High-integration-level integrated hydrogen production and power generation system and control method thereof

Abstract

The invention discloses a high-integration-level integrated hydrogen production and power generation system and a control method thereof, the system comprises a T-type three-level rectifier / inverter and a multi-phase multiple bidirectional buck-boost converter which are used as core power processing units, and hardware multiplexing is carried out between a hydrogen production mode and a power generation mode through a change-over switch. In the hydrogen production mode, the system carries out current closed-loop control on the electrolytic bath, and the overall efficiency of the system is improved through optimal current distribution among the phase converters. In the power generation mode, the system carries out voltage closed-loop control on the direct-current bus, and a double-loop control structure of a bus voltage outer loop and an inductive current inner loop is adopted to maintain the voltage stability of the bus. According to the system, the integration of hydrogen production and power generation functions is realized through hardware multiplexing, mode control and current distribution optimization. The bidirectional buck-boost converter provides core hardware support for bidirectional energy flow and wide voltage adaptation by means of its symmetric circuit topology and automatic mode switching capability based on hysteresis comparison.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy and new energy power generation control technology, specifically to a highly integrated hydrogen production and power generation system and its control method. Background Technology

[0002] Hydrogen-electric coupling constructs an efficient and flexible energy system through the mutual conversion and synergy of electricity and hydrogen energy. Its core approach is to use surplus renewable electricity to electrolyze water to produce "green hydrogen," which is then fed back to the grid through fuel cell power generation. This enables the regulation and distribution of energy in time and space, ultimately forming a clean energy closed loop of "electricity-hydrogen-electricity." This is of great significance for solving the problems of intermittency and volatility of renewable energy and enhancing the resilience of the power grid.

[0003] Traditional electro-hydrogen coupling systems have significant drawbacks: a) Complex system structure: The hydrogen production stage requires an AC / DC rectifier circuit + DC / DC current source, and the power generation stage requires a DC / DC voltage source + DC / AC inverter, involving a total of four independent power circuits with high device redundancy; b) Low circuit reuse rate: Hydrogen production in the electrolyzer and power generation in the fuel cell do not work simultaneously, resulting in time-sharing idleness of each power circuit and making it impossible to achieve hardware reuse; c) Low energy conversion efficiency: Electrical energy needs to undergo multiple conversions (such as AC → DC → DC → AC), and each conversion results in energy loss, thus limiting the overall efficiency.

[0004] Existing similar technologies include: CN202410475066.X New Energy Hydrogen Production Power Supply, System and Control Method Thereof; CN202411135906.4 Hydrogen Production Power Supply Circuit Based on First-Stage High-Frequency Conversion; CN202510365439.2 A Hydrogen Production Power Supply System and Control Method Thereof; CN202510494745.6 Hydrogen Production Power Supply System and Control Method Thereof; CN202310790842.0 Hydrogen Production Device and Fuel Cell Coupled Hydrogen Production Power Generation System. None of these technologies have solved the core problems of power hardware reuse, wide voltage adaptation, and precise control across different modes, making it difficult to balance system integration and energy conversion efficiency.

[0005] Therefore, there is an urgent need for a highly integrated hydrogen production and power generation system and its control method. Summary of the Invention

[0006] The purpose of this invention is to provide a highly integrated hydrogen production and power generation system and its control method to solve the defects of the prior art, such as complex system structure, low circuit reuse rate and low energy conversion efficiency.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The highly integrated hydrogen production and power generation system includes a power conversion unit, a switching unit, a hydrogen production unit, a power generation unit, a step-up transformer, and a control unit. The connection relationships and functions of each component are as follows: a) Power conversion unit: including a T-type three-level rectifier inverter and a multi-phase multi-bidirectional buck-boost converter; the T-type three-level rectifier inverter consists of 24 fully controlled switching devices (such as reverse-conducting IGBTs and MOSFETs), and has two operating modes: rectification and inversion. Its input terminal is connected to the power grid through a boost transformer, and its output terminal is connected to the left side of the multi-phase multi-bidirectional buck-boost converter; the multi-phase multi-bidirectional buck-boost converter consists of at least two bidirectional buck-boost converters connected in parallel (in this embodiment, it is a three-phase triple buck-boost converter), adopting a symmetrical topology, with a hydrogen production current detection resistor on the right side. The left and right sides are respectively equipped with inductor current sensing resistors for boost and buck modes. , It is used to realize bidirectional energy transmission and step-up / step-down conversion; b) Switching unit: including the first switch group ( / ) and the second switch group ( / ), used to control the on / off switching of the multiphase multi-stage bidirectional buck-boost converter and the hydrogen production / power generation unit; in hydrogen production mode / closure, / Disconnect, in power generation mode / closure, / disconnect; c) Hydrogen production unit: an alkaline electrolyzer, a PEM electrolyzer, or a solid oxide electrolyzer, used for hydrogen production by electrolysis of water; d) Power generation unit: a proton exchange membrane fuel cell used to convert hydrogen energy into direct current electricity; e) Step-up transformer: Connected between the T-type three-level rectifier inverter and the power grid to achieve voltage level conversion and electrical isolation; f) Control Unit: A microcontroller used to output PWM control signals, detect voltage / current signals, and execute mode-specific control algorithms.

[0008] This invention also discloses a highly integrated hydrogen production and power generation control method: This method achieves switching between hydrogen production mode and power generation mode through a switching unit, and combines closed-loop control and adaptive mode switching to achieve efficient energy conversion. (1) Hydrogen production mode control logic a) Switching unit actions: / closure, / Disconnect the right side of the multiphase bidirectional buck-boost converter from the hydrogen production unit. b) Rectification mode start-up: The T-type three-level rectifier inverter operates in rectification mode, rectifying the AC power on the low-voltage side of the step-up converter into adjustable DC power, which is then input to the left side of the multi-phase multi-multi-bidirectional step-up converter. c) Current optimization allocation: The control unit is based on the efficiency model of each phase converter obtained from offline testing. Construct the optimization objective function: ; In the formula, This is the current density versus voltage function of the electrolytic cell; The effective working area of ​​the electrolytic cell is in units of ; This refers to the number of electrolysis chambers in the electrolytic cell; The constraints are: ; ; In the above formula, and These are the minimum and maximum output currents of the i-th phase, respectively; d) Three-loop closed-loop control: using single-phase operating current and the detected value of the phase load current The difference is used as the input to construct an outer-loop PI controller for the load current. After limiting, the final output of this controller is... ; Single-phase given voltage and the output voltage detection value of this phase The difference is used as the input to construct a voltage-loop PI controller. After limiting, the final output of this controller is... ; Single-phase given inductor current and the detected value of the output inductor current of that phase The difference is used as the input to construct an inner-loop PI controller for the inductor current. After limiting, the final output of this controller is... ; e) Buck-boost mode switching: Using the hysteresis comparison method, a threshold value is set. When the voltage on the left side Switch to buck mode ( disconnect, closure, and (complementary conduction), when Switch to boost mode ( closure, disconnect, and (Complementary conduction), maintaining the previous time-to-time mode within the threshold range.

[0009] (2) Power generation mode control logic a) Switching unit actions: / closure, / Disconnect the right side of the multiphase multi-stage bidirectional buck-boost converter from the generator unit; b) Voltage closed-loop control: The control unit uses the bus voltage setpoint The deviation from the actual value is taken as the input, and the target current of the fuel cell is output after PI control of the bus voltage. and will The current is evenly distributed to each phase converter to obtain the target value of each phase current. ; c) Current closed-loop control: The deviation from the inductor current detection value is used as input, and the output duty cycle α is controlled by PI to adjust the working state of the converter. d) Buck-boost mode switching: Using the hysteresis comparison method, a threshold value is set. When the voltage on the right side Switch to buck mode ( disconnect, closure, and (complementary conduction), when Switch to boost mode ( closure, disconnect, and (Complementary conduction), maintaining the previous time-of-flight mode within the threshold range; e) Inverter grid connection: The T-type three-level rectifier inverter operates in inverter mode, converting the DC power output from the multi-phase multi-multi-bidirectional step-up and step-down converter into AC power with adjustable voltage and frequency, which is then fed into the grid via a step-up transformer.

[0010] (3) Phase interleaving mechanism The initial phase difference between each phase of the multiphase bidirectional buck-boost converter is 2π / N (where N is the total number of phases), making the total output current ripple frequency N times that of a single phase, thus reducing the filter inductance. The inductance value and the weight of the equipment.

[0011] The present invention has the following beneficial effects: a) High integration and low cost: Hydrogen production and power generation functions are realized through a set of power hardware (T-type three-level rectifier inverter + multi-phase multi-bidirectional buck-boost converter), reducing the number of power devices, magnetic components and control units, and reducing system size, weight and cost; b) High energy conversion efficiency: Reduce the number of energy conversions, and combine current optimization allocation and phase interleaving mechanism based on efficiency model to reduce energy loss under medium and low loads and improve overall efficiency; c) Wide voltage adaptability: The bidirectional buck-boost converter supports adaptive switching between boost and buck modes, adapting to electrolyzers and fuel cells of different voltage levels, thus improving equipment versatility; d) High reliability and fault tolerance: The multiphase parallel structure supports derating operation during single-phase failures, and the hysteresis comparison method enables smooth mode switching, avoids voltage fluctuations, and enhances system stability; e) Precise control and rapid response: The hierarchical closed-loop control strategy (outer loop + inner loop) ensures stable current in hydrogen production mode and stable voltage in power generation mode, with excellent dynamic response. Attached Figure Description

[0012] Figure 1 : Structure diagram of a highly integrated hydrogen production and power generation system; Figure 2 : Topology diagram of a bidirectional buck-boost converter; Figure 3 : Working principle diagram of the bidirectional buck-boost converter in buck mode under hydrogen production mode; Figure 4 : Working principle diagram of the bidirectional buck-boost converter in boost mode under hydrogen production mode; Figure 5 : Structure diagram of the multiphase boost / buck converter control system in hydrogen production mode; Figure 6 Schematic diagram of the hysteresis comparison method for boost / blow-down modes in hydrogen production mode; Figure 7 : Working principle diagram of the bidirectional buck-boost converter in buck mode under power generation mode; Figure 8 : Working principle diagram of the bidirectional buck-boost converter in boost mode under power generation mode; Figure 9 : Structure diagram of the multiphase step-up / step-down converter control system in power generation mode; Figure 10 Schematic diagram of the hysteresis comparison method for buck-boost mode in power generation mode. Detailed Implementation

[0013] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0014] Highly integrated hydrogen production and power generation system structure: The structure of a highly integrated hydrogen production and power generation system is as follows: Figure 1As shown (the 24 switching transistors shown in the figure are all fully controlled switching devices, such as reverse-conducting IGBTs and MOSFETs). It mainly consists of: a T-type three-level rectifier inverter, a multi-phase multi-step buck-boost converter, a step-up transformer, a switching switch, an electrolyzer, and a fuel cell. The specific functions of each part are as follows: (1) T-type three-level rectifier inverter: The main circuit is composed of a T-type three-level converter, which has two working modes: grid-connected inverter and rectification. Grid-connected inverter: Converts the DC power output from the left side of the multiphase step-up converter into AC power with continuously adjustable voltage and frequency, and then connects it to the grid via a step-up transformer; Rectification: Rectifying the AC power from the step-up transformer to the low-voltage side into DC power with an adjustable voltage within a certain range.

[0015] (2) Multiphase step-up / step-down converter: As the interface between the DC bus and the electrolyzer / fuel cell, it has two basic modes: input from the left and output from the right; and input from the right and output from the left. Left input, right output: In this mode, the converter is used as a hydrogen production power source, operating in current closed-loop control mode to provide a stable and adjustable DC power supply to the electrolyzer. Simultaneously, this mode can both boost and buck the voltage to adapt to electrolyzers of different voltage levels, improving the equipment's adaptability. Right-side input, left-side output: In this mode, the converter acts as a DC / DC converter for the fuel cell, converting its output DC current to the DC bus. Simultaneously, this mode allows for both boost and buck voltage adjustments to adapt to fuel cells of different voltage levels, improving the device's adaptability.

[0016] (3) Step-up transformer: responsible for realizing voltage level transformation and electrical isolation between grid-side converter and grid, ensuring that electrical energy can be safely and efficiently fed into or taken from the grid at a voltage that meets the grid requirements.

[0017] (4) Switching switch: Responsible for the electrical on / off control of the multiphase boost / buck converter and the electrolyzer or fuel cell. During hydrogen production, the switching tube... closure, Disconnect the multiphase step-up / step-down converter from the electrolytic cell; when generating electricity, the switching transistor... closure, Disconnect the multiphase boost / buck converter from the fuel cell.

[0018] (5) Electrolyzer: A device for producing hydrogen by electrolysis of water, usually an alkaline electrolyzer, a PEM electrolyzer or a solid oxide electrolyzer.

[0019] (6) Fuel cell: a hydrogen power generation device, usually a proton exchange membrane fuel cell.

[0020] Overall control strategy: (1) Hydrogen production When operating in hydrogen production mode, switch on / off. closure, Disconnect the electrolytic cell and the right side connection of the multiphase step-up / step-down converter.

[0021] The rectifier / inverter rectifies the AC power from the grid into DC power at a specific voltage; the multi-step buck-boost converter has the input on the left and the output on the right, and operates in load current closed-loop control mode. Depending on the voltage value required by the electrolytic cell, it can operate in either boost or buck conversion mode.

[0022] (2) Power generation

[0023] When operating in generator mode, switch closure, Disconnect the fuel cell and the right side connection of the multiphase boost / buck converter.

[0024] The multi-step buck-boost converter has its input on the right and its output on the left. Operating in closed-loop voltage control mode, it can boost or buck the voltage, converting the DC output from the fuel cell to a specific voltage to match the required DC bus voltage. The rectifier / inverter converts the DC power on the DC bus into AC power, which is then boosted and connected to the grid.

[0025] Multiphase step-up / step-down converter control: In the above process, the multiphase multi-step buck-boost converter is the core component of the highly integrated hydrogen production and power generation system. It consists of... Figure 2 The bidirectional buck-boost converter shown passes through multiple ( Figure 1 The three shown are connected in parallel to form a multiphase multi-step buck-boost converter. Figure 1 The image shows a three-phase triple bidirectional buck-boost converter. This converter has the following characteristics: (1) Overview of bidirectional buck-boost converter characteristics Symmetrical structure. Except for the additional output on the right side. Furthermore, it exhibits a symmetrical structure, which ensures the same characteristics when input is on the left and output is on the right, and vice versa. Therefore, both sides of the converter can be used as inputs, and the other side as an output. Used for detecting the operating current of the electrolyzer in hydrogen production mode. , They are used for inductor current detection in boost and buck modes, respectively.

[0026] It has two operating modes: boost and buck. When a specific voltage is input, the output voltage can be lower than that voltage (buck mode) or higher than that voltage (boost mode).

[0027] In both of the above operating modes, the microcontroller sends complementary switching signals to... The control switching device turns on, determining whether the converter enters buck / boost mode, and the voltage gain is determined by adjusting the PWM duty cycle signal. Simultaneously, the microcontroller detects the voltage on the left side. voltage on the right side Used in hydrogen production mode ( Figure 5 ) and power generation mode ( Figure 9 Voltage loop feedback in closed-loop control; detection of current flowing through , The current is used to determine the boost or buck mode of the inductor. Current in It is used for the inner current feedback in both modes of closed-loop control. (2) Boost and buck modes of the bidirectional boost-boost converter in hydrogen production mode In hydrogen production mode (input on the left, output on the right), the analysis of buck and boost working modes is as follows.

[0028] a) Buck mode. For example... Figure 3 As shown, in this mode, Keep disconnected. Keep closed. and Complementary conduction. Let... The time in the on-state is ,exist Inductor supplied by the inner left DC bus It supplies power to the load while charging. When In a state of discontinuity When in the on-state, let time be... At this time, the energy stored in the inductor is given Power supply. Since the energy in the inductor is conserved within one period T, we can obtain... ; In the formula, For duty cycle, it can be seen This means that the output voltage is reduced; b) Boost mode. For example... Figure 4 As shown, in this mode, Keep closed. Keep disconnected. and Complementary conduction. When When the circuit is closed, let the closing time be... ,at this time To inductor Charging, charging current is , The energy stored in an inductor over a given time is represented by WL, that is: ; exist Within a time period It is in the disconnected state. It is in a closed state. With inductance At the same time give During the charging and power supply process, the energy released by the inductor is: .

[0029] When the circuit is in a steady state, according to the law of conservation of energy, the energy stored in the inductor is equal to the energy released within one cycle, that is, ; Simplifying, we get ; visible This means that the output voltage is increased; (3) Control process of multiphase boost / buck converter in hydrogen production mode Current distribution The problem solved by the current distribution stage is given a total electrolysis current. How to distribute the electrolytic current to each phase in a multiphase step-up / step-down converter? Specific method: a) Offline testing of different DC bus voltages for each phase Different output currents ( N is the total number of phases; in this example, it is the efficiency characteristic under N 3). .

[0030] b) Construct the optimization problem: ; In the formula, This is the current density versus voltage function of the electrolytic cell; The effective working area of ​​the electrolytic cell is in units of ; This refers to the number of electrolysis chambers in the electrolytic cell.

[0031] The control variables for the above optimization problem are: and the number of phases n of the buck-boost converter in operation ( The optimization objective is to minimize J, and the constraints are: ; ; In the above formula, and These are the minimum and maximum output currents of the i-th phase, respectively.

[0032] c) The above optimization problem belongs to mixed integer nonlinear programming problem, which can be solved by algorithms such as particle swarm optimization algorithm, IPOPT solver, and dynamic programming (the specific solution method and process are not the subject of this invention).

[0033] d) Solution complete, output the optimal number of phases n and the operating current of each phase. .

[0034] Load current outer loop PI control With single-phase operating current and the detected value of the phase load current The difference is used as the input to construct an outer-loop PI controller for the load current. After limiting, the controller's final output is... ; In the formula, and For controller PI parameters; Let k be the load current deviation. ; To control the cycle; This is the maximum output voltage value on the right.

[0035] Voltage-controlled PI loop Single-phase given voltage and the output voltage detection value of this phase The difference is used as the input to construct a voltage-loop PI controller. After limiting, the final output of this controller is: ; In the formula, and For controller PI parameters; The voltage deviation at time k is the value from the given value. ; This represents the maximum value of the inductor current on the left and right sides.

[0036] In the above formula, when in buck mode, Keep disconnected. Keep closed. and Complementary conduction, inductor current flows through The feedback current is The current is given as In boost mode, Keep closed. Keep disconnected. and Complementary conduction, inductor current flows through The feedback current is The current is given as ; ④ Inner loop PI control of inductor current Single-phase given inductor current and the detected value of the output inductor current of that phase The difference is used as the input to construct an inner-loop PI controller for the inductor current. After limiting, the final output of this controller is... ; In the formula, and For controller PI parameters; Let k be the deviation of the inductor current from the given value. .

[0037] In the above formula, Indicates taking or When in buck mode, take In boost mode, take . Indicates taking or When in buck mode, take In boost mode, take .

[0038] ⑤ Determining the boost / buck mode The function of this step is based on and the set threshold The operating mode of each phase is determined. The specific method is the hysteresis comparison method.

[0039] like Figure 6 As shown, for each phase converter, the system operates in boost mode during startup, and a threshold value is set. Only when The phase switches from boost mode to buck mode; in buck mode, such as Switch to boost mode; to Within the interval, the phase mode is determined by the mode of the previous time step.

[0040] In boost mode, the duty cycle signal output by the inner loop PI controller of the inductor current. Effect to and Inductor current flows through The feedback current is In buck mode, the duty cycle signal output by the inner loop PI controller of the inductor current... Effect to and Inductor current flows through The feedback current is .

[0041] (4) Boost and buck modes of bidirectional buck-boost converter under power generation In power generation mode (right side is input, left side is output), the analysis of buck and boost working modes is as follows.

[0042] Buck mode. (For example) Figure 7 As shown, in this mode, Keep disconnected. Keep closed. and Complementary conduction. Let... The time in the on-state is ,exist The Inner Canon To inductor It supplies power to the load while charging. When In a state of discontinuity When in the on-state, let time be... At this time, the energy stored in the inductor is given Power supply. Since the energy in the inductor is conserved within one period T, we can obtain... ; In the formula, it can be seen that This means that the output voltage is reduced.

[0043] Boost mode. (For example...) Figure 8 As shown, in this mode, Keep closed. Keep disconnected. and Complementary conduction. When When the circuit is closed, let the closing time be... ,at this time To inductor Charging, charging current is , The energy stored in the inductor during the time period is used This means, that is: .

[0044] exist Within a time period It is in the disconnected state. It is in a closed state. With inductance At the same time give During the charging and power supply process, the energy released by the inductor is: .

[0045] When the circuit is in a steady state, according to the law of conservation of energy, the energy stored in the inductor is equal to the energy released within one cycle, that is: ; Simplifying, we get ; visible This means that the output voltage on the right side is increased; Control process of multiphase step-up / step-down converter in power generation mode; Bus voltage PI control The problem that bus voltage PI control solves is determining the generation current of the fuel cell system when the rectifier / inverter is operating in inverter mode and generating electricity at a specific power output. . Specific methods: bus voltage setpoint Actual value of bus voltage The difference is used as input to construct a bus voltage PI controller. After limiting, the final output of this controller is... ; In the formula, and For controller PI parameters; The bus deviation at time k ; This represents the maximum output current of the fuel cell stack. (The obtained value is missing from the original text.) The values ​​are sent to the fuel cell control system at the same time as the "phase current distribution" module, so that the fuel cell control system can control the anode pressure, cathode pressure, cathode flow and other parameters of the fuel cell stack at the optimal values ​​and output the corresponding electric power efficiently.

[0046] Current distribution in each phase The function of this module is: to... The operating current is evenly distributed to each phase of the multi-phase step-up / step-down converter to obtain the target value of the operating current for each phase. Here, since the "phase current distribution" is located in the inner loop of the bus voltage PI controller and requires high processing speed, an average distribution scheme is adopted for its current distribution.

[0047] Current PI control With single-phase given current * and the detected value of the output inductor current of that phase The difference is used as the input to construct an inductor current PI controller. After limiting, the final output of this controller is...

[0048] In the formula, and For controller PI parameters; Let k be the deviation of the inductor current from the given value. .

[0049] In the above formula, Indicates taking or When in buck mode, take In boost mode, take . Indicates taking or When in buck mode, take In boost mode, take .

[0050] Boost / buck mode determination The function of this step is based on and the set threshold The operating mode of each phase is determined. The specific method is the hysteresis comparison method. Here, ; , This refers to the output voltage of the fuel cell stack. like Figure 10 As shown, for each phase converter, the system operates in boost mode during startup, and a threshold value is set. Only when The phase switches from boost mode to buck mode; in buck mode, such as Switch to boost mode; to Within the interval, the phase mode is determined by the mode of the previous time step.

[0051] In boost mode, the duty cycle signal output by the current PI controller Effect to and Inductor current flows through The feedback current is In buck mode, the duty cycle signal output by the inner loop PI controller of the inductor current... Effect to and Inductor current flows through The feedback current is ; (6) Phase interleaving mechanism of multiphase step-up converter During hydrogen production and power generation, regardless of whether it is in buck or boost mode, the initial phase difference of the three phases in the multiphase boost / buck converter... Thus, the total output current ripple frequency is N times the ripple frequency of each phase, requiring a filter inductor. It has a smaller inductance value and is lighter.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly integrated hydrogen production and power generation system, characterized in that, It includes a power conversion unit, a switching unit, a hydrogen production unit, and a power generation unit; The power conversion unit includes a three-level rectifier / inverter and a multi-phase multi-bidirectional buck-boost converter. The three-level rectifier / inverter is connected to the power grid, and the multi-phase multi-bidirectional buck-boost converter is connected between the three-level rectifier / inverter and the switching unit. The switching unit is used to selectively connect the multiphase multi-bidirectional buck-boost converter to the hydrogen production unit, or the multiphase multi-bidirectional buck-boost converter to the power generation unit. In hydrogen production mode, the three-level rectifier / inverter converts the grid AC power into DC power, and the multi-phase multi-bidirectional buck-boost converter converts the DC power into DC power adapted to the hydrogen production unit. In power generation mode, the multiphase multi-bidirectional buck-boost converter converts the DC power output from the power generation unit into DC power adapted to the three-level rectifier / inverter, and the three-level rectifier / inverter inverts the DC power into AC power and feeds it into the power grid.

2. The highly integrated hydrogen production and power generation system according to claim 1, characterized in that, The multiphase multi-stage bidirectional buck-boost converter is composed of at least two bidirectional buck-boost converters connected in parallel. The bidirectional buck-boost converter adopts a left-right symmetrical circuit topology, and the right side of the bidirectional buck-boost converter is provided with a hydrogen production current detection resistor, while the left and right sides are respectively provided with inductor current detection resistors for boost and buck modes.

3. The highly integrated hydrogen production and power generation system according to claim 1, characterized in that, The switching unit includes a first switch group and a second switch group; The first switch group is used to control the on / off state of the multiphase multi-bidirectional buck-boost converter and the hydrogen production unit, and the second switch group is used to control the on / off state of the multiphase multi-bidirectional buck-boost converter and the power generation unit. In hydrogen production mode, the first switch group is closed and the second switch group is open; In power generation mode, the second switch group is closed and the first switch group is open.

4. The highly integrated hydrogen production and power generation system according to claim 1, characterized in that, The initial phase difference between each phase of the multiphase bidirectional buck-boost converter is 2π / N, where N is the total number of phases of the multiphase bidirectional buck-boost converter.

5. The highly integrated hydrogen production and power generation system according to claim 1, characterized in that, It also includes a step-up transformer, which is connected between the three-level rectifier / inverter and the power grid to achieve voltage level conversion and electrical isolation.

6. The highly integrated hydrogen production and power generation system according to claim 1, characterized in that, The hydrogen production unit is an alkaline electrolyzer, a PEM electrolyzer, or a solid oxide electrolyzer; the power generation unit is a proton exchange membrane fuel cell; and the three-level rectifier / inverter is a T-type three-level rectifier / inverter, which includes fully controlled switching devices.

7. A highly integrated hydrogen production and power generation control method, applied to the highly integrated hydrogen production and power generation system described in any one of claims 1-6, characterized in that, include: By selectively connecting the multiphase multi-bidirectional buck-boost converter to the hydrogen production unit or the multiphase multi-bidirectional buck-boost converter to the power generation unit through the switching unit, the switching between hydrogen production mode and power generation mode can be realized. In hydrogen production mode, the three-level rectifier / inverter is controlled to rectify the AC power from the grid into DC power, and the multi-phase multi-bidirectional buck-boost converter is controlled to work in the current closed-loop control mode to convert the DC power into DC power adapted to the hydrogen production unit. In power generation mode, the multi-phase bidirectional step-up / step-down converter is controlled to operate in voltage closed-loop control mode, converting the DC power output from the power generation unit into DC power adapted to the three-level rectifier / inverter, and controlling the three-level rectifier / inverter to invert the DC power into AC power and feed it into the power grid.

8. The highly integrated hydrogen production and power generation control method according to claim 7, characterized in that, It also includes the step of optimizing the multiphase output current allocation based on the efficiency characteristics of each phase bidirectional buck-boost converter: a) Offline testing of the efficiency model of each phase converter under different bus voltages and different output currents; b) Construct an optimization objective function that includes the current density-voltage function of the electrolytic cell, the number of electrolytic cells, and the efficiency model of each phase, and solve for the optimal number of phases to be put into operation and the operating current of each phase; c) The constraint condition of the optimization objective function is that the sum of the currents of each phase is equal to the total electrolysis current, and the current of each phase is between its minimum output current and maximum output current.

9. The highly integrated hydrogen production and power generation control method according to claim 7, characterized in that, The voltage closed-loop control includes bus voltage PI control and inductor current PI control: a) Using the deviation between the given value and the actual value of the bus voltage as input, the target current of the fuel cell is output through PI control; the target current is evenly distributed to each phase bidirectional buck-boost converter to obtain the target current value of each phase. b) Using the deviation between the target value of each phase current and the detected value of the inductor current as input, the duty cycle signal is output through PI control to adjust the working state of the converter.

10. The highly integrated hydrogen production and power generation control method according to claim 1, characterized in that, The multiphase, multi-stage, bidirectional buck-boost converter achieves automatic switching between boost and buck modes through a hysteresis comparator method. a) In hydrogen production mode, the voltage on the left side of the converter is compared with the voltage on the right side in real time. When the voltage on the left side is greater than the sum of the voltage on the right side and the threshold, the converter switches to buck mode. When the voltage on the left side is less than the difference between the voltage on the right side and the threshold, the converter switches to boost mode. b) In power generation mode, the voltage on the right side of the converter is compared with the voltage on the left side in real time. When the voltage on the right side is greater than the sum of the voltage on the left side and the threshold, the converter switches to buck mode. When the voltage on the right side is less than the difference between the voltage on the left side and the threshold, the converter switches to boost mode. When the voltage is within the threshold range, the operating mode of the previous moment is maintained.

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