# New energy grid-connected system voltage support strength evaluation method and system

## A technology of system voltage and support strength, applied in the direction of AC network voltage adjustment, AC network circuit, electrical components, etc., can solve the problem of inconsistent calculation of critical short-circuit ratio, no solution proposed, and difficult to evaluate the voltage support strength of new energy grid-connected systems Provide accurate, fast, intuitive, and practical methods and other issues to achieve the effect of fast methods, ensuring safe and stable operation, and simple evaluation

Active Publication Date: 2022-01-07

CHINA ELECTRIC POWER RES INST

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## AI-Extracted Technical Summary

### Problems solved by technology

[0003] At present, the short-circuit ratio is an important indicator for evaluating the voltage support strength of the new energy grid-connected system. There is a contradiction between its accuracy and practicability, and the calculation of the critical short-circuit ratio is not uniform due to the numerous construction methods. Support strength asse...

### Method used

Thus, the present invention firstly determines the first short-circuit ratio of the new energy grid-connected system based on the short-circuit capacity provided by the AC system in the new energy grid-connected system to the grid-connected point and the equivalent grid-connected capacity of the new energy at the grid-connected point index. Then, based on the voltage variation at the new energy grid-connected point, the second short-circuit ratio index of the new energy grid-connected system is determined. Secondly, based on the AC system parameters and the equivalent maximum transmission power delivered by the new energy to the AC system, the critical short-circuit ratio of the new energy grid-connected system is determined. Finally, based on the first short-circuit ratio index, the second short-circuit ratio index and the critical short-circuit rat...

## Abstract

The invention discloses a new energy grid-connected system voltage support strength evaluation method and system. The method comprises the steps of determining a first short-circuit ratio index of the new energy grid-connected system based on short-circuit capacity provided for a grid-connected point by an alternating current system in the new energy grid-connected system and equivalent grid-connected capacity of new energy at the grid-connected point; determining a second short-circuit ratio index of the new energy grid-connected system based on the voltage variation at the new energy access grid-connected point; determining a critical short-circuit ratio of the new energy grid-connected system based on parameters of the alternating current system and the equivalent maximum transmission power transmitted to the alternating current system by the new energy; and based on the first short-circuit ratio index, the second short-circuit ratio index and the critical short-circuit ratio, determining the voltage support strength provided by the new energy grid-connected system at the grid-connected point by using a preset voltage support strength evaluation rule.

Application Domain

Single network parallel feeding arrangementsAc network voltage adjustment

Technology Topic

Short circuit ratioAC - Alternating current +5

## Image

## Examples

- Experimental program(1)

### Example Embodiment

[0106] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of the embodiments of the present invention, and it should be understood that the present invention is not limited by the example embodiments described herein.

[0107] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the invention unless specifically stated otherwise.

[0108] Those skilled in the art can understand that terms such as "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, etc., and do not represent any specific technical meaning, nor do they represent any difference between them. the necessary logical order of .

[0109] It should also be understood that, in the embodiments of the present invention, "a plurality" may refer to two or more, and "at least one" may refer to one, two or more.

[0110] It should also be understood that, for any component, data or structure mentioned in the embodiments of the present invention, it can generally be understood as one or more in the case that there is no explicit definition or the contrary inspiration is given in the context.

[0111] In addition, the term "and/or" in the present invention is only an association relationship to describe associated objects, which means that there can be three kinds of relationships, for example, A and/or B, which can mean that A exists alone, and A and B exist at the same time. , there are three cases of B alone. In addition, the character "/" in the present invention generally indicates that the related objects are an "or" relationship.

[0112] It should also be understood that the description of the various embodiments of the present invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other, and for the sake of brevity, they will not be repeated.

[0113] Meanwhile, it should be understood that, for the convenience of description, the dimensions of various parts shown in the accompanying drawings are not drawn in an actual proportional relationship.

[0114] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0115] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, techniques, methods, and apparatus should be considered part of the specification.

[0116] It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further discussion in subsequent figures.

[0117] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, servers, etc., which can operate with numerous other general-purpose or special-purpose computing system environments or configurations. Examples of well-known terminal equipment, computing systems, environments and/or configurations suitable for use with terminal equipment, computer systems, servers, etc. electronic equipment include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients computer, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, minicomputer systems, mainframe computer systems, and distributed cloud computing technology environments including any of the foregoing, among others.

[0118] Electronic devices such as terminal devices, computer systems, servers, etc., may be described in the general context of computer system-executable instructions, such as program modules, being executed by the computer system. Generally, program modules may include routines, programs, object programs, components, logic, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer systems/servers may be implemented in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located on local or remote computing system storage media including storage devices.

[0119] Exemplary method

[0120] figure 1 It is a schematic flowchart of a method for evaluating the voltage support strength of a new energy grid-connected system provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic equipment, such as figure 1 As shown, the method 100 for evaluating the voltage support strength of a new energy grid-connected system includes the following steps:

[0121] Step 101 , based on the short-circuit capacity provided by the AC system in the new energy grid-connected system to the grid-connected point and the equivalent grid-connected capacity of the new energy at the grid-connected point, determine the first short-circuit ratio index of the new energy grid-connected system.

[0122] In the embodiment of the present invention, for the new energy grid-connected system, according to the concept of short-circuit ratio, the ratio of the short-circuit capacity of the AC system to the equivalent grid-connected capacity is used to calculate the first short-circuit ratio index of the new energy grid-connected system based on capacity. SCR-S.

[0123] Optionally, step 101 includes:

[0124] Step 101a: Determine the short-circuit capacity provided by the AC system in the new energy grid-connected system to the grid-connected point.

[0125] Optionally, the calculation formula of the short-circuit capacity provided by the AC system to the grid-connected point is:

[0126]

[0127] in, Ignore the comprehensive load for the AC system and connect the grid point before the new energy is connected to the grid i The no-load operation open circuit voltage; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; for the grid connection point i the nominal voltage.

[0128] Step 101b: Determine the equivalent grid-connected capacity of the new energy source at the grid-connected point.

[0129] Optionally, the calculation formula of the equivalent grid-connected capacity of the grid-connected point is:

[0130]

[0131] Among them, * represents the conjugate operation; , is connected to the grid i , j Directly connected new energy capacity; for the grid connection point i the line current; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i , j electrical distance between; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; , is the connection point i , j node voltage.

[0132] Step 101c: Determine the first short-circuit ratio index of the new energy grid-connected system based on the short-circuit capacity and the equivalent grid-connected capacity.

[0133] Optionally, the calculation formula of the first short-circuit ratio index of the new energy grid-connected system is:

[0134]

[0135] in, It is the first short-circuit ratio index of the new energy grid-connected system; For the AC system to the grid connection point i Provided short-circuit capacity; For new energy at the grid connection point i equivalent grid-connected capacity at , is the connection point i , j the node voltage; for the grid connection point i the nominal voltage; Ignore the comprehensive load for the AC system and connect the grid point before the new energy is connected to the grid i The no-load operation open circuit voltage; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i , j electrical distance between; , is connected to the grid i , j Directly connected new energy capacity.

[0136] Step 102: Determine the second short-circuit ratio index of the new energy grid-connected system based on the voltage change at the grid-connected point of the new energy.

[0137]Optionally, step 102 includes:

[0138] Step 102a: Determine the voltage reduction equation of the grid connection point when the new energy source is connected to the grid connection point.

[0139] Optionally, the voltage drop equation of the grid-connected point is:

[0140]

[0141] in, is the impedance matrix of the grid-connected point; It is the voltage change at the connection point caused by the connection of new energy to the grid; is the current injected by the new energy into the grid connection point; m It is the serial number of the grid connection point.

[0142] Step 102b: Based on the voltage drop equation, determine the voltage variation at the point where the new energy is connected to the grid.

[0143] Optionally, the calculation formula of the voltage change at the point where the new energy is connected to the grid is:

[0144]

[0145] in, for the grid connection point i The amount of voltage change; , It is a new energy injection connection point i, j the current; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i, j electrical distance between.

[0146] Step 102c: Determine the nominal voltage of the grid connection point.

[0147] Step 102d: Determine the second short-circuit ratio index of the new energy grid-connected system based on the voltage variation and the nominal voltage.

[0148] In this embodiment of the present invention, step 102d firstly determines a formula for calculating the ratio of the nominal voltage to the voltage variation. in

[0149] The formula for calculating the ratio of the nominal voltage to the voltage change is:

[0150]

[0151] in, for the grid connection point i the nominal voltage; for the grid connection point i The amount of voltage change; , It is a new energy injection connection point i , j the current; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i , j electrical distance between;

[0152] The calculation formula of the second short-circuit ratio index of the new energy grid-connected system is:

[0153]

[0154] in, is the second short-circuit ratio index of the new energy grid-connected system; for the grid connection point i the nominal voltage; Ignore the comprehensive load for the AC system and connect the grid point before the new energy is connected to the grid i The no-load operation open circuit voltage; for the grid connection point i The amount of voltage change; for the grid connection point i node voltage.

[0155] Step 103: Determine the critical short-circuit ratio of the new energy grid-connected system based on the AC system parameters and the equivalent maximum transmission power delivered by the new energy to the AC system.

[0156] Optionally, step 103 includes:

[0157] Step 103a: Determine the transmission power delivered by the new energy source to the AC system, wherein the calculation formula of the transmission power is:

[0158]

[0159] in, For new energy at the grid connection point i equivalent grid-connected capacity at P eq,i , Q eq,i are the equivalent active power and equivalent reactive power transmitted by the new energy to the AC system, respectively; E eq,i is the equivalent potential of the AC system; R eq,i is the Thevenin equivalent resistance of the AC system, X eq,i is the Thevenin equivalent reactance of the AC system; is the new energy grid-connected bus voltage; is the difference between the bus voltage phase angle and the equivalent potential phase angle; j is an imaginary number;

[0160] Step 103b: According to the trigonometric function sin 2 θ i +cos 2 θ i =1, establish about U i 2 The quadratic equation in one variable:

[0161]

[0162] in, λ , µ is the sensitivity factor; Δ is the discriminant of the equation;

[0163] Step 103c: When Δ=0, the transmission power delivered by the new energy source to the AC system is the equivalent maximum transmission power, and the calculation formula of the equivalent maximum transmission power is:

[0164]

[0165] in, P eq,imax The equivalent maximum transmission power for the new energy to the AC system, Q eq,i is the equivalent reactive power transmitted from the new energy to the AC system, E eq,i is the equivalent potential of the AC system; R eq,i is the Thevenin equivalent resistance of the AC system, X eq,i is the Thevenin equivalent reactance of the AC system;

[0166] Step 103d: Determine the critical short-circuit ratio CSCR of the new energy grid-connected system, which is:

[0167]

[0168] in, For the AC system to the grid connection point i Provided short-circuit capacity; Q eq,i The equivalent reactive power transmitted from the new energy to the AC system; P eq,imax The equivalent maximum transmission power for the new energy to the AC system, j is an imaginary number.

[0169] In the embodiment of the present invention, the AC system parameters include: the equivalent potential of the AC system E eq,i , AC system Thevenin equivalent resistance R eq,i and AC system Thevenin equivalent reactance X eq,i.

[0170] Step 104 , based on the first short-circuit ratio index, the second short-circuit ratio index, and the critical short-circuit ratio, and using a preset voltage support strength evaluation rule, determine the voltage support strength provided by the new energy grid-connected system at the grid-connected point.

[0171] In the embodiment of the present invention, the preset voltage support strength evaluation rule is as follows:

[0172] 1) The abstract concept of determining the voltage support strength of the new energy grid-connected system exists with reference to the strength of the new energy grid-connected system. As the coordinates, the evaluation of the voltage support strength of the new energy grid-connected system is realized.

[0173] 2) Determine the construction of two short-circuit ratio indicators with the same evaluation effect for the new energy grid-connected system: SCR-S (corresponding to the first short-circuit ratio indicator) and SCR-U (corresponding to the second short-circuit ratio indicator).

[0174] 3) Determine the stable state of the new energy grid-connected system by comparing the short-circuit ratio index and the critical short-circuit ratio of the new energy grid-connected system. When the new energy grid-connected system does not reach critical stability, there is a distance between the short-circuit ratio index and the critical short-circuit ratio, and the new energy grid-connected system has a safety margin. which is:

[0175] 3.1) When SCR-U (or SCR-S) is greater than CSCR (corresponding to the critical short-circuit ratio), the new energy grid-connected system operates in the stable region of P-V characteristics, and the new energy grid-connected system is in a stable state;

[0176] 3.2) When SCR-U (or SCR-S) is less than CSCR (corresponding to the critical short-circuit ratio), the new energy grid-connected system operates in an unstable region of P-V characteristics, and the new energy grid-connected system is in an unstable state.

[0177] 4) Determine the strength of the new energy grid-connected system by calculating the short-circuit ratio index of the new energy grid-connected system and comparing it with the strength and weakness division criteria of the new energy grid-connected system. Among them, a strong new energy grid-connected system means that the new energy grid-connected system provides a strong degree of voltage support at the grid connection point. A weak new energy grid-connected system means that the voltage support provided by the new energy grid-connected system at the grid connection point is weak.

[0178] 4.1) The short-circuit ratio index (SCR-U or SCR-S) is greater than 2, and the new energy grid-connected system is a strong system;

[0179] 4.2) The short-circuit ratio index (SCR-U or SCR-S) is less than 2, and the new energy grid-connected system is a weak system.

[0180] Optionally, step 104 includes:

[0181] Step 104a: Determine the extreme value of the critical short-circuit ratio of the new energy grid-connected system when the active power and reactive power of the new energy grid-connected system flow into the AC system from the new energy source.

[0182] In the embodiment of the present invention, referring to the calculation formula of the critical short-circuit ratio CSCR of the new energy grid-connected system, it can be known that when the active power and reactive power of the new energy grid-connected system flow into the AC system from the new energy, the critical short-circuit of the new energy grid-connected system The ratio exists with a maximum value of 2 (corresponding to an extreme value).

[0183] Step 104b: Determine the extreme value of the critical short-circuit ratio as the strength standard for dividing the voltage support degree of the new energy grid-connected system.

[0184] In this embodiment of the present invention, see figure 2As shown, the extreme value 2 of the critical short-circuit ratio is used as the criterion for dividing the strength of the new energy grid-connected system. Among them, a strong new energy grid-connected system means that the new energy grid-connected system provides a strong degree of voltage support at the grid connection point. A weak new energy grid-connected system means that the voltage support provided by the new energy grid-connected system at the grid connection point is weak.

[0185] Step 104c: when the first short-circuit ratio index or the second short-circuit ratio index is greater than the extreme value of the critical short-circuit ratio, it is determined that the voltage support degree of the new energy grid-connected system is strong.

[0186] Step 104d: When the first short-circuit ratio index or the second short-circuit ratio index is less than the extreme value of the critical short-circuit ratio, determine that the voltage support degree of the new energy grid-connected system is weak.

[0187] Optionally, the method further includes: determining a stable state of the new energy grid-connected system based on the first short-circuit ratio index, the second short-circuit ratio index, and the critical short-circuit ratio.

[0188] Optionally, based on the first short-circuit ratio index, the second short-circuit ratio index, and the critical short-circuit ratio, determine the stable state of the new energy grid-connected system, see figure 2 shown, including:

[0189] 1) When the first short-circuit ratio index or the second short-circuit ratio index is greater than the critical short-circuit ratio, it is determined that the new energy grid-connected system operates in the stable region of P-V characteristics, and the new energy grid-connected system is in a stable state;

[0190] 2) When the first short-circuit ratio index or the second short-circuit ratio index is less than the critical short-circuit ratio, it is determined that the new energy grid-connected system operates in an unstable region of P-V characteristics, and the new energy grid-connected system is in an unstable state.

[0191] Therefore, the present invention first determines the first short-circuit ratio index of the new energy grid-connected system based on the short-circuit capacity provided by the AC system in the new energy grid-connected system to the grid-connected point and the equivalent grid-connected capacity of the new energy at the grid-connected point. Then, based on the voltage change at the point where the new energy is connected to the grid, the second short-circuit ratio index of the new energy grid-connected system is determined. Secondly, based on the AC system parameters and the equivalent maximum transmission power delivered by the new energy to the AC system, the critical short-circuit ratio of the new energy grid-connected system is determined. Finally, based on the first short-circuit ratio index, the second short-circuit ratio index, and the critical short-circuit ratio, and using the preset voltage support strength evaluation rules, the voltage support strength provided by the new energy grid-connected system at the grid-connected point is determined. By constructing an accurate and practical short-circuit ratio index, the present invention proposes a practical critical short-circuit ratio calculation method, takes the critical short-circuit ratio as a reference point, and takes the short-circuit ratio of the system as a coordinate, so as to provide accurate, accurate and accurate evaluation of the voltage support strength of the new energy grid-connected system. Fast, intuitive, and practical methods and systems. Therefore, the present invention can more intuitively and simply evaluate the voltage support strength of the new energy grid-connected system, has the characteristics of accuracy and speed, and the method is simple and practical, and is of great significance to ensure the safe and stable operation of the new energy grid-connected system.

[0192] Exemplary System

[0193] image 3 It is a schematic structural diagram of a system for evaluating the voltage support strength of a new energy grid-connected system provided by an exemplary embodiment of the present invention. like image 3 As shown, system 300 includes:

[0194] The first short-circuit ratio index determination module 310 is configured to determine the first short-circuit capacity of the new energy grid-connected system based on the short-circuit capacity provided by the AC system in the new energy grid-connected system to the grid-connected point and the equivalent grid-connected capacity of the new energy at the grid-connected point. a short-circuit ratio indicator;

[0195] The second short-circuit ratio index determination module 320 is configured to determine the second short-circuit ratio index of the new energy grid-connected system based on the amount of voltage change at the new energy grid-connected point;

[0196] The critical short circuit ratio determination module 330 is configured to determine the critical short circuit ratio of the new energy grid-connected system based on the AC system parameters and the equivalent maximum transmission power delivered by the new energy to the AC system;

[0197] The voltage support strength determination module 340 is used to determine the voltage provided by the new energy grid-connected system at the grid-connected point based on the first short-circuit ratio index, the second short-circuit ratio index, and the critical short-circuit ratio, and using a preset voltage support strength evaluation rule Support strength.

[0198] Optionally, the first short circuit ratio index determination module 310 is specifically configured to:

[0199] Determine the short-circuit capacity provided by the AC system in the new energy grid-connected system to the grid-connected point;

[0200] Determine the equivalent grid-connected capacity of new energy sources at the grid-connected point;

[0201] Based on the short-circuit capacity and the equivalent grid-connected capacity, the first short-circuit ratio index of the new energy grid-connected system is determined.

[0202] Optionally, the calculation formula of the short-circuit capacity provided by the AC system to the grid-connected point is:

[0203]

[0204] in, Ignore the comprehensive load for the AC system and connect the grid point before the new energy is connected to the grid i The no-load operation open circuit voltage; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; for the grid connection point i the nominal voltage.

[0205] Optionally, the calculation formula of the equivalent grid-connected capacity of the grid-connected point is:

[0206]

[0207] Among them, * represents the conjugate operation; , is connected to the grid i , j Directly connected new energy capacity; for the grid connection point i the line current; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i , j electrical distance between; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; , is the connection point i , j node voltage.

[0208] Optionally, the calculation formula of the first short-circuit ratio index of the new energy grid-connected system is:

[0209]

[0210] in, It is the first short-circuit ratio index of the new energy grid-connected system; For the AC system to the grid connection point i Provided short-circuit capacity; For new energy at the grid connection point i equivalent grid-connected capacity at , is the connection point i , j the node voltage; for the grid connection point i the nominal voltage; Ignore the comprehensive load for the AC system and connect the grid point before the new energy is connected to the grid i The no-load operation open circuit voltage; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i , j electrical distance between; , is connected to the grid i , j Directly connected new energy capacity.

[0211] Optionally, the second short-circuit ratio index of the new energy grid-connected system is determined based on the voltage change at the new energy grid-connected point, including:

[0212] Determine the voltage drop equation of the grid-connected point when the new energy is connected to the grid-connected point;

[0213] Based on the voltage drop equation, determine the voltage change at the point where the new energy is connected to the grid;

[0214] Determine the nominal voltage of the grid connection point;

[0215] Based on the voltage variation and the nominal voltage, the second short-circuit ratio index of the new energy grid-connected system is determined.

[0216] Optionally, the voltage drop equation of the grid-connected point is:

[0217]

[0218] in, is the impedance matrix of the grid-connected point; It is the voltage change at the connection point caused by the connection of new energy to the grid; is the current injected by the new energy into the grid connection point; m It is the serial number of the grid connection point.

[0219] Optionally, the calculation formula of the voltage change at the point where the new energy is connected to the grid is:

[0220]

[0221] in, for the grid connection point i The amount of voltage change; , It is a new energy injection connection point i, j the current; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i, j electrical distance between.

[0222] Optionally, based on the voltage variation and the nominal voltage, determine the second short-circuit ratio index of the new energy grid-connected system, including:

[0223] Calculation formula to determine the ratio of nominal voltage and voltage change;

[0224] The calculation formula of the ratio between the nominal voltage and the voltage change is further deduced, and the second short-circuit ratio index of the new energy grid-connected system is determined;

[0225] The formula for calculating the ratio of the nominal voltage to the voltage change is:

[0226]

[0227] in, for the grid connection point i the nominal voltage; for the grid connection point i The amount of voltage change; , It is a new energy injection connection point i , j the current; is the diagonal element in the impedance matrix of the grid-connected point, and is the difference between the AC system and the grid-connected point. i Equivalent impedance of ; is the off-diagonal element in the impedance matrix of the grid connection point, reflecting the grid connection point i , j electrical distance between;

[0228] The calculation formula of the second short-circuit ratio index of the new energy grid-connected system is:

[0229]

[0230] in, is the second short-circuit ratio index of the new energy grid-connected system; for the grid connection point i the nominal voltage; Ignore the comprehensive load for the AC system and connect the grid point before the new energy is connected to the grid i The no-load operation open circuit voltage; for the grid connection point i The amount of voltage change; for the grid connection point i node voltage.

[0231] Optionally, the critical short circuit ratio determination module 330 is specifically used for:

[0232] Determine the transmission power delivered by the new energy to the AC system, where the calculation formula of the transmission power is:

[0233]

[0234] in, For new energy at the grid connection point i equivalent grid-connected capacity at P eq,i , Q eq,i are the equivalent active power and equivalent reactive power transmitted by the new energy to the AC system, respectively; E eq,i is the equivalent potential of the AC system; R eq,i is the Thevenin equivalent resistance of the AC system, X eq,i is the Thevenin equivalent reactance of the AC system; is the new energy grid-connected bus voltage; is the difference between the bus voltage phase angle and the equivalent potential phase angle; j is an imaginary number;

[0235] According to the trigonometric function sin 2 θ i +cos 2 θ i =1, establish about U i 2 The quadratic equation in one variable:

[0236]

[0237] in, λ , µ is the sensitivity factor; Δ is the discriminant of the equation;

[0238] When Δ=0, the transmission power delivered by the new energy source to the AC system is the equivalent maximum transmission power, and the calculation formula of the equivalent maximum transmission power is:

[0239]

[0240] in, P eq,imax The equivalent maximum transmission power for the new energy to the AC system, Q eq,i is the equivalent reactive power transmitted from the new energy to the AC system, E eq,i is the equivalent potential of the AC system; R eq,i is the Thevenin equivalent resistance of the AC system, X eq,i is the Thevenin equivalent reactance of the AC system;

[0241] Determine the critical short-circuit ratio CSCR of the new energy grid-connected system as:

[0242]

[0243] in, For the AC system to the grid connection point i Provided short-circuit capacity; Q eq,i The equivalent reactive power transmitted from the new energy to the AC system; P eq,imax The equivalent maximum transmission power for the new energy to the AC system, j is an imaginary number.

[0244] Optionally, the voltage support strength determination module 340 is specifically configured to:

[0245] Determine the extreme value of the critical short-circuit ratio of the new energy grid-connected system when the active power and reactive power of the new energy grid-connected system flow into the AC system from the new energy source;

[0246] The extreme value of the critical short-circuit ratio is determined as the strength standard for dividing the voltage support degree of the new energy grid-connected system;

[0247] When the first short-circuit ratio index or the second short-circuit ratio index is greater than the extreme value of the critical short-circuit ratio, it is determined that the voltage support degree of the new energy grid-connected system is strong;

[0248] When the first short-circuit ratio index or the second short-circuit ratio index is smaller than the extreme value of the critical short-circuit ratio, it is determined that the voltage support degree of the new energy grid-connected system is weak.

[0249] Optionally, the voltage support strength determination module 340 is further specifically configured to: determine the stable state of the new energy grid-connected system based on the first short-circuit ratio index, the second short-circuit ratio index, and the critical short-circuit ratio.

[0250] Optionally, the voltage support strength determination module 340 is further specifically configured to:

[0251] When the first short-circuit ratio index or the second short-circuit ratio index is greater than the critical short-circuit ratio, it is determined that the new energy grid-connected system operates in a stable region of P-V characteristics, and the new energy grid-connected system is in a stable state;

[0252] When the first short-circuit ratio index or the second short-circuit ratio index is smaller than the critical short-circuit ratio, it is determined that the new energy grid-connected system operates in an unstable region of P-V characteristics, and the new energy grid-connected system is in an unstable state.

[0253] The system 300 for evaluating the voltage support strength of a new energy grid-connected system according to an embodiment of the present invention corresponds to the method 100 for evaluating the voltage support strength of a new energy grid-connected system in another embodiment of the present invention, and details are not described herein again.

[0254] Exemplary Electronics

[0255] Figure 4 It is the structure of the electronic device provided by an exemplary embodiment of the present invention. The electronic device may be either or both of the first device and the second device, or a stand-alone device independent of them that can communicate with the first device and the second device to receive the collected data from them input signal. Figure 4 A block diagram of an electronic device according to an embodiment of the invention is illustrated. like Figure 4 As shown, electronic device 40 includes one or more processors 41 and memory 42 .

[0256] The processor 41 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and/or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0257] Memory 42 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and/or cache memory (cache). The non-volatile memory may include, for example, a read only memory (ROM), a hard disk, a flash memory, and the like. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 41 may execute the program instructions to implement the historical change recording of the software programs of the various embodiments of the present invention described above Methods for performing information mining and/or other desired functions. In one example, the electronic device may also include an input system 43 and an output system 44 interconnected by a bus system and/or other form of connection mechanism (not shown).

[0258] In addition, the input system 43 may also include, for example, a keyboard, a mouse, and the like.

[0259] The output system 44 can output various information to the outside. The output devices 44 may include, for example, displays, speakers, printers, and communication networks and their connected remote output devices, among others.

[0260] Of course, for simplicity, Figure 4 Only some of the components of the electronic device related to the present invention are shown in , and components such as buses, input/output interfaces, etc. are omitted. In addition to this, the electronic device may also include any other appropriate components depending on the specific application.

[0261] Exemplary computer program product and computer readable storage medium

[0262] In addition to the methods and apparatus described above, embodiments of the present invention may also be computer program products comprising computer program instructions that, when executed by a processor, cause the processor to perform the "exemplary method" described above in this specification The steps in the method for information mining of historical change records according to various embodiments of the present invention described in the section.

[0263] The computer program product may be written in any combination of one or more programming languages, including object-oriented programming languages, such as Java, C++, etc. , also includes conventional procedural programming languages, such as "C" language or similar programming languages. The program code may execute entirely on the user computing device, partly on the user device, as a stand-alone software package, partly on the user computing device and partly on a remote computing device, or entirely on the remote computing device or server execute on.

[0264] In addition, embodiments of the present invention may also be computer-readable storage media having computer program instructions stored thereon that, when executed by a processor, cause the processor to perform the above-described "Example Method" section of this specification The steps in the method for information mining for historical change records according to various embodiments of the present invention described in .

[0265] The computer-readable storage medium may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may include, for example, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or a combination of any of the above. More specific examples (non-exhaustive list) of readable storage media include: electrical connections with one or more wires, portable disks, hard disks, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM or flash memory), optical fiber, portable compact disk read only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above.

[0266] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, advantages, effects, etc. mentioned in the present invention are only examples rather than limitations, and these advantages, advantages, effects, etc. are not considered to be A must-have for each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of example and easy understanding, rather than limiting, and the above-mentioned details do not limit the present invention to be implemented by the above-mentioned specific details.

[0267] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments may be referred to each other. As for the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and for related parts, please refer to the partial description of the method embodiment.

[0268]The block diagrams of the devices, systems, devices, and systems referred to in the present invention are only illustrative examples and are not intended to require or imply that the connections, arrangements, or configurations must be in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, devices, systems may be connected, arranged, and configured in any manner. Words such as "including", "including", "having" and the like are open-ended words meaning "including but not limited to" and are used interchangeably therewith. As used herein, the words "or" and "and" refer to and are used interchangeably with the word "and/or" unless the context clearly dictates otherwise. As used herein, the word "such as" refers to and is used interchangeably with the phrase "such as but not limited to".

[0269] The method and system of the present invention may be implemented in many ways. For example, the methods and systems of the present invention may be implemented in software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above unless specifically stated otherwise. Furthermore, in some embodiments, the present invention can also be implemented as programs recorded in a recording medium, the programs comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.

[0270] It should also be pointed out that in the system, device and method of the present invention, each component or each step can be decomposed and/or recombined. These disaggregations and/or recombinations should be considered as equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0271] The foregoing description has been presented for the purposes of illustration and description. Furthermore, this description is not intended to limit embodiments of the invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

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