Three-section electrolytic cell hydrogen production power supply system and power supply control method thereof

Abstract

The invention relates to the field of clean energy electrolysis hydrogen production, in particular to a three-section electrolytic bath hydrogen production power supply system and a power supply control method thereof. According to the system, an alternating current bus module is connected with three-phase alternating current and provides a three-phase alternating current power supply; the power supply conversion module comprises three power supply conversion units, the three power supply conversion units are jointly connected to the alternating current bus module in parallel, and each power supply conversion unit converts the three-phase alternating current power supply into a working direct current power supply; the three-section type electrolytic bath comprises three sub-electrolytic baths which are connected in series, and each sub-electrolytic bath is correspondingly connected with one power supply conversion unit to obtain the working direct-current power supply; the power supply conversion unit comprises a rectification circuit, a three-level BUCK circuit and a resonance LLC cascade circuit which are connected in sequence. According to the invention, accurate power distribution and independent decoupling control of a load section are realized through the independent modular power supply; meanwhile, harmonic interference is restrained, the power factor is improved, and device stress and line loss are reduced.

Description

Technical Field

[0001] This invention relates to the field of clean energy electrolysis hydrogen production, and in particular to a three-stage electrolyzer hydrogen production power supply system and its power supply control method. Background Technology

[0002] Large-scale water electrolysis for hydrogen production is the current mainstream trend in green hydrogen production, with alkaline electrolyzers being widely used due to their maturity and low cost. Existing hydrogen electrolysis power supplies typically employ high-power converters, such as thyristor rectifiers or IGBT rectifiers, to provide high-current DC power to the electrolyzers.

[0003] In large-scale electrolytic cell applications, to increase system voltage and reduce transmission losses, electrolytic cells are often designed in a multi-stage series configuration, resulting in two main power supply modes: Single-channel high-power power supply: A single power supply is used for overall power supply.

[0004] Parallel power supply using multiple power supply modules: Multiple power supply modules are connected in parallel to output high current.

[0005] When an electrolyzer is designed as a multi-segment series connection, a single power supply or multiple power modules typically share an output circuit. In this case, the current in each electrolyzer segment must remain consistent. The operating state of the electrolyzer is affected by temperature, electrode activity, catalyst decay, and aging. In a series structure, taking a three-segment electrolyzer as an example, when the equivalent internal resistance of one electrolyzer segment changes, its voltage and current fluctuations will be transmitted to other series-connected electrolyzer segments. This interconnected connection makes precise, independent current density control of individual sub-electrolyzers impossible. Localized aging can drag down the hydrogen production efficiency of the entire system and may exacerbate uneven electrode aging, significantly shortening the overall lifespan of the electrolyzer. Current technology lacks a solution that can achieve series-connected module outputs while completely decoupling the control logic to address this technical problem.

[0006] Furthermore, with the integrated development of wind, solar, fishery, and hydrogen production, hydrogen production power sources are increasingly being integrated with unstable renewable energy sources such as offshore wind power or solar power. Existing high-power rectifier power supplies often have low tolerance for input voltage fluctuations. When the input AC voltage fluctuation range is large, such as exceeding ±10%, traditional rectifier circuits struggle to guarantee rapid stabilization and high precision of the output DC voltage. Traditional rectification and chopping schemes are also unable to control output voltage ripple and current harmonics to extremely low levels. High ripple can interfere with the current density distribution during electrolysis, negatively impacting the electrode life and hydrogen production efficiency of alkaline electrolyzers. Summary of the Invention

[0007] To address the aforementioned issues, in a first aspect, embodiments of this application provide a three-stage electrolyzer hydrogen production power supply system and its power supply method.

[0008] The system includes; The AC bus module connects to three-phase AC power and provides three-phase AC power. The power conversion module includes three power conversion units, which are connected in parallel to the AC bus module. Each power conversion unit converts the three-phase AC power into working DC power. The three-stage electrolytic cell includes three sub-electrolytic cells connected in series, and each sub-electrolytic cell is connected to a power conversion unit to obtain the working DC power. The power conversion unit includes a rectifier circuit, a three-level BUCK circuit, and a resonant LLC cascade circuit connected in sequence. The rectifier circuit converts the three-phase AC power supply into a first DC power supply. The three-level BUCK circuit performs a step-down DC-DC conversion on the first DC power supply and outputs a second DC power supply. The resonant LLC cascade circuit inverts the second DC power supply into a first AC power supply, obtains the second AC power supply through transformer isolation transmission of the first AC power supply, and outputs the working DC power supply to the corresponding sub-electrolytic cell after rectification of the second AC power supply.

[0009] The power supply system of this invention adopts a power supply method in which three power conversion units are connected in parallel at the power supply end and in series at the output end, and are respectively connected to a three-section electrolytic cell in series. The independent modular power supply realizes precise power distribution and independent decoupling control of the load section; the power factor is improved by rectifying to suppress harmonic interference, and green access to the power grid is realized; the three-level topology and the series output architecture effectively balance the contradiction between high voltage and high current, and reduce device stress and line loss.

[0010] In one possible implementation, the rectifier circuit further includes: The three input branches connect to three power supply lines of a three-phase AC power source; The bridge has three arms, including a first arm, a second arm, and a third arm. Each of the three arms includes a first power transistor and a second power transistor. The three input branches are respectively connected to the emitter of the first power transistor and the collector of the second power transistor in the three arms. The collectors of the three first power transistors are connected to the DC positive bus, and the emitters of the three second power transistors are connected to the DC negative bus. Two supporting capacitors are connected in series between the DC positive bus and the DC negative bus, and a DC neutral point is led out from between the two supporting capacitors.

[0011] In one possible implementation, each of the three input branches is provided with an input inductor.

[0012] In one possible implementation, the first power transistor and the second power transistor are each connected in anti-parallel to a freewheeling diode.

[0013] In one possible implementation, the three-level BUCK circuit decouples the current of each electrolytic cell by adjusting the PWM duty cycle of the power transistor.

[0014] In one possible implementation, the three-level BUCK circuit includes: The third power transistor has its collector connected to the DC positive bus. The fourth power transistor has its emitter connected to the DC negative bus. The first clamping diode has its cathode connected to the emitter of the third power transistor; The second clamping diode has its anode connected to the collector of the fourth power transistor and its cathode connected to the anode of the first clamping diode. The anode of the first clamping diode and the cathode of the second clamping diode are both connected to the DC neutral point; The power inductor has its input terminal connected to the common node between the emitter of the third power transistor and the cathode of the first clamping diode. The filter capacitor has its first end connected to the output terminal of the power inductor, and its second end connected to the common node between the emitter of the fourth power transistor and the DC negative bus of the input terminal.

[0015] In one possible implementation, the resonant LLC cascade circuit further includes: The full-bridge inverter circuit includes a fourth bridge arm and a fifth bridge arm. The fourth bridge arm and the fifth bridge arm are respectively composed of a fifth power transistor and a sixth power transistor connected in series. The midpoint of the two bridge arms serves as the AC output terminal of the full bridge. The resonant tank circuit includes a resonant inductor and a resonant capacitor. The first end of the resonant inductor is connected to the midpoint of the fourth bridge arm, and the second end of the resonant inductor is connected to the first end of the resonant capacitor. The high-frequency transformer includes a primary winding and a secondary winding; the input terminal of the primary winding is connected to the second terminal of the resonant capacitor and the midpoint of the fifth bridge arm; the secondary circuit includes an output rectifier diode bridge and an output support capacitor, the two ends of which are connected to the corresponding sub-electrolytic cell to output the working DC power supply.

[0016] In a second aspect, the present invention also provides a power supply control method based on the power supply system of the first aspect, the method comprising: Obtain three-phase AC power; The three-phase AC power supply is split into three parallel three-phase AC power supply lines; The three-phase AC power supply of each three-phase AC power supply line is converted into the first DC power supply. The first DC power supply is stepped down to DC-DC conversion to output a second DC power supply; The second DC unit is inverted and converted into a first AC power supply; The first AC power source is isolated and transmitted through a transformer to obtain the second AC power source; The second AC power supply is rectified and then output as a working DC power supply to the corresponding sub-electrolytic cell.

[0017] In one possible implementation, When the voltage of a sub-electrolyte cell drops, the equivalent resistance of that sub-electrolyte cell becomes constant, and the current decreases accordingly. The output voltage of the corresponding power conversion unit is controlled to drop to a set value, and the load current changes accordingly. By keeping the voltage difference between the positive and negative terminals of the power conversion units of the other two sub-electrolytes constant, the operating conditions of the sub-electrolytes can be controlled independently.

[0018] In one possible implementation, When the current in a sub-electrolyte decreases, the equivalent resistance of that sub-electrolyte becomes constant, and the voltage decreases accordingly. The corresponding control is that the load current of the power conversion unit is controlled to decrease to a set value, and the output voltage changes accordingly; By keeping the voltage difference between the positive and negative terminals of the power conversion units of the other two sub-electrolytes constant, the operating conditions of the sub-electrolytes can be controlled independently. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall system modules according to the first embodiment of the present invention; Figure 2 This is a schematic diagram of the power conversion unit circuit module according to the first embodiment of the present invention; Figure 3 This is a schematic diagram of the power supply control method of the present invention; Figure 4 The diagram shows the simulation test results for constant voltage and constant current control according to the present invention. Detailed Implementation

[0020] The following detailed description, in conjunction with specific embodiments and accompanying drawings, clarifies that the described embodiments are only a portion, not all, of the embodiments. All other embodiments obtained by those skilled in the art based on the following embodiments without inventive effort are also within the scope of protection of this invention.

[0021] It should be understood that if the controllers or control circuits involved in the embodiments are conventional control technologies or units for those skilled in the art, such as the controller's control circuit, they can be implemented by those skilled in the art using existing technologies.

[0022] The disclosure of the embodiments provides many different implementations or examples for different ways of implementing the present invention. To simplify the disclosure of the present invention, the embodiments describe components and arrangements of specific examples. Of course, these are merely examples and are not intended to limit the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples in the embodiments; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed. Moreover, if examples of various specific processes and materials are provided in the embodiments, those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0023] In some embodiments of this application, the specific working principle is described through the overall electrical topology architecture. The specific role of the devices in the embodiments is explained in conjunction with the circuit structure. The working principle of specific commonly used circuit components is not explained. For devices such as power transistors, in addition to their role in the circuit application, it should be known that the conventional methods used to control such devices are also known. For example, the controller controls the gate drive of the power transistor based on the feedback of the circuit signal. The technical purpose of this application can be achieved by combining the electrical topology and circuit structure of each embodiment with the conventional principle of the controller controlling the power transistor. The controller is not described in a restrictive way in the embodiments. It can be combined and set with the selection of devices in the existing technology.

[0024] like Figure 1 As shown, the first embodiment of the present invention provides a three-stage electrolyzer hydrogen production and power supply system, the system comprising: AC bus module 1 is connected to three-phase AC power and provides three-phase AC power. The power conversion module 2 includes three power conversion units 21, which are connected in parallel to the AC bus module. Each power conversion unit converts the three-phase AC power into working DC power. The three-section electrolytic cell 3 includes three sub-electrolytic cells 31 connected in series, and each sub-electrolytic cell 31 is connected to a power conversion unit 21 to obtain the working DC power. The power conversion unit 21 includes a rectifier circuit 211, a three-level BUCK circuit 212 and a resonant LLC cascade circuit 213 connected in sequence. The rectifier circuit 211 converts the three-phase AC power supply into a first DC power supply. The three-level BUCK circuit 212 performs a step-down DC-DC conversion on the first DC power supply and outputs a second DC power supply. The resonant LLC cascade circuit 213 inverts the second DC unit to convert it into a first AC power supply, obtains a second AC power supply through transformer isolation transmission of the first AC power supply, and outputs the working DC power supply to the corresponding sub-electrolytic cell 3 after rectification of the second AC power supply.

[0025] The overall working logic of the three-stage electrolyzer hydrogen production and power supply system in this embodiment follows the path of energy distribution—precision voltage regulation—high-frequency isolation—cascaded output, wherein: AC bus module 1 is connected to three-phase AC power, providing 380V three-phase AC power; The input terminals of the three-way power conversion unit 21 are connected in parallel to the three-phase bus module. Within each unit, the rectifier circuit 211 uses a three-phase full-bridge topology composed of six power transistors to convert AC power into DC power with a neutral point. The neutral point is led out through the series midpoint of the supporting capacitor, providing a potential reference for subsequent three-level conversion. The three-level BUCK circuit 212 uses the DC positive and negative terminals and the DC neutral point provided by the rectifier stage to chop the voltage through midpoint clamping logic. Due to the presence of the neutral point, the power transistors only bear half of the bus voltage at any given time, and the output voltage jump amplitude is reduced, thus achieving smoother initial voltage regulation. The resonant LLC cascade circuit 213 inverts the regulated DC power into high-frequency AC power. The high-frequency transformer achieves electrical isolation between the primary and secondary sides. The secondary side of the transformer is rectified and output to the corresponding sub-electrolytic cell.

[0026] Three independent power conversion units 21 are connected in parallel to the AC bus module 1 on the input side to share the total power, and their output terminals are connected in series externally, corresponding to the three sub-electrolytes respectively, together forming the total high-voltage DC environment that supports the operation of the electrolyzers.

[0027] Existing high-power hydrogen production power supplies typically employ a single high-voltage, high-current power supply to directly drive a series electrolyzer, which presents the following technical limitations: The impedance of each section of a series electrolyzer varies due to differences in temperature, pressure, and reaction state. Traditional power supplies cannot accurately compensate for local sections, leading to overload or underload of some sub-electrolyzers.

[0028] Low-voltage, high-current power transmission can lead to severe busbar heating losses and places high demands on the current-carrying capacity of power distribution equipment.

[0029] When faced with high voltage input, the power transistor experiences extreme voltage stress. In order to withstand the voltage, the switching frequency must be reduced, which in turn leads to increased output current ripple and damages the lifespan of the electrolytic cell electrodes.

[0030] This embodiment can solve and achieve the following: Three power conversion units are connected in parallel to the power grid, effectively distributing the heat load at the input and improving power density. The rectifier circuit, through a three-phase full-bridge design and neutral point lead-out, suppresses harmonics injected into the power grid at the source and achieves high power factor operation.

[0031] By superimposing the outputs in series, the system can obtain a high total output voltage with a low single module output current. This not only significantly reduces heat loss during DC transmission but also optimizes the impedance matching between the power module and the load, thereby improving the overall conversion efficiency of the system.

[0032] The three-level BUCK circuit 212, in conjunction with the DC neutral point of the support capacitor, halves the voltage stress on the power devices. Combined with the series cascading on the output side, ultra-high power output is safely achieved without sacrificing frequency and efficiency.

[0033] The high-frequency transformer of the resonant LLC cascade circuit 213 achieves complete isolation of the output terminals of each power conversion unit, allowing each sub-electrolyte to be connected in series in the circuit but decoupled in the electrical control. It can dynamically adjust the power supply of each section according to the real-time potential feedback from each section of the electrolyte, ensuring constant current accuracy and low ripple, and extending the chemical service life of the electrolyte electrodes.

[0034] In some embodiments, each of the three-phase power supply lines of the three-phase bus module is equipped with a fast-blow fuse FU. The fast-blow fuse FU is used for overload protection. When a severe short circuit occurs or a power device experiences a shoot-through fault, the loop current surges instantaneously. The fast-blow fuse, utilizing its extremely low melting time, rapidly melts the physical circuit before the semiconductor device is damaged, cutting off the energy input from the power grid. In a 100kW high-power system, a failure in a single power conversion module can affect the entire power supply bus. The presence of the fast-blow fuse ensures that when a power conversion module fails internally, it can be quickly disconnected from the AC parallel bus, thereby ensuring that other normal power conversion modules and the electrolytic cell section are not affected, achieving system redundancy and reliability.

[0035] like Figure 2 As shown, in some embodiments, the rectifier circuit 212 further includes: The three input branches connect to three power supply lines of a three-phase AC power source; The bridge consists of three arms: a first arm, a second arm, and a third arm. Each of the three arms includes a first power transistor (IGBT1) and a second power transistor (IGBT2). The three input branches are respectively connected to the emitter of the first power transistor (IGBT1) and the collector of the second power transistor (IGBT2) in each of the three arms. The collectors of the three first power transistors (IGBT1) are connected to the DC positive bus. The emitters of the three second power transistors (IGBT2) are connected to the DC negative bus. The DC positive bus With DC negative bus Two supporting capacitors C1 are connected in series between them, and a DC neutral point MP is drawn out from between the two supporting capacitors.

[0036] The rectifier circuit 212 uses a three-phase full-bridge rectifier topology composed of six power transistors to convert three-phase AC power into a DC bus with a neutral point. The neutral point is led out through the midpoint of the series connection of the supporting capacitor, providing a potential reference for the subsequent three-level conversion.

[0037] In some embodiments, the three-phase power supply lines of the power conversion module are respectively provided with incoming line inductors L1.

[0038] The input inductor L1 is used for electromagnetic energy conversion. It is connected in series between the AC input terminal and the rectifier bridge, working in conjunction with the high-frequency switching action of the power transistor. When the power transistor is turned on, the inductor stores magnetic field energy; when the power transistor is turned off, the inductor generates an induced electromotive force that is superimposed on the original power supply voltage, pumping the energy to the DC bus capacitor, thereby achieving voltage boost conversion.

[0039] The input inductor smooths the input current waveform and suppresses current spikes generated by high-frequency switching. Through its current-limiting and energy-storing functions, the input current can be modulated to track the voltage phase, thereby achieving excellent grid performance in terms of power factor and harmonic content. Simultaneously, the input inductor impedes current changes, effectively suppressing transient voltage surges from the grid and electromagnetic interference from switching operations, protecting downstream support capacitors and power transistors from excessively rapid voltage changes. As an energy storage element, the input inductor also provides a stable energy source for precise voltage regulation in the subsequent three-level BUCK circuit.

[0040] In some embodiments, the first power transistor IGBT1 and the second power transistor IGBT2 are respectively connected in anti-parallel to a freewheeling diode D1.

[0041] The anti-parallel freewheeling diode D1, together with the first or second power transistor, forms a fully controlled rectifier bridge. When connected, each diode is anti-parallel with a power transistor.

[0042] The anti-parallel connection means that the anode of the freewheeling diode D1 is connected to the emitter of the power transistor, and the cathode is connected to the collector of the power transistor.

[0043] By connecting the anti-parallel freewheeling diode D1, an inductive current discharge path can be provided, thus achieving freewheeling protection. Since the input circuit of the rectifier circuit has an input inductor connected in series, according to the law of electromagnetic induction, the inductor current cannot change abruptly. When the power transistor is turned off according to the PWM command, the induced electromotive force generated by the inductor needs a discharge path. At this time, the anti-parallel diode automatically turns on, providing a path for the inductor current to continue flowing and preventing the generation of high voltage spikes at the two ends of the power transistor that are sufficient to break down the device.

[0044] In the PWM rectification mode of three-phase full-bridge rectification, the inductor stores energy by controlling the high-frequency switching of the power transistor, and uses the anti-parallel freewheeling diode D1 as a one-way valve to input the energy accumulated by the inductor into the support capacitor of the subsequent stage, so as to ensure that the DC bus voltage can be stabilized at a level higher than the peak value of the AC input voltage, and provide a stable DC power supply for the subsequent three-level BUCK unit.

[0045] Meanwhile, the presence of the freewheeling diode D1 enables the rectifier bridge to handle reverse current. This allows for precise control of the switching phase of the power transistor, which in turn allows for active adjustment of the input current waveform to maintain consistency with the voltage phase, thereby achieving a high power factor and significantly reducing harmonics injected into the grid.

[0046] The freewheeling diode D1 limits the potential between the collector and emitter of the power transistor to within the range of the DC bus voltage, slightly higher than the bus voltage, thus playing a static and dynamic clamping role. At the moment of system startup or when there are fluctuations in the power grid, the diode can act as a passive rectification channel to prevent the IGBT from being damaged in the complex transient process before being controlled.

[0047] The freewheeling diode D1 and the corresponding power transistor together form a fully controlled rectifier branch with active grid interaction capability. This not only effectively suppresses voltage spikes caused by sudden changes in inductor energy and ensures the safe operation of power devices, but also achieves high-precision power factor correction and bus pump-up voltage regulation by providing a bidirectional current channel.

[0048] In some embodiments, the three-level BUCK circuit decouples the current of each electrolytic cell by adjusting the PWM duty cycle of the power transistor.

[0049] The three-level BUCK circuit mainly serves as a relay voltage regulator and ripple suppression circuit in the system. Utilizing the neutral point potential provided by the front-stage rectifier circuit, the output terminal transitions only between two adjacent potential levels in each switching cycle, such as between half the bus voltage and zero potential, or between full voltage and half voltage. Through the multi-potential control mode, the voltage jump amplitude experienced by the power device per unit time is significantly reduced, usually by half, thereby greatly reducing the ripple of the output current and providing an extremely stable DC input for the subsequent LLC converter.

[0050] The control logic of the three-level BUCK circuit lies in the dynamic feedback adjustment of pulse width modulation (PWM). The controller monitors the feedback parameters of the corresponding sub-electrolyte in real time, such as the segment current, and compares them with the set command value. Based on the feedback error, the controller independently adjusts the duty cycle of the power transistor in the three-level BUCK circuit within a power conversion module. When the impedance of a sub-electrolyte increases, causing the current to decrease, the energy input is increased by increasing the duty cycle; conversely, the duty cycle is decreased. Since each power conversion unit has independent three-level BUCK adjustment capability, and the modules are electrically isolated through LLC transformers, adjusting the duty cycle of one module will not affect the output of other modules. This achieves electrical decoupling control under physically series loads, ensuring that each segment of the electrolyte operates at the optimal current density.

[0051] It should be noted that in this embodiment, the three-level BUCK circuit not only plays a role in voltage reduction in the system, but also serves as the control part for decoupling control of the three electrolytic cells, thus solving the technical problem that a single control variable cannot take into account the local load differences in high-power series loads.

[0052] Specifically, such as Figure 2 As shown, in some embodiments, the three-level BUCK circuit 212 includes: The third power transistor, IGBT3, has its collector connected to the DC positive bus. The fourth power transistor, IGBT4, has its emitter connected to the DC negative bus. The cathode of the first clamping diode D2 is connected to the emitter of the third power transistor; The anode of the second clamping diode D3 is connected to the collector of the fourth power transistor, and the cathode is connected to the anode of the first clamping diode D2. The anode of the first clamping diode D2 and the cathode of the second clamping diode D3 are both connected to the DC neutral point; The input terminal of the power inductor L2 is connected to the common node between the emitter of the third power transistor IGBT3 and the cathode of the first clamping diode D2. The filter capacitor C2 is connected at one end to the output terminal of the power inductor L2, and at the other end to the common node between the emitter of the fourth power transistor IGBT4 and the DC negative input bus.

[0053] The three-level BUCK circuit in this embodiment adopts a simplified variant of the midpoint clamping topology. Through the series combination of the third power transistor IGBT3 and the fourth power transistor IGBT4, the first and second clamping diodes anchor the circuit midpoint to the DC neutral point provided by the front-stage rectifier. Due to the presence of the midpoint of the supporting capacitor, the voltage from the DC positive bus to the neutral point and the voltage from the neutral point to the negative bus are each half of the total bus voltage, VBUS / 2. When the power transistors operate, the clamping diodes ensure that the voltage across the third and fourth power transistors is limited to VBUS / 2 when they are in the off state. By using different switching combinations, three voltage levels, VBUS, VBUS / 2, and 0, can be generated at the input of the power inductor, thereby refining energy regulation and achieving the technical effect of halving the device voltage stress.

[0054] Meanwhile, because the voltage jump at the input of the power inductor is only half that of the bus due to the switching between the third power transistor and the first clamping diode, the output current ripple is reduced by more than 50% for the same inductance and switching frequency. Combined with the end-of-line filter capacitor, this achieves extremely high stability of the output current ripple. The third and fourth power transistors only bear half the voltage, significantly reducing dynamic losses during switching. The increased switching frequency further reduces the physical size of the bulky inductors and capacitors, improving the power density of the power module.

[0055] By controlling the PWM duty cycle of the third and fourth power transistors, the system can precisely control the proportion of energy entering the power inductor. Since the physical structure of each module is independent and the input energy is finely divided through this topology, the decoupled control of the current of each sub-electrolyte is guaranteed at the physical level.

[0056] like Figure 2 As shown, in some embodiments, the resonant LLC cascade circuit 213 includes: The full-bridge inverter circuit includes two bridge arms, each of which consists of the fifth power transistor IGBT5 and the sixth power transistor IGBT6 connected in series. The midpoint of the two bridge arms serves as the AC output terminal of the full bridge. The resonant tank circuit includes a resonant inductor LK and a resonant capacitor C3. One midpoint of the full bridge is connected to one end of the resonant inductor LK; the other end of the resonant inductor LK is connected to one end of the resonant capacitor C3. A high-frequency transformer consists of a primary winding and a secondary winding; the other end of the resonant capacitor is connected to the beginning of the primary winding of the high-frequency transformer; the end of the primary winding of the high-frequency transformer is connected to the other midpoint of the full bridge. The secondary circuit includes an output rectifier diode bridge and an output support capacitor C4.

[0057] Figure 2The resistor R in the diagram is an equivalent representation of a single sub-electrolytic cell.

[0058] During operation, the regulated DC power from the front-end three-level BUCK circuit enters the full-bridge circuit composed of four power transistors. By controlling the power transistors at the midpoints of the two bridge arms to conduct alternately, the DC power is modulated into a high-frequency square wave voltage.

[0059] A high-frequency square wave enters a series resonant tank circuit composed of a resonant inductor and a resonant capacitor. When the switching frequency approaches the resonant frequency of this tank circuit, the square wave current is modulated into an approximately sinusoidal current by utilizing the energy exchange between the inductor and capacitor.

[0060] After resonance, the high-frequency electrical energy flows into the primary winding of the high-frequency transformer. Utilizing the principle of magnetic coupling, the electrical energy induces the target voltage in the secondary winding. During this process, there is no physical electrical connection between the primary and secondary windings, thus achieving physical electrical isolation.

[0061] The induced high-frequency alternating current is converted back into direct current by the output rectifier diode bridge, and finally the voltage is smoothed by the output support capacitor and output to the corresponding sub-electrolytic cell load.

[0062] Due to the presence of a resonant tank circuit, the current phase can lag behind or lead the voltage. By controlling the full-bridge power transistors to only turn on when the voltage drops to zero, i.e., soft switching, switching losses can be eliminated.

[0063] The high-frequency transformer cuts off the direct path between the input-side power grid and the output-side electrolytic cell. Only with complete isolation can the outputs of the three power conversion modules be physically connected in series externally. Without LLC-level transformer isolation, the series connection would result in a short circuit between the three power conversion modules.

[0064] Precise voltage transformation and matching of high-frequency transformers can be achieved by flexibly designing the turns ratio according to the rated voltage requirements of a single section of the electrolytic cell, such as low voltage and high current. This eliminates the need for the system to rely solely on a three-level BUCK circuit for drastic differential voltage regulation, allowing the entire circuit to operate at its optimal efficiency point.

[0065] like Figure 3 As shown, an embodiment of this application provides a power supply control method for a three-stage electrolyzer hydrogen production power supply system based on the first aspect described above. The method includes: S1. Obtain three-phase AC power; S2. Divide the three-phase AC power supply into three parallel three-phase AC power supply lines; S3. Convert the three-phase AC power supply of each three-phase AC power supply line into the first DC power supply; S4. Perform a step-down DC-DC conversion on the first DC power supply to output a second DC power supply; S5. Invert the second DC unit to convert it into a first AC power supply; S6. Obtain a second AC power source by isolating and transmitting the first AC power source through a transformer; S7. After rectifying the second AC power supply, the working DC power supply is output to the corresponding sub-electrolytic cell.

[0066] Steps S1-S7 above have been explained in the first embodiment, and will not be repeated here. Based on the overall control method described above, there are also two specific control types: constant voltage control and constant current control, which specifically include: First, when the voltage of one electrolytic cell drops, since the equivalent resistance of the electrolytic cell can be regarded as a constant resistance, the current of the electrolytic cell drops accordingly. The output voltage of the corresponding power conversion module is controlled to drop to the set value, and the load current changes accordingly. Meanwhile, the voltage difference between the positive and negative terminals of the power conversion modules of the other two electrolytic cells remains unchanged. They do not change their own cell voltage difference due to the drop in reference potential, thereby ensuring that the current value in the other two electrolytic cells also remains unchanged, realizing the independent control of the operating conditions of the electrolytic cells.

[0067] The power supply control method is a constant voltage mode. In constant voltage mode, the core logic of the control system is potential floating ground shift. The controller of each power conversion module independently monitors the potential difference between the two ends of its corresponding electrolytic cell segment. When the equivalent resistance of a certain sub-electrolytic cell fluctuates due to the change of the internal chemical reaction state, or when the target voltage set by the system drops, the three-level BUCK circuit inside the corresponding power conversion unit will quickly reduce the PWM duty cycle. The reduction of the duty cycle reduces the voltage difference between the positive and negative terminals of the output of the power conversion module. Due to the impedance characteristics of the electrolytic cell segment, the current in that segment will decrease accordingly, thereby completing the adjustment of the operating conditions of that specific segment.

[0068] Therefore, although the three power conversion modules are physically connected in series on the output side, since the output of each module is isolated by a high-frequency transformer, the fluctuation of the output voltage of one power conversion unit is only manifested as the overall up-and-down shift of the reference potential of the other two power conversion units. For the other two power conversion units, the relative voltage difference between their positive and negative terminals is locked by their internal control loops. As long as their internal duty cycle remains unchanged, even if their zero potential reference point drops due to fluctuations, the voltage difference applied to the corresponding electrolytic cell section remains constant, so the cell current remains unchanged.

[0069] The constant voltage mode solves the problem of the requirement for equal current across all sections in traditional series electrolyzers. In traditional series electrolyzers, if one section performs poorly (e.g., scaling increases resistance), the total voltage must be increased to maintain the current, leading to overvoltage operation in other healthy sections. The constant voltage mode allows the poorly performing sub-cells to operate at lower voltages, while the healthy sub-cells continue to operate efficiently without interference, significantly extending the overall system lifespan. Furthermore, the three-level BUCK circuit's high voltage regulation resolution and small voltage steps, combined with the high-frequency characteristics of the LLC circuit, enable real-time tracking of minute electrochemical fluctuations within the electrolyzer.

[0070] Therefore, under conditions of severe load fluctuations or electrolytic cell switching, the system ensures extremely low voltage fluctuation rates across all sections, preventing electrode catalyst peeling or membrane electrode damage caused by localized overvoltage. Since the modules are electrically decoupled, the control algorithm does not require complex coupling compensation models. Each control loop can be simplified to a single-input, single-output control model, reducing the controller's computational load and improving the system's anti-interference capability. Even if noise occurs in one sampling path, it will not interfere with the stable output of the other two power supplies.

[0071] See the simulation results of constant voltage control mode. Figure 4 The chart in the upper middle section.

[0072] Second, when the current of one sub-electrolytic cell decreases, since the equivalent resistance of the sub-electrolytic cell can be regarded as a constant resistance, the voltage of the sub-electrolytic cell decreases accordingly. Correspondingly, the load current of the power conversion unit is controlled to decrease to the set value, and the output voltage changes accordingly. Meanwhile, the voltage difference between the positive and negative terminals of the power conversion units of the other two sub-electrolytic cells remains unchanged, and the voltage difference within the cell does not change due to the decrease in the reference potential. This ensures that the current value in the other two sub-electrolytic cells also remains unchanged, thus realizing the individual control of the operating conditions of the electrolytic cells.

[0073] The power supply control method is a constant current control mode. The specific working principle of this mode is based on the dynamic balance between local current closed loop and global potential fluctuation.

[0074] By acquiring the DC current at the output of the power conversion unit in real time, the controller compares the measured current with the preset constant current command value at high frequency. If the reaction inside a certain sub-electrolyte changes, such as the accumulation of bubbles leading to an increase in equivalent resistance, the current in that sub-electrolyte will show a downward trend. The controller inside the corresponding power conversion unit will respond immediately and actively increase the PWM duty cycle of its three-level BUCK circuit. According to Ohm's law U=I / R, when the equivalent resistance R changes, in order to maintain the current I constant, the BUCK unit will adjust the output voltage U to make it change accordingly to offset the effect of resistance fluctuation.

[0075] Since the resistance of the sub-electrolytic cell can be considered constant within a microscopic time, this voltage adjustment can precisely lock the current. When a power conversion module increases its output voltage to maintain constant current, it only raises the starting potential point connected to the adjacent power conversion unit. Since the adjacent power conversion unit is an independent constant current closed-loop system, the relative potential difference between its own output positive and negative terminals meets the standard, so its duty cycle will not change significantly. Therefore, the voltage adjustment of each power conversion unit is completely limited to the module and its corresponding sub-electrolytic cell, and will not generate current ripple or voltage disturbance coupled to other power conversion modules.

[0076] See the simulation results of constant current control mode. Figure 4 The chart in the lower middle section.

[0077] Constant current control ensures that even with differences in physical characteristics across different sections, the amount of charge flowing through each section is exactly equal. This guarantees the uniformity of hydrogen production rate in the three-section electrolyzer and avoids shortened electrolyzer life due to insufficient or excessive local reaction. If multiple power sources simultaneously adjust the current, mutual interference often occurs. Through electrical isolation, this system completely decouples the three control signals electrically, reducing the complexity and computational delay of the control system and achieving high dynamic performance with transient response.

[0078] When external power grid fluctuations occur or a transient impedance change occurs in one of the electrolyzer sections, due to the potential fluctuation characteristics, such fluctuations will not be converted into current surges and transmitted to adjacent sub-electrolyzers, ensuring the continuity and stability of the overall hydrogen production process.

[0079] In constant current mode, the three-level BUCK circuit can always operate in the optimal efficiency range closest to the current setting value according to the load demand. Combined with the soft switching characteristics of LLC, it not only achieves constant current accuracy, but also reduces switching losses caused by frequent and large voltage adjustments.

[0080] The above description is merely a preferred embodiment of the present application and does not limit the scope of disclosure of the embodiments of the present application. Any equivalent structural or procedural transformations made using the description and drawings of the embodiments of the present application, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection supported by the embodiments of the present application.

Claims

1. A hydrogen production power supply system for a three-stage electrolyzer, characterized by, The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system.

2. The three-stage electrolyzer hydrogen supply system of claim 1, wherein, The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system.

3. The three-cell hydrogen supply system of claim 2, wherein, The application relates to a three-phase alternating current power supply system.

4. The hydrogen supply system using a three-stage electrolyzer according to claim 2 or 3, wherein The application relates to a three-phase alternating current power supply system.

5. The three-cell hydrogen supply system of claim 4, wherein, The application relates to a three-phase alternating current power supply system.

6. The three-cell hydrogen supply system of claim 5, wherein, The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system.

7. The three-cell hydrogen supply system of claim 1, wherein, The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. The application relates to a three-phase alternating current power supply system. 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The application relates to a three-phase The full-bridge inverter circuit comprises a fourth bridge arm and a fifth bridge arm, the fourth bridge arm and the fifth bridge arm are respectively composed of a fifth power tube and a sixth power tube in series, and the midpoint of the two bridge arms is used as an AC output terminal of the full-bridge; The resonant tank comprises a resonant inductor and a resonant capacitor, the first end of the resonant inductor is connected to the midpoint of the fourth bridge arm, and the second end of the resonant inductor is connected to the first end of the resonant capacitor; The high-frequency transformer comprises a primary winding and a secondary winding; the input end of the primary winding is connected to the second end of the resonant capacitor and the midpoint of the fifth bridge arm; the secondary circuit comprises an output rectifier diode bridge and an output support capacitor, and the two ends of the output support capacitor are connected to output the working DC power supply.

8. A power feeding control method of the power feeding system according to any one of claims 1 to 7, characterized by, The method comprises: obtaining a three-phase AC power supply; dividing the three-phase AC power supply into three parallel three-phase AC power supply lines; converting the three-phase AC power supply of each three-phase AC power supply line into a first DC power supply; performing DC-DC conversion on the first DC power supply to output a second DC power supply; performing inverter conversion on the second DC unit to obtain a first AC power supply; obtaining a second AC power supply by transformer isolation transmission of the first AC power supply; and outputting the working DC power supply to the corresponding sub-electrolytic cell after rectifying the second AC power supply.

9. The control method according to claim 8, characterized by, Further comprising: When the voltage of a sub-electrolytic cell decreases, the equivalent resistance of the sub-electrolytic cell is a constant resistance, and the current decreases accordingly; the output voltage of the power conversion unit corresponding to the sub-electrolytic cell is controlled to decrease to a set value, and the load current changes accordingly; the voltage difference between the positive and negative electrodes of the power conversion units of the other two sub-electrolytic cells remains unchanged, and the operation condition of the sub-electrolytic cell is controlled individually.

10. The control method according to claim 8, characterized by, Further comprising: When the current of a sub-electrolytic cell decreases, the equivalent resistance of the sub-electrolytic cell is a constant resistance, and the voltage decreases accordingly; the load current of the power conversion unit corresponding to the sub-electrolytic cell is controlled to decrease to a set value, and the output voltage changes accordingly; the voltage difference between the positive and negative electrodes of the power conversion units of the other two sub-electrolytic cells remains unchanged, and the operation condition of the sub-electrolytic cell is controlled individually.

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