Impedance-aggregation-based electromechanical equivalent modeling method and system for photovoltaic power station

Abstract

The present application relates to the technical field of new energy modeling simulation, and more particularly to a photovoltaic power station electromechanical equivalent modeling method and system based on impedance aggregation, which comprises the following steps: obtaining the topological parameters, equipment parameters and line parameters of the photovoltaic power station, and establishing a detailed model of the photovoltaic power station; determining the range to be equivalent based on the detailed model, and dividing the equivalent object by taking the 35kV collection bus in the range to be equivalent as a unit; performing aggregation processing on the power generation unit and network parameters in the equivalent object to obtain equivalent parameters corresponding to the 35kV collection bus; constructing an electromechanical equivalent model of the photovoltaic power station based on the equivalent parameters; simulating the electromechanical equivalent model, and comparing the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model. Through the present application, the problems of complex modeling, low simulation efficiency and difficulty in considering equivalent accuracy in the existing photovoltaic power station electromechanical transient modeling are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of new energy modeling and simulation technology, and in particular to a method and system for electromechanical equivalent modeling of photovoltaic power plants based on impedance aggregation. Background Technology

[0002] In grid connection analysis and electromechanical transient simulation of photovoltaic power plants, it is usually necessary to establish a model that can reflect the overall operating characteristics of the plant. The purpose of electromechanical equivalent modeling is to reasonably simplify the internal equipment and their connection relationships of the plant while retaining the key electrical response characteristics of the plant to the outside world, so as to improve the applicability of system analysis and simulation.

[0003] In existing technologies, one approach is detailed modeling, which models each photovoltaic power generation unit, box-type transformer, collector line, collection line, and related equipment according to the actual topology. While this approach can comprehensively reflect the internal operating characteristics of the power station, it suffers from problems such as large model size, complex parameter processing, large modeling workload, and low simulation efficiency. Another approach is simplified equivalent modeling, which reduces model complexity by merging some power generation units. However, this method often focuses primarily on the equivalent of the power generation unit itself, neglecting network factors such as line impedance, transformer impedance, grounding capacitance, and admittance branches in the collector system, making it difficult to accurately reflect the overall electrical characteristics of the power station. Since the voltage, current, and active and reactive power responses at the grid connection point of a photovoltaic power station are not only related to the power generation unit but also closely related to the structure of the on-site collector network, existing technologies cannot simultaneously achieve both modeling efficiency and equivalent accuracy. Therefore, there is an urgent need for a method that can perform equivalent modeling of the entire photovoltaic power station collector system to solve the problems of complex detailed modeling, low simulation efficiency, and the inability of simplified modeling to maintain key electrical characteristics in existing technologies.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a method and system for electromechanical equivalent modeling of photovoltaic power plants based on impedance polymerization, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation, the method comprising: Obtain the topology parameters, equipment parameters, and line parameters of the photovoltaic power station, and establish a detailed model of the photovoltaic power station based on the topology parameters, equipment parameters, and line parameters; Determine the range to be equivalent based on the detailed model, and divide the equivalent objects by taking the 35kV collection busbar within the range to be equivalent as a unit; Aggregate the power generation units and network parameters in the equivalent objects to obtain equivalent parameters corresponding to the 35kV collection busbar, where the network parameters include impedance parameters, grounding capacitance parameters, and admittance parameters; Construct the electromechanical equivalent model of the photovoltaic power station based on the equivalent parameters; Simulate the electromechanical equivalent model, and compare the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model.

[0007] Further, establish the equivalent range, including: Determine the range to be equivalent as the in-field collector system starting from the low-voltage side of the main transformer within the station or connected to the booster station; Incorporate the collector lines below 35kV, photovoltaic power generation units on the low-voltage side, box-type transformers supporting the photovoltaic power generation units, and 35kV collection lines in the in-field collector system into the range to be equivalent; Take the 35kV collection busbar as the division unit of the equivalent objects, and perform equivalent modeling on the equipment and lines within the range to be equivalent.

[0008] Further, perform equivalent aggregation processing on the photovoltaic power generation units in the equivalent objects, including: Screen out multiple photovoltaic power generation units connected to the same 35kV collection busbar as the objects to be aggregated; Judge whether each of the photovoltaic power generation units in the objects to be aggregated is of the same model and has consistent technical parameters; When the judgment result is yes, perform equivalent aggregation processing on the multiple photovoltaic power generation units in the objects to be aggregated.

[0009] Further, perform equivalent aggregation processing on the multiple photovoltaic power generation units in the objects to be aggregated, including: Under the condition of keeping the busbar voltage level unchanged before and after equivalence, equivalent multiple photovoltaic power generation units connected to the same 35kV collection busbar into one photovoltaic power generation unit; Aggregate the active power, reactive power, and current parameters of the multiple photovoltaic power generation units in the way of power multiplication; Assign the aggregated active power, reactive power, and current parameters to the equivalent photovoltaic power generation unit.

[0010] Further, perform equivalent aggregation processing on the impedance parameters in the network parameters, including: Based on the network connection relationship in the equivalent object, the line impedance, the collection line impedance and the box transformer impedance are converted step by step. Impedance aggregation is performed on the line impedance, the combined line impedance, and the box-type transformer impedance using a series-then-parallel connection method. The output line impedance is selected as the equivalent output impedance, and the lines and box-type transformers under the 35kV busbar are equivalent to a box-type transformer and connected to the 35kV busbar through a cable line.

[0011] Furthermore, the grounding capacitance parameter in the network parameters is subjected to equivalent aggregation processing, including: It is determined that one end of each line within the equivalent object is connected to the 35kV collection bus. The grounding capacitance of each of the aforementioned lines is regarded as a parallel branch connected in parallel to the 35kV busbar. The grounding capacitances of each of the aforementioned lines are connected in parallel to obtain the equivalent grounding capacitance connected to the 35kV busbar.

[0012] Furthermore, the admittance parameter in the network parameters is subjected to equal-value aggregation processing, including: Each box-type transformer within the equivalent object is equivalent to a Γ-type transformer. The admittance branch after the Γ-type equivalent is moved forward to the 35kV collecting bus side; The parallel connection of each of the aforementioned admittance branches after being moved forward is equivalent to the equivalent admittance branch connected to the 35kV busbar.

[0013] Furthermore, the validity of the electromechanical equivalent model is verified, including: Simulations were performed on the electromechanical equivalent model and the detailed model in electromechanical modeling software. The simulation results of the electromechanical equivalent model and the detailed model in terms of grid connection point voltage, active power, reactive power, active current and reactive current are compared. The average deviation, average absolute deviation, and maximum deviation are calculated based on the comparison results of the steady-state and transient intervals, and the effectiveness of the electromechanical equivalent model is verified based on the calculation results.

[0014] An electromechanical equivalent modeling system for photovoltaic power plants based on impedance aggregation, the system comprising: The detailed model module obtains the topology parameters, equipment parameters, and line parameters of the photovoltaic power station, and establishes a detailed model of the photovoltaic power station based on the topology parameters, equipment parameters, and line parameters. The object partitioning module determines the range to be equalized based on the detailed model, and divides the equalization objects using the 35kV busbar within the range to be equalized as the unit; The aggregation equivalent module aggregates the generation units and network parameters in the equivalent object to obtain the equivalent parameters corresponding to the 35kV collection bus, where the network parameters include impedance parameters, grounding capacitance parameters and admittance parameters; The equivalent model module constructs an electromechanical equivalent model of a photovoltaic power station based on equivalent parameters; The effective verification module simulates the electromechanical equivalent model and compares the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model.

[0015] Furthermore, the aggregated equivalence module includes: The object filtering unit filters out multiple photovoltaic power generation units connected to the same 35kV bus as objects to be aggregated; The consistency judgment unit determines whether the photovoltaic power generation units in the object to be aggregated are photovoltaic power generation units of the same model and with the same technical parameters. The equivalent aggregation unit performs equivalent aggregation processing on multiple photovoltaic power generation units in the object to be aggregated when the judgment result is yes.

[0016] The technical solution of this invention can achieve the following technical effects: By acquiring detailed parameters of photovoltaic power plants and establishing detailed models, the impedance, grounding capacitance, and admittance of photovoltaic power generation units and collection systems are jointly and equivalently aggregated using the busbar as a unit. Then, an electromechanical equivalent model is constructed, and the effectiveness is verified by simulation comparison. This effectively solves the problems of complex modeling, low simulation efficiency, and difficulty in ensuring equivalent accuracy that are common in existing electromechanical transient modeling of photovoltaic power plants.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation. Figure 2A schematic diagram of the structure before and after equivalent modeling of a photovoltaic power plant based on impedance aggregation electromechanical equivalent modeling method; Figure 3 A schematic diagram of the equivalent method for impedance step-by-step reduction; Figure 4 This is a schematic diagram of the equivalent method for line grounding capacitance and box-type transformer admittance. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Example 1; like Figure 1 and Figure 2 As shown, this application provides a method for electromechanical equivalent modeling of photovoltaic power plants based on impedance aggregation. The method includes: S10: Obtain the topology parameters, equipment parameters, and line parameters of the photovoltaic power station, and establish a detailed model of the photovoltaic power station based on the topology parameters, equipment parameters, and line parameters; S20: Determine the range to be equalized based on the detailed model, and divide the equalization objects using the 35kV busbar within the range to be equalized as the unit; S30: Aggregate the generation units and network parameters in the equivalent object to obtain the equivalent parameters corresponding to the 35kV busbar, where the network parameters include impedance parameters, grounding capacitance parameters and admittance parameters; S40: Constructing an electromechanical equivalent model of a photovoltaic power station based on equivalent parameters; S50: Simulate the electromechanical equivalent model and compare the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model.

[0023] Specifically, the first step is to acquire basic data for the photovoltaic power station used for electromechanical transient modeling. This basic data preferably includes detailed primary wiring relationships and corresponding technical parameters for the equipment and lines within the station. The detailed primary wiring relationships should at least reflect the connection relationships between the photovoltaic power generation units, box-type transformers, various collector lines, the main transformer, reactive power compensation equipment, and transmission lines. The technical parameters preferably include the model, rated capacity, rated voltage, rated frequency, and power factor range of the photovoltaic power generation units; the rated capacity, rated voltage, short-circuit loss, no-load loss, wiring method, grounding method, short-circuit voltage, and no-load current of the box-type transformers; and the rated capacity, high and low voltage sides, rated voltage, short-circuit loss, no-load loss, wiring group, and short-circuit current of the main transformer. Voltage and no-load current, as well as parameters such as conductor length, conductor type, rated voltage, line cross-section, positive sequence resistance, positive sequence reactance, zero sequence resistance, zero sequence reactance, and grounding capacitance, are obtained. After obtaining these parameters, it is preferable to perform a one-to-one detailed modeling according to the actual site topology to form a detailed model that can serve as a reference for subsequent equivalence measurements. The detailed model preferably includes a site node model, a main transformer model, a collector line model, a photovoltaic inverter single-unit model, a reactive power compensation device model, and a fault test model. The collector line model preferably includes the actual connection relationships with the box-type transformer, towers, transformers, and inverters. After establishing the detailed model, it is preferable to determine the equivalence range starting from the main transformer within the site or the low-voltage side connected to the step-up substation. The photovoltaic (PV) power generation units with lower voltage levels in the on-site power collection system, their corresponding box-type transformers, on-site power collection lines, and collection lines are included in the scope to be equivalentd. Furthermore, it is preferable to use the same collection bus as the equivalence boundary, thus classifying PV power generation units, box-type transformers, and lines connected to the same collection bus as a single equivalent object. In specific implementation, to ensure the accuracy of the external characteristics after equivalence, it is preferable to aggregate only multiple PV power generation units connected to the same collection bus with the same model and consistent technical parameters. While maintaining the bus voltage level unchanged before and after equivalence, a power multiplication method is used to equate multiple PV power generation units to a single PV power generation unit, so that the equivalent PV power generation unit inherits the aggregated characteristics. The core response characteristics of the object include active power, reactive power, and current. Simultaneously, the network parameters in the equivalent object are jointly aggregated. For impedance parameters, a step-by-step series-then-parallel approach is preferred to convert the impedance of the lines, collection lines, and box-type transformers. The output line impedance is preferably selected as the equivalent output impedance, so that the originally dispersed lines and box-type transformers under the collection bus can be equivalent to a single box-type transformer connected to the collection bus via a cable line. For grounding capacitance parameters, based on the topology feature that one end of each line is connected to the common node of the collection bus, the grounding capacitance of each line is preferably reduced to the output of the collection line and equivalently calculated according to the parallel relationship, ultimately forming an equivalent grounding capacitance connected to the collection bus.For admittance parameters, it is preferable to first perform Γ-type equivalents on each box-type transformer, then move the admittance branch formed by the Γ-type equivalents to the busbar side, and perform equivalent processing on multiple admittance branches in parallel to form an equivalent admittance branch connected to the busbar. The admittance of each box-type transformer can be determined by its no-load loss, no-load current, and voltage parameters. After the above processing, it is preferable to treat the equipment under a busbar as a photovoltaic power generation unit, a box-type transformer including impedance and admittance, an equivalent outgoing impedance, and an equivalent grounding capacitor, while retaining the reactive power compensation device connected to the busbar, thus obtaining the electromechanical equivalent model of the photovoltaic power station. After the electromechanical equivalent model is constructed, it is preferable to input the electromechanical equivalent model and the detailed model into the electromechanical modeling software for simulation calculations, and verify the effectiveness of the electromechanical equivalent model by comparing the electrical quantity responses such as voltage, active power, reactive power, active current, and reactive current at the grid connection point. The effectiveness verification is preferably performed by calculating the equivalent values. The simulation is completed by measuring the average deviation, average absolute deviation, and maximum deviation between the simulation data of the value model and the simulation data of the detailed model. The simulation state preferably includes a steady-state interval and a transient interval, where the steady-state interval can further include the pre-fault and post-fault intervals. In a preferred embodiment, when the deviation results meet the allowable value requirements, it indicates that the electromechanical equivalent model has effectively simplified the complex internal structure of the power station while maintaining consistent power loss and grid connection point voltage. For example, for a typical power station branch connected to multiple photovoltaic power generation units of the same type, multiple box-type transformers, and multiple sections of collector lines along the same busbar, detailed modeling can be completed first based on the detailed wiring relationships. Then, using the busbar as the boundary, multiple photovoltaic power generation units are aggregated into an equivalent photovoltaic power generation unit, and the joint equivalence of line impedance, box-type transformer impedance, line grounding capacitance, and box-type transformer admittance is completed simultaneously. Finally, the branch is converted into a single-branch equivalent structure suitable for electromechanical transient analysis, thus achieving a balance between modeling efficiency and simulation accuracy.

[0024] The technical solution of this invention obtains detailed parameters of a photovoltaic power station and establishes a detailed model. Using the busbar as a unit, the impedance, grounding capacitance and admittance of the photovoltaic power generation unit and the collection system are jointly and equivalently aggregated. Then, an electromechanical equivalent model is constructed and its effectiveness is verified by simulation comparison. This effectively solves the problems of complex modeling, low simulation efficiency and difficulty in ensuring equivalent accuracy that are common in existing electromechanical transient modeling of photovoltaic power stations.

[0025] Furthermore, such as Figure 2 As shown, establish the equivalent range, including: The range to be equalized is defined as the on-site power collection system starting from the main transformer in the station or the low-voltage side connected to the step-up substation; Include the collector lines below 35 kV in the on-site collector system, the photovoltaic power generation units on the low-voltage side, the box-type transformers supporting the photovoltaic power generation units, and the 35 kV collection lines in the scope of equipment to be equivalent; Take the 35 kV collection bus as the dividing unit of the equivalent object, and perform equivalent modeling on the equipment and lines within the scope of equipment to be equivalent.

[0026] As a preferred embodiment of the above, the boundary of the objects requiring electromechanical equivalence within the power station is first determined based on a detailed wiring relationship. The boundary preferably begins from the low-voltage side of the main transformer within the power station. When the photovoltaic power station is connected to a step-up substation, the boundary can also preferably begin from the low-voltage side connected to the step-up substation. The purpose is to distinguish the high-voltage side of the main transformer and the external power grid from the power collection system within the power station, thereby concentrating the equivalence range on the power collection network within the power station, which has the most direct impact on the external electrical response of the power station and is most suitable for aggregation and simplification. Specifically, the boundary is preferably defined as follows: each section of the power collection line within the power collection system, the photovoltaic power generation units connected to the low-voltage side, the box-type transformers corresponding to each photovoltaic power generation unit, and the junction boxes connected to the power collection branches within the power station. The collection lines are included in the equivalence scope. Here, the on-site collection lines are preferably understood as lines located below the collection busbar that connect various photovoltaic power generation units and box-type transformers. The collection lines are preferably understood as lines that further collect multiple collection branches to the main transformer or step-up substation. By including the above equipment and lines in the same equivalence scope, the simplification of only the photovoltaic power generation units while ignoring the characteristics of the line and transformer network can be avoided, thus providing a unified boundary for the subsequent joint aggregation of impedance parameters, grounding capacitance parameters, and admittance parameters. Furthermore, to ensure that the equivalence process has a clear and stable dividing basis, this embodiment preferably uses the on-site 35kV collection busbar as the dividing unit for the equivalence object, that is, those connected to the same 35kV busbar... The photovoltaic power generation units, their associated box-type transformers, and the connected lines on the 35kV collection bus are collectively classified into a single equivalent object, and subsequent modeling is carried out based on this equivalent object. The advantage of this classification method is that the 35kV collection bus itself constitutes a common connection node for multiple branches within the site, reflecting the actual hierarchical relationship of the power collection system and facilitating the overall equivalence of equipment under the same bus according to a unified boundary. In a preferred embodiment, when multiple photovoltaic power generation unit branches are connected to a certain 35kV collection bus, the bus and all its subordinate equipment and lines can be identified first based on a detailed model, and then the photovoltaic power generation units, box-type transformers, and collection lines below the bus are collectively included in the same equivalent object. The equipment corresponding to different 35kV busbars is divided into different equivalent objects to ensure clear boundaries and internal connections between the equivalent objects. This provides a basis for subsequent aggregation of power generation units, impedance conversion, and equivalence of grounding capacitance and admittance based on busbar units. For example, in a typical photovoltaic power station, if multiple photovoltaic power generation units are connected to the same 35kV busbar through their respective box-type transformers, and the busbar is then connected to the low-voltage side of the main transformer through a collection line, the equipment and lines between the low-voltage side of the main transformer and the ends of each branch below the 35kV busbar can be identified as the range to be equivalentd. The 35kV busbar is used as the boundary for the equivalent division within this range, thus forming the equivalent objects required for subsequent electromechanical equivalent modeling.By establishing the equivalent range using the above method, the equivalent boundary can be kept consistent with the power station's collection topology. This ensures that subsequent modeling covers not only the photovoltaic power generation units themselves but also the lines and box-type transformers closely related to their electrical responses. This makes it easier to achieve electromechanical equivalent modeling of photovoltaic power stations while maintaining the basic consistency of key electrical characteristics at the grid connection point.

[0027] Furthermore, the process of performing equivalent aggregation on the photovoltaic power generation units within the equivalent object includes: Multiple photovoltaic power generation units connected to the same 35kV busbar were selected as the objects to be aggregated; Determine whether the photovoltaic power generation units in the object to be aggregated are photovoltaic power generation units of the same model and with the same technical parameters; If the judgment result is yes, perform equal-value aggregation on multiple photovoltaic power generation units in the object to be aggregated.

[0028] As a preferred embodiment of the above, after the equivalent range to be defined and the equivalent objects to be formed by the same 35kV collection bus, the process can be carried out. Specifically, based on the detailed wiring relationship and the connection relationship in the detailed model, all photovoltaic power generation units connected to the same 35kV collection bus are identified. Multiple photovoltaic power generation units belonging to the same collection branch level under this bus and jointly transmitted to the outside through the 35kV collection bus are identified as objects to be aggregated. On this basis, the consistency verification of each object to be aggregated is further carried out. The consistency verification preferably includes comparing the model, rated capacity, rated voltage, rated frequency, power factor range, and control and electrical parameters related to electromechanical transient simulation of each photovoltaic power generation unit. To determine whether they belong to the same type of photovoltaic power generation unit with consistent technical parameters, new energy units connected to the same 35kV bus are only considered as unified equivalent objects if they are of the same type and have consistent technical parameters. This avoids forcibly merging units with different control or electrical characteristics, which would affect the accuracy of the equivalent model. If the determination result is yes, then multiple photovoltaic power generation units are subjected to equivalent aggregation processing, preferably regarded as a set of parallel power generation units of the same type and structure. This provides the prerequisite for subsequent unified equivalence using the power multiplication method, so that multiple photovoltaic power generation units originally scattered on the bus can be merged into one equivalent photovoltaic power generation unit while maintaining the consistency of external response characteristics. Furthermore, In the preferred embodiment, the screening and judgment are not performed in isolation on a single device, but are completed as a whole in conjunction with the 35kV busbar as a common connection node. That is, only multiple photovoltaic power generation units that simultaneously meet the two conditions of being connected to the same 35kV busbar and having the same model and consistent technical parameters are included in the equivalent aggregation process. For photovoltaic power generation units that are connected to the same 35kV busbar but have different models, capacity levels, or technical parameters, they are preferably not included in the same aggregation group to ensure that the subsequently constructed electromechanical equivalent model can still accurately reflect the key electrical responses of the original detailed model at the grid connection point. For example, if multiple photovoltaic power generation units using phase-equivalent photovoltaics are connected to a single 35kV busbar... For photovoltaic power generation units with the same inverter type, rated parameters, and control parameters, multiple photovoltaic power generation units can be screened and judged as the same aggregation object first. After confirming that the conditions are met, they can then enter the unified equivalent processing. However, if some photovoltaic power generation units are connected to the same 35kV bus but use different models of equipment or have different technical parameter configurations, they should preferably be excluded from the current aggregation object or divided into another aggregation group for processing. By adopting the above method, the aggregation boundary of photovoltaic power generation units can be kept consistent with the actual collection topology of the power station, and the objects entering the equivalent processing can be consistent in electrical and control attributes, thus providing a reliable foundation for subsequent equivalent modeling based on impedance aggregation theory.

[0029] Furthermore, such as Figure 3 As shown, the process of performing equal-value aggregation on multiple photovoltaic power generation units in the object to be aggregated includes: Under the condition that the bus voltage level remains unchanged before and after the equivalence, multiple photovoltaic power generation units connected to the same 35kV bus are equivalent to one photovoltaic power generation unit. The active power, reactive power, and current parameters of multiple photovoltaic power generation units are aggregated using a power multiplication method. The aggregated active power, reactive power, and current parameters are assigned to the equivalent photovoltaic power generation unit.

[0030] As a preferred embodiment of the above, this process is carried out after screening photovoltaic power generation units connected to the same 35kV busbar and determining their similarity in model and technical parameters. Specifically, this can be achieved by maintaining the busbar voltage level before and after equivalence while uniformly merging the output capabilities of multiple photovoltaic power generation units. That is, the 35kV busbar is used as the aggregation boundary, and multiple photovoltaic power generation units connected to the same 35kV busbar are considered as a set of similar power generation units operating in parallel and jointly supplying power to the busbar. Without changing the 35kV busbar voltage level and its external connection relationship, multiple photovoltaic power generation units are equivalent to one photovoltaic power generation unit, thereby structurally replacing the original multiple photovoltaic power generation units with the equivalent photovoltaic power generation unit. The system participates in subsequent electromechanical equivalent modeling. Based on this, a power multiplication method is preferred to aggregate the active power, reactive power, and current parameters of multiple photovoltaic (PV) power generation units. This power multiplication method can be understood as merging the active, reactive, and current responses of multiple PV power generation units based on the number of units involved in the aggregation and the parameter consistency of each unit. This allows the equivalent PV power generation unit to inherit the total power output capacity and current response characteristics of the original multiple PV power generation units, rather than retaining the original form of independent modeling for each PV power generation unit. Furthermore, after aggregation, the aggregated active power, reactive power, and current parameters are preferably assigned to the equivalent PV power generation unit to ensure that the equivalent PV power generation unit... Even when the detailed model is simplified to an electromechanical equivalent model, the unit can still exhibit external electrical characteristics that are basically consistent with the original multiple photovoltaic power generation units at the 35kV busbar. Here, "preferred assignment" refers to writing the aggregated parameters as the operating parameters or rated parameters of the equivalent photovoltaic power generation unit into the equivalent model, so that the equivalent photovoltaic power generation unit directly represents the composite response of the original multiple photovoltaic power generation units in the simulation calculation. In the preferred embodiment, the equivalent aggregation process not only reduces the number of devices but also avoids additional errors caused by changing the access voltage level during the equivalence process by maintaining the busbar voltage level unchanged. Therefore, it can better maintain the voltage, current, and active and reactive power response characteristics of the original power station at the grid connection point. For example... When multiple photovoltaic (PV) power generation units of the same type and with identical technical parameters are connected to a 35kV busbar, the busbar voltage level and its external connection method can be kept unchanged. Then, these multiple PV power generation units can be merged into one equivalent PV power generation unit. The active power, reactive power, and current parameters corresponding to the original multiple PV power generation units can be merged and assigned to the equivalent PV power generation unit by multiplying the power. This allows multiple PV power generation units that originally needed to be modeled individually to be represented by one PV power generation unit in the equivalent model. By adopting the above preferred method, the PV power generation unit aggregation process not only conforms to the power multiplication equivalence, but also provides a unified and clear power generation unit-side basis for the subsequent joint aggregation of line impedance, grounding capacitance, and admittance parameters.

[0031] Furthermore, the impedance parameters in the network parameters undergo equal-value aggregation, including: Based on the network connection relationship in the equivalent object, the line impedance, the collection line impedance and the box transformer impedance are converted step by step. Impedance aggregation is performed on the line impedance, the combined line impedance, and the box-type transformer impedance using a series-then-parallel connection method. The output line impedance is selected as the equivalent output impedance, and the lines and box-type transformers under the 35kV busbar are equivalent to a box-type transformer and connected to the 35kV busbar through a cable line.

[0032] As a preferred embodiment of the above, after the equivalent range is defined and an equivalent object is formed using a 35kV busbar, the actual connection relationships between the photovoltaic power generation units, box-type transformers, collector lines, and collection lines within the equivalent object are considered. The key point is that the lines and transformers in each branch are no longer retained as independent and dispersed components in the equivalent model. Instead, based on the physical connection sequence and impedance series-parallel relationships of the power collection system within the substation, the line impedance, collection line impedance, and box-type transformer impedance are progressively reduced and uniformly merged. Specifically, it is preferable to first use the branch containing a single photovoltaic power generation unit as a basis, and then consider the connections between the photovoltaic power generation unit and the collection line. The impedance of the box-type transformer connected to the photovoltaic power generation unit and the line impedance between the photovoltaic power generation unit and the 35kV busbar are processed according to the actual connection sequence in the branches. This allows the impedances on the same current path to first form a series conversion result. Then, based on the topological relationship of multiple branches converging at the 35kV busbar, the impedance results formed by different branches are further aggregated in parallel, thus achieving impedance merging from the branch level to the busbar level step by step. In this process, the preferred step-by-step conversion is to calculate the line impedance and box-type transformer impedance on each branch along the direction of power convergence from the photovoltaic power generation unit side to the 35kV busbar. The impedance is calculated sequentially to avoid direct and coarse merging across levels, which could distort network characteristics. The preferred method of first series and then parallel connections ensures that the impedance aggregation sequence matches the actual wiring configuration of the substation. This means first preserving the longitudinal electrical relationships within a single branch, and then addressing the lateral parallel connections formed between multiple branches through common nodes. Furthermore, after completing the step-by-step aggregation of line impedance, collection line impedance, and box-type transformer impedance, the output line parameter impedance is preferably selected as the equivalent output impedance. This ensures that the equivalent line portion still reflects the main impedance characteristics of the original substation in the direction of transmission from the 35kV collection bus. Based on this, the 35kV... The lines and box-type transformers originally distributed in multiple branches under the busbar are equivalent to a single box-type transformer and connected to the 35kV busbar through a single cable line, thus forming a simplified topology suitable for electromechanical transient analysis. In the preferred embodiment, this impedance aggregation is not a simple deletion of branches, but rather a hierarchical merging of impedances within and between branches with a basis, while maintaining the basic consistency of the key electrical responses at the grid connection point before and after equivalence. Therefore, it can significantly reduce the number of lines and transformers in the model, while retaining the impedance characteristics of the original substation collection network that play a decisive role in voltage distribution, power loss, and transient response.For example, when multiple photovoltaic power generation unit branches, whose voltages are stepped up by box-type transformers and then connected to the busbar via their respective collector lines, are connected to the same 35kV busbar, the impedance of the box-type transformer and the corresponding line impedance within each branch can be first converted in series. Then, the impedance relationships formed by multiple branches at the 35kV busbar can be aggregated in parallel. Finally, the equivalent outgoing line impedance can be determined by combining the parameters of the sending line. This simplifies the original network consisting of multiple branches, multiple lines, and multiple box-type transformers into a structure where one equivalent box-type transformer is connected to the 35kV busbar via one equivalent cable line. By adopting the above preferred method, the equivalent aggregation of impedance parameters can be strictly based on the actual network connection relationship of the substation, thus providing an accurate, clear, and feasible network foundation for the subsequent equivalent processing of grounding capacitance and admittance parameters, as well as the construction of the electromechanical equivalent model of the entire substation.

[0033] Furthermore, such as Figure 4 As shown, the grounding capacitance parameter in the network parameters is subjected to equal-value aggregation processing, including: It is determined that one end of each line within the equivalent object is connected to the 35kV collection bus. The grounding capacitance of each line is regarded as a parallel branch connected to the 35kV busbar. The grounding capacitances of each line are connected in parallel to obtain the equivalent grounding capacitance connected to the 35kV busbar.

[0034] As a preferred embodiment of the above, after the equivalent range is defined and an equivalent object is formed using a 35kV busbar, the actual wiring relationship of each line within the equivalent object is considered. The key is to first identify the common connection characteristics between each line and the 35kV busbar, that is, to determine that one end of each collector line or cable line within the equivalent object is connected to the same 35kV busbar. Since the 35kV busbar constitutes the common node of each line within the equivalent object, the grounding capacitors that were originally scattered on the lines can be uniformly regarded as parallel branches connected to the 35kV busbar in electrical terms. On this basis, the grounding capacitors corresponding to each line are then... The grounding capacitance is consolidated into an equivalent grounding capacitance connected to the 35kV busbar, thus representing the combined effect of the original multiple lines on the busbar-side capacitance with a lumped parameter. In a preferred embodiment, the grounding capacitance is not simply omitted; instead, the grounding capacitance corresponding to each line is first determined based on a detailed model or line parameter information. Then, based on the common topology that all lines are connected to the same 35kV busbar, the grounding capacitance is uniformly converted and reduced to the point where the busbar exits. This preserves the influence of the lines on the busbar voltage response and network charging characteristics in the equivalent model, reducing the number of dispersed capacitor branches in the model and avoiding the influence of... To avoid neglecting the line grounding capacitance and thus reducing the ability of the equivalent model to represent the electrical characteristics of the original collector network, it is preferable to first group all line impedances and photovoltaic power generation units within the equivalent object according to the bus boundary, and then perform parallel equivalent balancing of the grounding capacitance of each line. This ensures that the equivalent grounding capacitance, together with the aforementioned equivalent photovoltaic power generation units, equivalent box-type transformers, and equivalent outgoing line impedances, constitutes a complete equivalent structure under the 35kV collection bus, thereby ensuring that the treatment of grounding capacitance parameters is consistent with the treatment of impedance and admittance parameters at the topological boundary. For example, when multiple cable lines are connected to the same 35kV collection bus, and each cable line is connected to photovoltaic power generation units of different branches... When constructing electrical units and box-type transformers, it can be first confirmed in the detailed model that one end of each cable line is connected to the 35kV collection bus. Then, the grounding capacitance corresponding to each cable line is regarded as a parallel branch and uniformly calculated to the 35kV collection bus. Finally, in the equivalent model, an equivalent grounding capacitance replaces the original dispersed grounding capacitance of multiple lines. By adopting the above preferred method, the equivalent aggregation processing of grounding capacitance parameters can be established on the basis of the parallel relationship of common nodes. Under the premise of not exceeding the original disclosure range, the line grounding capacitance can be effectively simplified, and the capacitance characteristics that are more consistent with the original station collection network can be provided for the subsequent construction and simulation verification of electromechanical equivalent models.

[0035] Furthermore, such as Figure 4 As shown, the admittance parameter in the network parameters is subjected to equal-value aggregation, including: Each box-type transformer within the equivalent object is equivalent to a Γ-type transformer. The admittance branch after the Γ-type equivalent is moved forward to the 35kV collection bus side; The parallel connection of each admittance branch after the forward movement is equivalent to the 35kV collection busbar.

[0036] As a preferred embodiment of the above, this process is carried out after the equivalent range is defined and an equivalent object is formed with the 35kV busbar as the boundary. The key is to retain and uniformly merge the parallel electrical characteristics of the box-type transformers, excluding series impedance, to avoid overlooking the impact of the box-type transformer's excitation branch on the busbar-side electrical response when only impedance conversion is performed. Specifically, based on the no-load loss, no-load current, voltage level, and parameters required for equivalent modeling of each box-type transformer, the box-type transformers within the equivalent object are first subjected to Γ-type equivalent modeling. This ensures that each box-type transformer, after equivalence, not only retains the impedance characteristics in its series path but also forms an admittance branch that characterizes the excitation and no-load characteristics. Based on this, and considering the connection relationship between each box-type transformer and the 35kV busbar, the position of the equivalent admittance branch is adjusted. Preferably, the admittance branch is moved forward from its original corresponding branch position to the 35kV busbar side, thus unifying the admittance effect originally dispersed in each branch and expressing it on the busbar side. Furthermore, since multiple box-type transformers within the equivalent object ultimately connect to the same 35kV busbar through corresponding branches, the forward-moved admittance branches can be considered as multiple parallel branches connected to the 35kV busbar in electrical terms. Therefore, it is preferable to perform parallel equivalent conversion on the forward-moved admittance branches to form an equivalent admittance branch connected to the 35kV busbar. In the equivalent model, the combined effect of the original multiple box-type transformer excitation branches is characterized by concentrated admittance. In the preferred embodiment, the treatment of moving the admittance branches forward and connecting them in parallel, together with the aforementioned step-by-step reduction of impedance parameters and the parallel equivalent of grounding capacitance parameters, jointly achieve the unified aggregation of various network parameters under the same 35kV busbar. Among them, impedance parameters mainly reflect the series characteristics on the current path, grounding capacitance parameters mainly reflect the capacitance effect of the line on the busbar, and admittance parameters mainly reflect the characteristics of the parallel branches of the box-type transformer. Therefore, by extracting the admittance parameters separately and moving them forward to the busbar side for parallel equivalent, the equivalent electromechanical model can simplify the structure while still retaining a relatively complete structure. The overall network external characteristics; for example, when multiple box-type transformers are connected to the same 35kV busbar, and each box-type transformer is located in a different photovoltaic power generation unit branch, the Γ-type equivalent value of each box-type transformer can be performed first, and then the admittance branches formed by each transformer can be moved forward from their original branch positions to the 35kV busbar side. Finally, the multiple admittance branches after the forward movement can be merged into one equivalent admittance branch connected to the 35kV busbar, thereby replacing the original multiple dispersed admittance branches with a lumped parameter. By adopting the above preferred method, the equivalent aggregation processing of the admittance parameters of the box-type transformers can be clearly realized, and effective support can be provided for the subsequent construction of a photovoltaic power station electromechanical equivalent model that takes into account both accuracy and efficiency.

[0037] Furthermore, the validity of the electromechanical equivalent model is verified, including: Simulations were performed on the equivalent and detailed electromechanical models in electromechanical modeling software. The simulation results of the electromechanical equivalent model and the detailed model in terms of grid connection point voltage, active power, reactive power, active current and reactive current are compared. The average deviation, average absolute deviation, and maximum deviation are calculated based on the comparison results of the steady-state and transient intervals, and the effectiveness of the electromechanical equivalent model is verified based on the calculation results.

[0038] As a preferred embodiment of the above embodiments, after completing the construction of the detailed model and the electromechanical equivalent model of the photovoltaic power station, the electromechanical equivalent model and the detailed model are simulated separately using the same electromechanical modeling software under the same operating conditions and the same simulation scenario to ensure the comparability of the comparison results. Specifically, it is preferable to input the electromechanical equivalent model and the detailed model into the same simulation platform and conduct simulation calculations under the same grid boundary conditions, the same initial operating state, and the same disturbance conditions. Then, the response of key electrical quantities such as voltage, active power, reactive power, active current, and reactive current at the grid connection point is extracted. As a result, the grid connection point, as the electrical connection location between the photovoltaic power station and the external power grid, can directly reflect the degree to which the equivalent model retains its external characteristics. Therefore, the aforementioned electrical quantities are selected as verification objects, which can cover both the power distribution and voltage level during steady-state operation and the dynamic response characteristics during disturbances. In the preferred embodiment, when comparing the simulation results of the electromechanical equivalent model and the detailed model, not only is the numerical consistency of each electrical quantity in the steady-state interval compared, but also its response trend over time in the transient interval is compared. The steady-state interval preferably includes the pre-fault and post-fault recovery stabilization stages, and the transient interval... The optimal selection process includes the stage where the system voltage, current, and power dynamically change after a disturbance occurs. After obtaining the comparison results, the average deviation, average absolute deviation, and maximum deviation of the computer-equivalent electromechanical model relative to the detailed model are further optimized. The deviation results are used as the basis for validity verification to determine whether the electromechanical equivalent model can maintain the key electrical response characteristics of the original detailed model at the grid connection point while simplifying the model scale. Among them, the average deviation is preferably used to characterize the overall offset degree, the average absolute deviation is preferably used to characterize the overall error level, and the maximum deviation is preferably used to characterize the error range under the most unfavorable condition. Through comprehensive consideration... By observing the above-mentioned deviation indicators, we can avoid the one-sidedness caused by judging the equivalent effect based on a single moment or a single electrical quantity. For example, in a preferred embodiment, the detailed model and the electromechanical equivalent model can be calculated under normal operating conditions and simulation conditions including disturbance processes, respectively. The full-process response curves of grid connection point voltage, active power, reactive power, active current and reactive current are extracted. Then, based on the corresponding data of the response curves in the steady-state and transient regions, the average deviation, average absolute deviation and maximum deviation are calculated. When the deviation results meet the allowable requirements, the electromechanical equivalent model can be considered to have good effectiveness.

[0039] Example 2; Based on the same inventive concept as the electromechanical equivalent modeling method for photovoltaic power plants based on impedance aggregation in the foregoing embodiments, the present invention also provides an electromechanical equivalent modeling system for photovoltaic power plants based on impedance aggregation, the system comprising: The detailed model module obtains the topology parameters, equipment parameters, and line parameters of the photovoltaic power station, and establishes a detailed model of the photovoltaic power station based on the topology parameters, equipment parameters, and line parameters. The object partitioning module determines the range to be equalized based on the detailed model, and divides the equalization objects using the 35kV busbar within the range to be equalized as the unit; The aggregation equivalent module aggregates the generation units and network parameters in the equivalent object to obtain the equivalent parameters corresponding to the 35kV collection bus, where the network parameters include impedance parameters, grounding capacitance parameters and admittance parameters; The equivalent model module constructs an electromechanical equivalent model of a photovoltaic power station based on equivalent parameters; The effective verification module simulates the electromechanical equivalent model and compares the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model.

[0040] The adjustment system described above in this invention can effectively realize a photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation, and the technical effects it can achieve are as described in the above embodiments, and will not be repeated here.

[0041] Furthermore, the aggregation equivalence module includes: The object filtering unit filters out multiple photovoltaic power generation units connected to the same 35kV bus as objects to be aggregated; The consistency judgment unit determines whether the photovoltaic power generation units in the object to be aggregated are photovoltaic power generation units of the same model and with the same technical parameters. The equivalent aggregation unit performs equivalent aggregation processing on multiple photovoltaic power generation units in the object to be aggregated when the judgment result is yes.

[0042] Similarly, the above-mentioned optimization schemes for the system can also achieve the optimization effects corresponding to the methods in Embodiment 1, which will not be repeated here.

[0043] Example 3; like Figure 3 As shown, the scope of equipment requiring equivalent value within the photovoltaic power station is defined. The equivalent part starts from the low-voltage side of the main transformer (or connected to the step-up substation) within the station, mainly including the collection lines below 35kV within the station, low-voltage level new energy units and their supporting box-type transformers, as well as 35kV collection lines. The 35kV busbar is used as an equivalent unit, and the new energy units, supporting box-type transformers, and lines connected to the same 35kV busbar are equivalent.

[0044] (1) Perform unified equivalent calculation for new energy generating units: Using the power multiplication method, n new energy generating units connected to the same 35kV bus are equivalent to one unit.

[0045] Keeping the bus voltage level unchanged before and after equivalence, the core equivalent parameters of the new energy unit include impedance, power, and current. Let P be the active power, reactive power, and rated current of a single new energy unit. i Q i I i Let P be the active power, reactive power, and rated current of n individual renewable energy generating units after their equivalent values. Σ Q Σ I Σ The equivalent formula for multiplication is: .

[0046] (2) Perform impedance conversion step by step for the lines, collection lines and box-type transformers. by Figure 3 Taking the typical substation structure shown as an example, the detailed model is equivalently represented by a step-by-step series-then-parallel connection method. The line impedance and the impedance of the connected box-type transformer are selected. ZT1, ZT2, and ZT3 are the impedances of the new energy unit's box-type transformer. The transformer's resistance and reactance are calculated from short-circuit loss, short-circuit voltage, and rated voltage. ZL1 and ZL2 are the impedances of the collecting lines participating in the step-by-step conversion. The output line parameter impedance ZL3 is selected as the equivalent output impedance, ultimately equivalent to the impedance Z of a single box-type transformer. eq3 and the outgoing line impedance ZL3. The equivalent formula is: ; ; Where P1, P2, and P3 represent the power parameters of the units corresponding to each branch participating in the equivalent aggregation; Z eq1 Z represents the equivalent impedance of the first-stage branch; eq2 This represents the equivalent impedance after the second-stage polymerization.

[0047] (3) Perform equivalent calculations for line grounding capacitance and box-type transformer admittance. like Figure 4 As shown, the grounding capacitance C of each cable line i After equivalent aggregation, the value is attributed to the outlet of the collector line. When aggregating the equivalent values ​​of n individual units, the formula for calculating the equivalent grounding capacitance of the cable lines for those n individual units is: ; When n box-type transformers are aggregated in equivalent value, the formula for calculating the equivalent admittance of n box-type transformers is: ; The admittance Y of each box-type transformer Δi It consists of conductivity and susceptance, and is calculated from no-load loss, no-load current and voltage.

[0048] After equivalence, the equipment under a 35kV bus can be equivalent to a new energy unit, a box-type transformer (including impedance and admittance), and connected to the main transformer (step-up substation) through an equivalent outgoing impedance. The bus is connected to an equivalent grounding capacitor and a reactive power compensation device.

[0049] In electromechanical modeling software, input the equivalent model data of the photovoltaic power station for simulation calculations. Verify the accuracy of the equivalent model by calculating the error between the equivalent model's calculation results and the detailed model's calculation results. The electrical quantities involved in the deviation calculation include: grid connection point voltage U, active power P, reactive power Q, active current Ip, and reactive current Iq, with U as the metric. Ei This represents the i-th simulation data of the grid-connected voltage in the equivalent model, denoted by U. Ri This represents the i-th simulation data of the detailed model, and similarly, Ip Ei IP Ri 、Iq Ei 、Iq Ri P Ei P Ri and Q Ei Q Ri Simulation data and detailed data representing active current, reactive current, active power, and reactive power, respectively; the deviation calculation method is as follows: ; Where x represents different electrical quantities; F x1 F represents the allowable average deviation over the steady-state range. x2 F represents the permissible value of the mean absolute deviation of the transient interval; x3 This represents the maximum permissible deviation within the steady-state range. The permissible deviation should meet the requirements of relevant standards.

[0050] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation, characterized in that, The method includes: Obtaining the topological parameters, equipment parameters and line parameters of the photovoltaic power station, and establishing a detailed model of the photovoltaic power station based on the topological parameters, the equipment parameters and the line parameters; Determining the equivalent range to be considered based on the detailed model, and dividing the equivalent objects by taking the 35 kV collection busbar within the equivalent range to be considered as a unit; Performing aggregation processing on the power generation units and network parameters in the equivalent objects to obtain equivalent parameters corresponding to the 35 kV collection busbar, where the network parameters include impedance parameters, grounding capacitance parameters and admittance parameters; Constructing an electromechanical equivalent model of the photovoltaic power station based on the equivalent parameters; Performing simulation on the electromechanical equivalent model, and comparing the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model.

2. The photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation according to claim 1, characterized in that, Establishing the equivalent range, including: Determining the equivalent range to be considered as the in-field collection system starting from the main transformer in the station or the low-voltage side connected to the booster station; Including the collection lines below 35 kV, the photovoltaic power generation units on the low-voltage side, the box-type transformers supporting the photovoltaic power generation units and the 35 kV collection lines in the in-field collection system in the equivalent range to be considered; Taking the 35 kV collection busbar as the division unit of the equivalent objects, and performing equivalent modeling on the equipment and lines within the equivalent range to be considered.

3. The method for electromechanical equivalent modeling of photovoltaic power plants based on impedance aggregation according to claim 1, characterized in that, Performing equivalent aggregation processing on the photovoltaic power generation units in the equivalent objects, including: Selecting multiple photovoltaic power generation units connected to the same 35 kV collection busbar as the objects to be aggregated; Judging whether each of the photovoltaic power generation units in the objects to be aggregated is a photovoltaic power generation unit of the same model and with consistent technical parameters; When the judgment result is yes, performing equivalent aggregation processing on the multiple photovoltaic power generation units in the objects to be aggregated.

4. The photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation according to claim 3, characterized in that, Performing equivalent aggregation processing on the multiple photovoltaic power generation units in the objects to be aggregated, including: Under the condition of keeping the busbar voltage level unchanged before and after equivalence, equivalently converting multiple photovoltaic power generation units connected to the same 35 kV collection busbar into one photovoltaic power generation unit; Aggregating the active power, reactive power and current parameters of the multiple photovoltaic power generation units in a power multiplication manner; Assigning the aggregated active power, reactive power and current parameters to the equivalently converted photovoltaic power generation unit.

5. The photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation according to claim 1, characterized in that, Performing equivalent aggregation processing on the impedance parameters in the network parameters, including: Based on the network connection relationship in the equivalent objects, performing step-by-step conversion on the line impedance, collection line impedance and box-type transformer impedance; Performing impedance aggregation on the line impedance, the collection line impedance and the box-type transformer impedance in a way of first series connection and then parallel connection; Selecting the impedance of the outgoing line parameter as the equivalent outgoing line impedance, and equivalently converting the lines and box-type transformers under the 35 kV collection busbar into one box-type transformer and connecting it to the 35 kV collection busbar through a cable line.

6. The method for electromechanical equivalent modeling of photovoltaic power plants based on impedance aggregation according to claim 1, characterized in that, Performing equivalent aggregation processing on the grounding capacitance parameters in the network parameters, including: Determining that one end of each line within the equivalent objects is connected to the 35 kV collection busbar; The grounding capacitance of each of the aforementioned lines is regarded as a parallel branch connected in parallel to the 35kV busbar. The grounding capacitances of each of the aforementioned lines are connected in parallel to obtain the equivalent grounding capacitance connected to the 35kV busbar.

7. The photovoltaic power plant electromechanical equivalent modeling method based on impedance aggregation according to claim 1, characterized in that, The admittance parameter in the network parameters is subjected to equalization aggregation, including: Each box-type transformer within the equivalent object is equivalent to a Γ-type transformer. The admittance branch after the Γ-type equivalent is moved forward to the 35kV collecting bus side; The parallel connection of each of the aforementioned admittance branches after being moved forward is equivalent to the equivalent admittance branch connected to the 35kV busbar.

8. The method for electromechanical equivalent modeling of photovoltaic power plants based on impedance aggregation according to claim 1, characterized in that, The validity of the electromechanical equivalent model is verified, including: Simulations were performed on the electromechanical equivalent model and the detailed model in electromechanical modeling software. The simulation results of the electromechanical equivalent model and the detailed model in terms of grid connection point voltage, active power, reactive power, active current and reactive current are compared. The average deviation, average absolute deviation, and maximum deviation are calculated based on the comparison results of the steady-state and transient intervals, and the effectiveness of the electromechanical equivalent model is verified based on the calculation results.

9. A photovoltaic power plant electromechanical equivalent modeling system based on impedance aggregation, characterized in that, The system includes: The detailed model module obtains the topology parameters, equipment parameters, and line parameters of the photovoltaic power station, and establishes a detailed model of the photovoltaic power station based on the topology parameters, equipment parameters, and line parameters. The object partitioning module determines the range to be equalized based on the detailed model, and divides the equalization objects using the 35kV busbar within the range to be equalized as the unit; The aggregation equivalent module aggregates the generation units and network parameters in the equivalent object to obtain the equivalent parameters corresponding to the 35kV collection bus, where the network parameters include impedance parameters, grounding capacitance parameters and admittance parameters; The equivalent model module constructs an electromechanical equivalent model of a photovoltaic power station based on equivalent parameters; The effective verification module simulates the electromechanical equivalent model and compares the simulation results of the electromechanical equivalent model with the simulation results of the detailed model to determine the effectiveness of the electromechanical equivalent model.

10. The photovoltaic power plant electromechanical equivalent modeling system based on impedance aggregation according to claim 9, characterized in that, The aggregation equivalence module includes: The object filtering unit filters out multiple photovoltaic power generation units connected to the same 35kV bus as objects to be aggregated; The consistency judgment unit determines whether the photovoltaic power generation units in the object to be aggregated are photovoltaic power generation units of the same model and with the same technical parameters. The equivalent aggregation unit performs equivalent aggregation processing on multiple photovoltaic power generation units in the object to be aggregated when the judgment result is yes.

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