "electrochemical cell" and "electrolyzer" may be used interchangeably. The terms "actuator," "contactor," and "relay" may each refer to any switching element recognized by those skilled in the art.

[0019] FIG1 shows a conventional EIS monitoring system.

[0020] The monitoring device 100 includes a cell electrolyzer stack 102, an EIS excitation 132 (typically an AC signal generator), and a measurement system that includes an EIS engine (e.g., 134) connected to one or more cells to allow cell-by-cell measurements. Typically, the AC signal generator 132 generates known sinusoidal voltage or current excitation signals of varying frequencies and relatively small amplitudes in gradually varying increments. These excitation signals are then applied to each electrolyzer in the stack 102.

[0021] The measurement system examines the relationship between the excitation signal and the response signal generated over a specified frequency spectrum to calculate the cell impedance. The response signal can be amplified and converted to an output voltage. Due to the impedance of the system, the response signal typically exhibits a phase shift and amplitude variation relative to the excitation signal. Demodulation techniques can be used to extract the amplitude and phase shift to separate the in-phase and out-of-phase components of the response signal to obtain the complex impedance at a specific excitation frequency.

[0022] The collected impedance data, such as the EIS spectra collected over time for each cell, can then be analyzed to gain insight into the electrochemical properties and, therefore, the performance and operating conditions of individual cells within the electrolyzer stack 102. For example, by monitoring and analyzing the impedance data, problems (inefficiency, degradation, and failures in specific cells) can be detected, maintenance schedules for the stack can be optimized, and the overall efficiency and life of the electrolyzer stack 102 can be improved.

[0023] Given the relatively small amplitude of the excitation signal, it is desirable to limit the measurement noise to achieve accurate impedance measurement. Therefore, in embodiments herein, during impedance measurement, the frequency of the sinusoidal excitation signal generated by the excitation block is therefore limited to a relatively narrow frequency range around the frequency of interest.

[0024] To further improve impedance measurement accuracy, the complex current provided by the stimulus block can be measured simultaneously with the complex voltage across the battery or entity being measured. In an embodiment, to achieve this synchronization, a communication network including an isoSPI bus can be used to connect the current and voltage measurements to the stimulus generator block. In an embodiment, the IC measuring the current and voltage can be triggered by commands transmitted over the communication network to perform measurements at a specified frequency.

[0025] Furthermore, if the current and voltage measurement blocks are implemented as discrete and separate units, the potential phase delay between them may affect the accuracy of the impedance measurement. Therefore, in some embodiments, the stimulus block can transmit the generated frequency to the measurement chip with relatively high accuracy to ensure that the IC matches and accurately measures the same frequency.

[0026] Figure 2 1 shows an electrolyzer system according to various embodiments of the present disclosure. In an embodiment, system 200 includes electrolyzer stacks 202, 204, measurement circuits 206, 208, an EIS excitation generator 210, and an EIS control system 212. It should be understood that system 200 may include some or all of the elements shown in FIG. 1. It is further understood that system 200 may also include amplifiers, power supplies, multiplexers, switches, and Figure 2 Other auxiliary devices not explicitly shown in the figure. The solid lines between the elements represent the wiring and assembly of the switches, while the dotted lines between the elements represent the communication paths between the elements. It should be understood that any type of communication protocol can be used, such as Ethernet or TCP / IP.

[0027] like Figure 2 As shown, each measurement circuit 206, 208 is located near its corresponding electrolyzer stack 202, 204 for cell measurement purposes. In contrast, in addition to the EIS control system 202, the EIS excitation generator 210 can also be located at a location away from the electrolyzer stacks 202, 204 and the measurement unit 206, 208, such as at location 232, which may be subject to less safety requirements. This arrangement allows the EIS excitation generator 210 to serve any number of electrolyzer stacks 202, 204 by sequentially applying the generated excitation signal to different electrolyzer stacks 202, 204, thereby significantly reducing development, equipment and operating costs, as known to those skilled in the art.

[0028] For example, placing the EIS excitation generator 210 away from the hydrogen production area 230 significantly simplifies thermal management. The EIS excitation generator 210 can generate considerable heat (e.g., 10 kW), which can be dissipated more efficiently due to less stringent cooling requirements to prevent unnecessary contact with flammable gases, thereby reducing design constraints and costs. Unlike existing designs, the EIS excitation generator 210 does not require special insulation to prevent accidental exposure to hydrogen.

[0029] In operation, the EIS excitation generator 210 can generate an AC voltage or current within a specified frequency range (e.g., 0.5kHz-25kHz) as an input excitation signal. In an embodiment, a perturbation technique can be utilized, which involves generating relatively small (e.g., 1%) excitation signals that are superimposed or modulated onto a DC signal that powers the electrolyzer stacks 202, 204. In an embodiment, the excitation signal can be directed to any number of electrolyzer stacks (e.g., 202, 204), for example, via a switching circuit (not shown) that performs multiplexing or switching operations, where they can be detected using any known contact or non-contact current measurement technology (e.g., magnetoresistive sensors). In response, each cell that receives the excitation signal can generate an output voltage that can be detected by the measurement circuits 206, 208.

[0030] Similarly, in an embodiment, each measurement circuit 206, 208 can be configured to perform multiplexing or switching operations to connect the excitation signal to the measurement points of different electrochemical cells or electrolyzer stacks 202, 204, for example, to apply one excitation signal at a time or to any combination of cells simultaneously. In an embodiment, the measurement circuit 206, 208 can be used to measure the DC signal and the excitation signal at each electrolyzer stack 202, 204, for example in the form of current, and any corresponding response signal, such as the voltage at each electrolyzer in each electrolyzer stack 202, 204. In an embodiment, the frequency range of the measurement circuit 206, 208 can be limited to reduce noise. In addition, the measurement circuit 206, 208 can generate its own reference signal at a frequency that reflects the frequency of the excitation signal, which may have been transmitted to the measurement circuit 206 and 208 on the data line, for example, to perform a demodulation operation. In addition, the measurement circuit 206, 208 can select the measurement time of the frequency of interest, for example based on the expected stabilization period.

[0031] Subsequent voltage and current measurements at each frequency may be used to calculate or derive impedance data. In embodiments, the control system 212 may send and receive signals to facilitate impedance measurements, for example, periodically or according to a measurement schedule. It should be appreciated that in embodiments, rather than utilizing cell-by-cell impedance measurements, the battery pack may be evaluated in combination. Similarly, the impedance of the stack as a whole may be evaluated.

[0032] The impedance data can then be stored, for example, for post-processing and data analysis by control system 212 or a remote server implementation (not shown). Exemplary data analysis can include examining individual EIS spectra, comparing them to each other, or tracking how these spectra change over time, etc.

[0033] It is desirable that the parasitic impedance of the connection between the electrolyzer stacks 202, 204 and their respective measurement circuits 206, 208 be as short as possible, e.g., on the order of 10 or less. In embodiments, this can be accomplished by using low impedance (e.g., gold plated) connectors and using cables of relatively short electrical length to help obtain accurate impedance measurements, which is particularly challenging at low impedances. For example, if the connectors to a cell extend the length of the cell by approximately 50 cm and the thickness of the cell by approximately 0.5 cm, assuming a simple copper conductor, a length of up to 1 m between the cell and the EIS measurement block may be permissible before reaching the 10 limit. Other measures may include reducing noise to improve the signal-to-noise ratio of the EIS measurement, eliminating or compensating for parasitic effects, and applying an appropriate calibration protocol.

[0034] Furthermore, it is desirable to simultaneously measure the input current generated by the excitation signal and the voltage measured across the battery to reduce phase errors that could negatively affect the measurement results.

[0035] In an embodiment, the impedance of the cells in the electrolyzer stacks 202, 204 is on the order of tens of μΩ to several mΩ, and in order to accurately measure these impedance values, the cell current and cell voltage should be measured in a synchronized manner to minimize noise. For example, in order to improve the accuracy of the EIS measurement, the excitation signal can be calibrated to provide a known waveform. In an embodiment, the command is used as a trigger signal to synchronize the waveform with the waveform measured at any given cell or cell combination. It should be understood that the calibrated excitation signal and / or any number of measurement signals can be further processed to improve measurement accuracy. In addition, in an embodiment, synchronization can be assisted by using a PLL circuit, a clock circuit, etc.

[0036] It should be noted that the electrolyzer systems shown herein are not limited to the structural details shown in their respective figures or described in the accompanying text. For example, those skilled in the art will appreciate that multiple stacks may be used and any number of components may be modified, added or deleted. Figure 3 is an exemplary block diagram showing the distance of a hydrogen generation plant layout according to various embodiments of the present disclosure. Figure 2 Components shown that are similar are labeled in the same manner. Items in the figures may not be drawn to scale. Figure 3 Any distances and metrics in represent one exemplary embodiment described therein and may vary between implementations depending on the application.

[0037] In an embodiment, the hydrogen generation device 300 includes an electrolyzer stack 202-205, a transformer / rectifier station 312-318, a hydrogen purification station 310, a water purification station 320, a substation 130, a central cooling system 340, an excitation generator 210, and an EIS control system 212. For the sake of brevity, the description or its function is not repeated here. Note that any number of components can be modified, added, or deleted. For example, a hydrogen purification system 310 that can be used to purify the fuel cells within the electrolyzer stack 202-205 can be optional.

[0038] In an embodiment, substation 330 steps down the high utility voltage to medium voltage AC power. Transformers and rectifiers 312-318 then convert the medium voltage AC power to DC power, which is provided to electrolyzer stacks 202-205 to facilitate the electrolysis process to decompose water molecules into hydrogen and oxygen. Central cooling system 340 provides cooling water that circulates through electrolyzer stacks 202-205 to maintain electrolysis efficiency.

[0039] Unlike existing plants, in existing plants, each electrolyzer stack 202-205 can be assigned its own dedicated excitation generator, such as Figure 3 As shown, the excitation generator 210 can be located at a distance from the electrolyzer stacks 202-205, for example, in a separate room 232 shown in dashed lines. This arrangement of sharing the excitation generator 210 between the electrolyzer stacks 202-205 advantageously reduces system-level size, weight, and cost, simplifies thermal design, and complies with applicable ATEX requirements.

[0040] Figure 4 is a schematic diagram of illustrative electrical interconnections of an exemplary system according to various embodiments of the present disclosure. Figure 2 Like numbers in the figures represent similar elements. Figure 2 In an embodiment, circuit 400 includes an electrolyzer stack (e.g., 202), an EIS measurement unit (e.g., 208), a multiplexer 402, a control system 404, an excitation signal generator 210 and / or an actuator (e.g., 412), a relay (e.g., 414), and a DC current source 418.

[0041] As shown, a first signal path connects a DC current source 418 to the electrolyzer stack, providing a DC current that can be delivered through the copper busbar 410. Similarly, a high current path 432, which can be implemented as a shielded conductor, can transmit an AC excitation signal generated by the excitation signal generator 210 to the electrolyzer stack. In addition, the digital data 420 and control paths 420 can carry respective data and control signals to various parts of the system 400. In addition, an exemplary actuator 412, which can be implemented as an analog device, can be used to actuate a relay 414 to enable the excitation signal to be provided to the electrolyzer stack 202. In an embodiment, the actuator 412 (implemented as an analog or digital control device) can also be used to actuate an EIS measurement.

[0042] In an embodiment, multiplexer 402 can be coupled to an actuator (e.g., 412) in high current path 432 to multiplex excitation signals between different electrolyzer stacks during measurement operations that may overlap with conventional electrolysis operations. In different states, the excitation signal can be superimposed on the DC current provided to the electrolyzer stacks 202, 204. The switching element can be implemented as a solid-state relay, a contactor, an electromagnetically operated relay, etc. It should be understood that the configuration and characteristics of actuator 412, such as rated power (e.g., response time, voltage, current, rated power), can be selected according to the specific application. In an embodiment, actuator 412 can have an AC rated current of 50-100A at 5kHz, and its operation can be controlled by control system 404.

[0043] As previously described, in embodiments, the control system 404 and the excitation generator 210 can be physically separated from the rest of the system 400, here by the high current wiring 432. The control system 404 can communicate with various components in the system 402, synchronizing their operation. For example, the control system 404 can instruct the excitation generator 210 to generate a signal at a specific frequency and amplitude, and can also instruct the multiplexer 402 which actuator to turn on at any given time. In addition, the control system 404 can receive measurement data from the EIS measurement circuit 208 and communicate with the substation (such as Figure 3 As shown) interaction, for example, determining which stack is turned on or off. It is understood that any type of communication protocol, such as Modbus (PLC), MQTT, ControlBus and CANBus, can be used for these types of interactions.

[0044] Figure 55 is a flow chart of an illustrative process for sharing an EIS between electrolyzer stacks according to various embodiments of the present disclosure. In an embodiment, when the EIS excitation circuit generates multiple voltage or current excitation signals, the sharing process 500 can begin at step 502. Each excitation signal can be generated at a specific frequency. The generated excitation signals can be sequentially applied to different stacks, each stack including a group of electrochemical cells. In an embodiment, the physical distance between the EIS excitation circuit and the stack allows the EIS excitation circuit to have reduced safety requirements.

[0045] At step 504, response signals generated by one or more electrochemical cells may be obtained.

[0046] At step 506 , the excitation signal and the response signal may be measured simultaneously to generate impedance data.

[0047] Finally, at 508 , the impedance data may be used to determine a condition of one or more electrochemical cells.

[0048] Those skilled in the art should recognize that: (1) certain steps may be performed optionally; (2) the steps may not be limited to the specific order described herein; (3) certain steps may be performed in a different order; and (4) certain steps may be performed simultaneously.

[0049] Aspects of the present invention may be encoded on one or more non-transient computer-readable media, containing instructions for one or more processors or processing units to perform steps. It should be noted that one or more non-transient computer-readable media should include volatile and non-volatile memory. It should be noted that alternative implementations are possible, including hardware implementations or software / hardware implementations. The functions of hardware implementations can be implemented using ASICs, programmable arrays, digital signal processing circuits, etc. Therefore, the term "means" in any claim is intended to cover software and hardware implementations. Similarly, the term "computer-readable medium" used herein includes software and / or hardware containing instruction programs thereon, or a combination thereof. In view of these embodiments, it should be understood that the drawings and accompanying descriptions provide those skilled in the art with the functional information required to write program code (i.e., software) and / or manufacture circuits (i.e., hardware) to perform the desired processing.

[0050] It should be noted that embodiments of the present invention may also relate to computer products with non-transitory tangible computer-readable media having computer code thereon for performing various computer-implemented operations. The media and computer code may be specially designed and constructed for the purposes of the present invention, or they may be of a type known or available to those skilled in the relevant art. Examples of tangible computer-readable media include, but are not limited to, magnetic media such as hard disks, floppy disks, and tapes; optical media such as CD-ROMs and holographic devices; magneto-optical media; and hardware devices specially configured to store or store and execute program code, such as application specific integrated circuits (ASICs), programmable logic devices (PLDs), flash memory devices, and ROM and RAM devices. Examples of computer code include machine code, such as code generated by a compiler, and files containing high-level code executed by a computer using an interpreter. Embodiments of the present invention may be implemented in whole or in part as machine executable instructions, which may be in program modules executed by a processing device. Examples of program modules include libraries, programs, routines, objects, components, and data structures. In a distributed computing environment, program modules may be physically located in a local, remote, or both setting.

[0051] Those skilled in the art will recognize that no computing system or programming language is essential to the practice of the present disclosure. Those skilled in the art will also recognize that the above-mentioned multiple elements can be physically and / or functionally separated into modules and / or sub-modules or combinations.

[0052] Those skilled in the art will appreciate that the foregoing examples and embodiments are illustrative and do not limit the scope of the present disclosure. It is intended that all permutations, enhancements, equivalents, combinations, and improvements that are apparent to those skilled in the art after reading the specification and studying the drawings are included within the true spirit and scope of the present disclosure. It should also be noted that the elements of any claim may be arranged differently, including having multiple dependencies, configurations, and combinations.

Claims

1. A system for sharing electrochemical impedance spectroscopy (EIS) excitation, the system comprising: An EIS excitation circuit generates a set of excitation signals including voltage or current; a switching circuit coupled to the EIS excitation circuit, the switching circuit applying the set of excitation signals to a battery stack in a set of electrochemical battery stacks; a measurement circuit coupled to the stack, the measurement circuit simultaneously measuring an excitation signal and a response signal generated by one or more electrochemical cells to obtain impedance data; as well as A processor, coupled to the measurement circuit, uses the response signal to determine a condition of one or more electrochemical cells in the stack.

2. The system of claim 1, wherein the distance between the EIS excitation circuit and the stack allows the EIS excitation circuit to have reduced safety requirements.

3. The system of claim 1, further comprising the processor analyzing the impedance data to predict a condition of the one or more electrochemical cells.

4. The system of claim 1, wherein the measurement circuit measures the impedance data within a frequency range of 5 kHz.

5. The system of claim 1, further comprising an impedance matching circuit that matches an impedance of a battery to an impedance of the measurement circuit.

6. The system of claim 1, further comprising a calibration circuit that calibrates one or more parameters of at least one of the EIS excitation circuit or the measurement circuit.

7. The system of claim 1, further comprising an error processing circuit that uses the response signal to detect a fault or condition associated with at least some of the one or more electrochemical cells.

8. The system of claim 1, further comprising at least one of a PLL circuit or a clock circuit to synchronize the stimulus signal and the response signal.

9. The system of claim 1, wherein the measurement circuit performs steps including compensating for phase delay between the excitation signal and the response signal to improve accuracy of the impedance data.

10. A method for sharing electrochemical impedance spectroscopy (EIS) excitation, the method comprising: applying a set of excitation signals to a battery stack in a set of electrochemical battery stacks, each excitation signal comprising a voltage or current and one or more frequencies generated by an EIS excitation circuit, wherein a distance between the EIS excitation circuit and the battery stack allows the EIS excitation circuit to have reduced safety requirements; obtaining a response signal generated by one or more electrochemical cells; simultaneously measuring the set of stimulus signals and responses to generate impedance data; and The impedance data is used to determine a condition of one or more electrochemical cells.

11. The method of claim 10, further comprising extracting amplitude and phase shift information from the response signal using a demodulation technique to enable separation of in-phase and out-of-phase components of the response information to obtain a complex impedance at an excitation frequency.

12. The method of claim 10, further comprising analyzing the impedance data to detect at least one of inefficiency, degradation, or failure associated with the one or more electrochemical cells.

13. The method of claim 10, wherein measuring comprises measuring impedance data within a frequency range of 5 kHz. The method of claim 10 , wherein measuring comprises a perturbation method.

15. The method of claim 10, further comprising matching an impedance of a battery to an impedance of the measurement circuit.

16. The method of claim 10, further comprising calibrating one or more parameters of the EIS excitation circuit using a calibration circuit to provide a known waveform.

17. The method of claim 10, further comprising using the response signal to detect an error associated with the one or more electrochemical cells.

18. The method of claim 10, wherein the current is an alternating current of less than 100A.

19. The method of claim 10, wherein the measurement circuit performs steps including compensating for phase delays between the set of excitation signals and the response signal to improve accuracy of the impedance data.

20. The method of claim 10, during impedance measurement, limiting one or more frequencies of the set of excitation signals to a relatively narrow frequency range around a frequency of interest to reduce measurement noise.

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