Grid-connected switching control method for micro-grid system of fusion electric hydrogen ammonia and related equipment

Abstract

This application provides a grid-connected switching control method and related equipment for a microgrid system integrating hydrogen, ammonium, and electricity. The microgrid system includes a DC bus and its connected grid-connected converter, hydrogen-ammonium energy device converter, and battery converter. The method includes: upon receiving a grid-connection command, real-time detection of electrical quantity data from the external power grid; controlling the hydrogen-ammonium energy device converter to freeze its power, and then controlling the battery converter to droop; fine-tuning the electrical quantity data of the grid-connected converter until it synchronizes with the electrical quantity data of the external power grid, controlling the microgrid system to establish an electrical connection with the external power grid, and then controlling the grid-connected converter to switch from VSG mode to PQ mode; when the microgrid system is in a grid-connected electrical steady state, acquiring the dispatch power of the hydrogen-ammonium energy device converter and controlling it to adjust its power at a preset ramp rate, while simultaneously controlling the battery converter to adjust its power in the opposite direction. This application can improve the safety of process industrial equipment during grid-connection switching.

Description

Technical Field

[0001] This application relates to the field of microgrid technology, and in particular to grid-connected switching control methods and related equipment for microgrid systems integrating electricity, hydrogen, and ammonia. Background Technology

[0002] In existing technologies, grid connection switching strategies for microgrid systems often focus on the seamless transition of electrical quantities such as voltage, frequency, and phase, seriously neglecting the sensitivity of process and industrial equipment such as hydrogen energy equipment and ammonia energy equipment included in the microgrid system to power fluctuations. Power surges generated during grid connection switching can easily lead to equipment damage, shortened equipment lifespan, or even safety accidents. Summary of the Invention

[0003] The main purpose of this application is to propose a grid-connected switching control method and related equipment for a microgrid system integrating electricity, hydrogen, and ammonia, which can improve the safety of process industrial equipment and the operational stability of the microgrid system during grid-connected switching.

[0004] To achieve the above objectives, one aspect of this application proposes a grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia. The microgrid system includes a DC bus and an energy router. The energy router includes a grid-connected converter, a hydrogen-ammonia energy device converter, and a battery converter connected to the DC bus. The method includes: Upon receiving a grid connection command, the electrical quantity data of the external power grid is monitored in real time. The power of the hydrogen-ammonia energy device converter is frozen, and the droop control of the battery converter is applied to stabilize the voltage of the DC bus. Fine-tune the electrical quantity data of the grid-connected converter until it is synchronized with the electrical quantity data of the external power grid, control the microgrid system to establish an electrical connection with the external power grid, and then control the grid-connected converter to smoothly switch from virtual synchronous generator mode to constant power control mode. When the microgrid system is in grid-connected electrical steady state, the dispatch power of the hydrogen-ammonia energy device converter is obtained, and the hydrogen-ammonia energy device converter is controlled to adjust its power at a preset ramp rate. The battery converter is simultaneously controlled to adjust its power in the opposite direction to maintain stable power exchange between the microgrid system and the external power grid.

[0005] Furthermore, before controlling the hydrogen-ammonia energy device converter to perform power freezing, the following steps are included: A power freeze preparation command is generated and sent to the hydrogen-ammonia energy device converter, and an impact power acceptance preparation command is generated and sent to the battery converter. Receive the ready signals fed back by the hydrogen-ammonia energy device converter and the battery converter.

[0006] Furthermore, the microgrid system is determined to be in a grid-connected electrical steady state in the following way: The voltage of the DC bus and the amplitude and frequency of the AC voltage at the common connection point between the microgrid system and the external power grid are monitored in real time. When the voltage of the DC bus and the amplitude and frequency of the AC voltage at the common connection point remain stable within a first preset time period, the microgrid system is determined to be in a grid-connected electrical steady state.

[0007] Furthermore, the hydrogen-ammonia energy equipment converter includes a hydrogen fuel cell converter, an electrolysis hydrogen production equipment converter, and an ammonia synthesis equipment converter connected to the DC bus; the energy router also includes a photovoltaic equipment converter connected to the DC bus; the method further includes: When the microgrid system is in grid-connected operation, droop control is performed on the battery converter, the hydrogen fuel cell converter, and the electrolytic hydrogen production equipment converter, respectively, and the planned power of the ammonia synthesis equipment converter is obtained and controlled. The voltage of the DC bus is monitored in real time. When the voltage of the DC bus remains higher than a preset voltage threshold for a second preset time period, the photovoltaic converter is controlled to operate with limited power.

[0008] Furthermore, droop control of the battery converter includes: Obtain the current voltage of the DC bus and, in conjunction with the rated voltage of the DC bus, calculate the voltage deviation of the DC bus; The planned power of the battery converter is obtained, and then the planned power of the battery converter is adjusted according to the voltage deviation of the DC bus and the first preset droop coefficient to obtain the target power of the battery converter. The battery converter is controlled according to the target power of the battery converter.

[0009] Furthermore, droop control of the hydrogen fuel cell converter includes: The voltage deviation of the DC bus is processed by a first low-pass filter to obtain the first voltage deviation of the DC bus; The planned power of the hydrogen fuel cell converter is obtained, and then the planned power of the hydrogen fuel cell converter is adjusted according to the first voltage deviation and the second preset droop coefficient of the DC bus to obtain the target power of the hydrogen fuel cell converter; wherein, the second preset droop coefficient is less than the first preset droop coefficient. The hydrogen fuel cell converter is controlled according to the target power of the hydrogen fuel cell converter.

[0010] Furthermore, droop control of the converter in the electrolysis hydrogen production equipment includes: The voltage deviation of the DC bus is processed by a second low-pass filter to obtain a second voltage deviation of the DC bus; wherein the filtering time constant of the second low-pass filter is greater than the filtering time constant of the first low-pass filter. The planned power of the converter of the electrolytic hydrogen production equipment is obtained, and then the planned power of the converter is adjusted according to the second voltage deviation of the DC bus and the third preset droop coefficient to obtain the target power of the converter of the electrolytic hydrogen production equipment; wherein, the third preset droop coefficient is less than the second preset droop coefficient. The converter of the electrolytic hydrogen production equipment is controlled according to the target power of the converter.

[0011] Furthermore, the microgrid system also includes a battery connected to the battery converter; controlling the photovoltaic converter to operate with limited power includes: The maximum allowable charging power of the battery, the local load power of the microgrid system, and the exchange power between the microgrid system and the external power grid are obtained. Combined with the target power of the hydrogen fuel cell converter, the target power of the electrolytic hydrogen production equipment converter, and the planned power of the ammonia synthesis equipment converter, the upper limit power of the photovoltaic equipment converter is calculated. The photovoltaic converter is controlled according to its upper limit power.

[0012] To achieve the above objectives, another aspect of this application proposes an electronic device comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia.

[0013] To achieve the above objectives, another aspect of this application proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia.

[0014] This application includes at least the following beneficial effects: For a microgrid system comprising a DC bus and connected to it a grid-connected converter, a hydrogen-ammonia energy device converter, and a battery converter, upon receiving a grid connection command, it begins to monitor the electrical quantity data of the external power grid in real time. First, it controls the hydrogen-ammonia energy device converter to freeze its power and performs droop control on the battery converter to stabilize the DC bus voltage. Then, it fine-tunes the electrical quantity data of the grid-connected converter until it synchronizes with the electrical quantity data of the external power grid. At the instant of this synchronization, it controls the microgrid system to establish an electrical connection with the external power grid. Finally, it controls the grid-connected converter to smoothly switch from virtual synchronous generator mode to constant voltage mode. In the power control mode, when the microgrid system is in grid-connected electrical steady state, the power of the hydrogen-ammonia energy device converter is adjusted according to the obtained dispatch power of the hydrogen-ammonia energy device converter at a preset ramp rate. At the same time, the battery converter is controlled to adjust the power in the opposite direction to maintain the stable power exchange between the microgrid system and the external grid. By adopting the above-mentioned active timing buffering mechanism of power freezing - battery bearing power impact - power gradual recovery, the impact of power fluctuations on process industrial equipment can be effectively reduced during grid connection switching, thereby improving the safety of process industrial equipment and the operational stability of the microgrid system. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the composition of the microgrid system integrating electricity, hydrogen, and ammonia provided in the embodiments of this application; Figure 2 This is a schematic flowchart of a grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia, provided in an embodiment of this application. Figure 3 This is a schematic diagram of the hardware structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of systems and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0017] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various concepts, but unless otherwise stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words “if,” “when,” or “in response to a determination” as used herein may be interpreted as “when…” or “when…” or “in response to a determination.”

[0018] As used in this application, the terms "at least one", "multiple", "each", "any", etc., "at least one" includes one, two or more, "multiple" includes two or more, "each" refers to each of the corresponding multiples, and "any" refers to any one of the multiples.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0020] Before providing a detailed description of the embodiments of this application, some of the nouns and terms involved in the embodiments of this application will be explained first. The nouns and terms involved in the embodiments of this application are subject to the following interpretations.

[0021] Virtual Synchronous Generator (VSG) mode is an advanced control strategy that uses control algorithms to enable grid-connected power electronic converters to simulate the external characteristics, inertia, and damping of traditional synchronous generators. Its core objective is to compensate for the decrease in system rotational inertia caused by the high proportion of renewable energy grid connection, so that the grid-connected power electronic converter can not only provide power, but also actively provide frequency and voltage support to the grid, thereby enhancing the stability and robustness of the grid.

[0022] Constant power control mode (PQ mode), also known as grid-connected inverter mode or controlled current source mode, is a strategy that prioritizes the precise and rapid adjustment of the active and reactive power output of the grid-connected power electronic converter. It is typically used in grid-connected applications. The core idea is to treat the grid-connected power electronic converter as a fully controllable, inertia-free power execution unit, enabling it to inject or absorb specified active and reactive power into the grid according to upper-level dispatch instructions or local settings.

[0023] Under the "dual carbon" goal, building a new power system based on new energy sources has become a national strategy. Renewable energy sources such as wind and solar power are highly volatile and intermittent, urgently requiring large-scale, long-term energy storage technologies to achieve cross-seasonal energy balance. Hydrogen and ammonia, as green energy carriers, possess advantages such as high energy density, convenient storage and transportation, and the ability to convert electricity to chemical energy, making them key pathways for solving renewable energy consumption and long-term energy storage. To this end, researchers have proposed constructing a microgrid system integrating electricity, hydrogen, and ammonia energy flows. However, current grid connection switching strategies for such microgrid systems mostly focus on the seamless transition of electrical quantities such as voltage, frequency, and phase, i.e., only considering the stability of electrical quantities on the grid side, seriously neglecting the sensitivity of process and industrial equipment such as hydrogen and ammonia energy devices included in the microgrid system to power fluctuations. Power surges generated during grid connection switching can easily lead to equipment damage, shortened equipment lifespan, or even safety accidents.

[0024] In view of this, embodiments of this application provide a grid-connected switching control method and related equipment for a microgrid system integrating hydrogen, ammonium, and electricity. This solution proposes a method for switching control of a microgrid system comprising a DC bus and connected grid-connected converters, hydrogen-ammonium energy converters, and battery converters. Upon receiving a grid-connection command, the method begins real-time monitoring of the electrical quantity data of the external power grid. First, it controls the hydrogen-ammonium energy converter to freeze its power and performs droop control on the battery converter to stabilize the DC bus voltage. Then, it fine-tunes the electrical quantity data of the grid-connected converter until it synchronizes with the electrical quantity data of the external power grid. At this instant, it controls the microgrid system to establish an electrical connection with the external power grid, and then controls the grid-connected converter to switch from... The virtual synchronous generator mode smoothly switches to constant power control mode. Subsequently, when the microgrid system is in grid-connected electrical steady state, the hydrogen-ammonia energy equipment converter is controlled to adjust its power at a preset ramp rate based on the obtained dispatch power of the hydrogen-ammonia energy equipment converter. At the same time, the battery converter is controlled to adjust its power in the opposite direction to maintain stable power exchange between the microgrid system and the external grid. By adopting the above-mentioned active timing buffer mechanism of power freezing - battery bearing power impact - power gradual recovery, the impact of power fluctuations on process industrial equipment during grid connection switching can be effectively reduced, thereby improving the safety of process industrial equipment and the operational stability of the microgrid system.

[0025] Please see Figure 1 , Figure 1This is an optional schematic diagram of a microgrid system integrating hydrogen, electricity, and ammonia provided in an embodiment of this application. The microgrid system includes a DC bus, an energy router, photovoltaic equipment, a battery, an electrolytic hydrogen production device, a hydrogen purification and compression device, a synthetic ammonia device, a liquid ammonia storage device, an ammonia cracking device, a hydrogen fuel cell, and a hydrogen storage device. The electrolytic hydrogen production device is an electrolyzer, and the energy router is a multi-port energy router, which includes a grid-connected converter, a hydrogen-ammonia energy device converter, a battery converter, a photovoltaic device converter, a hydrogen purification and compression device converter, a liquid ammonia storage device converter, and a hydrogen storage device converter connected to the DC bus. The hydrogen-ammonia energy device converter includes a hydrogen fuel cell converter, an electrolytic hydrogen production device converter, a synthetic ammonia device converter, and an ammonia cracking device converter connected to the DC bus.

[0026] exist Figure 1 In this system, the photovoltaic converter is the first DC / DC converter and is connected to the photovoltaic equipment; the battery converter is the second DC / DC converter and is connected to the battery; the electrolysis hydrogen production equipment converter is the third DC / DC converter and is connected to the electrolysis hydrogen production equipment; the hydrogen purification and compression equipment converter is the fourth DC / DC converter and is connected to the hydrogen purification and compression equipment; the ammonia synthesis equipment converter is the fifth DC / DC converter and is connected to the ammonia synthesis equipment; the liquid ammonia storage equipment converter is the sixth DC / DC converter and is connected to the liquid ammonia storage equipment; the ammonia cracking equipment converter is the first DC / AC converter and is connected to the ammonia cracking equipment; the hydrogen fuel cell converter is the second DC / AC converter and is connected to the hydrogen fuel cell; the hydrogen storage equipment converter is the third DC / AC converter and is connected to the hydrogen storage equipment; and the grid-connected converter is a bidirectional DC / AC converter and is connected to the external power grid.

[0027] In practical applications, this microgrid system can achieve a closed-loop multi-energy flow process of electricity-hydrogen-ammonia-hydrogen-electricity. Specifically, this includes: photovoltaic equipment converting solar energy into DC power and injecting it into the DC bus; batteries providing rapid charging and discharging capabilities to provide real-time power balancing and buffering for the DC bus; the microgrid system interacting bidirectionally with the external power grid through a grid-connected converter and supporting switching between grid-connected and off-grid islanded operation modes; the DC bus providing power to the electrolysis hydrogen production equipment to produce hydrogen through water electrolysis; and the produced hydrogen being purified and compressed by a hydrogen purification and compression device. After processing, the hydrogen can be directly applied to transportation, industry, and other scenarios according to user needs. It can also be directly fed into hydrogen storage equipment for storage, or further supplied to ammonia synthesis equipment to be converted into ammonia. The generated ammonia is then fed into liquid ammonia storage equipment for storage, thereby achieving long-term, high-density energy storage. The ammonia stored in the liquid ammonia storage equipment can be processed by an ammonia cracking equipment to release hydrogen back into hydrogen. The generated hydrogen can be directly fed into hydrogen storage equipment for storage. The hydrogen generated by the ammonia cracking equipment and / or the hydrogen stored in the hydrogen storage equipment can be supplied to hydrogen fuel cells for power generation to feed back to the DC bus.

[0028] To achieve efficient and stable autonomous coordination control within this microgrid system, each port is assigned a clear functional positioning and hierarchical control role based on its physical characteristics and dynamic response capabilities, as detailed below: The bidirectional DC / AC converter serves as the boundary and operating mode benchmark for system-level power balance, dominating grid-connected / off-grid switching; photovoltaic equipment, as a constrained renewable energy generation unit, accepts upper-level limiting dispatch based on maximum power point tracking; batteries, as the core fast power buffer unit, bear the key responsibility of maintaining the instantaneous stability of the DC bus voltage and the primary frequency regulation of the system with their millisecond-level response speed; electrolytic hydrogen production equipment and its supporting hydrogen purification and compression equipment together constitute a slow-speed adjustable load with strict ramp rate constraints, used to absorb excess electrical energy; ammonia synthesis equipment serves as a long-term energy storage load with extremely slow power changes and minimum load constraints; liquid ammonia storage equipment, as an energy state monitoring unit, directly affects upstream and downstream dispatch due to its ammonia storage status; and ammonia cracking equipment, as a controllable hydrogen source, can convert ammonia into hydrogen with a medium-speed response. The main power source is hydrogen fuel cell power generation, and surplus hydrogen can be stored in hydrogen storage equipment. Hydrogen fuel cells, as medium-speed controllable power generation units, provide adjustable power support at the second to minute level. Hydrogen storage equipment, as a flexible energy buffer and state decision node, decouples hydrogen production and consumption processes through its hydrogen storage state and serves as a core decision variable for upper-level energy management, complementing the battery on a time scale. The battery mainly deals with instantaneous power imbalances from seconds to hours, while the hydrogen storage equipment mainly manages medium- to long-term energy imbalances from hours to several days. When the hydrogen storage state of the hydrogen storage equipment reaches the high limit, the operation of the electrolysis hydrogen production equipment will be forcibly restricted or stopped to prevent overvoltage risks. When the hydrogen storage state of the hydrogen storage equipment is below the low limit, in order to prioritize the supply of hydrogen fuel, the hydrogen consumption of the ammonia synthesis equipment may be restricted or the ammonia cracking equipment may be urgently started to produce hydrogen.

[0029] By using the ammonia energy port as an independent and reversible energy source and long-cycle energy storage port, and coupling and flexibly exchanging energy with the electrical energy port and hydrogen energy port on the same DC bus, a physical architecture of ternary synergy of electricity, hydrogen and ammonia can be formed, which can expand the energy storage capacity and scheduling flexibility of multi-energy flow systems.

[0030] The grid-connected switching control method for the aforementioned integrated electric-hydrogen-ammonia microgrid system provided in this application relates to the field of microgrid technology. It can be applied to terminals, servers, or software running on either a terminal or server. In some embodiments, the terminal can be a smartphone, tablet, laptop, desktop computer, etc., but is not limited to these. The server can be configured as an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. The server can also be a node server in a blockchain network. The software can be an application implementing the above method, but is not limited to these forms.

[0031] Please see Figure 2 , Figure 2 This is an optional flowchart illustrating a grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia, provided in this application embodiment. The method may include, but is not limited to, the following steps S101 to S104: Step S101: Upon receiving the grid connection command, monitor the electrical quantity data of the external power grid in real time; Step S102: Control the hydrogen-ammonia energy equipment converter to freeze power, and then control the battery converter to droop, so as to stabilize the voltage of the DC bus. Step S103: Fine-tune the electrical quantity data of the grid-connected converter until it is synchronized with the electrical quantity data of the external power grid. Then, control the microgrid system to make an electrical connection with the external power grid. After that, control the grid-connected converter to smoothly switch from virtual synchronous generator mode to constant power control mode. Step S104: When the microgrid system is in grid-connected electrical steady state, obtain the dispatch power of the hydrogen-ammonia energy device converter, and control the hydrogen-ammonia energy device converter to adjust the power at a preset ramp rate, and synchronously control the battery converter to adjust the power in the opposite direction, so as to maintain the stable power exchange between the microgrid system and the external grid.

[0032] Steps S101 to S104 as shown in the embodiments of this application can improve the safety of process industrial equipment and the operational stability of microgrid systems by introducing an active timing buffer mechanism of power freezing - battery bearing power surge - power gradual recovery during grid connection switching.

[0033] In step S101 of some embodiments, the grid connection command can be a planned grid connection command issued by the application layer running on a host computer or cloud platform. It should be noted that before receiving the grid connection command, the microgrid system is in a stable off-grid operation state.

[0034] In some embodiments, before executing step S102, the process includes: generating a power freeze preparation command and sending it to the hydrogen-ammonia energy device converter, which allows the hydrogen-ammonia energy device converter to immediately process other currently executed operations and perform preparations before power freeze; generating an impulse power acceptance preparation command and sending it to the battery converter, which allows the battery converter to immediately enter the highest level of response preparation state, such as increasing the bandwidth of its control loop, reserving sufficient charging or discharging capacity, and being in a millisecond-level standby mode; and then receiving the preparation ready signals fed back by the hydrogen-ammonia energy device converter and the battery converter, thereby ensuring that the hydrogen-ammonia energy device converter and the battery converter are normal and meet the corresponding execution conditions.

[0035] In step S102 of some embodiments, regarding the control of the hydrogen-ammonia energy device converter to perform power freezing, the corresponding implementation methods include the following: Controlling the hydrogen fuel cell converter to freeze power specifically involves: generating a first power freeze command and sending it to the hydrogen fuel cell converter, causing the hydrogen fuel cell converter to stabilize its real-time power at the first frozen power until the microgrid system is in a grid-connected electrical steady state; wherein, the first frozen power is the power of the hydrogen fuel cell converter at the instant the first power freeze command is received, and the real-time power of the hydrogen fuel cell converter stabilizing at the first frozen power means that the absolute value of the deviation between the real-time power of the hydrogen fuel cell converter and the first frozen power is less than a first preset power deviation threshold. Controlling the power freeze of the electrolytic hydrogen production equipment converter is specifically manifested as follows: generating a second power freeze command and sending it to the electrolytic hydrogen production equipment converter, causing the converter to stabilize its real-time power at the second frozen power until the microgrid system is in a grid-connected electrical steady state; wherein, the second frozen power is the power of the electrolytic hydrogen production equipment converter at the instant of receiving the second power freeze command, and the real-time power of the converter is stabilized at the second frozen power, meaning that the absolute value of the deviation between the real-time power of the converter and the second frozen power is less than a second preset power deviation threshold; Controlling the power freeze of the ammonia synthesis equipment converter is specifically manifested as follows: generating a third power freeze command and sending it to the ammonia synthesis equipment converter, causing the ammonia synthesis equipment converter to stabilize its real-time power at the third frozen power until the microgrid system is in grid-connected electrical steady state; wherein, the third frozen power is the power of the ammonia synthesis equipment converter at the instant of receiving the third power freeze command, and the real-time power of the ammonia synthesis equipment converter is stabilized at the third frozen power, which means that the absolute value of the deviation between the real-time power of the ammonia synthesis equipment converter and the third frozen power is less than a third preset power deviation threshold; Controlling the power freeze of the ammonia cracking equipment converter specifically involves generating a fourth power freeze command and sending it to the ammonia cracking equipment converter, causing the converter to stabilize its real-time power at the fourth frozen power until the microgrid system reaches a grid-connected electrical steady state. The fourth frozen power is the power of the ammonia cracking equipment converter at the instant it receives the fourth power freeze command. The real-time power of the ammonia cracking equipment converter stabilizing at the fourth frozen power means that the absolute value of the deviation between the real-time power of the ammonia cracking equipment converter and the fourth frozen power is less than a fourth preset power deviation threshold.

[0036] By freezing the power of the hydrogen-ammonia energy device converter, the direct coupling between the hydrogen-ammonia energy device and the power surge of the grid can be actively isolated during grid-connection switching in the microgrid system to provide protection.

[0037] In step S102 of some embodiments, the content regarding droop control of the battery converter can be understood as: controlling the battery converter to immediately and dynamically compensate for all power differences caused by power freeze of process equipment through its rapid droop characteristics, thereby maintaining the voltage stability of the DC bus.

[0038] In step S103 of some embodiments, the electrical quantity data of the grid-connected converter includes the amplitude, frequency, and phase of the AC voltage generated by the grid-connected converter, which can be finely adjusted by operating the grid-connected converter in virtual synchronous generator mode. The electrical quantity data of the external power grid includes the amplitude, frequency, and phase of the AC voltage generated by the external power grid. Regarding the synchronization of the electrical quantity data of the grid-connected converter with the electrical quantity data of the external power grid, it can be understood that: the difference between the amplitude of the AC voltage generated by the external power grid and the amplitude of the AC voltage generated by the grid-connected converter falls within a preset amplitude deviation allowable range; the difference between the frequency of the AC voltage generated by the external power grid and the frequency of the AC voltage generated by the grid-connected converter falls within a preset frequency deviation allowable range; and the difference between the phase of the AC voltage generated by the external power grid and the phase of the AC voltage generated by the grid-connected converter falls within a preset phase deviation allowable range.

[0039] In step S103 of some embodiments, the content regarding controlling the electrical connection between the microgrid system and the external power grid can be understood as: controlling the static switch or circuit breaker connected between the grid-connected converter and the external power grid to switch from an open state to a closed state in order to achieve grid connection.

[0040] It should be noted that before the microgrid system is electrically connected to the external power grid, the grid-connected converter is always kept running in virtual synchronous generator mode.

[0041] In step S104 of some embodiments, by real-time monitoring of the DC bus voltage and the amplitude and frequency of the AC voltage at the point of common coupling (PCC) between the microgrid system and the external power grid, when the DC bus voltage and the amplitude and frequency of the PCC remain stable within a first preset time period—that is, when the absolute value of the deviation between the DC bus voltage at each sampling moment within the first preset time period and the DC bus voltage at the adjacent previous sampling moment is less than a first preset voltage deviation threshold, the absolute value of the deviation between the amplitude of the PCC at each sampling moment within the first preset time period and the amplitude of the PCC at the adjacent previous sampling moment is less than a second preset voltage amplitude deviation threshold, and the absolute value of the deviation between the frequency of the PCC at each sampling moment within the first preset time period and the frequency of the PCC at the adjacent previous sampling moment is less than a preset voltage frequency deviation threshold—it can be determined that the microgrid system is in a grid-connected electrical steady state. The first preset time period is preferably 200 ms.

[0042] In step S104 of some embodiments, the scheduling power of the hydrogen-ammonia energy device converter includes the scheduling power of the hydrogen fuel cell converter, the scheduling power of the electrolytic hydrogen production device converter, the scheduling power of the synthetic ammonia device converter, and the scheduling power of the ammonia cracking device converter. The scheduling power of each of the above converters can be issued by the application layer. The preset ramp rate includes a first preset ramp rate associated with the hydrogen fuel cell converter, a second preset ramp rate associated with the electrolytic hydrogen production device converter, a third preset ramp rate associated with the synthetic ammonia device converter, and a fourth preset ramp rate associated with the ammonia cracking device converter. Regarding the control of the hydrogen-ammonia energy device converter to adjust power according to the preset ramp rate, the corresponding implementation methods include the following: The hydrogen fuel cell converter is controlled to adjust its power at the first preset ramp rate, that is, the current power of the hydrogen fuel cell converter is adjusted to its dispatch power at the first preset ramp rate. The value range of the first preset ramp rate is preferably [1%P1, 5%P1], and its unit is W / min, where P1 is the rated power of the hydrogen fuel cell converter. The converter of the electrolytic hydrogen production equipment is controlled to adjust its power at the second preset ramp rate, that is, the current power of the converter of the electrolytic hydrogen production equipment is adjusted to its dispatch power at the second preset ramp rate. The value range of the second preset ramp rate is preferably [1%P2, 5%P2], and its unit is W / min, where P2 is the rated power of the converter of the electrolytic hydrogen production equipment. The converter of the ammonia synthesis equipment is controlled to adjust its power at the third preset ramp rate, that is, the current power of the converter of the ammonia synthesis equipment is adjusted to its dispatch power at the third preset ramp rate. The value range of the third preset ramp rate is preferably [1%P3, 5%P3], and its unit is W / min, where P3 is the rated power of the converter of the ammonia synthesis equipment. The power of the ammonia cracking equipment converter is adjusted by the fourth preset ramp rate, that is, the current power of the ammonia cracking equipment converter is adjusted to its dispatch power by the fourth preset ramp rate. The preferred value range of the fourth preset ramp rate is [1%P4, 5%P4], ​​and its unit is W / min, where P4 is the rated power of the ammonia cracking equipment converter.

[0043] Based on this, the corresponding implementation methods for synchronously controlling the battery converter to adjust power in reverse include the following: At each time step, the power change of the hydrogen fuel cell converter, the power change of the electrolytic hydrogen production equipment converter, the power change of the ammonia synthesis equipment converter, and the power change of the ammonia cracking equipment converter are determined and added together to obtain the total power change. The power change of each converter refers to the difference between the power of the converter at the current sampling time and the power of the converter at the adjacent previous sampling time. The interval between these two sampling times is the time step, which is determined according to the unit of the preset ramp rate, preferably 1 minute. Based on the total power change, the battery converter is controlled to adjust the power in reverse. Specifically, the absolute value of the total power change is used as the power adjustment amount. When the total power change is greater than zero, the battery converter is controlled to decrease its current power by the power adjustment amount. When the total power change is less than zero, the battery converter is controlled to increase its current power by the power adjustment amount. When the total power change is equal to zero, there is no need to control the battery converter to adjust its current power.

[0044] In some embodiments, when the grid-connected converter is operating stably in constant power control mode and performing planned power exchange with the external power grid, the grid-connected switching control method applied to the above-mentioned microgrid system integrating electricity, hydrogen, and ammonia may further include the following steps S105 to S106: Step S105: When the microgrid system is in grid-connected operation, droop control is performed on the battery converter, hydrogen fuel cell converter and electrolytic hydrogen production equipment converter respectively, and the planned power of the ammonia synthesis equipment converter is obtained and controlled. Step S106: Monitor the voltage of the DC bus in real time. When the voltage of the DC bus remains higher than the preset voltage threshold for a second preset time period, control the photovoltaic equipment converter to perform power-limited operation.

[0045] By performing steps S105 to S106 above, the stability of the microgrid system during grid-connected operation can be further improved, and it can wait to receive off-grid instructions.

[0046] In steps S102 and S105 of some embodiments, the battery converter mainly implements millisecond / second-level power fast adjustment function. Regarding the droop control of the battery converter, the corresponding implementation may include, but is not limited to, the following steps S201 to S203: Step S201: Obtain the current voltage of the DC bus and, in conjunction with the rated voltage of the DC bus, calculate the voltage deviation of the DC bus. This can be achieved using the following expression: ; In the formula, This refers to the voltage deviation of the DC bus. The current voltage of the DC bus. This is the rated voltage of the DC bus; Step S202: Obtain the planned power of the battery converter, and then adjust the planned power of the battery converter according to the voltage deviation of the DC bus and the first preset droop coefficient to obtain the target power of the battery converter. This can be achieved using the following expression: ; In the formula, The target power of the battery converter, The planned power of the battery converter can be issued by the application layer. The first preset droop coefficient is preferably set within the range of [100kW / V, 200kW / V], making it most sensitive to voltage fluctuations and ensuring that it can generate full power response even for small voltage deviations, thereby making the battery the main provider of system inertia or primary frequency regulation. Step S203: Control the battery converter according to its target power, that is, make the current power of the battery converter track its target power.

[0047] In step S105 of some embodiments, the hydrogen fuel cell converter mainly implements a power adjustment function at the second / minute level, which can intervene when the battery capacity is insufficient or long-term support is required, responding to continuous power shortages. Regarding the droop control of the hydrogen fuel cell converter, the corresponding implementation may include, but is not limited to, the following steps S301 to S303: Step S301: After calculating the DC bus voltage deviation according to the implementation principle of step S201 above, the DC bus voltage deviation is processed by the first low-pass filter to obtain the first DC bus voltage deviation, which can be achieved by the following expression: ; In the formula, This is the first voltage deviation of the DC bus. Refers to the first low-pass filter, the preferred range of which is [5s, 30s]; Step S302: Obtain the planned power of the hydrogen fuel cell converter, and then adjust the planned power of the hydrogen fuel cell converter according to the first voltage deviation of the DC bus and the second preset droop coefficient to obtain the target power of the hydrogen fuel cell converter. ; In the formula, The target power for the hydrogen fuel cell converter, The planned power output of the hydrogen fuel cell converter can be assigned by the application layer. The second preset droop coefficient is smaller than the first preset droop coefficient, and the preferred value range of the second preset droop coefficient is [10kW / V, 30kW / V]. Step S303: Control the hydrogen fuel cell converter according to its target power, that is, make the current power of the hydrogen fuel cell converter track its target power.

[0048] In step S105 of some embodiments, the converter of the electrolytic hydrogen production equipment mainly implements a slow power adjustment function at the minute / hour level to respond to long-term power excess. Regarding the droop control of the converter of the electrolytic hydrogen production equipment, the corresponding implementation may include, but is not limited to, the following steps S401 to S403: Step S401: After calculating the DC bus voltage deviation according to the implementation principle of step S201 above, the DC bus voltage deviation is processed by a second low-pass filter to obtain the second DC bus voltage deviation, which can be achieved using the following expression: ; In the formula, This is the second voltage deviation of the DC bus. Refers to a second low-pass filter, the filtering time constant of which is greater than that of the first low-pass filter, and the preferred range of the filtering time constant of the second low-pass filter is [1min, 5min]. Step S402: Obtain the planned power of the converter in the electrolysis hydrogen production equipment. Then, based on the second voltage deviation of the DC bus and the third preset droop coefficient, adjust the planned power of the converter to obtain the target power of the converter. This can be achieved using the following expression: ; In the formula, The target power for the converter in the electrolysis hydrogen production equipment. The planned power of the converter in the electrolysis hydrogen production equipment can be assigned by the application layer. The third preset droop coefficient is smaller than the second preset droop coefficient, and the preferred value range of the third preset droop coefficient is [1kW / V, 5kW / V]. Step S403: Control the converter of the electrolytic hydrogen production equipment according to the target power of the converter, that is, adjust the current power of the converter of the electrolytic hydrogen production equipment to its target power at the fifth preset ramp rate. The fifth preset ramp rate is preferably 10%P2, and its unit is W / min.

[0049] In step S105 of some embodiments, the ammonia synthesis equipment converter mainly implements hourly / day-level slow power adjustment. The planned power of the ammonia synthesis equipment converter can be issued by the application layer to control the converter, that is, to adjust the current power of the converter to its planned power at a sixth preset ramp rate, preferably 5%P3, with units of W / h. Because the response speed of the ammonia synthesis equipment converter is extremely slow and cannot follow real-time voltage changes, the droop control principle is not suitable for the ammonia synthesis equipment converter when connected to a microgrid system.

[0050] In step S106 of some embodiments, the DC bus voltage remains higher than a preset voltage threshold for a second preset time period. This means that the DC bus voltage is greater than the preset voltage threshold at each sampling moment within the second preset time period. The preset voltage threshold can be the sum of the rated voltage of the DC bus and the preset voltage allowable deviation. This indicates that the battery has failed to fully absorb the excess power on the DC bus. Regarding the control of the photovoltaic converter to operate with limited power, the corresponding implementation may include, but is not limited to, the following steps S501 to S502: Step S501: After obtaining the planned power of the ammonia synthesis equipment converter, calculating the target power of the hydrogen fuel cell converter according to the implementation principles of steps S301 to S302 above, and calculating the target power of the electrolysis hydrogen production equipment converter according to the implementation principles of steps S401 to S402 above, the maximum allowable charging power of the battery, the local load power of the microgrid system, and the exchange power between the microgrid system and the external power grid are obtained. Combined with the target power of the hydrogen fuel cell converter, the target power of the electrolysis hydrogen production equipment converter, and the planned power of the ammonia synthesis equipment converter, the upper limit power of the photovoltaic equipment converter is calculated. This can be achieved using the following expression: ; In the formula, This refers to the upper limit power of the photovoltaic converter. This refers to the local load power of the microgrid system, which can be issued by the application layer. The planned power of the converter in the ammonia synthesis unit. This refers to the maximum allowable charging power of the battery, which can be assigned by the application layer. This refers to the power exchanged between the microgrid system and the external power grid, which can be issued by the application layer. Step S502: Control the photovoltaic converter according to its upper limit power, that is, keep the current power of the photovoltaic converter from exceeding its upper limit power.

[0051] By transforming the safety concept into an irreversible, rigid operational sequence throughout the entire grid-connection switching process of a microgrid system—namely, freezing power to isolate impacts, then performing electrical connections and mode switching when synchronization conditions are met, establishing a grid-connected electrical steady state, and finally adjusting power ramp-up—the risk of applying any power disturbance to vulnerable process equipment such as hydrogen and ammonia before the microgrid system's electrical state reaches a steady state can be effectively reduced. Furthermore, the transitions between each switching state rely on explicit physical quantity judgment criteria rather than preset fixed delays, enabling the entire grid-connection switching process to adapt to the real-time dynamics of the microgrid system and exhibit stronger robustness and determinism in the face of different initial operating conditions and disturbances.

[0052] In some embodiments, the operational safety priority of the microgrid system should be higher than the grid connection switching process itself. If a fault is detected in the microgrid system, the grid connection switching process should be adjusted immediately, as detailed below.

[0053] In the first scenario, if any of the following faults occurs during the execution of the above steps S101, such as sending a power freeze preparation command to the hydrogen-ammonia energy equipment converter, sending an impact power acceptance preparation command to the battery converter, and waiting to receive the preparation ready signals from the hydrogen-ammonia energy equipment converter and the battery converter, the grid connection switching process will be immediately interrupted and the corresponding fault handling strategy will be executed.

[0054] Furthermore, the method for determining communication interruption of critical equipment may include: monitoring the periodic heartbeat signals or status words of the BMS (Battery Management System), FCS (Fuel Cell System), ECS (Electrolyzer Control System), and PCS (Power Conversion System). If there is no valid response or a status word indicating a communication failure is received for three consecutive communication cycles, a communication interruption of critical equipment is determined to have occurred. Each communication cycle is preferably 100ms.

[0055] Fault handling strategies for dealing with communication interruptions of critical equipment may include: attempting to monitor using redundant channels; if monitoring still fails, controlling the microgrid system to maintain / return to a stable off-grid operating state, and then issuing alarm information indicating a communication failure to await manual inspection.

[0056] Furthermore, the method for determining equipment preparation failure may include: if no preparation ready signal is received from the hydrogen-ammonia energy equipment converter and the battery converter within a preset timeout period, or if a preparation failure signal (such as a signal indicating that the electrolyzer pressure is not up to standard) is received from the hydrogen-ammonia energy equipment converter and / or the battery converter, then a equipment preparation failure is determined to have occurred. The preset timeout period is preferably 10 seconds.

[0057] Fault handling strategies developed to address equipment preparation failures may include: if a single point of failure occurs in the process-side equipment, i.e., only one converter among the hydrogen fuel cell converter, electrolytic hydrogen production equipment converter, synthetic ammonia equipment converter, ammonia cracking equipment converter, and battery converter fails, then first assess whether the equipment connected to the failed converter can be shut down and isolated before continuing grid-connected switching. If it is determined that shutdown and isolation are not possible, then control the microgrid system to maintain / return to a stable off-grid operating state.

[0058] Furthermore, the methods for determining critical measurement failures may include: monitoring the health status or data rationality of the DC bus voltage sensor, AC voltage / current sensor, and synchronous phase detection unit; if any sensor reports a fault status, or the data collected by any sensor remains unchanged for a long time, or the data collected by any sensor exceeds physical limits, then a critical measurement failure is determined to have occurred.

[0059] Fault handling strategies for addressing critical measurement failures may include: if a backup sensor of the same type as the failed sensor is pre-configured, then switch to using the backup sensor; if no backup sensor is configured, then control the microgrid system to maintain / return to a stable off-grid operating state.

[0060] In the second scenario, if either a power freeze failure or a DC bus voltage collapse occurs during the execution of step S102, the corresponding fault handling strategy will be executed.

[0061] Furthermore, the method for determining power freeze failure may include: if the absolute value of the deviation between the real-time power and the frozen power of at least one of the target converters (hydrogen fuel cell converter, electrolytic hydrogen production equipment converter, synthetic ammonia equipment converter, and ammonia cracking equipment converter) continuously exceeds a preset power threshold for a preset short period of time after the power freeze command is issued, then a power freeze failure is determined to have occurred. Preferably, the preset short period of time is 2 seconds, and the preset power threshold is preferably 5%P, where P is the rated power of the target converter.

[0062] Fault handling strategies to address power freeze failures may include: first, issuing an emergency shutdown command to the device connected to the target converter to forcibly disconnect the device from the microgrid system; then, reassessing the current power balance capability of the microgrid system. If the remaining dispatchable resources (usually provided by batteries) can still support the subsequent grid connection switching process, the subsequent grid connection switching process can continue without the device; if it cannot support the switching process, the microgrid system is controlled to maintain / return to a stable off-grid operating state.

[0063] Furthermore, the method for determining DC bus voltage collapse may include: real-time monitoring of the DC bus voltage; if the DC bus voltage continuously exceeds the safe range within a preset protection delay time, it indicates that the battery cannot effectively compensate for the power difference, and a DC bus voltage collapse fault is determined to have occurred. The preset protection delay time is preferably 100ms, and the safe range can be set to be below 0.85pu or above 1.15pu.

[0064] Fault handling strategies developed to address DC bus voltage collapse may include: controlling the microgrid system to enable a preset minimum safe operating mode, prioritizing attempts to quickly restore grid connection, and utilizing grid-supported voltage.

[0065] The implementation methods for this minimum safe operating mode may include, but are not limited to: immediately controlling the static switch or circuit breaker connected between the grid-connected converter and the external power grid to switch from an open state to a closed state, so that the microgrid system can be connected to the external power grid to utilize the unlimited capacity of the external power grid to stabilize the microgrid system; if the microgrid system cannot be connected to the grid, controlling the grid-connected converter to operate in voltage source mode and only carrying the most basic load; controlling the hydrogen fuel cell, electrolytic hydrogen production equipment, ammonia synthesis equipment and ammonia cracking equipment to perform emergency shutdown, and closing the front-end valves and back-end valves of each equipment, so that each equipment enters a safe isolation state; adopting an independent DC voltage control mode for the microgrid system, so that the battery becomes the only power balancing and voltage support unit in the microgrid system; switching the control system itself to the embedded protection logic of the lowest function set, separating it from the high-level coordination layer, maintaining only the most basic measurement, protection and circuit breaker control functions, and waiting for manual reset.

[0066] In the third scenario, if any of the following faults occurs during the execution of step S103 above: switch operation failure or asynchronous grid connection failure, then the corresponding fault handling strategy will be executed.

[0067] Furthermore, the method for determining a switch operation fault may include: after issuing a closing command to a static switch or circuit breaker connected between the grid-connected converter and the external power grid, if no closing confirmation signal is received from the static switch or circuit breaker within a specified time, a switch operation fault is determined to have occurred. Preferably, this specified time is 500ms.

[0068] Fault handling strategies for dealing with switch operation failures may include: attempting to reissue a closing command to the static switch or circuit breaker; if this fails again, locking the static switch or circuit breaker and then switching to control the pre-configured backup static switch or backup circuit breaker; or reconfiguring the safety control strategy according to the current actual electrical connection status.

[0069] Furthermore, the method for determining asynchronous grid connection may include: real-time monitoring of the amplitude, frequency, and phase of the AC voltage generated by the grid-connected converter operating in virtual synchronous generator mode, and real-time monitoring of the amplitude, frequency, and phase of the AC voltage generated by the external power grid. At the moment when a closing command is issued to the static switch or circuit breaker, if the absolute value of the difference between the amplitude of the AC voltage generated by the grid-connected converter and the amplitude of the AC voltage generated by the external power grid is greater than a preset amplitude deviation safety threshold, and / or the absolute value of the difference between the frequency of the AC voltage generated by the grid-connected converter and the frequency of the AC voltage generated by the external power grid is greater than a preset frequency deviation safety threshold, and / or the absolute value of the difference between the phase of the AC voltage generated by the grid-connected converter and the phase of the AC voltage generated by the external power grid is greater than a preset phase deviation safety threshold, then an asynchronous grid connection fault is determined to have occurred.

[0070] The fault handling strategy formulated to deal with asynchronous grid connection may include: if the static switch or circuit breaker has just switched to the closed state, then immediately issue a trip command to the static switch or circuit breaker; if the static switch or circuit breaker has not yet switched to the closed state, then immediately issue a stop closing command to the static switch or circuit breaker; then re-perform electrical quantity data synchronization adjustment; if synchronous grid connection still cannot be achieved, then determine that the synchronization device is faulty or the external power grid is abnormal. At this time, abandon the current grid connection operation and control the microgrid system to maintain / return to a stable off-grid operation state.

[0071] In the fourth scenario, during the establishment of grid-connected electrical steady state in the microgrid system: if a fault occurs where electrical quantities continuously exceed limits, the first fault handling strategy is executed; or if an emergency fault shutdown signal is received from any device in the microgrid system, differentiated isolation is performed according to the type of the device, the remaining capacity of the microgrid system is re-determined, and the microgrid system is controlled to activate the aforementioned minimum safe operating mode.

[0072] Furthermore, the method for determining the continuous over-limit of electrical quantities may include: real-time monitoring of the amplitude and frequency of the AC voltage at the point of common coupling between the microgrid system and the external power grid. If the amplitude of the AC voltage continuously exceeds a preset voltage amplitude range within a preset time, and / or the frequency of the AC voltage continuously exceeds a preset voltage frequency range within the preset time, then a fault of continuous over-limit of electrical quantities is determined to have occurred. Preferably, the preset time is 500ms, the preset voltage amplitude range is preferably [-2%V, 2%V], where V is the rated AC voltage amplitude, and the preset voltage frequency range is preferably [-2%f, 2%f], where f is the rated AC voltage frequency. These two ranges can be understood as the steady-state operating limits of the system.

[0073] The first fault handling strategy to deal with the continuous over-limit of electrical quantities may include: allowing the battery to support at a higher power; if the adjustment is ineffective, it indicates that there is a fundamental imbalance in the system power or the control loop is unstable. In this case, try to control the grid-connected converter to smoothly switch from constant power control mode to virtual synchronous generator mode, and then re-execute the grid connection operation, that is, control the static switch or circuit breaker connected between the grid-connected converter and the external grid to switch from closed state to open state, and then switch from open state to closed state when the synchronization condition is met. Then control the grid-connected converter to smoothly switch from virtual synchronous generator mode to constant power control mode.

[0074] In the fifth scenario, if either power recovery synchronization failure or the equipment reaching its safety limit occurs during the execution of step S104, the corresponding fault handling strategy will be executed.

[0075] Furthermore, the method for determining power recovery synchronization failure may include: real-time calculation and summing of the power changes of the hydrogen fuel cell converter, the electrolytic hydrogen production equipment converter, the synthetic ammonia equipment converter, and the ammonia cracking equipment converter to obtain the power change of the hydrogen-ammonia energy equipment converter; real-time calculation of the power change of the battery converter; and real-time calculation of the DC bus voltage fluctuation. If the absolute value of the sum of the power changes of the hydrogen-ammonia energy equipment converter and the battery converter is greater than a preset threshold, or if the DC bus voltage fluctuation is greater than a preset limit, it indicates that the reverse power complementary adjustment has failed, and a power recovery synchronization failure is determined to have occurred.

[0076] The fault handling strategy for power recovery synchronization failure may include: first, immediately suspending the power adjustment of the hydrogen-ammonia energy device converter and re-freezing the power of the hydrogen-ammonia energy device converter; then, checking whether the device communication status and control loop are abnormal, and after checking that there are no abnormalities, re-controlling the hydrogen-ammonia energy device converter to adjust the power at a preset ramp rate; if the power recovery synchronization failure still occurs, the current power of the hydrogen-ammonia energy device converter is taken as the new steady-state operating point and a degraded operation alarm is issued.

[0077] Furthermore, the method for determining when equipment reaches its safety limits may include: real-time monitoring of the battery's SOC value, the electrolyzer's temperature, the electrolyzer's pressure, and the hydrogen fuel cell's load; if the battery's SOC value is greater than 95% or less than 5%, or the electrolyzer's temperature reaches its upper limit, or the electrolyzer's pressure reaches its upper limit, or the hydrogen fuel cell's load is lower than its lower limit, then it is determined that the equipment has reached its safety limits.

[0078] Fault handling strategies for dealing with equipment reaching safety limits may include: for equipment that has reached its safety limits, immediately stop further power adjustments to the converters connected to the equipment and fix the power of the converters connected to the equipment at the limit boundary value; then, the upper-level scheduling or local autonomous coordination algorithm reallocates the power targets of other converters to meet the total demand; if reallocation is not possible, control the microgrid system to enter a preset power-constrained operation mode.

[0079] By detecting and responding to faults during the entire grid connection switching process of a microgrid system, reliable convergence from a local abnormal state to a global safe state can be achieved, which helps to improve the survivability of the microgrid system under extreme operating conditions.

[0080] This application also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia. This electronic device can include any smart terminal such as a tablet computer or desktop computer.

[0081] It is understood that the content of the above method embodiments is applicable to the present device embodiments. The specific functions implemented by the present device embodiments are the same as those implemented by the above method embodiments, and the beneficial effects achieved by the present device embodiments are also the same as those achieved by the above method embodiments.

[0082] Please see Figure 3 , Figure 3 This is a schematic diagram illustrating the hardware structure of an electronic device according to another embodiment. The electronic device includes: The processor 601 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application. The memory 602 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 602 can store the operating system and other applications. When the technical solutions provided in the embodiments of this application are implemented through software or firmware, the relevant program code is stored in the memory 602 and is called and executed by the processor 601. The input / output interface 603 is used to implement information input and output; The communication interface 604 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 605 transmits information between various components of the device (e.g., processor 601, memory 602, input / output interface 603, and communication interface 604); The processor 601, memory 602, input / output interface 603 and communication interface 604 are connected to each other within the device via bus 605.

[0083] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia.

[0084] It is understood that the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented by this storage medium embodiment are the same as those implemented by the above method embodiments, and the beneficial effects achieved by this storage medium embodiment are also the same as those achieved by the above method embodiments.

[0085] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0086] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0087] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0088] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, and the functional modules / units in the device, can be implemented as software, firmware, hardware, and suitable combinations thereof.

[0089] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0090] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0091] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia, characterized in that, The microgrid system includes a DC bus and an energy router, the energy router including a grid-connected converter, a hydrogen-ammonia energy device converter, and a battery converter connected to the DC bus; the method includes: Upon receiving a grid connection command, the electrical quantity data of the external power grid is monitored in real time. The power of the hydrogen-ammonia energy device converter is frozen, and the droop control of the battery converter is applied to stabilize the voltage of the DC bus. Fine-tune the electrical quantity data of the grid-connected converter until it is synchronized with the electrical quantity data of the external power grid, control the microgrid system to establish an electrical connection with the external power grid, and then control the grid-connected converter to smoothly switch from virtual synchronous generator mode to constant power control mode. When the microgrid system is in grid-connected electrical steady state, the dispatch power of the hydrogen-ammonia energy device converter is obtained, and the hydrogen-ammonia energy device converter is controlled to adjust its power at a preset ramp rate. The battery converter is simultaneously controlled to adjust its power in the opposite direction to maintain stable power exchange between the microgrid system and the external power grid.

2. The grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia as described in claim 1, characterized in that, Before controlling the hydrogen-ammonia energy device converter to freeze power, the following steps are included: A power freeze preparation command is generated and sent to the hydrogen-ammonia energy device converter, and an impact power acceptance preparation command is generated and sent to the battery converter. Receive the ready signals fed back by the hydrogen-ammonia energy device converter and the battery converter.

3. The grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia as described in claim 1, characterized in that, The microgrid system is in a grid-connected electrical steady state as determined by the following methods: The voltage of the DC bus and the amplitude and frequency of the AC voltage at the common connection point between the microgrid system and the external power grid are monitored in real time. When the voltage of the DC bus and the amplitude and frequency of the AC voltage at the common connection point remain stable within a first preset time period, the microgrid system is determined to be in a grid-connected electrical steady state.

4. The grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia as described in claim 1, characterized in that, The hydrogen-ammonia energy equipment converter includes a hydrogen fuel cell converter, an electrolysis hydrogen production equipment converter, and an ammonia synthesis equipment converter connected to the DC bus; the energy router also includes a photovoltaic equipment converter connected to the DC bus; the method further includes: When the microgrid system is in grid-connected operation, droop control is performed on the battery converter, the hydrogen fuel cell converter, and the electrolytic hydrogen production equipment converter, respectively, and the planned power of the ammonia synthesis equipment converter is obtained and controlled. The voltage of the DC bus is monitored in real time. When the voltage of the DC bus remains higher than a preset voltage threshold for a second preset time period, the photovoltaic converter is controlled to operate with limited power.

5. The grid-connected switching control method for a microgrid system integrating electro-hydrogen-ammonia as described in claim 4, characterized in that, Droop control of the battery converter includes: Obtain the current voltage of the DC bus and, in conjunction with the rated voltage of the DC bus, calculate the voltage deviation of the DC bus; The planned power of the battery converter is obtained, and then the planned power of the battery converter is adjusted according to the voltage deviation of the DC bus and the first preset droop coefficient to obtain the target power of the battery converter. The battery converter is controlled according to the target power of the battery converter.

6. The grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia as described in claim 5, characterized in that, Droop control of the hydrogen fuel cell converter includes: The voltage deviation of the DC bus is processed by a first low-pass filter to obtain the first voltage deviation of the DC bus; The planned power of the hydrogen fuel cell converter is obtained, and then the planned power of the hydrogen fuel cell converter is adjusted according to the first voltage deviation and the second preset droop coefficient of the DC bus to obtain the target power of the hydrogen fuel cell converter; wherein, the second preset droop coefficient is less than the first preset droop coefficient. The hydrogen fuel cell converter is controlled according to the target power of the hydrogen fuel cell converter.

7. The grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia as described in claim 6, characterized in that, Droop control of the converter in the electrolysis hydrogen production equipment includes: The voltage deviation of the DC bus is processed by a second low-pass filter to obtain a second voltage deviation of the DC bus; wherein the filtering time constant of the second low-pass filter is greater than the filtering time constant of the first low-pass filter. The planned power of the converter of the electrolytic hydrogen production equipment is obtained, and then the planned power of the converter is adjusted according to the second voltage deviation of the DC bus and the third preset droop coefficient to obtain the target power of the converter of the electrolytic hydrogen production equipment; wherein, the third preset droop coefficient is less than the second preset droop coefficient. The converter of the electrolytic hydrogen production equipment is controlled according to the target power of the converter.

8. The grid-connected switching control method for a microgrid system integrating electricity, hydrogen, and ammonia according to claim 7, characterized in that, The microgrid system also includes a battery, which is connected to the battery converter; controlling the photovoltaic converter to operate with limited power includes: The maximum allowable charging power of the battery, the local load power of the microgrid system, and the exchange power between the microgrid system and the external power grid are obtained. Combined with the target power of the hydrogen fuel cell converter, the target power of the electrolytic hydrogen production equipment converter, and the planned power of the ammonia synthesis equipment converter, the upper limit power of the photovoltaic equipment converter is calculated. The photovoltaic converter is controlled according to its upper limit power.

9. An electronic device, characterized in that, The electronic device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the grid-connected switching control method of the microgrid system integrating electric hydrogen and ammonia as described in any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the grid-connected switching control method for the microgrid system integrating electric hydrogen and ammonia as described in any one of claims 1 to 8.

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