Method for calculating equipment critical short-circuit ratio of large-scale new energy grid-connected system

Abstract

The invention discloses an equipment critical short-circuit ratio calculation method for a large-scale new energy grid-connected system, which is used for solving the technical problem that the equipment critical short-circuit ratio of the large-scale new energy grid-connected system is difficult to solve through an analysis mode in the prior art. The method comprises the following steps: acquiring alternating-current power grid data of the large-scale new energy grid-connected system and critical state data of each grid-following converter; constructing a small signal model of the large-scale new energy grid-connected system according to the AC power grid data and the critical state data, and constructing an equivalent isomorphic small signal model according to the small signal model; and solving the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, and taking the generalized short-circuit ratio as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state, thereby successfully solving the equipment critical short-circuit ratio of the large-scale new energy grid-connected system through an analysis mode.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy grid-connected systems, and in particular to a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, a device for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, an electronic device, and a storage medium. Background Art

[0002] With the continuous development of renewable energy sources such as wind power and photovoltaics, grid-connected capacity has increased annually. Large-scale renewable energy is being integrated into the AC grid via grid-connected converters. The large-scale integration of grid-connected converters reduces grid strength and leads to insufficient system inertia, which in turn triggers a series of subsynchronous and supersynchronous oscillation issues. This severely hinders the safe and stable operation of the power grid and the further development and utilization of renewable energy.

[0003] Currently, the short-circuit ratio (SCR) metric is commonly used to measure grid strength, revealing how grid-connected converters interact with the AC grid to influence the small-disturbance stability of renewable energy grid-connected systems. Existing research has further extended the SCR metric, proposing a generalized SCR metric to measure the grid strength of large-scale renewable energy grid-connected systems. Generally, the smaller the SCR, the weaker the grid strength. When a large-scale renewable energy grid-connected system experiences critical oscillation, this indicates that the equipment's tolerance to the grid has reached its limits. The SCR at this point represents the critical SCR of the equipment in the large-scale renewable energy grid-connected system.

[0004] The generalized short-circuit ratio method can quickly quantify the grid strength of large-scale renewable energy grid-connected systems. The difference in the critical short-circuit ratio of equipment can characterize the stability margin of large-scale renewable energy grid-connected systems. This method provides a quantitative indicator for the safe and stable operation of large-scale renewable energy grid-connected systems. However, previous studies have not directly provided an analytical calculation method for the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems. Determining the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems relies on experimental or complete information about the converter's internal parameters, making it difficult to apply in engineering practice. Therefore, there is an urgent need to find a method that can analytically and calculate the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems without relying on too much information. Summary of the Invention

[0005] The present invention provides a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, a device for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, an electronic device, and a storage medium, which are used to solve or partially solve the technical problem that it is difficult to obtain the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system through analytical means in current technology.

[0006] The present invention provides a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, the method comprising:

[0007] Acquire AC grid data of large-scale renewable energy grid-connected systems and critical state data of each grid-connected converter;

[0008] Constructing a small signal model of the large-scale new energy grid-connected system based on the AC power grid data and each of the critical state data, and constructing an equivalent isomorphic small signal model based on the small signal model;

[0009] The generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero is solved as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state.

[0010] Optionally, the AC grid data includes a grid admittance matrix, line and component parameters, and a grid topology; the critical state data includes a single-machine critical short-circuit ratio of the grid-following converter and a system oscillation frequency in a critical state.

[0011] Optionally, constructing a small signal model of the large-scale new energy grid-connected system based on the AC grid data and each of the critical state data includes:

[0012] For each of the grid-following converters, constructing an integral parameter model and a proportional coefficient model of a phase-locked loop (PI) control according to the critical short-circuit ratio of the single machine, the system oscillation frequency, the grid admittance matrix, the line and component parameters, and the grid topology; and constructing a state matrix, a control matrix, and an output matrix based on the integral parameter model and the proportional coefficient model.

[0013] Based on each of the state matrices, each of the control matrices, and each of the output matrices, combined with a state equation coefficient matrix, a rated power diagonal matrix, and a node impedance matrix of the AC power grid, a system state matrix of the large-scale new energy grid-connected system in a closed loop is constructed;

[0014] According to the system state matrix, combined with differential operators and state variables, a small signal model of the large-scale new energy grid-connected system is constructed.

[0015] Optionally, constructing an equivalent isomorphic small signal model according to the small signal model includes:

[0016] Introducing the identity matrix and the eigenvalues of the system state matrix to construct the characteristic equation of the small signal model;

[0017] Based on the characteristic equation and according to matrix perturbation theory, a small signal model of an equivalent isomorphic system equivalent to the dominant oscillation mode of the small signal model is constructed as the equivalent isomorphic small signal model.

[0018] Optionally, the weakest oscillation mode of the equivalent isomorphic system is equivalent to the weakest oscillation mode of the large-scale new energy grid-connected system; and the method further includes:

[0019] The equivalent isomorphic small signal model is decomposed based on time domain and frequency domain stability analysis to obtain the dominant pole real part model of the equivalent isomorphic system and the generalized short-circuit ratio model of the large-scale new energy grid-connected system.

[0020] Optionally, the real part model of the dominant pole of the equivalent isomorphic system is as follows:

[0021]

[0022] The generalized short-circuit ratio model of the large-scale new energy grid-connected system is as follows:

[0023]

[0024] in, It means to find the real part of a complex number; represents the eigenvalue of the system state matrix; For the The phase-locked loop PI proportional coefficient of the grid-type converter; Indicates resistance With inductor The ratio of Indicates the rated synchronous angular frequency; It represents the generalized short-circuit ratio of large-scale renewable energy grid-connected systems; For the Phase-locked loop PI integral parameters of a grid-type converter; Indicates finding the maximum value; Indicates finding the eigenvalue of a matrix; is the rated power diagonal matrix; For the Rated capacity of each grid-type converter; is the node impedance matrix of the AC grid.

[0025] Optionally, the critical short-circuit ratio of the equipment when the large-scale new energy grid-connected system is in a critical stable state is calculated by the following formula:

[0026]

[0027] in, Indicates the critical short-circuit ratio of equipment when the large-scale new energy grid-connected system is in a critical stable state; The original heterogeneous large-scale new energy grid-connected system Participation factor of a grid-connected converter; Indicates resistance With inductor The ratio of Indicates the rated synchronous angular frequency; Indicates the The critical short-circuit ratio of a single grid-type converter; Indicates the The system oscillation frequency of a grid-connected converter in a critical state.

[0028] The present invention also provides a device for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, comprising:

[0029] A data acquisition unit is used to obtain AC grid data of large-scale new energy grid-connected systems and critical state data of each grid-connected converter;

[0030] A small signal model construction unit is used to construct a small signal model of the large-scale new energy grid-connected system according to the AC power grid data and each of the critical state data, and to construct an equivalent isomorphic small signal model according to the small signal model;

[0031] The equipment critical short-circuit ratio solving unit is used to solve the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state.

[0032] The present invention further provides an electronic device, comprising a processor and a memory:

[0033] The memory is used to store program code and transmit the program code to the processor;

[0034] The processor is configured to execute the equipment critical short-circuit ratio calculation method for a large-scale new energy grid-connected system as described in any one of the above items according to the instructions in the program code.

[0035] The present invention also provides a computer-readable storage medium for storing program code, wherein the program code is used to execute the method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system as described in any one of the above items.

[0036] It can be seen from the above technical solutions that the present invention has the following advantages:

[0037] A method for calculating the critical short-circuit ratio of equipment in a large-scale renewable energy grid-connected system is provided. First, the AC grid data and critical state data of each grid-connected converter of the large-scale renewable energy grid-connected system are obtained. Then, based on the AC grid data and the critical state data, a small-signal model of the large-scale renewable energy grid-connected system is constructed, and an equivalent isomorphic small-signal model is constructed based on the small-signal model. Thus, the small-signal model of the large-scale renewable energy grid-connected system is established based on the collected relevant data. By constructing the equivalent isomorphic small-signal model, an equivalent isomorphic system with approximate dominant poles similar to the large-scale renewable energy grid-connected system is constructed to reveal the relationship between the critical short-circuit ratio of equipment and the parameters of each grid-connected converter and the grid. Finally, the generalized short-circuit ratio of the equivalent isomorphic small-signal model when the real part of the dominant pole is zero is solved, which is used as the critical short-circuit ratio of equipment when the large-scale renewable energy grid-connected system is in a critical stable state. By further providing an analytical expression for the critical short-circuit ratio and calculating the critical short-circuit ratio of equipment in the large-scale renewable energy grid-connected system, the problem of the lack of accurate boundaries when using the generalized short-circuit ratio method to analyze the stability of large-scale renewable energy grid-connected systems is resolved, enabling the large-scale renewable energy grid-connected system to operate stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 A flowchart of a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system;

[0040] Figure 2 A schematic diagram of the overall process of a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system;

[0041] Figure 3 This is a schematic diagram of the modified IEEE 39-bus system structure used in a specific simulation example verification;

[0042] Figure 4 Schematic diagram of the time domain response results of the active power output of grid-following converters 1 to 9 in a specific simulation verification;

[0043] Figure 5 The structure block diagram of a critical short-circuit ratio calculation device for a large-scale new energy grid-connected system. DETAILED DESCRIPTION

[0044] Embodiments of the present invention provide a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, a device for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, an electronic device, and a storage medium, which are used to solve or partially solve the technical problem that it is difficult to obtain the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system through analytical means in current technology.

[0045] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] In order to enable those skilled in the art to better understand the technical solutions provided by the embodiments of the present invention, some of the technical features involved in the solutions are briefly described first:

[0047] Equipment critical short-circuit ratio: This refers to the ratio of the maximum short-circuit current that the equipment can withstand to its normal operating current in the event of a short circuit. This ratio is used to assess the equipment's ability to withstand short-circuit faults, ensuring stable operation under various conditions.

[0048] As an example, the generalized short-circuit ratio method can quickly quantify the grid strength of large-scale renewable energy grid-connected systems. The difference in the critical short-circuit ratio of equipment can characterize the stability margin of large-scale renewable energy grid-connected systems. This method provides a quantitative indicator for the safe and stable operation of large-scale renewable energy grid-connected systems. However, previous studies have not directly provided an analytical calculation method for the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems. Obtaining the critical short-circuit ratio of equipment relies on experiments or full internal parameter information of the converter, making it difficult to apply in engineering practice. Therefore, there is an urgent need to find a method that can analyze and calculate the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems without relying on too much information.

[0049] Therefore, one of the core invention points of the embodiment of the present invention is: to solve the problem that the current technology based on the generalized short-circuit ratio index to evaluate the small-disturbance stability of large-scale new energy grid-connected systems is difficult to obtain the critical short-circuit ratio of the equipment of large-scale new energy grid-connected systems in an analytical way, a method for calculating the critical short-circuit ratio of the equipment of the grid-connected converter of the large-scale new energy grid-connected system is provided. First, the data of each grid-connected converter and the AC power grid data of the large-scale new energy grid-connected system are collected, and a small signal model of the large-scale new energy grid-connected system is established based on the rated operating conditions. Then, an equivalent isomorphic system containing approximate dominant poles with the large-scale new energy grid-connected system is constructed through matrix perturbation theory to reveal the relationship between the critical short-circuit ratio of the equipment and the parameters of each converter device and the power grid. Then, an analytical expression for the critical short-circuit ratio of the equipment is further given and the critical short-circuit ratio of the equipment of the large-scale new energy grid-connected system is calculated. By adopting the technical solution of the present invention, based on the time domain and frequency domain stability analysis methods and matrix perturbation theory, a small signal model of a large-scale new energy grid-connected system and a small signal model of a corresponding equivalent isomorphic system are constructed. At the same time, through theoretical derivation, the relationship between the critical short-circuit ratio of the equipment of the large-scale new energy grid-connected system and the single-machine critical short-circuit ratio and oscillation frequency of a single grid-following converter device and grid parameters is established. The critical short-circuit ratio of the equipment of the large-scale new energy grid-connected system under rated operating conditions can be accurately analyzed, thereby solving the problem of lack of accurate boundaries when using the generalized short-circuit ratio method to analyze the stability problem of the large-scale new energy grid-connected system, so that the large-scale new energy grid-connected system can operate stably.

[0050] Reference Figure 1 , shows a flowchart of a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system provided by an embodiment of the present invention, which may specifically include the following steps:

[0051] Step 101: Acquire AC grid data of a large-scale new energy grid-connected system and critical state data of each grid-connected converter;

[0052] This step mainly realizes the collection of data and related grid parameters of each grid-connected converter of the large-scale new energy grid-connected system.

[0053] In some embodiments, the AC grid data may primarily include a grid admittance matrix, line and component parameters, and grid topology. The critical state data of the grid-following converter may primarily include the critical short-circuit ratio of the grid-following converter and the system oscillation frequency in the critical state.

[0054] Specifically, the data of each grid-connected converter of the large-scale new energy grid-connected system is collected, including the critical short-circuit ratio of each grid-connected converter. and the system oscillation frequency corresponding to the critical state , subscript Indicates the devices.

[0055] The relevant grid parameters (i.e. AC grid data) collected for large-scale renewable energy grid-connected systems include the grid's admittance matrix, line and component parameters, topology, load data, power generation data, fault and event logs, system response data, and historical stability event data.

[0056] The admittance matrix contains the admittance parameters of the entire power grid or its relevant sections and is the basis for analyzing the electrical behavior of the power grid. Line and component parameters include the impedance values of all lines, transformer parameters, and any other electrical component characteristics that may affect the behavior of the power grid. The topology primarily includes the structural data of the power grid, such as node connections and line configurations.

[0057] Step 102: constructing a small signal model of the large-scale new energy grid-connected system based on the AC grid data and each of the critical state data, and constructing an equivalent isomorphic small signal model based on the small signal model;

[0058] This step mainly realizes the construction of a small signal model of a large-scale new energy grid-connected system based on the collected data and rated operating conditions, and the construction of a small signal model of an equivalent isomorphic system based on the small signal model.

[0059] In a specific implementation, the process of constructing a small signal model of a large-scale new energy grid-connected system based on AC grid data and various critical state data may include the following sub-steps S01 to S03:

[0060] Step S01: For each grid-following converter, construct an integral parameter model and a proportional coefficient model of a phase-locked loop (PI) control according to the critical short-circuit ratio of the single machine, the system oscillation frequency, the grid admittance matrix, the line and component parameters, and the grid topology. Based on the integral parameter model and the proportional coefficient model, construct a state matrix, a control matrix, and an output matrix respectively.

[0061] Step S02: Based on each state matrix, each control matrix and each output matrix, combined with the state equation coefficient matrix, the rated power diagonal matrix and the node impedance matrix of the AC power grid, a system state matrix of the large-scale new energy grid-connected system in a closed loop is constructed;

[0062] Step S03: Based on the system state matrix, combined with differential operators and state variables, a small signal model of the large-scale new energy grid-connected system is constructed.

[0063] Specifically, the small signal model of a large-scale new energy grid-connected system built based on rated operating conditions is:

[0064]

[0065] in, is the differential operator; is the Laplace operator; represents the state equation coefficient matrix; For micro increments; is a state variable; For the A state matrix of a grid-type converter; For the A control matrix for a grid-following converter; For the An output matrix of a grid-type converter; represents a diagonal matrix; is the node impedance matrix of the AC grid; is the rated power diagonal matrix; For the Rated capacity of each grid-type converter; Indicates resistance With inductor The ratio of , assuming that all network lines have the same ratio ; Indicates the rated synchronous angular frequency; For the Phase-locked loop PI integral parameters of a grid-type converter; For the The phase-locked loop PI proportional coefficient of the grid-type converter; 、 Respectively The voltage x-axis and y-axis components of a grid-following converter at the steady-state equilibrium point; 、 Respectively The x-axis and y-axis components of the current of a grid-type converter at the steady-state equilibrium point. When the steady-state equilibrium point The active power output by each grid-type converter after being normalized to its own rated capacity; When the steady-state equilibrium point The reactive power output by each grid-following converter after being normalized to its own rated capacity; For the The terminal voltage of a grid-following converter during steady-state operation; 、 、 According to the knowledge of circuit principles, 、 、 、 Calculated; Matrix It is the system state matrix of the closed loop of the large-scale new energy grid-connected system, reflecting the closed loop stability of the system.

[0066] Furthermore, an equivalent isomorphic small signal model is constructed according to the small signal model. Specifically, the following steps are performed: first, the eigenvalues of the unit matrix and the system state matrix are introduced to construct the characteristic equation of the small signal model; then, based on the characteristic equation and according to the matrix perturbation theory, a small signal model of an equivalent isomorphic system equivalent to the dominant oscillation mode of the small signal model is constructed as the equivalent isomorphic small signal model.

[0067] More specifically, the characteristic equation of the small signal model based on the large-scale renewable energy grid-connected system is:

[0068]

[0069] in, represents the identity matrix; Represents the system state matrix The eigenvalue of .

[0070] According to the matrix perturbation theory, a small signal model of an equivalent isomorphic system equivalent to the dominant oscillation mode of the small signal model of the large-scale renewable energy grid-connected system can be constructed as follows:

[0071]

[0072] in, is the state equation of the equivalent isomorphic system; is the governing equation of the equivalent isomorphic system; is the output equation of the equivalent isomorphic system; The original heterogeneous large-scale new energy grid-connected system Participation factor of a grid-connected converter; is the system state matrix of the closed loop of the equivalent isomorphic system, reflecting the closed loop stability of the system.

[0073] Therefore, based on the small signal model and matrix perturbation theory, an equivalent isomorphic system with the same dominant poles as the large-scale renewable energy grid-connected system can be constructed, and then the critical short-circuit ratio of the equipment of the large-scale renewable energy grid-connected system can be calculated subsequently.

[0074] Step 103 , solving the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state.

[0075] The previous steps used matrix perturbation theory to establish the relationship between the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems and the various grid-connected converter devices and grid parameters. Building on this, this step provides an analytical expression for the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems and calculates the corresponding critical short-circuit ratio.

[0076] Based on the small-signal model of the large-scale renewable energy grid-connected system and the small-signal model of the equivalent isomorphic system constructed in the aforementioned steps, it can be seen that the weakest oscillation mode of the equivalent isomorphic system is equivalent to the weakest oscillation mode of the large-scale renewable energy grid-connected system. Furthermore, the generalized short-circuit ratio of the large-scale renewable energy grid-connected system in the critical stable state can be derived, that is, the critical short-circuit ratio of the equipment of the large-scale renewable energy grid-connected system. When solving the problem, the equivalent isomorphic small-signal model can be first decomposed based on the time-domain and frequency-domain stability analysis to obtain the dominant pole real part model of the equivalent isomorphic system and the generalized short-circuit ratio model of the large-scale renewable energy grid-connected system. The short-circuit ratio calculation can then be considered for the case where the dominant pole real part is zero.

[0077] Specifically, the real part model of the dominant pole of the equivalent isomorphic system is as follows:

[0078]

[0079] Specifically, the generalized short-circuit ratio model of a large-scale renewable energy grid-connected system is as follows:

[0080]

[0081] in, It means to find the real part of a complex number; It represents the generalized short-circuit ratio of large-scale renewable energy grid-connected systems; Indicates finding the maximum value; It means to find the eigenvalues of a matrix.

[0082] The dominant poles of a large-scale renewable energy grid-connected system approximately coincide with the dominant poles of an equivalent isomorphic system. When the large-scale renewable energy grid-connected system is in a critical stable state, the real part of the dominant poles of the equivalent isomorphic system is zero. At this point, the generalized short-circuit ratio of the system is the critical short-circuit ratio of the equipment in the large-scale renewable energy grid-connected system. Specifically, the critical short-circuit ratio of the equipment in the critical stable state of the large-scale renewable energy grid-connected system can be calculated using the following formula:

[0083]

[0084] in, Indicates the critical short-circuit ratio of equipment when the large-scale new energy grid-connected system is in a critical stable state; Indicates the The critical short-circuit ratio of a single grid-type converter; Indicates the The system oscillation frequency of a grid-connected converter in a critical state.

[0085] Therefore, an analytical expression for the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems is given without the need for other experiments or additional information, which enables the rapid calculation of the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems, improves the flexibility and safety of power grid design and operation, reveals the relationship between the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems and various devices, and greatly improves the stability of the power grid when facing the grid connection of large-scale renewable energy.

[0086] In an embodiment of the present invention, a method for calculating the critical short-circuit ratio of equipment for a grid-connected converter in a large-scale renewable energy grid-connected system is provided. First, data from each grid-connected converter and AC grid data are collected for the large-scale renewable energy grid-connected system. A small-signal model of the large-scale renewable energy grid-connected system is established based on rated operating conditions. Matrix perturbation theory is then used to construct an equivalent isomorphic system containing approximate dominant poles to the large-scale renewable energy grid-connected system. This system reveals the relationship between the critical short-circuit ratio and the parameters of each converter and grid. An analytical expression for the critical short-circuit ratio is then provided, and the critical short-circuit ratio of the equipment for the large-scale renewable energy grid-connected system is calculated. By adopting the technical solution of the present invention, based on the time domain and frequency domain stability analysis methods and matrix perturbation theory, a small signal model of a large-scale new energy grid-connected system and a small signal model of a corresponding equivalent isomorphic system are constructed. At the same time, through theoretical derivation, the relationship between the critical short-circuit ratio of the equipment of the large-scale new energy grid-connected system and the single-machine critical short-circuit ratio, oscillation frequency and grid parameters of a single grid-following converter device is established. This can accurately analyze the critical short-circuit ratio of the equipment of the large-scale new energy grid-connected system under rated operating conditions, thereby solving the problem of lack of accurate boundaries when using the generalized short-circuit ratio method to analyze the stability problem of the large-scale new energy grid-connected system, so that the large-scale new energy grid-connected system can operate stably.

[0087] For better explanation, refer to Figure 2 , which shows a schematic diagram of the overall flow of a method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, provided by an embodiment of the present invention. It should be noted that this embodiment only briefly describes the general process of calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system. The specific implementation of each step can be understood by referring to the relevant content in the aforementioned embodiments and will not be elaborated here. It is understood that the present invention is not limited to this method.

[0088] Step 201: Acquire AC grid data of a large-scale new energy grid-connected system and critical state data of each grid-connected converter;

[0089] Step 202: Construct a small signal model of a large-scale new energy grid-connected system based on the AC grid data and each critical state data;

[0090] Step 203: Introduce the eigenvalues of the unit matrix and the system state matrix to construct the characteristic equation of the small signal model;

[0091] Step 204: Based on the characteristic equation and according to matrix perturbation theory, a small signal model of an equivalent isomorphic system equivalent to the dominant oscillation mode of the small signal model is constructed as the equivalent isomorphic small signal model;

[0092] Step 205: Calculate the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, and use it as the critical short-circuit ratio of the equipment when the large-scale new energy grid-connected system is in a critical stable state.

[0093] Based on the method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system provided in the aforementioned embodiment, in order to enable those skilled in the art to better understand the technical solution of the present invention and to verify the beneficial effects of the present invention, the following describes an embodiment of the present invention through a specific example combined with economic benefit calculations and simulation experiments.

[0094] Figure 4 Schematic diagram of the time domain response results of the active power output of grid-following converters 1 to 9 in a specific simulation verification;

[0095] First, a modified IEEE 39-bus system (i.e., a grid-connected system with a single grid-connected converter) is established in the simulation platform. Figure 3 As shown in Figure 1, nodes 1 through 9 are connected to IBRs (Inverter-Based Resources), a renewable energy grid-connected converter, via transformers. Node 39 is connected to the external grid, simplified as an infinite busbar. Each IBR represents a wind farm. See Table 1 for IBR capacity and Table 2 for IBR control parameters. See Table 3 for data required to calculate the critical short-circuit ratio of equipment in large-scale renewable energy grid-connected systems.

[0096]

[0097] Table 1: Rated capacity of normalized IBR

[0098]

[0099] Table 2: IBR control parameters

[0100]

[0101] Table 3: IBR data required for equipment critical short-circuit ratio calculation

[0102] The critical short-circuit ratio of the modified IEEE 39-bus system is 1.8372. Next, a calculation example is set for the modified IEEE 39-bus system to verify the effectiveness of the calculation method provided by the present invention.

[0103] When the generalized short-circuit ratio of the modified IEEE 39-bus system is set to 1.8102, , the system is in a critical oscillation state.

[0104] When the generalized short-circuit ratio of the modified IEEE 39-bus system is set to 2.1584, , the system is in a stable state.

[0105] When the generalized short-circuit ratio of the modified IEEE 39-bus system is set to 1.5743, , the system is in an unstable state.

[0106] Furthermore, this example also performs a time-domain simulation of the modified IEEE 39-bus system. At t = 0.1s, a disturbance is applied to the infinite bus, resulting in a 0.05 pu voltage drop that lasts for 0.05s. Figure 4 The time-domain responses of all IBR active power outputs under these three scenarios are presented. The time-domain simulation results are consistent with the stability analysis results obtained from theoretical calculations, thus verifying the effectiveness of the equipment critical short-circuit ratio calculation method for large-scale renewable energy grid-connected systems proposed in this embodiment of the present invention.

[0107] In summary, the equipment critical short-circuit ratio calculation method proposed in the embodiment of the present invention has achieved good results in terms of operability, accuracy, stability and adaptability.

[0108] Reference Figure 5 , shows a structural block diagram of a device for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system provided by an embodiment of the present invention, which may specifically include:

[0109] The data acquisition unit 501 is used to acquire AC grid data of a large-scale new energy grid-connected system and critical state data of each grid-connected converter;

[0110] A small signal model construction unit 502 is configured to construct a small signal model of the large-scale new energy grid-connected system based on the AC power grid data and each of the critical state data, and to construct an equivalent isomorphic small signal model based on the small signal model;

[0111] The equipment critical short-circuit ratio solving unit 503 is used to solve the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state.

[0112] In an optional embodiment, the AC grid data includes a grid admittance matrix, line and component parameters, and a grid topology; the critical state data includes a single-machine critical short-circuit ratio of the grid-following converter and a system oscillation frequency in a critical state.

[0113] In an optional embodiment, the small signal model building unit 502 includes:

[0114] a grid-type converter related matrix construction unit, configured to construct, for each of the grid-type converters, an integral parameter model and a proportional coefficient model of a phase-locked loop (PI) control according to the critical short-circuit ratio of the single machine, the system oscillation frequency, the grid admittance matrix, the line and component parameters, and the grid topology, and to construct, based on the integral parameter model and the proportional coefficient model, a state matrix, a control matrix, and an output matrix;

[0115] A system state matrix construction unit is configured to construct a system state matrix of the large-scale new energy grid-connected system in a closed loop based on each of the state matrices, each of the control matrices, and each of the output matrices, in combination with a state equation coefficient matrix, a rated power diagonal matrix, and a node impedance matrix of the AC power grid;

[0116] The small signal model construction subunit is used to construct a small signal model of the large-scale new energy grid-connected system based on the system state matrix, combined with differential operators and state variables.

[0117] In an optional embodiment, the small signal model building unit 502 includes:

[0118] a characteristic equation construction unit, configured to introduce the identity matrix and the eigenvalues of the system state matrix to construct the characteristic equation of the small signal model;

[0119] The equivalent isomorphic small signal model construction subunit is used to construct a small signal model of an equivalent isomorphic system equivalent to the dominant oscillation mode of the small signal model based on the characteristic equation and according to matrix perturbation theory, as an equivalent isomorphic small signal model.

[0120] In an optional embodiment, the weakest oscillation mode of the equivalent isomorphic system is equivalent to the weakest oscillation mode of the large-scale new energy grid-connected system; the equipment critical short-circuit ratio solving unit 503 further includes:

[0121] The model decomposition unit is used to decompose the equivalent isomorphic small signal model based on time domain and frequency domain stability analysis to obtain the dominant pole real part model of the equivalent isomorphic system and the generalized short-circuit ratio model of the large-scale new energy grid-connected system.

[0122] In an optional embodiment, the dominant pole real part model of the equivalent isomorphic system is as follows:

[0123]

[0124] The generalized short-circuit ratio model of the large-scale new energy grid-connected system is as follows:

[0125]

[0126] in, It means to find the real part of a complex number; represents the eigenvalue of the system state matrix; For the The phase-locked loop PI proportional coefficient of the grid-type converter; Indicates resistance With inductor The ratio of Indicates the rated synchronous angular frequency; It represents the generalized short-circuit ratio of large-scale renewable energy grid-connected systems; For the Phase-locked loop PI integral parameters of a grid-type converter; Indicates finding the maximum value; Indicates finding the eigenvalue of a matrix; is the rated power diagonal matrix; For the Rated capacity of each grid-type converter; is the node impedance matrix of the AC grid.

[0127] In an optional embodiment, the critical short-circuit ratio of equipment when the large-scale new energy grid-connected system is in a critical stable state is calculated by the following formula:

[0128]

[0129] in, Indicates the critical short-circuit ratio of equipment when the large-scale new energy grid-connected system is in a critical stable state; The original heterogeneous large-scale new energy grid-connected system Participation factor of a grid-connected converter; Indicates resistance With inductor The ratio of Indicates the rated synchronous angular frequency; Indicates the The critical short-circuit ratio of a single grid-type converter; Indicates the The system oscillation frequency of a grid-connected converter in a critical state.

[0130] As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the aforementioned method embodiment.

[0131] An embodiment of the present invention further provides an electronic device, the device including a processor and a memory:

[0132] The memory is used to store program codes and transmit the program codes to the processor;

[0133] The processor is configured to execute the method for calculating the equipment critical short-circuit ratio of a large-scale new energy grid-connected system according to any embodiment of the present invention according to the instructions in the program code.

[0134] An embodiment of the present invention further provides a computer-readable storage medium for storing program code, and the program code is used to execute the method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system according to any embodiment of the present invention.

[0135] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0136] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0137] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0138] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0139] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0140] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, characterized in that: include: Acquire AC grid data of large-scale renewable energy grid-connected systems and critical state data of each grid-connected converter; Constructing a small signal model of the large-scale new energy grid-connected system based on the AC power grid data and each of the critical state data, and constructing an equivalent isomorphic small signal model based on the small signal model; The generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero is solved as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state.

2. The method for calculating the critical short-circuit ratio of equipment according to claim 1, characterized in that: The AC grid data includes a grid admittance matrix, line and component parameters, and a grid topology; the critical state data includes a single critical short-circuit ratio of the grid-following converter and a system oscillation frequency in a critical state.

3. The method for calculating the critical short-circuit ratio of equipment according to claim 2, characterized in that: The step of constructing a small signal model of the large-scale new energy grid-connected system based on the AC grid data and each of the critical state data includes: For each of the grid-following converters, constructing an integral parameter model and a proportional coefficient model of a phase-locked loop (PI) control according to the critical short-circuit ratio of the single machine, the system oscillation frequency, the grid admittance matrix, the line and component parameters, and the grid topology; and constructing a state matrix, a control matrix, and an output matrix based on the integral parameter model and the proportional coefficient model. Based on each of the state matrices, each of the control matrices, and each of the output matrices, combined with a state equation coefficient matrix, a rated power diagonal matrix, and a node impedance matrix of the AC power grid, a system state matrix of the large-scale new energy grid-connected system in a closed loop is constructed; According to the system state matrix, combined with differential operators and state variables, a small signal model of the large-scale new energy grid-connected system is constructed.

4. The method for calculating the critical short-circuit ratio of equipment according to claim 3, characterized in that: The constructing of an equivalent isomorphic small signal model according to the small signal model includes: Introducing the identity matrix and the eigenvalues of the system state matrix to construct the characteristic equation of the small signal model; Based on the characteristic equation and according to matrix perturbation theory, a small signal model of an equivalent isomorphic system equivalent to the dominant oscillation mode of the small signal model is constructed as the equivalent isomorphic small signal model.

5. The method for calculating the critical short-circuit ratio of equipment according to claim 4, characterized in that: The weakest oscillation mode of the equivalent isomorphic system is equivalent to the weakest oscillation mode of the large-scale new energy grid-connected system; the method further includes: The equivalent isomorphic small signal model is decomposed based on time domain and frequency domain stability analysis to obtain the dominant pole real part model of the equivalent isomorphic system and the generalized short-circuit ratio model of the large-scale new energy grid-connected system.

6. The method for calculating the critical short-circuit ratio of equipment according to claim 5, characterized in that: The real part model of the dominant pole of the equivalent isomorphic system is shown below: The generalized short-circuit ratio model of the large-scale new energy grid-connected system is as follows: in, It means to find the real part of a complex number; represents the eigenvalue of the system state matrix; For the The phase-locked loop PI proportional coefficient of the grid-type converter; Indicates resistance With inductor The ratio of Indicates the rated synchronous angular frequency; It represents the generalized short-circuit ratio of large-scale renewable energy grid-connected systems; For the Phase-locked loop PI integral parameters of a grid-type converter; Indicates finding the maximum value; Indicates finding the eigenvalue of a matrix; is the rated power diagonal matrix; For the Rated capacity of each grid-type converter; is the node impedance matrix of the AC grid.

7. The method for calculating the critical short-circuit ratio of equipment according to claim 5 or 6, characterized in that: The critical short-circuit ratio of the equipment when the large-scale new energy grid-connected system is in a critical stable state is calculated by the following formula: in, Indicates the critical short-circuit ratio of equipment when the large-scale new energy grid-connected system is in a critical stable state; The original heterogeneous large-scale new energy grid-connected system Participation factor of a grid-connected converter; Indicates resistance With inductor The ratio of Indicates the rated synchronous angular frequency; Indicates the The critical short-circuit ratio of a single grid-type converter; Indicates the The system oscillation frequency of a grid-connected converter in a critical state.

8. A device for calculating the critical short-circuit ratio of equipment in a large-scale new energy grid-connected system, characterized in that: include: A data acquisition unit is used to obtain AC grid data of large-scale new energy grid-connected systems and critical state data of each grid-connected converter; A small signal model construction unit is used to construct a small signal model of the large-scale new energy grid-connected system according to the AC power grid data and each of the critical state data, and to construct an equivalent isomorphic small signal model according to the small signal model; The equipment critical short-circuit ratio solving unit is used to solve the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state.

9. An electronic device, characterized in that: The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the equipment critical short-circuit ratio calculation method of the large-scale new energy grid-connected system according to any one of claims 1 to 7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store program code, and the program code is used to execute the equipment critical short-circuit ratio calculation method of the large-scale new energy grid-connected system according to any one of claims 1 to 7.

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