Power coordination control method for electricity-hydrogen hybrid energy storage island microgrid

Abstract

The invention discloses an electricity-hydrogen hybrid energy storage island micro-grid power coordination control method, and belongs to the technical field of electricity-hydrogen hybrid energy storage island micro-grid control. The method comprises the following steps: acquiring system electrical parameters and an alkaline electrolytic cell operation temperature in real time; five operation modes of the electrolytic cell are divided according to the direct-current bus voltage, and adaptive droop control is executed on the electrolytic cell by combining the operation temperature and the bus voltage; based on the bus voltage and the voltage change rate, virtual-like synchronous generator control including virtual damping and virtual inertia is executed on the energy storage unit; and the power fluctuation is stabilized through the synergistic effect of the two. The method is mainly used for power coordination control of the electricity-hydrogen hybrid energy storage island micro-grid, can maintain the stability of the DC bus voltage, prolongs the service life of the electrolytic cell, and improves the operation reliability of the micro-grid.

Description

Technical Field

[0001] This invention belongs to the field of microgrid control technology, specifically relating to the power coordination control technology of an islanded microgrid with hybrid electric-hydrogen energy storage. Background Technology

[0002] With the increasing prominence of energy crises and environmental pollution, renewable and clean energy sources, such as solar and wind power, are being increasingly widely used in distributed generation. This can optimize the traditional energy structure and promote the sustainable development of the energy economy and the environment. Hydrogen, as a clean energy source, has the characteristics of high energy density, large capacity, and easy storage and transmission. It can serve as an energy medium to help the efficient utilization of renewable energy, thus giving rise to the development of hybrid electric-hydrogen energy storage island microgrids.

[0003] Hybrid hydrogen-electricity storage islanded microgrids need to operate independently from the main grid, and system power fluctuations rely entirely on self-regulation, which places high demands on control strategies. However, renewable energy generation is inherently intermittent and volatile, and the electrolysis hydrogen production load has specific requirements for power supply, leading to problems such as bus voltage fluctuations and uneven power distribution during the operation of existing microgrids.

[0004] Current control strategies for such microgrids are not fully adapted to the system characteristics. On the one hand, they fail to consider the impact of alkaline electrolyzer operating temperature on its output, making it impossible to dynamically adjust control parameters based on temperature changes. On the other hand, the coordinated control mechanism between the energy storage unit and the electrolyzer is not perfect, making it difficult to effectively mitigate power surges caused by renewable energy fluctuations. This results in significant power fluctuations in the electrolyzer, affecting not only hydrogen production stability but also potentially shortening equipment lifespan. Furthermore, unstable bus voltage can also impact the reliable operation of the entire microgrid. Developing a coordinated control strategy adapted to the characteristics of hybrid hydrogen-electricity storage islanded microgrids, balancing renewable energy fluctuations with equipment response speed, and suppressing bus voltage and equipment power fluctuations have become pressing technical challenges in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a power coordination control method for an islanded microgrid with hybrid electric-hydrogen energy storage, which can solve the problems of bus voltage fluctuation and electrolyzer power fluctuation caused by renewable energy fluctuations, improve the operational stability of the microgrid, and extend the service life of the equipment.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for coordinated power control of an isolated microgrid with hybrid electric-hydrogen energy storage includes the following steps:

[0008] The system operating parameters and alkaline electrolyzer operating temperature are acquired in real time, and the system operating parameters include the DC bus voltage;

[0009] The operating mode of the alkaline electrolyzer is determined based on the DC bus voltage.

[0010] Using the operating temperature and DC bus voltage, adaptive droop control is performed on the alkaline electrolyzer to obtain a reference value for the electrolyzer's operating power.

[0011] Based on the DC bus voltage and voltage change rate, virtual synchronous generator control with virtual damping and virtual inertia is performed on the energy storage unit to obtain the outer loop reference value of the energy storage unit voltage.

[0012] By using the reference value of the electrolytic cell's operating power and the reference value of the outer loop voltage of the energy storage unit, the system power fluctuations are mitigated in a coordinated manner, and the DC bus voltage is kept stable.

[0013] In one possible implementation, when obtaining the system operating parameters, the DC bus voltage is measured by a voltage sensor, and the bus-side output current and battery-side input current of the DC-DC converter in the energy storage unit, as well as the input current and input voltage of the alkaline electrolyzer, are measured by a current sensor; when obtaining the operating temperature of the alkaline electrolyzer, it is measured by a temperature sensor.

[0014] In one possible implementation, when classifying the operating modes of the alkaline electrolyzer, the operating modes are divided into constant power operating mode, bus voltage rise and fall control mode, bus voltage fall and fall control mode, maximum power operating mode, and minimum power operating mode according to the preset range of the DC bus voltage.

[0015] In one possible implementation, when determining the constant power operation mode, if the DC bus voltage is within a first preset range, then this mode is determined; when determining the bus voltage rise / fall control mode, if the DC bus voltage is within a second preset range, then this mode is determined; when determining the bus voltage fall / fall control mode, if the DC bus voltage is within a third preset range, then this mode is determined; when determining the maximum power operation mode, if the DC bus voltage reaches the safe operating upper limit, then this mode is determined; when determining the minimum power operation mode, if the DC bus voltage reaches the safe operating lower limit, then this mode is determined.

[0016] In one possible implementation, when performing the adaptive droop control, an adaptive droop control law is used to calculate the reference value of the electrolytic cell operating power for the constant power operation mode, the bus voltage rise droop control mode, and the bus voltage fall droop control mode; the adaptive droop control law is constructed by combining the droop coefficient, the DC bus voltage, the DC bus rated voltage, and the power reference value.

[0017] In one possible implementation, when calculating the reference value of the electrolytic cell's operating power, the maximum power of the alkaline electrolytic cell is obtained by fitting the current operating temperature; the minimum power of the alkaline electrolytic cell is set as a preset ratio of its rated power; and the range of the reference value of the electrolytic cell's operating power is limited by the maximum power and the minimum power.

[0018] In one possible implementation, when performing the virtual synchronous generator control, a control law is constructed based on the DC bus rated voltage, virtual damping, virtual inertia, and DC bus voltage to establish the outer loop reference value of the energy storage unit voltage; the virtual damping and virtual inertia are dynamically adjusted according to the initial values, adjustment coefficients, and DC bus voltage change rate under steady-state conditions.

[0019] In one possible implementation, when calculating the virtual damping, the initial value of the virtual damping under steady-state conditions and the adjustment coefficient are used, combined with the DC bus voltage change rate for dynamic calculation; when calculating the virtual inertia, the initial value of the virtual inertia under steady-state conditions and the adjustment coefficient are used, combined with the DC bus voltage change rate for dynamic calculation.

[0020] In one possible implementation, when coordinating the mitigation of system power fluctuations, the input power of the alkaline electrolyzer is adjusted by the reference value of the electrolyzer's operating power, and the charging and discharging power of the energy storage unit is adjusted by the reference value of the outer loop voltage of the energy storage unit; the two work together to respond to changes in system source load power and suppress DC bus voltage fluctuations.

[0021] In one possible implementation, the power reference value is given by the system output plan; the droop coefficient is set according to the operating characteristics of the alkaline electrolyzer and the system stability requirements, and is used to balance the power regulation sensitivity and system stability.

[0022] Compared with the prior art, the beneficial effects of this invention are as follows: Addressing the limitation of existing technologies that do not consider the impact of temperature on the output of the electrolyzer, this invention uses a temperature sensor to obtain the operating temperature of the alkaline electrolyzer in real time, and obtains the maximum power of the electrolyzer based on temperature fitting. This allows the reference value of the electrolyzer's operating power to adapt to temperature changes, thereby avoiding unreasonable fluctuations in output caused by temperature under fixed power control, reducing equipment wear, extending the service life of the electrolyzer, and ensuring the stable operation of the hydrogen production process.

[0023] Five operating modes based on DC bus voltage enable the electrolytic cell to accurately respond to different voltage conditions. It maintains constant power operation when voltage fluctuations are small, adjusts power through droop control when voltage rises or falls significantly, and operates at extreme power when the voltage reaches safety limits. Compared to existing single control modes, this more comprehensively suppresses source load power fluctuations and maintains stable bus voltage. The adaptive droop control law in normal operation mode dynamically adjusts power based on the difference between bus voltage and rated voltage, further enhancing the flexibility and targeting of voltage regulation.

[0024] The energy storage unit employs a quasi-virtual synchronous generator control system with virtual damping and virtual inertia, addressing the lack of inertial support in traditional energy storage control. The virtual damping and virtual inertia are dynamically adjusted according to the bus voltage change rate, enabling rapid response to voltage fluctuations while providing inertial buffering to reduce the impact of voltage surges. This control method provides stable support for the DC bus voltage, enhancing the microgrid's ability to cope with the intermittency and volatility of renewable energy sources.

[0025] The coordinated control mechanism of the electrolyzer and energy storage unit achieves complementary power regulation. The electrolyzer smooths out low- and medium-frequency power fluctuations through power adjustment, while the energy storage unit addresses high-frequency fluctuations through charging and discharging power regulation. Together, they respond to changes in system source-load power, more efficiently smoothing power fluctuations and stabilizing the bus voltage compared to single-device control. Simulation results show that, compared to traditional droop control, this invention significantly reduces bus voltage fluctuations and electrolyzer power fluctuations in photovoltaic power fluctuation scenarios, fully verifying the superiority of coordinated control.

[0026] Overall, this invention solves the problems of voltage fluctuation and uneven power distribution in existing hybrid electric-hydrogen energy storage islanded microgrids through targeted control strategy design, thereby improving the stability and reliability of microgrid operation. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a DC microgrid structure according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the relationship between the maximum power and operating temperature of the electrolytic cell in an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the photovoltaic power fluctuation curve according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the electrolytic cell power simulation results according to an embodiment of the present invention;

[0032] Figure 5 This is a comparative diagram of DC bus voltage simulation results in an embodiment of the present invention;

[0033] Figure 6This is a flowchart illustrating the power coordination control method for an islanded microgrid with hybrid electric-hydrogen energy storage, according to an embodiment of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0035] Example:

[0036] It should be noted that the terms "comprising" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0037] This embodiment presents a power coordination control method for an isolated microgrid with hybrid electric-hydrogen energy storage, applicable to... Figure 1 The DC microgrid system includes a photovoltaic power generation system, an alkaline electrolyzer for water electrolysis and hydrogen production, an energy storage system, AC loads, DC loads, and a DC bus. The photovoltaic power generation system and the energy storage system are directly connected to the DC bus, supplying power to it. The alkaline electrolyzer is directly connected to the DC bus, obtaining power from it. The DC loads are directly connected to the DC bus, obtaining power from it. The AC loads are connected to the DC bus via a power conversion device, obtaining power from it.

[0038] like Figure 6 As shown, the method may include the following steps:

[0039] Step 101: Real-time acquisition of system operating parameters and alkaline electrolytic cell operating temperature, wherein the system operating parameters include DC bus voltage.

[0040] Specifically, the system operating parameters can be DC bus voltage, converter current, electrolytic cell input current and voltage, etc., and the alkaline electrolytic cell operating temperature can be the shell temperature of the electrolytic cell during operation.

[0041] Specifically, when acquiring the system operating parameters, the DC bus voltage is measured by a voltage sensor, and the bus-side output current and battery-side input current of the DC-DC converter in the energy storage unit, as well as the input current and input voltage of the alkaline electrolyzer, are measured by a current sensor; the operating temperature of the alkaline electrolyzer is obtained by measuring it using a temperature sensor.

[0042] Specifically, the voltage sensor can be a Hall voltage sensor; the current sensor can be a closed-loop Hall current sensor; and the temperature sensor can be a PT100 platinum resistance sensor, with the DC bus voltage set. The bus-side output current of the DC-DC converter in the energy storage unit Input current on the battery side; input current of the alkaline electrolyzer. With input voltage Operating temperature of alkaline electrolytic cell .

[0043] Step 102: Determine the operating mode of the alkaline electrolyzer based on the DC bus voltage.

[0044] When classifying the operating modes of the alkaline electrolyzer, the operating modes are divided into constant power operating mode, bus voltage rise and fall control mode, bus voltage fall and fall control mode, maximum power operating mode, and minimum power operating mode according to the preset range of DC bus voltage.

[0045] Specifically, the constant power operation mode is the mode in which the electrolytic cell operates at a fixed power, which is suitable when the bus voltage fluctuation is small; the bus voltage rise-and-droop control mode is the mode in which the power of the electrolytic cell increases with the voltage when the bus voltage rises; the bus voltage fall-and-droop control mode is the mode in which the power of the electrolytic cell decreases with the voltage when the bus voltage falls; the maximum power operation mode is the mode in which the electrolytic cell operates at the maximum allowable power at the current temperature; and the minimum power operation mode is the mode in which the electrolytic cell operates at the minimum allowable power.

[0046] Furthermore, when determining the constant power operation mode, if the DC bus voltage is within a first preset range, then this mode is determined; when determining the bus voltage rise / fall control mode, if the DC bus voltage is within a second preset range, then this mode is determined; when determining the bus voltage fall / fall control mode, if the DC bus voltage is within a third preset range, then this mode is determined; when determining the maximum power operation mode, if the DC bus voltage reaches the safe operating upper limit, then this mode is determined; when determining the minimum power operation mode, if the DC bus voltage reaches the safe operating lower limit, then this mode is determined.

[0047] For example, constant power operation mode:

[0048] In this mode, the DC bus voltage fluctuation is relatively small. To reduce power fluctuations in the electrolyzer and extend its service life, the electrolyzer operates at a constant power. During operation, the power reference value is given by the output plan.

[0049] Bus voltage rise / fall control mode:

[0050] In this mode, the DC bus voltage increases significantly. The electrolyzer operates with droop control, and the operating power increases with the bus voltage to suppress source-load power fluctuations.

[0051] Bus voltage drop droop control mode:

[0052] In this mode, the DC bus voltage drops significantly. The electrolyzer operates with droop control, and the operating power decreases with the bus voltage to suppress source-load power fluctuations.

[0053] Maximum power operation mode:

[0054] In this mode, the DC bus voltage reaches the upper limit of the safe operating range. The electrolytic cell operates at maximum power. It operates to maintain a stable DC bus voltage.

[0055] Minimum power operation mode:

[0056] In this mode, the DC bus voltage reaches the lower limit of the safe operating range. The electrolytic cell operates at minimum power to maintain a stable DC bus voltage.

[0057] Step 103: Using the operating temperature and DC bus voltage, perform adaptive droop control on the alkaline electrolyzer to obtain a reference value for the electrolyzer's operating power.

[0058] Specifically, adaptive droop control is a dynamic droop adjustment method that takes into account temperature and bus voltage.

[0059] Specifically, when implementing the adaptive droop control, for constant power operation mode, bus voltage rise droop control mode, and bus voltage fall droop control mode, the adaptive droop control law is used to calculate the reference value of the electrolytic cell operating power; the adaptive droop control law is constructed by combining the droop coefficient, DC bus voltage, DC bus rated voltage and power reference value.

[0060] Specifically, the adaptive droop control law is a mathematical expression for dynamically adjusting the power of the electrolyzer; the droop coefficient is used to adjust the power sensitivity to voltage changes; and the power reference value can be given by the output plan.

[0061] For constant power operation mode, bus voltage rise-and-droop control mode, and bus voltage fall-and-droop control mode, the electrolytic cell adopts an adaptive droop strategy that considers operating temperature and DC bus voltage for control. The control law is as follows:

[0062] This is a reference value for the operating power of the electrolytic cell after adjustment. This is the droop coefficient; The minimum power required for hydrogen production in the electrolyzer is 20% of the electrolyzer's rated power.

[0063] Furthermore, when calculating the reference value of the electrolytic cell's operating power, the maximum power of the alkaline electrolytic cell is obtained by fitting the current operating temperature; the minimum power of the alkaline electrolytic cell is set as a preset ratio of its rated power; and the range of the reference value of the electrolytic cell's operating power is limited by the maximum power and the minimum power.

[0064] The parameters of the control law are determined according to the following formula:

[0065] In the formula, The minimum power required for hydrogen production in the electrolyzer is taken as 20% of the electrolyzer's rated power. This represents the maximum power of the electrolyzer at the current operating temperature. The relationship between operating temperature and temperature is shown in the graph below. Figure 2 As shown, its expression is obtained through fitting:

[0066] In the formula, This is the rated power of the electrolytic cell.

[0067] Step 104: Based on the DC bus voltage and voltage change rate, perform virtual synchronous generator control with virtual damping and virtual inertia on the energy storage unit to obtain the outer loop reference value of the energy storage unit voltage.

[0068] Specifically, virtual synchronous generator control is an energy storage control method that includes virtual damping and virtual inertia.

[0069] Specifically, when executing the virtual synchronous generator control, a control law is constructed based on the DC bus rated voltage, virtual damping, virtual inertia, and DC bus voltage to establish the outer loop reference value of the energy storage unit voltage; the virtual damping and virtual inertia are dynamically adjusted according to the initial value, adjustment coefficient, and DC bus voltage change rate under steady-state conditions.

[0070] Specifically, for the energy storage unit, a virtual synchronous generator (AVSG) control system with virtual damping and virtual inertia is adopted, and the control law is as follows:

[0071] In the formula: This is the rated voltage of the DC bus. For virtual damping, This is the outer loop reference value for the energy storage unit voltage. This is virtual inertia.

[0072] Furthermore, when calculating the virtual damping, the initial value and adjustment coefficient of the virtual damping under steady-state conditions are used, combined with the DC bus voltage change rate for dynamic calculation; when calculating the virtual inertia, the initial value and adjustment coefficient of the virtual inertia under steady-state conditions are used, combined with the DC bus voltage change rate for dynamic calculation.

[0073] Specifically, the virtual inertia and virtual damping are determined according to the following formula: ;

[0074] In the formula , For the virtual damping and virtual inertia in a steady state; , , , This is the adjustment coefficient; This represents the rate of change of bus voltage.

[0075] Step 105: By using the reference value of the electrolytic cell operating power and the reference value of the outer loop voltage of the energy storage unit, the system power fluctuations are smoothed in a coordinated manner to maintain the stability of the DC bus voltage.

[0076] Specifically, when coordinating the mitigation of system power fluctuations, the input power of the alkaline electrolyzer is adjusted using the reference value of the electrolyzer's operating power, and the charging and discharging power of the energy storage unit is adjusted using the outer loop reference value of the energy storage unit's voltage. These two methods work together to respond to changes in system source load power and suppress DC bus voltage fluctuations. The power reference value is given by the system output plan; the droop coefficient is set according to the operating characteristics of the alkaline electrolyzer and the system stability requirements, used to balance power regulation sensitivity and system stability.

[0077] For example, when the photovoltaic output suddenly increases by 10kW, causing the DC bus voltage to rise to 815V, the coordinating controller determines that the electrolytic cell is in the bus voltage rise-droop control mode, calculates the reference value of the electrolytic cell's operating power to be 39.5kW, and after receiving the instruction, the electrolytic cell increases its input power to absorb 7.5kW of the excess 10kW power. At the same time, the coordinating controller calculates the outer loop reference value of the energy storage unit voltage and controls the energy storage unit's DC-DC converter to discharge 3.5kW to absorb the remaining excess power. The two work together to make the bus voltage quickly drop back to 805V. When the load suddenly decreases by 8kW and the voltage drops to 785V, the electrolytic cell power reference value is adjusted to 24.5kW, reducing the input power by 7.5kW, and the energy storage unit charges by 0.5kW, coordinating to respond to the power gap and maintain voltage stability. The system output plan can be a daily output curve based on photovoltaic (PV) forecasts. The system output plan is formulated based on PV output forecasts, load demand, and hydrogen production demand. For example, if PV output is sufficient from 9:00 AM to 5:00 PM daily, the reference power for the electrolyzer is set at 32 kW. After 5:00 PM, PV output decreases, and the power is adjusted to 25 kW. The droop factor is set based on the electrolyzer's operating characteristics and system stability requirements. If the electrolyzer's power adjustment response is fast (200ms), and the system has high stability requirements, a droop factor of 0.3 kW / V is set to reduce power adjustment sensitivity and avoid system oscillation. If the electrolyzer's response is slow (500ms), and the system needs rapid adjustment, a droop factor of 0.7 kW / V is set to increase sensitivity and quickly respond to voltage changes. The droop factor can be adjusted through the coordinating controller's configuration interface to adapt to different operating scenarios.

[0078] To fully verify the practical application effect of the proposed electro-hydrogen hybrid energy storage islanded microgrid power coordination control method, this embodiment conducts a comparative simulation experiment between the coordination control strategy and the traditional droop control strategy.

[0079] The specific simulation parameters are set as follows: the rated power of the photovoltaic power generation system is 120 kW; the rated power of the alkaline electrolyzer is 50 kW; the rated capacity of the lithium battery energy storage unit is 15 kW; the system load is set to 40 kW; the rated voltage of the DC bus is 800 V; and the reference value for the hydrogen production power of the electrolyzer is 32 kW.

[0080] The results of this comparative simulation are as follows: Figure 3 , Figure 4 , Figure 5As shown in the figure, analysis of simulation data reveals that, compared to traditional droop control strategies, this invention effectively reduces the fluctuation amplitude of the DC bus voltage and also reduces the fluctuation of hydrogen production power in the alkaline electrolyzer when photovoltaic power fluctuates. Furthermore, this coordinated control strategy provides inertial support for the DC bus voltage, improving system stability. Simultaneously, the reduction in power fluctuations in the alkaline electrolyzer reduces losses during equipment operation, thereby extending the lifespan of the alkaline electrolyzer.

[0081] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0082] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A power coordination control method for an isolated microgrid with hybrid electric-hydrogen energy storage, characterized in that, Including the following steps: The system operating parameters and alkaline electrolyzer operating temperature are acquired in real time, and the system operating parameters include the DC bus voltage; The operating mode of the alkaline electrolyzer is determined based on the DC bus voltage. Using the operating temperature and DC bus voltage, adaptive droop control is performed on the alkaline electrolyzer to obtain a reference value for the electrolyzer's operating power. Based on the DC bus voltage and voltage change rate, virtual synchronous generator control with virtual damping and virtual inertia is performed on the energy storage unit to obtain the outer loop reference value of the energy storage unit voltage. By using the reference value of the electrolytic cell's operating power and the reference value of the outer loop voltage of the energy storage unit, the system power fluctuations are mitigated in a coordinated manner, and the DC bus voltage is kept stable.

2. The method according to claim 1, characterized in that, When obtaining the system operating parameters, the DC bus voltage is measured by a voltage sensor, and the bus-side output current and battery-side input current of the DC-DC converter in the energy storage unit, as well as the input current and input voltage of the alkaline electrolyzer, are measured by a current sensor; the operating temperature of the alkaline electrolyzer is obtained by measuring it with a temperature sensor.

3. The method according to claim 1, characterized in that, When classifying the operating modes of the alkaline electrolyzer, the operating modes are divided into constant power operating mode, bus voltage rise and fall control mode, bus voltage fall and fall control mode, maximum power operating mode, and minimum power operating mode according to the preset range of DC bus voltage.

4. The method according to claim 3, characterized in that, When determining the constant power operation mode, if the DC bus voltage is within a first preset range, then this mode is determined; when determining the bus voltage rise / fall control mode, if the DC bus voltage is within a second preset range, then this mode is determined; when determining the bus voltage fall / fall control mode, if the DC bus voltage is within a third preset range, then this mode is determined; when determining the maximum power operation mode, if the DC bus voltage reaches the safe operating upper limit, then this mode is determined; when determining the minimum power operation mode, if the DC bus voltage reaches the safe operating lower limit, then this mode is determined.

5. The method according to claim 1, characterized in that, When executing the adaptive droop control, for constant power operation mode, bus voltage rise droop control mode, and bus voltage fall droop control mode, the adaptive droop control law is used to calculate the reference value of the electrolytic cell operating power; the adaptive droop control law is constructed by combining the droop coefficient, DC bus voltage, DC bus rated voltage and power reference value.

6. The method according to claim 5, characterized in that, When calculating the reference value of the operating power of the electrolytic cell, the maximum power of the alkaline electrolytic cell is obtained by fitting the current operating temperature; the minimum power of the alkaline electrolytic cell is set as a preset ratio of its rated power; the range of the reference value of the operating power of the electrolytic cell is limited by the maximum power and the minimum power.

7. The method according to claim 1, characterized in that, When executing the virtual synchronous generator control, a control law is constructed based on the DC bus rated voltage, virtual damping, virtual inertia, and DC bus voltage to determine the outer loop reference value of the energy storage unit voltage. The virtual damping and virtual inertia are dynamically adjusted according to their initial values, adjustment coefficients, and DC bus voltage change rate under steady-state conditions.

8. The method according to claim 7, characterized in that, When calculating the virtual damping, the initial value and adjustment coefficient of the virtual damping under steady state are used, combined with the DC bus voltage change rate for dynamic calculation; when calculating the virtual inertia, the initial value and adjustment coefficient of the virtual inertia under steady state are used, combined with the DC bus voltage change rate for dynamic calculation.

9. The method according to claim 1, characterized in that, When coordinating to mitigate system power fluctuations, the input power of the alkaline electrolyzer is adjusted by the reference value of the electrolyzer's operating power, and the charging and discharging power of the energy storage unit is adjusted by the reference value of the outer loop voltage of the energy storage unit; the two work together to respond to changes in system source load power and suppress DC bus voltage fluctuations.

10. The method according to claim 5, characterized in that, The power reference value is given by the system output plan; the droop coefficient is set according to the operating characteristics of the alkaline electrolyzer and the system stability requirements, and is used to balance the power adjustment sensitivity and system stability.

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