Network-forming energy storage control method, device, equipment and medium for smooth switching of microgrid states

Abstract

This application is applicable to the field of microgrid control technology, and provides a grid-forming energy storage control method, device, equipment and medium for smooth switching of microgrid states. The method includes: sampling the interactive power of the connection line between the microgrid side and the distribution network side as the virtual unbalanced power, calculating the voltage phase deviation amount of the grid connection point before and after the microgrid switches from grid-connected to islanded state based on the virtual unbalanced power, and dynamically calculating the pre-compensation amount of the energy storage active power in combination with the damping integral response module and the second-order negative feedback loop; then iteratively correcting the phase angle through the power angle balance mechanism until the microgrid state switching constraint conditions are met. The technical solution provided by this application actively adjusts the output of the active power of the grid-forming energy storage, compensates for the voltage phase deviation caused by the unbalanced power of the connection line, significantly reduces the voltage phase difference between the microgrid side and the distribution network side, realizes the voltage phase synchronization during the microgrid grid-connected to islanded switching, and improves the reliability and stability of the microgrid state switching.

Description

Technical Field

[0001] This application belongs to the technical field of microgrid control, and particularly relates to a grid-forming energy storage control method, device, equipment and medium for smooth switching of microgrid states. Background Art

[0002] In a new power system, as a flexible distributed energy management system, a microgrid can operate independently in grid-connected mode and off-grid mode, with high energy utilization efficiency and environmental friendliness. However, during the process of the microgrid switching from the grid-connected state to the off-grid state, due to the significant deviation that may exist between the voltage phases on the microgrid side and the distribution grid side, it often leads to switching failures and even causes system instability problems. Therefore, how to effectively control the voltage phase deviation and ensure the smoothness of the microgrid grid-connected and off-grid state switching is an important research topic at present.

[0003] Traditional microgrid control methods are mostly based on passive control strategies, that is, mainly relying on the rapid response of the microgrid's own energy storage system to maintain grid stability. However, this method is difficult to effectively compensate for the voltage phase deviation caused by unbalanced power of the tie line. Especially when the transmission power of the tie line changes significantly, there is a risk of switching failure. In addition, existing control methods usually ignore the problem of voltage phase synchronization between the two ends of the microgrid and the distribution grid during the switching process, which greatly reduces the switching performance.

[0004] Therefore, how to improve the reliability and stability of microgrid state switching has become an urgent problem to be solved. Summary of the Invention

[0005] The embodiments of this application provide a grid-forming energy storage control method, device, equipment and medium for smooth switching of microgrid states, aiming to improve the reliability and stability of microgrid state switching.

[0006] In a first aspect, an embodiment of the present application provides a grid-forming energy storage control method for smooth switching of the microgrid state. The method includes: S1, sampling the interactive power of the connection line between the microgrid side and the distribution network side at time t as the first virtual unbalanced power; S2, based on the first virtual unbalanced power, calculating the voltage phase deviation amount of the connection point before and after the microgrid switches from the grid-connected state to the islanded state; S3, based on the voltage phase deviation amount, determining the active power set value of the grid-forming energy storage on the microgrid side; S4, based on the active power set value, calculating the first voltage phase angle of the connection point after the energy storage power is output on the microgrid side, and based on the voltage phase deviation amount and the first voltage phase angle, calculating the second voltage phase angle of the connection point after the energy storage power is output on the microgrid side at time t + 1; S5, calculating the target phase angle difference between the second voltage phase angle and the voltage phase angle of the connection point on the distribution network side, and based on the target phase angle difference and the preset microgrid grid-connected to islanded state switching constraint conditions, performing the microgrid grid-connected to islanded operation to achieve the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side when switching from the grid-connected state to the islanded state.

[0007] In a possible implementation manner, step S2 includes: using the absolute value of the first virtual unbalanced power as an input signal, and calculating the voltage phase deviation amount of the connection point before and after the microgrid switches from the grid-connected state to the islanded state by using a proportional-integral response module, and feeding back the voltage phase deviation amount to the grid-forming energy storage phase pre-synchronization link.

[0008] In a possible implementation manner, step S3 includes: based on the voltage phase deviation amount, calculating the active power pre-compensation amount required for the grid-forming energy storage on the microgrid side through a damping integral response module that resists voltage phase changes; based on the rated power of the energy storage and the active power pre-compensation amount, determining the active power set value of the grid-forming energy storage.

[0009] In a possible implementation manner, in step S4, the calculating the first voltage phase angle of the connection point after the energy storage power is output on the microgrid side based on the active power set value includes: in the active power phase conversion link of the grid-forming energy storage, calculating the target power deviation amount between the active power set value and the sampled value of the energy storage power output; based on the target power deviation amount, calculating the first voltage phase angle through a second-order negative feedback loop of power angle balance between the power deviation amount and the voltage phase amount.

[0010] In a possible implementation manner, calculating the second voltage phase angle of the grid connection point at the moment t+1 after the energy storage power output on the microgrid side based on the voltage phase deviation amount and the first voltage phase angle in step S4 includes: in the active power phase conversion link of the grid-forming energy storage, feeding back and superimposing the voltage phase deviation amount to the first voltage phase angle to correct the active power output by the grid-forming energy storage, so as to obtain the second voltage phase angle of the grid connection point at the moment t+1 after the energy storage power output on the microgrid side.

[0011] In a possible implementation manner, the preset grid connection / disconnection state switching constraint conditions of the microgrid include that the voltage phase angle difference between the grid connection point on the distribution network side and the microgrid side is less than the maximum phase angle allowed for the microgrid to operate in the off-grid state. The operation of switching the microgrid from grid connection to off-grid based on the target phase angle difference and the preset grid connection / disconnection state switching constraint conditions of the microgrid in step S5 includes: when the target phase angle difference is less than the maximum phase angle allowed for the microgrid to operate in the off-grid state, the microgrid controller issues a grid connection to off-grid switching instruction, and controls the disconnection of the tie switch between the microgrid and the distribution network based on the grid connection to off-grid switching instruction; when the target phase angle difference is greater than or equal to the maximum phase angle allowed for the microgrid to operate in the off-grid state, repeat step S4 until the target phase angle difference is less than the maximum phase angle allowed for the microgrid to operate in the off-grid state, and then the microgrid controller issues the grid connection to off-grid switching instruction, and controls the disconnection of the tie switch between the microgrid and the distribution network based on the grid connection to off-grid switching instruction.

[0012] In a possible implementation manner, step S5 further includes: sampling the interactive power of the tie line between the microgrid side and the distribution network side at the moment t+1 as the second virtual unbalanced power; determining the identification value of the power deviation flag bit based on the second virtual unbalanced power and the preset power deviation threshold of the microgrid grid connection to off-grid state; determining the identification value of the phase deviation flag bit based on the target phase angle difference and the maximum phase angle allowed for the microgrid to operate in the off-grid state; determining the identification value of the mode switching flag bit for the microgrid grid connection to off-grid based on the identification value of the power deviation flag bit and the identification value of the phase deviation flag bit; and performing the microgrid grid connection to off-grid operation based on the identification value of the mode switching flag bit for the microgrid grid connection to off-grid.

[0013] Second aspect, an embodiment of the present application provides a grid-forming energy storage control device for smooth switching of the microgrid state. The device includes: a data acquisition module, configured to sample the interactive power of the connection line between the microgrid side and the distribution network side at time t as the first virtual unbalanced power; a first calculation module, configured to calculate the voltage phase deviation amount of the grid connection point before and after the microgrid switches from the grid-connected state to the islanded state based on the first virtual unbalanced power; a second calculation module, configured to determine the set value of the active power of the grid-forming energy storage on the microgrid side based on the voltage phase deviation amount; a third calculation module, configured to calculate the first voltage phase angle of the grid connection point after the energy storage power is output on the microgrid side based on the set value of the active power, and calculate the second voltage phase angle of the grid connection point after the energy storage power is output on the microgrid side at time t+1 based on the voltage phase deviation amount and the first voltage phase angle; a state switching control module, configured to calculate the target phase angle difference between the second voltage phase angle and the voltage phase angle of the grid connection point on the distribution network side, and perform the microgrid grid-connected to islanded operation based on the target phase angle difference and the preset microgrid grid-connected to islanded state switching constraint conditions, so as to achieve the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side during the grid-connected to islanded state switching.

[0014] Third aspect, an embodiment of the present application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method described in the first aspect or any one of its implementation manners is implemented.

[0015] Fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the method described in the first aspect or any one of its implementation manners is implemented.

[0016] Fifth aspect, an embodiment of the present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the method described in the first aspect or any one of its implementation manners are implemented.

[0017] The beneficial effects of the embodiments of the present application compared with the prior art are as follows: extracting the interactive power of the connection line between the microgrid side and the distribution network side and converting it into virtual unbalanced power, calculating the voltage phase deviation based on the virtual unbalanced power, dynamically adjusting the set value of the active power of the energy storage based on the voltage phase deviation, and then compensating for the voltage phase deviation caused by the unbalanced power of the microgrid-distribution network connection line by actively regulating the output power of the network-forming energy storage, significantly reducing the deviation of the voltage phase between the microgrid and the distribution network, ensuring the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side during the grid-connected to off-grid state transition, achieving precise synchronization of the voltage phase, avoiding the problem of failure in the microgrid grid-connected to off-grid state switching due to excessive voltage phase deviation on both sides, and improving the reliability and stability of the microgrid state switching.

[0018] It can be understood that a network-forming energy storage control device, an electronic device, a computer-readable storage medium, and a computer program product for smooth switching of the microgrid state provided by the embodiments of the present application have the same beneficial effects as the above-mentioned network-forming energy storage control method for smooth switching of the microgrid state, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic flowchart of a network-forming energy storage control method for smooth switching of the microgrid state provided by an embodiment of the present application;

[0021] Figure 2 It is a schematic flowchart of another network-forming energy storage control method for smooth switching of the microgrid state provided by an embodiment of the present application;

[0022] Figure 3 It is a schematic diagram of the voltage phase deviation between the microgrid and the distribution network at both ends during the grid-connected to off-grid state provided by an embodiment of the present application;

[0023] Figure 4 It is a schematic diagram of the interactive power of the connection line between the microgrid side and the distribution network side during the grid-connected to off-grid state provided by an embodiment of the present application;

[0024] Figure 5 It is a structural block diagram of a network-forming energy storage control device for smooth switching of the microgrid state provided by an embodiment of the present application;

[0025] Figure 6Schematic structural diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0026] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system architectures and technologies are presented to provide a thorough understanding of the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.

[0027] It should be understood that when used in the specification of the present application and the appended claims, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0028] It should also be understood that the term "and / or" used in the specification of the present application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0029] As used in the specification of the present application and the appended claims, the term "if" can be interpreted as "when", "once", "in response to determining", or "in response to detecting" depending on the context. Similarly, the phrase "if determined" or "if detecting [the described condition or event]" can be interpreted as meaning "once determined", "in response to determining", "once detecting [the described condition or event]", or "in response to detecting [the described condition or event]" depending on the context.

[0030] In addition, in the description of the specification of the present application and the appended claims, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0031] Reference to "an embodiment" or "some embodiments" etc. described in the specification of the present application means that a specific feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, statements such as "in an embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in another way. The terms "comprising", "including", "having", and their variants all mean "including but not limited to", unless otherwise specifically emphasized in another way.

[0032] For ease of understanding, the technical solution of this application will be introduced in detail below in conjunction with the accompanying drawings.

[0033] Figure 1 It is a schematic flowchart of a grid-forming energy storage control method for smooth switching of microgrid states provided by an embodiment of this application. Figure 2 It is a schematic flowchart of another grid-forming energy storage control method for smooth switching of microgrid states provided by an embodiment of this application. For ease of description, only the parts related to this embodiment are shown, such as Figure 1 and Figure 2 As shown, the method provided by this embodiment includes the following steps:

[0034] S1. Sample the interactive power of the connection line between the microgrid side and the distribution network side at time t as the first virtual unbalanced power.

[0035] In a specific implementation, the microgrid side includes a data acquisition unit, a grid-forming energy storage, distributed power sources, loads, etc. The data acquisition unit collects the energy storage output power, distributed power source output power, and microgrid internal load power in the microgrid at time t, and takes the sum of the energy storage output power in the microgrid at time t and the difference between the distributed power source output power and the microgrid internal load power as the interactive power of the connection line between the microgrid side and the distribution network side at time t.

[0036] As an example, the interactive power of the connection line between the microgrid side and the distribution network side at time t, that is, the first virtual unbalanced power The calculation formula is:

[0037] ,

[0038] Where is the distributed power source output power in the microgrid at time t, is the microgrid internal load power at time t, is the energy storage output power in the microgrid at time t.

[0039] Exemplarily, the distributed power source output power in the microgrid at time t is 15 kilowatts (kW), the microgrid internal load power at time t is 20 kW; the energy storage output power in the microgrid at time t is 0 kW.

[0040] S2. Based on the first virtual unbalanced power, calculate the voltage phase deviation amount of the grid connection point before and after the microgrid switches from the grid-connected state to the islanded state.

[0041] In a possible implementation manner, the absolute value of the first virtual unbalanced power is used as the input signal, and a proportional-integral response module is used to calculate the voltage phase deviation amount of the grid connection point before and after the microgrid switches from the grid-connected state to the islanded state, and the voltage phase deviation amount is fed back to the grid-forming energy storage phase pre-synchronization link.

[0042] In a specific implementation, the voltage phase deviation calculation module of the microgrid controller uses the absolute value of the first virtual unbalanced power as the input signal, and adopts a proportional-integral response module to calculate the voltage phase deviation amount of the grid connection point before and after the switching of the microgrid connection and disconnection states , and feeds it back to the grid-forming energy storage phase pre-synchronization link.

[0043] As an example, the calculation formula for the voltage phase deviation amount of the grid connection point before and after the switching of the microgrid connection and disconnection states is:

[0044] ,

[0045] wherein, represents the response time constant of the power change amount to the voltage phase change amount; , respectively represent the proportional coefficient and the integral coefficient; s represents a complex variable in the Laplace transform, which is used for the conversion from the time-domain analysis system to the complex-frequency domain analysis system.

[0046] Exemplarily, during the calculation process, takes a value of 0.1, takes a value of 10, takes a value of 0.5.

[0047] S3. Based on the voltage phase deviation amount, determine the active power set value of the grid-forming energy storage on the microgrid side.

[0048] In a possible implementation manner, based on the voltage phase deviation amount, calculate the active power pre-compensation amount required by the grid-forming energy storage on the microgrid side through a damping integral response module that resists voltage phase changes; based on the rated power of the energy storage and the active power pre-compensation amount, determine the active power set value of the grid-forming energy storage.

[0049] In a specific implementation, the grid-forming energy storage controller uses the voltage phase deviation amount , and through a damping integral response module that resists voltage phase changes, calculates the active power pre-compensation amount required by the grid-forming energy storage, and uses the rated power of the energy storage to superimpose the active power pre-compensation amount as the active power set value of the grid-forming energy storage .

[0050] As an example, the calculation formula for the active power pre-compensation amount and the calculation formula for the active power set value are respectively:

[0051] ,

[0052] Among them, 、 represents the response time constant of the phase change amount and the active power increase amount, represents the damping coefficient against the phase change amount, is the voltage phase deviation amount, is the rated power of the energy storage, and s represents a complex variable in the Laplace transform, which is used for the conversion from the time-domain analysis system to the complex-frequency domain analysis system.

[0053] Exemplarily, during the calculation, takes a value of 0.1, takes a value of 0.2, takes a value of 5.

[0054] S4. Based on the active power set value, calculate the first voltage phase angle at the grid connection point after the energy storage power output on the microgrid side. Based on the voltage phase deviation amount and the first voltage phase angle, calculate the second voltage phase angle at the grid connection point after the energy storage power output on the microgrid side at time t + 1.

[0055] In a possible implementation manner, in step S4, calculating the first voltage phase angle at the grid connection point after the energy storage power output on the microgrid side based on the active power set value includes: in the active power phase conversion link of the grid-forming energy storage, calculate the target power deviation amount between the active power set value and the sampled value of the energy storage power output; based on the target power deviation amount, calculate the first voltage phase angle through the power angle balance second-order negative feedback loop of the power deviation amount and the voltage phase amount.

[0056] In a possible implementation manner, in step S4, calculating the second voltage phase angle at the grid connection point after the energy storage power output on the microgrid side at time t + 1 based on the voltage phase deviation amount and the first voltage phase angle includes: in the active power phase conversion link of the grid-forming energy storage, feedback and superimpose the voltage phase deviation amount to the first voltage phase angle to correct the active power output by the grid-forming energy storage, and obtain the second voltage phase angle at the grid connection point after the energy storage power output on the microgrid side at time t + 1.

[0057] In specific implementation, in the active power phase conversion link of the grid-forming energy storage, the grid-forming energy storage controller calculates the active power set value and the sampled value of the energy storage power output to obtain the target power deviation amount therebetween, and calculates the first voltage phase angle at the grid connection point after the energy storage power output through the power angle balance second-order negative feedback loop of the power deviation amount and the voltage phase amount , and further feedback and superimpose the voltage phase deviation amount to the first voltage phase angle , correct the active power output of the network-forming energy storage to obtain the second voltage phase angle after the energy storage power output on the microgrid side at the (t + 1)th moment at the grid connection point .

[0058] As an example, the calculation formula for the first voltage phase angle and the calculation formula for the second voltage phase angle are as follows:

[0059] ,

[0060] wherein, and respectively represent the set value of the active power of the energy storage at the tth moment and the sampled value of the energy storage power output; J and D respectively represent the inertia coefficient and damping coefficient of the second-order power angle balance link; and respectively represent the voltage amplitudes at the grid connection point on the distribution network side and the microgrid side; X represents the line impedance connecting the microgrid and the distribution network, represents the rated angular frequency of the microgrid operation, and s represents a complex variable in the Laplace transform, which is used for the conversion from the time-domain analysis system to the complex-frequency domain analysis system.

[0061] Exemplarily, in the calculation process, the value of J is 0.5, the value of D is 20, and the value of X is 0.005.

[0062] S5. Calculate the target phase angle difference between the second voltage phase angle and the voltage phase angle at the grid connection point on the distribution network side, and based on the target phase angle difference and the preset microgrid grid-connected / off-grid state switching constraint conditions, perform the microgrid grid-connected-to-off-grid operation to achieve the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side when switching from the grid-connected state to the off-grid state.

[0063] In a possible implementation manner, the preset microgrid grid-connected / off-grid state switching constraint conditions include that the voltage phase angle difference between the grid connection point on the distribution network side and the microgrid side is less than the maximum phase angle allowed for the microgrid off-grid operation. In step S5, based on the target phase angle difference and the preset microgrid grid-connected / off-grid state switching constraint conditions, performing the microgrid grid-connected-to-off-grid operation includes: when the target phase angle difference is less than the maximum phase angle allowed for the microgrid off-grid operation, the microgrid controller issues a grid-connected-to-off-grid switching command, and based on the grid-connected-to-off-grid switching command, controls the disconnection of the tie switch between the microgrid and the distribution network; when the target phase angle difference is greater than or equal to the maximum phase angle allowed for the microgrid off-grid operation, repeat step S4 until the target phase angle difference is less than the maximum phase angle allowed for the microgrid off-grid operation, and then the microgrid controller issues a grid-connected-to-off-grid switching command, and based on the grid-connected-to-off-grid switching command, controls the disconnection of the tie switch between the microgrid and the distribution network.

[0064] In a possible implementation, step S5 also includes: sampling the interactive power of the interconnection lines between the microgrid side and the distribution network side at time t+1 as the second virtual unbalanced power; determining the power deviation flag value based on the second virtual unbalanced power and the preset power deviation threshold of the microgrid's grid-connected to off-grid state; determining the phase deviation flag value based on the target phase angle difference and the maximum phase angle allowed for the microgrid's off-grid operation; determining the mode switching flag value of the microgrid's grid-connected to off-grid transition based on the power deviation flag value and the phase deviation flag value; and executing the microgrid's grid-connected to off-grid transition operation based on the mode switching flag value of the microgrid's grid-connected to off-grid transition.

[0065] In a specific implementation, when the second virtual unbalanced power is less than the preset power deviation threshold of the microgrid's grid-connected to off-grid state, the power deviation flag bit identification value is determined to be 1; when the second virtual unbalanced power is greater than or equal to the preset power deviation threshold of the microgrid's grid-connected to off-grid state, the power deviation flag bit identification value is determined to be 0; when the target phase angle difference is less than the maximum phase angle allowed for the microgrid's off-grid operation, the phase deviation flag bit identification value is determined to be 1; when the target phase angle difference is greater than or equal to the maximum phase angle allowed for the microgrid's off-grid operation, the phase deviation flag bit identification value is determined to be 0; the mode switching flag bit identification value of the microgrid's grid-connected to off-grid state is the result of the intersection of the power deviation flag bit identification value and the phase deviation flag bit identification value, and the mode switching flag bit identification value of the microgrid's grid-connected to off-grid state includes 1 and 0. When the mode switching flag bit identification value of the microgrid's grid-connected to off-grid state is 0, it indicates that the microgrid and the distribution network contact switch do not perform the grid-connected to off-grid operation. When the mode switching flag bit identification value of the microgrid's grid-connected to off-grid state is 1, it indicates that the microgrid and the distribution network contact switch perform the grid-connected to off-grid operation.

[0066] As an example, the calculation method of the mode switching flag bit S of the microgrid from grid-connected to off-grid is:

[0067] ,

[0068] in, Indicates the maximum power phase angle allowed for off-grid operation of the microgrid; and Respectively represent the power deviation flag and the phase deviation flag; Indicates the preset power deviation threshold of the microgrid from grid-connected to off-grid state; represents the second virtual unbalanced power, represents the target phase angle difference, , It represents the voltage phase angle of the grid connection point on the distribution network side at time t+1, Represents the second voltage phase angle.

[0069] Exemplarily, during the calculation process, takes a value of 0.2, takes a value of 5.

[0070] It should be noted that the maximum power phase angle allowed for the microgrid to operate in the off-grid mode and the preset power deviation threshold for the microgrid to switch from the grid-connected state to the off-grid state can be customized according to the actual situation, and the present application does not limit this.

[0071] As another example, the power deviation flag bit can also be determined by the first virtual unbalanced power to determine.

[0072] Exemplarily, when the first virtual unbalanced power is equal to 0, the identification value of the power deviation flag bit is 1, and when the first virtual unbalanced power is not equal to 0, the identification value of the power deviation flag bit is 0.

[0073] As an example, Figure 3 and Figure 4 are respectively the schematic diagram of the voltage phase deviation between the microgrid and the distribution network in the grid-connected to off-grid state and the schematic diagram of the interactive power of the connection line between the microgrid side and the distribution network side in the grid-connected to off-grid state after adopting the technical solution provided by the present application. As shown in Figure 3 and Figure 4 shown, the voltage phase deviation between the microgrid and the distribution network in the grid-connected to off-grid state and the interactive power of the connection line between the microgrid side and the distribution network side in the grid-connected to off-grid state both finally approach 0.

[0074] The technical solution provided by the present application extracts the interactive power of the connection line between the microgrid side and the distribution network side and converts it into virtual unbalanced power, calculates the voltage phase deviation amount based on the virtual unbalanced power, dynamically adjusts the set value of the energy storage active power based on the voltage phase deviation amount, and then compensates for the voltage phase deviation caused by the unbalanced power of the connection line between the microgrid and the distribution network by actively adjusting the output power of the grid-forming energy storage, significantly reducing the deviation of the voltage phase between the microgrid and the distribution network, ensuring the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side during the grid-connected to off-grid state, realizing the precise synchronization of the voltage phase, avoiding the problem of the failure of the microgrid to switch between the grid-connected and off-grid states due to too large voltage phase deviation on both sides, and improving the reliability and stability of the microgrid state switching.

[0075] Figure 5 is the structural block diagram of a grid-forming energy storage control device for smooth switching of the microgrid state provided by an embodiment of the present application. For the sake of convenience of description, only the parts related to the embodiment of the present application are shown. Refer to Figure 5, the grid-forming energy storage control device 500 for smooth switching of the microgrid state may include a data acquisition module 501, a first calculation module 502, a second calculation module 503, a third calculation module 504, and a state switching control module 505.

[0076] The data acquisition module 501 is configured to sample the interactive power of the connection line between the microgrid side and the distribution network side at time t as the first virtual unbalanced power.

[0077] The first calculation module 502 is configured to calculate the voltage phase deviation amount of the grid connection point before and after the state switching of the microgrid from grid-connected to islanded based on the first virtual unbalanced power.

[0078] The second calculation module 503 is configured to determine the set value of the active power of the grid-forming energy storage on the microgrid side based on the voltage phase deviation amount.

[0079] The third calculation module 504 is configured to calculate the first voltage phase angle of the grid connection point after the energy storage power output on the microgrid side based on the set value of the active power, and calculate the second voltage phase angle of the grid connection point after the energy storage power output on the microgrid side at time t+1 based on the voltage phase deviation amount and the first voltage phase angle.

[0080] The state switching control module 505 is configured to calculate the target phase angle difference between the second voltage phase angle and the voltage phase angle of the grid connection point on the distribution network side, and perform the operation of switching the microgrid from grid-connected to islanded based on the target phase angle difference and the preset microgrid grid-connected to islanded state switching constraint conditions, so as to achieve the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side when switching from grid-connected to islanded state.

[0081] The grid-forming energy storage control device for smooth switching of the microgrid state provided by the embodiment of the present application has the same beneficial effects as the above-mentioned grid-forming energy storage control method for smooth switching of the microgrid state.

[0082] It should be noted that for the information interaction, execution process, etc. between the above-mentioned device / units, since they are based on the same concept as the method embodiment of the present application, their specific functions and the technical effects brought can be specifically referred to in the method embodiment part, and will not be elaborated here.

[0083] Those skilled in the art can clearly understand that, for the convenience and conciseness of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of this application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0084] Figure 6 FIG. is a schematic structural diagram of an electronic device provided by an embodiment of the present application. As Figure 6 shown, the electronic device 6 of this embodiment includes: at least one processor 60 ( Figure 6 only one is shown in the figure), a memory 61, and a computer program 62 stored in the memory 61 and executable on at least one processor 60. When the processor 60 executes the computer program 62, it implements the above Figure 1 or Figure 2 steps in the method embodiment, or implements the functions of each module / unit in the above Figure 5 device embodiment.

[0085] The electronic device 6 can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The electronic device 6 may include but is not limited to the processor 60 and the memory 61. Those skilled in the art can understand that Figure 6 this is only an example of the electronic device 6 and does not constitute a limitation on the electronic device 6. It may include more or fewer components than shown in the figure, or combine some components, or different components. For example, it may also include input / output devices, network access devices, etc.

[0086] The processor 60 may be a Central Processing Unit (CPU), and the processor 60 may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0087] In some embodiments, the memory 61 may be an internal storage unit of the electronic device 6, such as the hard disk or memory of the electronic device 6. In other embodiments, the memory 61 may also be an external storage device of the electronic device 6, such as a plug-in hard disk equipped on the electronic device 6, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Further, the memory 61 may also include both the internal storage unit and the external storage device of the electronic device 6. The memory 61 is used to store an operating system, application programs, a BootLoader, data, and other programs, such as the program code of a computer program. The memory 61 may also be used to temporarily store data that has been output or is to be output.

[0088] The embodiments of the present application also provide a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0089] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, to implement all or part of the processes in the above-described embodiment methods of the present application, a computer program can be used to instruct relevant hardware to complete. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-described method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can at least include: any entity or device capable of carrying the computer program code to an electronic device, a recording medium, a computer memory, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), an electrical carrier signal, a telecommunication signal, and a software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk, or an optical disc, etc.

[0090] A computer-readable storage medium provided by an embodiment of the present application has the same beneficial effects as the above-described grid-forming energy storage control method for smooth switching of the microgrid state.

[0091] An embodiment of the present application provides a computer program product. The computer program product includes a computer program. When the computer program is executed by a processor, the steps in the above-described method embodiments can be implemented.

[0092] A computer program product provided by an embodiment of the present application has the same beneficial effects as the above-described grid-forming energy storage control method for smooth switching of the microgrid state.

[0093] In the above embodiments, the descriptions of each embodiment have their own emphases. For parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0094] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0095] In the embodiments provided in the present application, it should be understood that the disclosed device / equipment and method can be implemented in other ways. For example, the device / equipment embodiments described above are only illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some interfaces. The indirect coupling or communication connection of the device or unit can be in an electrical, mechanical or other form.

[0096] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0097] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A grid-forming energy storage control method for smooth switching of microgrid states, characterized in that The method includes: S1, sampling the interactive power of the connection line between the microgrid side and the distribution network side at time t as the first virtual unbalanced power; S2, calculating the voltage phase deviation amount of the grid connection point before and after the microgrid switches from grid-connected state to islanded state based on the first virtual unbalanced power; S3, determining the set value of the active power of the network-forming energy storage on the microgrid side based on the voltage phase deviation amount; S4, calculating the first voltage phase angle of the grid connection point after the energy storage on the microgrid side outputs power based on the set value of the active power, and calculating the second voltage phase angle of the grid connection point after the energy storage on the microgrid side outputs power at time t+1 based on the voltage phase deviation amount and the first voltage phase angle; S5, calculating the target phase angle difference between the second voltage phase angle and the voltage phase angle of the grid connection point on the distribution network side, and performing the microgrid grid-connected to islanded operation based on the target phase angle difference and the preset microgrid grid-connected to islanded state switching constraint conditions, so as to achieve the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side during the grid-connected to islanded state switching.

2. The method according to claim 1, wherein Step S2 includes: Taking the absolute value of the first virtual unbalanced power as the input signal, using a proportional-integral response module to calculate the voltage phase deviation amount of the grid connection point before and after the microgrid switches from grid-connected state to islanded state, and feeding back the voltage phase deviation amount to the network-forming energy storage phase pre-synchronization link.

3. The method according to claim 1, wherein Step S3 includes: Calculating the required active power pre-compensation amount of the network-forming energy storage on the microgrid side through a damping integral response module that resists voltage phase changes based on the voltage phase deviation amount; Determining the set value of the active power of the network-forming energy storage based on the rated power of the energy storage and the active power pre-compensation amount.

4. The method according to claim 1, characterized in that, In step S4, the calculation of the first voltage phase angle of the grid connection point after the energy storage on the microgrid side outputs power based on the set value of the active power includes: Calculating the target power deviation amount between the set value of the active power and the sampled value of the energy storage power output in the network-forming energy storage active phase conversion link; Calculating the first voltage phase angle through a second-order negative feedback loop of power angle balance between the target power deviation amount and the voltage phase amount.

5. The method according to claim 1, wherein In step S4, the calculation of the second voltage phase angle of the grid connection point after the energy storage on the microgrid side outputs power at time t+1 based on the voltage phase deviation amount and the first voltage phase angle includes: In the network-forming energy storage active phase conversion link, feeding back and superimposing the voltage phase deviation amount to the first voltage phase angle, correcting the active power output by the network-forming energy storage, and obtaining the second voltage phase angle of the grid connection point after the energy storage on the microgrid side outputs power at time t+1.

6. The method according to claim 1, wherein The preset microgrid grid-connected to islanded state switching constraint conditions include that the voltage phase angle difference between the distribution network side and the microgrid side of the grid connection point is less than the maximum phase angle allowed for the microgrid to operate in islanded mode. In step S5, the execution of the microgrid grid-connected to islanded operation based on the target phase angle difference and the preset microgrid grid-connected to islanded state switching constraint conditions includes: When the target phase angle difference is less than the maximum phase angle allowed for the microgrid to operate in the islanded mode, the microgrid controller issues a grid-connected to islanded switching command, and based on the grid-connected to islanded switching command, controls the disconnection of the tie switch between the microgrid and the distribution network; When the target phase angle difference is greater than or equal to the maximum phase angle allowed for the microgrid to operate in the islanded mode, repeat step S4 until the target phase angle difference is less than the maximum phase angle allowed for the microgrid to operate in the islanded mode. Then, the microgrid controller issues the grid-connected to islanded switching command, and based on the grid-connected to islanded switching command, controls the disconnection of the tie switch between the microgrid and the distribution network.

7. The method according to claim 6, wherein Step S5 further includes: Sampling the interactive power of the tie line between the microgrid side and the distribution network side at time t+1 as the second virtual unbalanced power; Determining the identification value of the power deviation flag bit based on the second virtual unbalanced power and the preset power deviation threshold for the grid-connected to islanded state of the microgrid; Determining the identification value of the phase deviation flag bit based on the target phase angle difference and the maximum phase angle allowed for the microgrid to operate in the islanded mode; Determining the identification value of the mode switching flag bit for the grid-connected to islanded operation of the microgrid based on the identification value of the power deviation flag bit and the identification value of the phase deviation flag bit; Performing the grid-connected to islanded operation of the microgrid based on the identification value of the mode switching flag bit for the grid-connected to islanded operation of the microgrid.

8. A grid-forming energy storage control device for smooth switching of microgrid states, characterized in that, The device includes: A data acquisition module for sampling the interactive power of the tie line between the microgrid side and the distribution network side at time t as the first virtual unbalanced power; A first calculation module for calculating the voltage phase deviation amount of the grid connection point before and after the grid-connected to islanded state switching of the microgrid based on the first virtual unbalanced power; A second calculation module for determining the active power set value of the network-forming energy storage on the microgrid side based on the voltage phase deviation amount; A third calculation module for calculating the first voltage phase angle of the grid connection point after the energy storage power output on the microgrid side based on the active power set value, and calculating the second voltage phase angle of the grid connection point after the energy storage power output on the microgrid side at time t+1 based on the voltage phase deviation amount and the first voltage phase angle; A state switching control module for calculating the target phase angle difference between the second voltage phase angle and the voltage phase angle of the grid connection point on the distribution network side, and performing the grid-connected to islanded operation of the microgrid based on the target phase angle difference and the preset grid-connected to islanded state switching constraint conditions, so as to achieve the consistency of the voltage phase angles at both ends of the microgrid side and the distribution network side during the grid-connected to islanded state switching.

9. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method according to any one of claims 1 to 7.

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 method according to any one of claims 1 to 7.

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