Pulse Current Hydrogen Production Circuit and Control Method for Alkaline Electrolyzer Based on Sliding Mode Control

Abstract

The present invention discloses a pulse current hydrogen production circuit and control method for an alkaline electrolyzer based on sliding mode control. The circuit realizes the sliding mode control method by designing a sliding mode controller to provide a pulse current for the alkaline electrolyzer for electrolytic hydrogen production. In this circuit, the positive pole of the voltage source is connected to the collector of the switching tube, the negative pole of the voltage source is connected to the positive pole of the fast recovery diode and the negative pole of the alkaline electrolyzer, the emitter of the switching tube is connected to the first end of the inductor and the negative pole of the fast recovery diode, and the second end of the inductor is connected to the positive pole of the alkaline electrolyzer. The duty cycle is obtained through the sliding mode controller, and the control signal on the base of the switching tube is obtained by modulating the duty cycle and the triangular carrier wave. The pulse current is output through the inductor and provided to the alkaline electrolyzer for electrolytic hydrogen production. The present invention can significantly reduce the output current ripple, improve the power quality, and thus improve the electrolysis efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by alkaline electrolysis in the new energy field, and particularly relates to a pulsed current hydrogen production circuit and control method for an alkaline electrolyzer based on sliding mode control. Background Art

[0002] As a clean and efficient energy carrier, hydrogen energy is of great significance in the energy transition. Alkaline electrolysis for hydrogen production is an important technical route for preparing hydrogen, and its principle is to decompose water into hydrogen and oxygen by using electric energy. However, traditional proportional control technology will generate significant current ripples during the electrolysis process, which not only reduces the electrical energy utilization efficiency, but also causes problems such as increased temperature fluctuations in the electrolyzer and accelerated electrode corrosion. In recent years, pulsed electrolysis technology has been widely used because it can improve the electrolysis efficiency of alkaline electrolyzers under low operating conditions. However, there is a lack of precise control means in the existing pulsed electrolysis technology, and it is difficult to maintain efficient operation under complex operating conditions. The present invention proposes a pulsed current hydrogen production method based on sliding mode control, which can greatly improve the electrolysis efficiency and power quality through a sliding mode control strategy with high robustness and high dynamic response. Summary of the Invention

[0003] The purpose of the present invention is to provide a pulsed current hydrogen production circuit and control method for an alkaline electrolyzer based on sliding mode control in view of the shortcomings of the existing proportional control technology. The present invention significantly reduces the output current ripple and current overshoot during pulsed current electrolysis, and greatly improves the power quality.

[0004] The purpose of the present invention is achieved through the following technical solutions: In the first aspect of the embodiments of the present invention, a pulsed current hydrogen production circuit for an alkaline electrolyzer based on sliding mode control is provided, including: a voltage source, a switching tube, an inductor, a fast recovery diode, an alkaline electrolyzer, and a sliding mode controller; wherein, the positive pole of the voltage source is connected to the collector of the switching tube, the negative pole of the voltage source is connected to the positive pole of the fast recovery diode and the negative pole of the alkaline electrolyzer, the emitter of the switching tube is connected to the first end of the inductor and the negative pole of the fast recovery diode, and the second end of the inductor is connected to the positive pole of the alkaline electrolyzer; a duty cycle is obtained through the sliding mode controller, and a control signal on the base of the switching tube is obtained by modulating the duty cycle and a triangular carrier wave, and a pulsed current is output through the inductor and provided to the alkaline electrolyzer for electrolysis to produce hydrogen.

[0005] In the second aspect of the embodiments of the present invention, a control method for the above-mentioned pulsed current hydrogen production circuit for an alkaline electrolyzer based on sliding mode control is provided, including:

[0006] Instantaneously obtain the instantaneous voltage and instantaneous current at both ends of the alkaline electrolyzer, and use the control quantity of the sliding mode controller to control the sliding mode controller to adjust the duty cycle; use the duty cycle and triangular carrier wave modulation to obtain the control signal of the base of the switching tube. This control signal is a pulse signal that generates pulsed power. After passing through the inductor, a pulsed current is output, and this pulsed current is provided to the alkaline electrolyzer for electrolytic hydrogen production, so that the alkaline electrolyzer intermittently operates at the optimal pulsed power corresponding to the maximum electrolysis efficiency under low working conditions. The optimal pulsed power includes the frequency, duty cycle, and amplitude of the optimal pulsed power;

[0007] Among them, the low working condition refers to the working state of the alkaline electrolyzer during the rising process of the electrolysis efficiency; the frequency, duty cycle, and amplitude of the optimal pulsed power are determined by the efficiency-power curve of the alkaline electrolyzer and the set pulsed power reference value.

[0008] Furthermore, the sliding mode controller is obtained based on the voltage and current at both ends of the alkaline electrolyzer, and is specifically obtained through the following steps:

[0009] S1. Design the sliding mode surface of the sliding mode controller according to the control objective, and its expression is:

[0010]

[0011] In the formula, represents the sliding mode surface; represents the current error, and the current error is obtained by calculating the difference between the current at both ends of the alkaline electrolyzer and the current reference value ; represents the current error of the first derivative; represents the slope of the sliding mode surface; among them, the control objective is the current error and the first derivative of the current error;

[0012] S2. Decompose the control quantity of the sliding mode controller based on the sliding mode equivalent control method, solve the equivalent control term of the linear sliding mode controller, and design the switching control term of the linear sliding mode controller according to the system performance requirements; among them, the system performance requirements include the sliding mode reaching condition and the stability condition;

[0013] S21. Take the derivative of the expression of the sliding mode surface of the sliding mode controller to obtain the derivative of the sliding mode surface, and let , and then substitute the unified differential equation of the Buck circuit into it for solution to obtain the equivalent control term , which is expressed as:

[0014]

[0015] Wherein, represents the input voltage at both ends of the alkaline solution electrolyzer; represents the inductor in the Buck circuit; represents the equivalent capacitance of the alkaline solution electrolyzer; represents the equivalent resistance of the alkaline solution electrolyzer; represents the current reference value;

[0016] Step S22, select the Lyapunov function , take the first derivative with respect to time to obtain the first derivative of the Lyapunov function , expressed as:

[0017]

[0018] To meet the sliding mode reaching condition , design the switching control term , expressed as:

[0019]

[0020] Wherein, represents the sign function;

[0021] At this time, , the system meets the stability condition.

[0022] Furthermore, in the step S21, the current reference value is obtained by calculating the ratio of the pulse power reference value to the voltage at both ends of the alkaline solution electrolyzer.

[0023] Furthermore, the frequency of the optimal pulse power is 10 Hz; the duty cycle of the optimal pulse power is determined by the ratio of the set pulse power reference value to the electrolysis power corresponding to the maximum electrolysis efficiency ; compare the duty cycle with a low-frequency pulse triangular carrier with an amplitude of 1 and a period of 10 Hz to obtain a modulated pulse signal, and then multiply the modulated pulse signal by the electrolysis power corresponding to the maximum electrolysis efficiency to obtain the pulse power reference value, which is used as the amplitude of the optimal pulse power.

[0024] Furthermore, the duty cycle is obtained by the following method:

[0025] First, obtain the instantaneous voltage and the instantaneous current at both ends of the alkaline solution electrolyzer in real time; then calculate the average power of the alkaline solution electrolyzer according to the following formula :

[0026]

[0027] Wherein, is the sampling time interval, t is the total time of the sampling process, and the instantaneous current is also the pulsed current input to the alkaline electrolyzer ; then, the average power of the alkaline electrolyzer is used as the set pulsed power reference value and the electrolysis power corresponding to the maximum electrolysis efficiency are divided to obtain the duty cycle:

[0028]

[0029] Wherein, is the duty cycle and also represents the pulse width of the pulsed power.

[0030] The beneficial effects of the present invention are as follows: While improving the electrolysis efficiency of the alkaline electrolyzer, the present invention reduces the ripple and current overshoot of the output pulsed current, which is of great significance for improving the power quality; By designing a sliding mode controller, the present invention realizes precise regulation of the pulsed current, can effectively reduce the current ripple, improve the electrolysis efficiency, significantly reduce the output current ripple and current overshoot during pulsed current electrolysis, and greatly improve the power quality; In the design of the sliding mode controller of the present invention, a control algorithm with excellent robustness and dynamic response is adopted, combined with the pulsed current optimization technology, to achieve efficient operation under various electrolysis conditions, and can be widely applied to the fields of industrial hydrogen production and energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the pulsed current control block diagram based on sliding mode control of the present invention; wherein, the red line represents the pulsed current , and the blue line represents the duty cycle of the pulsed power;

[0032] Figure 2 is the experimental waveform diagram under the sliding mode control of the present invention; wherein, the current of the red waveform represents the current of the alkaline electrolyzer, and the voltage of the blue waveform represents the voltage of the alkaline electrolyzer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0034] The terms used in the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "said", and "the" used in the present invention and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0035] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to a determination".

[0036] The present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the features in the following embodiments and implementation manners can be combined with each other.

[0037] The pulsed current hydrogen production circuit of an alkaline electrolyzer based on sliding mode control according to the present invention specifically includes a voltage source , a switching tube S, an inductor L, a fast recovery diode , an alkaline electrolyzer, and a sliding mode controller. The switching tube S is provided with a body diode, as Figure 1 shown. Among them, the positive pole of the voltage source is connected to the collector of the switching tube S, the negative pole of the voltage source is connected to the positive pole of the fast recovery diode and the negative pole of the alkaline electrolyzer. The emitter of the switching tube S is connected to the first end of the inductor L and the negative pole of the fast recovery diode . The second end of the inductor L is connected to the positive pole of the alkaline electrolyzer. The duty cycle is obtained through the sliding mode controller, and the control signal on the base of the switching tube S is obtained by modulating the duty cycle and the triangular carrier wave. The pulsed current is output through the inductor L, and this pulsed current is provided to the alkaline electrolyzer for electrolytic hydrogen production, which can improve the electrolysis efficiency.

[0038] On the other hand, the present invention also provides a control method for the pulsed current hydrogen production circuit of an alkaline electrolyzer based on sliding mode control in the above embodiment.

[0039] In this embodiment, the control method specifically includes: obtaining the instantaneous voltage and the instantaneous current , to utilize the control quantity of the sliding mode controller Control the sliding mode controller to adjust the duty cycle; utilize the duty cycle and triangular carrier modulation to obtain the control signal of the base of the switch tube S, and this control signal is a pulse signal, generating pulse power, and outputting a pulse current after passing through the inductor L , and supply this pulse current to the alkaline electrolyzer for electrolytic hydrogen production, so that the alkaline electrolyzer intermittently operates at the optimal pulse power corresponding to the maximum electrolysis efficiency under low working conditions. The optimal pulse power includes the frequency, duty cycle and amplitude of the optimal pulse power. Among them, the low working condition refers to the working state of the alkaline electrolyzer during the rising process of the electrolysis efficiency; the frequency, duty cycle and amplitude of the optimal pulse power are determined by the efficiency-power curve of the alkaline electrolyzer and the set pulse power reference value .

[0040] It should be understood that adopting the sliding mode control strategy to provide pulse power for the alkaline electrolyzer for electrolytic hydrogen production can improve the electrolysis efficiency, reduce the output current ripple, and can also significantly reduce the current overshoot phenomenon through the sliding mode controller while improving the electrolysis efficiency, and improve the output current quality. In this embodiment, a sliding mode controller is designed to implement the sliding mode control strategy, and the experimental waveforms under sliding mode control are as Figure 2 shown. It can be seen from this that the sliding mode control significantly reduces the current ripple and overshoot, and improves the power quality. In addition, due to the generated pulse power, the alkaline electrolyzer is in the working state during the pulse high level and in the stopped state during the pulse low level, so it is said to operate intermittently.

[0041] It should be noted that in the efficiency-power curve of the alkaline electrolyzer, the abscissa is the electrolysis power and the ordinate is the electrolysis efficiency. Therefore, according to the efficiency-power curve of the alkaline electrolyzer, the electrolysis efficiency of the alkaline electrolyzer is different at different electrolysis powers. As the power input to the alkaline electrolyzer increases, the electrolysis efficiency of the alkaline electrolyzer shows a trend of first rising and then falling. The working state during the rising process is called the low-load working condition, that is, the low working condition, and the working state during the falling process is called the high-load working condition, that is, the high working condition. Among them, in the low working condition, the electrolysis efficiency and the electrolysis power are positively correlated; in the high working condition, the electrolysis efficiency and the electrolysis power are negatively correlated.

[0042] In this embodiment, the sliding mode controller is obtained according to the voltage and current signals at both ends of the alkaline electrolyzer, and is specifically obtained through the following steps:

[0043] Step S1, design the sliding mode surface of the sliding mode controller according to the control target, and its expression is:

[0044]

[0045] In the formula, represents the sliding mode surface; Indicates the current error, which is the current error obtained by calculating the difference between the currents at both ends of the lye electrolyzer and the current reference value ; Indicates the first derivative of the current error , and a linear combination of the two constitutes a linear sliding mode surface; Indicates the slope of the sliding mode surface, which is used to indicate that the sliding mode surface is a linear sliding mode surface. Different values correspond to sliding mode surfaces with different slopes, thus determining the direction and trajectory of the system state approaching the sliding mode surface in the state space. Among them, the control objective is the current error and the first derivative of the current error , as Figure 1 shown.

[0046] It should be understood that is the current error, that is, the difference between the currents at both ends of the lye electrolyzer and the current reference value ; is the first derivative of the current error. According to the differential equation of the Buck circuit, it can be obtained that is related to the voltage at both ends of the lye electrolyzer.

[0047] Step S2: Decompose the control quantity of the sliding mode controller based on the sliding mode equivalent control method, solve for the equivalent control term of the linear sliding mode controller, and design the switching control term of the linear sliding mode controller according to the system performance requirements. Among them, the system performance requirements include the sliding mode reaching condition and the stability condition.

[0048] Step S21: Take the derivative of the expression of the sliding mode surface of the sliding mode controller to obtain the derivative of the sliding mode surface, and let , then substitute the unified differential equation of the Buck circuit into it for solution to obtain the equivalent control term , expressed as:

[0049]

[0050] In the formula, represents the input voltage at both ends of the lye electrolyzer, represents the inductor in the Buck circuit, represents the equivalent capacitance of the lye electrolyzer, represents the equivalent resistance of the lye electrolyzer, represents the current reference value.

[0051] Furthermore, the unified differential equation of the Buck circuit is:

[0052]

[0053] Where, The current representing the load, which in this embodiment can also be regarded as the current across the alkali electrolytic cell; represents the capacitor voltage, represents the inductance in the Buck circuit, represents capacitance, Represents resistive load, Indicates the input voltage, Represents the vector [1,0].

[0054] Step S22: Select Lyapunov function , and take the first-order derivative of the time to get the first-order derivative of the Lyapunov function , expressed as:

[0055]

[0056] It should be noted that the Lyapunov function plays an irreplaceable role in sliding mode control. It provides important theoretical support and mathematical tools for stability analysis, controller design, and robustness evaluation, and can help design efficient, stable, and robust sliding mode control systems. The form of the Lyapunov function is not unique. In this embodiment, a common Lyapunov function form used in sliding mode control and other fields is selected, namely Among them, the current error and current error The first derivative of After taking the derivative with respect to time, it contains and and other parameters.

[0057] To meet the sliding mode arrival condition , design switching control items , expressed as:

[0058]

[0059] Where, represents the sign function. hour, , , substitute it into middle, , at this time, the system meets the stability condition ;when hour, , , substitute it into Among them, , at this time, the system meets the stability condition ; when , , , substitute it into Among them, , at this time, the system meets the stability condition .

[0060] Combining the above steps, the sliding mode controller is designed and obtained according to the following formula:

[0061]

[0062] It should be noted that the core idea of sliding mode control is to design a sliding mode surface so that the system state reaches and remains on the sliding mode surface within a finite time, thereby achieving the control goal. Among them, the design of the sliding mode surface is specifically referred to the above step S1; the control quantity of the sliding mode controller is divided into an equivalent control term and a switching control term . The equivalent control term and the switching control term are used in combination to perform sliding mode control on the sliding mode controller. The equivalent control term makes the system state slide along the sliding mode surface, and the switching control term ensures that the system state reaches the sliding mode surface within a finite time, which is implemented by using a sign function; at the same time, stability analysis is also required, and usually a Lyapunov function is used to prove that the system state can reach the sliding mode surface and remain stable within a finite time.

[0063] Furthermore, the frequency of the optimal pulse power is 10 Hz; the duty cycle (pulse width) of the optimal pulse power is determined by the ratio of the set pulse power reference value to the electrolysis power corresponding to the maximum electrolysis efficiency ; compare the duty cycle with a low-frequency pulse triangular carrier with an amplitude of 1 and a period of 10 Hz to obtain a modulated pulse signal, and then multiply the modulated pulse signal by the electrolysis power corresponding to the maximum electrolysis efficiency to obtain a pulse power reference value, which is used as the amplitude of the optimal pulse power. Among them, the set pulse power reference value is determined by the average power of the alkaline electrolyzer, and the electrolysis power corresponding to the maximum electrolysis efficiency is determined by the efficiency-power curve of the alkaline electrolyzer.

[0064] It should be understood that the duty cycle of the pulse power is a value less than 1, which can be regarded as the amplitude, equivalent to a straight line with an amplitude less than 1. Then, this straight line is adjusted with the triangular carrier wave. When the amplitude of the triangular carrier wave is greater than the duty cycle, the adjusted signal is set to 0; when the amplitude of the triangular carrier wave is less than the duty cycle, the adjusted signal is set to 1. Therefore, after comparing the duty cycle with the low-frequency pulse triangular carrier wave with an amplitude of 1 and a period of 10 Hz a pulse signal is obtained. The amplitude of this pulse signal is 1. Multiply it by the electrolysis power corresponding to the maximum electrolysis efficiency to obtain the pulse power reference value, which is the amplitude of the optimal pulse power.

[0065] Furthermore, the duty cycle is obtained through the following method: First, the instantaneous voltage across the alkaline solution electrolyzer is obtained in real time and the instantaneous current ; then, the average power of the alkaline solution electrolyzer is calculated according to the following formula :

[0066]

[0067] In the formula, is the sampling time interval, t is the total time of the sampling process, and the instantaneous current is also the pulsed current input to the alkaline solution electrolyzer ; then, the average power of the alkaline solution electrolyzer is used as the set pulsed power reference value and the electrolysis power corresponding to the maximum electrolysis efficiency is taken as the ratio to obtain the duty cycle:

[0068]

[0069] In the formula, is the duty cycle, which also represents the pulse width of the pulse power. The duty cycle can be adjusted by a sliding mode controller so that the duty cycle is the duty cycle corresponding to the optimal pulse power.

[0070] It should be understood that the duty cycle of the pulse power is the width of the pulse power, and the duty cycle adjusted by the sliding mode controller is the same as the duty cycle of the pulse power.

[0071] Furthermore, in step S21, the current reference value is obtained by calculating the ratio of the pulse power reference value to the voltage across the alkaline solution electrolyzer, and is also regarded as the pulsed current reference value.

[0072] It should be understood that the reference value of the pulsed current is determined by the ratio of the reference value of the pulsed power and the voltage across the alkaline electrolyzer, and is directly proportional to the reference value of the pulsed power, in order for the alkaline electrolyzer to respond quickly to changes. The reference value of the pulsed power is for controlling the average power of the alkaline electrolyzer to reach the reference value. In actual control, the current of the alkaline electrolyzer is selected as the inner control loop, which can respond quickly, so the reference value of the pulsed current is set.

[0073] Based on an alkaline electrolyzer with a rated hydrogen production of 2 Nm 3 , the effects of the proposed method were tested. Among them, the improvement effect on the electrolysis efficiency is shown in Table 1. Under the condition of a duty cycle of 50%, the data of the current ripple are shown in Table 2, and the data of the current overshoot are shown in Table 3.

[0074] Table 1: Data of improved electrolysis efficiency

[0075]

[0076] Table 2: Data of current ripple

[0077]

[0078] Table 3: Data of current overshoot

[0079]

[0080] It can be seen from the data in Table 1, Table 2 and Table 3 that the present invention can improve the electrolysis efficiency and effectively reduce the output current ripple and current overshoot during pulsed current electrolysis.

[0081] In summary, while improving the electrolysis efficiency of the alkaline electrolyzer, the present invention reduces the ripple and current overshoot of the output pulsed current, which is of great significance for improving the power quality; by designing a sliding mode controller, the present invention realizes precise regulation of the pulsed current, can effectively reduce the current ripple, improve the electrolysis efficiency, significantly reduce the output current ripple and current overshoot during pulsed current electrolysis, and greatly improve the power quality; in the design of the sliding mode controller of the present invention, a control algorithm with excellent robustness and dynamic response is adopted, combined with the pulsed current optimization technology, to achieve efficient operation under various electrolysis conditions, and can be widely applied to the fields of industrial hydrogen production and energy storage.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A pulsed current hydrogen production circuit for an alkaline electrolyzer based on sliding mode control, characterized in that, Comprising: A voltage source, a switching transistor, an inductor, a fast-recovery diode, an alkaline electrolytic cell, and a sliding mode controller; wherein, the positive pole of the voltage source is connected to the collector of the switching transistor, the negative pole of the voltage source is connected to the positive pole of the fast-recovery diode and the negative pole of the alkaline electrolytic cell, the emitter of the switching transistor is connected to the first end of the inductor and the negative pole of the fast-recovery diode, and the second end of the inductor is connected to the positive pole of the alkaline electrolytic cell; the duty cycle is obtained through the sliding mode controller, and the control signal on the base of the switching transistor is obtained by modulating the duty cycle and a triangular carrier wave, and a pulsed current is output through the inductor, and this pulsed current is provided to the alkaline electrolytic cell for electrolytic hydrogen production; The control method of the pulsed current hydrogen production circuit for the alkaline electrolytic cell based on sliding mode control comprises: Obtaining the instantaneous voltage and instantaneous current at both ends of the alkaline electrolytic cell in real time to control the sliding mode controller to adjust the duty cycle by using the control quantity of the sliding mode controller; obtaining the control signal of the base of the switching transistor by modulating the duty cycle and a triangular carrier wave, this control signal is a pulsed signal, generating pulsed power, outputting a pulsed current after passing through the inductor, and providing this pulsed current to the alkaline electrolytic cell for electrolytic hydrogen production, so that the alkaline electrolytic cell intermittently operates at the optimal pulsed power corresponding to the maximum electrolysis efficiency under low working conditions, and the optimal pulsed power includes the frequency, duty cycle, and amplitude of the optimal pulsed power; Wherein, the low working condition refers to the working state during the rising process of the electrolysis efficiency of the alkaline electrolytic cell; the frequency, duty cycle, and amplitude of the optimal pulsed power are determined by the efficiency-power curve of the alkaline electrolytic cell and the set pulsed power reference value; The sliding mode controller is obtained according to the voltage and current at both ends of the alkaline electrolytic cell, and is specifically obtained through the following steps: S1. Design the sliding mode surface of the sliding mode controller according to the control target, and its expression is: s = λx1 + x2 Wherein, s represents the sliding mode surface; x1 represents the current error, and the current error x1 is obtained by calculating the difference between the current i L at both ends of the alkaline electrolyzer and the current reference value I ref ; x2 represents the first derivative of the current error x1; λ>0 represents the slope of the sliding mode surface; wherein, the control objectives are the current error x1 and the first derivative x2 of the current error; S2. Decompose the control quantity u of the sliding mode controller based on the sliding mode equivalent control method to solve the equivalent control term u of the linear sliding mode controller eq , and design the switching control term u of the linear sliding mode controller according to the system performance requirements n ; where the system performance requirements include the sliding mode reaching condition and the stability condition; S21. Take the derivative of the expression of the sliding surface of the sliding mode controller to obtain the derivative of the sliding surface and let Then substitute the unified differential equation of the Buck circuit into it for solution to obtain the equivalent control term u eq , which is expressed as: Where, V in represents the input voltage at both ends of the alkaline electrolyzer, L represents the inductor in the Buck circuit, C represents the equivalent capacitance of the alkaline electrolyzer, R represents the equivalent resistance of the alkaline electrolyzer, and I ref represents the current reference value; Step S22: Select the Lyapunov function \(V(x)=0.5s\) 2 , and take the first derivative of it with respect to time to obtain the first derivative of the Lyapunov function which is expressed as: To meet the sliding mode reaching condition Design the switching control term u n , which is expressed as: In the formula, sgn(·) represents the sign function; At this time, the system satisfies the stability condition; The frequency of the optimal pulse power is 10 Hz; the duty cycle of the optimal pulse power is determined by the ratio of the set pulse power reference value P ref to the electrolysis power P maxeff corresponding to the maximum electrolysis efficiency; compare the duty cycle with the low-frequency pulse triangular carrier wave S c with an amplitude of 1 and a period of 10 Hz to obtain the modulated pulse signal, and multiply the modulated pulse signal by the electrolysis power P maxeff corresponding to the maximum electrolysis efficiency to obtain the pulse power reference value, which is used as the amplitude of the optimal pulse power; The duty cycle is obtained through the following method: First, instantaneously obtain the instantaneous voltage U at both ends of the lye electrolyzer ele and the instantaneous current I ele ; then calculate the average power P of the lye electrolyzer according to the following formula aver : Wherein, T is the sampling time interval, t is the total time of the sampling process, and the instantaneous current I ele is also the pulsed current i input to the alkaline electrolyzer L ; then, the average power P of the alkaline electrolyzer aver is used as the set pulsed power reference value P ref and the electrolysis power P corresponding to the maximum electrolysis efficiency maxeff are used to calculate the ratio to obtain the duty cycle: In the formula, d is the duty cycle and also represents the pulse width of the pulsed power.

2. The pulsed current hydrogen production circuit for an alkaline electrolyzer based on sliding mode control according to claim 1, wherein In the step S21, the current reference value is obtained by calculating the ratio of the pulsed power reference value to the voltage at both ends of the alkaline electrolytic cell.

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