A hydrogen production station system with medium voltage power supply access

Abstract

The application discloses a kind of medium-voltage power supply access's electrolytic hydrogen station system, belongs to water electrolysis hydrogen production equipment technical field;A kind of medium-voltage power supply access's electrolytic hydrogen station system, including connection unit, current conversion unit and water flow control unit;The system proposed in the application can provide DC 750V voltage bus or DC 1500V / ±750V voltage bus, facilitate access photovoltaic, energy storage and other new energy equipment and electric vehicle and other direct current electrical equipment, while the control valve controlled by water pump connection to water storage tank can be adjusted according to the optimal power of photovoltaic panel to control the water inflow of electrolytic cell to achieve the maximum hydrogen production rate under current conditions, with the advantages of high efficiency, high reliability and good economy.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis hydrogen production equipment technology, specifically to an electrolysis hydrogen production station system connected to a medium-voltage power supply. Background Technology

[0002] Hydrogen is an energy carrier possessing both material and energy properties, and it has high potential market value in global decarbonization. Due to the rapid development of electric vehicles, the DC bus voltage connected to DC equipment is constantly increasing. To meet the high current input of water electrolysis hydrogen production equipment, the DC / DC converter used for water electrolysis hydrogen production needs to have a large step-down ratio. Simultaneously, water electrolysis hydrogen production stations can be combined with short-term energy storage to solve the problem of uneven seasonal photovoltaic power output caused by seasonal weather changes.

[0003] A prior art method and device for controlling hydrogen production and energy storage in a photovoltaic power plant (CN115117936A) utilizes a water electrolysis hydrogen production station on the power generation side of the photovoltaic power plant, requiring an energy storage battery device to ensure the stability of the hydrogen production system. To scientifically schedule the output of the photovoltaic power plant, battery energy storage, and the hydrogen production process, an energy management system is also configured, which formulates daily operation scheduling for the photovoltaic power plant based on photovoltaic power prediction and the operating characteristics of the hydrogen production system. However, the volatility and instability of solar photovoltaic power generation can lead to fluctuations in the input current of the electrolyzer, resulting in low hydrogen production efficiency. Therefore, the electrolyzer requires an additional energy storage battery device to ensure the stability of the hydrogen production system.

[0004] Another method and system for optimizing the capacity configuration of hydrogen-photovoltaic-storage-charging stations (CN114997544A) relates to the field of electric vehicle charging station technology. Based on a photovoltaic system, a cascaded battery energy storage system, a fuel cell system, an electrolyzer hydrogen production system, and a hydrogen storage tank, it constructs a capacity optimization configuration model for the hydrogen-photovoltaic-storage-charging station based on the acquired average photovoltaic power generation data and the average charging load data. However, the DC equipment that can be connected to this system, such as photovoltaic DC / DC converters, energy storage DC / DC converters, and hydrogen production DC / DC converters, is limited by the voltage of a single DC bus, resulting in poor flexibility. Furthermore, without access to the AC power grid, the hydrogen production efficiency is significantly affected by weather factors, leading to poor stability.

[0005] To overcome the technical problems in existing photovoltaic water electrolysis hydrogen production systems, such as uneven photovoltaic output leading to low hydrogen production efficiency and poor stability, as well as the limitation of DC bus voltage restricting the connection of DC equipment and poor flexibility, and to meet the connection of various electrolyzer equipment and achieve the best hydrogen production rate, this patent proposes a novel medium-voltage power supply-connected water electrolysis hydrogen production station system. Summary of the Invention

[0006] 1. The technical problem to be solved by the present invention The purpose of this invention is to provide an electrolytic hydrogen production station system with medium-voltage power supply access to solve the problems mentioned in the background art. The system provides two different DC voltage buses, which facilitates the connection of new energy equipment such as photovoltaics and energy storage, as well as DC power equipment such as electric vehicles. At the same time, it can adjust the water flow rate of the electrolyzer by adjusting the control valve connected to the water storage tank by the water pump according to the optimal power of the photovoltaic panel to achieve the maximum hydrogen production rate under the current conditions. It has the advantages of high efficiency, high reliability and good economy.

[0007] 2. Technical Solution To achieve the above objectives, the present invention provides the following technical solution: An electrolytic hydrogen production station system with medium-voltage power supply access includes a connection unit, a converter unit, and a water flow control unit; The connection unit includes a medium-voltage AC power supply, a circuit breaker, and a power frequency isolation transformer. One side of the circuit breaker is connected to the medium-voltage AC power supply, and the other side is connected to the high-voltage side of the power frequency isolation transformer. The converter unit is connected to the low-voltage side of the power frequency isolation transformer; the converter unit consists of two sets of cascaded three-phase H-bridge converters, several hydrogen production converters, charging converters, photovoltaic converters and energy storage converters; The water flow control unit includes a water level controller, a water pump, and a control valve. The water level controller, water pump, and control valve together form a water flow controller module. The water level controller is connected to the photovoltaic panel through a hydrogen production converter, a DC bus, and a photovoltaic converter. The control valve adjusts the inlet water flow of the electrolyzer through the water level controller.

[0008] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, the low-voltage side of the power frequency isolation transformer has two sets of independent three-phase windings. The voltage and phase of the two sets of three-phase windings are the same. The three windings of each set of windings are independent and not connected to each other. The AC side of the three-phase H-bridge converter is respectively connected to the two sets of low-voltage side windings of the power frequency isolation transformer. Each set of the three-phase H-bridge converter can be composed of multiple converter modules connected in parallel.

[0009] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, wherein: the DC side voltage of each group of three-phase H-bridge converters forms a rated voltage 750V bus; the DC sides of two groups of three-phase H-bridge converters can be cascaded to form a rated DC 1500V / ±750V DC bus, i.e., a positive bus, a negative bus, and a neutral bus. The DC sides of two groups of three-phase H-bridge converters can also be connected in parallel to form a rated DC 750V DC bus, i.e., a positive bus and a neutral bus.

[0010] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, each group of three-phase H-bridge converters adopts a single-stage frequency multiplication PWM modulation method, the two groups of three-phase H-bridge converters have the same carrier frequency for PWM modulation, and the phase difference is 180 degrees. Their AC output filters adopt LCL type or L type filter circuits for filtering.

[0011] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, wherein: the leakage inductance of the power frequency isolation transformer can be used as the grid-side inductance of the LCL filter or the inductance of the L-type filter in the three-phase H-bridge inverter; wherein, the photovoltaic panel is connected to the DC bus through a photovoltaic converter, the photovoltaic panel is connected to the photovoltaic converter, and the energy storage battery is connected to the energy storage converter.

[0012] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, the photovoltaic converter is a DC / DC converter, with the input side connected to a photovoltaic panel and the output side connected to a 750V DC bus or a 1500V / ±750V DC bus, realizing unidirectional energy flow from the photovoltaic panel to the DC bus; wherein, the energy storage battery is connected to the DC bus through an energy storage converter, storing the energy of the photovoltaic panel and AC power supply during off-peak electricity consumption periods, and discharging during peak electricity consumption periods to provide energy for electrolytic water hydrogen production.

[0013] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, the energy storage converter is an isolated DC / DC converter, with one side connected to a 750V bus or a DC 1500V / ±750V bus, and the other side being an energy storage unit. The energy flow direction is bidirectional, meaning it can flow from the DC bus to the energy storage unit or from the energy storage unit to the DC bus.

[0014] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, wherein: a hydrogen production converter, a water level controller, a water pump, and a control valve constitute a hydrogen production module; the input interface of the electrolyzer corresponds to a water level controller, a water pump, and a control valve; and the water level controller, water pump, and control valve constitute a water flow control module to regulate the inlet water flow of the electrolyzer.

[0015] As a preferred embodiment of the electrolytic water hydrogen production station system with medium-voltage power supply access described in this invention, the water level controller measures the influent flow rate corresponding to the optimal power of the photovoltaic panel and converts the measured value into an electrical signal. The control valve is connected to the water storage tank by a water pump, and the control valve extracts the optimal water flow for injection into the electrolytic cell based on the electrical signal.

[0016] 3. Beneficial effects The electrolytic water hydrogen production station topology of this invention uses a power frequency transformer for voltage isolation. The converter has low insulation withstand voltage, high reliability, and high efficiency. It provides two different DC voltage buses, which facilitates the connection of new energy equipment such as photovoltaics and energy storage, as well as DC power equipment such as electric vehicles. At the same time, it can control the water flow of the electrolyzer according to the optimal power regulation control valve of the photovoltaic panel to achieve the maximum hydrogen production rate under the current conditions. It has the advantages of high efficiency, high reliability, and good economy. Attached Figure Description

[0017] Figure 1 This is an overall block diagram of an electrolytic hydrogen production station system with medium-voltage power supply proposed in this invention; Figure 2 This is a structural diagram of the H-bridge converter described in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the water flow controller described in Embodiment 1 of the present invention; Figure 4 This is a topology diagram of the DC / DC converter described in Embodiment 1 of the present invention.

[0018] Explanation of the labels in the diagram: 101. Medium-voltage AC power supply; 102. Circuit breaker; 103. Power frequency isolation transformer; 104. Charging converter; 105. Electric vehicle; 106. Photovoltaic converter; 107. Photovoltaic panel; 108. Energy storage converter; 109. Energy storage battery; 201. Three-phase H-bridge converter; 202. Hydrogen production converter; 300. Water flow control unit; 301. Water level controller; 302. Water pump; 303. Control valve; 400. Electrolytic cell. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0022] Example 1: Please see Figure 1 , Figure 1 This is an overall block diagram of an electrolytic hydrogen production station system with medium-voltage power supply proposed in this invention, as shown below. Figure 1 As shown, it includes a connection unit, a converter unit, and a water flow control unit 300; The connection unit includes a medium-voltage AC power supply 101, a circuit breaker 102, and a power frequency isolation transformer 103. One side of the circuit breaker 102 is connected to the medium-voltage AC power supply 101, and the other side is connected to the high-voltage side of the power frequency isolation transformer 103. The converter unit is connected to the low-voltage side of the power frequency isolation transformer 103 and consists of two sets of cascaded three-phase H-bridge converters 201, multiple hydrogen production converters 202, charging converters 104, photovoltaic converters 106 and energy storage converters 108. The water flow control unit 300 includes a water flow controller module consisting of a water level controller 301, a water pump 302, and a control valve 303. The water level controller 301 is connected to the photovoltaic panel 107 through a hydrogen generator converter 202, a DC bus, and a photovoltaic converter 106. The control valve 303 adjusts the water flow rate into the electrolyzer 400 through the water level controller 301.

[0023] Specifically, such as Figure 1 As shown, this invention provides a hydrogen production station for water electrolysis with controllable influent flow. The connection unit includes a medium-voltage AC power supply 101, a circuit breaker 102, and a power frequency isolation transformer 103. One side of the circuit breaker 102 is connected to the medium-voltage AC power supply 101, and the other side is connected to the high-voltage side of the power frequency isolation transformer 103. The medium-voltage AC power supply 101 is a three-phase 10kV or 35kV power supply, and the circuit breaker 102 is a 10kV or 35kV three-phase circuit breaker. One side of the three-phase circuit breaker is connected to the three-phase 10kV or 35kV power supply, and the other side is connected to the high-voltage side of the power frequency isolation transformer 103.

[0024] Furthermore, the converter unit, connected to the low-voltage side of the power frequency isolation transformer 103, consists of two sets of cascaded three-phase H-bridge converters 201, multiple hydrogen production converters 202, photovoltaic converters 106, and energy storage converters 108; the water flow control unit 300 includes a water flow controller module consisting of a water level controller 301, a water pump 302, and a control valve 303. The water level controller 301 is connected to the photovoltaic panel 107 through the hydrogen production converter 202, the DC bus, and the photovoltaic converter 106. The control valve 303 regulates the water flow rate into the electrolyzer 400 through the water level controller 301.

[0025] Specifically, the system includes: a medium-voltage AC power supply 101, a circuit breaker 102, a power frequency isolation transformer 103, an AC / DC conversion module consisting of two cascaded three-phase H-bridge converters 201 connected to the low-voltage side of the transformer, a ±750V DC bus, a photovoltaic converter 106 and an energy storage converter 108 connected to the DC bus at their inputs, with their outputs connected to a photovoltaic panel 107 and an energy storage unit, respectively; multiple DC / DC hydrogen production modules connected to the DC bus; and an electrolyzer 400 connected to the output of the DC / DC hydrogen production modules, which includes a water flow controller module consisting of a water level controller 301, a water pump 302, and a control valve 303. The hydrogen production converters 202 in the hydrogen production module all feature an interleaved parallel Buck topology, providing fault tolerance and improving the converter's output current capability while reducing output ripple. The three-phase H-bridge converter 201 enables the connection of photovoltaic, energy storage equipment and electrolyzer 400, while achieving efficient hydrogen production from electrolyzer 400 with high fault tolerance and high reliability.

[0026] Example 2: Please see Figure 1-4 Based on Embodiment 1 but with a difference, the low-voltage side of the power frequency isolation transformer 103 has two sets of independent three-phase windings. The voltage and phase of the two sets of three-phase windings are the same, and the three windings of each set are independent and not connected. The AC side of the three-phase H-bridge converter 201 is connected to the two sets of low-voltage side windings of the power frequency isolation transformer 103 respectively. Each set of three-phase H-bridge converter 201 can be composed of multiple parallel converter 202 modules. The DC side of the three-phase H-bridge converter 201 has a positive bus, a negative bus, and a neutral bus. The DC side voltage of each set of three-phase H-bridge converter 201 forms a rated voltage 750V bus, i.e., the positive bus and the neutral bus, and the neutral bus and the negative bus. The DC sides of two sets of three-phase H-bridge converters 201 are cascaded to form a rated DC 1500V DC bus, i.e., the positive bus and the negative bus. The hydrogen converter 202 is the power supply module of the electrolyzer 400. Each electrolyzer 400 is also equipped with a water flow controller module consisting of a water level controller 301, a water pump 302, and a control valve 303. The input end of the hydrogen converter 202 is connected to the DC bus, and its output end is connected to the power input interface of the electrolyzer 400. The control valve 303 is connected to the water inlet of the electrolyzer 400.

[0027] Each three-phase H-bridge converter 201 adopts a single-stage frequency-doubling PWM modulation method. The carrier frequency of the PWM modulation of the two sets of three-phase H-bridge converters 201 is the same, and the phase difference is 180 degrees. Its AC output filter adopts an LCL type or L-type filter circuit for filtering. The leakage inductance of the power frequency isolation transformer 103 can be used as the grid-side inductance of the LCL filter or the inductance of the L-type filter in the three-phase H-bridge inverter. Among them, one end of the charging converter 104 is connected to the DC bus, and the other end is connected to the electric vehicle 105; one end of the photovoltaic converter 106 is connected to the DC bus, and the other end is connected to the photovoltaic panel 107; one end of the energy storage converter 108 is connected to the DC bus, and the other end is connected to the energy storage battery 109.

[0028] The photovoltaic converter 106 is a type of DC / DC converter. Its input side is connected to a photovoltaic panel 107, and its output side is connected to a 750V DC bus or a 1500V DC bus, enabling unidirectional energy flow from the photovoltaic panel 107 to the DC bus. The energy storage battery 109 is connected to the DC bus via an energy storage converter 108. During off-peak hours, it stores energy from the photovoltaic panel 107 and the AC power supply; during peak hours, it discharges to provide energy for hydrogen production via water electrolysis. The energy storage converter 108 is an isolated DC / DC converter. One side is connected to a 750V DC bus or a 1500V DC bus, and the other side is the energy storage unit. Energy flow is bidirectional; it can flow from the DC bus to the energy storage unit or vice versa.

[0029] Specifically, this invention uses a power frequency transformer for voltage isolation and step-down. The high-voltage side of the power frequency transformer is connected to the medium-voltage AC grid in a delta connection, while the low-voltage side uses two sets of independent three-phase windings. These two sets of independent three-phase windings are respectively connected to the AC input of two sets of three-phase H-bridge converters 201. The three-phase windings on the low-voltage side of the transformer are independent and not connected to each other, providing AC phase-to-phase isolation for the three-phase H-bridge converters 201. Simultaneously, the DC sides of the three-phase H-bridge converters 201 are cascaded. This invention uses a power frequency transformer for high-low voltage isolation, which is technically mature, highly reliable, and low-cost. Furthermore, the AC / DC converter of this invention adopts a main circuit topology of two sets of cascaded three-phase H-bridge converters 201. The H-bridge main circuit is a two-level circuit, with only two power electronic switching devices connected in series in each bridge arm. This simple topology facilitates easy control and ensures high converter reliability.

[0030] Furthermore, the AC / DC converter employs a three-phase H-bridge converter 201, using a unipolar PWM modulation method. Its AC-side output equivalent switching frequency is twice the actual switching frequency of the device. Simultaneously, the AC output filter uses an LCL filter, effectively reducing harmonic pollution to the AC power grid. Medium-voltage AC power is stepped down by a transformer and then inverted into DC power by two cascaded H-bridge converters. The inverter circuit uses a three-phase H-bridge, while the single-phase H-bridge structure is as follows: Figure 2As shown. L1 is the leakage inductance of the transformer, serving as the grid-side inductance of the inverter's LCL filter; L2 is the inverter-side filter inductance; C1 is the AC filter capacitor; C2 is the DC filter capacitor; Q1, Q2, Q3, and Q4 are all power electronic switching devices, which can be silicon-based IGBT / diode modules, MOSFETs, or silicon carbide or gallium nitride-based switching devices. D1 to D4 are the anti-parallel diodes of S1 to S4, respectively.

[0031] Furthermore, the two cascaded three-phase H-bridge converters 201 in this system can output three DC buses: a positive bus, a negative bus, and a neutral bus. The rated voltage between the positive and neutral buses is 750V, the rated voltage between the neutral and negative buses is 750V, and the rated voltage between the positive and negative buses is 1500V. Depending on the power requirements of different hydrogen electrolyzers 400, the hydrogen production converters can be connected to buses of different voltages. For lower hydrogen production voltage and power, a 750V DC bus can be connected; for higher hydrogen production voltage and power, a 1500V DC bus can be connected.

[0032] Furthermore, the three-phase H-bridge converter 201 in this system can output low DC bus voltages of 750V and 1500V, which facilitates connection to the photovoltaic converter 106 and the energy storage converter 108, thereby improving energy conversion efficiency.

[0033] Furthermore, the water level controller 301 can measure the inlet water flow rate corresponding to the optimal power of the photovoltaic panel 107 and convert the measured value into an electrical signal. This electrical signal controls the control valve 303 connected to the water storage tank by the water pump 302 to adjust the optimal inlet water flow rate injected into the electrolytic cell 400.

[0034] The DC / DC hydrogen converter in this invention adopts an interleaved parallel Buck topology, such as the two-phase interleaved parallel Buck topology. Figure 4 As shown, the circuit topology consists of power electronic switching devices S1 and S2, inductors L1 and L2, diodes D1 and D2, and output capacitor C. The power electronic switching devices S1 and S2 are interleaved in parallel. These devices can be silicon-based IGBT / diode modules, MOSFETs, or silicon carbide or gallium nitride-based switching devices. The number of phases N of the interleaved parallel Buck converter can be adjusted according to the requirements of the electrolytic cell 400.

[0035] The rest of the structure is the same as in Example 1.

[0036] Specifically: The medium-voltage AC voltage side is connected to the mains power supply line, which is connected to the high-voltage side of the isolation power frequency transformer via circuit breaker 102. The transformer is a three-phase, three-limb type, with its high-voltage side using a delta connection and its low-voltage side using two sets of independent three-phase windings. Two sets of AC / DC converter modules, each composed of three-phase H-bridge converters 201, are cascaded. The AC input terminals of each phase are connected to the low-voltage windings of the transformer, and the output terminals of the two sets of three-phase H-bridge converters 201 are led out to form a ±750V DC bus. Each hydrogen production module has a water flow controller module, which can adjust the corresponding water inlet flow of the electrolyzer 400 according to the optimal power of the photovoltaic panel. Figure 1 As shown, the hydrogen generator converter 202 includes a hydrogen generator converter A, a hydrogen generator converter B, and a hydrogen generator converter C. The input terminals of A and B are connected to DC+, DC0 and DC0, DC- respectively to connect to a 750V DC bus, and the input terminal of C is connected to DC+ and DC- to connect to a 1500V DC bus.

[0037] The photovoltaic converter 106 is a DC / DC converter, connected to a 750V or 1500V DC bus on one side and a photovoltaic panel on the other. Energy flows unidirectionally from the photovoltaic panel to the DC bus, and the converter can control the photovoltaic panel to operate at maximum power point tracking. The energy storage converter 108 is an isolated DC / DC converter, connected to a 750V or 1500V DC bus on one side and an energy storage unit (which can be a lithium battery or other battery energy storage unit) on the other side. Energy flows bidirectionally, from the 750V or 1500V bus to the energy storage unit, and vice versa. The distributed energy resources and energy storage devices can achieve on-site energy consumption in the hydrogen production station proposed in this invention. The energy in the distributed energy (photovoltaic) and energy storage devices provides electricity for hydrogen production through photovoltaic converter 106, energy storage converter 108, DC bus converter and other converters, respectively, so as to realize the local consumption of energy.

[0038] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A hydrogen electrolysis station system connected to a medium-voltage power supply, characterized in that, It includes a connection unit, a converter unit, and a water flow control unit (300). The connection unit includes a medium-voltage AC power supply (101), a circuit breaker (102), and a power frequency isolation transformer (103). One side of the circuit breaker (102) is connected to the medium-voltage AC power supply (101), and the other side is connected to the high-voltage side of the power frequency isolation transformer (103). The converter unit is connected to the low-voltage side of the power frequency isolation transformer (103); the converter unit consists of two sets of cascaded three-phase H-bridge converters (201), several hydrogen production converters (202), charging converters (104), photovoltaic converters (106) and energy storage converters (108); The DC side of the three-phase H-bridge converter (201) is provided with a positive bus, a negative bus and a zero bus. The DC side voltage of each group of the three-phase H-bridge converters (201) forms a rated voltage 750V bus. The DC sides of the two groups of three-phase H-bridge converters (201) can be connected in parallel to form a 750V DC bus, or they can be cascaded to form a rated DC 1500V / ±750V DC bus. The water flow control unit (300) includes a water level controller (301), a water pump (302), and a control valve (303). The water level controller (301), water pump (302), and control valve (303) together form a water flow controller module. The water level controller (301) is connected to the photovoltaic panel (107) through a hydrogen production converter (202), a DC bus, and a photovoltaic converter (106). The control valve (303) adjusts the inlet flow of the electrolyzer (400) through the water level controller (301). The water level controller (301) measures the inlet flow corresponding to the optimal power of the photovoltaic panel and converts the measured value into an electrical signal. The control valve (303) extracts the optimal water flow injected into the electrolyzer (400) according to the electrical signal.

2. The electrolytic hydrogen production station system with medium-voltage power supply access according to claim 1, characterized in that, The high-voltage side voltage of the power frequency isolation transformer (103) is 10kV or 35kV. The high-voltage side winding adopts a star connection or a delta connection. The low-voltage side is provided with two sets of independent three-phase windings. The voltage and phase of the two sets of three-phase windings are the same. The three windings of each set of windings are independent and not connected to each other. The AC side of the three-phase H-bridge converter (201) is connected to the two sets of low-voltage side windings of the power frequency isolation transformer (103). Each set of the three-phase H-bridge converter (201) is connected to multiple parallel hydrogen production converter (202) modules by a DC bus.

3. The electrolytic hydrogen production station system with medium-voltage power supply access according to claim 2, characterized in that, The three-phase H-bridge converter (201) adopts a single-stage frequency multiplication PWM modulation method. The two sets of three-phase H-bridge converters (201) have the same carrier frequency for PWM modulation and a phase difference of 180 degrees. Their AC output filters are filtered by LCL or L-type filter circuits.

4. The electrolytic hydrogen production station system with medium-voltage power supply access according to claim 3, characterized in that, The leakage inductance of the power frequency isolation transformer (103) serves as the grid-side inductance of the LCL filter or the inductance of the L-type filter in the three-phase H-bridge inverter; wherein, one end of the charging converter (104) is connected to the DC bus and the other end is connected to the electric vehicle (105); one end of the photovoltaic converter (106) is connected to the DC bus and the other end is connected to the photovoltaic panel (107); one end of the energy storage converter (108) is connected to the DC bus and the other end is connected to the energy storage battery (109).

5. The electrolytic hydrogen production station system with medium-voltage power supply access according to claim 4, characterized in that, The photovoltaic converter (106) is a DC / DC converter with a photovoltaic panel (107) connected to its input side and a DC 750V bus or a DC 1500V bus connected to its output side; wherein, the energy storage battery (109) is connected to the DC bus through the energy storage converter (108).

6. The electrolytic hydrogen production station system with medium-voltage power supply access according to claim 5, characterized in that, The energy storage converter (108) is an isolated DC / DC converter, with one side connected to a DC 750V bus or a DC 1500V / ±750V bus, and the other side being an energy storage unit; the energy flow direction between the DC bus and the energy storage unit is bidirectional.

7. The electrolytic hydrogen production station system with medium-voltage power supply access according to claim 6, characterized in that, The hydrogen converter (202) and the water flow control unit (300) together form a hydrogen production module. The input interface of the electrolyzer (400) corresponds to the water level controller (301), water pump (302) and control valve (303) of the water flow control unit (300).

8. A hydrogen electrolysis station system with medium-voltage power supply access according to claim 1 or 7, characterized in that, The control valve (303) is connected to the water storage tank by the water pump (302).

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