Water electrolysis hydrogen production system and cold start control method

Abstract

The invention discloses a water electrolysis hydrogen production system and a cold start control method, and belongs to the technical field of water electrolysis hydrogen production. A water electrolysis hydrogen production system comprises an electrolytic bath and further comprises a modulated hydrogen power source for providing electric energy for the electrolytic bath, the modulated hydrogen power source is used for providing current with adjustable alternating current and direct current components for the electrolytic bath, and the numerical value of the direct current component is larger than or equal to the maximum value of the alternating current component. The direct-current component is used for participating in a polarization reaction of electrolytic hydrogen production, and the alternating-current component is used for additionally heating the electrolytic cell in a cold start process. According to the water electrolysis hydrogen production system, by specially increasing the alternating current component proportion and / or frequency of the output current of the hydrogen production power supply, namely increasing the active power generated by the alternating current component, more power supply output power is used for heating the electrolytic cell; therefore, the temperature rise starting performance of the hydrogen production system is greatly improved on the basis of not changing the technological process of the hydrogen production system and not increasing additional system auxiliary machine parts.

Description

Technical Field

[0001] This application relates to the field of water electrolysis for hydrogen production technology, specifically to a water electrolysis hydrogen production system and a cold start control method. Background Technology

[0002] Hydrogen production through water electrolysis can utilize renewable energy to generate hydrogen that is easy to transport and store, making it a crucial part of the development of renewable energy and hydrogen energy technologies. Due to the intermittent nature of renewable energy sources, hydrogen electrolysis systems must cope with frequent potential shutdowns and restarts. However, starting up an electrolysis system requires heating the electrolyzer to its rated temperature (PEM ~60℃-80℃, alkaline ~80℃-90℃) to achieve rated operation. Failure to reach the rated operating temperature leads to increased energy consumption and decreased efficiency. This process of the electrolyzer reaching its rated operating temperature from ambient temperature is called a cold start.

[0003] Commercial hydrogen production systems typically employ a self-heating cold start method, where hydrogen is produced inefficiently using an electric current while the waste heat generated during hydrogen production gradually heats the electrolyzer. Taking alkaline hydrogen production systems as an example, a commercial alkaline hydrogen production system often requires one hour or even several hours for a self-heating cold start. This excessively slow cold start prevents the hydrogen production system from reaching its rated power for extended periods, making it difficult to keep up with renewable energy generation. This results in significant energy consumption without achieving the desired hydrogen production efficiency, leading to resource waste.

[0004] Publicly available literature and patents reveal the following mainstream solutions: 1. Electric heating-assisted cold start: Equipped with an electric heater, this method consumes additional electrical energy to heat the electrolyte during startup, thus achieving rapid temperature rise of the electrolyzer. However, electric heating-assisted cold start requires a high-power electric heater, resulting in high costs and making it impractical; it is generally only used in laboratory-level hydrogen production systems. 2. Thermal storage tank-assisted cold start: As exemplified by utility model patent application number CN202322172536.9, this method stores the hot electrolyte in the stack in a storage tank during shutdown, and then pumps it back into the hydrogen production system during cold start to achieve rapid temperature rise of the electrolyzer. However, for large-capacity hydrogen production systems, a large thermal storage tank is required, resulting in high costs and a large footprint, making it unsuitable for practical hydrogen production systems. 3. Large and small separator-assisted cold start. For example, in the invention patent application with application number CN202310650154.4, the separator of its hydrogen production system contains a large amount of electrolyte, resulting in a large heat sink and limiting the overall temperature rise of the hydrogen production system. During startup, the system first switches to a smaller separator to reduce the amount of electrolyte and heat sink in the system. Once the electrolyzer is operating at full power, it gradually switches to a larger separator to complete the cold start. However, this method cannot reduce the heat sink of the fuel cell stack itself, resulting in limited improvement in temperature rise and startup performance.

[0005] In summary, current solutions all require modifications to the existing hydrogen production system's process flow and the addition of extra system components, resulting in high overall costs. Therefore, there is an urgent need to research a cold start method to improve temperature-up start-up performance, enhance the operational flexibility and energy efficiency of hydrogen production systems, and enable large-scale off-grid application of electrolysis hydrogen production technology. Summary of the Invention

[0006] This application aims to at least partially solve one of the technical problems in the related field. To this end, this application provides an electrolytic water hydrogen production system and a cold start control method. By intentionally increasing the proportion and / or frequency of the AC component of the hydrogen production power supply output current, that is, increasing the active power generated by the AC component, more power output is used to heat the electrolyzer, thereby significantly improving the temperature rise and start-up performance of the hydrogen production system without changing the process flow of the hydrogen production system itself or adding additional auxiliary components.

[0007] To achieve the above objectives, in a first aspect, this application provides a water electrolysis hydrogen production system, including an electrolyzer and a modulated hydrogen power supply for providing electrical energy to the electrolyzer. The modulated hydrogen power supply is used to provide the electrolyzer with an adjustable current of AC and DC components, wherein the DC component value is greater than or equal to the maximum value of the AC component.

[0008] Preferably, the DC component is used to participate in the polarization reaction of hydrogen production by electrolysis, and the AC component applies active power to the electrolyzer to provide additional heating to the electrolyzer during cold start-up.

[0009] Preferably, the modulated hydrogen power supply provides an AC / DC adjustable current to the electrolyzer during the heating and startup process, so that the AC impedance of the branch where the electrolyzer is located is close to resistive, and the impedance angle range is -π / 4 to π / 4.

[0010] Preferably, the modulated hydrogen power supply is capable of outputting current with adjustable AC and DC component ratios and / or AC component frequency.

[0011] Preferably, the instantaneous voltage applied to the electrolyzer by the modulated hydrogen power source satisfies Formula 1:

[0012] 0V≤u stack ≤N cell Formula 1 for ×3V, where N cell u is the number of single cells in the electrolyzer. stack This represents the instantaneous voltage value of the electrolytic cell.

[0013] Preferably, 0V≤u stack ≤N cell ×2.5V.

[0014] Preferably, 0V≤u stack ≤Ncell ×2V.

[0015] Preferably, the modulated hydrogen power supply is a PWM power supply composed of turn-off switching devices, such as IGBT / MOSFET, or a multi-pulse rectified power supply with thyristors as switching devices, or a combination of DC and AC power supplies.

[0016] Preferably, the water electrolysis hydrogen production system further includes a reactor connected in series with the electrolyzer, which is used to offset the capacitive properties of the electrolyzer during the heating and start-up process.

[0017] Preferably, the reactor is composed of one or more inductor assemblies, the inductor assembly having a center tap for adjusting the inductance value.

[0018] Preferably, a switch is connected in parallel to the reactor, and the reactor is controlled to disconnect or connect to the corresponding circuit by controlling the closing or opening of the switch.

[0019] Preferably, the water electrolysis hydrogen production system further includes an AC power supply and an auxiliary machine. The AC power supply outputs power frequency current for powering the auxiliary machine, and the AC power supply is also used to power the modulated hydrogen power supply.

[0020] Secondly, this application provides a cold start control method for a water electrolysis hydrogen production system based on any of the above-described methods, comprising:

[0021] When the water electrolysis hydrogen production system is cold-started, the switch is disconnected and the reactor is connected to the corresponding circuit.

[0022] Power is supplied to the electrolytic cell, the frequency of the AC component of the output current of the modulated hydrogen power supply is adjusted, and / or the proportion of the AC component of the modulated hydrogen power supply is increased, and / or the inductance value of the reactor is adjusted, so that the circuit composed of the electrolytic cell and the reactor is in a near-resonant state.

[0023] Once the temperature of the electrolytic cell reaches the rated temperature, the switch is closed to short-circuit the reactor, and the proportion and frequency of the AC component of the output current of the modulated hydrogen power supply are adjusted to reduce or remove the AC component, thus completing the cold start.

[0024] Preferably, the step of bringing the circuit composed of the electrolyzer and the reactor to a near-resonant state includes: setting the impedance angle of the hydrogen production AC equivalent circuit to a range of -π / 6 to π / 6.

[0025] Based on the above technical solution, the water electrolysis hydrogen production system and cold start control method of this application have the following advantages compared with the prior art:

[0026] The hydrogen production system and cold start control method of this application improve the heating and start-up performance of the hydrogen production system by intentionally increasing the proportion and / or frequency of the AC component of the output current of the hydrogen production power supply, that is, increasing the active power generated by the AC component, so that more power output is used to heat the electrolyzer. This significantly improves the heating and start-up performance of the hydrogen production system without changing the process flow of the hydrogen production system itself or adding additional auxiliary components.

[0027] The water electrolysis hydrogen production system of this application includes a modulated hydrogen power supply connected in series with the electrolyzer, used to provide the electrolyzer with an adjustable AC and DC component current, wherein the DC component value is greater than or equal to the maximum value of the AC component. When the hydrogen production system is heated and started, the modulated hydrogen power supply increases the proportion and / or frequency of the AC component, making the AC equivalent circuit of the branch where the electrolyzer is located close to resistive. As a result, all the AC current is used to generate active power to heat the electrolyzer, which is beneficial to the rapid heating of the electrolyzer. When the electrolyzer reaches a certain temperature, the modulated hydrogen power supply is adjusted to reduce the proportion of the AC component or remove the AC component, so that all the input electrical energy is used for hydrogen production.

[0028] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description, or may be realized by practice of this application. The purpose and other advantages of this application can be realized and obtained by means of the structures particularly pointed out in the written description, claims and drawings. Attached Figure Description

[0029] Figure 1 This is a topology and current decomposition diagram of a typical existing industrial electrolysis hydrogen production system;

[0030] Figure 2 The equivalent circuit diagram of an existing alkaline electrolysis hydrogen production system;

[0031] Figure 3 The waveform diagram shows the superimposed current of DC current and AC triangular wave supplied to the electrolyzer by the modulated hydrogen power source of this application.

[0032] Figure 4 The waveform diagram shows the superimposed current of DC current and AC sine wave supplied to the electrolyzer by the modulated hydrogen power source of this application.

[0033] Figure 5 This is the equivalent circuit diagram for the application of this application in an alkaline electrolysis hydrogen production system;

[0034] Figure 6 This is a connection block diagram of the electrolysis hydrogen production system in this application;

[0035] Figure 7 This is a flowchart of the cold start control method for the water electrolysis hydrogen production system in this application. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0037] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0038] To address the shortcomings of existing technologies, the present invention aims to provide an electrolytic water hydrogen production system and a cold start control method, in order to significantly improve the temperature rise and start-up performance of the hydrogen production system without changing the process flow of the hydrogen production system itself or adding additional auxiliary components.

[0039] The basic idea of ​​this invention is that when a rippled DC current is applied to an electrolytic cell, the current passing through the electrolytic cell can be decomposed into a DC component and an AC component:

[0040] i tot =i dc +i ac

[0041]

[0042] It is known that only the DC component participates in hydrogen production and polarization reactions, while the AC component exists as a loss in the circuit between the electrolyzer and the power supply. For example... Figure 1 The diagram shows the topology and current decomposition of a typical industrial electrolytic hydrogen production system. Industrial transistor six-pulse rectifier power supplies are usually equipped with additional ripple smoothing circuits to reduce the proportion of AC component in the power supply output, thereby improving the overall hydrogen production efficiency of the system.

[0043] Based on this fundamental principle, the present invention is conceived to significantly improve the heating and start-up performance of the hydrogen production system by intentionally increasing the proportion and / or frequency of the AC component in the output current of the hydrogen production power source, that is, increasing the active power generated by the AC component, so that more power output is used to heat the electrolyzer. This is achieved without changing the process flow of the hydrogen production system itself or adding any additional auxiliary components.

[0044] Example 1

[0045] In order to develop a method to significantly improve the temperature rise and start-up performance of a hydrogen production system without changing the process flow of the system itself or adding additional auxiliary components, the inventors conducted in-depth research on the AC equivalent circuit of the electrolyzer. For example... Figure 2The diagram shown is an equivalent circuit diagram of an existing alkaline electrolysis hydrogen production system. Taking an alkaline electrolyzer as an example, the current i flowing through the electrolyzer is... tot Disassembled into DC component i dc and communication components i ac Among them, i dc It participates in polarization reactions for hydrogen production and generates a polarization voltage component u in the electrolyzer. dc i ac The AC voltage component u is then generated through the AC equivalent circuit of the electrolytic cell. ac The AC equivalent circuit of the electrolytic cell consists of the anode resistor R. an Anode capacitor C an Cathode resistance R ca Anode capacitor C ca and series resistance R c composition.

[0046] The total current i passing through the electrolytic cell tot The sum of the DC and AC components, with the DC component being the average value over the total current cycle:

[0047] i tot =i dc +i ac

[0048]

[0049] In the formula, t is the time index, and T is the period of the AC component of the current.

[0050] The total voltage u generated tot It is the superposition of DC voltage components and AC voltage components:

[0051] u tot =u dc +u ac

[0052] Among them, u dc Determined by the polarization reaction of the electrolyzer, u ac The heating power is determined by the AC equivalent impedance of the branch containing the electrolytic cell. To achieve rapid heating of the electrolytic cell, the heating power applied to it needs to be increased. The heating power of the electrolytic cell is the superposition of the heating power generated by the DC and AC components of the current.

[0053] H stack =H dc +H ac

[0054] In the formula, H stack H is the heating power of the electrolytic cell. dc and H acThese represent the heating power generated by the DC component and the AC component of the current, respectively.

[0055] Since the electrolytic hydrogen production reaction is endothermic, the heat generated by the DC component is:

[0056] H dc =i dc ×(u dc -U th ·N cell )

[0057] In the formula, N cell U represents the number of individual cells contained in the electrolyzer. th The thermal neutral voltage is set to 1.48V.

[0058] The heating power generated by the alternating current component is equal to the active power generated in the AC equivalent circuit, which can be expressed as:

[0059]

[0060] To simplify the problem, assume that the AC component of the current generated by the hydrogen production power source is a sine wave with an angular frequency of ω. Then, the instantaneous voltage, voltage amplitude, and active power generated on the AC equivalent circuit can be expressed as:

[0061] u ac =i ac ·Z stack

[0062] U ac =I ac ·|Z stack |

[0063]

[0064] In the formula, I ac and U ac The effective values ​​of alternating current and voltage, Z stack Let |Z| be the AC equivalent impedance of the electrolytic cell. stack | represents the magnitude of the impedance. It is the impedance angle.

[0065] according to Figure 2 It can be seen that the derivation formula of the equivalent impedance of the AC equivalent circuit of the electrolytic cell is:

[0066]

[0067] In the formula, j is the imaginary unit.

[0068] After sorting, we can obtain:

[0069] Z stack =R stack-jX stack

[0070]

[0071] The cosine value of the impedance angle of the AC equivalent circuit of the electrolytic cell can be expressed as:

[0072]

[0073] It can be seen that the AC impedance of the electrolytic cell is generally capacitive. stack The voltage is relatively high, resulting in high voltage and significant power dissipation, which is detrimental to the heating of the electrolytic cell.

[0074] Therefore, in this embodiment, by adjusting the AC and DC component ratio of the modulated hydrogen power supply while ensuring that the DC component value is greater than or equal to the maximum value of the AC component, the current supplied to the anode of the electrolyzer by the modulated hydrogen power supply is always positive, ensuring normal hydrogen production. Furthermore, by increasing the frequency of the AC component, i.e., increasing the value of ω, X... stack The value approaches 0, making the impedance of the branch where the electrolytic cell is located close to resistive, with an impedance angle range of -π / 4 to π / 4, which can accelerate the cold start configuration and thus achieve rapid start-up.

[0075] Furthermore, such as Figure 3 and Figure 4 As shown, two examples are presented where a modulated hydrogen power source supplies an electrolyzer with an adjustable AC / DC current composition. Among them, Figure 3 (a) is the constant 2A DC component i dc waveform diagram, Figure 3 (b) is the AC component i of a 100Hz triangular wave. ac The waveform shows that the current periodically varies between -1A and 1A. Figure 3 (c) shows the total current i after superposition with a 1A triangular wave AC component under a 2A DC component bias. tot The waveform diagram shows that the total current varies between 1A and 3A, exhibiting a periodic fluctuation with a period of 0.01 seconds.

[0076] Figure 4 (a) is the constant 1.5A DC component i dc waveform diagram, Figure 4 (b) is the AC component i of a 50Hz power frequency sine wave. ac The waveform shows that the current periodically varies between -0.5A and 0.5A. Figure 4 (c) shows the total current i after the DC and AC components are superimposed. totThe waveform diagram shows that the total current varies between 1A and 2A, exhibiting a periodic fluctuation with a period of 0.02 seconds. It should be further noted that by adjusting the amplitude or frequency of the aforementioned triangular / sine wave, the superimposed current will produce different waveforms.

[0077] It should be noted that, depending on the form of the hydrogen production power source, the alternating current component can have different shapes, such as triangular waves, sine waves, square waves, etc.

[0078] Therefore, by ensuring that the DC component of the output current of the modulated hydrogen power supply is greater than or equal to the maximum value of the AC component, the current supplied to the anode of the electrolyzer by the modulated hydrogen power supply can always be positive, ensuring that it can produce hydrogen normally.

[0079] Example 2

[0080] The difference between this embodiment and Embodiment 1 is that the water electrolysis hydrogen production system further includes a reactor connected in series with the electrolyzer. This reactor is used to counteract the capacitive properties of the electrolyzer during the temperature rise and start-up process. Specifically, as follows... Figure 5 As shown, this application proposes a water electrolysis hydrogen production system, including an electrolyzer, a reactor connected in series with the electrolyzer, and a modulated hydrogen power supply for providing electrical energy to the electrolyzer. The modulated hydrogen power supply provides the electrolyzer with a proportionally adjustable DC component and an AC component. The DC component participates in the polarization reaction of hydrogen electrolysis, while the AC component, after passing through the reactor, applies active power to the electrolyzer for additional heating during cold start-up. A switch is connected in parallel to the reactor; controlling the closing or opening of the switch controls the reactor to disconnect or connect to the corresponding circuit.

[0081] Among them, the modulated hydrogen power supply can adjust the proportion of AC component and / or frequency of the output current.

[0082] The reactor's function is to cancel out the capacitive capacitance of the electrolyzer during the heating and startup process, making the overall AC equivalent circuit nearly resistive. When the hydrogen production system starts up, the proportion of the AC component of the power supply output current is increased, the short-circuit switch S1 is disconnected, and the reactor is connected to the circuit. At this time, the impedance of the AC equivalent circuit is:

[0083] Z = R stack -jX stack +jωL re

[0084] when At this time, the inductive and capacitive properties cancel each other out, and the AC equivalent circuit is in a resonant state, exhibiting resistive behavior, with an impedance value of Z = R. stack All of the alternating current generates active power, which is used to heat the electrolytic cell, thus facilitating rapid heating of the electrolytic cell.

[0085] Once the electrolyzer reaches a certain temperature, the hydrogen production power supply is adjusted to reduce or eliminate the AC component of the current, ensuring that all input electrical energy is used for hydrogen production and polarization reactions. The corresponding switch S1 is then closed, and the startup is essentially complete. This application achieves rapid heating of the electrolyzer itself through power supply modulation, significantly improving the heating and startup performance of the hydrogen production system. It offers exceptional flexibility without drastically altering the hydrogen production system's process flow, and rapid startup can be achieved using a simple series reactor.

[0086] It should be further explained that during the cold start process, by modulating the modulated hydrogen power supply, the proportion and / or frequency of the AC component of the output current can be increased, so that the circuit composed of the resonant inductor and the electrolytic cell is in a near-resonant state, which can meet the usage requirements. Preferably, the reactor is used to cancel the capacitance of the electrolytic cell during the heating start process, so that the AC equivalent circuit of the branch where the electrolytic cell is located is close to resistive as a whole, and the impedance angle ranges from -π / 6 to π / 6.

[0087] The modulated hydrogen power supply can output current with adjustable AC and DC component ratios and / or AC component frequency, wherein the AC component accounts for ≥1%. Specifically, the above... Figure 3 In the total current after the superposition of the 2A DC component bias and the 1A triangular wave AC component, the AC component accounts for 38.87%. Figure 4 In the total current resulting from the superposition of the 1.5A DC component and the 0.5A AC component (power frequency sinusoidal wave), the AC component accounts for 23.57%. The modulated hydrogen power supply is characterized by its ability to output current with adjustable AC and DC components, and to adjust the proportion and / or frequency of the AC component in the output current. Preferably, the maximum AC component proportion is ≥5%, 20%, 50%, or 100%. The formula for calculating the AC component proportion is:

[0088]

[0089] In the formula, i tot The total output current of the power supply is given by t, where t is the time index, T is the period of the AC component, and i dc This represents the DC component of the power supply output current, i.e., the average value of the total current over the period:

[0090]

[0091] It should be noted that the type of modulated hydrogen power supply is not limited. It can be a PWM power supply composed of turn-off switching devices, such as IGBTs / MOSFETs, or a multi-pulse rectified power supply using thyristors as switching devices. In particular, a combination of a DC power supply and an AC power supply is also considered as the modulated hydrogen power supply.

[0092] During the start-up process of the electrolyzer, the equivalent impedance changes to some extent as the current density increases. Therefore, preferably, the modulated hydrogen power supply can adjust the frequency of the output AC component, with the maximum output AC component frequency being ≥50Hz, 300Hz, 1kHz, 10kHz, or 100kHz.

[0093] It should be noted that the reactor is an inductor assembly used to form a resonant circuit with the equivalent capacitance and resistance of the electrolyzer to counteract the capacitive properties of the AC equivalent circuit and increase the active power generated by the input AC components. The reactor needs to provide sufficient inductance to the branch containing the electrolyzer to counteract its own capacitive properties. The reactor can be a single inductor assembly or multiple inductor assemblies connected in series. If multiple inductor assemblies are used, the connection order between these inductors and other components in the circuit is not limited. The inductor assembly may include a center tap for adjusting the inductance value. In particular, the reactor or a portion thereof can be integrated into the hydrogen production power supply.

[0094] It should be noted that the electrolyzer and reactor are interconnected to form a circuit. The addition of other circuit components (such as switches, instruments, etc.) is not limited, and the order in which the components are connected is not restricted: it can be either the modulated hydrogen power source - electrolyzer - reactor, or the modulated hydrogen power source - reactor - electrolyzer. A short-circuit switch may be present in the circuit, which can short-circuit one or more components in the series circuit.

[0095] It should be noted that the instantaneous voltage applied to the electrolyzer by the hydrogen production power source satisfies the following:

[0096] 0V≤u stack ≤N cell ×3V

[0097] In the formula, N cell u is the number of single cells in the electrolyzer. stack This is the instantaneous output voltage value of the DC power supply. This setting is for the sake of the electrolytic cell's lifespan. Without affecting the lifespan, the voltage that a single cell can withstand should not be too high.

[0098] Preferably, 0V≤u stack ≤N cell ×2.5V.

[0099] Furthermore, 0V≤u stack ≤N cell ×2V.

[0100] like Figure 6The diagram shown is a connection block diagram of the electrolytic hydrogen production system in this application. In this embodiment, the electrolytic hydrogen production system further includes an AC power supply and auxiliary equipment. The AC power supply outputs a power frequency current to power the auxiliary equipment, and the AC power supply is also used to supply power to the modulated hydrogen power supply. The AC power supply outputs a power frequency current to power the hydrogen production auxiliary equipment, which includes, but is not limited to, pumps, compressors, and other process components that work in conjunction with the electrolyzer to produce hydrogen.

[0101] It should be noted that this embodiment is only used as an example of an alkaline water electrolysis hydrogen production system. However, the hydrogen production system applicable to this application can be an alkaline water electrolysis hydrogen production system, or a proton exchange membrane (PEM) or anion exchange membrane (AEM) water electrolysis hydrogen production system. The corresponding electrolyzer can be an alkaline electrolyzer, or a PEM or AEM electrolyzer. In all cases, by increasing the proportion and / or frequency of the AC component of the output current of the hydrogen production power supply, i.e., increasing the active power generated by the AC component, more power output can be used to heat the electrolyzer. This significantly improves the heating and start-up performance of the hydrogen production system without changing the process flow of the hydrogen production system itself or adding additional auxiliary components.

[0102] Example 3

[0103] like Figure 7 As shown, this embodiment proposes a cold start control method for a water electrolysis hydrogen production system based on any of the above-described methods, including:

[0104] S1. When the water electrolysis hydrogen production system is cold-started, disconnect the switch and connect the reactor to the corresponding circuit.

[0105] S2. Power on the electrolytic cell, adjust the frequency of the AC component of the output current of the modulated hydrogen power supply, and / or increase the proportion of the AC component of the modulated hydrogen power supply, and / or adjust the inductance value of the reactor so that the circuit composed of the electrolytic cell and the reactor is in a near-resonant state.

[0106] S3. Once the electrolytic cell reaches its rated temperature, close switch one to short-circuit the reactor, adjust the proportion and frequency of the AC component in the output current of the modulated hydrogen power supply, reducing or eliminating the AC component, thus completing the cold start. The specific value of the rated temperature can be selected based on actual conditions.

[0107] Preferably, the step of bringing the circuit composed of the electrolyzer and the reactor to a near-resonant state includes: making the impedance angle of the branch where the electrolyzer is located range from -π / 10 to π / 10, that is, the phase difference between the AC component of the output current of the hydrogen production power supply and the AC voltage component applied to the circuit range from -π / 10 to π / 10.

[0108] Specifically, the circuit consisting of the electrolyzer and the reactor can be brought into a near-resonant state by modulating the output ripple frequency of the hydrogen production power supply or by changing the inductance value of the series reactor (the inductance value of the reactor can be changed by using taps).

[0109] Modulorable hydrogen power supply current AC component and voltage AC component i ac and u ac The phase difference is further optimized to always satisfy:

[0110]

[0111] Once the electrolyzer reaches a certain temperature, the hydrogen production power supply is adjusted to reduce or remove the AC component, so that all the input electrical energy is used for hydrogen production, and the startup is basically complete.

[0112] Specifically, during the preparation phase of starting the electrolyzer, the overall heat capacity and temperature rise time of the system can be reduced by decreasing the amount of electrolyte in the separator (water for PEM hydrogen production and KOH or NaOH solution for alkaline hydrogen production). Simultaneously, the temperature rise time of the electrolyzer can be further reduced by decreasing the flow rate of the circulating electrolyte through the electrolyzer, thereby reducing heat exchange between the circulating electrolyte and the external environment.

[0113] This application proposes an electrolytic hydrogen production system and a cold start control method, which utilizes the control power input to rapidly heat up the electrolyzer itself, thereby significantly improving the heating and start-up performance of the hydrogen production system without changing the process flow of the hydrogen production system itself.

[0114] The foregoing has described specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0115] In the description of the embodiments of the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In the embodiments of the present invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in the embodiments of the present invention, as well as the features of the different embodiments or examples.

[0116] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features, excluding any ordering. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature and is used to distinguish it from another. In the description of embodiments of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0117] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen production system by electrolysis of water comprising an electrolyzer, characterized in that, The electrolytic cell is provided with a modulated hydrogen power supply for providing the electrolytic cell with an alternating and direct current component adjustable current, wherein the direct current component is greater than or equal to the maximum value of the alternating current component.

2. The hydrogen production system of claim 1, wherein The modulated hydrogen power supply provides the electrolytic cell with an alternating and direct current component adjustable current during the electrolytic cell temperature rising start-up process, so that the alternating impedance of the branch in which the electrolytic cell is located is close to the resistance, and the impedance angle range is -π / 4~π / 4.

3. The hydrogen production system of claim 1, wherein, The modulated hydrogen power supply can output an alternating and direct current component ratio adjustable current and / or an alternating current component frequency adjustable current.

4. The hydrogen production system of claim 1, wherein The voltage instantaneous value applied by the modulated hydrogen power supply on the electrolytic cell satisfies formula one: 0V≤u stack ≤N cell ×3Vformula one wherein, N cell is the number of single cells in the electrolytic cell, u stack is the voltage instantaneous value of the electrolytic cell.

5. The hydrogen production system of claim 1, wherein, The modulated hydrogen power supply adopts a PWM power supply composed of a controllable switching device such as IGBT / MOSFET, or a multi-pulse rectifier power supply with a thyristor as a switching device, or a combination power supply of a direct current power supply and an alternating current power supply.

6. The hydrogen production system of claim 1, wherein, The electrolytic water hydrogen production system further comprises a reactor connected in series with the electrolytic cell, and the reactor is used to offset the capacitance of the electrolytic cell during the temperature rising start-up process.

7. The hydrogen production system of claim 6, wherein the hydrogen production system further comprises a hydrogen storage tank. The reactor is composed of one or more inductor components, and the inductor components are provided with middle taps for adjusting the inductance value.

8. The hydrogen production system of claim 7, wherein, A switch one is connected in parallel on the reactor, and the reactor is disconnected or connected to the corresponding circuit by controlling the closing or opening of the switch one.

9. The hydrogen production system of any one of claims 1-8, wherein the electrolysis system is configured to produce hydrogen at a rate of at least 1 kg / hr. The electrolytic water hydrogen production system further comprises an alternating current power supply and auxiliary machines, the alternating current power supply outputs a power frequency current for power supply of the auxiliary machines, and the alternating current power supply is also used to power the modulated hydrogen power supply.

10. A cold start control method for the water electrolysis hydrogen production system according to claim 8, characterized by, Comprise: When the electrolytic water hydrogen production system is cold started, the switch one is opened to connect the reactor to the corresponding circuit; The electrolytic cell is powered, the alternating current component frequency of the modulated hydrogen power supply is adjusted, and / or the alternating current component ratio of the modulated hydrogen power supply is increased, and / or the inductance value of the reactor is adjusted, so that the circuit composed of the electrolytic cell and the reactor is in a nearly resonant state; When the temperature of the electrolytic cell reaches the rated temperature, the switch one is closed to short-circuit the reactor, the alternating current component ratio and frequency of the modulated hydrogen power supply output current are adjusted, the alternating current component ratio is reduced or the alternating current component is removed, and the cold start is completed.

11. The cold start control method according to claim 10, characterized by, The step of making the circuit composed of the electrolytic cell and the reactor in a nearly resonant state comprises: making the impedance angle range of the branch in which the electrolytic cell is located be -π / 6~π / 6.

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