Seamless switching control method and system for operation modes of photovoltaic micro-grid

Abstract

The invention discloses a seamless switching control method and system for a photovoltaic microgrid operation mode, and the method comprises the steps: obtaining the real-time power of an energy storage unit, a photovoltaic power generation unit and a tie line, and switching off a grid-connected switch after the power of the tie line is controlled to reach a preset target value when the microgrid is converted into an independent network construction mode from a grid-connected mode, smooth switching from a grid-connected mode to an independent network construction mode is completed; when the photovoltaic microgrid is switched from an independent grid construction operation mode to a grid connection operation mode, the microgrid automatically tracks the frequency, voltage and phase of a main grid under the adjustment of an energy management system, the grid connection condition is judged through a microgrid grid connection synchronous protection device, and the full-automatic reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid connection operation mode is completed. According to the method, the transient transition time can be shortened, the load power supply continuity and the power supply quality of the micro-grid are improved, the impact on the main grid in the grid connection process of the micro-grid is reduced, and good grid connection friends are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field, and in particular to a seamless switching control method and system for a photovoltaic microgrid operation mode. Background Art

[0002] As an advanced structural form of distributed power generation, microgrids can effectively organize a variety of distributed power sources, loads, and energy storage. They can be connected to the external large power grid through a public connection point (PCC) or run independently. With the development of microgrid technology, its power source type, grid connection mode, energy storage configuration, and load composition are complex and changeable. How to control the smooth and seamless switching of microgrid systems between grid connection and independent networking has become a technical difficulty that needs to be solved urgently.

[0003] The existing micro-power sources use PQ control when connected to the grid, and droop control when isolated, and add a droop rating point adjustment loop to the basic droop controller, and realize the smooth conversion of the grid-connected and independent grid control modes through the switching of this loop. However, the frequent switching of the control loop has a negative impact on the continuity of power supply to users, especially when the microgrid architecture is complex or the load has special requirements for uninterrupted power supply, it is more difficult to achieve seamless switching when the microgrid is connected to the grid and switched to an independent grid. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above existing problems, the present invention is proposed.

[0006] Therefore, the present invention provides a seamless switching control method and system for a photovoltaic microgrid operation mode to solve the power quality problems and the problem of long transient transition time that occur when the microgrid switches between grid-connected and independent grid construction.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, an embodiment of the present invention provides a method for seamless switching control of a photovoltaic microgrid operation mode, including: a photovoltaic storage microgrid including an energy storage unit, a photovoltaic power generation unit, a local load, an energy management system, and a microgrid grid-connected synchronous protection device; wherein the energy storage unit adopts a power autonomous synchronization control method, and the method includes:

[0009] Obtain the real-time power of the energy storage unit, photovoltaic power generation unit and tie line. When the microgrid switches from the grid-connected mode to the independent grid-connected mode, the grid-connected switch is disconnected after the tie line power reaches the predetermined target value, completing the smooth switching from the grid-connected mode to the independent grid-connected mode.

[0010] When switching from independent grid construction to grid-connected operation, the microgrid automatically tracks the frequency, voltage and phase of the main grid under the regulation of the energy management system, determines the grid connection conditions through the microgrid grid-connected synchronization protection device, and completes the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid-connected operation mode.

[0011] As a preferred solution of the seamless switching control method of the photovoltaic microgrid operation mode described in the present invention, wherein: disconnecting the grid-connected switch after controlling the tie line power to a predetermined target value includes: calculating the active power regulation compensation value and the adjustable potential range of the external exchange power of the energy storage unit;

[0012] Assume that the actual sampling value of the tie line power at the current moment is x(n), and the target value is P 恒定 , then the active power regulation demand value is:

[0013] ΔP 调节 =P 恒定 -x(n)

[0014] The maximum charge and discharge power of each energy storage unit is set as The current real-time power of each energy storage unit is The range of the adjustable potential of external exchange power of each energy storage unit is calculated as follows:

[0015]

[0016] Define the set φ n is the set of all energy storage units, then the adjustable potential range of the energy storage unit is

[0017]

[0018] As a preferred solution of the seamless switching control method of the photovoltaic microgrid operation mode described in the present invention, it also includes:

[0019] If the active power regulation demand value is within the adjustable potential range of the energy storage unit, the active power regulation demand value is fully borne by the energy storage unit; if the active power regulation demand value is not within the adjustable potential range of the energy storage unit, the active power regulation demand value cannot fully meet the power regulation needs;

[0020] When the active power regulation demand value cannot fully meet the power regulation needs, if the active power regulation demand value is greater than 0, part of the local load is cut off, the tie line power is adjusted to the target value, the grid-connected switch is cut off, and the grid-connected to independent grid mode switching is realized;

[0021] If the active power regulation demand value is not greater than 0, the photovoltaic power generation unit will operate with limited power, adjust the interconnection line power to the target value, cut off the grid-connected switch, and realize the switching from grid-connected to independent grid-connected mode.

[0022] As a preferred solution of the seamless switching control method of the photovoltaic microgrid operation mode described in the present invention, when the microgrid switches from an independent grid-connected mode to a grid-connected mode, the voltage and frequency support of the system is switched from the energy storage unit to the main grid, and the energy storage unit instantaneously bears the sudden changes in active power and reactive power caused by load transfer.

[0023] As a preferred solution of the seamless switching control method of the photovoltaic microgrid operation mode described in the present invention, when switching from independent grid construction to grid connection, the microgrid automatically tracks the main grid frequency, voltage and phase under the regulation of the energy management system, including:

[0024] When the microgrid is in the independent grid operation mode, the energy management system receives the microgrid grid connection closing command issued by the dispatcher and sends the grid connection closing command to the synchronous protection device;

[0025] The synchronous protection device sends frequency and voltage adjustment instructions to the energy storage unit to determine the grid-connected conditions. When the synchronous protection device checks the synchronization and the grid-connected conditions are met, it automatically controls the microgrid grid-connected switch to close, completing the switch from independent grid construction to grid-connected mode.

[0026] As a preferred solution of the seamless switching control method of the photovoltaic microgrid operation mode described in the present invention, the grid connection condition is determined by the microgrid grid-connected synchronous protection device, including:

[0027] When the energy storage unit receives a frequency adjustment instruction, the output phase of the inverter is adjusted by adjusting the self-generated angular frequency so that it tracks the phase of the upper common node, completing the phase pre-synchronization process of the energy storage unit; at the same time, the voltage amplitude of the bridge arm of the energy storage unit is adjusted so that the output voltage amplitude of the inverter tracks the voltage amplitude of the upper power grid, completing the amplitude pre-synchronization process of the energy storage unit.

[0028] As a preferred solution of the seamless switching control method of the photovoltaic microgrid operation mode described in the present invention, it also includes: when the microgrid is switched from unplanned grid-connected to independent grid-connected, the power impact in the transition process is borne by the energy storage unit of multiple machines in parallel.

[0029] In a second aspect, the present invention provides a seamless switching control system for a photovoltaic microgrid operation mode, which is applicable to a photovoltaic microgrid including an energy storage unit, a photovoltaic power generation unit, a local load, an energy management system, and a microgrid grid-connected synchronous protection device; wherein the energy storage unit adopts a power autonomous synchronous control method, and the system includes:

[0030] The first switching control module is used to obtain the real-time power of the energy storage unit, the photovoltaic power generation unit and the tie line. When the microgrid is switched from the grid-connected mode to the independent grid-connected mode, the grid-connected switch is disconnected after the tie line power reaches a predetermined target value, thereby completing a smooth switch from the grid-connected mode to the independent grid-connected mode.

[0031] The second switching control module is used for automatically tracking the frequency, voltage and phase of the main grid under the regulation of the energy management system when switching from independent grid construction to grid connection, judging the grid connection conditions through the microgrid grid connection synchronization protection device, and completing the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid connection operation mode.

[0032] In a third aspect, the present invention provides a computing device, comprising:

[0033] Memory and processor;

[0034] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the seamless switching control method of the photovoltaic microgrid operation mode are implemented.

[0035] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the seamless switching control method of the photovoltaic microgrid operation mode.

[0036] Compared with the prior art, the present invention has the following beneficial effects: on the one hand, the present invention controls the interconnection line power to the specified target value, reduces the transient transition time, and realizes the smooth switching of the grid-connected to independent grid-connected mode; on the other hand, the microgrid grid-connected synchronous protection device is utilized to realize the fully automatic and reliable switching of the independent grid-connected mode to the grid-connected mode, thereby improving the continuity and quality of power supply to the microgrid load, while reducing the impact on the main grid during the microgrid grid-connected process, and having good grid-connected friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0038] Figure 1 A method flow chart of a seamless switching control method and system for a photovoltaic microgrid operation mode according to an embodiment of the present invention;

[0039] Figure 2 A seamless switching control method for a photovoltaic microgrid operation mode and a tie line power control flow chart of the system according to an embodiment of the present invention;

[0040] Figure 3 A three-phase waveform diagram of a microgrid voltage and a grid voltage at the time of switching from grid connection to independent grid construction of a seamless switching control method and system for a photovoltaic microgrid operation mode according to an embodiment of the present invention;

[0041] Figure 4 A three-phase waveform diagram of the microgrid voltage and the grid voltage at the moment of independent grid construction to grid connection according to a seamless switching control method and system for a photovoltaic microgrid operation mode described in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0043] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0044] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0045] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0046] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0047] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] Example 1

[0049] Reference Figure 1-2 , is an embodiment of the present invention, which provides a seamless switching control method for a photovoltaic microgrid operation mode, which is applicable to a photovoltaic microgrid including an energy storage unit, a photovoltaic power generation unit, a local load, an energy management system, and a microgrid grid-connected synchronous protection device; wherein the energy storage unit adopts a power autonomous synchronous control method, and the method includes:

[0050] S100: Acquire the real-time power of the energy storage unit, the photovoltaic power generation unit and the tie line. When the microgrid is switched from the grid-connected mode to the independent grid-connected mode, the grid-connected switch is disconnected after the tie line power reaches a predetermined target value, thereby completing a smooth switch from the grid-connected mode to the independent grid-connected mode.

[0051] S200: When switching from independent grid construction to grid connection, the microgrid automatically tracks the frequency, voltage and phase of the main grid under the regulation of the energy management system, determines the grid connection conditions through the microgrid grid connection synchronization protection device, and completes the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid connection operation mode.

[0052] It should be noted that when the microgrid is switched from the grid-connected mode to the independent grid-connected mode, the power of the interconnecting line is controlled to the specified target value to reduce the impact of the switching transition process on the power quality and reduce the transient transition time. When switching from independent grid-connected mode to grid-connected mode, the microgrid automatically tracks the frequency, voltage and phase of the main grid under the regulation of the energy management system, and determines the grid-connected conditions through the microgrid grid-connected synchronous protection device, so as to realize the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid-connected operation mode to the grid-connected operation mode, thereby reducing the impact of the microgrid on the main grid during the grid-connected process.

[0053] It should be noted that when the photovoltaic microgrid is planned to switch from grid-connected to independent grid-connected operation, in order to reduce the impact of the transition process of switching from grid-connected to independent grid-connected operation on the power quality and reduce the transient transition time, the energy storage charging and discharging power is pre-adjusted through the microgrid energy management system before the switching test, so that the power of the interconnection line between the microgrid and the main grid is within an acceptable range, and the switching operation of grid-connected to independent grid-connected operation is performed. The main implementation process is described as follows: the background data of the energy management system is refreshed to obtain the real-time power of each energy storage unit, photovoltaic power generation unit and interconnection line in the microgrid; the required active power adjustment compensation value is calculated; the range of the adjustable potential of the external exchange power of the energy storage unit is calculated; the interconnection line power is controlled constantly, which is achieved by adjusting the energy storage unit, photovoltaic power generation unit and load power; the interconnection line power is adjusted to the target value, and the grid-connected switch is disconnected to realize the switching of the grid-connected to independent grid-connected mode.

[0054] In the embodiment of the present application, disconnecting the grid-connected switch after controlling the tie line power to a predetermined target value includes: calculating the active power regulation compensation value and the adjustable potential range of the external exchange power of the energy storage unit;

[0055] Assume that the actual sampling value of the tie line power at the current moment is x(n), and the target value is P 恒定 , then the active power regulation demand value is:

[0056] ΔP 调节 =P 恒定 -x(n)

[0057] The maximum charge and discharge power of each energy storage unit is set as The current real-time power of each energy storage unit is The range of the adjustable potential of external exchange power of each energy storage unit is calculated as follows:

[0058]

[0059] Define the set φ n is the set of all energy storage units, then the adjustable potential range of the energy storage unit is

[0060]

[0061] In the embodiment of the present application, it also includes:

[0062] If the active power regulation demand value is within the adjustable potential range of the energy storage unit, the active power regulation demand value is fully borne by the energy storage unit; if the active power regulation demand value is not within the adjustable potential range of the energy storage unit, the active power regulation demand value cannot fully meet the power regulation needs;

[0063] When the active power regulation demand value cannot fully meet the power regulation needs, if the active power regulation demand value is greater than 0, part of the local load is cut off, the tie line power is adjusted to the target value, the grid-connected switch is cut off, and the grid-connected to independent grid mode switching is realized;

[0064] If the active power regulation demand value is not greater than 0, the photovoltaic power generation unit will operate with limited power, adjust the interconnection line power to the target value, cut off the grid-connected switch, and realize the switching from grid-connected to independent grid-connected mode.

[0065] In an embodiment of the present application, when the microgrid switches from an independent grid-connected mode to a grid-connected mode, the voltage and frequency support of the system is switched from the energy storage unit to the main grid, and the energy storage unit instantaneously bears the sudden changes in active power and reactive power caused by the load transfer.

[0066] In the embodiment of the present application, when switching from independent grid construction to grid connection, the microgrid automatically tracks the frequency, voltage and phase of the main grid under the regulation of the energy management system, including:

[0067] When the microgrid is in the independent grid operation mode, the energy management system receives the microgrid grid connection closing command issued by the dispatcher and sends the grid connection closing command to the synchronous protection device;

[0068] The synchronous protection device sends frequency and voltage adjustment instructions to the energy storage unit to determine the grid-connected conditions. When the synchronous protection device checks the synchronization and the grid-connected conditions are met, it automatically controls the microgrid grid-connected switch to close, completing the switch from independent grid construction to grid-connected mode.

[0069] In the embodiment of the present application, the grid connection conditions are determined by the microgrid grid-connected synchronous protection device, including:

[0070] When the energy storage unit receives the frequency adjustment instruction, the output phase of the inverter is adjusted by adjusting the self-generated angular frequency so that it tracks the phase of the upper common node, completing the phase pre-synchronization process of the energy storage unit; at the same time, the voltage amplitude of the bridge arm of the energy storage unit is adjusted so that the output voltage amplitude of the inverter tracks the voltage amplitude of the upper grid, completing the amplitude pre-synchronization process of the energy storage unit.

[0071] In the embodiment of the present application, it also includes: when the microgrid switches from unplanned grid connection to independent grid construction, the power impact in the transition process is borne by the energy storage unit of multiple machines in parallel.

[0072] The above is a schematic scheme of a seamless switching control method for a photovoltaic microgrid operation mode of this embodiment. It should be noted that the technical scheme of the seamless switching control system for the photovoltaic microgrid operation mode and the technical scheme of the seamless switching control method for the photovoltaic microgrid operation mode described above belong to the same concept. For details not described in detail in the technical scheme of the seamless switching control system for the photovoltaic microgrid operation mode of this embodiment, please refer to the description of the technical scheme of the seamless switching control method for the photovoltaic microgrid operation mode described above.

[0073] In this embodiment, a seamless switching control system of a photovoltaic microgrid operation mode is applicable to a photovoltaic microgrid including an energy storage unit, a photovoltaic power generation unit, a local load, an energy management system, and a microgrid grid-connected synchronous protection device; wherein the energy storage unit adopts a power autonomous synchronous control method, and the system includes:

[0074] The first switching control module is used to obtain the real-time power of the energy storage unit, the photovoltaic power generation unit and the tie line. When the microgrid is switched from the grid-connected mode to the independent grid-connected mode, the grid-connected switch is disconnected after the tie line power reaches a predetermined target value, thereby completing a smooth switch from the grid-connected mode to the independent grid-connected mode.

[0075] The second switching control module is used for automatically tracking the frequency, voltage and phase of the main grid under the regulation of the energy management system when switching from independent grid construction to grid connection, judging the grid connection conditions through the microgrid grid connection synchronization protection device, and completing the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid connection operation mode.

[0076] This embodiment further provides a computing device, which is applicable to the case of a seamless switching control method of a photovoltaic microgrid operation mode, including:

[0077] Memory and processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the seamless switching control method for realizing the photovoltaic microgrid operation mode as proposed in the above embodiment.

[0078] This embodiment further provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for seamlessly switching the photovoltaic microgrid operation mode proposed in the above embodiment is implemented.

[0079] The storage medium proposed in this embodiment and the seamless switching control method for realizing the photovoltaic microgrid operation mode proposed in the above embodiment belong to the same inventive concept. The technical details not described in detail in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0080] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0081] Example 2

[0082] Reference Figure 3-4 , which is an embodiment of the present invention. This embodiment is different from the first embodiment in that this embodiment verifies the correctness and feasibility of the present invention by conducting field tests on the seamless switching control method of the photovoltaic microgrid operation mode.

[0083] Reference Figure 3 The three-phase waveforms of the microgrid voltage and the grid voltage at the time of grid-connected to independent grid construction are given. The experimental waveforms show that there is no distortion or impact on the microgrid side voltage during the switching process from grid-connected to independent grid construction, and a smooth transition is achieved. Figure 4 The three-phase waveforms of the microgrid voltage and the grid voltage at the moment of independent grid construction to grid connection are given. The experimental waveforms show that during the switching process from independent grid construction to grid connection, the microgrid did not cause any impact on the grid and achieved a smooth transition.

[0084] On the one hand, the present invention controls the interconnection line power to the specified target value, reduces the transient transition time, and realizes smooth switching from grid-connected to independent grid-connected mode; on the other hand, the microgrid grid-connected synchronous protection device is used to realize fully automatic and reliable switching from independent grid-connected mode to grid-connected mode, thereby improving the continuity and quality of power supply to the microgrid load, while reducing the impact on the main grid during the microgrid grid-connected process, and having good grid-connected friendliness.

[0085] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A seamless switching control method for photovoltaic microgrid operation mode, characterized in that: Applicable to a photovoltaic storage microgrid including an energy storage unit, a photovoltaic power generation unit, a local load, an energy management system, and a microgrid grid-connected synchronization protection device; wherein the energy storage unit adopts a power autonomous synchronization control method, the method comprising: Obtain the real-time power of the energy storage unit, photovoltaic power generation unit and tie line. When the microgrid switches from the grid-connected mode to the independent grid-connected mode, the grid-connected switch is disconnected after the tie line power reaches the predetermined target value, completing the smooth switching from the grid-connected mode to the independent grid-connected mode. When switching from independent grid construction to grid-connected operation, the microgrid automatically tracks the frequency, voltage and phase of the main grid under the regulation of the energy management system, determines the grid connection conditions through the microgrid grid-connected synchronization protection device, and completes the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid-connected operation mode.

2. The method for seamless switching control of photovoltaic microgrid operation mode according to claim 1, characterized in that: Disconnecting the grid-connected switch after controlling the tie line power to a predetermined target value includes: calculating the active power regulation compensation value and the adjustable potential range of the external exchange power of the energy storage unit; Assume that the actual sampling value of the tie line power at the current moment is x(n), and the target value is P 恒定 , then the active power regulation demand value is: ΔP 调节 =P 恒定 -x(n) The maximum charge and discharge power of each energy storage unit is set as The current real-time power of each energy storage unit is The range of the adjustable potential of external exchange power of each energy storage unit is calculated as follows: Define the set φ n is the set of all energy storage units, then the adjustable potential range of the energy storage unit is 3. The method for seamless switching control of photovoltaic microgrid operation mode according to claim 2, characterized in that: Also includes: If the active power regulation demand value is within the adjustable potential range of the energy storage unit, the active power regulation demand value is fully borne by the energy storage unit; If the active power regulation demand value is not within the adjustable potential range of the energy storage unit, the active power regulation demand value cannot fully meet the power regulation needs; When the active power regulation demand value cannot fully meet the power regulation needs, if the active power regulation demand value is greater than 0, part of the local load is cut off, the tie line power is adjusted to the target value, the grid-connected switch is cut off, and the grid-connected to independent grid mode switching is realized; If the active power regulation demand value is not greater than 0, the photovoltaic power generation unit will operate with limited power, adjust the interconnection line power to the target value, cut off the grid-connected switch, and realize the switching from grid-connected to independent grid-connected mode.

4. The method for seamless switching control of the photovoltaic microgrid operation mode according to claim 1 or 3, characterized in that: When the microgrid switches from an independent grid-connected mode to a grid-connected mode, the voltage and frequency support of the system is switched from the energy storage unit to the main grid, and the energy storage unit instantaneously bears the sudden changes in active power and reactive power caused by load transfer.

5. The method for seamless switching control of photovoltaic microgrid operation mode according to claim 4, characterized in that: When switching from independent grid construction to grid connection, the microgrid automatically tracks the frequency, voltage and phase of the main grid under the regulation of the energy management system, including: When the microgrid is in the independent grid operation mode, the energy management system receives the microgrid grid connection closing command issued by the dispatcher and sends the grid connection closing command to the synchronous protection device; The synchronous protection device sends frequency and voltage adjustment instructions to the energy storage unit to determine the grid-connected conditions. When the synchronous protection device checks the synchronization and the grid-connected conditions are met, it automatically controls the microgrid grid-connected switch to close, completing the switch from independent grid construction to grid-connected mode.

6. The method for seamless switching control of photovoltaic microgrid operation mode according to claim 5, characterized in that: The grid connection conditions determined by the microgrid grid-connected synchronous protection device include: When the energy storage unit receives a frequency adjustment instruction, the output phase of the inverter is adjusted by adjusting the self-generated angular frequency so that it tracks the phase of the upper common node, completing the phase pre-synchronization process of the energy storage unit; at the same time, the voltage amplitude of the bridge arm of the energy storage unit is adjusted so that the output voltage amplitude of the inverter tracks the voltage amplitude of the upper power grid, completing the amplitude pre-synchronization process of the energy storage unit.

7. The method for seamless switching control of photovoltaic microgrid operation mode according to claim 1, characterized in that: Also includes: When the microgrid switches from unplanned grid connection to independent grid construction, the power impact during the transition process is borne by the energy storage units with multiple machines in parallel.

8. A seamless switching control system for photovoltaic microgrid operation mode, characterized in that: Applicable to a photovoltaic storage microgrid including an energy storage unit, a photovoltaic power generation unit, a local load, an energy management system, and a microgrid grid-connected synchronization protection device; wherein the energy storage unit adopts a power autonomous synchronization control method, and the system includes: The first switching control module is used to obtain the real-time power of the energy storage unit, the photovoltaic power generation unit and the tie line. When the microgrid is switched from the grid-connected mode to the independent grid-connected mode, the grid-connected switch is disconnected after the tie line power reaches a predetermined target value, thereby completing a smooth switch from the grid-connected mode to the independent grid-connected mode. The second switching control module is used for automatically tracking the frequency, voltage and phase of the main grid under the regulation of the energy management system when switching from independent grid construction to grid connection, judging the grid connection conditions through the microgrid grid connection synchronization protection device, and completing the fully automatic and reliable switching of the photovoltaic microgrid from the independent grid construction operation mode to the grid connection operation mode.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the seamless switching control method of the photovoltaic microgrid operation mode described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for seamless switching control of photovoltaic microgrid operation modes as described in any one of claims 1 to 7.

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