A grid-constructing and grid-following energy storage islanded grid cooperative control method and system

Abstract

A kind of suitable for network type and follow network type energy storage isolated network collaborative control method and system, real-time monitoring network type energy storage remaining available capacity;Determine whether the active remaining available capacity of network type energy storage is less than active threshold, further determine whether the active remaining available capacity of follow network type energy storage is greater than power threshold, if greater, frequency deviation control is adopted to network type energy storage, and frequency additional control strategy is adopted to follow network type energy storage;Determine whether the reactive remaining available capacity of network type energy storage is less than reactive threshold, further determine whether the reactive remaining available capacity of follow network type energy storage is greater than reactive threshold, if greater, voltage amplitude deviation control is adopted to network type energy storage, and voltage additional control strategy is adopted to follow network type energy storage.The present application realizes the collaborative control of network type energy storage and follow network type energy storage in microgrid in isolated network mode, reduces artificial intervention operation, and ensures that power grid is safe, stable operation.

Description

TECHNICAL FIELD

[0001] The application relates to a grid-forming and grid-following energy storage islanded grid cooperative control method and system, and belongs to the technical field of new energy power transmission. BACKGROUND

[0002] The determination of the "double carbon" target will inevitably bring new challenges to the development of the energy and power industry. Energy supply, energy consumption, energy informatization, energy structure adjustment, and the use of emerging energy technologies all need to be adjusted and deployed. In a new energy high-penetration power system, with the increasing proportion of power electronic converters in the power system, the traditional grid dominated by synchronous generators is changing. The proportion of corresponding converters in the power system is increasing, the system inertia is greatly reduced, and the system frequency index is deteriorating, but the response of the converter is faster than that of the synchronous generator, and the power controllability is stronger. Energy storage technology is one of the means to solve the problem of reduced inertia of the power electronic AC grid system after the development of grid-forming energy storage technology, which can more realistically simulate synchronous generator technology. However, based on the current situation, grid-forming energy storage and grid-following energy storage will coexist in large quantities in the power grid, so it is necessary to further study the cooperative method of grid-forming energy storage and grid-following energy storage in islanded grid operation to achieve optimized operation of the system.

[0003] Chinese patent application CN202311157707.9 discloses a new energy-energy storage system cluster grid-forming and grid-following mode control method and system. After obtaining the data information of the power system structure and the new energy-energy storage system cluster in the region, the data information is normalized to obtain normalized data. The normalized data is used to evaluate the grid-forming capability of each new energy-energy storage system, and a new energy-energy storage system cluster grid-forming and grid-following mode combination optimization mathematical model for new energy-energy storage system cluster operation mode control is constructed. The mixed integer programming algorithm is used to determine the decision instruction and control instruction of each new energy-energy storage system cluster grid-forming operation mode, so as to plan and schedule each new energy and energy storage converter in the power grid. However, this patent technology does not fully consider the coordination and interaction of grid-forming energy storage and grid-following energy storage in islanded grid operation. SUMMARY

[0004] The purpose of the present application is to provide a grid-forming and grid-following energy storage islanded grid cooperative control method and system.

[0005] To achieve the above-mentioned application purposes, the following technical solutions are specifically adopted in the present application.

[0006] A grid-forming and grid-following energy storage islanded grid cooperative control method, a microgrid system is composed of grid-forming energy storage, grid-following energy storage, new energy power generation equipment and load, and the method comprises:

[0007] Step 1: In the island mode of the micro-grid system, the grid-forming energy storage operates in the AC voltage and frequency control mode, and the grid-following energy storage operates in the constant active power and constant reactive power mode; the remaining available capacity of the grid-forming energy storage is monitored in real time;

[0008] Step 2: Determine whether the active remaining available capacity of the grid-forming energy storage is less than a first active threshold value; when the active remaining available capacity of the grid-forming energy storage is less than the first active threshold value, the grid-forming energy storage adopts slope control, and then step 3 is entered, otherwise step 4 is entered;

[0009] Step 3: Further determine whether the active remaining available capacity of the grid-following energy storage is greater than a second active threshold value; if not, the grid-forming energy storage continues to adopt slope control, the grid-following energy storage continues to adopt the constant active power and constant reactive power control mode, and the relationship between the active remaining available capacity of the grid-following energy storage and the second active threshold value is continuously monitored; when the active remaining available capacity of the grid-following energy storage is greater than the second active threshold value, frequency deviation control is adopted for the grid-forming energy storage, and a frequency additional control strategy is adopted for the grid-following energy storage;

[0010] Step 4: After the frequency control of the grid-forming energy storage and the grid-following energy storage, determine whether the reactive remaining available capacity of the grid-forming energy storage is less than a first reactive threshold value; when the reactive remaining available capacity of the grid-forming energy storage is less than the first reactive threshold value, the grid-forming energy storage adopts slope control, and then step 5 is entered, otherwise step 1 is returned;

[0011] Step 5: Further determine whether the reactive remaining available capacity of the grid-following energy storage is greater than a second reactive threshold value; if not, the grid-forming energy storage continues to adopt slope control, the grid-following energy storage continues to adopt the constant active power and constant reactive power control mode, and the relationship between the reactive remaining available capacity of the grid-following energy storage and the second reactive threshold value is continuously monitored; if yes, voltage amplitude deviation control is adopted for the grid-forming energy storage, and a voltage additional control strategy is adopted for the grid-following energy storage.

[0012] Further preferably,

[0013] In step 2, the first active threshold value is 25% of the active capacity of the grid-forming energy storage.

[0014] Further preferably,

[0015] In step 3, the second active threshold value is 15% of the active capacity of the grid-forming energy storage.

[0016] Further preferably,

[0017] In step 3, the frequency deviation control is adopted for the grid-forming energy storage, and the frequency additional control strategy is adopted for the grid-following energy storage, which specifically includes:

[0018] The first-stage frequency deviation control of the grid-forming energy storage reduces the first-stage active output, and the isolated grid AC frequency drops to the first frequency threshold range;

[0019] The frequency additional control of the grid-following energy storage increases the active power output of the grid-following energy storage, and the isolated grid AC frequency is raised to the second frequency threshold range;

[0020] The second-stage frequency deviation control of the grid-forming energy storage reduces the second-stage active output, and the isolated grid AC frequency drops to the third frequency threshold range;

[0021] The frequency additional control of the grid-following energy storage continues to increase the active power output of the grid-following energy storage, and the isolated grid AC frequency is raised to the fourth frequency threshold range.

[0022] Further preferably,

[0023] In the first-stage frequency deviation control and the second-stage frequency deviation control, the grid-forming energy storage adopts droop control based on the active power capacity to be raised and generates frequency deviation control instructions, superimposes an AC frequency reference value to obtain active instructions, and the grid-forming energy storage reduces the first-stage and second-stage active outputs based on the active instructions, wherein the first frequency threshold range is 50±0.2 Hz, and the third frequency threshold range is 50±0.1 Hz.

[0024] Further preferably,

[0025] After the first-stage frequency deviation control of the grid-forming energy storage, the grid-following energy storage generates active output instructions to increase the active power output of the grid-following energy storage according to the deviation of the isolated grid AC frequency from the rated frequency; if the active power of the grid-following energy storage fails to be output according to the instructions, the deviation of the isolated grid frequency exists all the time, the grid-forming energy storage maintains the deviation frequency operation and sends an alarm; if the active power of the grid-following energy storage raises the isolated grid AC frequency to the second frequency threshold range, the grid-forming energy storage starts the second-stage frequency deviation control;

[0026] After the second-stage frequency deviation control of the grid-forming energy storage, the grid-following energy storage generates active output instructions to increase the active power output of the grid-following energy storage according to the deviation of the isolated grid AC frequency from the rated frequency, and raises the isolated grid AC frequency to the fourth frequency threshold range; if the active power of the grid-following energy storage fails to be output according to the instructions, the deviation of the isolated grid frequency exists all the time, the grid-forming energy storage maintains the deviation frequency operation and sends an alarm;

[0027] The second frequency threshold range is 50±0.15 Hz, and the fourth frequency threshold range is 50±0.1 Hz.

[0028] Further preferably,

[0029] In step 4, the first reactive threshold is 25% of the grid-forming energy storage capacity.

[0030] In step 5, the second reactive threshold is 15% of the grid-forming energy storage reactive capacity.

[0031] Further preferably,

[0032] In step 5, the grid-forming energy storage adopts voltage amplitude deviation control, and the grid-following energy storage adopts voltage additional control strategy, specifically including:

[0033] The grid-forming energy storage inputs the first-stage voltage deviation control to reduce the first-stage reactive output, and the isolated grid AC voltage amplitude drops to the first voltage amplitude threshold range;

[0034] The grid-following energy storage inputs the voltage additional control to increase the grid-following energy storage reactive power output, and the isolated grid AC voltage amplitude rises to the second voltage amplitude threshold range;

[0035] The grid-forming energy storage inputs the second-stage voltage deviation control to reduce the second-stage reactive output, and the isolated grid AC voltage amplitude drops to the third voltage amplitude threshold range;

[0036] The grid-following energy storage continues to input the voltage additional control to increase the grid-following energy storage reactive power output, and the isolated grid AC voltage amplitude rises to the fourth voltage amplitude threshold range.

[0037] Further preferably,

[0038] The first voltage amplitude threshold range is [0.95Ue, Ue], the second voltage amplitude threshold range is [0.98Ue, 1.05Ue], the third voltage amplitude threshold range is [0.96Ue, Ue], and the fourth voltage amplitude threshold range is [0.98Ue, 1.02Ue].

[0039] In another aspect, the application discloses a grid-forming and grid-following energy storage isolated grid cooperative control system based on the cooperative control method, including a grid-forming energy storage remaining available capacity judgment module, a grid-forming energy storage slope control module, a grid-following energy storage remaining capacity judgment module, a grid-forming energy storage deviation control module, and a grid-following energy storage additional control module, characterized in that:

[0040] The network type energy storage remaining available capacity judgment module judges whether the network type energy storage active remaining available capacity is less than a first active threshold. When the network type energy storage active remaining available capacity is less than the first active threshold, the network type energy storage slope control module is started. Otherwise, whether the active remaining available capacity of the grid-connected type energy storage is greater than a second active threshold is further judged. If it is not greater than, the network type energy storage slope control module remains started. Otherwise, the network type energy storage deviation control module inputs two-stage frequency deviation control, and the grid-connected type energy storage additional control module inputs frequency deviation control.

[0041] The network type energy storage remaining available capacity judgment module judges whether the network type energy storage reactive remaining available capacity is less than a first reactive threshold. When the network type energy storage reactive remaining available capacity is less than the first reactive threshold, the network type energy storage slope control module is started. Otherwise, whether the reactive remaining available capacity of the grid-connected type energy storage is greater than a second reactive threshold is further judged. If it is not greater than, the network type energy storage slope control module remains started. Otherwise, the network type energy storage deviation control module inputs two-stage voltage deviation control, and the grid-connected type energy storage additional control module inputs voltage deviation control.

[0042] The present application optimizes the power grid in the island and grid-connected mode, realizes the collaborative control of the network type energy storage and the grid-connected type energy storage in different states, and stabilizes the AC power grid voltage and frequency through seamless switching of the network type and grid-connected type energy storage modes. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a network type and grid-connected type energy storage island collaborative control system schematic diagram suitable for the present application.

[0044] Figure 2 It is a frequency deviation control process schematic diagram suitable for the network type and grid-connected type energy storage island collaborative control method of the present application.

[0045] Figure 3 It is a voltage deviation control process schematic diagram suitable for the network type and grid-connected type energy storage island collaborative control method of the present application. DETAILED DESCRIPTION

[0046] To make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. The embodiments described in the present application are only a part of the embodiments of the present application, not all the embodiments. Based on the spirit of the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0047] Referring to the drawings, Figures 2-3 The present application discloses a network type and grid-connected type energy storage island collaborative control method suitable for the present application, as shown in the drawingsFigure 1 As shown in the figure, the micro-grid system is composed of grid-forming energy storage, grid-following energy storage, new energy power generation equipment and load, and the method comprises the following steps:

[0048] Step 1: In the island mode of the micro-grid system, the grid-forming energy storage operates in the AC voltage and frequency control mode, and the grid-following energy storage operates in the constant active power and constant reactive power mode; the remaining available capacity of the grid-forming energy storage is monitored in real time;

[0049] The remaining available capacity includes the active remaining available capacity and the reactive remaining available capacity. In the embodiment of the application, the active remaining available capacity is detected and judged first, and then the reactive remaining available capacity is detected and judged after the active power of the island is controlled.

[0050] Step 2: It is judged whether the active remaining available capacity of the grid-forming energy storage is less than a first active threshold value. When the active remaining available capacity of the grid-forming energy storage is less than the first active threshold value, the grid-forming energy storage adopts slope control, and then enters step 3, otherwise enters step 4; wherein the first active threshold value is 25% of the active capacity of the grid-forming energy storage.

[0051] Step 3: It is further judged whether the active remaining available capacity of the grid-following energy storage is greater than a second active threshold value. If not, the grid-forming energy storage continues to adopt slope control, the grid-following energy storage continues to adopt the constant active power and constant reactive power control mode, and the relationship between the active remaining available capacity of the grid-following energy storage and the second active threshold value is continuously monitored and judged; when the active remaining available capacity of the grid-following energy storage is greater than the second active threshold value, frequency deviation control is adopted for the grid-forming energy storage, and frequency additional control strategy is adopted for the grid-following energy storage;

[0052] The second active threshold value is 15% of the active capacity of the grid-forming energy storage.

[0053] Referring to the accompanying drawings, Figure 2 The frequency deviation control is adopted for the grid-forming energy storage, and the frequency additional control strategy is adopted for the grid-following energy storage, which specifically comprises:

[0054] The grid-forming energy storage is put into the first stage frequency deviation control to reduce the first stage active output, and the island AC frequency is reduced to the first frequency threshold range;

[0055] The grid-following energy storage is put into the frequency additional control to increase the active power output of the grid-following energy storage, and the island AC frequency is increased to the second frequency threshold range;

[0056] The grid-forming energy storage is put into the second stage frequency deviation control to reduce the second stage active output, and the island AC frequency is reduced to the third frequency threshold range;

[0057] The grid-connected energy storage continues to invest in frequency additional control, increases the active power output of the grid-connected energy storage, and raises the isolated grid AC frequency to the fourth frequency threshold range.

[0058] In the first-stage frequency deviation control and the second-stage frequency deviation control, the grid-forming energy storage adopts droop control based on the active power capacity to be raised and generates frequency deviation control instructions, superimposes an AC frequency reference value to obtain an active instruction, and the grid-forming energy storage reduces the active output in the first stage and the second stage based on the active instruction, wherein the first frequency threshold range is 50±0.2 Hz, and the third frequency threshold range is 50±0.1 Hz.

[0059] After the first-stage frequency deviation control of the grid-forming energy storage, the grid-connected energy storage generates an active output instruction to increase the active power output of the grid-connected energy storage according to the deviation of the isolated grid AC frequency from the rated frequency; if the active power of the grid-connected energy storage fails to be output according to the instruction, the isolated grid frequency deviation exists all the time, the grid-forming energy storage maintains the deviation frequency operation and sends an alarm; if the active power of the grid-connected energy storage raises the isolated grid AC frequency to the second frequency threshold range, the grid-forming energy storage starts the second-stage frequency deviation control.

[0060] After the second-stage frequency deviation control of the grid-forming energy storage, the grid-connected energy storage generates an active output instruction to increase the active power output of the grid-connected energy storage according to the deviation of the isolated grid AC frequency from the rated frequency, and raises the isolated grid AC frequency to the fourth frequency threshold range; if the active power of the grid-connected energy storage fails to be output according to the instruction, the isolated grid frequency deviation exists all the time, the grid-forming energy storage maintains the deviation frequency operation and sends an alarm.

[0061] The second frequency threshold range is 50±0.15 Hz, and the fourth frequency threshold range is 50±0.1 Hz.

[0062] Step 4: After the frequency control of the grid-forming energy storage and the grid-connected energy storage, it is judged whether the remaining available capacity of the grid-forming energy storage is less than the first reactive threshold; when it is less than the first reactive threshold, the grid-forming energy storage adopts slope control, and then proceeds to step 5, otherwise returns to step 1.

[0063] The first reactive threshold is 25% of the capacity of the grid-forming energy storage.

[0064] Step 5: It is further judged whether the remaining available capacity of the grid-connected energy storage is greater than the second reactive threshold; if it is not greater than, the grid-forming energy storage continues to adopt slope control, the grid-connected energy storage continues to adopt the fixed active power and reactive power control mode, and the relationship between the remaining available capacity of the grid-connected energy storage and the second reactive threshold is continuously monitored and judged; if it is greater than, the grid-forming energy storage adopts voltage amplitude deviation control, and the grid-connected energy storage adopts voltage additional control strategy.

[0065] The second reactive threshold is 15% of the reactive capacity of the grid-constructing energy storage.

[0066] Referring to the accompanying drawings Figure 3 The voltage amplitude deviation control is adopted for the grid-constructing energy storage, and the voltage additional control strategy is adopted for the grid-following energy storage, and specifically includes:

[0067] The grid-constructing energy storage is put into the first-stage voltage deviation control to reduce the first-stage reactive output, and the AC voltage amplitude of the isolated network is reduced to the first voltage amplitude threshold range;

[0068] The grid-following energy storage is put into the voltage additional control to increase the reactive power output of the grid-following energy storage, and the AC voltage amplitude of the isolated network is increased to the second voltage amplitude threshold range;

[0069] The grid-constructing energy storage is put into the second-stage voltage deviation control to reduce the second-stage reactive output, and the AC voltage amplitude of the isolated network is reduced to the third voltage amplitude threshold range;

[0070] The grid-following energy storage continues to be put into the voltage additional control to increase the reactive power output of the grid-following energy storage, and the AC voltage amplitude of the isolated network is increased to the fourth voltage amplitude threshold range.

[0071] In the embodiment of the application, the first voltage amplitude threshold range is [0.95Ue, Ue], the second voltage amplitude threshold range is [0.98Ue, 1.05Ue], the third voltage amplitude threshold range is [0.96Ue, Ue], and the fourth voltage amplitude threshold range is [0.98Ue, 1.02Ue].

[0072] The application discloses a grid-constructing and grid-following energy storage isolated network collaborative control system based on the collaborative control method, which comprises a grid-constructing energy storage residual available capacity judgment module, a grid-constructing energy storage slope control module, a grid-following energy storage residual capacity judgment module, a grid-constructing energy storage deviation control module and a grid-following energy storage additional control module.

[0073] The grid-constructing energy storage residual available capacity judgment module judges whether the active residual available capacity of the grid-constructing energy storage is less than a first active threshold, and when the active residual available capacity of the grid-constructing energy storage is less than the first active threshold, the grid-constructing energy storage slope control module is started; otherwise, it is further judged whether the active residual available capacity of the grid-following energy storage is greater than a second active threshold, if not, the grid-constructing energy storage slope control module is kept started, otherwise, the grid-constructing energy storage deviation control module is put into two-stage frequency deviation control, and the grid-following energy storage additional control module is put into frequency deviation control;

[0074] The network-constructed energy storage remaining available capacity judgment module judges whether the network-constructed energy storage reactive power remaining available capacity is less than a first reactive power threshold. When the network-constructed energy storage reactive power remaining available capacity is less than the first reactive power threshold, the network-constructed energy storage slope control module is started; otherwise, it is further judged whether the reactive power remaining available capacity of the network-constructed energy storage is greater than a second reactive power threshold. If not, the network-constructed energy storage slope control module remains started; otherwise, the network-constructed energy storage deviation control module inputs two-stage voltage deviation control, and the network-constructed energy storage additional control module inputs voltage deviation control.

[0075] The present disclosure can be a system, a method, and / or a computer program product. The computer program product can include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

[0076] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or punched tape, a magnetically encoded device such as magnetic strip(s), an optically encoded device such as optical fiber, and / or any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0077] Computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0078] Computer readable program instructions for carrying out operations of the present disclosure can be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate array (FPGA), or programmable logic array (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present disclosure.

[0079] Embodiments of the present disclosure have been described above, and the description is intended to be illustrative of the various embodiments of the disclosure and not exhaustive. Numerous modifications and adaptations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The scope of the disclosure is defined by the appended claims and equivalents thereof. The choice of words in the description is intended to best explain the principles of the embodiments of the present disclosure, the practical application of the embodiments of the present disclosure, or the improvement over the technology in the art, or to enable others skilled in the art to understand the embodiments of the present disclosure disclosed herein.

Claims

1. A method for collaborative control of grid-forming and grid-following energy storage in islanded microgrid, the microgrid system comprising grid-forming energy storage, grid-following energy storage, new energy generation equipment and load, the method comprising: Step 1: in the islanded mode of the microgrid system, the grid-forming energy storage operates in an AC voltage and frequency control mode, and the grid-following energy storage operates in a constant active power and constant reactive power mode; real-time monitoring of the remaining available capacity of the grid-forming energy storage is performed; Step 2: determining whether the remaining available active capacity of the grid-forming energy storage is less than a first active threshold value; when the remaining available active capacity of the grid-forming energy storage is less than the first active threshold value, the grid-forming energy storage adopts a slope control, and then Step 3 is entered, otherwise Step 4 is entered; Step 3: further determining whether the remaining available active capacity of the grid-following energy storage is greater than a second active threshold value; if not, the grid-forming energy storage continues to adopt the slope control, the grid-following energy storage continues to adopt the constant active power and constant reactive power control mode, and the relationship between the remaining available active capacity of the grid-following energy storage and the second active threshold value is continuously monitored; when the remaining available active capacity of the grid-following energy storage is greater than the second active threshold value, frequency deviation control is adopted for the grid-forming energy storage, and a frequency additional control strategy is adopted for the grid-following energy storage; Step 4: after the frequency control of the grid-forming energy storage and the grid-following energy storage, determining whether the remaining available reactive capacity of the grid-forming energy storage is less than a first reactive threshold value; when the remaining available reactive capacity of the grid-forming energy storage is less than the first reactive threshold value, the grid-forming energy storage adopts a slope control, and then Step 5 is entered, otherwise Step 1 is returned; Step 5: further determining whether the remaining available reactive capacity of the grid-following energy storage is greater than a second reactive threshold value; if not, the grid-forming energy storage continues to adopt the slope control, the grid-following energy storage continues to adopt the constant active power and constant reactive power control mode, and the relationship between the remaining available reactive capacity of the grid-following energy storage and the second reactive threshold value is continuously monitored; if yes, voltage amplitude deviation control is adopted for the grid-forming energy storage, and a voltage additional control strategy is adopted for the grid-following energy storage. 2.The method for collaborative control of grid-forming and grid-following energy storage in islanded microgrid according to claim 1, wherein in Step 2, the first active threshold value is 25% of the active capacity of the grid-forming energy storage. 3.The method for collaborative control of grid-forming and grid-following energy storage in islanded microgrid according to claim 1, wherein in Step 3, the second active threshold value is 15% of the active capacity of the grid-forming energy storage. 4.The method for collaborative control of grid-forming and grid-following energy storage in islanded microgrid according to claim 1, wherein in Step 3, the frequency deviation control for the grid-forming energy storage and the frequency additional control strategy for the grid-following energy storage specifically comprise: the grid-forming energy storage is put into first-stage frequency deviation control to reduce first-stage active output, and the islanded AC frequency is lowered to a first frequency threshold range; the grid-following energy storage is put into frequency additional control to increase the active power output of the grid-following energy storage, and the islanded AC frequency is raised to a second frequency threshold range; the grid-forming energy storage is put into second-stage frequency deviation control to reduce second-stage active output, and the islanded AC frequency is lowered to a third frequency threshold range. ​ ​ ​ ​ ​ ​ The grid-connected energy storage continues to invest in frequency additional control, increases the active power output of the grid-connected energy storage, and raises the isolated grid AC frequency to the fourth frequency threshold range.

5. The isolated grid collaborative control method for grid-connected energy storage and grid-following energy storage according to claim 4, wherein: In the first stage frequency deviation control and the second stage frequency deviation control, the grid-connected energy storage adopts droop control based on the active power capacity to be raised and generates frequency deviation control instructions, and obtains active instructions after superimposing the AC frequency reference value, and the grid-connected energy storage reduces the active output in the first stage and the second stage based on the active instructions, wherein the first frequency threshold range is 50±0.2 Hz, and the third frequency threshold range is 50±0.1 Hz.

6. The isolated grid collaborative control method for grid-connected energy storage and grid-following energy storage according to claim 5, wherein: After the first stage frequency deviation control of the grid-connected energy storage, the grid-following energy storage adopts frequency additional control to generate active output instructions to increase the active power output of the grid-following energy storage according to the deviation of the isolated grid AC frequency from the rated frequency; if the active power of the grid-following energy storage fails to be output according to the instructions, the isolated grid frequency deviation exists all the time, the grid-connected energy storage maintains the deviation frequency operation and sends an alarm; if the active power of the grid-following energy storage raises the isolated grid AC frequency to the second frequency threshold range, the grid-connected energy storage starts the second stage frequency deviation control; After the second stage frequency deviation control of the grid-connected energy storage, the grid-following energy storage adopts frequency additional control to generate active output instructions to increase the active power output of the grid-following energy storage according to the deviation of the isolated grid AC frequency from the rated frequency, and raises the isolated grid AC frequency to the fourth frequency threshold range; if the active power of the grid-following energy storage fails to be output according to the instructions, the isolated grid frequency deviation exists all the time, the grid-connected energy storage maintains the deviation frequency operation and sends an alarm; wherein the second frequency threshold range is 50±0.15 Hz, and the fourth frequency threshold range is 50±0.1 Hz.

7. The isolated grid collaborative control method for grid-connected energy storage and grid-following energy storage according to claim 1, wherein: In step 4, the first reactive power threshold value is 25% of the capacity of the grid-connected energy storage.

8. The isolated grid collaborative control method for grid-connected energy storage and grid-following energy storage according to claim 7, wherein: In step 5, the second reactive power threshold value is 15% of the reactive power capacity of the grid-connected energy storage.

9. The isolated grid collaborative control method for grid-connected energy storage and grid-following energy storage according to claim 1, wherein: In step 5, voltage amplitude deviation control is adopted for the grid-connected energy storage, and voltage additional control strategy is adopted for the grid-following energy storage, specifically including: The grid-connected energy storage invests in the first stage voltage deviation control to reduce the first stage reactive power output, and the isolated grid AC voltage amplitude drops to the first voltage amplitude threshold range; The grid-following energy storage invests in voltage additional control to increase the reactive power output of the grid-following energy storage, and raises the isolated grid AC voltage amplitude to the second voltage amplitude threshold range; The grid-connected energy storage invests in the second stage voltage deviation control to reduce the second stage reactive power output, and the isolated grid AC voltage amplitude drops to the third voltage amplitude threshold range; The grid-forming energy storage continues to invest in voltage additional control, increases the reactive power output of the grid-following energy storage, and improves the isolated grid AC voltage amplitude to the fourth voltage amplitude threshold range.

10. The method according to claim 9, characterized in that: the first voltage amplitude threshold range is [0.95Ue, Ue], the second voltage amplitude threshold range is [0.98Ue, 1.05Ue], the third voltage amplitude threshold range is [0.96Ue, Ue], and the fourth voltage amplitude threshold range is [0.98Ue, 1.02Ue].

11. A system for the coordinated control of grid-forming and grid-following energy storages in an isolated grid based on the method of any one of claims 1-10, comprising a grid-forming energy storage remaining available capacity judgment module, a grid-forming energy storage slope control module, a grid-following energy storage remaining capacity judgment module, a grid-forming energy storage deviation control module, and a grid-following energy storage additional control module, characterized in that: the grid-forming energy storage remaining available capacity judgment module judges whether the active power remaining available capacity of the grid-forming energy storage is less than a first active power threshold, and when the active power remaining available capacity of the grid-forming energy storage is less than the first active power threshold, the grid-forming energy storage slope control module is started; otherwise, it is further judged whether the active power remaining available capacity of the grid-following energy storage is greater than a second active power threshold, and if it is not greater than, the grid-forming energy storage slope control module remains started, otherwise the grid-forming energy storage deviation control module invests in two-stage frequency deviation control, and the grid-following energy storage additional control module invests in frequency deviation control; the grid-forming energy storage remaining available capacity judgment module judges whether the reactive power remaining available capacity of the grid-forming energy storage is less than a first reactive power threshold, and when the reactive power remaining available capacity of the grid-forming energy storage is less than the first reactive power threshold, the grid-forming energy storage slope control module is started; otherwise, it is further judged whether the reactive power remaining available capacity of the grid-following energy storage is greater than a second reactive power threshold, and if it is not greater than, the grid-forming energy storage slope control module remains started, otherwise the grid-forming energy storage deviation control module invests in two-stage voltage deviation control, and the grid-following energy storage additional control module invests in voltage deviation control.

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