Wind power plant grid-connected system grid-following type and grid-constructing type fan proportion optimization method and device

Abstract

The invention belongs to the technical field of wind power generation, and particularly discloses a wind power plant grid-connected system grid-following type and grid construction type fan proportion optimization method and device, and the method comprises the steps: changing the initial proportion of a grid construction type fan, and changing the power grid strength under the update proportion; calculating power flow distribution of each node of the wind power plant grid-connected system under the updating proportion, and determining that the grid-connected system does not reach a capacity threshold value based on the power flow distribution; establishing a state space model of the grid-connected system, and judging whether the small signal of the grid-connected system is stable or not; under the condition that the small signal is stable, the stability margin of the grid-connected system is analyzed based on the dominant mode characteristic value, the adaptability of the wind power plant to the power grid strength change is evaluated by using a discrete coefficient, and the discrete coefficient is recorded; and circularly analyzing all power grid intensities and fan proportions to obtain discrete coefficients under all proportions, and selecting a network-forming fan proportion corresponding to the minimum discrete coefficient as an optimal proportion. According to the invention, the operation stability of the wind power plant configuration result can be improved.

Description

Technical Field

[0001] The present application belongs to the technical field of wind power generation, and more specifically, relates to a method and device for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system. Background Art

[0002] With the accelerated construction of new power systems, large-scale new energy and energy storage converters, high-voltage direct current transmission and other power electronic equipment are connected to the AC power grid, resulting in a rapid decrease in system strength and inertia, weakened frequency / voltage support capabilities, and increased risks of oscillation and instability in power electronic equipment. The "double high" power system faces severe challenges in safe and stable operation.

[0003] Grid-type wind turbines can stably access weak AC power grids, and have functions such as fast inertia frequency support, fast voltage support, grid-on and off-grid switching, and black start. They can be used to deal with prominent problems such as low system inertia and weak grid strength, and expand the stability boundary of high-proportion new energy systems. Replacing some grid-type wind turbines in traditional wind farms with grid-type wind turbines can improve the stable operation capability of wind farms, but grid-type wind storage turbines are not suitable for over-configuration due to problems such as equipment damage, fault ride-through, and strong interactions.

[0004] Therefore, under the development trend of new power systems, how to effectively evaluate the auxiliary support efficiency of grid-type wind turbines to the surrounding grid-type wind turbines, and how to verify and determine the minimum configuration ratio of grid-type wind turbines to maintain the stable operation of the power system and optimize the operating efficiency of the power system are key issues that urgently need to be studied and resolved in depth.

[0005] To this end, the small signal stability analysis method in the existing technology is widely used in the existing grid-type wind turbine ratio configuration research, which can effectively evaluate the impact of the change in the ratio of grid-type wind turbines on the short-term dynamic response and stability of the system, and then optimize the grid-type wind turbine ratio configuration. However, these methods ignore the long-term capacity limit problem of the converter caused by the weak grid AC voltage support demand, which leads to the wind farm configuration results being unable to meet the stable operation requirements in actual operation, posing a potential threat to the power system.

[0006] In summary, the technical problem of the present application is: how to solve the problem of poor operating stability of wind farm configuration results due to capacity exceeding the limit in the grid-type wind turbine ratio configuration method. Summary of the invention

[0007] In view of the defects of the prior art, the purpose of the present application is to provide a method and device for optimizing the ratio of grid-type and grid-forming wind turbines in a wind farm grid-connected system, aiming to solve the problem of capacity exceeding the limit in the grid-forming wind turbine ratio configuration method, resulting in poor operating stability of the wind farm configuration result.

[0008] To achieve the above objectives, in a first aspect, the present application provides a method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system, comprising: Change the initial ratio of grid-forming wind turbines and change the grid strength at the updated ratio; Calculating the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determining that the grid-connected system does not reach the capacity threshold based on the power flow distribution; Establishing a state space model of the grid-connected system, and judging whether the grid-connected system is small signal stable based on the state space model; Under the condition of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, and the adaptability of the wind farm to the change of grid strength is evaluated by using the discrete coefficient, and the discrete coefficient is recorded; The analysis of all grid strengths and wind turbine ratios is repeated cyclically to obtain the discrete coefficients under all ratios, and the grid-type wind turbine ratio corresponding to the minimum discrete coefficient is selected as the optimal ratio.

[0009] Optionally, the calculating the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determining that the grid-connected system has not reached a capacity threshold based on the power flow distribution, includes: Establishing an equivalent circuit of a wind farm grid-connected system and determining node voltage equations of the equivalent circuit; Calculating the power flow distribution of each node of the wind farm grid-connected system under different working conditions based on the node voltage equation, and determining that the active power of all wind turbines does not exceed the power limit when the power flow distribution has a solution; The grid-connected guidelines are used to determine that the reactive power per unit value of the wind turbine is within a preset range, so as to determine that the grid-connected system has not reached a capacity threshold.

[0010] Optionally, establishing an equivalent circuit of the wind farm grid-connected system and determining a node voltage equation of the equivalent circuit includes: According to the external power characteristics of grid-following wind turbines and grid-building wind turbines, the current source equivalent model and impedance equivalent model of the wind turbines are constructed; Constructing a system topology according to the current source equivalent model and the impedance equivalent model, and determining an admittance matrix based on the system topology and the wind turbine position distribution; A voltage matrix is ​​constructed according to the outlet voltage of each fan, and a current matrix is ​​constructed according to the output current of each fan; The node voltage equation is constructed based on the voltage matrix, the current matrix and the admittance matrix.

[0011] Optionally, the method for establishing the state space model includes: Based on differential algebraic equations, a state space model of the wind farm grid-connected system is established around the steady-state operation point:

[0012] in, is the rate of change of the state vector, is the state vector, is the input vector, is the state space matrix, is the input matrix, is the output matrix, is the transfer matrix.

[0013] Optionally, in the case of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, and the adaptability of the wind farm to the change of grid strength is evaluated using the discrete coefficient, including: updating the grid strength with a fixed step size, and selecting and recording the dominant modal eigenvalues ​​of the wind farm grid-connected system under different grid strengths based on the state space model; Calculating the real part average value of the dominant mode eigenvalue according to the dominant mode eigenvalue and the total number of grid strength changes to reflect the distance from the eigenvalue contained in the dominant mode to the imaginary axis; Calculate the standard deviation of the real part of the dominant modal eigenvalue based on the dominant modal eigenvalue, the total number of grid strength changes and the real part average value; Normalizing the discreteness of different dominant modes, and determining the discreteness coefficient according to the standard deviation and the real part average value; The adaptability to the change of the power grid strength is evaluated based on the dispersion coefficient.

[0014] Optionally, the small signal stability is determined based on a root locus of the state space model.

[0015] Optionally, it also includes: When the grid-connected system reaches the capacity threshold or the small signal of the wind farm grid-connected system is unstable, it is determined that the proportion of wind turbines in the grid configuration cannot meet the static stability requirements, and it is directly judged whether all grid strength and wind turbine proportion analyses are completed.

[0016] In a second aspect, the present application further provides a device for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system, comprising: A ratio update module is used to change the initial ratio of grid-forming wind turbines and change the grid strength under the updated ratio; A capacity judgment module, used to calculate the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determine that the grid-connected system does not reach the capacity threshold based on the power flow distribution; A stability judgment module, used for establishing a state space model of the grid-connected system, and judging whether the grid-connected system is small-signal stable based on the state space model; Adaptability evaluation module, which is used to analyze the stability margin of the grid-connected system based on the dominant modal eigenvalue when the small signal is stable, evaluate the adaptability of the wind farm to the change of grid strength by using the discrete coefficient, and record the discrete coefficient; The optimal selection module is used to cyclically analyze all power grid strengths and wind turbine ratios, obtain discrete coefficients under all ratios, and select the grid-type wind turbine ratio corresponding to the minimum discrete coefficient as the optimal ratio.

[0017] In a third aspect, the present application provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method described in the first aspect or any possible implementation of the first aspect.

[0018] In a fourth aspect, the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method described in the first aspect or any possible implementation of the first aspect.

[0019] In a fifth aspect, the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method described in the first aspect or any possible implementation of the first aspect.

[0020] It can be understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0021] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: (1) The method for optimizing the configuration of the proportion of grid-type and grid-forming wind turbines in the wind farm grid-connected system constructed in this application overcomes the configuration problem of grid-forming wind turbines under multiple constraints. It can systematically analyze the performance of wind farms under different grid conditions, optimize the proportion of wind turbines in the grid, and comprehensively consider the stability of the wind farm grid-connected system. By optimizing the proportion of wind turbines, analyzing the distribution of power flow, establishing a state space model, and evaluating the stability margin, it effectively improves the operating stability of the wind farm configuration results, thereby improving the safety of power system operation.

[0022] (2) This application constructs a typical paradigm in the future field of energy storage grid connection, which can promote the development of efficient, economical and reliable grid connection technology and improve the economy and operational flexibility of wind power grid connection systems.

[0023] (3) The present application proposes a method for optimizing the ratio of grid-connected and grid-forming wind turbines in wind farm grid-connected systems. This method can maximize the advantages of grid-forming wind turbines, improve grid stability, and ensure the continuous and reliable operation of the grid. At the same time, it can reduce the economic losses caused by excessive configuration of grid-forming and storage wind turbines, which is conducive to the large-scale development of new energy and saves energy costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is one of the flow diagrams of the method for optimizing the proportion of wind turbines of the grid-connected system of the wind farm and the grid-forming type provided in the embodiment of the present application; Figure 2 This is the second flow chart of the method for optimizing the proportion of wind turbines of the grid-connected system and the grid-forming type provided in the embodiment of the present application; Figure 3 It is a structural schematic diagram of a wind farm grid-connected system grid-following type and grid-forming type wind turbine ratio optimization device provided in an embodiment of the present application; Figure 4 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0027] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0028] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0029] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0030] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0031] Reference Figure 1 The present application provides a method for optimizing the proportion of grid-connected and grid-forming wind turbines in a wind farm grid-connected system, comprising: S101. Changing the initial ratio of the grid-forming wind turbines and changing the grid strength at the updated ratio; S102. Calculate the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determine that the grid-connected system does not reach the capacity threshold based on the power flow distribution; S103. Establishing a state space model of the grid-connected system, and determining whether the grid-connected system is small signal stable based on the state space model; S104. Under the condition of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, the adaptability of the wind farm to the change of grid strength is evaluated by using the discrete coefficient, and the discrete coefficient is recorded; S105. Analyze all grid strengths and wind turbine ratios in a loop to obtain discrete coefficients under all ratios, and select the grid-forming wind turbine ratio corresponding to the minimum discrete coefficient as the optimal ratio.

[0032] Specifically, the initial ratio is first changed through step S101, and the grid strength under the ratio is changed. Based on the actual grid working conditions, different grid strengths are simulated or calculated. The purpose is to ensure that the initial grid-type wind turbine ratio can meet the basic power generation needs, and to improve the flexibility and adaptability of the system by dynamically adjusting the wind turbine ratio.

[0033] Secondly, step S102 calculates the power flow distribution of each node of the wind farm grid-connected system under the update ratio. The power flow calculation process is to calculate the power distribution of the grid nodes under the update ratio through the power flow analysis method to identify the power flow characteristics and power distribution of each node in the grid-connected system.

[0034] According to the results of the power flow calculation, it is determined whether the system has reached or exceeded the capacity threshold. When the grid-connected system reaches the capacity threshold, it is determined that the proportion of wind turbines in the grid configuration cannot meet the static stability requirements, and it is directly determined whether all grid strength and wind turbine proportion analyses have been completed.

[0035] Furthermore, through step S103, a state space model of the grid-connected system is established, and the small signal stability of the system is determined. The state space model is established around the steady-state operation point using differential algebraic equations.

[0036] Based on differential algebraic equations, a state space model of the wind farm grid-connected system is established around the steady-state operation point:

[0037] in, is the rate of change of the state vector, is the state vector, is the input vector, is the state space matrix, is the input matrix, is the output matrix, is the transfer matrix.

[0038] Small signal stability analysis is performed by calculating the state matrix The eigenvalues ​​of are analyzed and the real part is analyzed to judge the small signal stability: if the real part of all eigenvalues ​​is negative, the system is small signal stable. If there is an eigenvalue with a real part of zero or positive, the system is unstable.

[0039] When the small signal of the wind farm grid-connected system is unstable, it is determined that the proportion of wind turbines in the grid configuration cannot meet the static stability requirements, and it is directly judged whether all grid strength and wind turbine proportion analyses are completed.

[0040] Through step S104, the stability margin is analyzed in the case of small signal stability.

[0041] First, the dominant modal eigenvalue analysis is performed. When the small signal is stable, the dominant eigenvalue of the system is calculated and its corresponding mode is determined. The dominant modal eigenvalue is used to estimate the stability margin of the system, which indicates the system's ability to resist disturbances. The adaptability of the wind farm to changes in grid strength is evaluated by calculating the discrete coefficient. This embodiment records and evaluates the discrete coefficient to optimize the response characteristics of the wind farm grid-connected system.

[0042] Finally, all grid strengths and wind turbine ratios are analyzed through the S105 loop. For all possible combinations of grid strength and wind turbine ratios, power flow calculations, state space modeling, and small signal stability analysis are performed. In each iteration, the corresponding discrete coefficients and stability results under various combinations are recorded. The discrete coefficients of all combinations are compared, and the grid-type wind turbine ratio corresponding to the minimum discrete coefficient is selected as the optimal ratio to ensure that the system adapts to changing grid conditions to the greatest extent.

[0043] The embodiment of the present application finds the optimal wind turbine ratio through comprehensive analysis to maximize the stability and efficiency of the wind farm when connected to the grid.

[0044] Optionally, the calculating the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determining that the grid-connected system has not reached a capacity threshold based on the power flow distribution, includes: Establishing an equivalent circuit of a wind farm grid-connected system and determining node voltage equations of the equivalent circuit; Calculating the power flow distribution of each node of the wind farm grid-connected system under different working conditions based on the node voltage equation, and determining that the active power of all wind turbines does not exceed the power limit when the power flow distribution has a solution; The grid-connected guidelines are used to determine that the reactive power per unit value of the wind turbine is within a preset range, so as to determine that the grid-connected system has not reached a capacity threshold.

[0045] Furthermore, the establishing of an equivalent circuit of the wind farm grid-connected system and determining a node voltage equation of the equivalent circuit includes: According to the external power characteristics of grid-following wind turbines and grid-building wind turbines, the current source equivalent model and impedance equivalent model of the wind turbines are constructed; Constructing a system topology according to the current source equivalent model and the impedance equivalent model, and determining an admittance matrix based on the system topology and the wind turbine position distribution; A voltage matrix is ​​constructed according to the outlet voltage of each fan, and a current matrix is ​​constructed according to the output current of each fan; The node voltage equation is constructed based on the voltage matrix, the current matrix and the admittance matrix.

[0046] Specifically, in this embodiment, the proportion of grid-connected wind turbines in the wind farm is changed within a range of 0% to 100%, the strength of the power grid is changed, an equivalent circuit of the wind farm grid-connected system is established, and the node voltage equation of the circuit is written as follows:

[0047] in, U gi and I i The wind farm i The outlet voltage and output current of the wind turbine, the admittance matrix Y depends on the system parameters and is determined according to the current source equivalent model, the impedance equivalent model and the location of the wind turbine.

[0048] Furthermore, the power flow distribution of each node of the wind farm grid-connected system under different working conditions is calculated to determine whether the grid-connected system has reached the capacity limit; the system power flow distribution is solved based on the node voltage equation. If the power flow has a solution, the active power of all wind turbines will not exceed the power limit.

[0049] Given active power P For reference P ref , further determine the reactive power per unit value of each fan Q Whether it has reached the limit, according to the grid connection guidelines, the wind turbine reactive power standard value should be within the range of ±0.312pu, that is Q min < Q < Q max , Q min =-0.312, Q max =0.312, at this time, the system meets the capacity constraint.

[0050] Optionally, in the case of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, and the adaptability of the wind farm to the change of grid strength is evaluated using the discrete coefficient, including: updating the grid strength with a fixed step size, and selecting and recording the dominant modal eigenvalues ​​of the wind farm grid-connected system under different grid strengths based on the state space model; Calculating the real part average value of the dominant mode eigenvalue according to the dominant mode eigenvalue and the total number of grid strength changes to reflect the distance from the eigenvalue contained in the dominant mode to the imaginary axis; Calculate the standard deviation of the real part of the dominant modal eigenvalue based on the dominant modal eigenvalue, the total number of grid strength changes and the real part average value; Normalizing the discreteness of different dominant modes, and determining the discreteness coefficient according to the standard deviation and the real part average value; The adaptability to the change of the power grid strength is evaluated based on the dispersion coefficient.

[0051] Specifically, in this embodiment, if the system small signal is stable, the stability margin of the system is analyzed based on the dominant modal eigenvalue of the system, and the discrete coefficient is designed to evaluate the adaptability of the system to changes in grid strength; Select and record the dominant modes of the system based on the root loci y 1… y n , in order to reflect the distance from the eigenvalue contained in the dominant mode to the imaginary axis, the average value of the real part of the eigenvalue needs to be calculated μ :

[0052] in, The grid strength changes with a fixed step size to j The dominant mode eigenvalue at step , nis the total number of grid strength changes. This distance affects the changing trend of system gain and phase margin. The farther the dominant mode is from the imaginary axis, the greater the phase margin and gain margin are, and the lower the risk of system instability is. In order to measure the degree of dispersion of the dominant mode when the power grid strength changes, the standard deviation of the real part of the dominant mode eigenvalue is calculated. σ :

[0053] The smaller the offset distance of the dominant mode when the grid strength changes, the stronger the system's adaptability to grid strength changes; Considering that the system state variables and dominant modes change with the proportion of grid-type wind turbines, the discrete degrees of different dominant modes are normalized and the standard deviation is used. σ With the average μ The relative dispersion degree is measured by the ratio of

[0054]

[0055] The smaller it is, the stronger the ability of the wind farm grid-connected system to maintain stable operation when the grid strength changes; By comparing the different configurations of the fan , determine the minimum The corresponding proportion of grid-type fans is the optimal proportion.

[0056] Reference Figure 2 , Figure 2 It is a complete flow chart of the embodiment of the present application, which includes the following steps: Step 1: Change the proportion of grid-connected wind turbines, change the grid strength under this proportion, and calculate the power flow distribution of each node of the wind farm grid-connected system; Step 2: Determine whether the grid-connected system has reached the capacity limit. If so, the proportion of wind turbines in the grid configuration cannot meet the static stability requirements, and further determine whether all grid strength and proportion analyses have been completed; if not, proceed to step 3; Step 3: Establish a state space model of the grid-connected system to determine whether the system is small-signal stable. If so, record the dominant modal eigenvalues ​​of the system under different grid strengths and proceed to step 4; if not, determine whether all grid strength and ratio analyses are completed; Step 4: Analyze the stability margin of the system based on the dominant modal eigenvalue, design the discrete coefficient to evaluate the adaptability of the wind farm to the change of grid strength, and record the discrete coefficient; Step 5: Determine whether the analysis of all grid strengths and grid-type wind turbine ratios has been completed. If yes, proceed to step 6; if not, return to step 1; Step 6: Summarize the discrete coefficients under all the above proportions, and select the proportion of grid-type wind turbines corresponding to the minimum discrete coefficient as the optimal proportion.

[0057] Reference Figure 3 The present application also provides a wind farm grid-connected system grid-following type and grid-forming type wind turbine ratio optimization device, comprising: A ratio update module 310, used to change the initial ratio of the grid-forming wind turbines and change the grid strength at the updated ratio; A capacity determination module 320 is used to calculate the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determine that the grid-connected system does not reach the capacity threshold based on the power flow distribution; A stability judgment module 330 is used to establish a state space model of the grid-connected system and judge whether the grid-connected system is small signal stable based on the state space model; The adaptability evaluation module 340 is used to analyze the stability margin of the grid-connected system based on the dominant modal eigenvalue when the small signal is stable, evaluate the adaptability of the wind farm to the change of the grid strength by using the discrete coefficient, and record the discrete coefficient; The optimal selection module 350 is used to cyclically analyze all grid strengths and wind turbine ratios, obtain discrete coefficients under all ratios, and select the grid-forming wind turbine ratio corresponding to the minimum discrete coefficient as the optimal ratio.

[0058] Optionally, the calculating the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determining that the grid-connected system has not reached a capacity threshold based on the power flow distribution, includes: Establishing an equivalent circuit of a wind farm grid-connected system and determining node voltage equations of the equivalent circuit; Calculating the power flow distribution of each node of the wind farm grid-connected system under different working conditions based on the node voltage equation, and determining that the active power of all wind turbines does not exceed the power limit when the power flow distribution has a solution; The grid-connected guidelines are used to determine that the reactive power per unit value of the wind turbine is within a preset range, so as to determine that the grid-connected system has not reached a capacity threshold.

[0059] Optionally, establishing an equivalent circuit of the wind farm grid-connected system and determining a node voltage equation of the equivalent circuit includes: According to the external power characteristics of grid-following wind turbines and grid-building wind turbines, the current source equivalent model and impedance equivalent model of the wind turbines are constructed; Constructing a system topology according to the current source equivalent model and the impedance equivalent model, and determining an admittance matrix based on the system topology and the wind turbine position distribution; A voltage matrix is ​​constructed according to the outlet voltage of each fan, and a current matrix is ​​constructed according to the output current of each fan; The node voltage equation is constructed based on the voltage matrix, the current matrix and the admittance matrix.

[0060] Optionally, the method for establishing the state space model includes: Based on differential algebraic equations, a state space model of the wind farm grid-connected system is established around the steady-state operation point:

[0061] in, is the rate of change of the state vector, is the state vector, is the input vector, is the state space matrix, is the input matrix, is the output matrix, is the transfer matrix.

[0062] Optionally, in the case of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, and the adaptability of the wind farm to the change of grid strength is evaluated using the discrete coefficient, including: updating the grid strength with a fixed step size, and selecting and recording the dominant modal eigenvalues ​​of the wind farm grid-connected system under different grid strengths based on the state space model; Calculating the real part average value of the dominant mode eigenvalue according to the dominant mode eigenvalue and the total number of grid strength changes to reflect the distance from the eigenvalue contained in the dominant mode to the imaginary axis; Calculate the standard deviation of the real part of the dominant modal eigenvalue based on the dominant modal eigenvalue, the total number of grid strength changes and the real part average value; Normalizing the discreteness of different dominant modes, and determining the discreteness coefficient according to the standard deviation and the real part average value; The adaptability to the change of the power grid strength is evaluated based on the dispersion coefficient.

[0063] Optionally, the small signal stability is determined based on a root locus of the state space model.

[0064] Optionally, a direct judgment module is further included, for: When the grid-connected system reaches the capacity threshold or the small signal of the wind farm grid-connected system is unstable, it is determined that the proportion of wind turbines in the grid configuration cannot meet the static stability requirements, and it is directly judged whether all grid strength and wind turbine proportion analyses are completed.

[0065] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the device are similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method, which will not be repeated here.

[0066] Based on the method in the above embodiment, the embodiment of the present application provides an electronic device, which may include: a processor (Processor) 410, a communication interface (Communications Interface) 420, a memory (Memory) 430 and a communication bus 440, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other through the communication bus 440. The processor 410 can call the logic instructions in the memory 430 to execute the method in the above embodiment.

[0067] In addition, the logic instructions in the above-mentioned memory 430 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application.

[0068] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0069] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0070] It is understandable that the processor in the embodiment of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0071] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0072] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions may be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)), etc.

[0073] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0074] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system, characterized in that: include: Change the initial ratio of grid-forming wind turbines and change the grid strength at the updated ratio; Calculating the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determining that the grid-connected system does not reach the capacity threshold based on the power flow distribution; Establishing a state space model of the grid-connected system, and judging whether the grid-connected system is small signal stable based on the state space model; Under the condition of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, and the adaptability of the wind farm to the change of grid strength is evaluated by using the discrete coefficient, and the discrete coefficient is recorded; The analysis of all grid strengths and wind turbine ratios is repeated cyclically to obtain the discrete coefficients under all ratios, and the grid-type wind turbine ratio corresponding to the minimum discrete coefficient is selected as the optimal ratio.

2. The method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system according to claim 1, characterized in that: The calculating of the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determining that the grid-connected system does not reach the capacity threshold based on the power flow distribution, includes: Establishing an equivalent circuit of a wind farm grid-connected system and determining node voltage equations of the equivalent circuit; Calculating the power flow distribution of each node of the wind farm grid-connected system under different working conditions based on the node voltage equation, and determining that the active power of all wind turbines does not exceed the power limit when the power flow distribution has a solution; The grid-connected guidelines are used to determine that the reactive power per unit value of the wind turbine is within a preset range, so as to determine that the grid-connected system has not reached a capacity threshold.

3. The method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system according to claim 2, characterized in that: The establishing of an equivalent circuit of the wind farm grid-connected system and determining a node voltage equation of the equivalent circuit includes: According to the external power characteristics of grid-following wind turbines and grid-building wind turbines, the current source equivalent model and impedance equivalent model of the wind turbines are constructed; Constructing a system topology according to the current source equivalent model and the impedance equivalent model, and determining an admittance matrix based on the system topology and the wind turbine position distribution; A voltage matrix is ​​constructed according to the outlet voltage of each fan, and a current matrix is ​​constructed according to the output current of each fan; The node voltage equation is constructed based on the voltage matrix, the current matrix and the admittance matrix.

4. The method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system according to claim 1, characterized in that: The method for establishing the state space model comprises: Based on differential algebraic equations, a state space model of the wind farm grid-connected system is established around the steady-state operation point: in, is the rate of change of the state vector, is the state vector, is the input vector, is the state space matrix, is the input matrix, is the output matrix, is the transfer matrix.

5. The method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system according to claim 1, characterized in that: In the case of small signal stability, the stability margin of the grid-connected system is analyzed based on the dominant modal eigenvalue, and the adaptability of the wind farm to the change of grid strength is evaluated using the discrete coefficient, including: updating the grid strength with a fixed step size, and selecting and recording the dominant modal eigenvalues ​​of the wind farm grid-connected system under different grid strengths based on the state space model; Calculating the real part average value of the dominant mode eigenvalue according to the dominant mode eigenvalue and the total number of grid strength changes to reflect the distance from the eigenvalue contained in the dominant mode to the imaginary axis; Calculate the standard deviation of the real part of the dominant modal eigenvalue based on the dominant modal eigenvalue, the total number of grid strength changes and the real part average value; Normalizing the discreteness of different dominant modes, and determining the discreteness coefficient according to the standard deviation and the real part average value; The adaptability to the change of the power grid strength is evaluated based on the dispersion coefficient.

6. The method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system according to claim 1, characterized in that: The small signal stability is determined based on the root locus of the state space model.

7. The method for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system according to claim 1, characterized in that: Also includes: When the grid-connected system reaches the capacity threshold, or the small signal of the wind farm grid-connected system is unstable, it is determined that the proportion of wind turbines in the grid configuration cannot meet the static stability requirements, and it is directly judged whether all grid strength and wind turbine proportion analyses are completed.

8. A device for optimizing the ratio of grid-connected and grid-forming wind turbines in a wind farm grid-connected system, characterized in that: include: A ratio update module is used to change the initial ratio of grid-forming wind turbines and change the grid strength under the updated ratio; A capacity judgment module, used to calculate the power flow distribution of each node of the wind farm grid-connected system under the update ratio, and determine that the grid-connected system does not reach the capacity threshold based on the power flow distribution; A stability judgment module, used for establishing a state space model of the grid-connected system, and judging whether the grid-connected system is small-signal stable based on the state space model; The adaptability evaluation module is used to analyze the stability margin of the grid-connected system based on the dominant modal eigenvalue when the small signal is stable, evaluate the adaptability of the wind farm to the change of grid strength by using the discrete coefficient, and record the discrete coefficient; The optimal selection module is used to cyclically analyze all power grid strengths and wind turbine ratios, obtain discrete coefficients under all ratios, and select the grid-type wind turbine ratio corresponding to the minimum discrete coefficient as the optimal ratio.

9. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute 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 runs on a processor, the processor is caused to execute the method according to any one of claims 1 to 7.

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